| At present,detection of single substance is common through SERS,while detection of two or more substances has not been particularly mature.Pigment and pesticide play a crucial role in life,and since their appearance in people’s vision,it can be said that advantages and disadvantages coexist.Reasonable use of pigment and pesticide can help to solve and enrich many problems in life.Will do harm to human health and even our lives.At present,people have developed a variety of methods for the detection of pigments and pesticides,such as high performance liquid chromatography,fluorescence spectrometry,and electrochemical analysis.However,these analytical methods are costly,time-consuming and require high samples.Compared with these methods,SERS has the advantages of high sensitivity,good selectivity,convenient detection and so on.Nowadays,many researchers detected pigments and pesticides through SERS.For example,Luo et al prepared a flexible Ag nanowire embedded PDMS film sensor and successfully applied it to the recyclable wipe detection of malachite green in fruits,where the linear range of SERS strips was measured from 0.5 to 1000μM and the detection limit was 10 n M.Based on the previous research,this paper expected to prepare a SERS composite base with high activity and characteristics of the material through the structural characteristics and performance advantages of the material itself,so as to amplify the signal of the molecules to be tested,and thus realize the high-sensitivity SERS detection and other advantages.It is well known that precious metals gold and silver have significant plasmon resonance（LSPR）.After the molecules to be tested were adsorped to the substrate,SERS"hot spot"would be generated due to the proximity of the micro-nano structure of precious metals.Therefore,in this paper,precious metal as the starting point,high activity as the foothold,through the Raman spectrometer to the hot spot for laser scattering,the vibration mode of organic molecules to be measured,so as to achieve sensitive quantitative detection of target analytes.The main contents are as follows:1.TNAs/g-C3N4/Au NPs composite SERS base was prepared to realize the highly sensitive and cyclic quantitative detection of organic dye crystal violet.Titanium dioxide nanotubes with different morphologies were prepared by one-step and two-step anodic oxidation,and gold nanoparticles with different particle sizes were synthesized by sodium citrate reduction.At the same time,the graphite phase carbon nitride（g-C3N4）with triazine structure was synthesized by calcination using dicyandiamine as the precursor,and g-C3N4and Au NPs were assembled on the titanium dioxide nanotubes by anodic deposition and drip coating method successively,so as to obtain TNAs/g-C3N4/Au NPs.Au NPs has good optical properties,catalytic properties and biocompatibility.The salient feature of Au NPs is that surface plasmon resonance（SPR）occurs when the frequency of the incident light matches the natural frequency of the free electrons in Au NPs,thus enhancing the Raman signal.Based on the strong oxidation capacity of Ti O2nanotube array and its band structure matching the new semiconductor material g-C3N4,the combination of the two is beneficial to the transfer of photogenerated carriers and increase the utilization rate of light energy,and has high photocatalytic activity,which can be used for photocatalytic degradation.For this reason,after the test of 10-6M crystal violet dye,after 10 cycles of full light irradiation,the Raman signal of the composite substrate can still be more than 84%of the original signal.The detection limit of TNAs/g-C3N4/Au NPs for crystal violet molecules was 10-10M.2.AuNPs grown in situ were embedded in two-dimensional g-C3N4stacked gaps to prepare a high performance SERS composite base g-C3N4@Au NPs.The porous structure of g-C3N4provides a supportive environment for sufficient embedment of Au NPs and avoids excessive aggregation of Au NPs on the surface of g-C3N4.Using crystal violet as SERS probe,the enhancement factor of this base was 6.8×105.g-C3N4@Au NPs composite substrate gives a good linear range（R2=0.9753）for the pesticide paraquat in the range of 1.0×10-6～1.0×10-4M,and the current standard detection limits of some countries that allow the use of paraquat are within this linear range.In this paper,the residual amount of paraquat in commercially available tea was also detected,and the results showed that the highly sensitive g-C3N4@Au NPs.compound SERS base had high application potential as SERS platform.3.By combining anodic oxidation and cathode deposition,silver nanotrees were deposited on titanium dioxide nanotubes to obtain TNAs/Ag NTs base,which was used as SERS sensor for pesticide detection.Ti O2nanotube array and its surface have high roughness,which provides the growth foundation for the growth of silver nanotree and makes it firm.The detection limit of 4-mercaptopyridine was 0.97 n M when silver nanotwigs were used as Raman sensitive substrate.In addition to the high homogeneity of the substrate,the detection limit of formediol and paraquat on this substrate was 12.3n M and 5.25 n M respectively.It is worth mentioning that the composite substrate realizes the mixed detection of pesticide bimolecules at low concentration.In this dissertation,based on the advantages of high sensitivity and narrow emission band of surface Raman enhanced spectroscopy technology,combined with the strong pathogenicity of pigments and pesticides to human body,it is expected to provide a new approach and strategy for real-time and quantitative detection of pigments and pesticides through surface Raman enhanced spectroscopy technology,as well as bimolecular detection in complex systems. |
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