Soluble pentacene thin-film transistor using a high solvent and heat resistive polymeric dielectric with low-temperature processability and its long-term stability

Solution processable organic thin-film transistors (OTFTs) were fabricated using 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) and low-temperature processable polyimide gate dielectric. The TIPS-pentacene OTFT with the dielectric was found to have a field-effect mobility of 0.15 cm²/Vs, which is comparable to that of OTFT with an inorganic dielectric. The OTFTs with the polyimide dielectric did not show any significant performance degradation as time passed. A field-effect mobility of the OTFTs in 60 days was found to be almost identical to that of pristine OTFT. The combination of TIPS-pentacene and our polyimide gate dielectric can be one of the potential candidates for the fabrication of stable OTFTs for large-area flexible electronics.     

Precious‐Metal‐Free Electrocatalysts for Activation of Hydrogen Evolution with Nonmetallic Electron Donor: Chemical Composition Controllable Phosphorous Doped Vanadium Carbide MXene

The insufficient strategies to improve electronic transport, the poor intrinsic chemical activities, and limited active site densities are all factors inhibiting MXenes from their electrocatalytic applications in terms of hydrogen production. Herein, these limitations are overcome by tunable interfacial chemical doping with a nonmetallic electron donor, i.e., phosphorization through simple heat‐treatment with triphenyl phosphine (TPP) as a phosphorous source in 2D vanadium carbide MXene. Through this process, substitution, and/or doping of phosphorous occurs at the basal plane with controllable chemical compositions (3.83–4.84 at%). Density functional theory (DFT) calculations demonstrate that the P? C bonding shows the lowest surface formation energy (ΔG_Surf) of 0.027 eV Å^?2 and Gibbs free energy (ΔG_H) of –0.02 eV, whereas others such as P‐oxide and P? V (phosphide) show highly positive ΔG_H. The P3–V₂CT_x treated at 500 °C shows the highest concentration of P? C bonds, and exhibits the lowest onset overpotential of –28 mV, Tafel slope of 74 mV dec^?1, and the smallest overpotential of ‐163 mV at 10 mA cm^?2 in 0.5 m H₂SO₄. The first strategy for electrocatalytically accelerating hydrogen evolution activity of V₂CT_x MXene by simple interfacial doping will open the possibility of manipulating the catalytic performance of various MXenes.     

Power law behavior of magnetoresistance in tris(8-hydroxyquinolinato)aluminum-based organic light-emitting diodes

Long-term current drift and dielectric relaxation in organic thin films of a single-layer structure pose a serious problem for the accurate measurement of magnetoresistance at low magnetic fields. A new measurement scheme was devised to minimize errors and to report that the magnetoresistance in tris(8-hydroxyquinolinato)aluminum obeys a power law on the magnetic field at 300, 100, and 4.2 K in an entire range from 1 to 140 mT. The exponent of the power increases gradually from 0.47 for a bias voltage of 3 V to 0.58 for a bias voltage of 8 V. The magnetoresistance was observable above the threshold voltage only and its sign was always negative.     

Organic Phenolic Configurationally Locked Polyene Single Crystals for Electro‐optic and Terahertz Wave Applications

We investigate a configurationally locked polyene (CLP) crystal 2‐(3‐(4‐hydroxystyryl)‐5,5‐dimethylcyclohex‐2‐enylidene)malononitrile (OH1) containing a phenolic electron donor, which also acts as a hydrogen bond donor. The OH1 crystals with orthorhombic space group Pna2₁ (point group mm2) exhibit large second‐order nonlinear optical figures of merit, high thermal stability and very favorable crystal growth characteristics. Higher solubility in methanol and a larger temperature difference between the melting temperature and the decomposition temperature of OH1 compared to analogous CLP crystals, are of advantage for solution and melt crystal growth, respectively. Acentric bulk OH1 crystals of large sizes with side lengths of up to 1 cm with excellent optical quality have been successfully grown from methanol solution. The microscopic and macroscopic nonlinearities of the OH1 crystals are investigated theoretically and experimentally. The OH1 crystals exhibit a large macroscopic nonlinearity with four times larger powder second harmonic generation efficiency than that of analogous CLP crystals containing dimethylamino electron donor. A very high potential of OH1 crystals for broadband THz wave emitters in the full frequency range of 0.1–3 THz by optical rectification of 160 fs pulses has been demonstrated.     

Ku-band antenna array feed distribution network with ferroelectric phase shifters on silicon

This paper presents the design, fabrication, and experimental results of a 1 : 4 monolithic power distribution network for Ku-band array antenna applications. The network integrated on a high-resistivity silicon (HRS) substrate surface stabilized by polysilicon consists of three Wilkinson power dividers, four dc blocking filters, and four coplanar waveguide (CPW)-to-microstrip (MS) transitions. Each output ports are fed with a barium-strontium-titanate phase shifter. It is found that the introduction of the polysilicon layer between the oxide and HRS reduces RF losses significantly, which will enable the monolithic integration of high-power controller modules onto silicon because of the existence of the oxide layer, preventing any degradation of RF performances. The individual components show insertion losses ranging from 0.4 to 2.6 dB at 15 GHz, and the interconnecting CPW lines result in a loss of 0.064 dB/mm. This network was successfully integrated with MS patch antennas monolithically, showing good performance of 32-dB return loss at 14.85 GHz, and 10/spl deg/ beam-steering capability.     

Activatable Photosensitizers: Agents for Selective Photodynamic Therapy

Recent developments in the design of bifunctional and activatable photosensitizers rejuvenate the aging field of photodynamic sensitization and photodynamic therapy. While systematic studies have uncovered new dyes that can serve as potential photosensitizers, the most promising results have come from studies aimed at gaining precise control over the location and rate of cytotoxic singlet oxygen generation. As a consequence, higher selectivities and efficiencies in photodynamic treatment protocols are now within reach. This feature article highlights the variety of approaches that have been pursued to improve photodynamic therapy and to transform simple photosensitizers into smarter theranostic agents.     

Biomimetic Nanomaterial Strategies for Virus Targeting: Antiviral Therapies and Vaccines

The ongoing coronavirus disease 2019 (COVID-19) pandemic highlights the importance of developing effective virus targeting strategies to treat and prevent viral infections. Since virus particles are nanoscale entities, nanomaterial design strategies are ideally suited to create advanced materials that can interact with and mimic virus particles. In this progress report, the latest advances in biomimetic nanomaterials are critically discussed for combating viral infections, including in the areas of nanomaterial-enhanced viral replication inhibitors, biomimetic virus particle capture schemes, and nanoparticle vaccines. Particular focus is placed on nanomaterial design concepts and material innovations that can be readily developed to thwart future viral threats. Pertinent nanomaterial examples from the COVID-19 situation are also covered along with discussion of human clinical trial efforts underway that might lead to next-generation antiviral therapies and vaccines.     

Intercell Interference Coordination Using Threshold-Based Region Decisions

IMT-Advanced mobile communication systems make it possible for any devices to access high-speed networks anytime and anywhere. To meet the needs of IMT-Advanced systems, cellular systems must solve the problem of intercell interference caused by frequency reuse. Intercell interference problems become severe when orthogonal frequency division multiplexing (OFDM) transmission, which is a key technology for 4G communication systems, is used in a cellular system. In this paper, a zone-based intercell interference coordination (ICIC) scheme with high flexibility and low cost is proposed, and its performance is evaluated through multicell system-level simulations carried out according to the simplified 3GPP (3rd Generation Partnership Project) Long Term Evolution (LTE) system parameters. In the proposed algorithm, each cell is divided into several regions based on threshold values. Each region reuses frequencies in different ways, and the regions have different maximum transmit (TX) powers according to the interference environment. Even though the proposed scheme can be implemented with low complexity by using only the existing user equipment (UE) measurement, simulation results have confirmed that it provides significant improvements in geometry distribution.     

Polymer‐Stabilized Chromonic Liquid‐Crystalline Polarizer

Robust coatable polarizer is fabricated by the self‐assembly of lyotropic chromonic liquid crystals and subsequent photo‐polymerizing processes. Their molecular packing structures and optical behaviors are investigated by the combined techniques of microscopy, scattering and spectroscopy. To stabilize the oriented Sunset Yellow FCF (H‐SY) films and to minimize the possible defects generated during and after the coating, acrylic acid (AA) is added to the H‐SY/H₂O solution and photo‐polymerized. Utilizing cross‐polarized optical microscopy, phase behaviors of the H‐SY/H₂O/AA solution are monitored by varying the compositions and temperatures of the solution. Based on the experimental results of two‐dimensional wide angle X‐ray diffraction and selected area electron diffraction, the H‐SY crystalline unit cell is determined to be a monoclinic structure with the dimensions of a = 1.70 nm, b = 1.78 nm, c = 0.68 nm, α = β = 90.0° and γ = 84.5°. The molecular arrangements in the oriented H‐SY films were further confirmed by polarized Fourier‐transform infrared spectroscopy. The polymer‐stabilized H‐SY films show good mechanical and chemical stabilities with a high polarizability. Additionally, patterned polarizers are fabricated by applying a photo‐mask during the photo‐polymerization of AA, which may open new doors for practical applications in electro‐optic devices.