The bio-molecules from various plant components and microbial species have been used as potential agents for the synthesis of silver nanoparticles (AgNPs). In spite of a wide range of bio-molecules assisting in the process, synthesizing stable and widely applicable AgNPs by many researchers still poses a considerable challenge to the researchers. The biological agents for synthesizing AgNPs cover compounds produced naturally in microbes and plants. More than 100 different biological sources for synthesizing AgNPs are reported in the past decade by various authors. Reaction parameters under which the AgNPs were being synthesized hold prominent impact on their size, shape and application. Available published information on AgNPs synthesis, effects of various parameters, characterization techniques, properties and their application are summarised and critically discussed in this review.

No abstract

Light driven, photon mediated green synthesis of silver nano-particles (AgNPs) was carried out using aqueous silver nitrate solution (1 mM) and aqueous extract of almond (Prunus amugdalus). Experiments were carried out in dark, diffused sunlight and direct sunlight to study the influence of light intensity as well as by wrapping the reaction tubes with colored cellophane filters (violet, green, yellow and red) to investigate the effect of light color on AgNP synthesis. It was observed that the violet filter enhanced the AgNPs synthesis appreciably. The FTIR spectroscopic analysis confirmed participation of bio-molecules with hydroxyl and amide groups present in the almond extract as reducing and capping or stabilizing agents, respectively. Dynamic light scattering (DLS) studies revealed the particle size distribution of nano-particles as 2 -400 nm, and scanning electron microscopy (SEM) confirmed their spherical shape with an average size of about 20 nm. Growth analysis of AgNPs revealed an increase in number of nano-particles with time, whereas their rate of growth decreased gradually. The AgNP suspension was stable even beyond 3 weeks.

Global iron and steel making industries generate immense number of by-products, among which few are already being utilized for the generation of high value products, while few are still struggling to gather a good market space. Waste utilization is the major concern for every industrial maker. In this context, iron powder which holds immense market in applications like powder metallurgy (PM) parts, welding electrodes, advanced oxidative agents for water treatment, food fortifying agents, metal injection moulding, catalysts, fuels etc., can now be a novel outcome from steel industry by-products. Iron powder can be manufactured by various techniques like reduction, atomization, electrolysis, etc., resulting in fine particles of various morphologies ranging from spherical to irregular shapes and low to high purity. The application of these iron powders is depended on the process, quality and purity of the desired product.

Mill scale, a potential raw material for recycling from hot rolling mill operations is chosen and one step thermo-chemical reduction technique is employed to beneficiate the iron content in the form of powdered iron. Experiments are conducted at various temperature (600-1 300°C) and time (1-4 h) combinations using hydrogen as reducing atmosphere. Physical and chemical properties of mill scale iron powders (MIP) are analysed using particle size analyser, gas pycnometer and wet chemical testing. MIP are also characterized for phase and morphology using X-ray diffractometer and scanning electron microscopy respectively. Effect of parameters like temperature of reduction, time of reduction, particle size of raw material, sintering and grinding on the iron powder synthesis is well studied. Mill scale iron powder with > 99% degree of metallization, 97% Fe (T), > 96% Fe (met) and 2.63 g/cc apparent density is obtained at 1 200°C, 4 h and 1 300°C, 4 h parameters and this material would stand promising for recycling through nutrition supplements, body warmers, water purification, sound insulators, etc applications.