A solvent-dependent chemosensor for fluorimetric detection of Hg2+ and colorimetric detection of Cu2+ based on a new diarylethene with a rhodamine B unit

A dual responsive bis-thiophene affixed thiosemicarbazide based chemosensor for colorimetrically Hg2+ and fluorometrically Cu2+ ions and their applications in live cell imaging

In this work, we developed a fast and straightforward colorimetric and photoluminescent chemosensor probe (P1), featuring bis-thiophene-thiosemicarbazide moieties as its signaling and binding unit. This probe exhibited rapid sensitivity to Hg2+ and Cu2+ ions in a semi-aqueous medium, resulting in distinct colorimetric and photoluminescent changes. In the presence of Cu2+, P1 displayed an impressive 50-fold increase in photoluminescence (PL) at 450 nm (with excitation at 365 nm). The probe P1 formed a 1:1 complex with Hg2+ and Cu2+ ions, featuring association constant values of 4.04 × 104 M-1 and 1.25 × 103 M-1, respectively. P1 has demonstrated its efficacy in the analysis of real samples, yielding promising results. Additionally, the probe successfully visualized copper ions on a mouse fibroblast cell line (NIH3T3), highlighting its potential as an intracellular probe for copper ion detection.

Facile synthesis of magnetic intelligent sensors for the pH-sensitive controlled capture of Cr(vi)

In this work, intelligent pH-sensitive sensors (Fe3O4/RhB@PAM) for Cr(vi) detection were successfully synthesized based on polyacrylamide (PAM) and Rhodamine B (RhB) co-modified Fe3O4 nanocomposites. The characterization results indicated that the sensors had many favorable properties, including suitable size, stable crystal structure and excellent magnetic response performance (47.59 emu g-1). In addition, the fluorescence changes during the detection process indicated that Fe3O4/RhB@PAM were "ON-OFF" intelligent sensors. When the Fe3O4/RhB@PAM sensors were placed in acidic Cr(vi) solution (pH 4), PAM acted as a pH-responsive "gatekeeper" releasing RhB, and the fluorescence intensity of released RhB was weakened by the complexation of Cr(vi). Furthermore, the fluorescence changes of the magnetic sensors were remarkably specific for Cr(vi) even in the presence of other competitive cations, and the limit of detection (LOD) for Cr(vi) was lower (0.347 μM) than the value recommended by the World Health Organization (0.96 μM). All the results presented in this study showed that the Fe3O4/RhB@PAM sensors had significant potential for Cr(vi) detection in acidic environmental samples.

Recent Advances in Photoswitchable Fluorescent and Colorimetric Probes

In recent years, significant advancements have been made in the research of photoswitchable probes. These probes undergo reversible structural and electronic changes upon light exposure, thus exhibiting vast potential in molecular detection, biological imaging, material science, and information storage. Through precisely engineered molecular structures, the photoswitchable probes can toggle between "on" and "off" states at specific wavelengths, enabling highly sensitive and selective detection of targeted analytes. This review systematically presents photoswitchable fluorescent and colorimetric probes built on various molecular photoswitches, primarily focusing on the types involving photoswitching in their detection and/or signal response processes. It begins with an analysis of various molecular photoswitches, including their photophysical properties, photoisomerization and photochromic mechanisms, and fundamental design concepts for constructing photoswitchable probes. The article then elaborates on the applications of these probes in detecting diverse targets, including cations, anions, small molecules, and biomacromolecules. Finally, it offers perspectives on the current state and future development of photoswitchable probes. This review aims to provide a clear introduction for researchers in the field and guidance for the design and application of new, efficient fluorescent and colorimetric probes.

Preparation and performance study of rhodamine B naphthylamide, a fluorescent probe, for the detection of Fe3

Fe3+ is essential for humans, and its deficiency or excess can be harmful to human health; thus, it is crucial to detect Fe3+. Herein, a novel 1,8-naphthylimide rhodamine-based fluorescent probe (NA-RhBEA) was prepared from rhodamine B, anhydrous ethylenediamine, and 1,8-naphthoic anhydride. This fluorescent probe complexes Fe3+ with N and O on the carboxyl groups of its spironolactam structure and part of the 1,8-naphthalenedicarboxylic anhydride structure, which results in spironolactam ring-opening and fluorescence. NA-RhBEA has high selectivity for Fe3+ in ethanol/buffer solution (4 : 1, v/v), and fluorescence is detected at an excitation wavelength λEX = 500 nm, an absorption peak appears at 585 nm, and a significant color change appears. The effect of the fluorescence intensity of Fe3+ under a series of different concentration conditions was investigated, and it was concluded that the fluorescence intensity increased with increasing Fe3+ concentration in the range of 0-500 μmol, and its detection limit was 0.84 μmol L-1. In addition, we explored the detection ability of NA-RhBEA in solutions with different pH values, mixed metal ions, and different solvents, and the results showed that the fluorescent sensor also has good anti-interference properties and some practical applicability.

Colorimetric Detection of Cu2+ and Ag+ Ions Using Multi-Responsive Schiff Base Chemosensor: A Versatile Approach for Environmental Monitoring

In this study, we have synthesized a novel Schiff base-centered chemosensor, designated as SB, with the chemical name ((E)-1-(((6-methylbenzo[d]thiazol-2-yl) imino)methyl)naphthalen-2-ol). This chemosensor was structurally characterized by FT-IR, 1H NMR, UV-Vis and fluorescence spectroscopy. After structural characterization the chemosensor SB was subsequently employed for the detection of Cu2+ and Ag+, using fluorescence spectroscopy. The chemosensor SB showed excellent ability to recognize the target metal ions, leading to fluorescence enhancement and color change from yellow to yellowish orange for Cu2+ and yellow to radish for Ag+ ions. The detection capabilities of this chemosensor were impressive, showing excellent selectivity and an exceptionally low detection limit of 0.0016 µM for Cu2+ and 0.00389 µM for Ag+. Most notably, our approach enables the quantitative detection both metal ions in different water and soil samples at trace level. This achievement holds great promise for analytical applications and offers significant contributions to the field of chemical sensing and environmental protection.

A Novel Rhodamine Probe Acting as Chemosensor for Selective Recognition of Cu2+ and Hg2+ Ions: An Experimental and First Principle Studies

Copper and Mercury ions have vital role to play in biological world as their excess or deficiency can cause different type of diseases in human being as well as biological species including plants and animals. Therefore, their detection at trace level becomes very important in term of biological. The current studies embody the fabrication, structural characterization and recognition behavior of a novel rhodamine B hydrazone formed when hydrazide of rhodamine B was condensed with 5-Allyl-3-methoxy salicylaldehyde (RBMA). RBMA was found to be responsive towards the very trace level of Cu2+ and Hg2+ among other tested cations so far. The sensing procedure is based on the classical opening of the spiroatom ring of rhodamine. The limit of detection (LOD) and binding constant is 5.35 ppm, 2.06 × 104 M-1 and 5.16 ppm, 1.26 × 104 M-1 for Cu2+ and Hg2+ ions respectively. The probable mechanism correlates the specific binding of RBMA with Cu2+ and Hg2+ ions. The 1:1 stoichiometry of RBMA with Cu2+ and Hg2+ ions have been supported by HRMS, FT-IR data, Job's plot, and binding constant data. Reversibility is well exhibited by RBMA by the involvement of CO32- ions via demetallation process. The real time application is well demonstrated by the use of paper strip test. The DFT study also carried out which agrees well with the experimental findings. The results displayed the novelty of this current work towards the trace level analysis of the Cu2+ and Hg2+ of the cations which are play the crucial role in industry.

Non-Conjugated Bis-(Dithienylethene)-Naphthalenediimide as a Dynamic Anti-Counterfeiting Agent: Driving the Wheel of Photoswitching Enactment

Photochromic fluorescent molecules dramatically extend their fields of applications ranging from optical memories, bioimaging, photoswitches, photonic devices, anti-counterfeiting technology and many more. Here, we have logically designed and synthesized a triazole appended bis-(dithienylethene)-naphthalenediimide based photo-responsive material, 5, which demonstrated fluorescence enhancement property upon photocyclization (ΦF =0.42), with high photocyclization (44 s, ksolution =0.0355 s-1 , ksolid =0.0135 s-1 ) and photocycloreversion (160 s, ksolution =0.0181 s-1 , ksolid =0.0085 s-1 ) rate and decent photoreaction quantum yield (Φo→c =0.93 and Φc→o =0.11). The open isomer almost converted to the closed isomer at photo-stationary state (PSS) with distinct color change from colorless to blue with 92.85 % conversion yield. A reversible noninvasive modulation of fluorescence through efficient photoinduced electron transfer (PET) process was observed both in solution as well as in solid state. The fluorescence modulation through PET process was further corroborated with thermodynamic calculations using the Rehm-Weller equation and quantum chemical studies (DFT). The thermally stable compound 5 exhibits high fatigue resistance property (up to 50 cycles) both in solution and solid state. Furthermore, the compound 5 was successfully applied as erasable ink and in deciphering secret codes (Quick Response/bar code) portending potential promising application in anti-counterfeiting.

A Novel Diarylethene-rhodamine Unit Based Chemosensor for Fluorimetric and Colorimetric Detection of Hg2

A novel fluorimetric and colorimetric chemosensor (1O) was synthesized with diarylethene-rhodamine unit and characterized by ESI-MS, ¹H NMR, and ¹³C NMR. The chemosensor can selectively recognize extremely low concentrations of Hg²⁺ over a variety of metal ions with remarkable colorimetric and fluorescent responses. The colorimetric and fluorescent changes were ascribed the reaction between 1O and Hg²⁺ destructed the rhodamine hydrazide into open-ring form which was proved by mass spectrometry and nuclear magnetic titration analyses. The detection limits of the UV absorption and fluorescence methods for Hg²⁺ were found to be 0.708 μM and 24.6 nM, respectively. Moreover, the chemosensor exhibited excellent photochromism and outstanding fatigue resistance property under alternating UV and visible light irradiation. The application potential of the chemosensor was demonstrated with the qualitative detection of Hg²⁺ in real water samples.

Characterization of a Hg2+-Selective Fluorescent Probe Based on Rhodamine B and Its Imaging in Living Cells

A small organic molecule P was synthesized and characterized as a fluorometric and colorimetric dual-modal probe for Hg2+. The sensing characteristics of the proposed probe for Hg2+ were studied in detail. A fluorescent enhancing property at 583 nm (>30 fold) accompanied with a visible colorimetric change, from colorless to pink, was observed with the addition of Hg2+ to P in an ethanol-water solution (8:2, v/v, 20 mM HEPES, pH 7.0), which would be helpful to fabricate Hg2+-selective probes with "naked-eye" and fluorescent detection. Meanwhile, cellular experimental results demonstrated its low cytotoxicity and good biocompatibility, and the application of P for imaging of Hg2+ in living cells was satisfactory.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-visible absorption

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu²⁺ and Hg²⁺ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu²⁺ and Hg²⁺ in CH₃CN-H₂O (4:1, v/v) with off-on fluorescence and ratiometric ultraviolet-visible (UV-Vis) absorption changes. Additionally, Cu²⁺ is identified by opening a rhodamine spirocycle with a UV-Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg²⁺ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV-Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu²⁺ and Hg²⁺ by off-on fluorescence and ratiometric UV-Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu²⁺ and Hg²⁺ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.

A Highly Selective Fluorescent Probe for Hg2+ Based on a 1,8-Naphthalimide Derivative

Hg2+ has a significant hazardous impact on the environment and ecosystem. There is a great demand for new methods with high selectivity and sensitivity to determine mercury in life systems and environments. In this paper, a novel turn-on Hg2+ fluorescent probe has been reported with a naphthalimide group. The Hg2+ fluorescent probe was designed by the inspiration of the well-known specific Hg2+-triggered thioacetal deprotection reaction. A 1,2-dithioalkyl group was chosen as the specific recognition site of Hg2+. The probe showed weak fluorescence without Hg2+, and the color of the solution was light yellow. In the presence of Hg2+, the probe reacted specifically with the mercury ion to produce an aldehyde and emitted strong fluorescence, and the color of the solution also turned light green, thus realizing the monitoring of the mercury ion. The Hg2+ fluorescent probe showed outstanding sensitivity and selectivity toward Hg2+. Furthermore, the Hg2+ fluorescent probe could work in a wide pH range. The linear relationship between the fluorescence intensity at 510 nm and the concentration of Hg2+ was obtained in a range of Hg2+ concentration from 2.5 × 10-7 to 1.0 × 10-5 M. The detection limit was found to be 4.0 × 10-8 M for Hg2+. Furthermore, with little cell toxicity, the probe was successfully applied to the confocal image of Hg2+ in PC-12 cells.