Preparation Of High-viscosity And Flexible SERS Substrate And Its Application In The Detection Of Pesticide Residues In Fruits And Vegetables

The traditional methods for the detection of harmful substances in food are usually characterized by expensive equipment and technology,long detection time,and incapability of rapid on-site detection.Surface enhanced Raman spectroscopy?SERS?technology is a high sensitive analysis tools,to provide strong structural characteristic information of the molecular level.With the development of nanotechnology,laser light source and computer technology,SERS has been widely applied in research fields such as food safety,biological medicine,environmental detection and public safety.At present,the development of a new SERS analysis method has been a hot area of research in the field of surface-enhanced Raman spectroscopy,which can be used for efficient extraction of on-site samples and rapid in situ detection.Due to the complexity of the sample surface,the traditional rigid SERS substract was unable to fully extract analytes from surface of targets.Recently,much attention has been paid to the flexible SERS substrate due to its powerful flexible properties that are more suitable contact with the targets.However,most of the existing flexible SERS substrates are based on fiber paper,tape and graphene,leading to unsatisfied SERS enhancement and reproducibility.Moreover,improving the stability and repeatability of the flexible SERS substract and fast in situ analysis of pesticide residues became the focus of our research.Main researchs and the obtained results are as fellows:1?The prepared silver nanosol was directly dropped onto the inside of a highly transparent fluorescent quantitative PCR membrane?HTFQ-PCR-M?.Then,the SERS substrate with uniformity,flexibility,viscosity and heat resistance was obtained.Compared with the common SERS substract based on adhesive tape,it overcomes the shortcomings of the traditional adhesive tape,which is easy to oxy-genated and fall off from surface of substract in heating.We directly pasted the SERS substract on the surface of the fruit to extract targets.Then pesticide residues on the surface of the fruit were successfully detected in situ.In addition,the methylene blue and rhodamine B were detected in situ by a simple pasting-stripping method.The heat stability has carried on the exploration of the SERS substract,the high-sticky and flexible SERS substract was used under 90?can still maintain good SERS activity.Therefore,the prepared high sticky and flexible SERS substract can provide a potential application prospect for the detection of trace substances in field samples through a simple"paste and peel"method.2?Based on the first work,we used the prepared SERS substract with high sticky and flexible to directly detect the acetamiprid molecules.Due to the SERS substract has better sensitivity,stability,repeatability and other characteristics,it was able to extract the target rapidly and efficiently,which made the target enter into the surface of nanoparticles,and thus the SERS method was used for detection directly.Due to the presence of cyano group in acetamiprid,vibration absorption peak will be generated in the Raman quiescent region,which is quantified at 2145 cm^-11 and the lowest detected concentration to 10^-99 mol·L^-1.The characteristic peak has particularity and is not disturbed by other impurity peaks.In addition,the aggregation of acetamiprid at different concentrations was studied.It proved that the small Raman displacement in the Raman quiescent region caused by the aggregation between molecules at high concentration.Due to the weak interaction between acetamiprid molecules and metal nanoparticles,the detection sensitivity of this process is low,which is not suitable for the analysis and detection of practical samples.Therefore,it is necessary to further improve the sensitivity of the detection method.3?Due to the weak interaction between acetamiprid and silver nanoparticles,in order to improve the detection sensitivity for acetamiprid,the aptamer was introduced into the system.After the combination of the aptamer and acetamiprid,the structure changed,and through direct detection of the changes of SERS signal of the adenine,the signal of acetamiprid was detected indirectly.This high viscosity and flexible SERS substract has a good specificity for the amidine molecule,and the minimum detection limit for amidine reach to 1 nM.It has a good linear relationship between concentrations of 10^-55 mol·L^-11 to 10^-99 mol·L^-1,R²=0.921.The recoveries of samples were between 87.1%and 110.4%,the RSD was below 11%.Therefore,this method has a great significance for the combination of aptamer and SERS technology in the application of pesticide detection.