Growth and morphology control of silver halide nanoparticles in templated Ag(I)-coordinated Langmuir-Schaefer films

Growth and morphology control of silver halide nanoparticles in templated organized molecular films have been investigated. Instead of using conventional Langmuir-Blodgett (LB) films, in this paper silver (I) coordinated Langmuir-Schaefer (LS) films of coumarin 7 (which have no long alkyl chains) were used. The nanoparticles and their aggregation patterns were obtained in the film upon gas exposure and immersion in aqueous solutions. Because of the lack of long alkyl chains, the halide anion can easily penetrate into the Ag(I)-coordinated LS films to form nanoparticles, and the formed silver halide nanoparticles can be directly aggregated into various morphologies in the LS films. Upon exposing the Ag(I)-containing coumarin 7 LS films to HCl or I-2 gases, globular, cubic, dendrite, and nanorod morphologies of the silver halide were observed. The formation and aggregation processes of the nanoparticles in the LS films were monitored at intervals. Different morphologies were observed when immersing the Ag(I)-coordinated LS films into the aqueous solutions containing potassium halide. In the case of immersion into a KI solution, a nanowire of AgI was obtained. We have found that globular nanoparticles were always formed in the initial aggregation stage. Different morphologies such as cubic, dendrite, nanorod, and nanowire were obtained in subsequent reactions depending on the conditions. Directional aggregation was suggested for the formation of these morphology patterns. The Ag(l)-coordinated LS film revealed itself to be a good template for the in situ generation of a nanosized silver (I) halide with different morphologies.