Properties, synthesis, and recent advancement in photocatalytic applications of graphdiyne: A review

In-situ sonochemical formation of N-graphyne modulated porous g-C3N4 for boosted photocatalysis degradation of pollutants and nitrogen fixation

Herein, Nitrogen-doped graphyne/porous g-C3N4 composites are firstly in-situ synthesized via the ultrasound vibration of CaC2, triazine, and porous g-C3N4 in absolute ethanol. A variety of characterizations are performed to investigate the morphology, microstructure, composition, and electrical/optical features of the obtained composites, such as transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and so forth. It is found that N-doped graphyne with flexible folds lamellar structure is intimately attached to flake g-C3N4 in the as-prepared composites. An enlargement of 1.68 and 1.44 folds for the photocatalytic degradation of levofloxacin, rhodamine B, Methylene blue, and Tetracycline is realized by N-doped graphyne/g-C3N4 in comparison with that of pristine g-C3N4, respectively. In addition, the highest NH3 production rate attains 1.71 mmol⋅gcat-1⋅h-1 for N-doped graphyne/g-C3N4, which is 5.89 times larger than that of g-C3N4 (0.29 mmol⋅gcat-1⋅h-1). The improved mechanism of photocatalysis including higher photo-response and carrier separation rate is verified by transient photo-current, transient photo-potential, Mott-Schottky plots, Tafel plots, electrochemical impedance spectroscopy, turn-over frequency, photoluminescence spectra, and UV-vis diffuse absorption spectra, etc. Overall, the current study shows that N-doped graphyne synthesized from CaC2 and triazine is a useful decoration to modulate the photocatalytic features of g-C3N4, which can also be widely extended for in-situ modification of other photocatalysts.

Properties, Synthesis and Emerging Applications of Graphdiyne: A Journey Through Recent Advancements

Graphdiyne (GDY) is a new variant of nano-carbon material with excellent chemical, physical and electronic properties. It has attracted wide attention from researchers and industrialists for its extensive role in the fields of optics, electronics, bio-medics and energy. The unique arrangement of sp-sp2 carbon atoms, linear acetylenic linkages, uniform pores and highly conjugated structure offer numerous potentials for further exploration of GDY materials. However, since the material is at its infancy, not much understanding is available regarding its properties, growth mechanism and future applications. Therefore, in this review, readers are guided through a brief discussion on GDY's properties, different synthesis procedures with a special focus on surface functionalization and a list of applications for GDY. The review also critically analyses the advantages and disadvantages of each synthesis route and emphasizes the future scope of the material.

Transition metals anchored on nitrogen-doped graphdiyne for an efficient oxygen reduction reaction: a DFT study

The search for highly active and low-cost single-atom catalysts for the oxygen reduction reaction (ORR) is essential for the widespread application of proton exchange membrane fuel cells. Transition metals anchored on nitrogen-doped graphdiyne (GDY) have attracted considerable interest as potentially excellent catalysts for the ORR. However, the relationship between the active site and nitrogen-doped GDY remains unclear. In this work, we conducted a systematic investigation of sp-hybridized N atoms anchoring single transition metal atoms of 3d and 4d on GDY (TMC2N2) as electrocatalysts for the ORR. Firstly, 18 kinds of TMC2N2 were determined to have good thermodynamic stability. Due to the extremely strong adsorption of *OH, TMC2N2 exhibits inferior ORR performance compared to traditional Pt(111). Considering that *OH adsorption hinders the catalytic activity of TMC2N2, we modified the OH ligand of TMC2N2 to develop the high-valent metal complex (TMC2N2-OH) aiming to enhance the electrocatalytic activity. The adsorption of intermediates on most TMC2N2-OH is weakened after the modification of the OH ligand, especially for the adsorption of *OH. Thus, by comparing the ORR overpotential of catalysts before and after ligand modification, we find that the catalytic activity of different TMC2N2-OHs improves to various degrees. MnC2N2-OH, TMC2N2-OH, and TcC2N2-OH exhibit relatively high ORR catalytic activity, with overpotentials of 0.93 V, 1.19 V, and 0.92 V, respectively. Furthermore, we investigated the cause of improved catalytic activity of TMC2N2-OH and found that the modified coordination environment of the catalyst led to adjusted adsorption of ORR intermediates. In summary, our work sheds light on the relationship between nitrogen-doped GDY and transition metal sites, thus contributing to the development of more efficient catalysts.

Precise Preparation of Triarylboron-Based Graphdiyne Analogues for Gas Separation

A series of triarylboron-based graphdiyne analogues (TAB-GDYs) with tunable pore size were prepared through copper mediated coupling reaction. The elemental composition, chemical bond, morphology of TAB-GDYs were well characterized. The crystallinity was confirmed by selected area electron diffraction (SAED) and stacking modes were studied in combination with high resolution transmission electron microscope (HRTEM) and structure simulation. The absorption and desorption isotherm revealed relatively high specific surface area of these TAB-GDYs up to 788 m2  g-1 for TMTAB-GDY, which decreased as pore size enlarged. TAB-GDYs exhibit certain selectivity for CO2 /N2 (21.9), CO2 /CH4 (5.3), CO2 /H2 (41.8) and C2 H2 /CO2 (2.3). This work has developed a series of boron containing two-dimensional frameworks with clear structures and good stability, and their tunable pore sizes have laid the foundation for future applications in the gas separation field.

A biosensor based on graphene oxide nanocomposite for determination of carcinoembryonic antigen in colorectal cancer biomarker

Colorectal cancer is still a major global health concern, and early detection and accurate biomarker analyses are critical to its successful management. This paper describes the design and testing of a new biosensor based on a graphene oxide (GO) nanocomposite for the exact measurement of carcinoembryonic antigen (CEA), a well-known biomarker for colorectal cancer. The current study attempted to create a highly sensitive immunosensor for sensitive measurement of CEA based on a polypropylene-imine-dendrimer (PPI) and GO nanocomposite on GCE (PPI/GO/GCE). The PPI/GO nanocomposite served as an appropriate biocompatible nanostructure with a large surface area for immobilizing carcinoembryonic antigen (anti-CEA) and bovine serum albumin (BSA) molecules (BSA/anti-CEA/PPI/GO/GCE), thereby promoting the selectivity of electrochemical immunosensors, according to structural and electrochemical studies. Results showed that the BSA/anti-CEA/PPI/GO/GCE as a selective, sensitive, and stable immunosensor revealed a wide linear response from 0.001 to 2000 ng/mL, and a limit of detection of 0.3 pg/mL, which indicated comparable or better performance towards the CEA immunosensors in recent reports in the literature. This was due to the synergetic effect of the GO nanosheets and PPI with porous structure and more conductivity. Analytical results showed values of RSD (4.49%-5.04%) and recovery (90.00%-99.98%) are suitable for effective and accurate practical assessments in CEA in clinical samples. The capacity of the BSA/anti-CEA/PPI/GO/GCE to determine CEA in human blood was studied.

Advancements in Plasma-Enhanced Chemical Vapor Deposition for Producing Vertical Graphene Nanowalls

In recent years, vertical graphene nanowalls (VGNWs) have gained significant attention due to their exceptional properties, including their high specific surface area, excellent electrical conductivity, scalability, and compatibility with transition metal compounds. These attributes position VGNWs as a compelling choice for various applications, such as energy storage, catalysis, and sensing, driving interest in their integration into next-generation commercial graphene-based devices. Among the diverse graphene synthesis methods, plasma-enhanced chemical vapor deposition (PECVD) stands out for its ability to create large-scale graphene films and VGNWs on diverse substrates. However, despite progress in optimizing the growth conditions to achieve micrometer-sized graphene nanowalls, a comprehensive understanding of the underlying physicochemical mechanisms that govern nanostructure formation remains elusive. Specifically, a deeper exploration of nanometric-level phenomena like nucleation, carbon precursor adsorption, and adatom surface diffusion is crucial for gaining precise control over the growth process. Hydrogen's dual role as a co-catalyst and etchant in VGNW growth requires further investigation. This review aims to fill the knowledge gaps by investigating VGNW nucleation and growth using PECVD, with a focus on the impact of the temperature on the growth ratio and nucleation density across a broad temperature range. By providing insights into the PECVD process, this review aims to optimize the growth conditions for tailoring VGNW properties, facilitating applications in the fields of energy storage, catalysis, and sensing.

Biogenic synthesis of reduced graphene oxide decorated with silver nanoparticles (rGO/Ag NPs) using table olive (olea europaea) for efficient and rapid catalytic reduction of organic pollutants

In this work, graphene oxide (GO) sheets were prepared via a facile electrochemical exfoliation of graphite in acidic medium and subsequent oxidation with potassium permanganate. The GO sheets were employed for preparation of reduced GO adorned with nanosized silver (rGO/Ag NPs) using green reduction of GO and Ag(I) via olive fruit extract as a reducing and immobilizing agent. The crystal phase, morphology, and nanostructure of the prepared catalyst were characterized by XRD, SEM, EDX, UV-Vis and Raman spectroscopy techniques. The as-prepared rGO/Ag NPs showed superior catalytic performance towards the complete reduction (up to 99%) of 4-nitrophenol (4-NPH) to 4-aminophenol (4-APH) and rhodamine B (RhB) to Leuco RhB within 180 s using NaBH₄ at ambient condition. The rate constant (k) values were found to be 0.021 and 0.022 s^-1 for 4-NPH and RhB reduction, respectively. In addition, the regenerated catalyst could be reused after seven cycles without losing any apparent catalytic efficiency. Accounting for the excellent catalytic capability, chemical stability and environment-friendly synthesis protocol, the rGO/Ag NPs has great potential working as a heterogeneous catalyst in the transforming harmful organic contaminants into less harmful or harmless compounds.

Recent advances in visible-light graphitic carbon nitride (g-C3N4) photocatalysts for chemical transformations

Graphitic carbon nitride (g-C3N4) has emerged as a new research hotspot, attracting broad interdisciplinary attention in the form of metal-free and visible-light-responsive photocatalysts in the field of solar energy conversion and environmental remediation. These photocatalysts have evolved as attractive candidates due to their non-toxicity, chemical stability, efficient light absorption capacity in the visible and near-infrared regions, and adaptability as a platform for the fabrication of hybrid materials. This review mainly describes the latest advances in g-C3N4 photocatalysts for chemical transformations. In addition, the typical applications of g-C3N4-based photocatalysts involving organic transformation reactions are discussed (synthesis of heterocycles, hydrosulfonylation, hydration, oxygenation, arylation, coupling reactions, etc.).