18 results on '"Brett W. Boote"'
Search Results
2. Unprecedented generation of 3D heterostructures by mechanochemical disassembly and re-ordering of incommensurate metal chalcogenides
- Author
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Scott L. Carnahan, Arjun K. Pathak, Prashant Singh, Vitalij K. Pecharsky, Viktor P. Balema, Yaroslav Mudryk, Ihor Z. Hlova, Oleksandr Dolotko, Lin Zhou, Aaron J. Rossini, Emily A. Smith, Ely M. Eastman, Jingzhe Li, Brett W. Boote, and Duane D. Johnson
- Subjects
Chemical process ,Materials science ,Annealing (metallurgy) ,Metal chalcogenides ,Science ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Condensed Matter::Materials Science ,Nanoscience and technology ,Monolayer ,lcsh:Science ,Alternative methods ,Multidisciplinary ,Synthesis and processing ,Heterojunction ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,0104 chemical sciences ,lcsh:Q ,0210 nano-technology - Abstract
Three-dimensional heterostructures are usually created either by assembling two-dimensional building blocks into hierarchical architectures or using stepwise chemical processes that sequentially deposit individual monolayers. Both approaches suffer from a number of issues, including lack of suitable precursors, limited reproducibility, and poor scalability of the preparation protocols. Therefore, development of alternative methods that enable preparation of heterostructured materials is desired. We create heterostructures with incommensurate arrangements of well-defined building blocks using a synthetic approach that comprises mechanical disassembly and simultaneous reordering of layered transition-metal dichalcogenides, MX2, and non-layered monochalcogenides, REX, where M = Ta, Nb, RE = Sm, La, and X = S, Se. We show that the discovered solid-state processes are rooted in stochastic mechanochemical transformations directed by electronic interaction between chemically and structurally dissimilar solids toward atomic-scale ordering, and offer an alternative to conventional heterostructuring. Details of composition–structure–properties relationships in the studied materials are also highlighted., 3D heterostructures offer properties that are inaccessible in bulk single-phase solids, but synthetic approaches are limited. The authors use mechanochemical reshuffling of binary precursors and subsequent annealing to design structurally aligned misfit heterostructures with well-defined atomic arrangements.
- Published
- 2020
3. Inorganic Semiconductor Quantum Dots as a Saturated Excitation (SAX) Probe for Sub‐Diffraction Imaging
- Author
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Emily A. Smith, Brett W. Boote, Avinash Kumar Singh, Sadie J. Burkhow, Chamari S. Wijesooriya, Jacob W. Petrich, Department of Chemistry [Ames, Iowa], and Iowa State University (ISU)
- Subjects
Diffraction ,Materials science ,business.industry ,Organic Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Analytical Chemistry ,Semiconductor ,Semiconductor quantum dots ,Quantum dot ,[CHIM]Chemical Sciences ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Saturation (chemistry) ,Excitation ,ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2021
4. Investigation of the photophysical properties of energy-relevant inorganic nanocrystals
- Author
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Brett W. Boote
- Subjects
Photoluminescence ,Materials science ,chemistry ,Nanocrystal ,chemistry.chemical_element ,Nanotechnology ,Germanium ,Energy (signal processing) ,Perovskite (structure) - Published
- 2019
5. Lead Halide Perovskites: Challenges and Opportunities in Advanced Synthesis and Spectroscopy
- Author
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Emily A. Smith, Javier Vela, Bryan A. Rosales, Michael P. Hanrahan, Brett W. Boote, and Aaron J. Rossini
- Subjects
Photoluminescence ,Renewable Energy, Sustainability and the Environment ,business.industry ,Chemistry ,Photovoltaic system ,Energy Engineering and Power Technology ,Halide ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Solar energy ,01 natural sciences ,0104 chemical sciences ,law.invention ,Fuel Technology ,Lead (geology) ,Chemistry (miscellaneous) ,law ,Solar cell ,Materials Chemistry ,0210 nano-technology ,business ,Spectroscopy - Abstract
Hybrid lead perovskites containing a mixture of organic and inorganic cations and anions have led to solar cell devices with performance and stability that are better than those of their single-halide analogs. 207Pb solid-state nuclear magnetic resonance and single-particle photoluminescence spectroscopies show that the structure and composition of mixed-halide and likely other hybrid lead perovskites are much more complex than previously thought and are highly dependent on their synthesis. While a majority of reports in the area focus on the construction of photovoltaic devices, this Perspective focuses instead on achieving a better understanding of the fundamental chemistry and photophysics of these materials, because this will aid not only in constructing improved devices but also in generating new uses for these unique materials.
- Published
- 2017
6. Transfer hydrogenation over sodium-modified ceria: Enrichment of redox sites active for alcohol dehydrogenation
- Author
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Emily A. Smith, Igor I. Slowing, Pranjali Naik, Aaron J. Rossini, Nicholas C. Nelson, and Brett W. Boote
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integumentary system ,Chemistry ,Sodium ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Transfer hydrogenation ,01 natural sciences ,Redox ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Adsorption ,Phenol ,Dehydrogenation ,Physical and Theoretical Chemistry ,0210 nano-technology ,Palladium - Abstract
Ceria (CeO 2 ) and sodium-modified ceria (Ce-Na) were prepared through combustion synthesis. Palladium was deposited onto the supports (Pd/CeO 2 and Pd/Ce-Na) and their activity for the aqueous-phase transfer hydrogenation of phenol using 2-propanol under liquid flow conditions was studied. Pd/Ce-Na showed a marked increase (6×) in transfer hydrogenation activity over Pd/CeO 2 . Material characterization indicated that water-stable sodium species were not doped into the ceria lattice, but rather existed as subsurface carbonates. Modification of ceria by sodium provided more adsorption and redox active sites (i.e. defects) for 2-propanol dehydrogenation. This effect was an intrinsic property of the Ce-Na support and independent of Pd. The redox sites active for 2-propanol dehydrogenation were thermodynamically equivalent on both supports/catalysts. At high phenol concentrations, the reaction was limited by 2-propanol adsorption. Thus, the difference in catalytic activity was attributed to the different numbers of 2-propanol adsorption and redox active sites on each catalyst.
- Published
- 2017
7. Unveiling the Photo- and Thermal-Stability of Cesium Lead Halide Perovskite Nanocrystals
- Author
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Himashi P. Andaraarachchi, Kalyan Santra, Feng Zhu, Jingzhe Li, Bryan A. Rosales, Malinda D. Reichert, Jacob W. Petrich, Javier Vela, Brett W. Boote, Rafael Blome-Fernández, and Emily A. Smith
- Subjects
Thermogravimetric analysis ,Materials science ,Halide ,Crystal growth ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Nanocrystal ,Thermal stability ,Physical and Theoretical Chemistry ,0210 nano-technology ,Luminescence ,Single crystal ,Perovskite (structure) - Abstract
Lead halide perovskites possess unique characteristics that are well-suited for optoelectronic and energy capture devices, however, concerns about their long-term stability remain. Limited stability is often linked to the methylammonium cation, and all-inorganic CsPbX3 (X=Cl, Br, I) perovskite nanocrystals have been reported with improved stability. In this work, the photostability and thermal stability properties of CsPbX3 (X=Cl, Br, I) nanocrystals were investigated by means of electron microscopy, X-ray diffraction, thermogravimetric analysis coupled with FTIR (TGA-FTIR), ensemble and single particle spectral characterization. CsPbBr3 was found to be stable under 1-sun illumination for 16 h in ambient conditions, although single crystal luminescence analysis after illumination using a solar simulator indicates that the luminescence states are changing over time. CsPbBr3 was also stable to heating to 250 °C. Large CsPbI3 crystals (34±5 nm) were shown to be the least stable composition under the same conditions as both XRD reflections and Raman bands diminish under irradiation; and with heating the γ (black) phase reverts to the non-luminescent δ phase. Smaller CsPbI3 nanocrystals (14±2 nm) purified by a different washing strategy exhibited improved photostability with no evidence of crystal growth but were still thermally unstable. Both CsPbCl3 and CsPbBr3 show crystal growth under irradiation or heat, likely with a preferential orientation based on XRD patterns. TGA-FTIR revealed nanocrystal mass loss was only from liberation and subsequent degradation of surface ligands. Encapsulation or other protective strategies should be employed for long-term stability of these materials under conditions of high irradiance or temperature.
- Published
- 2019
8. Haploid differentiation in maize kernels based on fluorescence imaging
- Author
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Thomas Lübberstedt, Basil J. Nikolau, Gerald N. De La Fuente, Emily A. Smith, Daniel J. Freppon, and Brett W. Boote
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0106 biological sciences ,Genetics ,Fluorescence-lifetime imaging microscopy ,Sorting algorithm ,010401 analytical chemistry ,Sorting ,Plant Science ,Lower intensity ,Biology ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,Inbred strain ,Ploidy ,Biological system ,Agronomy and Crop Science ,Fluorescence response ,010606 plant biology & botany - Abstract
A new fluorescence-based method for inbred haploid differentiation in maize kernels was developed by utilizing the R1-nj colour marker in combination with fluorescence microspectroscopy and imaging. Seven inbred lines with varying R1-nj expression were used in this study. The fluorescence response of the diploid kernels at the embryonic dye spot was shown to simultaneously exhibit lower intensity and occur at a higher wavelength than the fluorescence of the dye-lacking haploid embryos. Intensity and area thresholds were applied to fluorescence images to sort the haploids from mixed sample populations, and sorting efficiencies of greater than 80% were achieved in all seven inbred lines (with values greater than 90% for five lines). The potential for high-throughput sorting when fluorescence imaging is combined with existing technologies for seed handling as well as high sorting efficiency may make fluorescence a viable and promising alternative to current sorting methods for some inbred lines.
- Published
- 2016
9. Multi-principal element transition metal dichalcogenides via reactive fusion of 3D-heterostructures
- Author
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Vitalij K. Pecharsky, Arjun K. Pathak, Emily A. Smith, Viktor P. Balema, Oleksandr Dolotko, Ihor Z. Hlova, and Brett W. Boote
- Subjects
Fusion ,Reaction mechanism ,Materials science ,Metals and Alloys ,Heterojunction ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Exfoliation joint ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Chemical engineering ,Transition metal ,Materials Chemistry ,Ceramics and Composites ,Principal element ,0210 nano-technology - Abstract
Transition metal dichalcogenides combining multiple principal elements in their structures are synthesized via mechanochemical exfoliation and spontaneous reassembly of binary precursors into 3D-heterostructures that are converted into single-phase layered materials by high-temperature reactive fusion. Physical and chemical events enabling these transformations are summarized in the form of a conceivable reaction mechanism.
- Published
- 2018
10. Silver–Gold Bimetallic Nanoparticles and Their Applications as Optical Materials
- Author
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Brett W. Boote, Hongsik Byun, and Jun-Hyun Kim
- Subjects
Silver ,Materials science ,Biomedical Engineering ,Metal Nanoparticles ,Nanoparticle ,Bioengineering ,Nanotechnology ,Spectrum Analysis, Raman ,symbols.namesake ,General Materials Science ,Particle Size ,Absorption (electromagnetic radiation) ,Bimetallic strip ,Equipment Design ,General Chemistry ,Surface Plasmon Resonance ,Chromophore ,Photothermal therapy ,Condensed Matter Physics ,Characterization (materials science) ,Equipment Failure Analysis ,Refractometry ,Photochemotherapy ,symbols ,Gold ,Crystallization ,Raman spectroscopy ,Visible spectrum - Abstract
Recently, nanoscale metallic particles have been studied extensively due to their tunable and strong optical properties that are well beyond those of organic chromophores. As monometallic nanoparticles have shown strong but narrow absorption bands within the ultraviolet and visible wavelengths, the preparation of bimetallic core-shell structures can give rise to strong, wide, and tunable absorption bands across the visible to near infrared areas. The silver-gold bimetallic nanoparticles with core-shell structures can offer unique physical and optical properties inaccessible to monometallic systems. These nanoparticles have been utilized in many areas of research including chemical catalysis, surface-enhanced Raman spectroscopy, and photothermal therapy. This review article is a comprehensive overview of bimetallic nanoparticle systems consisting of gold and silver; it is based on the recent advances in wet-chemical synthetic methodologies, the characterization of size and shape-dependent optical properties, and various optically driven applications including catalysis, signal-enhancing devices, and biomedical purposes.
- Published
- 2014
11. One-pot synthesis of various Ag–Au bimetallic nanoparticles with tunable absorption properties at room temperature
- Author
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Jun-Hyun Kim, Hongsik Byun, and Brett W. Boote
- Subjects
Materials science ,medicine.diagnostic_test ,Inorganic chemistry ,One-pot synthesis ,Shell (structure) ,Nanoparticle ,Silver nanoparticle ,Ion ,Inorganic Chemistry ,Spectrophotometry ,medicine ,General Materials Science ,Absorption (chemistry) ,Bimetallic strip - Abstract
This report describes the formation of gold-coated silver bimetallic nanoparticles prepared by the one-pot synthetic approach which involves the subsequent reduction of silver and gold ions at ambient conditions. The reduction of silver ions by excess L-ascorbic acid initially led to the formation of silver cores. This step was followed by the addition of gold ions into the preformed cores, resulting in the formation of silver-core gold-shell type bimetallic nanoparticles at room temperature. This process systematically allowed for the formation of various bimetallic nanoparticles which exhibited tunable absorption properties corresponding to the visible and near-IR regions. The thickness of the gold shells and the diameter of the silver-core nanoparticles were readily controlled; the morphological and structural properties of the resulting bimetallic nanoparticles were thoroughly analyzed by SEM/TEM, DLS, and UV–Vis spectrophotometry. The overall results demonstrated not only that these gold-coated silver nanoparticles were reliably prepared by our one-pot synthetic approach, but also that their optical properties were tunable in the visible and near-IR areas as a function of the core size and shell thickness.
- Published
- 2013
12. Sub-100 nm anisotropic gold nanoparticles as surface-enhanced Raman spectroscopy substrates
- Author
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Hongsik Byun, Brett W. Boote, Wongi Jang, Rafael Augusto Alves Ferreira, and Jun-Hyun Kim
- Subjects
Materials science ,Nanostructure ,Mechanical Engineering ,Nanoparticle ,Bioengineering ,Nanotechnology ,General Chemistry ,Substrate (electronics) ,Surface-enhanced Raman spectroscopy ,Ion ,symbols.namesake ,Chemical engineering ,Mechanics of Materials ,Colloidal gold ,symbols ,General Materials Science ,Electrical and Electronic Engineering ,Absorption (electromagnetic radiation) ,Raman spectroscopy - Abstract
This study describes a reliable preparation of relatively small Ag/Au-based anisotropic nanostructures possessing tunable absorption bands and their use as surface-enhanced Raman spectroscopy (SERS) substrates. These Au nanostructures were prepared via the seed growth process of small Ag-core-Au-shell-type nanoparticles that were obtained by the subsequent reduction of Ag and Au ions by NaBH(4) and L-ascorbic acid at room temperature. The presence of Ag during the transformation process of the Ag-Au core-shell nanoparticles under light irradiation led to the formation of various small anisotropic Au nanoparticles which clearly exhibited different structural and optical properties from those of nanoparticles prepared from typical Ag-Au alloy or bare Ag or Au seeds. As the optimal size of Au-based substrates for SERS applications was reported to be below 100 nm in diameter under a constant concentration, we tested our moderately small anisotropic nanoparticles (∼55 nm in diameter) as a SERS substrate to examine the signal enhancement of 4-nitrobenzenethiol. These nanoparticles exhibited a greatly increased SERS response compared to those of similar sizes of uniform Ag and Au nanoparticles, presumably because of the increased surface area due to the nanoparticles' anisotropic nature (i.e., chemical effect) and partial overlap of their absorption bands with the SERS excitation wavelength (i.e., electromagnetic effect). In addition, these nanoparticles have shown a suitable stability to prevent significant SERS signal fluctuations caused by unpredictable aggregations. Due to our simple synthetic and modification approaches, relatively small Au-based anisotropic nanostructures can be easily designed to serve as attractive SERS templates.
- Published
- 2015
13. Photothermally enhanced catalytic activity of partially aggregated gold nanoparticles
- Author
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Jun-Hyun Kim, Brian W Lavin, Brett W. Boote, and Julie A. Pham
- Subjects
Materials science ,Aqueous solution ,Energy conversion efficiency ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,Photochemistry ,Atomic and Molecular Physics, and Optics ,Catalysis ,Reaction rate ,Absorption band ,Colloidal gold ,Modeling and Simulation ,General Materials Science ,Irradiation ,Absorption (electromagnetic radiation) - Abstract
This report describes the catalytic reduction of 4-nitrophenol (4-NP) using gold nanoparticles (GNPs) in aqueous solution upon exposure to a solar-simulated light. As monodispersed GNPs possess a strong but narrow absorption band in the visible areas, anisotropic/partially aggregated GNPs are designed to have a strong and wide absorption band across visible to near-infrared wavelengths of light. Given their strong and broad absorption properties, these partially aggregated GNPs exhibited slightly superior photothermally induced heating of the reaction medium (i.e., water) when compared to the monodispersed GNPs upon exposure to a solar-simulated light. Subsequently, the catalytic reduction of 4-NP to 4-aminophenol was examined in the presence of various GNPs with and without the irradiation of light. While the monodispersed GNPs exhibited a moderate increase in the reaction rates of 4-NP with the light irradiation, the partially aggregated GNPs afforded the notable enhancement of the reaction rate, presumably due to their higher photon-to-heat conversion efficiency.
- Published
- 2012
14. Controlled synthesis of gold nanoparticles by fluorescent light irradiation
- Author
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Jun-Hyun Kim, Roarke D. Burnett, Brian W Lavin, and Brett W. Boote
- Subjects
Materials science ,Mechanical Engineering ,Analytical chemistry ,Nanoparticle ,Bioengineering ,General Chemistry ,Photochemistry ,chemistry.chemical_compound ,Dynamic light scattering ,chemistry ,Mechanics of Materials ,Transmission electron microscopy ,Colloidal gold ,General Materials Science ,Irradiation ,Electrical and Electronic Engineering ,Spectroscopy ,Absorption (electromagnetic radiation) ,Trisodium citrate - Abstract
A novel photochemical synthesis of size-controlled gold nanoparticles was reliably accomplished via both a direct reduction and a seeded-growth method at room temperature under the irradiation of fluorescent light. These methods utilized the intensity of fluorescent light that closely resembles daily sunlight (~100 mW cm − 2). This effectively allowed for the formation of gold nanoparticles with tunable sizes simply by controlling the concentration of trisodium citrate and gold chloride. The broad band fluorescent light was found to be an efficient source for inducing the formation of gold nanoparticles at ambient conditions. The size distribution and absorption property of the resulting nanoparticles were thoroughly characterized by scanning/transmission electron microscopy, dynamic light scattering, UV–visible spectroscopy and powder x-ray diffraction. This photochemical synthesis demonstrates, for the first time, the reliable preparation of gold nanoparticles at room temperature upon irradiation with fluorescent light.
- Published
- 2011
15. Rapid and facile synthesis of siliceous MCM-48 mesoporous materials
- Author
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Koodali T. Ranjit, Hariharaputhiran Subramanian, and Brett W. Boote
- Subjects
Mesoporous organosilica ,Materials science ,Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,Nanotechnology ,General Chemistry ,Mesoporous material ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
A rapid and facile synthesis of cubic MCM-48 mesoporous material based on the modification of Stober synthesis in as little time as 30 minutes at room temperature is reported in this communication.
- Published
- 2007
16. Thermally tunable catalytic and optical properties of gold–hydrogel nanocomposites
- Author
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Hongsik Byun, Julie A. Pham, Jun-Hyun Kim, Brett W. Boote, and Jiayun Hu
- Subjects
In situ ,Hot Temperature ,Materials science ,Macromolecular Substances ,Surface Properties ,Molecular Conformation ,Nanoparticle ,Bioengineering ,Lower critical solution temperature ,Catalysis ,Materials Testing ,Organic chemistry ,General Materials Science ,Irradiation ,Particle Size ,Electrical and Electronic Engineering ,chemistry.chemical_classification ,Mechanical Engineering ,Hydrogels ,Selective catalytic reduction ,General Chemistry ,Polymer ,Hydrogel nanocomposites ,Nanostructures ,Refractometry ,chemistry ,Chemical engineering ,Thermography ,Mechanics of Materials ,Colorimetry ,Gold - Abstract
We have developed a very simple approach for preparing physically embedded gold cores in a temperature-responsive hydrogel polymer nanoparticle under fluorescent light irradiation. The complete encapsulation of the multiple gold core nanoparticles is confirmed by the catalytic reduction of 4-nitrophenol, whose reactivity is significantly retarded above the lower critical solution temperature (LSCT) due to the deswelled polymer structure; its increased hydrophobicity slows the access of hydrophilic reactants to the cores. Since these gold cores are physically embedded in the polymer nanoparticles, further growth of the cores is reliably achieved in situ under light irradiation. Interestingly, the resulting composite nanoparticles exhibit reversible solution color changes as well as absorption bands from the visible to near-IR regions below and above the LSCT.
- Published
- 2012
17. Palladium nanoshells coated with self-assembled monolayers and their catalytic properties
- Author
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Joon Seo Park, T. Randall Lee, Jun-Hyun Kim, Hae-Won Chung, and Brett W. Boote
- Subjects
Materials science ,Scanning electron microscope ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,Infrared spectroscopy ,Self-assembled monolayer ,General Chemistry ,Nanoshell ,X-ray photoelectron spectroscopy ,Chemical engineering ,Suzuki reaction ,chemistry ,Monolayer ,Palladium - Abstract
This report describes the preparation and characterization of palladium nanoshells protected with alkanethiol self-assembled monolayers (SAMs) and their application as efficient catalysts. Monodispersed silica core particles (∼100 nm in diameter) were prepared and coated with a thin layer of palladium (∼20 nm in thickness). Subsequently, the palladium nanoshells were treated with two separate alkanethiol adsorbates having different alkyl chain lengths: dodecanethiol (C12SH) and hexadecanethiol (C16SH). The optical properties, morphology, and chemical structure/composition of these nanoshells were thoroughly examined by ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. Additional studies revealed that these SAM-coated palladium nanoshells possessed enhanced colloidal stability in nonpolar solvents and in the solid state. Further, palladium nanoshells modified with C16SH SAM coatings were employed in the Suzuki coupling of phenylboronic acid with iodobenzene in organic solvents. Notably, these SAM-coated nanoshells afforded a greater conversion yield than that of related bare palladium nanoshells.
- Published
- 2012
18. Sub-100 nm anisotropic gold nanoparticles as surface-enhanced Raman spectroscopy substrates.
- Author
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Brett W Boote, Rafael Augusto Alves Ferreira, Wongi Jang, Hongsik Byun, and Jun-Hyun Kim
- Subjects
- *
GOLD nanoparticles , *NANOPARTICLES , *SERS spectroscopy , *RAMAN spectroscopy , *SILVER - Abstract
This study describes a reliable preparation of relatively small Ag/Au-based anisotropic nanostructures possessing tunable absorption bands and their use as surface-enhanced Raman spectroscopy (SERS) substrates. These Au nanostructures were prepared via the seed growth process of small Ag-core–Au-shell-type nanoparticles that were obtained by the subsequent reduction of Ag and Au ions by NaBH4 and L-ascorbic acid at room temperature. The presence of Ag during the transformation process of the Ag–Au core–shell nanoparticles under light irradiation led to the formation of various small anisotropic Au nanoparticles which clearly exhibited different structural and optical properties from those of nanoparticles prepared from typical Ag–Au alloy or bare Ag or Au seeds. As the optimal size of Au-based substrates for SERS applications was reported to be below 100 nm in diameter under a constant concentration, we tested our moderately small anisotropic nanoparticles (∼55 nm in diameter) as a SERS substrate to examine the signal enhancement of 4-nitrobenzenethiol. These nanoparticles exhibited a greatly increased SERS response compared to those of similar sizes of uniform Ag and Au nanoparticles, presumably because of the increased surface area due to the nanoparticles’ anisotropic nature (i.e., chemical effect) and partial overlap of their absorption bands with the SERS excitation wavelength (i.e., electromagnetic effect). In addition, these nanoparticles have shown a suitable stability to prevent significant SERS signal fluctuations caused by unpredictable aggregations. Due to our simple synthetic and modification approaches, relatively small Au-based anisotropic nanostructures can be easily designed to serve as attractive SERS templates. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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