Uniformity study of wafer-scale InP-to-silicon hybrid integration

β-SiC nanowires were synthesized by a simple carbothermal reduction of carbonaceous silica xerogel. The morphology and structure of the nanowires were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscopy. The results showed that the nanowires were hexagonal prism-shaped hierarchical nanostructures. The typical stacking faults and twin defects of SiC nanowires were also observed. Band-gap characterization and photoluminescence properties of SiC nanowires were investigated by UV-vis absorption spectroscopy and fluorescence photometry, respectively. The results showed the SiC nanowire was an indirect transition semiconductor and the band gap energy for the SiC nanowires was 2.85 eV. The photoluminescence peak value at 470 nm (2.64 eV) originating from the SiC nanowires was a little higher than the value of band-gap energy.     

Conductive,Monodisperse Polyaniline Nanofibers of Controlled Length Using Well‐Defined Cylindrical Block Copolymer Micelles as Templates

Stable colloidal dispersions of polyaniline (PAni) nanofibers with controlled lengths from about 200 nm–1.1 μm and narrow length distributions (L_w/L_n<1.04; L_w=weight average micelle length, L_n=number average micelle length) were prepared through the template‐directed synthesis of PAni using monodisperse, solution‐self‐assembled, cylindrical, block copolymer micelles as nanoscale templates. These micelles were prepared through a crystallization‐driven living self‐assembly method from a poly(ferrocenyldimethylsilane)‐b‐poly(2‐vinylpyridine) block copolymer (PFS₂₅‐b‐P2VP₄₂₅). This material was initially self‐assembled in iPrOH to form cylindrical micelles with a crystalline PFS core and a P2VP corona and lengths of up to several micrometers. Sonication of this sample then yielded short cylinders with average lengths of 90 nm and a broad length distribution (L_w/L_n=1.32). Cylindrical micelles of PFS₂₅‐b‐P2VP₄₂₅ with controlled lengths and narrow length distributions (L_w/L_n<1.04) were subsequently prepared using thermal treatment at specific temperatures between 83.5 and 92.0 °C using a 1D self‐seeding process. These samples were then employed in the template‐directed synthesis of PAni nanofibers through a two‐step procedure, where the micellar template was initially stabilised by deposition of an oligoaniline coating followed by addition of a polymeric acid dopant, resulting in PAni nanofibers in the emeraldine salt (ES) state. The ES–PAni nanofibers were shown to be conductive by scanning conductance microscopy, whereas the precursor PFS₂₅‐b‐P2VP₄₂₅ micelle templates were found to be dielectric in character.     

An Efficient Route to 2-(Formylmethyl)-Cyclopenten-3-one and Its 1-methyl-Congener

We describe a five-step synthesis of 2-(formylmethyl) - cyclopenten-3-one (1a) and its 1-methyl congener (1b) from 6-methylhept-5-ene-2-one by way of the respective 2-(3-methylbut-2-enyl)-cyclopenten-3-ones (5) and selective ozonolysis of these intermediates.     

WHAT ARE THE DIFFERENCES OF POLYMER SURFACE RELAXATION FROM THE BULK?

The polymer surface relaxation in thin films has been a long debating issue.We report a new method on studying surface relaxation behaviors of polymer thin films on a solid substrate.This method involved utilizing a rubbed polyimide surface with a pretilting angle in a liquid crystalline cell.Due to the surface alignment,the liquid crystals were aligned along the rubbing direction.During heating the liquid crystalline cell,we continuously monitored the change of orientation of the liquid crystals.It is u...     

Cosmic rays through the Higgs portal

We consider electroweak singlet dark matter with a mass comparable to the Higgs mass. The singlet is assumed to couple to standard matter through a perturbative coupling to the Higgs particle. The annihilation of a singlet in the mass range m_Sm_h is dominated by proximity to the W, Z and Higgs peaks in the annihilation cross section. We find that the continuous photon spectrum from annihilation of perturbatively coupled singlets in the galactic halo can reach a level of several per mil of the EGRET diffuse γ ray flux.     

Nanosecond laser-induced surface damage of optical multimode fibers and their preforms

High-power optical multimode fibers are essential components for materials processing and surgery and can limit the performance of expensive systems due to breakdown at the end faces. The aim of this paper is the determination of laser-induced damage thresholds (LIDT) of fibers (FiberTech) and preforms (Heraeus Suprasil F300). Preforms served as models. They were heated up to maximum temperatures of 1100, 1300 and 1500°C and cooled down to room temperature at rates of 10 K min⁻¹ (oven) and ∼10⁵ K min⁻¹ (quenched in air) to freeze in various structural states simulating different conditions similar to a drawing process during the production of fibers. Single- and multi-pulse LIDT measurements were done in accordance with the relevant ISO standards. Nd:YAG laser pulses with durations of 15 ns (1064 nm wavelength) and 8.5 ns (532 nm) at a repetition rate of 10 Hz were used. For the preforms, LIDT values (1-on-1) ranged from 220 to 350 J/cm² (1064 nm) and from 80 to 110 J/cm² (532 nm), respectively. A multi-pulse impact changed the thresholds to lower values. The LIDT (1064 nm wavelength) of the preforms can be regarded as a lower limit for those of the fibers.     

Defect orientation on the chain folded surfaces of two-arm poly(ethylene oxide) lamellar crystals

Two-arm poly(ethylene oxide) fractions (PEOs) with arm lengths of 2 220 g/mol were synthesized via a reaction using terephthaloyl (1,4-), isophthaloyl (1,3-) and phthaloyl (1,2-) dichorides as coupling agents. The center of each molecule thus includes a phenylene group as a configurational defect, and they are excluded to the crystal folded basal surfaces. In the lamellar crystals with the once-folded overall molecular conformation, observations of surface-enhanced Raman scattering experiments show that only the in-plane vibration modes are selectively enhanced. This implies that the arrangement of phenylene groups adopts a “stand-up” orientation on the basal surface, i. e., the π plane of phenylene groups in the defects is perpendicular to the lamellar basal surface.     

Modular Metal-Quinone Networks with Tunable Architecture and Functionality

Nanostructured materials with tunable structures and functionality are of interest in diverse areas. Herein, metal ions are coordinated with quinones through metal-acetylacetone coordination bonds to generate a class of structurally tunable, universally adhesive, hydrophilic, and pH-degradable materials. A library of metal-quinone networks (MQNs) is produced from five model quinone ligands paired with nine metal ions, leading to the assembly of particles, tubes, capsules, and films. Importantly, MQNs show bidirectional pH-responsive disassembly in acidic and alkaline solutions, where the quinone ligands mediate the disassembly kinetics, enabling temporal and spatial control over the release of multiple components using multilayered MQNs. Leveraging this tunable release and the inherent medicinal properties of quinones, MQN prodrugs with a high drug loading (>89 wt %) are engineered using doxorubicin for anti-cancer therapy and shikonin for the inhibition of the main protease in the SARS-CoV-2 virus.