Jiajie Yu,Muzhong Shen,Siyu Liu,Feng Li,Dongping Sun,Tianhe Wang
In this paper, we describe a simple technique for direct growth of gold nanoparticles (GNPs) into a nanostructured porous alumina layer on conductive glass slide (PAOCG). PAOCG was attached firmly with a small piece of steel and was then immersed in a HAuCl 4 solution. Electro-induced electrons from steel were employed to reduce AuCl 4 − on PAOCG. The galvanic replacement reaction (GRR) was adopted as the fundamental mechanism for reducing metal precursors. This mechanism was further studied by open circuit potential-time (OCP-t) experiment and the result demonstrated that steel induced the continuous proceeding of this reaction. This strategy presents a simple and general protocol for preparation of metal nanoparticles (MNPs) on conductive glass substrates. The SERS properties of Au/PAOCG were investigated using aqueous crystal violet (CV) and 4-mercaptopyridine (4-Mpy) as probe molecules. Au/PAOCG allowed as low as 10 −9 M CV and 10 −8 M 4-Mpy to be detected. The reusability of this substrate was achieved by measuring the SERS spectrum of the probe molecules followed with a 400 °C heat treatment for 10 min to remove the residuals. This substrate could be reused for at least ten cycles without any significantly reduced SERS performance. Therefore, this surface can serve as a portable, durable and reusable SERS substrate and has a potential for commercial applications.
Novel three-dimensional Ag nanoflowers (3DAN) were successfully synthesized through a facile Cu2+ mediated solution method using N,N-dimethylformamide (DMF), which serves as both a reducing agent and a solvent at room temperature. It was found that the introduction of a trace amount of Cu2+ could greatly slow the rate of the Ag+ reaction and thus this process effectively reduced the growth speed of Ag nanoparticles allowing 3DAN to be formed. The mechanism underlying the self-assembly process and shape evolution of 3DAN were systematically investigated by varying reaction time. X-Ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the obtained products. X-Ray photoelectron spectroscopy (XPS) was used to assess the chemical state and surface composition of the 3DAN. UV-vis absorption spectra of the products collected from the reaction solution at various stages were taken to study their optical properties. In the measurement of surface-enhanced Raman scattering using rhodamine 6G (R6G) as the probe, the 3DAN exhibited a significant enhancement factor, indicating their potential applications in biosensing and nanodevices.
In the propagating process along metal surface, surface plasmon polaritons (SPPs) mainly decay into thermal loss or release into photons, while a part of them were converted into electrons with high energy termed as hot electrons, which have great significance in photonics and electronics. In this work, the generation of plasmonic hot electrons was ascertained in the nanoparticle-film system through plasmon-driven surface catalysis (PDSC) reactions. The surface-enhanced Raman scattering (SERS) spectra of p,p'-dimercaptoazobenzene (DMAB) catalyzed by 4-nitrobenzenethiol (4NBT) experimentally demonstrated the essential catalysis electrons were generated in this hybrid plasmon mode. The results pointed out the priority of plasmonic hot electron generation in the dimer-film gap compared to the monomer-film gap which was analyzed by the surface electric and charge distribution. Furthermore, the SERS spectra of 4NBT in the metal nanoparticle-dielectric film system confirmed the necessity of hybrid plasmon mode in the generation of plasmonic hot electrons in the nanoparticle-film system. Because of the simple configuration and convenient fabrication of nanoparticle-film system, the work on this hybrid plasmon mode has a significant role in promoting the application of plasmonic hot electrons.
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