Fractional distribution of graphene oxide and its potential as an efficient and reusable solid catalyst for esterification reactions

Graphene oxide (GrO) prepared by the Hummers method was separated into three different fractions (GrO₅₀₀₀, GrO₂₀₀₀, and GrO_res) on the basis of their dispersion stability in the water. Infrared, nuclear magnetic resonance, X‐ray photoelectron spectroscopy, and elemental analyses revealed that GrO₅₀₀₀ possesses a high degree of oxygen functionalities including phenolic, carboxylic, and ?OSO₂H groups, compared with the other fractions. The GrO₅₀₀₀ was found to be a highly efficient and reusable solid catalyst for the esterification of various carboxylic acids with a variety of alcohols to furnish corresponding esters in high to excellent yields. The catalytic activity of the GrO₅₀₀₀ was attributed to the ability of highly polar GrO₅₀₀₀ scaffold to adsorb/attract reactants, where the acid functionalities of GrO₅₀₀₀ facilitated the esterification process efficiently. The chemical and structural features of GrO₅₀₀₀ were discussed to understand the improved catalytic activity compared with GrO₂₀₀₀ and conventional solid acid catalysts. Copyright © 2014 John Wiley & Sons, Ltd.     

碳纳米管制备蓝光石墨烯量子点及其在柔性有机存储器上的应用

通过化学裁剪法打开碳纳米管获得了粒径一致、性能稳定、具有蓝色荧光的石墨烯量子点。该方法属于化学溶液法，具有成本低廉、工艺简单、条件易控等优势。将该样品与半导体聚合物按一定比例混溶，通过旋涂技术形成基于石墨烯量子点掺杂的聚合物复合薄膜，进而制成柔性存储器。该柔性可弯曲存储器具有低驱动电压、接近10³的ON/OFF 比率、较好的循环次数，较好的重复性和稳定性。该研究结果为柔性有机存储器领域的研究展开了新的方向。     

Effect of addition of iron on morphology and catalytic activity of PdCu nanoalloy thin film as catalyst in Sonogashira coupling reaction

Palladium‐supported catalysts are complex assemblies with a challenging preparation. Minor changes in their preparation conditions can affect the activity, selectivity and lifetime of these catalysts. PdCuFe nanoparticle (NP) thin films were supported on reduced graphene oxide (RGO) by the reduction of the organometallic complex [PdCl_2‌(cod)] (cod = cis ,cis ‐1,5‐cyclooctadiene), and [Cu(acac)₂] and [Fe(acac)₃] (acac = acetylacetonate) complexes at a toluene–water interface. We have investigated the application of the liquid–liquid interface method for preparing ultrathin films of catalysts and have evaluated the catalytic activity of the prepared NPs for the Sonogashira coupling reaction in micelle media. Also, we have investigated the effect of the addition of iron on the morphology, size and catalytic activity of PdCu/RGO NPs. Our study shows that both of the prepared catalysts (PdCu/RGO and PdCuFe/RGO) are efficient and recoverable catalysts for the Sonogashira carbon–carbon coupling reaction. This method has advantages compared to other routes, such as short reaction times, high to excellent yields, facile and low‐cost method for the preparation of the catalysts, and easy separation and reusability of the catalysts.     

Synthesis and characterization of poly(2‐methacryloyloxyethyl phosphorylcholine) onto graphene oxide

The polyzwitterionic brushes comprised of poly(2‐methacryloyloxyethyl phosphorylcholine) (pMPC) segments, which are used for surface modification of polymers and biocompatible coatings, were investigated. In this work, reverse surface‐initiated atom transfer radical polymerization (RATRP) of zwitterionic 2‐methacryloyloxyethyl phosphorylcholine (MPC) is employed to tailor the functionality of graphene oxide (GeneO) in a well‐controlled manner and produce a series of well‐defined hemocompatible hybrids (termed as GeneO‐g‐pMPC). The complexes were characterized by FT‐IR, XRD, and Raman. Results show that MPC has been coordinated on the graphene oxide sheet. Thermal stability of the nanocomposites in comparison with the neat copolymer is revealed by thermogravimetric analysis and differential thermal analysis. Scanning electron microscopy and transmission electron microscope images of the nanoconposite displays pMPC chains were capable of existing on GeneO sheet by RATRP. The biocompatibility properties were measured by plasma recalcification profile tests, hemolysis test, and MTT assays, respectively. The results confirm that the pMPC grafting can substantially enhance the hemocompatibility of the GeneO particles, and the GeneO‐g‐pMPC hybrids can be used as biomaterials without causing any hemolysis. With the versatility of RATRP and the excellent hemocompatibility of zwitterionic polymer chains, the GeneO‐g‐pMPC nanoparticles with desirable blood properties can be readily tailored to cater to various biomedical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Injectable Graphene Oxide/Graphene Composite Supramolecular Hydrogel for Delivery of Anti-Cancer Drugs

Injectable hydrogels have attracted a lot of attention in drug delivery, however, their capacity to deliver water-insoluble or hydrophobic anti-cancer drugs is limited. Here, we developed injectable graphene oxide/graphene composite supramolecular hydrogels to deliver anti-cancer drugs. Pluronic F-127 was used to stabilize graphene oxide (GO) and reduced graphene oxide (RGO) in solution, which was mixed with α-cyclodextrin (α-CD) solution to form hydrogels. Native hydrogel was used as control. GO or RGO slightly shortened gelation time. The storage and loss moduli of the hydrogels were tracked by dynamic force measurement. The storage modulus of GO or RGO composite hydrogels was larger than that of the native hydrogel. Hydrogels were unstable in solution and eroded gradually. GO or RGO in Pluronic F-127 solution could potentially improve the solubility of the water-insoluble anti-cancer drug camptothecin (CPT), especially with large drug-loaded CPT amount. Drug release behaviors from solutions and hydrogels were characterized. The nanocomponents (GO or RGO) were able to bind more drug molecules either for CPT or for doxorubicin hydrochloride (DXR) in solution. Therefore, GO or RGO composite hydrogel could potentially enable better controlled and gentler drug release (for both CPT and DXR) than native hydrogel.     

Strong covalent bonding modulated graphene oxide/epoxy interfacial enhancement and advanced corrosion resistance

Abstract

Chemically functionalized graphene oxide [multi-amino functionalized graphene oxide (MAGO)] was achieved by building covalent bonds between graphene oxide (GO) and a small molecule containing benzene structure and multi-amino groups. Fourier transform infrared, X-ray diffraction, X-ray photo electron spectroscopy and TEM-EDX results certified that the molecule was successfully grafted onto GO nanosheets. Subsequently, functionalized GO was incorporated into waterborne epoxy (EP) coating through ball-milling method. This molecular design can significantly improve the dispersion of MAGO in EP matrix, as well as the compatibility and interaction between MAGO and EP. Compared with GO/EP, the water absorption of MAGO/EP decreased from 4.38 to 2.59%, the adhesion strength of MAGO/EP increased from 4.72 to 6.32?MPa after immersion of 40?days in 3.5% NaCl solution. Incorporation of 1?wt% of MAGO into EP matrix prominently improved the long-term corrosion resistance. The impedance modulus of GO/EP coating decreased by four orders after 40 days immersion, while that of MAGO/EP coating only decreased by one order. The impedance modulus was still 1.47?×?10⁸ Ω cm², and two-time constant wasn’t detected for MAGO/EP coating. This research developed a novel green anticorrosion coating with enhanced durability for metal protection.