Hierarchical nanocomposites of polyaniline scales coated on graphene oxide sheets for enhanced supercapacitors

The homogeneous polyaniline–graphene oxide (PANI-GO) nanocomposites were facilely assembled with a redox system in which cumene hydroperoxide (CHP) and iron dichloride (FeCl₂) acted as oxidant and reductant, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that PANI scales coated uniformly on the surface of GO sheets owing to the synergistic effect between the PANI and GO. The obtained PANI-GO nanocomposites exhibited improved electrochemical performance as an electrode material for supercapacitors compared with the pure PANI. The specific capacitance of the PANI-GO nanocomposites was high up to 308.3 F g^?1, much higher than that of the pure PANI with specific capacitance of 150 F g^?1 at a current density of 1 A g^?1 in 2 M H₂SO₄ electrolyte. The Raman and XPS results illustrated that enhanced electrochemical performance might be attributed to the π-π conjugation between the PANI and GO sheets.     

Facilely prepared polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate nanocomposites by in situ emulsion polymerization for high-performance supercapacitor electrodes

The layered polypyrrole-graphene oxide-sodium dodecylbenzene sulfonate (PPyGO-SDBS) nanocomposites were facilely fabricated via an in situ emulsion polymerization method with the assistance of SDBS as dopant and stabilizer. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electrochemical performance were employed to analyze the structure and the characteristics of the composites. The results showed that SDBS played an important role in improving the electrochemical performance of the PPyGO-SDBS, by dispersing the PPy between the layers of the GO. The obtained PPyGO-SDBS exhibited remarkable performance as an electrode material for supercapacitors, with a specific capacitance as high as 483 F g^?1 at a current density of 0.2 A g^?1 when the mass ratio of pyrrole to GO was 80:20. The attenuation of the specific capacitance was less than 20 % after 1,000 charge–discharge processes, supporting the idea that PPy inserted successfully into the GO interlayers. The excellent electrochemical performance seemed to arise from the synergistic effect between the PPy and the GO and the dispersion of the PPy induced by SDBS.     

Electrochemical application of titanium dioxide nanoparticle/gold nanoparticle/multiwalled carbon nanotube nanocomposites for nonenzymatic detection of ascorbic acid

Titanium dioxide nanoparticle/gold nanoparticle/carbon nanotube (TiO₂/Au/CNT) nanocomposites were synthesized, and then characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). A TiO₂/Au/CNT nanocomposite-modified glassy carbon (GC) electrode was prepared using the drop coating method and was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric current–time response (I-T). The modified material is redox-active. The nonenzymatically detected amount of ascorbic acid (AA) on the TiO₂/Au/CNT electrode showed a linear relationship with the AA concentration, for concentrations from 0.01 to 0.08 μM; the sensitivity was 117,776.36 μA?·?cm^?2?·?(mM)^?1, and the detection limit was 0.01 μM (S/N?=?3). The results indicated that the TiO₂/Au/CNT nanocomposite-modified GC electrode exhibited high electrocatalytic activity toward AA. This paper describes materials consisting of a network of TiO₂, Au, and MWCNTs, and the investigation of their synergistic effects in the detection of AA.     

氧化钛/氧化石墨纳米复合材料的制备、表征及性能

采用四氯化钛(TiCl₄)和氧化石墨为主要原料, 通过原位复合的方法制备了氧化钛/氧化石墨(TiO₂/GO)纳米复合材料. 采用傅里叶变换红外(FTIR)光谱仪、X射线衍射(XRD)仪、热重-差热分析(TG-DTA)仪、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)等手段研究了TiO₂/GO纳米复合材料的结构和性能. 结果表明, 石墨在氧化过程中结构层键合大量含氧官能团, 部分含氧官能团进一步与纳米TiO₂以化学键结合; 复合后氧化石墨原有衍射峰消失. 将TiO₂/GO添加到水性聚氨酯(WPU)中, 制备了TiO₂/GO-WPU复合涂膜. 紫外吸收光谱表明, 随着氧化石墨含量的增加, 复合涂膜的紫外吸收能力增强, 当GO含量达到一定数值时, 涂膜的紫外吸收最强, 随着GO含量继续增加吸收又呈下降趋势, 存在一较优浓度值. TiO₂/GO的添加显著提高了聚氨酯涂层的抗紫外线性能, 耐磨损性能和热稳定性能.     

In situ Synthesis of Poly(methyl methacrylate)/Graphene Oxide Nanocomposites Using Thermal-initiated and Graphene Oxide-initiated Polymerization

A facile and cost-effective method to prepare poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposites was developed by in situ polymerization. By using thermal-initiated and GO-initiated polymerization of methyl methacrylate (MMA), no extra radical initiator was added during the reaction. Without any pre-functionalization of GO, PMMA chains were covalently bonded to its surface, which was confirmed by Fourier-transform infrared, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy investigations. TGA analysis showed that the mass ratio of grafted PMMA and GO was as high as 1.7. Transmission electron microscopy and X-ray powder diffraction investigations demonstrated that the grafting of PMMA chains to GO surfaces resulted in homogeneous dispersion of GO sheets in PMMA matrix, which led to a commendable performance on its mechanical and thermal properties. Dynamic mechanical analysis showed that, at a loading level of just 0.5 wt% for the nanocomposites, the storage modulus of the nanocomposites was improved 14%, and the glass transition temperature was increased 12°C in comparison with that of neat PMMA. Thermogravimetric analysis showed that the onset degradation temperature of the nanocomposites was increased 13°C with a GO content of 0.25 wt%.     

钌/氮掺杂石墨烯催化硼氢化钠水解制氢的研究

本文采用原位合成法制备了钌/氮掺杂石墨烯(Ru/NGR)催化剂,并采用X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)等手段对催化剂的结构形貌进行了表征。将Ru/NGR催化剂应用于硼氢化钠水解制氢体系,考察了钌的负载量、硼氢化钠的浓度、反应温度等对硼氢化钠产氢的催化性能的影响。研究结果表明:当温度为25℃,硼氢化钠浓度为2 wt%,钌负载量为3.9%时,产氢速率可达32.95 L·(gRu·min)^-1。通过对Ru/NGR催化剂催化硼氢化钠水解反应动力学数据研究研究得出该催化剂的活化能为46 kJ·mol^-1。     

Preparation of polymeric modifier-attached graphene-supported bimetallic Pt–Pd nanocomposites,and their electrochemical properties as electro-catalysts

Graphene-supported bimetallic nanocomposites were synthesized by a modified sodium borohydride reduction method. Poly(diallyldimethylammonium chloride) (PDDA) was used as modifier for good dispersion and higher metal alloy content. The micro-structure and dispersive properties of the electro-catalysts were determined by X-ray diffraction, Fourier-transform-infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the Pt–Pd electro-catalysts were studied by cyclic voltammetry. This analysis confirmed that functional groups on the graphene oxide (GO) sheet were chemically bonded to the PDDA layer. The average particle diameter of Pt–Pd_{1 to 0.5}–PDDA–reduced graphene oxide (RGO) was found to be 2.4 ± 0.4 nm which is the smallest platinum metal particle size among Pt–Pd–PDDA–RGO electro-catalysts. The electrochemically active surface area was studied and the activity was found to be enhanced by use of the polymeric modifier.     

Synthesis and Characterization of a Novel Graphene Oxide/titanium Dioxide Solvent-free Nanofluid

A novel graphene oxide/titanium dioxide(GO/TiO_2) solvent-free nanofluid was firstly synthesized by employing GO, which was in-situ deposited by TiO_2 as the core and(3-Glycidyloxypropyl) trime thoxysilane(KH560) and polyetheramine-M2070 as the shell. The morphology and structure of GO/TiO_2 nanofluid were verified by Transmission electron microscopy(TEM), X-ray diffraction(XRD) analysis, Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS) and UV-vis absorption spectra. These studies confirmed that TiO_2 has been deposited onto GO with good dispersion, and the organic shell has been grafted onto the core successfully. Thermo gravimetric analysis(TGA) and viscosity analysis indicated that this nanoparticle hybrid material presented a liquid state without solvent at room temperature, and has great fluidity and thermal stability. The solubility investigation of GO/TiO_2 nanofluid revealed its excellent amphiphilicity and the potential as the functional nanocomposites.     

Synthesis of Ag Nanoparticle Doped MnO2/GO Nanocomposites at a Gas/Liquid Interface and its Application in H2O2 Detection

Ag/MnO₂/GO nanocomposites were synthesized via the method of gas/liquid interface based on silver mirror reaction, and a non‐enzymatic H₂O₂ sensor was fabricated through immobilizing Ag/MnO₂/GO nanocomposites on GCE. The composition and morphology of the nanocomposites were studied by energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Electrochemical investigation indicated that it exhibited a favorable performance for the H₂O₂ detection. Its linear detection range was from 3 μM to 7 mM with a correlation coefficient of 0.9960; the sensitivity was 105.40 μA mM^?1 cm^?2 and the detection limit was estimated to be 0.7 μM at a signal‐to‐noise ratio of 3.     

Ternary Ag/Polyaniline/Au nanocomposites: Preparation,characterization and electrochemical properties

Ternary Ag/Polyaniline/Au nanocomposites were synthesized successfully by immobilizing of Au nanoparticles (NPs) on the surface of Ag/Polyaniline (PANI) nanocomposites. Ag/PANI nanocomposites were prepared via in situ chemical polymerization of aniline in the presence of 4-aminothiophenol (4-ATP) capped silver colloidal NPs. Then, uniform gold (Au) NPs were assembled on the surface of resulted Ag/PANI nanocomposites through electrostatic interaction to get Ag/Polyaniline/Au nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), ultraviolet visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Moreover, Ag/PANI/Au nanocomposites were immobilized on the surface of a glassy carbon electrode and showed enhanced electrocatalytic activity for the reduction of H₂O₂ compared with Ag/PANI.     

Novel graphene oxide/bentonite composite for uranium(VI) adsorption from aqueous solution

A novel graphene oxide/bentonite composite (GO/bentonite) was synthesized and then characterized through powder X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and energy dispersive spectroscopy. Adsorption achieved equilibrium within 10 min. Moreover, U(VI) adsorption on GO/bentonite was highly dependent on solution pH and independent of ionic strength. These characteristics suggested that inner-sphere surface complexes of U(VI) formed on GO/bentonite. The adsorption of U(VI) from aqueous solution on GO/bentonite was fitted to the pseudo-second-order and Freundlich isotherm models. The maximum sorption capacity of GO/bentonite was 234.19 mg g^?1 under neutral pH at 303 K. GO/bentonite is a potentially powerful adsorbent for the efficient removal of U(VI) from aqueous solutions.     

Electrochemical studies of few-layered graphene as an anode material for Li ion batteries

Few-layered graphene (FLG) with specific surface area of only ~8.2 m² g^?1 was synthesized from graphene oxide (GO) using microwave-assisted exfoliation. GO was prepared using modified Hummers method. Few-layered nature of the exfoliated material was confirmed by electron microscopy, X-ray and electron diffraction, and Raman spectroscopy. Coin cells were fabricated using FLG as an anode and lithium metal as a counter electrode. The cells were tested using cyclic voltammetry and galvanostatic cycling techniques. FLG showed reversible capacity values of ~400 and ~250 mAh g^?1 at current rates of 0.1 and 1 C, respectively. Columbic efficiency was more than 98 % while cycle to cycle capacity fading was less than 2 %. Maximum discharge or charging capacity was below 0.3 V, a preferable characteristic for achieving ideal anodic behavior.     

Green synthesis of Copper oxide nanoparticles decorated with graphene oxide for anticancer activity and catalytic applications

Nanotechnology is an embryonic field that grips countless impacts on the drug delivery system. Nanoparticles as haulers increase the capability of target-specific drug delivery to many folds hence are used in the treatment of dreadful diseases such as cancer, diabetes, etc. This boom has aimed at, to synthesize Copper oxide nanoparticles (CuO-NPs) using Acalypha Indica leaf extract and then incorporated with graphene oxide (GO) to form GO-CuO nanocomposites. Secondly, to sightsee the photocatalytic activity of CuO-NPs and GO-CuO nanocomposites towards the decolorization of methylene blue-dye and to test its activity against HCT-116 Human colon cancer cell lines. Synthesized nanocomposites were characterized using FTIR, UV–vis, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray Photoelectron Spectroscopy (XPS) and transmission electron microscopy (TEM) analysis. The photocatalytic studies revealed that synthesized nanocomposites have the efficiency to degrade methylene blue dye by 83.20% and cytotoxic activity was found to be 70% against HCT-116 Human colon cancer cell lines at 100 μg/ml. GO-CuO nanocomposites have appreciable activity towards cancer cell lines and photocatalytic activity when compared to nanoparticles as such.     

Cobalt Phthalocyanine Immobilized on Graphene Oxide: An Efficient Visible‐Active Catalyst for the Photoreduction of Carbon Dioxide

New graphene oxide (GO)‐tethered–Co^II phthalocyanine complex [CoPc–GO] was synthesized by a stepwise procedure and demonstrated to be an efficient, cost‐effective and recyclable photocatalyst for the reduction of carbon dioxide to produce methanol as the main product. The developed GO‐immobilized CoPc was characterized by X‐ray diffraction (XRD), FTIR, XPS, Raman, diffusion reflection UV/Vis spectroscopy, inductively coupled plasma atomic emission spectroscopy (ICP‐AES), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). FTIR, XPS, Raman, UV/Vis and ICP‐AES along with elemental analysis data showed that Co^II–Pc complex was successfully grafted on GO. The prepared catalyst was used for the photocatalytic reduction of carbon dioxide by using water as a solvent and triethylamine as the sacrificial donor. Methanol was obtained as the major reaction product along with the formation of minor amount of CO (0.82 %). It was found that GO‐grafted CoPc exhibited higher photocatalytic activity than homogeneous CoPc, as well as GO, and showed good recoverability without significant leaching during the reaction. Quantitative determination of methanol was done by GC flame‐ionization detector (FID), and verification of product was done by NMR spectroscopy. The yield of methanol after 48 h of reaction by using GO–CoPc catalyst in the presence of sacrificial donor triethylamine was found to be 3781.8881 μmol g^?1 cat., and the conversion rate was found to be 78.7893 μmol g^?1cat. h^?1. After the photoreduction experiment, the catalyst was easily recovered by filtration and reused for the subsequent recycling experiment without significant change in the catalytic efficiency.     

Structure of mono- and bimetallic heterogeneous catalysts based on noble metals obtained by means of fluid technology and metal-vapor synthesis

Monometallic nanocomposites are obtained with the use of supercritical carbon dioxide (fluid technique) and metal-vapor synthesis (MVS), while bimetallic nanocomposites of Pt and Au noble metals and ??-Al₂O₃ oxide matrix are synthesized by a combination of these two methods. The structures, concentrations, and chemical states of metal atoms in composites are studied by means of small-angle X-ray scattering (SAXS), transparent electron microscopy (TEM), X-ray fluorescent analysis (XFA), and X-ray photoelectron spectroscopy (XPS). The neutral state of metal atoms in clusters is shown by XPS and their size distribution is found according to SAXS; as is shown, it is determined by the pore sizes of the oxide matrices and lies in the range of 1 to 50 nm. The obtained composites manifest themselves as effective catalysts in the oxidation of CO to CO₂.     

First-Row Transition-Metal Cations (Co2+, Ni2+, Mn2+, Fe2+) and Graphene (Oxide) Composites: From Structural Properties to Electrochemical Applications

Composites of graphene (oxide) (GO) and first-row transition-metal cations (Co²⁺, Ni²⁺, Mn²⁺, Fe²⁺) are prepared by mixing GO and aqueous metal salt solutions. The amount of metal cation bound to GO nanosheets is calculated by using inductively coupled plasma mass spectrometry (ICP-MS) and the possible binding sites of the metals are investigated by means of attenuated total reflectance infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. Electrodes loaded with the metal/GO composites are prepared by a simple drop-casting technique without any binders or conductive additives. The effect of electrochemical reduction on the structure of the composite electrodes is investigated by Raman spectroscopy, XPS, X-ray diffraction (XRD) analysis, and field emission scanning electron microscopy (FESEM). A detailed electrochemical characterization is performed for the utilization of the composite electrodes for electrochemical capacitors and possible oxygen reduction reaction electrocatalysts by cyclic voltammetry (CV) and rotating disk electrode measurements. The highest areal capacitance is achieved with the as-deposited Fe/GO composite (38.7 mF cm⁻² at 20 mV s⁻¹). In the cyclic stability measurements, rCo/GO, rNi/GO, rMn/GO, and rFe/GO exhibit a capacitance retention of 44, 1.1, 73, and 87 % after 3000 cycles of CV at 100 mV s⁻¹, respectively.     

Investigation of carbon-supported Ni@Ag core-shell nanoparticles as electrocatalyst for electrooxidation of sodium borohydride

Carbon-supported Ni@Ag core-shell nanoparticles were synthesized and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The morphology, structure, and composition of the as-prepared electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Electrochemical characterizations are performed by cyclic voltammetry (CV), chronoamperometry (CA), linear scan voltammetry with rotating disk electrode (LSV RDE), and fuel cell test. The catalytic behaviors and main kinetic parameters (e.g., Tafel slope, number of electrons exchanged, exchange current density, and apparent activation energy) toward BH ₄ ^‐ oxidation on Ag/C and Ni@Ag/C electrocatalysts are determined. Results show that the as-prepared nanoparticles have a core-shell structure with the average size approximately 13 nm. The kinetics of NaBH₄ oxidation is faster for Ni@Ag/C than that for Ag/C. Among the as-prepared catalysts, the highest transition electron value and the lowest apparent activation energy are obtained on Ni₁@Ag₁/C; the values are 4.8 and 20.23 kJ mol^?1, respectively. The DBHFC using Ni₁@Ag₁/C as anode electrocatalyst and Pt mesh (1 cm²) as cathode electrode obtains the maximum anodic power density as high as 8.54 mW cm^?2 at a discharge current density of 8.42 mA cm^?2 at 25 °C.     

Gold Nanorod‐Assembled PEGylated Graphene‐Oxide Nanocomposites for Photothermal Cancer Therapy

Gold nanorod‐attached PEGylated graphene‐oxide (AuNR‐PEG‐GO) nanocomposites were tested for a photothermal platform both in vitro and in vivo. Cytotoxicity of AuNR was reduced after encapsulation with PEG‐GO along with the removal of cetyltrimethylammonium bromide (CTAB) from AuNR by HCl treatment. Cellular internalization of the CTAB‐eliminated AuNR‐PEG‐GO nanocomposites was examined using dark‐field microscopy (DFM), confocal Raman microscopy and transmission electron microscopy (TEM). To determine the photothermal effect of the AuNR‐PEG‐GO nanocomposites, A431 epidermoid carcinoma cells were irradiated with Xe‐lamp light (60 W cm^?2) for 5 min after treatment with the AuNR‐PEG‐GO nanocomposites for 24 h. Cell viability significantly decreased by ~40% when the AuNR‐PEG‐GO‐encapsulated nanocomposites were irradiated with light as compared with the cells treated with only the AuNR‐PEG‐GO nanocomposites without any illumination. In vivo tumor experiments also indicated that HCl‐treated AuNR‐PEG‐GO nanocomposites might efficiently reduce tumor volumes via photothermal processes. Our graphene and AuNR nanocomposites will be useful for an effective photothermal therapy.     

Sucrose assisted hydrothermal synthesis of SnO2/graphene nanocomposites with improved lithium storage properties

SnO₂/graphene nanocomposites are synthesized by a new hydrothermal treatment strategy under the assistance of sucrose. From the images of the scanning electron microscope (SEM) and transmission electron microscope (TEM), it can be observed that SnO₂ nanoparticles with the size of 4~5 nm uniformly distribute on the graphene nanosheets. The result demonstrates that sucrose can effectively prevent graphene nanosheets from restacking during hydrothermal treatment and subsequently treatment. The charging/discharging test result indicates that the SnO₂/graphene nanocomposites exhibit high specific capacity and excellent cycleability. The first reversible specific capacity is 729 mAh.g^?1 at the current density of 50 mA.g^?1, and remains 646 mAh.g^?1 after 30 cycles at the current density of 100 mA.g^?1, 30 cycles at the current density of 200 mA.g^?1, 30 cycles at the current density of 400 mA.g^?1, 30 cycles at the current density of 800 mA.g^?1, and 30 cycles at the current density of 50 mA.g^?1.     

Titanium dioxide anchored graphene oxide nanosheets for highly selective voltammetric sensing of dopamine

The authors report on an efficient method for the voltammetric sensing of dopamine (DA) by using an electrode modified with alternating monolayers of graphene oxide (GO) and Titanium dioxide (TiO₂) nanoparticles anchored GO nanosheets (NSs)). The as-prepared nanostructures were characterized by photoluminescence spectroscopy, powder X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy and Energy Dispersive X-ray Analysis (EDAX) techniques. The GO/TiO₂ nanocomposite (NC) was deposited on a glassy carbon electrode (GCE), where it displayed an excellent electrocatalytic activity toward the oxidation of DA, owing to its excellent conductivity, high specific surface area, enhanced interfacial contact and more negative zeta potential. Figures of merit include (a) a fast response (5 s), (b) a wide linear range (between 0.2 and 10 μM of DA) (c) a particularly low detection limit (27 nM), (d) a working potential as low as 0.25 V (vs. Ag/AgCl) and (e) a sensitivity of 1.549 μA·μM^?1·cm^?2. The GO/TiO₂/GCE exhibited excellent selectivity over the other interferences as revealed by the differential pulse voltammetric and amperometric studies. The analysis of spiked urine samples resulted in recoveries in the range of 96 to 106%, with RSDs between 3.8 and 5.2%.

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Graphical abstract A GO/TiO₂ (graphene oxide/titanium dioxide) nanocomposite (NC) was prepared and exploited as electrochemical probes in DA detection. It displays a low detection limit, wide linear range and excellent selectivity.