Resonance Energy Transfer System Research Articles

Full-Color Dynamic Afterglow in Carbon Dot-Based Materials Regulated by Dual-Phosphorescence Resonance Energy Transfer.

Developing afterglow materials with wide-range and time-dependent colors is highly desirable but challenging. Herein, by calcinating the mixture of Rhodamine B and NH4Al(OH)2CO3, carbon dots (CDs) are generated and in situ embedded in the porous Al2O3, forming the CDs@Al2O3 composite, which exhibits time-dependent phosphorescence colors (TDPCs) from blue to green after excited by a UV lamp. Photophysical studies reveal that the blue phosphorescence with a short lifetime of 214ms originates from the carbon core state, while the green phosphorescence with a long lifetime of 915ms is associated with the surface state of CDs. Simultaneous activation of the blue and green phosphorescence with different lifetimes induces the TDPC performance. Using CDs@Al2O3 as the donor, a series of long-wavelength fluorescent dyes including Rhodamine 123, Rhodamine 6G, and Rhodamine B as the acceptors, and epoxy resin (ER) as the matrix, a dual-phosphorescence resonance energy transfer system (CDs@Al2O3-dye-ER) is constructed to rationally regulate the afterglow emission, conferring the full-color dynamic afterglow from blue to red at different decay times with high afterglow quantum yields of up to 48.2%. The fascinating afterglow properties of the CDs@Al2O3-dye-ER composites enable their successful applications in multidimensional information encryption and polychrome 3D artworks.

Aqueous Afterglow Dispersion Enabling On‐Site Ratiometric Sensing of Mercury Ions

AbstractPollution caused by heavy metal ions has become a global issue owing to their severe threat to the ecological environment and human health. However, it remains a considerable challenge to detect heavy metal ions in an efficient, selective, and high signal‐to‐noise ratio way. Herein, a portable and sensitive method is presented to probe Hg2+ by using an ultralong afterglow dispersion. The in situ encapsulation of phosphorescent carbon dots (CDs) within rigid hydrogen‐bonded organic frameworks (HOFs) leads to ultralong room temperature phosphorescence (RTP) in water with a maximum lifetime of up to 974.86 ms. Moreover, the resultant CDs@HOFs material exhibits robust and long‐term RTP emission with enhanced performance under strongly acidic or alkaline conditions, which contributes to the practical detection of Hg2+ in water. As such, an efficient and sensitive afterglow probe is facilely fabricated by integrating CDs@HOFs with a Hg2+ probe Rhodamine B derivative (RhBTh), demonstrating selective sensing of Hg2+ with greatly improved signal‐to‐noise ratios based on the triplet‐singlet Förster resonance energy transfer system (TS‐FRET). This work not only provides a reliable and versatile method for realizing robust RTP emission in water, but also expands the applications of afterglow materials in the field of optical sensing of toxic analytes.

Supramolecular Assembly of Hydrogen-Bonded Organic Frameworks with Carbon Dots: Realizing Ultralong Aqueous Room-Temperature Phosphorescence for Anticounterfeiting.

Room-temperature phosphorescent carbon dots (RTP-CDs) have received increasing attention due to their excellent optical properties and potential applications. Nevertheless, the realization of RTP-CDs in aqueous solutions remains a considerable challenge due to the water-molecule- and oxygen-induced deactivation of the triplet excitons, which leads to phosphorescence quenching. In this study, ultralong phosphorescence in water was achieved by in situ self-assembly of CDs encapsulated in a rigid hydrogen-bonded organic framework (HOF). The phosphorescence lifetime reaches an impressive 956.96 ms and exhibits long-lasting optical and structural stability in water for more than 90 days. The composite material not only has ultralong luminescence life and excellent luminescence stability but also has two-color phosphorescence emission, as well as excellent antiphotobleaching and phosphorescence stability in aqueous solution, which can solve the current problem that RTP is easily burst out by water and moisture. In addition, this study introduced a fluorescent dye based on the triplet-singlet Förster resonance energy transfer system (TS-FRET) to fine-tune the afterglow properties. This work will inspire the design of RTP systems with dual phosphor light sources and provide new strategies for the development of smart RTP materials in water.

Construction of core-triple shell upconversion nanostructures NaNdF4:Yb,Gd@NaGdF4:Yb@NaGdF4:Yb,Er@NaGdF4 with high FRET efficiency for the biochemical sensor

Upconversion nanoparticles (UCNPs) are excellent energy donors for Föster resonance energy transfer (FRET) systems. However, the lower FRET efficiency to some extend limits its application. To improve the efficiency of FRET, NaNdF4:Yb,Gd@NaGdF4:Yb@NaGdF4:Yb,Er@NaGdF4 core-triple shell (CTS) UCNPs with sensitizers in the core region and activators doped in the outer shell region were successfully prepared by changing the traditional core-shell structure design sequence. By introducing a certain amount of Gd3+ into the core nanoparticles, the crystal growth process of core nanoparticles was regulated, solving the problem of excessive and uneven size caused by high concentration of sensitizers. The insertion of Yb3+ doped transition layer weakens the negative effect between Nd3+ and activator ions, and enhances the luminescence intensity. In addition, comparing CTS UCNPs with UCNPs prepared in the traditional core-shell structure design sequence proves that CTS UCNPs have higher FRET efficiency. A biochemical sensing system was designed using this novel core-shell structure UCNPs, achieving simultaneous detection of GSH and Cd2+ with detection limits of 4.2 nM and 15.2 nM, respectively. The new core-shell structure UCNPs have broader application prospects in the field of biochemical sensing design.

Detection of urokinase based on ECL resonance energy transfer between block copolymers encapsulated iridium complex and ReS2 nanosheets

The encapsulation of water insoluble iridium complex in SiO2 nanoparticles can be used to fabricate aqueous electrochemiluminescence (ECL) sensor, however, the ECL signal is greatly reduced. It is urgent to explore more suitable method to encapsulate iridium complex and improve its ECL efficiency. Pluronic block copolymers has good biocompatibility and high load capacity, which might be used to encapsulate iridium complex. In the present work, one kind of concentric nanospheres were assembled by encapsulating iridium complexes into block copolymers using poly (styrene-co-maleicanhydride) (PSMA@Ir). Strong anodic ECL signal was obtained at PSMA@Ir nanospheres modified electrode without additional coreactant. The light absorption character of ReS2 nanosheets (ReS2NS) endowed it the ability to accept energy from PSMA@Ir ECL. As a result, a novel ECL resonance energy transfer (ECL-RET) system was constructed with PSMA@Ir as energy donor while ReS2NS as energy acceptor. Based on the above results, an ECL aptasensor was designed to detect urokinase (UPA). The ECL intensity changed linearly with the logarithm of UPA concentration in the range of 1.0 × 10−16–1.0 × 10−12 mol/L with a detection limit of 2.95 × 10−17 mol/L. The prepared sensor owned high sensitivity and selectivity, and provided new avenue for the application of water insoluble iridium complex in ECL sensing.

Supramolecular assembly activated single-molecule phosphorescence resonance energy transfer for near-infrared targeted cell imaging

Pure organic phosphorescence resonance energy transfer is a research hotspot. Herein, a single-molecule phosphorescence resonance energy transfer system with a large Stokes shift of 367 nm and near-infrared emission is constructed by guest molecule alkyl-bridged methoxy-tetraphenylethylene-phenylpyridines derivative, cucurbit[n]uril (n = 7, 8) and β-cyclodextrin modified hyaluronic acid. The high binding affinity of cucurbituril to guest molecules in various stoichiometric ratios not only regulates the topological morphology of supramolecular assembly but also induces different phosphorescence emissions. Varying from the spherical nanoparticles and nanorods for binary assemblies, three-dimensional nanoplate is obtained by the ternary co-assembly of guest with cucurbit[7]uril/cucurbit[8]uril, accompanying enhanced phosphorescence at 540 nm. Uncommonly, the secondary assembly of β-cyclodextrin modified hyaluronic acid and ternary assembly activates a single intramolecular phosphorescence resonance energy transfer process derived from phenyl pyridines unit to methoxy-tetraphenylethylene function group, enabling a near-infrared delayed fluorescence at 700 nm, which ultimately applied to mitochondrial targeted imaging for cancer cells.

Development of a FRET aptasensor based on MoS2-doped Zn-MOF as luminophore for selective detection of cadmium in aqueous solutions.

A robust "on-off" fluorescent aptasensor was developed using nanohybrids of molybdenum sulfide (MoS2) quantum dot (QD)-doped zinc metal-organic frameworks (Zn-MOF) for selective and sensitive detection of cadmium ions (Cd2+) in water. This nanohybrid (MoS2@Zn-MOF), synthesized via "bottle around the ship" methodology, exhibited a high-intensity fluorescence emission centered at 430nm (λEm) (blue) on excitation at 320nm (λEx). Further, the conjugation of this fluorophore to phosphate-modified cadmium aptamer (Cd-2-2) was achieved through carbodiimide reaction. The hybridization of prepared sensing probe (MoS2@Zn-MOF/Cd-2-2 aptamer) was done with dabcyl-conjugated complementary DNA (cDNA), acting as energy donor-acceptor pair in the fluorescence resonance energy transfer (FRET) system. This hybridizationcauses the fluorescence quenching of the nanohybrid. In the presence of Cd2+, the aptamer from the fabricated nano-biosensing probe binds to these ions, resulting in release of dabcyl-cDNA oligomer. This release of dabcyl-cDNA oligomer from the sensing probes restores the fluorescence of the nanohybrid. Under optimized conditions (sensing probe/dabcyl-cDNA ratio 1/7, pH 7.4, and temp 28°C), the sensing probe showed a fast response time of 1min. The fluorescence intensity of the nanohybrid can be utilizedto determine the concentration of Cd2+. The proposed aptasensor achieved highly sensitive detection of Cd2+ with a limit of detection (LOD) of 0.24ppb over the range of 1 × 10-9 to 1 × 10-4M along with minimal effects of interferences (e.g., Hg2+, Pb2+, and Zn2+) and good reproducibility. The designed aptasensor based on MoS2@Zn-MOF nanofluorophore offers a highly sensitive and selective approach for rapid screening of metal ions in aqueous environments.

CdSe/ZnS Quantum Rods (QRs) and Phenyl Boronic Acid BODIPY as Efficient Förster Resonance Energy Transfer (FRET) Donor-Acceptor Pair.

The reversibility of the covalent interaction between boronic acids and 1,2- or 1,3-diols has put the spotlight on this reaction for its potential in the development of sensors and for the fishing of bioactive glycoconjugates. In this work, we describe the investigation of this reaction for the reversible functionalization of the surface of CdSe/ZnS Quantum Rods (QRs). With this in mind, we have designed a turn-off Förster resonance energy transfer (FRET) system that ensures monitoring the extent of the reaction between the phenyl boronic residue at the meso position of a BODIPY probe and the solvent-exposed 1,2-diols on QRs' surface. The reversibility of the corresponding boronate ester under oxidant conditions has also been assessed, thus envisioning the potential sensing ability of this system.

Achieving Colorful Ultralong-Lifetime Room-Temperature Phosphorescence Based on Benzocarbazole Derivatives through Resonance Energy Transfer.

It is of practical significance to develop polymer-based room-temperature phosphorescence (RTP) materials with ultralong lifetime and multicolor afterglow. Herein, the benzocarbazole derivatives were selected and combined with a poly(vinyl alcohol) (PVA) matrix by a coassembly strategy. Owing to the hydrogen-bonding interactions between benzocarbazole derivatives and the PVA matrix, the nonradiative transition and the quenching of triplet excitons are effectively inhibited. Therefore, the maximum phosphorescence emission lifetime of 2202.17 ms from ABfCz-PVA and the maximum phosphorescence quantum efficiency of 34.97% from ABtCz-PVA were obtained, respectively. In addition, commercially available dye molecules were selected to construct phosphorescent resonance energy transfer (PRET) systems for energy acceptors, enabling full-color afterglow emission in blue, green, yellow, red, and even white. Based on the characteristics of prepared RTP materials, multifunctional applications to flexibility, information encryption, and erasable drawing were deeply explored.

Ultrasensitive Electrochemiluminescence Sensor Utilizing Aggregation-Induced Emission Active Probe for Accurate Arsenite Quantification in Rice Grains.

Arsenic (As) constitutes a substantial threat to global ecosystems and public health. An accurate quantification of inorganic arsenite (As(III)) in rice grains is crucial for ensuring food safety and human well-being. Herein, we constructed an electrochemiluminescence (ECL) biosensor utilizing aggregation-induced emission (AIE) active Pdots for the sensitive detection of As(III) in rice. We synthesized tetraphenylethylene-based AIE-active Pdots, exhibiting stable and highly efficient ECL emission in their aggregated states. Owing to the overlap of spectra, we employed an electrochemiluminescence resonance energy transfer (ECL-RET) system, with the Pdots as the donor and black hole quencher (BHQ) as the acceptor. Upon the introduction of As(III), the conformational changes of As(III)-specific aptamer could trigger the detachment of BHQ-labeled DNA aptamer from the electrode surface, leading to the recovery of the ECL signal. The target-induced "signal-on" bioassay enabled the sensitive and specific detection of As(III) with a linear range of 10 pM to 500 nM, with an ultralow limit of detection (LOD) of 5.8 pM/0.4 ppt. These values significantly surpass those of existing sensors designed for As(III) quantification in rice. Furthermore, by employing amylase hydrolysis for efficient extraction, we successfully applied our sensor to measure As(III) in actual rice samples sourced from diverse regions of China. The results obtained using our sensor were in close agreement with those derived from the reference method of HPLC-ICP-MS. This study not only presents a sensitive and reliable method for detecting arsenite but also underscores its potential applications in enhancing food safety, agriculture practices, and environmental monitoring.

Copper Nanosheet-Based Wash-Free Fluorescence Imaging of Cancer Cells.

Near-infrared fluorescence (NIRF) probes greatly facilitate in vivo imaging of various biologically important species. However, there are several significant limitations such as consuming washing steps, photobleaching, and low signal intensity. Herein, we synthesized fluorescent copper nanosheets templated with DNA scaffolds (DNS/CuNSs). We employ them and Cy5.5 of the fluorescence resonance energy transfer (FRET) system, which have a larger Stokes shift (∼12-fold) than the traditional NIRF dye Cy5.5. Based on their excellent fluorescence properties, we employ DNS/CuNSs-Cy5.5 for fluorescence probes in cancer cell imaging. Compared with the free Cy5.5 fluorescence probe, the novel fluorescence imaging probe implements wash-free imaging and exhibits enhanced anti-photobleaching ability (∼5.5-fold). Moreover, the FRET system constructed by DNS/CuNSs has a higher signal amplification ability (∼4.17-fold), which is more similar to that of Cu nanoclusters prepared with DNA nanomonomers as a template. This work provides a new idea for cancer cell MCF-7 imaging and is expected to promote the development of cancer cell fluorescence imaging.

Monitoring Hierarchical Assembly of Ring-in-Ring and Russian Doll Complexes Based on Carbon Nanoring by Förster Resonance Energy Transfer.

We presented the construction of the ring-in-ring and Russian doll complexes on the basis of triptycene-derived carbon nanoring (TP-[12]CPP), which not only acts as a host for pillar[5]arene (P5A) but also serves as an energy donor for building Förster resonance energy transfer (FRET) systems. We also demonstrated that their hierarchical assembly processes could be efficiently monitored in real time using FRET. NMR, UV-vis and fluorescence, and mass spectroscopy analyses confirmed the successful encapsulation of the guests P5A/P5A-An by TP-[12]CPP, facilitated by C-H···π and ···π interactions, resulting in the formation of a distinct ring-in-ring complex with a binding constant of Ka = 2.23 × 104 M-1. The encapsulated P5A/P5A-An can further reverse its role to be a host for binding energy acceptors to form Russian doll complexes, as evidenced by the occurrence of FRET and mass spectroscopy analyses. The apparent binding constant of the Russian doll complexes was up to 3.6 × 104 M-1, thereby suggesting an enhanced synergistic effect. Importantly, the Russian doll complexes exhibited both intriguing one-step and sequential FRET dependent on the subcomponent P5A/P5A-An during hierarchical assembly, reminiscent of the structure and energy transfer of the light-harvesting system presented in purple bacteria.

A comparative study on fluorescent performance of several heterocyclic dyes: In aqueous solution or immobilized on zirconia nanotube arrays

The solution pH values, cosolvent type, and immobilization of the fluorescent dyes affect their dispersion state and fluorescent performance significantly. Zirconia, with abundant resources, low cost and high refractive index, is a commonly used immobilization material for fluorescent dyes. In this paper, zirconia nanotube array films (ZNAF) prepared by anodic oxidation method were used as immobilization materials for common heterocyclic dyes (fluorescein, rhodamine B, acridine, acridine orange). A systematically comparative study on their fluorescent performance of aqueous solutions at different pH values with or without cosolvent sodium benzenesulfonate and of immobilization films with ZNAF as carriers was investigated. Moreover, the performances of acridine orange-rhodamine B fluorescence resonance energy transfer (FRET) system with different dispersion states were studied in detail. Results demonstrate that the solution pH values, immobilization and sodium benzenesulfonate have great influence on the performance of these fluorescent dyes, and the change rules of different fluorescent molecules are obviously different, which is closely related to their molecular structure and dispersion state. Compared with aqueous solutions, the fluorescence emission of acridine orange and rhodamine B is greatly improved by immobilization, which is 8.6 and 5.4 times higher than the original, respectively. Furthermore, energy transfer efficiency (E) and enhancement ratio of the acridine orange-rhodamine B system are significantly increased by loading it on ZNAF, with a maximum E value of 84.8% (pH = 13) and a maximum enhancement ratio of 5.27 (pH = 5).

Coreactant-free strong Ru(bpy)32+ ECL at ionic liquid modified electrode and its application in sensitive detection of glucose based on resonance energy transfer

In this work, we have realized the strong anodic ECL emission of Ru(bpy)32+ at ionic liquid (N-butylpyridinium tetrafluoroborate) modified electrode without additional coreactant. Methylene blue (MB) could accept the energy of Ru(bpy)32+ ECL to construct resonance energy transfer (ECL-RET) system, leading to the decrease of ECL signal. In the presence of glucose oxidase, hydrogen peroxide generated from the oxidation process of glucose could oxidize MB and block the ECL-RET route, resulting in the recovery of ECL signal. As a consequence, the designed sensor showed outstanding performance for “signal-on” detection of glucose in the concentration range of 10 μM to 1 mM, and the detection limit was determined as 1.75 μM. Importantly, this study revealed new roles of ILs in the fabrication of coreactant-free ECL sensing, which might open up a promising route for the potential design and implement in clinical analysis.

Im-SCC-FRET: improved single-cell-based calibration of a FRET system.

We recently developed a SCC-FRET (single-cell-based calibration of a FRET system) method to quantify spectral crosstalk correction parameters (β and δ) and system calibration parameters (G and k) of a Förster resonance energy transfer (FRET) system by imaging a single cell expressing a standard FRET plasmid with known FRET efficiency (E) and donor-acceptor concentration ratio (RC) (Liu et al., Opt. Express30, 29063 (2022)10.1364/OE.459861). Here we improved the SCC-FRET method (named as Im-SCC-FRET) to simultaneously obtain β, δ, G, k and the acceptor-to-donor extinction coefficient ratio (ε A ε D), which is a key parameter to calculate the acceptor-centric FRET efficiency (EA), of a FRET system when the range of β and δ values is set as 0-1. In Im-SCC-FRET, the target function is changed from the sum of absolute values to the sum of squares according to the least squares method, and the initial value of β and δ estimated by the integral but not the maximum value spectral overlap between fluorophore and filter. Compared with SCC-FRET, the experimental results demonstrate that Im-SCC-FRET can obtain more accurate and stable results for β, δ, G, and k, and add the ratio ε A ε D, which is necessary for the FRET hybrid assay. Im-SCC-FRET reduces the complexity of experiment preparation and opens up a promising avenue for developing an intelligent FRET correction system.

A Facile Strategy for Achieving Polymeric Afterglow Materials with Wide Color‐Tunability and Persistent Near‐Infrared Luminescence

AbstractPolymer‐based room‐temperature phosphorescence (RTP) materials show promising applications in anti‐counterfeiting. To further realize multiscale and/or multimodal anti‐counterfeiting, it is highly desirable to develop polymeric afterglow materials with multiple security features. Herein, a facile strategy is presented to endow polymeric afterglow materials with ultralong lifetime, wide color‐tunability, persistent near‐infrared (NIR) luminescence, and good water solubility via constructing non‐traditional phosphorescence resonance energy transfer (PRET) and two‐step sequential resonance energy transfer systems. Specifically, the 1‐bromocarbazole derivatives with ultralong blue‐color RTP property act as the energy donor while traditional dyes with red/NIR luminescence act as the energy acceptor. By simply regulating the doping composition and concentration of these non‐traditional energy transfer systems, persistent and multicolor organic afterglow covering from the visible to NIR region is successfully realized. Notably, compared to the single‐step PRET, the two‐step sequential resonance energy transfer has the unique advantages of higher transfer efficiency of triplet excitons from the initial donor, a wider range of color‐tunability mediated by the intermediary acceptor, and enhanced delayed fluorescence efficiency of the final acceptor. Finally, these water‐soluble polymeric afterglow materials with ultralong lifetime, wide color‐tunability, and persistent NIR luminescence show great potential applications in advanced anti‐counterfeiting and information security technologies.

Synthesis of a dual-emission fluorescent probe using graphitic carbon nitride as a carrier for the rapid detection of mesosulfuron-methyl

Pesticides play an irreplaceable role in ensuring increased food production and income, but the overuse of pesticides can also pose a threat to food and environmental safety. A novel dual-emission fluorescent probe was developed for the facile and accurate detection of sulfonylurea herbicides. A Förster resonance energy transfer system, based on N-doped carbon dots (N-CDs) and thioglycolic acid-capped cadmium telluride quantum dots (TGA-CdTe QDs) as energy donor–acceptor pairs, was established using graphitic carbon nitride (g-C3N4) as a substrate and successfully applied for the micro-detection of mesosulfuron-methyl (Mes). The CDs-CdTe/C3N4 probe exhibits emission peaks at 445 and 593 nm with strong fluorescence intensity under single-wavelength excitation. Mes was shown to significantly decrease the fluorescence intensity of each emission peak via different quenching mechanisms, and the degree of quenching was proportional to Mes concentration. The linear range of fluorescence measurement was 0–90 µM, with limits of detection at 1.3 µM (445 nm) and 0.8 µM (593 nm). The dual-emission fluorescent probe exhibited excellent selectivity for Mes compared with the other eleven herbicides. The fluorescent probe has a satisfying detection performance in environmental water samples and wheat samples, and has potential application in the portable detection of pesticide residues.

Highly sensitive fluorescent probe and portable test strip based on polyacrylic acid functionalized quantum dots for rapid visual detection of malachite green

Malachite green (MG) has been banned in aquaculture by many countries due to its high carcinogenicity, high teratogenicity, and easy residue. However, it is cheap and efficient characteristics have made it difficult to eliminate in recent decades, so it is essential to develop a rapid and accurate detection method for MG. Here, a highly Sensitive fluorescent probe based on polyacrylic acid (PAA) functionalized CdSe/CdxZn1-xS quantum dots (QDs) was prepared for the determination of MG. QDs functionalized by PAA (QDs@PAA) were used as energy donors, and MG was used as energy acceptor to construct fluorescence resonance energy transfer (FRET) system. The fluorescence of QDs@PAA could be linearly quenched by MG in the range of 0.05 ⁓ 2 μM, and the detection limit was 0.011 μM. In addition, a small amount of QDs@PAA (30 μL) was printed on the solid substrate by inkjet printing technology to prepare fluorescent test strips. When the concentration of MG was 2 μM, the fluorescent test strips were quenched and the detection process could be completed within 10 s, demonstrating significant potential for rapid visual detection of MG.

Carbon Dot‐Based Fluorescence Resonance Energy Transfer (FRET) Systems for Biomedical, Sensing, and Imaging Applications

AbstractCarbon dots (CDs) emerge as a potential group of photo‐luminescent nano‐materials due to their excellent optical, electrical, and chemical properties, as well as their competence in a wide range of environmental applications. CDs have unique and appealing properties such as excellent stability, low toxicity, water solubility, and derivability. When coupled with CDs, fluorescence resonance energy transfer (FRET) results in the development of highly sensitive ratiometric fluorescence sensor probes with potential applications in bio‐imaging, metal sensing, membrane dynamics, and environmental sensing. In this review, the progress and recent developments in CDs based FRET systems utilized for various environmental applications are conferred. An in‐depth description is provided regarding the numerous donor/acceptor systems which when integrated with CDs generate efficient FRET systems. The review enables researchers to identify and develop specific systems which can be utilized to generate a FRET pair with potential physico–chemical properties that aid the development of the same for various applications.

Carbon dots/Ruthenium(III) nanocomposites for FRET fluorescence detection and removal of mercury (II) via assembling into nanofibers

The determination and removal of mercury(II) (Hg2+) are essential for human health and environmental ecosystems. Herein, an ingenious carbon dots (CDs)-based Förster resonance energy transfer (FRET) system (N, S-CDs/Ru) was fabricated employing CDs and Ru3+ units as energy-transfer doner/acceptor pairs for visual detection and efficient removal of Hg2+. The treatment of Hg2+ induced a remarkable linear enhancement of the ratiometric fluorescence (F613 nm/F478 nm) with a detection limit (LOD) of 95 nM, along with continuous fluorescence color variations from blue to red. Given that the fluorescence color recognition and processing realized the real-time and rapid quantitation of Hg2+ by paper-based smartphone sensing platform. The mechanistic study revealed that the N/S/O-rich surface of the system enabled the Hg2+-triggered self-assembly from dots to nanofibers, combing with the active FRET process. Also, the efficient removal of Hg2+ with a removal efficiency of ∼98 % and an adsorption capacity of ∼372 mg/g was obtained. Furthermore, it was found that N, S-CDs/Ru loaded commercialized SiO2 or SBA-15 could facilitate the removal of Hg2+ with a removal efficiency over 99 % and an adsorption capacity up to ∼562 mg/g. This study provides a potential strategy for environmental monitoring and remediation.