Microwave-assisted insertion of silver nanoparticles into 3-d mesoporous zinc oxide nanocomposites and nanorods

The nanocomposite of mesoporous ZnO and Ag was synthesized by microwave radiation in a 15 min reaction conducted under an argon atmosphere. The 3.5 +/- 0.4 nm Ag particles were inserted into the pores, changing the pore structure. The particles are also present as clusters on the surface of ZnO. The hexagonal ZnO nanodisks were stacked one on top of the other for the Ag:ZnO molar ratio of 0.13, whereas for Ag:ZnO = 0.22, the nanodisks join in the form of nanorods, where Ag clusters catalyze nanorod formation. The mesoporous structure in the current study was prepared with the help of argon gas and ethylene glycol. The FTIR studies revealed the presence of the organic framework structure retained in the final products. The 14 +/- 2 nm hexagonal ZnO nanodisks are bound together by this organic framework, forming pores of 3.2 +/- 0.1 and 18.6 +/- 0.2 nm in diameter. The BET surface area increased from 40 +/- 0 (pristine ZnO) to 51 +/- 1 m(2)/g (Ag:ZnO = 0.22) due to formation of Ag clusters on the surface of ZnO with the increase in Ag concentration. Raman spectroscopy experiments indicate the modified surface characteristics of ZnO due to the porous structure and the presence of carbon in the products. The diffuse reflection optical absorption spectra show the ZnO excitonic absorption and Ag surface plasmon bands. The room-temperature photoluminescence experiments show emission bands assigned to the band edge exciton transitions in ZnO, oxygen defects, surface-deep traps, and impurity energy levels.