Study On The Preparation And Correlative Properties Of ZnSe,CdSe,Cu₂Se Nanomaterial

With the development of the science and technology, especially for semiconductor technology, the need for high efficiency material becomes more urgent. Especially, as the size of the nano-scaled materials and quantum dots are comparable to Bohr radius, novel electronic states and optical properties could be observed, therefore, there is great interest for researchers worldwide to study nano-semiconducting materials.We have first synthesized the crystalline nanorods of zinc selenide (ZnSe) by the composite-hydroxide-mediated (CHM) approach. The diameters of nanorods are about 200-300 nm, and the lengths are about 1-2μm. Humidity sensors based on ZnSe nanorods were fabricated. Their responsiveness to humidity for static and dynamic testing proved a high sensitivity of the sensors. The change of resistance is about three orders of magnitude as the relative humidity (RH) increases from 20% to 85%. The response-time and recovery-time of the resistance is 50 s and 81 s versus the changes of relative humidity from 20% to 85% and from 85% to 20%, respectively. The results indicate promising applications of ZnSe nanorods as a highly sensitive electronic device in environmental monitoring and humidity control.Single-crystalline CdSe nanostructures has been directly synthesized for the first time by the composite-hydroxide-mediated approach. The advantages of the method are of easy synthesis, at lower temperature, absence of capping agents and low cost, with a great potential for scale-up. The morphology of the CdSe can change from nanoparticles to uniform nanorods, whereas the phase transfers from zinc blende to wurtzite structure by adding small amount of water at fixed temperature. This result challenges the speculation that temperature is a cause of the phase transformation that has been proposed by other groups. Optical spectrum measurements of the two sorts of CdSe nanostructures exhibit same band gap. Humidity sensitivity is investigated for the first time on the sensors made from these CdSe nanostructures, exhibiting their ultrasensitive properties.Cu₂Se nanocrystals starting from CuCl₂.2H₂O and Se powder were synthesized through a novel approach based on chemical reactions in composite-hydroxide-melts at 200℃for 24h. The XRD indicated that the sample was cubic structured Cu₂Se with lattice constants of a = 5.787, and lattice symmetry group of pm 3m(225). SEM showed that the crystals were nanosheets with the thickness and width of were about 10-20 nm, 200～300 nm sheets, respectively. When a small amount of deionized water was added in the vessel during synthesis process, some stick shape amorphous products appeared in the samples, which reduced the quality of the Cu₂Se crystals. According to coordination polyhedron growth unit model, the binding energy of growth units has been calculated and the chemical interaction mechanism for synthesizing Cu₂Se nanocrystals has been discussed in detail.