Novel thiophene-based colorimetric and fluorescent turn-on sensor for highly sensitive and selective simultaneous detection of Al3+ and Zn2+ in water and food samples and its application in bioimaging

Portable sensing methods based on carbon dots for food analysis

Food analysis is significantly important in monitoring food quality and safety for human health. Traditional methods for food detection mainly rely on benchtop instruments and require a certain amount of analysis time, which promotes the development of portable sensors. Portable sensing methods own many advantages over traditional techniques such as flexibility and accessibility in diverse environments, real-time monitoring, cost-effectiveness, and rapid deployment. This review focuses on the portable approaches based on carbon dots (CDs) for food analysis. CDs are zero-dimensional carbon-based material with a size of less than 10 nm. In the manner of sensing, CDs exhibit rich functional groups, low biotoxicity, good biocompatibility, and excellent optical properties. Furthermore, there are many methods for the synthesis of CDs using various precursor materials. The incorporation of CDs into food science and engineering for enhancing food safety control and risk assessment shows promising prospects.

Colorimetric and Fluorometric N-Acylhydrazone-based Chemosensors for Detection of Single to Multiple Metal Ions: Design Strategies and Analytical Applications

The development of optical sensors for metal ions has gained significant attention due to their broad applications in biology, the environment, and medicine. Colorimetric and fluorometric detection methods are particularly valued for their simplicity, cost-effectiveness, high detection limits, and analytical power. Among various chemical probes, the hydrazone functional group stands out for its extensive study and utility, owing to its ease of synthesis and adaptability. This review provides a comprehensive overview of N-acylhydrazone-based probes, serving as highly effective colorimetric and fluorometric chemosensors for a diverse range of metal ions. Probes are categorized into single-ion, dual-ion, and multi-ion chemosensors, each further classified based on the detected metal(s). Additionally, the review discusses detection modes, detection limits, association constants, and spectroscopic measurements.

Hectorite/Phenanthroline-Based Nanomaterial as Fluorescent Sensor for Zn Ion Detection: A Theoretical and Experimental Study

The development of fluorescent materials that can act as sensors for the determination of metal ions in biological fluids is important since they show, among others, high sensitivity and specificity. However, most of the molecules that are used for these purposes possess a very low solubility in aqueous media, and, thus, it is necessary to adopt some derivation strategies. Clay minerals, for example, hectorite, as natural materials, are biocompatible and available in large amounts at a very low cost that have been extensively used as carrier systems for the delivery of different hydrophobic species. In the present work, we report the synthesis and characterization of a hectorite/phenanthroline nanomaterial as a potential fluorescent sensor for Zn ion detection in water. The interaction of phenanthroline with the Ht interlaminar space was thoroughly investigated, via both theoretical and experimental studies (i.e., thermogravimetry, FT-IR, UV-vis and fluorescence spectroscopies and XRD measurements), while its morphology was imaged by scanning electron microscopy. Afterwards, the possibility to use it as sensor for the detection of Zn2+ ions, in comparison to other metal ions, was investigated through fluorescent measurements, and the stability of the solid Ht/Phe/Zn complex was assessed by different experimental and theoretical measurements.

The new role of dipyrromethene chemosensor for absorbance-ratiometic and fluorescence "turn-on" sensing Zn2+ ions in water-organic solutions and real water samples

This study presents a dipyrromethene-based sensitive and selective probe for Zn2+ ions detection in aqueous and water-organic media. The probe demonstrates absorbance-ratiometric and "off-on" fluorescent sensing for Zn2+ in a DMSO/H2O (9:1, v/v) mixture. The 3,3',4,4',5,5'-hexamethyl-2,2'-dipyrromethene (HL), similar to its analogs, exhibits weak fluorescence (with a quantum yield of less than 0.001). However, upon the presence of Zn2+ ions in the sensor HL solution, there is a remarkable increase (up to 200-fold) in fluorescence intensity due to the formation of a stable intramolecular chelate complex [ZnL2]. This complex formation induces a significant hyperchromic effect and a red shift (57 nm) in the characteristic absorption bands. The sensing mechanism of the probe towards Zn2+ ions was thoroughly investigated through absorbance and fluorescent titrations, molar ratio plots, 1H NMR, and DFT/TDDFT studies. The fluorescence response exhibited a strong linear relationship with Zn2+ concentration within the range of 0 to 5.7 × 10-6 mol/L. The detection limit (LOD) and limit of quantitation (LoQ) for Zn2+ were determined as 2 × 10-8 mol/L and 6.6 × 10-8 mol/L, respectively. Moreover, the probe demonstrated high selectivity for Zn2+ ions over other metal ions (Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Pd2+, Cd2+, Hg2+, Pb2+). Test systems in the form of test-strips and cotton-pads were developed based on the dipyrromethene sensor for rapid "naked-eye" detection of zinc ions in water. The sensor was successfully applied for detecting Zn2+ ions in real water samples.

Ethyl 3-aminobenzo[b]thiophene-2-carboxylate Derived Ratiometric Schiff Base Fluorescent Sensor for the Recognition of In3+ and Pb2

An ethyl 3-aminobenzo[b]thiophene-2-carboxylate derived ratiometric Schiff base fluorescent sensor R was devised and synthesized. R exhibited a highly sensitive and selective ratiometric response to In3+ in DMF/H2O tris buffer solution. R exhibited a colorimetric/fluorescent dual-channel response to In3+. More importantly, R can distinguish In3+ from Ga3+ and Al3+ in less than 5 min. R exhibited a good linear correlation with the concentration of In3+ in the 5-25 μM range and the limit of detection for In3+ was found to be 8.36 × 10-9 M. According to the job`s plot and MS spectra, R formed a complex with In3+ at 1:2 with a complexation constant of 8.24 × 109 M2. Based on Gaussian theory calculations, the response mechanism of R to In3+ can be explained by photo-induced electron transfer (PET) and intramolecular charge transfer (ICT) mechanisms. In addition, R can be used for the detection of indium in tap water with satisfactory recoveries. Meanwhile, R displayed a linear relationship to micromolar concentrations (0-50 μM) of Pb2+ and recognized Pb2+ in a ratiometric response with a detection limit of 8.3 × 10-9 M.

N-doped carbon dots for the determination of Al3+ and Fe3+ using aggregation-induced emission

New portable hydrogel sensors for Al3+ and Fe3+ detection were designed based on the aggregation-induced emission (AIE) and color change of N-doped carbon dots (N-CDs). N-CDs with yellow fluorescence were prepared by a one-pot hydrothermal method from 2,5-dihydroxyterephthalic acid and acrylamide. The fluorescence of N-CDs was enhanced by Al3+ about 20 times and quenched by Fe3+. It was interesting that although Fe3+ showed obvious quenching on the fluorescence of N-CDs it did not cause a noticeable change in the fluorescence of N-CDs + Al3+. The colorless solution of N-CDs appeared blue in the presence of Fe3+ without the influence of Al3+. Therefore, the turn-on fluorometry and colorimetry systems based on N-CDs were constructed for the simultaneous detection of Al3+ and Fe3+. Furthermore, the portable sensing of Al3+ and Fe3+ was realized with the assistance of hydrogel, filter paper, cellulose acetate, and cellulose nitrate film. The proposed approach was successfully applied to the detection of Al3+ and Fe3+ in food samples and cell imaging.

Recent Advances in Fluorescent Probes for Zinc Ions Based on Various Response Mechanisms

Zinc is a vital metal element with extensive applications in various fields such as industry, metallurgy, agriculture, food, and healthcare. For living organisms, zinc ions are indispensable, and their deficiency can lead to physiological and metabolic abnormalities that cause multiple diseases. Hence, there is a significant need for selective recognition and effective detection of free zinc ions. As a probe method with high sensitivity, high selectivity, real-time monitoring, safety, harmlessness and ease of operation, fluorescent probes have been widely used in metal ion identification studies, and many convenient, low-cost and easy-to-operate fluorescent probes for Zn²⁺ detection have been developed. This article reviews the latest research advances in fluorescent chemosensors for Zn²⁺ detection from 2019 to 2023. In particular, sensors working through photo-induced electron transfer (PET), excited state intramolecular proton transfer (ESIPT), intramolecular charge transfer (ICT), fluorescence resonance energy transfer (FRET), chelation-enhanced fluorescence (CHEF), and aggregation-induced emission (AIE) mechanisms are described. We discuss the use of various recognition mechanisms in detecting zinc ions through specific cases, some of which have been validated through theoretical calculations.

NIR squaraine dyes for dual colorimetric and fluorescent determination of Fe3+, Cu2+, and Hg2+ ions

Four benzoindolenine-based squaraine dyes (SQs), which have the advantages of intense visible and near-infrared (NIR) absorption and emission (λ_abs/max 663-695 nm, λ_em/max 686-730 nm) were synthesized and characterized by UV-vis absorption, fluorescent emission spectrophotometry, FTIR, NMR and HRMS analysis. Among them, BBSQ showed excellent performance, which exhibited high selectivity to Fe³⁺, Cu²⁺, and Hg²⁺ in acetonitrile solution even in the presence of other competitive metal ions, accompanied by obvious color change easily detected by the naked eye. The detection limit was 14.17 μM for Fe³⁺ and 6.06 μM for Cu²⁺. Most importantly, the response mechanism of BBSQ to Fe³⁺, Cu²⁺, and Hg²⁺ involves the coordination of BBSQ and metal ions through the O atom on the central squarate ring, N atom, and olefin π bond of BBSQ and has been demonstrated by Job's plot, FTIR, and ¹H NMR titration analyses. Furthermore, BBSQ was applied successfully to detect Fe³⁺, Cu²⁺, and Hg²⁺ in thin-layer chromatography (TLC) plates with good precision and is quite promising for the quantitative detection of Fe³⁺ and Cu²⁺ ions in water samples.

A Simple Schiff Base as Fluorescent Probe for Detection of Al3+ in Aqueous Media and its Application in Cells Imaging

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.

Aryl-Phenanthro[9,10-d]imidazole: A Versatile Scaffold for the Design of Optical-Based Sensors

Fluorescent and colorimetric sensors are important tools for investigating the chemical compositions of different matrices, including foods, environmental samples, and water. The high sensitivity, low interference, and low detection limits of these sensors have inspired scientists to investigate this class of sensing molecules for ion and molecule detection. Several examples of fluorescent and colorimetric sensors have been described in the literature; this Review focuses particularly on phenanthro[9,10-d]imidazoles. Different strategies have been developed for obtaining phenanthro[9,10-d]imidazoles, which enable modification of their optical properties upon interaction with specific analytes. These sensing responses usually involve changes in the fluorescence intensity and/or color arising from processes like photoinduced electron transfer, intramolecular charge transfer, intramolecular proton transfer in the excited state, and Förster resonance energy transfer. In this Review, we categorized these sensors into two different groups: those bearing formyl groups and their derivatives and those based on other molecular groups. The different optical responses of phenanthro[9,10-d]imidazole-based sensors upon interaction with specific analytes are discussed.

A novel AIE fluorescent probe for the monitoring of aluminum ions in living cells and zebrafish

A novel fluorescent probe BTD with aggregation induced emission (AIE) characteristics for the monitoring of Al³⁺ was developed. This fluorescent probe could be used to detect Al³⁺ in aqueous solution under mild conditions, along with high sensitivity and high selectivity. The detection limit of the probe BTD for Al³⁺ is as low as 3.25 nM, which is below the WHO recommendation concentration (7.41 μM) for drinking water. Furthermore, this probe was successfully applied to the sensing of Al³⁺ in living cells and zebrafish.

A photoswitchable "turn-on" fluorescent chemosensor: Quinoline-naphthalene duo for nanomolar detection of aluminum and bisulfite ions and its multifarious applications

A quinoline-naphthalene duo-based Schiff base probe (R) was synthesized and characterized by the usual spectroscopic and single-crystal X-ray crystallographic techniques. Probe R detects Al³⁺ and HSO₃^- ions via the fluorescent turn-on approach by dual pathways i.e., i) when probe R interacts with Al³⁺, the restriction of CN single bond rotation, blocking of both photoinduced electron transfer (PET) and CN isomerization were observed, and ii) when the sensor R interacts with HSO₃^-, imine (CH = N) bond was cleaved via hydrolysis and produced the respective aldehyde and amine behaving as a chemodosimeter. The binding stoichiometric ratio of R + Al³⁺ (1:1) was confirmed by Job's plot, emission titration profile, NMR, and mass spectrometric analyses. This probe R is highly selective to both Al³⁺ -ions and HSO₃^- -ions, without any interference of other potentially competing cations and anions. Limit of detection (LOD) and quantification (LOQ) of R with Al³⁺ and HSO₃^- were downed to nanomolar concentrations, which is much lower than the recommended level of drinking water/food fixed by the World Health Organization (WHO). Furthermore, probe R was utilized in the detection of Al³⁺ and HSO₃^- ions in highly contaminated real samples, bioimaging in E. coli cells, multiple-targeting molecular logic gate, and in bovine serum albumin (BSA) binding.

A Review on Organic Colorimetric and Fluorescent Chemosensors for the Detection of Zn(II) Ions

Organic compounds display several electronic and structural features which enable their application in various fields, ranging from biological to non-biological. These compounds contain heteroatoms like sulfur, nitrogen and, oxygen, which provide coordination sites to act as ligands in the field of coordination chemistry and are used as chemosensors to detect various metal ions. This review article covers different organic compounds including Schiff bases, thiourea, pyridine, rhodamine, triazole, pyrene, coumarin, imidazole, diaminomaleonitrile, naphthoxazole, pyrimidine, thiophene, thioether, and other functional groups based chemosensors that contain heteroatoms like sulfur, nitrogen and, oxygen for fluorimetric and colorimetric detection of Zn(II) ions in different environmental, agricultural, and biological samples. Further, the sensing performances of these chemosensors have been compared and discussed which could help the readers for the future design of organic fluorescent and colorimetric chemosensors for the detection of Zn(II) ions. We hope this study will support the new thoughts to design a simple, efficient, selective, and sensitive chemosensor for the detection of Zn(II) ions in different samples (environmental, agricultural, and biological).

A visible-light-gated donor–acceptor Stenhouse adduct chemosensor: synthesis, photochromism and naked-eye colorimetric/fluorometric sensing of Al3+ and Zn2+

A visible-light-gated donor–acceptor Stenhouse adduct chemosensor is designed for the colorimetric/fluorometric sensing of Al3+ and Zn2+.

An isocamphanyl-based fluorescent "turn-on" probe for highly sensitive and selective detection of Ga3+ and application in vivo and in vitro

A novel fluorescent probe 2-(4-(diethylamino)-2-hydroxybenzylidene)-N-(2,3,3-trimethylbicyclo[2.2.1]heptan-2-yl)hydrazinecarbothioamide (HT) was prepared in this study by a condensation reaction. HT has been confirmed to possess high specificity toward Ga³⁺ over other metal ions (including Al³⁺ and In³⁺) via a distinct fluorescence light-up response. Moreover, HT exhibited good detection performances for Ga³⁺ including high selectivity, excellent anti-interference ability, a wide working pH range, and good reversibility. The association constant and limit of detection (LOD) were calculated to be 5.34 × 10³ M^-1 and 1.18 × 10^-6 M, respectively. The detection mechanism of HT toward Ga³⁺ was proposed and confirmed by ¹H NMR analysis, HRMS analysis, and DFT calculations. A simple test strip-based portable detecting device and a molecular INHIBIT logic circuit were established for improving its practical applicability. Furthermore, the desirable sensing performance of HT for Ga³⁺ was successfully reconfirmed in MCF-7 cells and zebrafish.

Recent advances of environmental pollutants detection via paper-based sensing strategy

Paper has become one of the most promising substrates for building low-cost and powerful sensing platforms due to its self-pumping ability and compatibility with multiple patterning methods. Paper-based sensors have been greatly developed in the field of environmental monitoring. In this review, we introduced the research and application of paper-based sensors in environmental monitoring, focusing on the deposition and patterning methods of building paper-based sensors, and summarized the applications of detecting environmental pollutants, including metal ions, anions, explosives, neurotoxins, volatile organic compounds, and small molecules. In addition, the development prospects and challenges of promoting paper-based sensors are also discussed. The current review will provide references for the construction of portable paper-based sensors, and has implications for the field of on-site real-time detection of the environment.

Molecularly Imprinted Polymers for Chemical Sensing: A Tutorial Review

The field of molecularly imprinted polymer (MIP)-based chemosensors has been experiencing constant growth for several decades. Since the beginning, their continuous development has been driven by the need for simple devices with optimum selectivity for the detection of various compounds in fields such as medical diagnosis, environmental and industrial monitoring, food and toxicological analysis, and, more recently, the detection of traces of explosives or their precursors. This review presents an overview of the main research efforts made so far for the development of MIP-based chemosensors, critically discusses the pros and cons, and gives perspectives for further developments in this field.

Development of a fluorescent probe for detecting Al3+ in cooked wheaten food based on phosphonic acid group functionalized polythiophene derivatives

As an unnecessary trace element, the content of aluminium in biological systems should be strictly controlled. Therefore, it was necessary to develop a convenient method for detection of aluminium ions. In this study, a fluorescent probe based on polythiophene derivatives was developed and used to detect Al³⁺ in Chinese traditional pasta. The fluorescence of this probe showed a significant decrease in hexamethylenetetramine-HCl buffer solution (pH 5) when Al³⁺ was present. In addition, the probe exhibited good sensitivity and selectivity to Al³⁺ over other metal ions when EDTA was used as the masking agent. Fluorescence intensity had a good linear relationship with the Al³⁺ concentration in the range 0.1-10 μM and the limit of detection for Al³⁺ was 39 nM. Furthermore, the probe was successfully applied to detect Al³⁺ in food samples and the results were consistent with ICP-AES.

A bifunctional fluorescent probe for sensing of Al3+ and H2S

Al3+ and H2S play essential roles in various physiological processes. However, excess Al3+ and H2S are harmful to health. Therefore, it is necessary to design a sensitive method for the detection of Al3+ and H2S. In this work, compound L was developed based on salicylaldoxime and 4-aminobenzamide. L displayed aggregation-induced emission (AIE) characteristics in the solid state due to a unique dimer formation via intermolecular hydrogen bonds. In addition, L could serve as a multi-responsive fluorescence probe for Al3+ based on the coordination reaction in a MeOH/H2O (9/1, v/v, pH = 7.4) medium and for H2S based on the addition reaction in EtOH/H2O (7/3, v/v, pH = 7.4) solution. In addition, L showed a fluorescence colorimetric response to Al3+ in the solid state. Furthermore, L was applied to detect Al3+ and H2S in actual water samples.

Reversible Chemosensor for Bioimaging and Biosensing of Zn(II) and hpH in Cells, Larval Zebrafish, and Plants with Dual-Channel Fluorescence Signals

Zinc/Zn(II) is an essential trace element for humans and acts as an important substance that maintains the normal growth, development, and metabolism of the body. Excess or deficient Zn(II) can cause abnormal metabolism in the human body, leading to a series of diseases. Moreover, biosystems have complex homeostasis systems, especially harsh pH (OH^-) environments. Thus, investigating the variation in the levels of Zn(II) and OH^- is extremely important in clinical, medical, and environmental testing. Nevertheless, the lack of practical and convenient fluorescence imaging tools limits the tracing of Zn(II) and OH^- in biosystems. In this work, a well-designed dual-channel fluorescent signal response chemosensor (DACH-fhba) was assembled for selective sensing of Zn(II) and OH^- in the biosystem using a fluorescence turn-on strategy. On encountering Zn(II), the chemosensor emitted a blue fluorescence signal (455 nm). Meanwhile, the bright green fluorescence signal (530 nm) increased with OH^- addition simultaneously. With the blue/green dual fluorescence response of DACH-fhba, the sensor exhibited high stability and reversibility. Notably, the bioimaging revealed that DACH-fhba successfully tracked Zn(II) and OH^- in live cells, larval zebrafish, and plants. Further results implied that DACH-fhba can be used to achieve visual detection of Zn(II) and OH^- in organisms. Altogether, this work is conducive to the monitoring of Zn(II) and OH^- in organisms and promotes the understanding of the function of Zn(II) and OH^- in biosystems.

Synthesis of fluorescent nanoprobe with simultaneous response to intracellular pH and Zn2+ for tumor cell distinguishment

A novel dual-functional nanoprobe was designed and synthesized by facile assembly of quinoline derivative (PEIQ) and meso-tetra (4-carboxyphenyl) porphine (TCPP) via electrostatic interaction for simultaneous sensing of fluorescence of Zn²⁺ and pH. Under the single-wavelength excitation at 400 nm, this nanoprobe not only exhibits "OFF-ON" green fluorescence at 512 nm by specific PEIQ-Zn²⁺ chelation, but also presents red fluorescence enhancement at 654 nm by H⁺-triggered TCPP release. The nanoprobe demonstrated excellent sensing performance with a good linear range (Zn²⁺, 1-40 μM; pH, 5.0-8.0), low detection limit (Zn²⁺, 0.88 μM), and simultaneous response towards Zn²⁺ and pH in pure aqueous solution within 2 min. More importantly, this dual-functional nanoprobe demonstrates the capability of discerning cancerous cells from normal cells, as evidenced by the fact that cancerous HepG2 cells in tumor microenvironment exhibit substantially higher red fluorescence and significantly lower green fluorescence than normal HL-7702 cells. The simultaneous, real-time fluorescence imaging of multiple analytes in a living system could be significant for cell analysis and tracking, cancer diagnosis, and even fluorescence-guided surgery of tumors.

A novel fluorescent probe of aluminium ions based on rhodamine derivatives and its application in biological imaging

A new type of probe can be used for the detection of Al³⁺ in biological cells.

Polyoxometalate based ionic crystal: dual applications in selective colorimetric sensor for hydrated ZnCl2 and antimicrobial activity

One-pot synthesis of POM-salt ([Himi]₄[SiMo₁₂O₄₀] (1)) was achieved by mixing silicomolybdic acid and imidazole in acidic conditions and characterized by FTIR, TGA, SEM, EDX, ICP-OES and XPS.

The fluorescence turn-off mechanism of a norbornene-derived homopolymer – an Al3+ colorimetric and fluorescent chemosensor

A norbornene-derived hydrazone polymer was developed for high selectivity, and to be used as an effective colorimetric and fluorescent chemosensor of Al³⁺ in aqueous solutions.

New thiophene hydrazide dual-functional chemosensor: Colorimetric sensor for Cu2+ & fluorescent sensor for Al3

A new thiophene hydrazide derivative TSB was synthesized and utilized as naked-eye colorimetric sensor for Cu²⁺ by the color changed from colorless to yellow as well as green fluorescent turn on sensor for Al³⁺ in DMSO/H₂O (1/1, V/V) solution. The dual-functional chemosensor TSB for Cu²⁺/Al³⁺ sensing displayed excellent properties of special selectivity, superior sensitivity, outstanding anti-interference performance, instantaneous response, wide pH working range and good reversibility. The detection limits of TSB for Cu²⁺/Al³⁺ were determined as low as 46.5 nM and 32.7 nM, respectively. The 1:1 binding mode of TSB with Cu²⁺/Al³⁺ was proved by spectrometric titrations, Job's plots, FTIR, ¹H NMR and HRMS analysis. Moreover, chemosensor TSB was successfully utilized for detection of Cu²⁺ and Al³⁺ in real environmental water and food samples with high reliability, demonstrating its practical applicability.

N-doped carbon quantum dots from osmanthus fragrans as a novel off-on fluorescent nanosensor for highly sensitive detection of quercetin and aluminium ion, and cell imaging

In this work, fluorescent N-doped carbon quantum dots (N-CQDs) have been synthesized by simple hydrothermal heating of natural osmanthus fragrans, without any toxic ingredients or surface chemical modifications. The N-CQDs possess a high quantum yield of 21.9 %, outstanding blue fluorescence, good water dispersity, and excellent optical stability. Because the favorable inner filter effect (IFE) between N-CQDs and quercetin (QT) occurs, the addition of QT to N-CQDs can cause their fluorescence quenching. When Al³⁺ was added to the N-CQDs/QT system solution, it was found that the inhibition of IFE leads to the fluorescence intensity of N-CQDs/QT system enhancement by virtue of a specific binding of QT to aluminum ion (Al³⁺). Therefore, we used the N-CQDs as a novel off-on fluorescent nanosensor to detect QT and Al³⁺. Under optimal conditions, the fluorescent nanosensor can detect QT within the wide linear response in the range of 0.003-80 μmol/L with as low as 1 nmol/L detection limit. For the detection of Al³⁺, the N-CQDs/QT system showed linearity response toward Al³⁺ in a range of 0.1∼100 μmol/L and the limit of detection was found at 26 nmol/L. In addition, N-CQDs have been successfully used to efficient quantification QT in human plasma and monitor Al³⁺ in serum samples. Noteworthy, the N-CQDs demonstrated low toxicity toward T24 cells, which realized sensing QT and Al³⁺ in the living cells.