Many techniques have been employed for fabrication of flexible and transparent SERS substrates, which have been widely used in real applications and fundamental studies.

Plasmonic nanostructures have been widely used for photochemical conversions due to their unique and easy-tuning optical properties in visible and near-infrared range. Compared with the plasmon-generated hot electrons, the hot holes usually have a shorter lifetime, which makes them more difficult to drive redox reactions. This review focuses on the photochemistry driven by the plasmon-generated hot holes. First, we discuss the generation and energy distribution of the plasmon-generated hot carriers, especially hot holes. Then, the dynamics of the hot holes are discussed at the interface between plasmonic metal and semiconductor or adsorbed molecules. Afterwards, the utilization of these hot holes in redox reactions is reviewed on the plasmon-semiconductor heterostructures as well as on the surface of the molecule-adsorbed plasmonic metals. Finally, the remaining challenges and future perspectives in this field are presented. This review will be helpful for further improving the efficiency of the photochemical reactions involving the plasmon-generated hot holes and expanding the applications of these hot holes in varieties of chemical reactions, especially the ones with high conversion rate and selectivity.

The creation of crystal phase heterostructures of transition metal chalcogenides, e.g., the 1T/2H heterostructures, has led to the formation of metal/semiconductor junctions with low potential barriers. Very differently, post-transition metal chalcogenides are semiconductors regardless of their phases. Herein, we report, based on experimental and simulation results, that alloying between 1T-SnS2 and 1T-WS2 induces a charge redistribution in Sn and W to realize metallic Sn0.5W0.5S2 nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS2 nanoplates to form vertical heterostructures. The ohmic-like contact formed at the Sn0.5W0.5S2/SnS2 heterointerface affords rapid transport of charge carriers, and allows for the fabrication of fast photodetectors. Such facile charge transfer, combined with a high surface affinity for acetone molecules, further enables their use as highly selective 100 ppb level acetone sensors. Our work suggests that combining compositional and structural control in solution-phase epitaxy holds promises for solution-processible thin-film optoelectronics and sensors.

The reaction efficiency of reactants near plasmonic nanostructures can be enhanced significantly because of plasmonic effects. Herein, we propose that the catalytic activity of molecular catalysts near plasmonic nanostructures may also be enhanced dramatically. Based on this proposal, we develop a highly efficient and stable photocatalytic system for the hydrogen evolution reaction (HER) by compositing a molecular catalyst of cobalt porphyrin together with plasmonic gold nanoparticles, around which plasmonic effects of localized electromagnetic field, local heating, and enhanced hot carrier excitation exist. After optimization, the HER rate and turn-over frequency (TOF) reach 3.21 mol g−1 h−1 and 4650 h−1, respectively. In addition, the catalytic system remains stable after 45-hour catalytic cycles, and the system is catalytically stable after being illuminated for two weeks. The enhanced reaction efficiency is attributed to the excitation of localized surface plasmon resonance, particularly plasmon-generated hot carriers. These findings may pave a new and convenient way for developing plasmon-based photocatalysts with high efficiency and stability.

A surface plasmon can drive many photochemical reactions, in which effective charge separation and migration is a key. In analogy to the plasmon–semiconductor interface, the plasmon–molecule interface may also be used to improve the separation and migration of hot carriers. In this work, by using in situ Raman spectroscopy, molecular grafting on silver nanostructures is found essential for modulating the charge separation and p-aminothiophenol (PATP) oxidation reaction. When the LUMO of the grafted molecules match well the energy distribution of the plasmon-generated hot electrons, the PATP oxidation process accelerates significantly. Moreover, compared with symmetrical grafting, asymmetrical grafting is more effective in regulating the charge separation and plasmon-mediated chemical reaction. This work provides an effective strategy for deep understanding and fine modulation of plasmon-mediated photochemistry.