Fluorescent Sensor Research Articles

New imidazole sensors synthesized for copper (II) detection in aqueous solutions

Water security, safety, availability and sustainability of water supply are increasingly problematic and difficult across the planet. Safe and rapid methods have been developed to purify water from cationic pollutants. New imidazole-derived fluorescent sensors, 2-(4,5-diphenyl-1-(p-tolyl)-1H-imidazol-2-yl) phenol (TS) and 2-(1-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazol-2-yl) phenol (AS), have been synthesized and characterized, and their possibility as fluorescence sensors for copper (II) has been examined. In CH3CN/H2O (90 v/v), the TS and AS revealed a noticeable an electronic band at 320.00 nm and fluorescence band at 460.90 nm. The ratio metric alterations in the absorption and fluorescence spectra of TS and AS due to the dative covalent bond between them and the copper (II) were shown by the findings of copper (II) titration. The sensing mechanism was validated by optical investigations and FT-IR spectra. In mixed solvent solutions, the selectivity of TS and AS to copper (II) as fluorescent sensors has been demonstrated, with sensitivity as low as 0.09 and 0.28 µM, significantly less than the limit permitted via the US EPA for drinking water (2.00 µM). The identification limits of TS and AS were assessed to be 0.05 and 0.50 µM, respectively, using the spectrophotometric procedure. Stoichiometry binding between TS and AS with copper (II) was found to be 2:1 (tetrahedral structure) as indicated by Job's method.

Preparation and application of copper nanoclusters as a fluorescent sensor for sensitive detection of tartrazine

As an important way to detect tartrazine, a probe with excellent fluorescence properties is of great significance in fluorescence detection method. Copper nanoclusters (Cu NCs) was prepared by chemical reduction method, in which copper sulfate as metal body, folic acid as capping reagent and ascorbic acid as reducing agent. In the light of inner filter effect and static quenching mechanism, a fluorescence sensor for tartrazine measurement was designed based on Cu NCs with excellent selectivity. The spherical Cu NCs with uniform size emitted blue fluorescence at 443 nm when the excitation wavelength was located at 353 nm. Under the optimum detecting condition, the corresponding linear range and LOD were 0.5–50 μM and 0.071 μM, respectively. Coupled with pleasing recovery experiments in real samples, this as-proposed platform was very promising for tartrazine detection.

Construction of rhodamine-based fluorescent sensor for fast, on-site quantitative detection of hazardous salicylic acid in practical sample analysis

Salicylic acid (SA) is widely used in food storage, preservatives, additives, healthcare, and the pharmaceutical industry. However, various poisoning symptoms are frequently reported upon ingestion of a large amount of SA. Therefore, discovering new tools for sensing SA with fast, simple, and portable performance is imperative. Herein, five rhodamine-based fluorescent sensors were constructed, and investigated their SA detection profiles. Probe 1 was excellent selective with a rapid response, highly sensitive (LOD = 2.5 μM), good interference resistance, and unaided eye recognition. The spray experiment and paper-based test strips indicating that probe 1 enables to the on-site and quantitatively detect SA on actual food surfaces by using a smartphone identifying the RGB values. The sensing performance was validated in soil samples, water, and various agricultural food samples. Overall, the constructed SA sensor can function as a promising, convenient, and affordable tool for point-of-care detection of SA in diversiform environmental samples.

Recyclable magnetic ratiometric fluorescence sensor based on Fe3O4-CDs and CdTe for rapid visualized detection brucine in complicated samples

Recyclable magnetic ratiometric fluorescence sensor based on Fe3O4-CDs and CdTe for rapid visualized detection brucine in complicated samples

A smartphone-assisted ratiometric fluorescence sensor based on dual-emission copper nanoclusters for visual detection lead ion

A smartphone-assisted ratiometric fluorescence sensor based on dual-emission copper nanoclusters for visual detection lead ion

A new Conjugated mesoporous polymer as fluorescence sensor for the detection of nerve agent simulant dimethyl chlorophosphonate via specific nucleophilic substitution reaction

Conjugated micro/mesoporous polymers (CMPs) represent a category of porous organic materials formed via covalent bonds. Here, DAC-TFP CMP was synthesized using 3,6-diaminocarbazole (DAC) and 2-hydroxy-1,3,5-benzenetricarbaldehyde (TFP) as building blocks. DAC-TFP CMP is a porous conjugation polymer with remarkable thermal and chemical stability. DAC-TFP CMP suspension demonstrates selective "on-off" fluorescence response towards nerve agent simulant dimethyl chlorophosphonate (DMCP) in 1,4-dioxane with exceptionally low detection limits. DMCP and DAC-TFP CMP undergo a nucleophilic substitution reaction, leading to the formation of an N-P bond between N atom on carbazole of DAC-TFP CMP and P atom of DMCP. The new polymer DAC-TFP CMP@DMCP has electron donor-acceptor structure and the fluorescence quenching can be ascribed to the intramolecular charge transfer (ICT) from DAC-TFP CMP unit to DMCP group, as supported by XPS results and DFT calculation. Upon the addition of DMCP to the 1,4-dioxane suspension of DAC-TFP CMP, a subtle blue shift is observed in both the fluorescence emission spectra and UV-vis absorption spectra, providing further validation of the ICT mechanism. DAC-TFP CMP shows excellent recoveries in detecting DMCP in both soil and pesticide samples containing mesotrione and atrazine, highlighting its strong potential as a reliable chemosensor for DMCP detection and analysis.

Multifunctional fluorescence sensor based on nitrogen-doped carbon dots and its application for toxoflavin detection

Multifunctional fluorescence sensor based on nitrogen-doped carbon dots and its application for toxoflavin detection

Synthesis, fluorescence and theoretical insights into a novel FRET-based dansyl-rhodamine sensor for the in vitro detection of toxic bioaccumulated Hg(II) ions

This work describes the successful design and synthesis of a new fluorescence resonance energy transfer (FRET)-based sensor, denoted as RD1. This sensor incorporates a robust dual-fluorophore design, which combines a rhodamine and a dansyl derivative, functionalized with a thiosemicarbazide group that acts as Hg(II) specific recognition site. A synthetic pathway was developed that allowed the efficient synthesis of RD1 with a remarkable overall yield of 44% over four steps, through microwave-assisted protocols. The influence of ethyl, benzyl and phenyl substituents of isothiocyanate in the preparation of the thiosemicarbazide moiety was studied, revealing a crucial dependence of the nature of the isothiocyanate in the formation of the recognition site.Owing to its characteristic ratiometric detection, RD1 exhibited remarkable robustness to external parameters such as pH and solvent composition. The sensor demonstrated a hybrid two-stage response to Hg(II), with an initial quenching of fluorescence followed by an enhancement of emission through a FRET mechanism, both stages being corroborated by DFT (density functional theory) calculations. In vitro studies demonstrated that RD1 presents excellent cytocompatibility and capacity to permeate cellular membranes and be effectively internalized by L929 cell line. Importantly, RD1 retained its sensory ability in a complex cellular environment, affirming its efficacy as a fluorescent sensor for the in vitro detection of bioaccumulated mercury species. These results suggest the potential of RD1 for the detection of toxic bioaccumulated mercury species, aiding in environmental and biomedical research.

Rhodamine 6G-conjugated β-cyclodextrin as a novel fluorescence sensor for meat spoilage detection

Meats are abundant in proteins and a variety of lipids that are essential for the human body. Nevertheless, they are susceptible to enzymatic reactions and bacterial microorganisms during various processes, which can result in food deterioration. This study endeavors to create an ammonia-sensitive sensor for the detection of meat decomposition by rhodamine 6G fluorophore and β-cyclodextrin which are joined together via a Schiff-base reaction, in recognition of the significance of appropriate food monitoring. The rhodamine 6G and β-cyclodextrin-based sensor (R6GBCD) was characterized using proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The R6GBCD sensor showed a pH-dependent fluorescent properties and also selective responsivity to ammonia. The sensor demonstrated its capability to detect ammonia and generate yellow fluorescence, enabling it to identify rotting meat. As a result, it shows great promise as a mean of verifying the safety of food.

Design of fluorescent sensors for the detection of human serum albumin structure employing nitrogen-by modulation of molecular containing heterocycles

Serum albumin is the most abundant protein in mammalian plasma. It occupies an extremely important position in organisms as an early indicator of the development of many diseases. The development of fluorescence sensing technology has revolutionized the drawbacks of traditional methods. In this strategy, we designed and synthesized three dual fluorophore organic sensors TPA-IPA-T1, TPA-QL-T2, and TPA-Py-T3 for the detection of serum albumin. The rotation of the C–C bond of sensors is restricted and the molecular structure forms a rigid plane that contributes to the fluorescent emission intensity of the sensor. The fluorescent skeletons were successfully constructed by triphenylamine composed the electron-withdrawing nitrogen-containing compounds benzopyrrole (indole), benzopyridine (quinoline), and pyridine, respectively, with piperazine as a rigid connecting bridge. The addition of human serum albumin (HSA) turned on the fluorescent emission of the sensor near 580–600 nm. The color of the sensor solution changed from colorless to pink and bright orange, respectively. The fluorescent intensity increased by 24, 67, and 31 fold, respectively. The sensors have the advantages of sensitivity and fast response, strong anti-interference ability, low detection limit and good water solubility. Drug experiments in artificial urine demonstrate the characteristics of sensors, which has a very high potential for biological feasibility and medical applications. The sensors facilitaty the binding of the HSA through electrostatic interactions. The sensors were explored to be able to efficiently bind the IB structural domain of HSA, which had a good meaningful of avoiding the interference of commonly drugs in clinical medicine and in artificial urine on the detection of HSA.

Carbon dots with high brightness and stability towards efficient Cr(Ⅵ) and l-arginine sensors

To create fluorescent sensors for Cr (VI) and l-arginine detection, blue-emitting carbon dots (CDs, named as M-CDs) were prepared via a solvothermal synthesis by using m-phenylenediamine. The introduction of sulfuric acid changed the blue-emitting of CDs into green-emitting (named as S-CDs), in which the photoluminescence (PL) peak wavelengths of samples M-CDs and S-CDs were 450 and 540 nm, while their PL efficiencies were 21.7 and 84.2 % respectively. Sulfuric acid resulted in the average fluorescent lifetime of the CDs was prolonged into 8.19 from 4.65 ns. The photo and thermal stable tests demonstrated that theses CDs revealed excellent stability. Meanwhile, CDs flexible films with bright blue- and green-emitting were prepared utilizing the favorable solubility of CDs in polar solvents. Mono-dispersed CDs as luminescent materials demonstrated it promising prospects in luminescent devices field. Furthermore, M-CDs exhibited excellent selectivity towards Cr(Ⅵ) and l-arginine. The detected limit (0.86 μM for Cr(Ⅵ) and 0.43 μM for l-arginine) was determined by assessing the response of M-CDs to various concentrations of Cr(Ⅵ) ion and l-arginine solutions. These bright CDs revealed great potential for accurate detection of Cr(Ⅵ) and l-arginine.

Water-Soluble Fluorescent Sensors for Quantification of Trace Cisplatin in Body Fluids from Clinical Cancer Patients.

Accurate quantification of cisplatin (cDDP) in body fluids (blood, urine, and ascites) is crucial in monitoring therapeutic processes, assessing drug metabolism, and optimizing treatment schedules for cancer patients. Nonetheless, due to the inherent fluorescence and complexity of the body fluid matrix, along with the low cDDP concentrations in these fluids during treatment, using fluorescent sensors for fluid detection remains a subject of ongoing research. Herein, a series of water-soluble cDDP-activatable fluorescent sensors was rationally constructed by introducing thioether groups to the xanthene skeleton based on the chalcogenophilicity of platinum. These sensors exhibit excellent sensitivity and certain anti-interference capabilities for sensing cDDP in living cells, rat tissues, and zebrafish. Especially, with a simplified sample pretreatment procedure, for the first time, Rh3 and Rh4 have enabled quantitative detection of cDDP levels in diversiform body fluids from clinical ovarian and bladder cancer patients. These results are highly consistent with those obtained by ICP-MS detection. This work paves the way for utilizing fluorescent sensors in clinical body fluid analysis, thus potentially revolutionizing the monitoring methods of cDDP in clinic settings.

Covalent Organic Framework as Selective Fluorescence Sensors for Cancer Inducing Volatile Organic Compounds.

Certain volatile organic compounds (VOCs), such as formaldehyde, acetone, and ethanol, are overexpressed in some terminal diseases like cancer, diabetes, Alzheimer's, etc. Therefore, high-precision detection and quantification of VOCs is imperative for early diagnosis of such detrimental diseases. Non-invasive and accurate fluorescence-based detection of such analytes has garnered widespread attention. The inherent luminescent properties of covalent organic frameworks (COFs), resulting from their extensive π-conjugation, have made them suitable for sensing applications. Structural tunability and strong covalent linkers facilitate sensing by COFs. Appropriate choices of linker and skeletal units of the COF can help detect various biologically important analytes selectively. The most common linkers used in this regard is the imine linker, which can undergo excellent hydrogen bonding with different protic VOCs e. g., ethanol, methanol, etc. Besides imine detection, hydrogen bonding also proved useful for detection of aldehydes. Suitable combinations of donors and acceptors enable the COFs to have specific charge transfer interactions with many electron-rich and electron-poor VOCs. In this review, we have highlighted the syntheses of selective COFs incorporating linkers designed for sensing cancer-inducing VOCs. A detailed discussion of the interaction mechanisms between COFs and these VOCs is provided, along with examples from recent literature in this field.

Excitation-Dependent pKa Extends the Sensing Range of Fluorescence Lifetime pH Sensors

Biological activity is strongly dependent on pH, which fluctuates within a variety of neutral, alkaline, and acidic local environments. The heterogeneity of tissue and subcellular pH has driven the development of sensors with different pKa values, and a huge assortment of fluorescent sensors have been created to measure and visualize pH in living cells and tissues. In particular, sensors that report based on fluorescence lifetime are advantageous for quantitation. Here, we apply a theoretical framework to derive how the apparent pKa of lifetime-based pH sensors depends on fluorescence excitation wavelength. We demonstrate that theory predicts the behavior of two different fluorescent protein-based pH sensors in solution as proofs-of-concept. Furthermore, we show that this behavior has great practical value in living cells because it extends the sensing range of a single sensor by simply choosing appropriate detection parameters to match the physiological pH range of interest. More broadly, our results show that the versatility of a single lifetime-based sensor has been significantly underappreciated, and our approach provides a means to use a single sensor across a range of pH environments.

Surface-controlled carbon dots with high brightness and tunable emission towards fluorescent anti-counterfeiting and pH sensors

Compared with luminescent semiconductor nanocrystals, nontoxic and metal-free carbon dots (CDs) are advantages for the significant applications in displaying and various sensors. In this paper, blue- and green-emitting CDs with high brightness and stability were created via solvothermal synthesis using m-phenylenediamine and terephthalic acid. Solvents were adjusted to control the surface of CDs attaining high brightness. The blue-emitting CDs with a photoluminescence (PL) peak wavelength of 480 nm revealed PL quantum yields (PLQYs) of 30.4% while the green-emitting one revealed a PL peak wavelength of 500 nm and a PLQY of 55.1%. The PL properties of these CDs exhibited excellent pH dependence. The effects of solvents, synthetic parameters, and pH values on the structure and PL properties of CDs were tested. These CDs were used for pH sensors and multi-stage anti-counterfeiting ink. The blue-emitting CDs revealed high stability in a broad pH range while green-emitting CDs were sensitive to aqueous solution in the pH region of 10.00–10.78 with a sensitivity of 0.99/pH and pKa value of 10.34 ± 0.51. Because of the high stability, fluorescent inks were prepared using these multi-color CDs via direct dispersion in water, in which the inks showed high stability after 6 months of storage time.

Glutathione-activated near-infrared II fluorescent probe for lung metastatic diagnosis and intraoperative imaging of tumor

Accurate identification of intraoperative tumor lesions and effective treatment are crucial for improving surgical outcomes. Near-infrared (NIR) fluorescence imaging demonstrates advantages over traditional medical approaches in tumor interventions, garnering significant attention. However, clinically available imaging agents are generally limited by their "always on" characteristics, which can lead to non-specific imaging interference and "false-positive" results. In this context, we present a glutathione-activated NIR-II probe, LJ-GSH, designed for metastatic tumor imaging and specific imaging-guided tumor resection. LJ-GSH initially exhibits quenched fluorescence due to the weak electron-donating effect of the thiophenol moiety, which is recovered at 815/910 nm upon activation by the overexpressed levels of glutathione (GSH) in tumor cells and tissues, significantly enhancing the specificity of tumor imaging. This unique characteristic positions LJ-GSH as a reliable fluorescent sensor for monitoring GSH dynamics during physiological events. Notably, the probe's NIR-II emission feature markedly improves imaging contrast and resolution, facilitating real-time identification and imaging of lung metastatic lesions. With the aid of high-specific NIR-II imaging guidance, tumor tissues can be precisely resected, with the residual negative margin diameter reduced to approximately 0.2 mm. We envision that our tailored probe may offer an attractive option for clinical applications.

Tb3+-modified covalent organic frameworks-based fluorescence sensor for anthrax biomarker and anionic contaminants

Covalent organic frameworks (COFs) with full π-conjugation can be obtained by tuning the building blocks and covalent bonds. Meanwhile, lanthanide ions (Ln3+) have attracted attention for their unique luminescent properties. In this study, we coordinated Tb ions with COF (TQBQ-COF), thereby constructing a fluorescent sensor for the detection of 2,6-pyridinedicarboxylic acid (DPA) as an anthrax biomarker. The prepared Tb3+@TQBQ-COF shows an ultra-low detection limit for DPA (3.58 nM), which is much lower than the required level of DPA for Bacillus anthracis to produce anthrax (60 μM). In addition, the prepared sensors showed good detection performance in detecting anionic pollutants when DPA was used as a photosensitizer. Our work provides a simple method for the detection of DPA.

A novel aggregation-induced emission-featured hyperbranched poly(amido amine)s stabilized copper nanoclusters‑cerium (III) sensor for detection of thiol flavor compounds in processed meat

Thiol flavor compounds are a class of flavoring ingredients that contribute significantly to food flavor. However, rapid discrimination of multiple thiol-flavor compounds remain a challenge. In this study, a ratiometric fluorescent sensor (TPE-ssHPA@Cu NCs-Ce3+) with dual-channel fluorescence features was developed using tetraphenylethene-embedded hyperbranched poly(amidoamine) as a template to stabilize the copper nanocluster‑cerium ions. The sensor was explored for the specific discrimination of six typical thiol flavor compounds, each producing diverse fluorescent fingerprints that were further identified using pattern recognition methods. The sensor achieved a rapid response in identifying thiol flavor compounds and multicomponent mixtures, with detection limits of 0.32–3.13 μM. Furthermore, it was successfully applied to differentiate between the different types and cooking times of meat broths.

Fluorescent TICT Probe for Precise Monitoring of Cellular Lipid Droplets.

Lipid droplets (LD) are crucial in pathological processes or conditions associated with abnormal lipid metabolism, such as obesity, diabetes, atherosclerosis, fatty liver diseases, and cancers. Cancer cells frequently contain elevated levels of nonpolar lipid droplets (LDs), serving as energy reserves. The proliferation of LDs, accompanied by an increase in viscosity, is a characteristic feature of cancer cells that prompted us to devise a fluorescent sensor for LD detection at physiological pH. However, developing fluorescent LD-specific probes with high polarity sensitivity and deep tissue/cell imaging capability remains challenging. Therefore, we present a TICT probe with strong solvatochromism, superior response to viscosity, microenvironment sensitivity, and a large Stokes shift. Additionally, it offers numerous advantages, including high sensitivity, specificity, high fluorescence quantum yield, and remarkable spatial resolution, which enables precise monitoring of lipid droplets (LD). Thus, this probe can effectively monitor alterations in viscosity and polarity of lipid droplet expression in live cells, thereby offering the potential for visualizing physiological abnormalities or pathological conditions. The probe offers excellent lipid droplet targeting and also sensitively monitors the oleic-acid-mediated lipid droplet accumulation and immunosuppressant/inflammatory drugs in HeLa cells.

Ampicillin-derived carbon dots as the sensitive probe for the detection of Fe3+ and Cu2+ in living cells and water samples.

Water-soluble N-doped fluorescent (FL) carbon dots (ACDs) were successfully fabricated hydrothermally using ampicillin sodium as sole precursor. The produced ACDs exhibit satisfactory optical behavior, favorable photostability, and acceptable water solubility. With bright blue emission at 450 nm, the ACDs were utilized for multivariate sensing Fe3+ and Cu2+ based on the synergistic effect of the inner filter effect (IFE) and static quenching with detection limits of 0.31 μM and 0.26 μM, respectively. Thepracticality of ACDs has been verified by the successful determination ofFe3+ and Cu2+ in real water and living cells. These findings confirm the feasibility of the proposed ACDs as FL sensors for efficient and selective detection of Fe3+ and Cu2+, which present promising prospects for real-time monitoring these two metal ionsin environmental and biological systems.