Synthesis of a b-cyclodextrin-modified Ag film by the galvanic displacement on copper foil for SERS detection of PCBs Jingpeng Yuan, Yongchao Lai, Junling Duan, Quanqin Zhao, Jinhua Zhan ⇑ Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Department of Chemistry, Shandong University, Jinan 250100, Shandong, PR China article info Article history: Received 6 July 2011 Accepted 28 August 2011 Available online 14 September 2011 Keywords: Polychlorinated biphenyls (PCBs) Detection Surface-enhanced Raman spectroscopy (SERS) Cyclodextrins (CDs) Silver films abstract A mono-6-thio-b-cyclodextrin-modified silver film was synthesized via galvanic displacement on copper foil. The prepared silver films could enrich non-polar polychlorinated biphenyls (PCBs) molecules from hydrophilic phase using thiolate b-cyclodextrins (SH-b-CDs) as receptors. The components of as-prepared Ag-coated-Cu (Ag–Cu) film were confirmed by powder X-ray diffraction (XRD). Both surface-enhanced Raman spectroscopy (SERS) and energy dispersive X-ray spectroscopy (EDS) measurements gave strong evidences that the thiolated b-cyclodextrins (SH-b-CDs) had been immobilized on the surface of silver film. Compared to the substrates prepared in the absence of SH-b-CD, the surface morphology of the CD-modified Ag films was obviously changed. The interfacial enrichment and the capability of substrates to form inclusion complexes with PCBs molecules were tested by using PCB-15 (4,4 0 -dichlorobiphenyl) as the probe molecules via SERS technique. The measured SERS spectra could distinguish the PCB-15 molecules at micro-molar level according to the most intense CCC bending in-plane mode of PCBs. The enhancement factor (EF) of the SERS substrates for PCB-15 was 1.2  10 5 , which was comparable with a number of previous reports. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction Polychlorinated biphenyls (PCBs), a group of synthetic organic chemicals with 1–10 chlorine atoms attached to biphenyl, have shown toxic and mutagenic effects by interfering with hormones in the body. Its products have been banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2001 [1]. PCBs can transport on a global scale and do not decompose readily. The extensive distribu- tion and the low-concentration residue in the environment make the detection of these PCBs molecules a challenging task [2–4]. The current ordinary method used for measuring PCBs is high- resolution gas chromatography–mass spectrometry (HRGC–MS). In this case, the compounds are separated in time and space via the differential partitioning into the stationary phase [2]. Its wide practical application is limited by the cumbersome pretreatment and analysis. An efficient and sensitive method for detecting PCBs is urgently needed. Raman spectroscopy can provide vibrational structural spectra of the detected molecules with the highly informative character [2]. Surface-enhance Raman spectroscopy (SERS) with an amplification of the Raman signal can be attributed to an enhancement of scatter- ing efficiencies when molecules localized near the nanostructured noble-metal surfaces (typically within 10 nm from the surface, at most) [5]. SERS is a powerful technique for detection and character- ization of the adsorbed molecules on rough metallic surface [6,7]. Surface plasmons (SPs) are excited and localized with incident light to produce a strong electric field for SERS enhancement [6,8]. Partic- ularly, the nanomorphology of silver particles is paramount to achieving maximum SERS enhancements. Theoretical models predict that curvature and shape of the noble-metal particles are responsible for enhancement of the field intensities, where the ac- tive hot spots occur at interstitial spots between adjacent nanopar- ticles [9,10]. Up to now, a number of preparation methods, including solvothermal synthesis, electron beam deposition, nanosphere lithography (NSL), vacuum evaporation deposition, and electro- chemical oxidation/reduction have been developed to fabricate SERS-active substrates with the well distributed ‘‘hot spots’’ [11–13]. It remains a challenge to fabricate SERS-active substrates through simple and low-cost methods [14]. For SERS detection, analyte molecules must be located near the metallic nanostructures, implying that a special chemical moiety should be incorporated on the SERS substrate for enriching trace organic species. Thus, lipophilic and poorly soluble in water are the physical properties of all PCBs. For molecule-binding chemis- try, we sought to exploit the binding properties of cyclodextrins (CDs) for special small organic molecule. CDs are a class of cyclic polysaccharide molecules commonly used in host–guest complex- ation chemistry [15–17]. b-Cyclodextrins (b-CDs) have a cavity whose dimension are depth 7 Å in width and 9 Å in depth, which 0021-9797/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2011.08.075 ⇑ Corresponding author. Fax: +86 0531 8836 6280. E-mail address: jhzhan@sdu.edu.cn (J. Zhan). Journal of Colloid and Interface Science 365 (2012) 122–126 Contents lists available at SciVerse ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis