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

Electrochemiluminescent properties of carbon nitride nanoflowers and their application to the detection of melatonin in foods

Carbon nitride nanoflower materials (CNNFs) modified electrodes were prepared and used as electrochemiluminescence (ECL) sensors for the sensitive detection of melatonin (MT) in food. The luminescence intensity of CNNFs is increased by 4.6 times compared with bulk g-C3N4. In addition, the effect of dissolved oxygen on the material was eliminated, and the stability of ECL intensity of CNNFs was improved. Under the optimal experimental conditions, there is a good linear relationship between the ECL intensity ratio and logCMT in a concentration range of 2.0 × 10-11-1.0 × 10-6 mol/L, and the detection limit is 6.2 × 10-13 mol/L. This experiment has been successfully used for the detection of MT in rice, black rice, oats, apples, bananas, grapes, carrots, tomatoes, cucumbers, bread, and beers. The results are consistent with those obtained by high-performance liquid chromatography (HPLC). Therefore, this sensor is a sensitive and effective method for detecting MT content in food.

Highly selective fluorescence detection of L-selenium-methylselenocysteine in selenium-enriched Cardamine violifolia

A feasible and practicable "off-on" type of fluorescence strategy for highly selective screening of L-selenium-methylselenocysteine (L-SeMC) in selenium-enriched Cardamine violifolia was developed using g-C3N4-MnO2 nanocomposites as fluorescent probes. The g-C3N4 nanosheets can emit blue fluorescence at 320 nm excitation wavelength with a fluorescence quantum yield of 28%. When MnO2 was deposited onto g-C3N4 nanosheets, the fluorescence of the g-C3N4 nanosheets was quenched due to fluorescence resonance energy transfer (FRET). After the addition of L-SeMC, MnO2 was reduced to Mn2+, which eliminated FRET and fluorescence was restored. Based on this, a quantitative method for the determination of L-SeMC was established. The fluorescence intensity of g-C3N4-MnO2 nanocomposites showed a good linear relationship with the concentration of L-SeMC in the range of 0-45 μg mL-1, the limit of detection (LOD, 3σ/K) was 8.25 ng mL-1 and the correlation coefficient was 0.9904. Common selenium compounds such as SeO2, Na2SeO3, SeMet and SeCys caused weak fluorescence intensity, which means that the developed method is highly selective to detect L-SeMC in a series of selenium compounds. Meanwhile, the technique was evaluated by spiking L-SeMC standards in C. violifolia extraction solutions and with 9 C. violifolia extraction specimens, receiving excellent accordance with results from the commercially available atomic fluorescence spectroscopy method.

Electrochemiluminescence Enhancement and Passivation Mitigation in Carbon Nitride Semiconductors via an Integrated Ternary Heterostructure Strategy

In recent years, carbon nitride (CN) has attracted substantial attention in the field of electrochemiluminescence (ECL) applications, owing to its outstanding optical and electronic properties. However, the passivation of CN during the ECL process has contributed to reduced stability and poor repeatability. While some studies have tried to boost ECL performance by altering CN through doping and vacancies, effectively suppressing CN passivation at high potentials continues to be challenge. In this study, the built-in electric field and the Schottky barrier effect is used to expedite the transfer of electrons from CN to the molybdenum disulfide (MoS2) conduction band. This transfer deterred excessive electron injection into the CN band, thus mitigating its electrochemical degradation. Moreover, by introducing nickel nanoparticles (Ni NPs) as catalytic active sites, it is facilitated that the decomposition of potassium persulfate (K2S2O8), thereby enhancing both the stability and intensity of ECL emission. In the end, the application of ternary heterostructure as sensing platform for the cancer biomarker carcinoembryonic antigen (CEA) demonstrated high sensitivity. This research introduces a novel approach to overcome CN passivation, paving the way for more promising applications of CN in energy, environmental, and biosensing fields.

Electrochemiluminescence quenching effect of Cu2O towards flower-like ferric ion-doped g-C3N4 and its application for Cyfra21-1 immunosensing

In this article, ferric ion-doped floral graphite carbon nitride (Fe-CN-3, energy donor) was used to construct the substrate of the immunosensor and copper oxide nanocubes (Cu2O, energy acceptor) were taken as an efficient ECL quenching probe. A sandwich quench electrochemiluminescence (ECL) immunosensor for soluble cytokeratin 19 fragment (Cyfra21-1) detection was preliminarily developed based on a novel resonant energy transfer donor-acceptor pair. Fe-CN-3, a carbon nitride that combines the advantages of metal ion doping as well as morphology modulation, is used in ECL luminophores to provide more excellent ECL performance, which makes a significant contribution to the application and development of carbon nitride in the field of ECL biosensors. The regular shape, high specific surface area and excellent biocompatibility of the quencher Cu2O nanocubes facilitate the labeling of secondary antibodies and the construction of sensors. Meanwhile, as an energy acceptor, the UV absorption spectrum of Cu2O can overlap efficiently with the energy donor's ECL emission spectrum, making it prone to the occurrence of ECL-RET and thus obtaining an excellent quenching effect. These merits of the donor-acceptor pair enable the sensor to have a wide detection range of 0.00005-100 ng/mL and a low detection limit of 17.4 fg/mL (S/N = 3), which provides a new approach and theoretical basis for the clinical detection of lung cancer.

Two Birds with one Stone: Dual-mode immunoassay constructed using a novel emitter ethylene glycol-induced perylene diimide and a multifunctional ANS probe

Perylene diimide (PDI) is a readily reducible electron-deficient dye that exhibits strong photoluminescent properties, providing new opportunities for synthesizing novel electrochemiluminescence (ECL) emitters. In this study, ethylene glycol (EG) was used to induce the self-assembly of PDI supramolecules for the preparation of ultrathin EG-PDI nanosheets characterized by low crystallinity and weak stacking interaction. Notably, EG-PDI integrates luminescent and catalytic functions into one device, accelerating the interfacial electron transfer and the faster charge transfer kinetics of EG-PDI with K2S2O8. Furthermore, the narrow band gap of EG-PDI facilitates its excitation at an ultra-low potential (-0.3 V). To improve the efficiency of tumor marker analysis, multifunctional Au nanostars (ANS) was introduced both as an energy acceptor of the ECL system and a probe for the photothermal system. Dual-mode immunoassay have demonstrated superior analytical performance in detecting alpha-fetoprotein (AFP), meeting the requirements of modern clinical diagnostics in resource-limited environments.

Etching of Ag nanoparticles triggered bidirectional regulation for electrochemiluminescence ratiometric immunoassay

A highly efficient ratiometric electrochemiluminescence (ECL) immunoassay was explored by bidirectionally regulating the ECL intensity of two luminophors. The immunoassay was conducted in a split-type mode consisting of an ECL detection procedure and a sandwich immunoreaction. The ECL detection was executed using a dual-disk glassy carbon electrode modified with two potential-resolved luminophors (g-C3N4-Ag and Ru-MOF-Ag nanocomposites), and the sandwich immunoreaction using glucose oxidase (GOx)-modified SiO2 nanospheres as labels was carried out in a 96-well plate. The Ag nanoparticles (NPs) acted as bifunctional units both for triggering the resonance energy transfer (RET) with g-C3N4 and for accelerating the electron transfer rate of the Ru-MOF-Ag ECL reaction. When the H2O2 catalyzed by GOx in the 96-well plate was transferred to the dual-disk glass carbon electrode, the doped Ag NPs in the two luminophors could be etched, thus destroying the RET between C3N4 and the accelerated reaction to Ru-MOF, resulting in an opposite trend in the ECL signal outputted from the dual disks. Using the ratio of the two signals for quantification, the constructed immunosensor for a model target, i.e. myoglobin, exhibited a low detection limit of 4.7 × 10-14 g/mL. The ingenious combination of ECL ratiometry, bifunctional Ag NPs, and a split-type strategy effectively reduces environmental and human errors, offering a more precise and sensitive analysis for complex samples.

Highly Active Coreactant-Capped and Water-Stable 3D@2D Core-Shell Perovskite Quantum Dots as a Novel and Strong Self-Enhanced Electrochemiluminescence Probe

Self-enhanced electrochemiluminescence (ECL) probes have attracted more and more attention in analytical chemistry for their significant simplification of the ECL sensing operation while improving the ECL sensing sensitivity. However, the development and applications of self-enhanced ECL probes are still in their infancy and mainly suffer from the requirement of a complicated synthesis strategy and relatively low self-enhanced ECL activity. In this work, we took advantage of the recently emerged perovskite quantum dots (PQDs) with high optical quantum yields and easy surface engineering to develop a new type of PQD-based self-enhanced ECL system. The long alkyl chain (C18) diethanolamine (i.e., N-octadecyldiethanolamine (ODA)) with high ECL coreactant activity was selected as a capping ligand to synthesize an ODA-capped PQD self-enhanced ECL probe. The preparation of the coreactant-capped PQDs is as simple as for the ordinary oleylamine (OAm)-capped PQDs, and the obtained ODA-capped PQDs exhibit very strong self-enhanced ECL activity, 82.5 times higher than that of traditional OAm-capped PQDs. Furthermore, the prepared ODA-PQDs have a unique nanostructure (ODA-CsPbBr3@CsPb2Br5), with the highly emissive 3D CsPbBr3 PQD as the core and the water-stable 2D CsPb2Br5 as the shell, which allows ODA-PQDs to be very stable in aqueous media. It is envisioned that the prepared ODA-3D@2D PQDs with the easy preparation method, strong self-enhanced ECL, and excellent water stability have promising applications in ECL sensing.

Graphitic Carbon Nitride Quantum Dots (g-C3 N4 QDs): From Chemistry to Applications

Since their emergence in 2014, graphitic carbon nitride quantum dots (g-C3 N4 QDs) have attracted much interest from the scientific community due to their distinctive physicochemical features, including structural, morphological, electrochemical, and optoelectronic properties. Owing to their desirable characteristics, such as non-zero band gap, ability to be chemically functionalized or doped, possessing tunable properties, outstanding dispersibility in different media, and biocompatibility, g-C3 N4 QDs have shown promise for photocatalysis, energy devices, sensing, bioimaging, solar cells, optoelectronics, among other applications. As these fields are rapidly evolving, it is very strenuous to pinpoint the emerging challenges of the g-C3 N4 QDs development and application during the last decade, mainly due to the lack of critical reviews of the innovations in the g-C3 N4 QDs synthesis pathways and domains of application. Herein, an extensive survey is conducted on the g-C3 N4 QDs synthesis, characterization, and applications. Scenarios for the future development of g-C3 N4 QDs and their potential applications are highlighted and discussed in detail. The provided critical section suggests a myriad of opportunities for g-C3 N4 QDs, especially for their synthesis and functionalization, where a combination of eco-friendly/single step synthesis and chemical modification may be used to prepare g-C3 N4 QDs with, for example, enhanced photoluminescence and production yields.

Nickel Single-Atom Catalyst Boosts Electrochemiluminescence of Graphitic Carbon Nitride for Sensitive Detection of HBV DNA

Owing to excellent catalytic activity, single-atom catalysts (SACs) have recently attracted considerable research interest in the electrochemiluminescence (ECL) field. However, the applications of SACs are mostly limited to conventional luminol ECL system. Hence, it is necessary to explore the application of SACs in more ECL systems. In this work, nickel single-atom catalysts (Ni SACs) were successfully applied in the graphitic carbon nitride (g-C3N4)-H2O2 ECL system to significantly enhance its cathodic emission. Notably, g-C3N4 acted not only as an ECL luminophore but also as a support to anchor Ni SACs. Ni SACs can significantly activate H2O2 to produce abundant OH• radicals for enhancing the cathodic ECL emission of g-C3N4. Ni SACs-anchored g-C3N4 (Ni SACs@g-C3N4) had a 10-fold enhanced ECL intensity as compared to g-C3N4. Finally, the Ni SACs@g-C3N4-H2O2 ECL system was developed to detect hepatitis B virus (HBV) DNA by incorporating an entropy-driven DNA walking machine-assisted CRISPR-Cas12a amplification strategy. The constructed biosensor exhibited excellent detection performance for HBV DNA with a limit of detection as low as 17 aM. This work puts forward a new idea for enhancing the cathodic ECL of g-C3N4-H2O2 and expands the application of SACs in the ECL system.

Synthesis and up-to-date applications of 2D microporous g-C3N4 nanomaterials for sustainable development

In recent years, with the development of industrial technology and the increase of people's environmental awareness, the research on sustainable materials and their applications has become a hot topic. Among two-dimensional (2D) materials that have been selected for sustainable research, graphitic phase carbon nitride (g-C3N4) has become a hot research topic because of its many outstanding advantages such as simple preparation, good electrochemical properties, excellent photochemical properties, and better thermal stability. Nevertheless, the inherent limitations of g-C3N4 due to its relatively poor specific surface area, rapid charge recombination, limited light absorption range, and inferior dispersion in aqueous and organic media have limited its practical application. In the review, we summarize and analyze the unique structure of the 2D microporous nanomaterial g-C3N4, its synthesis method, chemical modification method, and the latest application examples in various fields in recent years, highlighting its advantages and shortcomings, with a view to providing ideas for overcoming the difficulties in its application. Furthermore, the pressing challenges faced by g-C3N4 are briefly discussed, as well as an outlook on the application prospects of g-C3N4 materials. It is expected that the review in this paper will provide more theoretical strategies for the future practical application of g-C3N4-based materials, as well as contributing to nanomaterials in sustainable applications.

Facile Synthesis of Oxidized Boron Nanosheets for Chemo- and Biosensing

As recently emerging nanomaterials, boron nanosheets (BNSs) have attracted more and more attention in various fields such as supercapacitors, photodetectors, bioimaging, and electrocatalysis due to their advantages of good biological compatibility, environmental friendliness, and good electro-optical properties. However, the study and application of BNSs in chemical and biological sensing are still in the infant stage, mainly due to the requirement of complicated, high-cost, and time-consuming preparation strategies. In this work, a new class of BNSs, namely oxidized-BNSs (i.e., ox-BNSs), were easily and rapidly synthesized by chemically treating boron powder with diluted HNO₃ in a very short time (less than 15 min). The composition, morphology, optical property, and peroxidase mimetic activity of obtained ox-BNSs were investigated in detail. The prepared ox-BNSs were several-layered nanosheets with abundant oxygen-containing groups, emitted blue fluorescence, and possessed good intrinsic peroxidase mimetic activity, based on which a sensitive and selective colorimetric sensor was developed for detection of H₂O₂ and glucose. The new easy preparation strategy and good sensing performances of the prepared ox-BNSs would greatly stimulate the study and application of BNSs in chemo- and biosensing.

Highly Efficient Wavelength-Resolved Electrochemiluminescence of Carbon Nitride Films for Ultrasensitive Multiplex MicroRNA Detection

The development of electrochemiluminescence (ECL) emitters of different colors with high ECL efficiency (Φ_ECL) is appealing yet challenging for ultrasensitive multiplexed bioassays. Herein, we report the synthesis of highly efficient polymeric carbon nitride (CN) films with fine-tuned ECL emission from blue to green (410, 450, 470, and 525 nm) using the precursor crystallization method. More importantly, naked eye-observable and significantly enhanced ECL emission was achieved, and the cathodic Φ_ECL values were ca. 112, 394, 353, and 251 times those of the aqueous Ru(bpy)₃Cl₂/K₂S₂O₈ reference. Mechanism studies showed that the density of surface-trapped electrons, the associated nonradiative decay pathways, and electron-hole recombination kinetics were crucial factors for the high Φ_ECL of CN. Based on high Φ_ECL and different colors of ECL emission, the wavelength-resolved multiplexing ECL biosensor was constructed to simultaneously detect miRNA-21 and miRNA-141 with superior low detection limits of 0.13 fM and 25.17 aM, respectively. This work provides a facile method to synthesize wavelength-resolved ECL emitters based on metal-free CN polymers with high Φ_ECL for multiplexed bioassays.

Emerging Graphitic Carbon Nitride-based Nanobiomaterials for Biological Applications

Graphitic carbon nitride (g-CN) based nanostructures are distinctive materials with unique compositional, structural, optical, and electronic properties with exceptional band structure, moderate surface area, and exceptional thermal and chemical stability. Because of these properties, g-CN based nanomaterials have shown promising applications and higher performance in the biological avenue. This review covers the state-of-the-art synthetic strategies used for the preparation of the materials, the basic structure, and a panorama of different optimization strategies leading to improved physicochemical properties responsible for the biological application. The following sections include the recent progress in the use of g-CN based nanobiomaterials for biosensors, bioimaging, photodynamic therapy, drug delivery, chemotherapy, and the antimicrobial segment. Furthermore, we have summarized the role and evaluation of biosafety and biocompatibility of the material. Finally, the unresolved issues, plausible challenges, current status, and future perspectives for the development and design of g-CN have been summarized and are expected to promote a clinical path for the medical sector and human well-being.

Afterglow Electrochemiluminescence from Nitrogen-Deficient Graphitic Carbon Nitride

Almost all current electrochemiluminescent reagents require real-time electrochemical stimulation to emit light. Here, we report a novel electrochemiluminescent reagent, nitrogen-deficient graphitic carbon nitride (CN_x), that can emit afterglow electrochemiluminescence (ECL) after cessation of electric excitation. CN_x obtained by post-thermal treatment of graphitic carbon nitride (CN) with KSCN has a cyanamide group and a nitrogen vacancy, which created defects to trap electrically injected electrons. The trapped electrons can slowly release and react with coreactants to emit light with longevity. The cathodic afterglow ECL lasts for 70 s after pulsing the CN_x nanosheet (CN_xNS-1.6)-modified glassy carbon electrode at -1.0 V for 20 s in 2.0 M PBS containing 1 mM K₂S₂O₈. The afterglow ECL mechanism is revealed by investigation of its influencing factors and ECL wavelength. The discovery of afterglow ECL may open a new doorway for new significant applications of the ECL technique and provide a deeper understanding of the structure-property relationships of CN.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Recent progress in assembly strategies of nanomaterials-based ultrasensitive electrochemiluminescence biosensors for food safety and disease diagnosis

The Electrochemiluminescence (ECL)-based biosensors have received considerable attention in food contaminants and disease diagnosis, due to their fascinating advantages such as low cost, fast analysis speed, wide linear range, high sensitivity, and excellent anti-interference ability. Meanwhile, with the vigorous development and improvement of nanotechnology, biosensor assembly strategies tend to diversify and be multifunctional. This review focuses on the representative ECL biosensors in food safety and disease diagnosis reported by our research group and other research groups based on nanomaterials assembly strategies in recent years. According to the different roles of nanomaterials played in the constitution of ECL biosensors, nanomaterials would be divided into the following two categories to be summarized: (1) Nanomaterials for signal amplification. (2) Nanomaterials as ECL emitters. Finally, this review prospects the perspectives on the future development direction of ECL biosensor in food safety and disease diagnosis.

Controlled Synthesis of Nitro-Terminated Oligothiophene/Crystallinity-Improved g-C3N4 Heterojunctions for Enhanced Visible-Light Catalytic H2 Production

It is highly desired to explore closely contacted polymer semiconductor/g-C₃N₄ heterojunction photocatalysts with promoted photogenerated-carrier separation and extended visible-light response for efficient visible-light-driven H₂ production. Here, we first synthesized the nitro-terminated oligothiophene (OTh) by the controlled copolymerization of thiophene and 2-nitrothiophene monomers, then constructed the nitro-terminated oligothiophene/crystallinity-improved g-C₃N₄ (OTh/g-C₃N₄) heterojunctions by a grinding-induced combination strategy. The ratio-optimized 20OTh₅/g-C₃N₄ shows highly efficient H₂ production activity up to 3.63 mmol h^-1 g^-1 under visible-light irradiation, with ∼25.9-time enhancement compared to that of g-C₃N₄. As verified by time-resolved photoluminescence spectra, surface photovoltage spectra, and the fluorescence spectra related to •OH amounts, the improved photocatalytic activity is due to the promoted photogenerated-carrier transfer and separation in the heterojunctions and the expanded visible-light response. It is also confirmed that the controlled OTh chain length, improved g-C₃N₄ crystallinity, and tight interface contact dependent on the hydrogen bonds and N···S interactions between OTh and g-C₃N₄ are reasonable for enhanced photogenerated-carrier separation with the electron transfer from OTh to g-C₃N₄. This work illustrates a feasible strategy to construct efficient polymer semiconductor/g-C₃N₄ heterojunction photocatalysts for solar-light-driven H₂ production.

A Targeted Review of Current Progress, Challenges and Future Perspective of g-C3 N4 based Hybrid Photocatalyst Toward Multidimensional Applications

The increasing demand for searching highly efficient and robust technologies in the context of sustainable energy production totally rely onto the cost-effective energy efficient production technologies. Solar power technology in this regard will perceived to be extensively employed in a variety of ways in the future ahead, in terms of the combustion of petroleum-based pollutants, CO₂ reduction, heterogeneous photocatalysis, as well as the formation of unlimited and sustainable hydrogen gas production. Semiconductor-based photocatalysis is regarded as potentially sustainable solution in this context. g-C₃ N₄ is classified as non-metallic semiconductor to overcome this energy demand and enviromental challenges, because of its superior electronic configuration, which has a median band energy of around 2.7 eV, strong photocatalytic stability, and higher light performance. The photocatalytic performance of g-C₃ N₄ is perceived to be inadequate, owing to its small surface area along with high rate of charge recombination. However, various synthetic strategies were applied in order to incorporate g-C₃ N₄ with different guest materials to increase photocatalytic performance. After these fabrication approaches, the photocatalytic activity was enhanced owing to generation of photoinduced electrons and holes, by improving light absorption ability, and boosting surface area, which provides more space for photocatalytic reaction. In this review, various metals, non-metals, metals oxide, sulfides, and ferrites have been integrated with g-C₃ N₄ to form mono, bimetallic, heterojunction, Z-scheme, and S-scheme-based materials for boosting performance. Also, different varieties of g-C₃ N₄ were utilized for different aspects of photocatalytic application i. e., water reduction, water oxidation, CO₂ reduction, and photodegradation of dye pollutants, etc. As a consequence, we have assembled a summary of the latest g-C₃ N₄ based materials, their uses in solar energy adaption, and proper management of the environment. This research will further well explain the detail of the mechanism of all these photocatalytic processes for the next steps, as well as the age number of new insights in order to overcome the current challenges.

Highly Electrochemiluminescent Cs4PbBr6@CsPbBr3 Perovskite Nanoacanthospheres and Their Application for Sensing Bisphenol A

Perovskite quantum dots (PQDs) as recently emerging electrochemiluminescence (ECL) luminophores have been paid much attention due to their good ECL activity, narrow ECL spectra, and easy preparation. However, the PQDs used for ECL sensing were mainly inherited from those PQDs prepared as strong fluorescence (FL) luminophores, which would limit the finding of highly ECL PQDs for sensing due to the very different mechanisms in generating excited-state luminophores between ECL and FL. In order to obtain highly electrochemiluminescent PQDs, for the first time we proposed to synthesize PQDs for ECL sensing rather than for FL-based analysis by optimizing the synthesis conditions. It was revealed that the volume of the precursor solution, the concentrations of CsBr and PbBr₂, the amount of capping reagents, and the synthesis reaction temperature all significantly affect the ECL activity of PQDs. On the basis of the optimization of the synthesis conditions, we obtained a new type of PQDs with high ECL activity. The new PQDs were characterized by several technologies, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive X-ray spectrum, to be the hybrids of 3D PQDs (CsPbBr₃) and 0D PQDs (Cs₄PbBr₆) with unique morphologies, i.e., Cs₄PbBr₆@CsPbBr₃ PQD nanoacanthospheres (PNAs), in which Cs₄PbBr₆ was as the core and CsPbBr₃ served as the shell. The obtained Cs₄PbBr₆@CsPbBr₃ PNAs had much higher (>4 times) ECL activity than the prevailing 3D (CsPbBr₃) PQDs. Finally, the novel Cs₄PbBr₆@CsPbBr₃ PNAs have been applied for the ECL sensing of bisphenol A (BPA), showing a promising application of the highly electrochemiluminescent PQDs in analytical chemistry.

An "off-on" electrochemiluminescence aptasensor for determination of lincomycin based on CdS QDs/carboxylated g-C3N4

A novel electrochemiluminescence (ECL) aptasensor for the determination of lincomycin (LIN) was developed based on CdS QDs/carboxylated g-C₃N₄ (CdS QDs/C-g-C₃N₄). CdS QDs/C-g-C₃N₄ served as the substrate of the aptasensor, and then CdS QDs/C-g-C₃N₄-modified electrode was incubated with aptamer DNA (Apt-DNA). When the non-specific sites of the electrode surface was blocked by 6-mercaptohexanol, the ferrocene-labeled probe (Fer-DNA) was assembled onto the electrode surface through base complementation with Apt-DNA. In the absence of LIN, the ECL signal was quenched effectively by Fer-DNA and a decreased ECL emission (off state) was acquired. On the contrary, LIN was specifically bond with Apt-DNA, and Fer-DNA was detached from the aptasensor surface because of the deformation of Apt-DNA, resulting in an effectively enhanced ECL signal (on state). The constructed ECL aptasensor exhibited a wide detection range for LIN determination (0.05 ng mL^-1-100 μg mL^-1) with a low detection limit (0.02 ng mL^-1). Importantly, the proposed ECL aptasensor showed outstanding accuracy and specificity for LIN determination, and also provided a potential strategy for other antibiotic determinations.

Two-Dimensional Graphitic Carbon Nitride (g-C3N4) Nanosheets and Their Derivatives for Diagnosis and Detection Applications

The early diagnosis of certain fatal diseases is vital for preventing severe consequences and contributes to a more effective treatment. Despite numerous conventional methods to realize this goal, employing nanobiosensors is a novel approach that provides a fast and precise detection. Recently, nanomaterials have been widely applied as biosensors with distinctive features. Graphite phase carbon nitride (g-C₃N₄) is a two-dimensional (2D) carbon-based nanostructure that has received attention in biosensing. Biocompatibility, biodegradability, semiconductivity, high photoluminescence yield, low-cost synthesis, easy production process, antimicrobial activity, and high stability are prominent properties that have rendered g-C₃N₄ a promising candidate to be used in electrochemical, optical, and other kinds of biosensors. This review presents the g-C₃N₄ unique features, synthesis methods, and g-C₃N₄-based nanomaterials. In addition, recent relevant studies on using g-C₃N₄ in biosensors in regard to improving treatment pathways are reviewed.

Graphitic carbon nitride nanosheets as promising candidates for the detection of hazardous contaminants of environmental and biological concern in aqueous matrices

Monitoring of pollutant and toxic substances is essential for cleaner environment and healthy life. Sensing of various environmental contaminants and biomolecules such as heavy metals, pharmaceutics, toxic gases, volatile organic compounds, food toxins, and pathogens is of high importance to guaranty the good health and sustainable environment to community. In recent years, graphitic carbon nitride (g-CN) has drawn a significant amount of interest as a sensor due to its large surface area and unique electrochemical properties, low bandgap energy, high thermal and chemical stability, facile synthesis, nontoxicity, and electron rich property. Furthermore, the binary and ternary nanocomposites of graphitic carbon nitride further enhance their performance as a sensor making it a cost effective, fast, and reliable gadget for the purpose, and opens a wide area of research. Numerous reviews addressing a variety of applications including photocatalytic energy conversion, photoelectrochemical detection, and hydrogen evolution of graphitic carbon nitride have been documented to date. But a lesser attention has been devoted to the mechanistic approaches towards sensing of variety of pollutants concerned with environmental and biological aspects. Herein, we present the sensing features of graphitic carbon nitride towards the detection of various analytes including toxic heavy metals, pharmaceuticals, phenolic compounds, nitroaromatic compounds, volatile organic molecules, toxic gases, and foodborne pathogens. This review will undoubtedly provide future insights for researchers working in the field of sensors, allowing them to investigate the intriguing graphitic carbon nitride material as a sensing platform that is comparable to several other nanomaterials documented in the literature. Therefore, we hope that this study could reveal some intriguing sensing properties of graphitic carbon nitride, which may help researchers better understand how it interacts with contaminants of environmental and biological concern. Graphitic carbon nitride Nanosheets as Promising Analytical Tool for Environmental and Biological Monitoring of Hazardous Substances.

Nanomaterials-enriched sensors for detection of chiral pharmaceuticals

Advancements in nanoscience and nanotechnology have opened new pathways to fabricate novel nanostructures with interesting properties that would be used for different applications. In this respect, nanostructures comprising chirality are one of the most rapidly developing research fields encompassing chemistry, physics and biology. Chirality, also known as mirror asymmetry, describes the geometrical property of an object that is not superimposable on its mirror image. This characteristic plays a crucial role because these identical forms of chiral species in pharmaceuticals or food additives may exhibit different effects on living organisms. Therefore, chiral analysis is an important field of modern chemical analysis in health-related industries that are reliant on the production of enantiomeric compounds involving pharmaceuticals. This review covers the recent advances dealing with the synthesis, design and advantageous analytical performance of nanomaterials-enriched sensors used for chiral pharmaceuticals. We conclude this review with the challenges existing in this research field and our perspectives on some potential strategies with cutting-edge approaches for the rational design of sensors for chiral pharmaceuticals. We expect this comprehensive review will inspire future studies in nanomaterials-enriched chiral sensors.

A dual-mechanism-driven electrochemiluminescence aptasensor for sensitive detection of β-amyloid peptides

β-Amyloid (Aβ) peptides can bind both Cu²⁺ and heme cofactors simultaneously to form heme-Cu²⁺-Aβ complexes, which are proposed to generate toxic partially reduced oxygen species (PROS, e.g., H₂O₂) and play a vital role in Alzheimer's disease (AD). In this paper, a competitive dual-mechanism-driven electrochemiluminescence (ECL) aptasensor integrating the synergistic enhancement and steric hindrance effect was described for Aβ detection. Specifically, graphite carbon nitride (g-C₃N₄) as an effective ECL luminescent substrate and Au nanoparticles were sequentially assembled on the Au electrode surface, and then a thiol-modified aptamer for capturing Aβ peptide was attached to the surface of the electrode through the Au-S bond. Aβ peptides were simultaneously incubated with heme and Cu²⁺, and the forming heme-Cu²⁺-Aβ complexes were subsequently anchored on the electrode through the specific recognition between the target Aβ and the aptamer. When the concentration of the target Aβ is low, the synergistic enhancement effect arising from K₂S₂O₈ with in situ generated H₂O₂ is predominant, resulting in an increase in the ECL signal of g-C₃N₄. In contrast, when the concentration of Aβ is high, the steric hindrance effect generated from heme-Cu²⁺-Aβ complexes is dominant, leading to a decrease in the ECL signal. The present sensor exhibits a favorable linear response for the detection of Aβ with a relatively low detection limit of 0.24 pM, and provides a more sensitive and selective platform for bioanalysis.

Current advances on g-C3N4-based fluorescence detection for environmental contaminants

The development of highly-sensitive fluorescence detection systems for environmental contaminants has become high priority research in the past years. Special attention has been paid to graphitic carbon nitride (g-C₃N₄)-based nanomaterials, whose unique and superior optical property makes them promising and attractive candidates for this purpose. It is necessary to enhance the current understanding of the various classes of g-C₃N₄-based fluorescence detection systems and their mechanisms, as well as find suitable approaches to improve detection performance for environmental monitoring, protection, and management. In this review, the recent progresses on g-C₃N₄-based fluorescence detections for environmental contaminants, mainly including their basic principles, mechanisms, applications, modification strategies, and conclusions, are summarized. A particular emphasis is placed on the design and development of modification strategies for g-C₃N₄ with the objective of improving detection performance. High photoluminescence quantum yield, tunable fluorescence emission characteristics, and strong adsorption capacity of g-C₃N₄ could ensure the ultrasensitivity and selectivity of fluorescence detection of environmental contaminants. Concluding perspectives on the challenges and opportunities to design highly efficient g-C₃N₄-based fluorescence detection system are intensively put forward as well.

H2O2-activated independently bidirectional regulation for a sensitive and accurate electrochemiluminescence ratiometric analysis

A novel ECL ratiometric sensor was developed based on H2O2 activated independently bidirectional regulation strategy.

Modulating Anodic Electrochemiluminescence of Graphitic Carbon Nitride by Thiophene Doping

As an attractive electrochemiluminescence (ECL) emitter, graphitic carbon nitride (g-CN) still suffers from weak anodic ECL signal. In this work, a simple molecular engineering strategy is employed to modulate anodic...

Plasmon-Enhanced Nitrogen Vacancy-Rich Carbon Nitride Electrochemiluminescence Aptasensor for Highly Sensitive Detection of miRNA

The development of biosensors for biologically important substances with ultralow content such as microRNA is of great significance. Herein, a novel surface plasmon-enhanced electrogenerated chemiluminescence-based aptasensor was developed for ultrasensitive sensing of microRNA by using nitrogen vacancy-rich carbon nitride nanosheets as effective luminophores and gold nanoparticles as plasmonic sources. The introduction of nitrogen vacancies improved the electrochemiluminescence behavior due to improved conductance and electrogenerated chemiluminescence activity. The introduction of plasmonic gold nanoparticles increased the electrochemiluminescence signal intensity by more than eightfold. The developed surface plasmon-enhanced electrogenerated chemiluminescence aptasensor exhibited good selectivity, ultrasensitivity, excellent stability, and reproducibility for the determination of microRNA-133a, with a dynamic linear range of 1 aM to 100 pM and a limit of detection about 0.87 aM. Moreover, the surface plasmon-enhanced electrogenerated chemiluminescence sensor obtained a good recovery when detecting the content of microRNA in actual serum.

Nanostructural synergism as MnNC channels in manganese (IV) oxide and fluffy g-C3N4 layered composite with exceptional catalytic capabilities

The avenues of catalysis and material science are always accepted and it is hoped that a state-of-the-art catalyst with exceptional intrinsic redox characteristics would be produced. This study focused on developing a multi-featured catalyst of high economical and commercial standards to meet the multi-directional applications of environmental and energy demands. Manganese (IV) oxide nanosheets made of fluffy-sheet-like g-C₃N₄ material were successfully synthesized by pyrolysis method. The electron-rich g-C₃N₄ network and semiconducting metallic oxides of MnO₂ nanosheets generated high electron density interfaces within the intra-composite structure. The input of active interfaces along with strong metal-to-support interactions achieved between two parallel nanosheets in MnO₂/g-C₃N₄ catalyst intrinsically boosted up its electrochemical and optical characteristics for it to be used in multi-catalytic fields. Successful trails of catalysts' performance have been made in three major catalytic fields with enhanced activities such as heterogeneous catalysis (reduction of nitrobenzene with rate constant of "K = 0.734 min^-1" and hydrogenation of styrene with "100% conversion" efficiency, including negligible change in five consecutive cycles), photocatalysis (degradation of methylene blue dye model within 20 min with negligible change in five consecutive cycles) and electrocatalysis (oxygen reduction reactions having comparable "diffusion-limited-current density" behaviour with that of the commercial Pt/C catalyst). The enhanced performance of catalysts in transforming chemicals, degrading organic pollutant species and producing sustainable energy resources from air oxygen can mitigate the challenges faced in environmental and energy crises, respectively.

Contrary Logic Pair Library, Parity Generator/Checker and Various Concatenated Logic Circuits Engineered by a Label-Free and Immobilization-Free Electrochemiluminescence Resonance Energy Transfer System

Herein, a label-free and immobilization-free electrochemiluminescence resonance energy transfer (ECL-RET) system based on graphitic carbon nitride nanosheets (GCNNs)/Ru(phen)32+ donor/acceptor pair is developed, in which the ECL-RET is regulated by regulating the diffusivity of Ru(phen)32+ molecules toward the negatively charged GCNNs through logically programmed DNA hybridization reactions. The two optical signals of GCNNs (445 nm) and Ru(phen)32+ (593 nm) show completely opposite changes through the same one-time DNA hybridization reaction. Based on this ECL-RET system, a contrary logic pair (CLP) library, a parity generator/checker system for differentiating the erroneous bits during data transmission, the parity checker to identify the even/odd natural numbers from 0 to 9, and a series of concatenated logic circuits including a six-input logic gate capable of implementing of 64 input combinations for meeting the needs of computational complexity are developed. The ECL-RET-based molecular logic system avoids the time-consuming, costly and inefficient labeling procedures and the laborious processes of immobilization, presenting great potential for building more complicated and advanced logic gates, and providing a refreshing inspiration for the construction of combinatorial logic circuits based on ECL method.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Heptazine-Based π-Conjugated Materials for Light-Emitting

On the basis of planar and relatively rigid nitrogen-rich heterocyclic system of the heptazine core, heptazine-based π-conjugated materials have aroused widespread attention over the past decade by virtue of the fascinating electronic, optical, thermal, and mechanical properties in the fields of light-emitting, photocatalysis, sensors, environmental remediation, and so forth. However, there are still several obstacles to be solved before practical applications, such as low photoluminescence quantum efficiencies for light-emitting and weak visible absorption for photocatalysis. To further enhance various properties of heptazine-based π-conjugated materials, a series of strategies have been developed, including ingenious molecular design and modification, novel synthetic, and preparation methods. In this review, the significant progress of monomeric and polymeric heptazine-based π-conjugated materials and their applications typically in light-emitting are reviewed, which is beneficial for the acceleration of practical applications of heptazine-based materials and devices.

Tune the Fluorescence and Electrochemiluminescence of Graphitic Carbon Nitride Nanosheets by Controlling the Defect States

The effects of defect states on the fluorescence (FL) and electrochemiluminescence (ECL) properties of graphite phase carbon nitride (g-CN) are systematically investigated for the first time. The g-CN nanosheets (CNNSs) obtained at different condensation temperatures are used as the study models. It can be found that all the CNNSs have two kinds of defect states, one is originated from the edge of CNNSs (labeled as CN-defect) and the other is attributed to the partially carbonization regions (labeled as C-defect). Both two kinds of defect states substantially affect the luminescent properties of CNNSs. Both the FL and ECL signals of CNNSs contain a band gap emission and two defect emissions. For the FL of CNNSs, decreasing the density of defect states can increase efficiently the FL quantum yield, while increasing the density of defect states can make the FL spectra red shift. For the ECL of CNNSs, increasing the density of CN-defect states and decreasing the density of C-defect states are greatly important to improve the ECL activity. This work provides a deep insight into the FL and ECL mechanisms of g-CN, and is of significance in tuning the FL and ECL properties of g-CN. Also, it will greatly promote the applications of CNNSs based on the FL and ECL properties.

Recent advances in electrochemiluminescence luminophores

Electrochemiluminescence (ECL) has continued to receive considerable attention in various applications, owing to its intrinsic advantages such as near-zero background response, wide dynamic range, high sensitivity, simple instrumentation, and low cost. The ECL luminophore is one of the most significant components during the light generation processes. Despite significant progress that has been made in the synthesis of new luminophores and their roles in resolving various challenges, there are few comprehensive summaries on ECL luminophores. In this review, we discuss some of the recent advances in organic, metal complexes, nanomaterials, metal oxides, and near-infrared ECL luminophores. We also emphasize their roles in tackling various challenges with illustrative examples that have been reported in the last few years. Finally, perspective and some unresolved challenges in ECL that can potentially be addressed by introducing new luminophores have also been discussed. Graphical abstract.

Rapid, ultrasensitive and non-enzyme electrochemiluminescence detection of hydrogen peroxide in food based on the ssDNA/g-C3N4 nanosheets hybrid

Hydrogen peroxide (H2O2) is usually used as a fungicide in food, it is carcinogenic, accelerates aging or inducing toxic effects such as cardiovascular disease. Herein, to meet the demand for effective and fast detection of H2O2 in food, a novel non-enzymatic electrochemiluminescence (ECL) sensor based on single-stranded DNA (ssDNA)/g-C3N4 nanosheets (NS) was established. The ssDNA/g-C3N4 NS hybrid was prepared by simple mixing g-C3N4 NS and ssDNA solution together. The prepared ssDNA/g-C3N4 NS exhibited improved peroxidase-like activity and was modified on a glassy carbon electrode to catalyze the ECL reaction of luminol-H2O2 to amplify the luminescence signal. Under the optimized conditions, the proposed sensor exhibits high sensitivity with a limit of detection (LOD) as low as 33 aM H2O2, which is much lower than the vast majority of reported methods. This method enables the reliable responding to H2O2 from the milk samples within 1 min.