Creating Well-Defined Hot Spots for Surface-Enhanced Raman Scattering by Single-Crystalline Noble Metal Nanowire Pairs

Abstract

Well-defined surface-enhanced Raman scattering (SERS) active systems were fabricated by single-crystalline noble metal nanowires. Crossed and parallel nanowire pairs were constructed by using a nanomanipulator to create SERS hot spots in the form of nanowire junction. SERS spectra of brilliant cresyl blue (BCB), p-mercaptoaniline (pMA), and p-mercaptobenzoic acid (pMBA) were observed at the junction of two nanowires. The SERS enhancement and polarization dependence are correlated well with the enhanced electric field intensities calculated by the finite difference time domain (FDTD) method for specific nanowire geometries. These simple and effective SERS active systems have a practical advantage that the hot spots can be readily located and visualized by an optical microscope. These well-defined SERS active systems based on noble metal nanowires can be further developed to find applications in a variety of biological and chemical sensing.

Individual Ag Nanowire Dimer for Surface-Enhanced Raman Scattering

“…Different from that of isolated nanoparticle aggregates, the maximum SERS signals from the body of metallic NW-based structures were reported to appear when the excitation laser is polarized perpendicular to their long axes [12][13][14][15][16][17][18][19], while for the tip of individual AgNWs, the polarized SERS signals were reported to be either anisotropic [12] or isotropic [16], which needs to be clarified. It is also noted that SERS behaviors of individual dimeric AgNWs are still rarely studied [18]. Only recently, with the help of manipulator, SERS performances of individual dimeric AgNWs containing kissing NWs were discussed [18].…”

“…[14][15][16][17][18][19][20]. These are critical in designing metallic nanostructures to achieve the largest possible EM enhancement and to reveal their detailed enhancement origins as well.…”

“…This takes advantage of the fact that EM fields are normally (not exclusively) concentrated at the interstitial sites of the gaps/junctions between adjacent nanoparticles in the aggregates. Currently, SERS studies of individual AgNWs and the NW-based structures are receiving growing interest [12][13][14][15][16][17][18][19][20], which is due to the fact that among all noble metals, Ag shows the most effective SERS in the visible range and also to their advantage of being able to be conveniently located in situ by using an optical microscope. Different from that of isolated nanoparticle aggregates, the maximum SERS signals from the body of metallic NW-based structures were reported to appear when the excitation laser is polarized perpendicular to their long axes [12][13][14][15][16][17][18][19], while for the tip of individual AgNWs, the polarized SERS signals were reported to be either anisotropic [12] or isotropic [16], which needs to be clarified.…”

“…It is also noted that SERS behaviors of individual dimeric AgNWs are still rarely studied [18]. Only recently, with the help of manipulator, SERS performances of individual dimeric AgNWs containing kissing NWs were discussed [18]. Moreover, to the best of our knowledge, there have been no SERS reports on individual AgNW dimers containing two parallel NWs with a gap in between till now.…”

Patterned Multiplex Pathogen DNA Detection by Au Particle-on-Wire SERS Sensor

“…Au NWs with a diameter of ∼150 nm were synthesized on a c-sapphire substrate using a vapor transport method. 34,35 The synthesized NWs are highly single-crystalline without twins and have atomically smooth surfaces. The NWs were transferred to a Si substrate using a nanomanipulator after the surfaces of Au NWs were modified with the thiolated probe DNAs.…”