Preparation And Sensing Properties Of ZnS-supramolecular Organogel Composite Films

Amine is a kind of extremely toxic, even have strong carcinogenic effect, make its closely watched in the environment and food safety detecting. Therefore, there is an urgent need to constantly research and develop the detection method of amine. Currently, the methods for the determination of the amine are gas/liquid chromatography, mass spectrometry electrochemical and fluorescence method. Thin film sensors are reusable, easy to use, no pollution for under test system and easy device, etc. Fluorescence method have high sensitivity, high selectivity, suitable for multi-parameter analysis, Which make it gradually become a kind of functional thin film materials with great prospects.Unlike fluorescence sensors based upon organic fluorophores, inorganic semiconductor nanostructures have a broad excitation spectrum, narrow emission spectrum, tunable emission wavelength, and stable optical performance, etc. As a sensing element, has many unique advantages in the aspect of sensor. Supramolecular organic gel formed by the weak interaction provides a new idea for the preparation of novel nanometer material. This thesis is focsed on controlling the morphology, particle size, size distribution of the inorganic nanostructures and improving its sensing performance by changing the structure of the supramolecular aggregate.Based on the above consideration, in this thesis, ZnS-supramolecular hybrid film was prepared by in situ synthesis and mixture method, respectively. Inorganic semiconductor nanomaterials as a sensing element, supramolecular gels as a film-forming matrix, small molecular weight organic gelling agents was used to stabilize and confine the inorganic deposition reaction. Specifically, the main work is as follows:(1) A novel ZnS-supramolecular organogel hybrid film has been fabricated by exposing a supramolecular organogel film containing Zn(Ac)2 in H2 S atmosphere at room temperature. XRD, SEM, EDS, UV-vis, PL spectroscopy and PL lifetime were employed to characterize the hybrid film.The results showed that the organogel film acted as a template to control the morphology of the final hybrid films, and the network structure of organogel film effectively prevents the nanoparticles to aggregate. The quantities and sizes of the ZnS nanoparticles embedded in the organogel films can be easily altered by varying the initial concentration of Zn(Ac)2. The sensing measurements showed that is sensitive to some volatile organic monoamines and diamines, and the fluorescence signal obtained is completely reversible.(2) Considering the fact that the different preparation methods of nanomaterial would effect on the nanostructures. Firstly, oil-water interface was used to prepare the ZnS nanoparticles, then the ZnS nanoparticles were introduced into the supramolecular organogel system through the physical mixing and dried at room temperature to get composite film. The results showed that the ZnS nanoparticles is cubic crystalline. ZnS nanoparticles well d dispersed in composite films, and can be stabilized by the structure of supramolecular organogel, enhances the luminescent performance of the composite film.The influence of the content of the ZnS on fluorescence intensity of film and amine vapor sensor performance were systematically studied. The results showed that the higher content of ZnS in films, the stronger fluorescence intensity, the more sensitivity to volatile organic monoamine and diamine steam, and the sensing reversibility is very well.(3) Doping metal ions can effectively control the luminescence of inorganic nanomaterials, it expects to improve their luminescent properties by doping Mn2+ into ZnS nanoparticles, thereby to increase gas sensing properties for amines of the composite film. Firstly, the ZnS:Mn nanoparticles with different concentration of Mn2+ were prepared by the oil-water interface method, then, which were introduced into the supramolecular organogel system through physical mixing, dried at room temperature, to get hybrid film. XRD results showed that doping ZnS has no effect on the crystal type of ZnS. The PL of the ZnS:Mn-organogel hybrid films showed that the red-shift of the PL emissions of the hybrid film was observed with the Mn2+ concentration increases. The fluorescence intensity of the hybrid film firstly increased, then decreased. When the Mn2+ doping content was 1.5%, the fluorescence intensity is the strongest. Sensing performance showed that the quenching efficiency decreased, response time shortened and sensitivity increased with doping content increasing.