Cross-linked Graphene Research Articles

Deciphering Photoinduced Charge Transfer Dynamics in a Cross-Linked Graphene-Dye Nanohybrid.

The search for synthetic materials that mimic natural photosynthesis by converting solar energy into other more useful forms of energy is an ever-growing research endeavor. Graphene-based materials, with their exceptional electronic and optical properties, are exemplary candidates for high-efficiency solar energy harvesting devices. High photoactivity can be conveniently achieved by functionalizing graphene with small molecule organic semiconductors whose band-gaps can be tuned by structural modification, leading to interactions between the π-conjugated electronic systems in both the semiconductor and graphene. Here we investigate the ultrafast transient optical properties of a cross-linked graphene–dye (diphenyl-dithiophenediketopyrrolopyrrole) nanohybrid material, in which oligomers of the organic semiconductor dye are covalently bound to a random network of few-layer graphene flakes, and compare the results to those obtained for the reference dye monomer. Using a combination of ultrafast transient absorption and two-dimensional electronic spectroscopy, we provide substantial evidence for photoinduced charge transfer that occurs within 18 ps in the nanohybrid system. Notably, subpicosecond photoinduced torsional relaxation observed in the constituent dye monomer is absent in the cross-linked nanohybrid system. Through density functional theory calculations, we compare the competing effects of covalent bonding, increasing conjugation length, and the presence of multiple graphene flakes. We find evidence that the observed ultrafast charge transfer process occurs through a superexchange mechanism in which the oligomeric dye bridge provides virtual states enabling charge transfer between graphene–dye covalent bond sites.

Deciphering Photoinduced Charge Transfer Dynamics in a Cross-Linked Graphene–Dye Nanohybrid

Deciphering Photoinduced Charge Transfer Dynamics in a Cross-Linked Graphene–Dye Nanohybrid

Boosted 2D graphene nanosheets by organic-inorganic hybrid cross-linker for an efficient and stable supercapacitor

Using covalent graphene derivatives in energy storage applications is promising. From this view, covalently cross-linked graphene oxide (GO) nanosheets are designed using polyoligomeric silsesquioxanes-propyl-NH 2 (POPN). Then, by incorporating cobalt sulfide nanoparticles into the porous scaffold, a high-value nanocomposite is formed. In a typical three-electrode cell, this nanocomposite declared substantial specific capacity of 454 and 438 Fg -1 using cyclic voltammetry (CV) and charge-discharge (GCD) assessments. The device is assembled via two identical electrodes containing RGO-SiO 3 -NH2-poss-NH2-SiO 3 -RGO/cobalt sulfide (RGO-Si-POPN-Si-RGO/CoS 2 ). Utilizing CV and GCD methods, specific capacitances of 328 and 315 Fg -1 are realized at a sweep rate and current density of 2 mVs −1 and 0.5 Ag -1 , respectively. The device presents desirable energy density of 18.5 Whkg −1 at the power density of 325 Wkg -1 . More impressively, around 97.9% of the specific capacitance is retained after 5000 charge-discharge cycles. The results confirm exceptional capacitive capabilities and super stability of the nanocomposite suitable for practical systems. • The 3D GO nanoscaffold is developed using an organic-inorganic hybrid cross-linker. • The durability of the developed nanocomposite has been improved, mainly due to the introduction of the POPN. • The symmetric supercapacitor exhibits a high specific capacitance of 328 Fg -1 at the scan rate of 2 mVs −1 . • RGO-Si-POPN-Si-RGO/CoS 2 shows a high capacitance retention of 97.9% after 5000 cycles.

Anomalous elasticity and damping in covalently cross-linked graphene aerogels

Elasticity in materials is a phenomenon that provides a basis for widespread practical applications in engineering, medicine, and electronics. Most of the conventional materials can withstand only small deformations within the elastic limit, typically below 5% of their original size. Here, we report a graphene aerogel made of covalently cross-linked graphene sheets that exhibits anomalous superelastic behavior up to 92% of compressive and 68% tensile strain. We show that the graphene aerogel has a nonlinear stress-strain characteristic with the compressive and tensile yield strength of 4.5 GPa and 0.6 MPa, respectively. By considering the elastic bending of graphene sheets and buckle folding of pore walls, we develop a quantitative origami model that describes the stress-strain behavior of the aerogel. In addition, we analyze the mechanical oscillations of the graphene aerogel, observing superfast vibration damping within a time scale of 50–250 ns. Our study demonstrates the unusual coexistence of superelasticity and superfast damping within a cellular material with atomically thin pore walls, a phenomenon that does not occur in bulk elastic materials described by Hook’s law.

Efficient solid phase microextraction of organic pollutants based on graphene oxide/chitosan aerogel

The design and synthesis of novel high-performance solid phase microextraction (SPME) coatings towards organic pollutants with diverse chemical properties is still a challenge in sample preparation. Herein, a stable chitosan cross-linked graphene oxide (GOCS) aerogel was reported as a novel coating for solid phase microextraction. The interpenetrated meso- and macropores ensured the large surface area and high accessibility of the functional groups across the aerogel, resulting in high extraction performance towards target hydrophobic pollutants. The extraction capacities of the GOCS-coated SPME fiber towards analytes (e.g. polycyclic aromatic hydrocarbons, organophosphorus pesticides, organochlorine pesticides, pyrethroids, and polychlorinated biphenyls) were about 0.5–13 times as high as those obtained by the commercial fibers (30 μm polydimethylsiloxane (PDMS), 65 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB)), which was attributed to the hydrophobic, π-π, halogen bond and hydrogen bond interactions between the coating and the analytes. Under the optimized extraction conditions, superior analytical performances for PAHs were achieved with a wide linearity (0.5–1000 ng L−1), high enhancement factors (311–3740), and the low limits of detection (0.03–1.28 ng L−1). Finally, the GOCS-coated SPME fiber was successfully applied to the determination of PAHs in real water samples with good recoveries (91.6%–110%).

Largely desensitized and stabilized CL-20 crystals obtained through reinforcement with cross-linked graphene oxide

Preparation and structure of graphene intercalated CL-20 crystals.

Contact resistance based tactile sensor using covalently cross-linked graphene aerogels.

A movable electrical contact between two materials is one of the most fundamental, simple, and common components in electronics that is used for binary control of a conducting path in an electrical circuit. Here, variable contact resistance between a highly elastic graphene aerogel and a rigid metal electrode is used for the analysis of non-binary pushing and pulling mechanical forces acting on the contact, enabling superior strain and pressure measurements. The variable contact resistance based electromechanical sensors demonstrate superfast, ultrasensitive and quantitative measurements of compressive and tensile stress from -1.18 MPa to 0.55 MPa. The sensors can operate over the temperature range of -60 to 100 °C, cover the whole skin and human motion range, and determine the weight of a grasped object. The measurement of such high forces has only been possible due to the high-temperature induced covalent cross-linking of graphene in the aerogel that provides high strength, durability, and fast response (<0.5 ms) to the sensing element. The study demonstrates the great potential of the contact resistance-controlled sensing, which enables high-precision and reliable measurement of strain and pressure over a remarkable large sensing range, providing new opportunities for applications in human-machine interfaces, robotics, flexible electronics, and haptic technology.

Chemically Cross-Linked Graphene Oxide as a Selective Layer on Electrospun Polyvinyl Alcohol Nanofiber Membrane for Nanofiltration Application.

Graphene oxide (GO) nanosheets were utilized as a selective layer on a highly porous polyvinyl alcohol (PVA) nanofiber support via a pressure-assisted self-assembly technique to synthesize composite nanofiltration membranes. The GO layer was rendered stable by cross-linking the nanosheets (GO-to-GO) and by linking them onto the support surface (GO-to-PVA) using glutaraldehyde (GA). The amounts of GO and GA deposited on the PVA substrate were varied to determine the optimum nanofiltration membrane both in terms of water flux and salt rejection performances. The successful GA cross-linking of GO interlayers and GO-PVA via acetalization was confirmed by FTIR and XPS analyses, which corroborated with other characterization results from contact angle and zeta potential measurements. Morphologies of the most effective membrane (CGOPVA-50) featured a defect-free GA cross-linked GO layer with a thickness of ~67 nm. The best solute rejections of the CGOPVA-50 membrane were 91.01% for Na2SO4 (20 mM), 98.12% for Eosin Y (10 mg/L), 76.92% for Methylene blue (10 mg/L), and 49.62% for NaCl (20 mM). These findings may provide one of the promising approaches in synthesizing mechanically stable GO-based thin-film composite membranes that are effective for solute separation via nanofiltration.

Electrochemical investigation of free-standing reduced graphene oxide hydrogel

Free-standing reduced graphene oxide (RGO) hydrogel was synthesized through two-stepped hydrothermal reduction treatment of aqueous graphene oxide (GO) suspension. GO with high interface affinity for overlapping of cross-linking graphene sheets contributes to forming steady-state RGO hydrogel. RGO hydrogel shows higher B band/G band intensity ratio than GO suspension in Raman spectrum analysis, indicating well-restored hexagonal carbon rings with the enhanced crystal structure. Free-standing RGO hydrogel could be directly acted as supercapacitor electrode without using any substrate material. The specific capacitance decreases from 253.9 to 92.3 F g−1 in 1.0 M Na2SO4 electrolyte and from 275.3 to 125.9 F g−1 in 1.0 M KOH electrolyte when the current density increased from 0.3 to 4.0 A g−1, presenting the capacity retention of 36.4% and 45.7% respectively. Free-standing RGO hydrogel presents specific capacitance in alkaline KOH electrolyte rather than neutral Na2SO4 electrolyte. KOH electrolyte with superior ionic diffusion coefficient of hydroxyl ion leads to higher current response and electrical double-layer capacitance performance. The capacitance retention ratio of 97.8% at 4.0 A g−1 in 1.0 M KOH electrolyte after 1000 charge-discharge cycles presents superior cycling stability. Accordingly, free-standing RGO hydrogel applied well as superior supercapacitor electrode presents the promising energy storage application.

Thermal shock exfoliated and siloxane cross-linked graphene framework for high performance epoxy-based thermally conductive composites

Thermal shock exfoliated and siloxane cross-linked graphene framework for high performance epoxy-based thermally conductive composites

Calcium ion-sodium alginate double cross-linked graphene oxide nanofiltration membrane with enhanced stability for efficient separation of dyes

Graphene oxide (GO)-based membranes formed by stacking layered graphene oxide nanosheets have great application prospects for dye separation of textile wastewater. This paper proposes a simple vacuum-assisted method to prepare a double-crosslinked composite graphene oxide nanofiltration membrane (Ca/GO-SAx) by adding sodium alginate (SA) and calcium ions. This method adjusts the nanochannels of the membrane, expands the interlayer spacing, improves the water permeability, and increases the water flux from 10.14 L m-2h−1 bar−1 to 38.90 L m-2h−1 bar−1, which is 384% of the original GO membrane. Importantly, the Ca/GO-SA3 composite membrane has excellent dye separation performance, achieving more than 99% removal of multiple dyes (congo red, crystal violet, methylene blue). Furthermore, the structure of the Ca/GO-SA3 composite membrane is more compact and orderly, and the stability is obviously enhanced. It not only repels other cations in different chloride salt solutions, keeps the interlayer spacing stable, but also maintains excellent dye separation performance after being immersed in harsh aqueous solutions for one month. These findings demonstrate a simple and practical method to prepare GO nanofiltration membranes with a two-dimensional layered structure to achieve the purification treatment of textile wastewater.

Correction to Dirac Nodal Line Semimetal of Three-Dimensional Cross-Linked Graphene Network as Anode Materials for Li-Ion Battery beyond Graphite

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Dirac Nodal Line Semimetal of Three-Dimensional Cross-Linked Graphene Network as Anode Materials for Li-Ion Battery beyond GraphiteShuaiwei Wang*Shuaiwei WangMore by Shuaiwei Wanghttps://orcid.org/0000-0003-2409-9888 and Baocheng Yang*Baocheng YangMore by Baocheng YangCite this: ACS Appl. Energy Mater. 2021, 4, 7, 7393Publication Date (Web):July 14, 2021Publication History Published online14 July 2021Published inissue 26 July 2021https://doi.org/10.1021/acsaem.1c01813Copyright © 2021 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views229Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (493 KB) Get e-Alerts Get e-Alerts

Preparation of graphene/Al composites with a lamellar structure by silane cross-linking graphene oxide

Abstract In this study, the silane coupling agent 3-aminopropyltriethoxysilane (APS) was used to cross-link graphene oxide (GO) to large-sized films, and further to prepare nacre-like structure graphene/aluminum (Al) composites. The results show that APS was successfully grafted onto the GO, forming large continuous GO films, which were then attached to the surface of the Al flakes by semi-powder metallurgy. After hot pressing, the graphene/Al composites had a lamellar structure consisted of reduced graphene oxide (rGO) and Al. In addition, the interface was well bonded without defects and Al4C3 phase. Compared with the pure Al prepared under the same condition, the compressive strength, maximum compression ratio and hardness of the 0.15 wt.% graphene/Al composites increased by 58%, 23% and 64.8%, respectively. The approach of cross-linking GO through chemical modification can be applied to the design of other bioinspired materials.

Laminated graphene oxide membrane for recovery of mercury-containing wastewater by pervaporation

Mercury (Hg) is a toxic heavy metal contaminant and has very harmful effects for human health. In this work, Hg-containing wastewater with Hg concentration of 6.36 ppb and 9.4 ppb were recovered with polyethylenimine (PEI) cross-linked graphene oxide (GO) layered membrane (c-GO-PEI) by pervaporation. The influence of ionic type, the concentration of Hg and the feed temperature were investigated. The c-GO-PEI exhibited not only high rejection for salts (> 99.97%), Hg (77.5–100%) and non-purgeable organic carbon (NPOC) (67.3–90.8%) but also high flux (30.30 kg·m−2·h−1) to treat with the wastewater. In addition, the flux could be largely recovered after simple washing, indicating the excellent antifouling property of the membrane.

Preparation and characterization of graphene oxide/chitosan composite aerogel with high adsorption performance for Cr(VI) by a new crosslinking route

A new 3-glycidoxypropyltrimethoxysilane (KH-560) cross-linked graphene oxide/chitosan (GO/CS) composite aerogel was synthesized by sol-gel and freeze-drying methods. In this study, the three-dimensional porous network structure of composite aerogel was established by the self-assemble interaction between CS and GO, and by the crosslinking reaction between CS and KH-560. GO could enhance the strength of aerogels and keep porous structure stable, and KH-560 was used to avoid the dissolution of CS in acid conditions. The chemical properties, microstructure and thermal properties were investigated by FTIR, XPS, SEM, and TGA. The adsorption performance of composite aerogel was also studied. The results indicated that the process followed the Langmuir monolayer adsorption and pseudo-second-order kinetic model. The adsorption could reach equilibrium within 120 min, and the maximum adsorption capacity could reach up to 146 mg g −1 ; the aerogel adsorbent showed the good reusability and high adsorption capacity for Cr(VI) in coexistence with other ions.

3D cross-linked graphene or/and MXene based nanomaterials for electromagnetic wave absorbing and shielding

With the rapid digitalization and technological advancements of the modern society, the seriously increasing electromagnetic pollution has created stronger demand for advanced electromagnetic wave shielding and absorbing materials in both civilian and military fields. Multifunctional materials with ultra-lightweight, wide bandwidth, highly flexible and robustness are the future development direction to meet the applications. Graphene and MXene, as two typical 2D nanomaterials, have attracted considerable interests for the electromagnetic wave shielding and absorbing materials. More importantly, three dimensional (3D) cross-linked graphene or/and MXene based materials, where graphene or/and MXene sheets are interconnected into a macroscopic monolithic bulk material, can achieve excellent electromagnetic interference (EMI) shielding and microwave absorption (MA) performance, together with lightweight, exceptional mechanical properties and so on. This review addresses the construction methods of graphene and MXene based 3D cross-linked materials, and the effects of different fabrication methods toward the structure and EMI shielding and/or MA properties are discussed. Additionally, some perceptions and discussions are proposed for the future studies.

Dirac Nodal Line Semimetal of Three-Dimensional Cross-Linked Graphene Network as Anode Materials for Li-Ion Battery beyond Graphite

Li-ion batteries (LIBs) are common commercial rechargeable batteries with wide application. One of the huge challenges for LIBs is to find the high capacity anode materials. In this work, by employ...

Synergetic effect of physicochemical and electrostatic strategies on ion sieving for polymer cross-linked graphene oxide membranes

Graphene oxide membranes with polymer-crosslinked structures are designed to simultaneously modify the physicochemical and electrostatic properties of nanochannels for molecular separation.

A Novel CaO Nanocomposite Crosslinked Graphene Oxide for Cr(VI) Removal and Sensing from Wastewater

A Novel CaO Nanocomposite Crosslinked Graphene Oxide for Cr(VI) Removal and Sensing from Wastewater

Preparation of Stable Hydrophilic Polyethyleneimine Cross-Linked Graphene Oxide/Titanium Dioxide Membranes for Dye Separation

An excellent novel laminar and hierarchical polyethyleneimine cross-linked graphene oxide/titanium dioxide (GO–TiO2–PEI) membrane was successfully prepared by vacuum filtration technology using polyethyleneimine (PEI) as the cross-linking agent and a GO–TiO2 nanocomposite as the substrate. The resultant membrane (GO–TiO2–PEI) displayed a favorable antifouling performance with bovine serum albumin (BSA) and showed good hydrophilicity and wettability, with a static water contact angle of 13.2∘. The stability of the GO–TiO2–PEI membrane in aqueous solution obviously improved with the cross-linking of PEI compared with that of the GO and GO–TiO2 membranes. The GO–TiO2–PEI membrane also exhibited a satisfactory water flux of 48.6[Formula: see text]L m[Formula: see text] h[Formula: see text] bar[Formula: see text]. The GO–TiO2–PEI membrane exhibited a good performance for effectively separating different dyes including methylene blue (MB), rhodamine B (RB), methyl orange (MO), sunset yellow (SY), new coccine (NC) and amaranth. All the above results suggested that the GO–TiO2–PEI membrane could be used as an excellent stable hydrophilic membrane for efficiently separating dyes from aqueous solution.