Chloride ion concentration can be used as a biomarker for the level of pollen exposure in allergic asthma, chronic cough and airway acidification related to respiratory disease. AlGaN/GaN high electron mobility transistor (HEMT) with an InN thin film in the gate region was used for real time detection of chloride ion detection. The InN thin film provided surface sites for reversible anion coordination. The sensor exhibited significant changes in channel conductance upon exposure to various concentrations of NaCl solutions. The sensor was tested over the range of 100 nM to 100 μM NaCl solutions. The effect of cations on the chloride ion detection was also studied.

There has been significant recent interest in the use of surface-functionalized thin film and nanowire wide bandgap semiconductors, principally GaN, InN, ZnO and SiC, for sensing of gases, heavy metals, UV photons and biological molecules. For the detection of gases such as hydrogen, the semiconductors are typically coated with a catalyst metal such as Pd or Pt to increase the detection sensitivity at room temperature. Functionalizing the surface with oxides, polymers and nitrides is also useful in enhancing the detection sensitivity for gases and ionic solutions. The wide energy bandgap of these materials make them ideal for solar-blind UV detection, which can be of use for detecting fluorescence from biotoxins. The use of enzymes or adsorbed antibody layers on the semiconductor surface leads to highly specific detection of a broad range of antigens of interest in the medical and homeland security fields. We give examples of recent work showing sensitive detection of glucose, lactic acid, prostate cancer and breast cancer markers and the integration of the sensors with wireless data transmission systems to achieve robust, portable sensors.

AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized Polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an inkjet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change of surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors.

Aberrant expression or function of epidermal growth factor receptor (EGFR) or the closely related human epidermal growth factor receptor 2 (HER2) can promote cell proliferation and survival, thereby contributing to tumorigenesis. Specific antibodies and low-molecular-weight tyrosine kinase inhibitors of both proteins are currently in clinical trials for cancer treatment. Benzimidazole derivatives possess diverse biological activities, including antitumor activity. However, the anticancer mechanism of 5a (a 2-aryl benzimidazole compound; 2-chloro-N-(2-p-tolyl-1H-benzo[d]imidazol-5-yl)acetamide, C(16)H(14)ClN(3)O, MW299), a novel 2-aryl benzimidazole derivative, toward breast cancer is largely unknown. Here, we demonstrate that 5a potently inhibited both EGFR and HER2 activity by reducing EGFR and HER2 tyrosine phosphorylation and preventing downstream activation of PI3K/Akt and MEK/Erk pathways in vitro and in vivo. We also show that 5a inhibited the phosphorylation of FOXO and promoted FOXO translocation from the cytoplasm into the nucleus, resulting in the G1-phase cell cycle arrest and apoptosis. Moreover, 5a potently induced apoptosis via the c-Jun N-terminal kinase (JNK)-mediated death receptor 5 upregulation in breast cancer cells. The antitumor activity of 5a was consistent with additional results demonstrating that 5a significantly reduced tumor volume in nude mice in vivo. Analysis of the primary breast cancer cell lines with HER2 overexpression further confirmed that 5a significantly inhibited Akt Ser473 and Bad Ser136 phosphorylation and reduced cyclin D3 expression. On the basis of our findings, further development of this 2-aryl benzimidazole derivative, a new class of multitarget anticancer agents, is warranted and represents a novel strategy for improving breast cancer treatment.

Water droplets were either pushed or pulled with an ultra-violet (UV) light on vertically aligned ZnO nanorods. Steric acid-immobilized ZnO nanorods grown on quartz substrates exhibit a hydrophobic surface possessing high contact angles between water droplets and the substrates. Exposure of UV onto droplets on ZnO NRs led to reduction of contact angles and resulted the internal circulating flows inside the droplets. Droplets located at different sites under the spot of the UV light created different magnitudes of contact angle changes and the internal circulating flows which allowed us to push the droplets away or pull the droplets toward the centre of the UV spot.

The effect of cryogenic temperature deposition of Al and LiF contacts on the electrical and optical performance of organic light emitting diodes (OLEDs) was investigated. The reverse current of OLED with 77 K deposited contacts was reduced by one order of magnitude, and the output light intensity was dramatically improved compared to the device with conventional e-beam evaporated cathodes, due to the reduced damage on the metal contacts and the organic film interface. Atomic force microscope (AFM) imaging showed uniformly distributed smaller grains, and the X-ray diffraction (XRD) pattern indicated better crystallinity for the 77 K deposited metal film. Also, an abrupt interface between metal contact and polymer was observed from secondary ion mass spectroscopy (SIMS) depth profiling.

In this study, we report on a demonstration of hydrogen sensing at low temperature using SnO2 functionalized AlGaN/GaN high electron mobility transistors (HEMT). The SnO2 dispersion was synthesized via a hydrothermal method and selectively deposited on the gate region of a HEMT device through a photolithography process. The high electron sheet carrier concentration of nitride HEMTs provides an increased sensitivity relative to simple Schottky diodes fabricated on GaN layers. The morphology and crystalline properties of the SnO2-gate, together with the texture of the multilayer films on the device were investigated by SEM, HRTEM, EDS and XRD. The effects of annealing treatment on the crystalline properties of the SnO2-gate, and gas sensing properties of SnO2-gated HEMT sensors were studied. The SnO2-gated HEMT sensor showed fast and reversible hydrogen gas sensing response at low temperature.

Water droplets were either pushed or pulled with an UV light on the surface of vertically aligned and superhydrophobic ZnO nanorods (NRs). The contact angle of the droplets reduce to a lower value due to the absorption of UV by ZnO NRs and a circulating current was observed inside the droplet. The droplets were either pushed away from or pulled toward to the center of the UV light depending on the locations of the droplets to the UV light. It is obvious that in the pushing mode, the circulating current dominate the direction of the movement of the droplets, while in the pulling mode, the contact angle change dominate the direction of the droplet movement

Antibacterial coating approaches are being investigated to modify implants to reduce bacterial adhesion and viability in order to reduce implant-associated infection. Nanostructured materials possess unique surface properties, and nanotopographic surfaces have been reported to modulate bacterial adhesion. Zinc oxide (ZnO) films presenting well-controlled nanorod surface structures have recently been developed. To assess the efficacy of ZnO nanorod surfaces as an anti-bacterial coating, we evaluated bacterial adhesion and viability, compared to sputtered ZnO substrates (a relatively flat control) and glass substrates (as a reference). Common implant-associated pathogens, Pseudomonas aeruginosa and Staphylococcus epidermidis were investigated. The number of adherent P. aeruginosa on ZnO nanorod surfaces was found to be reduced compared to glass and sputtered ZnO, while the adherent number of S. epidermidis on the ZnO nanorods was equivalent to glass. Regarding bacteria viability, the ZnO nanorod and sputtered ZnO surfaces demonstrated a modest, but significant bactericidal effect on adherent P. aeruginosa, killing 2.5-fold and 1.7-fold more over the number of dead P. aeruginosa on glass, respectively. A greater bactericidal effect of ZnO substrates on S. epidermidis was found, with sputtered ZnO and ZnO nanorod substrates killing -20-fold and 30-fold more over the number of dead S. epidermidis on glass, respectively. These data support the further investigation and optimization of ZnO nanorod coatings with potential for bacterial adhesion resistance and bactericidal properties.

The characteristics of hydrogen detection using epitaxial graphene covered with platinum are reported. The multi-layered graphene was grown by chemical vapor deposition (CVD) on a Si-polar 4H-SiC substrate. Surface morphology was characterized by scanning electron and atomic force microscopy. Current–voltage measurements and real-time monitoring of the current flow through the graphene/platinum device were used to confirm the response to hydrogen gas. The background temperature was varied from room temperature to 175°C in order to measure the activation energy of hydrogen detection.

Chemical sensors have gained in importance in the past decade for applications that include homeland security, medical and environmental monitoring and also food safety.A desirable goal is the ability to simultaneously analyze a wide variety of environmental and biological gases and liquids in the field and to be able to selectively detect a target analyte with high specificity and sensitivity.In the area of detection of medical biomarkers, many different methods, including enzyme-linked immunsorbent assay (ELISA), particle-based flow cytometric assays, electrochemical measurements based on impedance and capacitance, electrical measurement of microcantilever resonant frequency change, and conductance measurement of semiconductor nanostructures.gas chromatography (GC), ion chromatography, high density peptide arrays, laser scanning quantitiative analysis, chemiluminescence, selected ion flow tube (SIFT), nanomechanical cantilevers, bead-based suspension microarrays, magnetic biosensors a n d m a s s s p e c t r o m e t r y ( M S ) h a v

The effect of Pt metal thickness on the hydrogen sensing sensitivity of Pt-coated, multi-layered graphene grown by chemical vapor deposition on Si-polar 4H-SiC, was investigated. As-grown graphene samples and graphene samples coated with 1nm or 4nm thick Pt films were used in this study. Compared to graphene without platinum, significantly improved hydrogen detection sensitivity was observed with the addition of platinum films. The highest hydrogen sensitivity was observed with the graphene sensor with 1nm platinum coating. The platinum coated graphene sensor also showed good selectivity for hydrogen detection over methane, ammonia, oxygen, and nitrogen oxide.

The effect of ambient temperature on the detection sensitivity of carbon monoxide (CO) using ZnO nanorod-gated AlGaN/GaN high electron mobility transistor (HEMT) sensors was studied over a range of temperatures from 25 to 400 °C. An increase of the HEMT drain current was observed for exposure to the CO-containing ambients, due to chemisorbed oxygen on the ZnO surface reacting with CO to form CO2 and releasing electrons to the oxide surface, increasing the counter charges in the two-dimensional electron gas channel of the HEMT. By increasing the detection temperature from 25 °C to 150 °C, the CO detection sensitivity, ΔI/I, and detection limit were significantly improved from 0.23% to 7.5% and from 100 ppm to ∼30 ppm, respectively. However, the sensitivity of the CO detection was degraded by the decrease of mobility and saturation drain current of HEMT at temperatures higher than 200 °C.

The carbon monoxide (CO) detection sensitivities of ZnO nanorod-gated AlGaN/GaN high electron mobility transistors were measured over a range of temperatures from 25–150 °C. Once the sensor was exposed to the CO-containing ambient, the drain current, I, of the high electron mobility transistors increased due to chemisorbed oxygen on the ZnO surface reacting with CO, forming CO2 and releasing electrons to the oxide surface. Although the sensor could detect CO as low as 100 ppm at room temperature, the detection sensitivity, ΔI/I, was only around 0.23%. By increasing the sensor temperature to 150 °C, the detection sensitivity was improved by a factor of over 30% to 7.5%.

Real time detection of vitellogenin in largemouth bass serum was demonstrated using AlGaN/GaN HEMTs. Antivitellogenin antibodies were chemically anchored to the gold-coated gate area of the HEMT by thioglycolic acid. The potential difference that occurred from the vitellogenin antigen/antibody interaction induced a drain current change. The sensor was able to detect as low as 4 mu g/mL Vtg. Successful detection in serum samples shows that HEMTs have the potential to be used as biological sensors in real-world applications. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Recent progress in the use of surface-functionalized GaN for sensing of gases, heavy metals, UV photons and biological molecules is reviewed. The use of such sensors for monitoring nerve cells is also explored. Additionally, we briefly review progress with InN-based chemical sensors. For the detection of gases such as hydrogen, the GaN is coated with a catalyst metal such as Pd or Pt to increase the detection sensitivity at room temperature. Functionalizing the surface with oxides, polymers, and nitrides is also useful in enhancing the detection sensitivity for gases and ionic solutions. The use of enzymes or adsorbed antibody layers on the semiconductor surface leads to highly specific detection of a broad range of antigens of interest in the medical and homeland security fields. We give examples of recent work showing sensitive detection of glucose, lactic acid, prostate cancer, and breast cancer markers. Nerve cell-GaN surface coupling allowed for the analysis of cell reactions to different neuroinhibitors. InN chemical sensors have also been shown to be viable for sensing anions, pH, and polarity.

The effect of Pt metal thickness on the hydrogen sensing sensitivity of Pt-coated, multi-layered graphene grown by chemical vapor deposition on Si-polar 4H-SiC, was investigated. As-grown graphene samples and graphene samples coated with 1 or 4 nm thick Pt films were used in this study. Compared to graphene without platinum, significantly improved hydrogen detection sensitivity was observed with the addition of platinum films. The highest hydrogen sensitivity was observed with the graphene sensor with 1 nm platinum coating. The platinum coated graphene sensor also showed good selectivity for hydrogen detection over methane, ammonia, oxygen, and nitrogen oxide. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3589250] All rights reserved.

The critical degradation voltage of AlGaN/GaN high-electron mobility transistors during OFF-state electrical stress was determined as a function of Ni/Au gate dimensions (0.1-0.17 mu m), drain bias voltage, and source/drain-gate contact distance. Devices with different gate lengths and gate-drain distances were found to exhibit the onset of degradation at different source-drain biases but similar electric field strengths, showing that the degradation mechanism is primarily field driven. The degradation field was calculated to be similar to 1.8 MV/cm by Automatically Tuned Linear Algebra Software simulations. Transmission electron microscopy imaging showed creation of defects under the gate after dc stress.