Fabrication of Silver Nanowires with Corrugated-Surface and Its SERS Performance

In order to create the effective number of surface-enhanced Raman scattering (SERS) active "hot spots" on the one-dimensional nanostructure surfaces for ensuring the maximum enhancement of SERS signal, smooth silver nanowires (Ag NWs) were firstly synthesized by the conventional polyol method, and then the smooth silver nanowires were subjected to chemical etching by the Fe(NO3)(3) aqueous solution at room temperature to obtain corrugated silver nanowires. This corrugated silver nanowires were systematically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) microscopy, Ultraviolet-visible (UV-vis) extinction spectroscopy and surface enhanced Raman spectroscopy (SERS). The SEM image of smooth silver nanowires shows that had a diameter of ca. 120 nm and lengths of about tens of micrometers, while the average thickness of corrugated nanowires was only about 100 nm. The XRD patterns for both smooth and corrugated silver nanowires indicate that the fcc structure was preserved after chemical etching. From the measurement of UV-vis spectra we can see that after the smooth silver nanowires were subjected to chemical etching, only one broad surface plasmon peak was observed at ca. 386 nm while two significant peaks were observed at 353 and 392 nm for the smooth silver nanowires. The slight blue-shift of this peak from 392 to 386 nm could be contributed by the decrease in diameter of silver nanowires, whereas the broadening of the plasmon peak was probably a result of increased surface roughness. The SEM images showed that the surface roughness of silver nanowires was dependent on the amount of Fe(NO3)(3), by increasing the amount of Fe(NO3)(3) added into the silver nanowires solution, the surface of silver nanowires become more and more rough. However, as the excess amount of etchant added, most silver nanowires would broke off into shorter rods, and even spherical particles. Raman analyses of crystal violet (CV) indicated that the SERS intensity changes depending on the surface roughness of etched silver nanowires, and the silver nanowires with corrugated surfaces exhibited higher enhancement of SERS signal than the smooth silver nanowires. In addition, the SERS detection of CV and 4-mercaptopyridine (4-Mpy) molecules exhibited high detection sensitivity and the detection concentration were as low as 10(-10) and 10(-9) mol/L, respectively, which means that the corrugated silver nanowires could be an efficient SERS active substrate.