Eco-Friendly Synthesis and Applicability to Silver Ink of Silver Nanoparticles Prepared via Stepwise-Modified Tollens Method.

Silver nanoparticles were eco-friendly synthesized at room temperature via a Tollens process modified with the stepwise method using eco-friendly precursors (citric acid and acetic acid). The field emission scanning electron spectroscopy was used to study the morphology of silver nanoparticles. The mean size of silver nanoparticles and the components of products were theoretically determined using UV-Vis and X-ray Diffraction spectra. The mole ratio between the silver ion, citric acid and the buffer acid solution (acetic acid) strongly influences the mean size and the composition of the product. The appearance of acetic acid in the buffer acid solution helped increase the efficiency of silver nanoparticles preparation. With the mole ratio n[Ag+]:ncitric:nacetic = 1.0:2.5:2.5, the highest preparation efficiency was obtained, the silver nanoparticles had an average dimension of ˜11 nm and narrow size distribution. The silver nanoparticles were dispersed into different solvents to examine their applicability to silver ink. The silver ink using propylene glycol solvent showed good applicability to silver ink which could work at room temperature.

Optical and Photocatalytic Properties of In-Situ Gr@ZnO Microspindle Composites Prepared by Hydrothermal Method.

In-Situ composite materials of graphene (Gr) and ZnO microspindle with different Gr contents (1, 2 and 5 wt.%) were prepared via a facile one-step hydrothermal route with the assistance of hexamethylenetetramine. Graphene does not affect the hexagonal wurtzite crystal structure of composite materials but strongly affects the morphological, structural, optical and photocatalytic properties of composite materials. In detail, Gr causes a decrease in both the dimensions of ZnO microspindle and photoluminescence efficiency. The average crystalline size and microstrain first increase from 28.9 nm and 0.00394 to 49.5 nm and 0.00524 when Gr content increases from 0 to 1 wt.%, respectively; then decrease to 39.6 nm and 0.00404 when Gr content increase from 1 to 5 wt.%, respectively. Both pristine and composite materials show high photocatalytic activity with high methylene blue degradation efficiency?more than 90%-just after 40 min under UV irradiation. Composite material having a Gr content of 5 wt.% shows the highest degradation efficiency of 96.5% which confirms the role of Gr in enhancing the photocatalytic activity of ZnO.