Reductant-assisted synthesis, characterization and photovoltaic characteristics of ligand-protected gold nanoparticles

Metal clusters (CLs) and nanoparticles (NPs) are promising on account of their unique properties which cannot be achieved from their bulk counterparts. Discrete electronic excitations in metal CLs and the characteristic surface plasmon resonance (SPR) phenomenon in metal NPs make them optically attractive and versatile photosensitizers in photovoltaic (PV) applications. A visible-light driven photoelectrochemical (PCE) response of a plasmonic sensitizer in a metal NP/semiconductor composite assembly can be tuned with plasmonic metal NP sizes. Therefore, it is highly desirable to explore the PEC response of a plasmonic sensitizer as a function of its NP size. In this work, a study focusing on the PEC performance of a plasmonic sensitizer as a function of its NP size has been realized through synthesizing a series of ligand-protected Au NPs at ambient conditions using various reductants, since each reductant in coordination with the ligand forms metal ion complexes which influence the reduction potentials of metals through variation in the pH of the system, and ultimately, these changes affect the reaction dynamics and tune the NP sizes and morphology. A superior PEC response of glucose-assisted synthesis of Au NPs in NP sensitized solar cells (NPSCs) with power conversion efficiency greater than 1.5% has been observed, and attributed to the relatively fine NP sizes and uniform distribution on TiO2 photoanodes. It is expected that our study will assist in exploration of different sized Au NPs in diverse applications.