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• The review explores the world of functional chromophores synthesized via MCRs. • MCR-synthesized functional chromophores are reshaping imaging research. • Bioimaging probes synthesized by MCRs with tunable properties. This review aims to provide a comprehensive overview of recent advancements and applications of fluorescence imaging probes synthesized via MCRs (multicomponent reactions). These probes, also known as functional chromophores, belong to a currently investigated class of fluorophores that are presently being successfully applied in bioimaging experiments, especially in various living cell lineages. We describe some of the MCRs that have been employed in the synthesis of these probes and explore their applications in biological imaging, with an emphasis on cellular imaging. The review also discusses the challenges and future perspectives in the field, particularly considering the potential impact of MCR-based fluorescence imaging probes on advancing this field of research in the coming years. Considering that this area of research is relatively new and nearly a decade has passed since the first publication, this review also provides a historical perspective on this class of fluorophores, highlighting the pioneering works published between 2011 and 2016. [ABSTRACT FROM AUTHOR]

AIE-active compounds have lately attracted considerable attention owing to their versatile applications, especially in OLED and bioimaging. Herein, a series of coumarin-3-formylhydrazone derivatives (CFH-1, 2, 3 and 4) were developed for investigating their AIE and solid-state luminescence behaviors. All the obtained compounds emit varying degrees of solid-state fluorescence. CFH-1 and 2 show the typical AIE characteristics, while CFH-3 and 4 exhibit stronger solution fluorescence than their aggregation-induced emission. The single crystal X-ray diffraction analysis of CFH-1 and CFH-3 showed that both of them adopt planar conformation and the CH···O hydrogen bonding plays a crucial role in their crystal packing. Meanwhile, there is a notable difference between them. Successive π-π stacking interaction was observed in the crystal packing of CFH-1, while the crystals of CFH-3 contain dimeric π-π stacking interaction. Their distinct crystal packing interactions result in their different fluorescence properties. Moreover, both CFH-1 and CFH-2 displayed excellent bioimaging performances in living cells. [ABSTRACT FROM AUTHOR]

The possibility to produce laser action involving biomaterials, in particular (single) biological cells, has fostered the development of cellular lasers as a novel approach in biophotonics. In this respect, cells that are engineered to carry gain medium (e.g., fluorescent dyes or proteins) are placed inside an optical cavity (i.e., typically a sandwich of highly reflective mirrors), allowing the generation of stimulated emission upon sufficient optical pumping. In another scenario, micron-sized optical resonators supporting whispering-gallery mode (WGM) or semiconductor-based laser probes can be internalized by the cells and support light amplification. This review summarizes the recent advances in the fields of biolasers and cellular lasers, and most importantly, highlights their potential applications in the fields of in vitro and in vivo cell imaging and analysis. They include biosensing (e.g., in vitro detection of sodium chloride (NaCl) concentration), cancer cell imaging, laser-emission-based microscope, cell tracking, cell distinction study, and tissue contraction monitoring in zebrafish. Lastly, several fundamental issues in developing cellular lasers including laser probe fabrication, biocompatibility of the system, and alteration of local refractive index of optical cavities due to protein absorption or probe aggregation are described. Cellular lasers are foreseen as a promising tool to study numerous biological and biophysical phenomena. Biolasers are generation of laser involving biological materials. Biomaterials, including single cells, can be engineered to incorporate laser probes or fluorescent proteins or fluorophores, and the resulting light emission can be coupled to optical resonator, allowing generation of cellular laser emission upon optical pumping. Unlike fluorescence, this stimulated emission is very sensitive and is capable of detecting small alterations in the optical property of the cells and their environment. In this review, recent development and applications of cellular lasers in the fields of in vitro and in vivo cell imaging, cell tracking, biosensing, and cell/tissue analysis are highlighted. Several challenges in developing cellular lasers including probe fabrication and biocompatibility as well as alteration of cellular environment are explained. [Display omitted] [ABSTRACT FROM AUTHOR]

Heavy metal contamination has become a global environmental problem and currently drawn much attention from researchers in worldwide. High exposure to heavy metals can lead to problems like kidney, liver and brain damage, skin and lung cancer, etc. Rapid and sensitive detection of heavy metals is of immense importance in environmental monitoring. Over the past few decades, enormous efforts have been made to design various sensors to identify and monitor these harmful metal ions. In Comparison with other methods, fluorescence‐based chemosensors have received extensive attention because of the advantages of high sensitivity, low cost, real‐time monitoring, simple operation, etc. The pyrene derivatives are significant polycyclic aromatic hydrocarbons (PAHs) with strong fluorescence. They are widely used as fluorescent probes in many applications due to their easy modification, high fluorescence quantum yield, and strong fluorescence emission in live cells, outstanding cell permeability, and very low cytotoxicity. The SDG 6: Clean water and sanitation alarm a strong strategy, and careful identification of the risk connected to environmental pollutants needs urgent attention in this situation. Therefore, we highlight different types of pyrene‐based fluorophores and the fluorescence mechanisms for the sensitive and selective detection methodology of Arsenic, Mercury, Cadmium, Lead, and Chromium heavy metals. [ABSTRACT FROM AUTHOR]

Herein, oxygen-doped g-C3N4 quantum dots (OCNQDs) were fabricated through sintering and ultrasonic-assisted liquid-phase exfoliation methods. The obtained OCNQDs with uniform size show high crystalline quality, and the average diameter is 6.7 ± 0.5 nm. Furthermore, the OCNQDs display excellent fluorescence properties, good water solubility, and excellent photo stability. The OCNQDs as fluorescence probe show high sensitivity and selectivity to Fe3+ ions. Furthermore, the fluorescent OCNQDs are applied for live cell imaging and Fe3+ ions detecting in living cells with low cytotoxicity, good biocompatibility, and high permeability. Overall, the fluorescent OCNQDs fabricated in this work can be promising candidates for a range of chemical sensors and bioimaging applications. [ABSTRACT FROM AUTHOR]

A fluorescent probe Eu(tdl) 2 abp for efficient and specific recognition of hydrogen sulfide (H 2 S) was successfully synthesized and characterized by NMR and MS. Eu(tdl) 2 abp showed "on-off" fluorescence signals for H 2 S and its color changes could be identified with naked eyes. Eu(tdl) 2 abp had short response time (2 min) to H 2 S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H 2 S existed, the azide group was reduced to amine group, resulting in closed-circuit fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H 2 S concentration. By calculation, the high sensitivity (LOD) is 0.64 μM. Eu(tdl) 2 abp was successfully used for the sensitive detection of H 2 S in natural water and living cells. [Display omitted] • A probe Eu(tdl) 2 abp was successfully prepared, synthesized, and applied for H 2 S detection. • Eu(tdl) 2 abp can perform high efficiency and specificity colorimetric and fluorescent double signal recognition for H 2 S. • The Eu(tdl) 2 abp has been successfully used for imaging H 2 S in living cells and natural water. Using 4-([2,2′: 6′, 2′- terpyridin] -4′-yl) -N, N-dimethylaniline (tdl) as auxiliary ligand and 6-azido-2,2′-bipyridine (abp) as recognition ligand, a europium complex fluorescent probe Eu(4-([2,2′: 6′, 2′-terpyridin] -4′ -yl) -N, N-dimethylaniline) 2 –6-azido-2,2′-bipyridine Eu(tdl) 2 abp for efficient and specific recognition of hydrogen sulfide (H 2 S) was successfully synthesized and characterized by NMR and MS. Eu(tdl) 2 abp represented "on-off" fluorescence signals for H 2 S and its color changes could be identified with naked eyes. Eu(tdl) 2 abp had short response time (2 min) to H 2 S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H 2 S existed, the azide group was reduced to amine group, resulting in closed fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H 2 S concentration with the detection limit (LOD) of 0.64 μM. The sensing mechanism of Eu(tdl) 2 abp to detect H 2 S was characterized by 1H NMR and HR-MS. Eu(tdl) 2 abp was used with success for the sensitive detection of H 2 S in natural water and living cells. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A nitrone‐modified 1,8‐naphthalimide was designed as a novel bioorthogonal‐activated turn‐on probe based on strain‐promoted alkyne‐nitrone cycloaddition (SPANC). The bioorthogonal cycloadducts were subsequently transformed into fluorescent rearrangement products by photo‐acceleration, which exhibited significant fluorescence enhancement, large stokes shift, and high fluorescence quantum yield. DFT calculations were performed to elucidate the fluorescence OFF‐ON mechanism. This fluorogenic strategy was successfully applied to labeling of proteins and visualizing mitochondria in live cells in real time. [ABSTRACT FROM AUTHOR]

A series of dithienothiophene S,S-dioxide (DTTDO) dyes was designed, synthesized, and investigated for their suitability in fluorescent cell imaging. Synthetized (D-π-A-π-D)-type DTTDO derivatives have molecule lengths close to the thickness of the phospholipid membrane, and they contain on both ends two positively charged or neutral polar groups to increase their solubility in water and to ensure simultaneous interaction with polar groups of the inner and outer part of the cellular membrane. DTTDO derivatives exhibit absorbance and emission maxima in the 517–538 nm and 622–694 nm range, respectively, and a large Stokes shift up to 174 nm. Fluorescence microscopy experiments revealed that these compounds selectively intercalate into cell membranes. Moreover, a cytotoxicity assay conducted on a model human live cells indicates low toxicity of these compounds at the concentrations required for effective staining. With suitable optical properties, low cytotoxicity, and high selectivity against cellular structures, DTTDO derivatives are proven to be attractive dyes for fluorescence-based bioimaging. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dots have garnered significant attention owing to their versatile and highly tunable optical properties; however, the origins and the underlying mechanism remains a subject of debate especially for dual fluorescent systems. Here, we have prepared carbon dots from glutathione and formamide precursors via a one-pot solvothermal synthesis. Steady state and dynamic techniques indicate that these dual fluorescent dots possess distinct emissive carbon-core and a molecular states, which are responsible for the blue and red optical signatures, respectively. To further glean information into the fluorescence mechanism, electrochemical analysis was used to measure the bandgaps of the two fluorescent states, while femtosecond transient absorption spectroscopy evidenced the two-state model based on the observed heterogeneity and bimodal spectral distribution. Our findings provide novel and fundamental insights on the optical properties of dual fluorescent dots, which can translate to more effective and targeted application development particularly in bioimaging, multiplexed sensing and photocatalysis. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) are unusual cyanine dyes with a unique resonance-stabilized zwitterionic structure. These dyes have attracted significant attention in the fields of organic electronics and organic photonics, due to their facile synthesis, intense and narrow visible and near-infrared absorption/emission, high photostability, low biotoxicity, etc. In this review, we summarize the recent progress of SQ-based fluorescent materials and their biomedical applications. After a brief introduction to SQs, general synthetic routes and design principles of SQ-based fluorescent materials, as well as their aggregation-induced luminescence behaviors, are discussed. Subsequently, their biomedical applications for cell imaging and as fluorescent sensors and therapeutic agents are introduced. Finally, a summary and perspective are given for promoting the development of SQs-based fluorescent materials. [ABSTRACT FROM AUTHOR]

A novel fluorescence probe for the detection of Al3+ was developed based on methionine protected gold nanoclusters (Met-AuNCs). A fluorescent Schiff base (an aldimine) is formed between the aldehyde group of salicylaldehyde (SA) and the amino groups of Met on the AuNCs, and developed for selective detection of Al3+ in aqueous solution. Al3+ can strongly bind with the Schiff base ligands, accompanied by the blue-shift and an obvious fluorescence emission enhancement at 455 nm. The limits of detection (LODs) of the probe are 2 pmol L−1 for Al3+. Moreover, the probe can successfully be used in fluorescence imaging of Al3+ in living cells (SHSY5Y cells), suggesting that the simple fluorescent probe has great potential use in biological imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A "dual-locked" probe for detection of noradrenaline and HClO was synthesized. • The probe shows excellent selectivity for noradrenaline and HClO in cells. • The probe was successfully applied to accurately detect depressed cells. Due to the serious harm of depression to human health and quality of life, an accurate diagnosis of depression is warranted. For the complex etiology of depression, a single biomarker diagnostic method often leads to misdiagnosis. As noradrenaline and HClO are closely related to depression, a "dual-locked" fluorescence probe R-NE-HClO for diagnosing of depression through the simultaneous detection of noradrenaline and HClO was designed and synthesized. Fluorescence of R-NE-HClO can only be restored in the presence of both noradrenaline and HClO. The probe demonstrates excellent selectivity for noradrenaline and HClO and low cytotoxicity in cell imaging experiments. It is to be observed that we successfully applied the probe to accurately detect depressed cells which provides a possible tool for diagnosing depression. [ABSTRACT FROM AUTHOR]

[Display omitted] • Switchable two-color graphene quantum dot was designed and synthesized by via one-step pyrolysis. • Synergy of histidine, serine, pentaethylenehexamine and boron realizes unique optical behavior. • Two-color fluorescence emissions can be sensitively switched by varying excitation wavelength. • The optical probe was successfully applied in pH detection and bioimaging with high sensitivity. • The study provides approach for design and synthesis of various functional graphene quantum dots. Graphene quantum dots have been widely applied in biosensing, fluorescence imaging, biomedicine, energy storage and conversion and catalysis, but design and synthesis of polychromatic graphene quantum dot with high luminous efficiency still faces great challenges. The study reports synthesis of histidine, serine and pentaethylenehexamine-functionalized and boron-doped graphene quantum dot (HSPB-GQD) via one-step pyrolysis. The resulting HSPB-GQD consists of graphene sheets of 2–5 nm with carboxyl, hydroxyl, amino, imino and imidazole. Synergy of histidine, serine, pentaethylenehexamine and boron atoms improves the luminescence behavior. This realizes unique switchable two-color luminescence. UV excitation of 370 nm produces one strong blue fluorescence with the maximum emission wavelength of 455 nm and quantum yield of 72.34%. Vis. excitation of 480 nm produces one strong yellow fluorescence with the maximum emission wavelength of 560 nm and quantum yield of 72.59%. The multiple proton dissociation system constructed by nitrogen-containing and oxygen-containing groups makes yellow fluorescence sensitive to environmental pH value. The intensity linearly increases with increasing pH in the range of 4.5–10.0. Organic molecules and inorganic ions do not interfere pH detection. HSPB-GQD as a promising fluorescence probe with negligible effect on cell viability was successfully applied to pH detection in biological and environmental water samples and cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple ratiometric fluorescence method for detection of alkaline phosphatase. • The ratiometric fluorescence method was constructed based on in situ reactions. • It was applied to detection of serum alkaline phosphatase and inhibitor screening. • Cellular imaging of alkaline phosphatase was performed in MCF-7 cells. Alkaline phosphatase (ALP) is an important biomarker, it is of great significance to develop a sensitive and efficient analytical method for ALP. In this study, an in situ reaction based ratiometric fluorescence assay for ALP was proposed. l -ascorbic acid-2-phosphate (AA2P) was used as a substrate for ALP, and Cu2+/ o -phenylenediamine (OPD) were involved in this system. Cu2+ can oxidize OPD to 2,3-diaminophenazine (OPDox) with an emission centered at 566 nm. The presence of ALP can catalyze the hydrolysis of AA2P to ascorbic acid (AA), which will inhibit the production of OPDox and reduce the corresponding fluorescence intensity, and AA will react with OPD to generate 3-(dihydroxyethyl)furan[3,4- b ]quinoxalin-1-one (DFQ) with an emission peak at 447 nm. The fluorescence ratio of F447/F566 has a linear relationship with ALP activity. The proposed method is highly sensitive, finely selective, cost efficiency and easy to operate, it exhibits good linearity in the range of 0.5–22 and 22–40 mU·mL−1, with a detection limit as low as 0.06 mU·mL−1. The excellent applicability of this strategy in human serum samples and MCF-7 cells imaging suggests that this method has promising prospects for biomedical research. [ABSTRACT FROM AUTHOR]

[Display omitted] • An indene-chalcone-based fluorescence probe with lysosome-targeting has been developed. • The crystal structure of the probe was reported. • The probe could monitor carboxylesterase (CEs) with a short response time (20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (155 nm). • The probe has been successfully applied to the imaging of endogenous CEs in the lysosomes of living cells and zebrafish. An indene-chalcone-based fluorescence probe 1 was synthesized and characterized. Under physiological conditions (containing 5% DMSO), probe 1 showed satisfactory stability with a low background signal and recognized carboxylesterases (CEs) based on the catalytic hydrolysis of ester groups, releasing a significant green fluorescence. Probe 1 presents several features including a short response time (within 20 min), low detection limit (1.3 × 10−4 U/mL) and large stokes shift (over 155 nm). Notably, commercial lysosomal dye co-staining experiments illustrated the lysosomal localization function of 1 , with the probe also being used for cell and zebrafish imaging of endogenous CEs. [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

Diethylenetriamine-β-cyclodextrin (3N-β-CD)-modified carbon quantum dots were synthesized for the first time via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin as the nitrogen source. The synthesized carbon quantum dots were used as fluorescent probes for the selective detection of Hg2+ and Fe3+ in an aqueous solution and live cell imaging application on Hela cancer cell line. [Display omitted] • 3 N -CQDs were synthesized readily using citric acid as the carbon source by hydrothermal method. • The 3 N -CQDs showed a favorable fluorescence performance towards Hg2+ and Fe3+ detection. • Cytotoxicity assay indicated that the 3 N -CQDs had extremely low cytotoxicity. • The 3 N -CQDs showed good biocompatibility and bioimaging property in the cell imaging. Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N -CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N -CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg2+ and Fe3+ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg2+ and Fe3+ in live cells. Therefore, 3 N -CQDs were ideal fluorescent probes for the detection of Hg2+ and Fe3+ in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-pot large-scale synthesis of C-dots from peptic digest of animal-tissue. • Emission of strong blue fluorescence at 350 nm comparable to synthetic organic dyes. • Prospective fluorescent probe for specific metal ions detection. • Excellent chelating agent for metal-ion toxicity for fast complexation & exocytosis. • Potential application in bioimaging due to quick uptake with minimal cytotoxicity. In recent years, there has been an increased interest in the use of fluorescent carbon dots (C-dots) as an alternative to toxic synthetic organic dyes in live cell imaging, medical diagnostics and other diverse biomedical applications. In the present work, highly fluorescent C-dots have been prepared from commercially available peptic digest of animal tissue, without using any additional chemical reagent for surface functionalization. The synthesized C-dots are monodispersed nanomaterials with hydroxyl, carboxyl and amino surface functionalities and remain stable in high ionic strength media and over a wide range of pH. They exhibit a strong blue fluorescence upon excitation at 350 nm with a high quantum yield of 61%. The potential use of these C-dots as fluorescent nanoprobe for specific metal ions (Cu2+ and Hg2+) detection through chelation, radical scavenging and cellular imaging has been investigated. These highly fluorescent labels show rapid cellular internalization without hampering cellular integrity. Cell proliferation assay demonstrates that these C-dots have minimal cell toxicity even at a high concentration of 3 mg/mL. They show significant quenching on incubation with cells pretreated with Cu2+ and Hg2+ ions. They also show rapid exocytosis from cells showcasing their high potential for chelation therapy. Thus, this study offers a scalable synthesis approach for highly fluorescent and bio-compatible C-dots from a cost-effective precursor, which can be used for specific metal ions detection and their removal from cells through chelation via exocytosis. They can also be used as an alternate to synthetic organic dyes for fluorescence-based cell-imaging. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are semiconductor materials, with a size range between 1–10 nm, showcasing unique size-dependent physical and chemical properties. Such properties have potentiated their use in areas like medical imaging and biosensing. Herein, we present an open-air approach for synthesis of QDs, reducing the need for controllable atmospheric conditions. Furthermore, we present a predictive mathematical model for maximum emission wavelength (λmax) control. Through a straightforward microwave-based aqueous synthesis of TGA-CdTe QDs, we investigated the influence of time, temperature, and Te:Cd and TGA:Cd molar ratios on λmax, using a chemometric experimental design approach. CdTe-QDs were characterized by UV-Vis and fluorescence spectroscopies. Additionally, Fourier-Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, Transmission Electron Microscopy, and Energy Dispersive X-ray were conducted. Stable QDs with fluorescence ranging from green to red (527.6 nm to 629.2 nm) were obtained. A statistical analysis of the results revealed that time and temperature were the most significant factors influencing λmax. After fine-tuning the variables, a mathematical model with 97.7% of prediction accurately forecasted experimental conditions for synthesizing TGA-CdTe QDs at predefined λmax. Stability tests demonstrated that the QDs retained their optical characteristics for over a month at 4 °C, facilitating diverse applications. [ABSTRACT FROM AUTHOR]

The few commercially available chemosensors and published probes for in vitro Zn2+ detection in two-photon microscopy are compromised by their flawed spectroscopic properties, causing issues in selectivity or challenging multistep syntheses. Herein, we present the development of an effective small molecular GFP chromophore-based fluorescent chemosensor with a 2,2′-bipyridine chelator moiety (GFZnP BIPY) for Zn2+ detection that has straightforward synthesis and uncompromised properties. Detailed experimental characterizations of the free and the zinc-bound compounds within the physiologically relevant pH range are presented. Excellent photophysical characteristics are reported, including a 53-fold fluorescence enhancement with excitation and emission maxima at 422 nm and 492 nm, respectively. A high two-photon cross section of 3.0 GM at 840 nm as well as excellent metal ion selectivity are reported. In vitro experiments on HEK 293 cell culture were carried out using two-photon microscopy to demonstrate the applicability of the novel sensor for zinc bioimaging. [ABSTRACT FROM AUTHOR]

A naked eye and fluorescence turn-on 1,8-naphtahlimide based chemosensor,1, possessing Schiff base linkage was utilized for the rapid detection of highly toxic triphosgene. The proposed sensor selectively detected triphosgene over various other competitive analytes including phosgene with the detection limit of 6.15 and 1.15 µM measured using UV-vis and fluorescence spectrophotometric techniques, respectively. Colorimetric changes observed in solution phase were processed by image analysis using smartphone leading to on-site and inexpensive determination of triphosgene. Further, solid phase sensing of triphosgene was carried out by 1 loaded PEG membranes and silica gel. [ABSTRACT FROM AUTHOR]

The intramolecular charge transfer behavior of push–pull dyes is the origin of their sensitivity to environment. Such compounds are of interest as probes for bioimaging and as biosensors to monitor cellular dynamics and molecular interactions. Those that are solvatochromic are of particular interest in studies of lipid dynamics and heterogeneity. The development of new solvatochromic probes has been driven largely by the need to tune desirable properties such as solubility, emission wavelength, or the targeting of a particular cellular structure. DFT calculations are often used to characterize these dyes. However, if a correlation between computed (dipole moment) and experimentally measured solvatochromic behavior can be established, they can also be used as a design tool that is accessible to students. Here, we examine this correlation and include case studies of the effects of probe modifications and conformation on dipole moments within families of solvatochromic probes. Indeed, the ground state dipole moment, an easily computed parameter, is correlated with experimental solvatochromic behavior and can be used in the design of new environment-sensitive probes before committing resources to synthesis. [ABSTRACT FROM AUTHOR]

Recent investigations have suggested that abnormally elevated levels of HOCl may be tightly related to the severity of neuroinflammation. Although some successes have been achieved, fluorescent probes with far-red fluorescence emission and capable of detecting HOCl with high specificity in pure aqueous solution are still urgently needed. Herein, a responsive far-red fluorescent probe, DCI-H, has been constructed to monitor HOCl activity in vivo and in vitro. DCI-H could rapidly respond to HOCl within 120 s and had a low detection limit for HOCl of 1.5 nM. Importantly, physiologically common interfering species, except for HOCl, did not cause a change in the fluorescence intensity of DCI-HOCl at 655 nm. The results of confocal imaging demonstrated the ability of DCI-H to visualize endogenous HOCl produced by MPO-catalyzed H[sub 2]O[sub 2]/Cl- and LPS stimulation. With the assistance of DCI-H, upregulation of HOCl levels was observed in the mice model of LPS-induced neuroinflammation. Thus, we believed that DCI-H provided a valuable tool for HOCl detection and diagnosis of inflammation-related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifunctional CDs were prepared hydrothermally from eco-friendly Coccinia Grandis. • EC-Dots exhibited uniform globular shape with an average size of 4 nm (QY of 17 %). • EC-Dots emit bright fluorescence that is dependent on the excitation wavelength. • The current research provided a new platform in the field of bioimaging. • Also, the EC-Dots are a versatile component in various types of fluorescent ink. This study adopted an eco-friendly approach for the one-step hydrothermal conversion of sustainable Coccinia grandis into well-dispersed, uniform-sized carbon dots. The resulting eco-friendly carbon dots (EC-Dots) were harnessed for bioimaging and fluorescent ink applications. EC-Dots exhibited an average size of 4 nm. Further, cytotoxicity assessments on live nematodes revealed cell viability > 95 %. In-vivo studies showed excellent uptake and their ability to emit light in multiple colors, including blue, green, and red, achieved by adjusting the excitation wavelength. Additionally, the EC-Dots exhibited robust fluorescence in aqueous solutions and exceptional resistance to photobleaching, rendering them highly effective for generating fluorescent ink for drawing and writing. Thus, this research showcases an environmentally sustainable, cost-effective, and straightforward hydrothermal method for creating biocompatible EC-Dots with diverse hydrophilic properties. These synthesized EC-Dots stand as a promising platform for applications in fluorescent ink and in vivo bioimaging, offering a high level of safety with minimal cytotoxicity. [ABSTRACT FROM AUTHOR]

Chemiluminescent probes based on 1,2‐dioxetane scaffold are one of the most sensitive imaging modalities for detecting disease‐related biomarkers and can obtain more accurate biological information in cells and in vivo. Due to the elimination of external light excitation, the background autofluorescence problem in fluorescence technology can be effectively avoided, providing ultrahigh sensitivity and signal‐to‐noise ratio for various applications. In this review, we highlight a comprehensive but concise overview of activatable 1,2‐dioxetane‐based chemiluminescent probes by reporting significant advances in accurate detection and bioimaging. The design principles and applications for reactive species, enzymes, and other disease‐related biomarkers are systematically discussed and summarized. The challenges and potential prospects of chemiluminescent probes are also discussed to further promote the development of new chemiluminescence methods for biological analysis and diagnosis. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) have emerged as one of the most promising nanomaterials in the carbon nanostructures family in recent years due to their low toxicity, simple synthetic methods, unique fluorescence emission, good photostability, excellent water solubility, high specific surface areas and outstanding electronic properties. They have thus been employed in a wide range of applications, including fluorescent sensing, electrochemical sensing, bioimaging, drug delivery, antimicrobial studies, antioxidants, and photocatalysis. CQDs drawn great interest in sensing applications due to their unique photochemical, electrochemical and electrochemiluminescence properties. They exhibit excitation wavelength-dependent or -independent photoluminescence (PL) behaviour, high quantum yield, and promising binding ability with analytes, which make them an ideal candidate for use in PL based sensing platforms. Excessive use of agrochemicals in farm fields can pollute the environment and have potentially adverse health effects on aquatic and human life. Since there are very few monitoring techniques are available for sensing such harmful substances, there is an urgent need to develop a sensor for the facile, rapid and on-site detection and quantification of agrochemical residues in the environment. Several CQD-based fluorophores for detecting agrochemical residues employing static or dynamic quenching processes have recently been published. The key quenching mechanisms involved in the sensing process include FRET, PET and IFE. The first part of this review intends to provide a comprehensive overview of various techniques to characterize CQDs such as UV–vis., FT-IR, PL, XRD, NMR, TEM, TGA, XPS and Raman analysis. In addition application of CQDs as fluorescent sensors for agrochemical residue in different media are summarized in this reiew. The LOD values and rapid action of the sensor demonstrates significant advantages of these methods over conventional analytical procedures. [ABSTRACT FROM AUTHOR]

The bioreductive enzymes typically upregulated in hypoxic tumor cells can be targeted for developing diagnostic and drug delivery applications. In this study, a new fluorescent probe 4−(6−nitro−1,3−dioxo−1H−benzo[de]isoquinolin−2(3H)−yl)benzaldehyde (NIB) based on a nitronaphthalimide skeleton that could respond to nitroreductase (NTR) overexpressed in hypoxic tumors is designed and its application in imaging tumor hypoxia is demonstrated. The docking studies revealed favourable interactions of NIB with the binding pocket of NTR-Escherichia coli. NIB, which is synthesized through a simple and single step imidation of 4−nitro−1,8−naphthalic anhydride displayed excellent reducible capacity under hypoxic conditions as evidenced from cyclic voltammetry investigations. The fluorescence measurements confirmed the formation of identical products (NIB-red) during chemical as well as NTR−aided enzymatic reduction in the presence of NADH. The potential fluorescence imaging of hypoxia based on NTR-mediated reduction of NIB is confirmed using in-vitro cell culture experiments using human breast cancer (MCF−7) cells, which displayed a significant change in the fluorescence colour and intensity at low NIB concentration within a short incubation period in hypoxic conditions. [ABSTRACT FROM AUTHOR]

A new fluorescent indolizine-based scaffold was developed using a straightforward synthetic scheme starting from a pyrrole ring. In this fluorescent system, an N,N-dimethylamino group in the aryl ring at the C-3 position of indolizine acted as an electron donor and played a crucial role in inducing a red shift in the emission wavelength based on the ICT process. Moreover, various electron-withdrawing groups, such as acetyl and aldehyde, were introduced at the C-7 position of indolizine, to tune and promote the red shift of the emission wavelength, resulting in a color range from blue to orange (462–580 nm). Furthermore, the ICT effect in indolizine fluorophores allowed the design and development of new fluorescent pH sensors of great potential in the field of fluorescence bioimaging and sensors. [ABSTRACT FROM AUTHOR]