Sensitive Fluorescent Sensor Research Articles

A Sensitive and Quick Fluorescent Sensor for the "Turn-On" Detection and Imaging of Glutathione Based on Sulfur Quantum Dots and MnO2 Nanosheets.

Glutathione (GSH) is one of the most abundant bioethanol antioxidants in living cells. Here, a fluorescent probe based on MnO2 nanosheets and sulfur quantum dots (SQDs) was fabricated. Because of the synergistic effect of IFE and FRET, the fluorescence from SQDs was quenched by MnO2 nanosheets. In the presence of GSH, the fluorescence of SQDs could be recovered because of the reduction of MnO2 nanosheets by GSH. The method can detect GSH in the concentration range of 5 ~ 1000 μM with the detection limit as low as 1.26 μM. This quick, easy, and cost-effective sensor could be used for the quantification of GSH in serum samples and the imaging of GSH in Escherichia coli O157:H7.

A highly sensitive fluorescent sensor for reversible visual detection of fluoride ion and trace water in food products

A simple diphenylimidazole-based fluorescent sensor (DIP) had been designed for reversible fluorescence sensing of F− and trace water. The sensor showed superior selectivity for F− compared to other anions with fluorescence “turn on” mode. After adding F− to CH3CN solution of DIP, the emission color of DIP changed markedly from weak blue to strong cyan, which could be facilely discerned by the naked eye. The various technical analysis, including spectroscopies, 1H NMR titration and DFT calculation, indicated that the deprotonation of imidazole –NH and –OH occurred in the presence of F−. The detection limit of DIP toward F− could reach as low as 72.3 nM. Moreover, F−-induced deprotonation of DIP-F− system exhibited high sensitivity for water with the detection limit of 0.0015 vol%. The reversible switching characteristic of DIP prompted it suitable for the construction of molecular logic gate. In addition, DIP and DIP-F− were successfully applied to the determination of F− content in toothpaste and water content in table salt, sugar and tea, respectively. Moreover, DIP and DIP-F−-coated filter paper strips could be used as fluorescent display materials for inkless writing with repeatability.

A Novel Rhodamine B Derivative as a "Turn-on" Fluorescent Sensor for Cu2+ with High Selectivity and Sensitivity.

The number of "turn-on" fluorescent probes for Cu2+ is relatively limited, and interference from other metal cations presents a significant challenge for these sensors. In this study, we synthesized and characterized a rhodamine B-based sensor, designated as RBHP, using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and rhodamine B hydrazide. Selectivity, sensitivity, solvent effects, water content, and pH of RBHP in relation to Cu²⁺ were conducted. RBHP exhibited an exceptionally low fluorescence background signal in acetonitrile and demonstrated a "turn-on" fluorescent response to Cu²⁺. The PMBP-based acylhydrazone moiety and acetonitrile as the detection solvent are crucial for the selective detection. RBHP shows potential as a highly selective and sensitive fluorescent sensor for Cu2+.

Luminescent Cd-MOF and its mixed matrix membrane as a chemical sensor for selective and reversible detection of folic acid and Fe3+, and visible fingerprint identifying

A new luminescent metal-organic framework (MOF), {Cd2(L)2(HCO2)(OH)(H2O)}n (1) (HL = 4-(4-(pyridin-4-yl)benzamido) benzoic acid) was synthesized under solvothermal conditions, which was then incorporated into poly(methyl methacrylate) (PMMA) to produce a flexible Cd-MOF-based MMM, 1@PMMA. 1@PMMA could serve as a selective and sensitive fluorescent sensor with remarkable recyclability for detecting folic acid (FA) and Fe3+. More fascinatingly, 1@PMMA displayed a visual and convenient detection for FA and Fe3+ by naked eyes. Furthermore, 1@PMMA was successfully applied for the determination of FA and Fe3+ in the bovine calf serum samples, which demonstrates that the luminescent MOF-based MMMs could serve as promising applicants for detecting biomolecules and metal ions in biological samples. In addition, 1 could be applied for the visible identification of fingerprints.

Synthesis of P-Rich Carbon Quantum Dots for Sensitive Fluorescent Detection of 2-Methylimidazole.

Using o-phenylenediamine as carbon source and phytic acid as phosphorus source, two P-rich carbon quantum dots RCDs and BCDs were synthesized successfully by changing the reaction temperature and time of hydrothermal method. It was found that RCDs with red emission could realize sensitive detection of 2-methylimidazole, and 2-methylimidazole had no obvious quenching effect on BCDs with blue emission, which made RCDs a sensitive, quick and selective fluorescence sensor for 2-methylimidazole detection. Under the optimal experimental conditions, the fluorescence intensity of RCDs decreased with the increasing of 2-methylimidazole concentration. The detection of 2-methylimidazole concentration by the carbon quantum dots sensor showed a good linear relationship in the range of 5 ~ 110 µM, and the low detection limit was 0.61 µM (S/N = 3). The sensor is able to detect 2-methylimidazole in lake water, enabling the application of real samples. The results show that this work provides a simple fluorescence method to detect 2-methylimidazole in water.

Efficient Mercury Ion Detection in Water: CdTe/CdS/ZnS Quantum Dots as a Simple, Sensitive, and Rapid Fluorescence Sensor.

Mercury (Hg), a notorious heavy metal with detrimental impacts on human health and the environment, necessitates the development of precise measurement methods. This study introduces an expeditious and straightforward photochemical approach to synthesize thioglycolic acid (TGA)-stabilized CdTe/CdS/ZnS core/multi-shell quantum dots (QDs). The synthesized CdTe/CdS/ZnS QDs were comprehensively characterized using fluorescence spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FESEM), and X-Ray diffraction (XRD). XRD and EDS results confirmed the successful formation of CdTe/CdS/ZnS structure. Also, FESEM and TEM results showed that CdTe/CdS/ZnS QDs were spherical. Results showed that synthesized Exhibiting vibrant green fluorescence and notable quenching in the presence of Hg2+ ions, these QDs emerge as promising candidates for fabricating a fluorescent sensor. The proposed sensor demonstrates notable sensitivity to Hg2+, featuring a detection limit of 16.32 nM and a linear range from 20 nM to 70 nM. The sensor's selectivity was confirmed by analyzing various anions and cations. Moreover, when tested with tap water, river water, and agricultural samples, the sensor exhibited reliable performance, validated by Inductively Coupled Plasma (ICP) analysis. Additionally, CdTe/CdS/ZnS QDs immobilized on micro pads proved effective for on-site water sample analysis, presenting a versatile solution for environmental monitoring.

Development of sensitive biomass xylan-based carbon dots fluorescence sensor for quantification detection Cu2+ in real water and soil

Copper ions (Cu2+) pose significant risks to both human health and the environment as they tend to accumulate in soil and water. To address this issue, an innovative method using biomass-derived fluorescent carbon dots (D-CDs) synthesized via a hydrothermal process, with xylan serving as the carbon source was developed. D-CDs solution exhibited remarkable sensitivity and selectivity as a fluorescence sensor for Cu2+, boasting a low detection threshold of 0.64 μM. In order to facilitate real-time monitoring of Cu2+, solid-state fluorescent nanofiber membrane (NFD-CDs) through electrospinning was engineered. Additionally, D-CDs demonstrated successful Cu2+ detection in various real water samples, including those sourced from Xuanwu Lake, the Yangtze River, tap water, and bottled water, with accurate recovery rates observed. As a result, this research introduces a dual-mode analytical system for onsite detection of Cu2+ in real scenarios. By harnessing biomass-derived fluorescent CDs materials and solid-state fluorescence sensors, this approach offers a promising solution for addressing the challenges associated with Cu2+ contamination.

Chemically modified graphitic carbon nitride nanosheets for the selective turn-off fluorescence detection of Al(III) ions in crabs (Brachyura).

The selective and sensitive detection of Al(III) is critically important for human health since the level of Al(III) is an indicator of many diseases in humans. Herein, we developed a simple and sensitive fluorescent sensor for the detection of Al(III) in an aqueous solution based on the fluorescence of hydroxyl-functionalized graphitic carbon nitride nanosheets (HO/g-CN). OH/g-CN nanosheets were synthesized via the thermal pyrolysis of 1,3,5-triazine-2,4,6-triamine (as raw material) at 550 °C for 2 hours, followed by thermal alkali treatment at 730 °C for 2 min. The fluorescence of HO/g-CN at 377 nm (at 290 nm excitation) can be quenched by Al(III) effectively and selectively, and the linear relationship between the concentration of Al(III) and fluorescence intensity is in the range of 1.85-14.82 μM with a detection limit of 0.272 μM. The fluorescence turn-off effect of the Al(III) ion on the prepared HO/g-CN nanosheets could be attributed to the presence of oxygen- and nitrogen-containing functional groups on the surface of HO/g-CN that have chelating interactions with Al(III), leading to quenching. The surface functional groups of OH/g-CN were confirmed using different characterization techniques (FTIR, EDX, and XPS). Moreover, the prepared HO/g-CN exhibited remarkable long-term fluorescence stability in water (>30 days) and minimal toxicity. Importantly, a prepared novel fluorescent sensor (HO/g-CN) was successfully applied for the detection and determination of Al(III) in commercially available crab (Brachyura) samples.

Highly Sensitive and Selective Fluorescence and Smartphone-Based Sensor for Detection of Rutin Using Boron Nitrogen Co-doped Graphene Quantum Dots.

This research explores the fluorescence properties and photostability of boron nitrogen co-doped graphene quantum dots (BN-GQDs), evaluating their effectiveness as sensors for rutin (RU). BN-GQDs are biocompatible and exhibit notable absorbance and fluorescence characteristics, making them suitable for sensing applications. The study utilized various analytical techniques to investigate the chemical composition, structure, morphology, optical attributes, elemental composition, and particle size of BN-GQDs. Techniques included X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The average particle size of the BN-GQDs was determined to be approximately 3.5 ± 0.3nm. A clear correlation between the emission intensity ratio and RU concentration was identified across the range of 0.42 to 4.1μM, featuring an impressively low detection limit (LOD) of 1.23nM. The application of BN-GQDs as fluorescent probes has facilitated the development of a highly sensitive and selective RU detection method based on Förster resonance energy transfer (FRET) principles. This technique leverages emission at 465nm. Density Functional Theory (DFT) analyses confirm that FRET is the primary mechanism behind fluorescence quenching, as indicated by the energy levels of the lowest unoccupied molecular orbitals (LUMOs) of BN-GQDs and RU. The method's effectiveness has been validated by measuring RU concentrations in human serum samples, showing a recovery range between 97.8% and 103.31%. Additionally, a smartphone-based detection method utilizing BN-GQDs has been successfully implemented, achieving a detection limit (LOD) of 49nM.

A highly selective and sensitive oligomers-based fluorescent sensor for Cu2+ detection in aqueous solution incorporating pillar[5]arene and imidazo[4,5-f][1,10]phenanthroline moieties

A conjugated oligomers (Co-P[5]ImPhen) containing pillar[5]arene (P[5]) unit as fluorophore and 1H imidazo[4,5-f][1,10]phenanthroline (ImPhen) unit as recognition group was designed and synthesized by Suzuki coupling. The Co-P[5]ImPhen has good fluorescent performance in DMSO aqueous solutions. The Co-P[5]ImPhen has an excellent selectivity and sensitivity for Cu2+ detection in DMSO/H2O (1:3, v:v) solution while showing fluorescence quenching response to Cu2+ (1 − I/I0= 94.2%) and excellent anti-interference ability against paraquat analogs and metal ions. Additionally, the Stern-Volmer quenching constant (Ksv) was calculated to be 2.544 × 106 M-1 by fluorescence titration, indicating that the oligomer has strong binding capacity to Cu2+. The detection limit for Cu2+ was remarkably low (1.17 × 10-10 M). The binding mechanism of Co-P[5]ImPhen with Cu2+ was verified utilizing 1H NMR spectra and quantum chemical calculations. The study indicated that the Co-P[5]ImPhen interacts with Cu2+ primarily through two nitrogen atoms on phenanthroline. Furthermore, the oligomers Co-P[5]ImPhen showed potential application in the detection of Cu2+ in practical samples.

A porous thiosemicarbazide functionalized covalent organic framework served as sensitive fluorescent sensor for Hg2+

The detection of heavy metal pollution in food and environment is of great significance for environmental pollution control and human health. 1,3,5-Tris(p-formylphenyl)benzene (TFPB) and thiosemicarbazide (TS) were used as building blocks to construct a thiosemicarbazide functionalized covalent organic framework (COF) through Schiff base condensation reaction. Hg2+ ions can significantly enhance the fluorescence of the prepared COF-TFPB-TS, and thus COF-TFPB-TS can be utilized for highly selective and sensitive detection of Hg2+ ions. Moreover, COF-TFPB-TS showed high performance for detecting Hg2+ in fresh fruit juice, mineral water and tap water, which demonstrated its ability to be applied in real sample testing.

A Highly Sensitive and Selective Fluorescent Sensor for Folic Acid Detection Based on D-penicillamine Stabilized Ag/Cu Alloy Nanoclusters.

In this work, a highly sensitive and selective method for detecting folic acid (FA) was developed using D-penicillamine (DPA) stabilized Ag/Cu alloy nanoclusters (DPA@Ag/Cu NCs). The yellow emission of DPA@Ag/Cu NCs was found to be quenched upon the addition of FA to the system. The fluorescence intensity quenching value demonstrated a linear relationship with FA concentrations ranging from 0.01 to 1200 μM, with a limit of detection (LOD) of 5.3 nM. Furthermore, the detection mechanism was investigated through various characterization analyses, including high resolution transmission electron microscopy, fluorescence spectra, ultraviolet-visible absorption spectra, and fluorescence lifetime. The results indicated that the fluorescence quenching induced by FA was a result of electron transfer from FA to the ligands of DPA@Ag/Cu NCs. The selectivity of the FA sensor was also evaluated, showing that common amino acids and inorganic ions had minimal impact on the detection of FA. Moreover, the standard addition method was successfully applied to detect FA in human serum, chewable tablets and FA tablets with promising results. The use of DPA@Ag/Cu NCs demonstrates significant potential for detecting FA in complex biological samples.

Smartphone-based ratiometric fluorescence sensor for sensitive visual detection of H2O2 and glucose based on B-CDs-Ag NPRs-OPD ternary system

A straightforward and highly sensitive ratiometric fluorescence sensor comprising blue emissive carbon dots, silver nanoprisms, and o-phenylenediamine (B-CDs-Ag NPRs-OPD) was developed for the detection of H2O2 and glucose. Ag NPRs were etched into Ag+ ions upon exposure to H2O2, which caused non-fluorescent OPD to be oxidized and produce 2,3-diaminophenazine (DAP), resulting in intense yellow fluorescence emission at 555 nm. DAP can quench the B-CDs based on inner filter effect (IFE), leading to a decrease in their fluorescence intensity at 435 nm. Because glucose oxidase may catalyze the oxidation of glucose to produce H2O2, this approach can also be used to detect glucose. The unique triangular structure leads to the easy etching of the edge and tip of Ag NPRs by H2O2 into Ag+ ions, allowing for the high sensitivity of detection of H2O2 and glucose with limit of detection (LOD) of 0.12 μM and 0.6 μM, respectively. Furthermore, with the increase of the concentrations of H2O2 and glucose, a visible color shift from blue to yellow-green occurs, which can be detected using a smartphone's color recognition application that captures the RGB channel values of the image. Real-time and on-spot detection of H2O2 and glucose were achieved based on smartphone sensing platform, presenting vast potential for applications in various fields.

A water-soluble fluorescent sensor accelerated with ortho-aldehyde for the detection of hydrogen sulfide in spoiled food and cells

In view of the important physiological and pathological roles of hydrogen sulfide (H2S) in living systems, the development of a highly sensitive and selective fluorescent sensor for the detection of H2S is crucial. A novel fluorescent sensor has been synthesized in this paper, which utilises thiolysis of thiophene esters assisted by an ortho-aldehyde group as a sensing strategy to achieve highly specific detection of H2S. It was shown that the sensor has excellent sensing performance for H2S with 300-fold fluorescence enhancement, Stokes shift up to 170 nm, fast response time up to 5 min, high sensitivity (limit of detection, LOD = 55 nM) and good selectivity. The sensor has been successfully used for colourimetric and fluorescence detection of H2S in solution. Test papers prepared with the sensor can be used to detect H2S gas in spoiled eggs and milk. In addition, the sensor can image H2S in living cells and zebrafish.

A Benzothiadiazole-Based Zn(II) Metal–Organic Framework with Visual Turn-On Sensing for Anthrax Biomarker and Theoretical Calculation

2,6-pyridine dicarboxylic acid (DPA) is an exceptional biomarker of notorious anthrax spores. Therefore, the rapid, sensitive, and selective quantitative detection of DPA is extremely significant and urgent. This paper reports a Zn(II) metal–organic framework with the formula of {[Zn6(NDA)6(DPBT)3] 2H2O·3DMF}n (MOF-1), which consists of 2,6-naphthalenedicarboxylic acid (2,6-NDA), 4,7-di(4-pyridyl)-2,1,3-benzothiadiazole (DPBT), and Zn(II) ions. Structural analysis indicated that MOF-1 is a three-dimensional (3D) network which crystallized in the monoclinic system with the C2/c space group, revealing high pH, solvent, and thermal stability. Luminescence sensing studies demonstrated that MOF-1 had the potential to be a highly selective, sensitive, and recyclable fluorescence sensor for the identification of DPA. Furthermore, fluorescent test paper was made to detect DPA promptly with color changes. The enhancement mechanism was established by the hydrogen-bonding interaction and photoinduced electron transfer transition between MOF-1 and DPA molecules.

A tailored ratiometric fluorescent sensor based on CdTe and MgF2 quantum dots for trace N-ethylpentylone detection.

The development of low-cost and highly sensitive ratiometric fluorescence sensor, CdTe@MIPs/MgF2, for N-Ethylpentylone (NEP) detection in wastewater samples is described. In this system, CdTe@MIPs (λex = 370, λem = 570) are employed as the receptor and response unit for NEP, with MgF2 (λex = 370, λem = 470) as the reference signal to enhance stability. Under optimal conditions, the sensor shows fluorescent quenching response at 570 nm to NEP in linear range of 2-200nM, with LOD of 0.6nM. Thesensor also demonstrates significant selectivity for NEP over other analogues and interferents, making it ideal for practical applications in wastewater analysis. This approach is potentially more cost-effective and sensitive than conventional mass spectrometry in detecting abused substances in sewage. Additionally, the MgF2 fluorescent nano-material was first-ever developed and investigated, which may be significant in future research.

A highly sensitive fluorescence sensor for tobacco mosaic virus RNA based on DSN cycle and ARGET ATRP double signal amplification

AbstractEarly and sensitive detection of tobacco mosaic virus (TMV) is of great significance for improving crop yield and protecting germplasm resources. Herein, we constructed a novel fluorescence sensor to detect TMV RNA (tRNA) through double strand specific nuclease (DSN) cycle and activator regenerative electron transfer atom transfer radical polymerization (ARGET ATRP) dual signal amplification strategy. The hairpin DNA complementarily paired with tRNA was used as a recognition unit to specifically capture tRNA. By the double‐stranded DNA hydrolyzed with DSN, tRNA is released to open more hairpin DNA, and more complementary DNA (cDNA) is bound to the surface of the magnetic beads (MBs) to achieve the first amplification. After binding with the initiator, the cDNA employed ARGET ATRP to attach more fluorescent signal molecules to the surface of MBs, thus achieving the second signal amplification. Under the optimal experimental conditions, the logarithm of fluorescence intensity versus tRNA concentration showed a good linear relationship in the range of 0.01–100 pM, with a detection limit of 1.03 fM. The limit of detection (LOD) was calculated according to LOD = 3 N/S. Besides, the sensor showed good reproducibility and stability, which present provided new method for early and highly sensitive detection for plant viruses.

Hollow Cu/CoS2 Nanozyme with Defect-Induced Enzymatic Catalytic Sites and Binding Pockets for Highly Sensitive Fluorescence Detection of Alkaline Phosphatase.

Along with an ever-deepening understanding of the catalytic principle of natural enzymes, the rational design of high-activity biomimetic nanozymes has become a hot topic in current research. Inspired by the active centers of natural enzymes consisting of catalytic sites and binding pockets, a Cu-doped CoS2 hollow nanocube (Cu/CoS2 HNCs) nanozyme integrating substitution defects and vacancies is developed through a defect engineering strategy. It is shown that the vacancies and substitution defects in the developed Cu/CoS2 HNC nanozymes serve as binding pockets and catalytic sites, respectively. The construction of this key active center and the accelerated electron transfer from the Co/Cu redox cycle significantly improve the substrate affinity and catalytic efficiency of the Cu/CoS2 HNCs nanozymes, which results in the excellent catalytic performance of the Cu/CoS2 HNC nanozymes. Using the superior enzymatic activity of Cu/CoS2 HNCs, a fluorescence detection platform for alkaline phosphatase (ALP) is established, which is a wider detection range and lower limit of detection (LOD) than previous work. This work broadens the family of nanozymes and provide a new idea for the development of novel nanozymes with high enzyme activity, as well as a guideline for the construction of highly sensitive fluorescent sensors.

A new water−soluble naphthalene diimide as a highly selective fluorescent chemosensor for Cu(II) ion: Synthesis, DFT calculations, photophysical and electrochemical properties

The highly selective, sensitive, and water-soluble fluorescent sensors are desideratum for optoelectronic, environmental, biological, and biomedical applications. An innovative fluorescence chemosensor, naphthalene diimide (3) with metal binding sites, was designed, synthesized and characterized. The chemosensor's optical, electrochemical, spectroelectrochemical, and morphological properties were investigated, and then the density functional theory (DFT) simulations were conducted. The selectivity of 3 for the metals Cu(II), Ag(I), Hg(II), Mg(II), Fe(III), Ca(II), Co(II), Zn(II), Pb(II) and Cd(II) were investigated through UV–visible and fluorescence spectroscopy techniques. 3 was highly selective and sensitive toward Cu(II) metal ions. The chemosensor can detect Cu(II) in water with a detection limit of 1.11 μM, which is lower than the WHO standard and has good repeatability. Further investigations through the IR, DPV, AFM, UV–visible and fluorescence spectroscopies, SEM, EDX and TEM techniques confirmed the binding capabilities of the 3 with Cu(II).

Symmetrical Ligand's Fabricated Porous Silicon Surface Based Photoluminescence Sensor for Metal Detection and Entrapment.

This study was based on the development of surface-based photoluminescence sensor for metal detection, quantification, and sample purification employing the solid sensory chip having the capability of metal entrapment. The Co(II), Cu(II) and Hg(II) sensitive fluorescence sensor (TP) was first synthesized and characterized its sensing abilities towards tested metal ions by using fluorescence spectral investigation while the synthesis and complexation of the receptor was confirmed by the chromogenic, optical, spectroscopic and spectrometric analysis. Under optical investigation, the ligand solution exhibited substantial chromogenic changes as well as spectral variations upon reacting with copper, cobalt, and mercuric ions, while these behaviors were not seen for the rest of tested metallic ions i.e., Na+, Ag+, Ni2+, Mn2+, Pd2+, Pb2+, Cd2+, Zn2+, Sn2+, Fe2+, Fe3+, Cr3+, and Al3+. These colorimetric alterations and spectral shifting could potentially be employed to detect and quantify these specific metal ions. After the establishment of the ligand's selective complexation ability towards selected metals, it was fabricated over the substituted porous silicon surface (FPS) keeping in view of the development of surface-based photoluminescence sensor (TP-FPS) for the selected metal sensation and entrapment to purify the sample just be putting off the metal entrapped sensory solid chip. Surface characterization and ligand fabrication was inspected by plan and cross sectional electron microscopic investigations, vibrational and electronic spectral analysis. The sensitivity of the ligand (TP) in the solution phase metal discrimination was determined by employing the fluorescence titration analysis of the ligand solution after progressive induction of Co2+, Cu2+, and Hg2+, which afford the detection limit values of 2.14 × 10- 8, 3.47 × 10- 8 and 3.13 × 10- 3, respectively. Concurrently, photoluminescence titration of the surface fabricated sensor (TP-FPS) revealed detection limit values of 3.14 × 10- 9, 7.43 × 10- 9, and 8.21 × 10- 4, respectively, for the selected metal ions.