Au/UiO-66（NH₂） Functional SERS Sensor For Adsorptive Detection Of Dyes In Food

Food synthetic colorants are critical to food processing to make products with better attractive appearance and higher acceptability.However,excessive consumption of synthetic colorants may incur threat to human health.In order to protect human health and prevent the illegal abuse of dyes in food,researchers have developed a variety of different analytical techniques for the identification and quantitative analysis of synthetic colorants in food,mainly including HPLC,LC/MS,TLC,capillary electrophoresis,etc.But most of these methods are time-consuming and laborious with complicated steps.Thus,growing studies have been performed aiming at developing accurate,sensitive and rapid techniques for the detection of synthesis dyes in foods.Surface-enhanced Raman scattering（SERS）spectroscopy is a novel technology with superior sensitivity,rapid detection speed and molecular specificity fingerprint.In recent years,due to the development of metal-organic framework（MOFs）materials,SERS substrate combining MOFs with adsorption ability has attracted certain attention in food analysis.In this study,MOFs was introduced into SERS substrate and Au/Ui O-66（NH₂）was fabricated as functional SERS sensor.MOFs with absorption property could narrow the distance between target molecules and plasma nanoparticles（PNPs）,which was beneficial to improve SERS effect.Then the functional SERS sensor was used in the adsorption and SERS detection of new coccine and acid orange II.The main contents and conclusions are as follows:（1）The synthesis of PNPs/Ui O-66（NH₂）.Ui O-66（NH₂）was prepared as MOFs materials through solvothermal method and gold nanoparticles（Au NPs）or silver nanoparticles（Ag NPs）were grown on Ui O-66（NH₂）via bonding and reduction reaction to synthesize Au/Ui O-66（NH₂）and Ag/Ui O-66（NH₂）,respectively.Then scanning electron microscopy（SEM）,X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FT-IR）were used to characterize the above three materials.The results indicated that the Ui O-66（NH₂）synthesized by solvothermal method showed octahedral crystal structure with an average particle size of230 nm,excellent crystallinity and complete-uniform morphology and that Au NPs or Ag NPs were successfully coated on Ui O-66（NH₂）without destroying the crystalline structure of Ui O-66（NH₂）.In addition,the absorption and SERS active of Au/Ui O-66（NH₂）and Ag/Ui O-66（NH₂）to new coccine and acid orange II were compared.The results demonstrated that Au/Ui O-66（NH₂）without Raman background peak has better adsorption capacity and fine SERS effect to the two kind of dyes,which was suitable to be used as the functional SERS sensor for the adsorption and detection research of new coccine and acid orange II.（2）Synthesis optimization and study on adsorption performance of Au/Ui O-66（NH₂）.Au/Ui O-66（NH₂）with different particle sizes of Au NPs were prepared by changing the concentration of HAu Cl₄ and characterized by SEM,adsorption performance and SERS activity test.The results showed that when the concentration of HAu Cl₄ was 20 m M,Au NPs on the MOFs are evenly distributed with an average particle size of 33.15 nm and the Au/Ui O-66（NH₂）have excellent performance for adsorption and SERS detection to new coccine and acid orange II.Further,the adsorption ability of optimized Au/Ui O-66（NH₂）was studied,which revealed that p H of dyes solution did not affect significantly the adsorption of Au/Ui O-66（NH₂）for dyes,while the concentration of Au/Ui O-66（NH₂）and incubation time had a great influence on the adsorption rate.The adsorption rate reached the maximum with 2 mg/m L of adsorbent,and the adsorption tended to balance when the incubation time was 120 min.（3）Study on SERS detection of new coccine and acid orange II.Based on optimized condition（the incubation time and volume ratio of substrate with dyes,the concentration of substrate and concentration multiple of mixture solution）,Au/Ui O-66（NH₂）functional SERS sensor achieved quantitative detection of new coccine and acid orange II,with the quantitative curves of y=712.478x+330.404 and y=192.923x+290.724,the linear ranges of 1-50 mg/L and 0.1-50 mg/L,and the detection limits of 0.4015 mg/L and 0.0546 mg/L,respectively.Then the SERS sensor was utilized to analyze the new coccine and acid orange II in food samples with recoveries of 82.92-109.63%,whose results were comparable to those of HPLC and proved the possibility of the practical application of the functional SERS sensor in food detection.