Journal of Hazardous Materials 265 (2014) 89–95 Contents lists available at ScienceDirect Journal of Hazardous Materials jou rn al hom epage: www.elsevier.com/locate/jhazmat Detection of the mycotoxin citrinin using silver substrates and Raman spectroscopy Dheeraj K. Singh a , Erdene-Ochir Ganbold a , Eun-Min Cho b , Kwang-Hwi Cho c , Doseok Kim d , Jaebum Choo e , Sehun Kim f , Cheol Min Lee g , Sung Ik Yang b , Sang-Woo Joo a,∗ a Department of Chemistry, Soongsil University, Seoul 156-743, South Korea b College of Environment and Applied Chemistry, Kyung Hee University, Yongin 446-701, South Korea c School of Systems Biomedical Science, Soongsil University, Sangdo-dong, Dongjak-gu, Seoul, South Korea d Department of Physics, Sogang University, Seoul 121-742, South Korea e Department of Bionano Engineering, Hanyang University, Sa-1-dong 1271, Ansan 426-791, South Korea f Molecular-level Interface Research Center and Department of Chemistry, KAIST, Daejeon 305-701, South Korea g Institute of Environmental and Industrial Medicine, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, South Korea h i g h l i g h t s • The mycotoxin citrinin was detected using Ag substrates and Raman spec- troscopy. • Prepared Ag substrates were charac- terized by electron microscopic tools. • Density functional theory calculation predicted the most stable geometry on Ag. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 7 July 2013 Received in revised form 20 October 2013 Accepted 19 November 2013 Available online 23 November 2013 Keywords: Citrinin Mycotoxin Silver substrates Raman spectroscopy Density functional theory calculations a b s t r a c t We detected a trace amount of the mycotoxin citrinin using surface-enhanced Raman scattering (SERS) on silver nanoparticle (Ag NP) surfaces. The SERS substrate on hydrophobic Teflon films was also introduced to observe the citrinin peaks. A broad band at ∼1382 cm -1 , which was ascribed to the symmetric car- boxylate stretching mode, was observed in addition to an antisymmetric carboxylate stretching mode at ∼1568 cm -1 in the Raman spectra. The spectral feature indicated that citrinin would adsorb on Ag NPs via its carboxylate form. Based on density functional theory (DFT) calculations, vibrational mode analysis was performed to compare the Raman spectra of citrinin. DFT calculations also predicted that a bidentate bridge configuration through O15 and O16 atoms in citrinin would be the most stable on three Ag atoms. After treating with Ag NPs, observation of citrinin peaks was attempted in fungal cells of Penicillium citrinum. This work may provide useful insights into the direct observation of the hazardous citrinin mycotoxin using SERS by understanding its adsorption behaviors on Ag surfaces. © 2013 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +82 2 820 0434. E-mail addresses: spica@hanyang.ac.kr (C.M. Lee), siyang@khu.ac.kr (S.I. Yang), sjoo@ssu.ac.kr (S.-W. Joo). 1. Introduction Research has paid much attention toward the detection of mycotoxin because of its effects in environmental and health issues [1,2]. Citrinin is a nephrotoxic contaminant produced by several fungal species, including Penicillium and Aspergillus [3,4]. Toxicologically, citrinin is associated with harmful synergistic 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2013.11.041