Photocatalytic And Chemical Sensing Properties Of Biomass/Zinc Sulfide Quantum Dots Composites

With the continuous development of society and increasing environmental pollution,it has become a hot spot for people to improve the environment through quantum dot photocatalytic treatment of environmental pollutants and chemical sensing to monitor pollutants in water.Semiconductor quantum dots（QDs）have unique advantages in photocatalysis and chemical sensing due to their unique optoelectronic properties.However,the existence of quantum dots alone has many problems in practical applications,such as complicated preparation methods,easy agglomeration,uncontrollable size,and poor biocompatibility,which limits its further application.Biomass resources,such as cellulose andβ-cyclodextrin（β-CD）,have numerous active sites,such as hydroxyl groups and carboxyl groups,which make biomass materials a good material for complex quantum dots.In this paper,biomass resources（cellulose andβ-CD）are combined with non-toxic semiconductor ZnS quantum dots,and a biomass-based quantum dot composite with excellent fluorescence properties and good biocompatibility is prepared by a simple method.The application of composite materials in the field of photocatalysis and chemical sensing was studied,and its basic properties were characterized by instruments.1.The ZnS quantum dot cellulose composite with good photocatalytic performance was prepared by using cellulose fiber as the substrate and then loading the ZnS quantum dots on the cellulose fibers by one-step hydrothermal method.When the hydrothermal reaction conditions are Zn²⁺concentration:0.075 mol/L,hydrothermal temperature:180°C,and hydrothermal time:12 h,the quantum dot has the best loading rate of 9.4%.The experimental results show that the photocatalytic degradation rate of the composite material to methyl orange was 83%within 30 min,and it had good photocatalytic cycle performance.After 6cycles of recycling,the photocatalytic degradation rate of the composite material could still reach 59%.At the same time,the quantum dots on the surface of the cellulose fiber are evenly distributed,there is no large agglomeration phenomenon,and the fluorescence performance is excellent.The maximum fluorescence emission is obtained at the excitation wavelength of380 nm,and the photoluminescence color is blue light.2.Using cellulose fiber as the substrate,ZnS quantum dots and graphene were assembled under a simple one-step hydrothermal reaction,and they were loaded on the surface of cellulose fibers,and the transition metal manganese was doped in the process,thereby obtaining ZnS/GO and Mn:ZnS/GO/cellulose composites with further enhanced photocatalytic activity.The experimental results show that the two composite materials have excellent photocatalytic activity,and the photocatalytic process follows the first-order reaction kinetics.The methyl orange can be almost completely photodegraded within 15 min.After 10cycles of recycling,the photocatalytic degradation rate of the composite materials could still reach 57%.At the same time,the ZnS QDs and Mn:ZnS QDs have uniform particle size and are dispersed on the graphene sheets on the surface of the fibers without obvious agglomeration.3.N-acetyl-L-cysteine（NAC）was used as a cross-linking agent to obtain thiolatedβ-CD by a simple one-step esterification reaction,and then theβ-CD-NAC/ZnS quantum dot composite with chemical sensing function was obtained by water synthesis method.The experimental results show thatβ-CD and NAC obtain thiolatedβ-CD（β-CD-NAC）by esterification reaction.The preparedβ-CD-NAC/ZnS quantum dot composites emit blue light and have excellent fluorescence characteristics,and the presence ofβ-CD reduces the agglomeration of ZnS QDs,and the dispersion uniformity is good.The particle size is mostly below 10 nm.Based on the fluorescence quenching ofβ-CD-NAC/ZnS quantum dot composites,a non-toxic and environmentally friendly detection of p-nitrophenol（4-NP）fluorescence sensing platform was developed with the fluorescence quenching constant K_svv of25969.67 M^-1 and detection limit LOD of 2.0μM,which has a good ability to detect p-nitrophenol.