Superstructured Optoionic Heterojunctions for Promoting Ion Pumping Inspired by Photoreceptor Cells

Photoreceptor cells of vertebrates feature ultrastructural membranes interspersed with abundant photosensitive ion pumps to boost signal generation and realize high gain in dim light. In light of this, superstructured optoionic heterojunctions (SSOHs) with cation-selective nanochannels are developed for manipulating photo-driven ion pumping. A template-directed bottom-up strategy is adopted to sequentially assemble graphene oxide (GO) and PEDOT:PSS into heterogeneous membranes with sculptured superstructures, which feature programmable variation in membrane topography and contain a donor-acceptor interface capable of maintaining electron-hole separation upon photoillumination. Such elaborate design endows SSOHs with a much higher magnitude of photo-driven ion flux against a concentration gradient in contrast to conventional optoionic membranes with planar configuration. This can be ascribed to the buildup of an enhanced transmembrane potential owing to the effective separation of photogenerated carriers at the heterojunction interface and the increase of energy input from photoillumination due to a synergistic effect of reflection reduction, broad-angle absorption, and wide-waveband absorption. This work unlocks the significance of membrane topographies in photo-driven transmembrane transportation and proposes such a universal prototype that could be extended to other optoionic membranes to develop high-performance artificial ion pumps for energy conversion and sensing.

Vanadate-based Fe-MOFs as promising negative electrode for hybrid supercapacitor device

In the supercapacitor field, negative electrodes are mainly concentrated in carbon-based materials, such as activated carbon, carbon nanotubes, graphene, and so forth. However, materials based on metal-organic frameworks (MOFs) as negative active components are relatively rare. Herein, a series of composite materials based on graphene oxide (GO) and vanadate-based Fe-organic frameworks have been prepared by hydrothermal method namely GO/Fe-VO4-BIPY. The deposition amount of polyoxometalate-based metal-organic frameworks (POMOFs) on the surface of graphene is adjusted by changing the content of POMOFs. Through the deposition, it can effectively reduce the accumulation between graphene, and increase the dispersion of POMOFs. As a result, the charge storage performance of the as-obtained materials is greatly improved. Among these materials, GO/Fe-VO4-BIPY-1 has the most prominent performance, with a specific capacitance of 190 F g-1at 0.5 A g-1, which is attributed to the excellent synergistic effect between the Faraday chemical reaction and electric double-layer capacitance. In comparison with pristine Fe-VO4-BIPY, GO/Fe-VO4-BIPY-1 delivers more excellent surface area and therefore exhibits abundant redox reaction sites, achieving better electrochemical performance the best. After assembly with the positive Ni(OH)2electrode, the maximum energy density of 46.84 W h kg-1at a power density of 850 W kg-1is achieved.

Introducing CuCo2S4 Nanoparticles on Reduced Graphene Oxide for High-Performance Supercapacitor

In this work, a bimetallic sulfide-coupled graphene hybrid was designed and constructed for capacitive energy storage. The hybrid structure involved decorating copper-cobalt-sulfide (CuCo2S4) nanoparticles onto graphene layers, with the nanoparticles anchored within the graphene layers, forming a hybrid energy storage system. In this hybrid structure, rGO can work as the substrate and current collector to support the uniform distribution of the nanoparticles and provides efficient transportation of electrons into and out of the electrode. In the meantime, CuCo2S4-active materials are expected to offer an evident enhancement in electrochemical activities, due to the rich valence change provided by Cu and Co. Benefiting from the integrated structure of CuCo2S4 nanoparticles and highly conductive graphene substrates, the prepared CuCo2S4@rGO electrode exhibited a favorable capacitive performance in 1 M KOH. At 1 A g-1, CuCo2S4@rGO achieved a specific capacitance of 410 F g-1. The capacitance retention at 8 A g-1 was 70% of that observed at 1 A g-1, affirming the material's excellent rate capability. At the current density of 5 A g-1, the electrode underwent 10,000 charge-discharge cycles, retaining 98% of its initial capacity, which indicates minimal capacity decay and showcasing excellent cycling performance.

Recyclable GO-Arginine Hybrids for CO2 Fixation into Cyclic Carbonates

New covalently modified GO-guanidine materials have been realized in a gram-scale synthesis and purified by an innovative microfiltration. The use of these composites in the fixation of CO₂ into cyclic carbonates is demonstrated. Mild operating conditions, high yields (up to 85 %), wide scope (15 examples) and recoverability/reusability (up to 5 cycles) of the material account for the efficiency of the protocol. Dedicated control experiments shed light on the activation modes exerted by GO-l-arginine during the ring-opening/closing synthetic sequence.

Two-Dimensional Nanofluidic Membranes with Intercalated In-Plane Shortcuts for High-Performance Blue Energy Harvesting

Two-dimensional nanofluidic membranes offer great opportunities for developing efficient and robust devices for ionic/water-nexus energy harvesting. However, low counterion concentration and long pathway through limited ionic flux restrict their output performance. Herein, it is demonstrated that rapid diffusion kinetics can be realized in two-dimensional nanofluidic membranes by introducing in-plane holes across nanosheets, which not only increase counterion concentration but also shorten pathway length through the membranes. Thus, the holey membranes exhibited an enhanced performance relative to the pristine ones in terms of osmotic energy conversion. In particular, a biomimetic multilayered membrane sequentially assembled from pristine and holey sections offers an optimized combination of selectivity and permeability, therefore generating a power density up to 6.78 W m^-2 by mixing seawater and river water, superior to the majority of the state-of-the-art lamellar nanofluidic membranes. This work highlights the importance of channel morphologies and presents a general strategy for effectively improving ion transport through lamellar membranes for high-performance nanofluidic devices.

Polymer Electrolyte Membranes Containing Functionalized Organic/Inorganic Composite for Polymer Electrolyte Membrane Fuel Cell Applications

To mitigate the dependence on fossil fuels and the associated global warming issues, numerous studies have focused on the development of eco-friendly energy conversion devices such as polymer electrolyte membrane fuel cells (PEMFCs) that directly convert chemical energy into electrical energy. As one of the key components in PEMFCs, polymer electrolyte membranes (PEMs) should have high proton conductivity and outstanding physicochemical stability during operation. Although the perfluorinated sulfonic acid (PFSA)-based PEMs and some of the hydrocarbon-based PEMs composed of rationally designed polymer structures are found to meet these criteria, there is an ongoing and pressing need to improve and fine-tune these further, to be useful in practical PEMFC operation. Incorporation of organic/inorganic fillers into the polymer matrix is one of the methods shown to be effective for controlling target PEM properties including thermal stability, mechanical properties, and physical stability, as well as proton conductivity. Functionalization of organic/inorganic fillers is critical to optimize the filler efficiency and dispersion, thus resulting in significant improvements to PEM properties. This review focused on the structural engineering of functionalized carbon and silica-based fillers and comparisons of the resulting PEM properties. Newly constructed composite membranes were compared to composite membrane containing non-functionalized fillers or pure polymer matrix membrane without fillers.

Remote Floating-Gate Field-Effect Transistor with 2-Dimensional Reduced Graphene Oxide Sensing Layer for Reliable Detection of SARS-CoV-2 Spike Proteins

Despite intensive research of nanomaterials-based field-effect transistors (FETs) as a rapid diagnostic tool, it remains to be seen for FET sensors to be used for clinical applications due to a lack of stability, reliability, reproducibility, and scalability for mass production. Herein, we propose a remote floating-gate (RFG) FET configuration to eliminate device-to-device variations of two-dimensional reduced graphene oxide (rGO) sensing surfaces and most of the instability at the solution interface. Also, critical mechanistic factors behind the electrochemical instability of rGO such as severe drift and hysteresis were identified through extensive studies on rGO-solution interfaces varied by rGO thickness, coverage, and reduction temperature. rGO surfaces in our RFGFET structure displayed a Nernstian response of 54 mV/pH (from pH 2 to 11) with a 90% yield (9 samples out of total 10), coefficient of variation (CV) < 3%, and a low drift rate of 2%, all of which were calculated from the absolute measurement values. As proof-of-concept, we demonstrated highly reliable, reproducible, and label-free detection of spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a saliva-relevant media with concentrations ranging from 500 fg/mL to 5 μg/mL, with an R² value of 0.984 and CV < 3%, and a guaranteed limit of detection at a few pg/mL. Taken together, this new platform may have an immense effect on positioning FET bioelectronics in a clinical setting for detecting SARS-CoV-2.

Microstructure and Biological Properties of Electrospun In Situ Polymerization of Polycaprolactone-Graft-Polyacrylic Acid Nanofibers and Its Composite Nanofiber Dressings

In this study, polycaprolactone (PCL)- and poly(acrylic acid) (PAA)-based electrospun nanofibers were prepared for the carriers of antimicrobials and designed composite nanofiber mats for chronic wound care. The PCL- and PAA-based electrospun nanofibers were prepared through in situ polymerization starting from PCL and acrylic acid (AA). Different amounts of AA were introduced to improve the hydrophilicity of the PCL electrospun nanofibers. A compatibilizer and a photoinitiator were then added to the electrospinning solution to form a grafted structure composed of PCL and PAA (PCL-g-PAA). The grafted PAA was mainly located on the surface of a PCL nanofiber. The optimization of the composition of PCL, AA, compatibilizer, and photoinitiator was studied, and the PCL-g-PAA electrospun nanofibers were characterized through scanning electron microscopy and 1H-NMR spectroscopy. Results showed that the addition of AA to PCL improved the hydrophilicity of the electrospun PCL nanofibers, and a PCL/AA ratio of 80/20 presented the best composition and had smooth nanofiber morphology. Moreover, poly[2 -(tert-butylaminoethyl) methacrylate]-grafted graphene oxide nanosheets (GO-g-PTA) functioned as an antimicrobial agent and was used as filler for PCL-g-PAA nanofibers in the preparation of composite nanofiber mats, which exerted synergistic effects promoted by the antibacterial properties of GO-g-PTA and the hydrophilicity of PCL-g-PAA electrospun nanofibers. Thus, the composite nanofiber mats had antibacterial properties and absorbed body fluids in the wound healing process, thereby promoting cell proliferation. The biodegradation of the PCL-g-PAA electrospun nanofibers also demonstrated an encouraging result of three-fold weight reduction compared to the neat PCL nanofiber. Our findings may serve as guidelines for the fabrication of electrospun nanofiber composites that can be used mats for chronic wound care.

Graphene Oxide-Assisted Covalent Triazine Framework for Boosting Photocatalytic H2 Evolution

Covalent triazine frameworks (CTFs) with two-dimensional structures have exhibited promising visible-light-induced H₂ evolution performance. However, it is still a challenge to improve their activity. Herein, we report π-conjugation-linked CTF-1/GO for boosting photocatalytic H₂ evolution. The CTF-1/GO hybrid material was obtained by a facile low-temperature condensation of 1,4-dicyanobenzene in the presence of GO. The results of photocatalytic H₂ evolution indicate that the optimum hybrid, CTF-1/GO-3.0, exhibited an H₂ evolution rate of 2262.4 μmol ⋅ g^-1  ⋅ h^-1 under visible light irradiation, which was 9 times that of pure CTF-1. The enhanced photocatalytic performance could be attributed to the fact that GO in CTF-1/GO hybrids not only acts as an electron collector and transporter like a "bridge" to facilitate the separation and transfer of photogenerated charges but also shortens the electron migration path due to its thin sheet layer uniformly distribution over CTF-1. This work could help future development of novel conjugated CTF-based composite materials as high-efficiency photocatalyst for photocatalysis.

Bioproduced Polymers Self-Assemble with Graphene Oxide into Nanocomposite Films with Enhanced Mechanical Performance

Graphene oxide (GO) has recently been highlighted as a promising multipurpose two-dimensional material. However, free-standing graphene oxide films suffer from poor strength and flexibility, which limits scaling-up of production and lifetime structural robustness in applications. Inspired by the relationship between the organic and inorganic components of the hierarchical structure of nacre found in mollusk shells, we have fabricated self-assembled, layered graphene-based composite films. The organic phase of our composite is produced via environmentally friendly and economical methods based on bacterial production of γ-poly(glutamic acid) (PGA). Composite films made of GO, PGA, and divalent cations (Ca²⁺) were prepared through a slow solvent evaporation method at ambient temperature, resulting in a nacre-like layered structure. These biobased nanocomposite films showed impressive mechanical properties, which resulted from a synergistic combination of hydrogen bonding with the bacterially produced PGA and ionic bonding with calcium ions (Ca²⁺). The GO/PGA/Ca²⁺ composite films possessed a high strength of 150 ± 51.9 MPa and a high Young's modulus of 21.4 ± 8.7 GPa, which represents an increase of 120% and over 70% with respect to pure GO films. We provide rational design strategies for the production of graphene-based films with improved mechanical performance, which can be applied in filtration purification of wastewater in the paper, food, beverage, pigment, and pharmaceuticals industries, as well as for manufacturing of functional membranes and surface coatings.

Boosting Redox-Active Sites of 1T MoS2 Phase by Phosphorus-Incorporated Hierarchical Graphene Architecture for Improved Li Storage Performances

Hybridizing and architecting two kinds of 2D nanomaterials are attractive for energy storage applications. Herein, the chemical and electronic coupling of redox active 1T MoS₂ phase with hierarchical phosphorus-doped graphene architecture (HMPGA) is accomplished by the strong interactions of 2D hybrid colloids. The spectroscopic analyses on the crystal structure, surface morphology, and composition confirm the efficient doping of phosphorus and the hybridization interaction of 1T MoS₂ with the phosphorus-incorporated graphene. The resulting HMPGA anode shows significant improvement in battery performances. The specific capacity is delivered to 1194 mAh g^-1 at 100 mA g^-1 with a cyclability of 93.3% over 600 cycles. This improvement is ascribed to the multicoupling effect arising from the abundant redox-actives sites of 1T MoS₂ phase boosted and stabilized by hierarchically architected, phosphorus-doped graphenes.

C60(OH)12 and Its Nanocomposite for High-Performance Lithium Storage

Organic carbon materials, such as graphene and nanotubes, with a high specific capacity show promise in improving the energy density for lithium ion batteries (LiBs). Here, we report on the synthesis and characterization of C₆₀(OH)₁₂ and the C₆₀(OH)₁₂/graphene oxide (GO) composite and demonstrate their use as anode materials in LiBs. We find that the C₆₀(OH)₁₂/GO composite forms due to the chemical reactions between the carboxyl and epoxy groups of GO and the hydroxyl of C₆₀(OH)₁₂ nanoparticles and that C₆₀(OH)₁₂ uniformly grows on the surface of GO nanosheets. Using a suite of spectroscopy probes, we unequivocally show the mixing between C₆₀(OH)₁₂ and GO at the molecular level, which leads to superior battery performances. This composite has a reversible capacity of 1596 mAh g^-1 at 0.2 A g^-1, higher than the capacities of C₆₀(OH)₁₂ and GO. This composite has a superior cycling stability and excellent rate performance, making it a promising organic anode material for high-performance LiBs.

Developing a Strontium-Releasing Graphene Oxide-/Collagen-Based Organic-Inorganic Nanobiocomposite for Large Bone Defect Regeneration via MAPK Signaling Pathway

Significant efforts have been dedicated to fabricating favorable biomaterial-based bone substitutes for the repair of large bone defects. However, the development of bone biomaterials with suitable physiochemical and osteoinductive properties remains a challenge. Here, novel strontium-graphene oxide (Sr-GO) nanocomposites that allow long-term release of Sr ions are fabricated, which are used to reinforce collagen (Col) scaffolds through covalent cross-linking. The prepared Sr-GO-Col scaffold demonstrates significantly high water retention rates and excellent mechanical properties compared with unmodified Col scaffolds. The Sr-GO-modified Col scaffolds display a strong effect on adipose-derived stem cells by facilitating cell adhesion and osteogenic differentiation and by promoting the secretion of angiogenic factors to stimulate the in vitro tube formation of endothelial cells. Additionally, the secretion of angiogenic VEGF and osteogenic BMP-2 proteins is increased, which may be attributed to the synergistic effects of GO and Sr on the activation of the MAPK signaling pathway. The Sr-GO-Col constructs were then transplanted into rat critical-size calvarial bone defects, which showed the best bone regeneration and angiogenesis outcome at 12 weeks. Moreover, histological staining results show that the Sr-GO-Col group achieved complete defect bridging with the newly formed bone tissue and the residual Sr-GO nanoparticles are phagocytosed and degraded by multinucleated giant cells. These findings reveal that the incorporation of inorganic Sr-GO nanocomposites into biocompatible Col scaffolds is a viable strategy for fabricating favorable substitutes that enhance the regeneration of large bone defects.

Thermally and Near-Infrared Light-Induced Shape Memory Polymers Capable of Healing Mechanical Damage and Fatigued Shape Memory Function

The fabrication of shape memory polymers that are mechanically robust and capable of being induced by near-infrared (NIR) light and healing mechanical damage and the fatigued shape memory function remains a challenge. In this study, thermally and NIR-light-induced shape memory polymers with self-healing ability and satisfactory mechanical robustness are fabricated by dispersing poly(acrylic acid) (PAA)-grafted graphene oxide (GO) (PAA-GO) into poly(vinyl alcohol) (PVA) matrix. The PVA/PAA-GO_3% films with a PAA-GO content of 3.0 wt % have a fracture stress of ∼70.4 MPa and a Young's modulus of ∼2.8 GPa. The PVA/PAA-GO_3% films exhibit an excellent shape memory performance because PVA and PAA-GO form a stable network through hydrogen-bonding interaction between them. Meanwhile, the PVA/PAA-GO_3% films are capable of recovering from temporary shape to permanent shape under NIR light irradiation because of excellent photothermal conversion property of the GO nanosheets. More importantly, benefiting from the reversibility of hydrogen-bonding interactions between PVA and PAA-GO nanosheets, the shape memory PVA/PAA-GO_3% films are capable of healing physical damage and the fatigued shape memory function with the assistance of water, which greatly enhance their reliability as shape memory materials and prolong their service life.

Enhanced Adsorption of Zn(II) onto Graphene Oxides Investigated Using Batch and Modeling Techniques

Graphene oxide (GO) was synthesized and employed as an adsorbent for Zn(II) removal from an aqueous solution. The adsorption isotherms showed that Zn(II) adsorption can be better described using the Freundlich model than the Langmuir model. The maximum adsorption capacity of Zn(II) on GO determined using the Langmuir model at pH 7.0 and 293 K was 208.33 mg/g. The calculation of thermodynamic parameters revealed that the process of Zn(II) adsorption on GO was chemisorptions, endothermic, and spontaneous. Kinetic studies indicated that the pseudo-second-order kinetic model showed a better simulation of Zn(II) adsorption than the pseudo-first-order kinetic model. On the basis of surface complexation modeling, the double layer model provided a satisfactory prediction of Zn(II) by inner-sphere surface complexes (for example, SOZn⁺ and SOZnOH species), indicating that the interaction mechanism between Zn(II) and GO was mainly inner-sphere complexation. In terms of reusability, GO could maintain 92.23% of its initial capability after six cycles. These findings indicated that GO was a promising candidate for the immobilization and preconcentration of Zn(II) from aqueous solutions.

Graphene Oxide Based Recyclable in Vivo Device for Amperometric Monitoring of Interferon-γ in Inflammatory Mice

Cytokine sensing is challenging due to their typically low abundances in physiological conditions. Nanomaterial fabricated interfaces demonstrated unique advantages in ultrasensitive sensing. Here, we demonstrate an amperometric sensing device based on graphene oxide (GO) and structure-switching aptamers for long-term detection of cytokines in a living organism. The device incorporates a single layer of GO acting as a signal amplifier on glassy carbon electrodes. The hairpin aptamers specific to interferon-γ (IFN-γ), which were loaded with redox probes, are covalently attached to GO to serve as biorecognition moieties. IFN-γ was able to trigger the configuration change of aptamers while releasing the trapped redox probes to introduce the electrochemical signal. This in vivo device was capable of quantitatively and dynamically detecting IFN-γ down to 1.3 pg mL^-1 secreted by immune cells in cell culture medium with no baseline drift even at a high concentration of other nonspecific proteins. The biocompatible devices were also implanted into subcutaneous tissue of enteritis mice, where they performed precise detection of IFN-γ over 48 h without using physical barriers or active drift correction algorithms. Moreover, the device could be reused even after multiple rounds of regeneration of the sensing interface.

Graphene Oxide Signal Reporter Based Multifunctional Immunosensing Platform for Amperometric Profiling of Multiple Cytokines in Serum

Cytokines are small proteins and form complicated cytokine networks to report the status of our health. Thus, accurate profiling and sensitive quantification of multiple cytokines is essential to have a comprehensive and accurate understanding of the complex physiological and pathological conditions in the body. In this study, we demonstrated a robust electrochemical immunosensor for the simultaneous detection of three cytokines IL-6, IL-1β, and TNF-α. First, graphene oxides (GO) were loaded with redox probes nile blue (NB), methyl blue (MB), and ferrocene (Fc), followed by covalent attachment of anti-cytokine antibodies for IL-6, IL-1β, and TNF-α, respectively, to obtain Ab₂-GO-NB, Ab₂-GO-MB, and Ab₂-GO-Fc, acting as the signal reporters. The sensing interface was fabricated by attachment of mixed layers of 4-carboxylic phenyl and 4-aminophenyl phosphorylcholine (PPC) to glassy carbon surfaces. After that, the capture monoclonal antibody for IL-6, IL-1β, and TNF-α was modified to the carboxylic acid terminated sensing interface. And finally a sandwich assay was developed. The quantitative detection of three cytokines was achieved by observing the change in electrochemical signal from signal reporters Ab₂-GO-NB, Ab₂-GO-MB, and Ab₂-GO-Fc. The designed system has been successfully used for detection of three cytokines (IL-6, IL-1β, and TNF-α) simultaneously with desirable performance in sensitivity, selectivity, and stability, and recovery of 93.6%-105.5% was achieved for determining cytokines spiked in the whole mouse serum.

Incorporating Graphene Oxide into Alginate Polymer with a Cationic Intermediate To Strengthen Membrane Dehydration Performance

Two-dimensional graphene oxide (GO) in hybrid membranes provides fast water transfer across its surface due to the abundant oxygenated functional groups to afford water sorption and the hydrophobic basal plane to create fast transporting pathways. To establish more compatible and efficient interactions for GO and sodium alginate (SA) polymer chains, cations sourced from lignin are employed to decorate GO (labeled as cation-functionalized GO (CG)) nanosheets via cation-π and π-π interactions, providing more interactive sites to confer synergetic benefits with polymer matrix. Cations from CG are also functional to partially interlock SA chains and intensify water diffusion. And with the aid of two-dimensional pathways of CG, fast selective water permeation can be realized through hybrid membranes with CG fillers. In dehydrating aqueous ethanol solution, the hybrid membrane exhibits considerable performance compared with bare SA polymer membrane (long-term stable permeation flux larger than 2500 g m^-2 h^-1 and water content larger than 99.7 wt %, with feed water content of 10 wt % under 70 °C). The effects of CG content in SA membrane were investigated, and the transport mechanism was correspondingly studied through varying operation conditions and membrane materials. In addition, such a membrane possesses long-term stability and almost unchanged high dehydration capability.

Graphene Oxide Thin Film with Dual Function Integrated into a Nanosandwich Device for in Vivo Monitoring of Interleukin-6

Graphene oxide (GO), with its exceptional physical and chemical properties and biocompatibility, holds a tremendous potential for sensing applications. In this study, GO, acting both as the electron-transfer bridge and the signal reporter, was attached on the interface to develop a label-free electrochemical nanosandwich device for detection of interleukin-6 (IL-6). First, a single layer of GO was covalently modified on gold electrodes, followed by attachment of anti-IL-6 capture antibody to form the sensing interface. The 4-aminophenyl phosphorylcholine was further attached to the surface of GO to minimize nonspecific protein adsorption. For reporting the presence of analyte, the anti-IL-6 detection antibody was covalently modified to the GO, which has been integrated with the redox probe Nile blue (NB). Finally, a nanosandwich assay was fabricated on gold surfaces for detection of IL-6 on the basis of the electrochemical signal of NB. The prepared nanosandwiches demonstrated high selectivity and stability for detection of IL-6 over the range of 1-300 pg mL^-1 with the lowest detectable concentration of 1 pg mL^-1. The device was successfully used for monitoring of IL-6 secretion in RAW cells and live mice. By tailoring the GO surface with functional components, such devices were able to detect the analyte in vivo without causing inflammatory response.

Pyrosequencing Reveals Soil Enzyme Activities and Bacterial Communities Impacted by Graphene and Its Oxides

Graphene (GN) and graphene oxides (GOs) are novel carbon nanomaterial; they have been attracting much attention because of their excellent properties and are widely applied in many areas, including energy, electronics, biomedicine, environmental science, etc. With industrial production and consumption of GN/GO, they will inevitably enter the soil and water environments. GN/GO may directly cause certain harm to microorganisms and lead to ecological and environmental risks. GOs are GN derivatives with abundant oxygen-containing functional groups in their graphitic backbone. The structure and chemistry of GN show obvious differences compared to those of GO, which lead to the different environmental behaviors. In this study, four different types of soil (S1-S4) were employed to investigate the effect of GN and GO on soil enzymatic activity, microbial population, and bacterial community through pyrosequencing of 16S rRNA gene amplicons. The results showed that soil enzyme activity (invertase, protease, catalase, and urease) and microbial population (bacteria, actinomycetes, and fungi) changed after GN/GO release into soils. Soil microbial community species are more rich, and the diversity also increases after GO/GN application. The phylum of Proteobacteria increased at 90 days after treatment (DAT) after GN/GO application. The phylum of Chloroflexi occurred after GN application at 90 DAT in S1 soil and reached 4.6%. Proteobacteria was the most abundant phylum in S2, S3, and S4 soils; it ranged from 43.6 to 71.4% in S2 soil, from 45.6 to 73.7% in S3 soil, and from 38.1 to 56.7% in S4 soil. The most abundant genera were Bacillus (37.5-47.0%) and Lactococcus (28.0-39.0%) in S1 soil, Lysobacter and Flavobacterium in S2 soil, Pedobacter in S3 soil, and Massilia in S4 soil. The effect of GN and GO on the soil microbial community is time-dependent, and there are no significant differences between the samples at 10 and 90 DAT.

Molecule Channels Directed by Cation-Decorated Graphene Oxide Nanosheets and Their Application as Membrane Reactors

Highly selective macromembranes, fabricated by cation-decorated graphene oxide, exhibit an excellent selectivity toward a wide range of solvents. Mixed solvents are successfully separated, based on which a membrane reactor is designed to promote a series of chemical reactions. The cations bonding to the graphene oxide nanosheets are found to be responsible for this selectivity by cation-π, electrostatic interactions, and hydrogen bonding.

Pyroprotein-Based Electronic Textiles with High Stability

Thermally reducible pyroprotein-based electronic textiles (e-textiles) are fabricated using graphene oxide and a pyroprotein such as cocoon silk and spider web without any chemical agents. The electrical conductivity of the e-textile is 11.63 S cm^-1 , which is maintained even in bending, washing, and temperature variation.

Electronic Activation of a DNA Nanodevice Using a Multilayer Nanofilm

A method to control activation of a DNA nanodevice by supplying a complementary DNA (cDNA) strand from an electro-responsive nanoplatform is reported. To develop functional nanoplatform, hexalayer nanofilm is precisely designed by layer-by-layer assembly technique based on electrostatic interaction with four kinds of materials: Hydrolyzed poly(β-amino ester) can help cDNA release from the film. A cDNA is used as a key building block to activate DNA nanodevice. Reduced graphene oxides (rGOs) and the conductive polymer provide conductivity. In particular, rGOs efficiently incorporate a cDNA in the film via several interactions and act as a barrier. Depending on the types of applied electronic stimuli (reductive and oxidative potentials), a cDNA released from the electrode can quantitatively control the activation of DNA nanodevice. From this report, a new system is successfully demonstrated to precisely control DNA release on demand. By applying more advanced form of DNA-based nanodevices into multilayer system, the electro-responsive nanoplatform will expand the availability of DNA nanotechnology allowing its improved application in areas such as diagnosis, biosensing, bioimaging, and drug delivery.

Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets Functionalized Thin Film Nanocomposite Membrane for Enhanced Antimicrobial Performance

Inspired by the rational design concept, a novel antimicrobial agent zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) was synthesized and utilized as a novel and efficient bactericidal agent to fabricate antimicrobial thin film nanocomposite (TFN) membranes via interfacial polymerization. The resultant hybrid nanosheets not only integrates the merits of both ZIF-8 and GO but also yields a uniform dispersion of ZIF-8 onto GO nanosheets simultaneously, thus effectively eliminating the agglomeration of ZIF-8 in the active layer of membranes. A ZIF-8/GO thin film nanocomposite (TFN-ZG) membrane with typical water permeability (40.63 L m(-2) h(-1) MPa(-1)) allows for efficient bivalent salt removal (rejections of Na2SO4 and MgSO4 were 100% and 77%, respectively). Furthermore, the synthesized ZIF-8/GO nanocomposites were verified to have an optimal antimicrobial activity (MIC,128 μg/mL) in comparison with ZIF-8 and GO separately, which sufficiently endowed the TFN-ZG membrane with excellent antimicrobial activity (84.3% for TFN-ZG3). Besides, the antimicrobial mechanisms of ZIF-8/GO hybrid nanosheets and TFN-ZG membranes were proposed. ZIF-8/GO functionalized membrane with high antimicrobial activity and salt retention denoted its great potential in water desalination, and we suggest that ZIF-8 based crystal may offer a new pathway for the synthesis of a multifunctional bactericide.

Graphene Oxide-Copper Nanocomposite-Coated Porous CaP Scaffold for Vascularized Bone Regeneration via Activation of Hif-1α

Graphene has been studied for its in vitro osteoinductive capacity. However, the in vivo bone repair effects of graphene-based scaffolds remain unknown. The aqueous soluble graphene oxide-copper nanocomposites (GO-Cu) are fabricated, which are used to coat porous calcium phosphate (CaP) scaffolds for vascularized bone regeneration. The GO-Cu nanocomposites, containing crystallized CuO/Cu2 O nanoparticles of ≈30 nm diameters, distribute uniformly on the surfaces of the porous scaffolds and maintain a long-term release of Cu ions. In vitro, the GO-Cu coating enhances the adhesion and osteogenic differentiation of rat bone marrow stem cells (BMSCs). It is also found that by activating the Erk1/2 signaling pathway, the GO-Cu nanocomposites upregulate the expression of Hif-1α in BMSCs, resulting in the secretion of VEGF and BMP-2 proteins. When transplanted into rat with critical-sized calvarial defects, the GO-Cu-coated calcium phosphate cement (CPC) scaffolds (CPC/GO-Cu) significantly promote angiogenesis and osteogenesis. Moreover, it is observed via histological sections that the GO-Cu nanocomposites are phagocytosed by multinucleated giant cells. The results suggest that GO-Cu nanocomposite coatings can be utilized as an attractive strategy for vascularized bone regeneration.

Ternary Artificial Nacre Reinforced by Ultrathin Amorphous Alumina with Exceptional Mechanical Properties

A novel ternary artificial nacre is developed through a vacuum-assisted filtration method, with reinforced ultrathin amorphous alumina that is grown in situ on the surface of GO. This ternary artificial nacre simultaneously shows exceptional strength and toughness, which have, up to now, been considered to be mutually exclusive. This novel material will play a role in the structuring of future materials.

Incorporating Zwitterionic Graphene Oxides into Sodium Alginate Membrane for Efficient Water/Alcohol Separation

For the selective water-permeation across dense membrane, constructing continuous pathways with high-density ionic groups are of critical significance for the preferential sorption and diffusion of water molecules. In this study, zwitterionic graphene oxides (PSBMA@GO) nanosheets were prepared and incorporated into sodium alginate (SA) membrane for efficient water permeation and water/alcohol separation. The two-dimensional GO provides continuous pathway, while the high-density zwitterionic groups on GO confer electrostatic interaction sites with water molecules, leading to high water affinity and ethanol repellency. The simultaneous optimization of the physical and chemical structures of water transport pathway on zwitterionic GO surface endows the membrane with high-efficiency water permeation. Using dehydration of water/alcohol mixture as the model system, the nanohybrid membranes incorporating PSBMA@GO exhibit much higher separation performance than the SA membrane and the nanohybrid membrane utilizing unmodified GO as filler (with the optimal permeation flux of 2140 g m(-2) h(-1), and separation factor of 1370). The study indicates the great application potential of zwitterionic graphene materials in dense water-permeation membranes and provides a facile approach to constructing efficient water transport pathway in membrane.

Highly Elastic and Conductive Human-Based Protein Hybrid Hydrogels

A highly elastic hybrid hydrogel of methacryloyl-substituted recombinant human tropoelastin (MeTro) and graphene oxide (GO) nanoparticles are developed. The synergistic effect of these two materials significantly enhances both ultimate strain (250%), reversible rotation (9700°), and the fracture energy (38.8 ± 0.8 J m(-2) ) in the hybrid network. Furthermore, improved electrical signal propagation and subsequent contraction of the muscles connected by hybrid hydrogels are observed in ex vivo tests.

Selective gas diffusion in graphene oxides membranes: a molecular dynamics simulations study

Designing membrane materials from one-atom-thick structures is highly promising in separation and filtration applications for the reason that they offer the ultimate precision in modifying the atomic structures and chemistry for optimizing performance, and thus resolving the permeation-selectivity trade-off. In this work, we explore the molecular dynamics of gas diffusion in the gallery space between functionalized graphene layers as well as within nanopores across the multilayers. We have identified highly selective gas permeation that agrees with recent experimental measurements and is promising for advancing gas separation technologies such as hydrogen separation, helium/nitrogen generation, and CO2 sequestration. The roles of structural and chemical factors are discussed by considering different types of gases including H2, He, CH4, N2, O2, CO, CO2, and H2O. The overall performance of graphene oxide membranes is also discussed with respect to their microstructures, and compared with recent experimental measurements. These understandings could advise high-performance gas-separation membrane development by engineering assemblies of two-dimensional layered structures.

Synergistic plasmonic effects of metal nanoparticle-decorated PEGylated graphene oxides in polymer solar cells

Metal nanostructures that trigger plasmonic near-field effects are often incorporated in organic photovoltaic devices (OPVs) to improve their light-harvesting ability. These nanostructures usually can be positioned in two different locations in a device: (i) within the photon absorption layers and (ii) at the interfaces between the active layer and the metal electrodes. In this study, we developed amphiphilic gold nanoparticles (Au NPs) for use in dual plasmonic nanostructures within OPVs. We employed graphene oxide as the template to anchor the Au NPs, thereby avoiding their aggregation. Furthermore, we added poly(ethylene glycol) (PEG) bis(amine) to the synthesis medium to improve the solubility of the nanocomposites, such that they could be dispersed well in water and in several organic solvents. Accordingly, we could incorporate the PEGylated Au NP/graphene oxides readily into both the buffer layer and photoactive layer of OPVs, which, as a result, exhibited obvious enhancements in their photocurrents and overall device efficiencies. Moreover, we observed different spectral enhancement regions when we positioned the nanocomposites at different locations, reflecting the different dielectric environments surrounding the NPs; this unexpected behavior should assist in enhancing the broadband absorption of solar irradiation.

Photothermal therapeutic response of cancer cells to aptamer-gold nanoparticle-hybridized graphene oxide under NIR illumination

The objective of this study was to synthesize a nanocomposite, aptamer-gold nanoparticle-hybridized graphene oxide (Apt-AuNP-GO), to facilitate targeted treatment of tumor cells by near-infrared (NIR) light-activatable photothermal therapy. We also investigated whether Apt-AuNP-GO with NIR illumination modulates heat shock proteins (HSPs) expression leading to therapeutic response in human breast cancer cells. These findings can provide strategies for improving the photothermal therapy efficacy of cancer. The self-assembled Apt-AuNP-GO nanocomposite could selectively target MUC1-positive human breast cancer cells (MCF-7) due to the specific interaction between the MUC1-binding-aptamer and the MUC1 (type I transmembrane mucin glycoprotein) on cell membrane. In addition, Apt-AuNP-GO has a high light-to-heat conversion capability for photoabsorption of NIR light, and it is able to exert therapeutic effects on MCF-7 cells at an ultralow concentration without inducing adverse effects in healthy cells. The Apt-AuNP-GO nanocomposites combine the advantages of GOs, AuNPs, and Apts, possess specific targeting capability, excellent biocompatibility, and tumor cell destruction ability, suggesting great potential for application in the photothermal therapy of breast cancer. Under NIR illumination, Apt-AuNP-GO induced transient increase in HSP70 expression, which decreased thereafter. This phenomenon may cause irreversible damage to Apt-AuNP-GO-treated MCF-7 cell under NIR illumination. We also demonstrated that the combination therapy of heat and HSP70 inhibitor could synergistically generate marked tumoricidal effects against breast cancer. These results suggest that the degree and duration of HSP70 protein expression are correlated with therapeutic effects against breast cancer for Apt-AuNP-GO-assisted photothermal therapy. We believe that such a nanocomposite can be readily extended to the construction of HSP70 inhibitors-loaded Apt-AuNP-GO, which could deliver both heat and HSP70 inhibitors to tumorigenic regions for the chemo-photothermal therapy.

Moisture-responsive graphene paper prepared by self-controlled photoreduction

A facile and cost-effective preparation of moisture-responsive graphene bilayer paper by focused sunlight irradiation is reported. The smart graphene paper shows moisture-responsive properties due to selective adsorption of water molecules, leading to controllable actuation under humid conditions. In this way, graphene-based moisture-responsive actuators including a smart claw, an orientable transporter, and a crawler paper robot are successfully developed.

Self-assembled reduced graphene oxide/polyacrylamide conductive composite films

Substrate supported conductive thin films are prepared by the self-assembly of graphene oxide (GO) on a cationic polyacrylamide (CPAM) layer followed by a subsequent chemical reduction. During self-assembly, the dispersed GO nanosheets with a negative zeta potential from solution are spontaneously assembled onto the positively charged CPAM adsorption layer. In addition, CPAM adsorption on the substrate is studied with an electrochemical quartz crystal microbalance (EQCM), showing adsorption stabilization could be established in less than 150 s. The electrostatic interactions between GO and CPAM are investigated by changing the polarization potential with EQCM for the first time, and optimal conditions for facilitating self-assembly are determined. The self-assembled GO/CPAM films are further characterized by Raman spectroscopy, infrared spectroscopy and atomic force microscopy. Importantly, reduced GO (R-GO)/CPAM composite films exhibiting a sheet resistance of 3.1 kΩ/sq can be obtained via in situ reduction in sodium borohydride for 20 min at room temperature. This provides a simple, highly effective, and green route to prepare conductive graphene-based composite thin films.

Reduced aggregation and cytotoxicity of amyloid peptides by graphene oxide/gold nanocomposites prepared by pulsed laser ablation in water

A novel and convenient method to synthesize the nanocomposites combining graphene oxides (GO) with gold nanoparticles (AuNPs) is reported and their applications to modulate amyloid peptide aggregation are demonstrated. The nanocomposites produced by pulsed laser ablation (PLA) in water show good biocompatibility and solubility. The reduced aggregation of amyloid peptides by the nanocomposites is confirmed by Thioflavin T fluorescence and atomic force microscopy. The cell viability experiments reveals that the presence of the nanocomposites can significantly reduce the cytotoxicity of the amyloid peptides. Furthermore, the depolymerization of peptide fibrils and inhibition of their cellular cytotoxicity by GO/AuNPs is also observed. These observations suggest that the nanocomposites combining GO and AuNPs have a great potential for designing new therapeutic agents and are promising for future treatment of amyloid-related diseases.

Excitonic Photoluminescence from Nanodisc States in Graphene Oxides

The origin of near-infrared (NIR) luminescence from graphene oxide (GO) is investigated by photoluminescence (PL) excitation spectroscopy, time-resolved PL spectroscopy, and density functional theory based many body perturbation theories. The energy of experimentally observed NIR PL peak depends on the excitation energy, and the peak broadens with increasing excitation energy. It is found that the PL decay curves in time-resolved spectroscopy show build-up behavior at lower emission energies due to energy transfer between smaller to larger graphene nanodisc (GND) states embedded in GO. We demonstrate that the NIR PL originates from ensemble emission of GND states with a few nanometers in size. The theoretical calculations reveal the electronic and excitonic properties of individual GND states with various sizes, which accounts for the inhomogeneously broadened NIR PL. We further demonstrate that the electronic properties are highly sensitive to the protonation and deprotonation processes of GND states using both the experimental and theoretical approaches.

Delivery of bone morphogenetic protein-2 and substance P using graphene oxide for bone regeneration

In this study, we demonstrate that graphene oxide (GO) can be used for the delivery of bone morphogenetic protein-2 (BMP-2) and substance P (SP), and that this delivery promotes bone formation on titanium (Ti) implants that are coated with GO. GO coating on Ti substrate enabled a sustained release of BMP-2. BMP-2 delivery using GO-coated Ti exhibited a higher alkaline phosphatase activity in bone-forming cells in vitro compared with bare Ti. SP, which is known to recruit mesenchymal stem cells (MSCs), was co-delivered using Ti or GO-coated Ti to further promote bone formation. SP induced the migration of MSCs in vitro. The dual delivery of BMP-2 and SP using GO-coated Ti showed the greatest new bone formation on Ti implanted in the mouse calvaria compared with other groups. This approach may be useful to improve osteointegration of Ti in dental or orthopedic implants.

Exploring the Origin of Blue and Ultraviolet Fluorescence in Graphene Oxide

We studied the fluorescence (FL) properties of highly exfoliated graphene oxide (GO) in aqueous solution using continuous-wave and time-resolved FL spectroscopy. The FL spectra of highly exfoliated GO showed two distinct peaks at ∼440 (blue) and ∼300 nm [ultraviolet (UV)]. The FL of GO in the UV region at ∼300 nm was observed for the first time. The average FL lifetimes of the emission peaks at ∼440 and ∼300 nm are 8-13 and 6-8 ns, respectively. The experimentally observed peak wavelengths of pH-dependent FL, FL excitation spectra, and the FL lifetimes are nearly coincident with those of aromatic compounds bound with oxygen functional groups, which suggests that the FL comes from sp(2) fragments consisting of small numbers of aromatic rings with oxygen functional groups acting as FL centers in the GO.

Metal ion-directed solution-phase tailoring: from large-area graphene oxide into nanoscale pieces

Due to fascinating electronic properties and great potential in various applications, graphene has attracted great interest. Recently, much work have focused on the synthesis of different sizes and properties of graphene or graphene oxides (GOs), for example, graphene nanoribbons, nanosized graphene pieces, and nanosized triangular and hexagonal graphene sheets terminated by zigzag edges. Herein, we have demonstrated a widely available approach to fabricate the nanoscale GO pieces by directly solution-phase cutting a large-area GO sheet into nanoscale pieces via spontaneous redox reactions at room temperature. In this process, GO acts with dual functions as a model and a reducing reagent. With a typical example of silver ions, we have investigated in detail the influence of the reaction time and concentration of metal ions on yield and size of nanoscale GO pieces. Moreover, we also obtain Ag nanoparticle coating on the GO surface. Finally, a possible mechanism is suggested to explain the formation of nanoscale GO pieces.