We demonstrate that micron-scale graphene field-effect transistor biosensors can be fabricated in a scalable fashion from large-area chemical vapor deposition derived graphene. We electrically detect the real-time binding and unbinding of a protein biomarker, thrombin, to and from aptamer-coated graphene surfaces. Our sensors have low background noise and high transconductance, comparable to exfoliated graphene devices. The devices are reusable and have a shelf-life greater than one week.

Previous studies of graphite from the University of Idaho thermolyzed asphalt reaction (GUITAR) indicated two unique properties that distinguish this material from other sp2 hybridized carbon electrodes. In property i, the standard heterogeneous rate constant across the basal plane (BP) of GUITAR with Fe(CN)63−/4− of 0.01 cm s−1 was 2–7 orders of magnitude greater than for BP‐graphite and graphene. With property ii, the anodic potential limit exceeds other graphite forms by 500 mV. Two new properties are now described. In iii, the hydrogen overpotential in 1 M H2SO4 exceeds other graphitic materials by 500 mV. The combination of ii and iii gives a 3 V window in 1 M H2SO4, which is the largest reported for a graphitic material and competitive with diamond electrodes. In iv, effects of air oxidation on the edge planes (EPs) is reversed by mild cathodic reduction and does not allow for electrolyte intercalation. Based on these characteristics and on atomic force micrographs, we hypothesize that GUITAR may be a new allotrope of carbon. Coupled with expected low costs, GUITAR will find a myriad of applications in electrochemical sensors, water purification, as well as energy storage and conversion.

The electrical and optoelectronic properties of nanometer-sized ZnO structures are highly influenced by its native point defects. Understanding and controlling these defects are essential for the development of high-performance ZnO-based devices. Here, an electrical device consisting of a polycrystalline ZnO-coated silica nanospring was fabricated and used to characterize the electrical and photoconductive properties of the ZnO layer using near-UV (405 nm) and sub-bandgap (532 and 633 nm) excitation sources. We observe a photocurrent response with all three wavelengths and notably with 532 nm green illumination, which is the energy associated with deep oxygen vacancies. The polycrystalline ZnO-coated silica nanospring exhibits a high responsivity of 1740 A W−1 with the 405 nm excitation source. Physical models are presented to describe the photocurrent rise and decay behavior of each excitation source where we suggest that the rise and decay characteristics are highly dependent on the energy of the excitation source and the trapping of electrons and holes in intermediate defect levels in the bandgap. The energy levels of the trap depths were determined from the photoconductive decay data and are matched to the reported energy levels of singly and doubly ionized oxygen vacancies. A phenomenological model to describe the dependence of the saturation photocurrent on excitation intensity is presented in order to understand the characteristics of the observed breaks in the slopes of the saturation photocurrent versus excitation intensity profile.

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MgZnO is emerging as a vital semiconductoralloy system with desirable optical properties that can span a large range of the UV spectrum. Due to its benign chemical character, MgZnO is considered to be an environmentally friendly material. This paper presents studies on annealing as a useful and straightforward approach for the enhancement of the optical and crystal quality of Mg 0.17 Zn 0.83 O nanocrystalline films grown via DC sputtering. The alloys were studied via several imaging and optical techniques. It was found that high-temperature annealing, *900°C, in Argon atmosphere, significantly improves the solubility of the alloy. This temperature range is consistent with the thermal diffusion temperature of Mg needed for the creation of a soluble alloy. Moreover, the annealing process was found to minimize the undesirable visible luminescence, attributed to Mg and Zn interstitials, while significantly enhancing the bandgap sharpness and the efficiency of the UV-luminescence at *3.5 eV. The analysis indicated that these optical attributes were achieved due to the combined effects of good solubility, an improved morphology, and a reduction of native defects. The annealing was also proven to be beneficial for the reduction of the compressive stress in the alloy: a relaxation *1.8 GPa was calculated via Raman scattering. The inherent stress was inferred to originate mainly from the granular morphology of the alloys.