Theoretical Design and Experimental Realization of Quasi-Single Electron Enhancement in Plasmonic Catalysis (original) (raw)
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Layer‐by‐layer photocatalyst films made of TiO2 nanoparticles (TiO2NP) assembled with both poly(sodium 4‐styrenesulfonate) (PSS) and graphene oxide (GO) are used for the photodeposition of plasmonic Ag nanoparticles (AgNPs) and subsequently used in surface‐enhanced Raman scattering (SERS). Both photocatalyst films, TiO2NP/PSS and TiO2NP/GO, are capable of driving the formation of AgNP when they are wetted with a drop of AgNO3 diluted solution and submitted to UV irradiation (254 nm). The photodeposition of AgNP, as monitored by UV–vis spectroscopy, follows a first‐order kinetics process in both films and is slightly faster in the TiO2NP/PSS. In addition, scanning electron microscopy reveals that in the TiO2NP/PSS film, the photodeposited AgNPs are larger and isolated, whereas in the TiO2NP/GO film, they are smaller and highly interconnected. The SERS activity of the substrates is evaluated with rhodamine B. When samples are excited in resonance with rhodamine B absorption (514 nm), ...
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Physical chemistry chemical physics : PCCP, 2018
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The Journal of Physical Chemistry C, 2014
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Electro-catalytic properties of graphene composites containing gold or silver nanoparticles
Electrochimica Acta, 2013
Composite nanostructures based on few-layers graphene with encased gold or silver nanoparticles (denoted as Gr-Au and Gr-Ag, respectively) were separately prepared in a single-step synthesis by radio frequency catalytic chemical vapor deposition (RF-cCVD) over Au x /MgO and Ag x /MgO catalytic system (where x = 3 wt.%), respectively. Their morphological properties were investigated by electron microscopy techniques (TEM/HRTEM), which demonstrated that the number of graphitic layers within the sheet varied between 2 and 7. Thorough TEM analysis also indicated that gold nanoparticles had a mean size of 22 nm, while silver nanoparticles were found to be larger with a mean size of 35 nm. X-ray powder diffraction proved that the crystallinity of the Gr-Au or Gr-Ag samples is less influenced by the type of metallic nanoparticles (silver or gold) encased between the graphitic layers. The mean value of the crystalline domain perpendicular to graphene (0 0 2) crystallographic plane was determined to be approximately 2.25 nm (for Gr-Au sample) and 2.14 nm (for Gr-Ag sample), both corresponding to 6 graphitic layers. Gr-Ag and Gr-Au nanostructures were used to modify platinum substrates and subsequently employed for the electrochemical analysis of carbamazepine. A significant decrease in the electrochemical oxidation potential of carbamazepine (150 mV) was obtained with both modified electrodes. The detection limit (DL) was found to be 2.75 × 10 −5 M and 2.92 × 10 −5 M for the Pt/Gr-Ag and Pt/Gr-Au electrode, respectively.
ACS Applied Materials & Interfaces, 2019
Selective chemical control of multiple reactions is incredibly important for the fabrication of sophisticated nanostructures for functional applications. A representative example is the synthesis of plasmonic nanomaterial−silver chloride (AgCl) conjugates, where metal ions should be selectively reduced into metallic nanostructures for plasmon-enhanced catalytic activity, while the reducible AgCl nanomaterials remain intact despite the presence of a chemical reductant. In addition to the selectively controlled reduction, the plasmonic nanostructures should be appropriately designed for the high stability and photoefficiency of catalysts. In this study, we demonstrate how AgCl nanocubes and nanospheres could be comprehensively wrapped by plasmonic three-dimensional nanomesh structures consisting of gold, silver, and palladium by the selective reduction of their ionic precursors while the AgCl nanostructures remain intact. Complete trimetallic wrapping provided the absorption of visible light, while the porosity of the nanomesh structures exposed the photocatalytic AgCl surface to catalyze desired reactions. Platinum in place of palladium was examined to demonstrate the versatility of the wrapping scheme, resulting in an extraordinary catalytic activity. Importantly, the detailed chemical mechanism behind the trimetallic wrapping of the AgCl nanostructures was systematically investigated to understand the roles of each reaction component in controlling the chemical selectivity. The synthesized AgCl−trimetal nanoconjugates excellently exhibit both metal-based and plasmon-enhanced catalytic properties for the removal of environmentally harmful Cr 6+. Moreover, their applications as surface-enhanced Raman-scattering (SERS) probes for the in situ monitoring of catalytic reduction in real-time and as single-nanoparticle SERS probes for molecular detection are thoroughly demonstrated.
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The localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles has been used to accelerate several catalytic transformations under visiblelight irradiation. In order to fully harness the potential of plasmonic catalysis, multimetallic nanoparticles containing a plasmonic and a catalytic component, where LSPR-excited energetic charge carriers and the intrinsic catalytic active sites work synergistically, have raised increased attention. Despite several exciting studies observing rate enhancements, controlling reaction selectivity remains very challenging. Here, by employing multimetallic nanoparticles combining Au, Ag, and Pt in an Au@Ag@Pt core− shell and an Au@AgPt nanorattle architectures, we demonstrate that reaction selectivity of a sequential reaction can be controlled under visible light illumination. The control of the reaction selectivity in plasmonic catalysis was demonstrated for the hydrogenation of phenylacetylene as a model transformation. We have found that the localized interaction between the triple bond in phenylacetylene and the Pt nanoparticle surface enables selective hydrogenation of the triple bond (relative to the double bond in styrene) under visible light illumination. Atomistic calculations show that the enhanced selectivity toward the partial hydrogenation product is driven by distinct adsorption configurations and charge delocalization of the reactant and the reaction intermediate at the catalyst surface. We believe these results will contribute to the use of plasmonic catalysis to drive and control a wealth of selective molecular transformations under ecofriendly conditions and visible light illumination.
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Abstract TiO2 nanopowder (P25) is the commonly used commercial photocatalyst. However, because only a small ultraviolet portion of solar spectrum can excite the electron-hole pairs and their recombination rate is high, its efficiency is limited. In this study, we proposed silver nanostructures and reduced graphene oxide (RGO) to construct ternary plasmonic catalyst to improve the catalytic performance of TiO2. We prepared three different geometries of Ag nanostructures including sphere, decahedron and prism. While the incorporated Ag nanostructures led to an increase in light absorption due to localized surface plasmon resonance (LSPR), the RGO inhibited the charge recombination and enhanced the electron-hole separation. The finite-difference time-domain method was adopted to simulate the electric field intensity distributions in the three different geometries of Ag nanoparticles irradiated by the florescent lamp to verify the corresponding LSPR effects. Both Ag nanodecahedrons/P25/RGO and Ag nanoprisms/P25/RGO hybrid photocatalysts possessed remarkable photocatalytic activity, which decolorized the dyes up to 80% under white light irradiation for only 1 h and displayed over 8 times higher photocatalytic efficiency than P25 photocatalyst.