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Purpose: Surface pretreatment of iron and its alloys to remove stains and inorganic contaminants on the metal surface undergoes dissolution by virtue of the strong acidic media thereby increasing its susceptibility to corrosion. The purpose of this study is to explore the corrosion mitigation prospects of green corrosion inhibitors on mild steel surface. Design/methodology/approach: Corrosion inhibition performance of Garcinia gummi-gutta leaf extract (GGLE) was explored against mild steel in 1 M HCl solution using the weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques. Surface characterization was carried out to study the mechanism of inhibitor action. Findings: The concentration of GGLE varied from 100 to 6,000 ppm and the result indicates that corrosion inhibition efficiency was amplified by raising the inhibitor concentration. The maximum inhibition efficiency was 82.2% at 6,000 ppm concentration. EIS results show the development of a protective layer of inhibitor molecule over the metal surface and PDP demonstrates that the inhibitor operates as a mixed-type inhibitor. Scanning electron microscopy and atomic force microscopy were executed to assess the surface morphology and roughness, respectively. Originality/value: To the best of the authors' knowledge, so far, no studies have been reported on the corrosion inhibition performance of GGLE which is rich in many bioactive components especially hydroxyl citric acid. This work encompasses the corrosion inhibition capability of GGLE against mild steel in an acidic medium. [ABSTRACT FROM AUTHOR]

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]

This manuscript presents a robust strategy for selective Pb(II) sensing based on a fluorescence turn‐off mechanism using ZnS quantum dots (QDs) biosynthesized using Aspergillus sp. The biogenic nanoprobe displayed marked sensing efficiency in the presence of Pb ions over concentration ranges from 5 to 100 μM with limits of detection of around 2.45 μM. Performance optimization studies revealed that the maximum fluorescence quenching efficiency was obtained in the presence of [ZnS NPs] at 4 mg/ml, and alkaline pH of 10 recorded under stable ambient temperature for approximately 5 min for the quenching process. Advanced morphological analysis indicated that the bio‐sensing mechanism was essentially a surface‐based phenomenon in which the Pb ions were in very close proximity to the QDs and formed stable ground‐state Pb–ZnS complexes, resulting in a quenched fluorescence of the QDs. Simultaneously, a larger fraction of Pb ions interacted via collisions with the excited ZnS QDs and resulted in an effective energy transfer from the excited QDs to the Pb ions, therefore resulting in an obvious decrease in QD fluorescence. These insights were well supported by theoretical analysis using Stern–Volmer plots and sphere‐of‐action models. [ABSTRACT FROM AUTHOR]

Nanotechnology is a rapidly growing scientific field and has attracted a great interest over the last few years because of its abundant applications. Green nanotechnology is a multidisciplinary field that has emerged as a rapidly developing research area, serving as an important technique that emphasize on making the procedure which are clean, non-hazardous, and especially environmentally friendly, in contrast with chemical and physical methods currently employed for nanosynthesis. The biogenic routes could be termed green as these do not involve the use of highly toxic chemicals or elevated energy inputs during the synthesis. Differences in the bio-reducing agents employed for nanosynthesis can lead to the production of nanoparticles (NPs) having distinct shapes, sizes, and bioactivity. The exquitiveness of the green fabricated NPs have capacitated their potential applications in various sectors such as biomedicine, pharmacology, food science, agriculture, and environmental engineering. The present review summarizes current knowledge on various biogenic synthesis methods, relying on plants, waste biomass, and biopolymers and their reducing and stabilizing agents to fabricate nanomaterials. The main emphasis has been given on the current status and future challenges related to the wide-scale fabrication of nanoparticles for environmental remediation, pathogenicity, and agricultural applications. [ABSTRACT FROM AUTHOR]

Experiments were conducted to study the Selenium (Se) biosorption and recovery by marine Aspergillus terreus in an upflow bioreactor for a period of 8 days. The Se tolerance of the marine fungus was initially confirmed by visual and microscopic observations that evinced intact fungal cells in an Se-amended medium with sparse changes in the spore texture and cellular number by the seventh day of biosorption studies in the upflow bioreactor. Further, the effect of pH and contact time on the percentage of Se biosorption, in an upflow bioreactor containing fungal pellets, was investigated. It was analyzed that pH ranges of 6-7 and a contact time of 5 days resulted in 85-87% biosorption of Se by the fungal biomass. The interaction of the fungus with the induced Se stress in the medium was monitored regularly for studying the uptake of the metalloid and the possible biosynthesis of Se nanoparticles. Analyses using ultraviolet visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) studies revealed the formation of crystalline Se nanocrystals with an average diameter of 500 nm on the fungal cell wall. Fourier transform infrared (FTIR) spectroscopic analysis indicated the possible involvement of fungal protein groups that aid the binding of the biosorbed Se nanoparticles on to the fungal cell wall. [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]