One of the most studied methods for producing hydrogen is photoelectrochemical (PEC) water splitting, which uses solar energy and semiconductors that are abundant in the Earth’s crust [1]. The efficiency of the H\(_{2}\) evolution process under solar illumination has been greatly enhanced using heterostructure photocatalysts made of semiconductor materials, coupled with plasmonic noble metal nanoparticles (NPs) carrying localized surface plasmon resonances (LSPR). The NPs expand the light optical wavelength absorption capacity of wide bandgap semiconductors through the excitations of the conduction band electrons at the metal-semiconductor interface. Additionally, periodic arrangements of NPs allow for guidance of 1\(^{st}\) order diffraction orders into the thin-film semiconductor, introducing guided modes, further enhancing light absorption characteristics. Achieving critical coupling between the LSPR of individual particles, in-plane propagation of diffraction orders and their sustainment through guided modes in the surrounding thin film media allows the steady state absorption to be maximized under energy conservation [2]. This work investigates the light trapping and extinction capacity of periodic Ag cuboctahedra/thin film TiO\(_{2}\) heterostructures through the experimental and computational evaluation (Fig. 1) of sustained hybrid plasmonic and photonic surface lattice resonances (SLRs), that show orders of magnitude stronger localized electromagnetic fields with respect to disordered arrangements of analogous particles [3]. 
HYBRID PLASMONIC-PHOTONIC MODES OF NANOPARTICLE ARRAYS IN HIGH REFRACTIVE INDEX THIN-FILM MEDIA
Klaudijus Midveris1, Gvidas Klyvis1, Mindaugas Juodenas1, Joel Henzie3, Tomas Klinavicius1, Andrius Vasiliauskas1, Asta Tamuleviciene1, 2, Tomas Tamulevicius1, 2
1 Institute of Materials Science, Kaunas University of Technology, Lithuania
2 Department of Physics, Kaunas University of Technology, Lithuania
3 Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Japan.
[1] ZHOU, Peng, NAVID, Ishtiaque Ahmed, MA, Yongjin, XIAO, Yixin, WANG, Ping, YE, Zhengwei, ZHOU, Baowen, SUN, Kai and MI, Zetian. Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting. Nature 2023.
[2] TSE, Joshua T. Y., MURAI, Shunsuke, TANAKA, Katsuhisa. Resonant Critical Coupling of Surface Lattice Resonances with a Fluorescent Absorptive Thin Film. J. Phys. Chem. C 2023.
[3] JUODENAS, Mindaugas, TAMULEVIČIUS, Tomas, HENZIE, Joel, ERTS, Donats and TAMULEVIČIUS, Sigitas. Surface Lattice Resonances in Self-Assembled Arrays of Monodisperse Ag Cuboctahedra. ACS Nano 2019.