Hg 2 þ -induced self-assembly of a naphthalimide derivative by selective ‘‘turn-on’’ monomer/excimer emissions Nantanit Wanichacheva a,n , Narupon Prapawattanapol b , Vannajan Sanghiran Lee c , Kate Grudpan d , Amorn Petsom e a Department of Chemistry, Faculty of Science, Silpakorn University, Nakorn Pathom 73000, Thailand b Petrochemistry and Polymer Science Program, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand c Department of Chemistry, Faculty of Science, University of Malaya 50603, Kuala Lumpur, Malaysia d Department of Chemistry, Center for Innovation in Chemistry, Faculty of Science, and Center of Excellence in Innovation for Analytical Science and Technology, Chiang Mai 50200, Thailand e Research Centre for Bioorganic Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand article info Article history: Received 30 March 2012 Received in revised form 4 July 2012 Accepted 16 July 2012 Available online 24 July 2012 Keywords: Naphthalimide probe Mercury sensor Hg 2 þ-selectivity Excimer abstract A novel fluorescent sensor bearing two naphthalimide fluorophores based on 2-(3-(2-aminoethylsulfa- nyl)propylsulfanyl)ethanamine, 1, was readily synthesized for the recognition of Hg 2 þ . The sensitive and selective binding behaviors of 1 were investigated by fluorescence spectroscopy. Sensor 1 selectively binds Hg 2 þ by exhibiting OFF–ON fluorescence enhancement behaviors of the monomer and excimer bands. The sensor provides excellent Hg 2 þ -selectivity in the presence of high concentrations of competitive ions, particularly Cu 2 þ and Pb 2 þ as well as Na þ ,K þ , Mn 2 þ , Cd 2 þ , Ni 2 þ , Ca 2 þ , Li þ , Zn 2 þ and Co 2 þ , with an available detection limit of 2.1  10 7 M or 42 ppb. & 2012 Elsevier B.V. All rights reserved. 1. Introduction Mercury is one of the most highly poisonous and hazardous pollutants with recognized accumulative and persistent characters in the environment and biota [1–3]. Inorganic mercury (Hg 2 þ ) can be converted into methylmercury by bacteria in the marine system and can easily enter the food chain and accumulate in the upper level, especially in large edible fish [1–3]. Mercury can cause serious human health problems including DNA damage, mitosis impairment and permanent damage to the central nervous system [4–5]. Current techniques for Hg 2 þ determination, including atomic absorption spectroscopy [6], inductively coupled plasma mass spectrometry [7] and electrochemistry [8] often require a large amount of samples, expensive and sophisticated instrumen- tations which pose serious limitations for on-site determination of Hg 2 þ in biological samples. On the other hand, fluorescence detection of Hg 2 þ presents many promising approaches because it allows nondestructive and rapid determination, high sensitivity and real time tracking for the detection of Hg 2 þ . A number of fluorescence chemosensors for Hg 2 þ have been devised by utilizing synthetic or commercial ionophores, includ- ing cyclen [9–10], hydroxyquinoline [11–12], azine [13], cyclams [14–17], diazatetrathia crown ethers [18], and calixarenes [19–21]. Although many fluorescent sensors have been designed for Hg 2 þ -sensing, many lack the suitability for commercial and practical uses due to multi-step syntheses, high costs of starting materials or high detection limits of Hg 2 þ [9–10,18,22]. Besides, they often suffer from cross-sensitivity toward other ions, parti- cularly potential competitors such as copper (Cu 2 þ ) and lead (Pb 2 þ ) due to their similar chemical behavior to Hg 2 þ [12–15,17–19,23–25]. In addition, most of the reported Hg 2 þ fluorescent chemosensors demonstrate a fluorescent quenching ‘‘turn-off’’ mechanism due to the quenching characteristic of Hg 2 þ ions. Conversely, there have been limited reports of fluor- escent enhancement ‘‘turn-on’’ Hg 2 þ -sensors which provide high sensitivity and selectivity [9,26–27]. In the present work, we report the synthesis of a new ‘‘turn- on’’ Hg 2 þ -fluorescence chemosensor which provides high sensi- tivity and selectivity towards interfering ions, but with a sig- nificantly reduced synthetic cost and effort. Our designed sensor was modified from the structure of the 2-[3-(2-aminoethylsulfa- nyl)propylsulfanyl]ethanamine which consisted of two sulfur and nitrogen atoms into the platform. Based on the fact that Hg 2 þ can Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jlumin.2012.07.009 n Corresponding author. Tel.: þ66 34 255 797; fax: þ66 34 271 356. E-mail addresses: wanichacheva.nantanit@gmail.com, nantanit@su.ac.th (N. Wanichacheva). Journal of Luminescence 134 (2013) 686–690