Localized surface plasmon resonance (LSPR)-induced hot-carrier transfer is a key mechanism for achieving artificial photosynthesis using the whole solar spectrum, even including the infrared (IR) region. In contrast to the explosive development of photocatalysts based on the plasmon-induced hot electron transfer, the hole transfer system is still quite immature regardless of its importance, because the mechanism of plasmon-induced hole transfer has remained unclear. Herein, we elucidate LSPR-induced hot hole transfer in CdS/CuS heterostructured nanocrystals (HNCs) using time-resolved IR (TR-IR) spectroscopy. TR-IR spectroscopy enables the direct observation of carrier in a LSPR-excited CdS/CuS HNC. The spectroscopic results provide insight into the novel hole transfer mechanism, named plasmon-induced transit carrier transfer (PITCT), with high quantum yields (19%) and long-lived charge separations (9.2 μs). As an ultrafast charge recombination is a major drawback of all plasmonic energy conversion systems, we anticipate that PITCT will break the limit of conventional plasmon-induced energy conversion.
A black Ti 3+ -doped single-crystal TiO 2 (Ti 3+ /TiO 2 ) was one-pot synthesized by treating metal Ti in an ionic liquid containing LiAc and HAc under mild ionothermal conditions. The ionic liquid(1-methyl-imidazolium tetrafluoroborate) supplied an environment enriched with fluoride ions for dissolving titanium foil at ionothermal condition, followed by reducing protons in acetic acid to form Ti 3+ ions, leading to Ti 3+ -doped single-crystal TiO 2 in black powder. EPR and XPS results indicated the high-concentrations of both Ti 3+ -dopants and oxygen vacancies. The Ti 3+ incorporated into TiO 2 lattice could narrow the energy band gap of TiO 2 via forming intermediate energy levels, leading to the visible photocatalyst. Meanwhile, the oxygen vacancies could inhibit the photoelectron-hole recombination. As expected, such a black Ti 3+ /TiO 2 exhibited high activity in photocatalytic degradation of organic pollutants and water splitting for H 2 production under irradiation with visible lights and/or simulated solar lights.
Infrared (IR) light represents an untapped energy source accounting for almost half of all solar energy. Thus, there is a need to develop systems to convert IR light to fuel and make full use of this plentiful resource. Herein, we report photocatalytic H 2 evolution driven by near-to shortwave-IR light (up to 2500 nm) irradiation, based on novel CdS/Cu 7 S 4 heterostructured nanocrystals. The apparent quantum yield reached 3.8% at 1100 nm, which exceeds the highest efficiencies achieved by IR light energy conversion systems reported to date. Spectroscopic results revealed that plasmon-induced hotelectron injection at p−n heterojunctions realizes exceptionally long-lived charge separation (>273 μs), which results in efficient IR light to hydrogen conversion. These results pave the way for the exploration of undeveloped low-energy light for solar fuel generation.
Pt-doped mesoporous Ti self-doped TiO (Pt-Ti/TiO) is in situ synthesized via an ionothermal route, by treating metallic Ti in an ionic liquid containing LiOAc, HOAc, and a HPtCl aqueous solution under mild ionothermal conditions. Such Ti-enriched environment, as well as oxygen vacancies, is proven to be effective for allowing the in situ reduction of Pt ions uniformly located in the framework of the TiO bulk. The photocatalytic H evolution of Pt-Ti/TiO is significantly higher than that of the photoreduced Pt loaded on the original TiO and commercial P25. Such greatly enhanced activity is due to the various valence states of Pt (Pt, n = 0, 2, or 3), forming Pt-O bonds embedded in the framework of TiO and ultrafine Pt metal nanoparticles on the surface of TiO. Such Pt-O bonds could act as the bridges for facilitating the photogenerated electron transfer from the bulk to the surface of TiO with a higher electron carrier density (3.11 × 10 cm), about 2.5 times that (1.25 × 10 cm) of the photoreduced Pt-Ti/TiO sample. Thus, more photogenerated electrons could reach the Pt metal for reducing protons to H.
The surface plasmon resonance (SPR) properties in the
deep-ultraviolet
(UV) to blue-light region of Al and Alcore/Al2O3shell in spherical and cylindrical nanostructures have
been investigated using the discrete dipole approximation method.
Simulation results show that the extremely short resonance wavelength
of the Al nanostructures means the SPR is highly sensitive to the
particle size and results in significant phase retardation and multipole
resonance. Cylindrical Al nanoparticles show multipole resonance peaks
with extremely strong intensity and narrow widths that are blue-shifted
and then red-shifted with an increase in the cylinder length. An expression
of the SPR peak wavelength, λmax, is derived and
related to the peak shift. Cylindrical Alcore/Al2O3shell nanostructures are shown to modulate the SPR through
changes to the aspect ratio and Al2O3 shell
thickness. The results will assist greatly in modulating or optimizing
SPR in the deep-UV to blue-light region for multimode optical filter,
enhanced spectroscopy, optical lithography, and waveguide applications.
A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs.
Fullerene (C60) enhanced mesoporous CdS/TiO2 architectures were fabricated by an evaporation induced self-assembly route together with an ion-exchanged method. C60 clusters were incorporated into the pore wall of mesoporous CdS/TiO2 with the formation of C60 enhanced CdS/TiO2 hybrid architectures, for achieving the enhanced photostability and photocatalytic activity in H2 evolution under visible-light irradiation. Such greatly enhanced photocatalytic performance and photostability could be due to the strong combination and heterojunctions between C60 and CdS/TiO2. The as-formed C60 cluster protection layers in the CdS/TiO2 framework not only improve the light absorption capability, but also greatly accelerated the photogenerated electron transfer to C60 clusters for H2 evolution.
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