A Study of Small Molecule-Based Rhodamine-Derived Chemosensors and their Implications in Environmental and Biological Systems from 2012 to 2021: Latest Advancement and Future Prospects

Rhodamine-based chemosensors have sparked considerable interest in recent years due to their remarkable photophysical properties, which include high absorption coefficients, exceptional quantum yields, improved photostability, and significant red shifts. This article presents an overview of the diverse fluorometric, and colorimetric sensors produced from rhodamine, as well as their applications in a wide range of fields. The ability of rhodamine-based chemosensors to detect a wide range of metal ions, including Hg+2, Al3+, Cr3+, Cu2+, Fe3+, Fe2+, Cd2+, Sn4+, Zn2+, and Pb2+, is one of their major advantages. Other applications of these sensors include dual analytes, multianalytes, and relay recognition of dual analytes. Rhodamine-based probes can also detect noble metal ions such as Au3+, Ag+, and Pt2+. They have been used to detect pH, biological species, reactive oxygen and nitrogen species, anions, and nerve agents in addition to metal ions. The probes have been engineered to undergo colorimetric or fluorometric changes upon binding to specific analytes, rendering them highly selective and sensitive by ring-opening via different mechanisms such as Photoinduced Electron Transfer (PET), Chelation Enhanced Fluorescence (CHEF), Intramolecular Charge Transfer (ICT), and Fluorescence Resonance Energy Transfer (FRET). For improved sensing performance, light-harvesting dendritic systems based on rhodamine conjugates has also been explored for enhanced sensing performance. These dendritic arrangements permit the incorporation of numerous rhodamine units, resulting in an improvement in signal amplification and sensitivity. The probes have been utilised extensively for imaging biological samples, including imaging of living cells, and for environmental research. Moreover, they have been combined into logic gates for the construction of molecular computing systems. The usage of rhodamine-based chemosensors has created significant potential in a range of disciplines, including biological and environmental sensing as well as logic gate applications. This study focuses on the work published between 2012 and 2021 and emphasises the enormous research and development potential of these probes.

A New bis(rhodamine)-Based Colorimetric Chemosensor for Cu2

A novel sensor (RD) bearing rhodamine B and 4-tert-Butyl phenol unit have been designed and synthesized using microwave irradiation. The sensor allows selective detection of Cu2+ by forming absorptive complex and trigger the formation of highly colored ring-open spirolactam. The recognition ability of the sensor was investigated by absorbance, Job's plot, infrared (IR) and time dependent-density functional theory (TD-DFT) calculations.

A rhodamine-based fluorescent sensor for selective detection of Cu2+ in aqueous media: synthesis and spectroscopic properties

Two new chemosensors, rhodamine B derivative bearing 3-formyl-6-nitrochromone (L ₁ ) and 3-formyl-6-methylchromone (L ₂ ) units were designed and synthesized using microwave irradiation for the selective detection of Cu²⁺ in aqueous media. Copper triggers the formation of highly fluorescent ring-open spirolactam. The fluorescence intensity was remarkably increased upon the addition of Cu²⁺ within a minute, while the other metal ions caused no significant effect. More importantly, the resulting complexes can be used as a reversible fluorescence sensor for CN^-. The recognition ability of the sensors was investigated by fluorescence titration, Job's plot, ¹H NMR spectroscopy and density functional theory (DFT) calculations.

Synthesis and fluorescence spectral studies of novel quinolylbenzothiazole-based sensors for selective detection of Fe3+ ion

Four novel fluorescence sensors bearing a quinolylbenzothiazole platform were synthesized and characterized. The sensors displayed excellent selectivity and highly sensitive fluorescence response to Fe3+ ion in H2O/DMSO buffer solution (1:4 volume ratio; Tris-HCl, 0.01 mol/L; pH = 7.40) at 500 nm originating from quinolylbenzothiazole fluorophore group. Other cations, namely Li+, Na+, K+, Mg2+, Ca2+, Co2+, Ni2+, Cd2+, Cu2+, Zn2+, Mn2+, Ba2+, Pb2+, Hg2+, Al3+, and Eu3+, showed no appreciable change in fluorescence spectrum. The binding stoichiometry between sensors L1, L2, L3, or L4 and Fe3+ was observed to be 1:1 based on fluorescence titration and Jobs plot analysis. The detection limits of L1, L2, L3, and L4 for Fe3+ were found to be 0.155, 0.362, 0.249, and 0.517 μmol/L, respectively. Furthermore, possible utilization of sensors to detect Fe3+ in living HeLa cells was also investigated by confocal fluorescence microscopy.