Two-dimensional Graphene Oxide Research Articles

Electrostatic-induced ion-confined partitioning in graphene nanolaminate membrane for breaking anion–cation co-transport to enhance desalination

Constructing nanolaminate membranes made of two-dimensional graphene oxide nanosheets has gained enormous interest in recent decades. However, a key challenge facing current graphene-based membranes is their poor rejection for monovalent salts due to the swelling-induced weak nanoconfinement and the transmembrane co-transport of anions and cations. Herein, we propose a strategy of electrostatic-induced ion-confined partitioning in a reduced graphene oxide membrane for breaking the correlation of anions and cations to suppress anion-cation co-transport, substantially improving the desalination performance. The membrane demonstrates a rejection of 95.5% for NaCl with a water permeance of 48.6 L m−2 h−1 bar−1 in pressure-driven process, and it also exhibits a salt rejection of 99.7% and a water flux of 47.0 L m−2 h−1 under osmosis-driven condition, outperforming the performance of reported graphene-based membranes. The simulation and calculation results unveil that the strong electrostatic attraction of membrane forces the hydrated Na+ to undergo dehydration and be exclusively confined in the nanochannels, strengthening the intra-nanochannel anion/cation partitioning, which refrains from the dynamical anion-cation correlations and thereby prevents anions and cations from co-transporting through the membrane. This study provides guidance for designing advanced desalination membranes and inspires the future development of membrane-based separation technologies.

Effects of Multidimensional Carbon-Based Nanomaterials on the Low-Carbon and High-Performance Cementitious Composites: A Critical Review.

Cementitious composites are ubiquitous in construction, and more and more research is focused on improving mechanical properties and environmental effects. However, the jury is still out on which material can achieve low-carbon and high-performance cementitious composites. This article compares the mechanical and environmental performance of zero-dimensional fullerenes, one-dimensional carbon nanotubes (CNTs), two-dimensional graphene oxide (GO), and three-dimensional nano-graphite platelets (NGPs) on cementitious composites. The literature review shows that two-dimensional (2D) GO has the best mechanical and environmental performance, followed by 3D NGPs, 1D CNTs, and 0D fullerenes. Specifically, GO stands out for its lower energy consumption (120-140 MJ/kg) and CO2 emissions (0.17 kg/kg). When the optimal dosage (0.01-0.05 wt%) of GO is selected, due to its high specific surface area and strong adhesion to the matrix, the compressive strength of the cementitious composites is improved by nearly 50%. This study will help engineers and researchers better utilize carbon-based nanomaterials and provide guidance and direction for future research in related fields.

Efficient antibiotic remediation from wastewater using a lamellar free-standing 2D graphene oxide/Ti3C2Tx hybrid membrane

The existence of elevated levels of antibiotics in wastewater has facilitated the emergence and spread of pathogens with antimicrobial resistance (AMR). When combined with the worldwide water scarcity issue, this situation results in detrimental impacts on both the ecosystem and human well-being. Traditional methods employed by wastewater treatment facilities exhibit limited effectiveness in eliminating antibiotics. This paper describes the synthesis and performance of two-dimensional (2D) lamellar free-standing graphene oxide (GO)/Ti3C2Tx membrane for the removal of antibiotics from wastewater. The 50 %GO/Ti3C2Tx composite membrane demonstrated a remarkable increase in water flux, achieving 61.9 L m−2 h−1, surpassing the performance of the pristine GO membrane, which achieved 22.8 L m−2 h−1. Additionally, the GO/Ti3C2Tx composite membranes exhibited outstanding tetracycline rejection, consistently exceeding 99 %, a significant improvement compared to the pristine Ti3C2Tx membrane. The composite membranes of with a ratio of GO to MXene of 50 %, 40 %, 30 % and 20 % had contact angles of 54.5°, 57.4°, 60.6°, and 61.6°, respectively. Combining GO and Ti3C2Tx at specific mass ratios enhanced properties, evidenced by altered interlayer spacing and hydrophilicity. Furthermore, the superior composite membrane demonstrated superior antifouling properties compared to both pristine GO and Ti3C2Tx membranes.

Removal of Commercial Textile Dye DRMD from Wastewater Using Two-Dimensional Mesoporous Graphene Oxide Adsorbent

Environmental toxins from textile effluents, including organic contaminants, heavy metals, and dyes, pose significant health risks such as renal illness, allergies, dermatitis, and cancer when released into the aquatic environment. While various dye removal methods exist, adsorption is highlighted as a potentially effective solution due to its low cost, simplicity, and ease of use. An adsorbent of two-dimensional mesoporous Graphene Oxide (GO) was produced using Hummer’s method from cost-effective graphite powder. This was then utilized to eliminate the Doracryl Red MD (DRMD) textile dye from the aqueous system. To characterize the synthesized material, XRD, FTIR, and SEM analyses were performed. Zeta Potential and AFM analysis were used to determine surface charge and roughness, respectively. BET analysis was performed to obtain information regarding the surface area and porosity of the mesoporous GO. The highest adsorption capacity for the adsorption of the dye DRMD was found at 917.62 mg/gm. A variety of factors, including the influence of solution pH, adsorbent dosage, adsorption temperature, concentration of dye solution, and contact time, were thoroughly investigated. Adsorption data best fit the Langmuir model and demonstrated pseudo-second-order reaction kinetics. After repeatedly washing used adsorbents with 2% HCl solution, 88.62% of its initial adsorption capacity was retained after the 4th cycle. Hence, the enhanced adsorption capacity and recyclability of Graphene Oxide (GO) render it a promising candidate for the treatment of wastewater polluted with organic dyes.

Recognition and separation of artemisinin by two-dimensional GO/MXene laminar imprinted composite membranes constructed based on self-supporting technology

In order to solve the problem that some of the imprinted sites were embedded inside the membranes due to the blending method, resulting in low utilization of the imprinted sites, a two-dimensional click graphene oxide (GO)/MXene self-supported layered imprinted composite membranes (CGMMs) was devised and prepared for the adsorption and efficient discriminative separation of artemisinin. Firstly, MXene was modified by self-polymerization using dopamine (PDA), and PDA hybrid coating was constructed on the surface of MXene, which was effective in improving the oxidation brittleness and hydrophilicity of MXene. Given the structural and hydrophilic similarities between GO and MXene nanosheets, the produced CGMMs exhibit an outstanding hydrophilicity and a characteristic lamellar shape. Subsequently, spherical imprinted polymers based on MXene were successfully constructed on the surface and interlayer of stacked GO/MXene nanosheets. The performance of CGMMs was explored by isothermal adsorption, kinetic adsorption, selective adsorption tests and selective permeation tests. The equilibrium adsorption capacity of CGMMs reached 36.10 mg g−1 with satisfactory selective separation capacity (αArtemisinin/ Artesunate = 4.10 and αArtemisinin/ Dihydroartemisinin = 3.03) and excellent permeation selectivity (βArtesunate/ Artemisinin = 5.71 and βDihydroartemisinin/ Artemisinin = 4.40), which implied the successful construction of effective artemisinin-imprinted sites on CGMMs. An essential aspect of the excellent adsorption property and selectivity exhibited by the prepared CGMMs is that the cross-section of CGMMs is composed of MXene nanosheets and GO nanosheets superimposed on a laminar structure dotted with imprinted polymers, which extends the molecular transport channels and facilitates the construction of more molecular imprinting sites.

Separation of hydrogen isotopic water by multi-walled carbon nanotube (MWCNT) membrane and graphene oxide (GO)-MWCNT composite membranes

Recently, membrane distillation (MD) processes using two-dimensional graphene oxide (GO) membranes exhibited good light water/deuteriated water (H2O/D2O) separation performance, which depended on membrane materials and structures. This raises the need for the development of novel membrane materials and revealing the relationship of membrane structure-separation performance to further increase separation performance. Here, one-dimensional (1D) MWCNT-based membrane was explored for the separation of H2O/D2O using the water source with specially chosen concentration of deuterium (D) in air–gap membrane distillation processes, and the resultant MWCNT membrane gave lower permeation flux and similar separation factor compared with the pristine GO membrane. Then GO-MWCNT composite membranes with different structures obtained by mixing various weight ratios of GO: MWCNTs were investigated, and their separation performance was found to be related with membrane structures. The resulted 3D hierarchical GO-MWCNT composite membrane (G/M−1:3) gave the highest permeation flux of 0.947 L·m−2·h−1 among all GO-MWCNT composite membranes, higher than that of the pristine GO membrane, while the separation factor of G/M−1:3 (1.045) and the pristine GO membrane (1.046) was comparable. Furthermore, the correlation of membrane structure-separation performance was reviewed. These results demonstrate the first example of MWCNT membrane and related composite membranes for H2O/D2O separation and suggest that H2O/D2O separation performance in membrane distillation processes can be improved by tailoring the structure of GO-MWCNT composite membranes. As the separation of H2O/D2O is usually used as a model in the laboratory for light water/tritiated water (H2O/HTO) separation process, this approach can guide for developing novel membrane materials and structures to deliver appropriate H2O/HTO separation processes needed in the nuclear energy field.

Polymer Binder-Free aqueous spinning of biomimetic CNT based hierarchical hollow fiber for structural and energy storage application

Assembly of functional nanomaterials into structural–functional integrated materials, such as structural-energy storage materials, are highly desirable for lightweight, high-performance wearable electronics, automobiles, and aviation/aerospace vehicles, yet extremely challenging due to the paradox between functional properties and the maintenance of mechanical properties. Herein, inspired by wheat-straw structures, we reported a polymer binder-free aqueous spinning strategy to manufacture biomimetic hollow carbon nanotube-based fibers (H-CNTF), where two-dimensional graphene oxide (GO) nanosheets are employed as an alternative to polymer binder for assisting the formation of hollow structures by rapid interaction with cations in coagulation, forming strong interaction with CNTs and tunning rheological property of spinning dope. The hierarchical hollow structure consisting of micron-scale hollow tubular space and porous walls endows H-CNTF with large surface area and abundant loading sites for guest materials, and the good CNT orientation and the absence of polymer binder enable H-CNTF excellent electrical and mechanical properties. As a proof of concept, the resulting H-CNTF supercapacitor electrodes exhibit high electrochemical energy storage performance with a specific capacity of 163 F/cm3 and high tensile strength of 0.35 N/tex. In addition, the polymer composite based on H-CNTF is about 100 % stronger than that based on solid fiber owing to the more uniform composite structure. The combination of outstanding electrochemical and mechanical properties makes this hollow fiber a promising material for future structural and energy storage applications.

Artificial ‘nacre-like’ architectures assembled using ice templating/freeze-drying from two-dimensional boron nitride and graphene oxide layers

Artificial ‘nacre-like’ architectures assembled using ice templating/freeze-drying from two-dimensional boron nitride and graphene oxide layers

A graphene oxide decorated BZT–CNF composite through hybrid microwave processing: an advanced multifunctional material for superior microwave shielding applications

A new composite with two-dimensional graphene oxide decoration is designed through microwave sintering for efficient microwave attenuation.

Application of Nanohybrid Substrates with Layer-by-Layer Self-Assembling Properties to High-Sensitivity Surface-Enhanced Raman Scattering Detection.

The present study was conducted to prepare and investigate large-area, high-sensitivity surface-enhanced Raman scattering (SERS) substrates. Organic/inorganic nanohybrid dispersants consisting of an amphiphilic triblock copolymer (hereafter referred to simply as "copolymer") and graphene oxide (GO) were used to stabilize the growth and size of gold nanoparticles (AuNPs). Ion-dipole forces were present between the AuNPs and copolymer dispersants, while the hydrogen bonds between GO and the copolymer prevented the aggregation of GO, thereby stabilizing the AuNP/GO nanohybrids. Transmission electron microscopy (TEM) revealed that the AuNPs had particle sizes of 25-35 nm and a relatively uniform size distribution. The AuNP/GO nanohybrids were deposited onto the glass substrate by using the solution drop-casting method and employed for SERS detection. The self-assembling properties of two-dimensional sheet-like GO led to a regular lamellar arrangement of AuNP/GO nanohybrids, which could be used for the preparation of large-area SERS substrates. Following removal of the copolymer by annealing at 300 °C for 2 h, measurements were obtained under scanning electron microscopy. The results confirmed that 2D GO nanosheets were capable of stabilizing AuNPs, with the final size reaching approximately 40 nm. These AuNPs were adsorbed on both sides of the GO nanosheets. Because the GO nanosheets were merely 5 nm-thick, a good three-dimensional hot-junction effect was generated along the z-axis of the AuNPs. Lastly, the prepared material was used for the SERS detection of rhodamine 6G (R6G), a commonly used highly fluorescent dye. An enhancement factor (EF) of up to 3.5 × 106 was achieved, and the limit of detection was approximately 10-10 M. Detection limits of 10-10 M and < 10-10 M were also observed with the detection of Direct Blue 200 and the biological molecule adenine. It is therefore evident that AuNP/copolymer/GO nanohybrids are large-area flexible SERS substrates that hold great potential in environmental monitoring and biological system detection applications.

Graphene-Oxide-Modified Metal-Organic Frameworks Embedded in Mixed-Matrix Membranes for Highly Efficient CO2/N2 Separation.

MOF-74 (metal-organic framework) is utilized as a filler in mixed-matrix membranes (MMMs) to improve gas selectivity due to its unique one-dimensional hexagonal channels and high-density open metal sites (OMSs), which exhibit a strong affinity for CO2 molecules. Reducing the agglomeration of nanoparticles and improving the compatibility with the matrix can effectively avoid the existence of non-selective voids to improve the gas separation efficiency. We propose a novel, layer-by-layer modification strategy for MOF-74 with graphene oxide. Two-dimensional graphene oxide nanosheets as a supporting skeleton creatively improve the dispersion uniformity of MOFs in MMMs, enhance their interfacial compatibility, and thus optimize the selective gas permeability. Additionally, they extended the gas diffusion paths, thereby augmenting the dissolution selectivity. Compared with doping with a single component, the use of a GO skeleton to disperse MOF-74 into Pebax®1657 (Polyether Block Amide) achieved a significant improvement in terms of the gas separation effect. The CO2/N2 selectivity of Pebax®1657-MOF-74 (Ni)@GO membrane with a filler concentration of 10 wt% was 76.96, 197.2% higher than the pristine commercial membrane Pebax®1657. Our results highlight an effective way to improve the selective gas separation performance of MMMs by functionalizing the MOF supported by layered GO. As an efficient strategy for developing porous MOF-based gas separation membranes, this method holds particular promise for manufacturing advanced carbon dioxide separation membranes and also concentrates on improving CO2 capture with new membrane technologies, a key step in reducing greenhouse gas emissions through carbon capture and storage.

Sulfonic acid (-HSO3) functionalization effect on graphene oxide membrane by (3 mercaptopropyl) trimethoxysilane and their applications in hydrogen membrane fuel cells

Conventional proton exchange membrane fuel cells (PEMFCs) use a perfluorinated ionomer membrane, e.g., Nafion®, which is expensive and subject to a rigorous synthesis process. Graphene oxide membrane (GOM) is acknowledged as a promising alternative electrolyte due to its hydrophilic nature and attractive proton conductivity in wet conditions. However, GOM loses its negative surface functional groups by hydrogen gas at the anode during operation in PEMFCs, resulting in increased electronic conductivity. In addition, two-dimensional graphene oxide (GO) nanosheets exhibited a larger anisotropy difference in proton conductivity compared to Nafion®. In this study, (3-mercaptopropyl)trimethoxysilane (MPTS, HS(CH2)3Si(OCH3)3) was reacted with the surface of GO nanosheet (M-GOM) by vigorous stirring, where unreacted MPTS was partially removed by a rinsing cycle except the M-GOM powder. Reactive MPTS has two essential reactions which were carried out by forming a hydrolysis reaction (Si-OCH3 to Si-OH) and a condensation reaction (Si-OH to Si-O-Si). The thiol groups of MPTS were oxidized to sulfonic acid groups (-HSO3) to provide high proton conducting stations with GO functional groups (M-GOM/oxid) and compared with non-oxidized thiol groups in a GO matrix (M-GOM/unoxid). The superior –HSO3 effect on M-GOM have reported for proton conductivity, physicochemical properties, ion exchange capacity, thermal stability, gas permeability and fuel cell performance. Furthermore, a hydrogen-permeable metal layer was deposited by a DC magnetron sputter to increase mechanical strength and reduce fuel crossover. A dual-layer membrane composed of M-GOM/unoxid or M-GOM/oxid and Pd thin film was analyzed as an electrolyte for a hydrogen membrane fuel cell (HMFC), which simultaneously performs two roles, an anode catalyst and an electrolyte.

Development of the supercapacitor efficiency of the two-dimensional graphene oxide decorated by nano magnetite through building novel nanocomposites using nanoparticles of cobalt, manganese, vanadium, and zirconium oxides

The targeting of the current work is enhancing the supercapacitor efficiency of the magnetite nanocomposite with graphene oxide (GO) nanostructure via the addition of metal oxide nanoparticles (NPs) such as cobalt, manganese, vanadium, and zirconium for building a novel nano combination. The sol/gel method is utilized to fabricate the nanocomposites, and the potentiostat device measures the electrochemical performances. The supercapacitors of the magnetite (Fe3O4) NPs that decorate the graphene oxide (GO) surface and the modified electrode building have been examined by different tests for supercapacitor applications, and are studied via the impedance spectroscopy (EIS) data that confirm the building progress of the electron transfer and surface structure that enable it to be a favorable candidate for supercapacitors applications. The areal capacitance (Carea) of NCPs was measured and presented at 622.65 mFcm−2 (GO@Fe3O4), 62.428 mFcm−2 (GO@ Fe3O4.Co3O4), 388.4 mFcm−2 (GO@ Fe3O4.Mn3O4), 851.1 mFcm−2 (GO@Fe3O4.V4O7), 966.4 mFcm−2 (GO@Fe3O4.ZrO2). The NCPs have capacitance values related to CPE (C = 9.404 nF/cm2), GO@Fe3O4 (C = 40.886 nF/cm2), GO@Fe3O4.Co3O4 (C = 13.17 nF/cm2), GO@Fe3O4.Mn3O4 (C = 17.56 nF/cm2), GO@Fe3O4.V4O7 (C = 126.9 nF/cm2), and GO@Fe3O4.ZrO2 (C = 183.6 nF/cm2). By adding cobalt, manganese, vanadium, and zirconium metal oxide NPs, the new building electrodes have capacitance at 13.17, 17.56, 183.6, and 126.9 nF/cm2, respectively. The capacitance retention finished at 100 cycles is recorded and exhibited good cycle stability. From the results, the fabricated NCPS electrodes are a promising candidate for supercapacitor manufacturing applications and other applications such as water treatment.

Nanochannel characteristics contributing to ion/ion selectivity in two-dimensional graphene oxide membranes

Selective ion/ion transport is of great importance in environmental and energy applications. Nanofiltration membranes possessing sub-nanometer pore sizes and charge characteristics have garnered significant attention in effectively separating target ions. Nevertheless, the contributions of pore size, charge, and their combined impact on ion/ion separation have remained relatively unexplored. In this study, a well-defined example is presented using multilayered graphene oxide membranes with ordered interlayer nanochannels. These membranes were utilized to prepare diverse nanochannel types, each possessing distinct channel sizes and charge properties. A systematic investigation was conducted to discern their separation selectivity for mono-/di-valent ion pairs. The dominant factor governing mono-/di-valent ion selectivity was not found to be the channel pore size within the sub-nanometer scale. This could be because nanochannels are flexible and cannot strictly sieve ions based on their specific size. Instead, the difference in electrostatic effects between mono- and di-valent ions plays a more significant role in enhancing ion/ion selectivity within the subnanometer channel. This study offers certain insights into selective ion transport in two-dimensional membrane nanochannels, potentially assisting in the design of nanochannels with single-ion selectivity.

Cesium lead iodide-decorated two-dimensional titanium dioxide/reduced graphene oxide nanofiber composites as photoanodes for inorganic perovskite solar cells

In this study, we developed photoanode materials based on inorganic cesium lead iodide (CsPbI3)-decorated two-dimensional titanium dioxide-reduced graphene oxide nanofibers (TiO2/rGO NFs22TiO2/rGO NFs - titanium dioxide-reduced graphene oxide nanofibers.) for perovskite solar cells (PSCs). CsPbI3 was prepared by a two-step solution process and TiO2/rGO NFs were prepared using the electrospinning method. The influence of the as-fabricated TiO2 NFs, TiO2/rGO NFs, and CsPbI3 perovskite on their optical, surface, and morphological properties were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, ultraviolet–visible–near-infrared spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and atomic force microscopy analyses. XRD analysis of the TiO2 NFs, TiO2/rGO NFs, and CsPbI3 perovskite showed a crystalline nature with cubic and anatase crystal faces. The surface morphology of the TiO2 NFs, TiO2/rGO NFs, and CsPbI3 perovskite appeared as a beat-free fiber with a polycrystalline nature. The chemical oxidative states and electronic structures of the electrospun TiO2/rGO NFs were determined by X-ray photoelectron spectroscopy analysis. PSCs device were assembled with TiO2 NFs, TiO2/rGO NFs as photoanode, 2,2′,7,7′-Tetrakis(N,N-di-P-methoxyphenylamine)− 9,9′-spirobifluorene (Spiro–OMeTAD) as hole transport materials, sputtered gold chloride as back electrode (counter electrode). In addition, the CsPbI3 perovskite coated on the electrospun TiO2 and TiO2/rGO NF photoanodes exhibited electrical conductivities of 1.352 × 10−3 and 1.650 × 10−3 S cm−1. Finally, power conversion efficiency of TiO2/rGO NFs (6.38 %) was achieved, which was significantly higher than that of conventional TiO2 NFs (5.54 %)-based devices.

In situ growth of flower-like ZnO onto graphene oxide for the synergistically enhanced anti-corrosion ability of epoxy coating

Two-dimensional graphene oxide (GO) has shown the favorable candidate as functional filler for enhancing the anticorrosive performance of epoxy coating, but its poor dispersion and low antimicrobial ability limited the further application in complex corrosive environment. To overcome these obstacles, a two-dimensional GO-based antimicrobial anticorrosion epoxy composite coating was developed via synergy of graphene oxide and zinc oxide. To achieve this goal, the flower-like ZnO with antimicrobial activity was situ grown on the surface of graphene oxide by hydrothermal route, which was further modified via the dopamine triggered chemical cross-linking with polyethyleneimine (GO-ZnO@DP). Thanks to the good dispersion and the excellent physical barrier property of the GO-ZnO@DP functional filler, the epoxy composite coating exhibited superior ability of corrosion resistance. With the addition of 1.0 wt% GO-ZnO@DP functional filler (G2/EP), the low frequency impedance modulus |Z|0.01Hz reached 1.57 × 109 Ω cm2 after immersion in 3.5 wt% NaCl medium for 30 days. Meanwhile, due to the introduction of flower-like ZnO, the composite coating exhibited the enhanced antibacterial properties toward the inhibitory experiment of E. coli. Besides, the results of salt spray test, EDS analysis, and mechanical properties strongly supported the long-term corrosion resistance of epoxy coating, which shows promising application of metal protection in the complicated corrosive environment.

Falling-Leaves Stacking Aggregation of Two-Dimensional Macromolecular Graphene Oxide in Solution.

Understanding the dynamical behaviors of two-dimensional (2D) macromolecules is of fundamental importance for the precise modulation of their assembled structures and material performances. However, considerably less is known about how discrete macromolecular sheets aggregate into extended macroscopic assemblies in solutions. The absence of a quantitative description of the assembly process limits the precise structural control of assemblies. Here, we investigated the aggregation thermodynamic transition and kinetic behavior of 2D macromolecules in the model of single layer graphene oxide (GO). Combining Flory-Huggins theory with experimental observations, we unveiled the critical thermodynamic transition of GO to correlate with the solvent property. We proposed a theoretical falling-leaf model to quantitatively describe the kinetic aggregation process of 2D GO sheets. Experimental analysis validated the theoretical prediction that the thickness of GO aggregates has a power law relation with the poor solvent content. Our work provides a fundamental understanding of phase separation of 2D macromolecules and offers an insight into modulating the aggregated structures of their assembled materials.

Synthesis of Graphene Oxide-Coupled CoNi Bimetallic MOF Nanocomposites for the Simultaneous Analysis of Catechol and Hydroquinone.

Herein, a three-dimensional flower-like cobalt-nickel bimetallic metal-organic framework (CoNi-MOF) coupled with two-dimensional graphene oxide (GO) nanocomposites was successfully synthesized for the selective and simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ). The three-dimensional flower-like structure of the CoNi-MOF/GO nanocomposite has a multilayer structure and a large surface area, which greatly improves its electrocatalytic activity towards CC and HQ. Differential pulse voltammetry (DPV) results showed that the peak-to-peak separation of CC (0.223 V) and HQ (0.120 V) was 103 mV at a CoNi-MOF/GO modified glassy carbon electrode (CoNi-MOF/GO/GCE), suggesting that the proposed modified electrode can selectively and simultaneously determine them. Under optimal conditions, the CoNi-MOF/GO/GCE showed an excellent analytical performance for the simultaneous determination of CC and HQ, including a wide linear range (0.1-100 μM), low detection limit (0.04 μM for HQ and 0.03 μM for CC) and high anti-interference ability. As expected, the developed modified electrode has been used to analyze CC and HQ in river water, with acceptable results.

MoS2-GO hybrid sensor: A discerning approach for detecting harmful H2S gas at room temperature

The molybdenum disulfide (MoS2)- graphene oxide (GO) hybrids have fashioned by a clean hydrothermal route. Initially, two-dimensional GO sheets have synthesized using the modified Hummer’s method and intercalated into the MoS2 nanoparticles (NPs). The sophisticated characterizations comprising X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analyzer, custom designed gas sensing set-up, etc. utilized for the analysis of as-prepared MoS2-GO (1 to 5 wt%) hybrids. The maximum sensor response exhibited by as-prepared MoS2-GO (3%) hybrid sensor was 39.16% towards 100 ppm hydrogen sulfide (H2S) gas at room temperature (RT, i.e., 28 °C) in a quickest response time (6.13 s) and least concentration of H2S detected was 1 ppm with response value 0.51%. This report investigated first time that as-prepared MoS2-GO (MG) hybrids with varied proportion of GO (1 to 5 wt%) demonstrated spectacularly improved gas sensing performance towards H2S at RT. The boosted gas sensing performance of MG hybrids could be attributed to the synergistic influence of constituents i.e., MoS2 NPs and GO sheets. An impedance spectroscopy has been exploited to study the interactions between H2S gas molecules and MG hybrid sensor surface.

Novel multi-responsive soft actuator assembled with a graphene oxide nanoribbons doped strain hydrogel sensor with high sensitive and NIR-triggered performances

Effectively integrating multiple properties of hydrogel materials for expanding the application field of soft materials is highly desirable. In this work, a fast initiation system was used to prepare hydrogels. Based on the dynamic hydrogen bonding interactions between two-dimensional graphene oxide nanoribbons (GONRs), polymer chains and metal ions, the hydrogel exhibited excellent mechanical properties, great sensing performance and great self-healing property. Especially, the hydrogel exhibited sensitive response performance to near-infrared (NIR) light. A bilayer hydrogel actuator was assembled by combining the hydrogel with the temperature-sensitive Poly-N-isopropylacrylamide (PNIPAM) hydrogel. The bilayer hydrogel actuator exhibited stable responses to temperature, pH, and NIR light. The bilayer hydrogel could achieve bending close to 360° with good cycling stability in these three environments. As a proof-of-concept, the bilayer hydrogel was used as an identifiable fluid valve with selective passage which released fluids of different properties into corresponding containers. At the same time, the self-healing properties of the hydrogel and the actuation performance of the bilayer hydrogel were successfully used to simulate the wagging motion of the tail of puppy. The developed self-healing and sensing hydrogel and the assembled bilayer hydrogel actuator are expected to open new application fields in the health monitoring and soft robotics.