Dual fluorescence response of calix[4]arene-1,8-naphthalimide derivatives towards Hg(II) /Cr(VI) and their antimicrobial studies of transparent biofilms with hyaluronic acid

In this study, 4-sulfo-1,8-naphthalimide calixarene of derivatives were prepared (3 and 4) then transparent biofilms of the Ag salts of these compounds were formed in the presence of hyaluronic acid (HA), and antimicrobial properties were investigated. In chemosensor studies, the sensing ability behavior of 3 and 4 towards some cations and anions was investigated by fluorescence spectroscopy. It was observed that the prepared chemosensors show selectivity towards Hg(II) and Cr(VI). Ligand-ion interaction occurs according to the photo-induced electron transfer (PET) mechanism. The stoichiometric ratio was calculated by using Stern-Volmer plot method and binding constant Ksv values were found as 5.2 × 107 M-1 and 5.5 × 107 M-1 for 3-Hg(II) and 4-Hg(II) complexes, respectively and 4.0 × 107 M-1 and 4.3 × 107 M-1 for 3-Cr(VI) and 4-Cr(VI) complexes. The detection limits of the complexes of 3-Hg(II) and 4-Hg(II) are 6.35 × 10-12and 6.81 × 10-12, while those of 3-Cr(VI) and 4-Cr(VI) are 1.41 × 10- 11and 8.37 × 10-12, respectively. As a result of the antimicrobial test performed with these compounds, it was observed that the most effective material was HA-3Ag, which showed a significant antibacterial effect against Sarcina lutea (S. lutea) at a minimum inhibitory concentration (MIC) value of 0.097 mg/mL.

Probe-impregnated monolithic polymer as a robust solid-state colorimetric chemosensor for selective sensing of Hg2+ in environmental water and cigarette samples

The current study developed a novel aqua-compatible and naked-eye portable solid-state opto-sensor for selective and sensitive detection of ultra-trace Hg²⁺ ions. The developed chemosensor was fabricated by the direct impregnation of a chromoionophoric probe composed of 2,3-bis((4-isopropylbenzylidene)amino)maleonitrile (PDPM) onto the surface of structurally tailored porous polymer monolithic framework. The template exhibited a highly porous network with greater surface area, which led to the effective anchoring of probe molecules onto the surface of the polymer template, thus serving as an efficient platform to constitute a regenerative solid-state chemosensor. The sensor rendered a superior color shift from dull white to dijon yellow after complexing with Hg²⁺. The surface, structural, and morphological aspects of the sensor were evaluated using FE-SEM, HR-TEM, EDAX, SAED, p-XRD, N₂ adsorption isotherm, and XPS. Rigorous optimization of the effects of different analytical parameters on the sensing performance of the PDPM sensor material was ensured. The monolithic sensor had an optimum sensing performance at pH 8.0, rapid signal response kinetics of 60s and a broad linear response range of 0.5-150.0 μg/L with a 0.22 μg/L detection limit. Furthermore, the sensor was also tolerant of foreign matrix constituents, thereby enabling it to be highly selective in detecting Hg²⁺. Sensor recovery was analyzed to be possible via Hg²⁺ desorption using 0.01 M EDTA without compromising its sensing performance. It had reutilization potential for up to eight regenerative cycles with excellent data reliability (recovery ≥99.4% and RSD ≤1.4%). The practicability of the fabricated sensor was investigated using various water and cigarette samples. Experimental data revealed that the developed chromoionophoric sensor was reusable, eco-friendly, low-cost, and possessed superior sensing capabilities, making it more feasible for on-site analysis of environmental samples. The designed sensor has the potential for further investigations and applications as a sensor kit for facilitating heavy metal detection in remote places.

Bimetallic molecularly imprinted nanozyme: Dual-mode detection platform

Molecularly imprinted polymer nanozyme (MIL-101(Co,Fe)@MIP) with bimetallic active sites and high-efficiency peroxidase-like (POD-like) activity were synthesized for the ratiometric fluorescence and colorimetric dual-mode detection of vanillin with high selectivity and sensitivity. Compared with the monometallic nanozyme, the POD-like activity of bimetallic nanozyme was greatly enhanced by changing the electronic structure and surface structure. Ratiometric fluorescence and colorimetric dual-mode detection of vanillin in aqueous solution was realized by vanillin entering specific imprinted cavities and blocking the molecular channels on the surface of MIL-101(Co,Fe)@MIP and the dual-mode visual detection was also realized. The limits of detection were as low as 104 nM and 198 nM, respectively. The method proposed in this paper was applied to the real samples of ice cream and candy. And the recoveries were between 93.3% and 105.5%, which also reached a satisfactory degree. The further detection of dexamethasone and prednisone, two drugs belonging to glucocorticoid, proved that the nanozyme analysis method based on MIL-101(Co,Fe)@MIP could be developed into a sensing platform.

Novel near-infrared fluorescent probe with a large Stokes shift for sensing hypochlorous acid in mitochondria

Hypochlorous acid (HOCl) plays a crucial role in various physiological and pathological processes. However, it is still a challenge to design a xanthene-based near-infrared (NIR) fluorescent probe with a large Stokes shift for sensing HOCl. In this work, a novel mitochondria-targeted fluorescent probe, MXS, with a large Stokes shift based on a xanthene-hemicyanine dyad structure, has been successfully designed and synthesized for the specific detection of HOCl. Gratifyingly, the peak-to-peak Stokes shift of MXS was found to be 130 nm, which was obviously larger than those of conventional rhodamine dyes and most reported xanthene-based hypochlorous acid probes. As expected, MXS exhibited high selectivity, high sensitivity, and fast response time (30 s) for the detection of HOCl via a specific HOCl-promoted intramolecular charge transfer process. The detection limit of MXS for HOCl is calculated to be as low as 72 nM, enabling its use within the physiological concentration range of HOCl (5-25 μM). Importantly, MXS is able to permeate cell membranes and accumulate in the mitochondria, which is convenient for monitoring the variation of hypochlorous acid concentration in the mitochondria of living cells.

Metal Ion Detection by Carbon Dots-A Review

Development of economical, sensitive, selective and robust sensors for metal ion sensing is always fascinating for a chemist because traditional routs for their detection involve complicated instrumentation and critical sample preparation procedures. A large number of metal ion detectors including carbon dots (CDs) have been reported for sensitive and selective detection of metal ions. This review comprehensively explores the use of CDs as metallic cation sensors. CDs are being fabricated from variety of carbon sources by employing various synthetic channels. CDs are proved to be efficient colorimetric and fluorimetric detectors due to surface oxygen moieties which are responsible to co-ordinate with metal ions. Doping of CDs with hetero atom such as N, S, B etc. may further enhance their activity toward metal detection. Therefore, designing of CDs having selective sensing properties with low detection limits has gained significant interest.HighlightsCDs have gained much attention as chemical sensors due to their dynamic features i.e. less toxicity, stability, solubility in various solvents, absorption in UV/Vis. region, fluorescence and tunable physico-chemical properties.These are coast effective, sensitive and selective colorimetric and fluorimetric metal ion sensors.Detection of metal ions by CDs involves different mechanisms such as complexation, aggregation, electron transfer, inner filter effect etc.LOD data is an evidence of their greater efficiency.

A lysosome-targeting viscosity-sensitive fluorescent probe based on a novel functionalised near-infrared xanthene-indolium dye and its application in living cells

The viscosity of lysosomes plays a significant role in modulating biological processes and reflects the status and function of this kind of organelle, e.g., locations, morphologies, and components.

A MnO2–[Ru(dpp)3]Cl2 system for colorimetric and fluorimetric dual-readout detection of H2O2

Two-dimensional (2D) MnO₂ nanosheets were synthesized by a template-free and one-step route, and the dye [Ru(dpp)₃]Cl₂ was linked onto the MnO₂ nanosheet surface via electrostatic interaction. The formed MnO₂–[Ru(dpp)₃]Cl₂ hybrid was used for a dual optical detection for H₂O₂, an important reactive oxygen species (ROS). Upon addition of H₂O₂, the reaction of MnO₂ with H₂O₂ results in the dissolution of MnO₂ nanosheets and simultaneous generation of O₂. The fading of the solution and simultaneous fluorescence change of [Ru(dpp)₃]Cl₂, sensitive to O₂, enables colorimetric and fluorimetric dual-mode detection of H₂O₂. The dual-output assay in a single probe provides a good sensitivity with a detection limit of 0.18 μM H₂O₂. The dual-signal strategy can efficiently overcome the shortcoming of the single detection mode, and improve the detection accuracy by an additional correction of output signals from each other. Moreover, the successful determination of H₂O₂ in the serum samples demonstrates the potential applicability of the MnO₂–[Ru(dpp)₃]Cl₂ based probe in biosensing and bioanalysis.

The MnO₂ nanosheets with anchored [Ru(dpp)₃]Cl₂ were prepared for colorimetric and fluorimetric dual-mode detection of H₂O₂.

A colorimetric and fluorometric dual-modal sensor for methanol based on a functionalized pentacenequinone derivative

A functionalized pentacenequinone derivative ZR1 shows specific selectivity toward methanol via the mechanism of intramolecular charge transfer (ICT).

A carbon dots/rutin system for colorimetric and fluorimetric dual mode detection of Al3+ in aqueous solution

Colorimetric and fluorimetric dual mode detection of Al³⁺ in aqueous solution was achieved using a carbon dots/rutin (CDs/rutin) coexisting system.

Synthesis, optical, and chemical properties of a π-extended rhodol derivative and its derivatives with selectivity and sensitivity for sensing Hg2+in aqueous media

A π-extended rhodol dye with optical signaling being controlled by two spirorings has been developed. A Hg²⁺-selective chemodosimeter based on this rhodol dye has been synthesized and evaluated.

A Novel Styryldehydropyridocolinium Homodimer: Synthesis and Fluorescence Properties Upon Interaction with DNA

A novel homodimer of the styryldehydropyridocolinium dye (TPTP) has been synthesized and characterized. Free TPTP exhibited low fluorescence quantum yield and large Stokes shift (over 160 nm) in water. However, it showed a significant fluorescence turn-on effect upon intercalation into DNA base pairs. Meanwhile, the fluorescence intensity of the intercalated structures formed by TPTP and DNA decreased quickly upon addition of deoxyribonuclease I, indicating that the dye can be used to monitor deoxyribonuclease I activity and DNA hydrolysis. Electrophoresis analysis revealed that the dye had intercalative binding to DNA and can potentially be used for DNA staining in electrophoresis. Thus, the innate nature of large Stokes shift and excellent fluorescence turn on effect upon interaction with DNA endue the dye with a wide range of applications.

Molecular design and synthesis of a pH independent and cell permeant fluorescent dye and its applications

A novel xanthene fluorescent dye with a combination of the desirable characters for fluorescent chemosensors and biomarkers including low molecular weight, water solubility, cell permeability, good biocompatibility, and strong tolerance to pH has been designed and synthesized.

A highly sensitive hemicyanine-based fluorescent chemodosimeter for mercury ions in aqueous solution and living cells

A novel hemicyanine-based fluorescence turn-on chemodosimeter for Hg²⁺ by mercury triggered hydrolysis of vinyl ether group has been reported.

Preferences of rhodamine coupled (aminoalkyl)-piperazine probes towards Hg(II) ion and their FRET mediated signaling

The metal ion induced absorption and emission signaling pattern of rhodamine coupled bis-(aminopropyl)-piperazine (1-3) and (aminoethyl)-piperazine (4) based probes evaluated in MeCN as well as in an MeCN-H2O binary mixture medium revealed that these probes exhibit optical signaling perturbations to a varying extent in MeCN, however, their complexation induced signaling could be tuned selectively towards Hg(II) in the presence of an aqueous component in the solvent medium where competitive interactions such as metal-probe interactions and hydration of metal ions play the determining factor to induce aqueous promoted Hg(II) selectivity. Attachment of another fluorophore (anthracene and nitrobenzofurazan moieties in 2 and 3 respectively) at the other end of the rhodamine coupled bis-(aminopropyl)-piperazine receptor enabled these probes to facilitate a complexation induced fluorescence resonance energy transfer (FRET) from the excited fluorophore to the ring-opened rhodamine along with contributions through operative PET inhibition and rhodamine delactonization processes. The enhancement in absorption transition of these probes at ~557 nm upon selective Hg(II)-complexation and consequent colourless to pink colour change in the solution imply a chromogenic signaling pattern whereas simultaneous fluorescence amplification and/or FRET initiation lead to fluorogenic signaling to facilitate detection at lower concentration. The Hg(II)-selective photo-physical spectral modulation in the presence of other competitive metal ions, and their reversible dual channel signaling pattern under the action of counter anions or chelating agents such as EDTA or ethylenediamine establish the potential of these probes for highly selective, sensitive and reversible 'OFF-ON-OFF' detection of Hg(II). The complexation induced optical signaling pattern of probes with a propyl-linker in their receptor (1-3) in comparison with that of 4 consisting of an ethyl-spacer indicate that signaling probe design with a substituted 'aminoalkyl-lactonized-rhodamine' subunit preferentially exhibit Hg(II) selective and sensitive dual mode signaling in an organic-aqueous mixture medium irrespective of carbon-length of the flexible alkyl spacer.

Ratiometric, reversible, and parts per billion level detection of multiple toxic transition metal ions using a single probe in micellar media

We present the selective sensing of multiple transition metal ions in water using a synthetic single probe. The probe is made up of pyrene and pyridine as signaling and interacting moiety, respectively. The sensor showed different responses toward metal ions just by varying the medium of detection. In organic solvent (acetonitrile), the probe showed selective detection of Hg2+ ion. In water, the fluorescence quenching was observed with three metal ions, Cu2+, Hg2+, and Ni2+. Further, just by varying the surface charge on the micellar aggregates, the probe could detect and discriminate the above-mentioned three different toxic metal ions appropriately. In neutral micelles (Brij 58), the probe showed a selective interaction with Hg2+ ion as observed in acetonitrile medium. However, in anionic micellar medium (sodium dodecyl sulfate, SDS), the probe showed changes with both Cu2+ and Ni2+ under UV-vis absorption spectroscopy. The discrimination between these two ions was achieved by recording their emission spectra, where it showed selective quenching with Cu2+.

A "turn-on" fluorescent Hg2+ chemosensor based on Ferrier carbocyclization

A "turn-on" fluorescent chemosensor with excellent selectivity and satisfactory sensitivity on Hg(2+) detection in 100% water media has been established employing a carbohydrate based Ferrier carbocyclization reaction. The probe has also presented satisfactory results for the imaging of Hg(2+) ions in cells and organisms.

Highly selective and sensitive fluorescent turn-on chemosensor for Al3+ based on a novel photoinduced electron transfer approach

A photoinduced electron transfer (PET)-based chemosensor possessing dual PET processes by simultaneously introducing both nitrogen and sulfur donors was achieved. The fluorescence signal of the free chemosensor is in a normal-off state due to the sulfur donor being insensitive to environmental pH stimuli. As a result, the device can be used over a wide pH span of 3-11. Upon binding Al(3+), a significant fluorescence enhancement with a turn-on ratio over 110-fold was triggered by the inhibition of PET processes from both the sulfur and the nitrogen donors to the fluorophore.