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Across a wide range of biomarker detection schemes, carboxyl-terminated thiol self-assembled monolayers (COOH-SAMs) on Au are utilized to functionalize the sensing surface with a bioreceptor via am...

Background. The Auto Manipulation Device for Acupuncture (AMDA) is designed for providing stable, quantified effects and higher frequency when doing lifting and thrusting manipulation. The purpose of this study is to investigate the safety of manipulation by AMDA in different frequency and duration in healthy rats. Methods. The study was divided into two parts: single intervention and once a day for a week. 12 rats and 15 rats were randomly allocated to different groups: Control (needle insertion only), AMDA (2Hz/10Mins), AMDA (2Hz/20Mins), AMDA (20Hz/10Mins), and AMDA (20Hz/20Mins) for single and repeated interventions. Real-time physiological functions, laboratory data, and the bilateral muscle tissue of acupoint (ST 36) were obtained after the intervention. Results. We found neither real-time physiological functions nor laboratory data differences between control group and AMDA groups in both parts. In the muscle tissue samples, the slight damage had been observed in the AMDA group with a frequency of 2 Hz for 20 minutes after once intervention, and the repeated session groups noted more obvious tissue damage with fibrotic change. Although the period was shorter, higher frequency manipulation caused more damage that fibroblast nuclei became more slender and obvious. However, no significant adverse effect was noted such as crippled and molting in the whole process. Conclusion. Our study suggested that the safety issue of AMDA operation in rats is feasible because there was no difference between control group and AMDA groups among real-time physiological functions and laboratory data. However, manipulation with higher frequency should be more preserved.

The development of processes to controllably dope two-dimensional semiconductors is critical to achieving next-generation electronic and optoelectronic devices. In this study, n- and p-doping of highly uniform large-area trilayer WSe2 is achieved by treatment with solutions of molecular reductants and oxidants. The sign and extent of doping can be conveniently controlled by the redox potential of the (metal−)organic molecules, the concentration of dopant solutions, and the treatment time. Threshold voltage shifts, the direction of which depends on whether a p- or n-dopant is used, and tunable channel current are observed in doped WSe2 field-effect transistors. Detailed physical characterization including photoemission (ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy) and Raman spectroscopy provides fundamental understanding of the underlying mechanism. The origin of the doping is the electron-transfer reactions between molecular dopants and 2D semiconductors and results in a sh...

In this work, lithium-doped zinc oxide nanoparticles (LZO NPs) with different Li/Zn molar ratios (Li/Zn = 0, 0.05, 0.2) are successfully prepared to form an electron transporting layer (cathode buffer layer) in the inverted-type P3HT:ICBA organic photovoltaic (OPV) devices. As compared with the undoped ZnO NPs buffer layer, a considerable improvement OPVs from 2.344% to 2.946% is obtained by using 5%-LZO NPs as a buffer layer, which owns Jsc of 7.22 mA/cm2, Voc of 0.86 V, and FF of 47.4%. X-ray absorption near-edge structure (XANES) spectra show the increase of unoccupied O 2p-derived states in 5%-LZO NPs, which leads to better carrier conductance. The energy levels of defects in 5%-LZO NPs analyzed by photoluminescence are found to facilitate electron extraction to the cathode. Impedance measurement results indicate that the carrier lifetime is effectively increased to 2176 μs by applying the 5%-LZO NPs buffer layer, showing the improvement of carrier extraction efficiency and resulting in its progressiv...

Quantitative point-of-care (POC) devices are the next generation for serological disease diagnosis. Whilst pathogen serology is typically performed by centralized laboratories using Enzyme-Linked ImmunoSorbent Assay (ELISA), faster on-site diagnosis would infer improved disease management and treatment decisions. Using the model pathogen Bovine Herpes Virus-1 (BHV-1) this study employs an extended-gate field-effect transistor (FET) for direct potentiometric serological diagnosis. BHV-1 is a major viral pathogen of Bovine Respiratory Disease (BRD), the leading cause of economic loss ($2 billion annually in the US only) to the cattle and dairy industry. To demonstrate the sensor capabilities as a diagnostic tool, BHV-1 viral protein gE was expressed and immobilized on the sensor surface to serve as a capture antigen for a BHV-1-specific antibody (anti-gE), produced in cattle in response to viral infection. The gE-coated immunosensor was shown to be highly sensitive and selective to anti-gE present in commercially available anti-BHV-1 antiserum and in real serum samples from cattle with results being in excellent agreement with Surface Plasmon Resonance (SPR) and ELISA. The FET sensor is significantly faster than ELISA (

Hybrid structures based on integration of two dimensional (2D) transition metal dichalcogenides (TMDCs) with optical resonators have recently earned significant attention. The enhanced interaction of light with 2D materials in such hybrid structures can enable devices such as efficient light emitting diodes and lasers. However one of the factors affecting the performance of such devices is the effect of the optically induced heat on the optoelectronic properties of the 2D materials. In this study we systematically investigate principal roots of heat generation in hybrid cavity coupled few atomic layer thick 2D TMDC films under optical pumping. The optical resonator exploited here is a Fabry–Perot (FP) resonator which can enhance the light–MoS2 interaction by a significant factor of 60 at its resonance wavelength. We have combined an accurate theoretical modeling with experimental Raman spectroscopy to determine the roots of heat generation in MoS2 films integrated with FP resonators. Our investigations reveal that the strong modulation of light absorption in the MoS2 film induced by excitation of an FP cavity at its resonant frequency plays the primary role in excess heat generation in 2D materials. Furthermore through varying the cavity length we show that on resonance and off resonance excitation of the cavity results in completely different temperature profiles in the cavity coupled MoS2 films. Also by changing the resonance medium of the FP cavity (SiO2 and air) we take into account the role of the heat sinking effect of the substrate in heat generation in MoS2 films. In this study the temperature dependent red shift of the Raman spectra is employed to monitor the local temperature of the MoS2 films. Our results show the importance of the heating effect in such hybrid structures and represent a step forward for the design of practical hybrid optical devices based on layered semiconducting 2D materials.

Tunneling devices based on vertical heterostructures of graphene and other 2D materials can overcome the low on-off ratios typically observed in planar graphene field-effect transistors. This study addresses the impact of processing conditions on two-dimensional materials in a fully integrated heterostructure device fabrication process. In this paper, graphene-molybdenum disulfide-graphene tunneling heterostructures were fabricated using only large-area synthesized materials, unlike previous studies that used small exfoliated flakes. The MoS2 tunneling barrier is either synthesized on a sacrificial substrate and transferred to the bottom-layer graphene or synthesized directly on CVD graphene. The presence of graphene was shown to have no impact on the quality of the grown MoS2. The thickness uniformity of MoS2 grown on graphene and SiO2 was found to be 1.8 ± 0.22 nm. XPS and Raman spectroscopy are used to show how the MoS2 synthesis process introduces defects into the graphene structure by incorporating sulfur into the graphene. The incorporation of sulfur was shown to be greatly reduced in the absence of molybdenum suggesting molybdenum acts as a catalyst for sulfur incorporation. Tunneling simulations based on the Bardeen transfer Hamiltonian were performed and compared to the experimental tunneling results. The simulations show the use of MoS2 as a tunneling barrier suppresses contributions to the tunneling current from the conduction band. This is a result of the observed reduction of electron conduction within the graphene sheets.

The synthesis of few-layer tungsten diselenide (WSe2) via chemical vapor deposition typically results in highly non-uniform thickness due to nucleation initiated growth of triangular domains. In this work, few-layer p-type WSe2 with wafer-scale thickness and electrical uniformity is synthesized through direct selenization of thin films of e-beam evaporated W on SiO2 substrates. Raman maps over a large area of the substrate show small variations in the main peak position, indicating excellent thickness uniformity across several square centimeters. Additionally, field-effect transistors fabricated from the wafer-scale WSe2 films demonstrate uniform electrical performance across the substrate. The intrinsic field-effect mobility of the films at a carrier concentration of 3 × 10(12) cm(-2) is 10 cm(2) V(-1) s(-1). The unprecedented uniformity of the WSe2 on wafer-scale substrates provides a substantial step towards producing manufacturable materials that are compatible with conventional semiconductor fabrication processes.

© 2015 American Chemical Society. Atomically thin molybdenum disulfide (MoS2) is a promising two dimensional semiconductor for high performance flexible electronics sensors transducers and energy conversion. Here piezoresistive strain sensing with flexible MoS2 field effect transistors (FETs) made from highly uniform large area films is demonstrated. The origin of the piezoresistivity in MoS2 is the strain induced band gap change which is confirmed by optical reflection spectroscopy. In addition the sensitivity to strain can be tuned by more than 1 order of magnitude by adjusting the Fermi level via gate biasing.

Highly uniform large-area MoS2 is chemically doped using molecular reductants and oxidants. Electrical measurements, photoemission, and Raman spectroscopy are used to study the doping effect and to understand the underlying mechanism. Strong work-function changes of up to ±1 eV can be achieved, with contributions from state filling and surface dipoles. This results in high doping densities of up to ca. 8 × 10(12) cm(-2) .

A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications.

Molybdenum disulfide (MoS2) is a layered semiconducting material with a tunable bandgap that is promising for the next generation nanoelectronics as a substitute for graphene or silicon. Despite recent progress the synthesis of high quality and highly uniform MoS2 on a large scale is still a challenge. In this work a temperature dependent synthesis study of large area MoS2 by direct sulfurization of evaporated Mo thin films on SiO2 is presented. A variety of physical characterization techniques is employed to investigate the structural quality of the material. The film quality is shown to be similar to geological MoS2 if synthesized at sufficiently high temperatures (1050 °C). In addition a highly uniform growth of trilayer MoS2 with an unprecedented uniformity of ±0.07 nm over a large area (> 10 cm2) is achieved. These films are used to fabricate field effect transistors following a straightforward wafer scale UV lithography process. The intrinsic field effect mobility is estimated to be about 6.5±2.2 cm2 V 1 s 1 and compared to previous studies. These results represent a significant step towards application of MoS2 in nanoelectronics and sensing. © 2014 WILEY VCH Verlag GmbH Co. KGaA Weinheim.

Efficient charge transport across proper interfacial contacts is crucial in organic solar cells. In this paper, the surface of the P3HT:PCBM bulk heterojunction (BHJ) layer is treated with ethylene...

Zn 2 GeO 4 nanorods were synthesized using a simple reflux method. The product with 0.05 M Zn 2 GeO 4 is an aggregation of short nanorods with the diameter ranging from 30 to 50 nm. If the Zn 2 GeO 4 molarity was increased, the nanorods became longer and aggregated as bundles. An intense white-bluish photoluminescence (PL) was observed from these nanorods, and the PL band can be dissolved into four Gaussian peaks that are associated with the native defects. Since the PL intensity of the nanorods is comparable to that of sintered particles, this reflux method provides a time- and energy-efficient route to prepare Zn 2 GeO 4 phosphor.

In this study, atomic layer deposition (ALD) has been applied to deposit aluminum doped zinc oxide (AZO) films as gas barriers, successfully. Diethylzinc and trimethylaluminum were used as precursors and water as oxidant. Sequential deposition steps of 400 ALD cycles have been adopted to prepare AZO films. Influences of deposition temperatures on electro-optical properties have studied by using Hall-effect measurement and transmittance spectrometer. AZO film deposited at 130 oC has a low resistivity of 5×10-3 Ω-cm. Water vapor transmittance rate has been carried out by using Mocon Permatran-W 3/61. The WVTR performances of ALD barriers, which highly related to the physical conditions of interfaces between nanolaminated structures, have been measured as 0.001 – 2 g/m2*25oC*day.

This work proposes design, optimization and validation of a new two degree-of-freedom (DOF) rotational optical image stabilizer (OIS) that is suitable for installing into a mobile-phone-camera. This OIS differs from the previous designs since it stabilizes the lens holder directly by two-DOF translational mechanisms that are actuated by voice coil motors. The work can be divided into three main parts: (1) designs of mechanism and genetic algorithm (GA) optimization of magnetic field, (2) establishments of the dynamic model and equation of motions (EOM) of a dual-axis rotational structure, and (3) realizations of a sliding mode control (SMC) controller with fine performance. The dynamic of the dual-axis rotational OIS system has been analyzed and the EOM has been derived. Based on the Lagrange’s method, the motions of the OIS have been modeled through considering kinetic energy and electromagnetic torques. In the last part, the theory of SMC is applied, and the associated simulations are conducted. Based on the simulation results, the SMC controller is forged with the assistances from MATLAB pre-simulation and tested by a microprocessor module. After a series of experiments and verifications, the prototype of the novel OIS is finally accomplished with satisfactory performance of vibration reduction.

This study performs precision positioning of a generic piezoelectric structure against hysteresis effects by finite elements, microscopic hysteresis cancellation and robust H ∞ compensation. The designed control algorithm is expected to be effective in enhancing servo performance of hard disk drives. The precision positioning is accomplished by adding a polarization term into the linear constitutive equations of piezoelectric materials. This polarization term is then described by the well-known Preisach model. Applying basic principles of finite elements and Hamilton’s thoery, the macroscopic governing equations of an arbitrary piezoelectric system in finite elements are obtained. Based on the macro-model, a controller consisting of two parts is designed to perform the precision positioning of a generic piezo-structure. The first part is responsible for direct hysteresis cancellation at the microscopic level, while the second one is a robust H ∞ controller to overcome inevitable cancellation errors. In this way, the control effort is then more effective than the conventional PI and double-lead controller without microscopic hysteresis cancellation. A simple piezoelectric structure of a bender-bimorph cantilever beam is considered for designs and experimental validation. Based on experimental results, the proposed control design is found effective to suppress hysteresis effects as opposed to conventional controllers.

In this work, we demonstrate the cell efficiency improvements by means of some technologies, which include reactive ion etching (RIE) texturing, selective emitter (SE), double printing (DP), and light induced plating (LIP). Besides, some potential issues to transfer these technologies into mass production are also discussed.

With atomic-layer-deposition grown zinc oxide as the electron selective layer, we developed plastic substrate compatible processing for organic photovoltaic devices and demonstrated flexible inverted organic solar cells on poly(ethylene naphthalate) with a power conversion efficiency of 4.18%.

The aim of this work is to compare the radiosensitizing effect between organic and inorganic germanium compounds and to investigate whether nanometer-sized germanium particles can act as radiosensitizers.Bis (2-carboxyethylgermanium) sesquioxide (Ge-132), germanium oxide (GeO(2)) and germanium nanoparticles were used in this study. Cell viability was determined by clonogenic survival assay. Cellular DNA damage was evaluated by alkaline comet assay, confocal microscopy and the cellular level of phospho-histone H2AX (gamma-H2AX).Nanometer-sized germanium particles were fabricated. They have a similar radiosensitizing effect as that of GeO(2). Conversely, Ge-132 did not enhance the radiosensitivity of cells. Comet assay was employed to evaluate the level of DNA damage and confirmed that inorganic germanium compounds enhanced cellular radiosensitivity. Notably, the comet assay indicated that the nanoparticle itself caused a higher level of DNA damage. The possibility that germanium nanoparticles per se caused DNA damage was ruled out when the cellular level of gamma-H2AX was examined.We demonstrated that inorganic but not organic germanium compounds exerted radiosensitizing effect in cells. Nanometer-sized germanium particles were fabricated and were able to enhance the radiosensitivity of cells. Confounding effect may occur when comet assay is used to estimate the level of DNA damage in the presence of germanium nanoparticles.

Single-crystalline Zn2GeO4 nanorods were formed by submerging Zn-containing Ge nanoparticles (ZCGNs) in water at room temperature. These nanorods with the diameter ranging from several tens to more than 100 nm and the length of several micrometers exhibit a blue-green luminescence peak at 450 nm. Due to the surface instability of Ge in water, the agglomerates of crystalline ZCGNs keep oxidizing, and gradually transform into amorphous membranes composed of Zn, Ge, and oxygen. Zn2GeO4 nanorods then grow out directly from the amorphous membranes after further aging. This novel transformation route may provide a new thinking for preparing similar 1-D Ge-based ternary oxides or other 1-D nanomaterials.

Si nanocrystallites of various sizes and oxygen-containing Si nanoparticles with different oxygen contents were prepared by vapor condensation. The Si nanocrystallites showed a visible light emission from 500 nm to 900 nm with the peak at 800 nm, and the intensity of photoluminescence increased with decreasing the particle size. This photoluminescence observed in vacuum could be quenched by air and hydrogen, and reappeared after the sample chamber was evacuated. The oxygen-containing Si nanoparticles consisting mainly of Si oxide were amorphous and had an average particle size of approximately 20 nm. Increasing the oxygen content of nanoparticles caused a blueshift of the absorption edge in the transmission spectra. A blue-green photoluminescence with two peaks at 500 nm and 800 nm was observed from these oxygen-containing Si nanoparticles. The luminescence intensity increased with the oxygen content of nanoparticles, and was very sensitive to the ambient atmosphere. Much lower intensity was observed in air, but higher intensity could be recovered in vacuum. Surface states and oxygen-induced luminescent centers were proposed to be responsible for the photoluminescence from the Si nanocrystallites and oxygen-containing Si nanoparticles, respectively. The reversible ambient effect in both cases could be explained by surface charge redistribution during the gas adsorption and desorption processes.

Si quantum dots (SiQDs) with sizes ranging from 5 to 20 nm were fabricated by vapor condensation. They showed red photoluminescence (PL) in vacuum with the peak located at around 750 nm. After the specimen was exposed to air, the PL intensity became higher, and continued to increase during the PL test with a cycling of vacuum-air-vacuum. In pure oxygen, the PL intensity exhibited an irreversible decrease, while in nitrogen a smaller amount of reversible increase of PL intensity was observed. Furthermore, the PL intensity exhibited a remarkable enhancement if the SiQDs were treated with water. With HF treatment, the PL peak position showed a blue-shift to 680 nm, and was recovered after subsequent exposure to air. Si–O–H complexes were suggested to be responsible for this red luminescence. The irreversible decrease of PL intensity due to oxygen adsorption was speculated to be caused by the modification of chemical bonds on the surface. In the case of nitrogen adsorption, the PL change was attributed to the surface charging during adsorption.

Focused ultrasound (FUS) exposure with the presence of microbubbles has shown its promise in temporally and targeted open the blood-brain barrier (BBB), and brings potential in delivering therapeutic agents into the brain for CNS disease treatment. Feasibility in using neuronavigation system to guide the FUS-BBB procedure in large animals has been demonstrated successfully, and the guidance precision has been measured to be acceptably low. However, it is still unknown whether same precision and power compensation strategy is valid when FUS beam is intend to penetrate the human skull. The purpose of this study is to verify that using neuronavigation system combined with a prior treatment plan can successfully guide FUS-BBB opening with the consideration of involvement of human skull. A human cadaver was employed to perform CT scan, and a treatment planning software was developed to simulate focal beam redistribution and pressure decay when transcranial FUS exposure were performed. During experiment, 4 groups were conducted to verify the success of BBB-opening when incorporating with the in-prior treatment plan. Our results suggest that under the guidance of neuronavigation and prior treatment planning is feasible to precisely guide the FUS-BBB opening procedure, and may have potential to be applied for future clinical brain drug delivery interventions.

Focused ultrasound (FUS) has been discovered its utility in targeted increase blood-to-brain permeability in the brain and capable of enhancing drug delivery for CNS disease treatment. To achieve successful treatment, the overall FUS exposure process relies on employing a sophisticated treatment planning procedure to precisely target the ultrasound energy to the aim and compensate the skull-induced energy loss and focal beam distortion issues. An interactive interface is therefore essential to be developed prior to the clinical application of the FUS brain treatment. In this study, we propose the development of an OpenGL-based interactive graphic interface realization for treatment planning of FUS-induced brain treatment. We demonstrate the usefulness of the proposed interface in providing functions including interactive 3D anatomical demonstration, co-registration, and FUS pattern prediction and simulation.

We demonstrate piezoresistive strain sensors based on flexible MoS 2 field-effect transistors made from a highly uniform large-area trilayer film. The origin of the piezoresistive effect in MoS 2 is explained to be a strain-induced band gap change, as confirmed by optical spectroscopy. The results are in good agreement with recently reported simulations and spectroscopic studies on strained exfoliated MoS 2 . In addition, the strain sensitivity can be tuned by over one order of magnitude via modulating the MoS 2 Fermi level with an applied gate voltage. The gate-tunable gauge factors can be as high as −40, comparable to polycrystalline silicon, but for a much thinner active layer (∼2 nm). For practical sensing applications, the gate-tunable piezoresistivity is a useful property of transistor-based devices, because the relative sensitivity to strain can be adjusted by changing the gate voltage.

Focused ultrasound (FUS) with the presence of microbubbles has been shown to induce transient and local opening of the blood-brain barrier (BBB) for the delivery of therapeutic molecules which normally cannot penetrate into the brain. The success of FUS brain-drug delivery relies on its integration with in-vivo imaging to monitor kinetic change of therapeutic molecules into the brain. In this study, we developed a dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) technique for kinetic analysis of delivered molecules during FUS-BBB opening. Three kinetic parameters (Ktrans, Ve, Kep) were characterized dynamically to describe BBB-permeability at two FUS exposure conditions (0.4 or 0.8MPa) over 24h. Ktrans, defined as the influx volume transfer constant from plasma to EES, and Ve, the EES volume fraction, were both found to be pressure-dependent. Ktrans and Ve showed a peak increase of 0.0086-0.0131min(-1) (for 0.4-0.8MPa pressure), and 0.0431-0.0692, respectively, immediately after FUS exposure. Both parameters subsequently decreased exponentially as a function of time, with estimated half-lives of decay of 2.89-5.3 and 2.2-4.93h, respectively. The kinetics of Kep, defined as the efflux rate constant from the extracellular extravascular space (EES) to the plasma, were complementary to Ktrans, with an initial decrease from 0.2010 to 0.1901min(-1) followed by a significantly longer recovery time (half-life of 17.39-99.92h). Our observations strongly supported the existence of imbalanced and mismatched kinetics of influx (Ktrans) and efflux (Kep) between the plasma and EES, indicating the existence of directional permeability during FUS-BBB opening. We further showed that kinetic change determined by DCE-MRI correlated well with the concentration of Evans Blue (EB)-albumin (coefficient of 0.74-0.89). These findings suggest that MRI kinetic monitoring may serve as an alternative method for in-vivo monitoring of pharmacokinetics and pharmacodynamics (PK/PD) change of therapeutic agents during drug delivery to the brain, and provide useful information for future optimization of FUS-BBB opening.

Molybdenum disulfide (MoS2) has recently received significant attention because of its interesting thickness dependent properties and its potential as a semiconducting substitute to graphene [12]. Most of the studies so far have focused on small (

Because of its well-defined surface configuration and creative chemical structure, an alkanethiol self-assembled monolayer (SAM) on gold is a model surface for a blood compatibility investigation. In this study two laboratory-synthesized long-chain alkanethiols, HS(CH 2 ) 10 PO 3 -(C 2 H 5 ) 2 and HS(CH 2 ) 10 PO 3 H 2 , were employed for the direct preparation of SAMs with nonionic and ionic functional groups. Various instrumental analyses confirmed the high purity of the phosphonate ester and phosphonic acid terminated alkanethiols. The surface characterization results showed the -PO 3 H 2 terminated SAM was more hydrophilic than the -PO 3 (C 2 H 5 ) 2 one. Higher hysteresis values for the -PO 3 (C 2 H 5 ) 2 and -PO 3 H 2 terminated SAMs were noted, which were possibly due to the steric hindrance of the bulky terminal groups. In addition, the O 2 plasma + EtOH-rinse pretreated Au sample was hydrophilic because of the residual gold oxide on the surface. This finding was supported by electron spectroscopy for chemical analysis (ESCA) as well. The ESCA analysis also indicated bulky and polar terminal groups [-PO 3 (C 2 H 5 ) 2 and -PO 3 H 2 ] were situated in the outermost layer of its monolayer. The platelet reactivity on the SAM with the nonionic group -PO 3 (C 2 H 5 ) 2 was less than those of the ionic terminated SAMs -COOH and -PO 3 H 2 . The O 2 plasma + EtOH-rinse pretreated gold substrate exhibited the least platelet-activating surface among the different pretreated Au substrates studied.

Two diastereomeric carboxylic acids, 2(S)-[2(R)-methylhexyloxy]propionic acid and 2(S)[2(S)-methylhexyloxy]propionic acid, were prepared from ethyl (S)-lactate and (R)-1-iodo2-methylhexane or (S)-1-iodo-2-methylhexane in the presence of Ag2O. From these acids two liquid crystals, 2 and 3, whose configurations are (S, R) and (S, S) were synthesized and their liquid crystal properties investigated. Although both LCs have the same phase sequence Cr-SmC*-N*-I as well as a wide SmC* phase range, the influence of the relative stereochemistry on their physical properties is clear. The liquid crystal with (S, S)-configuration possesses better properties: lower SmC* phase transition temperature, wider SmC* phase range and higher Ps value. The Ps value difference between the ferroelectric LCs 2 and 3 (97 and 131nCcm-2, respectively, at Tc - T = 10°C) is unexpectedly large. The consideration, alone, of a zigzag conformation at the chiral molecular part of 2 and 3 is insufficient to explain such a difference.

A diamine-containing oxyethylene unit, 2,2-bis[4-[2-(4-aminophenoxy)ethoxy]phenyl]propane (BAEPP), was used as a monomer with various aromatic tetracarboxylic dianhydrides to synthesize polyimides via a conventional two-step procedure. The diamine was prepared through the nucleophilic displacement of [2,2-bis(4-β-hydroxyethoxy)phenyl]propane with p -chloronitrobenzene in the presence of K 2 CO 3 , followed by catalytic reduction. Depending on the dianhydrides used, the poly(amic acid)s obtained had inherent viscosities of 0.97–1.57 dL g −1 . All the poly(amic acid)s could be cast from the DMAc solutions and thermally converted into transparent polyimide films. The polyimide films had a tensile strength range of 57–97 MPa, an elongation range at break of 3–7%. The polyimides derived from 4,4′-sulfonyldiphthalic anhydride and 4,4′-hexafluoro-isopropylidenediphathalic anhydride exhibited excellent solubility in organic solvents. These polyimides had glass transition temperatures between 252 and 314°C, and 10% mass loss temperatures were recorded in the range of 466–479°C in nitrogen. © 1997 Elsevier Science Ltd

Synthesis and Properties of Polyamides Derived from 2,2-Bis[4-[2-(4-aminophenoxy)-ethoxy]phenyl]propane by Direct Polycondensation

Quantitative point-of-care (POC) diagnostic tools are crucial for next-generation human (and animal) health monitoring and disease diagnosis to rapidly infer effective treatment decisions. ELISA based disease diagnostics is often performed off-site in centralized labs, requiring long turnaround times (>72hrs), reducing the effective period for disease intervention. In this study, a gold sensing surface is shown to provide ELISA-equivalent results across multiple label-free and rapid biosensing platforms including potentiometric field-effect transistor (FET) biosensors, electrochemical impedance spectroscopy (EIS) biosensors and surface plasmon resonance (SPR) devices. Using the model pathogen Bovine Herpes Virus 1 (BHV-1) (a major source of economic loss in the agri-food industry globally 1), BHV-1 glycoprotein E (gE) was attached to sensor surfaces to detect the immunological interaction against anti-BHV-1 antibodies. The use of a gold sensing surface offers access to the well-established thiol surface functionalization and protein immobilization via amine coupling. This functionalized gold sensing surface is used to compare the response of ELISA in four different sensing platforms: (1) as the gate electrode for graphene ion-sensitive field-effect transistor (ISFET), (2) as the gate electrode for extended-gate field-effect transistor (EGFET) sensors (3) as the working electrode (WE) for EIS sensors, and (4) as the sensing surface for SPR. The results show that the sensitivity of the EGFET biosensors is equivalent to the ISFETs.2 Moreover, EGFET biosensors provide many advantages including improved reliability by separating the sensor and transducer components, low-cost and easy fabrication, disposable chip design and high compatibility with state-of-art semiconductor technologies.3-5 While the mechanism for EIS is quite different than potentiometric FET-based sensing, the dynamic response is found to be equivalent. Similarly, the same Au surface can be used in optical SPR biosensors using the same surface chemistry. The universality of a Au sensing surface allows detection using multi-platforms but with a single chip and, therefore, simplifies the sample preparation and reduces the required sample volumes for diagnostics. All three electrical sensors demonstrate performance equivalent to SPR and ELISA, with dynamic range approaching the limit of detection for sera dilutions < 10-3of anti-BHV-1 antiserum. However, the potentiometric and EIS sensors provide results much faster (~10 min.) than SPR (~2 hr.) and ELISA (> 20 hr.) Additionally, the electronic biosensors are compact in size and are promising for POC devices. In conclusion, a gold surface is shown to provide universal and equivalent sensing across multiple platforms using well-established surface chemistry. Furthermore, the use of one surface to facilitate integration of multiple sensing mechanisms can potentially improve specificity. Among all of the available biosensor technologies, electrical biosensors provide rapid, label-free and cost-efficient sensing capability in a compact size, which is promising for quantitative point-of-care devices. 1G. D. Snowder et al. Journal of Animal Science 85, 1885 (2007). 2A. Tarasov et al. 2D Materials 2, 044008 (2015). 3L.-L. Chi et al. Materials Chemistry and Physics 63 , 19 (2000). 4P. Dak et al. Device Research Conference (DRC), 2013 71st Annual, 105 (2013). 5W. Guan et al. Biosensors and Bioelectronics 51, 225 (2014).

A new method to prepare amorphous Ca5Ge2O9 nanowires is demonstrated in the present study. Germanium nanoparticles with the size ranging from 10 to 50 nm were first prepared by a vapor condensation technique. Upon immersing the nanoparticles in Ca(OH)2 aqueous solution, hydrated Ca5Ge2O9 nanowires were formed rapidly. The phase was determined by X-ray diffraction, and the stoichiometry of Ca:Ge was further confirmed by energy-dispersive X-ray spectroscopic and inductively coupled plasma-mass spectrometric analyses. The diameter of nanowires varied from several tens to more than 100 nm, and the length increased with aging time up to the completion of reaction. After dehydrating at 400 °C, the nanowires became amorphous, and the stoichiometry of Ca:Ge remained unchanged. A blue-violet luminescence was detected from these amorphous nanowires. The emission band distributed from 300 to 550 nm, with the main peak locating at 380 nm. Ge-associated luminescence centers are proposed to be responsible for this emission. The formation of amorphous Ca5Ge2O9 nanowires may provide a new thinking to prepare other kinds of amorphous one-dimensional nanomaterials.

Field-effect transistors (FETs) based on large-area graphene and other 2D materials can potentially be used as low-cost and flexible potentiometric biological sensors. However, there have been few attempts to use these devices for quantifying molecular interactions and to compare their performance to established sensor technology. Here, gold-coated graphene FETs are used to measure the binding affinity of a specific protein–antibody interaction. Having a gold surface gives access to well-known thiol chemistry for the self-assembly of linker molecules. The results are compared with potentiometric silicon-based extended-gate sensors and a surface plasmon resonance system. The estimated dissociation constants are in excellent agreement for all sensor types as long as the active surfaces are the same (gold). The role of the graphene transducer is to simply amplify surface potential changes caused by adsorption of molecules on the gold surface.

This report describes a technique that used mixed self-assembled monolayer (SAM) as a model surface to evaluate the effect of steric hindrance on the SAM packing quality and its platelet compatibility. Two series of binary mixed SAMs were formed by mixing the bulky terminated alkanethiol (HS(CH 2 ) 10 PO 3 H 2 ) with a smaller terminated one (HS(CH 2 ) 9 CH 3 and HS(CH 2 ) 11 OH) respectively. Surface characterization results showed the hydrophilicity on these two series of mixed SAMs changed with the solution mole fraction of PO 3 H 2 terminated thiol, χ PO 3 H 2 ,soln , and reached to a nearly constant value as χ PO 3 H 2 ,soln was 0.6 for PO 3 H 2 + CH 3 SAM and 0.4 for PO 3 H 2 + OH SAM. This finding should be due to the gradual saturation of surface PO 3 H 2 functionality on these mixed SAMs. The XPS analysis indicated the addition of the CH 3 and OH terminated thiol could reduce the steric hindrance effect of PO 3 H 2 functionality on monolayer formation and, henceforth, improve the SAM packing quality. In vitro platelet adhesion assay revealed the platelet compatibility on the PO 3 H 2 + OH SAMs was better than that on the PO 3 H 2 + CH 3 and the pure PO 3 H 2 ones. Moreover, the PO 3 H 2 + OH SAM with a low χ PO 3 H 2 ,soln value exhibited the least platelet activating property of these two mixed SAM systems. These findings suggested that material's surface wettability and surface charge density should act collectively in affecting its platelet compatibility.

Self-assembled monolayer (SAM) formation of alkanethiols with ionic, hydrophilic terminal functionalities onto various O(2) plasma/ethanol pretreated gold substrates was characterized to explore the effect of gold surface oxide on the SAM packing quality. Oxygen adsorption induced by the Au(2)O(3) surface residuals are observed on the plasma-oxidized and O(2) plasma/ethanol-rinsed pretreated Au surfaces while no obvious adsorbed oxygen is found on freshly coated and O(2) plasma/ethanol sonication pretreated Au substrates. A model for the formation of hydrophilic terminated SAMs, -OH, -COOH, and -PO(3)H(2) is proposed. According to this model, the ionic and/or other binding interactions between the surface Au(2)O(3) and the alkanethiol hydrophilic terminal end as well as the interactions between the terminal SAM functionalities could cause the packing disorder found on these three SAMs formed on Au substrates containing Au(2)O(3) surface species. Copyright 2001 Academic Press.

Annealing of carbon nanotubes coated with thin and uniform TiO2 results in carbon diffusion into oxygen lattices and doping induced redshift is evident by an efficient photocatalysis at visible light. The underlying mechanism is discussed.

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We modified a digital versatile disk (DVD) pickup head as a DVD actuator with a laser diode package for sensing. Tuning a tilting coil in the DVD actuator causes the tilt of a laser diode to compensate misalignment between a target surface and the laser diode facet. Experimental results show that tuning the tilting coil compensates misalignment between both surfaces to achieve effective self-mixing signal. Furthermore, we present the conformity between the output voltage and the target surface displacement from a laser diode package using the self-mixing effect. The resolution in linear region of self-mixing signal is 100 mV/nm.

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The electrical transport properties of individual disordered multiwalled carbon nanotubes (MWCNTs), synthesized with the floating catalyst method, have been investigated. The resistivity of such disordered MWCNTs shows T1∕2 dependence over a temperature range of 4.2–263K. The experimental finding can be interpreted in terms of Al’tshuler-Aronov model [Solid State Commun. 30, 115 (1979); Sov. Phys. JETP 50, 968 (1979); Pis’ma. Zh. Eksp. Teor. Fiz. 27, 700 (1978)], in which strong electron-electron interaction leads to a Coulomb gap in the density of electronic states at the Fermi level. Such a wide fitting range of temperature for T1∕2 dependence has never been reported for other materials, implying an extremely short carrier scattering time of the order of femtoseconds.