Fluorescent Chemosensor Research Articles

Dipodal unsymmetrical diuryl conjugated naphthalene: A fluorescent chemosensor for silver ions and its practical applications

This study presents the synthesis and characterization of ICNOD, a highly selective chemosensor for detecting Ag+ ions in environmental and biological samples. ICNOD was synthesized by reacting n-phenyl-o-phenylenediamine with 1-isocyanate naphthalene in absolute ethanol, yielding a novel chemosensor. Fluorescence studies revealed ICNOD’s exceptional selectivity for Ag+ ions over other common metal ions, making it a promising detection tool. Competitive complexation experiments showed a strong affinity of ICNOD for Ag+ ions, with a 1:2 binding stoichiometry, highlighting its potential for sensitive detection. The detection mechanism involves a combination of Photoinduced Electron Transfer (PET OFF) and Intramolecular Charge Transfer (ICT ON), enabling selective Ag+ ion detection. The binding constant (Ka) of ICNOD for Ag+ ions was determined to be 3 × 10−2 M−1 using the Benesi-Hildebrand technique, with limits of detection (LOD) and quantification (LOQ) of 2.87 nM and 8.70 nM, respectively. Molecular modeling using DFT provided valuable insights into ICNOD’s structural features and its interaction with Ag+ ions, supporting the experimental findings. Spectroscopic techniques, including FT-IR, 1H NMR titration, and HR-mass spectroscopy, confirmed the binding interactions between ICNOD and Ag+ ions. Fukui function analysis identified potential binding sites within ICNOD for Ag+ ions, further elucidating the detection mechanism. The practical applicability of ICNOD was successfully demonstrated through real sample analysis, paper strip tests, and bioimaging, showcasing its potential for real-world applications.

Urea/thiourea based dipodal nanoreceptors: Aqueous medium fluorescent chemosensor for Zn(II) and Hg(II) ions by photoinduced electron transfer

Zinc (II) plays a pivotal role in sustaining life processes, whereas Mercury (II) stands out as a significant environmental contaminant. It is imperative to accurately identify these elements to gauge potential imbalances, whether in deficiency or excess, within biological and ecological systems. In this manuscript, four dipodal ligands JM-1 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(4-nitrophenyl)urea), JM-2 i.e. 1,1′-(2,2′-disulfanediylbis (ethane-2,1-diyl))bis(3-(4-nitrophenyl)thiourea), JM-3 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(naphthalen-1-yl)urea) and JM-4 i.e. 1,1′-(2,2′-disulfanediylbis(ethane-2,1-diyl))bis(3-(naphthalen-1-yl)thiourea) are synthesized and characterized by various spectroscopic methods. In order to minimize the organic solvent, organic nanoparticles (ONPs) (0.01 mM) of these ligands (2 mM) have been fabricated by reprecipitation method. ONPs of JM-1 has shown chemosensing towards Zn(II) with limit of detection upto nanomolar level i.e. 55.7 nM and ONPs of JM-4 had shown chemosensing towards Hg(II) with limit of detection as 1.35 µM while ONPs of JM-3 and JM-2 did not show any kind of chemosensing behavior towards any cation or anion. Both of ONPs of JM-1and ONPs of JM-4 showed recognition behavior via photoinduced electron transfer (PET)-off phenomenon. ONPs of JM-1 showed 18 fold enhancement in its fluorescence emission intensity when bound to Zn(II) with excellent linearity which was quite stable with respect to time.

Green Synthesis of Carbon Quantum Dots Using Barks of Ficus religiosa and their Application as a Selective Fluorescence Chemosensor

Green Synthesis of Carbon Quantum Dots Using Barks of Ficus religiosa and their Application as a Selective Fluorescence Chemosensor

Cellulose-based fluorescent chemosensor with controllable sensitivity for Fe3+ detection

Polymer-based sensors, particularly those derived from renewable polymers, are gaining attention for their superior properties compared to organic small molecules. However, their complex preparation and poor, uncontrollable sensitivity have hindered further development. Herein, cellulose-based polymer photoluminescence (PL) chemosensors were fabricated using a straightforward and adjustable strategy. Specifically, water-soluble cellulose acetoacetate (CAA) was used as the substance for the in-situ synthesis of 1,4-dihydropyridine (DHPs) fluorescent rings on cellulose chains via a catalyst-free, room-temperature Hantzsch reaction. Benefiting from the synergetic through-space conjugation of DHPs rings and semi-rigid cellulose chains with heteroatoms, the sensors exhibit bright and stable PL properties. Based on this performance, the cellulose-based sensor excels in the specific recognition of Fe3+ in aqueous systems, showing exceptional selectivity, stability, and anti-interference performance due to the synergy between the inner filter effect (IFE) and intramolecular charge transfer (ICT). Theoretical calculations confirm the role of the extended π-conjugated structure at the DHPs-4 position in modulating the sensor sensitivity, achieving a low limit of detection (LOD) of 0.48 μM. Furthermore, the versatility of the Hantzsch reaction shows the potential of this strategy for developing a new generation of biomass-based polymer portable sensors for real-time and on-site detection.

Pseudohalide Anion Passivation for Aqueous‐Stable Pure Red Perovskite Nanocrystals

AbstractRecently emerging perovskite nanocrystals (PNCs) have drawn considerable attention due to the superior optoelectronic performances. However, the terrible stability of red emissive PNCs (r‐PNCs) limits their broader application in aqueous media. Despite various encapsulation methods are proposed, the preparation of aqueous r‐PNCs with facile operation and excellent durability is still challenging. Herein, aqueous green emissive PNCs (g‐PNCs) by employing water as an external stimulus to treat oleyamine‐capped CsPbBr3 PNCs are synthesized initially, and then aqueous‐stable pure red emissive PNCs by anion‐exchange reaction and subsequently thiocyanate (SCN‐) passivation treatment (SCN‐r‐PNCs) are prepared. The obtained aqueous‐stable SCN‐r‐PNCs display high brightness, outstanding stability, and extended photoluminescence lifetime. Moreover, by combining aqueous r‐PNCs and portable smartphones, a fluorescence chemosensor for the detection of aqueous SCN− ions is constructed, which exhibits simple operation, high sensitivity, high selectivity, low detection limit, and visualized sensing. This work not only provides a new and facile strategy to prepare aqueous‐stable red emissive PNCs, but also further extends the application of red emissive PNCs in aqueous‐based fields.

5-Oxo-7,7-Dimethyl-5,6,7,8-Tetrahydro-4-H-Chromene Bearing N, N-Dimethylaniline as Turn-Off Fluorescent Chemosensor for Picric Acid in Real Water Sample.

We have synthesized a one-pot, three-component pyran-based fluorescence chemosensor using onion extract as a green catalyst. The confirmed structure of the 1:2 binding of receptor SPR-2-picric acid adduct revealed that the pyran-based receptor accommodated two guest picric acid molecules through non-covalent interactions. UV-Vis and fluorescence spectroscopy show high selectivity and sensitivity towards picric acid. The 1D/2D NMR and Job's plot analysis show the complexation and stoichiometric binding of the receptor SPR-2 with picric acid are 1:2. The 1H NMR spectral studies confirm that the formation of receptor SPR-2-picric acid adduct via weak hydrogen bonding. The cooperativity of the receptor SPR-2-picric acid adduct shows negative cooperativity due to the weak hydrogen bonding of receptor SPR-2 and picric acid. Further, the density functional theory (DFT) confirmed the molecular level interaction of the SPR-2 and receptor SPR-2-Picric acid adduct. The receptor was effectively used to assess picric acid concentrations in real water samples.

A 1,8-Naphthalimide-based Tripodal Fluorescent Chemosensor to Selectively Detect Copper Ions.

A 1,8-naphthalimide-based tripodal fluorescent ligand (L3) was synthesized through the copper (I) catalyzed Huisgen azide-alkyne cycloaddition reaction of 2-(2-azidoethyl)-6-morpholino-1H-benzo[de]isoquinoline-1,3(2H)-dione with triproparagylamine. Naphthalimide acts as the fluorophore while the triazole and amine nitrogens chelate the metal ion. L3 showed a selective fluorescence turn-off for Cu(II) over other metal ions in aqueous acetonitrile solution. A Job's plot, Benesi-Hildbrand plot and high-resolution mass spectrometry data confirm a 1:1 binding stoichiometry with a binding constant of 7.8 х105 M- 1 while addition of disodium EDTA demonstrates its reversibility. The structure and stability of the complex was supported by theoretical calculations. The limit of detection for Cu(II) was calculated to be 0.3 µM which is considerably lower than WHO recommended Cu(II) limit in drinking water.

Easy and fast detection of S2− by a new benzothiazole-based fluorescent probe in environmental, biological and food systems

The detection of S2− is required because of its harmful effects on human health. This led us to strategically design a new benzothiazole-based fluorescent chemosensor BTP (2-(benzo[d]thiazol-2-yl)-4,6-dichlorophenol). This sensor undergoes a fluorescence color change from orange to green in the presence of S2− via the deprotonation of phenol in near-perfect water. The detection limit for S2− reached 0.78 μM and BTP could selectively probe S2− over other competing analytes. The process whereby BTP responds to S2− was suggested to be improved intramolecular charge transfer (ICT), as was demonstrated by extensive DFT calculations. Particularly, BTP was successfully applied to detect S2− in zebrafish, real water, and beverage samples. Further, test strips coated with BTP were used to monitor the S2− released in raw meat. BTP is the first benzothiazole-based chemosensor developed to detect the S2− released from various types of food samples. The proposed method offers a novel tool for measuring S2− in biological and environmental systems, as well as the food quality under on-site conditions.

A ratiometric, turn-on fluorosensor for specific detection of Zn2+ ions

A potentially active fluorescent chemosensor (E)-2-(((2-(1H-benzo[d]imidazol-2-yl)phenyl)imino)methyl)-5-(diethylamino)phenol (BMDP) is developed by the condensation of 2-(2-aminophenyl)-1H-benzimidazole and 4-(diethylamino)salicylaldehyde. It shows an exceptional ratiometric fluorescence behavior when exposed to Zn2+ ions and the photoluminescence color is changed from blue to cyan under the exposure of a 365 nm UV light which is also strongly evident from the color chromaticity diagram. The exceptional ratiometric fluorescence behavior in the presence of Zn2+ ions is found to be due to the chelation-enhanced fluorescence (CHEF). The 1:1 stoichiometry of BMDP and Zn2+ ions in Zn2+ ions chelated BMDP complex is confirmed through Job’s plot analysis. Remarkably, Cd2+ does not interfere with the selective ratiometric fluorescence behavior induced by Zn2+ ions. The lowest detection limit and quantification limit are estimated to be 28 nM and 92 nM respectively. The cyan fluorescence of the Zn2+ ions chelated BMDP complex is interestingly reversed to the original BMDP in the presence of ethylenediamine tetraacetic acid (EDTA). At the molecular level, this can be thought of as a complimentary “INHIBIT” logic gate. Furthermore, it is possible to utilize the probe for on-site identification in test strips with improved Zn2+ ions selectivity. We have also used a smartphone-based method to demonstrate the usefulness of BMDP for the immediate quantification and detection of Zn2+ ions. In light of this, probe BMDP is a trustworthy fluorescence probe for on-site monitoring that can accurately identify Zn2+ ions even when some other metals and anions compete.

New porous organic framework Py-PDA CHOF as fluorescent chemosensor for detecting 2,4,6-trinitrophenol in environmental samples

Covalent bonds and hydrogen bonds linked porous organic frameworks (CHOFs) as a new type of porous organic framework connected by both covalent bonds and hydrogen bonds has been reported recently. Py-PDA CHOF was synthesized using 4,4′,4′’,4′’’-(pyrene-1,3,6,8-tetrayl)tetraaniline (Py) and 2,6-pyridinedicarboxaldehyde (PDA) as building blocks. It has porous crystalline framework and exceptional thermal stability. The suspension of Py-PDA CHOF in ethanol exhibits a highly selective and sensitive “on-off” fluorescence response towards 2,4,6-trinitrophenol (TNP), with exceptionally low detection limit. The powder X-ray diffraction (PXRD) confirmed the collapse of the Py-PDA CHOF after interaction with TNP and acid, and this result further indicated the presence of hydrogen bonds within the framework. The absorption competition quenching (ACQ) and photoinduced electron transfer (PET) mechanism are responsible for fluorescence quenching of Py-PDA CHOF by TNP. As a fluorescent chemosensor capable of detecting explosives, Py-PDA CHOF holds potential application for the identification and detection of TNP in water and soil samples.

Photophysical Investigation of One Pot Synthesized Novel Indenofluorene Derivative (BDP) as a Fluorescent Chemosensor for the Detection of Fe3+ Ion.

An Indane-1-one derivative 11-(1-benzyl-1H-indol-3-yl)-10,12-dihydrodiindeno[1,2-b:2',1'-e]-pyridine (BDP) has been synthesized by the reaction of Indan-1-one with 1-benzyl-1H-indole-3-carbaldehyde. FT-IR, 1H-NMR, 13N-NMR and Mass spectroscopic techniques has been used to confirmed the structure of BDP. The observed photophysical changes in BDP across various solvents were associated. The impact of various interactions on photophysical parameters, including Stokes shift, dipole moment, oscillator strength, and fluorescence quantum yields, has been assessed in relation to solvent polarity. Moreover, BDP demonstrates potential as a selective fluorescent chemosensor for detecting Fe3+ ion within a range of cations in an aqueous DMSO environment. A thorough investigation into the recognition mechanism of BDP towards Fe3+ ion has been conducted using Benesi-Hildebrand and Stern-Volmer, measurements. BDP forms a 2:1 complex with the Fe3+ ion, exhibiting fluorescent quenching behaviour.

A Julolidine Aldehyde Dansyl Hydrazine Schiff Base as Fluorescence Chemosensor for Zn2+ ions Recognition and its Application.

The Schiff base fluorescent probe (Dz-Jul), containing julolidine aldehyde and dansyl hydrazine, was derived using a simple condensation. This chemosensor showed high selectivity towards Zn2+ and quick response (170s) in DMSO/H2O solutions (8/2, v/v, pH 7.2 buffer). A fluorometric titration determined that Dz-Jul-Zn2+ has a binding ratio of 1:1, and the association constant (Ka) is 1.03 × 105M-1. The Dz-Jul detection limit of Zn2+ ions was 15nM, much lower than the WHO standard (76.0nM). DFT, ESI mass, and FTIR spectral demonstrated a plausible complexation mode between Dz-Jul and Zn2+ ions. In actual water samples, Zn2+ has been detected with good detection performance using Dz-Jul. Additionally, Dz-Jul-coated test strips allowed for rapid and qualitative monitoring of Zn2+ ions in a visible manner.

Detecting Pb2+ in aqueous environment and live cells by amphiphilic pillar[5]arene-assembled supramolecular sensor based on host-guest charge transfer mechanism

Water-soluble fluorescent chemosensors for lead ion are highly desirable in environmental detection and bioimagery. Based on a water-soluble pillar[5]arene WP5 and imidazolium terminal functionalized 2,2ʹ-bibenzimidazole derivative BIHB, we report a host-guest charge transfer assembly BIHB-2WP5 for sensitive and selective detection of Pb2+ in pure aqueous media. As a result of its high electron-rich cavity, WP5 can bind electron-deficiency guest BIHB with various host/guest stoichiometry to easily tune the microtopography of assembly from nanoparticle to nanocube. In view of the good biocompatibility and sensitivity, the supramolecular assembly BIHB-2WP5 was used as a fluorescent probe for the detection of Pb2+ in living cells and a smartphone Pb2+ detection device was constructed for the in situ test.

Development of a Cone Homooxacalix[3]arene-Based Fluorescent Chemosensor for the Selective Detection of Biogenic Ammonium Ions in Protic Solvents.

We report here on the development of a fluorescent cone homooxacalix[3]arene-based receptor with a pyrene unit on the wide rim of the macrocycle (Ox3F) for the selective detection of primary ammonium ions, including those of biological importance. Ox3F was synthesized efficiently via an innovative strategy that enables the regio- and iteroselective wide rim functionalization of the readily available p-tBu-substituted homooxacalix[3]arene precursor. Nuclear magnetic resonance studies and in silico methods highlighted the endo-complexation of primary ammonium ions, including the protonated form of biogenic dopamine, tryptamine, serotonin, mexamine, and 3-iodothyronamine. The binding mode is similar for all guests with the ion deeply inserted into the polyaromatic cavity, enabling the NH3+ head to establish three hydrogen bonds with the ethereal oxygens of the macrocycle. Fluorescence quenching of the pyrene unit was observed following the π-π interaction between the pyrene moiety and the aromatic groups of serotonin, mexamine, and 3-iodothyronamine. No quenching was observed upon complexation of the smaller aromatic neurotransmitter dopamine as well as aliphatic amines and polyamines. This study presents a novel approach for biologically relevant ammonium ion chemosensing with ongoing efforts focused on translating these systems for aqueous environment applications.

Mechanistic Innovations in Fluorescent Chemosensors for Detecting Toxic Ions: PET, ICT, ESIPT, FRET and AIE Approaches.

Fluorescent chemosensors have become vital tools for detecting toxic ions due to their exceptional sensitivity, selectivity, and rapid response times. These sensors function through various mechanisms, each providing unique advantages for specific applications. This review offers a comprehensive overview of the mechanistic innovations in fluorescent chemosensors, emphasizing five key approaches: Photoinduced Electron Transfer (PET), Fluorescence Resonance Energy Transfer (FRET), Intramolecular Charge Transfer (ICT), Aggregation-Induced Emission (AIE), and Excited-State Intramolecular Proton Transfer (ESIPT). We highlight the substantial progress made in developing these chemosensors, discussing their design principles, sensing mechanisms, and practical applications, with a particular focus on their use in detecting toxic ions relevant to environmental and biological contexts.

A Review on Small Molecule Based Fluorescence Chemosensors for Bioimaging Applications.

This review provides a thorough examination of small molecule-based fluorescence chemosensors tailored for bioimaging applications, showcasing their unique ability to visualize biological processes with exceptional sensitivity and selectivity. It explores recent advancements, methodologies, and applications in this domain, focusing on various designs rooted in anthracene, benzothiazole, naphthalene, quinoline, and Schiff base. Structural modifications and molecular engineering strategies are emphasized for enhancing sensor performance, including heightened sensitivity, selectivity, and biocompatibility. Additionally, the review offers valuable insights into the ongoing development and utilization of these chemosensors, addressing current challenges and charting future directions in this rapidly evolving field.

Green Fluorescence Property of Chromone-based Hydrazone Towards Zn2+ Ion

Excessive concentration of Zn in the environment may lead to bad toxicological responses that can affect human health and create numerous challenges in the environment. Therefore, it is very important to develop a sensitive method such as selective chemosensors based on fluorescence property which does not require laborious work in order to detect Zn metal ion. A formylchromone-thiosemicarbazide with two chloro derivatives namely DFCTSC was synthesized from reflux reaction of 6,8-dichloroformylchromone (DCF) and thiosemicarbazide (TSC) in ethanol. The characterisation of ligand structure was determined by using spectroscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-VIS) and nuclear magnetic resonance spectroscopy (NMR). Meanwhile, the fluorescence property of DFCTSC in the presence of Zn ion was recorded using fluorescence spectrophotometer. The result showed DFCTSC has a good fluorescence behaviour towards Zn ion by giving turn-on green fluorescence at peak 500 nm and emit light when it observed under UV light. The behaviour displayed the ability of ligand to be used as a potential fluorescent chemosensor for detecting Zn2+.

Dual-Site Chemosensor for Visualizing •OH-GSH Redox and Tracking Ferroptosis-Inducing Pathways In Vivo.

Oxidative stress, characterized by an imbalance between oxidative and antioxidant processes, results in excessive accumulation of intracellular reactive oxygen species. Among these responses, the regulation of intracellular hydroxyl radicals (•OH) and glutathione (GSH) is vital for physiological processes. Real-time in situ monitoring these two opposing bioactive species and their redox interactions is essential for understanding physiological balance and imbalance. In this study, we developed a dual-site fluorescence chemosensor OG-3, which can independently image both exogenous and endogenous •OH and GSH in separate channels both within cells and in vivo, eliminating issues of spatiotemporal inhomogeneous distribution and cross-interference. With its imaging capabilities of monitoring •OH-GSH redox, OG-3 elucidated two different pathways for ferroptosis induction: (i) inhibition of system xc- to block cystine uptake (extrinsic pathway) and (ii) GPX4 inactivation, leading to the loss of antioxidant defense (intrinsic pathway). Moreover, we assessed the antiferroptotic function and effects of ferroptosis inhibitors by monitoring •OH and GSH fluctuations during ferroptosis. This method provides a reliable platform for identifying potential ferroptosis inhibitors, contributing to our understanding of relevant metabolic and physiological mechanisms. It shows potential for elucidating the regulation of ferroptosis mechanisms and investigating further strategies for therapeutic applications.

Fluorescent and colorimetric dual-mode chemosensor for easy detection of Cu2+: Practical and smartphone-based application to test strip and water sample

A fluorescent and colorimetric dual-mode chemosensor HNHQ, based on the julolidine and naphthol moieties, was synthesized. Compound HNHQ exhibited unique photophysical properties of an intense fluorescence with a high quantum yield (Φ = 0.363) and a light yellow color through the ICT mechanism. HNHQ could detect Cu2+ through both a fluorescence turn-off and a colorimetry variation of light yellow to yellowish brown. HNHQ reacted with Cu2+ with a binding ratio of 1:1. The detection limit for Cu2+ was analyzed to be 1.60 μM for fluorescence and 1.32 μM for UV–vis, considerably below the safe value of 31.5 μM established by the World Health Organization (WHO). HNHQ analyzed Cu2+ in the pH range of 6–8 and reversibly identified Cu2+ by using ethylenediaminetetraacetic acid (EDTA). Moreover, HNHQ could effectively detect Cu2+ in mineral and tap water samples, in addition to test strips through fluorescent and colorimetric changes. As a portable probe, HNHQ was successfully applied to a smartphone-based RGB analysis for the quantitative examination of Cu2+. The detection mechanism of HNHQ for Cu2+ was illustrated by 1H NMR titration, ESI-MS analysis, and density functional theory (DFT) calculations.

A Review of Nanotechnology-Enabled Fluorescent Chemosensors for Environmental Toxic Ion Detection

A Review of Nanotechnology-Enabled Fluorescent Chemosensors for Environmental Toxic Ion Detection