Physical Study of the Primary and Secondary Photothermal Events in Gold/Cellulose Nanocrystals (AuNP/CNC) Nanocomposites Embedded in PVA Matrices

Inorganic/organic nanocomposites are a class of materials that have garnered a flurry of research because of their unusually independent tandem or synergistic physical and chemical properties. A unique class of nanocomposites has been prepared that is composed of tunable diameter (24-45 nm) gold nanoparticles (AuNPs) from cellulose nanocrystals (CNCs) by a one-step protocol at room temperature. The CNCs behave as reducing, capping, and stabilizing agents during the in situ synthesis. The morphology and diameter of the AuNPs were controlled by the number of CNCs. It was serendipitously discovered that the AuNPs displayed a photothermal effect upon laser irradiation at the AuNPs SPR frequency (532 nm). The as -generated AuNPs/CNC were blended as types of bifunctional nanofillers within a poly(vinyl alcohol) (PVA) film to provide a unique and desirable combination of high tensile strength and photothermal chemistry. The CNCs played a significant role in the AuNPs/CNC/PVA film by scattering incident light in the film as a secondary light source for AuNP absorbance. Remarkably, the photothermal efficiency of AuNPs in film improved similar to 50% because of CNC, a phenomenon that was enhanced by lower transparency CNCs (higher light scattering point sources).