Recent Development of Plasmonic Resonance-Based Photocatalysis and Photovoltaics for Solar Utilization

Wenguang Fan, Michael Leung
2016 Molecules  
Increasing utilization of solar energy is an effective strategy to tackle our energy and energy-related environmental issues. Both solar photocatalysis (PC) and solar photovoltaics (PV) have high potential to develop technologies of many practical applications. Substantial research efforts are devoted to enhancing visible light activation of the photoelectrocatalytic reactions by various modifications of nanostructured semiconductors. This review paper emphasizes the recent advancement in
more » ... dvancement in material modifications by means of the promising localized surface plasmonic resonance (LSPR) mechanisms. The principles of LSPR and its effects on the photonic efficiency of PV and PC are discussed here. Many research findings reveal the promise of Au and Ag plasmonic nanoparticles (NPs). Continual investigation for increasing the stability of the plasmonic NPs will be fruitful. Molecules 2016, 21, 180 2 of 26 positively-charged surface nuclei is present and induces collective oscillations of the charges in the particle, similar to an oscillating spring after stretch and release [13] . Such oscillations of electrons and electromagnetic fields are defined as localized surface plasmons. In the state of localized surface plasmonic resonance (LSPR) induced by radiation of a specific LSPR wavelength, the free electrons will oscillate with the maximum amplitude. LSPR is characterized by a build-up of intense, spatially non-homogeneous oscillating electrical fields in the vicinity of the nanostructure [20] . In such a way, the energy of the incident radiation is transferred to the plasmonic particles. The LSPR profile can be tuned by tailoring several parameters, such as nano-size, shape, interparticle distance and the nature of the surrounding medium [2] . The principles of the plasmonic resonance have been discussed in previous review papers [2, 13, [20] [21] [22] [27] [28] [29] [30] . Upon resonant excitation, the local electromagnetic field in the spatial region around the nanoparticle is intensified. The high-energy resonant state can decay in two possible forms: (1) either through re-emission (scattering) of photons or (2) the generation of energetic charge carriers, as shown in Figure 1a . These charge carriers can induce useful physical or chemical process or relax in the form of heat [21] . The functions of the plasmonic effect on photocatalysis and photovoltaics can be classified into the following three major aspects [31] . They are non-mutually exclusive; in other words, single or multiple mechanisms may contribute to the overall effect. Molecules 2016, 21, 180 2 of 25 and electromagnetic fields are defined as localized surface plasmons. In the state of localized surface plasmonic resonance (LSPR) induced by radiation of a specific LSPR wavelength, the free electrons will oscillate with the maximum amplitude. LSPR is characterized by a build-up of intense, spatially non-homogeneous oscillating electrical fields in the vicinity of the nanostructure [20] . In such a way, the energy of the incident radiation is transferred to the plasmonic particles. The LSPR profile can be tuned by tailoring several parameters, such as nano-size, shape, interparticle distance and the nature of the surrounding medium [2] . The principles of the plasmonic resonance have been discussed in previous review papers [2, 13, [20] [21] [22] [27] [28] [29] [30] . Upon resonant excitation, the local electromagnetic field in the spatial region around the nanoparticle is intensified. The high-energy resonant state can decay in two possible forms: (1) either through re-emission (scattering) of photons or (2) the generation of energetic charge carriers, as shown in Figure 1a . These charge carriers can induce useful physical or chemical process or relax in the form of heat [21] . The functions of the plasmonic effect on photocatalysis and photovoltaics can be classified into the following three major aspects [31] . They are non-mutually exclusive; in other words, single or multiple mechanisms may contribute to the overall effect. Figure 1. Plasmonic enhancement mechanisms. (a) High-energy resonant state decay in two possible forms: re-emission (scattering) of photons or the generation of energetic charge carriers; (b) scattering mechanism in which multiple reflections of light among nanocrystals prolong the mean photon path in plasmonic nanostructures and semiconductor composites; (c) excitation of electrons from occupied energy levels to a level above the Fermi energy; (d) hot electron overcoming the Schottky barrier and injected to the conduction band of the neighboring semiconductor; (e) optical simulations using finite-difference time-domain (FDTD) showing SPR-enhanced electric fields around photo-excited Au particles, permeating into a neighboring TiO2 structure; electric field intensity normalized by the light source intensity (|E| 2 /|E|0 2 ) shown by the color bar; (f) complementary energy transfer with plasmon-induced resonance energy transfer (PIRET) and Förster resonance energy transfer (FRET) in Au@SiO2@Cu2O. (a,c,d) Reproduced with permission [22].
doi:10.3390/molecules21020180 pmid:26848648 fatcat:in7tiu6ntbhktfue6fpemfv42u