Multifunctional Graphene Oxide Research Articles

Development of a hypoxic nanocomposite containing high-Z element as 5-fluorouracil carrier activated self-amplified chemoradiotherapy co-enhancement.

The synergetic effect of chemoradiotherapy achievement is encouraging but significantly hampered by the prevalence of hypoxia, leading to drug/radiation resistance in solid tumours. To address the problem and improve the efficiency of cancer therapy, a lamellar-structure multifunctional graphene oxide (GO) drug-delivery system with an average size of 243 nm, co-delivering of metronidazole (MI), 5-fluorouracil (5-FU) and FePt magnetic nanoparticles (MNPs), was successfully designed and synthesized in the study. The integration of hypoxic drug carrier loading radiosensitizers and chemotherapeutic drugs simultaneously, combines the properties of hypoxia-sensitivity and chemoradiotherapy co-enhancement within a single nanoplatform, which is expected to provide new ideas for cancer treatment. Through in vitro tests, the hypoxia-sensitivity and cytotoxicity of intracellular reactive oxygen species (ROS) of the nanocomposites (NCs) were proved. Moreover, the additive effect between MI, 5-FU and FePt MNPs in cytotoxicity and radiation sensitization aspects is disclosed. It performs an enhanced cell proliferation inhibition and makes up a self-amplified radiotherapy enhancement system that improves radiation efficiency and cell radiosensitivity simultaneously. In conclusion, the study recommended a novel and promising multifunctional nanoplatform which performed a self-amplified effect that activated chemoradiotherapy co-enhancement.

A Multifunctional Graphene Oxide Platform for Targeting Cancer.

Diagnosis of oncological diseases remains at the forefront of current medical research. Carbonic Anhydrase IX (CA IX) is a cell surface hypoxia-inducible enzyme functionally involved in adaptation to acidosis that is expressed in aggressive tumors; hence, it can be used as a tumor biomarker. Herein, we propose a nanoscale graphene oxide (GO) platform functionalized with magnetic nanoparticles and a monoclonal antibody specific to the CA IX marker. The GO platforms were prepared by a modified Hummers and Offeman method from exfoliated graphite after several centrifugation and ultrasonication cycles. The magnetic nanoparticles were prepared by a chemical precipitation method and subsequently modified. Basic characterization of GO, such as the degree of oxidation, nanoparticle size and exfoliation, were determined by physical and chemical analysis, including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and atomic force microscopy (AFM). In addition, the size and properties of the poly-L-lysine-modified magnetic nanoparticles were characterized. The antibody specific to CA IX was linked via an amidic bond to the poly-L-lysine modified magnetic nanoparticles, which were conjugated to GO platform again via an amidic bond. The prepared GO-based platform with magnetic nanoparticles combined with a biosensing antibody element was used for a hypoxic cancer cell targeting study based on immunofluorescence.

A Composite of Hyaluronic Acid-Modified Graphene Oxide and Iron Oxide Nanoparticles for Targeted Drug Delivery and Magnetothermal Therapy.

Graphene oxide (GO) nanoparticles have been developed for a variety of biomedical applications as a number of different therapeutic modalities may be added onto them. Here, we report the development and testing of such a multifunctional GO nanoparticle platform that contains a grafted cell-targeting functionality, active pharmaceutical ingredients, and particulates that enable the use of magnetothermal therapy. Specifically, we demonstrate the ability to covalently attach hyaluronic acid (HA) onto GO, and the resultant nanoparticulates (GO-HA) exhibited low inherent toxicity toward two different breast cancer cell lines, BT-474 and MDA-MB-231. Doxorubicin (Dox) and paclitaxel (Ptx) were successfully loaded onto GO-HA with high and moderate efficiencies, respectively. A GO-HA-Dox/Ptx system was significantly better than the GO-Dox/Ptx system at specifically killing CD44-expressing MDA-MB-231 cells but not BT-474 cells that do not express CD44. Further, modified iron oxide nanoparticles were loaded onto the GO-HA-Dox system, enabling the use of magnetic hyperthermia. Hyperthermia in combination with Dox treatment through the GO-HA system showed significantly better performance in reducing viable tumor cell numbers when compared to the individual systems. In summary, we showcase a multifunctional GO nanoparticle system that demonstrates improved efficacy in killing tumor cells.

Crystallization, thermal stability, barrier property, and aging resistance application of multi-functionalized graphene oxide/poly(lactide)/starch nanocomposites.

Poly(lactide)-starch matrix, blended with multi-functionalized graphene oxide, was synthesized by solution casting in this study. To improve its interface compatibility, the graphene oxide (GO) was grafted with maleic anhydride and subsequently modified by dodecyl amine. The chemical structure and morphology of functionalized GO (f-GO) were determined by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The crystallization property, surface wettability, morphology, thermal stability, and dynamic mechanical and aging resistance properties of the nanocomposite were determined. By XRD and morphological analysis, we observed the formation of well-dispersed nanocomposites. Thermo-gravimetric analysis revealed significant improvements in thermal stability. The isothermal and non-isothermal crystallization behavior of the PLA-starch-f-GO nanocomposites demonstrated that the f-GO that was added accelerated the heterogeneous nucleation of the nanocomposites. The surface hydrophobicity, UV-shielding capacity, and aging resistance properties of these nanocomposites were enhanced by the incorporation of the f-GO. The migration rate of plasticizer of the nanocomposites decreased compared with the group without f-GO. The storage modulus for these nanocomposites improved by dynamic mechanical analysis. These insights provide a strategy for constructing high-performance nanohybrids and broadening their application in the food packaging and pharmaceutical industries.

Multifunctional graphene oxide loaded nanofibrous membrane for removal of dyes and coliform from water

In this study, we fabricated a trifunctional polyurethane (PU)/graphene oxide (GO) electrospun membrane for adsorption of organic dyes such as methylene blue (MB) and rhodamine B (RB). Moreover, the prepared membrane showed antifouling property and inhibition against bacteria. The GO modified PU nanofiber shows a maximum adsorption capacity of 109.88 mg/g and 77.15 mg/g towards MB and RB respectively. Theoretical studies confirmed that the dye adsorption is followed pseudo-second-order kinetics and the Langmuir adsorption isotherm. The superhydrophilic PU/10GO membrane exhibits high water flux of 17,706 lm−2hr−1. This membrane also exhibits good antifouling property for separating oil-in-water emulsions with 99.99% separation efficiency. The Mechanism of antifouling was investigated using Hermia model. The results showed that PU/GO membranes also have antibacterial activity against Gram-negative and Gram-positive bacterias. Thus a superhydrophilic nanofibrous antifouling membrane that can reject both organic dye molecule and bacteria from contaminated water is developed using simple electrospinning technique.

Thermosensitive Microgels-Decorated Magnetic Graphene Oxides for Specific Recognition and Adsorption of Pb(II) from Aqueous Solution.

Herein, we report a novel type of smart graphene oxide nanocomposites (MGO@PNB) with excellent magnetism and high thermosensitive ion-recognition selectivity of lead ions (Pb2+). The MGO@PNB are fabricated by immobilizing superparamagnetic Fe3O4 nanoparticles (NPs) and poly(N-isopropylacrylamide-co-benzo-18-crown-6 acrylamide) thermosensitive microgels (PNB) onto graphene oxide (GO) nanosheets using a simple one-step solvothermal method and mussel-inspired polydopamine chemistry. The PNB are composed of cross-linked poly(N-isopropylacrylamide) (PNIPAM) chains with numerous appended 18-crown-6 units. The 18-crown-6 units serve as hosts that can selectively recognize and capture Pb2+ from aqueous solution, and the PNIPAM chains act as a microenvironmental actuator for the inclusion constants of 18-crown-6/Pb2+ host–guest complexes. The loaded Fe3O4 NPs endow the MGO@PNB with convenient magnetic separability. The fabricated MGO@PNB demonstrate remarkably high ion-recognition selectivity of Pb2+ among the coexisting metal ions because of the formation of stable 18-crown-6/Pb2+ inclusion complexes. Most interestingly, the MGO@PNB show excellent thermosensitive adsorption ability toward Pb2+ due to the incorporation of PNIPAM functional chains on the GO. Further thermodynamic studies indicate that the adsorption of Pb2+ onto the MGO@PNB is a spontaneous and endothermic process. The adsorption kinetics and isotherm data can be well described by the pseudo-second-order kinetic model and the Langmuir isotherm model, respectively. Most importantly, the Pb2+-loaded MGO@PNB can be more easily regenerated by alternatively washing with hot/cold water than the commonly used regeneration methods. Such multifunctional graphene oxide nanocomposites could be used for specific recognition and removal of Pb2+ from water environment.

Novel Smart Polymer-Brush-Modified Magnetic Graphene Oxide for Highly Efficient Chiral Recognition and Enantioseparation of Tryptophan Enantiomers.

Multifunctional graphene oxide nanocomposites simultaneously possessing high enantioselectivity, excellent thermosensitivity, and magnetism demonstrate great application potentials in direct enantioseparation. We herein report one novel smart graphene oxide nanocomposite (MGO@PNG-CD) with high enantioselectivity, excellent thermosensitivity, and magnetism for highly efficient chiral identification and enantioseparation of tryptophan enantiomers. The MGO@PNG-CD is composed of graphene oxide nanosheets with immobilized superparamagnetic Fe3O4 nanoparticles and grafted PNG-CD smart polymer brushes. The PNG-CD is made up of poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PNG) chains with numerous appended β-cyclodextrin (β-CD) units, which play a significant role in effective chiral discrimination and resolution of DL-tryptophan (DL-Trp). The β-CD units serve as chiral selectors capable of selectively recognizing and binding L-tryptophan (L-Trp) into their cavities to form stable host-guest inclusion complexes of β-CD/L-Trp. The PNIPAM chains in PNG act as a microenvironmental adjustor for the inclusion constants of β-CD/L-Trp complexes. The resulted MGO@PNG-CD demonstrates high thermosensitive enantioselectivity toward L-Trp over D-Trp based on the chiral discrimination ability of β-CD toward L-Trp and the thermosensitive volume phase transition of PNIPAM chains. Operating temperature and initial concentrations of DL-Trp are two significant factors affecting the separation efficiency of DL-Trp enantiomers. Moreover, the MGO@PNG-CD also displays satisfactory recycling and convenient magnetic separability from enantiomeric solution. Such a multifunctional graphene oxide nanocomposite developed in this study can serve as a high-performance nanoselector for highly efficient chiral recognition and enantioseparation of various chiral compounds.

Clean water generation with switchable dispersion of multifunctional Fe3O4-reduced graphene oxide particles

With the increased need for clean water and decreased supply of fresh water, purification of contaminated water can provide clean water that supplements the fresh water from nature. Physical adsorption, photo-degradation and solar-driven evaporation processes are promising ways to generate clean water with minimum environmental impact. However, different purification process requires different dispersion state of the treating agent to maximize its performance. Herein, we demonstrate that Fe3O4-reduced graphene oxide (MrGO) particles with switchable dispersion can be used as the multifunctional water treating agents to efficiently purify contaminated water through different processes. Under homogenously dispersed nanofluid mode, the MrGO particles have large exposed surface areas and can efficiently remove organic dye pollutants through physical adsorption. The uniform dispersion state also favors high contact efficiency facilitating decontamination of high concentration of organic compounds through solar-driven photocatalytic degradation by the MrGO particles. The excellent magnetic response of MrGO particles not only allows for easy collection of the treating agent from water but also enables assembly of MrGO at the air-water interface with external magnets. Under such interfacial assembled mode, clean water can be distilled out of the contaminated solution with high evaporation efficiency of 74.7% under simulated natural solar radiation. This work demonstrates that dispersion state can be used as another important means to optimize water purification performances.

Multifunctional graphene oxide paper embodied structural dielectric capacitor based on carbon fibre reinforced composites

In this study, the multifunctionality of structural dielectric capacitor made by integrating graphene oxide paper into carbon fibre reinforced composite has been investigated. The study is based on an earlier work on the use of graphene oxide for dielectric material in the structural dielectric capacitor, in which electrical properties have been characterized. In this work, an in-depth study on electrical and mechanical properties of this kind of structural dielectric capacitor have been carried out. In addition, the multifunctional efficiency of structural dielectric capacitors were evaluated and compared with existing structural dielectric capacitors. Through experiments, it is revealed that both electrical and mechanical properties of the structural dielectric capacitors were significantly enhanced by interleaving a graphene oxide paper in the middle of composite. Therefore, the multifunctional efficiency of this kind of structural dielectric capacitors has been ultimately improved, indicating the excellent potential of graphene oxide paper in the development of multifunctional materials for energy storage, potentially for high-strength required applications, such as electric vehicles and unmanned aerial vehicles.

Carnosine-graphene oxide conjugates decorated with hydroxyapatite as promising nanocarrier for ICG loading with enhanced antibacterial effects in photodynamic therapy against Streptococcus mutans

Antimicrobial photodynamic therapy (aPDT) has been emerged as a noninvasive strategy to remove bacterial contaminants such as S. mutans from the tooth surface. Photosensitizer (PS), like indocyanine green (ICG), plays a key role in this technique which mainly suffers from the poor stability and concentration-dependent aggregation. An appropriate nanocarrier (NC) with enhanced antibacterial effects could overcome these limitations and improve the efficiency of ICG as a PS. In this study, various ICG-loaded NCs including graphene oxide (GO), GO-carnosine (Car) and GO-Car/Hydroxyapatite (HAp) were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Filed Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Zeta Potential and Ultraviolet-Visible spectrometry (UV–Vis). The colony forming unit and crystal violet assays were performed to evaluate the antimicrobial and anti-biofilm properties of PSs against S. mutans. The quantitative real-time PCR approach was also applied to determine the expression ratio of the gtfB gene in S. mutans. The zeta potential analysis and UV–Vis spectrometry indicated successful loading of ICG onto/into NCs. GO-Car/HAp showed highest amount of ICG loading (57.52%) and also highest aqueous stability after one week (94%). UV–Vis spectrometry analyses disclosed a red shift from 780 to 800 nm for the characteristic peak of ICG-loaded NCs. In the lack of aPDT, GO-Car@ICG showed the highest decrease in bacterial survival (86.4%) which indicated that Car could significantly promote the antibacterial effect of GO. GO@ICG, GO-Car@ICG and GO-Car/HAp@ICG mediated aPDT, dramatically declined the count of S. mutans strains to 91.2%, 95.5% and 93.2%, respectively (P < 0.05). The GO@ICG, GO-Car@ICG, GO-Car/HAp@ICG significantly suppressed the S. mutans biofilm formation by 51.4%, 63.8%, and 56.8%, respectively (P < 0.05). The expression of gtfB gene was considerably reduced to 6.0, 9.0 and 7.9-fold after aPDT in the presence of GO@ICG, GO-Car@ICG, GO-Car/HAp@ICG, respectively (P < 0.05). It could be concluded that the multi-functionalized GO as a novel nanocarrier could significantly enhance the ICG loading, stability, and improve its inhibitory effects as a photosensitizer in aPDT against S. mutans. These findings might provide opportunity for efficient treatment of local dental infections.

Efficiency evaluation of arsenic(III) adsorption of novel graphene oxide@iron-aluminium oxide composite for the contaminated water purification

Abstract Prolong consumption of arsenic-rich drinking water causes serious health problem. Aiming to minimize the problem, it is attempted to develop cheap and advanced materials for arsenic extraction from the contaminated water. Thus, multifunctional graphene oxide (GO)-incorporated iron-aluminium mixed oxide (GIAMO) composite has been prepared with five different GO content, and evaluated by batch method for the arsenic(III) removal efficiency. Among the as-prepared GIAMO samples, three samples consisting 1.0, 2.0 and 3.0 g of GO show equally good (92–95%) arsenic(III) removal efficiency, which is 30–35% higher than pristine iron-aluminium oxide (IAMO) from an aqueous solution (5.0 mg AsIII·L−1) at pH 7.0 (± 0.2) and 303 K. Thus, 1.0 g GO-inserted GIAMO (GIAMO-1) sample was characterized as microcrystalline (10–15 nm) with BET surface area about 1.45 times higher than IAMO and investigated for the arsenic(III) adsorption. Optimized pH for arsenic(III) adsorption is 6.0–8.0. The kinetic data agree more closely with pseudo-first order equation (R2 = 0.98–0.99) than pseudo-second order equation (R2 = 0.92–0.93). The equilibrium data describe the Langmuir isotherm (R2 = 0.97–0.98) better than the Freundlich isotherm (R2 = 0.91–0.92), showing the Langmuir monolayer capacity 42.2836 mg·g−1 at 293 K which drops to 24.9170 mg·g−1 at 313 K. High negative enthalpy change (ΔH° ∼ −224 kJ. mol−1) is responsible for the spontaneous reaction (ΔG° = negative) despite unfavorable entropy change (ΔS° = −0.71 kJ. mol−1). The order of competitive effect of PO43−, SO42− and HCO3− on arsenic(III) removal efficiency is PO43− > SO42− > HCO3−. However, the high HCO3− (> 200 mg·L−1) enhances the arsenic(III) removal efficiency of this material. 2.0 M NaOH can regenerate arsenic adsorbed GIAMO-1 only up to 50–60%. 0.65 g. of composite per L of high arsenic (Astotal: 0.115 mg L−1) groundwater can upgrade to potable standard, encouraging possible safe use for high arsenic water treatment. Highly negative enthalpy change, poor regeneration, FTIR, XRD and CV analyses of arsenic-rich solid suggested that arsenic(III) is stabilized over the solid surface without oxidation by surface complex formation.

Multifunctional hybrid graphene oxide for circulating tumor cell isolation and analysis.

Even in 21st century, >90% cancer-associated deaths are caused by metastatic disease. Circulating tumor cells (CTCs), which circulate in the blood stream after release from primary tumors, extravasate and form fatal metastases in different organs. Several clinical trials indicate that CTCs can be used as a liquid biopsy of tumors for early diagnosis of cancers. Since CTCs are extremely rare and exhibit heterogeneous biology due to epithelial-mesenchymal transition (EMT), oncologists continue to face enormous challenges in using CTCs as a true "liquid biopsy" for cancer patients. Recent advancements in nanoscience allow us to design nano-architectures with the capability of targeted CTCs isolation and identification. In the current review, we discuss contribution from different groups on the development of graphene oxide based nanoarchitecture for effective isolation and accurate identification of CTCs from whole blood. In the last few years, using zero-dimensional (0D), two dimensional (2D) and three dimensional (3D) multifunctional hybrid graphene oxide (GO), different types of nanoarchitectures have been designed. These nanoarchitectures represent a highly powerful platform for CTC diagnosis. We discuss the major design criteria that have been used to develop hybrid GO nanoarchitectures for selective capture and accurate identification of heterogeneous CTCs from whole blood. At the end, we conclude with the promises, major challenges, and prospect to clinically translate the identification of CTCs using GO based nanotechnology.

Synergetic co-immobilization of SeO42−and Sr2+from aqueous solution onto multifunctional graphene oxide and carbon-dot based layered double hydroxide nanocomposites and their mechanistic investigation

A synergetic co-immobilization of a Sr2+and SeO42−was evaluated on sustainable multifunctional graphene oxide and carbon-dot based layered double hydroxide nanocomposites.

Multi-functionalization of GO with multi-cationic ILs as high efficient metal-free catalyst for CO2 cycloaddition under mild conditions

To optimize the synergistic effects among hydrogen bond donors, halogen anions and basic sites, we synthesized a series of graphene oxide (GO) materials multi-functionalized with silanol group, multi-cationic quaternary ammonium salt and tertiary amine in a one-pot approach. Hexamethylenetetramine which is cheap and rich with tertiary amine was used as precursor. As characterized by elemental analysis and X-ray photoelectron spectroscopy, the loading of quaternary ammonium salt and tertiary amine was up to 2.56 and 1.84 mmol/g, respectively. This is the first time that a multi-functionalized GO (MF-GO) enriched with multi-cationic quaternary ammonium salt was prepared and used for the cycloaddition of CO2 towards epoxides under mild conditions (90 °C, 2 MPa and 4 h) with high efficiency (TOF = 46.1 h−1) without the need of a solvent and a co-catalyst. The advantage of the combined use of the “multi-cationic approach” and “multi-synergetic strategy” was illustrated by comparing the performance of MF-GO with those of the GO samples that are endowed with different functional groups. A plausible mechanism is proposed for the cycloaddition reaction over MF-GO. Moreover, the MF-GO catalyst can be easily separated and reused for at least five times without significant loss of activity.

Nano-Formulation of Ethambutol with Multifunctional Graphene Oxide and Magnetic Nanoparticles Retains Its Anti-Tubercular Activity with Prospects of Improving Chemotherapeutic Efficacy.

Tuberculosis (TB) is a dreadful bacterial disease, infecting millions of human and cattle every year worldwide. More than 50 years after its discovery, ethambutol continues to be an effective part of the World Health Organization’s recommended frontline chemotherapy against TB. However, the lengthy treatment regimens consisting of a cocktail of antibiotics affect patient compliance. There is an urgent need to improve the current therapy so as to reduce treatment duration and dosing frequency. In this study, we have designed a novel anti-TB multifunctional formulation by fabricating graphene oxide with iron oxide magnetite nanoparticles serving as a nano-carrier on to which ethambutol was successfully loaded. The designed nanoformulation was characterised using various analytical techniques. The release of ethambutol from anti-TB multifunctional nanoparticles formulation was found to be sustained over a significantly longer period of time in phosphate buffer saline solution at two physiological pH (7.4 and 4.8). Furthermore, the nano-formulation showed potent anti-tubercular activity while remaining non-toxic to the eukaryotic cells tested. The results of this in vitro evaluation of the newly designed nano-formulation endorse its further development in vivo.

Ion Diffusion-Directed Assembly Approach to Ultrafast Coating of Graphene Oxide Thick Multilayers.

The layer-by-layer (LbL) assembly approach has been widely used to fabricate multilayer coatings on substrates with multiple cycles, whereas it is hard to access thick films efficiently. Here, we developed an ion diffusion-directed assembly (IDDA) strategy to rapidly make multilayer thick coatings in one step on arbitrary substrates. To achieve multifunctional coatings, graphene oxide (GO) and metallic ions were selected as the typical building blocks and diffusion director in IDDA, respectively. With diffusion of metallic ions from substrate to negatively charged GO dispersion spontaneously (i.e., from high-concentration region to low-concentration region), GO was assembled onto the substrate sheet-by-sheet via sol-gel transformation. Because metallic ions with size of subnanometers can diffuse directionally and freely in the aqueous dispersion, GO was coated on the substrate efficiently, giving rise to films with desired thickness up to 10 μm per cycle. The IDDA approach shows three main merits: (1) high efficiency with a μm-scale coating rate; (2) controllability over thickness and evenness; and (3) generality for substrates of plastics, metals and ceramics with any shapes and morphologies. With these merits, IDDA strategy was utilized in the efficient fabrication of functional graphene coatings that exhibit outstanding performance as supercapacitors, electromagnetic interference shielding textiles, and anticorrosion coatings. This IDDA approach can be extended to other building blocks including polymers and colloidal nanoparticles, promising for the scalable production and application of multifunctional coatings.

Thermo-responsive hydrogels with tunable transition temperature crosslinked by multifunctional graphene oxide nanosheets

Hydrogels consisting of reactive monomers can respond to external stimuli, which is promising for many applications such as sensors, soft robotics, and actuators, etc. However, most of responsive hydrogels are hard to fabricate into smart devices due to their poor mechanical properties. In this paper, vinyl-modified graphene oxide (GO-VTES) nanosheets were facilely prepared through the coupling reaction between hydroxyl or carboxylic acid groups from graphene oxide (GO) and hydroxyl groups from hydrolyzed vinyltriethoxysilane (VTES). By using the multifunctional GO-VTES nanosheets as crosslinkers, N-isopropylacrylamide (NIPAM) and acrylamide (AAm) were copolymerized to generate a series of tough and thermo-responsive composite hydrogels. The structures and morphologies of GO-VTES were investigated by FTIR, Raman, XPS, XRD, AFM and TEM. The obtained thermo-responsive composite hydrogels exhibit enhanced mechanical properties, which can be tuned by varying the content of GO-VTES and AAm. Moreover, these hydrogels were thermo-responsive with the LCST tunable by manipulating the contents of GO-VTES and/or AAm in the hydrogels. This strategy to prepare responsive composite hydrogels with enhanced mechanical properties has attractive applications for fabricating smart soft actuators.

Facilitating Proton Transport in Nafion-Based Membranes at Low Humidity by Incorporating Multifunctional Graphene Oxide Nanosheets.

Nafion, as a state-of-the-art solid electrolyte for proton exchange membrane fuel cells (PEMFCs), suffers from drastic decline in proton conductivity with decreasing humidity, which significantly restricts the efficient and stable operation of the fuel cell system. In this study, the proton conductivity of Nafion at low relative humidity (RH) was remarkably enhanced by incorporating multifunctional graphene oxide (GO) nanosheets as multifunctional fillers. Through surface-initiated atom transfer radical polymerization of sulfopropyl methacrylate (SPM) and poly(ethylene glycol) methyl ether methacrylate, the copolymer-grafted GO was synthesized and incorporated into the Nafion matrix, generating efficient paths at the Nafion-GO interface for proton conduction. The Lewis basic oxygen atoms of ethylene oxide (EO) units and sulfonated acid groups of SPM monomers served as additional proton binding and release sites to facilitate the proton hopping through the membrane. Meanwhile, the hygroscopic EO units enhanced the water retention property of the composite membrane, conferring a dramatic increase in proton conductivity under low humidity. With 1 wt % filler loading, the composite membrane displayed the highest proton conductivity of 2.98 × 10-2 S cm-1 at 80 °C and 40% RH, which was 10 times higher than that of recast Nafion. Meanwhile, the Nafion composite exhibited a 135.5% increase in peak power density at 60 °C and 50% RH, indicating its great application potential in PEMFCs.

A Novel Fabrication Approach for Multifunctional Graphene-based Thin Film Nano-composite Membranes with Enhanced Desalination and Antibacterial Characteristics

A practical fabrication technique is presented to tackle the trade-off between the water flux and salt rejection of thin film composite (TFC) reverse osmosis (RO) membranes through controlled creation of a thinner active selective polyamide (PA) layer. The new thin film nano-composite (TFNC) RO membranes were synthesized with multifunctional poly tannic acid-functionalized graphene oxide nanosheets (pTA-f-GO) embedded in its PA thin active layer, which is produced through interfacial polymerization. The incorporation of pTA-f-GOL into the fabricated TFNC membranes resulted in a thinner PA layer with lower roughness and higher hydrophilicity compared to pristine membrane. These properties enhanced both the membrane water flux (improved by 40%) and salt rejection (increased by 8%) of the TFNC membrane. Furthermore, the incorporation of biocidal pTA-f-GO nanosheets into the PA active layer contributed to improving the antibacterial properties by 80%, compared to pristine membrane. The fabrication of the pTA-f-GO nanosheets embedded in the PA layer presented in this study is a very practical, scalable and generic process that can potentially be applied in different types of separation membranes resulting in less energy consumption, increased cost-efficiency and improved performance.

A label-free electrochemical immunosensor based on multi-functionalized graphene oxide for ultrasensitive detection of microcystin-LR

In this paper, a label-free electrochemical immunosensor for ultrasensitive detection of microcystin-leucine-arginine (MC-LR) based on multi-functionalized graphene oxide was constructed. The graphene oxide has a large surface area for the immobilization of the antibody. Meanwhile, the introduction of the AuNPs and 1-butyl-3-methylimidazolium hexafluorophosphate could enhance the response of the current by improving the electrical conductivity. Thus the electrochemical immunosensor could be prepared through a one-step process and differential pulse voltammetry was employed to detect sensitively MC-LR. Under optimal conditions, the current response of the immunosensor decreased proportionally to the logarithmic concentrations of MC-LR in the range of 0.1–1000 ng/mL with a detection limit of 0.1 ng/mL (S/N = 3). This one-step label-free electrochemical immunosensor showed good performance in specificity, stability, reproducibility, and application.