Construction And Application Of Fluorescent Probes And SERS Substrates For Several Environmental Pollutants

Accurate detection of environmental pollutants provides a very important reference for environmental pollution assessment,treatment and management.For the harmful pollutants,the microanalysis of pollutants is particularly important.From the perspective of pollutants,formaldehyde,D-penicillamine,arsenite and uranyl were selected as representatives to explore the application of fluorescence and surface enhanced Raman spectroscopy（SERS）in environmental analysis.According to the characteristics of pollutants,this paper constructs microanalysis methods for different pollutants.Fluorescence analysis methods for formaldehyde and D-penicillamine were established by constructing fluorescence probe.By constructing SERS enhanced substrate,SERS analysis methods for arsenite（As（Ⅲ））and uranyl were established respectively,and these methods were verified.The main research contents and conclusions are as follows:Formaldehyde is an important volatile organic pollutant as well as a class of carcinogens and its sensitive detection is necessary.In this paper,a novel organic small molecule fluorescent probe is reported for highly sensitive and selective detection of formaldehyde.The fluorescent probe consists of fluorophore NBD（7nitrobenzofurazan）and a hydrazine group.The hydrazine group in probe molecule can be used not only as a fluorescence quenching agent based on photoinduced electron transfer（PET）mechanism,but also as a reactive site for selective identification of formaldehyde molecules.In the presence of formaldehyde,the fluorescent probe reacts with formaldehyde to form a Schiff base compound,which inhibits the PET process from hydrazine group to NBD fluorophore,thus making the fluorescence "turn-on".It is worth noting that fluorescent probe is more sensitive to formaldehyde under acidic conditions.Under the optimized conditions,the fluorescence probe showed a linear response to formaldehyde in the range of 0.015-0.8 mg·L-1,and the fluorescence intensity increased nearly 30 times.We successfully applied the probe to the quantitative detection of gaseous formaldehyde in indoor air,and prepared the fluorescent probe into fluorescent test paper to realize the visual detection of formaldehyde.D-Penicillamine is an important antibiotic hydrolyzate that can be used to indicate antibiotic contamination levels.In this paper,according to the properties of Dpenicillamine,a pH-regulated fluorescence-colorimetric dual-signal probe was reported for the detection of D-penicillamine.The dual signal probe consists of fluorescent carbon dots and monodisperse gold nanoparticles.The monodisperse or agglomerate state of gold nanoparticles will affect the fluorescence of carbon dots.Dpenicillamine is an amphoteric compound,which exists in different forms in different pH environments.The sulfhydryl group of D-penicillamine has a high affinity for the surface of gold nanoparticles and can replace its surface ligand.When the pH value of the environment is close to its isoelectric point（pH（Ⅰ））,the D-penicillamine on the surface of gold nanoparticles can promote the agglomeration of gold nanoparticles through hydrogen bonding and electrostatic interaction.The gold nanoparticles then release the carbon dots,making the fluorescence recovery.Under the optimal conditions,the probe showed a good linear response to D-penicillamine in the concentration range of 0.25-1.5 μM,with a detection limit of 0.085 μM.This method provides a new idea for sensitive detection of D-penicillamine.Arsenous acid（As（Ⅲ））is an important heavy metal pollutant with strong toxicity.Based on Raman signals generated by As-O stretching vibration,this paper developed a simple and feasible SERS method for on-site selective analysis of As（Ⅲ）.The SERS method relies on the synergy between nanoparticle aggregation and analyte adsorption.In order to improve the detection ability of As（Ⅲ）,phosphate was introduced in the detection process.The experimental results show that phosphate can regulate pH,promote agglomeration of nanoparticles and promote adsorption of As（Ⅲ）on the surface of silver nanoparticles.The method has a good selectivity and a linear relationship between 5×10-8-0.8×10-6 M and a detection limit of 1.8×10-9 M.Finally,we applied this method to actual water samples and successfully detected SERS signal of trace As（Ⅲ）,indicating that this method has application potential in actual detection scenarios.Uranyl is an important radioactive contaminant.In this paper,a core-shell structure SERS substrate Au@ZIF-8 was designed and constructed,which overcame the problems of uncontrollable agglomeration of nanoparticles and weak enhancement effect of single particles,and realized SERS detection of UO2²⁺ through the joint action of adsorption and local plasmonic resonance.Au@ZIF-8 is a core-shell nanomaterial composed of gold nanocores and ZIF-8 shells,and its shell ZIF-8 is formed at the gold nanocores nanointerface,which is beneficial to protect gold nanoparticles and adsorb uranyl.The experimental results show that Au@ZIF-8 can effectively enhance the Raman signal of UO2²⁺ and can detect UO2²⁺ at a concentration as low as 0.5 μM.Au@ZIF-8 was successfully applied to the detection of UO2²⁺ in actual samples,demonstrating its application potential.