Extracellular biosynthesis of cadmium sulphide quantum dot using cell-free extract of Pseudomonas chlororaphis CHR05 and its antibacterial activity

摘要

For the first time a novel aquatic bacterium belonging to strain of Pseudomonas chlororaphis was developed for the synthesis of cadmium sulfide quantum dots. The cadmium sulfate solution incubated with cell-free extract (CFE) of P. chlororaphis strain CHR05 to generate cadmium sulfide nanoparticles (CdSNps) which were characterized with combined spectroscopy and microscopy analyses. The preliminary confirmation on the formation of CdSNps was done by UV-vis and fluorescence analyses with the absorption and emission spectra at 435 and 475nm, respectively. EDX pattern shows that the CdSNps are composed of the elementals Cd and S. Also, XRD analysis of the purified nanoparticles confirmed the formation of CdSNps. FE-SEM, TEM, and DLS analyzed the size and morphology of the CdSNps. The biosynthesis of CdSNps with the strategy of cell free extract was investigated under optimum conditions. After 24 h of incubation, the results showed that the novel isolated strain can produce spherical CdSNps with an average size of 6.7 +/- 2.4 nm, after exposure to CdSO4 solution (2.5 mM) at pH 7.5 and 30 degrees C. The antibacterial activity CdSNps against some Gram-positive and -negative bacteria were determined using agar well diffusion method and microplate method which has growth-inhibitory effect all on tested bacteria.