Preparation And Properties Of Cross-linked Polymer Fluorescent Materials

The development of reliable methods for rapid and selective detection of trace nitro-explosives is crucial to national security and environmental protection.2,4,6-Trinitrophenol(TNP)is a strong explosive with low safety factor and high detonation velocity,which is widely used in mining,military and other fields.Because of its solubility in water and its wide application in various industries,TNP is likely to pollute soil and groundwater and endangers human health.Therefore,it is urgent to develop advanced methods for the sensitivity detection of TNP in aqueous phase.Fluorescence sensing based on organic luminescent materials is widely used in the detection of nitro-explosives due to its advantages of high sensitivity,low cost,easy realization of portable equipment,etc.However,the poor solubility or dispersibility of common organic luminescent materials in aqueous phase limits their applications in aqueous fluorescence sensing.In this paper,the fluorescence sensing systems based on a series of cross-linked polymer nanoparticles that could be uniformly dispersed in the aqueous phase were prepared by Suzuki-mini emulsion polymerization.Combined with the porosity of the polymer and the characteristics of the nanoparticles,the fluorescence sensing of nitro-explosives in the aqueous phase was realized,and the sensing mechanism was explored.The specific contents are as follows:Cross-linked conjugated polymer PFSiBT nanoparticles were prepared by Suzuki-miniemulsion polymerization with benzothiadi azole diboronic ester and tetrabromofluorenylsilane as monomers.The particle size of the nanoparticles is about 9 7 nm,which could be uniformly dispersed in the aqueous phase.The BET surface area of PFSiBT is 446.79 m2/g,and the pore size is concentrated at 0.86 nm.The porosity is beneficial to the adsorption and diffusion of explosive molecules.In fluorescence sensing experiments towards nitro-explosives,the sensitivity and selectivity detection of TNP in the aqueous phase was realized with the quenching constant of 3.53 × 104 M-1 and the limit of detection of 0.71 μM,and good anti-interference characteristics towards common ions was observed.The TNP in actual water samples was detected by standard addition/recovery method,and the recovery rate of TNP in different water samples was 95.50%-103.14%.The t-test data showed that there was no significant difference between the fluorescence detection method using polymer PFSiBT nanoparticles as sensing material and the HPLC method at the 95%confidence level.Cross-linked conjugated polymer PTPEBP nanoparticles based on aggregation-induced emission(AIE)active tetraphenylethene were prepared by Suzuki-miniemulsion polymerization.The average particle size of the nanoparticles was 5 6 nm,and the fluorescence quantum yield of PTPEBP aqueous dispersion was 8.14%.The BET surface area of PTPEBP nanoparticles is 69.1 m2/g,and the pore size is ca.2.5 nm.The high fluorescence quantum yield in aqueous phase and porosity are beneficial to realize the fluorescence sensing towards nitro-explosives in the aqueous phase.PTPEBP nanoparticles were used as sensing materials to detect nitro-explosives in aqueous phase,and the detection towards TNP exhibited high sensitivity and anti-interference characteristics.The quenching constant is 2.50 × 104 M-1,the limit of detection is 1.07 μM,and the limit of quantitation is 3.57 μM.The TNP in actual water samples was detected by standard addition/recovery method.The relative standard deviation of TNP detection in different water samples was 1.16%-2.18%,and the recovery rate was 98.00%-101.32%,demonstrating that the cross-linked conjugated polymer PTPEBP nanoparticles had the ability to detect TNP in actual water samples.Organic/inorganic hybrid nanomaterials have good water dispersibility.Three kinds of fluorescent silica nanoparticles MSNs-Cz,MSNs-ANT and MSNs-TPE were prepared by the reaction of vinyl carbazole,vinyl anthracene and vinyl tetraphenylethene with thiol-containing silica nanoparticles via thiol-ene click chemistry.The particle sizes of the three nanoparticles were concentrated in 75-85 nm,and the fluorescence quantum yields of their aqueous dispersions were 0.12%,0.22%and 9.73%,respectively.The higher fluorescence quantum yield of MSNs-TPE could be attributed to the introduction of AIE active TPE.MSNs-Cz,MSNs-ANT and MSNs-TPE aqueous dispersions were used to detect TNP.Among them,MSNs-TPE exhibited the best sensing performance due to its high fluorescence quantum yield.The quenching constant was 7.49 × 104 M-1,the limit of detection was 0.5 5 μM,and selective detection and ion anti-interference characteristics were realized.Through mechanism exploration,it is found that the fluorescence quenching is affected by multiple mechanisms,and the main mechanism of high sensitivity and selective detection towards TNP based on MSNs-TPE is the fluorescence inner filter effect.