Surface enhanced Raman scattering of a single molecular junction

Abstract

The characterization of a single molecular junction is essential to investigate and utilize the single molecular junction in single molecular devices. Vibration spectroscopy is a promising technique for characterizing the atomic structure of the single molecular junction. In this review paper, we describe the surface-enhanced Raman scattering (SERS) as a vibration spectroscopy of a single molecular junction. A strong electric field is formed in the nanogaps in the single molecular junction, which enhances the intensity of the Raman signal. The Raman signal from a single molecule in the nanogap is selectively observed thanks to the strong electric field. Simultaneous SERS and conductance measurements provide information of the geometric structure of the single molecular junction, which can clarify the single molecular dynamics.

Photonic nanojet‐mediated SERS technique for enhancing the Raman scattering of a few molecules

“…Therefore, the SERS community has been trying to achieve more η ( ν s ) value using various kinds of nanoparticles prepared by lithography technique and different chemical and physical vapour deposition methods. Recently, many researchers have involved in the fabrication of efficient and highly reproducible SERS substrates for studying the Raman scattering of single or a few molecules in real time …”

“…Real-time (label free) detection and studying the structural properties of single molecule at its native state are the paramount interests in chemistry, bioscience and biotechnology. [1][2][3][4] Recently, the researchers have succeeded in the detection of single molecules in real time using single nanoplasmonic antenna [5] and nanoplasmonic whispering gallery mode hybrid microresonator (WGM-h). [6] This detection was carried out by monitoring the change in free space resonance wavelength upon adsorbing single molecules at active sites on the surface of these sensors.…”

“…Alternatively, the Raman-based sensors have become useful for obtaining the structural information of a molecule from its chemical fingerprint (characteristic vibrational frequency). [3,4,8] However, it is extremely difficult to obtain the Raman scattering signal from a few or single molecules because of the lower Raman scattering cross section (typically in the order of 10 À30 to 10 À25 cm 2 /molecule). [9] Therefore, researchers have been widely using the surfaceenhanced Raman scattering (SERS) technique to improve the scattering signal.…”

“…Recently, many researchers have involved in the fabrication of efficient and highly reproducible SERS substrates for studying the Raman scattering of single or a few molecules in real time. [3,4,11,12] On the other hand, some researchers have demonstrated the enhancement in Raman scattering signal using photonic nanojet [13][14][15][16] that is a narrow focused high intense electromagnetic beam emerging from the shadow side surface of a lossless dielectric microcylinder or microsphere illuminated by a non-resonant plane wave or Gaussian wave. [17][18][19][20][21][22][23][24] However, the maximum enhancement factor obtained using photonic nanojet (PNJ) is lower than 100.…”

An ion-modified cluster model for studying the correlation of Raman intensity and electric conductance of single molecule in the molecular junction

“…2006年田等 [11] 将机械可控断裂结法 (mechanically controllable break junction, MCBJ)构造 MJ技术和SERS检测联用, 获得了MJ的拉曼光谱. 此后 其他课题组也报道了类似的工作 [12,13] . 除了MCBJ方法 外, 扫描隧道显微镜(STM)提拉法也被用来构筑MJ, 即 用STM金探针提拉吸附在光滑金衬底上的分子构筑 金针尖-分子-金衬底结.…”