Polymer-modified Graphene Oxide Research Articles

Synthesis and evaluation of poly(propylene fumarate)-grafted graphene oxide as nanofiller for porous scaffolds.

In an effort to obtain porous scaffolds with improved mechanical properties and biocompatibility, the current study discusses nanocomposite materials based on poly(propylene fumarate)/N-vinyl pyrrolidone(PPF/NVP) networks reinforced with polymer-modified graphene oxide (GO@PPF). The GO@PPF nanofiller was synthesized through a facile and convenient surface esterification reaction, and the successful functionalization was demonstrated by complementary techniques such as FT-IR, XPS, TGA and TEM. The PPF/NVP/GO@PPF porous scaffolds obtained using NaCl as a porogen were further characterized in terms of morphology, mechanical properties, sol fraction, and in vitro degradability. SEM and nanoCT examinations of NaCl-leached samples revealed networks of interconnected pores, fairly uniform in size and shape. We show that the incorporation of GO@PPF in the polymer matrix leads to a significant enhancement in the mechanical properties, which we attribute to the formation of denser and more homogenous networks, as suggested by a decreased sol fraction for the scaffolds containing a higher amount of GO@PPF. Moreover, the surface of mineralized PPF/NVP/GO@PPG scaffolds is uniformly covered in hydroxyapatite-like crystals having a morphology and Ca/P ratio similar to bone tissue. Furthermore, the preliminary biocompatibility assessment revealed a good interaction between PPF/PVP/GO@PPF scaffolds and murine pre-osteoblasts in terms of cell viability and proliferation.

Investigating the effect of polymer-modified graphene oxide coating on RO membrane fouling

The development of novel reverse osmosis (RO) membranes resistant to multiple types of fouling is a need to secure clean water production and meet rising water demands. In this paper, the RO membrane surface-functionalized with antibacterial graphene oxide (GO) and antiscalant maleic acid was prepared and tested. The polymerization of maleic acid on the GO functionalized RO membrane was achieved using microwave radiation. The membrane surface characterization showed a decrease in membrane surface roughness from 74.7 nm to 69.0 nm and an increase in membrane hydrophilicity as the contact angle decreased from 41.7 ± 4.50 to 22.0 ± 1.10. The modified membrane was tested against inorganic scaling and biofouling, and the results demonstrated that the modified membrane has improved resistance to multiple fouling types as compared to the unmodified RO membrane. When tested in the presence of calcium sulfate scaling solution (inorganic fouling), the normalized permeate flux was found to be stable at 0.91 and 0.95 for 0.01 and 0.02 wt% maleic acid-modified RO membranes, respectively. Moreover, the modified membranes also demonstrated bacteriostasis rates of 96.1 %–97.1 % showing their anti-bacterial characteristics. Both types of membrane fouling (inorganic and biofouling) were also studied simultaneously, and the results showed that the RO membranes with dual capabilities can inhibit both mineral formation and biofilm growth concurrently.

Synthesis of zwitterionic polymer modified graphene oxide for hydrophilic enrichment of N-glycopeptides from urine of healthy subjects and patients with lung adenocarcinoma

As one of the most common and important post-translational modifications, protein N-glycosylation plays essential roles in many biological processes and have long been considered closely correlated with the occurrence and progression of multiple diseases. Systematic characterization of these disease-related protein N-glycosylation is one of the most convenient ways for new diagnostic biomarker and therapeutic drug target discovering. However, the biological samples are extremely complex and the abundance of N-glycoproteins are especially low, which make highly efficient N-glycoprotein/glycopeptide enrichment before mass spectrometry analysis a prerequisite. In this work, a new type of hydrophilic material (GO-pDMAPS) was prepared by in situ growth of linear zwitterionic polymer chains on the surface of GO and it was successfully applied for N-glycopeptide enrichment from human urine. Due to the excellent hydrophilicity and the facilitate interactions between this GO-pDMAPS and the targets, a total of 1426 N-glycosylated sites corresponding to 766 N-glycoproteins as well as 790 N-glycosylation sites corresponding to 470 N-glycoproteins were enriched and identified from urine of healthy subjects and patients with lung adenocarcinoma, respectively. Among which, 27 N-glycoproteins were expressed exclusively and 4 N-glycoproteins were upregulated at least 3 times comparing with the healthy group, demonstrating the tremendous potential of this new hydrophilic material for large scale and in depth N-glycoproteome research.

S4-Containing hyperbranched polymer modified graphene oxide as strong linker for both rubber and carbon black to enhance the crosslinking and mechanical properties of nitrile butadiene rubber

• S 4 -containing hyperbranched polymer modified graphene oxide was synthesized. • It shows strong interaction with both nitrile butadiene rubber and carbon black. • The tensile strength of new composites increased from 8.9 MPa to 17.0 MPa. Graphene oxide (GO) nanosheets reinforced rubbers had been well studied. However, it is very difficult to make GO nanosheets uniformly dispersed in the polar nitrile butadiene rubber (NBR) matrix and non-polar carbon black simultaneously. The hyperbranched polymer of bis(triethoxysilylpropyl) tetrasulfide (BTESPT) grafted on the GO nanosheet (HSi-GO) has been synthesized through the catalytic condensation of the BTESPT monomer. The as-prepared S4-Containing hyperbranched polymer modified graphene oxide has strong interfacial interaction with both the polar NBR matrix and non-polar carbon black nanoparticles. Excitingly, HSi-GO has greatly improved the tensile strength of NBR/CB composites from 8.9 MPa to 17.0 MPa.

Functionalization of reverse osmosis membrane with graphene oxide and polyacrylic acid to control biofouling and mineral scaling

The polyamide reverse osmosis (RO) membrane was modified with graphene oxide (GO), followed by polymerization of acrylic acid (used as an antiscalant) for the reduction of both biofouling and mineral scaling. After functionalization, the water contact angle reduced from 41.7 ± 4.5° for unmodified RO membrane to 24.4 ± 1.3° for the modified RO membranes, which showed that membrane hydrophilicity was significantly enhanced, in addition to the improvement in surface smoothness. The modified membranes were tested for their anti-scaling and anti-biofouling characteristics. When the mineral scaling test was performed using CaSO4 solution as feedwater, the permeate flux was reduced by only 3% as compared to the unmodified RO membrane which encountered up to 22% decline in flux by the end of the experiment. After the scaling test, the membrane surface was characterized by Scanning electron microscopy – energy-dispersive X-ray spectroscopy, Fourier transform infrared, and X-ray diffraction techniques. The results showed that the unmodified RO membrane was fully covered with gypsum precipitates. Whereas, the precipitates were detected only at the highly saturated zones of the water channel i.e. towards the exit of water flow. Additionally, the anti-bacterial test was performed through bacteriostasis rate determination, which showed that the modified membranes inhibited the growth of nearly 95% of the bacterial cells. Further experiments were also performed to investigate the inhibition of both scaling and biofouling by modified RO membranes. Thus, it was found that the polymer-modified GO coated RO membranes were able to diminish both gypsum scaling and biofilm formation demonstrating their potential to control different types of membrane fouling.

Ultrasensitive Paper-based ELISA by Introducing Atom Transfer Radical Polymer-modified Graphene Oxide Sheets and Gold Nanoparticles

In recent years, enzyme-linked immunosorbent assay (ELISA) plate fabricated on paper (P-ELISA) has been well developed. However, low sensitivity is its main disadvantage and has limited its use. In this study, a modified strategy was developed by introducing atom transfer radical polymer (ATRP)-modified graphene oxide (GO) sheets and gold nanoparticles (GNs). The results suggest the ATRP/GO/GNs-modified P-ELISA (AGGP-ELISA) achieves 1024 fold amplification and is suitable for rapid identification and qualitative detection, especially in small laboratories, or developing countries.

In-situ synthesis of Ge/reduced graphene oxide composites as ultrahigh rate anode for lithium-ion battery

Germanium (Ge), as an anode material for lithium-ion batteries (LIBs), has received considerable attention because of its high theoretical capacity and excellent electrochemical performance. However, Ge anode usually undergoes large volume expansion during lithium insertion/extraction, resulting in severe structural pulverization and fast capacity fading. Here, we report an efficient cationic polymer-assisted in-situ reduction method for the preparation of highly uniform Ge/RGO composites (RGO = reduced graphene oxide) using GeO2, instead of expensive and toxic GeXn (X = Cl, Br and I), as Ge source. In this protocol, GeO32− anions are well adsorbed on cationic polymer-modified graphene oxide sheets by electrostatic interaction, followed by in-situ reduction, which results in the growth of ultrafine Ge nanoparticles (ca. 5 nm) on RGO sheets to form highly uniform sandwich-like structure. Benefiting from the tiny size of Ge nanoparticles and the well-conductive RGO sheets, the Ge/RGO anodes exhibit a high reversible capacity of 960 mAh g−1 after 100 cycles at 0.2 A g−1, an excellent rate capability of 631 mAh g−1 at 5 A g−1, and 705 mAh g−1 after 350 cycles at 1 A g−1 (with the capacity fading of only 0.07% per cycle based on the initial discharge capacity of 940 mAh g−1). More impressively, by coupling with LiFePO4 cathode, the full battery also shows a good electrochemical performance in terms of specific capacity and cycling stability. The simple, low-cost and environmental friendly synthesis strategy together with the outstanding lithium-storage performance of Ge/RGO composites affords a promising anode material for next-generation LIBs.

Enhanced and Tunable Electrorheological Capability using Surface Initiated Atom Transfer Radical Polymerization Modification with Simultaneous Reduction of the Graphene Oxide by Silyl-Based Polymer Grafting.

In this study, a verified process of the “grafting from” approach using surface initiated atom transfer radical polymerization was applied for the modification of a graphene oxide (GO) surface. This approach provides simultaneous grafting of poly(2-(trimethylsilyloxy)ethyl methacrylate) (PHEMATMS) chains and a controllable reduction of the GO surface. This allows the fine tuning of its electrical conductivity, which is a crucial parameter for applications of such hybrid composite particles in electrorheological (ER) suspensions. The successful coating was confirmed by transmission electron microscopy and Fourier-transform infrared spectroscopy. The molecular characteristics of PHEMATMS were characterized by gel permeation chromatography. ER performance was elucidated using a rotational rheometer under various electric field strengths and a dielectric spectroscopy to demonstrate the direct impact of both the relaxation time and dielectric relaxation strength on the ER effectivity. Enhanced compatibility between the silicone oil and polymer-modified GO particles was investigated using contact angle measurements and visual sedimentation stability determination. It was clearly proven that the modification of the GO surface improved the ER capability of the system due to the tunable conductivity during the surface-initiated atom transfer radical polymerization (SI-ATRP) process and the enhanced compatibility of the GO particles, modified by polymer containing silyl structures, with silicone oil. These unique ER properties of this system appear very promising for future applications in the design of ER suspensions.

Fabrication of terminal amino hyperbranched polymer modified graphene oxide and its prominent adsorption performance towards Cr(VI).

In order to increase the density and quantity of functional groups on adsorbent, three terminal amino hyperbranched polymer modified graphene oxide adsorbents including GO-HBP-NH2-DETA, GO-HBP-NH2-TETA and GO-HBP-NH2-TEPA with N-containing functional group density of 7.21 wt%, 10.20 wt% and 12.43 wt%, respectively, were prepared and used for the adsorption and reduction of toxic hexavalent chromium Cr(VI) to less toxic Cr(III). The morphology and structure of obtained adsorbents were characterized by FT-IR, SEM, XRD, Raman, BET, XPS and zeta potential. The density of receptor sites (Nm) of the three adsorbents calculated from statistical physics model with one energy site were found to be 456.62, 604.54 and 636.03, respectively. Adsorption experiments demonstrated that the high adsorption capacities of the three adsorbents obtained from Langmuir isotherm model towards Cr(VI) were 245.01, 257.26 and 300.88 mg/g, respectively, suggesting that GO-HBP-NH2-TEPA had better adsorption ability. The density functional theory calculation (DFT) indicated that GO-HBP-NH2-TEPA was more likely to adsorb HCrO4- rather than Cr2O72- at lower pH conditions. A possible adsorption mechanism was also proposed where electrostatic interaction between Cr(VI) (HCrO4- or Cr2O72-) and the N functional group (+) on GO-HBP-NH2-TEPA dominated the adsorption of Cr(VI) and reduction mechanism dominated the reduction of Cr(VI)-Cr(III).

Amphiphilic comb-like polymer-modified graphene oxide and its nanocomposite with polystyrene via emulsion polymerization

The synthesis of amphiphilic polymer-modified graphene oxide and its evaluation in the preparation of polystyrene nanocomposites via aqueous phase emulsion polymerization have been studied. The polymer modification was achieved via surface initiated atom transfer radical polymerization (SI-ATRP) from graphene oxide and subsequent sulphonation of the resulting brush-like polymer. Fluorimetric studies using pyrene as fluorescent probe gave a critical aggregation concentration (CAC) value of 1.29 mg/ml, comparable to that of polymeric surfactants. The surfactant was evaluated in the emulsion polymerization of styrene and on increasing the surfactant concentration from 0.5 to 2.0 wt%, the nanocomposite particle size varied from 160 to 220 nm, respectively. Nanocomposite films containing amphiphilic polymer-modified graphene surfactant show lower glass transition temperature and improved thermomechanical properties. The water contact angle of the film coated on a glass substrate increased from 84° to 124°, indicating a synergistic effect of graphene and the grafted polymer, suggesting that it was use as multifunctional additive for polymer nanocomposites.

Simultaneous Determination and Investigation of Nine Fungicides in Fruits Using Diethylenetriamine-Functional Magnetic Core-Shell Polymer Modified Graphene Oxide as an Efficient Adsorbent Coupled to UPLC-HRMS.

In this study, diethylenetriamine-functional magnetic core-shell polymer modified graphene oxide (DETA-MPs-GO) was prepared via precipitation polymerization and amidation reaction, and it was characterized by transmission electron microscopy (TEM), Fourier-transformed infrared spectroscopy (FTIR), and X-ray diffractometer (XRD). Subsequently, a magnetic solid-phase extraction (MSPE) procedure was applied to the as-synthesized DETA-MPs-GO for the detection of nine fungicides in fruit samples, prior to ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). The homogenized fruit samples, spiked with D-labelled internal standards, were firstly extracted by 5 mL of acetonitrile twice and then purified by DETA-MPs-GO adsorbents. The optimization of the adsorption and elution conditions of DETA-MPs-GO toward fungicides was carried out to attain a satisfactory adsorption performance and desorption efficiency. The adsorption mechanism was carefully investigated, and the results revealed that a synergistic adsorption mechanism, including hydrogen bond and a π–π stacking interaction, was confirmed. Moreover, the limits of quantitation (LOQs) of the proposed approach were in the range of 0.01 to 0.30 μg/kg under the optimum conditions. The average recoveries at three spiking levels were 84.9% to 105.2%, with relative standard deviations (RSDs) varying from 0.8% to 8.2% (n = 6). The developed method was successfully utilized for the screening and detection of fungicides in 81 fruit samples purchased from markets. A detailed survey was carried out about the concentration distribution, types of fungicides, and combined use of fungicides in different fruits.

Double-sided magnetic molecularly imprinted polymer modified graphene oxide for highly efficient enrichment and fast detection of trace-level microcystins from large-volume water samples combined with liquid chromatography–tandem mass spectrometry

Microcystins (MCs), a group of cyclic heptapeptide heaptoxins and tumor promoters, are generated by cyanobacteria occurring in surface waters, such as eutrophic lakes, rivers, and reservoirs. In this present study, a novel double-sided magnetic molecularly imprinted polymer modified graphene oxide (DS-MMIP@GO) based magnetic solid-phase extraction (MSPE) method was developed for fast, effective and selective enrichment, and recognition of trace MCs in environmental water samples combined with high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS). The synthesized novel DS-MMIP@GO was used as the adsorbents in this work and was carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectra. The adsorption and desorption conditions of DS-MMIP@GO toward MCs were optimized in detail to obtain the highest binding capacity, selectivity, and release efficiency. Under the optimum conditions, the enrichment factors of the method for eight target MCs were found to be 2000. The limits of quantitation (LOQs) of the method for eight MCs were in range of 0.1–2.0ngL−1. The double-sided MMIP modified structure provided DS-MMIP@GO with abundant adsorption sites and permitted it to exhibit excellent enrichment and selectivity toward trace-level MCs. The proposed method was successfully applied for the analysis of environmental water samples with recoveries ranging from 84.1 to 98.2%. Compared to conventional methods for MCs detection reported in literatures, the one developed in this work based on DS-MMIP@GO and LC–MS/MS showed much faster, more sensitive, and more convenient.

Biomimic modification of graphene oxide

Synthetic polymer modified graphene oxide was preparedviacombination of mussel inspired chemistry and Michael addition reaction in aqueous solution.

Graphene oxide enhances cellular delivery of hydrophilic small molecules by co-incubation.

The delivery of bioactive molecules into cells has broad applications in biology and medicine. Polymer-modified graphene oxide (GO) has recently emerged as a de facto noncovalent vehicle for hydrophobic drugs. Here, we investigate a different approach using native GO to deliver hydrophilic molecules by co-incubation in culture. GO adsorption and delivery were systematically studied with a library of 15 molecules synthesized with Gd(III) labels to enable quantitation. Amines were revealed to be a key chemical group for adsorption, while delivery was shown to be quantitatively predictable by molecular adsorption, GO sedimentation, and GO size. GO co-incubation was shown to enhance delivery by up to 13-fold and allowed for a 100-fold increase in molecular incubation concentration compared to the alternative of nanoconjugation. When tested in the application of Gd(III) cellular MRI, these advantages led to a nearly 10-fold improvement in sensitivity over the state-of-the-art. GO co-incubation is an effective method of cellular delivery that is easily adoptable by researchers across all fields.

Amine-functional magnetic polymer modified graphene oxide as magnetic solid-phase extraction materials combined with liquid chromatography–tandem mass spectrometry for chlorophenols analysis in environmental water

A novel planar-structure amine-functional magnetic polymer modified graphene oxide nanocomposite (NH2-MP@GO) was synthesized. The properties were characterized by transmission electron microscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The obtained adsorption results showed that the NH2-MP@GO had great adsorptive ability toward five chlorophenols (CPs), including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on these, an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the preconcentration and determination of the five CPs in environmental water samples was developed. Various experimental parameters that could affect the extraction efficiencies had been investigated in detail. Under the optimum conditions, the enrichment factors of the method for the target CPs were found to be 1000. The proposed method was successfully applied for the analysis of environmental water samples with recoveries ranging from 86.4 to 99.8% with correlation coefficients (R) higher than 0.9994. Good linearities were obtained ranging from 10 to 500ng/L for 2-CP, 5 to 500ng/L for 2,4-DCP, 2 to 500ng/L for 2,4,6-TeCP and 2,3,4,6-TeCP, and 1 to 500ng/L for PCP, respectively. The limits of quantitation for the five CPs were 0.6–9.2ng/L. It was confirmed that the planar-structure NH2-MP@GO was a kind of highly effective MSPE materials used for the trace CPs analyses.

Well-Coupled Graphene and Pd-Based Bimetallic Nanocrystals Nanocomposites for Electrocatalytic Oxygen Reduction Reaction

In this paper, a series of well-coupled graphene (G) and MPd3 (M = Fe, Cu, Ag, Au, Cr, Mo, W) nanocrystals nanocomposites (G-MPd3 NCPs) have been synthesized via a versatile electrostatic assembly and hydrogen reduction strategy, i.e., sequential assembly of coordination anions and cations on excess cationic polymer modified graphene oxide to form composite precursors and then thermal treating under H2/Ar gases atmosphere. In those NCPs, the MPd3 components are uniform and smaller than 10 nm, which are well anchored on G with "naked" or "clean" surfaces. By adjusting reaction temperature, the interplay of MPd3 nanocrystals and G can be well-controlled. Below 700 °C, no sintering phenomena are observed, indicating the unprecedented dispersion and stability effect of G for MPd3 nanocrystals. All the obtained NCPs can be directly used to catalyze oxygen reduction reaction in alkaline media. Compared with single component, monometallic, and some reported non-Pt catalysts, greatly enhanced electrocatalytic performances are observed in those NCPs due to strong synergistic or coupling of their constituents. Among them, G-FePd3 NCPs exhibit the highest catalytic activity, but their current density needs to be improved compared with G-CrPd3, G-MoPd3, and G-WPd3 ones. This work not only provides a general strategy for fabricating well-coupled G-MPd3 NCPs but also paves the way for future designing multicomponent NCPs with multiple interfaces to apply in alkaline fuel cells.