Fluorescent Sensor Research Articles

Dual-channel fluorescent sensor for rapid Cu2+ and Fe3+ detection: Enhanced sensitivity and selectivity with triazole-substituted acridinedione derivative

The AR-2 sensor, derived from a triazole-substituted acridinedione, exhibits distinct responses to Cu2⁺ and Fe³⁺ ions. It shows fluorescence enhancement in the presence of Cu2⁺ ions and a reduction in fluorescence with Fe³⁺ ions. This sensor is distinguished by its high sensitivity, selectivity, rapid response time, reversibility, and broad operating pH range, with shallow detection limits for both ions. Structural and photophysical analyses of AR-2 were conducted using density functional theory (DFT) and various spectroscopic techniques. The binding modes and recognition mechanisms for Cu2⁺ and Fe³⁺ ions were elucidated through multiple experimental approaches. Additionally, AR-2 demonstrated efficacy in the rapid, visual detection of these ions via paper test strips and swab tests. It successfully identified Cu2⁺ and Fe³⁺ ions in real water and food samples, achieving notable recovery rates. The AR-2 sensor also excelled in fluorescence imaging, effectively visualizing iron and copper pools in seed sprouts.

Novel sulfonylurea fluorescence probes for antiproliferative activity, detection and imaging of fluoride ions in living cells

In this study, four novel triphenylpyrazoline 4-toluenesulfonylureas (PYSUs) were synthesized to develop potential anticancer drugs and fluorescent probes for the detection of F− ions. The compounds were synthesized via a two-step microwave-assisted method. The antiproliferative activity of the PYSUs was tested against two cancer cell lines: HepG2 and MDA-MB-231. Among the compounds, 3a exhibited strong activity against both cell lines, while 3b showed strong activity against MDA-MB-231 cells but weaker inhibition of HepG2 cells. Furthermore, compound 3b was identified as the best fluorescent probe, with an increase in emission intensity in the presence of F− ions from tetrabutylammonium fluoride (TBAF). In DMSO, the emission wavelength was found to be 518 nm (green) with an excitation wavelength of 469 nm. The limit of detection (LOD) was calculated to be 0.269 mM in the linear range of 5–10 mM. The interaction mechanism between F− ions and compound 3b was further explored via DFT/TDDFT calculations. Additionally, fluorescent imaging of TBAF-incubated MDA-MB-231 and HepG2 cells confirmed the potential of PYSUs as fluorescent sensors for F− ions in living cancer cells.

Fluorescent aptasensor based on competitive recognition strategies and point-of-care testing system for brain natriuretic peptide detection

Brain natriuretic peptide (BNP) is the preferred biomarker for clinical analysis, widely used in early screening and prognostic monitoring of cardiovascular and neurological diseases. Due to the low concentration and short half-life of BNP in the blood, its sensitive detection remains a challenge that must be overcome. With the rapid development of molecular diagnosis and point-of-care testing (POCT), developing a BNP biosensor with high sensitivity, good stability, accuracy, speed, and low-cost is of great significance for clinical applications and emergency diagnosis. However, BNP in human blood exists in various forms, and traditional fluorescence sensors may lead to overestimation of the concentration. In this work, we constructed an “on” fluorescent aptasensor based on competitive recognition strategy for quantitative detection of BNP, and built a fluorescence sensing detection system based on smartphone to achieve rapid on-site detection. We designed a specific aptamer labeled with carboxyfluorescein (FAM) with a simple structure and high biological affinity for selective capture of BNP, and utilized the large specific surface area and excellent fluorescence quenching effect of carboxylated graphene oxide (GO-COOH) as a carrier and quencher for the aptasensor. By optimizing experimental parameters such as aptamer and GO-COOH concentrations, as well as quenching/recovery time, linear sensitive detection of BNP was achieved in the concentration range of 0.01 ng/mL–10 ng/mL, with a detection limit as low as 10 pg/mL, good specificity, and excellent application potential in artificial serum spiking experiments. Additionally, a stable and sensitive fluorescence signal collection system has been developed to meet the needs of portable detection, breaking through the usage environment of traditional fluorescence detection equipment and filling the gap of portable fluorescence biosensing. In summary, we have creatively proposed a fluorescent aptasensor that enables rapid and sensitive detection of BNP and the development of low-cost fluorescent biosensors. The combination with POCT has shown broad application prospects and also provides some ideas for the fluorescence detection of other protein biomarkers.

Chiral fluorescent carbon dots for tyrosine enantiomers: Discrimination, mechanism and cell imaging

The development of chiral analytical methods for tyrosine enantiomers, characterized by superior recognition performance and selectivity, holds significant potential for application in the biochemical and biomedical domains associated with tyrosine. Herein, a straightforward and effective strategy for tyrosine enantiomers identification and purity analysis by chiral carbon dots (CDs) fluorescence sensor were reported. The chiral CDs were designed by using L-cysteine and 2,4-diaminophenol hydrochloride through a gentle one-step synthesis strategy at room temperature. The resulting chiral CDs exhibited completely different fluorescence response to L-tyrosine and D-tyrosine, that is, L-tyrosine could enhance the fluorescence of the chiral CDs, but D-tyrosine made no difference. The fluorescent differential recognition factor for enantiomers was as high as 23.2, which was the highest be achievement to our best knowledge so far. The varying discriminatory capabilities of chiral CDs towards tyrosine enantiomers were also applicable to HeLa cells. To confirm the recognition mechanism of chiral CDs to tyrosine enantiomers, the chiral CDs-modified SiO2 stationary phase were synthesized and applied to separate the tyrosine enantiomers in reverse-phase HPLC mode. Furthermore, density functional theory was combined with the fluorescence spectroscopy and chromatographic results to verify that the recognition ability was related to the difference of weak interaction energy and Gibbs free energy between the precursor molecule of the chiral CDs and the tyrosine enantiomers. This cost-effective and highly selectivity assay not only provided a valuable tool for tyrosine enantiomers identification and purity analysis, but also delivered an important reference for the recognition and purity identification of other chiral drugs.

Luminescent Metal-Organic Framework-Based Fluorescent Sensor Array for Screening and Discrimination of Bisphenols.

Extensive applications of bisphenols in industrial products have led to their release into aquatic environments, causing a great threat to human health due to their endocrine-disrupting effects, whereas existing methods are difficult to implement the rapid and high-throughput detection of multiple bisphenols. To circumvent this issue, we constructed a sensor array using two luminescent metal-organic frameworks (LMOFs) (Zr-BUT-12 and Ga-MIL-61) for the rapid discrimination of six bisphenol contaminants (BPA, BPS, BPB, BPF, BPAF, and TBBPA). Wherein, Zr-BUT-12 and Ga-MIL-61 exhibited different fluorescence-emission properties and good luminescent stability. Interestingly, bisphenols with different structures had diverse quenching effects on the fluorescence intensity of Zr-BUT-12 and Ga-MIL-61 via the adsorptive interaction, resulting in unique fluorescent fingerprints. Based on pattern recognition methods, different bisphenols were successfully identified, with the limit of detection in the range of 1.59-16.7 ng/mL for six bisphenols. More importantly, the developed sensor array could be effectively utilized for distinguishing different ratios of mixed bisphenols, which was further applied for bisphenol discrimination in real water samples. Consequently, our finding provides a promising strategy for the simultaneous recognition of multiple bisphenols, which encourages the development of a sensor array for the detection of multiple contaminants in environmental monitoring and food safety.

A Dy(III) Coordination Polymer Material as a Dual-Functional Fluorescent Sensor for the Selective Detection of Inorganic Pollutants.

A Dy(III) coordination polymer (CP), [Dy(spasds)(H2O)2]n (1) (Na2Hspasds = 5-(4-sulfophenylazo)salicylic disodium salt), has been synthesized using a hydrothermal method and characterized. 1 features a 2D layered structure, where the spasda3- anions act as pentadentate ligands, adopting carboxylate, sulfonate and phenolate groups to bridge with four Dy centers in η3-μ1: μ2, η2-μ1: μ1, and monodentate coordination modes, respectively. It possesses a unique (4,4)-connected net with a Schläfli symbol of {44·62}{4}2. The luminescence study revealed that 1 exhibited a broad fluorescent emission band at 392 nm. Moreover, the visual blue color has been confirmed by the CIE plot. 1 can serve as a dual-functional luminescent sensor toward Fe3+ and MnO4- through the luminescence quenching effect, with limits of detection (LODs) of 9.30 × 10-7 and 1.19 × 10-6 M, respectively. The LODs are relatively low in comparison with those of the reported CP-based sensors for Fe3+ and MnO4-. In addition, 1 also has high selectivity and remarkable anti-interference ability, as well as good recyclability for at least five cycles. Furthermore, the potential application of the sensor for the detection of Fe3+ and MnO4- was studied through simulated wastewater samples with different concentrations. The possible sensing mechanisms were investigated using Ultraviolet-Visible (UV-Vis) absorption spectroscopy and density functional theory (DFT) calculations. The results revealed that the luminescence turn-off effects toward Fe3+ and MnO4- were caused by competitive absorption and photoinduced electron transfer (PET), and competitive absorption and inner filter effect (IFE), respectively.

A new coumarin-based “OFF–ON” fluorescent sensor for H2S detection in HeLa cells

A new “OFF–ON” coumarin-based fluorescent probe for H2S detection was designed and successfully developed through O-sulfonylation between a dabsyl quencher and 7-hydroxy-4-methylcoumarin as a fluorescent reporter, based on a FRET approach. This H2S responsive probe, utilizing H2S assisted thiolysis of a sulfonate ester as the sensing strategy, demonstrated excellent performance towards H2S with a limit of detection (LoD) of 1.64 µM, along with superb selectivity, good stability and high specificity towards H2S without interference from other biomarkers and analytes. Moreover, dabsyl-7-hydroxy-4-methylcoumarin (dabsylcoumarin) is capable of permeating the cell membrane and effectively visualizing the level of H2S in the living HeLa cells without cytotoxicity.

A Fluorescence Enhancement Sensor Based on Silver Nanoclusters Protected by Rich-G-DNA for ATP Detection.

In this study, a turn-on fluorescence sensor for the detection of adenosine 5'-triphosphate (ATP) was developed and tested using ATP-DNA2-Ag NCs. The results showed that the fluorescence of ATP-DNA2-Ag NCs was significantly enhanced with the addition of ATP. The fluorescence enhancement was a result of the specific binding activity of the ATP aptamer and ATP, which caused G-rich sequences to approach the dark DNA-Ag NCs, owing to the alteration in ATP aptamer conformation. The proposed sensor demonstrated a good linear range of 18-42 mM and a limit of detection (LOD) of 2.8 μM. The sensor's features include sensitivity, selectivity, and simple operation. In addition, the proposed sensor successfully measured ATP in 100-fold diluted fetal bovine serum.

A simple benzothiazolium-based sensor for cyanide detection: Applications in environmental analysis and bioimaging

A new sensor based on Ethylbenzothiazolium-2-hydroxynaphthaldehyde conjugate-based fluorescent sensor, (E)-3-ethyl-2-(2-(2-hydroxynaphthalen-1-yl) vinyl) benzo[d]thiazol-3-ium iodide (SU-1) was designed and synthesized. The structure of SU-1 was confirmed by 1H NMR, 13C NMR, HRMS, and single crystal XRD spectral analysis. SU-1 displayed a colorimetric and fluorometric response in a DMSO:H2O (1:1,v/v) matrix, changing color from pale yellow to colorless visible to the naked eye, accompanied by a ∼ 120 nm red-shift in the absorption spectra upon CN− addition. This shift, due to formation of deprotonation followed by the nucleophilic attack on the benzothiazolium ring’s double bond, disrupts π-conjugation, blocking intramolecular charge transfer within SU-1. However, competitive anions showed negligible interference while detecting CN−. The Limit of detection for CN− was determined to be 0.27 nM, significantly below the WHO’s permissible CN− concentration in drinking water (1.9 μM). Job’s plot analysis shows that the binding stoichiometry of SU-1 to CN− is a 1:1, with a stability constant (Ka) of 1.58 x 104 M−1. The sensor demonstrated practical applications in environmental water samples and fluorescence imaging of intracellular CN− in CAD cell line.

Genetically encoded epigenetic sensors for visualization of H3K9me3, H3K9ac and H3K4me1 histone modifications in living cells

Post-translational modifications of histones play a crucial role in chromatin structure maintenance and epigenetic regulation. The LiveMIEL (Live-cell Microscopic Imaging of Epigenetic Landscape) method represents a promising approach for tracking histone modifications. It involves visualization of epigenetic modifications using genetically encoded fluorescent sensors and further analysis of the obtained intranuclear patterns by multiparametric image analysis. In this study, we designed three new red fluorescent sensors—MPP8-Red, AF9-Red and DPF3-Red—for live-cell visualization of patterns of H3K9me3, H3K8ac and H3K4me1, respectively. The observed fluorescent patterns were visually distinguishable, and LiveMIEL analysis clearly classified them into three corresponding groups. We propose that these sensors can be used for live-cell dynamic analysis of changes in organization of three epigenetic types of chromatin.

Ultrahigh-sensitivity vinyl-COF fluorescent sensor for trace organic arsenic detection

Ultrahigh-sensitivity vinyl-COF fluorescent sensor for trace organic arsenic detection

Golden Guardians: Advanced pH Sensors with Built‐in Antimicrobial Defense

AbstractGold nanoclusters (Au NCs) capped with a small biomolecule, namely (+)‐norephedrine, (Au@Nore) display exceptional performance as fluorescent pH sensors. They display high emission quantum yield (ΦPL of ≈33% in strongly basic media); absence of nanocluster (NC) aggregation and/or induced rigidification of the organic shell; a linear dependency of their emission on the pH in the 8.2–9.5 range; and reversible pH sensing. In addition, excitation at 310 nm, where both the NC and the ligand absorb, enables ratiometric sensing. Studies on the fungus Candida albicans and bacterium Bacillus subtilis demonstrate that while Au@Nore do not cause any impact on the growth of the fungus, it inhibited the growth of the Bacillus, showing the lowest cell viability of 18% at the highest pH values via a mechanism of action involving the disruption of the bacterial wall.

Improving monitoring of dissolved organic matter from the wastewater treatment plant to the receiving environment: A new high-frequency in situ fluorescence sensor capable of analyzing 29 pairs of Ex/Em wavelengths

A high-frequency, in situ fluorescence probe, called Fluocopée®, has been developed in order to better monitor variations in both the quality and quantity of dissolved organic matter within various aquatic environments (e.g. wastewater, receiving environments) thanks to a wide choice of 29 measured Excitation/Emission wavelength pairs. This advance pave the way to new measurement possibilities in comparison with existing probes, which are usually only able to measure 1–4 fluorophores. The qualification tests of the Fluocopée® probe indicate a high level of accuracy for the measurements of tyrosine, tryptophan and humic acids solutions. Good repeatability and reproducibility are also observed. For the first time, this tool has been deployed in an urban watershed (Bougival, Seine River, downstream of Paris) and in the settled effluent from a wastewater treatment plant (Seine aval, Achères, France). This new high-frequency in situ probe offers great application potential, including organic matter quality and quantity monitoring at drinking and wastewater treatment plants (treatment optimization) and in continental and marine waters (the fate of organic matter in biogeochemical cycles).

Ratiometric fluorescence sensor based on dye-encapsulated Zn-MOF for highly sensitive detection of diquat in tap water and apple samples

The development of convenient and intelligent visualization of rapid pesticide detection methods is key to ensuring food quality and safety. This paper presents a smartphone-based ratiometric fluorescence sensor for smart field visualization and detection of diquat (DQ). Three-dimensional Zn-MOFs are prepared by the solvothermal method using the rigid ligand 4,4′,4″-s-triazine-2,4,6-triyltribenzoic acid (H3TATB), the flexible ligand 1,4-bis((1H-imidazol-1-yl)methyl)benzene (bimb), and the transition metal (Zn2+), which shows good structural and thermal stability. Zn-MOF is a three-dimensional framework crystallizing in a triclinic crystal system in the Pī space group. Then, RhB@Zn-MOF is obtained by introducing rhodamine B (RhB) into the Zn-MOF framework using the same method. Internal Filter Effect (IFE) quenches red fluorescence and Fluorescence Resonance Energy Transfer (FRET) enhances blue fluorescence, enabling high sensitivity and visual detection of DQ. The sensor has a low detection limit of 10.50 nM and is linear over the 0–70.00 μM concentration range. Compared to Zn-MOF (detection limit of 16.90 nM), the introduction of RhB significantly improved the precision and sensitivity of DQ detection. The combination of a smartphone and RGB analysis enables fast and accurate quantitative analysis of DQ in tap water and apple samples. The sensor platform has the advantages of convenience, intelligent real-time detection, etc. It has a wide prospect of practical application and consolidates a solid foundation for food safety control.

Synthesis of fluorometric carbon nano dots(CNDs) for selective sensing of biologically important Fe3+ and Cu2+ metal ions and evaluating their antioxidant capacity.

In this research, CNDs were prepared by a green and cost effective method using Cinnamomum Tamala (bay leaf) as carbon sources. TEM, UV, FTIR, ZETA Potential, PL and Fluorescence methods were used to characterize the produced CNDs and the average particle size is 3.42nm. This research was conducted on the development of fluorescent sensors for various metal ions, including Fe3+, Cu2+, Zn2+, Ni2+, Pb2+, Cr3+, Mg2+, Na+ 1 and Cd2+. The CNDs demonstrated selective sensing of biologically important Fe+ 3 and Cu+ 2 metal ions. The CNDs antioxidant assay was tasked with DPPH• radical scavenging properties. CNDs made from Cinnamomum Tamala had the highest DPPH free radical scavenging activity at 100mg/L (42.06%) with the IC50 of 130.68mg/L. The outcome implies that Indian spices are among the best materials for optical metal ion detection and sensing, and they also have therapeutic benefits.

Reaction Time Induced a Two-Step Dissolution and Recrystallization Structural Transformation with Three Eu Metal-Organic Frameworks: Crystal Structures and Multiresponsive Fluorescence Detection.

Under solvothermal conditions, three 3D lanthanide metal-organic frameworks (Ln-MOFs): [Eu(H2DHTA)1.5(DMF)2]·DMF (1), [Eu(H2DHTA)0.5(DHTA)0.5(DMF)(H2O)]·2H2O (2), and Eu(HCOO)3 (3) (H4DHTA = 2,5-dihydroxyterephthalic acid) have been synthesized by different reaction times. Interestingly, induced by reaction time, compounds 1-3 underwent a two-step dissolution and recrystallization structural transformation (DRST) reaction. Investigations on the DRST processes were carried out, and the transformation pathway was deduced, which was verified by XRD analyses. Notably, compound 2 demonstrates pronounced luminescence as well as high stability in water and other organic solvents. The fluorescent detection of furan antibiotics can serve as turn-off effects, and glutamic acid (Glu), aspartic acid (Asp), and riboflavin (VB2) can serve as the turn-on effect. To explain the enhancing and quenching mechanisms, XRD, UV-visible absorption spectroscopy, electrochemistry, IR spectra, theoretical calculation, fluorescence lifetimes, and XPS were discussed. Additionally, MOF-coated test strips were utilized to detect these analytes, exhibiting excellent agreement with fluorescence spectroscopy. This work provides an example for more effective designs to employ Ln-MOFs as multiresponsive fluorescent sensors for detection of environmental pollutants in aqueous solution.

Simultaneous detection of CaMV35S and NOS using fluorescence sensors with dual-emission silver nanoclusters and catalytic hairpin amplification strategy.

Adual-emission fluorescent biosensing method was developed for simultaneous determinationof CaMV35S and NOS in genetically modified(GM) plants. Two designed hairpin DNA (H1, H2) sequences were used as templates to synthesize H1-AgNCs (λex = 570nm, λem = 625nm) and H2-AgNCs (λex = 470nm, λem = 555nm). By using H1-AgNCs and H2-AgNCs as dual-signal tags, combined with signal amplification strategy of magnetic separation to reduce background signal and an enzyme-free catalytic hairpin assembly (CHA) signal amplification strategy, a novel multi-target fluorescent biosensor was fabricated to detect multiple targets based on FRET between signal tags (donors) and magnetic Fe3O4 modified graphene oxide (Fe3O4@GO, acceptors). In the presence of the target NOS and CaMV35S, the hairpin structures of H1 and H2 can be opened respectively, and the exposed sequences will hybridize with the G-rich hairpin sequences HP1 and HP2 respectively, displacing the target sequences to participate in the next round of CHA cycle. Meanwhile, H1-HP1 and H2-HP2 double-stranded DNA sequences (dsDNA) were formed, resulting in the desorption of dsDNA from the surface of Fe3O4@GO due to weak π-π interaction between dsDNA and Fe3O4@GO and leading to the fluorescence recovery of AgNCs. Under optimal conditions, the linear ranges of this fluorescence sensor were 5 ~ 300nmol L-1 for NOS and 5 ~ 200nmol L-1 CaMV35S, and the LODs were 0.14nmol L-1 and 0.18nmol L-1, respectively. In addition, the fluorescence sensor has good selectivity for the detection of NOS and CaMV35S in GM soybean samples, showing the potential applications in GM screening.

A Smartphone-Integrated Ratiometric Fluorescence Sensor for the Ultrasensitive and Selective Detection of 5-Heneicosylresorcinol in Whole Wheat Foods.

Precise on-site monitoring of alkylresorcinols, a vital biomarker, is crucial for verifying whole wheat foods and accurately quantifying the whole wheat content in various consumer and industrial products. Herein, for the first time, we introduce a novel ratiometric fluorescence sensor (CDs@ZIF-8/CdTe@MIP) for ultrasensitive and selective detection of alkylresorcinols. 5-Heneicosylresorcinol (C21:0 AR), the primary alkylresorcinol homologue in whole wheat grains, was selected as the target analyte. This analyte was specifically and selectively recognized by the incorporation of a molecularly imprinted polymer (MIP) layer. Within this nanoreactor, blue-emitting carbon dots embedded in zeolitic imidazolate framework-8 (CDs@ZIF-8) and orange-emitting CdTe quantum dots served as the self-calibration signal and response signal, respectively. Exploiting a photoinduced electron transfer effect between CdTe and C21:0 AR, the established fluorescence sensor exhibited remarkable sensing performance, offering wide linear responses in 0.005-1 μg·mL-1 and 1-80 μg·mL-1 concentration ranges, and achieving a low detection limit of 1.14 ng·mL-1. The proposed assay effectively detected C21:0 AR in real samples, including 8 whole wheat foods and 19 whole wheat grains, demonstrating good recoveries and relative standard deviation. Furthermore, an intelligent sensing platform was established by integrating CDs@ZIF-8/CdTe@MIP with a smartphone-assisted device, thus validating the feasibility of visual and on-site monitoring of C21:0 AR. Because of its rapid response, portability, cost-effectiveness, superior sensitivity, and high selectivity, the proposed sensor serves as a reliable method for the analysis of C21:0 AR, thus having substantial potential for on-site monitoring of whole wheat foods.

New 1,4-bis(1-imidazolyl)-2,5-dimethylbenzene ligand based Cd(II) MOF displaying pcu topology: Insights into antibiotics sensing and photocatalytic properties

In this work synthesis, spectroscopic and crystallographic characterization of a new Cd(II)-based metal-organic framework comprising 1,4-bis(1-imidazolyl)-2,5-dimethylbenzene (bdb) ligand having formula {[Cd(bdb)3]·2ClO4-}n (1) have been reported. The single crystal X-ray analysis reveals that MOF 1 shows octahedral coordination geometry and a two-fold interpenetrated pcu topology. MOF 1 have been employed as fluorescent sensor for the sensitive and selective detection of antibiotics and study suggests that 1 can be employed as an apt sensor for the detection of nitrofurazone (NFZ) antibiotic with KSV value of 2.94 × 104 M-1. Also, MOF 1 has been employed as light driven catalyst for the photodegradation of NFZ antibiotic and it photo-decomposes up to 91.79 % of NFZ in 20 min. The plausible sensing as well as photocatalytic mechanism employing which MOF 1 detects and photodecomposes NFZ, respectively have been explained with the aid of integrated experimental and theoretical calculations.

An intelligent device with double fluorescent carbon dots based on smartphone for visual and point-of-care testing of Copper(II) in water and food samples

The excessive presence of Cu2+ could be harmful to human health. Therefore, a ratiometric fluorescence sensor based on multicolor fluorescent carbon dots (CDs) was developed for Cu2+ detection. The blue and yellow carbon dots (B-CDs/Y-CDs) were synthesized by one-step hydrothermal method. After adding Cu2+, it is captured by the amino groups of B-CDs to form complexes, resulting in a strong fluorescence quenching via photoinduced electron transfer (PET). Meanwhile, the amino groups from Y-CDs also binds with Cu2+ that inhibit the internal PET thus enhancing the fluorescence of Y-CDs. The sensor has the merits in rapid, visual, and selective with a low limit of detection (LOD) at 2.29 nM. Furthermore, an intelligent device composed of portable optical detector and smartphone is constructed, which realizes the visual point-of-care testing (POCT) of Cu2+ with a LOD of 7.51 nM. The strategy provides an accessible approach for monitoring heavy metal pollution and food safety.