Adsorption of polyelectrolyte modified graphene to silica surfaces: monolayers and multilayers

Exfoliated graphene particles stabilised by the cationic polyelectrolyte polyethyleneimine (PEI) were used in conjunction with an anionic polyelectrolyte, poly(acrylic acid), to construct multilayers using the layer-by-layer technique on a silica substrate. In the first adsorption step, the surface excess of the cationic graphene was dependent on the overall charge on the nanoparticle which in turn can be tuned through modifying solution pH as PEI has weakly ionisable charged amine groups. The adsorbed amount onto the silica surface increased as the solution pH increased. Subsequently, a layer of PAA was adsorbed on top of the cationic graphene through electrostatic interaction. The multilayer could be assembled through this alternate deposition, with the influence of solution conditions investigated. The pH of the adsorbing solutions was the chief determinant of the overall adsorbed amounts, with more mass added at the elevated pH of 9 in comparison with pH 4. Atomic force microscopy confirmed that the graphene particles were adsorbed to the silica interface and that the surface coverage of the disc-like nanoparticles was complete after the deposition of five graphene-polyelectrolyte bi-layers. Furthermore, the graphene nanoparticles themselves could be modified through the consecutive addition of the oppositely charged polymers. A multilayered assembly of negatively charged graphene sheets modified with a bi-layer of PEI and PAA was also deposited on a silica surface with adsorbed PEI.     

Noble metal doped graphene nanocomposites and its study of photocatalytic hydrogen evolution

This work reports the deposition of platinum (Pt) nanoparticles on the surface of graphene nanosheet by a simple approach, using a microwave-assisted method. The photocatalytic activity has been investigated for hydrogen evolution. The hydrogen evolutions were attributed to graphene, due to its high photoelectron transport properties, and the Pt nanoparticles attached on the surface of graphene sheet, which act as reaction centers for H₂ evolution. The “as-prepared” composites were characterized by Brunauer Emmett Teller (BET) surface area measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). This work highlights the potential application of graphene-based materials in the field of energy conversion.     

Improvement of interfacial adhesion performance of the kevlar fiber mat by depositing SiC/TiO2/Al2O3/graphene nanoparticles

Modern world seeks dramatic progress in composite materials use in numerous applications. Scientists worldwide are researching on fabricating new composites and attempting to have more applications using these materials. Serious attempts have also been taken to improve the properties of these materials. In this circumstance, a conscious attempt has been made in this present work that studies the effect of SiC/TiO₂/Al₂O₃/ graphene nanoparticles (NPs) deposition on Kevlar fiber. In this process, SiC/TiO₂/Al₂O₃/ graphene NPs have been deposited on Kevlar fiber by dip coating process. For the analysis, physical observation has been performed well at first which confirms nanoparticle deposition on the fiber and formation of adhesive bonding. SEM analysis followed by surface topography has been conducted to observe and further analysis of nanoparticle deposition. Atomic bonding mechanism shows how chemical bonding between fiber and nanoparticles. TGA analysis shows thermal improvement of the fiber by NPs deposition where graphene with binder makes 21.6% improvement in decomposition temperature. Tensile strength and young’s modulus of binder inclusion coated kevlar fabric are improved up to 26% and 5.7%, respectively. Finally, the IR-spectra confirms successful deposition of nanoparticles on the fiber.     

Magnetic property and structural study of nickel supported on reduced graphene oxide prepared by chemical vapor deposition

Nickel supported on reduced graphene oxide was synthesized by chemical vapor deposition technique. The crystal structure and magnetic properties of the prepared sample were studied by means of Raman spectrometry, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), and vibrating sample magnetometry (VSM). The result of Raman spectroscopy revealed the structure of few-layer graphene as the support for Ni nanoparticles. XP spectrum confirmed the presence of metallic Ni on the a few-layer graphene surface. TE micrograph showed that the nickel nanoparticles were sphere shaped and the mean particle size is about 20 nm deposited on the reduced graphene oxide. The magnetic study showed the ferromagnetic behavior of 3.2 wt% nickel over reduced graphene oxide at room temperature.     

石墨烯对Ni（OH）2超级电容器材料电化学行为的影响

研究了氧化缺陷石墨烯对Ni(OH)2电化学性能的增强作用.实验上,由恒电位沉积法在石墨烯基底上制备Ni(OH)2纳米粒子/石墨烯复合材料.TEM观察和电化学测试表明,Ni(OH)2纳米粒子均匀地分散在石墨烯基底上,其粒径为5.0±0.5 nm,体系的质量比电容值为1928 F.g-1.量化计算表明,上述复合材料乃是通过Ni(OH)2与石墨烯表面功能基团的强化学作用相结合而导电的,电子则是自石墨烯基底经氧化缺陷向Ni(OH)2传递,导致Ni(OH)2带负电,从而形成Ni(OH)2纳米粒子的单向导电行为.     

Towards Catalytically Active Porous Graphene Membranes with Pulsed Laser Deposited Ceria Nanoparticles

Porous graphene with catalytically active ceria nanometre-size particles were prepared using pulsed laser deposition (PLD) on graphene produced through chemical vapour deposition (CVD). The reported process provided porous graphene containing ceria nanoparticles as confirmed by HR TEM and XPS. Isotopically labelled ¹³C graphene was employed to study desorption of the species containing carbon. Methanol adsorption was utilised to probe the nature of the catalytic activity of prepared ceria decorated graphene. The important role of graphene support for the stabilization of reduced ceria nanoparticles was finally confirmed. Increased dehydrogenation activity of graphene with ceria nanoparticles leading to CO and H₂ formation was demonstrated.     

Enhanced Peroxidase‐Like Properties of Graphene–Hemin‐Composite Decorated with Au Nanoflowers as Electrochemical Aptamer Biosensor for the Detection of K562 Leukemia Cancer Cells

Graphene composites with hemin and gold nanoparticles show a better performance for hydrogen peroxide decomposition compared to that of the three components alone or duplex/hybrid complexes. Our previous studies showed that the morphology of the Au nanoparticles may greatly influence the catalytic activity of graphene‐family peroxidase mimics. Recently, we found that Au nanoflowers could grow in situ and form on the surface of hemin/RGO (reduced graphene oxide). The prickly morphology of this Au nanoflower brought a higher catalytic ability with enhanced kinetic parameters than traditional Au nanoparticles that showed a smooth surface. Therefore, based on this discovery, a smart electrochemical aptamer biosensor for K562 leukemia cancer cells was further presented with good performance in selectivity and sensitivity attributed to the excellent mimetic peroxidase catalytic activity of this newly synthesized Au nanoflower decorated graphene–hemin composite (H‐RGO‐Au NFs).     

还原氧化石墨烯/金纳米修饰电极在新冠病毒检测中的应用

研究使用电化学沉积法在丝网印刷碳电极表面制备了还原氧化石墨烯和金纳米颗粒,构建了一种用于新冠病毒检测的石墨烯电化学传感器。通过扫描电子显微镜(SEM)和相应的电化学方法对纳米复合材料在电极表面的成功修饰进行了表征分析。并采用差分脉冲伏安法对传感器的性能进行检测,实验构建的电化学传感器具有良好的灵敏度,该传感器检线性范围为10_-10^-10_-6^mol/L,具有良好的重复性和特异性。     

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.     

Label‐free Electrochemical Aptasensor for Carcino‐embryonic Antigen Based on Ternary Nanocomposite of Gold Nanoparticles,Hemin and Graphene

In this report, a label‐free electrochemical aptasensor for carcino‐embryonic antigen (CEA) was successfully developed based on a ternary nanocomposite of gold nanoparticles, hemin and graphene nanosheets (AuNPs‐HGNs). This nanocomposite was prepared by decorating gold nanoparticles on the surface of hemin functionalized graphene nanosheets via a simple wet‐chemical strategy. The aptamer can be assembled on the surface of AuNPs‐HGNs/GCE (glassy carbon electrode) through Au‐S covalent bond to form the sensing interface. Hemin absorbed on the graphene nanosheets not only acts as a protective agent of graphene sheets, but also as an in situ probe base on its excellent redox properties. Gold nanoparticles provide with both numerous binding sites for loading CEA binding aptamer (CBA) and good conductivity to promote the electron transfer. The current changes, which are caused by CEA specifically binding on the modified electrode, are exploited for the label‐free detection of CEA in a very rapid and convenient protocol. Therefore, the method has advantages of high sensitivity, wide linear range (0.0001–10 ng mL^?1), low detection limit (40 fg mL^?1) and attractive specificity. The results illustrate that the proposed label‐free electrochemical aptasensor has a potential application in the biological or clinical target analysis for its simple operation and low cost.     

Electrochemical synthesis of a graphene sheet and gold nanoparticle-based nanocomposite, and its application to amperometric sensing of dopamine

We describe a simple, green and controllable approach for electrochemical synthesis of a nanocomposite made up from electrochemically reduced graphene oxide (ERGO) and gold nanoparticles. This material possesses the specific features of both gold nanoparticles and graphene. Its morphology was characterized by scanning electron microscopy which reveals a homogeneous distribution of gold nanoparticles on the graphene sheets. Cyclic voltammetry was used to evaluate the electrochemical properties of this nanocomposite towards dopamine by modification of it on surface of glassy carbon electrode (GCE). Compared to the bare GCE, the electrode modified with gold nanoparticles, and the electrode modified with ERGO, the one modified with the nanocomposite displays better electrocatalytic activity. Its oxidation peak current is linearly proportional to the concentration of dopamine (DA) in the range from 0.1 to 10?μM, with a detection limit of 0.04?μM (at S/N?=?3). The modified electrode also displays good storage stability, reproducibility, and selectivity.

Surface‐Enhanced Raman Scattering Based on Controllable‐Layer Graphene Shells Directly Synthesized on Cu Nanoparticles for Molecular Detection

Graphene shells with a controllable number of layers were directly synthesized on Cu nanoparticles (CuNPs) by chemical vapor deposition (CVD) to fabricate a graphene‐encapsulated CuNPs (G/CuNPs) hybrid system for surface‐enhanced Raman scattering (SERS). The enhanced Raman spectra of adenosine and rhodamine 6G (R6G) showed that the G/CuNPs hybrid system can strongly suppress background fluorescence and increase signal‐to‐noise ratio. In four different types of SERS systems, the G/CuNPs hybrid system exhibits more efficient SERS than a transferred graphene/CuNPs hybrid system and pure CuNPs and graphene substrates. The minimum detectable concentrations of adenosine and R6G by the G/CuNPs hybrid system can be as low as 10^?8 and 10^?10 M , respectively. The excellent linear relationship between Raman intensity and analyte concentration can be used for molecular detection. The graphene shell can also effectively prevent surface oxidation of Cu nanoparticles after exposure to ambient air and thus endow the hybrid system with a long lifetime. This work provides a basis for the fabrication of novel SERS substrates.     

Zinc oxide nanoparticles immobilized on graphene flake

Interactions of ZnO nanoparticles with graphene oxide in isopropanol were studied; graphene oxide was shown to perform as an efficient substrate to immobilize zinc oxide nanoparticles on its surface. Interactions of nanocomposites consisting of graphene oxide-zinc oxide nanoparticles with supercritical isopropanol were studied. The conversion of graphene oxide into graphene does not appreciably changes the composition, morphology, or structure of ZnO nanoparticles.     

基于电泳沉积法碳纤维表面改性的研究进展及应用

近些年来,碳纤维(CF)由于具有优异的力学性能,被用作复合材料的增强体。但CF表面缺少极性基团,呈现化学惰性,使CF与树脂(EP)之间的界面粘结性能较差。为了改善该问题,需要对CF表面进行改性。氧化石墨烯(GO)和碳纳米管(CNT)具有大的比表面积,且表面含有大量的极性基团,将二者引入CF表面,可以有效改善CF与EP之间的界面问题。利用电泳沉积技术成功地制备了GO和CNT/EP复合材料,并显示出各种优异的界面性能。本文对国内外通过电泳沉积方法在CF表面沉积CNT和GO的改性以及电泳沉积GO和CNT的应用现状进行了综述和分析,并在此基础上,对电泳沉积碳纳米材料改性CF的研究趋势及前景进行展望。     

Decoration of Graphitic Surfaces with Sn Nanoparticles through Surface Functionalization Using Diazonium Chemistry

Composites of tin nanoparticles (Sn NP) and graphene are candidate materials for high capacity and mechanically stable negative electrodes in rechargeable Li ion batteries. A uniform dispersion of Sn NP with controlled size is necessary to obtain high electrochemical performance. We show that the nucleation of Sn particles on highly ordered pyrolitic graphite (HOPG) from solution can be controlled by functionalizing the HOPG surface by aryl groups prior to Sn deposition. On the contrary, we observe heterogeneous deposition of micrometer sized Sn islands on HOPG subjected to oxidation prior to deposition in the same conditions. We demonstrate that functional groups act as nucleation sites for Sn NP nucleation, and that homogeneous nucleation of small particles can be achieved by combining surface functionalization with diazonium chemistry and appropriate stabilizers in solution.     

PDMS microfludic device for optical detection of protein immunoassay using gold nanoparticles

A simple but highly specific immunoassay system for goat anti-human IgG has been developed using gold nanoparticles and microfluidic techniques. The assay is based on the deposition of gold nanoparticles that are coated with protein antigens in the presence of their corresponding antibodies to microfluidic channel surface. The effects of time accumulation, the flow velocity, and the concentration of antibodies to the red light absorption percentage (RAP) of deposition were investigated with an ordinary optical microscope. By controlling the reaction time and flow velocity, a dynamic range of 3 orders of magnitude and a detection sensitivity of 10 ng ml(-1) of goat anti-human IgG were achieved. Because of its simplicity and flexibility, this new technique should be useful for fast, highthroughput screening of antibodies in clinical diagnostic applications.     

纳米基因扩增技术及其应用

聚合酶链式反应(PCR)是20世纪80年代中期发展起来的一种应用广泛的体外DNA扩增技术,但目前该技术仍然存在着一些问题,如特异性差、灵敏度低和假阳性等.近年来,随着纳米科技的发展,一些纳米粒子如金属纳米粒子、碳纳米材料、量子点和纳米金属氧化物等被引入到PCR反应体系中,即纳米基因扩增技术(NanoPCR).该技术大幅度提高了PCR的扩增效率、选择性、灵敏度和特异性,推动了生物学技术的发展,具有非常重要的理论意义和应用价值.本文综述了近年来纳米基因扩增技术的主要研究进展、反应机理,并探讨了其应用研究.     

小尺寸金石墨纳米颗粒的合成与表征

在表面增强拉曼光谱(SERS)的研究领域中,基于局域表面等离子体共振效应的等离子体SERS基底的制备成为过去几十年的研究热点。然而,通常开发的等离子体金属基底具有较差的稳定性和重现性。对于SERS而言,石墨烯类材料具有拉曼化学增强效应,除此之外,还具有分子富集、强的稳定性与荧光猝灭能力等优点,因此基于石墨金属复合纳米材料的SERS基底受到了研究人员的重视。我们利用化学气相沉积(CVD)法制备了小尺寸的金石墨核壳纳米颗粒(Au@G),其粒径约为17 nm。我们通过在Au NP上包覆介孔二氧化硅来控制Au@G的尺寸,同时还研究了包覆二氧化硅过程中,正硅酸乙酯(TEOS)的浓度对于石墨壳层形成的影响。结果表明当TEOS在一定浓度范围内,其浓度的降低有利于得到石墨化程度高的Au@G。进一步利用Au@G对结晶紫分子进行拉曼检测,也表明了Au@G具有较好的拉曼增强效果。这种小尺寸的Au@G在分子检测与细胞成像分析领域中具有广泛的应用潜力。     

Frequency Shift in Graphene‐Enhanced Raman Signal of Molecules

Graphene‐enhanced Raman scattering (GERS) is emerging as an important method due to the need for highly reproducible, quantifiable, and biocompatible active substrates. As a result of its unique two‐dimensional carbon structure, graphene provides particularly large enhanced Raman signals for molecules adsorbed on its surface. In this work, the GERS signals of a test molecule, 4‐mercaptobenzoic acid (4‐MBA), with reproducible enhancement factors are discussed and compared with surface‐enhanced Raman scattering (SERS) signals from highly active substrates, covered with spherical silver nanoparticles. It is shown that chemical interactions between the molecule and graphene can result in a frequency shift in the graphene‐enhanced Raman signal of the molecule.     

石墨烯负载Pt催化剂的制备及催化氧还原性能

采用直接化学还原法, 以金属钠为还原剂, 四氯乙烯为碳源, 在石蜡油中不经氧化石墨(GO)和氧化石墨烯(GrO)而直接制备石墨烯(Gr), 然后将Pt纳米粒子担载在Gr基体上, 得到Pt/Gr催化剂, 并对其催化氧还原(OR)性能进行了研究. 通过X射线衍射(XRD), 透射电镜(TEM)和电化学测试对合成催化剂的结构、形貌和电化学性质进行了表征. 实验结果表明: 所制备的Pt/Gr催化剂具有较好的分散性, 平均粒径为3.1 nm; 氧还原起始电位比商业JM-Pt/C催化电极正移了24 mV; 交换电流密度达到1×10^-3 mA·cm^-2, 是商业JM-Pt/C催化电极的2.5倍.