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.     

光子石墨烯多方位探测传感器研究

为了实现多方位的探测,针对光子石墨烯特殊的光传输机制,在了解光子石墨烯谷依赖波束输运的基础上,选择光子石墨烯的相关参数,并设计了合适的结构模型,用COMSOL软件对其进行仿真计算.结果表明:在二维光子石墨烯结构中放置点源,点源发射的光束在平面内可以沿6个方向进行传输,此结构用于传感器即可以实现多方位的探测,可为多方位探测传感器的研制提供新的思路.     

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.     

Insight into the interaction between DNA bases and defective graphenes: Covalent or non-covalent

Although some metal clusters and molecules were found to more significantly bind to defective graphenes than to pristine graphenes, exhibiting chemisorptions on defective graphenes, the present investigation shows that the adsorption of DNA bases on mono- and di-vacant defective graphenes does not show much difference from that on pristine graphene, and is still dominantly driven by noncovalent interactions. In the present study the adsorptions of the nucleobases, adenine (A), cytosine (C), guanine, (G), and thymine (T) on pristine and defective graphenes, are fully optimized using a hybrid-meta GGA density functional theory (DFT), M06-2X/6-31G*, and the adsorption energies are then refined with both M06-2X and B97-D/6-311++G**. Graphene is modeled as nano-clusters of C₇₂H₂₄, C₇₁H₂₄, and C₇₀H₂₄ for pristine, mono- and di-vacant defective graphenes, respectively, supplemented by a few larger ones. The result shows that guanine has the maximum adsorption energy in all of the three adsorption systems; and the sequence of the adsorption strength is G > A > T > C on the pristine and di-vacant graphene and G > T > A > C on the mono-vacant graphene. In addition, the binding energies of the DNA bases with the pristine graphene are less than the corresponding ones with di-vacant defective graphene; however, they are greater than those of mono-vacant graphene with guanine and adenine, while it is dramatic that the binding energies of mono-vacant graphene with thymine and cytosine appear larger than those of pristine graphene.     

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.     

基于氧化石墨烯/金纳米粒子放大电信号的二茂铁标记型溶菌酶适体传感器

设计了一种简单的信号衰减型电化学溶菌酶适体传感器。以氧化石墨烯修饰的玻碳电极为基底（GO/GCE）,通过循环伏安法电沉积金纳米粒子在电极表面,得到AuNPs/GO/GCE。将3’端修饰巯基的单链DNA通过金硫键共价连接于电极上,而在与前者可部分杂交的适体探针链5’端标记上二茂铁甲酸。当目标物溶菌酶与适体探针链发生特异性结合,通过示差脉冲伏安法检测到二茂铁甲酸还原峰电流相应的改变,从而实现对溶菌酶的识别及定量检测。结果表明,该传感器对溶菌酶具有较好的选择性和灵敏度,对于溶菌酶的检测范围为1.08×10-11～1.08×10-8mol/L,检出限达到6.02×10-12mol/L。     

Epitaxially grown graphene based gas sensors for ultra sensitive NO2 detection

Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO₂. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO₂ detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO₂ indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO₂ making holes the majority carriers.     

臭氧处理对石墨烯基NO_2气体传感器气敏性影响

通过臭氧处理制备了一种简单、高效、可重复使用的单层石墨烯基NO2气体传感器,并研究了纯的和经过臭氧处理的NO2气体传感器的响应特性和恢复特性。实验表明:经臭氧处理75s后的石墨烯基气体传感器对10×10-6NO2响应度可达到30%以上,是未经臭氧处理的石墨烯基气体传感器的2.8倍,且其响应的最低体积分数达150×10-9,低于世界卫生组织(WHO)空气质量标准(200×10-9,1h平均值)。     

基于Pt/石墨烯纳米复合材料的甲醛电化学传感器

采用电沉积的方法制备了Pt/石墨烯纳米复合材料,考察了该复合材料的电化学性能,用于甲醛的检测,表现出良好的检测性能.实验结果表明:在0. 1 mol/L的H2 SO4 溶液中,Pt/石墨烯纳米复合材料修饰电极可以实现在2 ×10 -6 ~2 ×10-3 mol/L浓度范围内甲醛浓度的检测,最低检测限为1 ×10-6 mol/L,并且具有高的灵敏度和良好的重现性.     

Hydrogen sensing of N-polar and Ga-polar GaN Schottky diodes

N-polar and Ga-polar GaN grown on c-plane sapphire were used to fabricate platinum deposited Schottky contacts for hydrogen sensing at room temperature. After exposure to hydrogen, Ga-polar GaN Schottky barrier reduced by 3–4 meV, while the N-polar GaN Schottky contacts became fully Ohmic. The N-polar GaN Schottky diodes showed stronger and faster response to 4% hydrogen than that of Ga-polar Schottky diodes. The abrupt current increase from N-polar GaN Schottky exposure to hydrogen was attributed to the high reactivity of the N-face surface termination. The surface termination dominates the sensitivity and response time of the hydrogen sensors made of GaN Schottky diodes.     

荷电对石墨烯的声子结构和电- 声子耦合的影响研究

石墨烯材料需要经过不同的改性处理才能够在电子器件领域大规模应用,其中荷电就是一种非常有效的手段。文章通过第一性原理计算方法研究了带有少量电荷(电子或空穴)的单层石墨烯的电子和声子态特征,以及电-声子相互作用变化,发现荷电可以使费米能级发生移动,导致石墨烯展现金属特征。在石墨烯中引入电荷没有改变 z 轴方向声学的振动模,不会引起石墨烯的弯曲。在石墨烯中注入电子,可以引起声子模式的软化,电-声耦合强度随着引入的电子浓度增加而增强。由于引入电荷可以调节纵向光学的声子频率的变化并且导致一个更强的电-声子相互作用,推断通过该途径可以提高石墨烯中载流子的迁移率。     

Low temperature hydrogen detection at high concentrations: comparison of platinum and iridium

A comparison of platinum and iridium in work-function measurements with regard to hydrogen sensitivity is presented. The measurements were performed by means of a Kelvin probe and an ISFET-based measurement setup. They are concentrated towards high concentrations of hydrogen and low temperature in order to develop room temperature operated FET-based sensors which can withstand H₂-concentrations of some percent. With both materials the detection of H₂ up to 2% is possible. However, iridium shows very-slow reactions with adsorption as well as with desorption times of some hours. In contrast, the response times of platinum could be determined to be below 10 s in the case of 0.1% H₂. Therefore, platinum is the most promising candidate with air-gap configurations of FET like hybrid suspended gate FET (HSGFET).     

基于石墨烯-海藻酸钠复合材料的辣根过氧化物酶传感器研究

构建了一种以海藻酸钠-石墨烯(SA-GR)为基底的新型过氧化氢电化学酶传感器。利用滴涂法将生物相容性良好的海藻酸钠-石墨烯复合物固定在玻碳电极表面,再通过酰胺键将HRP连接在SA-GR复合膜上,从而制备出了性能良好的过氧化氢电化学酶传感器。该传感器重现性好、灵敏度较高,并且响应速度快(3 s),米氏常数较低(Km=0.663),对H2O2检测的线性范围为1.0×10-4～1.2×10-3mol/L,检测下限为5.7×10-6mol/L。     

基于纳米金／石墨烯－壳聚糖－离子液体／L－半胱氨酸包覆CdTe量子点的双酚A传感器

在石墨烯、壳聚糖和1-乙基－3－甲基眯唑四氟硼酸盐（[BMIM]）复合材料（Graphene—Chits-[BMIM]）表面电沉积金,并自组装L－半胱氨酸包覆CdTe量子点,制备了修饰玻碳电极新型双酚A传感器。采用循环伏安法和电化学交流阻抗等方法研究了修饰电极的电化学特性。由于Graphene-Chits－[BMIM]复合材料中,石墨烯和[BMIMI都具有良好的导电性,该修饰电极对于双酚A有较好的电流响应。在最佳条件下,该传感器对双酚A的检测浓度范围：5．0×10^-8～7．05×10^-6mol／L,检测限为2．0×10^-8mol／L（3倍信噪比）,相关系数为0．999。     

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.     

一种检测莱克多巴胺的复合碳纳米材料修饰电化学传感器

将双壁碳纳米管(DWCNT)和氧化石墨烯(GO)超声分散在Nafion的乙醇溶液中,滴涂于玻碳电极(GCE)表面制得氧化石墨烯/双壁碳纳米管-Nafion复合材料修饰电极(GO/DWCNT-Nafion/GCE),可用于莱克多巴胺的灵敏检测。通过扫描电镜(SEM)对修饰电极表面形貌进行表征。使用差分脉冲伏安法(DPV)对莱克多巴胺在修饰电极上的电化学行为进行研究。实验结果表明,该修饰电极对莱克多巴胺表现出了强的电催化氧化效应。在pH=7.0的PBS缓冲体系中于-0.3 V下富集120 s后,该修饰电极对莱克多巴胺浓度在1.0×10-8~1.0×10-6mol/L范围内有着良好的线性响应,检测限为5.4×10-9 mol/L。同时,该电极选择性良好,表明该方法在食品安全检测领域具有实际应用前景。     

带裂纹石墨烯增强金属泡沫梁的振动特性研究

分析了带裂纹功能梯度石墨烯增强金属泡沫梁的自由振动.采用Timoshenko梁理论进行建模,裂纹由无质量扭转弹簧模拟,利用Halpin Tsai微观力学模型预测材料的有效性能.通过哈密顿原理,得到了带裂纹功能梯度石墨烯增强金属泡沫(FG GPLRMF)梁的运动方程及其边界条件.采用微分变换法分析带裂纹FG GPLRMF梁的自由振动.结果表明,带裂纹FG GPLRMF梁的振动特性受到石墨烯几何尺寸、孔隙类型和石墨烯分布的影响显著.     

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.     

Flow-injection determination of iron(III) in soil by biamperometry using two independent redox couples

A flow-injection biamperometric method for the determination of iron(III) has been described. The detector consists of two chambers separated by a salt bridge, and one platinum wire working electrode is embedded in each chamber, respectively. When iron(III) solution and hydrogen peroxide solution simultaneously flow through two chambers, the reduction of iron(III) at one platinum electrode is associated with the oxidation of hydrogen peroxide at the other platinum electrode, forming such a system as similar to a reversible couple one. The biamperometric system can perform the determination of iron(III) without any external potential difference. The linear relationship is obtained from 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol l⁻¹ with a detection limit of 6.0 × 10⁻⁷ mol l⁻¹. The proposed method exhibits the satisfactory reproducibility with a relative standard derivation (R.S.D.) of 1.4% for 17 successive determinations of 2.0 × 10⁻⁵ mol l⁻¹ iron(III) and is applied to the determination of iron(III) in soil.     

三维泡沫石墨烯在抗坏血酸的干扰下检测尿酸

该文采用化学气相沉积法在泡沫镍上生长石墨烯,通过扫描电镜、X射线衍射、拉曼光谱对生成产物的形貌和结构分别进行了表征。结果表明：所制得的石墨烯为具有三维网状结构且层数较少的石墨烯。将三维泡沫石墨烯转移到ITO玻璃上制成生物传感器的工作电极,利用电化学工作站对尿酸和抗坏血酸进行检测．电化学测试结果表明：三维泡沫石墨烯修饰电极在抗坏血酸的干扰下可以准确的检测尿酸,其灵敏度为0．274μA／（μmol／L）,线性范围为10-100μmol／L。