The Preparation And Shape-control Of Bi₂S₃ Nanocrystals

As the development of science and technology, more and more nano technologies are applied in the area of biomedicine. Nowadays, we use them in the area of medical imaging. We try to find a new imaging contrast consisted of Bi₂S₃ nanocrystals in order to raise the exactitude of the CT and achieve the forepart diagnosis for some serious diseases.In this thesis, we mainly discussed the synthesis of the Bi₂S₃ nanocrystals with the method of wet chemistry. We used different polymeric dispersants in the reaction system such as Polyvinylpyrrolidone (PVP), sodium dodecyl sulfona (SDS), thioglycolic acid (MA), polyethylene glycol (PEG), dextran. The dispersants were good for the dispersing and stabilization of nanocrystals, and also they can form the models for the preparation of different shapes of the Bi₂S₃ nanocrystals, such as nanorods, nanodots, nanobranchs, nanoscissors. X-ray powder diffraction (XRD), Transmission electronmicrograph (TEM), Infrared spectrascope (IR), Ultraviolet spectrascope were employed to characterize the nanocrystals. The major research works might be summarized as follows:1. By using different polymeric dispersants, ammonium bismuth citrate (CBA) and sodium sulfide (NS) were used to synthesize the Bi₂S₃ nanocrystals. XRD analyses substantiated that the product of the reaction is Bi₂S₃ nanocrystals. We used UV-Vis to analyse the radii of nanocrystals and use TEM analysed the shapes.2. We changed the temperature, from 25℃to boiling temperature, to shape-controlled the nanocrstals. In this case,we tried to find the optimal temperature for preparing stable Bi₂S₃ nanocrystals with narrow-dispersion. We tested the acidity of the Bi₂S₃ colloids and used TEM to observe the shape of the Bi₂S₃ nanocrystals prepared at 95℃.3. We changed the reacting times from 0s to 1500s, used UV-Vis to analyze the radii of nanocrystals and use TEM analyzed the shapes of the samples at just 0s, 100s, 200s, 600s, 900s and 1500s.4. Keeping the total volume unchanged, we varied the proportions of the distilled water and the alcohol to shape-controlled the Bi₂S₃ nanocrystals. We used TEM and acidity apparatus to analyse the Bi₂S₃ nanocrystals.5. By changing the proportions of PVP and MA, we synthesized the Bi₂S₃ nanocrystals at 95℃. TEM photos showed that the Bi₂S₃ nanocrystals had different shapes such as nanorods, nanodots, nanobranchs, or nanoscissors.