Superior Lithium‐Ion Storage Properties of Mesoporous CuO–Reduced Graphene Oxide Composite Powder Prepared by a Two‐Step Spray‐Drying Process

Mesoporous CuO–reduced graphene oxide (rGO) composite powders were prepared by using a two‐step spray‐drying process. In the first step, hollow CuO powders were prepared from a spray solution of copper nitrate trihydrate with citric acid and were wet milled to obtain a colloidal spray solution. In the second step, spray drying of the colloidal solution that contained dispersed GO nanosheets produced mesoporous CuO–rGO composite powders with particle sizes of several microns. Thermal reduction of GO nanosheets to rGO nanosheets occurred during post‐treatment at 300 °C. Initial discharge capacities of the hollow CuO, bare CuO aggregate, and CuO–rGO composite powders at a current density of 2 A g^?1 were 838, 1145, and 1238 mA h g^?1, respectively. Their discharge capacities after 200 cycles were 259, 380, and 676 mA h g^?1, respectively, and their corresponding capacity retentions measured from the second cycle were 67, 48, and 76 %, respectively. The mesoporous CuO–rGO composite powders have high structural stability and high conductivity because of the rGO nanosheets, and display good cycling and rate performances.     

三维多孔还原氧化石墨烯气凝胶的制备及其在锂离子电池中的应用

以天然鳞片石墨为原料,采用改良的Hummers方法,制备了高纯度的薄层或单层氧化石墨(GO);并以抗坏血酸为还原剂,通过自组装还原的方式成功制备了具有三维多孔独巨石结构的还原氧化石墨烯(rGO)气凝胶,其形貌和结构经FT-IR, SEM, TEM, XRD和XPS表征。并对其作为锂离子电池负极材料的电化学性能进行了测试。结果表明：rGO气凝胶独特的形貌和结构提高了其比容量和循环性能,在100 mA·g^-1电流密度下首周放电比容量可达1 700 mAh·g^-1,首周充电比容量达710 mAh·g^-1,经过100周循环后放电比容量仍可保持在450 mAh·g^-1,库伦效率保持在98%。     

Graphene–carbon 2D heterostructures with hierarchically-porous P,N-doped layered architecture for capacitive deionization

Exploring a new-family of carbon-based desalinators to optimize their performances beyond the current commercial benchmark is of significance for the development of practically useful capacitive deionization (CDI) materials. Here, we have fabricated a hierarchically porous N,P-doped carbon–graphene 2D heterostructure (denoted NPC/rGO) by using metal–organic framework (MOF)-nanoparticle-driven assembly on graphene oxide (GO) nanosheets followed by stepwise pyrolysis and phosphorization procedures. The resulting NPC/rGO-based CDI desalinator exhibits ultrahigh deionization performance with a salt adsorption capacity of 39.34 mg g⁻¹ in a 1000 mg L⁻¹ NaCl solution at 1.2 V over 30 min with good cycling stability over 50 cycles. The excellent performance is attributed to the high specific surface area, high conductivity, favorable meso-/microporous structure together with nitrogen and phosphorus heteroatom co-doping, all of which are beneficial for the accommodation of ions and charge transport during the CDI process. More importantly, NPC/rGO exhibits a state-of-the-art CDI performance compared to the commercial benchmark and most of the previously reported carbon materials, highlighting the significance of the MOF nanoparticle-driven assembly strategy and graphene–carbon 2D heterostructures for CDI applications.

MOF nanoparticle-driven assembly on 2D nanosheets produces the graphene–carbon heterostructure with hierarchically-porous P,N-doped layered architecture.     

One-dimensional self-assembled Co2SnO4 nanosphere to nanocubes intertwined in two-dimensional reduced graphene oxide: an intriguing electrocatalytic sensor toward mesalamine detection

The present work deals with the preparation of hybridized electrode material with electrostatic self-assembly strategy for mesalamine (MES) detection. Grabbing significant abilities between the one-dimensional bimetallic oxides and two-dimensional nanosheets network, a nanohybrid was designed. The developed cobalt stannate/reduced graphene oxide (Co₂SnO₄/rGO)-1D/2D heterostructure will possess improvised anisotropic electron transport, earth abundant, highly conducting, multiple actives site, and higher surface area. The 1D/2D nanostructured architecture will enhance faster electron and mass transport during the electrochemical analysis, which is more significant for MES detection. Progressive testing of Co₂SnO₄/rGO for structural analysis was done, and highly crystalline nature was proved. The self-assembled nanospheres to form nanocube such as Co₂SnO₄ strongly attached over the rGO matrix was confirmed with field emission scanning microscope, and nanocube structure is more visible with high-resolution transmission electron microscopy. The hierarchical highly electroactive material establishes lower detection limit at 4.9 nM with sensitivity of about 8.57 μA/μM/cm². The interfacial area of nanocomposite with higher conducting channels to improve the interactions with MES resulted in enhanced selectivity. The practical analysis in environmental, pharmaceutical, and biological fluids (human urine and serum) showed good recovery. The Co₂SnO₄/rGO will be more prominent and significant as electrode material in electrochemical sensing.     

Porous bowl-shaped VS_2 nanosheets/graphene composite for high-rate lithium-ion storage

Two-dimensional (2D) layered vanadium disulfide (VS_2) is a promising anode material for lithium ion batteries (LIBs) due to the high theoretical capacity.However,it remains a challenge to synthesize monodispersed ultrathin VS_2 nanosheets to realize the full potential.Herein,a novel solvothermal method has been developed to prepare the monodispersed bowl-shaped NH_3-inserted VS_2 nanosheets (VS_2).The formation of such a unique structure is caused by the blocked growth of (001) or (002) crystal planes in combination with a ripening process driven by the thermodynamics.The annealing treatment in Ar/H_2creates porous monodispersed VS_2(H-VS_2),which is subsequently integrated with graphene oxide to form porous monodispersed H-VS_2/rGO composite coupled with a reduction process.As an anode material for LIBs,H-VS_2/rGO delivers superior rate performance and longer cycle stability:a high average capacity of 868/525 mAh g~(-1) at a current density of 1/10 A g~(-1);a reversible capacity of 1177/889 mAh g~(-1) after 150/500 cycles at 0.2/1 A g~(-1).Such excellent electrochemical performance may be attributed to the increased active sites available for lithium storage,the alleviated volume variations and the shortened Li-ion diffusion induced from the porous structure with large specific surface area,as well as the protective effect from graphene nanosheets.     

Reduced graphene oxide-porous In2O3 nanocubes hybrid nanocomposites for room-temperature NH3 sensing

Metal oxide semiconductors(MOS)-reduced graphene oxide(rGO) nanocomposites have attracted great attention for room-tempe rature gas sensing applications.The development of novel sensing materials is the key issue for the effective detection of ammoniagas at room temperature.In the present work,the novel reduced graphene oxide(rGO)-In₂ O₃ nanocubes hybrid materials have been prepared via a simple electrostatic self-assembly strategy.Characterization re sults exhibit that the...     

A Direct Hybridization between Isocharged Nanosheets of Layered Metal Oxide and Graphene through a Surface‐Modification Assembly Process

An efficient and universal method to directly hybridize isocharged nanosheets of layered metal oxide and reduced graphene oxide (rGO) is developed on the basis of the surface modification and an electrostatically driven assembly process. On the basis of this synthetic method, the CoO₂–rGO nanocomposite can be synthesized with exfoliated CoO₂ and rGO nanosheets, and transformed into CoO–CoO₂–rGO nanocomposites with excellent electrode performance for lithium‐ion batteries. Also, this surface‐modification assembly route is successfully applied for the synthesis of another mesoporous TiO₂–rGO nanocomposite. This result provides clear evidence for the usefulness of the present method as a universal way of hybridizing isocharged anionic nanosheets of inorganic solids and graphene.     

One-step construction of MoO_2 uniform nanoparticles on graphene with enhanced lithium storage

Transition-metal oxides are considered to be a promising anode material for lithium-ion batteries(LIBs)due to their high capacities,low cost,and ease of synthesis.Herein,a hybrid nanosheet composed of uniform MoO_2 nanoparticles(NPs) homogeneously immobilized on the reduced graphene oxide nanosheets(MoO_2 NP@rGO) is first synthesized by a self-templating and subsequent calcination treatment.The unique two-dimensional hybridnanosheets provides several merits.rGO can be used as a favorable support for the loading of electrochemically active MoO_2 NPs.Meanwhile,MoO_2 NPs can effectively prevent the stacking of the rGO.The effective combination of MoO_2 NPs and rGO nanosheets furnish additional electrochemically interfacial active sites for extra lithium ion sto rage.Noticeably,the as-fabricated hybrid nanosheets deliver a reversible capacity of 641 mAh/g after 350 cycles at a current density of 1000 mA/g with a good rate capability.The greatly enhanced lithium storage properties of MoO_2 NP@rGO indicate the importance of elaborate construction of novel hybrid hierarchical structures.     

Ultrathin Titanate Nanosheets/Graphene Films Derived from Confined Transformation for Excellent Na/K Ion Storage

Confined transformation of assembled two‐dimensional MXene (titanium carbide) and reduced graphene oxide (rGO) nanosheets was employed to prepare the free‐standing films of the integrated ultrathin sodium titanate (NTO)/potassium titanate (KTO) nanosheets sandwiched between graphene layers. The ultrathin Ti‐based nanosheets reduce the diffusion distance while rGO layers enhance conductivity. Incorporation of graphene into the titanate films produced efficient binder‐free anodes for ion storage. The resulting flexible NTO/rGO and KTO/rGO electrodes exhibited excellent rate performances and long cycling stability characterized by reversible capacities of 72 mA h g^?1 at 5 A g^?1 after 10000 cycles and 75 mA h g^?1 after 700 cycles at 2 A g^?1 for sodium and potassium ion batteries, respectively. These results demonstrate the superiority of the unique sandwich‐type electrodes.     

Free‐standing and Flexible MoS2/rGO Paper Electrode for Amperometric Detection of Folic Acid

The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact devices. We report a new type of flexible electrochemical sensor fabricated by integrating graphene and MoS₂ nanosheets. A highly flexible and free‐standing conductive MoS₂ nanosheets/reduced graphene oxide (MoS₂/rGO) paper was prepared by a two‐step process: vacuum filtration and chemical reduction treatment. The MoS₂/graphene oxide (MoS₂/GO) paper obtained by a simple filtration method was transformed into MoS₂/rGO paper after a chemical reduction process. The obtained MoS₂/rGO paper was characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy. The electrochemical behavior of folic acid (FA) on MoS₂/rGO paper electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that flexible MoS₂/rGO composite paper electrode exhibited excellent electrocatalytic activity toward the FA, which can be attributed to excellent electrical conductivity and high specific surface area of the MoS₂/rGO paper. The resulting biosensor showed highly sensitive amperometric response to FA with a wide linear range.     

Segregated reduced graphene oxide polymer composite as a high performance electromagnetic interference shield

Herein, we report the synthesis of a graphene/polymer composite via a facile and straightforward approach for electromagnetic interference (EMI) shielding applications. Polystyrene (PS) beads were added in graphene oxide (GO)/water solution followed by the addition of hydroiodic acid (HI) for in situ reduction of GO. The composite solution (rGO/PS) was filtered, hot compressed and tested for EMI shielding and dielectric measurements. A 2-mm thick segregated rGO/PS sample with 10 wt% filler loading delivered a high EMI shielding effectiveness (SE) of 29.7 dB and an AC electrical conductivity of 21.8 S m^?1, which is well above the commercial requirement for EMI shielding applications. For comparison with the segregated rGO/PS composite, a control polymer composite sample utilizing a thermally reduced graphene oxide was synthesized by following a conventional coagulation approach. The as-synthesized conventional rGO/PS yield an EMI SE of 14.2 dB and electrical conductivity of 12.5 S m^?1. The high EMI shielding of segregated rGO/PS is attributed to the better filler-to-filler contact among graphene layers surrounded by PS beads and also to the better reduction and preservation of graphene structure during reduction process that makes the low temperature chemically reduced segregated rGO/PS approach a viable route compared to high temperature thermally reduced conventional rGO/PS approach.     

Preparation of reduced graphene oxide/montmorillonite composite hydrogel and its applications for chromium(VI) and organic compounds adsorption

A novel 3D porous reduced graphene oxide/montmorillonite composite hydrogel (rGO–MMT) was prepared by solvent method, where the MMT nanosheets were homogenously dispersed in 3D rGO hydrogel. The porous 3D structure and the high dispersion of MMT nanosheets can promote the adsorption capacity. The effects of MMT content (wt%), the initial concentration of Cr(VI) solution (C0), pH value (pH0), the adsorption dose and temperatures on the adsorption capacity of rGO–MMT for Cr(VI) ions have been investigated. The optimum pH value for Cr(VI) adsorption is 2, and the adsorption capacity increases with MMT content and adsorption temperature. The rGO–MMT composite hydrogel displays the excellent adsorption property for both the heavy metal and organic pollutants. The adsorption capacity of rGO–MMT composite hydrogel is obviously higher than those of single rGO hydrogel and MMT due to the synergistic adsorption of rGO hydrogel and MMT. The adsorption of Cr(VI) ions on the rGO–MMT composite hydrogel follows linear pseudo-second-order kinetics, and the Langmuir model describes the adsorption process much better. Thermodynamic parameters indicate that adsorption is spontaneous, favorable and endothermic in nature.

Graphic abstract

     

层状钒青铜纳米片的制备及其锂离子电池阳极材料性能

室温下, 在水溶液中将铵根离子和水分子插入到商用V₂O₅纳米颗粒的层间, 制得了层状的钒青 铜[(NH₄)₂V₆O₁₆·H₂O]纳米片. 该纳米片的尺寸为2~10 μm, 厚度为50~250 nm. 与商用V₂O₅纳米颗粒相比, (NH₄)₂V₆O₁₆·H₂O纳米片用作锂离子电池(LIBs)的阳极材料时, 其性能得到较大提升, 包括大的可逆放电容量 (0.1 A/g时为1148 mA·h/g)、 出色的循环性能(循环70圈后在0.1 A/g时具有1002 mA·h/g的高容量)和高倍率性能(在0.1 A/g时具有1070 mA·h/g的可逆性能). 研究结果表明, (NH₄)₂V₆O₁₆·H₂O纳米片可以作为锂离子电池优良的阳极材料, 也有望应用于其它(如钠离子电池和锌离子电池等)可再充电电池.     

Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability

Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ～1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (～0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical stability.     

Three-in-one Fe-porphyrin based hybrid nanosheets for enhanced CO2 reduction and evolution kinetics in Li-CO2 battery

Efficient cathode-catalysts with multi-functional properties are essential for Li-CO₂ battery, while the construction of them with simultaneously enhanced CO₂ reduction and evolution kinetics is still challenging. Here, a kind of hybrid nanosheets based on Ru nanoparticles, Fe-TAPP and grapheme oxide (GO) has been designed through a one-pot self-assembly strategy. The Ru, Fe-porphyrin and GO based hybrid nanosheets (denoted as Ru/Fe-TAPP@GO) with integrated multi-components offer characteristics of ultrathin thickness (∼4 nm), high electro-redox property, uniformly dispersed morphology, and high electrical conductivity, etc. These features endow Ru/Fe-TAPP@GO with ultra-low overpotential (0.82 V) and fully reversible discharge/charge property with a high specific-capacity of 39,000 mAh/g within 2.0–4.5 V at 100 mA/g, which are much superior to Ru@GO and Fe-TAPP@GO. The achieved performance was presented as one of the best cathode-catalysts reported to date. The synergistically enhanced activity originated from the integrated hybrid nanosheets may provide a new pathway for designing efficient cathode-catalysts for Li-CO₂ batteries.     

Self-assembly of graphene oxide nanosheets in t-butanol/water medium under gamma-ray radiation

Graphene oxide (GO) nanosheets dispersed in strong acidic t-butanol/water medium can be reduced and self-assembled into a self-standing graphene hydrogel under γ-ray radiation, providing a facile and economical preparation method for hydroxylalkylated graphene-based aerogel.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Incorporation of two‐dimensional nanomaterials into silk fibroin nanofibers for cardiac tissue engineering

Mimicking the extracellular matrix to have a similar nanofibrous structure regarding electrical conductivity and mechanical properties would be highly beneficial for cardiac tissue engineering. The molybdenum disulfide, MoS₂, and reduced graphene oxide, rGO, nanosheets are two‐dimensional nanomaterials which can be considered as great candidates for enhancing the electrical and mechanical properties of biological scaffolds for cardiac tissue engineering applications. In this study, MoS₂ and rGO nanosheets were synthesized and incorporated into silk fibroin nanofibers, SF, via electrospinning method. Then, the human iPSCs transfected with TBX‐18 gene, TBX18‐hiPSCs, were seeded on these scaffolds for in vitro studies. The MoS₂ and rGO nanosheets were studied by Raman spectroscopy. After incorporation of the nanosheets into SF nanofibers, the associated characterizations were carried out including scanning electron microscopy, transmission electron microscopy, water contact angle, and mechanical test. Furthermore, SF, SF/MoS₂, and SF/rGO scaffolds were used for in vitro studies. Herein, the scaffolds exhibited acceptable biocompatibility and considerable attachment to TBX18‐hiPSCs confirmed by 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyl tetrazolium bromide, MTT, assay, and scanning electron microscopy. Also, the real‐time PCR and immunostaining studies confirmed the maturity and upregulation of cardiac functional genes, including GATA‐4, c‐TnT, and α‐MHC in the SF/MoS₂ and SF/rGO scaffolds compared with the bare SF one. Therefore, the reinforcement of these SF‐based scaffolds with MoS₂ and rGO endues them as a suitable candidate for cardiac tissue engineering.     

基于AuNPs/PDDA-GO纳米复合物的电化学免疫传感器的构建及对SirT1蛋白的检测

基于AuNPs/PDDA-GO纳米复合物制备了一种新型电化学免疫传感器, 并将其用于SirT1的检测. 首先, 在电极表面修饰复合材料AuNPs/PDDA-GO, 然后将目标蛋白SirT1固定到修饰了AuNPs/PDDA-GO的电极表面, 再通过特异性免疫反应结合一抗(Ab₁)和辣根过氧化酶标记的二抗分子(HRP-Ab₂), 最后用示差脉冲伏安法检测电流信号, 实现了对SirT1蛋白水平的测定. 在优化的实验条件下, SirT1蛋白的浓度在0.1~100 ng/mL范围内与响应电流呈良好线性关系, 检出限为0.029 ng/mL.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.