Due to the wide range of applications and biological significance, the development of optical probes for silver, gold and platinum ions has been an active research area in the past few years. This tutorial review focuses on the recent contributions concerning the fluorescent or colorimetric sensors for these metal ions, and is organized according to their structural classifications (for Ag(+) detection) and unique mechanisms between the sensors and metal ions (for Au(3+) and Pt(2+) detection).

A naphthalimide-based highly selective colorimetric and ratiometric fluorescent probe for the fluoride ion displayed both one- and two-photon ratiometric changes. Upon reaction with the F(-) (TBA(+) and Na(+) salts) anion in CH(3)CN as well as in aqueous buffer solution, probe 1 shows dramatic color changes from colorless to jade-green and remarkable ratiometric fluorescence enhancements signals. These properties are mechanistically ascribed to a fluoride-triggered Si-O bond cleavage that resulted in a green fluorescent 4-amino-1,8-naphthalimide.

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A novel calix[4]arene derivative locked in the 1,3-alternate conformation (2) bearing two pyrene and rhodamine fluorophores was synthesized as a selective sensor for the Hg(2+) ion. The sensoring is based on FRET from pyrene excimer emissions to ring-opened rhodamine absorption upon complexation of the Hg(2+) ion. Addition of Hg(2+) to a mixed solution of 2 gave significantly enhanced fluorescence at ∼576 nm via FRET with excitation at 343 nm. We also found that the pyrene excimer emissions formed by the intramolecular π-π interactions are more effective in obtaining strong FRET bands than those by intermolecular π-π interactions.

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1271 introductionMercury pollution is a global problem. 1,2 Owning to the grisly immunotoxic, genotoxic, and neurotoxic effects, mercury is considered to be a highly dangerous element by the United States Environmental Protection Agency. 3,4 For the purposes of detection and quantitative determination of mercury ions, much effort has been devoted to the development of appropriate methods that are low-cost, rapid, deft and applicable to natural environmental and biological milieus. 5,6 In contrast with many of the traditional quantitative approaches to Hg 2+ analysis that require intricate, multistep sample preparation and/or sophisticated instrumentation, fluorometric detections following the changes in the emission of light are more convenient and suitable for monitoring Hg 2+ in either natural or biological environments. 6There are multiple advantages in using fluorescence: (i) its powerful visual effects; (ii) its greater sensitivity than that of absorption spectroscopy; (iii) its simple equipment, commonly available in many scientific laboratories. 7,8 As a consequence, for fluorometric determination of Hg 2+ , a large number of fluorescent sensors including two components, an ionophore (receptor) for selective binding of the substrate and a fluorophore (transducer) for providing the means of signaling this binding, have recently been designed and synthesized. 8 This review focuses mainly on the small-molecular fluorescent chemosensors for Hg 2+ ion in organic or aqueous solution that were developed by our research laboratories and other groups in recent years. Fluorescent chemosensors in this review are divided into two sections based on the bearing fluorophore. The first section focuses on the development of rhodamine-derived Hg 2+ ion sensors, while the other section gave a brief introduction about Hg 2+ ion sensors bearing other functional fluorophores. Mechanisms generally used in explaining the response of a fluorophore to Hg 2+ binding include photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), internal charge transfer (ICT), photoinduced charge transfer (PCT) and excimer/exciplex formation or extinction. 8,92 Rhodamine-derived hg 2+ ion SensorsNoelting and Dziewonski first reported the preparation of the rhodamine in 1905. 10 However, it was only from the 21th century that the rhodamine-B derivatives and its ring-opening reaction received a great deal of attention and have been applied as fluorescent metal ion sensors in organic and biological researches. 11As schematically shown in Fig. 1

We report a novel fluorescent molecular conjugate, V-M1, enabling an accurate visualization of tumor tissues.

A lysosome-targeted fluorescent chemodosimeter, 1, was developed for monitoring endogenous and exogenous H2S by in vivo imaging of HeLa cells, D. melanogaster and C. elegans. In the tests of mutated C. elegans (SRP-6 nulls), chemodosimeter 1 could trace the accumulation of lysosome and lysosomal injury with a high resolution.