Radiation synthesis of graphene oxide/composite hydrogels and their ability for potential dye adsorption from wastewater

A high yield of graphene oxide (GO) was chemically synthesized from graphite powder utilizing adjusted Hummer's method. The contents of acidic functional groups in GO were determined using potentiometric titration. Composite hydrogels dependent on graphene oxide/poly(2-acrylamido-2-methylpropanesulfonic acid)/polyvinyl alcohol (GO/PAMPS/PVA) were synthesized utilizing a ⁶⁰Co gamma irradiation source at different doses. The synthesized graphene oxide and composite hydrogels were portrayed via X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared analysis. The morphology of composite hydrogels was characterized by scanning electron microscope. The gel % and swelling % for the prepared hydrogel demonstrated that the swelling % of hydrogel increased with raising AMPS content. Whereas the increment of GO and increasing the irradiation dose lead to a reduction in the swelling %. The influences of pH, GO percentage, initial dye concentration, the adsorbent dosage, contact time, and temperature on the adsorption of basic blue 3 dye were evaluated and the adsorption capacity was 194.6 mg/g at optimum conditions; pH = 6, GO/PAMPS/PVA composite hydrogels with 5 wt% of GO, initial dye concentration = 200 mg/L, adsorbent dose = 0.1 g, solution volume = 50 mL after 360 min at room temperature (25°C). The adsorption of dye onto the GO/PAMPS/PVA composite hydrogels follows Pseudo-second-order adsorption kinetics, fits the Freundlich adsorption isotherm model.     

Hydrous-ferric oxide nanorods grown on PEGylated graphene oxide with superior capacity for selective adsorption of albumin

A ferrate functionalized graphene-based composite is prepared by growth of hydrous ferric oxide (FeOOH) on the polyethylene glycol (PEG) modified graphene oxide (GO) sheets. The obtained GO–PEG–FeOOH composite is characterized by ATR-FTIR, TEM, AFM, XPS and ICP-MS. The PEGylation significantly changes the surface property of the bare graphene oxide, which not only generates a nano-bio-interface for protein interaction but also reduces the non-specific adsorption of proteins. The PEGylation and growth of FeOOH nanorods on GO sheets obviously enhanced the selectivity toward the adsorption of albumin through strong hydrogen bonding interaction, exhibiting an ultra-high adsorption capacity of 1377.4 mg g⁻¹ for bovine serum albumin (BSA). It is obviously higher than those achieved by any hitherto reported graphene based materials and other carbon nanomaterials. Albumin retained by the composite could be effectively recovered with a 4.0 mM B–R buffer through the affinity of boronic acid toward protein, giving rise to a recovery of 70%. Circular dichroism (CD) spectra indicate no conformational change for BSA during the process of adsorption/desorption. The practical applicability of the GO nanocomposite is further demonstrated by the selective adsorption/isolation of albumin from complex biological samples matrixes, e.g., human whole blood.     

In situ crosslinking of poly(vinyl alcohol)/graphene oxide Nano-composite hydrogel: intercalation structure and adsorption mechanism for advanced Pb(II) removal

Based on the industrialized graphene oxide (GO) product, poly(vinyl alcohol) (PVA)/GO nano-composite hydrogels were prepared through in situ crosslinking by incorporation of N-[(trimethoxysilyl)propyl] ethylenediamine-triacetic acid sodium (CSA) as a compatibilizer. Introduction of CSA led to more efficient grafting of PVA molecules onto GO surface with increasing average layer thickness through covalent and hydrogen bonding interaction, while GO was exfoliated and uniformly distributed in PVA matrix. Addition of appropriate content of GO can improve the storage modulus and the effective crosslinking density (υ_e) of the composite hydrogel, and the network structure with GO as crosslinking point formed, resulting in the remarkable increase of the hydraulic impact resistance, mechanical strength and toughness of the hydrogel. Pb²⁺ adsorption capacity of the hydrogel increased with GO content, while the adsorption belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model, indicating the homogeneous nature of monolayer chemical adsorption of Pb²⁺. A relatively good reusability of the composite hydrogel beads for Pb²⁺ removal can be achieved.     

Functionalization of polyvinyl alcohol hydrogels with graphene oxide for potential dye removal

Because of highly frozen macromolecule chains, polyvinyl alcohol (PVA) hydrogels have never been used for dye removal. This work focuses on improving the adsorption capacity of the PVA hydrogel by using amphiphilic graphene oxide to improve its macromolecular chain mobility in crystal domain and introduce new functional groups. To evaluate its effectiveness, crystal structure, swelling kinetics, and model dye methylene blue (MB) adsorption of the as‐prepared PVA hybrid hydrogels were systematically investigated. The results indicate that the hybrid PVA hydrogels have lower crystallinity and less crystal stability, demonstrating the improved macromolecular chain mobility. Moreover, improved swelling ratios of PVA/GO hydrogels also illustrate the enhanced macromolecular chain mobility. MB adsorption experiment indicates that GO introduced can result in great improvement in MB adsorption. And the adsorption process follows the second‐order kinetic model and Morris–Weber model, which is determined by the intraparticle diffusion. Furthermore, MB adsorption isotherm follows Freundlich model and the adsorption is heterogeneous. Desorption studies indicate that the interaction between PVA hydrogels and MB consists of both physisorption and chemisorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39872.     

近红外光响应氧化石墨烯/微凝胶复合智能水凝胶

设计合成了一种包含氧化石墨烯（GO）片层、聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶球体和PNIPAM链段的复合结构水凝胶。通过控制聚合时间得到负载双键且粒径不同的PNIPAM微凝胶,将其作为交联点与N-异丙基丙烯酰胺（NIPAM）聚合,GO作为纳米填料掺入水凝胶体系,GO片层上的含氧基团与NIPAM上的胺基产生氢键物理交联。此方法制备的复合水凝胶同时具有温度敏感和近红外光敏感特性,通过改变GO浓度、微凝胶的合成时间、NIPAM浓度等条件,水凝胶的光敏感性和温度敏感性得到提升。相比于传统PNIPAM水凝胶,此种复合水凝胶能够对光响应,实现非接触式控制形变,且响应速率快、响应程度高,可应用于光控开关等领域。     

Application of graphene-based adsorbents in the treatment of dye-contaminated wastewater; kinetic and isotherm studies

The adsorption of methylene blue (MB) on graphene-based adsorbents was tested through the batch experimental method. Two types of graphene-based adsorbents as graphene oxide (GO) and reduced graphene oxide (RGO) were compared to investigate the best adsorbent for MB removal. So that optimizing the MB removal for the selected type of graphene-based adsorbent, the diverse experimental factors, as pH (2–10), contact time (0–1440 min), adsorbent dosage (0.5–2 g/L), and initial MB concentration (25–400 mg/L) were analyzed. The conclusions indicated that the MB removal rised with an increase in the initial concentration of the MB and so rises in the amount of adsorbent used and initial pH. Maximum dye removal was calculated as 99.11% at optimal conditions after 240 min. Adsorption data were compiled by the Langmuir isotherm (R²: 0.999) and pseudo-second-order kinetic models (R²: 0.999). The Langmuir isotherm model accepted that the homogeneous surface of the GO adsorbent covering with a single layer. And the adsorption energy was calculated as 9.38 kJ mol⁻¹ according to the D-R model indicating the chemical adsorption occurred. The results show that GO could be utilized for the treatment of dye-contaminated aqueous solutions effectively.     

Preparation and adsorption mechanism of polyvinyl alcohol/graphene oxide-sodium alginate nanocomposite hydrogel with high Pb(II) adsorption capacity

A series of polyvinyl alcohol (PVA)/graphene oxide (GO)-sodium alginate (SA) nanocomposite hydrogel beads were prepared through in situ crosslinking for Pb²⁺ removal. It was found that PVA and SA molecules were intercalated into GO layers through hydrogen bonding interactions, leading to the destruction of orderly structure of GO, while GO uniformly distributed in PVA matrix. With increasing PVA solution concentration, the hydrogel beads became more regular, a large number of polygonal pores with thin walls and open pores formed, the average pore size decreased, and the dense network structure formed. Meanwhile, the permeability of the composite hydrogel decreased, leading to the decline of Pb²⁺ adsorption capacity of the composite hydrogel. With increasing GO content, the ballability of the hydrogel beads was weakened, the pore size increased, and relatively loose network structure formed, resulting in an increase in permeability and Pb²⁺ adsorption capacity of the hydrogel, reaching up to 279.43 mg g⁻¹. Moreover, the composite hydrogel presented relatively good reusability for Pb²⁺ removal. The adsorption mechanism was explored and showed that the adsorption system of the composite hydrogel belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model for Pb²⁺ removal, which might be mono-layer chemical adsorption. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47318.     

基于PHMG的丙烯酰胺/琼脂双网络抗菌水凝胶

以琼脂（Agar）、丙烯酰胺（Am）、单宁酸（TA）、氧化石墨烯（GO）为主要原料制备双网络水凝胶辅料。通过TA将GO还原成rGO，以TA/rGO为微反应器与聚六亚甲基胍酸盐（PHMG）反应，将其固定于水凝胶骨架中，制备双网络抗菌水凝胶。对凝胶进行力学性能、热力学性能、抗菌性能等测试。结果表明，琼脂的加入使凝胶的断裂伸长率提高了60%，抗压强度提高，凝胶内部孔隙进一步缩小，力学性能得到提高；质量分数为2.0%PHMG水溶液浸泡后得到的抗菌水凝胶对大肠杆菌和金黄色葡萄球菌的抑菌率均达到99.80%以上；无抑菌圈形成，说明PHMG被固定于凝胶中；红细胞（RBC）溶血实验表明凝胶溶血率均低于5%，抗菌水凝胶有着良好的生物相容性。     

负载白芨多糖的PU/PAM双网络水凝胶的制备与性能

采用聚乙二醇、Ymer N120、聚丙二醇和异佛尔酮二异氰酸酯为原料,以三乙醇胺作交联剂合成聚氨酯(PU)预聚物,浸入白芨多糖(BSP)和丙烯酰胺(AM)混合溶液,通过自由基聚合制备了负载BSP的PU/PAM双网络水凝胶.采用FTIR、SEM对水凝胶的结构和形貌进行了表征,通过拉力试验机和生物实验对其力学性能和生物性能进行了测试.结果表明,当三乙醇胺用量为多元醇物质的量的60％时,双网络水凝胶具有高溶胀率(256％)的同时保持一定的拉伸强度(1.9 MPa)和高压缩强度(22.7 MPa).双网络水凝胶具有抗菌抗氧化作用,其中,双网络水凝胶对大肠杆菌和金黄色葡萄球菌的抑菌带宽度分别为0.5～4.0和0.5～3.5 mm,羟基自由基清除率最高为28％;溶血率低于5％,细胞存活率最高达101.3％±3.6％,表明双网络水凝胶具有良好的生物相容性.     

石墨烯水凝胶的制备及其吸附性能研究

通过改进的Hummers法制备氧化石墨烯(GO),利用乙二胺(EDA)作还原剂,制得三维网状结构石墨烯水凝胶.利用紫外分光光度计考察了其对Pb2+的吸附性能,结果表明:120 min左右达到吸附平衡,并且在吸附剂用量为18 m g、氯化铅溶液质量分数为80 m g/L时,吸附效果最好,并且其吸附行为更符合准二级吸附动力...     

金刚烷胺/氧化石墨烯复合材料的制备及其吸附性能

以氧化石墨烯和金刚烷为原料，通过水相合成法制备了金刚烷胺功能化氧化石墨烯复合材料A/GO，以FT-IR、XRD和XPS对A/GO进行了结构表征，并考察了A/GO对有机染料的吸附性能。结果表明，与氧化石墨烯相比，A/GO对甲基蓝（AB93）表现出高效吸附性，其吸附动力学和吸附等温模型分别符合拟二级动力学和Langmuir模型，理论最大吸附容量（qm）为1250.0 mg/g。热力学分析表明，A/GO吸附AB93是自发的放热过程。A/GO吸附AB93对盐（NaCl和KCl）表现出良好的耐盐性，而CaCl2能有效地促进A/GO吸附AB93。对于刚果红和AB93等的混合染料体系，A/GO能选择性吸附AB93。     

Poly (vinyl alcohol)/graphene oxide nanocomposite films and hydrogels prepared by gamma ray

ABSTRACT

Poly (vinyl alcohol)/graphene oxide (PVA/GO) gamma irradiated nanocomposite films and hydrogels were prepared. In composite films, GO was initially irradiated by gamma ray in order to improve interactions between GO and PVA. The film containing 1?wt-% GO was very strong where tensile modulus and tensile yield strength were 45 and 115% higher than those of pure PVA. In the second set of experiments PVA/GO hydrogels were made by irradiating PVA/GO suspensions by gamma ray at various doses. It was an interesting finding that GO increased the gel portion of hydrogels through contribution of H-bonds between PVA and GO. The hydrogels prepared at 20?kGy had remarkable water swelling ratio that reached as high as 20 at water temperature of 80°C. The hydrogel metal ion adsorption capability was tested on Cu²⁺ ions. It was shown that the GO contributed significantly to the adsorption capacity of PVA hydrogels.     

Graphene oxide–tripolyphosphate hybrid used as a potent sorbent for cationic dyes

Graphene oxide–tripolyphosphate material (GPM) was synthesized through an ethanolamine (EA) mediated graphene oxide (GO) self-assembly. The synthesis route to GPM is simple and benign. GPM was composed of GO nanosheets as building blocks and the tripolyphosphate as cross-linkers and chelators of cations in solutions. GPM showed higher potency for adsorption of cationic dyes than anionic dyes, and the adsorption process was through electrostatic and π–π interactions. Adsorption was spontaneous and exothermic, and the adsorption capacity of GPM for cationic dyes (>2540 mg g⁻¹) far exceeded those reported in literature for GO materials.     

The effect of ambient humidity on the electrical properties of graphene oxide films

ABSTRACT: We investigate the effect of water adsorption on the electrical properties of graphene oxide (GO) films using the DC measurement and AC complex impedance spectroscopy. GO suspension synthesized by a modified Hummer's method is deposited on Au interdigitated electrodes. The strong electrical interaction of water molecules with GO films was observed through electrical characterizations. The DC measurement results show that the electrical properties of GO films are humidity- and applied voltage amplitude dependent. The AC complex impedance spectroscopy method is used to analyze the mechanism of electrical interaction between water molecules and GO films in detail. At low humidity, GO films exhibits poor conductivity and can be seen as an insulator. However, at high humidity, the conductivity of GO films increases due to the enhancement of ion conduction. Our systematic research on this effect provides the fundamental supports for the development of graphene devices originated from solution-processed graphene oxide.     

制备方法对GO/P(NIPAM-MA)水凝胶La3+吸附性能的影响

用冷冻聚合法和非冷冻聚合法制备了氧化石墨烯/聚(N-异丙基丙烯酰胺-顺丁烯二酸)(GO/P(NIPAM-MA))水凝胶,比较制备方法对GO/P(NIPAM-MA)水凝胶La³⁺吸附能力的影响,发现通过冷冻聚合法合成的水凝胶,具有更加优异的溶胀-退溶胀性能和吸附性能。NIPAM与MA摩尔比为10∶1的冷冻聚合法水凝胶,在370 mg/L的LaCl₃溶液中平衡吸附量为(29.87±0.073)mg/g,而相同条件下的非冷冻聚合法水凝胶平衡吸附量仅为(20.29±0.395)mg/g。冷冻聚合法水凝胶的Freundlich等温线拟合参数n值随着MA含量的增加呈线性增加,而非冷冻聚合法水凝胶增加幅度小于冷冻聚合法。经过5次吸附-解吸循环,冷冻聚合法水凝胶的形状和体积没有明显变化且吸附能力没有明显下降,而非冷冻聚合法水凝胶经过3次吸附-解吸循环就出现破碎,无法再使用。冷冻聚合法合成的GO/P(NIPAM-MA)水凝胶具有La³⁺平衡吸附量大、可重复使用等优点。     

A green approach for the reduction of graphene oxide nanosheets using non-aromatic amino acids

A simple and green chemistry approach for the preparation of reduced graphene oxide nanosheets through the reduction of graphene oxide (GO) using non-aromatic and thiol-free amino acids as the reductant was successfully demonstrated. l-Aspartic acid and valine amino acids were used as models to prove that the reduction method is generic to other amino acids. The significance of the proposed method is that it eliminates the use of toxic and harmful chemicals to humans and the environment, which makes it compatible for the large-scale production of graphene. Reduced GO nanosheets showed good stability in aqueous dispersions due to the strong electrostatic repulsion on the graphene surface. Structural studies confirmed the deoxygenation of GO from the loss of hydroxyl, carbonyl and epoxy groups, and preparation of graphene sheets between 20 and 70 nm suitable for broad biomedical applications.     

Improvement in phase-change hybrid nanocomposites material based on polyethylene glycol/epoxy/graphene for thermal protection systems

Polyethylene glycol (PEG) is established as an organic solid–liquid phase-change material (PCM) offering a wide range of enthalpies and phase transition temperatures as a function of its molecular weight. PCMs are known for their high-energy absorbance; however, they also have two main drawbacks of leakage and enthalpy reduction during melting. In this work, polyethylene glycol as a phase-change material and graphene oxide (GO), expanded graphene (EG), and epoxy resin (EP) as shape stabilizing materials were used and designed based on experimental design—Taguchi method to find the composition with the least molten PEG leakage and the highest enthalpy of melting. Based on improvements made on main drawbacks, two samples were introduced, while their only difference was epoxy content. The results showed that the epoxy resin and graphene oxide caused a significant reduction in molten PEG leakage by hydrogen bonding and trapping of PEG between GO plates and the barrier effect. Also, the expanded graphene by heterogeneous nucleation of molten PEG in a cooling cycle caused a dramatic increment in crystallinity and enthalpy of melting. Among the achievements of this research is the attainment of hybrid nanocomposites samples without leakage (less than 5 wt%) and samples with enthalpy of melting more than that of pure polyethylene glycol (8%).

     

Superabsorbent,Breathable Graphene Oxide-Based Nanocomposite Hydrogel as a Dense Membrane for Use in Protective Clothing

This study examines the synthesis, fabrication and characterization of poly acrylamido methyl propane sulfonic acid (PAMPS)/graphene oxide (GO) nanocomposites. PAMPS-GO nanocomposite hydrogel was synthesized by radical initiated polymerization and its swelling properties, water vapor permeability (WVP), and stress-strain behavior were evaluated. The swelling behavior of hydrogel nanocomposites were improved at the presence of 0.2 wt% GO, as confirmed by water uptake experiments. It should be noted that as GO loading increased, so did the WVP of the hydrogel. The stress-strain test also revealed that the incorporation of just 0.1% of GO raised the tensile strength and young modulus of the hydrogels by 42% and 37% respectively. These fabricated dense membranes can have applications in protective clothing and wound dressing.     

聚羧酸减水剂/氧化石墨烯复合物的制备与性能

通过氧化石墨烯（GO）与聚羧酸系减水剂单体甲基丙烯酸聚乙二醇单甲醚（MAAPEGME）、甲基丙烯酸（MAA）及甲基丙烯磺酸盐（SMAS）进行自由基共聚反应制备了氧化石墨烯与聚丙烯酸系减水剂（PCs）单体的共聚物（GO-PCs）,旨在解决GO掺入水泥基材料时存在的分散不均匀及流动性降低的问题,制备GO-PCs时各组分的质量比为m（MAAPEGME）: m（MAA）: m（MAS）: m（GO）=17:2:1:0.2。检测结果表明GO与单体之间发生了共聚反应,GO纳米片层均匀的分布PCs中,达到了GO在水泥材料中分布均匀、不影响水泥流动性及增强增韧的目的,SEM形貌说明GO-PCs对水泥浆体的微观结构有较好的调控作用,研究结果对于制备高性能长寿命混凝土具有积极的意义。     

Highly soluble polyetheramine-functionalized graphene oxide and reduced graphene oxide both in aqueous and non-aqueous solvents

Among many methods to synthesize graphene, solution-based processing provides many advantages owing to its low cost, high productivity, chemical versatility, and scalability. In particular, graphene oxide (GO) is one of the most promising nanocarbons that enable the incorporation of graphene and related materials into bulk materials and nanocomposites. GO has hydrophilic nature that enables straightforward dispersion in aqueous solution by sonication, but GO show poor dispersibility in common organic solvents, which prevent much wider applications such as solution-mixing polymer nanocomposites. Here we prepared highly soluble, functionalized GO in both aqueous and non-aqueous solvents. This was achieved by reacting polyetheramine consisting of amphiphilic components, e.g., polypropylene oxide and polyethylene oxide, with carboxylic acid groups at GO edges. Moreover, the reduced GO (rGO) was also highly dispersible in aqueous solution as well as non-aqueous solutions. These functionalized GO and rGO can be used for many solution-processed graphene composites.