Green fabrication of porous chitosan/graphene oxide composite xerogels for drug delivery

Porous chitosan (CS)/graphene oxide (GO) composite xerogels were prepared through a simple and “green” freeze‐drying method. Scanning electron microscopy, Fourier transform infrared spectrometry, powder X‐ray diffraction, and compressive strength measurements were performed to characterize the microstructures and mechanical properties of as‐prepared composite xerogels. The results show that the incorporation of GO resulted in an observable change in the porous structure and an obvious increase in the compressive strength. The abilities of the composite xerogels to absorb and slowly release an anticancer drug, doxorubicin hydrochloride (DOX), in particular, the influence of different GO contents, were investigated systematically. The porous CS/GO composite xerogels exhibited efficient DOX‐delivery ability, and both the adsorption and slow‐release abilities increased obviously with increasing GO content. Additionally, the best adsorption concentration of DOX was 0.2 mg/mL, and the cumulative release percentage of DOX from the xerogels at pH4 much higher than that at pH 7.4. Therefore, such porous CS/GO composite xerogels could be promising materials as postoperation implanting stents for the design of new anticancer drug‐release carriers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40006.     

聚丙烯酸/氧化石墨烯复合水凝胶制备及对亚甲基蓝吸附

以丙烯酸(AA)为原料,二丙烯酸酯(Pul DA)分散的氧化石墨烯(GO)纳米胶粒(GO-Pul DA)为增强剂,N,N'-亚甲基双丙烯酰胺(BIS)为交联剂,通过自由基共聚合制备了一系列结构均一的聚丙烯酸/氧化石墨烯复合水凝胶(PAA/GO-Pul DA)。考察了BIS质量浓度、GO质量浓度以及溶液pH值对复合水凝胶力学性能、吸水性和亚甲基蓝(MB)吸附量的影响。结果表明,当GO质量浓度从0.1 g/L增加至1.0 g/L时,复合水凝胶拉伸强度从5.0 k Pa增加至10.4 k Pa,断裂伸长率高于100%,当GO的质量浓度为0.3 g/L时,复合水凝胶的断裂伸长率最高为151%;复合水凝胶表现出pH敏感的高吸湿性,pH从3.0增加至6.8时,平衡溶胀比(SRe)变化可达386 g/g,pH=6.8时最大SRe高达490 g/g。当溶液pH值从3.0增加至11.0时,PAA/GO-Pul D对MB的平衡吸附量(qe)可增加1 400~1 500 mg/g,pH=11.0时最大的qe高达1 789 mg/g。复合水凝胶对MB的吸附行为符合准一级动力学模型。5次吸附-解吸附循环后,相对于首次吸附,PAA/GO-Pul D对MB的吸附能力仍保持高达60%,解吸附效率高于90%。     

Study on EDTA‐chelated copper adsorption by granular activated carbon

Equilibrium and kinetic experiments on uptake of single‐species copper, EDTA, and EDTA‐chelated copper by an H‐type granular activated carbon under various factors, such as pH, ionic strength and EDTA concentration were carried out in this study. Adsorption of copper ions was increased with an increase in solution pH when the solution contained single‐species or EDTA‐chelated copper ions. The solution pH increased significantly from its lower initial value, which resulted from the adsorption of hydrogen ions by the carbon. The efficiency for the single‐species metal ion removal was increased from 5 to 95% when the solution pH was increased from 2 to 7.5. EDTA‐chelated metal ion removal, however, was increased from 7 to 97% as the pH was increased from 1.5 to 7.5. EDTA adsorption percentages increased when the solution pH was increased and the initial concentration was decreased. Slightly higher EDTA‐chelated copper removal was observed when the ionic strength was higher and the ratio of EDTA to copper concentrations was 1:1. Kinetic experiments demonstrated that the copper adsorption occurred rapidly in the first hour. No further change in the removal was observed after 3 and 6 h for single‐species or EDTA‐chelated, respectively. The EDTA‐chelated copper adsorption kinetics was enhanced with an increase in EDTA concentration and a decrease in ionic strength. © 2000 Society of Chemical Industry     

Enhanced removal of nickel(II) ions from aqueous solutions by SDS-functionalized graphene oxide

In this paper, a one-pot and easy-to-handle method at room temperature without additional chemicals for the modification of graphene oxide (GO) with surfactant is found. Removal of nickel (II) ions from aqueous solutions by GO and surfactant (sodium dodecyl sulphate) modified graphene oxide (SDS-GO) was studied spectrophotometrically at room temperature as a function of time, initial concentration and pH. Adsorption capacity of the adsorbent was increased dramatically (from 20.19 to 55.16 mg/g found by Langmuir model) due to the functionalization of the surface by SDS. The driving force of the adsorption of Ni(II) ions is electrostatic attraction and Ni(II) ions adsorbed on the GO surface chemically besides ion exchange.     

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.     

Microwave assisted ultrafast synthesis of graphene oxide based magnetic nano composite for environmental remediation

We have successfully synthesized multi-layer graphene oxide and graphene oxide based magnetic nanocomposite (M/GO) by microwave-assisted modified Hummers’ method for removal of toxic lead (Pb²⁺) and cadmium (Cd²⁺) ions from aqueous solution. The X-ray diffraction spectra of synthesized graphene oxide and M/GO confirm increased interlayer spacing along c-axis. Raman spectra revealed the good quality of synthesized GO and M/GO. The wrinkles were seen in the SEM images of synthesized graphene oxide. The presence of conjugated double bond (CC) and carbonyl (CO) were confirmed by using the UV–Vis spectroscopic spectra. Brunauer–Emmett–Teller (BET) analysis showed high (126 m²/g) surface area M/GO composite which accounts for large number of active binding sites for the adsorption of heavy metal ions. The adsorption studies revealed that Pb²⁺ ions were efficiently adsorbed on GO sheets. Interestingly, M/GO showed better adsorption for cadmium ions.     

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。     

Functionalized graphene oxide/carboxymethyl chitosan composite aerogels with strong compressive strength for water purification

A new type of polydopamine functionalized graphene oxide/carboxymethyl chitosan (DGO/CMC) composite aerogels was synthesized via sol–gel once-forming self-assembly and lyophilization. Polydopamine (PDA) on the surface of GO nanosheets replaced those traditional crosslinking agents to connect CMC chains via hydrogen bonding for the establishment of 3D porous aerogels. With the increasing proportion of CMC, the microstructure of aerogels changed from small pores to large plate-bridge-like pores. In addition, their maximum compressive strengths were 6.767, 11.94, and 16.98 MPa under 90% compressions, respectively, which increased in accordance with CMC content. Furthermore, the adsorption system of the aerogels was simulated well by the pseudo second-order kinetic model and the Langmuir isotherm model, with maximum mass adsorption capacities of 170.3, 186.8, and 312.8 mg/g for Cu²⁺, Ni²⁺, and Pb²⁺ ions, respectively. These composite materials have potential applications for water purification because of their simple and efficient synthesis and excellent recyclability and reusability.     

Additive Manufacturing of Graphene–Hydroxyapatite Nanocomposite Structures

In this article, a powder‐bed class of additive manufacturing (AM) is incorporated into the manufacturing of graphene nanocomposite 3D structures. For AM of graphene‐based 3D structures, graphene oxide (GO)/hydroxyapatite (Hap) nanocomposite (GHN) was synthesized at different GO to Hap percentage (wt.%), including 0.2% and 0.4% to develop a printable powder. The synthesized powder was utilized in a powder‐bed AM system to fabricate 3D porous structures of GHN powder. It was shown that at layer thickness of 125 μm and core binder saturation level of 400%, the compressive mechanical strength of the samples with higher content of graphene was improved significantly.     

聚醚砜膜接枝氧化石墨烯改性膜吸附铅离子的研究

聚醚砜膜和氧化石墨烯都是良好的吸附材料,通过改性、接枝将二者组合,制备一种新型吸附材料聚醚砜膜接枝氧化石墨烯改性膜用于吸附Pb^2+。通过IR对膜进行了表征,考察了该膜对Pb^2+的吸附性能。研究了吸附时间、温度、溶液pH、溶液浓度、氧化石墨烯含量和氨基化剂量对吸附量的影响,检验了膜的重复使用性能。实验结果表明,在最佳吸附条件为温度55℃、pH=6.18、氧化石墨烯含量3.3%、3 mL氨基化试剂;膜重复使用4次后吸附量仍能达到初次吸附量的72.75%,表明聚醚砜膜接枝改性氧化石墨烯氨基羧酸是一种优良的吸附材料。     

Polymer brushes on graphene oxide for efficient adsorption of heavy metal ions from water

The pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface-initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g⁻¹ for Pb(II), 258.6 mg g⁻¹ for Ag(I), 192.2 mg g⁻¹ for Cu(II), and 167.9 mg g⁻¹ for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer brushes in water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48156.     

纳米二氧化硅/氧化石墨烯复合物对普通硅酸盐水泥力学性能的影响

氧化石墨烯(GO)在水泥中的分散性较差,限制了其提高水泥基复合材料性能。采用溶胶-凝胶法制备了纳米二氧化硅/氧化石墨烯复合物(GOS),在模拟的水泥孔隙溶液中对比了GO和GOS的分散稳定性;同时,制备了添加纳米片的水泥浆体,研究了GO和GOS对其力学性能的影响。结果表明:GOS在水泥环境中的分散稳定性明显优于GO;与对照组相比,GO/水泥基复合材料的28 d抗折和抗压强度分别提高了20.48%和13.14%,而GOS/水泥基复合材料分别提高了35.42%和23.90%。微观分析表明,GO/水泥基复合材料内部形成花状水化晶体,GOS/水泥基复合材料内部的水化晶体彼此交联,结构致密,降低了水泥脆性,提高了韧性。     

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.     

Application of graphene oxide sheets incorporated in the porous calcium alginate films on the glassy carbon electrode for biosensor construction based on myoglobin

In this work, graphene oxide (GO) sheets were assembled within the porous calcium alginate (CA) films, and applied to fabricate electroactive biosensor by incorporating with myoglobin (Mb). The porous Mb–GO–CA films were fabricated and characterized by scanning electron microscopy (SEM), UV–Vis adsorption, and electrochemistry techniques. UV–Vis spectrum demonstrated that Mb retained its secondary structure in the porous Mb–GO–CA films at medium pH. Cyclic voltammetry of the porous Mb–GO–CA films showed a pair of well-defined and nearly reversible peaks for MbFe(III)/Fe(II) redox couple at ?0.350 V versus saturated calomel electrode in pH 7.0 buffers. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k _s) and formal potential (E ^ο′) were estimated by fitting the data of square-wave voltammetry with nonlinear regression analysis. The porous Mb–GO–CA films exhibited excellent electrocatalytic reduction to sodium nitrite, oxygen, and hydrogen peroxide, and showed good reproducibility and stability, which may provide a promising platform for the fabrication of the third-generation biosensor.     

Direct ink writing of porous SiC ceramics with geopolymer as binder

We herein report a novel strategy for direct ink writing of porous SiC parts by using geopolymers (GP) as binders and sintering SiC/GP composites at high temperatures via carbothermal reduction. The effects of treatment temperatures on the microstructure, pore size distribution and compressive strength of SiC/GP composites were systematically investigated. The total porosity of porous SiC carriers was as high as 76.4 vol% after being sintered at 1800 °C and exhibited a much broader pore size distribution (pore volumes) between 39 nm and 13.951 µm (~1.68 mL/g) accompanied by an interconnected hierarchical porous structure. After loading lamellar graphene oxide into the porous SiC carrier to form GO/SiC adsorbents, they exhibited fast and near-unity removal of methylene blue, and the adsorption efficiency still exceeded 82.0% after multiple times usage. These results prove that it is possible to remove hazardous materials from wastewater using reusable porous SiC ceramics as reusable adsorbent carriers.     

Fire retardant cellulose aerogel with improved strength and hydrophobic surface by one-pot method

Bio-based materials with multifunctional performance are getting immense attention nowadays for their environment friendly and renewable character. Inspired by toughening effect of graphene nanosheets and borate chemistry, a simple in-situ borate crosslinking in water and freeze-drying method was employed to fabricate a fire retarded bio-based aerogel. The structure of the material was evaluated and analysis by SEM, XRD, FTIR, Raman and XPS. Importantly, the bio-based aerogel has improved strength and adsorption properties due to unique structure. The compressive strength of rGO(reduced graphene oxide) + CMC (carboxymethyl cellulose) aerogel could reach 128 ± 2.1 kPa which is five times that of neat CMC aerogel. The bio-based aerogel can load more than 2500 times of self-weight. The adsorption capacity for organic solvents and oil of rGO+CMC aerogel is also greatly improved by a little rGO (1%) introducing due to its unique porous structure and hydrophobic nature of rGO. Additionally, rGO+CMC aerogel is also found fire resistant with relatively low thermal conductivity due to the borate and GO introduction.     

Graphene oxide/polybenzimidazole composites fabricated by a solvent-exchange method

Homogenous organic dispersion of graphene oxide (GO) sheets was prepared by a solvent-exchange method. This method enabled the simultaneous achievement of full exfoliation and high concentration of GO in several organic solvents such as dimethyl sulfoxide, which would facilitate the fabrication of individual graphene reinforced polymer composites through a solution-based process. To this end, poly [2,2′-(p-oxydiphenylene)-5,5′-bibenzimidazole] (OPBI)/GO composites were fabricated. X-ray diffraction characterization showed that the GO sheets were individually incorporated into the OPBI matrix. Scanning electron microscope images that taken of the fracture surface of the composites revealed that the GO sheets were spontaneous aligned parallel to the surface of the composite films as the content of GO exceeded 0.3 wt.%. The incorporation of GO also showed profound effects on the macroscopic properties of OPBI. Compared to pure OPBI, the composites showed a 17% increase in Young’s modulus, 33% increase in tensile strength and 88% improvement in toughness by the addition of only 0.3 wt.% of GO. Moreover, although the thermal stability of GO is far inferior to OPBI, it is found the thermal stability of OPBI is still improved by the addition of GO.     

Graphene oxide-containing isocyanate-based polyimide foams: Enhanced thermal stability and flame retardancy

Isocyanate-based graphene oxide-containing polyimide foams were synthesized by a semi-prepolymer method. In this method, while the first solution containing pre-polymer was derived from pyromellitic dianhydride and excess polymethylene polyphenylene isocyanate (PM200), the second solution contains dianhydride derivatives, water, catalysts, surfactants, and graphene oxide. PIFs were prepared with 0%, 0.25%, 0.50%, 0.75%, and 1% graphene oxide by weight, respectively. PIFs exhibited a minimum side reaction and urea generation was not seen for all PIFs instead of imide bonding. The addition of graphene oxide (GO) leads to a more close-packed structure. Therefore, crosslinking density and thermal stability of graphene oxide-containing polyimide foams increased. Upon the addition of 1% GO, almost seven times higher compression strength was obtained compared to neat PIFs. Also, LOI values supported the theory that thermally stable and flame retardant PIFs can be synthesized via the isocyanate-based process with GO.     

聚羧酸原位改性氧化石墨烯减水剂的制备及对混凝土性能的影响

通过异戊烯醇聚氧乙烯醚（IPEG）对氧化石墨烯（GO）进行原位酯化改性,合成了氧化石墨烯-异戊烯醇聚氧乙烯醚中间体（GO-IPEG）,与丙烯酸通过自由基共聚合反应制备了聚羧酸原位改性氧化石墨烯减水剂GO-PCE。利用FTIR、Raman、UV-Vis及Zeta电位分别对GO-IPEG和GO-PCE结构进行了表征。红外结果表明,IPEG接枝到GO表面,而后GO-IPEG与丙烯酸发生原位接枝聚合反应。UV-Vis及Zeta电位结果表明,GO-PCE依靠IPEG的空间位阻作用使GO在基体中具有较优的分散效果。水泥及混凝土性能结果显示,当GO-PCE折固掺量为0.15%（以水泥质量为基准）时,即可达到饱和吸附,水泥净浆流动度高达280 mm,混凝土28 d抗压强度为57 MPa、28 d收缩率为190×10-6、28 d电通量为1950 C。     

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.