Flexible transparent electrodes made of electrochemically exfoliated graphene sheets from low-cost graphite pieces

Graphene is a highly promising candidate to replace oxide-based conducting materials for fabrication of transparent electrodes used in flexible displays and electronic devices. However, so far an appropriate method is still not found to provide high-quality, low-cost graphene in a large quantity. To overcome this issue, we demonstrate that massive graphene sheets can be synthesized by electrochemical exfoliation process using artificial graphite as a starting material. The product is mainly composed of bilayer thin graphene sheets. Their lateral size can be up to several to 20 μm, and the quality determined by Raman spectroscopy is better than the reduced graphene oxide derived from graphene oxide. The transparent conducting films made of electrochemically exfoliated graphene can be simply prepared by an airbrush spraying method, which is easy to scale up for large-area deposition, and compatible with flexible polymer substrates.     

Characteristics of electroactive polymer actuators using graphene electrodes

As alternatives to precious gold/platinum electrodes, graphene-based ionic polymer-metal composite actuators were successfully demonstrated by reduced graphene oxide and direct grown graphene on both sides of the perfluorinated sulfonic acid polymer layer using electronic spray coating and wet transfer methods. In addition, a platinum electrode was prepared as a reference. We characterized the electrical and structural properties of the graphene electrodes using a four-point probe system and atomic force microscopy. The static actuation ranges were analyzed, and a modeling procedure was carried out to obtain the linear curvature–voltage relations. Furthermore, the periodic actuation range was dynamically tested to evaluate the changes in the actuation performance over time. The experimental results showed that the reduced graphene oxide electrodes are a good alternative to platinum electrode that provide better flexibility and restoration of the original shape. And also direct grown graphene electrode is also valuable to access the stacked actuator owing to the hydrophobic sub-nanometer electrode.     

Effect of graphene oxide on the conformational transitions of amyloid beta peptide: A molecular dynamics simulation study

The interactions between nanomaterials (NMs) and amyloid proteins are central to the nanotechnology-based diagnostics and therapy in neurodegenerative disorders such as Alzheimer's and Parkinson's. Graphene oxide (GO) and its derivatives have shown to modulate the aggregation pattern of disease causing amyloid beta (Aβ) peptide. However, the mechanism is still not well understood. Using molecular dynamics simulations, the effect of graphene oxide (GO) and reduced graphene oxide (rGO) having carbon:oxygen ratio of 4:1 and 10:1, respectively, on the conformational transitions (alpha-helix to beta-sheet) and the dynamics of the peptide was investigated. GO and rGO decreased the beta-strand propensity of amino acid residues in Aβ. The peptide displayed different modes of adsorption on GO and rGO. The adsorption on GO was dominated by electrostatic interactions, whereas on rGO, both van der Waals and electrostatic interactions contributed in the adsorption of the peptide. Our study revealed that the slight increase in the hydrophobic patches on rGO made it more effective inhibitor of conformational transitions in the peptide. Alpha helix-beta sheet transition in Aβ peptide could be one of the plausible mechanism by which graphene oxide may inhibit amyloid fibrillation.     

Single-Mode Modified Tapered Fiber Structure Functionalized With GO-PVA Composite Layer for Relative Humidity Sensing

A sensitive tapered optical fiber sensor incorporating graphene oxide(GO)and polyvinyl alcohol(PVA)composite film for the rapid measurement of changes in relati...     

Thermal vibration analysis of embedded graphene oxide powder-reinforced nanocomposite plates

In this research, thermal vibration analysis of a graphene oxide powder-reinforced (GOPR) nanocomposite embedded plate is carried out once the plate is exposed to different types of thermal...     

Characterization of reduced graphene oxide obtained from vacuum-assisted low-temperature exfoliated graphite

Microsystem Technologies - Graphene consists of sheets of two-dimensional allotrope carbons and is a basic element of graphite. Herein, reduced graphene oxide (rGO) were exfoliated from graphite...     

Enhanced photocatalytic efficiency by layer-by- layer self-assembly of graphene and titanium dioxide on shrink thermoplastic film

Microsystem Technologies - In this work, reduced graphene oxide/titanium dioxide (rGO/TiO2) composite material was immobilized on shrink thermoplastic film using layer-by-layer (LBL) self-assembly...     

Electrochemical deposition of polypyrrole/graphene oxide composite on microelectrodes towards tuning the electrochemical properties of neural probes

By exploiting the electrostatic interaction between positively charged pyrrole cation radicals and negatively charged graphene oxide (GO) sheets, we prepared polypyrrole/graphene oxide (PPy/GO) composite films by a one-step electrochemical process. We studied the effects of the polymerization current density and the GO content in electrolyte on the formation of PPy/GO coatings onto platinum neural microelectrode sites. As compared with pure PPy film, PPy/GO coatings show a rougher surface feature with micrometer-scale bulges. The impedance of the PPy/GO coated Pt electrode is only about 10% of the bare Pt electrode at the biological relevant 1 kHz, while the charge capacity density is more than two orders of the magnitude of the bare Pt electrode. Moreover, the PPy/GO coated Pt electrodes show higher performance than the PPy coated electrodes for the application of neural probe.     

Reconfigurable frequency and steerable beam of monopole antenna based on graphene pads

This article presents a reconfigurable frequency and steerable beam monopole antenna based on tunable graphene pads operating in both 4G and 5G bands. The proposed antenna consists of printed CPW‐fed circular monopole shapes, with five rectangular strips added with a separation angle of 45°. These strips are connected to monopole by using graphene pads. The monopole antenna operates in the lower 5G band from 3 up to 7.8 GHz at ?6 dB reflection coefficient. The antenna has an omni‐radiation pattern over the operating band without any applied bias voltage to the graphene pads. By applying the DC bias voltage, the rectangular strips are connected to the monopole and the designed antenna start to resonate from 1.8 to 8 GHz adding the 4G band frequencies. The steering of the proposed antenna beam started from ?60° to 60° according to the bias of the connected graphene pads. The graphene pad exhibits a variable resistance realizing an almost short to an open circuit with and without voltage bias, respectively. The designed antenna is simulated using high frequency structure simulation (HFSS) Ansys ver. 19 and equivalent circuit model of the graphene. The antenna is fabricated using reduced graphene oxide (RGO) pads. Reflection coefficient and radiation pattern measurements as well as simulations are presented with a positive agreement between the results.     

纸纤维基柔性还原氧化石墨烯、聚苯胺超级电容器复合电极材料的制备与性能研究

文章研究了一种石墨烯复合电极材料制备方法,以低成本的纸纤维材料为柔性基板,结合双电层电容碳材料氧化石墨烯和赝电容导电聚合物聚苯胺的互补优势,通过超声分散和真空抽滤的方法,实现了纸纤维基-聚苯胺-还原氧化石墨烯复合电极材料的制备。采用场发射扫描电子显微镜、Zahner电化学工作站对电极材料的循环伏安曲线、充放电性能进行测试分析。结果表明,柔性电极材料在100次弯曲测试后,没有发生明显分层和活性物质剥落现象,在电流密度为1 A/g时比电容为458 F/g,10 A/g电流密度下比电容为250 F/g,经过1000次充放电循环后,比电容仍能保持80%左右。这种高性能低成本的柔性复合电极材料在可穿戴式电子设备领域具有广阔的应用前景。     

In-situ formation of graphene–lead oxide composite and its use in trace arsenic detection

Reduced graphene oxide–lead dioxide composite is formed when EGO coated surface is electrochemically reduced along with lead ions in the solution. This composite has been shown to be an excellent material for low level detection of arsenic. Various functional groups present on EGO, in a wide pH range of 2–11, are responsible for the favorable interaction between metal ion and the modified electrode surface and subsequent trace level detection. X-ray photoelectron spectroscopy and Raman spectroscopic techniques confirm the formation of composite and its composition. Thin layer of lead dioxide along with reduced exfoliated graphene oxide has been shown to be responsible for the enhanced activity of the surface. The detection limit of arsenic is found to be 10 nM. This study opens up the possibility of using the composites for sensing applications and possibly simultaneous detection of arsenic and lead.     

基于氧化石墨烯修饰的DNA生物传感器用于苯酚的检测

作为一种典型的优先控制污染物,苯酚一直是环境监测和污染控制的重要对象。基于氧化石墨烯大的比表面积、优良的电子传导性等特性,以其为桥梁,为DNA在玻碳电极上的固定提供了可能,并加大了DNA在电极上的电化学响应信号,由此而构建了一种性能优良的DNA生物传感器。将该传感器浸在含有苯酚的溶液中,由于苯酚对DNA的损伤作用,降低了DNA在电极上的电化学响应。实验发现,响应信号与苯酚的浓度对数呈现良好的线性关系,响应范围为1.0×10-8～1.0×10-4mol/L,此外,该生物传感器表现出良好的稳定性和重现性。     

石墨烯/聚二甲基硅氧烷三维非织造结构压阻柔性压力传感器

压阻式压力传感器是可穿戴器件中的关键元件。由于优异的弹性性能,本文以三维聚酯非织造布作为基材,还原氧化石墨烯(rGO)作为活性材料,聚二甲基硅氧烷(PDMS)作为柔性材料,组装三维(3D)压阻式压力传感器。该传感器具有良好的感应特性,包括短响应时间(120ms)和微弱的迟滞性(6.8%)。此外,该压力传感器可以用于检测人体的关节以及喉咙的运动情况。因此,该压阻传感器成本低、灵敏度高、耐久性优良,可以作为穿戴智能设备的理想的三维压阻式压力传感器。     

Pt/Ni—氧化石墨烯修饰电极用于莱克多巴胺测定

将石墨烯作为基底材料修饰到玻碳电极上,并在其表面沉积Pt/Ni二元金属制得定量检测莱克多巴胺的电化学传感器。探讨了石墨烯表面金属合金沉积时间和样品富集时间等条件对传感器性能的影响。在最优条件下,测定莱克多巴胺的浓度线性范围为1.98×10-7～2.67×10-4mol/L,其检测限为6.66×10-8mol/L。实验结果表明:该传感器灵敏度高、稳定性好。     

Technologies for trapped-ion quantum information systems

Scaling up from prototype systems to dense arrays of ions on chip, or vast networks of ions connected by photonic channels, will require developing entirely new technologies that combine miniaturized ion trapping systems with devices to capture, transmit, and detect light, while refining how ions are confined and controlled. Building a cohesive ion system from such diverse parts involves many challenges, including navigating materials incompatibilities and undesired coupling between elements. Here, we review our recent efforts to create scalable ion systems incorporating unconventional materials such as graphene and indium tin oxide, integrating devices like optical fibers and mirrors, and exploring alternative ion loading and trapping techniques.

     

中国微米纳米----石墨烯纳米带谐振频率的分子动力学模拟

石墨烯因其独特的结构和特性,具有广泛的应用前景.采用分子动力学的方法模拟石墨烯被硅探针压变形后弯曲振动的动力学过程,探讨了石墨烯纳米带的尺寸和温度对石墨烯纳米带谐振特性的影响.模拟结果表明,石墨烯纳米带的谐振频率随着石墨烯纳米带的长度、宽度、层数(厚度)以及温度变化.其中宽度、厚度和温度对石墨烯纳米带谐振频率的影响较小,影响石墨烯纳米带谐振频率的主要因素是长度.     

石墨烯量子点和量子比特

本文主要回顾了石墨烯量子点的制备以及基于石墨烯量子点自旋和电荷量子比特操作的研究进展,由于石墨烯材料相对较轻的原子重量使其具有较小的自旋轨道相互作用,另外含有核自旋的碳同位素13C在自然界中的含量大约只占1%,这使得超精细相互作用(即核自旋和电子自旋相互作用)较弱,所以石墨烯比其他材料具有较长的自旋退相干时间,在量子计算和量子信息中有非常好的应用前景.本文计算了5种静电约束制备的石墨烯量子点:1)扶手型单层石墨烯纳米条带,2)单层石墨烯圆盘,3)双层石墨烯圆盘,4)ABC堆积型三层石墨烯圆盘,5)ABA堆积型三层石墨烯圆盘.石墨烯量子点中自旋比特应用的关键是破坏谷简并,在1)中,主要是利用边界条件破坏谷简并,而2)–5)中是利用外磁场破坏谷简并.文章进一步介绍了自旋轨道相互作用和超精细相互作用对石墨烯量子点中自旋操作的影响.     

基于石墨烯/聚二甲基硅氧烷复合材料的正己烷气体传感器

设计了一种基于石墨烯/聚二甲基硅氧烷(PDMS)复合材料的正己烷电阻式气体传感器.石墨烯/PDMS复合材料是由液相剥离的石墨烯与PDMS在异丙醇中混合而成,该复合材料的导电性与石墨烯含量正相关,电导率逾渗阈值低至0.41 wt%.当石墨烯质量分数为0.45 wt%时,对正己烷的检测极限达到了200×10-9,并且拥有非常好的可重复性.该传感器制备方法简单,成本低,且灵敏度高,在工业领域有非常大的应用潜力.     

A computational study on the quantum transport properties of silicene–graphene nano-composites

Graphene has been conjugated with Silicene which is a 2D nanosheet of silicon crystal to analyze myriad physico-chemical properties. Upon intercalation of silicene between two graphene nanosheets, there has been a significant shift in the energy of electronic configuration at different isovalues from − 0.12 to + 0.12. Similarly, by analyzing the electronic energy states of silicene–graphene–silicene, a range of isovalues from − 0.08 to + 0.08 were observed. I–V curve exhibited a linear response for graphene–silicene–graphene sandwiched structure and a semiconducting like behavior for silicene–graphene–silicene structure. Band gap measurement in case of graphene–silicene–graphene system is reported to be ~ 0.18 eV, which is a narrow region. While in case of silicene–graphene–silicene, a band gap value of ~ 1.01 eV is calculated that appears to be a pretty broad region. Transmission spectrum also shows intensity in peaks for Gr–Si–Gr case as compared to Si–Gr–Si combinations. Silicon is widely perceived to exhibit outstanding semiconducting behavior and has already been used in devising various electronic devices. In this present work, we try to analyze the outcome of the silicene and graphene at the nanometer scale in various combinations in a bid to understand the potential interaction mechanism between the two nanosheets which would help in the fabrication of the silicene–graphene based optoelectronic devices.

     

Reconfigurable terahertz Vivaldi antenna based on a hybrid graphene‐metal structure

This paper presents a reconfigurable terahertz Vivaldi antenna based on a hybrid graphene‐metal structure. The proposed antenna uses a novel tapered slot edge with hybrid graphene‐metal structure to improve the electromagnetic characteristics of classical metallic Vivaldi antennas. The results show that the proposed hybrid graphene‐metal Vivaldi antenna can be dynamically reconfigured via electric field bias, and has a low reflection coefficient. Moreover, this study demonstrates that the proposed antenna has excellent gain and radiation efficiency than that of the graphene Vivaldi antenna, and brings more possibilities to the realization and application of graphene antennas in the terahertz band, which is expected to use in terahertz wireless communication in the future.