Hydrothermal Synthesis And Photoluminescence Properties Of Managanese Doped-ZnS Nanoparticles

Zinc sulfide is an important kind ofⅡ-Ⅵcompounds, existing cubic phase of sphalerite structure and hexagonal phase of wurtzite structure in nature, with the wide band gap of 3.66 eV and 3.8 eV, respectively. Due to the unique optical,chemical and physical properties, much more attention was attracted by the chemist, physicist, and materials scientists. Since Bhargava firstly found luminescent quantum effciency of Mn2+ doped-ZnS was significantly enhanced in 1994, many attempts were carried out to exploit transition metal ions doped-ZnS. Extensive researches and attention were taken to study Mn, Cu, Fe, Co doped-ZnS and Mn,Cu co-doped ZnS or Co,Cu co-doped ZnS. Especially Mn-doped ZnS materials, low-dimensional ZnS:Mn materials such as nanowires, nanoparticls and thin-films were obtained, lots of efforts were taken to study synthesis of ZnS:Mn quantum dots and their applications. However, the researches of mesoporous/porous ZnS:Mn nanomaterials were not so sufficient that less mesoporous/porous ZnS:Mn materials were reported. Therefore the first thing was to prepare mesoporous/porous ZnS:Mn nanomaterial.The main contents of this paper were as follows:One is synthesis of flower-like ZnS:Mn micro/nano materials by using CTAB assistant-solvothermal method, another is synthesis of monodisperse ZnS:Mn prorous nanospheres by using hydrothermal method, using trisodium citric dihydrate as complexing agent. In addition, the influence factors in the synthesis process were discussed, the microstructure and optical properties were also characterized. The detailed research works are as follows: 1. Synthesis of flower-like ZnS:Mn materialsUsing zinc nitrate hexahydrate, manganese acetate tetrahydrate, thiourea as the starting materials, micro/nano ZnS:Mn with hexagonal phase of wurtzite structure was synthesized successfully by using CTAB assistant-solvothermal method. The surface of ZnS:Mn material possessed porous structure owing to lots of nano-flake with the thickness of 10 nm self-assembling. The systematical study illustrated nano-flakes didn't appear until the reaction to the certain time. Below critical micelle concentration, increasing the amount of CTAB had little influence on sample morphologies other than size. However, concentrations of inorganic raw materials and pH values of solution affected seriously on sample morphologies. And flower-like ZnS:Mn materials with smaller size were obtained after adding orgnaic solvent with viscosity. In addition, the growth mechanism of flower-like ZnS:Mn were discussed. 2. Synthesis of monodisperse ZnS:Mn porous nanospheresUsing zinc nitrate hexahydrate, manganese acetate tetrahydrate, thiourea as the starting materials, besides that, using trisodium citric dihydrate as complexing agent, monodispersed ZnS nanospheres were synthesized. Research suggested that samples were the mixture of ZnO and ZnS synthesized at reaction temperature of 170℃. The photoluminescence spectra showed some new emission peaks were found due to new luminous generated by new band energy. The BET results showed samples possessed porous structure. Because of disorder apertures, the specific surface area of samples just only reach to 7.8 m2/g, and the average diameter of the pore was 16.5 nm. The specific surface area of samples somewhat decreased along with the increase of pore width after annealed at 550℃. Well-monodispersed ZnS nanospheres were obtained at lower reactants' concentration with the reaction temperature of 120℃. The small angle X-ray diffration of single scattered (SAXS) on ZnS nanospheres suggested samples also possessed porous structure with short-range disorder. In the synthesis of ZnS nanospheres based on experimental conditions, Mn2+ doped ZnS nanospheres were prepared after adding manganese source. Results showed fluorescence intensity of Mn2+ doped-ZnS stronger than that of undoped ZnS. And the intensity could reach maximum while the doped amount was 10%. Interestingly, a new emission peak was appeared at～530 nm. Combined with XRD data and lattice distortion parameters, Mn2+ may not occupy the tehrahedron lattice state ion instead of Zn2+.