124 results on '"Kotov, A."'
Search Results
2. Terahertz Circular Dichroism Spectroscopy of Molecular Assemblies and Nanostructures
- Author
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Won Jin Choi, Sang Hyun Lee, Bum Chul Park, and Nicholas A. Kotov
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Abstract
Chemical, physical, biological and materials engineering disciplines use a variety of chiroptical spectroscopies to probe geometrical and optical asymmetry in molecules and particles. Electronic (ECD) and vibrational (VCD) circular dichroism are the most common of these techniques and collectively enable the studies of electronic and vibronic transitions with energies between 0.1 and 5.0 eV. The vibrational states with characteristic energies in the range of 0.001-0.01 eV carry valuable information about concerted intermolecular motions in molecules and crystals involving multiple atoms. These vibronic transitions located in the terahertz (THz) part of the spectrum become increasingly more important for the chemistry, physics, and biology of complex molecules and materials However, the methodology and hardware of THz circular dichroism (TCD) are much less developed than the chiroptical spectroscopies for ultraviolet, visible, near- and mid infrared photons. Here we provide theoretical foundations, practical implementations, comparative assessments, and exemplary applications of TCD spectroscopy. We show that the sign, intensity, and position of TCD peaks are highly sensitive to the three-dimensional structure and long-range organization of molecular crystals, which offer unique capabilities to study (bio) molecules, their crystals, and nanoscale assemblies and apply the novel data processing methodologies. TCD also offers a convenient toolbox to identify new physical phenomena, such as chiral phonons and their propagation in nanostructured matter. We also discuss the major challenges, emerging opportunities and promising research directions, including broad investigation of chiral phonons observed in chiral (nano) crystals and emerging machine learning methodologies for TCD in biological and nanoscale structures. Ubiquity of low-frequency vibrations with rotational components in biomolecular structures, combined with sharpness of peaks in TCD spectra, enables a variety of technological translations.
- Published
- 2022
3. Chiral 2D Organic Inorganic Hybrid Perovskite with Circular Dichroism Tunable Over Wide Wavelength Range
- Author
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Sunihl Ma, Woo Seok Yang, Jihoon Ahn, Nicholas A. Kotov, Jooho Moon, Jung Ah Lim, Ji Young Kim, and Jihoon Kyhm
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Circular dichroism ,Band gap ,Chemistry ,General Chemistry ,Crystal structure ,010402 general chemistry ,Polarization (waves) ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Wavelength ,Crystallography ,Colloid and Surface Chemistry ,Phase (matter) ,Electronic band structure ,Perovskite (structure) - Abstract
The effect of chemical-composition modification on the chiroptical property of chiral organic ammonium cation-containing organic inorganic hybrid perovskite (chiral OIHP) is investigated. Varying the mixing ratio of bromide and iodide anions in S- or R-C6H5CH2(CH3)NH3)2PbI4(1-x)Br4x modifies the band gap of chiral OIHP, leading to a shift of the circular dichroism (CD) signal from 495 to 474 nm. However, it is also found that an abrupt crystalline structure transition occurs, and the CD signal is turned off when iodide-determinant phases are transformed into the bromide-determinant phase. To obtain CD in the wavelength range where the bromide-determinant phase is supposed to exhibit chiroptical activity, that is
- Published
- 2020
4. Self-Assembly Mechanism of Complex Corrugated Particles
- Author
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Jun Lu, Xiaoxing Fan, Thi Vo, Drew Vecchio, Harrison Hou, Lanqin Tang, Nicholas A. Kotov, Sharon C. Glotzer, and Tao Ma
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Chemistry ,Nanoparticle ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrostatics ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,symbols.namesake ,Colloid and Surface Chemistry ,Chemical physics ,Dispersion stability ,symbols ,Cluster (physics) ,Particle ,Nanorod ,Self-assembly ,van der Waals force ,0210 nano-technology - Abstract
A variety of inorganic nanoscale materials produce microscale particles with highly corrugated geometries, but the mechanism of their formation remains unknown. Here we found that uniformly sized CdS-based hedgehog particles (HPs) self-assemble from polydisperse nanoparticles (NPs) with diameters of 1.0-4.0 nm. The typical diameters of HPs and spikes are 1770 ± 180 and 28 ± 3 nm, respectively. Depending on the temperature, solvent, and reaction times, the NPs self-assemble into nanorods, nanorod aggregates, low-corrugation particles, and other HP-related particles with complexity indexes ranging from 0 to 23.7. We show that "hedgehog", other geometries, and topologies of highly corrugated particles originate from the thermodynamic preference of polydisperse NPs to attach to the growing nanoscale cluster when electrostatic repulsion competes with van der Waals attraction. Theoretical models and simulations of the self-assembly accounting for the competition of attractive and repulsive interactions in electrolytes accurately describe particle morphology, growth stages, and the spectrum of observed products. When kinetic parameters are included in the models, the formation of corrugated particles with surfaces decorated by nanosheets, known as flower-like particles, were theoretically predicted and experimentally observed. The generality of the proposed mechanism was demonstrated for the formation of mixed HPs via a combination of CdS and Co3O4 NPs. With unusually high dispersion stability of HPs in unfavorable solvents including liquid CO2, mechanistic insights into HP formation are essential for their structural adaptation for applications from energy storage, catalysis, water treatment, and others.
- Published
- 2021
5. Self-Assembly Mechanism of Complex Corrugated Particles
- Author
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Tang, Lanqin, primary, Vo, Thi, additional, Fan, Xiaoxing, additional, Vecchio, Drew, additional, Ma, Tao, additional, Lu, Jun, additional, Hou, Harrison, additional, Glotzer, Sharon C., additional, and Kotov, Nicholas A., additional
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- 2021
- Full Text
- View/download PDF
6. Omnidispersible Hedgehog Particles with Multilayer Coatings for Multiplexed Biosensing
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Joong Hwan Bahng, Aydin Eskafi, Nicholas A. Kotov, Harrison Hou, and Douglas G. Montjoy
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Polymers ,Surface Properties ,Metal Nanoparticles ,Nanoparticle ,Nanotechnology ,Biosensing Techniques ,02 engineering and technology ,Spectrum Analysis, Raman ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,symbols.namesake ,Colloid and Surface Chemistry ,Particle Size ,Nanoscopic scale ,chemistry.chemical_classification ,Chemistry ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Ionic strength ,Dispersion stability ,symbols ,Gold ,Particle size ,van der Waals force ,0210 nano-technology ,Hydrophobic and Hydrophilic Interactions ,Biosensor - Abstract
Hedgehog particles (HPs) replicating the spiky geometry of pollen grains revealed surprisingly high dispersion stability regardless of whether their hydrophobicity/hydrophilicity matches that of the media or not. This property designated as omnidispersibility is attributed to the drastic reduction of van der Waals interactions between particles coated with stiff nanoscale spikes as compared to particles of the same dimensions with smooth surfaces. One may hypothesize but it remains unknown, however, whether HPs modified with polymers or nanoparticles (NPs) would retain this property. Surface modifications of the spikes will expand the functionalities of HPs, making possible their utilization as omnidispersible carriers. Here, we show that HPs carrying dense conformal coatings made by layer-by-layer (LBL/LbL) assembly maintain dispersion stability in environments of extreme polarity and ionic strength. HPs, surface-modified by multilayers of polymers and gold NPs, are capable of surface-enhanced Raman scattering (SERS) and overcome the limited colloidal stability of other SERS probes. The agglomeration resilience of HPs leads to a greater than one order of magnitude increase of SERS intensity as compared to colloids with smooth surfaces and enables simultaneous detection of several targets in complex media with high ionic strength. Omnidispersible optically active colloids open the door for rapid multiplexed SERS analysis in biological fluids and other applications.
- Published
- 2018
7. Spontaneous CdTe forward alloy forward CdS transition of stabilizer-depleted CdTe nanoparticles induced by EDTA
- Author
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Zhiyong Tang, Ying Wang, Shanbhag, Sachin, and Kotov, Nicholas A.
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Tellurium -- Chemical properties ,Ethylenediaminetetraacetic acid -- Chemical properties ,Nanoparticles -- Chemical properties ,Selenium compounds -- Chemical properties ,Chemistry - Abstract
CdTe nanoparticles stabilized by L-cysteine are chemically transformed into CdS nanoparticles of the same diameter through an intermediate CdTeS alloy without any auxiliary source of sulfur and this reaction is induced by ethylenediaminetetraacetic acid dipotassium salt dehydrate. The slow rate of the CdTe forward alloy forward CdS transition is vital for minimizing defects in the crystal lattice and results in a substantial increase of the quantum yield of photoluminescence over the course of the transition.
- Published
- 2006
8. CNT-CdTe versatile donor-acceptor nanohybrids
- Author
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Guldi, Dirk M., Rahman, G.M. Aminur, Sgobba, Vito, Kotov, Nicholas A., Bonifaz, Davide, and Prato, Maurizio
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Tellurium -- Chemical properties ,Electron donor-acceptor complexes -- Chemical properties ,Electron donor-acceptor complexes -- Structure ,Nanotubes -- Structure ,Chemistry - Abstract
Organic (CNT)-inorganic (CdTe) nanohybrids were systematically devised and tested as donor-acceptor nanohybrids in dilute condensed media and as integrative components at electrode surfaces. The novel nanohybrids were characterized both in the ground and excited states with specific accent on electron-transfer chemistry.
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- 2006
9. CdS nanoparticles modified to chalcogen sites: new supramolecular complexes, butterfly bridging, and related optical effects
- Author
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Ni, Tong, Nagesha, Dattatri K., Robles, Juvencio, Materer, Nicholas F., Mussig, Stefan, and Kotov, Nicholas A.
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Chemical research -- Analysis ,Nanotechnology -- Usage ,Molecules -- Physiological aspects ,Cadmium -- Physiological aspects ,Particles -- Models ,Surface chemistry -- Research ,Chemistry - Abstract
Research has been conducted on the II-VI semiconductor nanoparticles including cadmium chalcogen. The use of the chalcogen sites of the nanoparticle surface in investigating the nanoparticle surface interaction with organic chromophore p-orbitals is described.
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- 2002
10. Chiral 2D Organic Inorganic Hybrid Perovskite with Circular Dichroism Tunable Over Wide Wavelength Range
- Author
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Ahn, Jihoon, primary, Ma, Sunihl, additional, Kim, Ji-Young, additional, Kyhm, Jihoon, additional, Yang, Wooseok, additional, Lim, Jung Ah, additional, Kotov, Nicholas A., additional, and Moon, Jooho, additional
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- 2020
- Full Text
- View/download PDF
11. Self-Assembly Mechanism of Complex Corrugated Particles.
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Lanqin Tang, Thi Vo, Xiaoxing Fan, Vecchio, Drew, Tao Ma, Jun Lu, Harrison Hou, Glotzer, Sharon C., and Kotov, Nicholas A.
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- 2021
- Full Text
- View/download PDF
12. Mechanism of and defect formation in the self-assembly of polymeric polycation-montmorillonite ultrathin films
- Author
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Kotov, N.A., Haraszti, T., Turi, L., Zavala, G., Geer, R.E., Dekany, I., and Fendler, J.H.
- Subjects
Polyelectrolytes -- Observations ,Montmorillonite -- Usage ,Chemistry - Abstract
Polydiallyldimethylammonium chloride, P, with a positive charge, was demonstrated to have a strong bond to the surface of anionic montmorrillonite, M, platelets in aqueous dispersions. The thickness of the M layer depended on external voltage applied. Clay platelets formed stacks upon adsorption to the polymer layer. Uniformity and regularity of deposited layers was improved with application of a negative potential during self-assembly of P.
- Published
- 1997
13. Dual-Mode Ultrasensitive Quantification of MicroRNA in Living Cells by Chiroplasmonic Nanopyramids Self-Assembled from Gold and Upconversion Nanoparticles
- Author
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Wei Ma, Liguang Xu, Wu Xiaoling, Chuanlai Xu, Hua Kuang, Nicholas A. Kotov, Si Li, Libing Wang, and Maozhong Sun
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Circular dichroism ,Metal Nanoparticles ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Nanomaterials ,Colloid and Surface Chemistry ,Microscopy, Electron, Transmission ,Limit of Detection ,Detection limit ,Chemistry ,Circular Dichroism ,RNA ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,MicroRNAs ,Linear range ,Biophysics ,Spectrophotometry, Ultraviolet ,Gold ,0210 nano-technology ,Luminescence ,Chirality (chemistry) - Abstract
Chiral self-assembled nanomaterials with biological applications have attracted great interest. In this study, DNA-driven gold-upconversion nanoparticle (Au-UCNP) pyramids were fabricated to detect intracellular microRNA (miRNA) in real time. The Au-UCNP pyramids are doubly optically active, displaying strong plasmonic circular dichroism (CD) at 521 nm and significant luminescence in 500-600 nm, and therefore can be monitored by both of them. CD will decrease while the luminescence intensity increases in the presence of miRNA. The experimental results show that the CD intensity had an outstanding linear range from 0.073 to 43.65 fmol/10 μg(RNA) and a limit of detection (LOD) of 0.03 fmol/10 μg(RNA), whereas the luminescence intensity ranged from 0.16 to 43.65 fmol/10 μg(RNA) with a LOD of 0.12 fmol/10 μg(RNA). These data indicate that the CD signal is much more sensitive to the concentration of miRNA than the luminescent signal, which is attributed to the strong CD intensity arising from the spin angular momentum of the photon interaction with chiral nanostructures and the plasmonic enhancement of the intrinsic chirality of DNA molecules in the pyramids. This approach opens up a new avenue to the ultrasensitive detection and quantification of miRNA in living cells.
- Published
- 2015
14. A Helicene Nanoribbon with Greatly Amplified Chirality
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Raúl Hernández Sánchez, Colin Nuckolls, Nathaniel J. Schuster, Michael L. Steigerwald, Fay Ng, Daria Bukharina, Nicholas A. Kotov, and Nina Berova
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Circular dichroism ,010405 organic chemistry ,Context (language use) ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,Monomer ,chemistry ,Helicene ,Visible range ,Chirality (chemistry) ,Superstructure (condensed matter) ,Order of magnitude - Abstract
We report the synthesis and characterization of a chiral, shape-persistent, perylene-diimide-based nanoribbon. Specifically, the fusion of three perylene-diimide monomers with intervening naphthalene subunits resulted in a helical superstructure with two [6]helicene subcomponents. This π-helix-of-helicenes exhibits very intense electronic circular dichroism, including one of the largest Cotton effects ever observed in the visible range. It also displays more than an order of magnitude increase in circular dichroism for select wavelengths relative to its smaller homologue. These impressive chiroptical properties underscore the potential of this new nanoribbon architecture in the context of chiral electronic materials.
- Published
- 2018
15. Assembly of Gold Nanoparticles into Chiral Superstructures Driven by Circularly Polarized Light
- Author
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Kim, Ji-Young, primary, Yeom, Jihyeon, additional, Zhao, Gongpu, additional, Calcaterra, Heather, additional, Munn, Jiyoun, additional, Zhang, Peijun, additional, and Kotov, Nicholas, additional
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- 2019
- Full Text
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16. Template-Free Hierarchical Self-Assembly of Iron Diselenide Nanoparticles into Mesoscale Hedgehogs
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Nicholas A. Kotov, Changlong Hao, Dawei Deng, Petr Král, Soumyo Sen, and Chuanlai Xu
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Nanostructure ,Chemistry ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Fractal dimension ,Catalysis ,0104 chemical sciences ,Core (optical fiber) ,Monocrystalline silicon ,Diselenide ,Colloid and Surface Chemistry ,Self-assembly ,0210 nano-technology ,Nanoscopic scale - Abstract
The ability of semiconductor nanoparticles (NPs) to self-assemble has been known for several decades. However, the limits of the geometrical and functional complexity for the self-assembled nanostructures made from simple often polydispersed NPs are still continuing to amaze researchers. We report here the self-assembly of primary ∼2–4 nm FeSe2 NPs with puck-like shapes into either (a) monocrystalline nanosheets ∼5.5 nm thick and ∼1000 nm in lateral dimensions or (b) mesoscale hedgehogs ∼550 nm in diameter with spikes of ∼250 nm in length, and ∼10–15 nm in diameter, the path of the assembly is determined by the concentration of dodecanethiol (DT) in the reaction media. The nanosheets represent the constitutive part of hedgehogs. They are rolled into scrolls and assembled around a single core with distinct radial orientation forming nanoscale “needles” approximately doubling its fractal dimension of these objects. The core is assembled from primary NPs and nanoribbons. The size distribution of the mesoscal...
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- 2017
17. Chiral Ceramic Nanoparticles and Peptide Catalysis
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Yuangang Liu, Bin Li, Mahshid Chekini, Yichun Wang, Aydan Yeltik, Tianyong Zhang, Hilmi Volkan Demir, Shuang Jiang, Zhibei Qu, Nicholas A. Kotov, Alex Kotlyar, and Demir, Hilmi Volkan
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Polymethyl methacrylates ,Circular dichroism ,Ceramics ,Dichroism ,Nano-scale materials ,Nanoparticle ,Crystal atomic structure ,02 engineering and technology ,01 natural sciences ,Biochemistry ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Stereochemistry ,Ceramic materials ,Ceramic ,Chirality ,Chirality transfer ,Nanoparticle (NPs) ,Oxides ,021001 nanoscience & nanotechnology ,Metals ,Ceramic nanoparticles ,visual_art ,visual_art.visual_art_medium ,Amino acids ,Biocompatibility ,0210 nano-technology ,inorganic chemicals ,Inorganic chemistry ,Oxide ,Metal nanoparticles ,Atomistic molecular dynamics simulations ,Molecular dynamics ,010402 general chemistry ,Tungsten ,Catalysis ,Metal ,Polymer chemistry ,Particle Size ,Biomedical science ,technology, industry, and agriculture ,Chemical technologies ,General Chemistry ,0104 chemical sciences ,chemistry ,Technological opportunity ,Nanoparticles ,Tungsten compounds ,Hydrate ,Chirality (chemistry) ,Peptides - Abstract
The chirality of nanoparticles (NPs) and their assemblies has been investigated predominantly for noble metals and II-VI semiconductors. However, ceramic NPs represent the majority of nanoscale materials in nature. The robustness and other innate properties of ceramics offer technological opportunities in catalysis, biomedical sciences, and optics. Here we report the preparation of chiral ceramic NPs, as represented by tungsten oxide hydrate, WO3-x·H2O, dispersed in ethanol. The chirality of the metal oxide core, with an average size of ca. 1.6 nm, is imparted by proline (Pro) and aspartic acid (Asp) ligands via bio-to-nano chirality transfer. The amino acids are attached to the NP surface through C-O-W linkages formed from dissociated carboxyl groups and through amino groups weakly coordinated to the NP surface. Surprisingly, the dominant circular dichroism bands for NPs coated by Pro and Asp are different despite the similarity in the geometry of the NPs; they are positioned at 400-700 nm and 500-1100 nm for Pro- and Asp-modified NPs, respectively. The differences in the spectral positions of the main chiroptical band for the two types of NPs are associated with the molecular binding of the two amino acids to the NP surface; Asp has one additional C-O-W linkage compared to Pro, resulting in stronger distortion of the inorganic crystal lattice and greater intensity of CD bands associated with the chirality of the inorganic core. The chirality of WO3-x·H2O atomic structure is confirmed by atomistic molecular dynamics simulations. The proximity of the amino acids to the mineral surface is associated with the catalytic abilities of WO3-x·H2O NPs. We found that NPs facilitate formation of peptide bonds, leading to Asp-Asp and Asp-Pro dipeptides. The chiroptical activity, chemical reactivity, and biocompatibility of tungsten oxide create a unique combination of properties relevant to chiral optics, chemical technologies, and biomedicine.
- Published
- 2017
18. Phase-Pure FeSex (x = 1, 2) Nanoparticles with One- and Two-Photon Luminescence
- Author
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Xiang Mao, Jishu Han, Jin Gyu Kim, Nicholas A. Kotov, Sang Gil Lee, Hyun Suk Jung, and Jaebeom Lee
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Photoluminescence ,Chemistry ,business.industry ,Chalcogenide ,Nanoparticle ,Quantum yield ,Nanotechnology ,General Chemistry ,Biochemistry ,Catalysis ,Crystallinity ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Semiconductor ,Transmission electron microscopy ,business ,Nanoscopic scale - Abstract
Iron chalcogenides hold considerable promise for energy conversion and biomedical applications. Realization of this promise has been hindered by the lack of control over the crystallinity and nanoscale organization of iron chalcogenide films. High-quality nanoparticles (NPs) from these semiconductors will afford further studies of photophysical processes in them. Phase-pure NPs from these semiconductors can also serve as building blocks for mesoscale iron chalcogenide assemblies. Herein we report a synthetic method for FeSe(x) (x = 1, 2) NPs with a diameter of ca. 30 nm that satisfy these needs. The high crystallinity of the individual NPs was confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray analysis. TEM tomography images suggest pucklike NP shapes that can be rationalized by bond relaxation at the NP edges, as demonstrated in large-scale atomic models. The prepared FeSe(x) NPs display strong photoluminescence with a quantum yield of 20%, which was previously unattainable for iron chalcogenides. Moreover, they also show strong off-resonant luminescence due to two-photon absorption, which should be valuable for biological applications.
- Published
- 2014
19. Omnidispersible Hedgehog Particles with Multilayer Coatings for Multiplexed Biosensing
- Author
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Montjoy, Douglas G., primary, Bahng, Joong Hwan, additional, Eskafi, Aydin, additional, Hou, Harrison, additional, and Kotov, Nicholas A., additional
- Published
- 2018
- Full Text
- View/download PDF
20. A Helicene Nanoribbon with Greatly Amplified Chirality
- Author
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Schuster, Nathaniel J., primary, Hernández Sánchez, Raúl, additional, Bukharina, Daria, additional, Kotov, Nicholas A., additional, Berova, Nina, additional, Ng, Fay, additional, Steigerwald, Michael L., additional, and Nuckolls, Colin, additional
- Published
- 2018
- Full Text
- View/download PDF
21. Template-Free Hierarchical Self-Assembly of Iron Diselenide Nanoparticles into Mesoscale Hedgehogs
- Author
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Deng, Dawei, primary, Hao, Changlong, additional, Sen, Soumyo, additional, Xu, Chuanlai, additional, Král, Petr, additional, and Kotov, Nicholas A., additional
- Published
- 2017
- Full Text
- View/download PDF
22. Inkjet deposition of layer-by-layer assembled films
- Author
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Andres, Christine M. and Kotov, Nicholas A.
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Ammonium chloride -- Chemical properties ,Ammonium chloride -- Electric properties ,Ammonium compounds -- Chemical properties ,Ammonium compounds -- Electric properties ,Ammonium paratungstate -- Chemical properties ,Ammonium paratungstate -- Electric properties ,Coating processes -- Analysis ,Nanoparticles -- Chemical properties ,Nanoparticles -- Electric properties ,Polyelectrolytes -- Chemical properties ,Chemistry - Abstract
Inkjet technology is used for delivering the necessary quantities of layer-by-layer assembly (LBL) components required for film buildup without excess, eliminating the need for repetitive rinsing steps. The additive nature of LBL deposition based on the formation of insoluble nanoparticle-polyelectrolyte complexes of various compositions has provided good opportunity for versatile and noncontact patterning for the simple production of stratified patterns that are needed in advanced devices.
- Published
- 2010
23. Similar topological origin of chiral centers in organic and nanoscale inorganic structures: effect of stabilizer chirality on optical isomerism and growth of CdTe nanocrystals
- Author
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Yunlong Zhou, Ming Yang, Kai Sun, Zhiyong Tang, and Kotov, Nicholas A.
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Cadmium -- Chemical properties ,Cadmium -- Optical properties ,Chirality -- Analysis ,Cysteine -- Chemical properties ,Cysteine -- Thermal properties ,Quantum theory -- Usage ,Tellurium -- Chemical properties ,Tellurium -- Optical properties ,Chemistry - Abstract
The chirality of cysteine stabilizers has a distinct impact on both the growth kinetics and the optical properties of CdTe nanocrystals prepared in aqueous solution. Quantum mechanical calculations have shown that the thermodynamically preferred configuration of CdTe nanocrystals is S type when the stabilizer is D-cysteine and R type when L-cysteine is used as a stabilizer and these findings have helped in clarifying the nature of chirality in inorganic nanomaterials.
- Published
- 2010
24. Formation and assembly-disassembly processes of ZnO hexagonal pyramids driven by dipolar and excluded volume interactions
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Ming Yang, Kai Sun, and Kotov, Nicholas A.
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Dipole moments -- Analysis ,Nanoparticles -- Structure ,Nanoparticles -- Chemical properties ,Polymers -- Structure ,Polymers -- Chemical properties ,Zinc oxide -- Structure ,Zinc oxide -- Chemical properties ,Chemistry - Abstract
The formation of ZnO hexagonal pyramids has involved recrystallization of larger amorphous nanoparticles (NPs) followed by the multistage disassembly of intermediate aggregates into individual virtually perfectly shaped nanocrystals. The assemblies of ZnO pyramids with collective behavior of individual building blocks as well as distinct and controlled stages of assembly and disassembly have presented an interesting NP system with rich dynamic behavior.
- Published
- 2010
25. Self-Assembly of Chiral Nanoparticle Pyramids with Strong R/S Optical Activity
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Hua Kuang, Wei Ma, Nicholas A. Kotov, Chuanlai Xu, Liguang Xu, Libing Wang, and Wenjing Yan
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3D optical data storage ,Silver ,Nanostructure ,Optical Phenomena ,Surface Properties ,Chemistry ,Nanoparticle ,Stereoisomerism ,Nanotechnology ,DNA ,General Chemistry ,Biochemistry ,Catalysis ,Crystallography ,Colloid and Surface Chemistry ,Semiconductors ,Quantum Dots ,Nano ,Tetrahedron ,Nanoparticles ,Gold ,Self-assembly ,Particle Size ,Chirality (chemistry) ,Pyramid (geometry) - Abstract
Chirality at the nanometer scale represents one of the most rapidly developing areas of research. Self-assembly of DNA-nanoparticle (NP) hybrids enables geometrically precise assembly of chiral isomers. The concept of a discrete chiral nanostructure of tetrahedral shape and topology fabricated from four different NPs located in the corners of the pyramid is fundamental to the field. While the first observations of optical activity of mixed pyramidal assemblies were made in 2009 (Chen, W.; Nano Lett. 2009, 9, 2153-2159), further studies are difficult without finely resolved optical data for precisely organized NP pyramidal enantiomers. Here we describe the preparation of a family of self-assembled chiral pyramids made from multiple metal and/or semiconductor NPs with a yield as high as 80%. Purposefully made R- and S-enantiomers of chiral pyramids with four different NPs from three different materials displayed strong chiroptical activity, with anisotropy g-factors as high as 1.9 × 10(-2) in the visible spectral range. Importantly, all NP constituents contribute to the chiroptical activity of the R/S pyramids. We were able to observe three different circular dichroism signals in the range of 350-550 nm simultaneously. They correspond to the plasmonic oscillations of gold, silver, and bandgap transitions of quantum dots. Tunability of chiroptical bands related to these transitions is essential from fundamental and practical points of view. The predictability of optical properties of pyramids, the simplicity of their self-assembly in comparison with lithography, and the possibility for polymerase chain reaction-based automation of their synthesis are expected to facilitate their future applications.
- Published
- 2012
26. Reversible loading and unloading of nanoparticles in 'exponentially' growing polyelectrolyte LBL films
- Author
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Srivastava, Sudhanshu, Ball, Vincent, Podsiadlo, Paul, Jungwoo Lee, Ho, Peter, and Kotov, Nicholas A.
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Dynamics -- Analysis ,Hydration (Chemistry) -- Analysis ,Nanoparticles -- Structure ,Nanoparticles -- Chemical properties ,Nanoparticles -- Mechanical properties ,Polyelectrolytes -- Structure ,Polyelectrolytes -- Chemical properties ,Polyelectrolytes -- Mechanical properties ,Chemistry - Abstract
Postassembly reversible loading and unloading of nanoparticles (NPs) is shown in a swollen polyelectrolyte film. The variations of the structure of the layer-by-layer (LBL) layers and the NPs can be used for controlling the incorporation and release of the NPs.
- Published
- 2008
27. Spontaneous Self-Organization Enables Dielectrophoresis of Small Nanoparticles and Formation of Photoconductive Microbridges
- Author
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Joong Hwan Bahng, Bongjun Yeom, Chen Chen, Sudhanshu Srivastava, Sang Ho Cha, Nicholas A. Kotov, Seung-Ho Jung, Shaoqin Liu, Ming Yang, and Jian Zhu
- Subjects
Orders of magnitude (temperature) ,Chemistry ,business.industry ,Photoconductivity ,Nanoparticle ,Nanotechnology ,General Chemistry ,Dielectrophoresis ,Biochemistry ,Catalysis ,Colloid and Surface Chemistry ,Semiconductor ,Electrode ,business ,Nanoscopic scale ,Microscale chemistry - Abstract
Detailed understanding of the mechanism of dielectrophoresis (DEP) and the drastic improvement of its efficiency for small size-quantized nanoparticles (NPs) open the door for the convergence of microscale and nanoscale technologies. It is hindered, however, by the severe reduction of DEP force in particles with volumes below a few hundred cubic nanometers. We report here DEP assembly of size-quantized CdTe nanoparticles (NPs) with a diameter of 4.2 nm under AC voltage of 4–10 V. Calculations of the nominal DEP force for these NPs indicate that it is several orders of magnitude smaller than the force of the Brownian motion destroying the assemblies even for the maximum applied AC voltage. Despite this, very efficient formation of NP bridges between electrodes separated by a gap of 2 μm was observed even for AC voltages of 6 V and highly diluted NP dispersions. The resolution of this conundrum was found in the intrinsic ability of CdTe NPs to self-assemble. The species being assembled by DEP are substantia...
- Published
- 2011
28. Transparent Conductors from Carbon Nanotubes LBL-Assembled with Polymer Dopant with π−π Electron Transfer
- Author
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Jian Zhu, Bong Sup Shim, Nicholas A. Kotov, and Matthew Di Prima
- Subjects
Models, Molecular ,Polymers ,Surface Properties ,Nanotechnology ,Carbon nanotube ,Conductivity ,Microscopy, Atomic Force ,Biochemistry ,Article ,Catalysis ,law.invention ,Surface conductivity ,Colloid and Surface Chemistry ,law ,Cellulose ,Transparent conducting film ,chemistry.chemical_classification ,Dopant ,Nanotubes, Carbon ,Chemistry ,Doping ,Electric Conductivity ,General Chemistry ,Polymer ,Ketones ,Indium tin oxide ,Chemical engineering ,Ethers - Abstract
Single-walled carbon nanotube (SWNT) and other carbon-based coatings are being considered as replacements for indium tin oxide (ITO). The problems of transparent conductors (TCs) coatings from SWNT and similar materials include poor mechanical properties, high roughness, low temperature resilience, and fast loss of conductivity. The simultaneous realization of these desirable characteristics can be achieved using high structural control of layer-by-layer (LBL) deposition, which is demonstrated by the assembly of hydroethyl cellulose (HOCS) and sulfonated polyetheretherketone (SPEEK)-SWNTs. A new type of SWNT doping based on electron transfer from valence bands of nanotubes to unoccupied levels of SPEEK through π-π interactions was identified for this system. It leads to a conductivity of 1.1 × 10(5) S/m at 66 wt % loadings of SWNT. This is better than other polymer/SWNT composites and translates into surface conductivity of 920 Ω/◻ and transmittance of 86.7% at 550 nm. The prepared LBL films also revealed unusually high temperature resilience up to 500 °C, and low roughness of 3.5 nm (ITO glass -2.4 nm). Tensile modulus, ultimate strength, and toughness of such coatings are 13 ± 2 GPa, 366 ± 35 MPa, and 8 ± 3 kJ/m(3), respectively, and exceed corresponding parameters of all similar TCs. The cumulative figure of merit, ∏(TC), which included the critical failure strain relevant for flexible electronics, was ∏(TC) = 0.022 and should be compared to ∏(TC) = 0.006 for commercial ITO. Further optimization is possible using stratified nanoscale coatings and improved doping from the macromolecular LBL components.
- Published
- 2011
29. Similar Topological Origin of Chiral Centers in Organic and Nanoscale Inorganic Structures: Effect of Stabilizer Chirality on Optical Isomerism and Growth of CdTe Nanocrystals
- Author
-
Nicholas A. Kotov, Kai Sun, Yunlong Zhou, Ming Yang, and Zhiyong Tang
- Subjects
Circular dichroism ,Aqueous solution ,Photoluminescence ,Chemistry ,Chemical modification ,Stereoisomerism ,General Chemistry ,Biochemistry ,Catalysis ,Crystallography ,Colloid and Surface Chemistry ,Nanocrystal ,Microscopy ,Cadmium Compounds ,Nanoparticles ,Nanotechnology ,Thermodynamics ,Cysteine ,Tellurium ,Crystallization ,Chirality (chemistry) ,Spectroscopy - Abstract
It is observed in this study that the chirality of cysteine stabilizers has a distinct effect on both the growth kinetics and the optical properties of CdTe nanocrystals synthesized in aqueous solution. The effect was studied by circular dichroism spectroscopy, temporal UV-vis spectroscopy, photoluminescence spectroscopy, and several other microscopy and spectroscopic techniques including atomic modeling. Detailed analysis of the entirety of experimental and theoretical data led to the hypothesis that the atomic origin of chiral sites in nanocrystals is topologically similar to that in organic compounds. Since atoms in CdTe nanocrystals are arranged as tetrahedrons, chirality can occur when all four atomic positions have chemical differences. This can happen in apexes of nanocrystals, which are the most susceptible to chemical modification and substitution. Quantum mechanical calculations reveal that the thermodynamically preferred configuration of CdTe nanocrystals is S type when the stabilizer is D-cysteine and R type when L-cysteine is used as a stabilizer, which correlates well with the experimental kinetics of particle growth. These findings help clarify the nature of chirality in inorganic nanomaterials, the methods of selective production of optical isomers of nanocrystals, the influence of chiral biomolecules on the nanoscale crystallization, and practical perspectives of chiral nanomaterials for optics and medicine.
- Published
- 2010
30. Formation and Assembly−Disassembly Processes of ZnO Hexagonal Pyramids Driven by Dipolar and Excluded Volume Interactions
- Author
-
Nicholas A. Kotov, Kai Sun, and Ming Yang
- Subjects
Models, Molecular ,Time Factors ,Light ,Molecular Conformation ,Nanoparticle ,Biochemistry ,Catalysis ,law.invention ,Colloid ,Colloid and Surface Chemistry ,Microscopy, Electron, Transmission ,X-Ray Diffraction ,law ,Scattering, Radiation ,Crystallization ,Chemistry ,food and beverages ,Recrystallization (metallurgy) ,General Chemistry ,Amorphous solid ,Crystallography ,Nanocrystal ,Chemical physics ,Excluded volume ,Spectrophotometry, Ultraviolet ,Crystallite ,Zinc Oxide - Abstract
ZnO hexagonal pyramids were obtained in hydrophilic media without any traditional stabilizers (capping agents). The absence of a thick organic shell reducing the anisotropy of nanoparticle (NP) interactions, oxide nature of the materials, and new geometry of the nanocrystals makes possible the observation of new self-organization phenomena. Several new features not present in the previous cases of NP self-organization were identified and discussed. The formation of ZnO pyramids involved recrystallization of larger amorphous NPs followed by the multistage disassembly of intermediate aggregates into individual virtually perfectly shaped nanocrystals. The evolution of NPs begins with crystallization of clustered plates within the original amorphous spherical colloids, and then agglomerated truncated pyramids are formed. These agglomerates further transform into chained pyramids, which eventually separate from each other. The crystallization and disassembly processes can be associated with the decrease of potential and anisotropy of the attractive force field around the crystallites represented in part by dipole moments. The reassembly of the pyramids can still be attained via engaging excluded volume interaction after adding similarly charged polymer. Overall, in this system, we see the first examples of (1) coupled crystallization and disassembly process; (2) induced assembly of nanoscale particles using excluded volume interactions, which were previously used only for aggregation of microscale colloids; and (3) nanoparticle assemblies with variable and experimentally verifiable relative orientation of dipoles including head-to-tail, tail-to-tail pairs, and antiparallel chains. Described assemblies of ZnO pyramids with collective behavior of individual building blocks as well as distinct and experimentally controlled stages of assembly and disassembly present a fundamentally interesting nanoparticle system with rich dynamic behavior.
- Published
- 2010
31. Spontaneous transformation of CdTe nanoparticles into angled Te nanocrystals: From particles and rods to checkmarks, X-marks, and other unusual shapes
- Author
-
Zhiyong Tang, Ying Wang, Shanbhag, Sachin, Giersig, Michael, and Kotov, Nicholas A.
- Subjects
Tellurium -- Structure ,Tellurium -- Properties ,Anisotropy -- Analysis ,Transmission electron microscopes -- Observations ,Chemistry - Abstract
The spontaneous transformation process starting from destabilized CdTe nanoparticles (NPs) and producing branched Te nanocrystals (NCs) with unique anisotropic structure is described. It shows that high-energy crystal faces on their apexes act as the sticky points causing the particles to join in the ends.
- Published
- 2006
32. Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations
- Author
-
Sinani, Vladmir A., Gheith, Muhammed K., Yaroslavov, Alexander A., Kotov, Nicholas, Rakhnyanskaya, Anna A., Wicksted, James P., Kai Sun, and Mamedov, Arif A.
- Subjects
Carbon compounds -- Chemical properties ,Aqueous solution reactions -- Research ,Chemistry - Abstract
A simple method for the preparation of exceptionally stable aqueous suspensions of nanotubes (NTs) in mixed water/DMF solvents, which also imparts strong positive charge to NT dispersions, is demonstrated. The efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles.
- Published
- 2005
33. Chiral Ceramic Nanoparticles and Peptide Catalysis
- Author
-
Jiang, Shuang, primary, Chekini, Mahshid, additional, Qu, Zhi-Bei, additional, Wang, Yichun, additional, Yeltik, Aydan, additional, Liu, Yuangang, additional, Kotlyar, Alex, additional, Zhang, Tianyong, additional, Li, Bin, additional, Demir, Hilmi Volkan, additional, and Kotov, Nicholas A., additional
- Published
- 2017
- Full Text
- View/download PDF
34. Versatile organic (fullerene)-inorganic (CdTe nanoparticle) nanoensembles
- Author
-
Guldi, Dirk M., Zilbermann, Israel, Anderson, Greg, Kotov, Nicholas A., Tagmatarchis, Nikos, and Prato, Maurizio
- Subjects
Electrostatic precipitation -- Research ,Electron transport -- Research ,Chemistry - Abstract
The use of electrostatic interactions as a versatile means to bind two water-soluble C(sub 60) derivatives (C(sub 60)) to size-quantized CdTe nanoparticles (NP) is reported. The electrostatic binding of C(sub 60)) to NP facilitates the rapid photoinduced electron transfer and the versatility of nanoparticle chemistry opens the possibilities of the redox processes in solution and on the electrodes.
- Published
- 2004
35. Spontaneous CdTe → Alloy → CdS Transition of Stabilizer-Depleted CdTe Nanoparticles Induced by EDTA
- Author
-
Nicholas A. Kotov, Sachin Shanbhag, Zhiyong Tang, and Ying Wang
- Subjects
chemistry.chemical_classification ,Inorganic chemistry ,Metal Nanoparticles ,Substrate (chemistry) ,Nanoparticle ,Ethylenediaminetetraacetic acid ,General Chemistry ,Biochemistry ,Catalysis ,Cadmium sulfide ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Microscopy, Electron, Transmission ,chemistry ,Chemical engineering ,Alloys ,Cadmium Compounds ,Thiol ,Nanotechnology ,Reactivity (chemistry) ,Cysteine ,Tellurium ,Edetic Acid ,Stabilizer (chemistry) - Abstract
CdTe nanoparticles stabilized by l-cysteine are chemically transformed into CdS nanoparticles of the same diameter via an intermediate CdTeS alloy without any auxiliary source of sulfur. The reaction is induced by ethylenediaminetetraacetic acid dipotassium salt dehydrate (EDTA), which was demonstrated experimentally to act as a catalyst by partially removing thiol stabilizers from the nanoparticle surface. It is hypothesized that addition of EDTA facilitates Te(2-) release, and oxidation of Te(2-) drives the nanoparticle transition process. Unlike many reports on reactions catalyzed by nanocolloids, this is likely to be the first observation of a catalytic reaction in which nanoparticles function as a substrate rather than a catalyst. It opens new pathways for the synthesis of novel nanoscale II-VI and other semiconductors and represents an interesting case of chemical processes in nanocolloids with reactivity increased by depletion of the surface layer of thiol stabilizers. This includes but is not limited to accurate control over the particle composition and crystallization rate. The slow rate of the CdTe --alloy --CdS transition is important for minimizing defects in the crystal lattice and results in a substantial increase of the quantum yield of photoluminescence over the course of the transition.
- Published
- 2006
36. Aqueous Dispersions of Single-wall and Multiwall Carbon Nanotubes with Designed Amphiphilic Polycations
- Author
-
Arif A. Mamedov, A. A. Rakhnyanskaya, James P. Wicksted, Vladimir A. Sinani, Alexander A. Yaroslavov, Muhammed K. Gheith, Kai Sun, and Nicholas A. Kotov
- Subjects
Nanotube ,Chemistry ,Graphene ,Analytical chemistry ,General Chemistry ,Carbon nanotube ,Biochemistry ,Catalysis ,Polyelectrolyte ,law.invention ,Hydrophobic effect ,Colloid and Surface Chemistry ,Chemical engineering ,law ,Amphiphile ,Side chain ,Macromolecule - Abstract
Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.
- Published
- 2005
37. Template-Free Hierarchical Self-Assembly of Iron Diselenide Nanoparticles into Mesoscale Hedgehogs
- Author
-
Deng, Dawei, Hao, Changlong, Sen, Soumyo, Xu, Chuanlai, Král, Petr, and Kotov, Nicholas A.
- Abstract
The ability of semiconductor nanoparticles (NPs) to self-assemble has been known for several decades. However, the limits of the geometrical and functional complexity for the self-assembled nanostructures made from simple often polydispersed NPs are still continuing to amaze researchers. We report here the self-assembly of primary ∼2–4 nm FeSe2NPs with puck-like shapes into either (a) monocrystalline nanosheets ∼5.5 nm thick and ∼1000 nm in lateral dimensions or (b) mesoscale hedgehogs ∼550 nm in diameter with spikes of ∼250 nm in length, and ∼10–15 nm in diameter, the path of the assembly is determined by the concentration of dodecanethiol (DT) in the reaction media. The nanosheets represent the constitutive part of hedgehogs. They are rolled into scrolls and assembled around a single core with distinct radial orientation forming nanoscale “needles” approximately doubling its fractal dimension of these objects. The core is assembled from primary NPs and nanoribbons. The size distribution of the mesoscale hedgehogs can be as low as 3.8%, indicating a self-limited mechanism of the assembly. Molecular dynamics simulation indicates that the primary FeSe2particles have mobile edge atoms and asymmetric basal surfaces. The top-bottom asymmetry of the puck-like NPs originates from the Fe-rich/Se-rich stripes on the (011) surface of the orthorhombic FeSe2crystal lattice, displaying 2.7 nm periodicity that is comparable to the lateral size of the primary NPs. As the concentration of DT increases, the NPs bind to additional metal sites, which increases the chemical and topographic asymmetry and switches the assembly pathways from nanosheets to hedgehogs. These results demonstrate that the self-assembly of NPs with non-biological surface ligands and without any biological templates results in morphogenesis of inorganic superstructures with complexity comparable to that of biological assemblies, for instance mimivirus. The semiconductor nature of FeSe2hedgehogs enables their utilizations in catalysis, drug delivery, optics, and energy storage.
- Published
- 2024
- Full Text
- View/download PDF
38. Two Modes of Linear Layer-by-Layer Growth of Nanoparticle−Polylectrolyte Multilayers and Different Interactions in the Layer-by-layer Deposition
- Author
-
John W. Ostrander, and Arif A. Mamedov, and Nicholas A. Kotov
- Subjects
Layer by layer ,Yttrium iron garnet ,Nanoparticle ,Nanotechnology ,General Chemistry ,Biochemistry ,Catalysis ,Polyelectrolyte ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Chemical engineering ,Deposition (phase transition) ,Particle ,Layer (electronics) - Abstract
The structure of the multilayer assemblies of yttrium iron garnet nanoparticles (YIG) with polyelectrolytes was investigated with the emphasis on the control of the particle density in the adsorption layers. It was found that the growth of YIG films prepared by the layer-by-layer assembly can occur via two deposition modes: (1) sequential adsorption of densely packed adsorption layers (normal growth mode) and (2) in-plane growth of isolated particle domains (lateral expansion mode). Importantly, the dependence of the optical density on the number of deposition cycles remains linear in both cases. Microscopy results indicate that the origin of the lateral growth is in the interplay of particle/particle and particle/polyelectrolyte interactions rather than in a substrate effect. The lateral expansion mode is a general attribute of the layer-by-layer deposition and can be observed for various aqueous colloids. For the preparation of sophisticated multifunctional assemblies on nanoparticles, the film growth via domain expansion should be avoided, and therefore, one must be able to control the growth pattern. The switch from lateral to normal growth mode can be effected by grafting charged organic groups to YIG nanoparticles. Hydrophobic interactions between the hydrocarbon groups of the modified YIG and polyelectrolyte significantly increase the attractive component of the particle/polyelectrolyte and particle/particle interactions. The films from modified YIG display densely packed nanoparticle layers with a greatly reduced number of defects.
- Published
- 2001
39. Template-Free Hierarchical Self-Assembly of Iron Diselenide Nanoparticles into Mesoscale Hedgehogs.
- Author
-
Dawei Deng, Changlong Hao, Soumyo Sen, Chuanlai Xu, Petr Král, and Kotov, Nicholas A.
- Published
- 2017
- Full Text
- View/download PDF
40. Regiospecific plasmonic assemblies for in situ Raman spectroscopy in live cells
- Author
-
Hua Kuang, Chuanlai Xu, Liguang Xu, Libing Wang, Nicholas A. Kotov, and Wei Ma
- Subjects
Cell Survival ,Nanoparticle ,DNA, Single-Stranded ,Metal Nanoparticles ,Nanotechnology ,Stereoisomerism ,Spectrum Analysis, Raman ,Biochemistry ,Catalysis ,Article ,Colloid and Surface Chemistry ,Humans ,Nanoscopic scale ,Plasmon ,Nanotubes ,Base Sequence ,Chemistry ,General Chemistry ,In situ raman spectroscopy ,Yield (chemistry) ,Nanorod ,Spectrophotometry, Ultraviolet ,Gold ,Experimental methods ,HeLa Cells - Abstract
Multiple properties of plasmonic assemblies are determined by their geometrical organization. While high degree of complexity was achieved for plasmonic superstructures based on nanoparticles (NPs), little is known about the stable and structurally reproducible plasmonic assemblies made up from geometrically diverse plasmonic building blocks. Among other possibilities, they open the door for the preparation of regiospecific isomers of nanoscale assemblies significant both from a fundamental point of view and optical applications. Here, we present a synthetic method for complex assemblies from NPs and nanorods (NRs) based on selective modification of NRs with DNA oligomers. Three types of assemblies denoted as End, Side, and Satellite isomers that display distinct elements of regiospecificity were prepared with the yield exceeding 85%. Multiple experimental methods independently verify various structural features, uniformity, and stability of the prepared assemblies. The presence of interparticle gaps with finely controlled geometrical parameters and inherently small size comparable with those of cellular organelles fomented their study as intracellular probes. Against initial expectations, SERS intensity for End, Side, and Satellite isomers was found to be dependent primarily on the number of the NPs in the superstructures rationalized with the help of electrical field simulations. Incubation of the label-free NP-NR assemblies with HeLa cells indicated sufficient field enhancement to detect structural lipids of mitochondria and potentially small metabolites. This provided the first proof-of-concept data for the possibility of real-time probing of the local organelle environment in live cells. Further studies should include structural optimization of the assemblies for multitarget monitoring of metabolic activity and further increase in complexity for applications in transformative optics.
- Published
- 2011
41. Inkjet deposition of layer-by-layer assembled films
- Author
-
Christine M. Andres and Nicholas A. Kotov
- Subjects
Chemistry ,Layer by layer ,Nanoparticle ,Nanotechnology ,General Chemistry ,Electrolyte ,Biochemistry ,Catalysis ,Article ,Quaternary Ammonium Compounds ,Electrolytes ,Colloid and Surface Chemistry ,Colloidal gold ,Advanced composite materials ,Particle ,Deposition (phase transition) ,Nanoparticles ,Polyethylenes ,Nanoscopic scale - Abstract
Layer-by-layer assembly (LBL) can create advanced composites with exceptional properties unavailable by other means, but the laborious deposition process and multiple dipping cycles hamper their utilization in microtechnologies and electronics. Multiple rinse steps provide both structural control and thermodynamic stability to LBL multilayers, but they significantly limit their practical applications and contribute significantly to the processing time and waste. Here we demonstrate that by employing inkjet technology one can deliver the necessary quantities of LBL components required for film buildup without excess, eliminating the need for repetitive rinsing steps. This feature differentiates this approach from all other recognized LBL modalities. Using a model system of negatively charged gold nanoparticles and positively charged poly(diallyldimethylammonium) chloride, the material stability, nanoscale control over thickness, and particle coverage offered by the inkjet LBL technique are shown to be equal or better than the case of multilayers made with traditional dipping cycles. The opportunity for fast deposition of complex metallic patterns using a simple inkjet printer is also shown. The additive nature of LBL deposition based on the formation of insoluble nanoparticle-polyelectrolyte complexes of various compositions provides an excellent opportunity for versatile, multicomponent, and noncontact patterning for the simple production of stratified patterns that are much needed in advanced devices.
- Published
- 2010
42. What is the effective charge of TGA-stabilized CdTe nanocolloids?
- Author
-
Yaroslavov, Alexander A., Sinani, Vladimir A., Efimova, Anna A., Yaroslavova, Ekaterina G., Rakhnyanskaya, Anna A., Ermakov, Yury A., and Kotov, Nicholas A.
- Subjects
Luminescence -- Research ,Tellurium -- Electric properties ,Cadmium -- Electric properties ,Chemistry - Abstract
A simple method of quantitive evaluation of the net charge of nanoparticles (Q) in aqueous dispersions, which should be applicable to many families of luminescent nanoparticles (NPs), is described. The utilization of CdTe NPs stabilized by thioglycolic acid (TGA), which is structurally similar to Cd54Te32(SR)(sub 52) is highlighted.
- Published
- 2005
43. Multicolor luminescence patterning by photoactivation of semiconductor nanoparticle films
- Author
-
Wang, Ying, Tang, Zhiyong, Correa-Durate, Miguel A., Liz-Marzan, Luis M., and Kotov, Nicholas A.
- Subjects
Luminescence -- Research ,Semiconductors -- Optical properties ,Dielectric films -- Optical properties ,Thin films -- Optical properties ,Chemistry - Abstract
Production of user-defined 2D patterns of semiconductor nanoparticles is a fundamental milestone for many photonic, biophotonic, and optoelectronic applications for quantum-confined species. For mesoscale patterns required for most currently used devices, the dominant approach to the problem involves spatially controlled chemical derivatization of the surface by affinity elements that subsequently bind nanoparticles.
- Published
- 2003
44. Spontaneous transformation of CdTe nanoparticles into angled Te nanocrystals: from particles and rods to checkmarks, X-marks, and other unusual shapes
- Author
-
Nicholas A. Kotov, Ying Wang, Zhiyong Tang, Sachin Shanbhag, and Michael Giersig
- Subjects
Fabrication ,business.industry ,Chemistry ,Nanoparticle ,Metal Nanoparticles ,Nanotechnology ,General Chemistry ,Colloidal crystal ,Biochemistry ,Catalysis ,Rod ,Crystal ,Colloid and Surface Chemistry ,Nanocrystal ,Microscopy, Electron, Transmission ,Optoelectronics ,Particle ,Crystallite ,Cysteine ,Tellurium ,business ,Cadmium - Abstract
CdTe nanoparticles spontaneously transform into the branched Te nanocrystals with the unique, highly anisotropic shape of checkmarks after partial removal of the stabilizers of L-cysteine. The Te checkmarks are made in a relatively high yield and uniformity; the length of the arms is ca. 150 nm, whereas the angle between the arms is 74 degrees . Subsequent growth of the particle yields mothlike nanocrystals retaining geometrical anisotropy. Unlike the previous synthesis methods of branched nanocrystals, they are formed via a merger of individual rod-shaped crystallites. High-energy crystal faces on their apexes act as the sticky points causing the particles to join in the ends. This is the first demonstration of spontaneous transformation of binary semiconductor particles into highly anisotropic nanocolloids in an angled conformation. The end reactivity of starting Te rods can be used both for bottom-up fabrication of nanoscale electronics and relatively safe and nontoxic method of synthesis of Te-based optical and other materials.
- Published
- 2006
45. Quantum dot on a rope
- Author
-
Westenhoff, Sebastian, Kotov, Nicholas A., Uppenberg, Jonas, Schultz, Johan, and Wikstrom, Mats
- Subjects
Polymers -- Research ,Quantum theory -- Analysis ,Chromophores -- Research ,Chromophores -- Mechanical properties ,Chromophores -- Optical properties ,Chemistry - Abstract
A novel bichromophor system constructed from a quantum dot tethered to a semi conducting polymer is described. CdTe-PEG-aPPE is an example of an organized nanoparticles (NP) system with tunable optical coupling, which is gradual and experimentally straight forward.
- Published
- 2002
46. Chiral Ceramic Nanoparticles and Peptide Catalysis.
- Author
-
Shuang Jiang, Chekini, Mahshid, Zhi-Bei Qu, Yichun Wang, Yeltik, Aydan, Yuangang Liu, Kotlyar, Alex, Tianyong Zhang, Bin Li, Demir, Hilmi Volkan, and Kotov, Nicholas A.
- Published
- 2017
- Full Text
- View/download PDF
47. What is the effective charge of TGA-stabilized CdTe nanocolloids?
- Author
-
A. A. Rakhnyanskaya, E.G. Yaroslavova, Yury A. Ermakov, Nicholas A. Kotov, A. A. Efimova, Alexander A. Yaroslavov, and Vladimir A. Sinani
- Subjects
Aqueous solution ,Chemistry ,Fluorescence spectrometry ,Analytical chemistry ,Charge density ,General Chemistry ,Biochemistry ,Catalysis ,Effective nuclear charge ,Polyelectrolyte ,Ion ,Colloid and Surface Chemistry ,Adsorption ,Surface charge - Abstract
The surface charge of semiconductor nanoparticles, Q, is an important parameter which determines their electrokinetic behavior, stability in water and polar solvents, functions of optical and electronic devices, self-assembly properties, and interactions with cell membranes. We have developed a simple method for quantitative determination of Q in their native aqueous environment. The method does not require the knowledge of exact atomic structure or make assumptions about effects of drying on charge distribution. The method is based on titration of nanoparticle dispersion with a solution of oppositely charged polyelectrolyte. The point of complete neutralization is recognized as an inflection point on the dependence of fluorescence intensity on the amount of polyelectrolyte added. Thioglycolic acid-stabilized CdTe nanoparticles 2 nm in diameter were found to carry an average Q from -2.6 to -5.5 for pH 7.5 to 10, respectively. This charge is found to be smaller than that calculated theoretically for an analogous structure (i.e., Q = -8), presumably due to adsorption of Cd(2+) ions on the stabilizer shell and on Te atoms with unsaturated valence located on the side planes of CdTe tetrahedrons.
- Published
- 2005
48. Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations
- Author
-
Vladimir A, Sinani, Muhammed K, Gheith, Alexander A, Yaroslavov, Anna A, Rakhnyanskaya, Kai, Sun, Arif A, Mamedov, James P, Wicksted, and Nicholas A, Kotov
- Subjects
Light ,Nanotubes, Carbon ,Polyamines ,Solvents ,Scattering, Radiation ,Water ,Polyvinyls ,Spectrophotometry, Ultraviolet ,Microscopy, Atomic Force ,Polyelectrolytes ,Pyrrolidinones - Abstract
Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.
- Published
- 2005
49. Nanorainbows: Graded semiconductor films from quantum dots
- Author
-
Memedov, Arif A., Belov, Artem, Giersig, Michael, Mamedova, Nataliya N., and Kotov, Nicholas A.
- Subjects
Semiconductors -- Research ,Chemistry - Abstract
The potential for the layer-by-layer production of one-dimensionally graded semiconducting films is reported.
- Published
- 2001
50. Versatile organic (fullerene)-inorganic (CdTe nanoparticle) nanoensembles
- Author
-
Dirk M. Guldi, Nikos Tagmatarchis, Maurizio Prato, Nicholas A. Kotov, Greg Anderson, and Israel Zilbermann
- Subjects
Fullerene ,Chemistry ,Analytical chemistry ,Nanoparticle ,Charge (physics) ,General Chemistry ,Electrostatics ,Biochemistry ,Catalysis ,Cadmium telluride photovoltaics ,Condensed Matter::Materials Science ,Colloid and Surface Chemistry ,Chemical engineering ,Homogeneous ,Transmission electron microscopy ,Physics::Chemical Physics ,Electrostatic interaction - Abstract
Novel organic (positively charged fullerene)−inorganic (negatively charged CdTe nanoparticle) nanoensembles were devised through electrostatic interactions and probed as versatile donor−acceptor hybrids. Photoirradiation of their homogeneous solutions, containing the electrostatically packed components, let to very long-lived (1.3 ms) charge separated states.
- Published
- 2004
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