Synthesis of silver nanoparticles on a solid surface using a classical photographic method

A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.