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A new furfuran-based rhodamine B fluorescent probe (RBFF) has been designed and synthesized, and its sensing behavior towards various metal ions was evaluated via UV–vis and fluorescence spectroscopic techniques. RBFF exhibits a highly sensitive and selective “turn-on” fluorescent response toward Fe3+ ion and a fluorescence “turn-off” response when added B4O72− to the RBFF-Fe3+ in the EtOH/H2O solution (1:1, v/v, HEPES, 1 mM, pH 7.20). The detection limit of RBFF for Fe3+ was calculated to be 0.025 μM. The fluorescence microscopy experiment suggested that RBFF could also be served as a biological fluorescence probe for the detection of Fe3+ in human cervical carcinoma cells (HeLa).

A new fluorescent probe ( TRDM-F ) based on a molecular chain of open-loop maleic anhydride, rhodamine B and fluorescein was designed, synthesized and evaluated to develop a chemosensor. Photochemical studies show that fluorescence properties of TRDM-F are dominated by fluorescein group in the pH range of 2–10. UV–vis absorption and fluorescence spectroscopic studies further display a high selectivity towards Cys over GSH/Hcy and other amino acids and a high sensitivity towards Cys (0.088–270 μM) with 95-fold fluorescence enhancement in a HEPES buffer solution (10 mM, pH = 7.4) containing 20% MeCN at room temperature. We further demonstrated that the proposed method was satisfactorily applied to the discrimination of Cys in living Hela cells with low cell toxicity.

A new rhodamine B derivative, namely, N1-(benzo[d]thiazol-2-yl)-N4-(2-(3′,6′-bis (diethylamino)-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)ethyl)malea-mide (RDBSF), was designed, synthesized, and structurally characterized to develop a new chemosensor. UV–vis absorption and fluorescence spectroscopic studies show that RDBSF exhibits high sensitivity and selectivity toward Fe3+ in the presence of many other metal cations in a Tris-HCl solution (1 mM, pH = 7.4) containing 30% MeCN by forming a 1:1 complex with Fe3+. The binding association constant (Ka) of RDBSF for Fe3+ was estimated as 1.52 × 104 M−1 in the solution. The detection limit of Fe3+ by RDBSF was further determined as 11.6 nM. Intracellular imaging applications demonstrated that RDBSF can be used as a fluorescent probe for the detection of Fe3+ in HepG-2 cells.

Graphene oxide (GO) displays advantageous characteristics as a quencher due to its excellent quenching capacity toward organic fluorescent molecules. In this paper, GO is used as a quencher of RhBPy [2]rotaxane based on the mechanism of fluorescence resonance energy transfer (FRET), and a GO-based fluorescent probe that allows rapid, sensitive and selective detection of doxorubicin (DOX) in a MeOH/H2O solution is reported. The results show that the efficient fluorescence quenching that occurs between GO and RhBPy [2]rotaxane is due to their strong noncovalent interactions via energy transfer, leading to very weak emission in the absence of DOX, while a strong red fluorescence is observed upon the addition of DOX into the RhBPy-GO solution. As a consequence, it is possible to employ the RhBPy-GO platform in DOX detection with high sensitivity and selectivity by monitoring changes in the fluorescence intensity of the MeOH/H2O (3:2, v: v) solution.

A new rhodamine spirolactam derivative bearing a thiodiacetamide moiety and two rhodamine B fluorophores (RBTDA) was designed, synthesized and structurally characterized to develop a chemosensor. The interactions of RBTDA with different metal ions have been studied over UV–vis absorption spectra and fluorescent spectra. The results indicated that RBTDA exhibited a highly sensitive and selective turn-on fluorescent response for Cr3+ in the presence of many other metal cations in a methanol-HEPES buffer (3:1, v/v, 0.5 mM, pH 7.25) solution. The binding analysis based on mass spectroscopic data and a Job plot suggested that the RBTDA formed a 1:1 complex with Cr3+. The binding association constant (Ka) for Cr3+ based on a 1:1 stoichiometry was estimated to be 5.01 × 104 M−1 in the solution. The detection limit of Cr3+ by RBTDA was further determined to be 0.378 μM.

A novel rhodamine B-based sensor 1 consisting of a rhodamine B moiety linked to the amine end of a 1,4,7,10-tetraoxa-13-azacyclopentadecane was designed and synthesized. Sensor 1 exhibits a high selectivity for Fe 3+ in the presence of many other metal cations in a MeOH/H 2 O (1:1, v/v, pH = 7.4) solution. The binding analysis using a Job plot suggested that sensor 1 formed a 1:1 complex with Fe 3+ . The Fe 3+ binding ability of 1 was further demonstrated by DFT calculations. Fluorescence microscopy experiments demonstrated that sensor 1 can be used as a fluorescent probe for the detection of Fe 3+ in human liver cells (L-02) and rat neuronal cells (PC12).