Two-dimensional nanozyme nanoarchitectonics customized electrochemical bio diagnostics and lab-on-chip devices for biomarker detection

Recent developments in nanomaterials and nanotechnology have advanced biosensing research. Two-dimensional (2D) nanomaterials or nanozymes, such as metal oxides, graphene and its derivatives, transition metal dichalcogenides, metal-organic frameworks, carbon-organic frameworks and MXenes, have garnered substantial attention in recent years owing to their unique properties, including high surface area, excellent electrical conductivity, and mechanical flexibility. Moreover, 2D nanozymes exhibit intrinsic enzyme-mimicking properties, including those of peroxidase, oxidase, catalase, and superoxide dismutase, making them well-suited for detecting biomarkers of interest and developing bio diagnostics at the point-of-care. Since 2D nanosystems offer ultra-high sensitivity, label-free detection, and real-time analysis, point-of-care testing and multiplexed biomarker detection, the demand is growing. Additionally, their biocompatibility and scalable fabrication make them cost-effective for widespread adoption. This review discusses the advantages of 2D nanozymes and their recent advancements in biosensing applications. This review summarizes the latest developments in 2D nanozymes, focusing on their synthesis, biocatalytic capabilities, and advancements in developing bio diagnostics and lab-on-chip devices for detecting cancer and non-cancer biomarkers. In addition, existing challenges and prospects in 2D nanozyme-based biosensors are identified, highlighting their biosensing potential and advocating for their expanded application in bio diagnostics and lab-on-chip devices.

Porous carbon nitride fullerenes: a novel family of porous cage molecules

A novel family of cage molecules, porous carbon nitride fullerenes (PCNFs), is designed, proposed and studied theoretically. PCNFs can be considered the zero-dimensional counterparts of two-dimensional porous graphitic carbon nitrides, in analogy with icosahedral fullerenes, being the zero-dimensional counterparts of graphene. The study is focused on two representative members of the PCNF family: icosahedral C60N60 and C120N60, which are the first members of the two main sub-families of these structures. Given the advanced potential of two-dimensional graphitic carbon nitrides for several interesting applications, it is reasonable to expect that this potential extends to their zero-dimensional counterparts. The present study demonstrates the electronic, vibrational, and thermal stability of the two representative PCNFs utilizing density functional theory and molecular dynamics simulations with ReaxFF potentials. In addition, their structural, vibrational, and electronic properties are revealed.

Maximization of Photocatalytic Rhodamine B Dye Degradation and Hydrogen Production over g-C3N4-NaTaO3 Heterostructure

Visible active binary g-C3N4 (CN) embedded NaTaO3 (NTO) photocatalyst is synthesized via hydrothermal method, followed by annealing. The phase and morphology were confirmed as monoclinic NaTaO3 and layered g-C3N4. The light-response properties of NTO-CN is significantly broadened in the visible spectrum. The elemental composition, binding energy, oxidation states of the constituent elements, and surface adsorption of the synthesized materials are characterized. The percentage of degradation of Rhodamine B (RhB) dye employing NTO-CN heterostructure photocatalyst is computed to be 92.3%. This value is 1.66 times and 1.49 times greater than NaTaO3 and g-C3N4, respectively. Pseudo-first-order rate constant value for NTO-CN heterostructure photocatalyst is calculated to be 0.0288 min-1. This value is 3.43 times and 2.82 times greater than NaTaO3 and g-C3N4, respectively. Photocatalytic water splitting experiment is performed and amount of hydrogen evolved for 5 h is measured to be 1104 μmol g-1 for NTO-CN, which is greater by a factor of 2.32 and 1.43 as that of NaTaO3 and g-C3N4, respectively. In comparison to bare g-C3N4 and NaTaO3, the NTO-CN heterostructure photocatalyst demonstrates maximized photocatalytic performance. Incorporation of g-C3N4, broadens the visible-light harvesting ability and diminishes electron-hole recombination. This study analyzes advancing practical application of NaTaO3 photocatalysts by forming heterostructure with g-C3N4.

Heteroepitaxial Growth of Narrow Band Gap Carbon-Rich Carbon Nitride Using In Situ Polymerization to Empower Sunlight-Driven Photoelectrochemical Water Splitting

We describe an in situ-polymerized conformal thin layer coating of narrow band gap carbon-rich carbon nitride (NBG-CRCN) on titania nanorod arrays to design a binary semiconductor heterojunction photocatalyst. The in situ polymerization creates a strong interaction between the TiO2 nanorod substrate and the carbon nitride film, which prevents leaching of CRCN in liquid electrolytes. A unique aspect of our work is developing an easy and inexpensive technique for the heteroepitaxial growth of mechanically and photochemically stable carbon nitride thin films with intimate contact at the CN:TNR heterojunction interface. This method aids in overcoming one of the main problems with carbon nitride (CN), namely, the inability to produce an evenly distributed CN coating on a substrate. The synthesized NBG-CRCN@TNR extends the visible light absorption to 700 nm (Eg = 1.7 eV) and red-shifts the photoluminescence (PL) emission peak to 580 nm. The peak shifts and broadening in the Raman spectra of the NBG-CRCN@TNR hybrid compared to those in TNR confirm an unusually strong interaction between TiO2 and NBG-CRCN. An easy and inexpensive technique to heteroepitaxially grow CRCN (002) on rutile TiO2 (110) is confirmed by advanced characterization. High-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), and grazing-incidence wide-angle X-ray scattering (GIWAXS) suggest the heteroepitaxial growth of (002) CRCN on rutile TiO2 (110). Under AM1.5G solar illumination, the NBG-CRCN@TNR hybrid shows superior performance in photoelectrochemical water splitting, generating a photocurrent density as high as 4.3 mA cm-2 in 1 M KOH under 0.6 V external bias, rising to 8.4 mA cm-2 in the presence of a hole scavenger (methanol). An impressive hydrogen evolution rate of 26.51 μmol h-1 with 88.12% Faradaic efficiency is recorded. Establishing a high-quality interface between g-C3N4 and titania permits effective charge carrier separation, leading to enhanced photocatalytic activity.

Radical initiated polymerization of p-styrenesulfonate on graphitic carbon nitride for interconnected water networks in short-side-chain PFSA membranes for low-humidity hydrogen fuel cells

Interfacial ionic transport resistance, caused by sparsely connected water networks in polymer electrolyte membranes (PEMs) at low relative humidity (RH), limits the performance of hydrogen fuel cells. This challenge is addressed by employing a radical-initiated polymerization of p-styrenesulfonate (SS) on graphitic carbon nitride (CN) to enrich sulfonic acid groups via covalent grafting which are then incorporated into a short-side chain perfluoro sulfonic acid (SSC PFSA) ionomer matrix. This promotes the formation of interconnected water networks, even at low RH, and reduces the activation energy without negatively impacting the transport-stability trade-off. With the synergistic improvement in proton conductivity, water retention and mechanical stability, at 0.6 V, composite membranes demonstrated a 30% improvement in current density (1.12 A cm-2) at 30% RH and a 42% improvement (0.93 A cm-2) under dry gas conditions. The peak power density achieved for the composite membrane was 1.3 W cm-2 at 100% RH. Furthermore, the composite membrane reinforces critical mechanical properties such as Young's modulus, tensile strength and dimensional stability, ensuring durability under operational stresses, evidenced by only a 10% reduction in the initial Open Circuit Voltage (OCV) during the accelerated stress test. Current density comparisons before and after the stability test also showed minimal losses, attributed to the ability of the additive to maintain interconnected water networks and reduce ionic transport resistance, thus enhancing proton conduction and fuel cell performance, particularly in low RH environments.

Navigating the evolution of two-dimensional carbon nitride research: integrating machine learning into conventional approaches

Carbon nitride research has reached a promising point in today's research endeavours with diverse applications including photocatalysis, energy storage, and sensing due to their unique electronic and structural properties. Recent advances in machine learning (ML) have opened new avenues for exploring and optimizing the potential of these materials. This study presents a comprehensive review of the integration of ML techniques in carbon nitride research with an introduction to CN classifications and recent advancements. We discuss the methodologies employed, such as supervised learning, unsupervised learning, and reinforcement learning, in predicting material properties, optimizing synthesis conditions, and enhancing performance metrics. Key findings indicate that ML algorithms can significantly reduce experimental trial-and-error, accelerate discovery processes, and provide deeper insights into the structure-property relationships of carbon nitride. The synergistic effect of combining ML with traditional experimental approaches is highlighted, showcasing studies where ML driven models have successfully predicted novel carbon nitride compositions with enhanced functional properties. Future directions in this field are also proposed, emphasizing the need for high-quality datasets, advanced ML models, and interdisciplinary collaborations to fully realize the potential of carbon nitride materials in next-generation technologies.

Short-Side-Chain Membranes with Stabilized Superacid on Graphitic Carbon Nitride for Polymer Electrolyte Fuel Cells under Low-Humidity Conditions

The integration of superacid-like heteropolyacids offers a promising route to develop highly proton-conducting membranes for energy storage and conversion. However, the inherent hydrophilicity of these acids can cause leaching, which undermines the fuel cell performance. In our research, we engineered a proton-conductive membrane with a facile hydrothermal synthesis approach to form stabilized hybrid superacids, namely, phosphotungstic acid (PTA), with graphitic carbon nitride (PCN) and its incorporation in a short-side-chain ionomer, namely, Aquivion. This unique approach via PCN nanohybrids enhances the proton transport within the membrane. These nanohybrids effectively combined the strong acidity of PTA with continuous 2D proton-transport pathways via a short side chain, resulting in a notable proton conductivity of 0.228 S cm-1 at 80 °C under 95% relative humidity. The real impact was evident in the performance of fuel cells using the Aquivion/PCN nanocomposite membrane, which demonstrated a significant improvement of 34% in the peak power density (1.0 W cm-2), and 44% cell performance (0.98 A cm-2) was retained for the nanocomposite membrane at a low relatively humidity (30% RH) at 0.6 V. This advancement represents a major leap in energy conversion and storage technologies at low-humidity conditions.

Sheets Copper-Cobalt Graphitic Carbon Nitride Dual Single-Atom Catalysts for the Epoxidation of Styrene

Dual single-atom catalysts have attracted considerable research interest due to their higher metal atom loading and more flexible active sites compared to single-atom catalysts (SACs). We pioneered the one-step synthesis of sheets copper-cobalt graphitic carbon nitride dual single-atom (S-Cu/Co-g-C3N4) using folding fan-shaped aluminum foil as a template, and used them as catalysts in the epoxidation of styrene respectively. Through XAFS (X-ray Absorption Fine Structure) and other characterizations, it is found that Cu and Co single atoms are stabilized separately on g-C3N4 via coordination with nitrogen (N), hindered the ordered growth of sheets, and formed more pore structures, which not only increased more catalytically active sites, but also effectively prevented the flakes re-aggregate during the catalytic process. And the synergistic effect between Cu and Co changes the energy band structure of the material and facilitates electron transfer during catalysis, hence an excellent catalytic effect of 89 % styrene conversion and 85 % styrene oxide selectivity was achieved when S-Cu/Co-g-C3N4-1 : 1 was applied in the epoxidation of styrene. Furthermore, the mechanisms of the epoxidation of styrene with S-Cu/Co-g-C3N4-1 : 1 was probed by the density functional theory (DFT) based on the slab model.

Novel Graphitic Oxynitrides as Photocatalysts for Sustainable H2 Production and CO2 Valorization. The Importance of Self-Assembly for Catalytic Activity

The field of carbocatalysis, often portrayed by paradigmatic graphitic carbonaceous structures, has become a booming topic tailored for multiple applications. To this end, a new metal-free carbocatalyst has been constructed from simple prebiotic monomers such as cyanamide and glyoxal. The resulting material shows an excellent performance as photocatalyst for H2 production and CO2 valorization, thus unveiling its real value to tackle sustainable goals. The unique oxygen-rich carbonaceous structure has been characterized in detail, which is consistent with a graphitic layered network. The described performance in two major societal concerns along with a facile preparation from C1/C2 platforms, makes this type of overlooked oxynitride carbocatalysts promising for real-life environmental endeavors.

Z-Scheme Enabled 1D/2D Nanocomposite of ZnO Nanorods and Functionalized g-C3 N4 Nanosheets for Sustainable Degradation of Terephthalic Acid

The urgent need to mitigate water pollution and achieve Sustainable Development Goal 14 (SDG 14)-Life below water, necessitates developing efficient and eco-friendly wastewater treatment technologies. This research addresses this challenge by photocatalytic degradation of terephthalic acid, a precursor for PET bottles using environment-friendly and biocompatible photocatalysts. The 1D/2D nanocomposite comprising zinc oxide (ZnO) nanorods and functionalized graphitic carbon nitride (Zn-TG) nanosheets were synthesized and thoroughly characterized. The nanocomposite effectively mitigated the individual drawbacks of Zn-TG agglomeration and the wide band gap of ZnO as confirmed through zeta potential and Tauc's plot studies, respectively. The synthesized nanocomposite achieved ~100 % degradation within 60 minutes, exhibiting superior kinetics (~2.5 times) compared to pristine samples. The enhanced degradation efficiency was elucidated by efficient charge carrier transfer (~5 times faster) and separation (~2 times improved) as confirmed through electrochemical impedance spectroscopy and time-resolved photoluminescence studies. The proposed Z-scheme pathway provides mechanistic insights. This proposed mechanism is supported by extensive electron paramagnetic resonance (EPR) and scavenger studies. The liquid chromatography-mass spectrometry (LC-MS) analysis confirms the formation of less toxic byproducts for ensuring that the wastewater treatment process is efficient and environmentally friendly. This research helps in developing a highly effective and sustainable wastewater treatment technology.

Dual Active Sites with Charge-asymmetry in Organic Semiconductors Promoting C-C Coupling for Highly Efficient CO2 Photoreduction to Ethanol

Selective CO2 photoreduction into high-energy-density and high-value-added C2 products is an ideal strategy to achieve carbon neutrality and energy shortage, but it is still highly challenging due to the large energy barrier of the C-C coupling step and severe exciton annihilation in photocatalysts. Herein, strong and localized charge polarization is successfully induced on the surface of melon-based organic semiconductors by creating dual active sites with a large charge asymmetry. Confirmed by multiscale characterization and theoretical simulations, such asymmetric charge distribution, originated from the oxygen dopants and nitrogen vacancies over melon-based organic semiconductors, reduces exciton binding energy and boosts exciton dissociation. The as-formed charge polarization sites not only donate electrons to CO2 molecules but also accelerate the coupling of asymmetric *CO*CO intermediates for CO2 photoreduction into ethanol by lowering the energy barrier of this process. Consequently, an exceptionally high selectivity of up to 97 % for C2H5OH and C2H5OH yield of 0.80 mmol g-1 h-1 have been achieved on this dual active sites organic semiconductor. This work, with its potential applicability to a variety of non-metal multi-site catalysts, represents a versatile strategy for the development of advanced catalysts tailored for CO2 photoreduction reactions.

Atomically thin 2D materials for solution-processable emerging photovoltaics

Atomically thin 2D materials, such as graphene and graphene oxide, covalent organic frameworks, layered carbides, and metal dichalcogenides, reveal a unique variability of electronic and chemical properties, ensuring their prospects in various energy generation, conversion, and storage applications, including light harvesting in emerging photovoltaic (ePV) devices with organic and perovskite absorbers. Having an extremely high surface area, the 2D materials allow a broad variability of the bandgap and interband transition type, conductivity, charge carrier mobility, and work function through mild chemical modifications, external stimuli, or combination with other 2D species into van-der-Waals heterostructures. This review provides an account of the most prominent "selling points" of atomically thin 2D materials as components of ePV solar cells, including highly tunable charge extraction selectivity and work function, structure-directing and stabilizing effects on halide perovskite light absorbers, as well as broad adaptability of 2D materials to solution-based manufacturing of ePV solar cells using sustainable and upscalable printing technologies. A special focus is placed on the large potential of the materials discovery and design of ePV functionalities based on van-der-Waals stacking of atomically thin 2D building blocks, which can open a vast compositional domain of new materials navigable with machine-learning-based accelerated materials screening.

Simultaneous monitoring of multiple prohibited drugs in various aquatic products

Both sedative and antipathogenic drugs are often found to be illegally used in aquaculture, but there is a lack of simultaneous monitoring methods. A method for simultaneously monitoring multiple prohibited drugs in various aquatic product samples was developed in this work, including fish, shrimp, crab, and shellfish. Sulfonic acid-functionalized magnetic graphitic carbon nitride (S-MGCN) was synthesized and validated to efficiently co-extract all targets (adsorption efficiency over 90.07%) through various adsorption mechanisms such as electrostatic interaction, hydrogen bonding, and π-π interaction while demonstrating good sample matrix purification ability (matrix effect below 13.60%). A new magnetic solid-phase extraction method based on S-MGCN was subsequently established. Coupled with UPLC-MS/MS, the detection limits were 0.030.075 μg /kg, and the recoveries ranged from 88.76% to 111.74% with the RSDs lower than 14.60%, indicating that the developed method has good sensitivity, accuracy, and precision. Further validation of its practicality was achieved through actual sample analysis.

Covalently Anchored Molecular Catalyst onto a Graphitic Carbon Nitride Surface for Photocatalytic Epoxidation of Olefins

This study explores an innovative photocatalytic approach using pristine graphitic carbon nitride (C3N4) to anchor iron salen-type complexes (FeSalenCl2) without the need for additional linkers or heterojunctions. The resulting hybrid catalyst, [C3N4-FeCl(Salen)]Chem, exhibits a promising catalytic performance in the selective epoxidation of cyclic and linear olefins using gaseous oxygen as the oxidant. The catalyst's selectivity closely resembles that of the free iron complex, and its effectiveness varies depending on the olefin substrate. Additionally, solvent selection plays a critical role in achieving optimal performance, with acetonitrile proving to be the best choice. The study demonstrates the potential of C3N4 as an environmentally friendly, recyclable, and efficient support for molecular catalysts. The results highlight the versatility and significance of C3N4-based materials in advancing light-driven catalysis.

Influence of gadolinium doping on structural, optical, and electronic properties of polymeric graphitic carbon nitride

Polymeric graphitic carbon nitride (gCN) materials have received great attention in the fields of photo and electrocatalysis due to their distinct properties in metal-free systems with high physicochemical stability. Nevertheless, the activity of undoped gCN is limited due to its relatively low specific surface area, low conductivity, and poor dispersibility. Doping Gd atoms in a gCN matrix is an efficient strategy to fine-tune its catalytic activity and its electronic structure. Herein, the influence of various wt% of gadolinium (Gd) doped in melon-type carbon nitride was systematically investigated. Gadolinium-doped graphitic carbon nitride (GdgCN) was synthesized by adding gadolinium nitrate to dicyandiamide during polymerization. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the crystallinity and the morphological properties are influenced by the % of Gd doping. Furthermore, X-ray photoelectron spectroscopy (XPS) studies revealed that the gadolinium ions bonded with nitrogen atoms. Complementary density functional theory (DFT) calculations illustrate possible bonding configurations of Gd ions both in bulk material and on ultrathin melon layers and provide evidence for the corresponding bandgap modifications induced by gadolinium doping.

Unveiling Versatile Applications and Toxicity Considerations of Graphitic Carbon Nitride

Metal-free, low-cost, organic photocatalytic graphitic carbon nitride (g-C3N4) has become a promising and impressive material in numerous scientific fields due to its unique physical and chemical properties. As a semiconductor with a suitable band gap of ~2.7 eV, g-C3N4 is an active photocatalytic material even after irradiation with visible light. However, information regarding the toxicity of g-C3N4 is not extensively documented and there is not a comprehensive understanding of its potential adverse effects on human health or the environment. In this context, the term "toxicity" can be perceived in both a positive and a negative light, depending on whether it serves as a benefit or poses a potential risk. This review shows the applications of g-C3N4 in sensorics, electrochemistry, photocatalysis, and biomedical approaches while pointing out the potential risks of its toxicity, especially in human and environmental health. Finally, the future perspective of g-C3N4 research is addressed, highlighting the need for a comprehensive understanding of the toxicity of this material to provide safe and effective applications in various fields.

Exploring the synergistic effect of palladium nanoparticles and highly dispersed transition metals on carbon nitride/super-activated carbon composites for boosting electrocatalytic activity

In the present work, multifunctional electrocatalysts formed by palladium nanoparticles (Pd NPs) loaded on Fe or Cu-containing composite supports, based on carbon nitride (C3N4) and super-activated carbon with a high porosity development (SBET 3180 m2/g, VDR 1.57 cm3/g, and VT 1.65 cm3/g), were synthesised. The presence of Fe or Cu sites favoured the formation of Pd NPs with small average particle size and a very narrow size distribution, which agreed with Density Functional Theory (DFT) calculations showing that the interaction of Pd clusters with C3N4 flakes is weaker than with Cu- or Fe-C3N4 sites. The electroactivity was also dependent on the composition and, as suggested by preliminary DFT calculations, the Pd-Cu catalyst showed lower overpotential for hydrogen evolution reaction (HER) while bifunctional oxygen reduction reaction/ oxygen evolution reaction (ORR/OER) behaviour was superior in Pd-Fe sample. The Pd-Fe electrocatalyst was studied in a zinc-air battery (ZAB) for 10 h, showing a performance similar to a commercial Pt/C + RuO2 catalyst with a high content of precious metal. This study demonstrates the synergistic effect between Pd species and transition metals and shows that transition metals anchored on C3N4-based composite materials promote the electroactivity of Pd NPs in HER, ORR and OER due to the interaction between both species.

In situ growth of N-doped carbon nanotubes from the products of graphitic carbon nitride etching by nickel nanoparticles

The in situ growth of N-doped multi-walled carbon nanotubes (N-MWCNTs) from the products of graphitic carbon nitride (g-C3N4) etching by Ni nanoparticles in a hydrogen atmosphere has been confirmed for the first time. During the etching process of g-C3N4, the building blocks, notably methane, ammonia, and hydrogen cyanide, are formed. The formation of N-MWCNTs was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning (SEM) and transmission electron microscopy (TEM). A sponge-like carbonaceous structure was obtained with a specific surface area of 384 m2 g-1 from initial g-C3N4 (32 m2 g-1).

Exploring Highly Efficient Broadband Self-Trapped-Exciton Luminophors: from 0D to 3D Materials

The review summarizes our recent reports on brightly-emitting materials with varied dimensionality (3D, 2D, 0D) synthesized using "green" chemistry and exhibiting highly efficient photoluminescence (PL) originating from self-trapped exciton (STE) states. The discussion starts with 0D emitters, in particular, ternary indium-based colloidal quantum dots, continues with 2D materials, focusing on single-layer polyheptazine carbon nitride, and further evolves to 3D luminophores, the latter exemplified by lead-free double halide perovskites. The review shows the broadband STE PL to be an inherent feature of many materials produced in mild conditions by "green" chemistry, outlining PL features general for these STE emitters and differences in their photophysical properties. The review is concluded with an outlook on the challenges in the field of STE PL emission and the most promising venues for future research.

Defective Potassium Poly(Heptazine Imide) Preventing Spin Delocalization and Hole Transfer Deactivation for Efficient Solar Energy Conversion and Storage

Anti-site defective potassium poly(heptazine imide) (KPHI) with the central nitrogen atoms partially replaced by graphitic carbon atoms in the flawed heptazine rings is prepared by direct ionothermal treatment of the rationally designed supramolecular complex in KSCN salt molten. Compared to the KPHIs without the anti-site defect, the anti-site defective KPHI demonstrates significantly improved photocatalytic and dark photocatalytic performances for H2 evolution reaction (HER). In the presence of the hole scavenger, the anti-site defective KPHI exhibits superior photocatalytic stability for HER lasting 20 h, whereas the deactivation is observed from the ordinary KHPIs after 3 h HER. Moreover, the H2 yield in the dark by the stored photoelectrons in the anti-site defective KPHI increases by more than an order of magnitude. Density functional theory calculations reveal that the anti-site defective unit in KPHI not only prevents spin delocalization but also inhibits the deactivation of hole transfer, which are beneficial to photoelectron storage and photocatalytic activity. The findings in this study provide insight into the photophysical and catalytic properties of KPHI, which conclude a strategy to improve the performances for solar energy conversion and storage by incorporating intrinsic anti-site defects in KPHI.

Transition mechanism of the coverage-dependent polymorphism of self-assembled melamine nanostructures on Au(111)

Molecular self-assembled films have recently attracted increasing attention within the field of nanotechnology as they offer a route to obtain new materials. However, careful selection of the molecular precursors and substrates, as well as exhaustive control of the system evolution is required to obtain the best possible outcome. The three-fold rotational symmetry of melamine molecules and their capability to form hydrogen bonds make them suitable candidates to synthesize this type of self-assembled network. In this work, we have studied the polymorphism of melamine nanostructures on Au(111) at room temperature. We find two coverage-dependent phases: a honeycomb structure (α-phase) for submonolayer coverage and a close-packed structure (β-phase) for full monolayer coverage. A combined scanning tunnel microscopy and density functional theory based-calculations study of the transition regime where both phases coexist allows describing the mechanism underlying this coverage driven phase transition in terms of the changes in the molecular lateral tension.

Self-assembled Fe3O4-NH2 @g-C3N4 composite for magnetic solid-phase extraction of benzophenones in sea water and lake water coupled with LC-MS/MS determination

Magnetic solid-phase extraction (MSPE) was developed based on a well-designed Fe3O4-NH2 @g-C3N4 nanocomposite as sorbent for a mixture of six benzophenones (BPs) in environmental water samples. The composite fabricated via in-situ self-assembled g-C3N4 shell with homogeneous polymerization of cyanuric chloride and cyanuric acid on Fe3O4-NH2 core. While high adsorption capacity was derived from g-C3N4 via hydrophobic, π-π and hydrogen bonding interactions to the targets, the fast magnetic separation was realized with Fe3O4 core for less solvent consumption. In combination with LC-MS/MS, the Fe3O4-NH2 @g-C3N4 sorbent minimized the interfering components, reduced the matrix effects, and provided the enrichment factors of 121-150 for six BPs with relative standard deviations ≤ 9.7% even after 20 times extraction-desorption cycles. The present method gave the detection limits of 0.3-2.5 ng/L for six BPs with the linear ranges of 1.0-2000 ng/L, and the recoveries of 84.6%-104% in sea water and 86.2%-107% in lake water samples. Thus, the Fe3O4-NH2 @g-C3N4-based MSPE coupled with LC-MS/MS method provided a convenient, efficient, and reliable alternative to monitor trace BPs in environmental water samples.

Flexo-/Piezoelectric Polarization Boosting Exciton Dissociation in Curved Two-Dimensional Carbon Nitride Photocatalyst

Two-dimensional (2D) carbon nitride (CN) materials have received tremendous attention as photocatalysts for clean energy and environmental treatment. However, the photocatalytic efficiency of CN is constrained by the high exciton binding energy and sluggish charge kinetics due to weak dielectric screening, impeding the overall process. Herein, localized flexo-/piezoelectric polarization is introduced via strain engineering, boosting exciton dissociation and promoting charge separation to enhance the multielectron photocatalytic process. Consequently, the exciton binding energy of polarized CN is reduced from 52 to 34 meV, and the hydrogen evolution yield increased by 2.9 times compared to that of the pristine CN. For other photocatalytic reactions (e.g., H2O2 production), the polarized CN also maintained a 2.1-fold increase compared to the pristine CN. This strategy of inducing localized polarization via strain engineering provides new insights for boosting photocatalytic reactions involving electrons.

Carbon Nitrides from Supramolecular Crystals: From Single Atoms to Heterojunctions and Advanced Photoelectrodes

Carbon nitride materials (CN) have become one of the most studied photocatalysts within the last 15 years. While CN absorbs visible light, its low porosity and fast electron-hole recombination hinder its photoelectric performance and have motivated the research in the modification of its physical and chemical properties (such as energy band structure, porosity, or chemical composition) by different means. In this Concept we review the utilization of supramolecular crystals as CN precursors to tailor its properties. We elaborate on the features needed in a supramolecular crystal to serve as CN precursor, we delve on the influence of metal-free crystals in the morphology and porosity of the resulting materials and then discuss the formation of single atoms and heterojunctions when employing a metal-organic crystal. We finally discuss the performance of CN photoanodes derived from crystals and highlight the current standing challenges in the field.

Graphitic carbon nitride-adorned PDMS self-cleaning floating photocatalyst for simultaneous removal of Rhodamine B, Crystal Violet and Malachite Green from a ternary dye mixture

Graphitic carbon nitride-adorned polydimethylsiloxane (PDMS) floating catalyst was prepared by a simple procedure. The prepared catalyst was utilized for the simultaneous mitigation of recalcitrant organic pollutants such as Rhodamine B, Crystal Violet and Malachite Green from their ternary mixture for the first time. Derivative spectroscopic method was used to calculate the degradation efficiencies of individual dyes in the mixture. The prepared catalyst showed a consistent degradation performance up to 4 cycles inducing a degradation of 94.02%, 92.1% and 97.13% of Rhodamine B, Crystal Violet and Malachite Green, respectively, in a dye(s) solution with a catalytic loading of 0.5 g L-1. A kinetic analysis of the dye(s) degradation under visible light was carried out during the course of this work up to 120 min. A detailed characterization of the surface of this novel catalyst was carried out in this study by SEM, EDX, XRD, DRS, DTG, FTIR, Raman spectroscopy and UV-Vis spectroscopy and provided the experimental proof for the catalyst presenting high hydrophobicity, self-cleaning ability, good recyclability and high chemical stability.

Amphoteric dissolution of two-dimensional polytriazine imide carbon nitrides in water

Crystalline two-dimensional carbon nitrides with polytriazine imide (PTI) structure are shown to act amphoterically, buffering both HCl and NaOH aqueous solutions, resulting in charged PTI layers that dissolve spontaneously in their aqueous media, particularly for the alkaline solutions. This provides a low energy, green route to their scalable solution processing. Protonation in acid is shown to occur at pyridinic nitrogens, stabilized by adjacent triazines, whereas deprotonation in base occurs primarily at basal plane NH bridges, although NH2 edge deprotonation is competitive. We conclude that mildly acidic or basic pHs are necessary to provide sufficient net charge on the nanosheets to promote dissolution, while avoiding high ion concentrations which screen the repulsion of like-charged PTI sheets in solution. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

Controllable Anchoring of Graphitic Carbon Nitride on MnO2 Nanoarchitectures for Oxygen Evolution Electrocatalysis

The design and fabrication of eco-friendly and cost-effective (photo)electrocatalysts for the oxygen evolution reaction (OER) is a key research goal for a proper management of water splitting to address the global energy crisis. In this work, we focus on the preparation of supported MnO2/graphitic carbon nitride (g-CN) OER (photo)electrocatalysts by means of a novel preparation strategy. The proposed route consists of the plasma enhanced-chemical vapor deposition (PE-CVD) of MnO2 nanoarchitectures on porous Ni scaffolds, the anchoring of controllable g-CN amounts by an amenable electrophoretic deposition (EPD) process, and the ultimate thermal treatment in air. The inherent method versatility and flexibility afforded defective MnO2/g-CN nanoarchitectures, featuring a g-CN content and nano-organization tunable as a function of EPD duration and the used carbon nitride precursor. Such a modulation had a direct influence on OER functional performances, which, for the best composite system, corresponded to an overpotential of 430 mV at 10 mA/cm2, a Tafel slope of ≈70 mV/dec, and a turnover frequency of 6.52 × 10-3 s-1, accompanied by a very good time stability. The present outcomes, comparing favorably with previous results on analogous systems, were rationalized on the basis of the formation of type-II MnO2/g-CN heterojunctions, and yield valuable insights into this class of green (photo)electrocatalysts for end uses in solar-to-fuel conversion and water treatment.

Modification of the electronic structure of g-C3N4 using urea to enhance the visible light-assisted degradation of organic pollutants

Graphitic carbon nitride has been proven to be a good candidate for using solar energy for photo-induced pollutant degradation. However, the high photo-induced holes-electron recombination rate, unfavorable morphology, and textural properties limited their application. In this study, we present a novel g-C3N4 with a novel electronic structure and physiochemical properties by introducing a single nitrogen in the graphitic network of the g-C3N4 through a novel method involving step-by-step co-polycondensation of melamine and urea. Through extensive characterization using techniques such as XPS, UPS-XPS, Raman, XRD, FE-SEM, TEM, and N2 adsorption-desorption, we analyze the electronic and crystallographic properties, as well as the morphology and textural features of the newly prepared g-C3N4 (N-g-C3N4). This material exhibits a lower C/N ratio of 0.62 compared to conventional g-C3N4 and a reduced band gap of 2.63 eV. The newly prepared g-C3N4 demonstrates a distinct valance band maxima that enhances its photo-induced oxidation potential, improving photocatalytic activity in degrading various organic pollutants. We thoroughly investigate the photocatalytic degradation performance of N-g-C3N4 for Congo red (CR) and sulfamethoxazole (SMX), and removal of up to 90 and 86% was attained after 2 h at solution pH of 5.5 for CR and SMX. The influence of different parameters was examined to understand the degradation mechanism and the influence of reactive oxygenated species. The catalytic performance is also evaluated in the degradation of various organic pollutants, and it showed a good performance.

Streamlining efficient and selective synthesis of benzoxanthenones and xanthenes with dual catalysts on a single support

Using two catalysts on a single support can improve reaction efficiency, higher yields, improved selectivity, and simplified reaction conditions, making it a valuable approach for industrial transformation. Herein, we describe the development of a novel and effective heterogeneous catalyst, WCl6/CuCl2, supported on graphitic carbon nitride (W/Cu@g-C3N4), which was synthesized under hydrothermal conditions. The structure and morphology properties of the W/Cu@g-C3N4 were characterized using various spectroscopic techniques, including FTIR, XRD, TEM, TGA, EDX, and SEM. The W/Cu@g-C3N4 support material enabled the rapid and efficient synthesis of benzoxanthenones and xanthenes derivatives in high yields under mild reaction conditions and short reaction times. The W/Cu@g-C3N4 catalyst was also found to be easily recyclable, and its catalytic performance did not significantly decrease after five times use. The findings suggest that W/Cu@g-C3N4 is a promising chemical synthesis catalyst with significant implications for sustainable and cost-effective organic synthesis.

Screen-Printed Carbon Electrodes with Cationic Cyclodextrin Carbon Nanotubes and Ferrocenyl-Carnosine for Electrochemical Sensing of Hg(II)

The study reports the use of nanoassembly based on cationic cyclodextrin carbon nanotubes (CNT-CDs) and ferrocenylcarnosine (FcCAR) for electrochemical sensing of Hg(II) in aqueous solution. β-cyclodextrins (CDs) were grafted onto CNTs by a click chemistry reaction between heptakis-(6-azido-6-deoxy)-β-cyclodextrin and alkyne-terminated CNTs. The cationic amine groups on the CD units were produced by the subsequent reduction of the residual nitrogen groups. The chemical composition and morphology of CNT-CDs were analyzed by X-ray photoelectron spectroscopy, scanning electron microscopy, and thermogravimetric analysis. A N,N-dimethylformamide dispersion of CNT-CDs was cast on the surface of screen-printed carbon electrodes (SPCEs), and the electrochemical response was evaluated by cyclic voltammetry (CV) using [Fe(CN)6]3- as the redox probe. The ability of SPCE/CNT-CD to significantly enhance the electroactive properties of the redox probe was combined with a suitable recognition element (FcCAR) for Hg(II). The electrochemical response of the CNT-CD/FcCAR nanoassembly was evaluated by CV and electrochemical impedance spectroscopy. The analytical performance of the Hg(II) sensor was evaluated by differential pulsed voltammetry and chronoamperometry. The oxidative peak current showed a linear concentration dependence in the range of 1-100 nM, with a sensitivity of 0.12 μA/nM, a limit of detection of 0.50 nM, and a limit of quantification of 1 nM.

Laser-Carbonization - A Powerful Tool for Micro-Fabrication of Patterned Electronic Carbons

Fabricating electronic devices from natural, renewable resources is a common goal in engineering and materials science. In this regard, carbon is of special significance due to its biocompatibility combined with electrical conductivity and electrochemical stability. In microelectronics, however, carbon's device application is often inhibited by tedious and expensive preparation processes and a lack of control over processing and material parameters. Laser-assisted carbonization is emerging as a tool for the precise and selective synthesis of functional carbon-based materials for flexible device applications. In contrast to conventional carbonization via in-furnace pyrolysis, laser-carbonization is induced photo-thermally and occurs on the time-scale of milliseconds. By careful selection of the precursors and process parameters, the properties of this so-called laser-patterned carbon (LP-C) such as porosity, surface polarity, functional groups, degree of graphitization, charge-carrier structure, etc. can be tuned. In this critical review, a common perspective is generated on laser-carbonization in the context of general carbonization strategies, fundamentals of laser-induced materials processing, and flexible electronic applications, like electrodes for sensors, electrocatalysts, energy storage, or antennas. An attempt is made to have equal emphasis on material processing and application aspects such that this emerging technology can be optimally positioned in the broader context of carbon-based microfabrication.

ZnO-Doped gC3N4 Nanocapsules for Enhancing the Performance of Electroless NiP Coating-Mechanical, Corrosion Protection, and Antibacterial Properties

A carbon nitride (C₃N₄) nanomaterial has superior mechanical, thermal, and tribological properties, which make them attractive for various applications, including corrosion-resistant coatings. In this research, newly synthesized C₃N₄ nanocapsules with different concentrations (0.5, 1.0, and 2.0 wt %) of ZnO as a dopant were incorporated into the NiP coating using an electroless deposition technique. The nanocomposite coatings either ZnO-doped (NiP-C₃N₄/ZnO) or undoped (NiP-C₃N₄) were heat-treated at 400 °C for 1 h. The as-plated and heat-treated (HT) nanocomposite coatings were characterized by their morphology, phases, roughness, wettability, hardness, corrosion protection, and antibacterial properties. The results indicated that the microhardness of as-plated and heat-treated nanocomposite coatings was significantly improved after the incorporation of 0.5 wt % ZnO-doped C₃N₄ nanocapsules. The outcomes of electrochemical studies revealed that the corrosion resistance of the HT coatings is higher than the corresponding as-plated ones. The highest corrosion resistance is achieved on the heat-treated NiP-C₃N₄/1.0 wt % ZnO coatings. Although the presence of ZnO in the C₃N₄ nanocapsules increased its surface area and porosity, the C₃N₄/ZnO nanocapsules prevented localized corrosion by filling the microdefects and pores of the NiP matrix. Furthermore, the colony-counting method used to evaluate the antibacterial behavior of the different coatings demonstrated superior antibacterial properties, namely, after heat treatment. Therefore, the novel perspective C₃N₄/ZnO nanocapsules can be utilized as a reinforcement nanomaterial in improving the mechanical and anticorrosion performance of NiP coatings in chloride media, together with providing superior antibacterial properties.

Exploring the potential of ZnO-Ag@AgBr/SBA-15 Z-scheme heterostructure for efficient wastewater treatment: synthesis, characterization, and real-world applications

This study reports on the synthesis and characterization of ZnO-Ag@AgBr/SBA-15 composites using natural halloysite clay from Yenbai Province, Vietnam, as a silica aluminum source. The synthesized materials demonstrated visible light absorption with a band gap energy range of 2.63-2.98 eV. The dual Z-scheme ZnO-Ag@AgBr/SBA-15 heterojunction exhibited superior catalytic performance compared to ZnO/SBA-15 and Ag@AgBr/SBA-15, owing to its improved electron transfer and reduced electron and hole recombination rate. In particular, the photocatalytic efficiency of ZnO-Ag@AgBr/SBA-15 was evaluated for the removal of harmful phenol red from wastewater under visible light irradiation. The photocatalytic process was optimized by varying the phenol red concentration, pH, and catalyst dosage, and showed that 98.8% of phenol red in 100 mL wastewater (pH = 5.5) can be removed using 40 mg of 20%ZnO-Ag@AgBr/SBA-15 within 120 min. Furthermore, the degradation pathway of phenol red was predicted using liquid chromatographic-mass spectrometry (LC-MS). Finally, the photocatalytic process was successfully tested using water samples collected from the four main domestic waste sources in Hanoi, including the To Lich River, the Hong River, the Hoan Kiem Lake, and the West Lake, demonstrating the high potential of the ZnO-Ag@AgBr/SBA-15 photocatalyst for phenol red degradation in real-world wastewater treatment applications.

Inequivalent Solvation Effects on the N 1s Levels of Self-Associated Melamine Molecules in Aqueous Solution

This work shows how the N 1s photoemission (PE) spectrum of self-associated melamine molecules in aqueous solution has been successfully rationalized using an integrated computational approach encompassing classical metadynamics simulations and quantum calculations based on density functional theory (DFT). The first approach allowed us to describe interacting melamine molecules in explicit waters and to identify dimeric configurations based on π-π and/or H-bonding interactions. Then, N 1s binding energies (BEs) and PE spectra were computed at the DFT level for all structures both in the gas phase and in an implicit solvent. While pure π-stacked dimers show gas-phase PE spectra almost identical to that of the monomer, those of the H-bonded dimers are sensibly affected by NH···NH or NH···NC interactions. Interestingly, the solvation suppresses all of the non-equivalences due to the H-bonds yielding similar PE spectra for all dimers, matching very well our measurements.

Efficient CO2 methanation using nickel nanoparticles supported mesoporous carbon nitride catalysts

The CO₂ methanation technique not only gives a solution for mitigating CO₂ emissions but can also be used to store and convey low-grade energy. The basic character and large surface area of mesoporous carbon nitride, (MCN), are considered promising properties for the methanation of CO₂. So, a series (5-20 wt.%) of Ni-doped mesoporous carbon nitride catalysts were synthesized by using the impregnation method for CO₂ methanation. the prepared catalysts were characterized by several physicochemical techniques including XRD, BET, FT-IR, Raman spectroscopy, TEM, TGA analysis, Atomic Absorption, H₂-TPR, and CO₂-TPD. The catalytic performance was investigated at ambient pressure and temperature range (200-500 °C) using online Gas chromatography system. The prepared catalysts showed good performance where 15%Ni/MCN exhibited the best catalytic conversion and methane yield with 100% methane selectivity at 450 °C for investigated reaction conditions.

Unravelling the doping effect of potassium ions on structural modulation and photocatalytic activity of graphitic carbon nitride

Graphitic carbon nitride (GCN), as a promising photocatalyst, has been intensely investigated in the photocatalytic fields, but its performance is still unsatisfactory. To date, metal ion doping has been proven to be an effective modification method to improve the photocatalytic activity of GCN. More importantly, comprehensive understanding of the doping mechanism will be of benefit to synthesize efficient GCN based photocatalysts. In this work, K⁺-doped GCN samples were prepared via heating the mixture of the preheated melamine and a certain amount of KCl at different synthetic temperatures. XRD and Raman characterization studies indicated that the introduction of K⁺ could improve its crystallinity at higher temperature but reduce its crystallinity at lower temperature. Moreover, FTIR and SEM-EDS measurements implied that K⁺ are found dominantly in the surface of the ion-doped sample prepared at lower temperature, while they are found both in the surface and bulk of the ion-doped sample prepared at higher temperature. These observations revealed that K⁺ distributed in the surface of the ion-doped GCN could inhibit its crystal growth, while K⁺ distributed inside of the ion-doped GCN could promote its crystallinity. Owing to the greater inducing effect of the bulk K⁺ than the disturbing effect of the surface K⁺, the improvement of the crystallinity for K⁺-doped GCN was achieved. As a result, the K⁺-doped GCN with higher crystallinity yielded an obviously higher H₂ evolution rate than that with lower crystallinity under visible light irradiation (>420 nm). Besides, it was observed that the K⁺-doped GCN prepared at higher temperature exhibits significantly greater adsorption capacity for methylene blue than the K⁺-doped GCN prepared at lower temperature. This work would provide an insight into optimizing metal ion doped GCN with high photocatalytic activity.

Charge transport and heavy metal removal efficacy of graphitic carbon nitride doped with CeO2

Doping of graphitic carbon nitride (g-C₃N₄) with semiconductors prevents electron-hole recombination and enhances adsorption capacity. This work investigates the synthesis of a water remediation material using g-C₃N₄ doped with CeO₂ using two different techniques. The chemical structures of the doped g-C₃N₄ samples were confirmed using FTIR, XRD, XPS and their morphology was studied using SEM-EDX. Charge transport through the doped materials was illustrated by a comprehensive dielectric study using broadband spectroscopy. The ability of doped g-C₃N₄ to adsorb heavy metals was investigated thoroughly in the light of applying different parameters such as temperature, pH, time, and concentration. The results showed that the mode of doping of g-C₃N₄ by CeO₂ strongly affected its adsorption capacity. However, g-C₃N₄ doped with CeO₂ using the first mode adsorbed 998.4 mg g^-1 in case of Pb²⁺ and 448 for Cd²⁺. Kinetic study revealed that the adsorption process obeyed PSORE as its q ^exp _e is close to its q ^cal _e and the rate-controlling step involved coordination among the synthetic materials and the heavy metal ions. The recovery of Pb²⁺ and Cd²⁺ ions from various sorbents was investigated by utilizing different molar concentrations of HNO₃ and indicated no significant change in the sorption capability after three different runs. This study has demonstrated an efficient method to obtain a highly efficient adsorbent for removing heavy metals from waste water.

Novel Nafion/Graphitic Carbon Nitride Nanosheets Composite Membrane for Steam Electrolysis at 110 °C

Hydrogen is expected to have an important role in future energy systems; however, further research is required to ensure the commercial viability of hydrogen generation. Proton exchange membrane steam electrolysis above 100 °C has attracted significant research interest owing to its high electrolytic efficiency and the potential to reduce the use of electrical energy through waste heat utilization. This study developed a novel composite membrane fabricated from graphitic carbon nitride (g-C₃N₄) and Nafion and applied it to steam electrolysis with excellent results. g-C₃N₄ is uniformly dispersed among the non-homogeneous functionalized particles of the polymer, and it improves the thermostability of the membranes. The amino and imino active sites on the nanosheet surface enhance the proton conductivity. In ultrapure water at 90 °C, the proton conductivity of the Nafion/0.4 wt.% g-C₃N₄ membrane is 287.71 mS cm^-1. Above 100 °C, the modified membranes still exhibit high conductivity, and no sudden decreases in conductivity were observed. The Nafion/g-C₃N₄ membranes exhibit excellent performance when utilized as a steam electrolyzer. Compared with that of previous studies, this approach achieves better electrolytic behavior with a relatively low catalyst loading. Steam electrolysis using a Nafion/0.4 wt.% g-C₃N₄ membranes achieves a current density of 2260 mA cm^-2 at 2 V, which is approximately 69% higher than the current density achieved using pure Nafion membranes under the same conditions.

Highly dispersed Rh single atoms over graphitic carbon nitride as a robust catalyst for the hydroformylation reaction

Rhodium-catalysed hydroformylation, effective tool in bulk and fine-chemical synthesis, predominantly uses soluble metal complexes. For that reason, the metal leaching and the catalyst recycling are still the major drawbacks of this process. Single-atom catalysts have emerged as a powerful tool to combine the advantages of both homogeneous and heterogeneous catalysts. Since using an appropriate support material is key to create stable, finely dispersed, single-atom catalysts, here we show that Rh atoms anchored on graphitic carbon nitride are robust catalysts for the hydroformylation reaction of styrene.

Kinetic Study of the Effective Thermal Polymerization of a Prebiotic Monomer: Aminomalononitrile

Aminomalononitrile (AMN), the HCN formal trimer, is a molecule of interest in prebiotic chemistry, in fine organic synthesis, and, currently, in materials science, mainly for bio-applications. Herein, differential scanning calorimetry (DSC) measurements by means of non-isothermal experiments of the stable AMN p-toluenesulfonate salt (AMNS) showed successful bulk AMN polymerization. The results indicated that this thermally stimulated polymerization is initiated at relatively low temperatures, and an autocatalytic kinetic model can be used to appropriately describe, determining the kinetic triplet, including the activation energy, the pre-exponential factor, and the mechanism function (E_α, A and f(α)). A preliminary structural characterization, by means of Fourier transform infrared (FTIR) spectroscopy, supported the effective generation of HCN-derived polymers prepared from AMNS. This study demonstrated the autocatalytic, highly efficient, and straightforward character of AMN polymerization, and to the best of our knowledge, it describes, for the first time, a systematic and extended kinetic analysis for gaining mechanistic insights into this process. The latter was accomplished through the help of simultaneous thermogravimetry (TG)-DSC and the in situ mass spectrometry (MS) technique for investigating the gas products generated during these polymerizations. These analyses revealed that dehydrocyanation and deamination processes must be important elimination reactions involved in the complex AMN polymerization mechanism.

Ionic-Wind-Enhanced Raman Spectroscopy without Enhancement Substrates

Raman spectra are often masked by strong fluorescence, which severely hinders the applications of Raman spectroscopy. Herein, for the first time, we report ionic-wind-enhanced Raman spectroscopy (IWERS) incorporated with photobleaching (PB) as a noninvasive approach to detect fluorescent and vulnerable samples without a substrate. In this study, ionic wind (IW) generated by needle-net electrodes transfers charges to the sample surface in air on the scale of millimeters rather than nanometers in surface-enhanced Raman spectroscopy. Density functional theory calculations reveal that the ionic particles in IW increase the susceptibility of the sample molecules, thus enhancing the Raman signals. Meanwhile, the incorporation of IW with PB yields a synergistic effect to quench fluorescence. Therefore, this approach can improve the signal-to-noise ratio of Raman peaks up to three times higher than that with only PB. At the same time, IWERS can avoid sample pollution and destruction without substrates as well as high laser power. For archeological samples and a red rock as an analogue to Mars geological samples, IWERS successfully identified weak but key Raman peaks, which were masked by strong florescence. It suggests that IWERS is a promising tool for characterizations in the fields of archeology, planetary science, biomedicine, and soft matter.

Enhanced stability of sub-nanometric iridium decorated graphitic carbon nitride for H2 production upon hydrous hydrazine decomposition

Stabilizing metal nanoparticles is vital for large scale implementations of supported metal catalysts, particularly for a sustainable transition to clean energy, e.g., H₂ production. In this work, iridium sub-nanometric particles were deposited on commercial graphite and on graphitic carbon nitride by a wet impregnation method to investigate the metal-support interaction during the hydrous hydrazine decomposition reaction. To establish a structure-activity relationship, samples were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic performance of the synthesized materials was evaluated under mild reaction conditions, i.e. 323 K and ambient pressure. The results showed that graphitic carbon nitride (GCN) enhances the stability of Ir nanoparticles compared to graphite, while maintaining remarkable activity and selectivity. Simulation techniques including Genetic Algorithm geometry screening and electronic structure analyses were employed to provide a valuable atomic level understanding of the metal-support interactions. N anchoring sites of GCN were found to minimise the thermodynamic driving force of coalescence, thus improving the catalyst stability, as well as to lead charge redistributions in the cluster improving the resistance to poisoning by decomposition intermediates.

Graphitic Carbon Nitride Nanoheterostructures as Novel Platforms for the Electrochemical Sensing of the Chemotherapeutic and Immunomodulator Agent MTX

We report on the electrochemical determination of one the most effective and widely used chemotherapeutic, anti-inflammatory, and immunomodulator agents, methotrexate (MTX), using low-cost, green, and facile one-pot prepared graphitic carbon nitride (g-CN ) nanosheets. The g-CN nanosheets have been characterized utilizing Fourier transform infrared spectroscopy, X-ray diffraction(XRD), scanning electron microscopy(SEM), and density functional theory (DFT). In comparison to the bare carbon paste electrode (CPE), the g-CN -modified electrode showed a spectacular enhancement in the electrochemical oxidation and detection abilities of MTX. The proposed material exhibits very low limits of detection (12.45 nM) and quantification (41.5 nM), while possessing a wide linear range of 0.22-1.11 μM and 1.11-27.03 μM under optimized conditions at pH 7.0. Due to the ease of preparation of g-CN, it can be adopted for the cost-effective detection of MTX in industrial and clinical analyses.

Black graphitic carbon nitride nanosheets with mid-gap states realizing highly efficient near-infrared photo-thermal conversion for photoacoustic imaging

Developing metal-free photo-thermal transduction nanoagents (PTNAs) with high conversion efficiency addresses the balance between superior photothermal performance and good biocompatibility in the field of bio-applications of PTNAs. Herein, we highlight the bandgap-engineered black graphitic carbon nitride nanosheets (denoted as B-g-C₃N₄) as a novel metal-free PTNA with high conversion efficiency (62% at 808 nm) for photoacoustic imaging. The B-g-C₃N₄ absorbed infrared light with a narrowed bandgap and electronic states within the band (known as mid-gap states) due to the synergistic effect of sulfur incorporation, nitrogen vacancies and the porous structure. Notably, the mid-gap states mediated the non-irradiative recombination of electrons and holes, bringing about energy dissipated as phonons. Owing to the high conversion efficiency as well as superior biocompatibility, HeLa cells incubated with B-g-C₃N₄ can be ablated under 808 nm light illumination. Furthermore, the B-g-C₃N₄ realized cross-sectional multispectral optoacoustic tomography (MSOT) imaging of the U14-tumor-bearing mouse. This work expands the catalogue of highly efficient metal-free PTNAs, showing great promise in biological applications.

A Comprehensive Review on Graphitic Carbon Nitride for Carbon Dioxide Photoreduction

Inspired by natural photosynthesis, harnessing the wide range of natural solar energy and utilizing appropriate semiconductor-based catalysts to convert carbon dioxide into beneficial energy species, for example, CO, CH₄ , HCOOH, and CH₃ COH have been shown to be a sustainable and more environmentally friendly approach. Graphitic carbon nitride (g-C₃ N₄ ) has been regarded as a highly effective photocatalyst for the CO₂ reduction reaction, owing to its cost-effectiveness, high thermal and chemical stability, visible light absorption capability, and low toxicity. However, weaker electrical conductivity, fast recombination rate, smaller visible light absorption window, and reduced surface area make this catalytic material unsuitable for commercial photocatalytic applications. Therefore, certain procedures, including elemental doping, structural modulation, functional group adjustment of g-C₃ N₄ , the addition of metal complex motif, and others, may be used to improve its photocatalytic activity towards effective CO₂ reduction. This review has investigated the scientific community's perspectives on synthetic pathways and material optimization approaches used to increase the selectivity and efficiency of the g-C₃ N₄ -based hybrid structures, as well as their benefits and drawbacks on photocatalytic CO₂ reduction. Finally, the review concludes a comparative discussion and presents a promising picture of the future scope of the improvements.