| Raman Spectroscopy has some shortcomings,such as weak signal and low sensitivity.The generation of surface-enhanced Raman scattering(SERS)spectroscopy can help to overcome the disadvantages and expand the application of Raman detection.SERS is one kind of widely used technology for non-destructive testing and molecular recognition.It can provide fingerprint information of chemical and biological molecular.For SERS,the substrate plays a vital role.Noble metal nanoparticles are commonly used as substrate in SERS detection.Gold nanoparticles are the best choice among numerous noble metal nanoparticles due to its controllable size,good stability and biological compatibility.Among these,gold nanoparticles with appropriate size and multibranched structure have better surface-enhanced effect.However,the multibranched structure will bring the disadvantage of instability.Hence,fabrication of nanomaterials with high sensitivity and stability has become the hotspot in SERS research.In this work,SERS substrate with good sensitivity and stability has been prepared for environment pollutants monitor and DNA detection.The research contents and conclusions are presented as follows:We developed a two-step approach to synthesize popcorn-liked gold nanoparticles(gold nanopopcorn)without any surfactant.The sizes of gold nanopopcorn are controllable by tuning the amount of reducing agents.Besides,the whole synthesis process can be completed at room temperature within 18 minutes.Hence,the method is green,simple and fast.Pairing with portable Raman spectrometers,the gold nanopopcorn are used for CPF detection in fruits at micromolar level(10-6 M).It is prospective that the proposed gold nanopopcorn has great potential to be applied in the on-site assessment process.In the previous work,gold nanopopcorn with good surface-enhanced effect has been prepared fastly and simply.However,the substrate has a deficiency of instability.In order to improve the stability of substrate,we prepared stabilized two-dimensional SERS substrates by using self-assembly of negative charged gold nanopopcorn on the surface of positive charged ITO through electrostatic interaction.Under an optimized condition,the SERS substrate has good surface-enhanced effect and stability.Using4-mercaptopyridine(4-Mpy)as the probe molecule,the limit of detection(LOD)of4-Mpy is 0.1 μM in water with an excellent linear range of 1-100 μM.The substratecan be stored at room temperature for nine months.The substrate can also be used to detect DNA.This method can greatly improve the stability of the substrate and has very good practical value.In the previous work,we have prepared two-dimensional gold nanopopcorn with good stability.However,the sensitivity for detection of biological samples such as DNA needs to be improved.The addition of reducing agent in the synthesis of gold nanopopcorn may disturb/suppress molecule close to the substrate.Hence,it is necessary to find a method to improve the sensitivity of the substrate.In this work,Fenton reagent has been used to sensitize the substrate.The hydroxyl radical generated from Fenton reaction can oxidize organics adsorbed nonspecifically on the substrate.Just because of this,the organics on the surface of substrate can be cleaned.The purpose of sensitizing substrate has been achieved due to the release of more active site.The research showed that the method indeed improved the sensitivity of detection and the substrate can achieve the best enhanced effect when the concentration of Fe2+ and H2O2 are 100 μM and 400 μM respectively.The sensitivity for DNA detection can be enhanced by 11.7 times.Thus,this method has made up for the lack of last work and the substrate prepared in our work has a good application prospect.The research shows that Fenton reagent sensitized two-dimensional gold nanopopcorn has good stability and homogeneity.It has solved the problem of unstability and uncleanness for the nanoparticles.There is no doubt that this method has good development and utilization prospects. |
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