A strong electronic coupling between graphene nanosheets and layered titanate nanoplates: a soft-chemical route to highly porous nanocomposites with improved photocatalytic activity

One-step and room-temperature fabrication of carbon nanocomposites including Ni nanoparticles for supercapacitor electrodes

With the increasing importance of power storage devices, demand for the development of supercapacitors possessing both rapid reversible chargeability and high energy density is accelerating. Here we propose a simple process for the room temperature fabrication of pseudocapacitor electrodes consisting of a faradaic redox reaction layer on a metallic electrode with an enhanced surface area. As a model metallic electrode, an Au foil was irradiated with Ar+ ions with a simultaneous supply of C and Ni at room temperature, resulting in fine metallic Ni nanoparticles dispersed in the carbon matrix with local graphitization on the ion-induced roughened Au surface. A carbon layer including fine Ni nanoparticles acted as an excellent faradaic redox reaction layer and the roughened surface contributed to an increase in surface area. The fabricated electrode, which included only 14 μg cm-2 of Ni, showed a stored charge ability three times as large as that of the bulky Ni foil. Thus, it is believed that a carbon layer including Ni nanoparticles fabricated on the charge collective electrode with an ion-irradiation method is promising for the development of supercapacitors from the viewpoints of the reduced use of rare metal and excellent supercapacitor performance.

Soft template-assisted copper-doped sodium dititanate nanosheet/graphene oxide heterostructure for photoreduction of carbon dioxide to liquid fuels

Photoreduction of CO₂ to a high-value product is an interesting approach that not only captures CO₂ but also converts it into other products that can be sold or used in industry. The mechanism for the CO₂ conversion relies strongly on photo-generated electrons that further couple with CO₂ and form active radicals for the reaction. In this research, we synthesized a heterostructure of copper-doped sodium dititanate nanosheets and graphene oxide (CTGN) following a one-step hydrothermal process with assistance from a sodium hydroxide soft template. The role of the template here is to facilitate the formation of the nanosheets, creating the nanosheet–graphene 2D–2D heterostructure. The heterostructure yields excellent charge mobility and a low charge recombination rate, while the nanosheet–graphene interfaces house active radicals and stabilize intermediates. The CTGN exhibits an outstanding photoactivity in the photoreduction of CO₂, producing liquid fuels, including acetone, methanol, ethanol and i-propanol.

The copper-doped sodium dititanate nanosheets/graphene oxide heterostructure (CTGN) was synthesized following a one-step hydrothermal process, exhibiting an outstanding photoactivity in converting CO₂ to acetone, methanol, ethanol and i-propanol.

Synergetic Advantages of Atomically Coupled 2D Inorganic and Graphene Nanosheets as Versatile Building Blocks for Diverse Functional Nanohybrids

2D nanostructured materials, including inorganic and graphene nanosheets, have evoked plenty of scientific research activity due to their intriguing properties and excellent functionalities. The complementary advantages and common 2D crystal shapes of inorganic and graphene nanosheets render their homogenous mixtures powerful building blocks for novel high-performance functional hybrid materials. The nanometer-level thickness of 2D inorganic/graphene nanosheets allows the achievement of unusually strong electronic couplings between sheets, leading to a remarkable improvement in preexisting functionalities and the creation of unexpected properties. The synergetic merits of atomically coupled 2D inorganic-graphene nanosheets are presented here in the exploration of novel heterogeneous functional materials, with an emphasis on their critical roles as hybridization building blocks, interstratified sheets, additives, substrates, and deposited monolayers. The great flexibility and controllability of the elemental compositions, defect structures, and surface natures of inorganic-graphene nanosheets provide valuable opportunities for exploring high-performance nanohybrids applicable as electrodes for supercapacitors and rechargeable batteries, electrocatalysts, photocatalysts, and water purification agents, to give some examples. An outlook on future research perspectives for the exploitation of emerging 2D nanosheet-based hybrid materials is also presented along with novel synthetic strategies to maximize the synergetic advantage of atomically mixed 2D inorganic-graphene nanosheets.

Graphene-semiconductor nanocomposites for cancer phototherapy

Being a carbon-based hybrid, graphene-semiconductor composites have attracted considerable attention in recent decades owing to their potential features such as high photosensitivity, extended light absorption, and effective separation of charge carriers, thus have been regarded as a promising platform for environmental and biomedical applications, respectively. In this mini-review, we first summarized the recent advancements in the development of graphene-based semiconductor nanocomposites via sol-gel, solution mixing, in situ growth, hydrothermal, and solvothermal approaches, and then comprehensively reviewed their potential light activated cancer phototherapeutic applications. Finally, we rationally analyze the current challenges and new perspectives for the future development of more effective phototherapeutic nanoagents. We hope to offer enriched information to harvest the utmost fascinating properties of graphene as a platform to construct efficient graphene/semiconductor hybrids for cancer phototherapy.

Pharmaceuticals and personal care products in water and wastewater: a review of treatment processes and use of photocatalyst immobilized on functionalized carbon in AOP degradation

The presence of emerging contaminants such as pharmaceutical and personal care products in many aqueous matrices have been reported. One of such matrix is streams of wastewater, including wastewater treatment plants inflows and outflows and wastewater flow by-passing wastewater treatment plants. Their persistence arises from their resistant to breakdown, hence they may remain in the environment over long time, with a potential to cause adverse effects including endocrine disruption, gene toxicity, the imposition of sex organs, antibiotic resistance and many others in some aquatic organisms exposed to arrays of residues of pharmaceutical and personal care products. Among the treatment techniques, advanced oxidation processes have been reported to be a better technique through which these PPCPs can be degraded in the WWTPs. Heterogeneous photocatalysis using various photocatalyst immobilized on solid support such as activated carbon, graphene and carbon nanotubes in AOPs have been shown to be a viable and efficient method of PPCPs degradation. This is because, the performance of most WWTPs is limited since they were not designed to degrade toxic and recalcitrant PPCPs. This review highlight the occurrence, concentration of PPCPs in wastewater and the removal efficiency of heterogeneous photocatalysis of TiO2 immobilized on solid supports.

Synthesis and Surface Modification of TiO2-Based Photocatalysts for the Conversion of CO2

Among all greenhouse gases, CO2 is considered the most potent and the largest contributor to global warming. In this review, photocatalysis is presented as a promising technology to address the current global concern of industrial CO2 emissions. Photocatalysis utilizes a semiconductor material under renewable solar energy to reduce CO2 into an array of high-value fuels including methane, methanol, formaldehyde and formic acid. Herein, the kinetic and thermodynamic principles of CO2 photoreduction are thoroughly discussed and the CO2 reduction mechanism and pathways are described. Methods to enhance the adsorption of CO2 on the surface of semiconductors are also presented. Due to its efficient photoactivity, high stability, low cost, and safety, the semiconductor TiO2 is currently being widely investigated for its photocatalytic ability in reducing CO2 when suitably modified. The recent TiO2 synthesis and modification strategies that may be employed to enhance the efficiency of the CO2 photoreduction process are described. These modification techniques, including metal deposition, metal/non-metal doping, carbon-based material loading, semiconductor heterostructures, and dispersion on high surface area supports, aim to improve the light absorption, charge separation, and active surface of TiO2 in addition to increasing product yield and selectivity.

Photocatalytic activity of exfoliated graphite-TiO2 nanoparticle composites

We investigate the photocatalytic performance of composites prepared in a one-step process by liquid-phase exfoliation of graphite in the presence of TiO₂ nanoparticles (NPs) at atmospheric pressure and in water, without heating or adding any surfactant, and starting from low-cost commercial reagents. These show enhanced photocatalytic activity, degrading up to 40% more pollutants with respect to the starting TiO₂-NPs, in the case of a model dye target, and up to 70% more pollutants in the case of nitrogen oxides. In order to understand the photo-physical mechanisms underlying this enhancement, we investigate the photo-generation of reactive species (trapped holes and electrons) by ultrafast transient absorption spectroscopy. We observe an electron transfer process from TiO₂ to the graphite flakes within the first picoseconds of the relaxation dynamics, which causes the decrease of the charge recombination rate, and increases the efficiency of the reactive species photo-production.

Enhanced photocatalytic performance of a Ti-based metal-organic framework for hydrogen production: Hybridization with ZnCr-LDH nanosheets

Novel hybrid composites of NH₂-MIL-125(Ti) and ZnCr-layered double hydroxide nanosheets (ZnCr-LDH NSs) are developed for use as visible-light-active photocatalysts for hydrogen production based on water photolysis. The hybrid composites are obtained by growing NH₂-MIL-125(Ti) in the presence of exfoliated ZnCr-LDH NSs using a solvothermal reaction. Hybridization of NH₂-MIL-125(Ti) with exfoliated ZnCr-LDH NSs leads to significant effects on the morphology and optical properties of NH₂-MIL-125(Ti). To find the optimum photocatalytic activity for hydrogen production by the hybrid composite photocatalysts, the content of ZnCr-LDH in this work is controlled. Compared to that of pristine NH₂-MIL-125(Ti) and ZnCr-LDH, the hybrid composites exhibit an improved photocatalytic activity for hydrogen production under visible-light irradiation. In addition, the hybrid composite photocatalyst shows excellent photo-chemical stability. The improved photocatalytic activity is believed to benefit from the synergy of strong electronic coupling between NH₂-MIL-125(Ti) and ZnCr-LDH NSs, expanded light absorption and band alignment to enhance the lifetime of photo-induced electrons and holes.

TiO2 Nanowires from Wet-Corrosion Synthesis for Peptide Sequencing Using Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

In this work, TiO₂ nanowires synthesized from a wet-corrosion process were presented for peptide sequencing by photocatalytic reaction with UV radiation. For the photocatalytic decomposition of peptides, the peptide sample was dropped on a target plate containing synthesized TiO₂ nanowire zones and UV-irradiated. Subsequently, the target plate was analyzed by laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry using the synthesized TiO₂ nanowires as a solid matrix. The feasibility of peptide sequencing based on the photocatalytic reaction with the synthesized TiO₂ nanowires was demonstrated using six types of peptides GHP9 (G₁-H-P-Q-G₂-K₁-K₂-K₃-K₄, 1006.59 Da), BPA-1(K₁-S₁-L-E-N-S₂-Y-G₁-G₂-G₃-K₂-K₃-K₄, 1394.74 Da), PreS1(F₁-G-A-N₁-S-N₂-N₃-P₁-D₁-W-D₂-F₂-N₄-P₂-N₅, 1707.68 Da), HPQ peptide-1 (G-Y-H-P-Q-R-K, 884.45 Da), HPQ peptide-2 (K-R-H-P-Q-Y-G, 884.45 Da), and HPQ peptide-3 (R-Y-H-P-Q-G-K, 884.45 Da). The identification of three different peptides with the same molecular weight was also demonstrated by using the synthesized TiO₂ nanowires for their photocatalytic decomposition as well as for LDI-TOF mass spectrometry as a solid-matrix.

Photodegradation of pharmaceuticals and personal care products in water treatment using carbonaceous-TiO2 composites: A critical review of recent literature

The high concentrations of pharmaceuticals and personal care products (PPCP) that found in water in many locations are of concern. Among the available water treatment methods, heterogeneous photocatalysis using TiO₂ is an emerging and viable technology to overcome the occurrence of PPCP in natural and waste water. The combination of carbonaceous materials (e.g., activated carbon, carbon nanotubes and graphene nanosheets) with TiO₂, a recent development, gives significantly improved performance. In this article, we present a critical review of the development and fabrication of carbonaceous-TiO₂ and its application to PPCP removal including its influence on water chemistry, and the relevant operational parameters. Finally, we present an analysis of current priorities in the ongoing research and development of carbonaceous-TiO₂ for the photodegradation of PPCP.

The Research Development of Quantum Dots in Electrochemical Energy Storage

Quantum dots, which are made from semiconductor materials, possess tunable physical dimensions and outstanding optoelectronic characteristics, and they have aroused widespread interest in recent years. In addition to applications in biomolecular analysis, sensors, organic photovoltaic devices, fluorescence, solar cells, photochemical reagents, light-emitting diodes, and catalysis, quantum dots have attracted mounting attention in the field of electrochemical energy storage owing to their size confinement and anisotropic geometry. In this review, a comprehensive summary is given and the research progress of the study of quantum dots for batteries and electrochemical capacitors in recent years, including their synthesis methods, micro/nanostructural features, and electrochemical performance, is appraised.

Recent Progress on Titanium Dioxide Nanomaterials for Photocatalytic Applications

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO₂ under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO₂ and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO₂ to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO₂ -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO₂ -based materials further.

In-Situ Synthesis of Hydrogen Titanate Nanotube/Graphene Composites with a Chemically Bonded Interface and Enhanced Visible Photocatalytic Activity

Hydrogen titanate nanotube (HTT)/graphene nanocomposites are synthesized by hydrothermal reduction of graphene oxide (GO) and simultaneous preparation of nanotubular HTT via an alkaline hydrothermal process. By using this facile in-situ compositing strategy, HTT are densely supported upon the surface of graphene sheets with close interface contacts. The as-prepared HTT/graphene nanocomposites possess significantly enhanced visible light catalytic activity for the partial oxidation of benzylic alcohols. The amount of graphene has significant influence on catalytic activity and the optimal content of graphene is 1.0 wt %, giving a normalized rate constant k of 1.71 × 10⁻³ g/m²·h, which exceeds that of pure HTT and HTT/graphene-1.0% mixed by a factor of 7.1 or 5.2. Other than the general role of graphene as a high-performance electron acceptor or transporter, the observed enhancement in photocatalytic activity over HTT/graphene can be ascribed to the improved interfacial charge migration from enhanced chemical bonding (Ti–C bonds) during the in-situ compositing process. The formation of Ti–C bonds is confirmed by XPS analysis and the resulting enhanced separation of photoinduced charge carriers is demonstrated by electrochemical impedance spectra and transient photocurrent response.

Magnetism-tuning strategies for graphene oxide based on magnetic oligoacene oxide patches model

Graphene oxide (GO) has wide application potential owing to its 2D structure and diverse modification sites for various targeted uses. The introduction of magnetism into GO structures has further advanced the controllability of the application of GO materials. Herein, the concept of modular design and modeling was applied to tune the magnetism of GO. To obtain desirable magnetic properties, diradical-structured GO patches were formed by the introduction of two functional groups to break the Kekule structure of the benzene ring. In these diradical GO patches, the energy of the triplet state was lower than those of the open-shell broken-symmetry singlet state and closed-shell singlet state. To create such multi-radical patches, a practical approach is to determine a substantial spatial separation of the α and β spin densities in the molecule. Thus, systematic design strategies and tests were evaluated. The first strategy was extending the distance between the distribution center of the α and β spin densities; the second was controlling the delocalization directions of the α and β electrons; the third was controlling the delocalization extension of the α and β electrons by oxidative modification, and finally introducing multi-radical structures into the molecular system and controlling the position of each radical. Herein, successful molecular models with a large magnetic coupling constant (∼3600 cm^-1) were obtained. This study paves the way to explore ferromagnetic MGO guided by theoretical study, which may become reality soon.

Unique physicochemical properties of two-dimensional light absorbers facilitating photocatalysis

The emergence of two-dimensional (2D) materials with a large lateral size and extremely small thickness has significantly changed the development of many research areas by producing a variety of unusual physicochemical properties.

Synthesis of Pt/K2CO3/MgAlOx-reduced graphene oxide hybrids as promising NOx storage-reduction catalysts with superior catalytic performance

Pt/K₂CO₃/MgAlO_x–reduced graphene oxide (Pt/K/MgAlO_x–rGO) hybrids were synthesized, characterized and tested as a promising NO_x storage and reduction (NSR) catalyst. Mg–Al layered double hydroxides (LDHs) were grown on rGO via in situ hydrothermal crystallization. The structure and morphology of samples were thoroughly characterized using various techniques. Isothermal NO_x adsorption tests indicated that MgAlO_x–rGO hybrid exhibited better NO_x trapping performance than MgAlO_x, from 0.44 to 0.61 mmol · g⁻¹, which can be attributed to the enhanced particle dispersion and stabilization. In addition, a series of MgAlO_x–rGO loaded with 2 wt% Pt and different loadings (5, 10, 15, and 20 wt%) of K₂CO₃ (denoted as Pt/K/MgAlO_x–rGO) were obtained by sequential impregnation. The influence of 5% H₂O on the NO_x storage capacity of MgAlO_x–rGO loaded with 2 wt% Pt and 10% K₂CO₃ (2Pt/10 K/MgAlO_x–rGO) catalyst was also evaluated. In all, the 2Pt/10 K/MgAlO_x–rGO catalyst not only exhibited high thermal stability and NO_x storage capacity of 1.12 mmol · g⁻¹, but also possessed excellent H₂O resistance and lean–rich cycling performance, with an overall 78.4% of NO_x removal. This work provided a new scheme for the preparation of highly dispersed MgAlO_x–rGO hybrid based NSR catalysts.

In situ chemical transformation synthesis of Bi4Ti3O12/I–BiOCl 2D/2D heterojunction systems for water pollution treatment and hydrogen production

Enhancing visible light response and inhibiting the recombination of photogenerated charge carriers are vital for Bi₄Ti₃O₁₂ nanosheets to achieve high activity in the fields of hydrogen generation and water pollutant treatment.

A novel microporous amorphous-ZnO@TiO2/graphene ternary nanocomposite with enhanced photocatalytic activity

Configuration model of the amorphous-TiO₂/RGO heterostructure and the photocatalytic activities.

Graphene in Photocatalysis: A Review

In recent years, heterogeneous photocatalysis has received much research interest because of its powerful potential applications in tackling many important energy and environmental challenges at a global level in an economically sustainable manner. Due to their unique optical, electrical, and physicochemical properties, various 2D graphene nanosheets-supported semiconductor composite photocatalysts have been widely constructed and applied in different photocatalytic fields. In this review, fundamental mechanisms of heterogeneous photocatalysis, including thermodynamic and kinetics requirements, are first systematically summarized. Then, the photocatalysis-related properties of graphene and its derivatives, and design rules and synthesis methods of graphene-based composites are highlighted. Importantly, different design strategies, including doping and sensitization of semiconductors by graphene, improving electrical conductivity of graphene, increasing eloectrocatalytic active sites on graphene, strengthening interface coupling between semiconductors and graphene, fabricating micro/nano architectures, constructing multi-junction nanocomposites, enhancing photostability of semiconductors, and utilizing the synergistic effect of various modification strategies, are thoroughly summarized. The important applications including photocatalytic pollutant degradation, H₂ production, and CO₂ reduction are also addressed. Through reviewing the significant advances on this topic, it may provide new opportunities for designing highly efficient 2D graphene-based photocatalysts for various applications in photocatalysis and other fields, such as solar cells, thermal catalysis, separation, and purification.

Charge transport-driven selective oxidation of graphene

Due to the tunability of the physical, electrical, and optical characteristics of graphene, precisely controlling graphene oxidation is of great importance for potential applications of graphene-based electronics. Here, we demonstrate a facile and precise way for graphene oxidation controlled by photoexcited charge transfer depending on the substrate and bias voltage. It is observed that graphene on TiO2 is easily oxidized under UV-ozone treatment, while graphene on SiO2 remains unchanged. The mechanism for the selective oxidation of graphene on TiO2 is associated with charge transfer from the TiO2 to the graphene. Raman spectra were used to investigate the graphene following applied bias voltages on the graphene/TiO2 diode under UV-ozone exposure. We found that under a reverse bias of 0.6 V on the graphene/TiO2 diode, graphene oxidation was accelerated under UV-ozone exposure, thus confirming the role of charge transfer between the graphene and the TiO2 that results in the selective oxidation of the graphene. The selective oxidation of graphene can be utilized for the precise, nanoscale patterning of the graphene oxide and locally patterned chemical doping, finally leading to the feasibility and expansion of a variety of graphene-based applications.

The Application of Graphene and Its Derivatives to Energy Conversion, Storage, and Environmental and Biosensing Devices

Graphene (GR) and its derivatives are promising materials on the horizon of nanotechnology and material science and have attracted a tremendous amount of research interest in recent years. The unique atom-thick 2D structure with sp(2) hybridization and large specific surface area, high thermal conductivity, superior electron mobility, and chemical stability have made GR and its derivatives extremely attractive components for composite materials for solar energy conversion, energy storage, environmental purification, and biosensor applications. This review gives a brief introduction of GR's unique structure, band structure engineering, physical and chemical properties, and recent energy-related progress of GR-based materials in the fields of energy conversion (e.g., photocatalysis, photoelectrochemical water splitting, CO2 reduction, dye-sensitized and organic solar cells, and photosensitizers in photovoltaic devices) and energy storage (batteries, fuel cells, and supercapacitors). The vast coverage of advancements in environmental applications of GR-based materials for photocatalytic degradation of organic pollutants, gas sensing, and removal of heavy-metal ions is presented. Additionally, the use of graphene composites in the biosensing field is discussed. We conclude the review with remarks on the challenges, prospects, and further development of GR-based materials in the exciting fields of energy, environment, and bioscience.

Earth Abundant Iron-Rich N-Doped Graphene Based Spacer and Cavity Materials for Surface Plasmon-Coupled Emission Enhancements

We demonstrate for the first time the use of Fe-based nanoparticles on N-doped graphene as spacer and cavity materials and study their plasmonic effect on the spontaneous emission of a radiating dipole. Fe-C-MF was produced by pyrolizing FeOOH and melamine formaldehyde precursor on graphene, while Fe-C-PH was produced by pyrolizing the Fe-phenanthroline complex on graphene. The use of the Fe-C-MF composite consisting of Fe-rich crystalline phases supported on N-doped graphene presented a spacer material with 116-fold fluorescence enhancements. On the other hand, the Fe-C-PH/Ag based cavity resulted in an 82-fold enhancement in Surface Plasmon-Coupled Emission (SPCE), with high directionality and polarization of Rhodamine 6G (Rh6G) emission owing to Casimir and Purcell effects. The use of a mobile phone as a cost-effective fluorescence detection device in the present work opens up a flexible perspective for the study of different nanomaterials as tunable substrates in cavity mode and spacer applications.

Water-floating nanohybrid films of layered titanate–graphene for sanitization of algae without secondary pollution

A novel efficient and safe methodology to sanitize algae in natural water without secondary pollution is developed by fabricating floating graphene–inorganic hybrid films.

A F-ion assisted preparation route to improve the photodegradation performance of a TiO2@rGO system-how to efficiently utilize the photogenerated electrons in the target organic pollutants

F-doped TiO₂ densely and uniformly decorated on rGO sheets could adsorb more RhB on TiO₂ and efficiently utilize the photogenerated electrons of excited RhB to improve the photodegradation efficiency.

A Crucial Role of Rh Substituent Ion in Photoinduced Internal Electron Transfer and Enhanced Photocatalytic Activity of CdS-Ti(5.2-x)/6 Rhx /2 O2 Nanohybrids

The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh-substituted layered titanate nanosheet even at very low Rh substitution rate (<1%). Mesoporous CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids are synthesized by a self-assembly of exfoliated Ti(5.2-x)/6 Rhx/2O2 nanosheets with CdS QDs. The partial substitution of Rh(3+)/Rh(4+) ions for Ti(4+) ions in layered titanate is quite effective in enhancing an electronic coupling between hybridized CdS and titanate components via the formation of interband Rh 4d states. A crucial role of Rh substituent ion in the internal electron transfer is obviously evidenced from in situ X-ray absorption spectroscopy showing the elongation of (RhO) bond under visible light irradiation. This is the first spectroscopic evidence for the important role of substituent ion in the photoinduced electron transfer of hybrid-type photocatalyst. The CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids show much higher photocatalytic activity for H2 production and better photostability than do CdS and unsubstituted CdS-TiO2 nanohybrid. This result is ascribable to the enhancement of visible light absorptivity, the depression of electron-hole recombination, and the enhanced hole curing of CdS upon Rh substitution. The present study underscores that the hybridization with composition-controlled inorganic nanosheet provides a novel efficient methodology to optimize the photo-related functionalities of semiconductor nanocrystal.

One-Pot Hydrothermal Synthesis of FeMoO₄ Nanocubes as an Anode Material for Lithium-Ion Batteries with Excellent Electrochemical Performance

Metal molybdates nanostructures hold great promise as high-performance electrode materials for next-generation lithium-ion batteries. In this work, the facial design and synthesis of monodisperse FeMoO4 nanocubes with the edge lengths of about 100 nm have been successfully prepared and present as a novel anode material for highly efficient and reversible lithium storage. Well-defined single-crystalline FeMoO4 with high uniformity are first obtained as nanosheets and then self-aggregated into nanocubes. The morphology of the product is largely controlled by the experimental parameters, such as the reaction temperature and time, the ratio of reactant, the solution viscosity, etc. The molybdate nanostructure would effectively promote the insertion of lithium ions and withstand volume variation upon prolonged charge/discharge cycling. As a result, the FeMoO4 nanocubes exhibit high reversible capacities of 926 mAh g(-1) after 80 cycles at a current density of 100 mA g(-1) and remarkable rate performance, which indicate that the FeMoO4 nanocubes are promising materials for high-power lithium-ion battery applications.

Porous Hybrid Network of Graphene and Metal Oxide Nanosheets as Useful Matrix for Improving the Electrode Performance of Layered Double Hydroxides

Mesoporous hybrid network of reduced graphene oxide (rG-O) and layered MnO(2) nanosheets could act as an efficient immobilization matrix for improving the electrochemical activity of layered double hydroxide (LDH). The control of MnO(2) /rG-O ratio is crucial in optimizing the porous structure and electrical conductivity of the resulting hybrid structure. The immobilization of Co-Al-LDH on hybrid MnO(2) /rG-O network is more effective in enhancing its electrode activity compared with that of on pure rG-O network. The Co-Al-LDH-rG-O-MnO(2) nanohybrid deliveres a greater specific capacitance than does MnO(2) -free Co-Al-LDH-rG-O nanohybrid. The beneficial effect of MnO(2) incorporation on the electrode performance of nanohybrid is more prominent for higher current density and faster scan rate, underscoring the significant enhancement of the electron transport of Co-Al-LDH-rG-O. This is supported by electrochemical impedance spectroscopy. The present study clearly demonstrates the usefulness of the porously assembled hybrid network of graphene and metal oxide nanosheets as an effective platform for exploring efficient LDH-based functional materials.

An Effective Way to Optimize the Functionality of Graphene-Based Nanocomposite: Use of the Colloidal Mixture of Graphene and Inorganic Nanosheets

The best electrode performance of metal oxide-graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO2 and graphene nanosheets as a precursor. The intervention of layered CoO2 nanosheets in-between graphene nanosheets is fairly effective in optimizing the pore and composite structures of the Co3O4-graphene nanocomposite and also in enhancing its electrochemical activity via the depression of interaction between graphene nanosheets. The resulting CoO2 nanosheet-incorporated nanocomposites show much greater discharge capacity of ~1750 mAhg(-1) with better cyclability and rate characteristics than does CoO2-free Co3O4-graphene nanocomposite (~1100 mAhg(-1)). The huge discharge capacity of the present nanocomposite is the largest one among the reported data of cobalt oxide-graphene nanocomposite. Such a remarkable enhancement of electrode performance upon the addition of inorganic nanosheet is also observed for Mn3O4-graphene nanocomposite. The improvement of electrode performance upon the incorporation of inorganic nanosheet is attributable to an improved Li(+) ion diffusion, an enhanced mixing between metal oxide and graphene, and the prevention of electrode agglomeration. The present experimental findings underscore an efficient and universal role of the colloidal mixture of graphene and redoxable metal oxide nanosheets as a precursor for improving the electrode functionality of graphene-based nanocomposites.

Green and facile synthesis of highly biocompatible carbon nanospheres and their pH-responsive delivery of doxorubicin to cancer cells

Carbon nanospheres with size below 71 nm are synthesized from bacterial cellulose nanofibers using a one-pot hydrothermal synthesis method.

Synthesis of Pt doped Mg–Al layered double oxide/graphene oxide hybrid as novel NOx storage–reduction catalyst

We report the synthesis of Pt doped Mg–Al layered double oxide/graphene oxide (Pt–LDO/GO) hybrid as novel NO_x storage and reduction (NSR) catalyst.

Graphene-based photocatalysts for oxygen evolution from water

Recent achievements of GR-based photocatalysts for oxygen evolution from water are summarized with perspectives on major challenges and opportunities.

Unique Advantages of Exfoliated 2D Nanosheets for Tailoring the Functionalities of Nanocomposites

Hybridization with exfoliated two-dimensional (2D) nanosheets provides a very effective and powerful way not only to control the physicochemical properties of hybridized species but also to explore nanocomposites with novel functionalities. Deliberate coupling between the hybridized species is critically important in maximizing the effect of hybridization on the physicochemical properties and functionality of hybridized components. The very small thickness and extremely large surface of exfoliated 2D nanosheets render these materials ideal candidates for achieving a strong coupling with diverse guest species. This Perspective focuses on the unique characteristics of exfoliated 2D nanosheets as building blocks for designing hybrid materials. Several intriguing examples of strong interaction between exfoliated 2D nanosheets and hybridized species are summarized with an emphasis on the effective control of electronic, optical, structural, and morphological characteristics. An outlook on the future research directions is provided along with new strategies to maximize the coupling in the 2D nanosheet-based hybrid materials.

A facile exfoliation-crystal growth route to multicomponent Ag2CO3/Ag-Ti5NbO14 nanohybrids with improved visible light photocatalytic activity

A novel visible light active photocatalyst is developed via a direct crystal growth of silver oxosalts on exfoliated titanoniobate nanosheets.

Two-dimensional interface engineering of a titania-graphene nanosheet composite for improved photocatalytic activity

A graphene-based two-dimensional (2D) nanoplatform provides new opportunities for fabricating 2D heterojunction interfaces to fortify charge transfer in semiconductor assemblies. In this report, TiO2 nanosheet/graphene composite based 2D-2D heterojunctions were fabricated by a solvothermal process. Microscopic and spectroscopic characterization revealed a homogeneous sheetlike morphology with intimate interfacial contact between the TiO2 nanosheet and graphene due to chemical interactions. Compared with 0D-2D Degussa P25 (TiO2)/graphene and 1D-2D TiO2 nanotube/graphene composites, the 2D-2D TiO2 nanosheet/graphene hybrid demonstrated higher photocatalytic activity toward the degradation of rhodamine B and 2,4-dichlorophenol under UV irradiation. Radical trapping and ESR experiments revealed the enhanced generation of ·OH and O2(•-) in the 2D-2D heterojunction system. By analyzing TiO2 excited state deactivation lifetime, the interfacial electron transfer rates determined for 0D-2D, 1D-2D, and 2D-2D TiO2/graphene composites were 1.15 × 10(8) s(-1), 3.47 × 10(8) s(-1), and 1.06 × 10(9) s(-1), respectively. It was therefore proposed that the fast charge separation in the TiO2 nanosheet/graphene photocatalyst promoted the generation of reactive oxygen species and enhanced the photodegradation reactions. The results underscore the key role of nanomaterial dimensionality in interfacial charge transfer processes.

Cross-linked g-C3 N4 /rGO nanocomposites with tunable band structure and enhanced visible light photocatalytic activity

Cross-linked rather than non-covalently bonded graphitic carbon nitride (g-C3 N4 )/reduced graphene oxide (rGO) nanocomposites with tunable band structures have been successfully fabricated by thermal treatment of a mixture of cyanamide and graphene oxide with different weight ratios. The experimental results indicate that compared to pure g-C3 N4 , the fabricated CN/rGO nanocomposites show narrowed bandgaps with an increased in the rGO ratio. Furthermore, the band structure of the CN/rGO nanocomposites can be readily tuned by simply controlling the weight ratio of the rGO. It is found that an appropriate rGO ratio in nanocomposite leads to a noticeable positively shifted valence band edge potential, meaning an increased oxidation power. The tunable band structure of the CN/rGO nanocomposites can be ascribed to the formation of C-O-C covalent bonding between the rGO and g-C3 N4 layers, which is experimentally confirmed by Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) data. The resulting nanocomposites are evaluated as photocatalysts by photocatalytic degradation of rhodamine B (RhB) and 4-nitrophenol under visible light irradiation (λ > 400 nm). The results demonstrate that the photocatalytic activities of the CN/rGO nanocomposites are strongly influenced by rGO ratio. With a rGO ratio of 2.5%, the CN/rGO-2.5% nanocomposite exhibits the highest photocatalytic efficiency, which is almost 3.0 and 2.7 times that of pure g-C3 N4 toward photocatalytic degradation of RhB and 4-nitrophenol, respectively. This improved photocatalytic activity could be attributed to the improved visible light utilization, oxidation power, and electron transport property, due to the significantly narrowed bandgap, positively shifted valence band-edge potential, and enhanced electronic conductivity.