Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+Recognition in Aqueous Media

The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg2+ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg2+over other metal ions including Na+, K+, Ba2+, Mg2+, Ca2+, Fe3+, and Cd2+. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions

Nanofabrication with Pulsed Lasers

An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics

Size and shape dependences of the colloidal silver nanoparticles on the light sources in photo-mediated citrate reduction technique

Colloidal silver nanoparticles (Ag NPs) with different sizes and shapes were synthesized by photo-mediated citrate reduction of aqueous solution under UV, sun and visible-infrared (VIS-IR) light sources. Pale yellow colour colloid was obtained under VIS-IR light exposure, whereas reddish yellow colour colloid was yielded under UV light. The colloid prepared under natural sunlight initially appeared as yellow, which turns out to be deep green after 10 h exposure. The colloid prepared under UV light contains fine spherical NPs with diameter ranging from 5 to 10 nm. In addition to spherical NPs, some low-dimensional features like triangles, hexagonal platelets, nanorods were also formed under sunlight. Similar low-dimensional features including spherical particles, long chains of particles and large leaf-like platelets were grown under VIS-IR light. The colloid prepared under UV light exhibits single plasmonic absorption peak in the violet region of the visible spectra with absorption peak centred at nm. However, the colloid prepared under sun and VIS-IR light demonstrates multiple plasmonic absorption peaks related to the multi-dimensional nanoparticles. All the NPs were made of pure silver and single crystalline. The colloid prepared under VIS-IR light exhibited significant ageing with time; whereas, the colloids prepared under UV and sunlight seem very stable against ageing even after long time