Abstract
Cadmium selenide quantum dots (CdSe QDs) were synthesized by using Providencia vermicola BGRW, which has discriminatory ability to resist many metals such as Selenium, Cadmium, Silver, Zinc, Copper, Lead, Nickel, Cobalt and Bismuth metals. BGRW was able to grow in the presence of 6 mM of CdCl2. The best conditions for extra/intracellular CdSe QDs synthesis were 0.1 mM SeO2: 0.9 mM CdCl2, 37°C, pH 9 within 24 h. The biosynthesis of CdSe QDs was monitored by UV–Visible spectrum that showed surface plasmon resonance (SPR) peaks at 388 nm. Depending on fluorescence property of quantum dots, photoluminescence characteristics of the biogenic CdSe QDs were at 385 nm. Further characterization of synthesized CdSe QDs was carried out using the X-ray Diffraction (XRD), Transmission Electron Microscope (TEM) and Fourier Transform Infrared (FTIR) spectroscopy. TEM and XRD analysis revealed that CdSe QDs was cubic in shape with a size range of ∼2 to 4 nm. EDS analysis confirmed the composition of QDs from cadmium and selenium ions. FTIR spectroscopy confirmed the presence of proteins as the stabilizing agent surrounding the quantum dots. Key words: Quantum dots, cadmium selenide quantum dots, capping agent, transmission electron microscope, fluorescence spectroscopy, X-ray and FTIR analysis.
Highlights
Quantum dots (QDs) are 1-10 nm semiconductor nanoparticles that possess size-dependent luminescence, the QDs usually refer to the II−VI, III−V and IV−VI binary and their alloyed semiconductor materials with a confined size in three dimensions (Kumar et al, 2007)
BGRW strain of Providencia vermicola has a discriminatory ability to produce selenium nanoparticles, resist many metals such as selenium, cadmium, silver, zinc, copper, lead, nickel, cobalt and bismuth metals and able to grow in the presence of 6 mM of CdCl2 (El-Deeb et al, 2018)
It was observed that upon addition of the SeO2 and CdCl2 into the flask containing the TSB medium inoculated with Providencia vermicola BGRW, the color of the medium changed to yellow-orange color (Figure 1) and cadmium selenide (CdSe) QDs were found extra/intracellularly; these QDs persisted for eight months in liquid suspension
Summary
Quantum dots (QDs) are 1-10 nm semiconductor nanoparticles that possess size-dependent luminescence, the QDs usually refer to the II−VI, III−V and IV−VI binary and their alloyed semiconductor materials with a confined size in three dimensions (Kumar et al, 2007). Similarity, Ayano et al (2014) isolated Pseudomonas aeruginosa strain RB from a soil sample, which has capacities of both selenite reduction and cadmium resistance. This bacterium can synthesize 10-20 nm CdSe particles inside and outside the cells from selenite and Cd ion by a onevessel reaction particle larger than 100 nm were noticed outside the cells. This study investigated effects of culture conditions such as pH, temperature and Se/Cd ratios on the rate of CdSe synthesis of the strain BGRW, which have ability to produce CdSe QDs isolated from a rhizosphere in the farm at Taif, KSA
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