Rhodamine-Based Fluorescent Probe for Highly Selective Determination of Hg2

Biothiols-activated near-infrared frequency up-conversion luminescence probe for early evaluation of drug-induced hepatotoxicity

A novel biothiols-sensitive near-infrared (NIR) fluorescent probe RhDN based on a rhodamine skeleton was developed for early detection of drug-induced hepatotoxicity in living mice. RhDN can be used not only as a conventional large stokes shift fluorescent (FL) probe, but also as a kind of anti-Stokes frequency upconversion luminescence (FUCL) molecular probe, which represents a long wavelength excitation (808 nm) to short wavelength emission (760 nm), and response to Cys/Hcy/GSH with high sensitivity. Compared with traditional FL methods, the FUCL method exhibited a lower detection limit of Cys, Hcy, and GSH in 75.1 nM, 101.8 nM, and 84.9 nM, respectively. We exemplify RhDN for tracking endogenously biothiols distribution in living cells and further realize real-time in vivo bioimaging of biothiols activity in mice with dual-mode luminescence system. Moreover, RhDN has been successfully applied to visualize the detection of drug-induced hepatotoxicity in living mice. Overall, this report presents a unique approach to the development of large stokes shift NIR FUCL molecular probes for in vitro and in vivo biothiols biosensing.

Thiourea Functionalised Receptor for Selective Detection of Mercury Ions and its Application in Serum Sample

A thiourea functionalised fluorescent probe 1-phenyl-3-(pyridin-4-yl)thiourea was synthesized and utilised as a fluorescent turn-on chemosensor for the selective recognition of Hg2+ ion over competitive metal ions including Na+, Mn2+, Li+, Cr2+, Ni2+, Ca2+, Cd2+, Mg2+, K+, Co2+, Cu2+, Zn2+, Al3+ and Fe2+ ions based on the inter-molecular charge transfer (ICT). Intriguingly, the receptor demonstrated unique sensing capabilities for Hg2+ in DMSO: H2O (10:90, v/v). The addition of Hg2+ ions to the sensor resulted in a blue shift in the absorption intensity and also enhancement in fluorescence intensity at 435 nm. Fluorescence emission intensity increased linearly with Hg2+ concentration ranging from 0 to 80 µL. The detection limit and binding constant were determined as 0.134 × 10-6 M and 1.733 × 107 M-1, respectively. The sensing behavior of Hg2+ was further examined using DLS, SEM and FTIR. The probe could detect Hg2+ ions across a wide pH range. Furthermore, the receptor L demonstrated good sensing performance for Hg2+ in bovine serum albumin and actual water samples.

A colorimetric and fluorescent probe of lignocellulose nanofiber composite modified with Rhodamine 6G derivative for reversible, selective and sensitive detection of metal ions in wastewater

Heavy metal ions have extremely high toxicity. As the top of food chain, human beings certainly will accumulate them by ingesting food and participating other activities, which eventually result in the damage to our health. Therefore, it is very meaningful and necessary to design a simple, portable, stable and efficient material for heavy metal ions detection. Based on the spirolactam Rhodamine 6G (SRh6G) fluorescent probe, we prepared two types of nanocomposite materials (membrane and aerogel) by vacuum filtration and freeze-drying methods with lignocellulose nanofiber (CNF) as a carrier, polyvinyl alcohol (PVA) and glutaraldehyde (GA) as the cross-linkers. Then the microstructure, chemical composition, wetting property, fluorescence intensity and selectivity of as-prepared SRh6G/PVA/CNF would be characterized and analyzed. Results showed that SRh6G/PVA/CNF nanocomposites would turn red in color under strong acidic environment and produced orange fluorescence under ultraviolet light. Besides, they were also to detect Al3+, Cu2+, Hg2+, Fe3+ and Ag+ through color and fluorescence variations. We had further tested its sensitivity, selectivity, adsorption, fluorescence limits of detection (LOD) to Fe3+ and Cu2+. The test towards real water samples (hospital wastewater, Songhua River and tap water) proved that SRh6G/PVA/CNF nanocomposites could detect the polluted water with low concentrations of Fe3+ and Cu2+. In addition, SRh6G/PVA/CNF nanocomposites have excellent mechanical property, repeatability, superhydrophilicity and underwater superoleophobicity, which may offer a theoretical reference for the assembly strategy and detection application of cellulose-based fluorescent probe.

Tackling the water solubility dilemma of spiroring-closing rhodamine: Sulfone-functionalization enabling rational designing water-soluble probe for rapid visualizing mercury ions in cosmetics

Rhodamine derivatives possessing spiroring-closing structures exhibit colorlessness, while the induction of spiroring-opening by metal ions results in notable color changes, rendering them as ideal platform for the development of functional probes with broad applications. However, the spiroring-closing form of rhodamine-based probes exhibits limited water solubility due to its neutral character, necessitating the incorporation of organic solvents to enhance solubility, which may adversely affect the natural system. Designing rhodamine probes with high solubility in both the zwitterionic and neutral form is of utmost importance and presents a significant challenge. This study presents a sulfone-rhodamine-based probe that exhibits good water solubility both in the spiroring opening and closing for detecting Hg2+. Upon the presence of Hg2+, the color undergoes a noticeable change from colorless to pink, with a response time of less than 1 min. probe 1 demonstrates an excellent linear relationship with Hg2+ concentrations within the range of 0-8 μM, and achieves a detection limit is 17.26 nM. The effectiveness of probe 1 was confirmed through the analysis of mercury ions in cosmetic products. Utilizing this probe, test paper strips have been developed to enhance the portability of Hg2+ detection naked eyes.

Triphenylamine-Based Polythioacetal for Selective Sensing of Mercury(II) with High Specificity and Sensitivity

Utilizing the mercury (Hg2+)-triggered deprotection of thioacetals to aldehyde groups, we constructed a water-soluble triphenylamine (TPA)-based polythioacetal PTA-TPA with thioacetal groups in the backbones for efficient sensing of Hg2+ in aqueous solutions. PTA-TPA is conveniently prepared by polycondensation of 3, 6-dioxa-1,8-octanedithiol (DODT) with 4-(N,N-diphenylamino) benzaldehyde (TPA-CHO) using thiol-terminated mPEG2k-SH as a capping agent. The interaction of Hg2+ with PTA-TPA activates the aggregation-induced emission (AIE) process of TPA-CHO molecules, which makes the emission enhanced, and the emission color changes to sky blue, while other metal ions do not interfere with the sensing process. PTA-TPA can be used as a highly selective and ultrafast detection system for Hg2+ with a low detection limit (LOD) of 9.88 nM and a fast response of less than 1 min. In addition, the prepared test strips report the presence of Hg2+ with an LOD as low as 1 × 10-5 M. Intracellular imaging applications have demonstrated that PTA-TPA acts as a biocompatible fluorescent probe for efficient Hg2+ sensing in HeLa cells. Overall, the PTA-TPA fluorescence probes have the characteristics of easy synthesis, cost-effective, ultrafast detection speed, high selectivity, and high sensitivity, which can be used in practical applications.

A highly selective fluorescence turn-on sensor for Hg2+ based on quinolimide in aqueous media and its applications

Herein, a novel fluorescent sensor QPE based on quinolimide was developed, which displayed the highly selective response to Hg2+ through the turn-on signal in aqueous media. The corresponding recognition mechanism of QPE for Hg2+ was investigated by the titration experiments, Job's plots, HRMS, and DFT calculations analysis. QPE could detect Hg2+ in a broad pH range (pH = 4-9) with the LOD of 20 nM and the LOQ of 66 nM. Meanwhile, QPE-loaded test strips were demonstrated in the visual detection of Hg2+. Importantly, QPE exhibited the reliable capability to track Hg2+ in real water and soil samples and yeast cells, indicating that QPE could be used as a prospective tool for monitoring Hg2+ in wide fields.

A multifunctional fluorescent sensor for Ag+ and Hg2+ detection in seawater

In order to detect Ag+ and Hg2+ in seawater, we explored a multifunctional fluorescence sensor. A multifunctional Ag+ and Hg2+ sensor was designed by using gold nanoparticles (AuNPs) as quenching agent, PicoGreen dye as fluorescent probe of base pairing double-stranded deoxyribonucleic acid (DNA), and combining the characteristics of Ag+ making C base mismatch and Hg2+ making T base mismatch. Meanwhile, the DNA logic gate was constructed by establishing logic circuit, truth table, and logic formula. The relevant performances of the sensor were investigated. The results revealed that the sensor can detect Ag+ in the range of 100 to 700 nM with R2 = 0.98129, and its detection limit is 16.88 nM (3σ/slope). The detection range of Hg2+is 100-900 nM with R2 = 0.99725, and the detection limit is 5.59 nM (3σ/slope). An AND-AND-NOR-AND molecular logic gate has been successfully designed. With the characteristics of high sensitivity, multifunction, and low cost, the recommended detection method has the potential to be applied to the detection of Ag+ and Hg2+ in seawater.

A FRET Based Composite Sensing Material Based on UCNPs and Rhodamine Derivative for Highly Sensitive and Selective Detection of Fe3

The existence of excessive concentration of iron ion (Fe3+) in water will do harm to the environment and biology. Presently, sensitive and selective determination of Fe3+ directly in real environment samples is still a challenging job because of the high complexity of the sample matrix. In this work, we reported a new sensor system for Fe3+ based on fluorescence resonance energy transfer (FRET) from upconversion nanoparticles (UCNPs) to Rhodamine derivative probe (RhB). The NaYF4: Yb, Er@SiO2@P(NIPAM-co-RhB) nanocomposites was constructed, in which PNIPAm was used as the probe carrier. The nanocomposites can not only be excited by infrared light to avoid the interference of background light in the Fe3+ detection process, but also enhance the detection signal output through temperature control. Under the optimum conditions, the RSD (Relative standard deviation) of actual sample measurements ranges was from 1.95% to 4.96%, with the recovery rate from 97.4% to 103.3%, which showed high reliability for Fe3+ detection. This work could be extended to sensing other target ions or molecules and may promote the widespread use of FRET technique.

Recent Development in Fluorescent Probes for the Detection of Hg2+ Ions

Mercury, a highly toxic heavy metal, poses significant environmental and health risks, necessitating the development of effective and responsive techniques for its detection. Organic chromophores, particularly small molecules, have emerged as promising materials for sensing Hg²⁺ ions due to their high selectivity, sensitivity, and ease of synthesis. In this review article, we provide a systematic overview of recent advancements in the field of fluorescent chemosensors for Hg²⁺ ions detection, including rhodamine derivatives, Schiff bases, coumarin derivatives, naphthalene derivatives, BODIPY, BOPHY, naphthalimide, pyrene, dicyanoisophorone, bromophenol, benzothiazole flavonol, carbonitrile, pyrazole, quinoline, resorufin, hemicyanine, monothiosquaraine, cyanine, pyrimidine, peptide, and quantum/carbon dots probes. We discuss their detection capabilities, sensing mechanisms, limits of detection, as well as the strategies and approaches employed in their design. By focusing on recent studies conducted between 2022 and 2023, this review article offers valuable insights into the performance and advancements in the field of fluorescent chemosensors for Hg²⁺ ions detection.