Printing graphene-carbon nanotube-ionic liquid gel on graphene paper: Towards flexible electrodes with efficient loading of PtAu alloy nanoparticles for electrochemical sensing of blood glucose

The increasing demands for portable, wearable, and implantable sensing devices have stimulated growing interest in innovative electrode materials. In this work, we have demonstrated that printing a conductive ink formulated by blending three-dimensional (3D) porous graphene–carbon nanotube (CNT) assembly with ionic liquid (IL) on two-dimensional (2D) graphene paper (GP), leads to a freestanding GP supported graphene–CNT–IL nanocomposite (graphene–CNT–IL/GP). The incorporation of highly conductive CNTs into graphene assembly effectively increases its surface area and improves its electrical and mechanical properties. The graphene–CNT–IL/GP, as freestanding and flexible substrates, allows for efficient loading of PtAu alloy nanoparticles by means of ultrasonic-electrochemical deposition. Owing to the synergistic effect of PtAu alloy nanoparticles, 3D porous graphene–CNT scaffold, IL binder and 2D flexible GP substrate, the resultant lightweight nanohybrid paper electrode exhibits excellent sensing performances in nonenzymatic electrochemical detection of glucose in terms of sensitivity, selectivity, reproducibility and mechanical properties.     

Palladium Nanoparticles Embedded into Graphene Nanosheets: Preparation,Characterization, and Nonenzymatic Electrochemical Detection of H2O2

A novel nonenzymatic H₂O₂ sensor based on a palladium nanoparticles/graphene (Pd‐NPs/GN) hybrid nanostructures composite film modified glassy carbon electrode (GCE) was reported. The composites of graphene (GN) decorated with Pd nanoparticles have been prepared by simultaneously reducing graphite oxide (GO) and K₂PdCl₄ in one pot. The Pd‐NPs were intended to enlarge the interplanar spacing of graphene nanosheets and were well dispersed on the surface or completely embedded into few‐layer GN, which maintain their high surface area and prevent GN from aggregating. XPS analysis indicated that the surface Pd atoms are negatively charged, favoring the reduction process of H₂O₂. Moreover, the Pd‐NPs/GN/GCE could remarkably decrease the overpotential and enhance the electron‐transfer rate due to the good contact between Pd‐NPs and GN sheets, and Pd‐NPs have high catalytical effect for H₂O₂ reduction. Amperometric measurements allow observation of the electrochemical reduction of H₂O₂ at 0.5 V (vs. Ag/AgCl). The H₂O₂ reduction current is linear to its concentration in the range from 1×10^?9 to 2×10^?3 M, and the detection limit was found to be 2×10^?10 M (S/N=3). The as‐prepared nonenzymatic H₂O₂ sensor exhibits excellent repeatability, selectivity and long‐term stability.     

Fabrication of a graphene–cuprous oxide composite

A composite of graphene–cuprous oxide (Cu₂O) was prepared using copper acetate-adsorbed graphene oxide (GO) sheets as precursors. In this composite, in-situ formed Cu₂O particles were derived from the adsorbed copper acetate which attached to graphene sheets and prevented the aggregation of the reduced graphene oxide sheets. The as-synthesized Cu₂O crystals were cube-like particles distributed randomly on the sheets due to the template effect of GO, consequently forming a graphene–Cu₂O cubes composite. A preliminary study on the electrochemical behavior of the graphene–Cu₂O composite used as anode material for lithium ion batteries was carried out.     

Pd@GO/Fe3O4/PAA/DCA: a novel magnetic heterogeneous catalyst for promoting the Sonogashira cross-coupling reaction

Abstract

A hybrid system involving graphene oxide (GO), magnetic oxide (Fe₃O₄), acrylamide and dicyandiamide was prepared via amine functionalization of GO/Fe₃O₄ by means of covalent bonding with acrylamide and subsequent reaction with dicyandiamide to provide a multinitrogen containing polymer on the surface of GO. This hybrid system was utilized as a heterogeneous catalyst support for immobilizing Pd nanoparticles to provide the hybrid, Pd@GO/Fe₃O₄/PAA/DCA. This nano-Pd composite was characterized using Fourier transform infrared, transmission electron microscopy, scanning electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, X-ray diffraction, and ICP techniques and used for promoting Sonogashira cross-coupling under mild reaction conditions. This heterogeneous and magnetic catalyst was easily separated by external magnet and was reused in a model reaction, efficiently up to six times with slight loss of catalytic activity and Pd leaching, showing the suitability of GO/Fe₃O₄/PAA/DCA for embedding Pd nanoparticles. To check the effect of the number of surface nitrogens of the polymeric chain on the catalytic performance, the activity of the catalyst was compared with Pd@GO/Fe₃O₄/PAA; increased number of the surface nitrogens on the chain polymer leads to higher loading of Pd and lower the Pd leaching.     

Graphene–Pt nanocomposite for nonenzymatic detection of hydrogen peroxide with enhanced sensitivity

A sensitive hydrogen peroxide (H₂O₂) sensor was fabricated based on graphene–Pt (GN–Pt) nanocomposite. The GN–Pt was synthesized by photochemical reduction of K₂PtCl₄ on GNs, and characterized by atomic force microscope (AFM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical investigations indicated that the GN–Pt exhibited a high peak current and low overpotential towards the reduction of H₂O₂. The GN–Pt modified glass carbon electrode displayed a wide linear range (2–710 μM), low limit of detection (0.5 μM) and good selectivity for detection of H₂O₂ with a much higher sensitivity than that of Pt nanoparticles or graphene modified electrode.     

An ultrasensitive hydrogen peroxide biosensor based on electrocatalytic synergy of graphene–gold nanocomposite, CdTe–CdS core–shell quantum dots and gold nanoparticles

We first reported an ultrasensitive hydrogen peroxide biosensor in this work. The biosensor was fabricated by coating graphene–gold nanocomposite (G–AuNP), CdTe–CdS core–shell quantum dots (CdTe–CdS), gold nanoparticles (AuNPs) and horseradish peroxidase (HRP) in sequence on the surface of gold electrode (GE). Cyclic voltammetry and differential pulse voltammetry were used to investigate electrochemical performances of the biosensor. Since promising electrocatalytic synergy of G–AuNP, CdTe–CdS and AuNPs towards hydrogen peroxide was achieved, the biosensor displayed a high sensitivity, low detection limit (S/N = 3) (3.2 × 10⁻¹¹ M), wide calibration range (from 1 × 10⁻¹⁰ M to 1.2 × 10⁻⁸ M) and good long-term stability (20 weeks). Moreover, the effects of omitting G–AuNP, CdTe–CdS and AuNP were also examined. It was found that sensitivity of the biosensor is more 11-fold better if G–AuNP, CdTe–CdS and AuNPs are used. This could be ascribed to improvement of the conductivity between graphene nanosheets in the G–AuNP due to introduction of the AuNPs, ultrafast charge transfer from CdTe–CdS to the graphene sheets and AuNP due to unique electrochemical properties of the CdTe–CdS, and good biocompatibility of the AuNPs for horseradish peroxidase. The biosensor is of best sensitivity in all hydrogen peroxide biosensors based on graphene and its composites up to now.     

静电自组装方法合成的具有多孔三维网络结构的Fe3O4/石墨烯复合材料作为高性能锂离子电池负极材料

采用静电自组装方法,分两步合成Fe（OH）₃/GO前驱体（GO：氧化石墨烯）,再通过水热反应和600 ℃高纯氮气气氛下煅烧,获得了Fe₃O₄/石墨烯复合材料. 通过X射线衍射（XRD）、扫描电镜（SEM）、高分辨透射电镜（HRTEM）、拉曼（Raman）光谱等多种分析,发现该复合材料具有三维多孔石墨烯网络结构. 把合成的这种Fe₃O₄/石墨烯复合材料作为锂离子电池负极材料,电化学测试结果表明其具有优良的电化学性能：首次放电容量为1390 mAh·g^-1,50次循环后容量为819 mAh·g^-1. 通过对比实验表明,三维石墨烯网络结构的形成对复合材料的电化学循环稳定性起着关键作用.     

Palladium Nanoparticles Bonded to Two‐Dimensional Iron Oxide Graphene Nanosheets: A Synergistic and Highly Reusable Catalyst for the Tsuji–Trost Reaction in Water and Air

Low cost, high activity and selectivity, convenient separation, and increased reusability are the main requirements for noble‐metal‐nanocatalyst‐catalyzed reactions. Despite tremendous efforts, developing noble‐metal nanocatalysts to meet the above requirements remains a significant challenge. Here we present a general strategy for the preparation of strongly coupled Fe₃O₄ and palladium nanoparticles (PdNPs) to graphene sheets by employing polyethyleneimine as the coupling linker. Transmission electron microscopic images show that Pd and Fe₃O₄ nanoparticles are highly dispersed on the graphene surface, and the mean particle size of Pd is around 3 nm. This nanocatalyst exhibits synergistic catalysis by Pd nanoparticles supported on reduced graphene oxide (rGO) and a tertiary amine of polyethyleneimine (Pd/Fe₃O₄/PEI/rGO) for the Tsuji–Trost reaction in water and air. For example, the reaction of ethyl acetoacetate with allyl ethyl carbonate afforded the allylated product in more than 99 % isolated yield, and the turnover frequency reached 2200 h^?1. The yield of allylated products was 66 % for Pd/rGO without polyethyleneimine. The catalyst could be readily recycled by a magnet and reused more than 30 times without appreciable loss of activity. In addition, only about 7.5 % of Pd species leached off after 20 cycles, thus rendering this catalyst safer for the environment.     

Facile and green solvothermal synthesis of palladium nanoparticle-nanodiamond-graphene oxide material with improved bifunctional catalytic properties

We developed a selective solvothermal synthesis of palladium nanoparticles on nanodiamond (ND)–graphene oxide (GO) hybrid material in solution. After the GO and ND materials have been added in PdCl₂ solution, the spontaneous redox reaction between the ND–GO and PdCl₂ led to the creation of nanohybrid Pd@ND@GO material. The resulting Pd@ND@GO material was characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectrometry, scanning electronic microscopy (SEM), and atomic absorption spectrometry methods. The Pd@ND@GO material has been used for the first time as a catalyst for the reduction for 2-nitrophenol and the degradation of methylene blue in the presence of NaBH₄. GO plays the role of 2D support material for Pd nanoparticles, while NDs act as a nanospacer for partly preventing the re-stacking of the GO. The Pd@ND@GO material can lead to high catalytic activity for the reduction reaction of 2-nitrophenol and degradation of methylene blue with 100% conversion within ~15 s for these two reactions even when the content of Pd in it is as low as 4.6 wt%.     

Three‐Dimensional Nitrogen‐Doped Reduced Graphene Oxide–Carbon Nanotubes Architecture Supporting Ultrafine Palladium Nanoparticles for Highly Efficient Methanol Electrooxidation

A three‐dimensional (3D) nitrogen‐doped reduced graphene oxide (rGO)–carbon nanotubes (CNTs) architecture supporting ultrafine Pd nanoparticles is prepared and used as a highly efficient electrocatalyst. Graphene oxide (GO) is first used as a surfactant to disperse pristine CNTs for electrochemical preparation of 3D rGO@CNTs, and subsequently one‐step electrodeposition of the stable colloidal GO–CNTs solution containing Na₂PdCl₄ affords rGO@CNTs‐supported Pd nanoparticles. Further thermal treatment of the Pd/rGO@CNTs hybrid with ammonia achieves not only in situ nitrogen‐doping of the rGO@CNTs support but also extraordinary size decrease of the Pd nanoparticles to below 2.0 nm. The resulting catalyst is characterized by scanning and transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectroscopy. Catalyst performance for the methanol oxidation reaction is tested through cyclic voltammetry and chronoamperometry techniques, which shows exceedingly high mass activity and superior durability.     

A Facile and In-situ Methanol-mediated Fabrication of Low Pd Loading,High-efficiency and Size-selectivity Pd@ZIF-8 Hydrogenation Catalyst

In-situ encapsulation of tiny and well-dispersed Pd nanoparticles (Pd NPs) in zeolitic imidazolate frameworks (ZIFs) was firstly achieved using a one-pot and facile methanol-mediated growth approach, in which methanol served as both solvent and a mild reductant. The microstructure, morphology, crystallinity, porosity as well as evolution process of the catalysts were determined by TEM, XRD, N₂ adsorption and UV-vis spectra. Due to the complete encapsulation of such Pd NPs combined with ultrahigh surface area and uniform microporous structure of ZIF-8, the resulting Pd@ZIF-8-60 min nanocomposite exhibited more superior catalytic activity for olefins hydrogenation with TOF of 7436 h⁻¹ and excellent size selectivity than previously reported catalysts. Furthermore, the catalyst displays excellent recyclability for 1-octene hydrogenation and without any loss of the Pd active species.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.     

石墨烯负载高活性Pd催化剂对乙醇的电催化氧化

以石墨粉为原料, 采用Hummers法液相氧化合成了氧化石墨(GO), 然后用化学一步还原制得石墨烯负载钯催化剂. X射线衍射(XRD)、透射电镜(TEM)表征表明, Pd在石墨烯载体上有较好的分散度, 粒径为3-5 nm. 电化学活性面积(EASA)、循环伏安(CV)、计时电流(CA)和计时电位(CP)等电化学测试表明, 与传统Pd/Vulcan XC-72相比, Pd/石墨烯催化剂对碱性介质中乙醇电催化氧化的催化活性有了很大的提高.