We have exfoliated hexagonal boron nitride by ultrasonication in solutions of polyvinylalcohol in water.The resultant nanosheets are sterically stabilised by adsorbed polymer chains. Centrifugation-based sizeselection was used to give dispersions of nanosheets with aspect ratio (length/thickness) of $1400.Such dispersions can be used to produce polyvinylalcohol-BN composite films. Helium ion microscopy of fracture surfaces shows the nanosheets to be well dispersed and the composites to fail by pull-out. We find both modulus, Y, and strength, s B , of these composites to increase linearly with volume fraction, V f , up to V f $ 0.1 vol% BN before falling off. The rates of increase are extremely high; dY/dV f ¼ 670 GPa and ds B /dV f ¼ 47 GPa. The former value matches theory based on continuum mechanics while the latter value is consistent with remarkably high polymer-filler interfacial strength. However, because the mechanical properties increase over such a narrow volume fraction range, the maximum values of both modulus and strength are only $40% higher than the pure polymer. This phenomenon has also been observed for graphene-filled composites and represents a serious hurdle to the production of high performance polymer-nanosheet composites.

Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication methods typically involve electron-beam lithography—a technique that enables high fidelity patterning but suffers from significant limitations in terms of low throughput, poor scalability to large areas and restrictive choice of substrate and electrode materials. Here, we describe a versatile method for the rapid fabrication of asymmetric nanogap electrodes that exploits the ability of selected self-assembled monolayers to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method may be carried out under ambient conditions using simple equipment and a minimum of processing steps, enabling the rapid fabrication of nanogap electrodes and optoelectronic devices with aspect ratios in excess of 100,000.

Over the last decade, there has been increasing interest in transferring the research advances in radiofrequency (RF) rectifiers, the quintessential element of the chip in the RF identification (RFID) tags, obtained on rigid substrates onto plastic (flexible) substrates. The growing demand for flexible RFID tags, wireless communications applications and wireless energy harvesting systems that can be produced at a low-cost is a key driver for this technology push. In this topical review, we summarise recent progress and status of flexible RF diodes and rectifying circuits, with specific focus on materials and device processing aspects. To this end, different families of materials (e.g. flexible silicon, metal oxides, organic and carbon nanomaterials), manufacturing processes (e.g. vacuum and solution processing) and device architectures (diodes and transistors) are compared. Although emphasis is placed on performance, functionality, mechanical flexibility and operating stability, the various bottlenecks associated with each technology are also addressed. Finally, we present our outlook on the commercialisation potential and on the positioning of each material class in the RF electronics landscape based on the findings summarised herein. It is beyond doubt that the field of flexible high and ultra-high frequency rectifiers and electronics as a whole will continue to be an active area of research over the coming years.

Keywords: Schottky diode, radio frequency diodes, RFID, nanogap electrode, 13.56 MHz Main TextRadio Frequency Identification (RFID) is a rapidly growing technology used for wireless communication and the identification of objects in close proximity through radio waves. [1] Although already a billion dollar industry [2] , RFID technology promises substantial further growth by adopting fully printable processing routes. However, there remain several bottlenecks to be overcome before this opportunity can be realised, particularly pertaining to the high frequency performance of printable electronics.RFID tags are generally composed of a coupling element, or antenna, a direct current (DC) rectifier and integrated circuitry (IC). The rectifying element is by far the most important component in terms of high-frequency (HF) operation, as the logic may take place at much J. Semple et al., Small (2016), DOI: 10.1002/smll.201503110 2 lower frequencies than the RF base carrier frequency. Different frequency bands exist for different applications, though the current target for printable RFID is the widely employed 13.56 MHz band. [1] Conventionally, complementary metal-oxide-semiconductor (CMOS) technology favours the use of diode-connected metal-oxide-semiconductor field-effect transistors (MOSFETs) for rectification within this element. However, Schottky diodes, with their inherently lower voltage operation, lower series resistance and exponential currentvoltage relationship offer a superior choice for rectifiers. [4] There has been extensive work carried out in recent years to develop high frequency organic Schottky diodes following the pioneering work of Steudel et al. who demonstrated pentacene-based Schottky diode rectifiers operating at 50 MHz. [5] More recently C60-basedSchottky diodes with a cut-off frequency (fCO) up to 0.7 GHz have also been reported. [6] Diodes based on metal oxide materials (particularly In-Ga-Zn-O) have recently emerged as a promising material, demonstrating device performance up to and above 1 GHz. [7][8][9] Despite such promising results, manufacturing of these conventional staggered diodes relies on vacuum processing, which renders them incompatible with cost-effective large-volume product integration. To address this important bottleneck, recent work has been devoted to solutionprocessable organic diodes with adequate performance. [10][11][12] Si nanoparticles have recently been demonstrated as a potential route to solution processed diodes with cut-off frequencies as high as 1.6 GHz.[13] However, demonstrating high yield manufacturing of solution-processed diodes with cut-off frequency 50 MHz still remains a significant challenge.The operational frequency of Schottky diodes is inversely proportional to the product of the series resistance (RS) and junction capacitance (Cj). A common approach to boosting the device cut-off frequency is by reducing RS through the use of a high charge carrier mobility J. Semple et al., Small (2016) However, there are inherent problems with implementing...

We report the syntheses and activities of a wide range of thiazolides [viz. 2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis B virus replication, with QSAR analysis of our results. The prototypical thiazolide, nitazoxanide [2-hydroxybenzoyl-N-(5-nitrothiazol-2-yl)amide; NTZ] 1 is a broad spectrum antiinfective agent, effective against anaerobic bacteria, viruses and parasites. By contrast, 2-hydroxybenzoyl-N-(5-chlorothiazol-2-yl)amide 3 is a novel, potent and selective inhibitor of hepatitis B replication (EC50 = 0.33 μm) but is inactive against anaerobes. Several 4′- and 5′-substituted thiazolides show good activity against HBV; by contrast, some related salicyloylanilides show a narrower spectrum of activity. The ADME properties of 3 are similar to 1, viz. the O-acetate is an effective prodrug and the O-aryl glucuronide is a major metabolite. The QSAR study shows a good correlation of observed EC90 s for intracellular virions with thiazolide structural parameters. Finally we discuss the mechanism of action of thiazolides in relation to the present results.

Inexpensive radiofrequency devices that can meet the ultrahigh-frequency needs of fifth-and sixth-generation wireless telecommunication networks are required. However, combining high performance with cost-effective scalable manufacturing has proved challenging. Here, we report the fabrication of solution-processed zinc oxide Schottky diodes that can operate in microwave and millimetre-wave frequency bands. The fully coplanar diodes are prepared using wafer-scale adhesion lithography to pattern two asymmetric metal electrodes separated by a gap of around 15 nm, and are completed with the deposition of a zinc oxide or aluminium-doped ZnO layer from solution. The Schottky diodes exhibit a maximum intrinsic cutoff frequency in excess of 100 GHz, and when integrated with other passive components yield radiofrequency energy-harvesting circuits that are capable of delivering output voltages of 600 mV and 260 mV at 2.45 GHz and 10 GHz, respectively.

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We report the activities of a number of thiazolides [2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis C virus (HCV) genotypes IA and IB, using replicon assays. The structure-activity relationships (SARs) of thiazolides against HCV are less predictable than against hepatitis B virus (HBV), though an electron-withdrawing group at C(5') generally correlates with potency. Among the related salicyloylanilides, the m-fluorophenyl analogue was most promising; niclosamide and close analogues suffered from very low solubility and bioavailability. Nitazoxanide (NTZ) 1 has performed well in clinical trials against HCV. We show here that the 5'-Cl analogue 4 has closely comparable in vitro activity and a good cell safety index. By use of support vector analysis, a quantitative structure-activity relationship (QSAR) model was obtained, showing good predictive models for cell safety. We conclude by updating the mode of action of the thiazolides and explain the candidate selection that has led to compound 4 entering preclinical development.