| Surface-enhanced Raman spectroscopy(SERS)is a highly sensitive and easy-to-operate fingerprint vibrational spectroscopy technique.Gold and silver nanoparticles,as traditional SERS enhancement substrates,have the advantages of good enhancement effect and mature preparation technology.But the disadvantages of high cost and easy aggregation cannot be ignored.In order to overcome the long-standing limitations of traditional SERS substrates in terms of materials and morphology,the core-shell structure came into being,which can not only increase the stability of the substrate,but also endow the substrate with functions such as catalysis,enrichment,separation,and specific molecular recognition,thereby make SERS more widely used.The main research contents of this paper are as follows:(1)Detection of malachite green in tilapia based on SG@Si O2 NPs core-shell structure SERS substrateThe label-free quantitative detection of malachite green(MG)provides critical guarantee in aquatic product safety and human health.Although It has been proven that SGNPs have good enhancement properties,the practical application remains challenging for SERS due to the presence of lower stability.In this work,a controllable and rapid method was developed to prepare sea urchin-like Au@Si O2nanoparticles(SG@Si O2 NPs).The branch length of sea urchin-like gold nanoparticles can be controlled by adjusting the concentration of Ag NO3.We also have studied the effect of nanoparticle morphology and Si O2 shell thickness on SERS performance.The as-prepared SG@Si O2 NPs active substrate exhibited that84.02%of the original signal intensity at room temperature for 30 days.After the optimization of SERS conditions included incubation time,dosage ratio and the concentrations of KCl,SERS signal intensity was linear for MG,CV and MB at1619 cm-1,1623 cm-1 and 1627 cm-1.This substrate was used to detect MG with a limit of detection(LOD)as low as 1.5×10-9 M.The substrate was used for the actual sample detection of MG in tilapia with recoveries ranging from 90%to 110%.The results indicated that the SERS substrate can be effectively used for the detection of trace amounts of MG in tilapia,demonstrating the great potential of the SG@Si O2NPs SERS substrate in food analysis.(2)Recyclable detection of methylene blue by flower-like Au@Mo S2/Ag NPs core-shell structure as a stable SERS substrateIn this work,Au@Mo S2 NPs were prepared by hydrothermally growing Mo S2nanoflowers onto Au NPs,then used sodium borohydride to reduce Ag NO3 to Ag NPs,used PVP to modify Ag NPs onto Mo S2 nanosheets of Au@Mo S2 NPs,successfully synthesized Au@Mo S2/Ag NPs ternary nanocomposite with a core-shell structure,and based on this composite material,a SERS substrate for detecting methylene blue was constructed.The effect of the amount of modified Ag NPs on the SERS activity was explored by adjusting the concentration of PVP and the amount of Ag NO3.The results showed that with MB as the probe molecule,the substrate has good signal uniformity and batch stability.At the same time,the fitting of the Raman peak intensity at 1625 cm-1 showed a good linear relationship in the concentration range of 10-5-10-10 M,the correlation coefficient R~2=0.9821.On the other hand,the photocatalytic performance of the substrate was investigated.Au@Mo S2/Ag NPs could degrade 97.1%of MB under the irradiation of xenon lamp for 100 min.In addition,after 8 cycles of detection,the SERS signal still had 62.8%of the original signal.The reusable SERS substrate is expected to be used as an environmentally friendly sensor in resource-limited environments.(3)Magnetic Fe3O4@Mo S2/Ag NPs core-shell structure SERS substrate for cyclic detection of crystal violetCrystal Violet,as a triphenylmethane-based dye disinfectant,competes with the microbial enzyme system of hydrogen ions,makes the enzyme in an inactive oxidation state,thereby exerts a bactericidal effect,and often uses for treating fungal and parasitic infections in aquatic products.However,CV was banned from aquaculture due to its potential carcinogenic properties.Fe3O4 NPs,which can rapidly enrich target molecules through an external magnetic field,are used as core nanoparticles to effectively detect trace CV in this work.Mo S2 is used to uniformly coat Fe3O4 NPs by a facile hydrothermal method,Ag NO3 was reduced to Ag NPs by Na BH4,and Ag NPs were modified onto Mo S2 nanosheets of Fe3O4@Mo S2 NPs with PVP,and a magnetic recyclable multifunctional composite material Fe3O4@Mo S2/Ag NPs was successfully synthesized.The research results show that CV is a probe molecule,the substrate has good signal uniformity and batch stability,and the intensity of the Raman peak at 1621 cm-1 is fitted,showed a good linear relationship in the concentration range of 10-4-10-9 M,and the correlation coefficient R~2=0.9914.The photocatalytic degradation performance of the substrate was explored.After 50 min of xenon lamp irradiation,the degradation rate of Fe3O4@Mo S2/Ag NPs substrate to CV was close to 92.2%.In addition,after 5 cycles of detection,the SERS signal still had 74.4%of the original signal,which showed the substrate will provide a new solution for recyclable SERS detection. |
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