SERS Detection Of Traditional Chinese Medicines Meloxicam Based On Silicon Nanowire Arraies

Meloxicam is a non-steroidal drug with anti-inflammatory and analgesic effects,which can selectively inhibit the activity of cyclooxygenase-2 with a strong anti-inflammatory analgesic effect.China has marked the Meloxicam as“List of substances that may be illegally added in anti-rheumatic health products”,but some companies were still illegally added it to anti-rheumatic traditional Chinese Medicines and Health Products in order to quickly achieve the analgesic and anti-inflammatory effects,which brings potential risks to consumers.In this study,silicon nanowire arraies were synthesized as the substrate for surface enhanced Raman spectroscopy（SERS）,and the following results were obtained.The structural optimization and theoretical calculations of Meloxicam molecule were carried out by using density functional theory and Gaussian 09.The best structural formula and theoretical Raman spectrum of Meloxicam was obtained accordingly.Compared with the experimental Raman spectrum of the solid control,the match ratio was high.Moreover,the vibration attribution of the obtained Raman characteristic peak was analyzed by Veda 4 to determine the Raman characteristic peak of the Meloxicam molecule,i.e.670,1032,1116,1160,1264,1304,1470,1530,and 1592 cm^-1.The theoretical basis for qualitative and quantitative detection was provided.The metal assisted chemical etching was used to prepare two different modified elements.The modified silicon nanowire arraies and its preparation conditions were optimized.In the preparation process,a two-step method was used.The silicon wafer was entered the HF:AgNO₃solution for 10 seconds so that a silver network was formed on the surface.The silicon wafer was then immersed into the HF:H₂O₂ solution for 25 minutes,and lastly,the processed silicon wafer was immersed into HF:AgNO₃ solution for 120 seconds to obtain silver nano-dendrites decorated silicon nanowire arraies（AgND/SiNWs）.Graphene oxide（GO）was electrodeposed on the surface of silicon nanowire arraies by using electrochemical deposition.The optimal concentration of graphene oxide was 2 mg/m L,and the electrodeposition time was 300 seconds to obtain the graphene oxide modified silicon nanowire arraies（GO/SiNWs）.The amount of the reducing agent sodium borohydride was optimized to prepare positively charged silver nanoparticles with a better SERS effect.And the AgNPs were adsorbed on GO/SiNWs by electrostatic action to prepare the AgNPs/GO/SiNWs.The performance of the two substrates was investigated.Both of them were reused 7 times after being washed with sodium borohydride,which still had a certain SERS activity after stored in air for more than 90 days.The relative standard deviation was used to evaluate the reproducibility of the two substrates,in which AgND/SiNWs was 11%,and AgNPs/GO/SiNWs was 20%.The SERS detection method for Meloxicam on two substrates was established,and the detection conditions were optimized.The LOD of Meloxicam for droplets to be tested on AgND/SiNWs substrate was 0.04μg/mL（S/N=3）,which showed a good linear relationship between 0.1 and 25μg/mL at 1160 cm^-1（y=8.6887x+89.9459,R2=0.9923）.The average recovery of the spike was between 80.0%to 112.4%.The AgNPs/GO/SiNWs was immersed into the test liquid for 90 seconds,and the LOD of Meloxicam reached to 0.004μg/mL（S/N=3）,which showed a good linear relationship between 0.01 to 1μg/m L at 1592 cm^-1（y=845.89x+183.37,R2=0.9868）.The average recovery of the spike was between 61.5%and111.0%.