Rapid Synthesis Of Flower-like Gold Nanoparticles And Their SERS Effect

Gold nanoparticles have unique properties of optics,electricity,and catalysis,and are widely used in optics,electronics,biomedical and catalysis.Because the flower-like gold nanoparticles have rough surface,high specific surface area,more active sites,the tips with a strong electromagnetic field effect,they are good catalysts and SERS active substrates.At present,the flower-like gold nanoparticles are normally prepared by seed-mediated methods,which need to synthesize seeds in advance.Not only the synthesis steps are complicated,and time-consuming but also various surfactants,capping agents or stabilizers were used.It’s difficult to remove,which limit the use of nanoparticles.Regarding the issues above,We have developed a simple,rapid,and mild reaction condition for synthesizing flower-like gold nanoparticles and explore their optical properties and catalytic activity.The specific research contents are as follows:1.At room temperature,using HAuCl4 as a precursor,NH2OH·HCl as a reducing agent,and NaOH was used to adjust the pH of the solution.Gold nanoparticles with different morphology were rapidly synthesized in one step.The results showed that spherical gold nanoparticles were obtained under acidic conditions,and under neutral and alkaline conditions were flower-like gold nanoparticles with small protrusions on the surface.A series of control experiments have demonstrated that pH modulates the oxidation performance of HAuCl4 and the reduction performance of NH2OH·HCl,which in turn affects the growth and riping rates of particles to achieve the regulation of the morphology of gold nanoparticles.2.At room temperature,using HAuCl4 as a precursor,NH2OH·HCl as a reducing agent,and NaOH,Na2CO3,and Na3PO4 as pH regulators,we further confirmed the effect of pH on the growth of gold nanoparticles.It was found that gold nanoparticles with different morphology were synthesized under acidic,neutral and alkaline conditions.For the three regulators,the gold nanoparticles obtained in the acidic condition are all spherical,and the rough surface flower-like gold nanoparticles are obtained under neutral and alkaline conditions,and the stronger the alkalinity,the rougher the surface.When R6G was used as a probe and measured the characteristic Raman peak at 1364 cm-1,the Raman enhancement effect was:alkaline>neutral>acidic.That is to say,the SERS activity of the flower-like gold nanoparticles was greater than that of the sphere,and the surface was more Roughness,SERS activity is stronger.The NaBH4 reduced p-nitrophenol(4-NP)as a model reaction,spherical and flower-like gold nanoparticles show good catalytic activity,but due to the increase of surface roughness leads to the catalytic activity of flower-like gold nanoparticles is significantly higher than that of spherical gold nanoparticles.3.Using HAuCl4 as the precursor,NH2OH·HCl as the reducing agent and AgNO3 as the inducer,the gold nanoparticles with different morphology were synthesized in one step at room temperature.The morphology of the nanoparticles was related to the amount of AgNO3.The method can obtain three kinds of Au nanoparticles no-thorns,short-thorns and long-throns.The mechanism indicates that the process is derived from the growth induced by AgCl interface.Using R6G as a probe,the SERS activity of no-thorns,short-thorns and long-throns gold nanoparticles was measured.The results show the Raman intensity at 1364 cm-1 was directly related to their morphology,and the long-throns gold nanoparticles have the most significant SERS enhancement effect.In summary,we used a one-step synthesis method to achieve the rapid synthesis of flower-like and thorny gold nanoparticles only by adjusting the pH and introducing Ag+.The unique morphological structure of the gold nanoparticles has significant SERS enhancement and catalytic performance,which will have broad application in the field of analysis,biomedicine,and catalysis.