Wearable And Flexible Nanoporous SERS Substrate For Sweat Enrichment And Analysis

The rapid development and growth of the global economy and technology have brought convenience to human life but also contributed to the proliferation of various environmental and health issues.As a result,people are paying close attention to health and the environment.The need for continuous monitoring of environmental pollution and personal health has also contributed to the development of various technologies.Surface-enhanced Raman spectroscopy（SERS）,with its sensitive,rapid,universal,non-invasive detection and molecular fingerprinting characteristics,has shown great potential for trace detection analysis and identification of materials,so it’s a promising spectroscopic analysis technique.Nowadays,more and more SERS substrates are being designed as wearable biosensors to provide non-invasive medical diagnosis and personal health monitoring.However,the complex procedures for sample pre-treatment and the preparation and practicality of SERS substrates limit the wide application of this technology.To solve the above problems,a scheme to design a flexible nanoporous SERS substrate for contaminant and human sweat pathological component detection was proposed.Therefore,a flexible nanoporous SERS substrate was prepared by in situ synthesis of gold nanoparticles（Au NPs）on a polycarbonate（PC）ion-track etched membrane by a one-step reduction method without the addition of surfactants,and a series of SERS tests were performed on the gold nanostars（Au NSs）/PC substrate with optimal particle distribution density,size and morphology by tuning the particle distribution,and the experimental results showed that the substrate possessed the merits of high sensitivity,uniformity,mechanical strength,stability and versatility.In addition,further optimizing the substrate for wearable biosensors proved the potential application in human wearable devices for sweat analysis,which is important for the development of wearable devices for autonomous testing and non-invasive analysis.In this work,a flexible Au NSs/PC SERS sensor with a nanoporous structure was developed to obtain information on environmental contaminants and sweat by enriched analytes.The main comments are as follows:（1）Heavy ion track PC membrane was prepared based on the Heavy Ion Research Facility in Lanzhou（HIRFL）irradiation technique.And then was sensitized and chemically etched to obtain PC ion-track etched membrane.Substrate optimization was achieved by adjusting the pore size and pore density of the PC base film and the p H of the solution.The solution diffusion order was controlled and a series of Au NPs were synthesized in situ on the surface of the PC ion-track etched membrane for SERS detection,and the results showed that the Au NSs/PC substrate had an optimal SERS signal response.The Au NSs were characterized by SEM,TEM,and XRD,and the particles were observed to have a more symmetric sharp structure with uniform distribution,a large number of hot spots,and a structure superior to（111）surface growth.（2）To investigate the advantages of the extraction method for sample processing and the versatility of Au NSs/PC substrate SERS performance,for contaminant detection by this method.The SERS detection of methylene blue（MB）in a wide range of concentrations from 10^-4to 10^-13M was performed by filtration,and the results showed that the substrate not only achieved a minimum detection limit of 10^-13M for MB with a corresponding enhancement factor of 4×10⁷,but also effectively reduced the backbone signal and enabled the identification of different substances.The relative standard deviations（RSDs）were 6.82%and 5.71%for the random multipoint initial signal intensity at 446 cm^-1and 1623 cm^-1peaks,respectively,which showed good uniformity.In addition,trace detection was achieved for the antibiotics clenbuterol hydrochloride CL,chloramphenicol CAP,tetracycline TH and the preservative sodium benzoate SB.（3）To investigate the substrate stability and the corresponding SERS performance as a sweat sensor.The flexible SERS substrate was found to work well after 2000 bends and exhibited excellent long-term usage stability（at least 270 days）without additional protection.The fabrication process was simple,low cost,and reusable after cleaning,further reducing the use-cost and promising to be ready for mass preparation.Human sweat experiments demonstrated that the SERS sensor can effectively identify urea（Urea）,glucose（Glu）,lactic acid（LA）and uric acid（UA）components in sweat.In addition,the sensor can dynamically monitor the change of sweat UA after ingesting different diets,which was expected to enable gout management by monitoring the change of sweat UA.In summary,this SERS substrate achieved the detection of multiple contaminant molecules and related pathological components in sweat,providing a reference significance and effective way to achieve rapid and stable contaminant detection as well as the development and promotion of medical health monitoring devices for independent,non-invasive detection and analysis.