Preparation of graphite-like carbon nitride nanoflake film with strong fluorescent and electrochemiluminescent activity

An electrochemiluminescence energy resonance transfer system for highly sensitive detection of brombuterol

In this work, an electrochemiluminescence resonance energy transfer (ECL-RET) system was established based on the modified graphite phase carbon nitride to detect brombuterol residues in food. The ultrasonic-assisted acidification exfoliation modification improved the conductivity and specific surface area of the graphite phase carbon nitride (g-C₃N₄). In addition, the carboxylated g-C₃N₄ nanosheets as ECL donors and the Au-Ag alloy nanoparticles as ECL acceptors could respectively directly carry antigen and antibody. Therefore, the trouble of introducing additional bridge molecules was avoided. A competitive immunoassay strategy was used for the detection of brombuterol, where brombuterol in the sample would compete with the coating antigen for the limited binding sites on antibody. The proposed ECL immunosensor for brombuterol detection exhibited high sensitivity with a wide linear range from 0.001 ng mL^-1 to 1000 ng mL^-1 and a low detection limit at 0.31 pg mL^-1. This work adopts a very simple way to design the sensor without losing its sensitivity, bringing convenience to its possible future applications.

An insect acetylcholinesterase biosensor utilizing WO3/g-C3N4 nanocomposite modified pencil graphite electrode for phosmet detection in stored grains

This study was undertaken to assess the potential of Tribolium castaneum (Red flour beetle) acetylcholinesterase (Tc-AChE) based electrochemical biosensor integrating WO₃/g-C₃N₄ nanocomposite modified Pencil graphite electrode to detect an organophosphate insecticide, Phosmet. The WO₃/g-C₃N₄ nanocomposite provides a non-toxic, biocompatible surface for binding the enzyme on the electrode surface, attributed to its large surface area, high conductivity, and low ohmic resistance. The proposed biosensor shows a very good analytical performance with LOD 3.6 nM for Phosmet and effectively determined Phosmet in wheat with a 99% recovery rate. Furthermore, molecular docking deciphers the binding interactions of Phosmet with Tc-AChE using a modified AutoDock LGA algorithm and an AMBER03 force field in YASARA. The kinetic parameters strongly suggest the high potency of inhibitor with the enzyme. This study presents an adaptable, rapid, and straightforward approach that opens ways towards real progress in developing commercial biosensors for pesticide detection.

Emerging Chemical Functionalization of g-C3N4: Covalent/Noncovalent Modifications and Applications

Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C₃N₄), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C₃N₄ is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C₃N₄ possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C₃N₄ has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C₃N₄ and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C₃N₄ chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C₃N₄ structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π-π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C₃N₄ in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.

A triple-channel sensing array for protein discrimination based on multi-photoresponsive g-C3N4

Graphitic carbon nitride (g-C₃N₄) as an outstanding photoresponsive nanomaterial has been widely used in biosensing. Other than the conventional single channel sensing mode, a triple-channel sensing array was developed for high discrimination of proteins based on the photoresponsive g-C₃N₄. Besides the photoluminescence and Rayleigh light scattering features of g-C₃N₄, we exploit the new photosensitive colorimetry of g-C₃N₄ as the third channel optical input. The triple-channel optical behavior of g-C₃N₄ can be synchronously changed after interaction with the protein, resulting in the distinct response patterns related to each specific protein. Such a triple-channel sensing array is demonstrated for highly discriminative and precise identification of nine proteins (hemoglobin, trypsin, lysozyme, cytochrome c, horseradish peroxidase, transferrin, human serum albumin, pepsin, and myoglobin) at 1 μM concentration levels with 100% accuracy. It also can discriminate proteins being present at different concentration and protein mixtures with different content ratios. The practicability of this sensor array is validated by high accuracy identification of nine proteins in human urine samples. This indicates that the array has a great potential in terms of analyzing biological fluids. Graphic abstract .

Hydrogen Evolution Reaction Monitored by Electrochemiluminescence Blinking at Single-Nanoparticle Level

Monitoring and characterization methods that provide performance tracking of hydrogen evolution reaction (HER) at the single-nanoparticle level can greatly advance our understanding of catalysts' structure and activity relationships. Electrochemiluminescence (ECL) microscopy is implemented for the first time to identify HER activities of single nanocatalysts and to provide a direction for further optimization. Here, we develop a novel ECL blinking technique at the single-nanoparticle level to directly monitor H₂ nanobubbles generated from hollow carbon nitride nanospheres (HCNSs). The ECL ON and OFF mechanisms are identified being closely related to the generation, growth, and collapse of H₂ nanobubbles. The power-law distributed durations of ON and OFF states demonstrate multiple catalytic sites with stochastic activities on a single HCNS. The power-law coefficients of ECL blinking increase with improved HER activities from modified HCNSs with other active HER catalysts. Besides, ECL blinking phenomenon provides an explanation for the low cathodic ECL efficiency of semiconductor nanomaterials.

A self-enhanced electrochemiluminescent ratiometric zearalenone immunoassay based on the use of helical carbon nanotubes

A self-enhanced electrochemiluminescent ratiometric immunoassay for zearalenone is described. A system composed of N-aminobutyl-N-ethylisoluminol (ABEI) and glutathione (GSH) produces a strong electrochemiluminescence (ECL) at an applied potential of 0.8 V, probably because of short electron transfer distance and reduced energy loss. The method also uses octahedral anatase mesocrystals (OAM) with a large specific surface facilitating immobilization of ABEI and GSH. Helical carbon nanotubes, possessing a large specific surface, superior mechanical stability, and excellent electrical conductivity which serve as a solid support, greatly enhanced the loading capacity for g-C₃N₄ nanosheets and horseradish peroxidase-labeled anti-antibody. The peroxidase accelerates the decomposition of H₂O₂ to produce reactive oxygen species (ROSs), amplifying the blue ECL of ABEI and the green ECL of g-C₃N₄. The ratiometric sandwich immunoassay (performed by the ratio of ECL intensity at - 1.3 V and 0.8 V) allows for sensitive and reliable determination of ZEN in a wide linear range from 1.0 × 10^-4 ng/mL to 10 ng/mL. The method was successfully applied to the analysis of corn hazelnut samples for ZEN. Graphical abstract Schematic presentation of a self-enhanced electrochemiluminescent ratiometric immunosensor based on octahedral anatase mesocrystals (OAM) supported ABEI-glutathione (GSH) and g-C₃N₄ functionalized helical carbon nanotubes (HCNT) for zearalenone (ZEN) determination.

Copper ion modified graphitic C3N4 nanosheets enhanced luminol-H2O2 chemiluminescence system: Toward highly selective and sensitive bioassay of H2S in human plasma

A high-efficient chemiluminescence (CL) platform for highly selective and sensitive H₂S detection was constructed on the basis of the quenching effect of S^2- on the copper ion modified graphitic carbon nitride nanosheets (Cu²⁺-g-C₃N₄ NSs) enhanced luminol-H₂O₂ system. Cu²⁺-g-C₃N₄ NSs with horseradish peroxidase-like catalytic activity were prepared and provide a great improvement for luminol-H₂O₂ system. The presence of S^2- induced the formation of CuS precipitate on g-C₃N₄ NSs surface. The precipitate can block the catalytic Cu²⁺ sites on the g-C₃N₄ NSs surface, resulting in a great CL decrease of CL system. Based on such a mechanism, a simple, highly selective and sensitive CL biosensor for H₂S detection was designed. Under the optimized conditions, luminol-H₂O₂-Cu²⁺-g-C₃N₄ NSs system gave a decrease of CL intensity with the Na₂S concentration increasing. The CL biosensor is in a linear range of 10.0 pM-50.0 nM and the detection limit for detecting Na₂S is as low as 2.0 pM. Moreover, the method here has enjoyed a successful application for determining H₂S in human plasma samples and the recovery is between 95.7% and 110.0%.

Electrochemiluminescent aptamer-sensor for alpha synuclein oligomer based on a metal-organic framework

The alpha synuclein (α-syn) oligomer is one of the biomarkers used for the early diagnosis of Parkinson's disease. In this paper, two electrochemiluminescent (ECL) biosensors with an aptamer as the recognition element for α-syn oligomer detection were prepared. A functionalized indium tin oxide (ITO) glass with metal-organic framework (MOF) materials provides an adequate sensing platform. Here the gold nanoparticles/metal organic frameworks (MOFs) composite (AuNPs@MOFs) using 3-aminopropyltrimethoxysilane as a binding agent, or to connect the MOFs onto the ITO directly via glutaraldehyde, both give a strong ECL emission for luminol, even under weak alkaline conditions. Thereafter, the thiolated or carboxylated aptamer was coalesced onto the MOF material functionalized electrode using an Au-S bond or amide bond via the classic 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide (EDC-NHS) coupling, respectively. Thus, the ECL emission of the sensors significantly reduced after the specific binding of the α-syn oligomer to the aptamer. The good linear relationship of the ECL sensing signals upon the logarithm of the α-syn oligomer concentration were established, from 2.43 fM to 0.486 pM or 1.39 fM to 0.243 pM, and the limit of detection reached as low as 0.42 or 0.38 fM, for these two sensors. Both of the obtained sensors have the advantages of a high sensitivity, selectivity, and reproducibility and are capable of detecting the target in human serum.

Recent advances in co-reaction accelerators for sensitive electrochemiluminescence analysis

In electrochemiluminescence sensing platforms, co-reaction accelerators are specific materials used to catalyze the dissociation of co-reactants into active radicals, which can significantly boost the ECL emission of luminophores.

Gold nanoparticles decorated carbon nitride nanosheets as a coreactant regulate the conversion of the dual-potential electrochemiluminescence of Ru(bpy)32+ for Hg2+ detection

Dual-potential electrochemiluminescence of Ru(bpy)₃²⁺ for Hg²⁺ assay using Au–g-C₃N₄ NSs as on-electrode coreactant.

Facile synthesis of highly fluorescent free-standing films comprising graphitic carbon nitride (g-C3N4) nanolayers

The free-standing g-C₃N₄ films were fabricated by thermal condensation of C₂H₄N₄ at 600 °C in a low pressure of Ar atmosphere. The as-synthesized g-C₃N₄ films exhibited stable and strong photoluminescence emission centered around 455–460 nm.

Ultra-high quantum yield ultraviolet fluorescence of graphitic carbon nitride nanosheets

Graphitic carbon nitride (g-CN) nanosheets (CNNs) with an ultra-high quantum yield (80.1%) ultraviolet fluorescence (FL) were prepared. The effects of the lateral size and the polymerization temperature on the optical properties of CNNs have been studied. The ultraviolet FL was proved to have originated from the isolated melem units according to the density functional theory calculation and mass spectra. The obtained CNNs are further used as a pH probe due to the dependence of the FL signal on the pH of the solution.

Strong Electrochemiluminescence Emission from Oxidized Multiwalled Carbon Nanotubes

Carbon nanotubes (CNTs) as well-known nanomaterials are extensively studied and widely applied in various fields. Nitric acid (HNO₃ ) is often used to treat CNTs for purification purposes and preparing oxidized CNTs for various applications. However, too little attention is paid to investigating the effect of HNO₃ treatment on the optical properties of CNTs. In this work, it is observed for the first time that HNO₃ -oxidized multiwalled carbon nanotubes (ox-MWCNTs) have strong electrochemiluminescence (ECL) activity, which enables ox-MWCNTs to become new and good ECL carbon nanomaterials after carbon quantum dots (CQDs) and graphene quantum dots (GQDs). Various characterization technologies, such as transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, are used to reveal the relationship between ECL activity and surface states. The ECL behaviors of ox-MWCNTs are investigated in detail and a possible ECL mechanism is proposed. Finally, the new ECL nanomaterials of ox-MWCNTs are envisioned to have promising applications in sensitive ECL sensing and in the study of CNT-based catalysts.

A novel hybrid platform of g-C3N4 nanosheets /nucleic-acid-stabilized silver nanoclusters for sensing protein

The fabrication of nanomaterials-based sensing platform has attracted a great deal of interest due to their unique properties. Here, we report a novel hybrid platform of g-C₃N₄ nanosheets/DNA-stabilized Ag nanoclusters (CNNS/AgNCs) for sensing application. In this platform, the fluorescent AgNCs was synthesized using a pair of double-functional ssDNA sequence as a template, including the aptamer segment against thrombin and C-rich segment for AgNCs. Next, the interaction between the fluorescent Apt-AgNCs and CNNS was investigated. It is verified that DNA-stabilized AgNCs could absorb on the CNNS surface via the stronger π-π interaction to form the hybrid platform, whose fluorescence is quenched by CNNS through the photoelectron transfer effect (PET). When targets are introduced into the system, target/Apt-AgNCs complex will fall off from the CNNS surface, resulting in the fluorescence recovery. This hybrid platform can achieve the detection of biomolecule with high sensitivity and selectivity. Considering the fluorescence variability of DNA scaffold AgNCs, this hybrid platform is promising to extend to other target and even multi-target detection.

Potential-Resolved Electrochemiluminescence Nanoprobes for Visual Apoptosis Evaluation at Single-Cell Level

In this work, a potential-resolved electrochemiluminescence (ECL) method is developed and used for the apoptosis diagnosis at the single-cell level. The apoptosis of cells usually induces the decreasing expression of epidermal growth factor receptor (EGFR) and promotes phosphatidylserine (PS) eversion on the cell membrane. Here, Au@L012 and g-C₃N₄ as ECL probes are functionalized with epidermal growth factor (EGF) and peptide (PSBP) to recognize the EGFR and PS on the cell surface, respectively, showing two well-separated ECL signals during a potential scanning. Experimental results reveal that the relative ECL change of g-C₃N₄ and Au@L012 correlates with the degree of apoptosis, which provides an accurate way to investigate apoptosis without interference that solely changes EGFR or PS. With a homemade ECL microscopy, we simultaneously evaluate the EGFR and PS expression of abundant individual cells and, therefore, achieve the visualization analysis of the apoptosis rate for normal and cancer cell samples. This strategy contributes to visually studying tumor markers and pushing the application of ECL imaging for the disease diagnosis at the single-cell level.

Single-stranded DNA modified protonated graphitic carbon nitride nanosheets: A versatile ratiometric fluorescence platform for multiplex detection of various targets

Facile and cost-effective detection of multiple targets is essential for a variety of applications ranging from life sciences to environmental monitoring. Here, we report a versatile ratiometric fluorescence platform for multiple detection of various targets based on the conjugation of single-stranded DNA (ssDNA) with protonated graphitic carbon nitride nanosheets (Pg-C₃N₄ NSs). We demonstrate that intrinsic peroxidase-like activity of Pg-C₃N₄ NSs is enhanced by conjugating with ssDNA, and thus the oxidation of substrate o-phenylenediamine (OPD) is promoted in the presence of H₂O₂. The oxidation product 2,3-diaminophenazine (DAP) can deliver a new fluorescence signal at 564 nm, and concurrently quench the intrinsic fluorescence of conjugates ssDNA/Pg-C₃N₄ NSs at 443 nm upon excitation at 370 nm. The transformation of fluorescence provides us a novel strategy for ratiometric fluorescence-based analytical sensing. Taking ssDNA as the target-recognition element of the conjugates ssDNA/Pg-C₃N₄ NSs, we favorably present ratiometric fluorescence detection of various targets including heavy metal ions (Hg²⁺) and biomolecules (Aflatoxin B1 (AFB1) and adenosine triphosphate (ATP)) in real samples by varying the ssDNA sequences. The present work provides a new strategy to develop facile methods for quantitative determination of various analytes and uncovers an innovative horizon for Pg-C₃N₄ NSs-based sensing platform fabrication.

In situ sulfur-doped graphitic carbon nitride nanosheets with enhanced electrogenerated chemiluminescence used for sensitive and selective sensing of l-cysteine

In this study, in situ sulfur-doped carbon nitride nanosheets (S-g-C₃N₄ NSs) are used for the sensitive and selective sensing of l-cysteine (l-Cys) based on the competitive coordination chemistry of Cu²⁺ between l-Cys and S-g-C₃N₄ NSs.

Emerging trends in sensors based on carbon nitride materials

A new class of functional materials, carbon nitrides, has recently attracted the attention of researchers.

Construction of Acetaldehyde-Modified g-C3N4 Ultrathin Nanosheets via Ethylene Glycol-Assisted Liquid Exfoliation for Selective Fluorescence Sensing of Ag. ACS APPLIED MATERIALS & INTERFACES 2018;10:44624-44633. [PMID: 30511564 DOI: 10.1021/acsami.8b15501]

We successfully prepared acetaldehyde-modified graphitic carbon nitride (g-C₃N₄) ultrathin nanosheets (ACNNSs) by a simple ethylene glycol-assisted liquid exfoliation method. The introduction of acetaldehyde regulated the surface energy of g-C₃N₄ to better match with that of water, which improved the exfoliation efficiency. Moreover, acetaldehyde introduces defects into the g-C₃N₄ structure, which can act as excitation energy traps and cause considerable variation in the fluorescence emission. Benefiting from the stable photoluminescence emission, good water solubility, and biocompatibility, the obtained ACNNSs showed a selective fluorescent response to Ag⁺ in both aqueous solution and living cells. The strong absorption and intimate contact with Ag⁺ and its appropriate redox potential of ACNNSs contributed to this excellent fluorescent response. A simple and environmental friendly approach was proposed to simultaneously achieve modification and exfoliation of g-C₃N₄ in aqueous solution. These findings might lead to wider applications of carbon-based nanomaterials as active materials for fluorescence detection in the environment.

Fabrication of eco-friendly nanofibrous membranes functionalized with carboxymethyl-β-cyclodextrin for efficient removal of methylene blue with good recyclability

Considering the excellent thermo-mechanical properties, chemical stability and low cost of biodegradable aliphatic-aromatic copolyesters, they are an ideal matrix when functionalized for capturing pollutants in wastewater. In this work, biodegradable poly((butylene succinate-co-terephthalate)-co-serinol terephthalate) (PBSST) copolyesters with amino side group (-NH₂) were first synthesized through copolymerization, followed by grafting carboxymethyl-β-cyclodextrin (CM-β-CD) into PBSST molecular chains via amidation reaction to prepare PBSST-g-β-CD. The corresponding nanofibrous membranes were then fabricated by electrospinning as adsorbents for efficiently removing cationic dye methyl blue (MB) from aqueous solutions. The adsorption performance of the nanofibrous membranes was fitted well with pseudo-second-order model and Langmuir isotherm model. The maximum adsorption capacity was 543.48 mg g^-1 for MB along with a removal efficiency of 98% after five regeneration cycles, indicating the high adsorption capacity and good recyclability of nanofibrous membranes. The adsorbents possess features of high adsorption capacity, eco-friendliness and easy operation, and exhibit great potential for disposing of printing-dying wastewater.

Coupled Fluorometer-Potentiostat System and Metal-Free Monochromatic Luminophores for High-Resolution Wavelength-Resolved Electrochemiluminescent Multiplex Bioassay

The sensitive simultaneous detection of multiple biomarkers is critical for the early diagnosis of diseases. Electrochemiluminescence (ECL) offers outstanding advantages, e.g., low background, over other optical sensing techniques. However, multiplexed ECL bioassay is hindered not only by the lack of generally available ECL spectrometers but also by the limited number of biocompatible monochromatic ECL luminophores for decades. Herein, we report addressing these issues by re-examination of the recent tabletop spectrofluorometer coupled potentiostat as a high-resolution ECL spectrum acquisition system and using carbon nitrides as monochromatic luminophores. A wavelength-resolved multiplexing ECL biosensor is demonstrated to simultaneously detect CA19-9 and mesothelin, two pancreatic cancer biomarkers, at a single-electrode interface. This work could initiate new opportunities for more general multiplex ECL biosensors with competitive performances.

UV-Assisted Cataluminescent Sensor for Carbon Monoxide Based on Oxygen-Functionalized g-C3N4 Nanomaterials

Cataluminescence (CTL) is one of the most important sensing-transduction principles for the real-time monitoring of atmospheric pollutants. Highly sensitive CTL-based CO detection still remains a challenge because of the relatively poor reactivity of CO and the low catalytic efficiency of the catalysts. Herein, combining ultraviolet (UV)-light activation and chemical modification of the sensing element, we have successfully established a UV-assisted CTL sensor for gaseous CO based on g-C₃N₄ with high sensitivity, selectivity, and stability. UV irradiation can efficiently activate CO molecules and induce the generation of reactive oxygen species (ROS) for CO oxidation. Furthermore, carboxyl groups greatly facilitate the chemisorption of CO on functionalized g-C₃N₄ nanomaterials, thus enhancing the CTL sensitivity. The influences of experimental conditions and the possible catalytic mechanism of CO on functionalized g-C₃N₄ have been investigated in detail. Under the optimal experimental conditions, the proposed CTL sensor presents a detection limit (3σ) toward CO of 0.008 μg mL^-1, which is much lower than the maximum allowable emission concentration of CO in atmospheric conditions (0.030 μg mL^-1). The UV-CTL system is green, sensitive, stable, and low cost, and thus it possesses great potential application in gas sensing.

Strong electrochemiluminescent interactions between carbon nitride nanosheet-reduced graphene oxide nanohybrids and folic acid, and ultrasensitive sensing for folic acid

Graphite-like carbon nitride nanosheets (g-C3N4 NSs) have recently emerged as electrochemiluminescent (ECL) nanomaterials and have attracted more and more attention due to their excellent ECL properties and promising applications in ECL sensing. However, the ECL study of g-C3N4 NSs is still in the early stages. Many studies are required to reveal the exact ECL mechanisms of g-C3N4 NSs and thus boost their sensing applications. In this paper, we have investigated ECL interactions between folic acid (FA) and a g-C3N4 NS/S2O8(2-) ECL system at a g-C3N4 NS-reduced graphene oxide (rGO) nanohybrid/glassy carbon electrode in aqueous solutions. Compared with bare g-C3N4 NSs, the nanohybrids of g-C3N4 NS-rGO give a much stable ECL emission due to the prevention of over electrochemical reduction of g-C3N4 by rGO. The stable ECL emission from the g-C3N4 NS-rGO/S2O8(2-) ECL system can be strongly quenched by FA, even in a very low concentration (pM levels). The ECL quenching mechanisms are investigated and discussed in detail. Based on the strong interactions between FA and g-C3N4 NSs, a novel, sensitive, stable and selective ECL sensor has been constructed for the detection of FA, with a wide linear response range from 0.1 to 90 nM, and an excellent detection limit (62 pM). This work not only further clarifies ECL mechanisms of g-C3N4 NSs, but also suggests a promising application of the newly emerging ECL nanomaterial.

Confined Synthesis of Carbon Nitride in a Layered Host Matrix with Unprecedented Solid-State Quantum Yield and Stability

Fluorescent carbon nanomaterials have drawn tremendous attention for their intriguing optical performances, but their employment in solid-state luminescent devices is rather limited as a result of aggregation-induced photoluminescence quenching. Herein, ultrathin carbon nitride (CN) is synthesized within the 2D confined region of layered double hydroxide (LDH) via triggering the interlayer condensation reaction of citric acid and urea. The resulting CN/LDH phosphor emits strong cyan light under UV-light irradiation with an absolute solid-state quantum yield (SSQY) of 95.9 ± 2.2%, which is, to the best of our knowledge, the highest value of carbon-based fluorescent materials ever reported. Furthermore, it exhibits a strong luminescence stability toward temperature, environmental pH, and photocorrosion. Both experimental studies and theoretical calculations reveal that the host-guest interactions between the rigid LDH matrix and interlayer carbon nitride give the predominant contribution to the unprecedented SSQY and stability. In addition, prospective applications of the CN/LDH material are demonstrated in both white light-emitting diodes and upconversion fluorescence imaging of cancer cells.