Insight into plasmonic hot-electron transfer and plasmon molecular drive: new dimensions in energy conversion and nanofabrication

Localized surface plasmon resonance (LSPR) of plasmonic nanoparticles and nanostructures has attracted wide attention because the nanoparticles exhibit a strong near-field enhancement through interaction with visible light, enabling subwavelength optics and sensing at the single-molecule level. The extremely fast LSPR decays have raised doubts that such nanoparticles have use in photochemistry and energy storage. Recent studies have demonstrated the capability of such plasmonic systems in producing LSPR-induced hot electrons that are useful in energy conversion and storage when combined with electron-accepting semiconductors. Due to the femtosecond timescale, hot-electron transfer is under intense investigation to promote ongoing applications in photovoltaics and photocatalysis. Concurrently, hot-electron decay results in photothermal responses or plasmonic heating. Importantly, this heating has received renewed interest in photothermal manipulation, despite the developments in optical manipulation using optical forces to move and position nanoparticles and molecules guided by plasmonic nanostructures. To realize plasmonic heating-based manipulation, photothermally generated flows, such as thermophoresis, the Marangoni effect and thermal convection, are exploited. Plasmon-enhanced optical tweezers together with plasmon-induced heating show potential as an ultimate bottom-up method for fabricating nanomaterials. We review recent progress in two fascinating areas: solar energy conversion through interfacial electron transfer in gold-semiconductor composite materials and plasmon-induced nanofabrication. Quantum-level interactions between light and metal nanoparticles could boost the efficiency of solar cells and be used for nanoengineering. A photon and numerous electrons on the surface of a metal can couple together to form a hybrid particle known as a plasmon. Akihiro Furube and Shuichi Hashimoto from Tokushima University review how plasmons can both improve solar energy conversion and provide a means of nanoscale engineering. When plasmons decay, they can create high-energy electrons. Furube and Hashimoto summarize how these ‘hot’ electrons broaden the range of wavelengths over which solar cells operate so that they absorb more light. They also review how researchers can harness the heat created by hot electrons to physically move DNA, proteins and other tiny objects, which will enable complex nanostructures to be constructed with a high level of precision. In this review, we highlight the recent progress in two rising areas: solar energy conversion through plasmon-assisted interfacial electron transfer and plasmonic nanofabrication. Localized surface plasmon resonance (LSPR) of plasmonic nanoparticles and nanostructures has attracted increasing attention because of their strong near-field enhancement by interacting with visible light. Recent studies have demonstrated the capability of such plasmonic systems in producing ‘LSPR-induced hot-electrons’ that are useful in photoenergy conversion and storage when combined with electron-accepting semiconductors. Concurrently, ‘hot-electron decay’ results in strong photothermal responses or plasmonic local heating. This heating has received renewed interest in photothermal manipulation of nanoparticles and molecules.