We demonstrate that silver nanoparticles undergo an interaction with Hg2+ found in traces. The PEG-PVP-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with surface plasmon resonance UV/Vis spectroscopy. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ ion. A linear and inversely proportional relationship was found between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ ion over the range from 10？ppm to 1？ppm at absorption on 411？nm. The detection limit for Hg2+ ions in homogeneous aqueous solutions is estimated to be 1？ppm. This system shows excellent selectivity for Hg2+. The results found have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions. The proposed method was successfully applied to quantify the amount of mercury in seafood. 1. Introduction Pollution is the introduction of contaminants into a natural environment resulting in instability, disorder, harm, or discomfort to the ecosystem including physical systems and living organisms. Among the pollutants and particularly among heavy metals, mercury is one of the most commonly encountered toxic pollutant in the environment which may be a result of natural processes and emissions from coal burning power plants and gold mining [1]. Similarly, in aqueous solution, bacteria can transform water-soluble mercuric ion (Hg2+) into methylmercury, which is the most common form of mercury in fish, and subsequently bioaccumulates through the food chain [2]. Methylmercury is a potent neurotoxin known to cause health problems such as sensory, motor, and neurological damage. It is particularly dangerous for children, because it can cause developmental delays [3]. Although the traditional instrumental techniques, such as absorption spectroscopy, cold vapor atomic fluorescence spectrometry, and gas chromatography, give the direct and quantitative detection of Hg2+ concentration [4, 5], it is highly desirable to develop facile and quick methods for measuring the level of this detrimental metallic ion in the environment with high sensitivity and selectivity. To date, several methods providing the optical feedback for the detection of Hg2+ based upon fluorophores [6–10] chromogenic redox based fluorescent method [11], chromophores [12], polymer [13], and noble metal-based probes [14–18] have been developed. In this
References
[1]
C. S？nnichsen, B. M. Reinhard, J. Liphardt, and A. P. Alivisatos, “A molecular ruler based on plasmon coupling of single gold and silver nanoparticles,” Nature Biotechnology, vol. 23, no. 6, pp. 741–745, 2005.
[2]
H. H. Harris, I. J. Pickering, and G. N. George, “The chemical form of mercury in fish,” Science, vol. 301, no. 5637, p. 1203, 2003.
[3]
P. Grandjean, P. Weihe, R. F. White, and F. Debes, “Cognitive performance of children prenatally exposed to “safe” levels of methylmercury,” Environmental Research, vol. 77, no. 2, pp. 165–172, 1998.
[4]
S. Yoon, A. E. Albers, A. P. Wong, and C. J. Chang, “Screening mercury levels in fish with a selective fluorescent chemosensor,” Journal of the American Chemical Society, vol. 127, no. 46, pp. 16030–16031, 2005.
[5]
J. Wang and B. Liu, “Highly sensitive and selective detection of Hg2+ in aqueous solution with mercury-specific DNA and Sybr Green I,” Chemical Communications, no. 39, pp. 4759–4761, 2008.
[6]
X.-J. Zhu, S.-T. Fu, W.-K. Wong, J.-P. Guo, and W.-Y. Wong, “A near-infrared-fluorescent chemodosimeter for mercuric ion based on an expanded porphyrin,” Angewandte Chemie International Edition, vol. 45, no. 19, pp. 3150–3154, 2006.
[7]
J. V. Ros-Lis, M. D. Marcos, R. Mártinez-Má？ez, K. Rurack, and J. Soto, “A regenerative chemodosimeter based on metal-induced dye formation for the highly selective and sensitive optical determination of Hg2+ ions,” Angewandte Chemie International Edition, vol. 44, no. 28, pp. 4405–4407, 2005.
[8]
Y.-K. Yang, K.-J. Yook, and J. Tae, “A rhodamine-based fluorescent and colorimetric chemodosimeter for the rapid detection of Hg2+ ions in aqueous media,” Journal of the American Chemical Society, vol. 127, no. 48, pp. 16760–16761, 2005.
[9]
X. Guo, X. Qian, and L. Jiat, “A highly selective and sensitive fluorescent chemosensor for Hg2+ in neutral buffer aqueous solution,” Journal of the American Chemical Society, vol. 126, no. 8, pp. 2272–2273, 2004.
[10]
S. Yoon, E. W. Miller, Q. He, P. H. Do, and C. J. Chang, “A bright and specific fluorescent sensor for mercury in water, cells, and tissue,” Angewandte Chemie International Edition, vol. 46, no. 35, pp. 6658–6661, 2007.
[11]
A. Caballero, R. Martínez, V. Lloveras et al., “Highly selective chromogenic and redox or fluorescent sensors of Hg2+ in aqueous environment based on 1,4-disubstituted azines,” Journal of the American Chemical Society, vol. 127, no. 45, pp. 15666–15667, 2005.
[12]
E. Coronado, J. R. Galán-Mascarós, C. Martí-Gastaldo et al., “Reversible colorimetric probes for mercury sensing,” Journal of the American Chemical Society, vol. 127, no. 35, pp. 12351–12356, 2005.
[13]
Y. Zhao and Z. Zhong, “Tuning the sensitivity of a foldamer-based mercury sensor by its folding energy,” Journal of the American Chemical Society, vol. 128, no. 31, pp. 9988–9989, 2006.
[14]
J.-S. Lee, M. S. Han, and C. A. Mirkin, “Colorimetric detection of mercuric ion (Hg2+) in aqueous media using DNA-functionalized gold nanoparticles,” Angewandte Chemie International Edition, vol. 46, no. 22, pp. 4093–4096, 2007.
[15]
G. K. Darbha, A. K. Singh, U. S. Rai, E. Yu, H. Yu, and P. C. Ray, “Selective detection of mercury (II) ion using nonlinear optical properties of gold nanoparticles,” Journal of the American Chemical Society, vol. 130, no. 25, pp. 8038–8043, 2008.
[16]
D. Li, A. Wieckowska, and I. Willner, “Optical analysis of Hg2+ ions by oligonucleotide-gold-nanoparticle hybrids and DNA-based machines,” Angewandte Chemie International Edition, vol. 47, no. 21, pp. 3927–3931, 2008.
[17]
Y. Fan, Z. Liu, L. Wang, and J. Zhan, “Synthesis of starch-stabilized Ag nanoparticles and Hg2+ recognition in aqueous media,” Nanoscale Research Letters, vol. 4, no. 10, pp. 1230–1235, 2009.
[18]
R. K. Bera, A. K. Das, and C. R. Raj, “Enzyme-cofactor-assisted photochemical synthesis of Ag nanostructures and shape-dependent optical sensing of Hg(II) ions,” Chemistry of Materials, vol. 22, no. 15, pp. 4505–4511, 2010.
[19]
S. Schultz, D. R. Smith, J. J. Mock, and D. A. Schultz, “Single-target molecule detection with nonbleaching multicolor optical immunolabels,” Proceedings of the National Academy of Sciences of the United States of America, vol. 97, no. 3, pp. 996–1001, 2000.
[20]
J.-J. Zhu, X.-H. Liao, X.-N. Zhao, and H.-Y. Chen, “Preparation of silver nanorods by electrochemical methods,” Materials Letters, vol. 49, no. 2, pp. 91–95, 2001.
[21]
D. D. Evanoff Jr. and G. Chumanov, “Synthesis and optical properties of silver nanoparticles and arrays,” ChemPhysChem, vol. 6, no. 7, pp. 1221–1231, 2005.
[22]
M. T. Morrissey, R. Rasmussen, and T. Okada, “Mercury content in pacific troll-caught albacore tuna (Thunnus alalunga),” Journal of Aquatic Food Product Technology, vol. 13, no. 4, pp. 41–52, 2004.
[23]
S. L. Blanco, J. C. González, and J. M. Vieites, “Mercury, cadmium and lead levels in samples of the main traded fish and shellfish species in Galicia, Spain,” Food Additives and Contaminants B, vol. 1, no. 1, pp. 15–21, 2008.
