Study Of Room Temperature Ammonia Sensors With Tin-based Compound Nanomaterials

As modern agriculture and industry rapidly develop,ammonia emissions are increas-ing significantly.As a common toxic gas pollutant,ammonia can affect people’s health when it is present in high concentrations in the environment.However,currently available commercial sensors for ammonia detection operate at relatively high temperatures and are generally costly.The high operating temperatures not only lead to high power consumption but also to safety risks,which has created an urgent need for ammonia detection technology at room temperature.In this paper,we firstly synthesized self-assembled three-dimensional hierarchical SnS₂nanoflowers,S-SnO₂nanoflowers and raspberry-like Zn-SnS nanomate-rials as sensitive materials to prepare gas sensors,and systematically carried out the testing and analysis of gas-sensitive properties;secondly,we analysed the microscopic morphol-ogy,elemental composition and valence state of the materials;finally,we used the micro-scopic morphology,elemental composition and valence state of the materials to analyse the gas-sensitive mechanism of the materials.The gas-sensitive mechanism of the materials was then analysed in terms of their microscopic morphology,elemental composition and valence state,etc.Finally,the adsorption characteristics of ammonia gas on the surface of the materials were modelled and simulated using the first principles approach.The main studies are as follows.（1）The self-assembled SnS₂nanoflower was synthesised based on a simple one-step solvothermal method.The characterization results show that the SnS₂materials were suc-cessfully synthesized and well crystallized,and nanosheets with a thickness of 30～40 nm self-assembled to form three-dimensional hierarchical nanoflower-like SnS₂materials with a diameter of about 5～7m.The ammonia-sensitive properties of the SnS₂materials were tested at room temperature,and the experimental results showed that the nanoflower-like SnS₂showed good selectivity towards ammonia at room temperature,but the response val-ues did not reach the expected results.（2）The three-dimensional graded nanoflower-like S-SnO₂material was obtained by high temperature oxidation in air using nano-flower-like SnS₂as the precursor material.After high temperature oxidation,many SnO₂nanoparticles were formed on the surface of the self-assembled nano-flower-like SnS₂material,which were uniformly dispersed on the surface of the nano-flower.After testing,the response value of the S-SnO₂sensor to ammonia gas was approximately three times higher compared to the SnS₂sensor at room temperature,and other gas-sensitive properties,such as response value and selectivity,were substantially improved.In addition,the ammonia-sensitive mechanism is discussed from both material morphology and heterojunction perspectives.（3）The raspberry-like Zn-SnS nanomaterials were synthesized by a one-step solvother-mal method,and the response of the materials to ammonia gas was tested at room tempera-ture using SnS as a control group.The results showed that the Zn doping greatly improved the response of the material to ammonia,with a response value of 567%at 50 ppm ammo-nia,and a rapid response and short recovery time.In addition,the response mechanism of the Zn-SnS material to ammonia gas was analysed in terms of electronegativity differences and adsorption energy by density flooding theory（DFT）calculations.