447 results on '"Jochen Feldmann"'
Search Results
52. Electron Transfer Rate vs Recombination Losses in Photocatalytic H2 Generation on Pt-Decorated CdS Nanorods
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Jochen Feldmann, Thomas Simon, Michael T. Carlson, and Jacek K. Stolarczyk
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Materials science ,Renewable Energy, Sustainability and the Environment ,Chalcogenide ,Energy Engineering and Power Technology ,Nanoparticle ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Platinum nanoparticles ,Photochemistry ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Electron transfer ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Chemistry (miscellaneous) ,Materials Chemistry ,Photocatalysis ,Nanorod ,0210 nano-technology - Abstract
Cadmium chalcogenide nanocrystals combined with co-catalyst nanoparticles hold promise for efficient solar to hydrogen conversion. Despite the progress, achieving high efficiency is hampered by high charge recombination rates and sample degradation. Here, we vary the decoration of platinum nanoparticles on CdS nanorods to demonstrate the important role of pathways for the photoelectrons to the co-catalyst. Contrary to expectations, the shortening of the path, by increasing the number of co-catalyst particles, increases the transfer rate but decreases the photocatalytic performance. This is because subsequent electron transfer to the acceptor is much slower; therefore, the recombination rate with the nearby holes increases. We show that with tip-decorated nanorods, the quantum yield of H2 production can reach and sustain nearly 90%, provided an efficient mechanism of mediated hole extraction is employed. The approach demonstrates that highly efficient photocatalysts may be prepared with only a minimal amou...
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- 2016
53. Controlling Multiphoton Absorption Efficiency by Chromophore Packing in Metal-Organic Frameworks
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Aurora Manzi, Alexander Pöthig, Benedikt Winkler, Roland A. Fischer, Gregor Kieslich, Christian Schneider, Jochen Feldmann, David C. Mayer, and Raghavender Medishetty
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chemistry.chemical_classification ,Photoluminescence ,Chemistry ,Crystal chemistry ,business.industry ,Rational design ,Nanotechnology ,General Chemistry ,Polymer ,Chromophore ,010402 general chemistry ,Network topology ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Colloid and Surface Chemistry ,Metal-organic framework ,Photonics ,business - Abstract
Coordination polymers show great potential for the tailored design of advanced photonic applications by employing crystal chemistry concepts. One challenge for achieving a rational design of nonlinear optically active MOF materials is deriving fundamental structure-property relations of the interplay between the photonic properties and the spatial arrangements of optically active chromophores within the network. We here investigate two-photon-absorption (TPA)-induced photoluminescence of two new MOFs based on a donor-acceptor tetraphenylphenylenediamine (tPPD) chromophore linker (H4TPBD) and Zn(II) and Cd(II) as metal centers. The TPA efficiencies are controlled by the network topologies, degree of interpenetration, packing densities, and the specific spatial arrangement of the chromophores. The effects can be rationalized within the framework of established excited-state theories of molecular crystals. The results presented here demonstrate the key effect of chromophore orientation on the nonlinear optical properties of crystalline network compounds and allow for establishing quantitative design principles for efficient TPA materials.
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- 2019
54. Using Polar Alcohols for the Direct Synthesis of Cesium Lead Halide Perovskite Nanorods with Anisotropic Emission
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Stephen V. Kershaw, Andrey L. Rogach, Yuan Xiong, Alexander F. Richter, He Huang, Yanxiu Li, and Jochen Feldmann
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Materials science ,Photoluminescence ,business.industry ,General Engineering ,General Physics and Astronomy ,Nanoparticle ,Quantum yield ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Semiconductor ,Nanocrystal ,General Materials Science ,Nanorod ,0210 nano-technology ,business ,Perovskite (structure) - Abstract
Semiconductor nanorods (NRs) offer the useful property of linearly polarized light emission. While this would be an attractive functionality for strongly emitting perovskite nanoparticles, to date, there has been limited success in demonstrating a direct chemical synthesis of cesium lead halide perovskite NRs. In this work, we realized the direct synthesis of CsPbBr3 NRs with an average width of around 5 nm and average lengths of 10.8 and 23.2 nm, respectively, in two samples, which show a high photoluminescence quantum yield of 60-76% and reasonably high emission anisotropy of about 0.2 for longer rods. Both CsPbCl3 and CsPbI3 NRs with similar dimensions have then been derived from the CsPbBr3 NRs by anion-exchange reactions. Remarkably, the synthesis of the NRs has been achieved in polar alcohols, a class of solvents not usually found to be beneficial in classical perovskite nanoparticle synthesis. This work not only offers the possibility to control the shape of chemically synthesized perovskite nanocrystals but also constitutes the hitherto less common strategy of synthesizing perovskite nanoparticles in polar rather than nonpolar or only weakly polar solvents.
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- 2019
55. Spontaneous Crystallization of Perovskite Nanocrystals in Nonpolar Organic Solvents: AVersatile Approach for their Shape-Controlled Synthesis
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Lakshminarayana Polavarapu, Maximilian W. Feil, Andrey L. Rogach, En-Ping Yao, He Huang, Alexander F. Richter, Yanxiu Li, Jochen Feldmann, Markus Döblinger, and Yu Tong
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Spontaneous Crystallization ,FAPbX3 nanoplatelets ,Materials science ,perovskite nanocrystals ,010402 general chemistry ,01 natural sciences ,Catalysis ,law.invention ,Divalent ,FAPbX3 nanocubes ,law ,Crystallization ,Inert gas ,Perovskite (structure) ,chemistry.chemical_classification ,ligand-assisted reprecipitation ,010405 organic chemistry ,Communication ,General Chemistry ,Organic media ,Communications ,0104 chemical sciences ,Formamidinium ,chemistry ,Nanocrystal ,Chemical engineering ,FAPbX3 nanocubes · FAPbX3 nanoplatelets · ligand-assisted reprecipitation · perovskite nanocrystals · spontaneous crystallization - Abstract
The growing demand for perovskite nanocrystals (NCs) for various applications has stimulated the development of facile synthetic methods. Perovskite NCs have often been synthesized by either ligand‐assisted reprecipitation (LARP) at room temperature or by hot‐injection at high temperatures and inert atmosphere. However, the use of polar solvents in LARP affects their stability. Herein, we report on the spontaneous crystallization of perovskite NCs in nonpolar organic media at ambient conditions by simple mixing of precursor–ligand complexes without application of any external stimuli. The shape of the NCs can be controlled from nanocubes to nanoplatelets by varying the ratio of monovalent (e.g. formamidinium+ (FA+) and Cs+) to divalent (Pb2+) cation–ligand complexes. The precursor–ligand complexes are stable for months, and thus perovskite NCs can be readily prepared prior to use. Moreover, we show that this versatile synthetic process is scalable and generally applicable for perovskite NCs of different compositions., Faster than fast: Shape‐controlled lead halide perovskite nanocrystals crystallize spontaneously at ambient conditions when precursor–ligand complexes are mixed directly in a nonpolar organic medium. Nanocubes and nanoplatelets have been obtained. This versatile synthetic process is generally applicable for a wide range of halide perovskite nanocrystals.
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- 2019
56. Chemically synthesized carbon nanorods with dual polarized emission
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Yuan Xiong, Yanxiu Li, Jochen Feldmann, Alexander F. Richter, Stephen V. Kershaw, Seung Jo Yoo, Weitao Zheng, Jin-Gyu Kim, Wei Zhang, Xiaoyu Zhang, Aaron Döring, Peter Kasak, Andrey L. Rogach, Julian Schneider, Elena V. Ushakova, and Anton Popelka
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Carbon nanorods ,Nanostructure ,Materials science ,Inverse micelles ,General Physics and Astronomy ,Quantum yield ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Pulmonary surfactant ,Emission anisotropy ,General Materials Science ,Anisotropy ,Range (particle radiation) ,Dual polarized emission ,General Engineering ,021001 nanoscience & nanotechnology ,Silsesquioxane ,Polycyclic aromatic hydrocarbons ,0104 chemical sciences ,chemistry ,Chemical engineering ,Nanorod ,0210 nano-technology ,Carbon - Abstract
We realized the synthesis of carbon nanorods—monodisperse colloidal particles with a length of 50 nm and a width of 20 nm—which can be considered an addition to the family of light-emitting carbon-based nanostructures. Their anisotropic shape is determined by the use of the surfactant aminopropylisobutyl polyhedral oligomeric silsesquioxane, and their optical properties originate from domains of polycyclic aromatic hydrocarbons incorporated within an inorganic framework. The nanorods show dual polarized emission with a quantum yield of 15–20% and emission anisotropy of ∼0.3, which changes from blue (460 nm) to yellow (565 nm) depending on the excitation wavelength. These carbon nanorods expand the range of light-emitting carbon nanomaterials available for optoelectronic and biolabeling applications. This work was supported by NPRP grant no. 8-878-1-172 from the Qatar National Research Fund (a member of the Qatar Foundation), the Research Grant Council of Hong Kong S.A.R. (CityU 11306619), the Ministry of Education and Science of the Russian Federation (grant 14.Y26.31.0028), by the RFBR Project No. 18-29-19122 mk, the National Natural Science Foundation of China (51702115), the Bavarian State Ministry of Science, Research, and Arts through the grant -Solar Technologies go Hybrid (SolTech), and the Alexander von Humboldt Foundation. Scopus
- Published
- 2019
57. Trans-membrane fluorescence enhancement by carbon dots: ionic interactions and energy transfer
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Stefanie D. Pritzl, Jochen Feldmann, Fernando Pschunder, Theobald Lohmüller, Santanu Bhattacharyya, María Ana Cristina Huergo, and Florian Ehrat
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Ciencias Físicas ,Ionic bonding ,Bioengineering ,02 engineering and technology ,Photochemistry ,CARBON DOTS ,purl.org/becyt/ford/1 [https] ,chemistry.chemical_compound ,Molecule ,Membrane sensing ,Carbon dots ,General Materials Science ,Surface charge ,Fluorescein ,MEMBRANE SENSING ,Óptica ,LIPID BILAYER MEMBRANES ,Mechanical Engineering ,Vesicle ,Bilayer ,General Chemistry ,purl.org/becyt/ford/1.3 [https] ,Química ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Fluorescence ,Lipid bilayer membranes ,Membrane ,chemistry ,Ionic interactions ,IONIC INTERACTIONS ,TRANS-MEMBRANE ENERGY TRANSFER ,lipids (amino acids, peptides, and proteins) ,0210 nano-technology ,CIENCIAS NATURALES Y EXACTAS ,Trans-membrane energy transfer - Abstract
We report on trans-membrane interactions between blue-emitting carbon dots (CDs) and fluorescein. Hydrophobic CDs with a positive surface charge are embedded as-synthesized in the lipophilic sheet of the bilayer membrane of large synthetic phospholipid vesicles. The vesicles are prepared by mixing DOPC phospholipids and lipid molecules that contain anionic fluorescein attached to their hydrophilic head. Due to attractive electrostatic interactions, the CDs and fluorescein conjoin within the vesicle membrane, which leads to photoluminescence enhancement of fluorescein and facilitates trans-membrane energy transfer between the CDs and the dye., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
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- 2019
58. Identifying and Reducing Interfacial Losses to Enhance Color-Pure Electroluminescence in Blue-Emitting Perovskite Nanoplatelet Light-Emitting Diodes
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Weiwei Li, Tiarnan Doherty, Yu Tong, Robert L. Z. Hoye, Krzysztof Galkowski, Sebastian Mackowski, Samuel D. Stranks, Miguel Anaya, Tahmida N. Huq, Jochen Feldmann, Richard H. Friend, Judith L. MacManus-Driscoll, Lakshminarayana Polavarapu, May Ling Lai, Alexander S. Urban, Magdalene College, University of Cambridge, Royal Academy of Engineering, Hoye, Robert [0000-0002-7675-0065], Li, Weiwei [0000-0001-5781-5401], Friend, Richard [0000-0001-6565-6308], Stranks, Samuel [0000-0002-8303-7292], and Apollo - University of Cambridge Repository
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Materials science ,Photoluminescence ,Photoemission spectroscopy ,FOS: Physical sciences ,Energy Engineering and Power Technology ,Applied Physics (physics.app-ph) ,02 engineering and technology ,Electroluminescence ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,law.invention ,law ,Materials Chemistry ,Perovskite (structure) ,Common emitter ,Diode ,Renewable Energy, Sustainability and the Environment ,business.industry ,Physics - Applied Physics ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Fuel Technology ,Chemistry (miscellaneous) ,Optoelectronics ,physics.optics ,Quantum efficiency ,physics.app-ph ,0210 nano-technology ,business ,Optics (physics.optics) ,Light-emitting diode ,Physics - Optics - Abstract
Perovskite nanoplatelets (NPls) hold great promise for light-emitting applications, having achieved high photoluminescence quantum efficiencies (PLQEs) approaching unity in the blue wavelength range, where other metal-halide perovskites have typically been ineffective. However, the external quantum efficiency (EQE) of blue-emitting NPl light-emitting diodes (LEDs) have only reached 0.12%, with typical values well below 0.1%. In this work, we show that the performance of NPl LEDs is primarily hindered by a poor electronic interface between the emitter and hole-injector. Through Kelvin Probe and X-ray photoemission spectroscopy measurements, we reveal that the NPls have remarkably deep ionization potentials (>=6.5 eV), leading to large barriers for hole injection, as well as substantial non-radiative decay at the interface between the emitter and hole-injector. We find that an effective way to reduce these non-radiative losses is by using poly(triarylamine) interlayers. This results in an increase in the EQE of our blue LEDs emitting at 464 nm wavelength to 0.3%. We find that our results can be generalized to thicker sky-blue-emitting NPls, where we increase the EQE to 0.55% using the poly(triarylamine) interlayer. Our work also identifies the key challenges for further efficiency increases.
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- 2019
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59. Optical and thermophoretic control of Janus nanopen injection into living cells
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Peer Fischer, Theobald Lohmüller, Christoph M. Maier, Carla Pernpeintner, Jochen Feldmann, Sara Milosevic, María Ana Cristina Huergo, Miao Li, Dhruv P. Singh, and Debora Walker
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Materials science ,CELL INJECTION ,Light ,Optical Tweezers ,JANUS NANOPARTICLES ,Ciencias Físicas ,Nanoparticle ,DNA, Single-Stranded ,Metal Nanoparticles ,Bioengineering ,Nanotechnology ,02 engineering and technology ,CHO Cells ,010402 general chemistry ,01 natural sciences ,Injections ,Heating ,Cell injection ,Cricetulus ,Drug Delivery Systems ,OPTICAL TWEEZER ,Aluminum Oxide ,Animals ,BIOMOLECULE DELIVERY ,General Materials Science ,Janus ,Plasmon ,Óptica ,THERMOPHORESIS ,Mechanical Engineering ,technology, industry, and agriculture ,Gene Transfer Techniques ,Temperature ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,PLASMONICS ,Optical tweezers ,Delayed-Action Preparations ,Drug delivery ,Surface modification ,Gold ,Nanocarriers ,0210 nano-technology ,CIENCIAS NATURALES Y EXACTAS - Abstract
Devising strategies for the controlled injection of functional nanoparticles and reagents into living cells paves the way for novel applications in nanosurgery, sensing, and drug delivery. Here, we demonstrate the light-controlled guiding and injection of plasmonic Janus nanopens into living cells. The pens are made of a gold nanoparticle attached to a dielectric alumina shaft. Balancing optical and thermophoretic forces in an optical tweezer allows single Janus nanopens to be trapped and positioned on the surface of living cells. While the optical injection process involves strong heating of the plasmonic side, the temperature of the alumina stays significantly lower, thus allowing the functionalization with fluorescently labeled, single-stranded DNA and, hence, the spatially controlled injection of genetic material with an untethered nanocarrier. Fil: Maier, Christoph M.. Ludwig Maximilians Universitat; Alemania. Nanosystems Initiative Munich; Alemania Fil: Huergo, María Ana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Milosevic, Sara. Ludwig Maximilians Universitat; Alemania Fil: Pernpeintner, Carla. Ludwig Maximilians Universitat; Alemania. Nanosystems Initiative Munich; Alemania Fil: Li, Miao. Ludwig Maximilians Universitat; Alemania Fil: Singh, Dhruv P.. Max Planck Institute for Intelligent Systems; Alemania Fil: Walker, Debora. Max Planck Institute for Intelligent Systems; Alemania Fil: Fischer, Peer. Max Planck Institute for Intelligent Systems; Alemania Fil: Feldmann, Jochen. Ludwig Maximilians Universitat; Alemania. Nanosystems Initiative Munich; Alemania Fil: Lohmüller, Theobald. Nanosystems Initiative Munich; Alemania. Ludwig Maximilians Universitat; Alemania
- Published
- 2018
60. Highly Luminescent Cesium Lead Halide Perovskite Nanocrystals with Tunable Composition and Thickness by Ultrasonication
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Jochen Feldmann, Verena A. Hintermayr, Yu Tong, Alexander S. Urban, Karolina Z. Milowska, Aurora Manzi, Pablo Docampo, Sara Bals, Meltem F. Aygüler, Eva Bladt, and Lakshminarayana Polavarapu
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Photoluminescence ,Chemistry ,Analytical chemistry ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Cubic crystal system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Dark field microscopy ,Catalysis ,0104 chemical sciences ,Nanocrystal ,Quantum dot ,Scanning transmission electron microscopy ,0210 nano-technology ,Luminescence ,Perovskite (structure) - Abstract
We describe the simple, scalable, single-step, and polar-solvent-free synthesis of high-quality colloidal CsPbX3 (X=Cl, Br, and I) perovskite nanocrystals (NCs) with tunable halide ion composition and thickness by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) revealed the cubic crystal structure and surface termination of the NCs with atomic resolution. The NCs exhibit high photoluminescence quantum yields, narrow emission line widths, and considerable air stability. Furthermore, we investigated the quantum size effects in CsPbBr3 and CsPbI3 nanoplatelets by tuning their thickness down to only three to six monolayers. The high quality of the prepared NCs (CsPbBr3) was confirmed by amplified spontaneous emission with low thresholds. The versatility of this synthesis approach was demonstrated by synthesizing different perovskite NCs.
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- 2016
61. Starke Lumineszenz in Nanokristallen aus Caesiumbleihalogenid- Perowskit mit durchstimmbarer Zusammensetzung und Dicke mittels Ultraschalldispersion
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Lakshminarayana Polavarapu, Jochen Feldmann, Verena A. Hintermayr, Karolina Z. Milowska, Yu Tong, Sara Bals, Eva Bladt, Meltem F. Aygüler, Aurora Manzi, Pablo Docampo, and Alexander S. Urban
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02 engineering and technology ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences ,0104 chemical sciences - Abstract
Wir berichten uber eine einfache, skalierbare, einstufige Synthese von kolloidalen Perowskit-Nanokristallen (NCs) aus CsPbX3 (X=Cl, Br und I) mit durchstimmbarer Halogenidionenzusammensetzung und Dicke mittels Ultraschalldispersion der entsprechenden Eduktlosungen im Gegenwart von organischen Liganden und ohne Verwendung von polaren Losungsmitteln. Die kubische Kristallstruktur sowie Oberflachenterminierung wurden mittels HAADF-STEM mit atomarer Prazision aufgelost. Die NCs weisen hohen Photoluminenszenzquantenausbeuten, schmale Emissionslinien und hohe Stabilitat gegenuber Luft auf. Zusatzlich untersuchen wir die Quanteneinschrankungseffekte in Nanoplattchen aus CsPbBr3 und CsPbI3 mit reduzierten Dicken von 3 bis 6 Monolagen. Die hohe optische Qualitat der NCs (CsPbBr3) wird durch verstarkter Spontanemission (ASE) mit extrem niedrigen Schwellen gezeigt. Weiterhin wird durch den Einsatz an verschiedenen Perowskiten die Flexibilitat der Synthesemethode demonstriert.
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- 2016
62. Tuning the Optical Properties of Perovskite Nanoplatelets through Composition and Thickness by Ligand-Assisted Exfoliation
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Verena A. Hintermayr, Markus Döblinger, Jochen Feldmann, Jasmina A. Sichert, Yu Tong, Alexander F. Richter, Lakshminarayana Polavarapu, Florian Ehrat, Alexander S. Urban, and Willem Vanderlinden
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Materials science ,Ligand ,Mechanical Engineering ,Radiative decay ,Halide ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Exfoliation joint ,0104 chemical sciences ,Wavelength ,Chemical engineering ,Nanocrystal ,Mechanics of Materials ,Quantum dot ,General Materials Science ,0210 nano-technology ,Perovskite (structure) - Abstract
High-quality hybrid halide perovskite nanocrystals are fabricated through a simple, versatile, and efficient two-step process involving a dry step followed by a ligand-assisted liquid-phase exfoliation step. The emission wavelength of the resulting nanocrystals can be tuned either through composition by varying the halide content or by reducing their thickness.
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- 2016
63. Cover Picture: Templated‐Assembly of CsPbBr 3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission (Angew. Chem. Int. Ed. 40/2020)
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Juan Luis Garcia-Pomar, Luis M. Liz-Marzán, Lakshminarayana Polavarapu, Jochen Feldmann, David Vila-Liarte, Agustín Mihi, He Huang, Maximilian W. Feil, Aurora Manzi, and Markus Döblinger
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Amplified spontaneous emission ,Materials science ,Nanocrystal ,business.industry ,Optoelectronics ,Cover (algebra) ,General Chemistry ,Self-assembly ,Photonics ,business ,Catalysis ,Perovskite (structure) - Published
- 2020
64. Titelbild: Template‐basierte Herstellung von 2D‐photonischen Superkristallen mit verstärkter spontaner Emission aus CsPbBr 3 ‐Perowskit‐Nanokristallen (Angew. Chem. 40/2020)
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Juan Luis Garcia-Pomar, Luis M. Liz-Marzán, He Huang, Agustín Mihi, Maximilian W. Feil, Markus Döblinger, Lakshminarayana Polavarapu, Aurora Manzi, David Vila-Liarte, and Jochen Feldmann
- Subjects
General Medicine - Published
- 2020
65. Bioinspired Molecular Bridging in a Hybrid Perovskite Leads to Enhanced Stability and Tunable Properties
- Author
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Jochen Feldmann, Iryna Polishchuk, Eva Seknazi, Boaz Pokroy, Alexander Katsman, and Arad Lang
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Bridging (networking) ,Materials science ,Band gap ,Halide ,Nanotechnology ,Condensed Matter Physics ,Thermal expansion ,Ion ,law.invention ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Lattice constant ,Chemical engineering ,law ,Lattice (order) ,Electrochemistry ,Crystallization ,Perovskite (structure) - Abstract
Hybrid organic-inorganic halide perovskites demonstrate high potential in several applications such as solar cells, field-effect transistors, light-emitting diodes and more. However, the main drawback which limits their use in such applications is their low stability in humid conditions. In this paper we implement one of Nature’s strategies found in bio-crystals in order to improve the stability of the hybrid perovskite methylammonium lead bromide (MAPbBr3) in water, as well as to tune its structure, optical and thermal properties. This was achieved, for the first time, by the incorporation of amino acids into the lattice of MAPbBr3. The amino acid lysine, which possesses two NH3+groups, is incorporated into the hybrid unit cell, by substituting two methylammonium ions and serves as a “molecular bridge”. This incorporation induces a decrease in the lattice parameter of the host, accompanied with an increase in the band gap and noticeable changes in its morphology. Furthermore, we observed an increase in thermal expansion coefficient and a shift of the phase transformation temperature of the hybrid crystal. The level of amino acid incorporation depends on the conditions of crystallization, which also influence the extent of MAPbBr3band gap changes. Notably, lysine incorporation strongly increases the perovskite stability in water. This study demonstrates the unique and promising approach to tune the properties and stability of hybrid perovskites via this novel bio-inspired route.
- Published
- 2020
66. Rücktitelbild: Mangan‐Dotierung von Perowskit‐Nanokristallen: Quanteneinschränkung Aufgrund von Ruddlesden‐Popper‐Defekten (Angew. Chem. 17/2020)
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Lakshminarayana Polavarapu, Eva Bladt, Yu Tong, Sharmistha Paul, Jochen Feldmann, Alexander F. Richter, Tushar Debnath, Markus Döblinger, Sara Bals, Amrita Dey, and He Huang
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General Medicine - Published
- 2020
67. Back Cover: Manganese‐Doping‐Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden–Popper Defects (Angew. Chem. Int. Ed. 17/2020)
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Sara Bals, Markus Döblinger, Lakshminarayana Polavarapu, Yu Tong, Sharmistha Paul, Alexander F. Richter, Tushar Debnath, Eva Bladt, Amrita Dey, Jochen Feldmann, and He Huang
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Materials science ,Nanocrystal ,Chemical physics ,Quantum dot ,Cover (algebra) ,General Chemistry ,Catalysis ,Manganese doping ,Perovskite (structure) - Published
- 2020
68. All-in-one visible-light-driven water splitting by combining nanoparticulate and molecular co-catalysts on CdS nanorods
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Michael T. Carlson, Frank Würthner, Christian M. Wolff, Panajotis Livadas, Jochen Feldmann, Peter D. Frischmann, Jacek K. Stolarczyk, Robin Wein, Frank Jäckel, Marcus Schulze, and Bernhard J. Bohn
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Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Redox ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Catalysis ,Fuel Technology ,Chemical engineering ,chemistry ,Nanocrystal ,ddc:540 ,Institut für Chemie ,Water splitting ,Nanorod ,0210 nano-technology ,Photocatalytic water splitting ,Visible spectrum - Abstract
Full water splitting into hydrogen and oxygen on semiconductor nanocrystals is a challenging task; overpotentials must be overcome for both half-reactions and different catalytic sites are needed to facilitate them. Additionally, efficient charge separation and prevention of back reactions are necessary. Here, we report simultaneous H-2 and O-2 evolution by CdS nanorods decorated with nanoparticulate reduction and molecular oxidation co-catalysts. The process proceeds entirely without sacrificial agents and relies on the nanorod morphology of CdS to spatially separate the reduction and oxidation sites. Hydrogen is generated on Pt nanoparticles grown at the nanorod tips, while Ru(tpy)(bpy)Cl-2-based oxidation catalysts are anchored through dithiocarbamate bonds onto the sides of the nanorod. O-2 generation from water was verified by O-18 isotope labelling experiments, and time-resolved spectroscopic results confirmed efficient charge separation and ultrafast electron and hole transfer to the reaction sites. The system demonstrates that combining nanoparticulate and molecular catalysts on anisotropic nanocrystals provides an effective pathway for visible-light-driven photocatalytic water splitting.
- Published
- 2018
69. Exciton dephasing times and binding energies in methyl ammonium lead iodide perovskite nanoplatelets (Conference Presentation)
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Alexander F. Richter, Moritz Gramlich, Thomas Simon, Jochen Feldmann, Alexander S. Urban, Bernhard J. Bohn, Lakshminarayana Polavarapu, and Verena A. Hintermayr
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chemistry.chemical_classification ,chemistry.chemical_compound ,Materials science ,chemistry ,Exciton ,Dephasing ,Binding energy ,Iodide ,Ammonium ,Photochemistry ,Perovskite (structure) - Published
- 2018
70. Spontaneous Self-Assembly of Perovskite Nanocrystals into Electronically Coupled Supercrystals: Toward Filling the Green Gap
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Lakshminarayana Polavarapu, Eva Bladt, En-Ping Yao, Yu Tong, Sara Bals, Peter Müller-Buschbaum, Kun Wang, Aurora Manzi, Jochen Feldmann, Markus Döblinger, and Alexander S. Urban
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Materials science ,Photoluminescence ,Fabrication ,business.industry ,Mechanical Engineering ,Superlattice ,Physics ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Wavelength ,Chemistry ,Nanocrystal ,Mechanics of Materials ,Optoelectronics ,General Materials Science ,Self-assembly ,0210 nano-technology ,business ,Nanoscopic scale ,Engineering sciences. Technology ,Perovskite (structure) - Abstract
Self-assembly of nanoscale building blocks into ordered nanoarchitectures has emerged as a simple and powerful approach for tailoring the nanoscale properties and the opportunities of using these properties for the development of novel optoelectronic nanodevices. Here, the one-pot synthesis of CsPbBr3 perovskite supercrystals (SCs) in a colloidal dispersion by ultrasonication is reported. The growth of the SCs occurs through the spontaneous self-assembly of individual nanocrystals (NCs), which form in highly concentrated solutions of precursor powders. The SCs retain the high photoluminescence (PL) efficiency of their NC subunits, however also exhibit a redshifted emission wavelength compared to that of the individual nanocubes due to interparticle electronic coupling. This redshift makes the SCs pure green emitters with PL maxima at approximate to 530-535 nm, while the individual nanocubes emit a cyan-green color (approximate to 512 nm). The SCs can be used as an emissive layer in the fabrication of pure green light-emitting devices on rigid or flexible substrates. Moreover, the PL emission color is tunable across the visible range by employing a well-established halide ion exchange reaction on the obtained CsPbBr3 SCs. These results highlight the promise of perovskite SCs for light emitting applications, while providing insight into their collective optical properties.
- Published
- 2018
71. Tracking the Source of Carbon Dot Photoluminescence: Aromatic Domains versus Molecular Fluorophores
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Achim Löf, Alexander S. Urban, Regina Wyrwich, Jochen Feldmann, Jacek K. Stolarczyk, Santanu Bhattacharyya, Andrey L. Rogach, Julian Schneider, and Florian Ehrat
- Subjects
chemistry.chemical_classification ,Photoluminescence ,Fluorophore ,Mechanical Engineering ,Polycyclic aromatic hydrocarbon ,chemistry.chemical_element ,Bioengineering ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Photochemistry ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,chemistry.chemical_compound ,Citrazinic acid ,chemistry ,Hydrothermal synthesis ,General Materials Science ,0210 nano-technology ,Luminescence ,Carbon - Abstract
Carbon dots (CDs) are an intriguing fluorescent material; however, due to a plethora of synthesis techniques and precursor materials, there is still significant debate on their structure and the origin of their optical properties. The two most prevalent mechanisms to explain them are based on polycyclic aromatic hydrocarbon domains and small molecular fluorophores, for instance, citrazinic acid. Yet, how these form and whether they can exist simultaneously is still under study. To address this, we vary the hydrothermal synthesis time of CDs obtained from citric acid and ethylenediamine and show that in the initial phase molecular fluorophores, likely 2-pyridone derivatives, account for the blue luminescence of the dots. However, over time, while the overall size of the CDs does not change, aromatic domains form and grow, resulting in a second, faster decay channel at similar wavelengths and also creating additional lower energetic states. Electrophoresis provides further evidence that the ensemble of CDs consists of several subsets with different internal structure and surface charge. The understanding of the formation mechanism enables a control of the chemical origin of these emitters and the ensuing optical properties of the CDs through synthetic means.
- Published
- 2017
72. Light-Induced Cation Exchange for Copper Sulfide Based CO2 Reduction
- Author
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Clemens Sonnleitner, Jacek K. Stolarczyk, Regina Wyrwich, Jochen Feldmann, Markus Döblinger, Thomas Simon, Omar Stern, and Aurora Manzi
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Aqueous solution ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Biochemistry ,Copper ,Catalysis ,Methane ,chemistry.chemical_compound ,Copper sulfide ,Colloid and Surface Chemistry ,chemistry ,Nanocrystal ,Photocatalysis ,Carbon monoxide - Abstract
Copper(I)-based catalysts, such as Cu2S, are considered to be very promising materials for photocatalytic CO2 reduction. A common synthesis route for Cu2S via cation exchange from CdS nanocrystals requires Cu(I) precursors, organic solvents, and neutral atmosphere, but these conditions are not compatible with in situ applications in photocatalysis. Here we propose a novel cation exchange reaction that takes advantage of the reducing potential of photoexcited electrons in the conduction band of CdS and proceeds with Cu(II) precursors in an aqueous environment and under aerobic conditions. We show that the synthesized Cu2S photocatalyst can be efficiently used for the reduction of CO2 to carbon monoxide and methane, achieving formation rates of 3.02 and 0.13 μmol h(-1) g(-1), respectively, and suppressing competing water reduction. The process opens new pathways for the preparation of new efficient photocatalysts from readily available nanostructured templates.
- Published
- 2015
73. Carbon Dots: A Unique Fluorescent Cocktail of Polycyclic Aromatic Hydrocarbons
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Alexander S. Urban, Jacek K. Stolarczyk, Ming Fu, Yu Wang, Karolina Z. Milowska, Andrey L. Rogach, Jochen Feldmann, Claas J. Reckmeier, and Florian Ehrat
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chemistry.chemical_classification ,Materials science ,Photoluminescence ,Mechanical Engineering ,Exciton ,chemistry.chemical_element ,Polycyclic aromatic hydrocarbon ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Fluorescence ,Condensed Matter::Materials Science ,symbols.namesake ,chemistry ,Chemical physics ,Stokes shift ,symbols ,General Materials Science ,Spectroscopy ,Carbon ,Astrophysics::Galaxy Astrophysics ,Excitation - Abstract
Carbon dots (CDs) have attracted rapidly growing interest in recent years due to their unique and tunable optical properties, the low cost of fabrication, and their widespread uses. However, due to the complex structure of CDs, both the molecular ingredients and the intrinsic mechanisms governing photoluminescence of CDs are poorly understood. Among other features, a large Stokes shift of over 100 nm and a photoluminescence spectrally dependent on the excitation wavelength have so far not been adequately explained. In this Letter we investigate CDs and develop a model system to mimic their optical properties. This system comprised three types of polycyclic aromatic hydrocarbon (PAH) molecules with fine-tuned concentrations embedded in a polymer matrix. The model suggests that the Stokes shift in CDs is due to the self-trapping of an exciton in the PAH network. The width and the excitation dependence of the emission comes from a selective excitation of PAHs with slightly different energy gaps and from energy transfer between them. These insights will help to tailor the optical properties of CDs and help their implementation into applications, e.g., light-emitting devices and biomarkers. This could also lead to "artificial" tunable carbon dots by locally modifying the composition and consequently the optical properties of composite PAH films.
- Published
- 2015
74. Optical Injection of Gold Nanoparticles into Living Cells
- Author
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Jochen Feldmann, Miao Li, and Theobald Lohmüller
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Materials science ,Optical force ,Metal Nanoparticles ,Nanoparticle ,Bioengineering ,Nanotechnology ,Biosensing Techniques ,CHO Cells ,Cell membrane ,Cricetulus ,Cricetinae ,medicine ,Animals ,General Materials Science ,Nanoscopic scale ,Plasmon ,Lasers ,Mechanical Engineering ,Cell Membrane ,General Chemistry ,Condensed Matter Physics ,medicine.anatomical_structure ,Colloidal gold ,Gold ,Short exposure ,Biosensor - Abstract
The controlled injection of nanoscopic objects into living cells with light offers promising prospects for the development of novel molecular delivery strategies or intracellular biosensor applications. Here, we show that single gold nanoparticles from solution can be patterned on the surface of living cells with a continuous wave laser beam. In a second step, we demonstrate how the same particles can then be injected into the cells through a combination of plasmonic heating and optical force. We find that short exposure times are sufficient to perforate the cell membrane and inject the particles into cells with a survival rate of >70%.
- Published
- 2014
75. Resonantly enhanced multiple exciton generation through below-band-gap multi-photon absorption in perovskite nanocrystals
- Author
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Jochen Feldmann, En-Ping Yao, Alexander S. Urban, Julius Feucht, Aurora Manzi, Lakshminarayana Polavarapu, and Yu Tong
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Photoluminescence ,Materials science ,Band gap ,Science ,Exciton ,General Physics and Astronomy ,Physics::Optics ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Molecular physics ,General Biochemistry, Genetics and Molecular Biology ,Article ,Condensed Matter::Materials Science ,Absorption (electromagnetic radiation) ,lcsh:Science ,Multidisciplinary ,Condensed Matter::Other ,Energy conversion efficiency ,Optical physics ,Nonlinear optics ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,0104 chemical sciences ,Multiple exciton generation ,lcsh:Q ,0210 nano-technology - Abstract
Multi-photon absorption and multiple exciton generation represent two separate strategies for enhancing the conversion efficiency of light into usable electric power. Targeting below-band-gap and above-band-gap energies, respectively, to date these processes have only been demonstrated independently. Here we report the combined interaction of both nonlinear processes in CsPbBr3 perovskite nanocrystals. We demonstrate nonlinear absorption over a wide range of below-band-gap excitation energies (0.5–0.8 Eg). Interestingly, we discover high-order absorption processes, deviating from the typical two-photon absorption, at specific energetic positions. These energies are associated with a strong enhancement of the photoluminescence intensity by up to 105. The analysis of the corresponding energy levels reveals that the observed phenomena can be ascribed to the resonant creation of multiple excitons via the absorption of multiple below-band-gap photons. This effect may open new pathways for the efficient conversion of optical energy, potentially also in other semiconducting materials., The effects of the combined interplay of below-band-gap multi-photon absorption and multiple exciton generation have not been investigated. Here, the authors show the combined interaction of these processes in perovskite nanocrystals, leading to an enhanced interband photoluminescence emission under resonant conditions.
- Published
- 2017
76. From Precursor Powders to CsPbX
- Author
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Yu, Tong, Bernhard J, Bohn, Eva, Bladt, Kun, Wang, Peter, Müller-Buschbaum, Sara, Bals, Alexander S, Urban, Lakshminarayana, Polavarapu, and Jochen, Feldmann
- Abstract
The colloidal synthesis and assembly of semiconductor nanowires continues to attract a great deal of interest. Herein, we describe the single-step ligand-mediated synthesis of single-crystalline CsPbBr
- Published
- 2017
77. Effect of nitrogen atom positioning on the trade-off between emissive and photocatalytic properties of carbon dots
- Author
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Regina Wyrwich, Jacek K. Stolarczyk, Florian Ehrat, Santanu Bhattacharyya, Patrick Urban, Markus Döblinger, Roland Teves, Alexander S. Urban, and Jochen Feldmann
- Subjects
Photoluminescence ,Materials science ,Luminescence ,Nitrogen ,Science ,General Physics and Astronomy ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Catalysis ,Citric Acid ,Article ,Nanomaterials ,Quantum Dots ,lcsh:Science ,Microwaves ,Hydrogen production ,Multidisciplinary ,General Chemistry ,021001 nanoscience & nanotechnology ,Photochemical Processes ,Carbon ,0104 chemical sciences ,Chemical engineering ,chemistry ,Photocatalysis ,Light emission ,lcsh:Q ,0210 nano-technology - Abstract
Carbon dots (CDs) are a versatile nanomaterial with attractive photoluminescent and photocatalytic properties. Here we show that these two functionalities can be easily tuned through a simple synthetic means, using a microwave irradiation, with citric acid and varying concentrations of nitrogen-containing branched polyethyleneimine (BPEI) as precursors. The amount of BPEI determines the degree of nitrogen incorporation and the different inclusion modes within the CDs. At intermediate levels of BPEI, domains grow containing mainly graphitic nitrogen, producing a high photoluminescence yield. For very high (and very low) BPEI content, the nitrogen atoms are located primarily at the edge sites of the aromatic domains. Accordingly, they attract photogenerated electrons, enabling efficient charge separation and enhanced photocatalytic hydrogen generation from water. The ensuing ability to switch between emissive and photocatalytic behavior of CDs is expected to bring substantial improvements on their efficiency for on-demand light emission or energy conversion applications., Carbon dots are an emergent class of nanomaterials that hold promise for innovations in imaging, sensing, and catalytic technologies. Here, Stolarczyk and colleagues control the nitrogen-atom content and location within carbon dots, reporting the resulting impact on emissivity and photocatalytic behaviour.
- Published
- 2017
78. Linear and nonlinear optics of hybrid plexitonic nanosystems
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Mikolaj K. Schmidt, Javier Aizpurua, Yury P. Rakovich, Dzmitry Melnikau, Jochen Feldmann, Alexander A. Govyadinov, Alexander S. Urban, Ruben Esteban, Diana Savateeva, Ana Sánchez-Iglesias, Luis M. Liz-Marzán, Thomas Simon, and Marek Grzelczak
- Subjects
Plasmonic nanoparticles ,Materials science ,Photoluminescence ,Condensed Matter::Other ,business.industry ,Magnetic circular dichroism ,Nonlinear optics ,Physics::Optics ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Condensed Matter::Materials Science ,0103 physical sciences ,Ultrafast laser spectroscopy ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business ,Spectroscopy ,Absorption (electromagnetic radiation) ,Plasmon - Abstract
Resumen del trabajo presentado a la 19th International Conference on Transparent Optical Networks (ICTON), celebrada en Girona (España) del 2 al 6 de julio de 2017., We report our recent results of investigation of the interactions between localized plasmons in gold nanorods and excitons in J-aggregates. We were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy, we show that nonmagnetic organic molecules exhibit magneto-optical response due to binding to a plasmonic nanoparticles. In our experiments, we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states.
- Published
- 2017
79. Strong coupling effects in hybrid plexitonic systems
- Author
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Ruben Esteban, Ana Sánchez-Iglesias, Marek Grzelczak, Luis M. Liz-Marzán, Mikolaj K. Schmidt, Dzmitry Melnikau, Alexander A. Govyadinov, Alexander S. Urban, Yury P. Rakovich, Javier Aizpurua, Diana Savateeva, Jochen Feldmann, Thomas Simon, Ministry of Education and Science of the Russian Federation, European Research Council, and Ministerio de Economía y Competitividad (España)
- Subjects
Plasmons ,Photoluminescence ,Materials science ,Exciton ,Physics::Optics ,02 engineering and technology ,01 natural sciences ,Molecular physics ,Magneto-optical effect ,Condensed Matter::Materials Science ,0103 physical sciences ,Ultrafast laser spectroscopy ,010306 general physics ,Spectroscopy ,Plasmon ,Rabi splitting ,Strong coupling ,Plasmonic nanoparticles ,Condensed Matter::Other ,Magnetic circular dichroism ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Nonlinear effects ,Nanorod ,Excitons ,0210 nano-technology ,Plexitons - Abstract
Trabajo presentado a la 3rd International Conference on Applications of Optics and Photonics, celebrado en Faro (Portugal) del 8 al 12 de mayo de 2017., We investigated the interactions between localized plasmons in gold nanorods and excitons in J-aggregates and were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy we showed that nonmagnetic organic molecules exhibit magneto-optical response due to binding to a plasmonic nanoparticles. In our experiments we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states., We acknowledge financial support from Project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economía y Competitividad). L.L.-M. acknowledges funding from the European Research Council (ERC Advanced Grant 267867, Plasmaquo). This study was supported by the Ministry of Education and Science of the Russian Federation, grant no. 14.Y26.31.0011.
- Published
- 2017
80. Urea-Modified Carbon Nitrides: Enhancing Photocatalytic Hydrogen Evolution by Rational Defect Engineering
- Author
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Volker Blum, Tiago Botari, Thomas Simon, Jacek K. Stolarczyk, Florian Ehrat, Jochen Feldmann, Vincent Wing-hei Lau, Bettina V. Lotsch, Igor L. Moudrakovski, Viola Duppel, Victor Yu, and Elise Medina
- Subjects
Materials science ,Heptazine ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Graphitic carbon nitride ,chemistry.chemical_element ,02 engineering and technology ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Photocatalysis ,Surface modification ,General Materials Science ,Methanol ,0210 nano-technology ,Carbon nitride - Abstract
The primary amine groups on the heptazine-based polymer melon, also known as graphitic carbon nitride (g-C3N4), can be replaced by urea groups using a two-step postsynthetic functionalization. Under simulated sunlight and optimum Pt loading, this urea-functionalized carbon nitride has one of the highest activities among organic and polymeric photocatalysts for hydrogen evolution with methanol as sacrificial donor, reaching an apparent quantum efficiency of 18% and nearly 30 times the hydrogen evolution rate compared to the nonfunctionalized counterpart. In the absence of Pt, the urea-derivatized material evolves hydrogen at a rate over four times that of the nonfunctionalized one. Since “defects” are conventionally accepted to be the active sites in graphitic carbon nitride for photocatalysis, the work here is a demonstrated example of “defect engineering,” where the catalytically relevant defect is inserted rationally for improving the intrinsic, rather than extrinsic, photocatalytic performance. Furthermore, the work provides a retrodictive explanation for the general observation that g-C3N4 prepared from urea performs better than those prepared from dicyandiamide and melamine. In-depth analyses of the spent photocatalysts and computational modeling suggest that inserting the urea group causes a metal-support interaction with the Pt cocatalyst, thus facilitating interfacial charge transfer to the hydrogen evolving centers.
- Published
- 2017
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81. Quantitative Understanding of the Optical Properties of a Single, Complex-Shaped Gold Nanoparticle from Experiment and Theory
- Author
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Frank Jäckel, Christina Scheu, Andreas Wisnet, Markus Döblinger, Jochen Feldmann, Eduardo Marcelo Perassi, Calin Hrelescu, and Eduardo A. Coronado
- Subjects
Materials science ,General Physics and Astronomy ,Nanoparticle ,Near and far field ,Nanotechnology ,INGENIERÍAS Y TECNOLOGÍAS ,tomography ,Discrete dipole approximation ,Molecular physics ,symbols.namesake ,purl.org/becyt/ford/2.10 [https] ,Rayleigh ,General Materials Science ,Rayleigh scattering ,Spectroscopy ,enhancement ,Raman ,dark-field ,Nanotecnología ,Scattering ,nanoparticle ,General Engineering ,Nano-materiales ,purl.org/becyt/ford/2 [https] ,Electron tomography ,symbols ,DDA ,Raman spectroscopy - Abstract
We report on a combined study of Rayleigh and Raman scattering spectroscopy, 3D electron tomography, and discrete dipole approximation (DDA) calculations of a single, complex-shaped gold nanoparticle (NP). Using the exact reconstructed 3D morphology of the NP as input for the DDA calculations, the experimental results can be reproduced with unprecedented precision and detail. We find that not only the exact NP morphology but also the surroundings including the points of contact with the substrate are of crucial importance for a correct prediction of the NP optical properties. The achieved accuracy of the calculations allows determining how many of the adsorbed molecules have a major contribution to the Raman signal, a fact that has important implications for analyzing experiments and designing sensing applications. Fil: Perassi, Eduardo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Hrelescu, Calin. Ludwig Maximilians Universitat; Alemania Fil: Wisnet, Andreas. Ludwig Maximilians Universitat; Alemania Fil: Doblinger, Markus. Ludwig Maximilians Universitat; Alemania Fil: Scheu, Christina. Ludwig Maximilians Universitat; Alemania Fil: Jäckel, Frank. Ludwig Maximilians Universitat; Alemania Fil: Coronado, Eduardo A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Feldmann, Jochen. Ludwig Maximilians Universitat; Alemania
- Published
- 2014
82. Quantum-Dot-Sensitized Solar Cells with Water-Soluble and Air-Stable PbS Quantum Dots
- Author
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Thomas Bein, Jochen Feldmann, Daniel Böhm, Felix Deschler, Askhat N. Jumabekov, and Laurence M. Peter
- Subjects
Auxiliary electrode ,Photoluminescence ,Materials science ,Analytical chemistry ,Nanoparticle ,Electrolyte ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Dielectric spectroscopy ,Electron transfer ,General Energy ,Chemical engineering ,Quantum dot ,Physical and Theoretical Chemistry ,Short circuit - Abstract
The sensitization of dispersed P25 TiO2 nanoparticles (NPs) and macroporous TiO2 films with water-soluble and air-stable PbS quantum dots (QDs) capped with l-glutathione (GSH) ligands was investigated. Optimum sensitization was achieved by careful adjustment of the surface charges of TiO2 and PbS QDs by controlling the pH of the QD solution. Efficient electron transfer from photoexcited PbS QDs via the GSH ligands into the conduction band of TiO2 was demonstrated by photoluminescence (PL) spectroscopy of PbS-sensitized P25 nanoparticles. The PbS QD-sensitized porous TiO2 electrodes were used to prepare quantum-dot-sensitized solar cells (QDSSCs) utilizing a CuxSy counter electrode and aqueous polysulfide electrolyte. Cells with up to 64% injection efficiency, 1.1% AM 1.5 conversion efficiency, and short circuit current density of 7.4 mA cm–2 were obtained. The physical parameters of the cells were investigated using impedance spectroscopy.
- Published
- 2014
83. Perovskite nanocrystals for light-emitting and energy harvesting applications (Conference Presentation)
- Author
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Yu Tong, Jacek K. Stolarczyk, Jasmina A. Sichert, Alexander S. Urban, Lakshminarayana Polavarapu, Verena A. Hintermayr, and Jochen Feldmann
- Subjects
Photoluminescence ,Materials science ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,law.invention ,Quantum dot ,law ,Nano ,Optoelectronics ,Quantum efficiency ,Light emission ,0210 nano-technology ,Absorption (electromagnetic radiation) ,business ,Light-emitting diode ,Perovskite (structure) - Abstract
We focus on fabricating organic/inorganic halide perovskites with controlled dimensionality, size and composition and studying the optical and electrical properties of the resulting nanocrystals. By partially exchanging the most commonly used organic cation methylammonium for a cation with a larger chain we are able to fabricate two-dimensional nanoplatelets down to a single unit cell thickness.1 Through absorption and photoluminescence measurements we find that this leads to a strong-quantum size effect in the perovskites while additionally increasing the exciton bind energy to several hundreds of meV. We employ several fabrication techniques to increase the fluorescence quantum yield to be able to investigate single particles, and to study energy transport between individual nanocrystals by time-resolved spectroscopic methods. Our findings can lead to improvements in not only photovoltaic devices, but also for light-harvesting and light-emitting devices, such as LEDs and lasers. (1) Sichert, J. A.; Tong, Y.; Mutz, N.; Vollmer, M.; Fischer, S.; Milowska, K. Z.; Garcia Cortadella, R.; Nickel, B.; Cardenas-Daw, C.; Stolarczyk, J. K.; Urban, A. S.; Feldmann, J. Nano Letters 2015, 15, 6521.
- Published
- 2016
84. Coupled plasmon-exciton hybrid excitations in colloidal gold nanorods coated with J-aggregated dye molecules (Conference Presentation)
- Author
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Marek Grzelczak, Luis M. Liz-Marzán, D. Melnikau, Jochen Feldmann, Thomas Simon, Yury P. Rakovich, Alexander S. Urban, and Ana Sanchez-Iglesia
- Subjects
Materials science ,Absorption spectroscopy ,Exciton ,Physics::Optics ,Nanotechnology ,Molecular physics ,chemistry.chemical_compound ,chemistry ,Colloidal gold ,Ultrafast laser spectroscopy ,Nanorod ,Cyanine ,Spectroscopy ,Plasmon - Abstract
Strong coupling of plasmons and excitons can form hybrid states, the so called “plexcitons”. Especially with molecular J-aggregated dye molecules strong interaction becomes observable even under ambient conditions. In our work we investigate the nature of plexcitonic states formed in gold nanorods coated with a cyanine dye by transient absorption spectroscopy. We demonstrate that plexcitons show tunable plasmonic and excitonic non-linear optical behaviour. Our experimental data can be explained on the basis of a simple Lorentz oscillator model. We find that both the quality factor and the coupling strength between plasmons and excitons can be optically manipulated on an ultrashort time scale. T. Simon, D. Melnikau, A. Sanchez-Iglesias, M. Grzelczak, L. Liz-Marzan, Y. Rakovich, J. Feldmann and A. Urban, Exploring the optical non-linearities of plasmon-exciton hybrid resonances in coupled colloidal nanostructures, submitted (2016)
- Published
- 2016
85. Tuning the optical bandgap in layered hybrid perovskites through variation of alkyl chain length
- Author
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Carlos Cardenas Daw, Annick Hemmerling, Jasmina A. Sichert, Jochen Feldmann, and Alexander S. Urban
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Diffraction ,Materials science ,Photoluminescence ,Absorption spectroscopy ,Band gap ,lcsh:Biotechnology ,FOS: Physical sciences ,02 engineering and technology ,Crystal structure ,01 natural sciences ,lcsh:TP248.13-248.65 ,0103 physical sciences ,General Materials Science ,Alkyl ,Perovskite (structure) ,010302 applied physics ,chemistry.chemical_classification ,Condensed Matter - Materials Science ,General Engineering ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,lcsh:QC1-999 ,Blueshift ,chemistry ,Chemical physics ,0210 nano-technology ,lcsh:Physics - Abstract
Recently, layered hybrid perovskites have been attracting huge interest due to a wide range of possible chemical compositions and the resulting tunability of the materials’ properties. In this study, we investigate the effect of the chain length of the organic ligands on the optical properties of stacks of two-dimensional perovskite layers consisting of alkylammonium lead iodide (CnH2n+1NH3)2PbI4 with n = 4, …, 18. Photoluminescence and absorption spectroscopy reveal a blueshift with increasing chain length n including a jump of 110 meV between the n = 10 and n = 12 ligands due to a change in octahedral tilting. Using X-ray diffraction, we determine the crystal structure and find the octahedral tilting to be the main cause of this blueshift. However, for very short chain lengths, additional effects further reduce the transition energy. Results of effective mass approximation model calculations show good agreement between the expected reduction of transition energy and measured photoluminescence emission wavelength for these samples. This highlights how octahedral tilting plays a major role in determining the optical bandgap and suggests that miniband formation plays only a minor role in this material.
- Published
- 2019
86. Exciton Diffusion Lengths and Dissociation Rates in CsPbBr 3 Nanocrystal–Fullerene Composites: Layer‐by‐Layer versus Blend Structures
- Author
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Yu Tong, En-Ping Yao, Bernhard J. Bohn, He Huang, Lakshminarayana Polavarapu, and Jochen Feldmann
- Subjects
Materials science ,Fullerene ,Nanocrystal ,Chemical physics ,Exciton ,Layer by layer ,Atomic and Molecular Physics, and Optics ,Dissociation (chemistry) ,Electronic, Optical and Magnetic Materials - Published
- 2019
87. Photonic Crystal Nanocavities Containing Plasmonic Nanoparticles Assembled Using a Laser-Printing Technique
- Author
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Kieran Deasy, Jochen Feldmann, David G. Lidzey, Jaekwon Do, Khalid N. Sediq, Jessica Rodríguez-Fernández, and David M. Coles
- Subjects
Electromagnetic field ,Plasmonic nanoparticles ,Materials science ,Laser printing ,business.industry ,Physics::Optics ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Optoelectronics ,Time domain ,Surface plasmon resonance ,Photonics ,0210 nano-technology ,business ,Photonic crystal - Abstract
An optical printing technique is used to accurately position a 150 nm diameter gold nanoparticle onto a submicrometer linear three-hole defect of a photonic crystal nanocavity. It is shown (using both experiment and finite-difference time domain modelling), that there is an electromagnetic interaction between the nanoparticle and the cavity mode, with the electromagnetic field within the cavity being dissipated by driving the nanoparticle plasmon resonance. The use of a printing technique to selectively position nanoparticles onto a surface-accessible cavity potentially allows the hybridisation between electronic, excitonic, and optical states to be explored with high precision. Furthermore, through its scalable nature it also opens possibilities for the routine construction of new types of photonic devices and sensors.
- Published
- 2013
88. Tuning DNA Binding Kinetics in an Optical Trap by Plasmonic Nanoparticle Heating
- Author
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Frank Jäckel, Sol Carretero-Palacios, Andrey A. Lutich, Jochen Feldmann, Joachim Stehr, and Lidiya Osinkina
- Subjects
Materials science ,Light ,Binding energy ,Kinetics ,Analytical chemistry ,Metal Nanoparticles ,Physics::Optics ,Nanoparticle ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Heating ,Coated Materials, Biocompatible ,Materials Testing ,Physics::Atomic and Molecular Clusters ,General Materials Science ,Surface plasmon resonance ,Plasmon ,Binding Sites ,Mechanical Engineering ,technology, industry, and agriculture ,DNA ,General Chemistry ,Surface Plasmon Resonance ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,Energy Transfer ,Optical tweezers ,Colloidal gold ,Chemical physics ,Gold ,0210 nano-technology ,Order of magnitude - Abstract
We report on the tuning of specific binding of DNA attached to gold nanoparticles at the individual particle pair (dimer) level in an optical trap by means of plasmonic heating. DNA hybridization events are detected optically by the change in the plasmon resonance frequency due to plasmonic coupling of the nanoparticles. We find that at larger trapping powers (i.e., larger temperatures and stiffer traps) the hybridization rates decrease by more than an order of magnitude. This result is explained by higher temperatures preventing the formation of dimers with lower binding energies. Our results demonstrate that plasmonic heating can be used to fine tune the kinetics of biomolecular binding events.
- Published
- 2013
89. Spectral Signatures of Polarons in Conjugated Co-polymers
- Author
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Enrico Da Como, Jochen Feldmann, Stefan Schumacher, Raphael Tautz, Elizabeth von Hauff, Christian Wiebeler, Photo Conversion Materials, LaserLaB - Energy, and Publica
- Subjects
Quantitative Biology::Biomolecules ,Chemistry ,media_common.quotation_subject ,Molar absorptivity ,Conjugated system ,Polaron ,Asymmetry ,Surfaces, Coatings and Films ,Ion ,Chemical physics ,Materials Chemistry ,Molecule ,Molecular orbital ,Physical and Theoretical Chemistry ,Absorption (chemistry) ,Atomic physics ,media_common - Abstract
We study electronic and optical properties of the low-bandgap co-polymer PCPDT-BT (poly-cyclopentadithiophene-co-benzothiadiazole) and compare it with the corresponding homo-polymer PCPDT (poly-cyclopentadithiophene). We investigate the linear absorptivity in these systems for neutral molecules and for their singly charged ions based on quantum-chemical calculations and experiments. One of our main findings is that the ions of the homo-polymer show a polaron absorption that is symmetric between anion and cation, whereas for polaron excitations in the co-polymer this symmetry is strongly lifted. We demonstrate that this asymmetry can be attributed to the absence of symmetry between the high-lying occupied and low-lying unoccupied molecular orbitals in the co-polymer with type-II orbital alignment between the moieties constituting the chain. This notion is of importance for the qualitative and quantitative interpretation of spectroscopic polaron data and is not specific t o the system studied here but similarly applies to other co-polymers.
- Published
- 2013
90. Synthesis of Gold Nanostar Arrays as Reliable, Large-Scale, Homogeneous Substrates for Surface-Enhanced Raman Scattering Imaging and Spectroscopy
- Author
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Jochen Feldmann, Theobald Lohmüller, Frank Jäckel, and Lidiya Osinkina
- Subjects
Fabrication ,Materials science ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Micelle ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,General Energy ,Nanolithography ,Colloidal gold ,Monolayer ,symbols ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy ,Raman spectroscopy ,Raman scattering - Abstract
We report a two-step approach for the fabrication of quasi-hexagonal ordered arrays of star-shaped gold nanoparticles (gold nanostars) as reliable, large-scale homogeneous substrates for surface-enhanced Raman scattering (SERS) spectroscopy by a combination of block-copolymer micelle nanolithography and electroless deposition. The applicability of this platform for SERS imaging is demonstrated by pH-sensitive Raman measurements of 4-mercaptobenzoic acid adsorbed to the nanostars in the array. A homogeneous enhancement factor of ∼105 was observed on the nanostar monolayer over an area of several hundreds of square micrometers.
- Published
- 2013
91. Charge Photogeneration in Donor–Acceptor Conjugated Materials: Influence of Excess Excitation Energy and Chain Length
- Author
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Giulia Grancini, Giulio Cerullo, Christian Wiebeler, Ines Dumsch, Stefan Schumacher, Raphael Tautz, Sybille Allard, Jochen Feldmann, Nils Fröhlich, Ullrich Scherf, Giancarlo Soavi, and Enrico Da Como
- Subjects
education.field_of_study ,Exciton ,Population ,General Chemistry ,Electron ,Conjugated system ,Photochemistry ,Polaron ,Biochemistry ,Oligomer ,Molecular physics ,Catalysis ,Photoexcitation ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,education ,Excitation - Abstract
We investigate the role of excess excitation energy on the nature of photoexcitations in donor-acceptor π-conjugated materials. We compare the polymer poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[1,2-b;3,4-b']dithiophene)-4,7-benzo[2,1,3]thiadiazole) (PCPDTBT) and a short oligomer with identical constituents at different excitation wavelengths, from the near-infrared up to the ultraviolet spectral region. Ultrafast spectroscopic measurements clearly show an increased polaron pair yield for higher excess energies directly after photoexcitation when compared to the exciton population. This effect, already observable in the polymer, is even more pronounced for the shorter oligomer. Supported by quantum chemical simulations, we show that excitation in high-energy states generates electron and hole wave functions with reduced overlap, which likely act as precursors for the polaron pairs. Interestingly, in the oligomer we observe a lifetime of polaron pairs which is one order of magnitude longer. We suggest that this behavior results from the intermolecular nature of polaron pairs in oligomers. The study excludes the presence of carrier multiplication in these materials and highlights new aspects in the photophysics of donor-acceptor small molecules when compared to polymers. The former are identified as promising materials for efficient organic photovoltaics.
- Published
- 2013
92. Shrink-to-fit Plasmonic Nanostructures
- Author
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Alexander S. Urban, Michael Fedoruk, Andrey A. Lutich, Spas Nedev, Theobald Lohmueller, and Jochen Feldmann
- Subjects
Plasmonic nanoparticles ,Materials science ,Optical force ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Plasmonic metamaterials ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,0210 nano-technology ,Plasmonic nanostructures ,Plasmon - Published
- 2013
93. Hierarchical assembly of metal nanoparticles, quantum dots and organic dyes using DNA origami scaffolds
- Author
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Robert D. Schreiber, Jaekwon Do, Tao Zhang, Verena Schüller, Philipp C. Nickels, Jochen Feldmann, Tim Liedl, and Eva-Maria Roller
- Subjects
Materials science ,Biomedical Engineering ,Coloring agents ,Physics::Optics ,Metal Nanoparticles ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Nanoclusters ,Quantum Dots ,DNA origami ,General Materials Science ,Electrical and Electronic Engineering ,Metal nanoparticles ,Coloring Agents ,food and beverages ,DNA ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,humanities ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,3. Good health ,Quantum dot ,Gold ,0210 nano-technology - Abstract
The self-assembly of nanoscale elements into three-dimensional structures with precise shapes and sizes is important in fields such as nanophotonics, metamaterials and biotechnology. Short molecular linkers have previously been used to create assemblies of nanoparticles, but the approach is limited to small interparticle distances, typically less than 10 nm. Alternatively, DNA origami can precisely organize nanoscale objects over much larger length scales. Here we show that rigid DNA origami scaffolds can be used to assemble metal nanoparticles, quantum dots and organic dyes into hierarchical nanoclusters that have a planet-satellite-type structure. The nanoclusters have a tunable stoichiometry, defined distances of 5-200 nm between components, and controllable overall sizes of up to 500 nm. We also show that the nanoscale components can be positioned along the radial DNA spacers of the nanostructures, which allows short- and long-range interactions between nanoparticles and dyes to be studied in solution. The approach could, in the future, be used to construct efficient energy funnels, complex plasmonic architectures, and porous, nanoengineered scaffolds for catalysis.
- Published
- 2016
94. Reversible control of current across lipid membranes by local heating
- Author
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Silke R. Kirchner, Christian Mühlbauer, Theobald Lohmüller, Patrick Urban, and Jochen Feldmann
- Subjects
0301 basic medicine ,Hot Temperature ,Materials science ,Lipid Bilayers ,02 engineering and technology ,Article ,Cell Line ,03 medical and health sciences ,Electric Impedance ,Membrane fluidity ,Humans ,Semipermeable membrane ,Low-Level Light Therapy ,Surface plasmon resonance ,Lipid bilayer ,Ion channel ,Membranes ,Multidisciplinary ,Bilayer ,Biological membrane ,021001 nanoscience & nanotechnology ,030104 developmental biology ,Membrane ,Biochemistry ,Biophysics ,Nanoparticles ,Gold ,0210 nano-technology - Abstract
Lipid membranes are almost impermeable for charged molecules and ions that can pass the membrane barrier only with the help of specialized transport proteins. Here, we report how temperature manipulation at the nanoscale can be employed to reversibly control the electrical resistance and the amount of current that flows through a bilayer membrane with pA resolution. For this experiment, heating is achieved by irradiating gold nanoparticles that are attached to the bilayer membrane with laser light at their plasmon resonance frequency. We found that controlling the temperature on the nanoscale renders it possible to reproducibly regulate the current across a phospholipid membrane and the membrane of living cells in absence of any ion channels.
- Published
- 2016
95. Optical Nanoparticle Sorting Elucidates Synthesis of Plasmonic Nanotriangles
- Author
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Marcos F. Castez, Spas Nedev, Roberto Carlos Salvarezza, Jochen Feldmann, Christoph M. Maier, Carolina Vericat, Alexander S. Urban, and María Ana Cristina Huergo
- Subjects
Materials science ,Cancer therapy ,SORTING DE NANOPARTÍCULAS ,General Physics and Astronomy ,Nanoparticle ,PRINTING ÖPTICO ,Nanotechnology ,Plasmon ,02 engineering and technology ,INGENIERÍAS Y TECNOLOGÍAS ,010402 general chemistry ,01 natural sciences ,Optical printing ,purl.org/becyt/ford/2.10 [https] ,TERAPIA PARA CÄNCER ,Gold nanoparticles ,General Materials Science ,Surface plasmon resonance ,Spectroscopy ,Nanotecnología ,Nanoshells ,General Engineering ,Resonance ,Física ,PLASMONES ,021001 nanoscience & nanotechnology ,Nano-materiales ,Nanoparticle sorting ,Nanoshell ,0104 chemical sciences ,Blueshift ,purl.org/becyt/ford/2 [https] ,Colloidal gold ,NANOPARTÍCULAS DE ORO ,NANOCÁSCARAS ,0210 nano-technology - Abstract
We investigate the optical and morphological properties of gold nanoparticles grown by reducing a gold salt with Na2S. Lasers are tuned to the observed plasmon resonances, and the optical forces exerted on the nanoparticles are used to selectively print individual nanoparticles onto a substrate. This enables us to combine dark-field spectroscopy and scanning electron microscopy to compare the optical properties of single nanoparticles with their morphology. By arresting the synthesis at different times, we are able to investigate which type of nanoparticle is responsible for the respective resonances. We find that thin Au nanotriangles are the source of the observed near infrared (NIR) resonance. The initial lateral growth of these triangles causes the plasmon resonance to redshift into the NIR, whereas a subsequent thickening of the triangles and a concomitant truncation lead to a blueshift of the resonance. Furthermore, we find that the nanotriangles produced have extremely narrow line widths (187 ± 23 meV), show nearly isotropic scattering, and are stable for long periods of time. This shows their vast potential for applications such as in vivo imaging and bio(chemical) sensing. The method used here is generally applicable to other syntheses, and shows how complex nanostructures can be built up on substrates by selectively printing NPs of varying plasmonic resonances., Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas
- Published
- 2016
96. Exploring the optical nonlinearities of plasmon-exciton hybrid resonances in coupled colloidal nanostructures
- Author
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Marek Grzelczak, Dzmitry Melnikau, Alexander S. Urban, Ana Sánchez-Iglesias, Yury P. Rakovich, Luis M. Liz-Marzán, Jochen Feldmann, Thomas Simon, European Commission, European Research Council, Bavarian State Ministry of Education, Science and the Arts, and Ministerio de Economía y Competitividad (España)
- Subjects
Physics ,Exciton ,Strong interaction ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,Molecular physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nonlinear system ,General Energy ,Quality (physics) ,Quantum mechanics ,0103 physical sciences ,Ultrafast laser spectroscopy ,Nanorod ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology ,Spectroscopy ,Plasmon - Abstract
Strong coupling of plasmons and excitons can form hybrid states, the so-called “plexcitons”. Although plasmons have a low quality factor, the exceptionally high coupling strength with molecular aggregates, in particular J-aggregates, allows the realization of strong interaction. Despite several studies in recent years showing the formation of plexcitonic states, their nature, especially at very short times, is still insufficiently investigated. In this article, we identify the nonlinear optical behavior of plexcitons formed on gold nanorods coated with J-aggregated cyanine molecules at short times by transient absorption spectroscopy and a simple Lorentz oscillator model. We control the spectral overlap of the two resonances and analyze the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states. We demonstrate that at ultrashort time scales plexcitons show tunable plasmonic and excitonic nonlinear performance according to the hybridization model. In a first approach, we discover a way to optically manipulate the quality factor and study the effects on the coupled hybrid states. As a second approach, we find that the coupling strength can also be influenced on an ultrashort time scale in the strong coupling regime when plexcitons are excited., This work has been financially supported by the ERC Advanced Grant HYMEM and the Bavarian State Ministry of Science, Research, and Arts through “Solar Technologies Go Hybrid” (SolTech) as well as through Projects FIS2013-41184-P and MAT2013-46101-R of the Spanish Ministry of Economy and Competitiveness (MINECO).
- Published
- 2016
97. Delayed electron relaxation in CdTe nanorods studied by spectral analysis of the ultrafast transient absorption
- Author
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Guglielmo Lanzani, Francesco Tassone, Ilka Kriegel, Rosaria Brescia, Giancarlo Soavi, Francesco Scotognella, Jochen Feldmann, and Jessica Rodríguez-Fernández
- Subjects
Analytical chemistry ,General Physics and Astronomy ,02 engineering and technology ,Electron ,Trapping ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Spectral line ,Carrier relaxation ,Effective mass approximation ,Hole trapping ,Semiconductor nanorods ,Ultrafast transient absorption ,Physics and Astronomy (all) ,Physical and Theoretical Chemistry ,Ultrafast laser spectroscopy ,Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Multiple exciton generation ,Excited state ,Relaxation (physics) ,Nanorod ,0210 nano-technology - Abstract
In transient absorption (TA) spectra, the bleach features originating from state filling are overlapped by their energy-shifted derivatives, arising from excited state energy level shifts. This makes the direct extraction of carrier dynamics from a single-wavelength time-trace misleading. Fitting TA spectra in time, as Gaussian functions and their derivative-like shifted Gaussians, allows to individually extract the real dynamics of both photobleached transitions, and their energy shifts. In CdTe nanorods (NRs) we found a delayed heating of holes due to the release of the large excess energy in the electron relaxation process. The slow hole-trapping process is consistent with a high number of surface trap states in these model NRs. Our results show that only a correct disentanglement of bleaching and energy shift contributions provides a reliable framework to extract the underlying carrier relaxation dynamics, including trapping, non-radiative recombination, and eventually carrier multiplication.
- Published
- 2016
98. Size-Selected Subnanometer Cluster Catalysts on Semiconductor Nanocrystal Films for Atomic Scale Insight into Photocatalysis
- Author
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Martin Tschurl, Florian F. Schweinberger, Maximilian J. Berr, Christian M. Wolff, Frank Jäckel, Markus Döblinger, Andrew S. Crampton, Jochen Feldmann, Johannes Breimeier, Claron J. Ridge, Kai E. Sanwald, and Ulrich Heiz
- Subjects
Materials science ,Mechanical Engineering ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Atomic units ,Catalysis ,Cluster (physics) ,Photocatalysis ,General Materials Science ,Quantum efficiency ,Nanorod ,Thin film ,Hydrogen production - Abstract
We introduce size-selected subnanometer cluster catalysts deposited on thin films of colloidal semiconductor nanocrystals as a novel platform to obtain atomic scale insight into photocatalytic generation of solar fuels. Using Pt-cluster-decorated CdS nanorod films for photocatalytic hydrogen generation as an example, we determine the minimum amount of catalyst necessary to obtain maximum quantum efficiency of hydrogen generation. Further, we provide evidence for tuning photocatalytic activities by precisely controlling the cluster catalyst size.
- Published
- 2012
99. Enhancing Single-Nanoparticle Surface-Chemistry by Plasmonic Overheating in an Optical Trap
- Author
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Weihai Ni, Andrey A. Lutich, Frank Jäckel, Jochen Feldmann, and Haojin Ba
- Subjects
Materials science ,Optical Tweezers ,Macromolecular Substances ,Surface Properties ,Molecular Conformation ,Metal Nanoparticles ,Physics::Optics ,Nanoparticle ,Bioengineering ,Nanotechnology ,Article ,Heating ,Materials Testing ,General Materials Science ,Particle Size ,Surface plasmon resonance ,Plasmon ,Overheating (electricity) ,Plasmonic nanoparticles ,business.industry ,Mechanical Engineering ,Interface and colloid science ,General Chemistry ,Surface Plasmon Resonance ,Condensed Matter Physics ,Optical tweezers ,Optoelectronics ,Nanorod ,Gold ,Crystallization ,business - Abstract
Surface-chemistry of individual, optically trapped plasmonic nanoparticles is modified and accelerated by plasmonic overheating. Depending on the optical trapping power, gold nanorods can exhibit red-shifts of their plasmon resonance (i.e. increasing aspect ratio) under oxidative conditions. In contrast, in bulk exclusively blue shifts (decreasing aspect ratios) are observed. Supported by calculations, we explain this finding by local temperatures in the trap exceeding the boiling point of the solvent which can not be achieved in bulk.
- Published
- 2012
100. Surface‐Enhanced Raman Scattering Using Complex‐Shaped Metal Nanostructures
- Author
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Frank Jäckel and Jochen Feldmann
- Subjects
Surface (mathematics) ,symbols.namesake ,Materials science ,symbols ,Metal nanostructures ,Surface plasmon resonance ,Molecular physics ,Raman scattering - Published
- 2012
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