Construction Of Molecularly Imprinted QCM Sensor Based On Formaldehyde Detection In Environment

Formaldehyde（HCHO）is an important chemical raw material.Because of its low cost and comprehensive utilization rate,it is widely used in the production of chemical products,construction materials,textile industry and other fields.In addition,due to its bactericidal and antiseptic effects,HCHO has also been abused as a preservative for vegetables,fish,and other products,posing a potential threat to human health.The free HCHO in the environment is a substance that will cause serious harm during production and use.Prolonged contact,inhalation or ingestion will inevitably bring harm to human life and health.Therefore,while HCHO benefits mankind,it also brings disasters to mankind.Molecular imprinting technology is to dissolve functional monomers and template molecules in a solvent to form a stable complex.Because polymers can provide people with molecular combinations with desired structures and unique physical and chemical properties,they have become a research hotspot at home and abroad,and are widely used in environmental testing,drug separation,food safety monitoring and other fields.In recent years,many scholars have begun to establish molecular models to simulate the design and preparation of MIPs.Here,by using Gaussian 09 program,the B3LYP method in quantum chemical density functional theory was adopted,HCHO was used as the template molecule,the functional monomers were selected from methacrylic acid（MAA）,itaconic acid（IA）,4-vinylpyridine（4-VPY）,and acrylamide（AM）,cross-linking agents were selected from divinylbenzene（DVB）,ethylene glycol dimethacrylate（EGDMA）,pentaerythritol triacrylate（PETA）,and trihydroxymethylpropol trimethylacrtlate（TRIM）,the solvents were selected among six types of acetonitrile,water,methanol,chloroform,tetrahydrofuran,and toluene.The configuration of the molecularly imprinted self-assembly system of HCHO and different functional monomers was simulated,and the optimal functional monomers that formed a stable complex configuration with HCHO template molecules were screened.The cross-linking agents and solvents were optimized,and the essence of HCHO imprinting was revealed with the aid of the atom in molecule theory（AIM）.The calculation results showed that the HCHO template molecule and AM functional monomer interact through hydrogen bonding.When the ratio between HCHO and AM was 1:4 and PETA was used as the cross-linking agent,the HCHO-AM complex formed in methanol solvent was arranged in an orderly manner.The complex configuration had the lowest energy and the best selectivity for HCHO.Then,using the theoretical calculation results as the guide,AM was used as the functional monomer,PETA as the cross-linking agent,methanol as the solvent,the HCHO molecularly imprinted polymers（MIPs）and non-molecularly imprinted polymers（NIPs）were prepared by precipitation polymerization with the molar ratio of HCHO,AM and PETA of 1:4:16.Then its performance and morphology had been characterized.The experimental results showed that the HCHO-MIPs samples were spherical,the average particle size was 250 nm,and the maximum apparent adsorption quantity Q_max and the dissociation equilibrium constant K_d were 54.67 mg/g and 72.46 mg/L,respectively.The adsorption capacity was fit the quasi-second-order kinetic equation.The selectivity test showed that HCHO-MIP_S had the best selectivity to HCHO when HCHO and benzaldehyde coexisted.The results of thermogravimetric analysis showed that MIPs was more stable before 300℃,and the polymer almost completely decomposed at491℃.Finally,the HCHO molecularly imprinted QCM sensor was constructed and applied to detect ultra-low residues of HCHO in aquatic products.The experimental results showed that under the detection conditions of 20 mg of HCHO-MIPs,p H=7,and coating volume of 20μL,the molecularly imprinted QCM sensor had the strongest response frequency,with the lowest detection limit LOD=10.72 ng/m L.The selectivity analysis results of molecularly imprinted QCM sensor showed that MIPs had strong adsorption capacity for HCHO.The circulation rate of the sensor was 97.56%～98.60%in 4 times of testing of aquatic products.