Green chemistry synthesis of biocompatible ZnS quantum dots (QDs): their application as potential thin films and antibacterial agent

Abstract

We are presenting here the synthesis of quantum dots (QDs) of direct band gap semiconductor, cubic ZnS through modified green chemistry-mediated chemical precipitation reaction. Green chemistry-synthesized (GCS) ZnS QDs were characterized using powder X-ray diffraction and high-resolution transmission electron microscope techniques. Analysis of results, revealed by both the techniques for the synthesized QDs, is complementary as far as the size range (2-6 nm) of ZnS QDs is concerned. UV-Vis spectrophotometric spectrum (λ max = 314 nm) showed a conspicuous blue shift than the bulk. The Fouriertransformed infrared spectra convincingly reported a Zn-S bond stretching frequency at 649 cm −1. The characterized QDs were subjected to the preparation of thin films over SiO 2 template (57 nm thickness) using photoresist spin coating technique at the ambient condition. The surface topology of nanoscale-thick films was studied by atomic force microscope (roughness parameter-33.28 nm, rms; for a scan area of 3.48 × 3.48 μm 2). The symmetrical (skewness = 1.68) and random distribution (kurtosis = 2.93) of the peaks and valleys revealed the nanoscale-thick films of ZnS QDs. Zeta potential (− 9.2 mV) fairly proved stable existence of ZnS QDs. The GCS QDs were found to be non-toxic toward L929 mouse fibroblastic cells and human erythrocytes. However, they demonstrated significant inhibitory effects against seven bacterial pathogens with an average zone of inhibition of 1.5 cm at 100 μg/ml concentration. The minimum inhibitory concentrations determined were in the range of 75 to 125 μg/ml for gram-positive and 100 to 150 μg/ml for gram-negative bacterial pathogens.

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“…Interestingly, in the present study, the CQDs show more inhibition toward Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholera, and Escherichia coli, and their antibacterial activity is compared with those of other CQDs (Table ). − Therefore, the synthesized CQDs can be used for pharmaceutical applications.…”

A slow, efficient and safe nanoplatform of tailored ZnS QD-mycophenolic acid conjugates for in vitro drug delivery against dengue virus 2 genome replication

“…The control cells treated with plain ZnS QD were also set up and in all the cases, the viability remained at values close to 100% suggesting that only the presence of the MPA and ZnS QD-MPA influences the reduction of cytotoxicity values. As a supporting evidence, we conjugated the ZnS QDs with Curcumin or Celgosivir which are also known as antiviral drugs 33,34 and the LD 50 was found to be significantly enhanced (Fig. S6, ESI † ).…”

Biosynthesis of quantum dots and their usage in solar cells: insight from the novel researches

“…thin film growth by molecular beam epitaxy and nanostructure formation by electron beam lithography, and bottom-up, i.e. nanomaterials obtained as results of the reaction in solution from opportune precursors, approaches [49][50][51][52]. Each process utilizes dissimilar features of chemistry to provide QDs with the anticipated optical characteristics such as extraordinary quantum yield, constricted fluorescence radiation, wide absorption, and steadiness towards photo-bleaching [53,54].…”