The use of polyethyleneimine-modified reduced graphene oxide as a substrate for silver nanoparticles to produce a material with lower cytotoxicity and long-term antibacterial activity

In order to improve the stability and decrease the cytotoxicity of silver nanoparticle (AgNP), a polyethyleneimine-modified reduced graphene oxide (PEI-rGO) was used as the substrate of AgNPs, and a PEI-rGO–AgNP hybrid was prepared by anchoring the AgNPs on the reduced graphene oxide surface. Such a hybrid showed substantially higher antibacterial activity than polyvinyl pyrrolidone (PVP)-stabilized AgNP, and the AgNPs on PEI-rGO were more stable than the AgNPs on PVP, resulting in long-term antibacterial effects. The hybrid showed excellent water-solubility and lower cytotoxicity, suggesting the great potential application as a sprayable graphene-based antibacterial solution.     

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.     

The effects of graphene oxide on the properties and drug delivery of konjac glucomannan hydrogel

Konjac glucomannan (KGM) hydrogel has good potential application in food and medical science, although to achieve this, the physical and mechanical properties need further improvement. In this study, graphene oxide (GO) was used to improve the functionality of KGM hydrogel. KGM/GO hydrogels were prepared by freezing the alkaline KGM/GO sols. Rotational rheometer was used to study the rheological properties of different alkaline KGM/GO sols. Fourier transform infrared, Raman, differential scanning calorimetry, thermogravimetric analyses, and scanning electron microscopy were used to evaluate the structure and properties of the hydrogels. In addition, different pH solutions and an in vitro assay were used to study the swelling property and the release behavior of KGM/GO hydrogels, respectively. The result revealed strong hydrogen‐bond interaction between KGM and GO. The incorporation of GO highly improved the gel properties of KGM/GO sol, higher thermal stability, and more compact structure of KGM/GO hydrogels. KGM/GO hydrogels showed better swelling properties in deionized‐distilled water and pH 7.2 PBS. The release of 5‐aminosalicylic acid (5‐ASA) from KGM/GO (KG4) hydrogel was different in various pH media, but the initial burst release effect was very severe. Therefore, incorporation of GO have a good potential in enhancing the properties of KGM hydrogel, but KGM/GO hydrogel is not an ideal carrier for 5‐ASA release. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45327.     

Magnetic lamellar nanohydroxyapatite as a novel nanocarrier for controlled delivery of 5-fluorouracil

Magnetic nanoparticles are attractive carriers for drug delivery and layered materials intercalated by drug molecules exhibit improved safety and effectiveness of drug delivery. In this work, we report the loading of a model anticancer drug, 5-fluorouracil (5FU), into a magnetic layered nanohydroxyapatite (ML-HAP) by intercalation technique. The as-prepared ML-HAP nanoparticles with loaded 5FU were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and vibrating sample magnetometer. We find that, within a certain drug concentration, the drug molecules can be intercalated into the gallery of ML-HAP without breaking its lamellar structure. The drug loading capacity of ML-HAP is extremely large. The drug release profiles display pH-dependent behavior and the drug release mechanisms are a combination of drug diffusion and HAP dissolution. Furthermore, ML-HAP/5FU shows strong superparamagnetism and good biocompatibility. The ML-HAP can be an efficient platform for targeted anticancer drug delivery.     

Preparation and characterization of Sr-substituted hydroxyapatite/reduced graphene oxide 3D scaffold as drug carrier for alendronate sodium delivery

Due to the characteristics of bone metabolic microenvironment in the local area of osteoporotic bone defect, it is often difficult for ordinary bone repair materials to achieve satisfactory repair effect. In this study, a multifunctional Sr-substituted hydroxyapatite/reduced graphene oxide (Sr-HAp/RGO) 3D scaffold was fabricated by a one-step hydrothermal reduction method. Sr-HAp colloids with good dispersion stability were firstly prepared to prevent precipitation and aggregation during hydrothermal process. The Sr-HAp/RGO composite scaffold with porous structure has a high compressive strength due to the reinforcement of Sr-HAp nanoparticles. Alendronate sodium (ALN), a commonly used drug for the treatment of osteoporosis, can be effectively loaded on the Sr-HAp/RGO scaffold and released for a prolonged time. The as-prepared ALN-loaded Sr-HAp/RGO scaffold shows promising potential for osteoporotic bone defect repair.     

Tubular graphene nanoribbons with attached manganese oxide nanoparticles for use as electrodes in high-performance supercapacitors

Graphene nanoribbons (GNRs) with tubular shaped thin graphene layers were prepared by partially longitudinal unzipping of vapor-grown carbon nanofibers (VGCFs) using a simple solution-based oxidative process. The GNR sample has a similar layered structure to graphene oxide (GO), which could be readily dispersed in isopropyl alcohol to facilitate electrophoretic deposition (EPD). GO could be converted to graphene after heat treatment at 300 °C. The multilayer GNR electrode pillared with open-ended graphene tubes showed a higher capacitance than graphene flake and pristine VGCF electrodes, primarily due to the significantly increased surface area accessible to electrolyte ions. A GNR electrode with attached MnO₂ nanoparticles was prepared by EPD method in the presence of hydrated manganese nitrate. The specific capacitance of GNR electrode with attached MnO₂ could reach 266 F g⁻¹, much higher than that of GNR electrode (88 F g⁻¹) at a discharge current of 1 A g⁻¹. The hydrophilic MnO₂ nanoparticles attached to GNRs could act as a redox center and nanospacer to allow the storage of extra capacitance.     

The production of organogels using graphene oxide as the gelator for use in high-performance quasi-solid state dye-sensitized solar cells

We report the formation of organogels of 3-methoxypropionitrile (MPN) using graphene oxide (GO) as the gelator and the use of these gels as the quasi-solid state electrolyte of dye-sensitized solar cells (DSCs). GO–MPN gels are prepared by mechanically grinding or ultrasonicating GO in MPN. The GO sheets form 3-dimensional solid networks in the gels, which hold the MPN solvent. The GO loading can be as low as 2.5 wt.% for the gel formation. Gel electrolytes were prepared by dispersing I₂, 1-methyl-3-propylimidazolium iodide, guanidine thiocynate and 4-tert butyl pyridine into GO–MPN gels, and these were used for DSCs. The GO sheets can be fragmented into small pieces by ultrasonication, and smaller GO sheets can lead to a higher diffusion constant of the triiodide and a higher photovoltaic efficiency for the DSCs. DSCs with a GO–MPN gel electrolyte exhibit a photovoltaic efficiency of 6.70% under AM 1.5 G illumination (100 mW cm⁻²), quite close to that (7.18%) of the control liquid DSCs.     

石墨烯基疏水单体的制备及其防水乳液的应用

采用新癸酸缩水甘油酯（E10P）、甲基丙烯酸羟乙酯（HEMA）、异佛尔酮二异氰酸酯（IPDI）对氧化石墨烯（GO）进行接枝疏水烷基链,得到可水分散性的含碳碳双键的石墨烯基疏水单体（IHGOE）。在壳中引入IHGOE和丙烯酸酯类单体通过自由基聚合得到石墨烯改性的丙烯酸酯有机无机杂化核壳乳液。并通过FTIR、XPS、TG、SEM、粒径等测试对乳液进行了结构分析,并测试了乳液配方中IHGOE含量对涂膜的接触角、附着力、硬度、耐水煮、耐水性、耐酸碱性等性能的影响。结果表明,当乳液配方中IHGOE质量分数为20%时,涂膜的接触角达到最大,即为110.8°,比纯丙烯酸酯乳液涂膜接触角74.3°高出49.1%,显著提高了涂膜的防水性能。同时,涂膜附着力为0级,硬度为2H,耐水煮≥1h,耐水浸泡大于48h,耐丁酮擦拭（1kg）大于100次,耐5%NaOH水溶液浸泡大于24h,耐5%HCl水溶液浸泡大于24h。     

Synthesis of smart hydrogels by radiation polymerisation for use as slow drug delivery devices

This article deals with the modification of medicinally important psyllium polysaccharide with acrylamide through radiation crosslinked polymerisation for the design of double potential hydrogels meant for slow release of insulin. Here the double potential is due to the inherent blood sugar lowering ability of psyllium and release of insulin in controlled manner from the drug loaded hydrogels. Synthesis of hydrogels and their characterisation by scanning electron micrography (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and swelling studies have been discussed. The release dynamics of model drug insulin from the hydrogels has been studied for the evaluation of the release mechanism. The release of the drug from the hydrogels occurred through non‐Fickian diffusion mechanism.     

Structural,magnetic, and textural properties of iron oxide-reduced graphene oxide hybrids and their use for the electrochemical detection of chromium

Superparamagnetic Fe₃O₄ nanoparticles were anchored on reduced graphene oxide (RGO) nanosheets by co-precipitation of iron salts in the presence of different amounts of graphene oxide (GO). A pH dependent zeta potential and good aqueous dispersions were observed for the three hybrids of Fe₃O₄ and RGO. The structure, morphology and microstructure of the hybrids were examined by X-ray diffraction, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy. TEM images reveal lattice fringes (d₃₁₁ = 0.26 nm) of Fe₃O₄ nanoparticles with clear stacked layers of RGO nanosheets. The textural properties including the pore size distribution and loading of Fe₃O₄ nanoparticles to form Fe₃O₄–RGO hybrids have been controlled by changing the concentration of GO. An observed maximum (～10 nm) in pore size distribution for the sample with 0.25 mg ml^?1 of GO is different from that prepared using 1.0 mg ml^?1 GO. The superparamagnetic behavior is also lost in the latter and it exhibits a ferrimagnetic nature. The electrochemical behavior of the hybrids towards chromium ion was assessed and a novel electrode system using cyclic voltammetry for the preparation of an electrochemical sensor platform is proposed. The textural properties seem to influence the electrochemical and magnetic behavior of the hybrids.     

The use of rhodamine B-decorated graphene as a reinforcement in polyvinyl alcohol composites

Individually dispersed graphene colloid is prepared using cationic dye rhodamine B (RhB) as a non-covalent modifier. Characterizations by UV–vis, photoluminescence and Raman, the graphene-RhB interactions are shown to be cation-π and π-π. Subsequently, the obtained graphene is incorporated into polyvinyl alcohol (PVA) to fabricate PVA/graphene composites by simple solution casting. On addition of 1.0 wt% graphene, the tensile strength and tensile modulus are increased by 178% and 139%, respectively. Interestingly, the strain of the composites is greatly maintained, which is related to the uniqueness interfacial structure and morphology of the composites. This work provides a promising methodology to fabricate high performance graphene-based composites with superior strength and ductility by simultaneously combining the reinforcement of graphene sheets and the uniqueness interfacial structure.     

The use of nitrogen-doped graphene supporting Pt nanoparticles as a catalyst for methanol electrocatalytic oxidation

Nitrogen-doped graphene (N-G) was prepared by thermal annealing of graphene oxide in ammonia at different temperatures. The resultant N-G was used as a conductive support for Pt nanoparticles (Pt/N-G) and the electrocatalytic activity of the Pt/N-G catalysts towards methanol oxidation was examined. To investigate the microstructure and morphology of the synthesized catalysts, X-ray diffraction, scanning and transmission electron microscopy and X-ray photoelectron spectroscopy were used. The catalytic activity of the catalysts towards the oxidation of methanol was evaluated by cyclic voltammetry. Compared to a control catalyst of Pt loaded on undoped graphene, the Pt/N-G materials show higher electrochemical activity towards methanol oxidation. The excellent electrochemical performance of Pt/N-G is mainly attributed to the nitrogen doping and the uniform distribution of Pt particles on the doped graphene support. These results indicate that N-doped graphene has great potential as a high-performance catalyst support for fuel cell electrocatalysis.     

Platinum supported on reduced graphene oxide as a catalyst for hydrogenation of nitroarenes

Reduced graphene oxide (RGO)-supported platinum (Pt) catalyst was prepared by simple ethylene glycol (EG) reduction and used for hydrogenation of nitroarenes. Characterizations showed that EG as a reductant exhibited more advantages than the widely used hydrazine hydrate to fabricate monodispersed, small sized Pt nanoparticles on the surface of RGO. The yield of aniline over the Pt/RGO-_EG catalyst reached 70.2 mol-_AN/(mol-_Pt min) at 0 ^oC, which is 12.5 and 19.5 times higher than that of multi-walled carbon nanotube- and active carbon-supported Pt catalysts, respectively. When the reaction temperature was increased to 20 ^oC, the catalytic activity of Pt/RGO-_EG jumped to 1138.3 mol-_AN/(mol-_Pt min), and it was also extremely active for the hydrogenation of a series of nitroarenes. The unique catalytic activity of Pt/RGO-_EG is not only related to the well dispersed Pt clusters on the RGO sheets but also the well dispersion of Pt/RGO-_EG in the reaction mixture.     

Chemical and magnetic functionalization of graphene oxide as a route to enhance its biocompatibility

The novel approach for deposition of iron oxide nanoparticles with narrow size distribution supported on different sized graphene oxide was reported. Two different samples with different size distributions of graphene oxide (0.5 to 7 μm and 1 to 3 μm) were selectively prepared, and the influence of the flake size distribution on the mitochondrial activity of L929 with WST1 assay in vitro study was also evaluated. Little reduction of mitochondrial activity of the GO-Fe₃O₄ samples with broader size distribution (0.5 to 7 μm) was observed. The pristine GO samples (0.5 to 7 μm) in the highest concentrations reduced the mitochondrial activity significantly. For GO-Fe₃O₄ samples with narrower size distribution, the best biocompatibility was noticed at concentration 12.5 μg/mL. The highest reduction of cell viability was noted at a dose 100 μg/mL for GO (1 to 3 μm). It is worth noting that the chemical functionalization of GO and Fe₃O₄ is a way to enhance the biocompatibility and makes the system independent of the size distribution of graphene oxide.     

One pot preparation of reduced graphene oxide (RGO) or Au (Ag) nanoparticle-RGO hybrids using chitosan as a reducing and stabilizing agent and their use in methanol electrooxidation

An environment-friendly approach to synthesizing reduced graphene oxide (RGO) was developed by using chitosan (CS) as both a reducing and a stabilizing agent. Factors that affect the reduction of graphene oxide (GO), such as the ratio of CS/GO, pH and temperature, were explored to obtain optimum reaction conditions. The RGO was characterized with UV visible absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction spectroscopy, thermo-gravimetric analysis, and X-ray photoelectron spectroscopy and transmission electron microscopy. Analysis shows that CS macromolecules can efficiently reduce GO at a comparatively low temperature and their adsorption onto the RGO nanosheets allows a stable RGO aqueous dispersion to be formed. Since CS is a natural, nontoxic and biodegradable macromolecule, this approach provides a new green method for GO reduction that would facilitate the large scale production of RGO, which has great value for graphene applications. Moreover, CS can reduce GO and AgNO₃ (or HAuCl₄) in one pot to obtain Ag nanoparticle-RGO hybrids or Au nanoparticle-RGO hybrids that exhibit good electrochemical activity.     

One dose or two? The use of polymers in drug delivery

Controlled‐release delivery systems are designed to prolong the release of drugs within the body. They consist of drug molecules encapsulated within biodegradable polymers which degrade safely into small, non‐toxic fragments, resulting in the release of the drug. Because different polymers have different degradation times, the system can be tailored to achieve the desired release rate and this can be very useful in treatments where daily dosing is required, such as epilepsy. Despite this obvious advantage, there are problems with this type of delivery, including an increased risk of overdosing. This article examines the pros and cons of controlled‐release drug‐delivery systems. Copyright © 2007 Society of Chemical Industry     

The use of iron oxide as oxygen carrier in a chemical-looping reactor

Chemical-looping combustion (CLC) is a method for the combustion of fuel gas with inherent separation of carbon dioxide. This technique involves the use of two interconnected reactors, an air reactor and a fuel reactor. The oxygen demanded in the fuel combustion is supplied by a solid oxygen carrier, which circulates between both reactors. Fuel gas and air are never mixed and pure CO₂ can be obtained from the flue gas exit. This paper presents the results from the use of an iron-based oxygen-carrier in a continuously operating laboratory CLC unit, consisting of two interconnected fluidized beds. Natural gas or syngas was used as fuel, and the thermal power was between 100 and 300 W. Tests were performed at four temperatures: 1073, 1123, 1173 and 1223 K. The prototype was successfully operated for all tests and stable conditions were maintained during the combustion. The same particles were used during 60 h of hot fluidization conditions, whereof 40 h with combustion. The combustion efficiency of syngas was high, about 99% for all experimental conditions. However, in the combustion tests with natural gas, there was unconverted methane in the exit flue gases. Higher temperature and lower fuel flows increase the combustion efficiency, which ranged between 70% and 94% at 1123 K. No signs of agglomeration or mass loss were detected, and the crushing strength of the oxygen carrier particles did not change significantly. Complementary experiments in a batch fluidized bed were made to compare the reactivity of the oxygen carrier particles before and after the 40 h of operation, but the reactivity of the particles was not affected significantly.     

The use of graphite oxide to produce mesoporous carbon supporting Pt, Ru, or Pd nanoparticles

Mesoporous carbon having platinum, ruthenium or palladium nanoparticles on exfoliated graphene sheets were produced from graphite oxide (GO) and metal complexes. The Pt included carbon was made by heating of the intercalation compound including tetraammineplatinum (II) chloride monohydrate. Samples having Ru or Pd are producible by heating in nitrogen gas atmosphere using hexaammineruthenium (III) chloride or tetraamminepalladium (II) chloride monohydrate instead of Pt complex. The particle sizes of platinum, ruthenium, and palladium were, respectively, 1-3, 1-2, and 3-7 nm. The platinum- or palladium-containing sample showed catalytic activity for oxygen reduction.     

Design and characterization of PNVCL-based nanofibers and evaluation of their potential applications as scaffolds for surface drug delivery of hydrophobic drugs

In this work, nanofiber scaffolds for surface drug delivery applications were obtained by electrospinning poly(N-vinylcaprolactam) (PNVCL) and its blends with poly(ε-caprolactone) and poly(N-vinylcaprolactam)-b-poly(ε-caprolactone). The process parameters to obtain smooth and beadless PNVCL fibers were optimized. The average fibers diameter was less than 1 μm, and it was determined by scanning electron microscopy analyses. Their affinity toward water was evaluated by measuring the contact angle with water. The ketoprofen release behavior from the fibers was analyzed using independent and model-dependent approaches. The low values of the release exponent (n < 0.5) obtained for 20 and 42 °C, indicating a Fickian diffusion mechanism for all formulations. Dissolution efficiencies (DEs) revealed the effect of polymer composition, methodology used in the electrospinning process, and temperature on the release rate of ketoprofen. PNVCL/poly(N-vinylcaprolactam)-b-poly(ε-caprolactone)-based nanofibers showed greater ability to control the in vitro release of ketoprofen, in view of reduced kinetic constant and DE, making this material promising system for controlling release of hydrophobic drugs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48472.