Fluorescein Based Three-channel Probe for the Selective and Sensitive Detection of CO32- Ions in an Aqueous Environment and Real Water Samples.

We have constructed a novel fluorescein-based fluorescent chemosensor, FL-In, functionalised with an indole moiety and capable of sensing by both the optical "turn-on" and electrochemical detection of carbonate ions (CO32-) in aqueous media. The probe exhibits excellent selectivity and a low detection limit (0.27 µM) regarding carbonate ions by a possible coordination and hydrolysis reaction mechanism. The developed probe successfully detected CO32- ions in different samples of water. Also, in a simple filter paper experiment, we documented its ability to allow the monitoring of CO32- with the naked eye.

Triazatruxene-Rhodamine-Based Ratiometric Fluorescent Chemosensor for the Sensitive, Rapid Detection of Trivalent Metal Ions: Aluminium (III), Iron (III) and Chromium (III).

We investigated the ability of a novel triazatruxene-rhodamine-based (TAT-ROD) chemosensor to detect the trivalent metal ions aluminium (Al3+), iron (Fe3+) and chromium (Cr3+). Operating via the through-bond energy transfer (TBET) pathway, the chemosensor exhibited low detection limits of 23.0, 25.0 and 170.0 nM for Al3+, Fe3+ and Cr3+, respectively, along with high sensitivity and selectivity during a brief period (<15 s). The binding ratio of the chemosensor and trivalent metal ions achieved by Job's method was 3:1, and when we added ethylenediaminetetraacetic acid (EDTA), the sensing process reversed. Altogether, our TAT-ROD chemosensor marks the first triazatruxene-based colorimetric and fluorometric metal ion sensor reported in the literature.

A BODIPY-Based Fluorescent Probe to Visually Detect Phosgene: Toward the Development of a Handheld Phosgene Detector.

A boron-dipyrromethene (BODIPY)-based fluorescent probe with a phosgene-specific reactive motif shows remarkable selectivity toward phosgene, in the presence of which the nonfluorescent dye rapidly transforms into a new structure and induces a fluorescent response clearly observable to the naked eye under ultraviolet light. Given that dynamic, a prototypical handheld phosgene detector with a promising sensing capability that expedites the detection of gaseous phosgene without sophisticated instrumentation was developed. The proposed method using the handheld detector involves a rapid response period suitable for issuing early warnings during emergency situations.

Electrophilic Cyanate As a Recognition Motif for Reactive Sulfur Species: Selective Fluorescence Detection of H2S.

An ESIPT-based fluorescent dye, 3-hydroxyflavone, is chemically masked with an electrophilic cyanate motif in order to construct a fluorescent probe for cellular sulfur species. This novel probe structure, displays an extremely fast, highly sensitive and selective "turn-on" type fluorescent response toward H2S. We have also documented its utility for imaging of H2S in the living cells.

A rare γ-pyranopyrazole skeleton: design, one-pot synthesis and computational study.

Drawing upon a consecutive amide coupling and intramolecular cyclisation pathway, a one-pot, straightforward synthetic route has been developed for a range of pyrazole fused γ-pyrone derivatives. The reaction mechanism proposed for the chemoselective formation of γ-pyranopyrazole is furthermore fully supported by experimental and computational studies.

A Ratiometric Fluorescent Probe for Gold and Mercury Ions.

A fluorescent probe that displays a ratiometric fluorescence response towards gold and mercury ions has been devised. Emitting at a relatively longer wavelength, the conjugated form of the fluorescent dye transforms in the presence of the gold or mercury ions into a new dye, the molecular structure of which lacks the conjugation and consequently emits at a distinctly shorter wavelength.

A novel thienothiophene-based "dual-responsive" probe for rapid, selective and sensitive detection of hypochlorite.

BACKGROUND: Hypochlorite/hypochlorous acid (ClO-/HOCl) is a biologically crucial reactive oxygen species (ROS), produced in living organisms and has a critical role as an antimicrobial agent in the natural defense system. However, when ClO- is produced excessively, it can lead to the oxidative damage of biomolecules, resulting in organ damage and various diseases. Therefore, it is imperative to have a straightforward, quick and reliable method for over watching the minimum amount of ClO- in different environments. RESULTS: Herein, a new probe TTM, containing thienothiophene and malononitrile units, was developed for exceptionally selective and sensitive hypochlorite (ClO-) detection. TTM demonstrated a rapid "turn-on" fluorescence response (<30 s), naked-eye detection (colorimetric), voltammetric read-out with anodic scan, low detection limit (LOD = 0.58 µM and 1.43 µM for optical and electrochemical methods, respectively) and applicability in detecting ClO- in real water samples and living cells. SIGNIFICANCE AND NOVELTY: This study represents one of the rare examples of a small thienothiophene-based molecule for both optical and electrochemical detections of ClO- in an aqueous medium.

A rhodamine based "turn-on" chemodosimeter for monitoring gold ions in synthetic samples and living cells.

A rhodamine-based fluorescent probe, functionalized with an alkyne moiety, shows highly selective recognition towards Au(i) and Au(iii) ions over other metal ions. Probe is successfully employed for the determination of residual gold species in synthetic samples and monitoring the accumulation of gold ions in living cells.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits.

A novel signal-enhanced electrochemical sensing strategy was constructed for quercetin determination with a peculiarly developed poly(chromotrope fb)-modified activated pencil graphite electrode in vegetables and fruits. The oxidation signal of quercetin at 118 mV in an alcoholic solution served as the analytical response. The produced platform, characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, could detect 1.9 nM of quercetin in the range of 0.01-1.2 µM. The extracted quercetin contents of red onion, red cabbage, cranberry, black mulberry, black raisin, and carob were determined by both the developed method and UV-visible spectroscopy. The results were statistically evaluated at the 95% confidence level, and no significant difference between the results was found.

A unique triple-channel fluorescent probe for discriminative detection of cyanide, hydrazine, and hypochlorite.

Herein, the first triple-channel fluorescent probe, TTB, excited at the same wavelength (λex = 360 nm) in the same sensing medium for the detection and discrimination of cyanide, hydrazine, and hypochlorite, is disclosed. While a fluorescent white color appeared (λem = 470 nm) with the addition of cyanide ion into the probe solution, upon addition of hydrazine and hypochlorite, green (λem = 503 nm) and orange (λem = 585 nm) fluorescent colors, respectively, were observed. A naked-eye detection for the three ions was documented. With the appearance of orange color, a mega Stokes shift of 175 nm was observed. The probe exhibited excellent selectivity and lower detection limits of 0.24 µM, 4.1 nM and 0.27 µM, and dynamic ranges of 0.0-2.0 µM, 0.0-0.05 µM and 0.0-2.0 µM for cyanide, hydrazine and hypochlorite, respectively. The sensing mechanism was investigated through computational studies before and after the addition of cyanide, hypochlorite, and hydrazine, applying density functional theory (DFT), along with the calculation of optical properties by time-dependent DFT (TD-DFT) method. The results were found to be in good agreement with the experimental values. Remarkably, the probe, TTB, successfully detected cyanide, hydrazine, and hypochlorite in complex water samples. Moreover, the detection of cyanide was successfully performed in apricot kernels, as well as hypochlorite in fruits and vegetables.

Monitoring of Hypochlorite Level in Fruits, Vegetables, and Dairy Products: A BODIPY-Based Fluorescent Probe for the Rapid and Highly Selective Detection of Hypochlorite.

Hypochlorite/hypochlorous acid (ClO-/HOCl), among the diverse reactive oxygen species, plays a vital role in various biological processes. Besides, ClO- is widely known as a sanitizer for fruits, vegetables, and fresh-cut produce, killing bacteria and pathogens. However, excessive level of ClO- can lead to the oxidation of biomolecules such as DNA, RNA, and proteins, threatening vital organs. Therefore, reliable and effective methods are of utmost importance to monitor trace amounts of ClO-. In this work, a novel BODIPY-based fluorescent probe bearing thiophene and a malononitrile moiety (BOD-CN) was designed and constructed to efficiently detect ClO-, which exhibited distinct features such as excellent selectivity, sensitivity (LOD = 83.3 nM), and rapid response (<30 s). Importantly, the probe successfully detected ClO- in various spiked water, milk, vegetable, and fruit samples. In all, BOD-CN offers a clearly promising approach to describe the quality of ClO--added dairy products, water, fresh vegetables, and fruits.

Tetraphenylethylene-thiosemicarbazone based ultrafast, highly sensitive detection of hypochlorite in aqueous environments and dairy products.

We have designed and synthesised a novel fluorescent probe with a tetraphenylethylene (TPE) scaffold as an active fluorescent unit and thiosemicarbazide (TSC) group as a recognition unit. The probe, TPE-TSC, exhibited superior selectivity towards hypochlorite (ClO-) with a low limit of detection (2.0 nM). It also demonstrated a turn-off response for a brief period (<30 s) via an oxidation reaction. Furthermore, high-resolution mass spectrometry (HRMS) revealed that TPE-TSC reacted with ClO- by forming a carboxylic acid moiety in nearly 100% aqueous environments. More significantly, the probe detected ClO- in disinfectant, spiked milk samples, and spiked water samples. In all, TPE-TSC proposes an optimistic approach precisely for the determining the quality of milk and water contaminated with ClO- and trace amounts of ClO- in disinfectants.

Rapid, ultrasensitive, highly selective detection of toxic Hg(II) ions in seabass, swordfish and water samples.

A novel fluorescent probe bearing triphenylamine, thiophene and thiosemicarbazide (TPA-TSC) was developed, and its distinct features were investigated. TPA-TSC demonstrated excellent selectivity towards Hg2+ ions, with a limit of detection (0.14 nM) among the lowest reported to date. It also exhibited a turn-off response by forming stable complex for a brief period (<30 s). Job plot analysis and high-resolution mass spectrometry (HRMS) revealed that TPA-TSC bound to Hg2+ with a 2:1 stoichiometry in an aqueous environment, remarkably the probe successfully detected Hg2+ ions in seabass, swordfish and different samples of water. In all, TPA-TSC offers a promising method for accurately determining the quality of seafood and water samples polluted with Hg2+.

Rhodium- and palladium-catalyzed 1,5-substitution reactions of 2-en-4-yne acetates and carbonates with organoboronic acids.

Two methods involving the rhodium-catalyzed reaction of 2-en-4-yne acetates and the palladium-catalyzed reaction of 2-en-4-yne carbonates with organoboronic acids were investigated; both afforded exclusively the (E)-configured vinylallenes. The coordinative interaction of the rhodium with the acetate group promoted the δ-elimination of Rh(I)-OAc from the alkenylrhodium intermediate II in both syn and anti modes, with the syn-elimination being the major path. DFT calculations revealed that a conformer of this intermediate (II), which can lead to the (E)-configured vinylallene product via the syn-elimination mode, is energetically the most favorable conformer. The rhodium-catalyzed procedure is not applicable to reactions involving (E)-configured enyne acetates, because the geometry of the alkenylrhodium intermediate that is derived from the corresponding (E)-enyne acetate would not allow such coordinative interaction to occur. The palladium-catalyzed method, which proceeds through formation of the σ-vinylallenylpalladium intermediate, B, is suitable for both the (E)- and (Z)-configured enyne carbonates and appears to have a wider scope for both organoboronic acids and enyne substrates. The palladium-catalyzed reaction of an enantiomerically enriched enyne carbonate proceeded with racemization.

A novel voltammetric method for the sensitive and selective determination of carbonate or bicarbonate ions by an azomethine-H probe.

Our study involved a simple, sensitive voltammetric method of determining either carbonate or bicarbonate ions independently with azomethine-H and a disposable pencil graphite electrode. The reduction of azomethine-H-carbonate complexes at approximately -930 mV formed in acetic acid-acetate buffer solution (pH: 4.25) was evaluated as a response. Among the results, the limits of detection and analytical ranges for carbonate ions were 3.7 µg L-1 and 9.9-700.0 µg L-1 and for bicarbonate ions were 9.0 µg L-1 and 35.0-700.0 µg L-1, and the relative standard deviations for carbonate and bicarbonate ions ranged from 1.33% and 6.93% at different concentrations. After the proposed method was applied to water, sparkling water, seawater and baking powder samples, the results were statistically evaluated and compared with those obtained from the potentiometric auto-titration system. Last, the complex stoichiometry of both carbonate and bicarbonate ions was comprehensively investigated with fluorescence and 1H-NMR spectroscopy.

Colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with a gold nanoparticle-based biosensor.

Since emerging in China in December 2019, COVID-19 has spread globally, wreaked havoc for public health and economies worldwide and, given the high infectivity and unexpectedly rapid spread of the virus responsible-that is, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-urged the World Health Organization to declare it a pandemic. In response, reducing the virus's adverse effects requires developing methods of early diagnosis that are reliable, are inexpensive and offer rapid response. As demonstrated in this article, the colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with gold nanoparticle-based biosensors may be one such method. In the presence of the SARS-CoV-2 spike antigen, gold nanoparticles aggregated rapidly and irreversibly due to antibody-antigen interaction and consequently changed in colour from red to purple, as easily observable with the naked eye or UV-Vis spectrometry by way of spectral redshifting with a detection limit of 48 ng/mL. Moreover, electrochemical detection was achieved by dropping developed probe solution onto the commercially available and disposable screen-printed gold electrode without requiring any electrode preparation and modification. The method identified 1 pg/mL of the SARS-CoV-2 spike antigen and showed a linear response to the SARS-CoV-2 spike antigen ranging from 1 pg/mL to 10 ng/mL. Both methods were highly specific to detecting the SARS-CoV-2 spike antigen but not other antigens, including influenza A (i.e. H1N1), MERS-CoV and Streptococcus pneumoniae, even at high concentrations.

BODIPY-vinyl dibromides as triplet sensitisers for photodynamic therapy and triplet-triplet annihilation upconversion.

We devised a new generation of halogen-based triplet sensitisers comprising geminal dibromides at the vinyl backbone of a BODIPY fluorophore. Incorporating geminal dibromides into the π-conjugation of BODIPY enhanced intersystem crossing due to the heavy atom effect, which in turn improved the extent of excited triplet states.

An anthracene based fluorescent probe for the selective and sensitive detection of Chromium (III) ions in an aqueous medium and its practical application.

An anthracene based fluorescent probe, integrated with thiophene moiety, exhibited selective and sensitive detection of chromium (III) ions over other metal ions. Its synthesis was achieved by simple mixing of two commercially available compounds, 2-aminoanthracene, and 2-thiophenecarboxaldehyde, in onestep without the needed complex purification process. The probe molecule ( ANT-Th ) offered exceptional features such as "turn-on" fluorescence response, low detection limit (0.4 µM), and fast response time (<1 min) via C=N bond hydrolysis. Also, a simple test paper system was developed for the rapid detection of chromium (III) ions with the naked eye.

Fluorescein propiolate: a propiolate-decorated fluorescent probe with remarkable selectivity towards cysteine.

A fluorescent probe decorated with an alkynyl ester unit (e.g. propiolate) displayed a selective turn-on type fluorescent response towards cysteine. Following a sequential addition-cyclisation pathway mediated by the addition of cysteine, the pre-fluorescent dye rapidly transformed into a new structure and induced a fluorescent response clearly observable with the naked eye.

BODIPY-Au(I): A Photosensitizer for Singlet Oxygen Generation and Photodynamic Therapy.

Upon complexation with Au(I), a photoinactive BODIPY derivative was transformed into a highly photoactive triplet sensitizer. Along with high efficiency in singlet oxygen generation (ΦΔ = 0.84), the new BODIPY-Au(I) skeleton showed excellent photocytotoxic activity against cancer cell lines (EC50 = 2.5 nM).