Construction Of Microporosity-based Sers Sensing Platform Integrated With Sieving/enrichment Functionality And Its Sers Application

Surface-enhanced Raman spectroscopy（SERS）is a rapid,highly sensitive and fingerprint identification analytical technique whose applications have expanded from environmental and food safety to biomedical life sciences.Among them,the rapid and sensitive detection of gaseous molecules and drugs and their metabolites is extremely important for public safety and human health,but there are still some problems to be solved for their rapid analysis and detection applications.Firstly,the highly active silver nanostructures are susceptible to erosion by oxygen,and their chemical instability can lead to reduced activity or irreducible spectra.Secondly,gas molecules have a small scattering cross-section,diffuse quickly and are prone to escape.Drugs and their metabolites are complex in composition,with no obvious chemically active sites to interact with the SERS substrate.Thirdly,the targets are present in complex matrices,often in trace form,and analogues and co-occurring components with high concentration can cause serious interference in the SERS spectra,affecting the identification and analytical detection of the trace targets.The combination of sample pre-treatment and SERS techniques can be effective in the separation and enrichment of targets before trace detection,but in practice there are still drawbacks in terms of long pre-treatment time and high detection costs.In this thesis,three types of composite nanomaterials with integrated microporous sieving/enrichment function and SERS detection were developed based on polymeric microspheres embedded with silver nanoparticles（Ag NPs）or polymeric membranes loaded with Ag NPs,combined with the intrinsic microporous properties of polymeric mesh or metal-organic skeleton（ZIF-8）structures,and achieved the detection of methamphetamine（MAMP）and some volatile organic pollutant gases（VOCs）for rapid trace detection.The main studies are as follows.（1）The development of rapid field detection of trace drugs in complex biological samples is essential for combating drug crime and maintaining public safety.Aiming at the problems of complex matrix interference and complex operation process of SERS technology application,a SERS-active microsphere based on microdroplet template was designed and developed for the rapid field detection of MAMP in whole blood,saliva and hair.The polymeric grid forming the hydrogel has 5-7 nm micropores,which can both immobilize Ag NPs without causing more significant aggregation and oxidation,and exclude large molecules from the biological matrix,enabling highly selective and sensitive detection of target small molecules.The highly sensitive detection of MAMP in the three biological substrates can be achieved without pre-treatment of whole blood and saliva samples,and only acidification and hydrolysis of hair samples.The linear range is 0.1-100 ppm,and the lowest detectable concentration is as low as 0.1ppm,which meets the actual detection requirements.The established hydrogel SERS-active microspheres have the advantages of universal applicability,simple operation,low cost and high throughput synthesis,without the assistance of other pre-treatment instruments,and are expected to provide practical applications for rapid real-time analysis in drug enforcement sites.（2）Sensing detection of aldehyde volatile gases has been widely applied in many fields such as environmental detection and health monitoring,and it is of great significance to develop a sensing method for trace aldehyde gases based on SERS technology.CNF@Ag NPs and CNF@ZIF-8 solutions were prepared using cellulose nanofibers（CNF）as the carrier,and CNF@Ag NP/CNF@ZIF-8 composite membranes were obtained by vacuum filtration after mixing the two solutions.The highly sensitive detection and analysis of aldehydes was achieved by an indirect detection method using p-aminothiophenol（PATP）as the probe molecule and aldehyde gas trapping agent.It was shown that the SERS detection performance was dependent on the amount of PATP grafted,the ZIF-8 content and the thickness of the membrane,and that the best adsorption and detection of benzaldehyde and formaldehyde gas molecules was achieved at n _{CNF@Ag NPs}:n _CNF@ZIF=40:1.The minimum concentration for benzaldehyde detection was 2×10^-8v/v and for formaldehyde detection was 2×10^-6 v/v at 80°C ambient at 1 Bar.Furthermore,effective differentiation of other different species of aldehydes can be achieved based on the molecular fingerprint properties and stoichiometry of Raman spectroscopy.（3）Aromatic and halogenated VOCs can be a serious health hazard and may even be carcinogenic.In the detection of such gas molecules,combining Ag NPs with ZIF-8 for gas sensing is a better strategy due to the lower concentration and the short time for the gas to reach adsorption equilibrium on the substrate surface.Based on the study in the previous chapter,effectively increasing the specific surface area of nanocomposite films is one of the ways to solve the problem of low adsorption and fast diffusion of VOCs.CNF@Ag NPs@ZIF-8nanocomposite membranes were prepared by growing ZIF-8 in situ on CNF@Ag NPs.Modulation of the ZIF-8 content can effectively increase the specific surface area for this SERS sensing platform to achieve direct detection of target gas molecules.The results show that the best enrichment and SERS detection of toluene and chloroform gas molecules is achieved when n _CNF@Ag:n _ZIF-8=1:75,under 1 Bar conditions and 80°C ambient atmosphere,with the minimum concentrations of 2×10^-7 v/v and 2×10^-6 v/v for toluene and chloroform respectively,which is expected to enable the differentiation and quantification of the gas mixture according to the molecular fingerprinting properties of Raman spectroscopy.The molecular fingerprinting properties of Raman spectroscopy are expected to enable the differentiation and quantification of mixed gases.In addition,the identification of CO₂ gas molecules adsorbed on the surface of composite membrane materials can be achieved by using CO₂ gas molecules as the object of study.