title: Photo-formation of gold nanoparticles: photoacoustic studies on solid monoliths of Au(III)-chitosan-silica aerogels.
abstract: Photo-formation of gold nanoparticles in the solid monoliths of Au(III)-chitosan-silica aerogels with different Au/NH(2) molar ratios has been investigated using photoacoustic spectroscopy. Upon exposing to 320 nm UV light, a new absorption feature in the visible region around 525 nm could be seen due to the surface plasmon resonance of gold particles that are generated as a result of UV-induced reduction of Au(III) to Au(0). The plasmon band becomes stronger and shows saturation effects upon increasing the UV exposure time. A blue shift of about 7 nm is also noticed on exposing the sample (Au/NH(2)=1/5) for 6h, indicating a slight decrease in the nanoparticle size due to light-induced annealing with increasing the UV exposure time. The PA signals monitored as a function of chopping frequency show omega(-1) dependence, implying the thermally thin character of Au(III)-chitosan-silica aerogels.
authors.affiliation: Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424, USA. kuthirummaln@cofc.edu
authors.forename: Narayanan
authors.initials: N
authors.lastname: Kuthirummal
authors.forename: Adam
authors.initials: A
authors.lastname: Dean
authors.forename: Chunhua
authors.initials: C
authors.lastname: Yao
authors.forename: William
authors.initials: W
authors.lastname: Risen
mesh_terms: D000162:Acoustics; D048271:Chitosan / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008027:Light; D053758:Nanoparticles / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D020349:Surface Plasmon Resonance; D014466:Ultraviolet Rays
chemical_list: D006046:Gold; D012822:Silicon Dioxide; D048271:Chitosan