Multifunctional reduced graphene oxide-CVD graphene core-shell fibers

Development of photoluminescent viscose fibers integrated with polymer containing lanthanide-doped phosphor

Smart clothing refers to textiles that can sense an external stimulus by changing their physical properties such as colorimetric and fluorescent fabrics. The pad-dry-curing coloration approach was used to apply a luminous and hydrophobic composite coating onto cellulose-based materials. This novel method includes incorporating phosphor nanoparticles made from lanthanide-doped strontium aluminum oxide (LSAO) into room temperature vulcanizing silicone rubber (RTV). The LSAO nano-sized particles (3-8 nm) must be mixed evenly throughout RTV without aggregation to allow for the formation of a colorless layer onto viscose surface. Pad-dry-curing the film onto viscose cloth worked well at room temperature. The contact angles of the luminous fibers enhanced from 138.6° to 158.2° as the LSAO ratio increased. The antimicrobial and ultraviolet (UV) protection of the LSAO-finished viscose were investigated. The transparent fluorescent film on viscose surface was excited at 367 nm to display an emission peak at 518 nm. According to CIE Lab coordinates and luminescence analyses, the fluorescent viscose fibers showed various colors, including white under visible light, intense green beneath UV device, and greenish-yellow under darkness. The comfort properties of the LSAO-finished viscose were assessed by measuring their bend length and permeability to air. Transmission electron microscopic analysis of LSAO nanoparticles was explored. Energy dispersive x-ray, x-ray fluorescence, and scanning electron microscopy were utilized to describe the spectroscopic outcomes of the treated textiles. The colorfastness of the LSAO-finished viscose fabrics was examined. The coated fabrics exhibited a non-fatigable reversible luminous photochromism in response to UV illumination. RESEARCH HIGHLIGHTS: Multifunctional LSAO@RTV nanocomposite was pad-dry-cured onto viscose textile. Photochromism to green under UV light and greenish-yellow in the dark was detected. Efficient antimicrobial, UV protective, and superhydrophobic activity were observed. The antimicrobial properties were maintained for 24 washing cycles. Pad-dry-cured viscose showed good comfortability and photostability.

Chemically Edge-Carboxylated Graphene Enhances the Thermal Conductivity of Polyetherimide-Graphene Nanocomposites

In this work, we demonstrate that edge oxidation of graphene can enable larger enhancement in thermal conductivity (k) of graphene nanoplatelet (GnP)/polyetherimide (PEI) composites relative to oxidation of the basal plane of graphene. Edge oxidation offers the advantage of leaving the basal plane of graphene intact, preserving its high in-plane thermal conductivity (k_in > 2000 W m^-1 K^-1), while, simultaneously, the oxygen groups introduced on the graphene edge enhance interfacial thermal conductance through hydrogen bonding with oxygen groups of PEI, enhancing the overall polymer composite thermal conductivity. Edge oxidation is achieved in this work by oxidizing graphene in the presence of sodium chlorate and hydrogen peroxide, thereby introducing an excess of carboxyl groups on the edge of graphene. Basal plane oxidation of graphene, on the other hand, is achieved through the Hummers method, which distorts the sp² carbon-carbon network of graphene, dramatically lowering its intrinsic thermal conductivity, causing the BGO/PEI (BGO = basal-plane oxidized graphene or basal-plane-functionalized graphene oxide) composite's k value to be even lower than pristine GnP/PEI composite's k value. The resulting thermal conductivity of the EGO/PEI (EGO = edge-oxidized graphene or edge-functionalized graphene oxide) composite is found to be enhanced by 18%, whereas that of the BGO/PEI composite is diminished by 57%, with respect to the pristine GnP/PEI composite with 10 wt % GnP content. Two-dimensional Raman mapping of GnPs is used to confirm and distinguish the location of oxygen functional groups on graphene. The superior effect of edge bonding presented in this work can lead to fundamentally novel pathways for achieving high thermal conductivity polymer composites.

Electronic Textiles Fabricated with Graphene Oxide-Coated Commercial Textiles

Demand for wearable and portable electronic devices has increased, raising interest in electronic textiles (e-textiles). E-textiles have been produced using various materials including carbon nanotubes, graphene, and graphene oxide. Among the materials in this minireview, we introduce e-textiles fabricated with graphene oxide (GO) coating, using commercial textiles. GO-coated cotton, nylon, polyester, and silk are reported. The GO-coated commercial textiles were reduced chemically and thermally. The maximum e-textile conductivity of about 10 S/cm was achieved in GO-coated silk. We also introduce an e-textile made of uncoated silk. The silk-based e-textiles were obtained using a simple heat treatment with axial tension. The conductivity of the e-textiles was over 100 S/cm.

One-step phosphating synthesis of CoP nanosheet arrays combined with Ni2P as a high-performance electrode for supercapacitors

A transition metal phosphide is an excellent candidate for supercapacitors due to its superior electrical conductivity and high theoretical capacity. In addition, compared with traditional 3D nano-materials, 2D nanosheets possess a greater specific surface area and shorter electron transport distance. In this study, a reasonable approach is proposed for the synthesis of ZIF-67 nanosheets on nickel foam with subsequent phosphorization by chemical vapor deposition (CVD) to obtain flake-like CoP combined with Ni2P (NCP/NF), in which nickel foam serves as the current collector as well as the resource of Ni to form Ni2P. Benefiting from the nanosheet array of CoP, the NCP/NF can improve the capacity of Ni2P from 0.57 C cm-2 to 1.43 C cm-2 at 1 mA cm-2. Furthermore, the NPC/NF/reduced graphene oxide (RGO) asymmetric supercapacitor (ASC) shows an energy density of 26.9 μW h cm-2 at a power density of 0.896 mW cm-2, and excellent cycling performance with a capacity retention of 93.75% after 5000 cycles at 10 mA cm-2.

Study on the preparation and mechanism of chitosan-based nano-mesoporous carbons by hydrothermal method

In this paper, the hydrothermal method to synthesize and characterize nano-mesoporous carbons and their synthesis mechanism are reported. Using tri-block Pluronic F127 as a structuring agent and chitosan (CS) as a carbon source, the nano-mesoporous carbons were synthesized by a one-step sol polymerization and hydrothermal process, followed by carbonization at high temperature. The pore structure of the carbon materials was characterized by physical adsorption analyzer, and the morphology was characterized by SEM and TEM. Fourier-transform infrared, Raman and x-ray photoelectron spectroscopy were used to study the synthesis mechanism. The results showed that the self-assembly polymerization reaction between CS and F127 in a weakly acidic system was only implemented driven by the hydrogen bond auxiliary electrostatic interactions initiated by protonated amino groups. The nitrogen from amino groups and acetylamino groups, the oxygen in acetylamino groups, hydroxyl groups and the glycosidic bonds of CS, and the oxygen from the hydrophilic segments of F127 were the main active sites. The mesoporous material possesses a high Brunauer-Emmett-Teller surface area (163 m²/g) and large pore volume (0.462 cm³/g) with pore diameter around 2.1 nm. The nitrogen content was 1.08% and existed in the pore wall as the form of pyridine, pyrrole and quaternary nitrogen.

Influence of the presence of cations on the water and salt dynamics inside layered graphene oxide (GO) membranes

Although over the past few years, graphene oxide (GO) has emerged as a promising membrane material, the applicability of layered GO membranes in water purification/seawater desalination is still a challenging issue because of the undesirable swelling of GO laminates in the aqueous environment. One of the ways to tune the interlayer spacing and to arrest the undesirable swelling of layered GO membranes in the aqueous environment is to intercalate the interlayer spacing of the GO laminates with cations. Although the cation intercalation imparts stabilization to GO laminates in the aqueous environment, their effect on the performance of the membrane is yet to be addressed in detail. In the present study we have investigated the effect of cation intercalation on the performance of layered GO membranes using molecular dynamics simulation. For the same interlayer spacing, the cation intercalated layered GO membranes have a higher water flux as compared to the corresponding pristine layered GO membranes. In the presence of the cations, the water molecules inside the interlayer gallery get more compactly packed. The presence of the cations also increases the stability of the hydrogen bond network among the water molecules inside the membrane. This can be attributed to slow water reorientation dynamics inside the interlayer gallery in the presence of the cations. The synergistic effect of all these changes is that the water permeability through the cation intercalated layered GO membranes is higher as compared to that through the corresponding pristine layered GO membranes. On the other hand, the intercalation of the cations (K+, Mg2+) leads to higher rejection of Na+ ions whereas the rejection of Cl- ions slightly decreases.

Memristive Non-Volatile Memory Based on Graphene Materials

Resistive random access memory (RRAM), which is considered as one of the most promising next-generation non-volatile memory (NVM) devices and a representative of memristor technologies, demonstrated great potential in acting as an artificial synapse in the industry of neuromorphic systems and artificial intelligence (AI), due its advantages such as fast operation speed, low power consumption, and high device density. Graphene and related materials (GRMs), especially graphene oxide (GO), acting as active materials for RRAM devices, are considered as a promising alternative to other materials including metal oxides and perovskite materials. Herein, an overview of GRM-based RRAM devices is provided, with discussion about the properties of GRMs, main operation mechanisms for resistive switching (RS) behavior, figure of merit (FoM) summary, and prospect extension of GRM-based RRAM devices. With excellent physical and chemical advantages like intrinsic Young's modulus (1.0 TPa), good tensile strength (130 GPa), excellent carrier mobility (2.0 × 105 cm2∙V-1∙s-1), and high thermal (5000 Wm-1∙K-1) and superior electrical conductivity (1.0 × 106 S∙m-1), GRMs can act as electrodes and resistive switching media in RRAM devices. In addition, the GRM-based interface between electrode and dielectric can have an effect on atomic diffusion limitation in dielectric and surface effect suppression. Immense amounts of concrete research indicate that GRMs might play a significant role in promoting the large-scale commercialization possibility of RRAM devices.

Properties of Mg/graphite and Mg/graphene as cathode electrode on primary cell battery

Since graphene was first isolated in 2004, it has become an attractive material on electrochemical energy storage devices. The purpose of this study is to compare Mg/graphite and Mg/graphene electrodes to commercial primary battery cathodes. This research is an experimental laboratory research. Graphene was synthesized with Hummer's method modified. Electrodes cathode of primary battery (Mg/graphite and Mg/graphene) were prepared using impregnation method. Graphene and electrodes cathode were analyzed with X-Ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) and conductivity, respectively. The XRD data of graphene show that there is a weak and sharp peak on 2θ = 26,5o, indicating graphene is formed. The peaks shape of 2θ = 35o are totally different for Mg/graphite and Mg/graphene. At Mg/graphite, the sharp and narrow peak appears on 2θ = 35o. It means Mg is well deposited on graphite. Interestingly, Mg/graphene has narrow and weak peak on 2θ = 35o, indicating the Mg was deposited on graphene and properties of Mg has been changed by graphene. This data is also well confirmed by EDX data. Mg atoms exist on graphene (1.47 wt%) (EDX data). SEM images of Mg/graphite and Mg/graphene are significantly different, probably support material effect. The properties of Mg/graphite and Mg/graphene comparing to commercial primary battery cathode were evaluated using conductivity. The conductivity of Mg/graphene (1080 μS/cm) is highest among Mg/graphite (90 μS/cm) and commercial battery cathode (10 μS/cm). All of data show that the Mg/graphene is potentially used as a primary battery cathode.

Progress in the functional modification of graphene/graphene oxide: a review

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties. This review focuses on the functional modification of graphene and graphene oxide. First, the basic structure, preparation methods and properties of graphene and graphene oxide are briefly described. Subsequently, the methods for the reduction of graphene oxide are introduced. Next, the functionalization of graphene and graphene oxide is mainly divided into covalent binding modification, non-covalent binding modification and elemental doping. Then, the properties and application prospects of the modified products are summarized. Finally, the current challenges and future research directions are presented in terms of surface functional modification for graphene and graphene oxide.

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties.