Luminescence Studies of Individual Quantum Dot Photocatalysts

Amirav, Lilac; Alivisatos, A. Paul

doi:10.1021/ja404918z

Cited by 68 publications

(62 citation statements)

References 12 publications

(22 reference statements)

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“…This may indicate that electron-transfer rate is comparable to (or larger than) the kinetics limit of CO formation rate. For the case of Pt-decorated GaN, the diffusion of electrons to nanoparticles could be the rate-determining step due to the Coulomb repulsion induced by accumulated electrons on Pt nanoparticles 94 . Further investigation is required to determine the reaction pathway and the ratedetermine step.…”

Section: Resultsmentioning

confidence: 99%

Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

et al. 2015

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We report on the first demonstration of high-conversion-rate photochemical reduction of carbon dioxide (CO2) on gallium nitride (GaN) nanowire arrays into methane (CH4) and carbon monoxide (CO). It was observed that the reduction of CO2 to CO dominates on as-grown GaN nanowires under ultraviolet light irradiation. However, the production of CH4 is significantly increased by using the Rh/Cr2O3 core/shell cocatalyst, with an average rate of ∼3.5 μmol gcat –1 h–1 in 24 h. In this process, the rate of CO2 to CO conversion is suppressed by nearly an order of magnitude. The rate of photoreduction of CO2 to CH4 can be further enhanced and can reach ∼14.8 μmol gcat –1 h–1 by promoting Pt nanoparticles on the lateral m-plane surfaces of GaN nanowires, which is nearly an order of magnitude higher than that measured on as-grown GaN nanowire arrays. This work establishes the potential use of metal-nitride nanowire arrays as a highly efficient photocatalyst for the direct photoreduction of CO2 into chemical fuels. It also reveals the potential of engineered core/shell cocatalysts in improving the selectivity toward more valuable fuels.

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Section: Resultsmentioning

confidence: 99%

Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

et al. 2015

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“…53 This can also help answer a particular interesting question concerning the effect of Coulomb repulsion of the first electron on the second electron transfer step. 52,53 7. CdS−Pt AND CdSe/CdS−Pt NANORODS FOR LIGHT-DRIVEN H 2 GENERATION Despite near unity charge separation yields and long-lived charge-separated states of CdS−Pt and CdSe/CdS−Pt NRs, the best reported H 2 generation QY using these heterostructures is ∼20%.…”

Section: Charge Separation In Cds−pt and Cdse/cds−pt Hetero-nanorodsmentioning

confidence: 99%

Ultrafast Exciton Dynamics and Light-Driven H₂ Evolution in Colloidal Semiconductor Nanorods and Pt-Tipped Nanorods

2015

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Colloidal quantum confined one-dimensional (1D) semiconductor nanorods (NRs) and related semiconductor-metal heterostructures are promising new materials for efficient solar-to-fuel conversion because of their unique physical and chemical properties. NRs can simultaneously exhibit quantum confinement effects in the radial direction and bulk like carrier transport in the axial direction. The former implies that concepts well-established in zero-dimensional quantum dots, such as size-tunable energetics and wave function engineering through band alignment in heterostructures, can also be applied to NRs; while the latter endows NRs with fast carrier transport to achieve long distance charge separation. Selective growth of catalytic metallic nanoparticles, such as Pt, at the tips of NRs provides convenient routes to multicomponent heterostructures with photocatalytic capabilities and controllable charge separation distances. The design and optimization of such materials for efficient solar-to-fuel conversion require the understanding of exciton and charge carrier dynamics. In this Account, we summarize our recent studies of ultrafast charge separation and recombination kinetics and their effects on steady-state photocatalytic efficiencies of colloidal CdS and CdSe/CdS NRs and related NR-Pt heterostructures. After a brief introduction of their electronic structure, we discuss exciton dynamics of CdS NRs. By transient absorption and time-resolved photoluminescence decay, it is shown that although the conduction band electrons are long-lived, photogenerated holes in CdS NRs are trapped on an ultrafast time scale (∼0.7 ps), which forms localized excitons due to strong Coulomb interaction in 1D NRs. In quasi-type II CdSe/CdS dot-in-rod NRs, a large valence band offset drives the ultrafast localization of holes to the CdSe core, and the competition between this process and ultrafast hole trapping on a CdS rod leads to three types of exciton species with distinct spatial distributions. The effect of the exciton dynamics on photoreduction reactions is illustrated using methyl viologen (MV(2+)) as a model electron acceptor. The steady-state MV(2+) photoreduction quantum yield of CdSe/CdS dot-in-rod NRs approaches unity under rod excitation, much larger than CdSe QDs and CdSe/CdS core/shell QDs. Detailed time-resolved studies show that in quasi-type II CdSe/CdS NRs and type II ZnSe/CdS NRs strong quantum confinement in the radial direction facilitates fast electron transfer and hole removal, whereas the fast carrier mobility along the axial direction enables long distance charge separation and slow charge recombination, which is essential for efficient MV(2+) photoreduction. The NR/MV(2+) relay system can be coupled to Pt nanoparticles in solution for light-driven H2 generation. Alternatively, Pt-tipped CdS and CdSe/CdS NRs provide fully integrated all inorganic systems for light-driven H2 generation. In CdS-Pt and CdSe/CdS-Pt hetero-NRs, ultrafast hole trapping on the CdS rod surface or in CdSe core enables efficient electron ...

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“…C ombining multiple components within individual nanoparticles (NPs) is a simple way to control chemical and physical properties at the nanoscale to obtain efficient catalysts and advanced energy-conversion and storage systems [1][2][3][4][5][6][7][8][9] . A broad range of heterostructures at the nanoscale that combine different constituents, such as metals, metal oxides and semiconductors, can be obtained through wet chemistry approaches as a result of the nucleation and growth of the overgrowth phase on the preformed seed NPs (refs [10][11][12][13].…”

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confidence: 99%

Heterogeneous nucleation and shape transformation of multicomponent metallic nanostructures

et al. 2014

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To be able to control the functions of engineered multicomponent nanomaterials, a detailed understanding of heterogeneous nucleation at the nanoscale is essential. Here, by using in situ synchrotron X-ray scattering, we show that in the heterogeneous nucleation and growth of Au on Pt or Pt-alloy seeds the heteroepitaxial growth of the Au shell exerts high stress (∼2 GPa) on the seed by forming a core/shell structure in the early stage of the reaction. The development of lattice strain and subsequent strain relaxation, which we show using atomic-resolution transmission electron microscopy to occur through the slip of {111} layers, induces morphological changes from a core/shell to a dumbbell structure, and governs the nucleation and growth kinetics. We also propose a thermodynamic model for the nucleation and growth of dumbbell metallic heteronanostructures.

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Luminescence Studies of Individual Quantum Dot Photocatalysts

Cited by 68 publications

References 12 publications

Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

Ultrafast Exciton Dynamics and Light-Driven H₂ Evolution in Colloidal Semiconductor Nanorods and Pt-Tipped Nanorods

Heterogeneous nucleation and shape transformation of multicomponent metallic nanostructures

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Luminescence Studies of Individual Quantum Dot Photocatalysts

Cited by 68 publications

References 12 publications

Wafer-Level Artificial Photosynthesis for CO2 Reduction into CH4 and CO Using GaN Nanowires

Wafer-Level Artificial Photosynthesis for CO2 Reduction into CH4 and CO Using GaN Nanowires

Ultrafast Exciton Dynamics and Light-Driven H2 Evolution in Colloidal Semiconductor Nanorods and Pt-Tipped Nanorods

Heterogeneous nucleation and shape transformation of multicomponent metallic nanostructures

Contact Info

Product

Resources

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Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

Wafer-Level Artificial Photosynthesis for CO₂ Reduction into CH₄ and CO Using GaN Nanowires

Ultrafast Exciton Dynamics and Light-Driven H₂ Evolution in Colloidal Semiconductor Nanorods and Pt-Tipped Nanorods