Silver Nanoparticles supported on Silica Nanospheres, CNTs and Graphene towards Light Harvesting

Abstract

Light harvesting is important for the function of volumetric heating of nanofluids, photosynthesis, solar cells, and thermo-photovoltaics. Therefore, exploring the operation of natural light-harvesting complexes provides an excellent platform for understanding how to amplify optical response to maximize the sunlight absorption using nanomaterials such as silver (Ag) nanoparticles(NPs) supported on silica nanospheres (SiO2 NSs) carbon nanotubes (CNTs), and CVD graphene. In order to maximize the utilization of energy harvested from sunlight it is of paramount importance to understand and improve; the controlled synthesis and the optical characterization of designed structure. The focus of the work is to design nanostructured materials for volumetric receiver and solar absorber. Therefore, Ag NPs@SiO2 complexes are synthesized using several methods and characterized for the broadband light absorption. FDTD (finite domain time difference) method has been used to study the optical properties as well as to investigate the structural effect on the localization of electromagnetic field towards amplifying the light absorption response. The results show the significant enhancement in SPR (surface plasmon resonance) absorption with the increase in Ag NPs density on the surface of SiO2 NSs. Moreover, Ag@SiO2 complexes are suspended in water for producing steam at high efficiencies upon solar illumination. Arrays of CNTs are grown in low pressure chemical vapor deposition (LPCVD) at different catalyst annealing time and growth pressure. Homogeneity and vertical alignment of as-grown SWCNTs arrays are optically studied using UV/Vis/NIR Spectrophotometer. Wavelength-independent and low reflectance are resulted from the growth of uniform arrays of CNTs. CVD graphene sandwiched in between thin film of Ag NPs can enhance broadband near infrared light absorption. Therefore, a continuous film of monolayer CVD graphene has been deposited on copper foil that is transferred via wet process in the fabrication of solar absorber. Broadband near infrared light absorption is a consequence of the resonant behavior of Ag NPs spaced by monolayer CVD graphene which strongly localizes the incident light at the interface. The hypothesis is substantiated by examining the plasmonic response of the Ag NPs film using both transfer matrix calculation and experimental characterization.

Date of Award	May 2017
Original language	American English