Preparation Of Gold And Silver Bimetallic SERS Substrate And Its Application In Food Inspection

Each year, a large quantity of people worldwide face a variety of health risks due to food safety. Illegal traders added food additives illegally, which would pose a serious threat on consumers’ health and economics in general. Therefore, rapid identification and detection of the presence of the poisonous substances in food is one of the vital tasks in analytical chemistry. Studies have shown that azodicarbonamide may cause respiratory issues, allergies and asthma. More seriously, semicarbazide, azodicarbonamide‘s decomposition product, shows limited genotoxicity in vitro and carcinogenicity and has been proved to cause tumors. The residues of ciprofloxacin in chicken can break the balance of vivo environment. Moreover, the more intense use of ciprofloxacin is associated with the emergence and diffuse of drug resistant or even multi-drug resistant pathogen strains. Di(2-ethylhexyl) phthalate is one of the endocrine disrupting chemicals, it can interfere with the hormone system in humans. The residues of it in juice can increase the risk of developing reproductive cancers; what‘s more, it also causes lowered fertility, birth malformations, and sexual development problems.Surface enhanced Raman scattering(SERS) Spectroscopy has shown the advantage of overcoming the low sensitivity of conventional Raman spectroscopy, which makes progress in determination of trace samples. The synthesis of SERS substrate which can enhance SERS signal is the key to the application of SERS. The bimetal nanoparticles are used as SERS substrates widely due to easy preparation and the better enhancement factor. The stability of nanoparticles will be strengthened after adding stabilizer which prevents nanoparticles from aggregation.Phytic acid is economical and ?green‘ reagents and liable to chelate with metal ions because of its structure containing six phosphates separately on both sides of the cyclohexane. As a result, its salts(IP6) were chosen as a stabilizer and bridging agent in the process of synthesis of nanoparticles. Therefore, an optimal SERS approach was used to monitor the trace poisonous addives: azodicarbonamide, ciprofloxacin and di(2-ethylhexyl) phthalate existed in food in order to establish a simple and fast method, and enlarge the applicable area of SERS. The main contents of this article are as follows:We proposed a label-free method to detect trace azodicarbonamide in flour and its relative products by means of the dispersed Au@Ag core-shell nanoparticles, which has a high sensitivity and spectral selectivity and turns out to be reproducibility and reliability. The economic and easy-done proposal Raman assay yielded that the limit of detection(LOD) of azodicarbonamide is 10-7 mol/L in water with an excellent linear range of 10-4 mol/L to 10-3 mol/L which are below the FDA‘s and National standard of China tolerance level of 45 ppm in flour. The recoveries of SERS measurement of flour and steamed bread are in the range from 81% to 95%. This SERS-based method may be suggested as an alternative method to realize rapid, sensitive and online detection of ADA in product by a portable Raman spectrometer for food safety.Ciprofloxacin, a member of the fluoroquinolones family of drugs, is a synthetic antibiotic with broad-spectrum antibacterial activity. It can prevent and control the abuse of antibiotics effectively by detection of ciprofloxacin existed in meat. We aim to make a new type of Au-Ag heterostructured cubes(HSCs) for identification of ciprofloxacin residue in chicken. As a model application as well as a good result, this Au-Ag-HSCs-based SERS method is extremely simple, sensitive, rapid and cost-effective. The LOD of ciprofloxacin is 8×10-8 mol/L in water with an excellent linear range of 10-7 mol/L to 10-6 mol/L. The recoveries of SERS measurement of real samples are both in the range from 91% to 105%.Plasticizing agent is an endocrine disrupting chemical, so rapid identification and detection of the presence of it in food is important for human healths. We controllably prepare the IP6 stabilized Au@Ag core–shell nanoparticles(Au@Ag@IP6) and modificate it in order to make the substrate hydrophobic. Au@Ag@IP6-based SERS method is extremely cost-effective simple, green, rapid and has a high sensitivity. The LOD of di(2-ethylhexyl) phthalate is 10-7 mol/L in water with an excellent linear range of 10-6 mol/L to 10-5 mol/L. The recoveries of SERS measurement of real samples are both in the range from 94% to 102%, demonstrating this approach could be a quick and promising method to screen trace di(2-ethylhexyl) phthalate in real samples.