Fluorescence Color Change Research Articles

A Reusable Fluorescent Molecular Self-Assembly Cage for Simultaneous Detection and Recycling of Silver(I) Ion.

Although molecular self-assembled porous materials capable of ratiometric fluorescence probing and recycling of metal ions are both economically and environmentally attractive, very few current efforts have been devoted. Herein, we demonstrated a three-dimensional pure organic cage, namely 4-cage, which can serve as a fluorescent probe for simultaneous ratiometric detection and recycling of Ag+ ion. Taking advantage of the promising emission behavior of its rigidified tetraphenylethylene scaffolds and the chelating ability of its dynamically reversible imine moieties, on one hand, upon the addition of Ag+ , 4-cage undergoes coordination to form a stable but poorly soluble fluorescent complex, Ag+ @4-cage, accompanied by a fluorescence color change from bluish-green to yellowish-green. This allows us to differentiate Ag+ from other cations with high selectivity. On the other hand, upon the addition of Cl- anion, Ag+ @4-cage can be effectively converted into free 4-cage due to the competitive coordination of Cl- with Ag+ . Through this process, secondary usage of 4-cage and the recycling of Ag+ ion can be achieved.

Near-infrared fluorescent probe with large Stokes shift for specific detection of lysine

A new near-infrared (NIR) fluorescent probe CL based on coumarin- dicyanoisophorone was synthesized. Addition of Lys to probe CL solution in DMF/H2O (9:1, v/v) medium resulted in noticeable enhancement in the intensity of the fluorescence emission at 702 nm, accompanying distinct color change from yellow to pink. While addition of other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about substantial changes in both fluorescence emission and color. The detection limit was calculated to be 0.51 μM. Job’s plot test revealed that probe CL and Lys formed a complex of 1:1 stoichiometry. Probe CL showed high stability and could be used to recognize Lys in a wide pH range of 4.0–10.0. The sensing mechanism was proposed and verified by 1H NMR spectral measurement. The dual-modal fluorescence turn-on and colorimetric NIR probe with an extremely large Stokes shift of 280 nm may be utilized for highly specific and practical sensing of Lys.

Real-time intelligent detection of ethephon based on a high-throughput ratiometric fluorescent probe

Ethephon (ETH) is a common pesticide, and its overuse has resulted in a variety of health problems for humans. However, the existing ETH detection methods are tedious and time-consuming, and real-time ETH identification remains a significant difficulty. To mitigate this concern, a dual-emission ratiometric fluorescent probe Ru@ZrMOF was rationally synthesized for the detection of ETH. In the presence of ETH, the emission peak at 435 nm gradually increased, while the peak at 600 nm remained constant, accompanied by the fluorescence color change from red, pink, blue-violet to blue. The fluorescence intensity ratio (F435/F600) demonstrated two linear relations with the ETH concentration ranges at 3 − 50 μM and 50 − 500 μM, with a lowest detection limit at 1 μM. This was attributed to the formation of Zr−O−P bonds which attenuated the ligand-metal charge transfer (LMCT) process, resulting in the recovery of blue fluorescence of the ligand 2-Aminoterephthalic acid (2-APDC). To validate the practical application of the developed platform, a YOLO v5x-based WeChat applet "96 Speckles" was developed, and a 96-well plate and smartphone-embedded 3D-printed portable toolbox was designed for the real-time intelligent detection of ETH. This smart platform allows for real-time and efficient ETH analysis in various real samples including apples, pears and tomatoes.

Colorimetric Detection of Cu2+ and Ag+ Ions Using Multi-Responsive Schiff Base Chemosensor: A Versatile Approach for Environmental Monitoring.

In this study, we have synthesized a novel Schiff base-centered chemosensor, designated as SB, with the chemical name ((E)-1-(((6-methylbenzo[d]thiazol-2-yl) imino)methyl)naphthalen-2-ol). This chemosensor was structurally characterized by FT-IR, 1H NMR, UV-Vis and fluorescence spectroscopy. After structural characterization the chemosensor SB was subsequently employed for the detection of Cu2+ and Ag+, using fluorescence spectroscopy. The chemosensor SB showed excellent ability to recognize the target metal ions, leading to fluorescence enhancement and color change from yellow to yellowish orange for Cu2+ and yellow to radish for Ag+ ions. The detection capabilities of this chemosensor were impressive, showing excellent selectivity and an exceptionally low detection limit of 0.0016 µM for Cu2+ and 0.00389 µM for Ag+. Most notably, our approach enables the quantitative detection both metal ions in different water and soil samples at trace level. This achievement holds great promise for analytical applications and offers significant contributions to the field of chemical sensing and environmental protection.

Bioinspired Multistimuli-Induced Synergistic Changes in Color and Shape of Hydrogel and Actuator Based on Fluorescent Microgels.

Fluorescent hydrogels have emerged as one of the most promising candidates for developing biomimetic materials and artificial intelligence owing to their unique fluorescence and responsive properties. However, it is still challenging to fabricate hydrogel that exhibits synergistic changes in fluorescence color and shape in response to multistimulus via a simple method. Herein, blue- and orange-emitting fluorescent microgels (MGs) both are designed and synthesized with pH-, thermal-, and cationic-sensitivity via one-step polymerization, respectively. The two fluorescent MGs are incorporated into transparent doubly crosslinked microgel (DX MG) hydrogels with a preset ratio. The DX MG hydrogels can tune the fluorescent color accompanied by size variation via subjecting to external multistimulus. Thus, DX MG hydrogels can be exploited for multiresponsive fluorescent bilayer actuators. The actuators can undergo complex shape deformation and color changes. Inspired by natural organisms, an artificial morning glory with color and size changes are showcased in response to buffer solutions of different pH values. Besides, an intelligent skin hydrogel, imitating natural calotes versicolor, by assembling four layers of DX MG with different ratios of MGs, is tailored. This work serves as an inspiration for the design and fabrication of novel biomimetic smart materials with synergistic functions.

Ratiometric fluorescence determination of alkaline phosphatase activity based on carbon dots and Ce3+-crosslinked copper nanoclusters.

A new ratiometric fluorescent probe for efficient determination of ALP was developed. The probe was constructed by combining Ce3+-crosslinked copper nanoclusters (Ce3+-CuNCs) which exhibit the aggregation-induced emission (AIE) feature with carbon dots (CDs). The introduction of phosphate (Pi) induced the generation of CePO4 precipitation, resulting in significant decrease of fluorescence emission of CuNCs at 634nm. At the same time, the fluorescence of CDs at 455nm was obviously enhanced, thus generating ratiometric fluorescence response. Based on the fact that the hydrolysis of pyrophosphate (PPi) by ALP can produce Pi, the CD/Ce3+-CuNCs ratiometric probe was successfully used to determine ALP. A good linear relationship between the ratiometric value of F455/F634 and ALP concentrations ranging from 0.2 to 80 U·L- 1 was obtained, with a low detection limit of 0.1 U·L- 1. The ratiometric responses of the probe resulted in the visible fluorescence color change from orange red to blue with the increase of ALP concentration. The smartphone-based RGB recognition of the fluorescent sample images was used for ALP quantitative determination. A novel ratiometric fluorescent system based on Ce3+-CuNCs with AIE feature and CDs were constructed for efficient detection of ALP.

A low-background and wash-free signal amplification F-CRISPR biosensor for sensitive quantitative and visible qualitative detection of Salmonella Typhimurium

In traditional CRISPR-based biosensors, the cleavage-induced signal generation is insufficient because only a signals is generated at a CRISPR-induced cleavage. Herein, we developed an improved CRISPR/Cas12a-based biosensor with an enlarged signal generation which integrated the hybridization chain reaction (HCR) and low-background Förster Resonance Energy Transfer (FRET) signal output mode. The HCR with nucleic acid self-assembly capability was used as a signal carrier to load more signaling molecules. To get the best signal amplification, three different fluorescence signal output modes (fluorescence recovery, FRET and low-background FRET) generated by two fluoresceins, FAM and Cy5, were fully investigated and compared. The results indicated that the low-background FRET signal output mode with the strictest signal generation conditions yielded the highest signal-to-noise ratio (S/N) (19.17) and the most obvious fluorescence color change (from red to yellow). In optimal conditions, the proposed biosensor was successfully applied for Salmonella Typhimurium (S. Typhimurium) detection with 6 h (including 4 h for sample pre-treatment) from the initial target processing to the final detection result. The qualitative sensitivity, reliant on color changes, was 103 CFU/mL. The quantitative sensitivity, calculated by the fluorescence value, were 1.62 × 101 CFU/mL, 3.72 × 102 CFU/mL, and 8.71 × 102 CFU/mL in buffer solution, S. Typhimurium-spiked milk samples, and S.Typhimurium-spiked chicken samples, respectively. The excellent detection performance of the proposed biosensor endowed its great application potential in food and environment safety monitoring.

A novel thioketal containing fluorescent dye for mercury(II) detection via Hg2+-triggered ACQ to AIE transformation

A novel thioketal containing fluorescent dye 1OS was elaborately designed for mercury(II) determination, which not only integrated the benefits of the remarkable specificity of Hg2+-promoted deprotection reaction and the robust emission of AIEgen in aggregated state, but also provided a surprising platform for ACQ-to-AIE switching, i.e. Hg2+-triggered ACQ to AIE transformation. Once encountered Hg2+ ions, the deprotection reaction happened immediately within seconds, accompanied with a conversion of 1OS (ACQ) to 1O (AIE). Excitedly, the probe shows remarkable selectivity and specificity towards Hg2+ both in solution, aggregated and solid states with significant fluorescence color change. When added trace Hg2+ ions into 1OS solution, its PL intensity declined completely with emission color changed from bright green to darkness with LOD as 0.36 μM. Oppositely, a “turn on” signal was achieved in the aggregated state (fw = 98 %), which exhibited a dramatically enhancement of PL intensity along with fluorescent emission altered from darkness to brilliant yellow. Other common metal cations gave no interference to the probe. Meanwhile, the constructed test strip could “turn on” signify Hg2+ in water solution.

Rapid Detection of Sodium Hexametaphosphate by Visualization of Ratiometric Fluorescent Probes Based on Carbon Dots and Copper Nanoclusters

A method for ratiometric fluorescence detection of sodium hexametaphosphate based on carbon dots and copper nanoclusters was established. In this probe, aggregation-induced emission (AIEE) between Al3+ and CuNCs resulted in fluorescence enhancement accompanied by carbon dot fluorescence burst. When sodium hexametaphosphate was added, Al3+ was coordinated with sodium hexametaphosphate to release Al3+ from the surface of Cu nanoclusters to achieve Cu nanocluster fluorescence burst. The different response of the dual emission to sodium hexametaphosphate leads to a change in fluorescence color, which makes macroscopic visualization easy. With a smartphone, the fluorescence color change can be observed more clearly than with a single fluorescent nanoprobe, and the response is linearly increasing, so the nanoprobe can be applied for rapid measurements. In addition, the dual-emission nanoprobe was successfully used for beverage analysis. Accurate concentrations were obtained by constructing calibration maps using a fluorescence spectrometer and a smartphone app; recoveries ranged from 97.5% to 102.5% with a relative standard deviation of less than 3.1%. Thus, this dual-emission detection system integrated with a smartphone holds promise as a new portable method for on-site measurement of sodium hexametaphosphate.

A novel 2-(2-aminophenyl) imidazo [1,5-a] pyridine-based fluorescent probe for rapid detection of phosgene.

Phosgene is a highly concealed and highly toxic gas that seriously threatens human health and public security. Therefore, the detection of phosgene is of great significance to world security. Herein, a new type of fluorescent probe based on 2-(2-aminophenyl) imidazo [1,5-a] pyridine is reported for the rapid detection of phosgene. The probe itself only emits a faint green fluorescence, while phosgene allows it to produce a strong blue fluorescence. During the recognition process, phosgene interacts simultaneously with both amino site and imidazole moiety in the probe molecule, resulting in a four-ring-fused rigid structure with high fluorescence quantum yield. The probe not only has the characteristics of high efficiency, high sensitivity (detection limit 2.68 nM), and high selectivity, but also has remarkable spectral changes. Finally, a portable test strip is used to detect phosgene in the gas phase, and the fluorescent color change of the test strip can be easily observed. The most exciting thing is that the portable test strip with the probe PMPY-NH2 can produce a strong fluorescence response to 1 ppm of phosgene, which is far lower than the level of phosgene that seriously threatens to human health.

Dynamic multicolor luminescent anti-counterfeiting based on spiropyran-engineered gold nanoclusters

Multicolor luminescent materials with time-dependent optical responses are attractive for developing advanced anti-counterfeiting techniques, but it still remains challenging to rationally design and fabricate these emerging materials. Herein, we report the design of novel dynamic luminescent materials based on spiropyran-engineered gold nanoclusters (AuNCs) for anti-counterfeiting applications. Encapsulating fluorescent AuNCs with spiropyran-labeled bovine serum albumin enables the construction of dynamic multicolor luminescent nanoparticles (DML NPs) based on fluorescence resonance energy transfer. These AuNCs-based DML NPs exhibit photochromism and dynamic fluorescence color change from green to yellow to orange-red with the extension of UV irradiation time. Moreover, the photochromism and dynamic fluorescent behavior is highly reversible when exposed to the irradiation of visible light. By taking advantage of photochromic and time-dependent dynamic fluorescence, potential application in optical information storage, dynamic anti-counterfeiting authentication and multi-mode anti-counterfeiting are successfully demonstrated based on DML NPs-deposited polyvinyl alcohol film. This study provides a new strategy of designing novel dynamic multicolor luminescent materials with promising optical properties, which can further advance the practical application of AuNCs-based luminescent materials in the field of information encryption and anti-counterfeiting.

In Situ Generated Dye@MOF/COF Heterostructure for Fluorescence Detection of Chloroquine Phosphate and Folic Acid via Different Luminescent Channels.

Metal-organic framework (MOF) and covalent-organic framework (COF) hybrid materials can combine the unique properties of MOF and COF components, and their applications in fluorescence sensing have attracted more and more attention. Herein, ZIF-90 is grown on 3D-COF by a simple in situ growing method in which the 7-amino-4-methylcoumarin (AMC) is encapsulated in ZIF-90 to construct a fluorescent sensor. Chloroquine phosphate (CQP) can coordinate with Zn2+ to decompose the ZIF-90 and release AMC. At 365 nm excitation, the ratiometric fluorescence signal AMC/3D-COF (I430/I598) increases linearly with CQP in a linear range of 4 × 10-5 to 4 × 10-4 M in urine. Under 340 nm excitation, quantitative analysis of CQP in the serum (3 × 10-6 to 4 × 10-5 M) is based on the fluorescence intensity of Zn-CQP/3D-COF (I384/I598). In addition, AMC@ZIF-90/3D-COF (1) exhibits high anti-interference and selectivity in sensing of FA with a "turn off" mode, with a correlation range of 1 × 10-5 to 1 × 10-3 M. The fluorescence color changes triggered by CQP under different excitation conditions, and the different fluorescence responses caused by CQP make it a highly secure anticounterfeiting platform. The synthesized dye@MOF/COF hybrids not only provide a new way to integrate multiple emission to design fluorescent probes for differentiation detection but also offer ideas for the design of anticounterfeiting platforms.

Tracking photosynthetic phenology using spectral indices at the leaf and canopy scales in temperate evergreen and deciduous trees

Vegetation photosynthetic phenology is an important indicator to characterize the biological responses of terrestrial carbon cycle to climate change. Remote sensing-derived spectral indices have been used to estimate photosynthetic phenology of terrestrial ecosystems, yet there are large uncertainties due to differences in leaf structure and canopy function between evergreen and deciduous trees. In this study, we used in-situ measured meteorology, the maximum rate of leaf-level CO2 assimilation (Amax), chlorophyll fluorescence and canopy color changes in evergreen and deciduous species to evaluate and compare the abilities of spectral indices for photosynthetic phenology modeling. Seasonal variation in Amax is used as a proxy for photosynthetic phenology. Several indices were used, including the normalized difference vegetation index (NDVI), near-infrared reflectance vegetation index (NIRv), photochemical reflectance index (PRI), chlorophyll/carotenoid index (CCI), green-red vegetation index (GRVI), and green chromaticity coordinates (Gcc). We found that NIRv and PRI estimated phenological periods for Cedrus deodara and three deciduous trees all differed from Amax by less than 5 days, and all were linearly related to Amax (R2 > 0.6). CCI had less potential for Amax modeling, while NDVI had the largest error in predicting Amax. Gcc was a more accurate proxy for photosynthetic phenology than GRVI at the canopy scale. In addition, we found that the variability of different spectral indices in tracking photosynthetic phenology of evergreen and deciduous species was related to non-photochemical quenching processes. Especially for the fraction of absorbed light quenched by dynamic NPQ (ɸNPQ) and the fraction of absorbed light quenched by sustained NPQ (ɸf,D), they contribute more than 40 % to the variations of the NIRv and PRI spectral signals. Therefore, NIRv and PRI provide powerful tools for monitoring photosynthetic phenology, and future exploration of NIRv and PRI at larger spatial scales will favor the global plant phenology and carbon uptake modeling.

Rapid and dual optical CO2-responsive polydimethylsiloxane elastomer with fluorinated cyanine dye.

We found that our optically CO2-responsive polydimethylsiloxane (PDMS) elastomer rapidly and reversibly underwent both visible and fluorescent color changes in the presence of CO2 gas. Unlike conventional optically CO2-responsive polymeric materials, it functions in totally dry gaseous conditions. The visible color and fluorescence of the elastomer sheet change after only 1 min of exposure to CO2, and the sheet exhibits excellent repeatability in terms of color switching that persists for at least 20 times.

Lysosome-targeted dual-emissive carbon dots for ratiometric optical dual-readout and smartphone-assisted visual determination of Hg2+ and SO32−

Smartphone-assisted visual assay not only expands quantitative analysis but also enhance real-time on-site sensing capabilities. Herein, lysosome-targeted dual-emissive carbon dots (L-CDs) can not only recognize Hg2+ and SO32− by ratiometric fluorescence and ratiometric absorption, but also visually quantify Hg2+ and SO32− by smartphone-assisted method. With monitoring of intrinsic ratiometric fluorescent variation (I580/I468), L-CDs are developed as an effective sensing platform for ratiometric fluorescent successive identification of Hg2+ and SO32− accompanying with continuous fluorescence variation of blue, purplish pink, pink, and light yellow. With detecting of inherent ratiometric absorption change (A538/A206), L-CDs are also constructed as an efficacious sensing terrace for ratiometric absorption consecutive discrimination of Hg2+ and SO32−. More crucially, integrating continuous fluorescence color change and color recognizer APP in the smartphone, visual quantification of Hg2+ and SO32− can be accomplished on the basis of the ratio of red value and blue value (R/B) with linear ranges of 0–130 and 0–850 µM, respectively, as well as LOD of 8.4 and 12.9 nM, respectively. More interestingly, confocal fluorescent imaging of HeLa cells further verifies that L-CDs can be regarded as favorable biosensors for on-site, real-time differentiation of Hg2+ and SO32− in vitro and in vivo with ratiometric manners.

A new supramolecular fluorescent probe based on cucurbit[8]uril for visual determination of norfloxacin: Multi-color, quantitative detection, and practical applications

In recent years, the excessive use of antibiotics in agricultural by-products and aquaculture has attracted great attention due to its impact on human health and damage to ecosystems. Therefore, it is of great significance to detect antibiotics with sensitive and intuitive. In this paper, we report a novel fluorescence probe based on multiple chromaticity response for the rapid and sensitive detection of norfloxacin, in which the fluorescence probe was assembled through host–guest coordination between cucurbit[8]uril (Q[8]) and dibromoxanthen-9-one phenylpyridine cationic derivative (DBXPY), named DBXPY@Q[8]. With the addition of norfloxacin, the probe DBXPY@Q[8] provides a continuous fluorescence color change from yellow to blue, and even white fluorescence appears. In the presence of amino acids, pesticides, and other antibiotics, the probe remains unaffected in the detection of norfloxacin with a low detection limit (1.08 × 10−7 M). Interestingly, combined with smart phone RGB analysis, the probe DBXPY@Q[8] enables visual and quantitative detection of norfloxacin without any precision instrument and can be applied to the detection of norfloxacin in food and water. In contrast to traditional NOF detection methods, which are time-consuming, costly, and complex to operate, the use of fluorescent probes allows for the visual analysis and detection of NOF in water and food. It’s simple to operate, responsive, and can be monitored in real time, offering a significant improvement over conventional methods and has great application potential in field and quantitative analysis.

AIE-based ratiometric fluorescent probe for mercury ion, medium-dependent fluorescence color change and optimized sensitivity in solid state

A new AIE-based luminogen TPES, as a ratiometric fluorescence probe for mercury(II) was readily synthesized. The probe combined the advantages of the outstanding specificity of Hg2+-triggered deprotection reaction of thioketal and the brilliant emission of AIEgens in aggregated state. Once encountered aqueous Hg2+, fluorescent color of TPES in THF-H2O (fw = 98%) altered from blue to green rapidly, while other metal cations gave no interference to the probe. And the mechanism of this chemosensor was carefully verified by 1H NMR analysis, FTIR and MS spectra. As expected, TPES exhibits excellent selectivity and sensitivity towards Hg2+ in the solid state. When using filter paper as the solid medium, the fabricated test strips could signify Hg2+ ions with the LOD as 1 × 10−5 M (Hg2+ in aqueous solution), accompanied with a distinct emitting altered from blue to green. Furthermore, by changing the medium from filter paper to silica gel plate, a more significant fluorescence alteration from blue to yellow was achieved, and the LOD was further optimized to 1 × 10−6 M as discerned by naked-eye.

A wearable gloved sensor based on fluorescent Ag nanoparticles and europium complexes for visualized assessment of tetracycline in food samples.

The abuse of tetracycline antibiotics leads to accumulating residues in the human body, seriously affecting human health. Establishing a sensitive, efficient, and reliable method for qualitative and quantitative detection of tetracycline (TC) is necessary. This study integrated silver nanoclusters and europium-based materials into the same nano-detection system to construct a visual and rapid TC sensor with rich fluorescence color changes. The nanosensor has the advantages of a low detection limit (10.5nM), high detection sensitivity, fast response, and wide linear range (0-30μM), which can meet the analysis requirements of different types of food samples. In addition, portable devices based on paper and gloves were designed. Through the smartphone's chromaticity acquisition and calculation analysis application (APP), the real-time rapid visual intelligent analysis of TC in the sample can be realized, which guides the intelligent application of multicolor fluorescent nanosensors.

A ratiometric fluorescent indicator-displacement assay for on-site determination and intracellular imaging of nitroxinil

Nitroxinil (NIT) is a widely using veterinary medicine to protect cattle and sheep yet may threaten human health when ingested through food chain. Developing fluorescent analytical methods in ratiometric manners was essential for the on-site detection and in-situ monitoring of NIT but still challenging. Here, we improved the indicator-displacement assay (IDA)-based method and designed the first ratiometric fluorescent probe for NIT by using an albumin host and an Aggregation-induced emission (AIE) guest. This probe exhibited fast response (10 s), high sensitivity (limit of detection: 4.6 ppb), good selectivity (over twelve medicines) and eye-discriminable fluorescent color change (green–red) upon responding to NIT. Based on these properties, this probe enabled quantitative determination of NIT in real food samples, on-site analysis via a paper-based test strip, and fluorescence imaging of NIT in living cells.

A fluorescence and colorimetric bifunctional probe for recognition of Al3+ and Cu2+ and its applications in cells and environmental water systems

A highly sensitive bifunctional probe (1) for Al3+ and Cu2+ by the reaction of 2-hydroxyl-1-naphthalene formaldehyde with indole-3-formyl hydrazine was synthesized. In THF-H2O (v/v = 3:7) solution, 1 only shows fluorescence enhanced recognition for Al3+ in 17 common metal ions, which shows that 1 can be used as a highly selective fluorescence enhancement probe for Al3+. When the concentration of Al3+ is 20.0 µM (1.0 equivalent), the fluorescence intensity of 1 is increased by 195 times, and the detection limit of 1 for Al3+ is calculated to be 3.8 nM, which shows that 1 is fluorescence probe for Al3+ with an ultra-high sensitivity. Trace Al3+ (For example, the WHO drinking water quality standard 7.4 μM) can be clearly observed by the fluorescence test paper covering 1 through the change of fluorescence color. In addition, the vivo-detection ability of 1 is verified by detected the Al3+ in living GS cells of epinephelus coioides. Furthermore, 1 can also be used as a high selective and sensitive colorimetric probe for Cu2+. In THF-H2O (v/v = 3:7) buffer solution (pH = 7.0), the addition of Cu2+ results in a 69 nm red shift in the UV–visible absorption spectrum of 1 solution, causing the color of 1 solution to change from colorless to yellow. In addition, 1 shows a low detection limit of 39.3 nM, a fast response time, excellent recyclability and anti-interference for Cu2+. Therefore, 1 can be used for fluorescence detection of Cu2+ in environmental water systems.