Probes to dye for: Rhodamine-inspired Si-pyronine, Si-rhodamine, Te-rhodamine, and Changsha NIR dyes have been developed recently. These dyes show fluorescence in the far-red to near-infrared region, while retaining the advantages of the original rhodamines, such as high fluorescence quantum yield, tolerance to photobleaching, good water solubility, and exhibit great potential for biological application.

A fluorescent turn-on probe for Cys/Hcy based on inhibiting the C═N isomerization quenching process by an intramolecular hydrogen bond was reported. The probe exhibited higher selectivity toward Cys/Hcy over other amino acids as well as thiol-containing compounds.

A new ratiometric fluorescent cyanide probe was developed based on the nucleophilic attack of CN(-) toward the indolium group of a hybrid coumarin-hemicyanine dye, by which high selectivity as well as large emission shift could be achieved.

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A new rhodamine B-based dual-function chromo- and fluorogenic probe for Cu(2+) and ClO(-) has been designed, synthesized, and characterized. The probe comprises a spectroscopic unit of rhodamine B and a Cu(2+)-specific chelating unit of pyridinecarboxamide as well as a ClO(-)-specific reactive moiety of diacylhydrazine, and is a highly selective and extremely sensitive fluorescent and colorimetric sensor for Cu(2+) and ClO(-) in different pH conditions. Compared with the reported probes for Cu(2+) or ClO(-), this is the first chemosensor based on a small molecule that can detect both Cu(2+) and ClO(-), respectively, at 1 nM level.