Biological Synthesis Of Cadmium Sulfide Quantum Dots By Phanerochaete Chrysosporium And Its Mechanism

Quantum dots (QDs), a special kind of quasi zero dimensional nano grain, is a tiny point on the appearance. For example, CdS and CdSe, CdTe QDS are popular QDs, nanometer gold and silver nanoparticles also belong to the category of quantum dots. The size of QDs are generally between1to10nm. Due to the quantum confined effect, quantum dots have very unique optical and electrical properties. In recent years, quantum dots attracted more and more attention. More and more researches on quantum dots are seen on papers. At present the synthesis of QDs are mainly concentrated on physical and chemical synthesis methods, while biosynthesis research is less. This article explores a new type biological synthesis method of CdS quantum dots, and the synthetic mechanisms are analyzed.The work carried out and conclusions proposed of this paper are as follows:1. The adsorption of cadmium ions by Phanerochaete chrysosporium was explored including the synthetic effect with different cadmium source, sulfur source and different stabilizers. Cadmium nitrate was ultimately determined to use as cadmium source, thioacetamide as sulfur source and mercaptoacetic acid as stabilizer. The optimal addition amount of the materials were137.5mg,6.68mg and lmL respectively.2. The following characterization of the structure and properties of quantum dots were conducted by UV-vis spectrophotometer and fluorescence spectrometer analysis. The growth situation and optical properties of cadmium sulfide quantum dots was studied. The results showed that the quantum dot size increased with the increase of pH. Under the specific excitation wavelength, quantum dots showed a blue fluorescence. By using powder diffraction analyzer (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), the quantum dot size and microstructure were analyzed, and the micro structure of CdS quantum dots was face-centered cubic and the particle size was about2nm. Thermogravimetric analysis (TGA) showed that cadmium sulfide quantum dots had very good stability. The TGA curves indicated that the quantum dots could resist the high temperature of1300℃. By using infrared (IR) and energy spectrum instrument, the functional groups on the surface of the quantum dots were studied. The change of functional groups showed that cysteine and protein substances played an important role for the synthesis of quantum dots.3. Because the QDs synthesized in this article were capped by cysteine and protein, they had a good stability and biocompatibility. The stability and biocompatibility determined the value of quantum dots in the application of life science. Therefore, the surface modification of the QDs will be the focus of the study of quantum dots in the future.