| Surface-enhanced Raman(SERS)spectroscopy is a powerful analytical tool used to detect and identify various molecules.It has attracted wide attention due to its low detection limit,high sensitivity,and good selectivity.The research on SERS active substrates is of great significance for practical applications.Recently,semiconductor materials have been preliminarily explored due to their low cost,controllable band gap and good chemical stability.Yet,the enhancement factor of semiconductor substrate based on chemical enhancement mechanism is very low(only 10-103),which is difficult to be applied in practical scenarios.However,some recent studies found that the SERS activity of the modified semiconductor substrate was greatly improved.The development of a novel semiconductor SERS active substrate could not only solve the problem of SERS substrate material shortage,but also provide more possibilities for SERS application research.In this paper,a low cost and simple method was used to prepare SERS active substrate based on semiconductor molybdenum disulfide(MoS2)and to explore its enhancement mechanism,and the research on the trace detection of pollutants in detail.The specific research contents are as follows:1.Combining MoS2 with semiconductor titanium dioxide(TiO2)to obtain an efficient and versatile SERS substrate(MoS2@TiO2).The optimal MTi20 active substrate was obtained by adjusting the loading of TiO2.It not only shows an ultra-high SERS response,but also has excellent catalytic degradation performance for the pollutant methylene blue(MB),which provided a new material for real-time and in-situ monitoring of the photodegradation.The detection limit of MB is as low as 10-13 M,the degradation rate is as high as 97.2%within 180s,and the SERS activity of MTi20 is almost unchanged for 60 days.In addition,as a practical SERS substrate,MTi20 can also detect other trace hazardous substances,including malachite green(MG),bisphenol A(BPA)and endosulfan.This research proposed a new direction for real-time and in-situ monitoring of photocatalytic reactions and is expected to be applied in the field of food safety and environmental testing.2.A two-step chemical method was used to combine the MoS2 with zinc oxide(ZnO)to obtain a substrate material(MoS2@ZnO)with ultra-high SERS activity,and a novel oxygen bidirectional strategy.This strategy refers to combining an oxide semiconductor with a non-oxide semiconductor.Under the action of external forces,part of oxygen will escape from the oxide semiconductor as the active center into the non-oxide semiconductor,thus obtaining both oxygen vacancy and oxygen doping effect simultaneously.Through this strategy,the interaction between the semiconductor substrate and the molecule was amplified,and the charge transfer resonance was increased,thus greatly improving the SERS performance.In this work,the enhancement factor(1.13×106)of the MoS2@ZnO substrate is comparable to traditional noble metals.In addition,MoS2@ZnO can also achieve trace detection of harmful substances such as MB,which has high practical application value.The oxygen bidirectional strategy provides a new idea for the development of ultra-sensitive semiconductor SERS technology.3.We have prepared the MoS2@ZnO@Ag biosensor with strong SERS capability,which can be used for ultra-sensitive detection of free bilirubin in serum and may be used for accurate diagnosis of related diseases.The substrate is evolved from the noble metal Ag nanoparticles attached to MoS2@ZnO,integrating the advantages of low cost,simple pretreatment,and high sensitivity,and can accurately qualitatively and quantitatively analyze bilirubin samples.Experiments have proved that MoS2@ZnO@Ag substrate has a high sensitivity to 10-3 M?10-9 M bilirubin.The successful preparation of this substrate provides a new potential biosensing technology for the detection of free bilirubin,which may be applied in clinical diagnosis. |
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