Electrospun PEO/rGO Scaffolds: The Influence of the Concentration of rGO on Overall Properties and Cytotoxicity

Reduced graphene oxide (rGO) is one of the graphene derivatives that can be employed to engineer bioactive and/or electroactive scaffolds. However, the influence of its low and especially high concentrations on scaffolds’ overall properties and cytotoxicity has yet to be explored. In this study, polyethylene oxide (PEO)-based scaffolds containing from 0.1 to 20 wt% rGO were obtained by electrospinning. Morphological, thermal and electrical properties of the scaffolds were characterized by SEM, Raman spectroscopy, XRD, DSC and electrical measurements. The diameter of the fibers decreased from 0.52 to 0.19 µm as the concentration of rGO increased from 0.1 wt% to 20 wt%. The presence of rGO above the percolation threshold (5.7 wt%) resulted in a significantly reduced electrical resistivity of the scaffolds. XRD and Raman analysis revealed delamination of the graphene layers (interlayer spacing increased from 0.36 nm to 0.40–0.41 nm), and exfoliation of rGO was detected for the samples with an rGO concentration lower than 1 wt%. In addition, an evident trend of increasing cell viability as a function of the rGO concentration was evidenced. The obtained results can serve as further guidance for the judicious selection of the rGO content incorporated into the PEO matrix for constructing electroactive scaffolds.     

Thiourea assisted one-pot easy synthesis of CdS/rGO composite by the wet chemical method: Structural,optical, and photocatalytic properties

We report on the synthesis of CdS/reduced graphene oxide (rGO) composite by a wet chemical method. Thiourea was used both as a sulfur source and as a reducing agent to convert graphene oxide to rGO. The structural and morphological confirmation for the reduction of graphene oxide and the formation of the CdS/rGO composite was demonstrated by X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. Photoluminescence spectra of the composite exhibited a more efficient luminescence quenching in comparison with pure CdS nanoparticles. The composite demonstrated 99% photodegradation of methyl orange under UV irradiation, which is much superior than the photodegradation of methyl orange under similar conditions exhibited by CdS nanoparticles (72%).     

Fabrication of ZrO2/rGO nanocomposites by flash sintering under AC electric fields

Ceramic matrix nanocomposites containing graphene possess superior mechanical properties. However, these nanocomposites are very difficult to be prepared using the conventional methods due to severe grain growth and simultaneous degradation of the graphene at high sintering temperatures and long dwell time. Herein, the dense ZrO₂/rGO (reduced graphene oxide) nanocomposites are successfully fabricated by flash sintering of the green compacts consisting of ZrO₂ nanoparticles and graphene oxide (GO) at 893–951℃ in merely 5 seconds under the alternating current (AC) electric fields of 130–150 V cm⁻¹. The GO can be in situ thermal reduced during the flash sintering. The as-prepared ZrO₂/rGO nanocomposites exhibit excellent mechanical properties. This study presents a green and simple approach to fabricate the dense ceramic matrix nanocomposites reinforced with graphene at low temperatures in a short time.     

Influence of reduced graphene oxide (rGO) on phase development and porosity of SiOC/rGO ceramic composites

Ceramic materials based on silicon oxycarbide (SiOC) and reduced graphene oxide (rGO) were produced by polymer pyrolysis and evaluated in terms of phase development and porosity. Carbonaceous phase, initially prepared from graphite oxide, was incorporated into silicone dihydroxy terminated in different amounts (0, 5, 15 and 25 wt%) and submitted to pyrolysis at 1500 °C to obtain SiOC/rGO ceramics. Higher ceramic yields and more thermally stable materials were obtained after rGO addition, whose results were associated to the chemical interaction degree between rGO and polymer structure. C_graphite and SiC phases were generated in rGO-containing ceramics and a mixture of α- and β-SiC was achieved from 15 wt% rGO, enhancing their crystallinity with increasing of rGO content. Porosity features were influenced by the carbonaceous phase amount and different rGO-polymer interaction degrees. SiOC/rGO ceramics demonstrated desirable structural characteristics for future investigations in electrical and/or electrochemical applications.     

The production of rGO/ RuO2 aerogel supercapacitor and analysis of its electrochemical performances

In this study, ruthenium was bonded to the reduced graphene oxide in an ultrasonic bath. The aerogel of the mixture was produced at −78 °C. Structural characterization of aerogels was done with XRD and FTIR, surface characterization was performed with STEM, and elemental analysis was conducted by EDX analysis. The produced aerogel composites were transformed into electrodes on conductive Nickel foam. IviumStat, a potentiostat/galvanostat device, was used for the electrochemical characterization of the symmetrical supercapacitors. According to CV voltammograms, rGO/RuO₂ aerogels' highest specific capacitance was calculated as 328.6 F g⁻¹ at a potential scan rate of 5 mV s⁻¹. The assembled rGO/RuO₂ aerogel-based supercapacitor cell offered a high energy density value of 31.1 W h kg⁻¹ even at the power density of 8.365 kW kg⁻¹; this is comparable to that of lead-acid and nickel-metal hybrid batteries.     

One-step electrosynthesis of MnO2/rGO nanocomposite and its enhanced electrochemical performance

We present a facile one-step electrochemical approach to generate MnO₂/rGO nanocomposite from a mixture of Mn₃O₄ and graphene oxide (GO). The electrochemical conversion of Mn₃O₄ into MnO₂ through potential cycling is expedited in the presence of GO while the GO is reduced into reduced graphene oxide (rGO). The MnO₂ nanoparticles are evenly distributed on the rGO nanosheets and act as the spacer to prevent rGO nanosheets from restacking. This unique structure provides high electroactive surface area (1173?m² g^?1) that improves ions diffusion within the MnO₂/rGO structure. As a result, the MnO₂/rGO nanocomposite exhibits high specific capacitance of 473?F?g^?1 at 0.25?A?g^?1, which is remarkably higher (3 times) than the Mn₃O₄/GO prior conversion. In addition, the electrosynthesized nanocomposite shows higher conductivity and excellent potential cycling stability of 95% at 2000 cycles.     

Enhanced through-plane thermal conductive properties of Ag/rGO nanocomposite

High thermal conductivity of nanocomposite-based polymer matrix is one of the most important keys in developing many heat exchanger instruments. Here, we report a novel nanocomposite system based on silver-coated reduced graphene oxide (Ag/rGO) in silane cross-linked low-density polyethylene (XLPE) matrix with unprecedented through-plane thermal conductivity. Compared to the virgin rGO, Ag/rGO nanocomposite showed 67% higher thermal conductivity due to the Ag nanoparticles (NPs) decoration. The Ag NPs within the nanocomposites are believed to act as a thermal conductor among rGO nanosheets and eventually enhance the heat conduction in 3D manner.     

Electrochemical performance of polydopamine modified PANI/rGO composites: Dependency on preparation sequence

Compounding polyaniline (PANI) and reduced graphite oxide (rGO) is a fascinating cost-effective way to combine the high energy density of faradic material and high power density of carbonaceous material. In this study, in-situ polymerization of dopamine was used to reduce graphite oxide and to modify the rGO product with polydopamine (PDA) simultaneously. This modification prevented restacking of rGO, and enhanced the interactions between PANI and rGO. The partial reduction of GO during the polymerization of dopamine was proven by X-ray diffraction, Fourier transform infrared attenuated total reflectance, and UV–vis spectroscopy. Surprisingly, the electrochemical performance of the composites depends strongly on the preparation sequence. PANI/(rGO-PDA) composites obtained by the synthesis of PANI in the presence of rGO-PDA show better electrochemical performance than (PANI/rGO)-PDA composites, which were produced by polymerizing dopamine in the presence of PANI/GO composite. At a given scan rate of 20 mV s⁻¹, the highest specific capacity of PANI/(rGO-PDA) composites was 230.7 F g⁻¹, which was higher than those of all (PANI/rGO)-PDA composites. This phenomenon is tightly related to the differences in morphologies, conductivities and specific surface areas of the two types of composites.     

Photovoltaic and UV detector applications of ZnS/rGO nanocomposites synthesized by a green method

The effect of graphene concentration on the photovoltaic and UV detector applications of ZnS/graphene nanocomposites was investigated. The nanocomposites were synthesized by a green, cost-effective, and simple co-precipitation method with different graphene concentrations (5, 10, and 15 wt%) using L-cysteine amino acid as a surfactant and graphene oxide (GO) powder as a graphene source. Transmission electron microscopy (TEM) images showed that the ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in ZnS diameter size. The results of X-ray diffraction (XRD) patterns, Raman, and Fourier transform infrared (FTIR) spectroscopy indicated that the GO sheets were changed into reduced graphene oxide (rGO) during synthesis process. Therefore, L-cysteine amino acid played its role as a reducing agent to reduce the GO. Photovoltaic measurements showed that the graphene caused to increase the efficiency of solar-cell application of ZnS/rGO nanocomposites. In addition, our observation showed that the nanocomposites were suitable as ultraviolet (UV) detectors and graphene concentration increased the responsibility of the detectors.     

Synthesis of rGO/nanoclay/PVK nanocomposites,electrochemical performances of supercapacitors

ABSTRACT

In this study, graphene oxide (GO) was chemically reacted with sodium borohydride (NaBH₄) to form reduced graphene oxide (rGO). rGO, Montmorillonite nanoclay, and polyvinylcarbazole (PVK) were used to form a ternary nanocomposite via chemical reaction. These nanocomposite qualities were described via scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy-attenuated transmission reflectance (FTIR-ATR). In addition, these materials were used in supercapacitor device as an active material to test electrochemical performances via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The rGO/nanoclay/PVK nanocomposite shows significantly improved specific capacitance (C_sp = 168.64 Fg^?1) compared to that of rGO (C_sp = 63.26 Fg^?1) at the scan rate of 10 mVs^?1 by CV method. The enhanced capacitance results in high power density (P = 5522.6 Wkg^?1) and energy density (E = 28.84 Whkg^?1) capabilities of the rGO/nanoclay/PVK nanocomposite material. The addition of nanoclay and PVK increased the specific capacitance of rGO material due to a dopant effect for supercapacitor studies. Ragone plots were drawn to observe energy and power density of supercapacitor devices. The C_sp of rGO/nanoclay/PVK nanocomposite has only 86.4% of initial capacitance for charge/discharge performances obtained by CV method for 5000 cycles.     

Effect of annealing temperature and graphene concentrations on photovoltaic and NIR-detector applications of PbS/rGO nanocomposites

The effect of annealing temperature on photovoltaic and near-infrared (NIR) detector applications of PbS nanoparticles (NPs) and PbS/graphene nanocomposites was investigated. The products were synthesized by a simple co-precipitation method and graphene oxide (GO) sheets were used as graphene source. Several characterization techniques were used to show transfer of the GO into reduced graphene oxide (rGO) during the synthesis process. In addition, the effect of graphene concentrations on morphology, structure, photovoltaic, and detector parameters of the samples were studied. Transmission electron microscope (TEM) images showed that, the PbS NPs were agglomerated, while, the PbS/rGO nanocomposites were dispersed completely after annealing under H₂/Ar gas atmosphere. UV–visible spectrometer showed an absorption peak for all samples in the near infrared red (NIR) region of the electromagnetic spectrum. The results indicated that, photocurrent intensity, responsivity of the samples to an NIR source, and solar-cell efficiency were affected by annealing of samples and graphene concentrations.     

UV-assisted sonochemical synthesis and optoelectrical properties of Bi2S3/rGO nanocomposites

In the present study, a simple UV-assisted sonication method is used for the development of bismuth sulfide (Bi₂S₃) nanostructures on graphene sheets. X-ray diffraction (XRD) and Raman results indicated that graphene oxide (GO) layers are reduced. Field emission scanning electron microscopy (FESEM) images also indicated that Bi₂S₃ particles without rGO sheets are agglomerated. In comparison, when adding these sheets, the particles are uniformly spread (decorated) and their size is reduced significantly due to the incorporation of rGO sheets. UV–Vis studies reveal that the band gap in Bi₂S₃/rGO nanocomposites compared with Bi₂S₃ has a shift toward shorter wavelengths, suggesting some changes in the electronic band structure of Bi₂S₃ due to the existence of rGO sheets. Photoluminescence (PL) analysis indicated emission bands in infrared and visible regions resulting from the band edge emission and crystal defects in the samples, respectively. The electrical investigations showed reduced recombination of photogenerated carriers in the nanocomposites. Moreover, the results indicated that the concentration of rGO is an important factor in determining the optoelectrical behavior of these devices.     

CoO/rGO composite prepared by a facile direct-flame approach for high-power supercapacitors

In this study, CoO nanoparticles (NPs) measuring approximately 20?nm in size are successfully grown on reduced graphene oxide (rGO) layers through a facile direct-flame approach. The obtained CoO/rGO nanocomposites are applied as electrode materials and show a high specific capacitance, reaching 1615.0?F?g^?1 at a current of 1?A?g^?1 (737.5?F?g^?1 at 50?A?g^?1), and good cycling stability (88.12% retention after more than 15,000 cycles at 5?A?g^?1), which are outstanding characteristics compared with those of recently reported pseudosupercapacitors. Furthermore, an asymmetric supercapacitor (ASC) produced using CoO/rGO as a positive electrode material and activated graphene (AG) as a negative electrode achieves a high cell voltage of 1.6?V and delivers a maximum energy density of 62.46?Wh?kg^?1 at a power density of 1600?W?kg^?1. The fabrication technique is facile and represents a promising means of obtaining metal oxide/graphene composites for high-performance supercapacitors.     

BiVO4/rGO复合物的制备及其 光催化还原CO2研究

采用水热法制备了颗粒状单斜相钒酸铋（BiVO4）/还原氧化石墨烯（rGO）复合催化剂。采用傅里叶红外光谱、拉曼光谱、X射线衍射和紫外-可见漫反射光谱对合成的复合材料做了表征。采用透射电镜、扫描电镜和氮吸附脱附实验对复合材料的表面形貌和表面积做了分析测试。实验结果表明,BiVO4复合物能选择性将CO2还原成甲醇,石墨烯的引入能很好地改善BiVO4光催化还原CO2的性能。当石墨烯的加入量为3%（质量分数）时,在氙灯功率为600 W的条件下,光照6 h后,BiVO4/rGO复合材料光催化还原CO2生成的甲醇产量达到513.1 μmol/L,比相同形貌的纯BiVO4的甲醇产量高73.6%。     

新型还原氧化石墨烯/氮化碳复合纳滤膜制备及其性能

高性能石墨烯基复合膜的制备是目前国际研究热点,但是石墨烯基纳滤膜在脱盐中水通量较低,限制其在脱盐中的应用。采用聚多巴胺(PDA)改性聚砜(PSF)膜为基膜,将还原氧化石墨烯(rGO)和超薄氮化碳(uCN)纳米片通过真空抽滤法在基膜表面自组装制备新型还原氧化石墨烯/氮化碳复合纳滤膜。通过场发射扫描电子显微镜、透射电子显微镜、X 射线衍射仪、傅里叶变换红外光谱仪和X射线光电子能谱仪等研究uCN添加对膜结构和形貌的影响,并考察不同uCN添加比例、rGO用量及压力复合纳滤膜性能变化规律。结果显示当在100 mg·L^-1的rGO中添加uCN为20 mg·L^-1时所制备的rGO/uCN复合纳滤膜不仅保持良好盐离子截留率(对Na₂SO₄截留率85.86%,对NaCl截留率30.17%),且水渗透系数是rGO膜的2.15倍(88.50 L·m^-2·h^-1·MPa^-1)。     

中空硫球-MoS2/rGO材料的制备及其在锂硫电池中的应用

锂硫电池凭借高理论能量密度和高理论比容量的优势成为极具发展前景的储能设备。然而,单质硫和硫化锂的绝缘性、放电过程中产生的体积膨胀及多硫化物溶解导致的“穿梭效应”等问题,限制其商业化发展。为解决上述问题,采用低温液相法合成中空硫球（HS）,通过水热法制备纳米花状MoS₂/还原氧化石墨烯（MoS₂/rGO）,随后将MoS₂/rGO包覆在HS表面获得HS-MoS₂/rGO复合正极材料。利用XRD、SEM、TEM、XPS等对该材料的晶体结构、形貌等性质进行表征,采用循环伏安法、交流阻抗法以及恒流充放电对复合正极进行电化学测试。研究表明,MoS₂/rGO对多硫化物具有强吸附能力和高催化活性,能够有效限制多硫化物的穿梭;同时硫球的中空结构能够缓解体积膨胀,保持正极结构稳定。HS-MoS₂/rGO正极展现出优异的倍率性能和循环稳定性。     

中空硫球-MoS2/rGO材料的制备及其在锂硫电池中的应用

锂硫电池凭借高理论能量密度和高理论比容量的优势成为极具发展前景的储能设备。然而,单质硫和硫化锂的绝缘性、放电过程中产生的体积膨胀及多硫化物溶解导致的“穿梭效应”等问题,限制其商业化发展。为解决上述问题,采用低温液相法合成中空硫球（HS）,通过水热法制备纳米花状MoS₂/还原氧化石墨烯（MoS₂/rGO）,随后将MoS₂/rGO包覆在HS表面获得HS-MoS₂/rGO复合正极材料。利用XRD、SEM、TEM、XPS等对该材料的晶体结构、形貌等性质进行表征,采用循环伏安法、交流阻抗法以及恒流充放电对复合正极进行电化学测试。研究表明,MoS₂/rGO对多硫化物具有强吸附能力和高催化活性,能够有效限制多硫化物的穿梭;同时硫球的中空结构能够缓解体积膨胀,保持正极结构稳定。HS-MoS₂/rGO正极展现出优异的倍率性能和循环稳定性。     

纳米二氧化钛/石墨烯改性水性聚氨酯抗菌涂料的制备与评价

通过简单高效的方法制备纳米二氧化钛 /还原氧化石墨烯（ TiO₂/rGO）复合材料,对复合材料进行红外光谱（ FT-IR）、扫描电镜（ SEM）以及 X射线衍射（XRD）表征,结果表明：成功制备了氧化石墨烯、锐钛型纳米 TiO₂,并将纳米 TiO₂均匀负载于氧化石墨烯片层,经水热还原得到 TiO₂/rGO复合材料。将制备的 TiO₂/rGO复合材料添加到水性聚氨酯涂料中,制备涂膜并测定其光催化降解能力,结果表明：纳米 TiO₂/rGO填料复合的聚氨酯涂膜具有较高的光催化能力。依据 HG/T 3950—2007标准测定涂膜抗菌性能,结果表明：水性聚氨酯涂料的抗菌能力达到国家 Ⅰ级标准,可以有效替代有机抗菌剂。该环保复合涂料在物理性质和应用性能上均符合化工行业标准要求。     

Construction of biocompatible bilayered light-driven actuator composed of rGO/PNIPAM and PEGDA hydrogel

To construct an actuator with biocompatibility and potential use in biomedicine field, a light-driven actuator composed of reduced graphene oxide (rGO)/poly (N-isopropyl acrylamide) (PNIPAM) and poly (ethylene glycol) diacrylate (PEGDA) hydrogel is constructed. First, rGO/PNIPAM hydrogel is prepared by free radical polymerization and l -ascorbic acid reduction, of which the surface temperature increases quickly under near-infrared (NIR) laser indicating the efficient photothermal conversion of rGO. The results of cytotoxicity tests demonstrate that rGO/PNIPAM is biocompatible and has no obvious toxicity to myoblast line C2C12 cells. Second, bilayer hydrogel composed of rGO/PNIPAM and PEGDA is prepared using a similar method layer-by-layer. The bilayer strip bends towards rGO/PNIPAM under NIR laser. The bending is improved after reduction. The laser power density has a strong impact on the bending rate and degree. The reversible bending deformation indicates the structural stability. All the above results approve that the bilayer actuator has great potential to be applied in biomedicine fields such as organ-on-chip, drug-carrier, or surgical aid.     

Magnetic and optical properties of Nd/TiO2- rGO nanocomposites

Graphene, the thinnest 2-dimensional atomic material, is successively used as a composite material has it significantly improves optical, thermal, mechanical and electrical properties. Neodymium being a strong paramagnetic substance is capable of storing large amount of magnetic energy because of their greater number of unpaired electrons in their electron orbital structure. This paper focuses on the influence of graphene on the structural, optical and magnetic properties of rare earth neodymium (Nd) doped TiO₂ nanoparticles. Nd doped TiO₂ nanoparticles are deposited on reduced graphene oxide (rGO) sheets forming the nanocomposites by hydrothermal treatment. The nano size, structure and phase of the composites are analysed by X-ray diffraction and Raman spectra. Dispersion of pure TiO₂ and Nd/TiO₂ nanoparticles on the rGO sheets is studied with FESEM and HRTEM micrographs alongside the elemental composition confirmed by EDAX. Increased surface area and pore size analysis is revealed by BET isotherms and BJH data. Absorption edges are blue shifted owing to particle size and experimental conditions. PL and EPR spectra confirm the presence of paramagnetic defect centres in the nanocomposites. The M − H hysteresis curves of the composites reveal the ferromagnetic behaviour at room temperature.