Integration of Pakistan's stock market with the stock markets of top ten developed economies.

This study examines the integration of Pakistan's Stock Market with the stock markets of the top ten largest economies in the world-USA, China, Japan, Germany, the UK, India, France, Italy, Brazil, and Canada-from January 2015 to October 2020. To examine long- and short run integration, this study employed Johansen and Juselius co-integration and pair-wise Granger causality tests. In the long run, the results indicated that Pakistan's Stock Market is not integrated with these markets. This implies that the market is more attractive in portfolio diversification for international investors, and vice versa. In the short run, the results revealed that, except for China, Pakistan's stock market integrates with the remaining nine markets. However, Pakistan's stock market exhibits a bidirectional relationship with the USA, Japan, Germany, the UK, and France in the lead-lag relationship. However, its relationship with India, Italy, Brazil, and Canada is unidirectional, with Pakistan's stock market leading, while these markets are following. For Pakistani investors, China is the optimal market, and vice versa. Importantly, our findings help policymakers to comprehend Pakistan's dynamic relationship with its trading partners. To the best of our knowledge, no prior study has employed advanced techniques to address the time-varying correlation among the selected markets. By determining Pakistan's stock market integration with its trading partners, this study aimed to fill this empirical literature gap.

Did the COVID-19 Lockdown Reduce Smoking Rate in Adolescents?

This study examined the temporal trend of smoking use and the prevalent differences in the use of different types of cigarettes for Korean adolescents before and during the COVID-19 pandemic. In Korea, all use of e-cigarettes, including regular cigarettes, is considered smoking. Since adolescents are susceptible to peer influences in risky behaviors including smoking, social distancing could affect the smoking behaviors of youth under these unusual circumstances during the pandemic. In this study, we analyzed the Korea Youth Risk Behavior Web-based Survey (KYRBW) data collected from 2018 to 2021 to examine the association between smoking status and other covariates during the COVID-19 pandemic. As a result, it was confirmed that the influence of second-hand smoke on the smoking rate decreased before and after COVID-19, which is interpreted as a result of the social distancing policy caused by the pandemic.

Bevel Structure Based XPS Analysis as a Non-Destructive Chemical Probe for Complex Interfacial Structures of Organic Semiconductors.

The bevel structure of organic multilayers produced by finely controlled Ar gas cluster ion beam sputtering preserves both the molecular distribution and chemical states. Nevertheless, there is still an important question of whether this method can be applicable to organic multilayer structures composed of complex or ambiguous interfaces used in real organic optoelectronic devices. Herein, various bevel structures are fabricated from different types of organic semiconductors using a solution-based deposition technique: complicatedly intermixed electron-donor and electron-acceptor bulk heterojunction structure, thin film structure with an internal donor-acceptor concentration gradient, and multi-layered structure with more than three layers. For these organic material combinations listed above, the bevel structure is fabricated with finely tuned Ar gas cluster ion beam sputtering. The location-dependent X-ray photoelectron spectroscopy (XPS) results obtained for each bevel structure exactly correspond to the XPS depth profiles. This result demonstrates that the bevel structure analysis is a powerful method to distinguish subtle differences in chemical component distributions and chemical states of organic semiconductors even with complex or ambiguous interfaces. Ultimately, due to its reliability as verified by this study, the proposed bevel structure analysis is expected to greatly expand other analytical techniques with a limited spatial or depth resolution.

Fabrication of Large-Area Molybdenum Disulfide Device Arrays Using Graphene/Ti Contacts.

Two-dimensional (2D) molybdenum disulfide (MoS2) is the most mature material in 2D material fields owing to its relatively high mobility and scalability. Such noticeable properties enable it to realize practical electronic and optoelectronic applications. However, contact engineering for large-area MoS2 films has not yet been established, although contact property is directly associated to the device performance. Herein, we introduce graphene-interlayered Ti contacts (graphene/Ti) into large-area MoS2 device arrays using a wet-transfer method. We achieve MoS2 devices with superior electrical and photoelectrical properties using graphene/Ti contacts, with a field-effect mobility of 18.3 cm2/V∙s, on/off current ratio of 3 × 107, responsivity of 850 A/W, and detectivity of 2 × 1012 Jones. This outstanding performance is attributable to a reduction in the Schottky barrier height of the resultant devices, which arises from the decreased work function of graphene induced by the charge transfer from Ti. Our research offers a direction toward large-scale electronic and optoelectronic applications based on 2D materials.

Self-Stratified Versatile Coatings for Three-Dimensional Printed Underwater Physical Sensors Applications.

A new strategy for developing versatile nanostructured surfaces utilizing the swelling of polymers in solvents is described. The self-stratified coating on 3D printed acrylonitrile-butadiene-styrene (ABS) copolymers with nanoparticles enables mechanically durable superhydrophobic characteristics. Unlike other methods, it was capable to produce superhydrophobicity on complex 3D structured surfaces. Mechanically durable superhydrophobic coatings that can withstand an abrasion cycle were obtained. Partial embedding of the nanoparticles into the ABS surface due to the swelling and self-stratification is considered as the reason for the increased mechanical strength of the coating. Utilizing this idea, the original concept of power-free physical sensors responding to changes in temperature, pressure, and surface tension was proposed.

Nanotube and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) composite film for the electrode applications in organic thin-film transistor and dye-sensitized solar cells.

In this study, composite films made of coiled carbon nanotubes (CCNTs) and poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS) were fabricated with different composition ratios. The variations in film properties (including surface morphology, work function, and electrical conductivity) in accordance with the amount of CCNT dosing were investigated. Subsequently, through HCl-methanol treatment, we achieved a significant enhancement in electrical conductivity with little damage to the CCNT features. The characteristics of CCNT/PEDOT:PSS composite film are generally comparable to those of PEDOT:PSS film, and some of them, such as catalytic activity and work function, are significantly higher. On the basis of these versatile features, the CCNT/PEDOT:PSS composite films exhibit excellent performance as source/drain electrode in organic thin-film transistors and as catalytic counter electrode in dye-sensitized solar cells.

A Highly Versatile and Adaptable Artificial Leaf with Floatability and Planar Compact Design Applicable in Various Natural Environments.

As a promising means of solar energy conversion, photovoltaic (PV) cell-based electrolysis has recently drawn considerable attention for its effective solar fuel generation; especially the generation of hydrogen by solar water splitting. Inspired by remarkable accomplishments in enhancing the solar-to-hydrogen conversion efficiency, various efforts have aimed at fostering convenient and practical uses of PV electrolysis to make this technology ubiquitous, manageable, and efficient. Here, the design and function of a monolithic photoelectrolysis system-a so-called artificial leaf-for use in various environments are highlighted. The uniquely designed artificial-leaf system facilitates an unbiased water-splitting reaction by combining superstrate PV cells in series with single-face electrodes in a compact 2D catalytic configuration. Floatability is a new feature of the water-splitting artificial leaf; this feature maximizes solar light utilization and allows for easy retrieval for recycling. Additionally, its planar design enables operation of the device in water-scarce conditions. These characteristics endow the artificial leaf with versatility and a high adaptability to natural environments, widening the applicability of the device.

A light incident angle switchable ZnO nanorod memristor: reversible switching behavior between two non-volatile memory devices.

A light incident angle selectivity of a memory device is demonstrated. As a model system, the ZnO resistive switching device has been selected. Electrical signal is reversibly switched between memristor and resistor behaviors by modulating the light incident angle on the device. Moreover, a liquid passivation layer is introduced to achieve stable and reversible exchange between the memristor and WORM behaviors.

Photo-stimulated resistive switching of ZnO nanorods.

Resistive switching memory devices are promising candidates for emerging memory technologies because they yield outstanding device performance. Storage mechanisms for achieving high-density memory applications have been developed; however, so far many of them exhibit typical resistive switching behavior from the limited controlling conditions. In this study, we introduce photons as an unconventional stimulus for activating resistive switching behaviors. First, we compare the resistive switching behavior in light and dark conditions to describe how resistive switching memories can benefit from photons. Second, we drive the switching of resistance not by the electrical stimulus but only by the modulation of photon. ZnO nanorods were employed as a model system to demonstrate photo-stimulated resistive switching in high-surface-area nanomaterials, in which photo-driven surface states strongly affect their photoconductivity and resistance states.

Effects of postannealing process on the properties of RuO2 films and their performance as electrodes in organic thin film transistors or solar cells.

RuO(2) films were deposited on SiO(2) (300 nm)/N++Si substrates using radio frequency magnetron sputtering at room temperature. As-deposited RuO(2) films were annealed at different temperatures (100, 300, and 500 °C) and ambients (Ar, O(2) and vacuum), and the resulting effects on the electrical and physical properties of RuO(2) films were characterized. The effect of annealing atmosphere was negligible, however the temperature highly influenced the resistivity and crystallinity of RuO(2) films. RuO(2) films annealed at high temperature exhibited lower resistivity and higher crystallinity than as-deposited RuO(2). To investigate the possibility to use RuO(2) film as alternative electrodes in flexible devices, as-deposited and annealed RuO(2) films were applied as the source/drain (S/D) electrodes in organic thin film transistor (OTFT), catalytic electrodes in dye sensitized solar cell (DSSC) and as the hole-injection buffer layer (HIL) in organic photovoltaic (OPV). Except for OTFTs (µ ≈ 0.45 cm(2)/(V s) and on/off ratio ≈ 5× 10(5)) with RuO(2) S/D electrodes, the DSSC and OPV (3.5% and 2.56%) incorporating annealed RuO(2) electrodes showed higher performance than those with as-deposited RuO(2) electrodes (3.0% and 1.61%, respectively).

Resistive switching WOx-Au core-shell nanowires with unexpected nonwetting stability even when submerged under water.

The resistive switching (RS) characteristics of a tungsten oxide (WO(x) )-Au core-shell nanowire device array is demonstrated for the first time. In addition to the stable bipolar RS characteristics, the nanowire structure of our RS devices provides superhydrophobic properties. The superhydrophobic RS nanowires repelled water that was poured over, such that the device was protected from failure by water contact-driven leakage currents. Moreover, surprisingly, the devices still work even with when the device is submerged underwater.

Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 µm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (µ: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.