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Graphene paper (GP) has attracted great attention as a heat dissipation material due to its unique thermal transfer property exceeding the limit of graphite. However, the relatively poor thermal transfer properties in the normal direction of GP restricts its wider applications in thermal management. In this work, a 3D bridged carbon nanoring (CNR)/graphene hybrid paper is constructed by the intercalation of polymer carbon source and metal catalyst particles, and the subsequent in situ growth of CNRs in the confined intergallery spaces between graphene sheets through thermal annealing. Further investigation demonstrates that the CNRs are covalently bonded to the graphene sheets and highly improve the thermal transport in the normal direction of the CNR/graphene hybrid paper. This full-carbon architecture shows excellent heat dissipation ability and is much more efficient in removing hot spots than the reduced GP without CNR bridges. This highly thermally conductive CNR/graphene hybrid paper can be easily integrated into next generation commercial high-power electronics and stretchable/foldable devices as high-performance lateral heat spreader materials. This full-carbon architecture also has a great potential in acting as electrodes in supercapacitors or hydrogen storage devices due to the high surface area.

Solar-blind photodetectors (PDs) are widely applicable in special, military, medical, environmental, and commercial fields. However, high performance and flexible PD for deep ultraviolet (UV) range is still a challenge. Here, it is demonstrated that an upconversion of photon absorption beyond the energy bandgap is achieved in the ZnO nanoarray/h-BN heterostructure, which enables the ultrahigh responsivity of a solar-blind photodetecting paper. The direct growth of ultralong ZnO nanoarray on polycrystalline copper paper induced by h-BN 2D interlayer is obtained. Meanwhile, strong photon trapping takes place within the ZnO nanoarray forest through the cyclic state transition of surface oxygen ions, resulting in an extremely high absorption efficiency (99.5%). A flexible photodetecting paper is fabricated for switchable detections between near UV and deep UV signals by critical external bias. The device shows robust reliability, ultrahigh responsivity up to 700 A W

Flexible graphene paper (GP) pillared by carbon black (CB) nanoparticles using a simple vacuum filtration method is developed as a high-performance electrode material for supercapacitors. Through the introduction of CB nanoparticles as spacers, the self-restacking of graphene sheets during the filtration process is mitigated to a great extent. The pillared GP-based supercapacitors exhibit excellent electrochemical performances and cyclic stabilities compared with GP without the addition of CB nanoparticles. At a scan rate of 10 mV s(-1) , the specific capacitance of the pillared GP is 138 F g(-1) and 83.2 F g(-1) with negligible 3.85% and 4.35% capacitance degradation after 2000 cycles in aqueous and organic electrolytes, respectively. At an extremely fast scan rate of 500 mV s (-1) , the specific capacitance can reach 80 F g(-1) in aqueous electrolyte. No binder is needed for assembling the supercapacitor cells and the pillared GP itself may serve as a current collector due to its intrinsic high electrical conductivity. The pillared GP has great potential in the development of promising flexible and ultralight-weight supercapacitors for electrochemical energy storage.

Recent portable electronic devices have strict requirements regarding size, weight, and power. The power needed directly impacts the size of the required batteries, and larger batteries compromise the sizes and weights of portable devices. In order to design successful portable devices that maximize power and minimize size, devices should be operated in lowpower-consuming or self-powered mode. There has been increasing demand for highly effi cient portable energy harvesters due to the development and mass consumption of portable electronic devices. Photovoltaic, thermoelectric, and piezoelectric energy scavengers have become strong candidates for portable energy harvesters in future self-powered portable electronic device applications. [ 1–6 ]

Functional surfaces with tunable and patternable wettability have attracted significant research interests because of remarkable advantages in biomedicine, environmental, and energy storage applications. Based on combined defocusing and grafting strategy for processing laser-induced graphene papers (LIGPs) with variable surface roughness (58.18-6.08 µm) and F content (0-25.9%), their wettability can be tuned continuously from superlyophilicity (contact angle CA ≈ 0° ) to superlyophobicity (CA > 150° ), for various liquids with a wide range of surface tensions from 27.5 to 72.8 mN m-1 . In addition to reaching multiple wetting characteristics including amphiphilic, amphiphobic, and hydrophobic-oleophilic states, three designable processes are further developed for achieving LIGPs with various wetting patterns, including hydrophilic arrays or channels, hydrophobic-to-hydrophilic gradients, and Janus. Activated by the customly designed structures and properties, multifunctional and multi-scenario applications are successfully attempted, including 2D-/3D- directional cell cultivation, water transportation diode, self-triggered liquid transfer & collection, etc.

Freestanding, flexible/foldable, and wearable bifuctional ultrathin graphene paper for heating and cooling is fabricated as an active material in personal thermal management (PTM). The promising electrical conductivity grants the superior Joule heating for extra warmth of 42 °C using a low supply voltage around 3.2 V. Besides, based on its high out-of-plane thermal conductivity, the graphene paper provides passive cooling via thermal transmission from the human body to the environment within 7 s. The cooling effect of graphene paper is superior compared with that of the normal cotton fiber, and this advantage will become more prominent with the increased thickness difference. The present bifunctional graphene paper possesses high durability against bending cycles over 500 times and wash time over 1500 min, suggesting its great potential in wearable PTM.

Recycling of noble metal from waste materials, namely from electronic wastes (e-waste), spent catalyst, and industrial wastewater, is attracting growing attention due to the scarcity, economic importance, and criticality of those noble metals. Traditional techniques reported to date require toxic reagent and strict extraction conditions, which deeply hinders the development of precious metal recovery in complex environments. Here, an approach is proposed that uses flexible metallic transition metal dichalcogenide (TMD) paper, which provides abundant active sites for spontaneous adsorption and reduction of noble metal ions, as an Alchemy-inspired template to recover noble metal in an efficient and green way without the aid of reductant and heating. The metallic TMD (MoS2 , WS2 ) paper is shown to rapidly extract five noble metal ions (Au, Pd, Pt, Ag, and Ru) from complex samples containing various interferents. This unique property endows the metallic TMD paper with gifted ability in extracting gold from e-waste, and recovering platinum group metals (palladium and platinum) from spent catalysts, which provides a blueprint for the design of next-generation green platforms for noble metal regeneration.

Free-standing paper-like thin-film electrodes have great potential to boost next-generation power sources with highly flexible, ultrathin, and lightweight requirements. In this work, silver-quantum-dot- (2-5 nm) modified transition metal oxide (including MoO3 and MnO2 ) paper-like electrodes are developed for energy storage applications. Benefitting from the ohmic contact at the interfaces between silver quantum dots and MoO3 nanobelts (or MnO2 nanowires) and the binder-free nature and 0D/1D/2D nanostructured 3D network of the fabricated electrodes, substantial improvements on the electrical conductivity, efficient ionic diffusion, and areal capacitances of the hybrid nanostructure electrodes are observed. With this proposed strategy, the constructed asymmetric supercapacitors, with Ag quantum dots/MoO3 "paper" as anode, Ag quantum dots/MnO2 "paper" as cathode, and neutral Na2 SO4 /polyvinyl alcohol hydrogel as electrolyte, exhibit significantly enhanced energy and power densities in comparison with those of the supercapacitors without modification of Ag quantum dots on electrodes; present excellent cycling stability at different current densities and good flexibility under various bending states; offer possibilities as high-performance power sources with low cost, high safety, and environmental friendly properties.

Flexible energy storage electronics have gained increasing attention in recent years, but the simultaneous acquiring of high volumetric and high areal capacities as well as excellent flexibility in order to truly implement wearable and portable electronics in practice remains challenging. Here, a conductive and highly deformable freestanding all-pseudocapacitive paper electrode (Ti3 C2 Tx /MnO2 NWs) is fabricated by solution processing of hybrid inks based on Ti3 C2 Tx MXene and ultralong MnO2 nanowires. The resulting Ti3 C2 Tx /MnO2 NWs hybrid paper manifests a remarkable areal capacitance of up to 205 mF cm-2 and outstanding volumetric capacitance of 1025 F cm-3 . Both the values are highly comparable with, or in most cases much higher than those of previously reported MXene-based flexible electrodes. The excellent energy storage performance is well maintained with a capacitance retention of 98.38% during 10 000 charge-discharge cycles. In addition, the flexible supercapacitor demonstrates excellent flexibility and electrochemical stability during repeated mechanical bendings of up to 120°, suggesting great potentials for the applications in future flexible and portable electronics.

A versatile and readily scalable approach to fabricate a cheap and sensitive paper gas sensor is described. Chemically acidified single-walled carbon nanotubes are assembled in paper, forming continuous sensing arrays with a low detection limit and high detection selectivity for ammonia gas.

A top-down approach, i.e., creating small particles by mechanical force starting from bulk materials, probably presents the most logical approach to particle size reduction and, therefore, top-down techniques are among the first to achieve small particles. A new solvent-free, amazingly simple approach is reported, suitable to achieve nanoparticles and sub-micro particles.

Efficient utilization of abundant solar energy for clean water generation is considered a sustainable and environment friendly approach to mitigate the global water crisis. For this purpose, this study reports a flexible fire-resistant photothermal paper by combining carbon nanotubes (CNTs) and fire-resistant inorganic paper based on ultralong hydroxyapatite nanowires (HNs) for efficient solar energy-driven water steam generation and water purification. Benefiting from the structural characteristics of the HN/CNT photothermal paper, the black CNT surface layer exhibits a high light absorbability and photothermal conversion capability, the HN-based inorganic paper acts as a thermal insulator with a high temperature stability, low thermal conductivity, and interconnected porous structure. By combining these advantages, high water evaporation efficiencies of 83.2% at 1 kW m-2 and 92.8% at 10 kW m-2 are achieved. In addition, the HN/CNT photothermal paper has a stable water evaporation capability during recycling and long-time usage. The promising potential of the HN/CNT photothermal paper for efficient production of drinkable water from both actual seawater and simulative wastewater samples containing heavy metal ions, dyes, and bacteria is also demonstrated. The highly flexible HN/CNT photothermal paper is promising for application in highly efficient solar energy-driven seawater desalination and wastewater purification.

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real-time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose-based secondary matrix.

Fabricating cost-effective, bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in basic media is critical for renewable energy generation. Here, NiSe/CP, Ni0.85 Se/CP, and NiSe-Ni0.85 Se/CP heterostructure catalysts with different phase constitutions are successfully prepared through in situ selenylation of a NiO nanoflake array oriented on carbon paper (CP) by tuning the original Ni/Se molar ratio of the raw materials. The relationship between the crystal phase component and electrocatalytic activity is systematically studied. Benefiting from the synergetic effect of the intrinsic metallic state, facile charge transport, abundant catalytic active sites, and multiple electrolyte transmission paths, the optimized NiSe-Ni0.85 Se/CP exhibits a remarkably higher catalytic activity for both the HER and OER than single-phase NiSe/CP and Ni0.85 Se/CP. A current density of 10 mA cm-2 at 1.62 V and a high stability can be obtained by using NiSe-Ni0.85 Se/CP as both the cathode and anode for overall water splitting under alkaline conditions. Density functional theory calculations confirm that H and OH- can be more easily adsorbed on NiSe-Ni0.85 Se than on NiSe and Ni0.85 Se. This study paves the way for enhancing the overall water splitting performance of nickel selenides by fabricating heterophase junctions using nickel selenides with different phases.

A graphene oxide rolled‐up tube production process is reported using wax‐printed membranes for the fabrication of on‐demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. The resultant graphene oxide rolled‐up tubes can show magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene‐oxide‐modified wax‐printed membranes prior to the scrolling process. As a proof of concept, the as‐prepared catalytic graphene oxide rolled‐up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator‐friendly, fast, and cost‐efficient wax‐printed paper‐based method and may offer a myriad of hybrid devices and applications., This work was supported by the Severo Ochoa Program (MINECO, Grant No. SEV‐2013‐0295) and Generalitat de Cataluña (Grant No. 2014 SGR 260). The ICN2 is funded by the CERCA programme/Generalitat de Catalunya.

Sodium-ion batteries (NIBs) are an emerging technology, which can meet increasing demands for large-scale energy storage. One of the most promising cathode material candidates for sodium-ion batteries is Na3V2(PO4)3 due to its high capacity, thermal stability, and sodium (Na) Superionic Conductor 3D (NASICON)-type framework. In this work, the authors have significantly improved electrochemical performance and cycling stability of Na3V2(PO4)3 by introducing a 3D interconnected conductive network in the form of carbon fiber derived from ordinary paper towel. The free-standing Na3V2(PO4)3-carbon paper (Na3V2(PO4)3@CP) hybrid electrodes do not require a metallic current collector, polymeric binder, or conducting additives to function as a cathode material in an NIB system. The Na3V2(PO4)3@CP cathode demonstrates extraordinary long term cycling stability for 30 000 deep charge–discharge cycles at a current density of 2.5 mA cm−2. Such outstanding cycling stability can meet the stringent requirements for renewable energy storage.

Flexible supercapacitors have attracted great interest as energy storage devices because of their promise in applications such as wearable and smart electronic devices. Herein, a novel flexible supercapacitor electrode based on gallium nitride nanowire (GaN NW)/graphite paper (GP) nanocomposites is reported. The outstanding electrical conductivities of the GaN NW (6.36 × 102 S m-1 ) and GP (7.5 × 104 S m-1 ) deliver a synergistically enhanced electrochemical performance that cannot be achieved by either of the components alone. The composite electrode exhibits excellent specific capacitance (237 mF cm-2 at 0.1 mA cm-2 ) and outstanding cycling performance (98% capacitance retention after 10 000 cycles). The flexible symmetric supercapacitor also manifests high energy and power densities (0.30 mW h cm-3 and 1000 mW cm-3 ). These findings demonstrate that the GaN/GP composite electrode has significant potential as a candidate for the flexible energy storage devices.

The ongoing global novel coronavirus pneumonia COVID‐19 outbreak has engendered numerous cases of infection and death. COVID‐19 diagnosis relies upon nucleic acid detection; however, currently recommended methods exhibit high false‐negative rates and are unable to identify other respiratory virus infections, thereby resulting in patient misdiagnosis and impeding epidemic containment. Combining the advantages of targeted amplification and long‐read, real‐time nanopore sequencing, herein, nanopore targeted sequencing (NTS) is developed to detect SARS‐CoV‐2 and other respiratory viruses simultaneously within 6–10 h, with a limit of detection of ten standard plasmid copies per reaction. Compared with its specificity for five common respiratory viruses, the specificity of NTS for SARS‐CoV‐2 reaches 100%. Parallel testing with approved real‐time reverse transcription‐polymerase chain reaction kits for SARS‐CoV‐2 and NTS using 61 nucleic acid samples from suspected COVID‐19 cases show that NTS identifies more infected patients (22/61) as positive, while also effectively monitoring for mutated nucleic acid sequences, categorizing types of SARS‐CoV‐2, and detecting other respiratory viruses in the test sample. NTS is thus suitable for COVID‐19 diagnosis; moreover, this platform can be further extended for diagnosing other viruses and pathogens., A detection technology, nanopore targeted sequencing (NTS), for the accurate and comprehensive detection of SARS‐CoV‐2 and other respiratory viruses within 6–10 h is developed, which is suitable for the identification of suspected cases and used as a supplementary technique for the SARS‐CoV‐2 test. NTS can also monitor mutations in the virus and the type of virus.

Nacre-mimetic 2D nanofluidic materials with densely packed sub-nanometer-height lamellar channels find widespread applications in water-, energy-, and environment-related aspects by virtue of their scalable fabrication methods and exceptional transport properties. Recently, light-powered nanofluidic ion transport in synthetic materials gained considerable attention for its remote, noninvasive, and active control of the membrane transport property using the energy of light. Toward practical application, a critical challenge is to overcome the dependence on inhomogeneous or site-specific light illumination. Here, asymmetric photonic-ionic devices based on kirigami-tailored graphene oxide paper are fabricated, and directional nanofluidic ion transport properties therein powered by full-area light illumination are demonstrated. The in-plane asymmetry of the graphene oxide paper is essential to the generation of photoelectric driving force under homogeneous illumination. This light-powered ion transport phenomenon is explained based on a modified carrier diffusion model. In asymmetric nanofluidic structures, enhanced recombination of photoexcited charge carriers at the membrane boundary breaks the electric potential balance in the horizontal direction, and thus drives the ion transport in that direction under symmetric illumination. The kirigami-based strategy provides a facile and scalable way to fabricate paper-like photonic-ionic devices with arbitrary shapes, working as fundamental elements for large-scale light-harvesting nanofluidic circuits.

Combinations of 2D materials with different physical properties can form heterostructures with modified electrical, mechanical, magnetic, and optical properties. The direct observation of a lateral heterostructure synthesis is reported by epitaxial in‐plane graphene growth from the step‐edge of hexagonal BN (h‐BN) within a scanning transmission electron microscope chamber. Residual hydrocarbon in the chamber is the carbon source. The growth interface between h‐BN and graphene is atomically identified as largely N–C bonds. This postgrowth method can form graphene nanoribbons connecting two h‐BN domains with different twisting angles, as well as isolated carbon islands with arbitrary shapes embedded in the h‐BN layer. The electronic properties of the vertically stacked h‐BN/graphene heterostructures are investigated by electron energy‐loss spectroscopy (EELS). Low‐loss EELS analysis of the dielectric response suggests a robust coupling effect between the graphene and h‐BN layers.

Paper-based assays for detection of physiologically important species are needed in medical theranostics owning to their superiorities in point of care testing, daily monitoring, and even visual readout by using chromogenic materials. In this work, a facile test strip is developed for visual detection of a neurotransmitter dopamine (DA) based on dual-emission fluorescent molecularly imprinted polymer nanoparticles (DE-MIPs). The DE-MIPs, featured with tailor-made DA affinity and good anti-interference, exhibit DA concentration-dependent fluorescent colors, due to the variable ratios of dual-emission fluorescence caused by DA binding and quenching. By facile coating DE-MIPs on a filter paper, the DA test strips are obtained. The resultant test strip, like the simplicity of a pH test paper, shows the potential for directly visual detection of DA levels just by dripping a tiny amount of biofluid sample on it. The test result of real serum samples demonstrates that the DA strip enables to visually and semiquantitatively detect DA within 3 min by using only 10 µL of serum samples and with a low detection limit ((100-150) × 10-9 m) by naked eye. This work thus offers a facile and efficient strategy for rapid, visual, and on-site detection of biofluids in clinic.

Despite the vast progress in chemical vapor deposition (CVD) graphene grown on metals, the transfer process is still a major bottleneck, being not devoid of wrinkles and polymer residues. In this paper, a structure is introduced to directly synthesize few layer graphene on insulating substrates by a laser irradiation heating process. The segregation of graphene layers can be manipulated by tuning the metal layer thickness and laser power at different scanning rates. Graphene deposition and submicrometer patterning resolution can be achieved by patterning the intermediate metal layer using standard lithography methods in order to overcome the scalability issue regardless the resolution of the laser beam. The systematic analysis of the process based on the formation of carbon microchannels by the laser irradiation process can be extended to several materials, thicknesses, and methods. Furthermore, hole and electron mobilities of 500 and 950 cm(2) V(-1) s(-1) are measured. The laser-synthesized graphene is a step forward along the direct synthesis route for graphene on insulators that meets the criteria for photonics and electronics.

Graphene flakes (GFs) with minimized defects and oxidation ratios are incorporated into polyethylene (PE) to enhance the moisture barrier. GFs produced involving solvothermal intercalation show extremely low oxidation rates (3.17%), and are noncovalently functionalized in situ, inducing strong hydrophobicity. The fabricated composite possesses the best moisture barrier performance reported for a polymer-graphene composite.

For the first time, pristine graphene can be controllably crumpled and unfolded. The mechanism for graphene is radically different than that observed for graphene oxide; a multifaced crumpled, dimpled particle morphology is seen for pristine graphene in contrast to the wrinkled, compressed surface of graphene oxide particles, showing that surface chemistry dictates nanosheet interactions during the crumpling process. The process demonstrated here utilizes a spray-drying technique to produce droplets of aqueous graphene dispersions and induce crumpling through rapid droplet evaporation. For the first time, the gradual dimensional transition of 2D graphene nanosheets to a 3D crumpled morphology in droplets is directly observed; this is imaged by a novel sample collection device inside the spray dryer itself. The degree of folding can be tailored by altering the capillary forces on the dispersed sheets during evaporation. It is also shown that the morphology of redispersed crumpled graphene powder can be controlled by solvent selection. This process is scalable, with the ability to rapidly process graphene dispersions into powders suitable for a variety of engineering applications.

Freestanding, mechanically stable, and highly electrically conductive graphene foam (GF) is formed with a two-step facile, adaptable, and scalable technique. This work also demonstrates the formation of graphene foam with tunable densities and its use as strain/pressure sensor for both high and low strains and pressures.

The development of new mechanical actuators that convert external stimuli such as thermal, light, electrical, or chemical energy to mechanical energy depends on the development of new materials. Reversible mechanical actuators based on carbon nanotubes (CNTs) and hydrogel polymers have suggested applications in robotics, sensors, mechanical instruments, microscopy tips, switches, and memory chips. Recently, electromechanical resonators composed of singleand multilayer graphene sheets were reported. We present here a novel macroscopic graphene-based actuator that shows actuation that depends on variation of humidity and/or temperature. The actuator is a free standing ‘‘paper-like’’ material made by sequential filtration of CNT, and then graphene oxide, aqueous colloidal suspensions. ‘‘Paper-like’’ materials composed of stacked graphene oxide platelets produced by simple filtration of an aqueous graphene oxide suspension exhibited good mechanical properties, with a modulus of about 40 GPa and a fracture strength of about 130 MPa. Chemical modification of graphene oxide paper with divalent ions can enhance its mechanical properties. Based on these results that show excellent mechanical properties of individual graphene sheets and of paper-like materials composed of them, we have tried to make mechanical actuators by using graphene oxide platelets. Graphite oxide (GO) is generated by oxidation of graphite and contains a wide range of oxygen functional groups, such as hydroxyl and epoxy groups on the basal plane and carboxylic acid groups at the edges, which make the GO hydrophilic. The oxygen functional groups in the GO, which contains a layered structure of graphene oxide platelets, allow dynamic intercalation of water molecules into the gallery between the layers. The interlayer distance between the graphite oxides reversibly varies from 6 to 12 A depending on the relative humidity, with increased interlayer distance as the relative humidity increases. Graphene oxide paper contains a layered structure similar to, but not identical to, GO (the coherence length in the paperlike material is 6–7 platelets

Stoichoimetric graphene fluoride monolayers are obtained in a single step by the liquid-phase exfoliation of graphite fluoride with sulfolane. Comparative quantum-mechanical calculations reveal that graphene fluoride is the most thermodynamically stable of five studied hypothetical graphene derivatives; graphane, graphene fluoride, bromide, chloride, and iodide. The graphene fluoride is transformed into graphene via graphene iodide, a spontaneously decomposing intermediate. The calculated bandgaps of graphene halides vary from zero for graphene bromide to 3.1 eV for graphene fluoride. It is possible to design the electronic properties of such two-dimensional crystals.

A polymer-free technique for generating nanopatterns on both synthesized and exfoliated graphene sheets is proposed and demonstrated. A low-energy (5-30 keV) scanning electron beam with variable repetition rates is used to etch suspended and unsuspended graphene sheets on designed locations. The patterning mechanisms involve a defect-induced knockout process in the initial etching stage and a heat-induced curling process in a later stage. Rough pattern edges appear due to inevitable stochastic knockout of carbon atoms or graphene structure imperfection and can be smoothed by thermal annealing. By using this technique, the minimum feature sizes achieved are about 5 nm for suspended and 7 nm for unsuspended graphene. This study demonstrates a polymer-free direct nanopatterning approach for graphene.

An effective approach to fabricate micropatterned reduced graphene oxide sheets is explored on the basis of the pressure-assisted thermal graphitization as a concept of eco-friendly method. The high pressure can considerably reduce the graphitization temperature and substantially accelerate the kinetics of phase transformation of non-crystalline graphene domain, leading to enhance the degree of graphitization.

The assembly of plasmonic nanoparticles with precise spatial and orientational order may lead to structures with new electromagnetic properties at optical frequencies. The directed self-assembly method presented controls the interparticle-spacing and symmetry of the resulting nanometer-sized elements in solution. The self-assembly of three-dimensional (3D), icosahedral plasmonic nanosclusters (NCs) with resonances at visible wavelengths is demonstrated experimentally. The ideal NCs consist of twelve gold (Au) nanospheres (NSs) attached to thiol groups at predefined locations on the surface of a genetically engineered cowpea mosaic virus with icosahedral symmetry. In situ dynamic light scattering (DLS) measurements confirm the NSs assembly on the virus. Transmission electron micrographs (TEM) demonstrate the ability of the self-assembly method to control the nanoscopic symmetry of the bound NSs, which reflects the icosahedral symmetry of the virus. Both, TEM and DLS show that the NCs comprise of a distribution of capsids mostly covered (i.e., 6-12 NS/capsid) with NSs. 3D finite-element simulations of aqueous suspensions of NCs reproduce the experimental bulk absorbance measurements and major features of the spectra. Simulations results show that the fully assembled NCs give rise to a 10-fold surface-averaged enhancement of the local electromagnetic field.

Facile exfoliation of graphite: High-quality graphene sheets are produced directly from graphite by a facile chemical approach. The new strategy for non-oxidized chemical exfoliation of graphite is based on a pre-intercalated process with oleum and a further strong reaction with sodium in the graphite layers under grinding conditions. This method is facile, low cost, and high throughput.

We present a straightforward method for simultaneously enhancing the electrical conductivity, environmental stability, and photocatalytic properties of graphene films through one-step transfer of CVD graphene and integration by introducing TiO2/graphene oxide layer. A highly durable and flexible TiO2 layer is successfully used as a supporting layer for graphene transfer instead of the commonly used PMMA. Transferred graphene/TiO2 film is directly used for measuring the carrier transport and optoelectronic properties without an extra TiO2 removal and following deposition steps for multifunctional integration into devices because the thin TiO2 layer is optically transparent and electrically semiconducting. Moreover, the TiO2 layer induces charge screening by electrostatically interacting with the residual oxygen moieties on graphene, which are charge scattering centers, resulting in a reduced current hysteresis. Adsorption of water and other chemical molecules onto the graphene surface is also prevented by the passivating TiO2 layer, resulting in the long term environmental stability of the graphene under high temperature and humidity. In addition, the graphene/TiO2 film shows effectively enhanced photocatalytic properties because of the increase in the transport efficiency of the photogenerated electrons due to the decrease in the injection barrier formed at the interface between the F-doped tin oxide and TiO2 layers.

Graphene has immense potential for future applications in the electrochemical field, such as in supercapacitors, fuel cells, batteries, or sensors. Graphene materials for such applications are typically fabricated through a top-down approach towards oxidation of graphite to graphite oxide, with consequent exfoliation/reduction to yield reduced graphenes. Such a method allows the manufacture of graphenes in gram/kilogram quantities. However, graphenes prepared by this method can contain residual metallic impurities from graphite which dominate the electrochemical properties of the graphene formed. This dominance hampers their electrochemical application. The fabrication of transition metal-depleted graphene is described, using ultrapure CO2 (with benefits of low cost and easy availability) and elemental lithium by means of reduction of CO2 to graphene. This preparation method produces graphene of high purity with electrochemical behavior that is not dominated by any residual transition metal impurities which would dramatically alter its electrochemical properties. Wide application of such methodology in industry and research laboratories is foreseen, especially where graphene is used for electrochemical devices.