Showing papers by "Bin Ren published in 2004"
TL;DR: Tip-enhanced Raman spectroscopy is reported on with smooth single crystalline surfaces as substrates, based on the optical excitation of localized surface plasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tip apex.
Abstract: Tip-enhanced Raman spectroscopy (TERS) is based on the optical excitation of localized surface plasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tip apex. We report on TERS with smooth single crystalline surfaces as substrates. The adsorbates were CN- ions at Au(111) and malachite green isothiocyanate (MGITC) molecules at Au(111) and Pt(110) using either Au or Ir tips. The data analysis yields Raman enhancements of about 4 x 10(5) for CN- and up to 10(6) for MGITC at Au(111) with a Au tip, probing an area of less than 100 nm radius.
561 citations
TL;DR: In this paper, a method of preparing gold scanning tunneling microscopy (STM) tips by direct current electrochemical etching in concentrated HCl and ethanol solution is described, which can be efficiently used for STM imaging, tipenhanced Raman spectroscopy, and light emission investigations on the same sample.
Abstract: We describe a method of preparing gold scanning tunneling microscopy (STM) tips by direct current electrochemical etching in concentrated HCl and ethanol solution. Gold tips with tip apex radius lower than 30 nm can be reproducibly prepared by this method. The influence of the solution composition, etching voltage on the surface structure, and sharpness has been investigated. These tips can be efficiently used for STM imaging, tip-enhanced Raman spectroscopy, and light emission investigations on the same sample.
373 citations
TL;DR: This review presents the recent progress achieved mainly in the laboratory on the improvement of detection sensitivities as well as spectral, temporal, and spatial resolutions in SERS.
Abstract: Over the past three decades, surface-enhanced Raman spectroscopy (SERS) has gone through a tortuous pathway to develop into a powerful surface diagnostic technique for in situ investigation of surface adsorption and reactions on electrodes. This review presents the recent progress achieved mainly in our laboratory on the improvement of detection sensitivities as well as spectral, temporal, and spatial resolutions. Various surface roughening procedures for electrodes of different metals coupled with maximum use of a high-sensitivity confocal Raman microscope enable us to obtain good-quality SER spectra on the electrode surfaces made from net Pt, Ni, Co, Fe, Pd, Rh, Ru, and their alloys that were traditionally considered to be non-SERS active. A novel technique called potential-averaged SERS (PASERS) has been developed for the quantitative study of electrochemical sorption. Applications are exemplified on extensively studied areas such as coadsorption, electrocatalysis, corrosion, and fuel cells, and several advantages of in situ electrochemical SERS are demonstrated. Finally, further developments in this field are briefly discussed with emphasis on the emerging methodology.
330 citations
TL;DR: In this article, a template-less and non-seed process was used to synthesize high-quality nanoparticles, which is low-cost and proceeds at moderate temperatures, using a simple and effective approach to the aqueous-phase synthesis of crystalline silver nanorods and nanowires.
Abstract: A simple and effective approach to the aqueous-phase synthesis of crystalline silver nanorods and nanowires is demonstrated, using which their diameters and aspect ratios can be effectively controlled. The synthesis involves a template-less and non-seed process to high-quality nanoparticles, which is low-cost and proceeds at moderate temperatures. The nanorods and nanowires were synthesized by the reduction of silver nitrate with tri-sodium citrate in the presence of sodium dodecylsulfonate. The concentration of tri-sodium citrate plays a critical role while sodium dodecylsulfonate, as a capping agent, only plays an assistant role in controlling the diameters and aspect ratios of the products. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) investigations show that the silver nanocrystals are generated with a twinned crystalline structure. We also put forward a primary experimental model to shed light on their growth mechanisms.
287 citations
TL;DR: It was revealed that it is thermodynamically favorable for a colloidal particle in bulk colloids to adsorb to the air-water interface; however, a finite sorption barrier between it and the nearby particles usually restrains the adsorption process.
Abstract: In our previous paper, a method for preparing enormous surface-enhanced Raman scattering (SERS) active substrates through the aggregation of silver particles trapped at an air−water interface was reported. Here, further efforts were devoted to investigate the origin of assembling silver particle films by adsorbing nanoparticles from bulk colloids to the air−water interface. It was revealed that it is thermodynamically favorable for a colloidal particle in bulk colloids to adsorb to the air−water interface; however, a finite sorption barrier between it and the nearby particles usually restrains the adsorption process. When an electrolyte such as KCl, which is commonly used as an activating agent for additional SERS enhancement, was added into silver colloids, it largely reduced the sorption barrier. Thus, silver nanoparticles can break through the sorption barrier, pop up, and be trapped at the air−water interface. The trapped silver particles are more inclined to aggregate at the interface than those in b...
56 citations
TL;DR: In this article, the SERS spectra obtained in a wide frequency region provide not only the vibrations reflecting the internal bonding of CO, but also the bonding between CO or O with Rh (at ca. 450 cm-1).
Abstract: By using the previously developed roughening method for producing SERS-active Rh electrode, and assisted by the highly sensitive confocal microprobe Raman system, we carried out a detailed SERS study on the dissociation and electrooxidation of C1 molecules on a Rh surface. The SERS spectra obtained in a wide frequency region provide not only the vibrations reflecting the internal bonding of CO (at ca. 2000 cm-1) but also the bonding between CO or O with Rh (at ca. 450 cm-1). A complementary electrochemical study was also performed on the roughened Rh surface in order to correlate the electrochemical and vibrational information. Both electrochemical and SERS studies show that Rh has no discernible activity toward the electrooxidation or dissociation of methanol in acidic solutions. Rh becomes active and its activity increases with the decrease of the solution acidity. For HCHO and HCOOH, the electrooxidation activity of Rh increases with increasing pH. On the basis of the result of the model CO system, dis...
18 citations
TL;DR: Using confocal Raman microscopy, potential dependent surface-enhanced Raman spectra (SERS) of pyridine adsorbed on a bare zinc (Zn) bulk electrode were observed for the first time, and the adsorption behavior of Pyridine on zinc was discussed as mentioned in this paper.
Abstract: Using confocal Raman microscopy, potential dependent surface-enhanced Raman spectra (SERS) of pyridine adsorbed on a bare zinc (Zn) bulk electrode were observed for the first time, and the adsorption behavior of pyridine on zinc was discussed. An electrochemical oxidation−reduction method was employed to roughen Zn electrodes for creating SERS. Related SEM measurement was performed to obtain the morphological information of the roughened electrode for understanding the SERS mechanism on it. An enhancement factor of around two orders of magnitude for pyridine adsorbed on a roughened Zn electrode was estimated.
14 citations