Facile synthesis of gold nanoflowers as SERS substrates and their morphological transformation induced by iodide ions

We report a new strategy to prepare gold nanoflowers （AuNFs） using a two-step seed-mediated method. The as-prepared AuNFs were employed as surface-enhance Raman scattering （SERS） substrates, showing strong signal enhancement. We further found that iodide ions （I^-） could selectively induce the morphological transformation of AuNFs to spheres, resulting in a blue-shift of the localized surface plasmon resonance （LSPR） bands, a color change of the AuNFs solution from blue to red, and decreased SERS activity. This behavior allows the AuNFs to be used in the determination of I^-.

Polydopamine Modified Biomimetic Gold Nanoparticles for Dual Photothermal Therapy

Our study producted Polydopamine modified gold nanoflowers with controlled morphology for anti-tumor photothermal therapy.The branch structure containsabundant(Au NFs).By adjusting the reduction rate,the dosage of reducing agent(sodium borohydride)and the reduction temperature,we can adjust tthe morphology and particle size of Au NFs.We found that the lower reaction temperature is,the more abundant the surface branching structure of gold nanoflowers is,by adjusting the reaction temperature.and the largest specific surface area of golden nanopowder was found at 0℃.The results of TEM indicated that with the increase of sodium borohydride,the diameter of gold nano flowers gold nanoflowers decreased and was in the range of 60~100nm,and it has good EPR effect After that,we modify poly(dopamine)(PDA)biomimetic layer on the surface of golden nanoparticles to obtain Au NFS@PDA.Poly(dopamine)has the ability,of photothermal conversion,which can enhance the plasma resonance ability and biocompatibility of gold nanoflowers in the near infrared region.We can control the thickness of polydopamine layer on the surface of gold nanoflowers between 7~15nm by adjusting dopamine DA concentrationgold nanoflowers.Au NFS@PDA was characterized by its morphology and physical properties.We detect(UV-Vis)spectra in the near infrared region.And it showed obvious absorption peaks in the near infrared region of 575~650nm.Under the 808nm irradiation laser,the photothermal conversion of gold nanoflowers and polydopamine can be rapidly increased to 57°C.Fourier Transform Infrared Absorption Spectroscopy(FTIR)and X-ray Diffraction(XRD)analysis showed that polydopamine was modified successfully,Au NFS@PDA and Au NFs had no obvious difference in crystal form.The cell viability test showed that the bionic Au NFS@PDA had good biocompatibility and showed good antitumor activity against HeLa cells under NIR irradiation.The cell viability was only 12%.Therefore,we can use Au NFS@PDA with good biocompatibility as a promising photothermal conversion agent in tumor therapy.

Denatured proteins as a novel template for the synthesis of well-defined,ultra-stable and water-soluble metal nanostructures for catalytic applications

The templated synthesis of noble metal nanoparticles using biomass,such as proteins and polysaccharides,has generated great interest in recent years.In this work,we report on denatured proteins as a novel template for the preparation of water-soluble metal nanoparticles with excellent stability even after high speed centrifugation or storage at room temperature for one year.Different noble metal nanoparticles including spherical gold and platinum nanoparticles as well as gold nanoflowers are obtained using sodium borohydride or ascorbic acid as the reducing agent.The particle size can be controlled by the concentration of the template.These metal nanoparticles are further used as catalysts for the hydrogenation reaction of p-nitrophenol to p-aminophenol.Especially,spherical gold nanoparticles with an average size of 2 nm show remarkable catalytic performance with a rate constant of 1.026×10^(-2) L s^(-1) mg^(-1).These metal nanoparticles with tunable size and shape have great potential for various applications such as catalysis,energy,sensing,and biomedicine.