Antifungal activity of wide band gap Thioglycolic acid capped ZnS:Mn semiconductor nanoparticles against some pathogenic fungi

Thioglycolic Acid FTIR Spectra on Ag2S Quantum Dots Interfaces

The mechanism features of colloidal quantum dots (QDs) passivation with thioglycolic acid molecules (TGA) for cases of different luminescent properties is considered using FTIR. This problem is considered based on FTIR spectra analysis for various ionic forms of TGA. Experimental TGA molecules FTIR spectra is interpreted, basing on the data on modeling of TGA vibrational modes, realized in the framework of density functional method (DFT /B3LYP/6-31+G(d)) taking into account the vibrations anharmonicity of every functional group. This approach provides a significant improvement in the agreement between the experimental and calculated data. FTIR spectra of Ag2S/TGA QDs with exciton and recombination luminescence are differ from each other and B “freeB” TGA molecules. The ν(S−H) TGA peak (2559 cm−1) disappears in FTIR spectra of Ag2S/TGA QD samples. This fact indicates the interactions between TGA thiol group and dangling bonds of Ag2S nanocrystals. Ag2S QDs passivation with TGA molecules leads to emergence νas(COO−) (1584 cm−1) and νs(COO−) (1387 cm−1) peaks. It indicates TGA adsorption in ionic form. For Ag2S/TGA QDs with exciton luminescence we observed (a) significant low-frequency shift of νs(COO−) peak from 1388 cm−1 to 1359 cm−1 and high-frequency shift of νas(COO−) peak from 1567 cm−1 to 1581 cm−1; (b) change in the ratio of intensities of νas(COO−) and νs(COO−) vibrations. This feature is caused by the change in the symmetry of TGA molecules due to passivation of Ag2S quantum dots.For Ag2S/TGA QDs with recombination luminescence, the insignificant high-frequency shift of 7–10 cm−1 for νas (COO−) at 1567 cm−1 and low-frequency shift of 3–5 cm−1 for νs (COO−) at 1388 cm−1, probably caused by the interaction of thiol with Ag2S surface is observed. Using FTIR spectra, it was found that IR luminescence photodegradation is also accompanied by changes in the thioglycolic acid molecules, which capped Ag2S QDs. In the case of Ag2S QDs with exciton luminescence, the degradation process is non-reversible. It is accompanied by TGA photodegradation with the formation of α-thiol-substituted acyl radical (S-CH2-CO•) TGA.

Zinc fortification as a tool for improving sprout hygienic and nutritional quality: a factorial design approach

BACKGROUND

Sprouting is known to improve cereal and pulse nutritional properties. However, several outbreaks of illness have been reported after raw sprout consumption. This research aimed to improve wheat sprout hygienic properties through the use of zinc diacetate. Sprouting conditions (sprouting temperature, soaking time and zinc diacetate solution concentration) were optimized to decrease total plate count, coliforms, and molds and yeasts using a factorial design approach and a desirability function.

RESULTS

Based on the responses, the effects of variables were calculated and the interactions between them were determined. Optimal conditions were defined as follows: sprouting temperature 18 °C, soaking time 0.66 h and zinc diacetate concentration 400 mg L^-1 . These conditions led to the elimination of coliforms and a decrease in total flora count by 2 log. Interestingly, zinc sprouting increased the zinc content of sprouts and improved their nutritional properties.

CONCLUSION

Results showed that the use of zinc solution is a useful tool to improve sprout hygienic and nutritional properties. © 2019 Society of Chemical Industry.