Study Of Illicit Drugs Detection Based On SERS Methods Under Different Systems

The abuse of illicit drugs has been a serious problem in the world and rapid detection of drugs is important for crack down on drug crimes precisely.Spectroscopy is a good detection technique due to the variety of controlled drugs.Raman spectroscopy also plays an important role in the field of illicit drugs detection.Raman spectroscopy,one of vibrational spectroscopic methods,has the ability to provide a highly specific molecular fingerprint even samples are in aqueous solutions and various forms of packaging.However,one of the main limitations of Raman spectroscopy is that the Raman scattering is inherently weak.Surface-enhanced Raman spectroscopy(SERS)is effective in ultra-trace analysis via selectively enhancing Raman signals via noble metal nanostructures The SERS technique has potential to resolve a mixture into its individual components because of molecular specificity.Thus,it may develop to be a viable method for identification of illicit drugs in complex systems.In addition,no single technology or sample can provide all the toxicological information,and only through various analytical methods and different biopsies can more information be obtained.Considering the actual demand under different systems,we carried out the works about illicit drugs detection methods based on SERS with "reproducibility,easy operation,low cost" as the guideline.We attempt to promote the SERS technology in the practical application.The specific work includes the following parts:(1)A sodium chloride crystals-driven spontaneously hot spots structure was demonstrated as SERS-active platform to get reproducible SERS signals and eliminated the need for mapping large areas in comparison with solution phase.During the process of solvent evaporation,the crystals produced in colloids and induced silver aggregates to assemble around themselves.And the micro-scale crystals can act as the template to obtain optical position,such that the assembled hot area is conventionally located during SERS measurements.More importantly,the chlorine ions added in colloids can also replace the citrate and corresponding decomposition coated on the surface of the silver sol,and further decrease the background interference.The high quality SERS spectra from heroin,methamphetamine(MAMP)and cocaine have been obtained on crystals-driven hot spots structure with high sensitivity and credible reproducibility.This approach can not only bring the nanoparticles to form plasmonic hot spots in a controlled way thus provide high sensitivity,but also potentially be explored as active substrate for label-free detection of other illicit drugs or additives.(2)In the case of heroin,this is of fundamental importance considering that,once placed on the market,the drug is often "cut" with a variety of substances to stretch the amount of the product and increase profits.As a consequence,the main objective of this work was to demonstrate the capability of Raman spectroscopy to detect small amounts of street heroin,and to distinguish heroin from the most widely used cutting agents.To achieve this purpose,a spectroscopic study on standard samples was initially performed.In this paper,we develop a facile lab-on-a-chip device for instant,ultra-sensitive detection of heroin from real street samples using plasmonics enhanced diatomaceous thin film,which can simultaneously perform on-chip separation using thin layer chromatography(TLC)and highly specific sensing using surface-enhanced Raman scattering(SERS)spectroscopy.Diatomite is a kind of nature-created photonic crystal biosilica with periodic pores and was used both as the stationary phase of the TLC plate and photonic crystals to enhance the SERS sensitivity.The on-chip chromatography capability of the TLC plate was verified by isolating the mixture of actual street heroin,while SERS sensing was achieved by spraying gold colloidal nano-cubes into the sensing spot with the help of iodine stainment.This on-chip TLC-SERS biosensor based on diatomite biosilica can function as a cost-effective,ultra-sensitive,and reliable technology for screening heroin and many other illicit ingredients to enhance public safety.(3)Morphine,a kind of illicit drugs,is also one of the main heroin metabolites.In consideration of a noninvasive way to monitor and identify drug abuse during forensic cases,the urine samples are usually detected.Here,colloidal gold nanorods(Au NRs)were introduced to act as active substrate,because of the strong optical extinction and spectral tunability of the longitudinal surface plasmon resonance(SPR).Thus,well surface-enhanced Raman spectra of morphine even at low concentrations could be obtained by portable Raman spectrometer.For the complex matrix environment of urine,liquid-liquid micro-extraction(LLME),a simple and inexpensive pretreatment,was employed to avoid the interferences.And then,the coupled surface-enhanced Raman spectroscopy(SERS)can give full play to the advantages of high sensitivity and unique spectroscopic fingerprint.According to the zwitterionic structure and physicochemical parameters of morphine molecules,the pH value of urine sample was adjusted to about 9 by buffer solution(KOH/NaB4O7)and the mixture of chloroform and isopropyl alcohol(V/V=9:1)was chosen as extractant.Moreover,such pretreatment was proved to be appropriate for separation and concentration of morphine from urine.The developed LLME-SERS method could provide a detection limit less than 1 ppm in the human urine environment and the whole process of detection just needed take 5?6 min.What's more,the results of urine samples from heroin users exhibited application value of the proposed technique.The excellent performance makes it promising to become a rapid,reliable,and on-spot analyzer,especially for public safety and healthcare.(4)As a special carrier,hair has an incomparable advantage in drug identification.At present,there is no work to introduce SERS technology into the detection of drugs in hair.On the basis that we used Au NRs as the active substrate to detect the low concentration of high-purity methamphetamine molecules,the biopsies were extended to the hair.After cleaning the hairs with dichloromethane and water,they must be lapped and hydrolyzed to destroy the structure of the hair,so that the amphetamines in the medulla can be dissolved in the strong alkali solution.And then,cyclohexane as the extractant was used to extract and enrich drug molecules from hair hydrolysate via LLME method and the organic phase composition was analyzed by SERS method.According to the experimental results,LLME-SERS method can achieve high sensitive detection of amphetamines in hair hydrolysate environment and we can still obtain SERS signal of amphetamines in the hair of drug addicts.The developed method was expected to monitor the history of drug abuse.