Zhu et al. Nanoscale Research Letters 2012, 7:613 http://www.nanoscalereslett.com/content/7/1/613 N A N O E X P R E S S Open Access Gold nanoparticle thin films fabricated by electrophoretic deposition method for highly sensitive SERS application Sheng-Qing Zhu1,2,3, Tong Zhang1,2,3*, Xin-Li Guo4, Qi-Long Wang1,2, Xuefeng Liu5 and Xiao-Yang Zhang1,2,3 Abstract We report an electrophoretic deposition method for the fabrication of gold nanoparticle (GNP) thin films as sensitive surface-enhanced Raman scattering (SERS) substrates. In this method, GNP sol, synthesized by a seed-mediated growth approach, and indium tin oxide (ITO) glass substrates were utilized as an electrophoretic solution and electrodes, respectively. From the scanning electron microscopy analysis, we found that the density of GNPs deposited on ITO glass substrates increases with prolonged electrophoresis time. The films possess high mechanical adhesion strength and exhibit strong localized surface plasmon resonance (LSPR) effect by showing high SERS sensitivity to detect 1 × 10−7 M rhodamine 6 G in methanol solution. Finally, the relationship between Raman signal amplification capability and GNP deposition density has been further investigated. The results of our experiment indicate that the high-density GNP film shows relatively higher signal amplification capability due to the strong LSPR effect in narrow gap regions between the neighboring particles on the film. Keywords: Gold nanoparticle, Electrophoretic deposition, SERS Background Films composed of noble metal nanoparticles (typically, Au or Ag) currently have attained wide popularity and aroused intense research interest in nanotechnology due to the intriguing optical properties introduced by localized surface plasmon resonances (LSPRs). LSPRs, which are optical phenomenona arising from the collective oscilla- tion of conduction electrons in noble metal nanoparticles when the electrons are disturbed from their equilibrium positions, lead to enormous optical local-field enhance- ment at the nanoscale and obtain potential applications in many fields such as chemical or biosensors [1-4], solar cell designs [5-8], and surface-enhanced Raman scattering (SERS) [9-11]. Due to the exceptional optical properties of noble metal nanoparticle films, many available methods for the fabrica- tion of these films have been proposed in the past two * Correspondence: tzhang@seu.edu.cn 1School of Electronic Science and Engineering, Southeast University, Nanjing 210096, People's Republic of China 2Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, Nanjing 210096, People's Republic of China Full list of author information is available at the end of the article decades. In order to obtain a strong LSPR effect, it is often necessary to engineer the particle deposition density on substrates for practical application because the deposition density can greatly affect the optical property of the films [12]. The most recently available methods for the fabrica- tion of these films include electron beam lithography and nanoimprint lithography, both can completely control the micromorphology of the nanostructures for the design with unique LSPR spectrum [13,14]. However, these meth- ods require sophisticated fabrication equipment and are limited by either expensive cost or small sample size in practical applications. Instead, some simpler bottom-up approaches based on self-assembly, e.g., Langmuir-Blodgett, dip coating, and electrochemical deposition, have shown great conveniency in large-scale fabrication and much less defectivity [15-19]. Such techniques can surely produce noble metal nanoparticle thin films with large areas, but the resulting films usually lack mechanical adhesion strength of nanoparticles to substrate materials required for device construction. In this paper, we report a rapid, simple, and room- temperature electrophoretic deposition method using gold nanoparticle (GNP) sol as an electrophoretic solution to © 2012 Zhu et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.