Analytical modelling of monolayer graphene-based ion-sensitive FET to pH changes

Graphene has attracted great interest because of unique properties such as high sensitivity, high mobility, and biocompatibility. It is also known as a superior candidate for pH sensing. Graphene-based ion-sensitive field-effect transistor (ISFET) is currently getting much attention as a novel material with organic nature and ionic liquid gate that is intrinsically sensitive to pH changes. pH is an important factor in enzyme stabilities which can affect the enzymatic reaction and broaden the number of enzyme applications. More accurate and consistent results of enzymes must be optimized to realize their full potential as catalysts accordingly. In this paper, a monolayer graphene-based ISFET pH sensor is studied by simulating its electrical measurement of buffer solutions for different pH values. Electrical detection model of each pH value is suggested by conductance modelling of monolayer graphene. Hydrogen ion (H⁺) concentration as a function of carrier concentration is proposed, and the control parameter (Ƥ) is defined based on the electro-active ions absorbed by the surface of the graphene with different pH values. Finally, the proposed new analytical model is compared with experimental data and shows good overall agreement.     

The C-V-f and G/ω-V-f characteristics of Al/SiO2/p-Si (MIS) structures

The frequency dependence of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the Al/SiO₂/p-Si metal-insulator-semiconductor (MIS) structures has been investigated taking into account the effect of the series resistance (R_s) and interface states (N_ss) at room temperature. The C-V and G/ω-V measurements have been carried out in the frequency range of 1 kHz to 1 MHz. The frequency dispersion in capacitance and conductance can be interpreted only in terms of interface states and series resistance. The N_ss can follow the ac signal and yield an excess capacitance especially at low frequencies. In low frequencies, the values of measured C and G/ω decrease in depletion and accumulation regions with increasing frequencies due to a continuous density distribution of interface states. The C-V plots exhibit anomalous peaks due to the N_ss and R_s effect. It has been experimentally determined that the peak positions in the C-V plot shift towards lower voltages and the peak value of the capacitance decreases with increasing frequency. The effect of series resistance on the capacitance is found appreciable at higher frequencies due to the interface state capacitance decreasing with increasing frequency. In addition, the high-frequency capacitance (C_m) and conductance (G_m/ω) values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance. Experimental results show that the locations of N_ss and R_s have a significant effect on electrical characteristics of MIS structures.     

闭环真空压力调节阀的设计

通过难点分析、计算,介绍闭环真空压力调节阀的设计要点与方案确定.经生产实践应用证明,该调节阀设计方案切实可行.     

Coupling effects on the conductance fluctuations in GaAs/AlGaAs double quantum dots

Electron wave interference effects in GaAs/AlGaAs coupled quantum dots have been studied at 30 mK in magnetic fields with different coupling strength between two dots. In a strong coupling regime, the existence of global trajectories which span two dots was suggested, while in a weak coupling regime, the trajectories were found to be limited in each single dot.     

关于各向异性基本电子元件欧姆定律的两种形式

由于各向异性电阻元件的导电各向异性，使电流密度方向和电场强度方向不一致，从而欧姆定律表现为两种形式：电流密度方向的欧姆定律和电场强度方向的欧姆定律。相应地存在一个二阶电阻张量和一个二阶电导张量。并给出了它们的计算公式。分析表明各向异性电阻元件的欧姆定律具有近似性。     

Modulating the Aggregation Behavior of 1-Methyl-3-Octylimidazolium Chloride by Alcohols in Aqueous Media

The self-organization and aggregation behavior of a surface active ionic liquid (SAIL) 1-methyl-3-octylimidazolium chloride [C₈mim]Cl, was investigated in aqueous solutions of alcohols 1,2-propanediol and 1-propanol in different compositions using conductivity, surface tension and fluorescence measurements at room temperature. This surface active ionic liquid was synthesized by the reaction of 1-methylimidazole with 1-chlorooctane. Fluorescence spectroscopy was employed to get detailed insight into the local microenvironment of the aggregates, critical aggregation concentrations (CAC) and aggregation number (N _agg.). Degree of ionization (α), CAC and various thermodynamic parameters like the standard Gibbs free energy of aggregation (ΔG _agg. ⁰ ), standard enthalpy of aggregation (ΔH _agg. ⁰ ) and standard entropy of aggregation (ΔS _agg. ⁰ ) were calculated using conductivity measurements at different temperatures (288.15, 298.15 and 308.15 K). The surface activity of the IL in various mixed solvents was evaluated from surface tension measurements by calculating various surface parameters like the minimum surface area occupied by a single ionic liquid molecule (A _min), adsorption efficiency (pC ₂₀), maximum excess concentration at the surface (Γ _max), effectiveness of surface tension reduction(Π _CAC), surface tension at CAC (γ _CAC), p (packing parameter) and CAC at different compositions. Increases in the CAC values were observed with the increase in the amount of alcohols which is attributed to the balancing between electrostatic and hydrophobic interactions. The results from different techniques show that the CAC increases with increase in the amount of the alcohol which is due to the solubilization of the IL molecules which delays the aggregation process. This shows that the spontaneity of the aggregation process of IL decreases with the increase in the concentration of alcohols in water.     

Interactions of Molecules with Metallic Quantum Wires

Can you imagine how to detect a single molecule? Techniques, such as fluorescent spectroscopy and scanning probe microscopy have become available for us to probe single molecules. Described in this article is a simple approach based on atomically thin metallic wires. The interactions of even a single molecule with the wire may cause a large change in the conductance and mechanical properties of the wire and can thus be used to detect single molecules.     

密封铅蓄电池的电导与容量的关系

采用不同的方法对不同型式的铅蓄电池内阻测试结果表明 :荷电态高于 50 %的密封铅蓄电池 ,其内阻或电导值基本不变 ,只是在 50 %以下时才会迅速下降。对多组密封铅蓄电池统计数据证实 :失效前的铅蓄电池容量和电导之间并不存在相关关系 ,因而用密封铅蓄电池的电导值去推测电池放电容量是欠妥的     

W/O型微乳液最大增容水量的研究

研究了电导率测定微乳液的最大增溶水量及最大增溶水量的影响因素。以Span80和Tween80为复配表面活性剂,正辛烷作为油相,在超声波作用下制备微乳液;利用电导率仪测定微乳液的电导率,利用Original lab绘图软件对得到的电导率作图,通过曲线的突变点来确定微乳液的最大增溶水量。亲水亲油平衡值(HLB)和表面活性剂浓度是微乳液最大增溶水量的两个主要影响因素,通过研究它们的变化对最大增溶水量的影响,我们得出了较佳的微乳液最大增溶水量。     

金属膜材料后向反射1.06微米激光实验测试与分析

金属膜在光学应用中作用各异,用1.06 μm激光从不同入射角对5种镀金属薄膜材料作了相关后向反射实验,反射率的起伏与入射角和偏振性能有关,同时做了具体的理论分析.