Synthesis, Characterization And Toxicity Assay Of CdS Nanomaterials With Different Shapes

CdS is one of the most vitalâ…¡-â…¥group semiconductors with a direct band gap of 2.4 eV at room temperature, as a classical fluorescent semiconductor materials, CdS nanomaterials has unique photoelectric properties, which can be widely used in biology and medicine fields. The optoelectronic properties of CdS nanomaterials are strongly affected by their morphologies and structures. Therefore, it is very important to develop simple and mild methods to synthesize CdS nanomaterials with variegated structure. However, owing to their inherent chemical composition, the toxicity of CdS nanomaterials is considered to be very crucial to their widespread applications and has received more and more attention in recent years. In the present work, we have successfully synthesized six kinds of CdS nanomaterials. In addition, we reported here on the first systematic investigation of toxicity of three different shapes of CdS nanomaterials based on bioluminescence inhibition assay with luminous bacteria. The main research works are summarized as follows:(1) We reported a facile approach for the synthesis of highly luminescent multi-armed CdS nanorods by thermal decomposition of cadmium diethyldithiocarbamate (CDC) with olylamine as a coordinating solvent. Furthermore, the influence of various experimental variables, including reaction time, ratio of S to Cd, on the fluorescent properties of the CdS nanocrystals has been systematically investigated. The result demonstrated that the prepared CdS nanocrystals were a multi-armed nanostructure and the average size were 5 nm (diameter) x 36 nm (length). Adopting dihydrolipoic acid (DHLA) as modifying reagents, on the basis of strong bidentate interactions of the DHLA ligands with the CdS surface via their dithiol polar heads, high quality water-soluble CdS nanorods were obtained. While rice-like CdS nanorods were synthesized in water phase, which average diameter and the arm length were about 23 nm and 33 nm, respectively.(2) With the DHLA, mercaptosuccinic acid (MSA) and mercaptoacetic acid (MAA) as the stabilizers, we prepared three kinds of CdS quantum dots (QDs) in aqueous phase. Then, we established another facile approach for the synthesis of the CdS QDs by thermal decomposition of CDC with ODE as a coordinating solvent in organic solution.(3) The toxicity of CdS nanomaterials (multi-armed nanorods, rice-like nanorods and QDs) stabilized with DHLA were evaluated respectively by luminous bacteria as a microbial sensor. Moreover, through UV irradiation experiments, vitamin C experiments and TEM of Luminous Bacteria, the mechanism of toxicity of CdS nanomaterials were investigated. Our results demonstrated that the multi-armed CdS nanorods had the highest toxicity because it had several arms which could punct the bacteria in any direction, while the rice-like CdS nanorods were much less toxic than multi-armed CdS nanorods as which only had two arms could demolish the bacteria, and then the rule of CdS QDs was sphere, it could not punct the bacteria, so it had the lowest toxicity. In addition, we also found that UV irradiation could increase the toxicity of three kinds of CdS nanomaterials, VC could reduce the toxicity of CdS QDs, but increase the toxicity of two CdS nanorods.