Anthocyanin-based Colorimetric Sensor For Detecting Ammonia Gas

Ammonia（NH₃）is a common alkaline gas with a wide range of applications in many fields such as agriculture and the chemical industry.However,it is also corrosive and irritating,which can cause serious damage to human.Therefore,NH₃ sensors have become research hotspots in recent years,such as semiconductor sensors,metal oxide-based sensors,and gas chromatography.These sensors always bring accurate detection but require complex and expensive fabrication processes.Colorimetric sensors respond in a simple and intuitive way and the fabrication is simple and low-cost.In this work,porous colorimetric sensor and colorimetric sensing yarn were prepared by using anthocyanin as the responsive material,hemp fiber and cotton yarn as the substrate material,respectively.The main contents are as follows.（1）A biomass-based colorimetric sensor was prepared by using anthocyanin and hemp fiber,which was denoted Anth-foam.The physical structure and chemical composition of obtained Anth-foam were characterized by SEM,FTIR,and UV-Vis spectroscopy.The degumming conditions of hemp fiber and the dyeing concentration of dye anthocyanin were explored.The results showed that fibers can be degummed effectively when treated at 100℃with 5%Na OH.The obtained Anth-foam showed a porous structure with a high specific surface area.It achieved the optimal sensitivity to NH₃ when anthocyanin concentration was 35 g/L.The FTIR results indicated strong hydrogen bonding interaction between anthocyanin and hemp fibers.（2）The porous colorimetric sensor Anth-foam and the film-based colorimetric sensor Anth-film were prepared to compare the substrate effect on the sensing performance towards,NH₃.The results showed that Anth-foam has a better response to NH₃,and the response behavior showed a good linear relationship with the increase of NH₃concentration.Anth-foam had a strong acid-base response,reversibility,and reusability.The as-prepared colorimetric sensor showed color change with food spoilage,which indicated the potential application in food freshness monitoring.（3）To improve the sensitivity to NH₃,an environment-friendly colorimetric sensing yarn was prepared by using anthocyanin as the responsive material and cotton yarn as the supporting material,which was denoted 3%WP@PVA-anth.The specific surface area of the colorimetric sensor was significantly increased because of the addition of wool powder.Furthermore,more functional groups were exposed after micronized,which was beneficial to NH₃ adsorption.Results showed the colorimetric sensing yarn exhibited the optimum response behavior to NH₃with a minimum detection of 20 ppm,with a fast response speed,good selectivity,and reusability when the wool powder was 3%and the binder was Polyvinyl alcohol（PVA）.This work provided a new strategy for fabricating NH₃ colorimetric sensors with high sensitivity for practical applications.