In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.

No abstract

This present paper reports the study of cadmium sulphide (CdS) nanoparticles prepared under controlled condition in methanolic solution and also in polyethylene oxide polymer electrolyte matrix. The sulphurations of the cadmium salts were done in situ by a sodium sulphide solution. The concentration of the precursors has been controlled as detailed in the paper. All the preparation and characterization were carried out at room temperature. The nanoparticles were characterized by UV/Vis spectra in the range of 600 to 250 nm. The absence of bulk/micron size particles was noted in either of the system. The absorption edge near 510 nm indicates the presence of bulk CdS, whereas the presence of nanometer-sized particles is also reflected in low wavelength region. The sizes of the particles as well as particle distribution have been estimated using X-ray diffraction and scanning electron microscopy, respectively. A comparison in the spectra has been done for the sample prepared in either of the matrices. The particle size distribution in the polymeric matrix has been found to be more in comparison to that in the methanolic suspension. The polymer is reported to work as a binder, but not as a capping agent.

No abstract

Starch, being a polymer of excessive demand for the development of products of pharmaceutical importance, has been tremendously treated in many ways for improving the desired characteristics such as viscosity, paste clarity, digestibility, swelling, syneresis, and so forth. In the present study, alkali-extracted starch of mandua grains ( Eleusine coracana ; family Poaceae) was treated with epichlorohydrin for cross-linking and the modified starch was assessed for swelling, solubility, water binding capacity, moisture content, and degree of cross-linking. The digestion resistibility of modified starch was analyzed in simulated gastric fluid (pH 1.2), simulated intestinal fluid (pH 6.8), and simulated colonic fluid (pH 7.4). The structural modifications in treated mandua starch were analyzed by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy, thermogravimetric analysis, and C 13 nuclear magnetic resonance ( 13 C NMR). The results of the study reflected the significant modification in mandua starch after treatment with epichlorohydrin (1.0% w/w sdb, solid dry basis). The degree of cross-linking of treated mandua starch was 85.15%, and the swelling capacity of mandua starch changed from 226.51 ± 2.175 to 103.14 ± 1.998% w/w after cross-linking with epichlorohydrin. A remarkable increment in digestion resistibility was observed in modified mandua starch. The XRD pattern and FTIR spectra revealed the presence of resistant starch after chemical modification. The decomposition pattern of modified mandua starch was also different from extracted mandua starch. All the results reflected the effective modification of mandua starch by epichlorohydrin and the formation of resistant starch to a significant content. The treated mandua starch may have the potential in developing various preparations of food, nutraceuticals, and pharmaceuticals.