Graphene and its derivatives as versatile templates for materials synthesis and functional applications

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.

Nano-antivirals: A comprehensive review

Nanoparticles can be used as inhibitory agents against various microorganisms, including bacteria, algae, archaea, fungi, and a huge class of viruses. The mechanism of action includes inhibiting the function of the cell membrane/stopping the synthesis of the cell membrane, disturbing the transduction of energy, producing toxic reactive oxygen species (ROS), and inhibiting or reducing RNA and DNA production. Various nanomaterials, including different metallic, silicon, and carbon-based nanomaterials and nanoarchitectures, have been successfully used against different viruses. Recent research strongly agrees that these nanoarchitecture-based virucidal materials (nano-antivirals) have shown activity in the solid state. Therefore, they are very useful in the development of several products, such as fabric and high-touch surfaces. This review thoroughly and critically identifies recently developed nano-antivirals and their products, nano-antiviral deposition methods on various substrates, and possible mechanisms of action. By considering the commercial viability of nano-antivirals, recommendations are made to develop scalable and sustainable nano-antiviral products with contact-killing properties.

Potential of graphene based photocatalyst for antiviral activity with emphasis on COVID-19: A review

Coronavirus disease-2019 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been one of the most challenging worldwide epidemics of recent times. Semiconducting materials (photocatalysts) could prove effectual solar-light-driven technology on account of variant reactive oxidative species (ROS), including superoxide (^•O₂ ^- ) and hydroxyl (^•OH) radicals either by degradation of proteins, DNA, RNA, or preventing cell development by terminating cellular membrane. Graphene-based materials have been exquisitely explored for antiviral applications due to their extraordinary physicochemical features including large specific surface area, robust mechanical strength, tunable structural features, and high electrical conductivity. Considering that, the present study highlights a perspective on the potentials of graphene based materials for photocatalytic antiviral activity. The interaction of virus with the surface of graphene based nanomaterials and the consequent physical, as well as ROS induced inactivation process, has been highlighted and discussed. It is highly anticipated that the present review article emphasizing mechanistic antiviral insights could accelerate further research in this field.

Interfacial assembled mesoporous polydopamine nanoparticles reduced graphene oxide for high performance of waterborne epoxy-based anticorrosive coatings

Embedding two-dimension micro/nanocontainers containing corrosion inhibitors into organic coating is a well-established concept to impart the coating with enhanced barrier and self-healing feature. Herein, a versatile nanoemulsion assembly approach was used to synthesis nanocarriers combing mesoporous polydopamine nanoparticles (MPDA) with reduced graphene oxide (GO), which was employed to encapsulate corrosion inhibitors (benzotriazole, BTA) to improve the anticorrosion performance of waterborne epoxy coating. The BTA release profiles from synthesized GO with MPDA (PDAG) demonstrated the rapid pH-triggered activities to acidic corrosion environment. With the addition of BTA-loaded PDAG, the composited epoxy coatings presented self-repairing behavior and enhanced corrosion resistance during long-term immersion. The outstanding anticorrosion performance is attributed to dual-protection mechanism provided by BTA-loaded PDAG: (1) MPDA endows GO with satisfactory interface compatibilities and thus provides impermeable barrier to delay the penetration process of corrosive electrolyte; (2) corrosion inhibitors including BTA and polydopamine form the adsorption layers on bare steel surface to resist continuous corrosion at metal/coating interface.

Synthesis, Characterization and Photodegradation Studies of Copper Oxide–Graphene Nanocomposites

In this work, a simple hydrothermal method was employed to prepare a pristine sample of copper oxide (CuO) and three samples of copper oxide–graphene nanocomposites (CuO-xG) with x = 2.5, 5, and 10 mg of graphene. The synthesized samples were characterized using X-ray powder diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV-Vis) spectroscopy. The XRD patterns of CuO-xG nanocomposites exhibited the diffraction peaks related to the crystal planes of monoclinic CuO and hexagonal graphite. The surface morphology of the prepared samples was investigated using FESEM images. EDX analysis was used to investigate the chemical composition of the synthesized samples. FTIR spectroscopy identified the vibrational modes of the covalent bonds present in the samples. The allowed direct optical bandgap energy was calculated for all prepared samples using UV-Vis absorption spectra. The small bandgap of CuO-xG nanocomposites indicates their potential use as an effective photocatalyst in the presence of visible light. Photocatalytic activity of the samples was explored for the degradation of methylene blue (MB) dye contaminant under visible light irradiation. The results showed that the CuO-5G sample has the highest photodegradation efficiency (~56%).

Roles of Graphene Oxide in Heterogeneous Photocatalysis

Graphene oxide (GO) has been widely utilized as the precursor of graphene (GR) to fabricate GR-based hybrid photocatalysts for solar-to-chemical energy conversion. However, until now, the properties and roles that GO played in heterogeneous photocatalysis have remained relatively elusive. In this Review, we start with a brief discussion of synthesis and structure of GO. Then, the photocatalysis-related properties of GO, including electrical conductivity, surface chemistry, dispersibility, and semiconductor properties, are concisely summarized. In particular, we have highlighted the fundamental multifaceted roles of GO in heterogeneous photocatalysis, which contain the precursor of GR, cross-linked framework for constructing aerogel photocatalyst, macromolecular surfactant, two-dimensional growth template, and photocatalyst by itself. Furthermore, the future prospects and remaining challenges on developing effective GO-derived hybrid photocatalysts are presented, which is expected to inspire further research into this promising research domain.

A NiFe layered double hydroxide-decorated N-doped entangled-graphene framework: a robust water oxidation electrocatalyst

Three dimensional (3D) porous carbon materials are highly desirable for electrochemical applications owing to their high surface area and porosity. Uniformly distributed porosity in the 3D architecture of carbon support materials allows reactant molecules to access more electrochemically active centres and simultaneously facilitate removal of the product formed during electrochemical reactions. Herein, we have prepared a nitrogen-doped entangled graphene framework (NEGF), decorated with NiFe-LDH nanostructures by an in situ solvothermal method followed by freeze-drying at high vacuum pressure and low temperature. The freeze-drying method helped to prevent the restacking of the graphene sheets and the formation of a high surface area nitrogen-doped entangled graphene framework (NEGF) supported NiFe-LDHs. The incorporation of the NEGF has significantly reduced the overpotential for the electrochemical oxygen evolution reaction (OER) in 1 M KOH solution. This corresponds to an overpotential reduction from 340 mV for NiFe-LDHs to 290 mV for NiFe-LDH/NEGF to reach the benchmark current density of 10 mA cm^-2. The preparation of the catalyst is conceived through a low-temperature scalable process.

Green graphene nanoplates for combined photo-chemo-thermal therapy of triple-negative breast cancer

Aim: Green graphene oxide (GO) nanoplates, which are reduced and stabilized by quercetin and guided by folate receptors (quercetin reduced and loaded GO nanoparticles-folic acid [FA]), were developed to mediate combined photo-chemo-thermal therapy of triple-negative breast cancer. Materials & methods: Modified Hummers method was used for the synthesis of GO followed by its reduction using quercetin, FA was then conjugated as a targeting ligand. A cytotoxicity assay, apoptosis assay and cellular uptake assay were performed in vitro in MDA-MB-231 cell line with and without irradiation of a near-infrared 808 nm laser. Results & conclusion: Quercetin reduced and loaded GO nanoparticles-FA showed significantly high cellular uptake (p < 0.001) and cytotoxic effects in MDA-MB-231 cells, which was even more prominent under the situation of near-infrared 808 nm laser irradiation, making it a potential option for treating triple-negative breast cancer.

Effect of Hybrid mono/bimetallic Nanocomposites for an enhancement of Catalytic and Antimicrobial Activities

Exploring the new catalytic systems for the reduction of organic and inorganic pollutants from an indispensable process in chemical, petrochemical, pharmaceutical and food industries, etc. Hence, in the present work, authors motivated to synthesize bare reduced graphene oxide (rGO), polyaniline (PANI), three different ratios of rGO-PANI_{(80:20,50:50, 10:90)} composites and rGO-PANI_{(80:20,50:50, 10:90)} supported mono (Pd) & bimetallic [Pd: Au_{(1:1,1:2, 2:1)}] nanocomposite by a facile chemical reduction method. Also, it investigated their catalytic performances for the reduction of organic/inorganic pollutants and antimicrobial activities. All the freshly prepared bare rGO, PANI, three different ratios of rGO-PANI_{(80:20, 50:50,10:90)} composites and rGO-PANI_{(80:20, 50:50,10:90)}/Pd & Pd: Au_{(1:1, 1:2,2:1)} nanocomposite hybrid catalysts were characterized using UV-Vis, FT-IR, SEM, FE-SEM, EDAX, HR-TEM, XRD, XPS and Raman spectroscopy analysis. Among them, an optimized best composition of rGO-PANI_(80:20)/Pd: Au_(1:1) bimetallic nanocomposite hybrid catalyst exhibits better catalytic reduction and antimicrobial activities than other composites, as a result of strong electrostatic interactions between rGO, PANI and bimetal (Pd: Au) NPs through a synergistic effect. Hence, an optimized rGO-PANI_(80:20)/Pd:Au_(1:1) bimetallic nanocomposite catalyst would be considered as a suitable catalyst for the reduction of different nitroarenes, organic dyes, heavy metal ions and also significantly inhibit the growth of S. aureus, S. Typhi as well as Candida albicans and Candida kruesi in wastewater.

Synthesis of Graphene Oxide Interspersed in Hexagonal WO3 Nanorods for High-Efficiency Visible-Light Driven Photocatalysis and NH3 Gas Sensing

WO₃ nanorods and GO (at 1 wt% loading) doped WO₃ were synthesized using a template free deposition-hydrothermal route and thoroughly characterized by various techniques including XRD, FTIR, Raman, TEM-SAED, PL, UV-Vis, XPS, and N₂ adsorption. The nano-materials performance was investigated toward photocatalytic degradation of methylene blue dye (20 ppm) under visible light illumination (160 W, λ> 420) and gas sensing ability for ammonia gas (10–100 ppm) at 200°C. HRTEM investigation of the 1%GO.WO₃ composite revealed WO₃ nanorods of a major d-spacing value of 0.16 nm indexed to the crystal plane (221). That relevant plane was absent in pure WO₃ establishing the intercalation with GO. The MB degradation activity was considerably enhanced over the 1%GO.WO₃ catalyst with a rate constant of 0.0154 min⁻¹ exceeding that of WO₃ by 15 times. The reaction mechanism was justified dependent on electrons, holes and •OH reactive species as determined via scavenger examination tests and characterization techniques. The drop in both band gap (2.49 eV) and PL intensity was the main reason responsible for enhancing the photo-degradation activity of the 1%GO.WO₃ catalyst. The later catalyst initiated the two electron O₂ reduction forming H₂O₂, that contributed in the photoactivity improvement via forming •OH moieties. The hexagonal structure of 1%GO.WO₃ showed a better gas sensing performance for ammonia gas at 100 ppm (R_a-R_g/R_g = 17.6) exceeding that of pure WO₃ nanorods (1.27). The superiority of the gas-sensing property of the 1%GO.WO₃ catalyst was mainly ascribed to the high dispersity of GO onto WO₃ surfaces by which different carbon species served as mediators to hinder the recombination rate of photo-generated electron-hole pairs and therefore facilitated the electron transition. The dominancy of the lattice plane (221) in 1%GO.WO₃ formed between GO and WO₃ improved the electron transport in the gas-sensing process.

Promoting charge separation of biochar-based Zn-TiO2/pBC in the presence of ZnO for efficient sulfamethoxazole photodegradation under visible light irradiation

A novel and effective photocatalyst namely titanium dioxide doped with zinc elements stacked on reed straw biochar which was pretreated by acid (Zn-TiO₂/pBC) with visible light response was successfully prepared by a simple modified sol-gel method firstly. The prepared samples were characterized by scanning microscopy (SEM), energy dispersive X-ray spectrum (EDS), X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and UV-Vis diffuse reflectance spectra (DRS). The photocatalytic activity of Zn-TiO₂/pBC was further investigated through the photodegradation of sulfamethoxazole (SMX). Compared with TiO₂ and TiO₂/pBC, Zn-TiO₂/pBC had better photocatalytic activity under visible light due to zinc elements effectively inhibiting the agglomeration of TiO₂ and hindering the combination of photogenerated electrons and holes. The removal rate of SMX could reach 81.21%, which was 1.37 times higher than that of TiO₂/pBC(300). Three common anions (SO₄^2-, Cl^-, NO₃^-) existing in the Yellow River exhibited detrimental effects on the SMX photodegradation to a certain degree. It might mainly occurred hydroxylation, cleavage of SN bond and opening of isoxazole ring reactions during the photodegradation process of SMX. Meanwhile, there might be four main degradation pathways proposed throw the LC/MS/MS analysis. Finally, good reusability and stability illustrated Zn-TiO₂/pBC owned good practicality and feasibility for removal of organic pollutants in environment remediation area.

Soluble Graphene Nanosheets for the Sunlight-Induced Photodegradation of the Mixture of Dyes and its Environmental Assessment

Currently, the air and water pollutions are presenting the most serious global concerns. Despite the well known tremendous efforts, it could be a promising sustainability if the black carbon (BC) soot can be utilized for the practical and sustainable applications. For this, the almost complete aqueous phase photodegradation of the three well-known organic pollutant dyes as crystal violet (CV); rhodamine B (RhB); methylene blue (MB) and their mixture (CV + RhB + MB), by using water-soluble graphene nanosheets (wsGNS) isolated from the BC soot under the influence of natural sunlight is described. The plausible mechanism behind the photocatalytic degradation of dyes and their mixture has been critically analyzed via the trapping of active species and structural analysis of photodegraded products. The impact of diverse interfering ions like Ca2+, Fe3+, SO42-, HPO42-, NO3-, and Cl- on the photodegradation efficiency of wsGNS was also investigated. Importantly, the environmental assessment of the whole process has been evaluated towards the growth of wheat plants using the treated wastewater. The initial studies for the fifteen days confirmed that growth of wheat plants was almost the same in the photodegraded wastewater as being noticed in the control sample, while in case of dyes contaminated water it showed the retarded growth. Using the natural sunlight, the overall sustainability of the presented work holds the potential for the utilization of pollutant soot in real-practical applications related to the wastewater remediation and further the practical uses of treated water.

Planting carbon nanotubes onto supramolecular polymer matrices for waterproof non-contact self-healing

Supramolecular polymers show unique and excellent properties due to the reversible and designable nature of the non-covalent interactions. Herein, ureido-pyrimidinone (UPy)-based supramolecular polymers were employed to fabricate the thermo-responsive composite materials with multi-walled carbon nanotubes (MWCNTs) by planting the MWCNTs onto the supramolecular polymer matrices via a simple surface spraying procedure. The MWCNTs coating on the surface of the supramolecular polymer matrices gave the composite film superhydrophobic and conductive properties, and it had a non-contact healable ability underwater under 808 nm near-infrared light (NIR) irradiation. Moreover, the UPy-based supramolecular polymers acted as thermo-responsive matrices to guarantee the self-healing properties at a relatively low temperature, such as body temperature (33 °C-34 °C). The supramolecular polymer/MWCNTs composite materials exhibited excellent strain sensitivities and could be used to prepare human motion-monitoring devices. This line of research may find a promising practical application in healable wearable devices used in underwater environments.

Coumarin–graphene turn-on fluorescent probe for femtomolar level detection of copper(ii)

A novel coumarin–graphene moiety was suggested as an excellent optical sensor for Cu²⁺ ions.

Recent advances in carbon quantum dot (CQD)-based two dimensional materials for photocatalytic applications

This review presents up-to-date research findings and critical insights on trending topics of pristine CQDs and CQDs-based 2D nanomaterial composites.

Template-oriented synthesis of hydroxyapatite nanoplates for 3D bone printing

The design of hydroxyapatite (HA) nanoarchitecture is critical for fabricating artificial bone tissues as it dictates the biochemical and the mechanical properties of the final product.

Facile scalable fabrication of ultra-thin freestanding SiO2-based hybrid nanosheets with multifunctional properties

Two-dimensional (2D) nanomaterials with unique features like a large surface-to-volume ratio and the quantum confinement effect have attracted great attention for applications in energy storage, catalysis, sensing, membranes, etc. Silica (SiO₂)-based nanosheets, as members of the 2D material family, are extremely intriguing because of their unique electronic insulation, bio-compatibility and profound chemical and thermal stability. However, there is still a lack of available approaches for fabricating SiO₂ nanosheets in a simple, large-scale and cost-effective fashion. In the present research, we have proposed a facile and mass fabrication method for ultra-thin freestanding SiO₂-based hybrid nanosheets (SS) with a uniform thickness by crashing hollow microcapsules through ultrasonication treatment. The morphology, composition, and application of the hybrid nanosheets are investigated in detail. The experimental results demonstrate that SS nanosheets with an inorganic-organic hybrid structure display a Janus-type composition with double bonds residing on one side and hydroxyl groups on the other. Additionally, the SS nanosheets could be easily modified by introducing various functional components such as aluminium hydroxide (AH). The as-prepared SS nanosheets and AH modified nanosheets (SS-AH) could considerably enhance the thermal stability of silicone rubber with remarkably increased thermal decomposition temperatures and residues compared with the reference samples. SS and SS-AH sheets are highly superior in usage as polymer thermal stability fillers because of the following aspects: the hybrid nature of SS and SS-AH is advantageous to facilitate the filler-polymer interaction, so these particles could be readily dispersed into silicone without any hydrophobicity modification; these fillers could improve the thermal stability of elastomers at a much lower filler loading (<8%) than the previously reported filler system (e.g. >20 wt%). Furthermore, the nanosheets are also proved to be efficient in usage as emulsifiers for the immiscible oil-water system with a higher efficiency and emulsion stability than the commonly used emulsifiers. Consequently, the hybrid nanosheets fabricated in this work will not only enrich the family of ultra-thin 2D materials but also attract more interest in potential applications in functional nanocomposites and solid emulsifiers.

Palladium nanoparticle functionalized graphene xerogel for catalytic dye reduction

We report a method to synthesize a palladium-functionalized porous graphene xerogel structure. A graphene xerogel nanocomposite with a three-dimensional microstructure was obtained by chemical reduction of an aqueous dispersion of graphene oxide at mild temperature. After the graphene hydrogel has been placed in a K2PdCl4 solution, the spontaneous redox reaction between the reduced graphene and Pd2+ takes place, leading to the formation of nanohybrid materials consisting of a graphene porous matrix decorated with Pd nanoparticles. The final porosity of the material was tuned through drying the graphene hydrogel by solvent evaporation. The palladium functionalized porous graphene xerogels were successfully used for the catalytic reduction of Rhodamine 6G.

Surfactant/organic solvent free single-step engineering of hybrid graphene-Pt/TiO2 nanostructure: Efficient photocatalytic system for the treatment of wastewater coming from textile industries

In this study, hybrid graphene-Pt/TiO₂ nanostructure were synthesized by single-step, inexpensive and surfactant/organic solvent free route; hydrothermal technique. The physicochemical properties of hybrid graphene-Pt/TiO₂ nanostructure were carefully analyzed by multiple techniques, including X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The synthesized hybrid nanostructures were utilized as photocatalyst for the degradation of methylene blue (MB) dye under natural environment at average ambient temperature and mean daily global solar radiation, of about 22–25 °C and 374.9 mWh/cm², respectively. The activity performance indicated considerable degradation of methylene blue (MB) dye and was in the following order Gr (13%), TiO₂ (60%) and hybrid graphene-Pt/TiO₂ nanostructure (90%) over 21 min under the natural light illumination. The physiochemical characterization suggests that, the tightly attached metalized TiO₂ nanoparticles (Pt-TiO₂) on the high surface area graphene sheets improved utilization of visible light and increased separation and transfer of photo-excited electron (ē) hole (h⁺) pairs. Notably, the hybrid graphene-Pt/TiO₂ nanostructure exhibited an excellent cyclic stability for methylene blue (MB) dye removal. Finally, the kinetic behavior indicated that the photocatalytic degradation reaction of the dye obeyed the pseudo-first order (Langmuir-Hinshelwood) kinetics model.

Low temperature synthesis of NbC/C nano-composites as visible light photoactive catalyst

A facile carbothermal route was adopted to obtain niobium carbide nanoparticles (NPs) embedded in carbon network from Nb2O5 to study photocatalytic behavior. Optimization of synthesis parameters to obtain single phase NbC NPs has been successfully done. The phase identification, morphology and nature of carbon were determined with the help of X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) suggested the presence of multiple oxidation states of Nb associated to NbC and NbCxOy centers on the surface of NPs. Due to the presence of NbCxOy on the surface of NPs, absorption under visible region of EM spectrum has been observed by UV-visible spectroscopy. Different organic dyes (RhB, MB and MO) were used to study the effect of holding time on the photocatalytic performance of as-synthesized samples. RhB dye was found to be the most sensitive organic molecule among all the considered dyes and degraded 78% in 120 min.

Bubble-wrap carbon: an integration of graphene and fullerenes

Graphene and fullerene, two types of C allotropes with very different structures and properties, have attracted considerable attention from the scientific community as new forms of carbon for several decades. It will be a great advantage to combine the geometrical features of the two. Herein, we report a series of novel two-dimensional carbon allotropes that possess fullerene-like hollow structures (bubbles) embedded in a graphene sheet. These carbon allotropes are both thermally and dynamically stable. Calculations using hybrid functionals show that these two-dimensional carbon allotropes could be metals or semiconductors depending on the size and the pattern of the bubbles. The band gap can be as large as 1.66 eV. Due to the unique atomic configuration, some bubble-wrap carbons have unusual negative Poisson's ratios. The combination of graphene and fullerenes provides an appealing approach to design carbon-based materials with dexterous properties. For example, the insertion of the metal atoms inside the bubbles may greatly enhance the functions of such materials in photovoltaics and catalysis.

Revealing the Double-Edged Sword Role of Graphene on Boosted Charge Transfer versus Active Site Control in TiO2 Nanotube Arrays@RGO/MoS2 Heterostructure

Charge separation/transfer is generally believed to be the most key factor affecting the efficiency of photocatalysis, which however will be counteracted if not taking the active site engineering into account for a specific photoredox reaction. Here, a 3D heterostructure composite is designed consisting of MoS₂ nanoplatelets decorated on reduced graphene oxide-wrapped TiO₂ nanotube arrays (TNTAs@RGO/MoS₂ ). Such a cascade configuration renders a directional migration of charge carriers and controlled immobilization of active sites, thereby showing much higher photoactivity for water splitting to H₂ than binary TNTAs@RGO and TNTAs/MoS₂ . The photoactivity comparison and mechanistic analysis reveal the double-edged sword role of RGO on boosted charge separation/transfer versus active site control in this composite system. The as-observed inconsistency between boosted charge transfer and lowered photoactivity over TNTAs@RGO is attributed to the decrease of active sites for H₂ evolution, which is significantly different from the previous reports in literature. The findings of the intrinsic relationship of balanced benefits from charge separation/transfer and active site control could promote the rational optimization of photocatalyst design by cooperatively manipulating charge flow and active site control, thereby improving the efficiency of photocatalysis for target photoredox processes.

Ultrasonication-assisted synthesis of high aspect ratio gold nanowires on a graphene template and investigation of their growth mechanism

We report a facile synthesis of Au nanowires (AuNWs) with a high aspect ratio (l/D) of up to 5000 on a plasma activated graphene template with ultrasound assistance. We demonstrate that the ultrasonication induced symmetry breaking of Au clusters facilitates the growth of AuNWs from the embryonic stages. Furthermore, the growth mechanism of AuNWs is systematically investigated using high resolution electron transmission microscopy (HRTEM), which reveals the unique role of the defective graphene template in directing the growth of AuNWs.

Graphene template-induced growth of single-crystalline gold nanobelts with high structural tunability

Assembling Au nanocrystals with tunable dimensions and shapes on graphene templates has attracted increasing attention recently. However, directly growing anisotropic Au nanobelts on a graphene support has been rarely reported. Here, a facile, one-pot, and surfactant-free route is demonstrated to synthesize well-defined Au nanobelts with the induction of a multilayer graphene (mlG) template. The obtained Au nanobelts are single-crystalline with a preferable (111) orientation. More importantly, their structural evolution starting from Au clusters is systematically investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results confirm that mlG consistently induces the growth of Au nanobelts from nucleation to the growth completion. The interfacial interaction between Au atoms and the graphene lattice is a predominant factor to direct the shapes and structures of Au nanocrystals, which makes the structures of Au nanobelts highly tunable with the surface modification of the mlG template. The assembly of mlG-Au nanobelts also presents extraordinary detection sensitivity when employed as a flexible surface-enhanced Raman scattering (SERS) substrate, suggesting their great potential application in high-performance sensors. This report strengthens the fundamental understanding of the interactions between noble metals and carbon interfaces, which paves the way to construct and manipulate the complex structures of metals on graphitic substrates.

Novel penta-graphene nanotubes: strain-induced structural and semiconductor-metal transitions

Research into novel one-dimensional (1D) materials and associated structural transitions is of significant scientific interest. It is widely accepted that a 1D system with a short-range interaction cannot have 1D phase transition at finite temperature. Herein, we propose a series of new stable carbon nanotubes by rolling up penta-graphene sheets, which exhibit fascinating well-defined 1D phase transitions triggered by axial strain. Our first-principles calculations show that such penta-graphene nanotubes (PGNTs) are dynamically stable by phonon calculations, but transform from a tri-layer structure to a highly defective single-walled nanotube at low temperature in molecular dynamics simulations. We show that moderate compressive strains can drive structural transitions of (4,4), (5,5), and (6,6) PGNTs, during which the distances of neighboring carbon dimers in the inner shell have a sudden drop, corresponding to dimer-dimer nonbonding to bonding transitions. After such transition, the tubes become much more thermally stable and undergo semiconductor-metal transitions under increasing strain. The band gaps of PGNTs are not sensitive to chirality whereas they can be tuned effectively from visible to short-wavelength infrared by appropriate strain, making them appealing materials for flexible nano-optoelectronics. These findings provide useful insight into unusual phase transitions in low-dimensional systems.

Multichannel Charge Transfer and Mechanistic Insight in Metal Decorated 2D-2D Bi2 WO6 -TiO2 Cascade with Enhanced Photocatalytic Performance

Promising semiconductor-based photocatalysis toward achieving efficient solar-to-chemical energy conversion is an ideal strategy in response to the growing worldwide energy crisis, which however is often practically limited by the insufficient photoinduced charge-carrier separation. Here, a rational cascade engineering of Au nanoparticles (NPs) decorated 2D/2D Bi₂ WO₆ -TiO₂ (B-T) binanosheets to foster the photocatalytic efficiency through the manipulated flow of multichannel-enhanced charge-carrier separation and transfer is reported. Mechanistic characterizations and control experiments, in combination with comparative studies over plasmonic Au/Ag NPs and nonplasmonic Pt NPs decorated 2D/2D B-T composites, together demonstrate the cooperative synergy effect of multiple charge-carrier transfer channels in such binanosheets-based ternary composites, including Z-scheme charge transfer, "electron sink," and surface plasmon resonance effect, which integratively leads to the boosted photocatalytic performance.

Flexible Graphene-Based Wearable Gas and Chemical Sensors

Wearable electronics is expected to be one of the most active research areas in the next decade; therefore, nanomaterials possessing high carrier mobility, optical transparency, mechanical robustness and flexibility, lightweight, and environmental stability will be in immense demand. Graphene is one of the nanomaterials that fulfill all these requirements, along with other inherently unique properties and convenience to fabricate into different morphological nanostructures, from atomically thin single layers to nanoribbons. Graphene-based materials have also been investigated in sensor technologies, from chemical sensing to detection of cancer biomarkers. The progress of graphene-based flexible gas and chemical sensors in terms of material preparation, sensor fabrication, and their performance are reviewed here. The article provides a brief introduction to graphene-based materials and their potential applications in flexible and stretchable wearable electronic devices. The role of graphene in fabricating flexible gas sensors for the detection of various hazardous gases, including nitrogen dioxide (NO₂), ammonia (NH₃), hydrogen (H₂), hydrogen sulfide (H₂S), carbon dioxide (CO₂), sulfur dioxide (SO₂), and humidity in wearable technology, is discussed. In addition, applications of graphene-based materials are also summarized in detecting toxic heavy metal ions (Cd, Hg, Pb, Cr, Fe, Ni, Co, Cu, Ag), and volatile organic compounds (VOCs) including nitrobenzene, toluene, acetone, formaldehyde, amines, phenols, bisphenol A (BPA), explosives, chemical warfare agents, and environmental pollutants. The sensitivity, selectivity and strategies for excluding interferents are also discussed for graphene-based gas and chemical sensors. The challenges for developing future generation of flexible and stretchable sensors for wearable technology that would be usable for the Internet of Things (IoT) are also highlighted.

Sugar Blowing-Induced Porous Cobalt Phosphide/Nitrogen-Doped Carbon Nanostructures with Enhanced Electrochemical Oxidation Performance toward Water and Other Small Molecules

Rational design of high active and robust nonprecious metal catalysts with excellent catalytic efficiency in oxygen evolution reaction (OER) is extremely vital for making the water splitting process more energy efficient and economical. Among these noble metal-free catalysts, transition-metal-based nanomaterials are considered as one of the most promising OER catalysts due to their relatively low-cost intrinsic activities, high abundance, and diversity in terms of structure and morphology. Herein, a facile sugar-blowing technique and low-temperature phosphorization are reported to generate 3D self-supported metal involved carbon nanostructures, which are termed as Co₂ P@Co/nitrogen-doped carbon (Co₂ P@Co/N-C). By capitalizing on the 3D porous nanostructures with high surface area, homogeneously dispersed active sites, the intimate interaction between active sites, and 3D N-doped carbon, the resultant Co₂ P@Co/N-C exhibits satisfying OER performance superior to CoO@Co/N-C, delivering 10 mA cm^-2 at overpotential of 0.32 V. It is worth noting that in contrast to the substantial current density loss of RuO₂ , Co₂ P@Co/N-C shows much enhanced catalytic activity during the stability test and a 1.8-fold increase in current density is observed after stability test. Furthermore, the obtained Co₂ P@Co/N-C can also be served as an excellent nonprecious metal catalyst for methanol and glucose electrooxidation in alkaline media, further extending their potential applications.