The change of photon statistics in the fluorescence of a single CdSe/ZnS core/shell colloidal nanocrystal quantum dot (NQD) accompanying the atomic force microscopy (AFM) manipulation of a cubic Au ...nanoparticle (AuCube) was investigated to elucidate the effect of plasmonic nanostructures on the multiexciton dynamics of the NQD. Upon coupling to an AuCube of a well-defined size and shape, we directly observed the conversion of a single-photon emission from an individual NQD to a multiphoton emission, and this was accompanied by an increase in fluorescence intensity and a reduction in fluorescence lifetime. The multiphoton emission then returned to a single-photon emission upon separating the AuCube from the single NQD. The efficiency of the multiphoton emission was enhanced 6.9 times through the use of the AuCube. The enhancement of the multiphoton emission was attributable mainly to the augmentation of the biexciton emission rate. These results provide evidence that quantum dot photon statistics can be manipulated by plasmonic nanostructures, and NQD-plasmonic nanostructure systems can be desirable for many technological applications.
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Alkaline salt of platinum‐incorporated heteropolyoxoniobate Pt(Nb6O19)212− (Pt(Nb6)2) was fabricated and applied for N‐formylation of various amines including piperidine under CO2 and H2 atmosphere. ...Pt(Nb6)2 achieved the selective formation of 1‐formylpiperidine, whereas the absence of Pt species, H2, and CO2 resulted in a trace amount of the product. The structural characterization revealed that the sandwich‐type structure of Pt(Nb6)2 was transformed into Pt nanoparticles incorporated with polyoxoniobates (Nb6O198−) on the NbOx bulk matrix (NbPOM‐PtNPs/NbOx) under reaction conditions. The N‐formylation of amines in the presence of CO2 and H2 proceeded by the bifunctional NbPOM‐PtNPs/NbOx where the basic sites of Nb6O198− and the redox property of Pt promoted the generation of formamides.
The catalytic properties of alkaline salts of sandwich‐type Pt(Nb6O19)212− ((Pt(Nb6)2) were elucidated by N‐formylation of amines under CO2 and H2, which resulted in highly selective formamides. After reactions, a formation of Pt nanoparticles and incorporated with Nb6O198− clusters on NbOx support (NbPOM‐PtNPs/NbOx) occurred, which acted as the bifunctional catalyst for N‐formylation of amines using CO2 as a carbonyl source.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Rhombic Coulomb diamonds are clearly observed in a chemically anchored Au nanoparticle single-electron transistor. The stability diagrams show stable Coulomb blockade phenomena and agree with the ...theoretical curve calculated using the orthodox model. The resistances and capacitances of the double-barrier tunneling junctions between the source electrode and the Au core (
R
1
and
C
1
, respectively), and those between the Au core and the drain electrode (
R
2
and
C
2
, respectively), are evaluated as 4.5 MΩ, 1.4 aF, 4.8 MΩ, and 1.3 aF, respectively. This is determined by fitting the theoretical curve against the experimental Coulomb staircases. Two-methylene-group short octanedithiols (C8S2) in a C8S2/hexanethiol (C6S) mixed self-assembled monolayer is concluded to chemically anchor the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes even when the Au nanoparticle is protected by decanethiol (C10S). This is because the
R
1
value is identical to that of
R
2
and corresponds to the tunneling resistances of the octanedithiol chemically bonded with the Au core and the Au electrodes. The dependence of the Coulomb diamond shapes on the tunneling resistance ratio (
R
1
/
R
2
) is also discussed, especially in the case of the rhombic Coulomb diamonds. Rhombic Coulomb diamonds result from chemical anchoring of the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes.
Rhombic Coulomb diamonds in a single-electron transistor based on an Au nanoparticle chemically anchored by two-methylene-group short alkanedithiols at both ends.
A simple method is proposed to control the size of alkanethiol-protected Au nanoparticles by heat treatment in the solid state. The mean diameter of the Au nanoparticles prepared by Brust's two-phase ...method (∼1.5 nm) was evolved to 3.4−9.7 nm by heating to 150−250 °C in air. The uniform growth of nanoparticles was not observed when tetraoctylammonium bromide (TOAB), which was used as a phase-transfer agent during the preparation of Au nanoparticles, was removed before the particle growth process. The crystal structures of Au nanoparticles and alkanethiol ligand structures on Au nanoparticles were characterized before and after the heat treatment. The size-evolution mechanism was discussed on the basis of the thermodynamic model. The heat-treated Au nanoparticles easily formed self-assembled 2D superlattices with hexagonal packing, where the alkanethiol protective agents with an all-trans conformation were estimated to interpenetrate each other.
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Photocatalytic conversion of solar energy to chemical energy is an efficient process in green chemistry because it facilitates room temperature chemical transformations by generating electronically ...excited states in photocatalysts. We report here on the robust synthesis, detailed structural characterization, and especially photocatalytic properties of plasmonic Pd hexagonal nanoplates for chemical reactions. The Pd hexagonal nanoplates are twin crystals, and composed of the top and bottom faces enclosed by the {111} planes with stacking faults and the side surfaces bound by mixed six {111} and six {100} planes. The Pd hexagonal nanoplates with well-defined and tunable longitudinal localized surface plasmon resonance (LSPR) have enabled the direct harvesting of visible to near-infrared light for catalytic cross coupling reactions. Upon plasmon excitation, the catalytic Suzuki coupling reactions of iodobenzene and phenylboronic acid accelerate by a plasmonic photocatalytic effect of plasmon induced hot electrons. The turnover frequency (TOF) of the Pd hexagonal nanoplates in a reaction illuminated with a λ = 300-1000 nm Xenon lamp at 176 mW cm(-2) was 2.5 and 2.7 times higher than that of non-plasmonic {111}-enclosed Pd nanooctahedra and {100}-enclosed Pd nanocubes, respectively, and 1.7 times higher than the TOF obtained when the reaction was thermally heated to the same temperature.
Efficient, robust and environmentally friendly cocatalysts for photocatalysts are important for large-scale solar hydrogen production. Herein, we demonstrate that a Rh-Zr mixed oxide is an efficient ...cocatalyst for hydrogen evolution. Impregnation of Zr and Rh precursors (Zr/Rh = 5 wt/wt%) formed RhZrO
x
cocatalyst particles on Al-doped SrTiO
3
, which exhibited 31× higher photocatalytic water-splitting activity than a RhO
x
cocatalyst. X-ray photoelectron spectroscopy proved that the dissociation of Cl
−
ions from preformed Rh-Cl-Zr-O solid led to formation of the active phase of RhZrO
x
, in which the Zr/Rh ratio was critical to high catalytic activity. Additional CoO
x
loading as an oxygen evolution cocatalyst further improved the activity by 120%, resulting in an apparent quantum yield of 33 (±4)% at 365 nm and a long durability of 60 h. Our discovery could help scale up photocatalytic hydrogen production.
An efficient, robust and environmentally friendly Rh-Zr mixed oxide formed though the activation of Rh-Cl-Zr-O solid efficiently functions as a HER cocatalyst on Al-doped SrTiO
3
.
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Charge separation in semiconducting materials is an essential process that determines the efficiency of photovoltaic devices and photocatalysts. Herein, we report the charge-separation dynamics in ...type-II CdS/CdTe heterostructured nanorods revealed by femtosecond transient-absorption (TA) measurements with a broad-band white-light probe. Under selective excitation of the CdTe segment, bleaching signals at the band gap energy of CdS were clearly observed with a rise component on a subpicosecond time scale, which indicates efficient electron transfer from CdTe to CdS. The pump-energy dependence of the TA dynamics shows that hot electrons rapidly relax to the bottom of the conduction band of CdTe, and then the electrons transfer to the CdS segment.
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The original version of this Article omitted the fourth author Taizo Yoshinaga, who is from the 'Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Japan'. ...Consequently, the third sentence of the Author Contributions, 'M.S. and M.K. synthesized the ITO NCs and ITO/semiconductor oxides' was revised to 'M.S., M.K. and T.Y. synthesized the ITO NCs and ITO/semiconductor oxides'. This has been corrected in both the PDF and HTML versions of the Article.
The high overpotential of the oxygen evolution reaction is a critical issue to be overcome to realize efficient overall water splitting and enable hydrogen generation powered by sunlight. Homogeneous ...and stable nanoparticles (NPs) dispersed in solvents are useful as both electrocatalysts and cocatalysts of photocatalysts for the electro- and photo-catalytic oxygen evolution reaction, respectively, through their adsorption on various electrode substrates. Here, phase-segregated NiPx@FePyOz core@shell NPs are selectively synthesized by the reaction of Fe(CO)5 with amorphous NiPx seed-NPs. The NiPx@FePyOz NPs on conductive substrates exhibit higher electrocatalytic activity in the oxygen evolution reaction than those of other metal phosphide-based catalysts. The NiPx@FePyOz NPs can also be used as a cocatalyst of an anodic BiVO4 photocatalyst to boost the photocatalytic water oxidation reaction. The excellent catalytic activity and high stability of the NiPx@FePyOz NPs without any post-treatments are derived from in situ activation through both the structural transformation of NiPx@FePyOz into mixed hydroxide species, (Ni, Fe)OxHy, and the spontaneous removal of the insulating organic ligands from NPs to form a smooth and robust (Ni, Fe)OxHy/substrate heterointerface during the oxygen evolution reaction.
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