Optical limiting properties of hydrophobic poly(etherimide) membranes embedded with isolated and aggregated gold nanostructures

A simple method to incorporate spherical or aggregated nanostructures of gold into hydrophobic poly (etherimide) membranes is demonstrated and their comparative nonlinear optical properties are investigated. When excited at 532 nm using laser pulses of 7 ns duration, a reduced transmission behaviour in both the cases, viz. polymers embedded with isolated nanoparticles and their aggregates is observed. This fits to a three-photon type nonlinear absorption process and is attributed to excited state absorption occurring in the nanostructures. Interestingly, the nonlinearity is more prominent in the aggregated nanostructures compared to the spherical nanostructures. These materials are potential candidates for optical limiting applications

Biological synthesis of metallic nanoparticles: plants, animals and microbial aspects

The green synthesis (GS) of different metallic nanoparticles (MNPs) has re-evaluated plants, animals and microorganisms for their natural potential to reduce metallic ions into neutral atoms at no expense of toxic and hazardous chemicals. Contrary to chemically synthesized MNPs, GS offers advantages of enhanced biocompatibility and thus has better scope for biomedical applications. Plant, animals and microorganisms belonging to lower and higher taxonomic groups have been experimented for GS of MNPs, such as gold (Au), silver (Ag), copper oxide (CuO), zinc oxide (ZnO), iron (Fe2O3), palladium (Pd), platinum (Pt), nickel oxide (NiO) and magnesium oxide (MgO). Among the different plant groups used for GS, angiosperms and algae have been explored the most with great success. GS with animal-derived biomaterials, such as chitin, silk (sericin, fibroin and spider silk) or cell extract of invertebrates have also been reported. Gram positive and gram negative bacteria, different fungal species and virus particles have also shown their abilities in the reduction of metal ions. However, not a thumb rule, most of the reducing agents sourced from living world also act as capping agents and render MNPs less toxic or more biocompatible. The most unexplored area so far in GS is the mechanism studies for different natural reducing agents expect for few of them, such as tea and neem plants. This review encompasses the recent advances in the GS of MNPs using plants, animals and microorganisms and analyzes the key points and further discusses the pros and cons of GS in respect of chemical synthesis.Fil: Das, Ratul Kumar. Université du Québec a Montreal; Canadá. The Energy and Resources Institute; IndiaFil: Pachapur, Vinayak Laxman. Université du Québec a Montreal; CanadáFil: Lonappan, Linson. Université du Québec a Montreal; CanadáFil: Naghdi, Mitra. Université du Québec a Montreal; CanadáFil: Pulicharla, Rama. Université du Québec a Montreal; CanadáFil: Maiti, Sampa. Université du Québec a Montreal; CanadáFil: Cledón, Maximiliano. Université du Québec a Montreal; Canadá. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; ArgentinaFil: Dalila, Larios Martinez Araceli. Université du Québec a Montreal; CanadáFil: Sarma, Saurabh Jyoti. University of Calgary; CanadáFil: Brar, Satinder Kaur. Université du Québec a Montreal; Canad