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Sulfate reducing bacteria present in anaerobic granular sludge mediate the metabolic conversion of sulfate to sulfide. In the presence of heavy metals, sulfides precipitate as metal sulfides. In this study, dissimilatory sulfate reduction was coupled to the precipitation of zinc as ZnS quantum dots (QDs) at ambient conditions. The biogenic ZnS QDs had average sizes of 5–7 nm and were formed within 2–4 days of incubation. X-ray diffraction analysis indicated that the biosynthesised ZnS QDs possessed a crystalline cubic lattice structure. The organics present during ZnS biosynthesis were characterized using 3D-fluorescence excitation–emission measurements (FEEM) and the presence of an organic coating on the biogenic ZnS QDs was affirmed using FTIR analysis. The UV–visible absorption spectra of the samples exhibited a prominent absorption peak below 325 nm, which is the characteristic of the surface plasmon resonance of ZnS QDs. The band gap energy of the biogenic ZnS QDs was estimated to be 3.84 eV, comparable to the values reported for chemically synthesised ZnS QDs. The direct band gap energy indicates a large redox potential and carrier mobility, which capacitate the application of these QDs as effective photocatalysts for the photo-assisted decolourization of dyes, as illustrated for the dye congo red. [ABSTRACT FROM AUTHOR]

Corrosion inhibition and control are of great significance in metal industries due to the economic benefits. In recent years, the utilization of plant extract as an alternative to the chemical counterparts has advocated the concept of a green approach that is eco-friendly nature and efficient as corrosion control agents. Literature review reveals that the inhibition efficiency of a plant extract could be improved by the addition of cationic or anionic salts along with it. Majorly, the effect of halogen and zinc ion based salts has been reported to produce an effective synergistic corrosion control in the presence of plant extracts. The present review is a collection of published work on the synergistic effect of different types of salt on the corrosion inhibitive action of plant extract. The comprehensive data directs that the effective use of ionic salts along with plant extracts can maximize the inhibition efficiency and minimize the requirement of the plant extract required to produce an effective corrosion inhibition. Further, the corrosion inhibition mechanism of the mixture of plant extract and salt directs attention that these ionic compounds improve the corrosion inhibition efficiency by assisting the formation of the plant extract-based protective layer on metallic surface. [ABSTRACT FROM AUTHOR]

Chalcogenide semiconductor quantum dots are emerging as promising nanomaterials due to their size tunable optoelectronic properties. The commercial synthesis and their subsequent integration for practical uses have, however, been contorted largely due to the toxicity and cost issues associated with the present chemical synthesis protocols. Accordingly, there is an immediate need to develop alternative environment-friendly synthesis procedures. Microbial factories hold immense potential to achieve this objective. Over the past few years, bacteria, fungi and yeasts have been experimented with as eco-friendly and cost-effective tools for the biosynthesis of semiconductor quantum dots. This review provides a detailed overview about the production of chalcogen-based semiconductor quantum particles using the inherent microbial machinery. [ABSTRACT FROM AUTHOR]