A new rhodamine B-based ‘off-on’ colorimetric chemosensor for Pd2+ and its imaging in living cells

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.

An Isoniazid Based Schiff Base Sensor for Selective Detection of Pd2+ Ions

Here, we developed a novel isoniazid based fluorescent probe (E)-N'-(thiophen-2-ylmethylene)isonicotinohydrazide (TINH) through simple condensation reaction and employed for selective detection of Pd2+ ions with a low detection limit of 4.102 × 10-11 M. Among the many existing cations, TINH bound Pd2+ ions with an association affinity of 9.794 × 105 M-1. Adding Pd2+ ions to ligand solution increased the absorption intensity in UV-Visible and quenched the emission intensity in fluorescence spectroscopic experiments. More importantly, this TINH complexed to Pd2+ ions in 1:1 stoichiometric ratio. To evaluate the stability of complexed system, pH experiments has been performed. The binding insights among the ligand and Pd2+ ions has been confirmed by IR spectroscopic and MASS spectrometric methods. Additionally, TINH also applied to real water samples for the identification and measurement of Pd2+ ions. Hence, this system could be highly applicable for detection of Pd2+ ions in environmental and industrial samples with in low detection range.

A Fluorescent and Colorimetric Chemosensor Detecting Pd2+ Based on Chalcone Structure with Triphenylamine

A fluorometric and colorimetric chemosensor DiPP ((E)-3-(4-(diphenylamino)phenyl)-1-(pyridin-2-yl)prop-2-en-1-one) based on chalcone structure with a triphenylamine group was synthesized. Sensor DiPP detected Pd2+ with fluorescence turn-off and via colorimetry variation of yellow to purple. The binding ratio of DiPP to Pd2+ turned out to be 1 : 1. Detection limits for Pd2+ by DiPP were analyzed to be 0.67 µM and 0.80 µM through the fluorescent and colorimetric methods. Additionally, the fluorescent and colorimetric test strips were applied for probing Pd2+ and displayed that DiPP could obviously discriminate Pd2+ from other metals. The binding feature of DiPP to Pd2+ was presented by ESI-mass, Job plot, NMR titration, ESI-mass, and DFT calculations.

Discovery of a novel camphor-based fluorescent probe for Co2+ in fresh vegetables with high selectivity and sensitivity

Cobalt is an essential micronutrient for human beings. The excessive intake of cobalt may lead to heart-related diseases. In this work, a novel fluorescent probe 1,1'-(((6,11,11-trimethyl-6,7,8,9-tetrahydro-6,9-methanopyridazino[4,5-b]quinoxaline-1,4-diyl)bis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol) (PDS) was synthesized from camphor. The probe PDS could be utilized to selectively recognize Co²⁺ over other metal ions. There is a good linear relationship between fluorescence intensity of PDS and Co²⁺ concentration within 0-20 μM, and its detection limt was found to be 0.925 μM, which is far lower than the national standard for cobalt in drinking water in China. The possible coordination mechanism of PDS with Co²⁺ was determined by nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS) and density functional theory (DFT). The probe PDS was also successfully applied in detection of Co²⁺ in tap water and fresh vegetables.

A selective purine-based fluorescent chemosensor for the “naked-eye” detection of zinc ions (Zn2+): applications in live cell imaging and test strips

In this work, a novel purine based probe PTAHN was successfully designed and synthesized. PTAHN displayed high selectivity towards Zn²⁺via turn-on fluorescence. What's more, PTAHN can be proficiently employed for imaging Zn²⁺ in living cells.

An umbelliferone-derivated fluorescent sensor for selective detection of palladium(II) from palladium(0) in living cells

Palladium (Pd) has drawn worldwide attentions because its connections to industry, chemistry, biological material and public health. Quantitative and selective detection tools for Pd and its ion forms are in urgent necessity. Here an umbelliferone derivative Umb-Pd2 was provided as a small, steady, safe and selective sensor for detecting Pd(II). It indicated advantages including sensitive (LOD 1.1 nM), wide pH tolerance (5.0-10.0), applicable linear range (0-1.8 equivalent) and low toxicity. The most attractive point was its explicit selectivity towards Pd(II) from Pd(0) in both independent and coexistence systems. This distinguishing ability was further utilized in imaging in living cells, raising this work as a rare and important example among all the published papers on palladium sensing. Thus, Umb-Pd2 supplied a potential approach for further improvement and applications in both daily chemistry and public health.