Platinum and zinc oxide modified carbon nitride electrode as non-enzymatic highly selective and reusable electrochemical diabetic sensor in human blood

Development of non-enzymatic glucose sensor is essential to reduce the cost of diabetes regular monitoring. Here, graphitic carbon nitride (g-C₃N₄) is modified with platinum and zinc oxide for non-enzymatic electrochemical glucose sensing in physiological conditions for the first time in the literature. The interactions between Pt, g-C₃N₄ and the ZnO are studied using different physicochemical characterization techniques. The Electrochemical glucose sensing at the ZnO-Pt-gC₃N₄ occurs at low applied potential of +0.20 V (vs. Ag/AgCl) with high sensitivity 3.34 μA/mM/cm² and fast response (5 s) time. This sensor exhibited a wide linear range 0.25-110 mM with lower limit of detection of 0.1 µM. The architectured sensor was evaluated in human blood, serum and urine samples. The sensor is 4 time reusable in whole blood without activity deterioration. This reusable surface helps to reduce the cost of strip.

Preparation of C3N5 nanosheets with enhanced performance in photocatalytic methylene blue (MB) degradation and H2-evolution from water splitting

Ultrathin C₃N₅ nanosheets with enhanced photocatalytic methylene blue (MB) degradation and H₂-evolution performance were prepared from thermal treatment of 3-amino-1,2,4-triazole (3-AT) and NH₄Cl followed with a protonate procedure. The characterization results revealed that the protonating process could contribute to the exfoliation of C₃N₅ with large surface area, the effective charge transfer capability and the modified band structure. The as-prepared C₃N₅ nanosheets exhibited enhanced properties in photocatalytic reactions such as MB photodegradation and H₂-evolution from water splitting. This study offered a feasible route to prepare highly-efficient two-dimensional photocatalyst, which could be applied potentially for implementation in wide range of energy generation and environmental applications.

Resistive switching characteristics of carbon nitride supported manganese oxysulfide: an evidence for the sweep dependent transformation of polarity

As part of a program to investigate the materials for resistive random access memory (ReRam) applications, a study has been conducted using embedded manganese oxysulfide (MOS) nanoparticles on the thin film of carbon nitride (CN). A high-temperature in-situ route was employed to synthesis CN-MOS composite where thiourea and manganese chloride was used as the precursor. The electrical property of the CN-MOS composite system (active layer), sandwiched between two gold electrodes, was measured under different sweeping (voltage) conditions. The device displayed different types of switching patterns, unipolar, and bipolar, by changing the sweep direction. The CN-MOS based device also exhibited good endurance and memory retention performances for the period of 104 cycles and 104 s, respectively, for both the polarities.

Tale of Two Layered Semiconductor Catalysts toward Artificial Photosynthesis

The ever-increasing reliance on nonrenewable fossil fuels due to massive urbanization and industrialization created problems such as depletion of the primary feedstock and raised the atmospheric CO₂ levels causing global warming. A smart and promising approach is artificial photosynthesis that photocatalytically valorizes CO₂ into high-value chemicals. The inexpensive layered semiconductors like g-C₃N₄ and rGO or GO have the potential to make the process practically feasible for real applications. The suitable band positions with respect to the reduction potentials coupled with the typical surface properties of these layered semiconductors play a beneficial role in photoreduction of CO₂. Additionally, the creation of heterojunction interfaces to achieve the Z-scheme by anchoring g-C₃N₄ and rGO with another semiconductor with proper band alignment and dispersing plasmonic nano metals to obtain Schottky barriers on the layered surfaces also help retarding the electron-hole recombination and boost up the catalytic efficacy. Extensive exploration happened in recent years toward artificial photosynthesis over these materials, which needs a critical compendium. Surprisingly, in spite of the recent explosion of studies on photocatalytic reduction of CO₂ over metal-free semiconductors, there is not a single review on comparing the mechanistic aspects of photoreduction of CO₂ over the layered semiconductors g-C₃N₄ and rGO. This review stands out as a unique documentation, where the mechanism of photocatalytic reduction of CO₂ over this set of materials is critically examined in the context of band and surface modifications. An overall conclusion and outlook at the end indicates the need to develop prototypes for artificial photosynthesis with these well-studied semiconducting layered materials to yield solar fuels.

A facile strategy for photocatalytic degradation of seven neonicotinoids over sulfur and oxygen co-doped carbon nitride

Mounting evidence highlights the negative impacts of neonicotinoids on non-target organisms and ecosystem, yet there are a few of methods to address the residual neonicotinoids in environment. Herein, series of sulfur and oxygen co-doped carbon nitride (SOCNx) were successfully synthesized via one-step thermal polymerization and applied in photodegradation of multi-neonicotinoids (dinotefuran, acetamiprid, clothianidin, thiacloprid, imidacloprid, nitenpyram and thiamethoxam) simultaneously for the first time. Unique tubular structure was observed at the specific doping ratio, which enhanced both mass transfer and specific surface area of graphitic carbon nitride (g-C₃N₄). The doping process changed the morphology of g-C₃N₄ materials and also affected its photocatalytic performance. The degradation rate of optimized material (SOCN₈) for nitenpyram could surpass 90% just in 30 min under visible light in aqueous matrix. The degradation for target insecticide increased maximum efficiency of 57.6% compared to bulk g-C₃N₄. Moreover, the possible mechanism of the degradation process was proposed. The results revealed that photon-induced hole (h⁺) was the primary active species during the degradation of seven investigated neonicotinoids. Moreover, the SOCN₈ showed excellent recyclability after four consecutive cycles, which implied promising applications for pesticide-contaminated water remedy.

Influence of High Temperature Synthesis on the Structure of Graphitic Carbon Nitride and Its Hydrogen Generation Ability

Graphitic carbon nitride (g-C₃N₄) was obtained by thermal polymerization of dicyandiamide, thiourea or melamine at high temperatures (550 and 600 °C), using different heating rates (2 or 10 °C min⁻¹) and synthesis times (0 or 4 h). The effects of the synthesis conditions and type of the precursor on the efficiency of g-C₃N₄ were studied. The most efficient was the synthesis from dicyandiamide, 53%, while the efficiency in the process of synthesis from melamine and thiourea were much smaller, 26% and 11%, respectively. On the basis of the results provided by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), thermogravimetric analysis (TGA), elemental analysis (EA), the best precursor and the optimum conditions of synthesis of g-C₃N₄ were identified to get the product of the most stable structure, the highest degree of ordering and condensation of structure and finally the highest photocatalytic activity. It was found that as the proton concentration decreased and the degree of condensation increased, the hydrogen yields during the photocatalytic decomposition of water–methanol solution were significantly enhanced. The generation of hydrogen was 1200 µmol g⁻¹ and the selectivity towards hydrogen of more than 98%.

Ultrasensitive detection of amoxicillin by TiO2-g-C3N4@AuNPs impedimetric aptasensor: Fabrication, optimization, and mechanism

The trace amount of antibiotics in water can be enriched in the human body through the food chain, leading to extremely harmful effects on people's health. Therefore, it is urgent to develop new methods to detect trace pollutants in various aquatic phase. An analytical method utilizing the synergistic effect between the sensing strategy and catalytic material with high electron transfer capacity can be used to detect trace antibiotics. In this paper, an ultrasensitive impedimetric aptasensor was fabricated by the synergy between functionalized materials (TiO₂-g-C₃N₄) and gold nanoparticles (Au NPs). Due to the formation of the 'Au-S' bond between the thiol-aptamer and Au NPs, amoxicillin and the aptamer can be specifically recognized on the modified glassy carbon electrode (GCE), and the impedance signal increased rapidly. Meanwhile, the Box-Behnken Design (BBD) strategy was used to reduce the random error of the experiment, so that the prepared aptasensor has the highest sensitivity to the detection of amoxicillin. Under optimized conditions, the sensor successfully achieved the detection of amoxicillin in the ultra-low detection range (0.5-3 nM) and reached the ultra-low detection limit (0.2 nM). The detection strategy has good selectivity, reproducibility, and stability, and thus has good potential to detect amoxicillin in actual wastewater.

Shallow trap state-enhanced photocatalytic hydrogen evolution over thermal-decomposed polymeric carbon nitride

We investigate the photogenerated electron kinetics of a thermal-decomposed polymeric carbon nitride (TCN) synthesized in air using femtosecond time-resolved diffuse reflectance spectroscopy. We find that the oxygen functional groups in TCN contribute to the formation of reactive shallow trap states for photogenerated electrons, leading to an enhanced activity for photocatalytic hydrogen evolution.

Recent progress on the enhancement of photocatalytic properties of BiPO4 using π-conjugated materials

Semiconductor photocatalysis is regarded as most privileged solution for energy conversion and environmental application. Recently, photocatalysis methods using bismuth-based photocatalysts, such as BiPO₄, have been extensively investigated owing to their superior efficacy regarding organic pollutant degradation and their further mineralization into CO₂ and H₂O. It is well known that BiPO₄ monoclinic phase exhibited better photocatalytic performance compared to Degussa (Evonik) P25 TiO₂ in term of ultraviolet light driven organic pollutants degradation. However, its wide band gap, poor adsorptive performance and large size make BiPO₄ less active under visible light irradiation. However, extensive research works have been conducted in the past with the aim of improving visible light driven BiPO₄ activity by constructing a series of heterostructures, mainly coupled with π-conjugated architecture (e.g., conductive polymer, dye sensitization and carbonaceous materials). However, a critical review of modified BiPO₄ systems using π-conjugated materials has not been published to date. Therefore, this current review article was designed with the aim of presenting a brief current state-of-the-art towards synthesis methods of BiPO₄ in the first section, with an especial focuses onto its crystal-microstructure, optical and photocatalytic properties. Moreover, the most relevant strategies that have been employed to improve its photocatalytic activities are then addressed as the main part of this review. Finally, the last section presents ongoing challenges and perspectives for modified BiPO₄ systems using π-conjugated materials.

Preparation of nitrogen-containing carbon using a one-step thermal polymerization method for activation of peroxymonosulfate to degrade bisphenol A

Nitrogen-containing carbon materials (NCC-x) are promising metal-free catalysts for activation of peroxymonosulfate (PMS) to treat with aqueous organic pollutants. In this study, NCC-x were synthesized via a facile thermal polymerization method using urea and terephthalaldehyde as precursors. This method was derived from the polymerization method of graphitic carbon nitride (g-C₃N₄) and the reaction between the precursors was based on Schiff base chemistry. Compared with the synthesis of g-C₃N₄ using urea as the precursor, formation of a melamine ring was inhibited and the cyano groups were produced in NCC-x during the polymerization process. The obtained NCC-x catalysts had high specific surface areas, many graphite-nitrogen active sites, and high degrees of graphitization, thus exhibiting excellent activities for the degradation of bisphenol A via PMS activation. This study introduces a convenient method to obtain a highly efficient nitrogen-containing carbon PMS activator and the results are useful for the development of bisphenol A treatment by PMS activation using carbon-containing materials.

Intimate coupling of photocatalysis and biodegradation for wastewater treatment: Mechanisms, recent advances and environmental applications

Due to the increase of emerging contaminants in water, how to use new treatment technology to make up for the defects of traditional wastewater treatment method has become one of the research hotspots at present. Intimate coupling of photocatalysis and biodegradation (ICPB) as a novel wastewater treatment method, which combines the advantages of biological treatment and photocatalytic reactions, has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology. The system mainly consists of photocatalytic materials, porous carriers and biofilm. The key principle of ICPB is to transform bio-recalcitrant pollutants into biodegradable products by photocatalysis on the surface of porous carriers. The biodegradable products were mineralized simultaneously through the biofilm inside the carriers. Because of the protection of the carriers, the microorganism can remain active even under the UV-light, the mechanical force of water flow or the attack of free radicals. ICPB breaks the traditional concept that photocatalytic reaction and biodegradation must be separated in different reactors, improves the purification capacity of sewage and saves the cost. This review summarizes the recent advances of ICPB photocatalysts, carriers and biofilm being applied, and focuses on the mechanisms and reactor configurations which is particularly novel. Furthermore, the possible ongoing researches on ICPB are also put forward. This review will provide a valuable insight into the design and application of ICPB in environment and energy field.

Cobalt-Based Multicomponent Oxygen Reduction Reaction Electrocatalysts Generated by Melamine Thermal Pyrolysis with High Performance in an Alkaline Hydrogen/Oxygen Microfuel Cell

A series of cobalt-based multicomponent electrocatalysts (Co-Cat-T) for the oxygen reduction reaction (ORR) were synthesized by thermal pyrolysis of activated carbon-supported cobalt and melamine mixture from 500 to 800 °C. Their corresponding electrocatalytic performance was systematically investigated toward ORR in an alkaline electrolyte. The electrocatalyst chemical composition and structure evolution (e.g., microstrain, crystallite size, and cell volume) were confirmed by X-ray diffraction Rietveld analyses. The material generated at 550 °C (Co-Cat-T550) showed the largest cell volume of the C₃N₄ phase with a crystallite size of 4.1 ± 0.1 nm. Independent of the heat-treatment temperature, the cobalt atom was coordinated to nitrogen moieties. The following findings: cobalt inserted in the carbon nitride framework (Co-g-C₃N₄), abundant Co-N_x and pyridinic-N species, unique encapsulated cross-tubular structure, and disordered carbon domains performed better in the ORR with Co-Cat-T550 among the obtained electrocatalysts. In addition, Co-Cat-T550 showed performance comparable to Pt/C in an alkaline hydrogen/oxygen microfuel cell platform.

Defects Engineering Leads to Enhanced Photocatalytic H2 Evolution on Graphitic Carbon Nitride-Covalent Organic Framework Nanosheet Composite

Graphitic carbon nitride nanosheet (CNS) represents an attractive candidate for solar fuel production. However, the abundant defects in CNS lead to serious charge recombination and limit the photocatalytic performance. Herein, the synthesis of a CNS-covalent organic framework (CNS-COF) nanosheet composite is presented for the first time. CNS with significantly reduced defects is first obtained by rationally tuning the thermal exfoliation conditions of bulk carbon nitride. Subsequent modification of the CNS with trace COF nanosheet through chemical imine bonding can not only passivate the surface termination of carbon nitride in the boundary region, but also establish strong electronic coupling between these two components. As a consequence, enhanced charge separation and photocatalytic activity are realized on the resulting CNS-COF nanosheet composite. Under optimum conditions, hydrogen is evolved at a rate of 46.4 mmol g^-1 h^-1 . This corresponds to an apparent quantum efficiency of 31.8% at 425 nm, which is among the best values ever reported for carbon nitride-based materials.

A novel strategy to construct a visible-light-driven Z-scheme (ZnAl-LDH with active phase/g-C3N4) heterojunction catalyst via polydopamine bridge (a similar "bridge" structure)

A novel strategy to construct a visible-light-driven Z-scheme heterojunction catalyst was employed by crosslinking ZnAl-layered double hydroxide (ZnAl-LDH) nanosheets with the active phase on carbon nitride (g-C₃N₄) substrates via a polydopamine bridge (a similar "bridge" structure). In this paper, multiple optical and electrochemical detection methods indicated that the 0.5P-LDH_500CN photocatalyst demonstrated excellent visible-light absorption properties, photo-generated electron-hole separation ability and photocatalytic activity for p-nitrophenol under visible-light (> 420 nm), etc. A Z-scheme charge transfer mechanism via PDA bridge was proposed to achieve heterojunction charge separation. This mechanism involved the recombination of photo-induced electrons directly on the ZnAl-LDH_500 valence band through the PDA channel and the holes were captured at the conduction band energy level of the g-C₃N₄. The detection of active species, including O₂-, h⁺ and OH, further proofed the Z-scheme charge transfer mechanism, which could be speculated that all active species affected the photocatalytic reaction with the order of h⁺ >OH >O₂-. Meanwhile, this work also exposed that the formation of active phase in ZnAl-LDH could synergize with PDA to promote the application of visible-light-active photocatalysts based on g-C₃N₄ materials in high-efficiency energy.

ZnO-Modified g-C3N4: A Potential Photocatalyst for Environmental Application

Solar energy-driven practices using semiconducting materials is an ideal approach toward wastewater remediation. In order to attain a superior photocatalyst, a composite of g-C3N4 and ZnO (GCN-ZnO) has been prepared by one-step thermal polymerization of urea and zinc carbonate basic dihydrate [ZnNO3]2·[Zn(OH)2]3. The GCN-ZnO0.4 sample showed an evolved morphology, increased surface area (116 m2 g-1), better visible light absorption ability, and reduced band gap in comparison to GCN-pure. The GCN-ZnO0.4 sample also showed enhanced adsorption and photocatalytic activity performance, resulting in an increased reaction rate value up to 3 times that of GCN-pure, which was attributed to the phenomenon of better separation of photogenerated charge carriers resulting because of heterojunction development among interfaces of GCN-pure and ZnO. In addition, the GCN-ZnO0.4 sample showed a decent stability for four cyclic runs and established its potential use for abatement of organic wastewater pollutants in comparison to GCN-pure.

The enhanced photodegradation of bisphenol A by TiO2/C3N4 composites

A new photocatalyst of TiO₂/C₃N₄ composite (TiO₂/g-C₃N₄) was synthesized by the hydrothermal method. The characterization showed that TiO₂/g-C₃N₄ extended absorption light range and enhanced generation efficiency of photo-induced electron. Under the simulated solar irradiation, the photodegradation rate of bisphenol A (BPA) by TiO₂/g-C₃N₄ was twice as fast as that of g-C₃N₄. Furthermore, TiO₂/g-C₃N₄ presented the good stability and excellent selectivity for BPA degradation. The high degradation rate of BPA by TiO₂/g-C₃N₄ was demonstrated to be superoxide radical (·O₂^-) and singlet oxygen (¹O₂) by radical quenching experiment, which was further evidenced by EPR, XPS, DRS and PL analysis. These findings revealed that TiO₂/g-C₃N₄ can be used as a potential photocatalyst for removing organic pollutants in actual environmental remediation.

Precursor-Engineering Coupled Microwave Molten-Salt Strategy Enhances Photocatalytic Hydrogen Evolution Performance of g-C3 N4 Nanostructures

A precursor-engineering strategy coupled with a microwave molten-salt process (PE-MWMS) is developed to synthesize graphitic carbon nitride (g-C₃ N₄ ) with an isotype triazine/heptazine-based g-C₃ N₄ heterojunction as a photocatalyst for the hydrogen evolution reaction (HER) under visible light illumination. Four hybrid precursor combinations-thiourea/melamine, thiourea/dicyandiamide, urea/melamine, and urea/dicyandiamide-are used to synthesize g-C₃ N₄ heterojunctions by the PE-MWMS process. Control experiments indicate that the precursor components and microwave treatment have a great effect on the HER performance of the g-C₃ N₄ samples. Samples synthesized with the optimal molar ratios of thiourea/melamine (2:1), thiourea/dicyandiamide (2:1), urea/melamine (3:1), and urea/dicyandiamide (3:1), exhibit the highest HER rates of 3135, 2519, 2844, and 2565 μmol g^-1  h^-1 , respectively. The amounts of heptazine and triazine units in the g-C₃ N₄ samples can be easily adjusted by changing the ratios of the hybrid precursors and play a decisive role in improving the photocatalytic HER activity. Because of the unique composition and microstructure, the efficient separation of electron-hole pairs, the broadened photo-absorption edges, and the narrowed band gaps, the as-obtained triazine/heptazine-based g-C₃ N₄ nanostructures exhibit promising activity for HER application.

Influence of C3N4 Precursors on Photoelectrochemical Behavior of TiO2/C3N4 Photoanode for Solar Water Oxidation

Photoelectrochemical water splitting is considered as a long-term solution for the ever-increasing energy demands. Various strategies have been employed to improve the traditional TiO2 photoanode. In this study, TiO2 nanorods were decorated by graphitic carbon nitride (C3N4) derived from different precursors such as thiourea, melamine, and a mixture of thiourea and melamine. Photoelectrochemical activity of TiO2/C3N4 photoanode can be modified by tuning the number of precursors used to synthesize C3N4. C3N4 derived from the mixture of melamine and thiourea in TiO2/C3N4 photoanode showed photocurrent density as high as 2.74 mA/cm2 at 1.23 V vs. RHE. C3N4 synthesized by thiourea showed particle-like morphology, while melamine and melamine with thiourea derived C3N4 yielded two dimensional (2D) nanosheets. Nanosheet-like C3N4 showed higher photoelectrochemical performance than that of particle-like nanostructures as specific surface area, and the redox ability of nanosheets are believed to be superior to particle-like nanostructures. TiO2/C3N4 displayed excellent photostability up to 20 h under continuous illumination. Thiourea plays an important role in enhancing the photoelectrochemical performance of TiO2/C3N4. This study emphasizes the fact that the improved photoelectrochemical performance can be achieved by varying the precursors of C3N4 in TiO2/C3N4 heterojunction. This is the first report to show the influence of C3N4 precursors on photoelectrochemical performance in TiO2/C3N4 systems. This would pave the way to explore different precursors influence on C3N4 with respect to the photoelectrochemical response of TiO2/C3N4 heterojunction photoanode.

A Codoped Polymeric Photocatalyst with Prolonged Carrier Lifetime and Extended Spectral Response up to 600 nm for Enhanced Hydrogen Evolution

The intrinsic properties of photocatalysts, such as electron state and energy band structure, contribute significantly to their catalytic performance. However, it is difficult to alter these properties of semiconductors by conventional modifications. To adjust the intrinsic properties while preserving long-term conjugation of the polymeric photocatalysts, a post-thermal treatment is proposed to codope P and Na into polymeric carbon nitride in this work. After codoping, the absorption of visible irradiation is strongly extended up to 639 nm. Additionally, the lifetime of charge carriers is almost tripled from 1.09 to 2.93 ns. The photocatalytic hydrogen evolution performance under visible light is improved to 2032 μmol·h^-1 g^-1 in the optimized sample, corresponding to apparent quantum efficiencies of 6.79% and 0.09% at 420 and 600 nm, respectively. The enhanced catalytic activity is ascribed to the synergistic effects of prolonged lifetime and increased charge density that resulted from lattice distortion and extended visible utilization due to the formation of subgap state. Our work provides new pathways for the modification of polymeric catalysts toward high-performance and full-spectrum photocatalysis.

Synthesis of narrow-band curled carbon nitride nanosheets with high specific surface area for hydrogen evolution from water splitting by low-temperature aqueous copolymerization to form copolymers

Carbon nitride has become a focus of photocatalytic materials research in recent years, but the low specific surface area, the bad separation efficiency of photocarriers, poor quantum efficiency, terrible photocatalytic activity hinder the development of carbon nitride in the field of photocatalysis. The preparation of carbon nitride nanosheets is one of the effective methods to improve the photocatalytic efficiency of carbon nitride, but the traditional top-down stripping process is time-consuming, complicated and expensive. Here we report a simple, cheap, non-toxic and environmentally friendly bottom-up method to prepare a curled g-C₃N₄ nanosheet (NS-C₃N₄), which is performed at low temperature and normal pressure. In the aqueous solution, melamine and cyanuric acid are copolymerized to form a copolymer. Glycerol is inserted between the molecular layers of the prepolymer by thermal diffusion. Finally, high-quality and high-yield curled g-C₃N₄ nanosheets (NS-C₃N₄) are obtained by thermal peeling and polycondensation. The NS-C₃N₄ has an highly efficient photocatalytic hydrogen production of 4061.8 μmol h⁻¹ g⁻¹, and the hydrogen evolution activity is 37.5 times that of bulk-C₃N₄ (B-C₃N₄). The specific surface area of NS-C₃N₄ is 60.962 m² g⁻¹. UV-vis absorption spectra, steady-state and time-resolved photoluminescence, and photoelectrochemical tests were used to study its photocatalytic mechanism.

Curled carbon nitride nanosheets with narrow-band gap for ultra-high hydrogen production efficiency.

Graphitic carbon nitride-based materials for photocatalytic reduction of U(vi)

This work reports the photocatalytic reduction of U(vi) using g-C₃N₄-based materials and discusses the factors affecting the photocatalytic reduction of U(vi).

Catalytic activity of porous carbon nitride regulated by polyoxometalates under visible light

A series of porous carbon nitrides modified by different polyoxometalates (POMs) were prepared by the ultrasonic method. POMs were assembled on the surface of mpg-C₃N₄via electrostatic attraction. The catalyst has visible light degradation activity for phenol (λ > 420 nm). mpg-C₃N₄ modified by H₄SiW₁₂O₄₀ with a mass ratio of 1 : 5 showed the highest catalytic activity, which was 3.5 times higher than that of mpg-C₃N₄. As an electron acceptor, polyoxometalate can capture the photoelectron of C₃N₄, which can promote the separation of photocharge and improve the photocatalytic activity. ESR also confirmed that the superoxide radicals play a major role in degradation. The results show that the charge separation efficiency and catalytic activity can be enhanced by polyacids.

A porous composite catalyst is prepared by modifying mpg-C₃N₄ with polyacids through ultrasound. When the mass ratio of SiW₁₂ to mpg-C₃N₄ was 1 : 5, the degradation of phenol showed the best catalytic activity, which was 3.5 times that of mpg-C₃N₄.

Enhanced production of H2 under visible light via co-deposited Pt and Ir species on g-C3N4

Synergism between PtO-mediated electron transfer and IrO₂-mediated hole transfer enhanced the photocatalytic hydrogen evolution of g-C₃N₄.

Enhanced mineralization of oxalate by highly active and Stable Ce(III)-Doped g-C3N4 catalyzed ozonation

The degradation of carboxylic acid has been identified as one of the rate-determining steps in the mineralization of organic pollutants by ozonation. In this study, Ce(III)-doped graphitic carbon nitride (Ce-CN) composites with different Ce(III) contents were synthesized and used as catalysts for the ozonation of oxalate. The morphology and structure of the Ce-CN were comprehensively characterized using various techniques such as SEM, XRD, FTIR, and XPS. The results show that the structure of g-C₃N₄ provided an ideal site for the accommodation of Ce(III) and thus facilitated the formation of surface hydroxyl groups. With 2.5%Ce-CN as a catalyst, the degradation efficiency of oxalate was increased by 47.1% after reaction for 30 min. The decomposition of ozone was accelerated in the presence of Ce-CN. Hydroxyl radicals were recorded by electron spin resonance and identified as the major actives species. Under the catalysis of 2.5%Ce-CN, the production of hydroxyl radicals was increased by 40%. The Ce(III) and surface hydroxyl groups that distributed uniformly on the surface of Ce-CN were speculated as the dual catalytic sites for the complexation of oxalate and activation of ozone, respectively. Ce-CN had a high stability and reutilization capability. It is proposed that a complex was formed between surface Ce(III) and oxalate, and this complex could be more easily attacked by the surrounding ozone and hydroxyl radicals than free oxalate. As oxalate is a typical recalcitrant carboxylic acid, the findings from this study are expected to promote the application of ozonation in the removal of organic pollutants.

Palladium nanoparticles supported on nanosheet-like graphitic carbon nitride for catalytic transfer hydrogenation reaction

Pd/g-C₃N₄ catalysts with well-dispersed, electron-enriched Pd nanoparticles immobilized on pyridinic N atoms of g-C₃N₄ are active for catalytic transfer hydrogenation under ambient conditions.

Enhanced reduction and oxidation capability over the CeO2/g-C3N4 hybrid through surface carboxylation: performance and mechanism

The charge separation efficiency of the CeO₂/g-C₃N₄ heterojunction was greatly enhanced through surface carboxylation of the g-C₃N₄ substrate.

Template-free fabrication of hierarchical graphitic carbon nitride via self-assembled aggregates for enhanced photocatalytic hydrogen evolution activity under visible light

A structure-retention strategy for hierarchical graphitic carbon nitride with enhanced photocatalytic hydrogen evolution activity by direct calcination of self-assembled melamine aggregates.

Intelligent Platform for Simultaneous Detection of Multiple Aminoglycosides Based on a Ratiometric Paper-Based Device with Digital Fluorescence Detector Readout

A digital fluorescence detector (DFD), a handheld fluorescence detection device, can convert the fluorescence signal of samples into the corresponding fluorescer concentration. Herein, by adopting a DFD as the readout, a novel intelligent platform was developed based on a ratiometric paper-based device (RPD) for multiple aminoglycoside detection. There are five layers and four parallel channels contained in the designed RPD, functioning as reagent storage, fluidic path control and signal processing, respectively. The rationale of this design lies in the fact that aptamer/graphitic carbon nitride nanosheet (Apt/g-C₃N₄ NS) modified layers can catalyze o-phenylenediamine to fluorescent 2,3-diaminophenazine (DAP) in the presence of H₂O₂. When Apt was removed from nanosheets via the Apt-target reaction, the peroxidase-like activity would be decreased, thus decreasing the production of DAP. All the changes of the fluorescence DAP signal can be read out using a portable DFD. Based on the DFD signal change related to the concentration of the target, a quantitative reaction platform was established. Furthermore, the sample flow and Apt-target reaction time can be reasonably regulated using the H₂O₂-cleavable hydrophobic compound modified layer placed between the target recognition region and detection region. Then, the practicality of this platform was verified through realizing sensitive analysis of streptomycin, tobramycin, and kanamycin simultaneously. Overall, with merits including portability and ease of operation, the platform shows great potential in on-site simultaneous detection of multiple targets, especially in resource-limited settings.

Rational Ionothermal Copolymerization of TCNQ with PCN Semiconductor for Enhanced Photocatalytic Full Water Splitting

Photocatalytic full water splitting remains the perfect way to generate oxygen (O₂) and hydrogen (H₂) gases driven by sunlight to address the future environmental issues as well as energy demands. Owing to its exceptional properties, polymeric carbon nitride (PCN) has been one of the most widely investigated semiconductor photocatalysts. Nevertheless, blank PCN characteristically displays restrained photocatalytic performance due to high-density defects in its framework that may perhaps perform the part of the recombination midpoint for photoproduced electron-hole pairs. Therefore, to overcome this problem, a simple approach to introduce 7,7,8,8-tetracyanoquinodimethane (TCNQ) with an electron-withdrawing characteristic modifier into the pristine PCN framework by the ionothermal method to enhance its optical, conductive, and photocatalytic properties has been undertaken. Results show that such integration of TCNQ results in the delocalization of the π-conjugated structure; significant changes in its chemical electronic configuration, band gap, and surface area; and enhanced production of electrons under visible light. As a result of this facile integration, our best sample (CNU-TCNQ_9.0) produced a hydrogen evolution rate (HER) of 164.6 μmol h^-1 for H₂ and an oxygen evolution rate (OER) of 14.8 μmol h^-1 for O₂, which were found to be 2.4- and 2.6-fold greater than those produced with pure carbon nitride (CNU) sample, respectively. Hence, this work provides a reasonable alternative method to synthesize and design novel CNU-TCNQ backbone photocatalyst for organic photosynthesis, CO₂ reduction, hydrogen evolution, etc.

Synthesis of Thiocyameluric Acid C6 N7 S3 H3 , Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates

Thiocyameluric acid C6 N7 S3 H3 , the tri-thio analogue of cyameluric acid, is a key compound for the synthesis of new s-heptazine (tri-s-triazine) derivatives. Here, two different routes for the synthesis of thiocyameluric acid and its reaction to tris(aryldithio)- and tris(alkyldithio)cyamelurates C6 N7 (SSR)3 are reported as well as transformation to alkali metal thiocyamelurates M3 [C6 N7 S3 ], M=Na, K. These compounds were characterised by FTIR, Raman, solution 13 C and 1 H NMR spectroscopies, thermal gravimetric analysis (TGA) and elemental analysis. The three (de)protonation steps of thiocyameluric acid were investigated by acid-base titration followed via UV/Vis absorption spectroscopy. While it was not possible to determine the three pKa values, it could be postulated that the acid strength probably increases in the following order: cyanuric acid (C3 N3 O3 H3 ) < thiocyanuric acid (C3 N3 S3 H3 ) < cyameluric acid (C6 N7 O3 H3 ) < thiocyameluric acid (C6 N7 S3 H3 ). Single crystals of Na3 [C6 N7 S3 ]⋅10 H2 O and K3 [C6 N7 S3 ]⋅6 H2 O were obtained and the structures analyzed by single crystal X-ray diffraction. Additionally, quantum chemical calculations were performed to get insights into the electronic structure of thiocyameluric acid and to clarify the thiol-thione tautomerism. Based on a comparison of calculated and measured vibrational spectra it can be concluded that thiocyameluric acid and the di- and mono-protonated anions exist in the thione form.

Molecular Cooperative Assembly-Mediated Synthesis of Ultra-High-Performance Hard Carbon Anodes for Dual-Carbon Sodium Hybrid Capacitors

Although sodium hybrid capacitors (NHCs) have emerged as one of the most promising next-generation energy storage systems, further advancement is delayed primarily by the absence of high-performance battery-type anodes. Herein, we report a nature-inspired synthesis route to prepare hard carbon anodes with high capacity, rate capability, and cycle stability for dual-carbon NHCs. Shape- and size-controllable crystal aggregates of inexpensive triazine molecules are utilized as reactive templates that perform triple duties of structure-directing agent, porogen, and nitrogen source. This enables the fine control of microstructure/morphology/composition and thereby electrochemical reactions toward Na-ion. The resulting hard carbon optimized in terms of lateral size, interlayer spacing, and surface affinity of graphene-like layers achieves a specific capacity of ∼380 mAh/g after 100 cycles at a current density of 250 mA/g mainly via intercalation, the current record of hard carbons. Combined with a commercial microporous carbon fiber cathode, the full cell is able to deliver a volumetric energy density of 2.89 mWh/cm³ and a volumetric power density of 160 mW/cm³, outperforming NHCs based on inorganic Na-ion anode materials. More importantly, such performance could not only be retained for 10000 cycles (4.5 F/cm³ at 10 mA/cm³) with 0.000 028 6% loss per cycle at >97% Coulombic efficiency but also successfully transferred to flexible pouch cells without significant performance loss after 300 bending cycles or during wrapping at a 10R condition. Simple preparation of hard carbon anodes using organic crystal reactive templates, therefore, demonstrates great potential for the manufacture of high-performance flexible NHCs using only carbon electrode materials.