| Plenty of contaminant exists in environment on account of incomplete com bustion of various organics in nature and other factors, among which the most destructive to human is the organic contaminant with more than two Benzene r ing structure, called Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are very difficult to dissolve in water, which can be accumulated, concentration will rea ch to hazardous level after taken into the body, and be harmful to human bod y such as being carcinogenic, teratogenic, and mutagenic. As the PAHs’ Benze ne ring quantity increases, its water solubility will be lower, but PAHs can bee ome more harmful, hence high molecular weight Polycyclic Aromatic Hydrocarbon s are particularly hazardous to human being. Traditional physical-chemical detec t methods have certain limitation, such as tedious operation, costly equipment, complex pretreatment, etc. Surface Enhanced Raman Spectroscopy technology h as overcome the poor sensitivity of Raman spectroscopy technology, and becom e a reliable detect method of rapid detection of PAHs in aquatic environment.This article introduces using L-dopa reducts chloroauric acid near the silve r seed surface to synthesize Au-Ag alloy nanourchin, and using Frens method t o reduction and synthesize colloid solution of spherical Au. By mixing these t wo nano materials and adjusting pH to promote their degree of polymerization, and optimized parameters such as temperature, proportions, pH values, etc. to make active substrate to achieve the best results. To characterization the optimi zed mixture materials, then measure the diameter of Au-Ag alloy nanourchin aro und 340nm, core diameter is about 300nm, the length of raised part is dozens of nanometers; the diameter of spherical Au is 50nm, spherical Au distributed i ntensively in the spine raised part gap of Au-Ag alloy nanourchin. The portable laser Raman detection system is consisted of a Raman laser device which laser wave length is 785nm and a portable laser Raman spectrometer. To use the well-optimized hybrid-active substrate, our lab configurate and detect high mole cular weight PAHs pyrene (4 rings), benzoanthracene (4 rings) and benzo[a]pyrene (5 rings) in aqueous solution. After treatment to these three high molecular we ight PAHs solid by Raman spectroscopy and different concentrations of SERS spectroscopy, then take characteristic peak attribution analysis, we found that P AHs water solution SERS characteristic peak compared to solid Raman peak, a few wave number drifted. It is speculated that the phenomenon is caused by charge transfer. In addition, experimental data of more than 5 times experiment was selected for processing in each experiment detection, then we get average small SERS characteristic peak intensity variances. indicating the mixture subs trate material has excellent stability and good repeatability of experiment metho d. At the range of lower concentration, intensity of SERS characteristic peak h as a good linear relationship with the concentration of aqueous solution. Accor ding to the calculation formula of Limit of Detection(LOD). using mixed subst rates stated in this article to calculate LOD of high molecular weight PAHs py rene (4 rings), benzoanthracene (4 rings) and benzo[a]pyrene (5 rings), which is 0. 44nM.2.92nM and 1.64nM,respectively.The above-mentioned result indicates that with the mixture nano substrate, three kinds of high molecular weight PAHs were detected and the detect results is in the domestic leading level. This technology could be used for detection o f high molecular weight PAHs in aquatic environment, and also expected to achi eve the in-situ detection of high molecular weight PAHs in the aquatic environmen t in real-time with portable devices supporting. |
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