Entity

Time filter

Source Type


Wang W.,Key Laboratory of Carbon Fiber and Functional Polymers
Applied Mechanics and Materials | Year: 2012

The growth details of strained GaAsSb layers on GaAs(001) substrates were studied by reflection high energy electron diffraction (RHEED) beam intensity oscillations as a function of both substrate temperature and Sb/As flux ratio. Both the RHEED intensity and RHEED oscillation cycles are reduced with decreasing substrate temperature and Sb/As flux ratio. InAs QDs with high dot density, small dot size and narrow size distribution have been achieved on strained GaAs / GaAsSb buffer layer. The average lateral size of dots shows a trend toward to smaller size and dots' density shows a trend toward to higher density as the surface Sb composition increasing. The QDs with higher density and smaller size distributions at high Sb composition, indicates that the Sb plays an important role in the dot formation under this growth condition. The lattice mismatch of InAs layer with the GaAsSb buffer layer is reduced with increasing of Sb composition in the GaAsSb interlayer. This result indicates that the density, size and size distribution of self-assembled quantum dots (QDs) can be controlled through the manipulation of the Sb-mediated strain field in the lattice mismatched system. © (2012) Trans Tech Publications, Switzerland. Source


Wang W.,Key Laboratory of Carbon Fiber and Functional Polymers
Advanced Materials Research | Year: 2012

XPS characterization of self-assembled monolayers (SAMs) of tetraphenylporphyrin bearing a rigid tripodal linker by chemisorption of the thiol-derivatized terminal groups on gold substrate is described. The surface structure of the SAMs bearing tripodal linker were analyzed by X-ray photoelectron spectroscopy (XPS), and electrochemical cyclic voltammetry (CV) measurements. XPS confirms the formation of porphyrin SAMs on Au surface and identified bonding configurations of porphyrin molecules in the chemisorption of SAMs. The film thickness values (36 Å) obtained by XPS agree well with the estimated value by assuming the vertical orientation of the molecules on the gold surface. Using the Au4f 7/2 as an internal standard, a lower binding energies shift (1.8 eV) of S2p in the SAMs reveals that the porphyrins were chemisorbed onto the surface via sulfur-gold bonds. Electrochemical CV measurements suggest near monolayer coverage of the tripodal porphyrins with good stability of the redox SAMs, which have promising application in the development of molecular based electronic device and memory architectures. © (2012) Trans Tech Publications, Switzerland. Source


Wang W.,Beijing University of Chemical Technology | Li R.,Beijing University of Chemical Technology | Tian M.,Key Laboratory of Carbon Fiber and Functional Polymers | Liu L.,Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials | And 4 more authors.
ACS Applied Materials and Interfaces | Year: 2013

A facile method was developed to fabricate highly electrically conductive aramid fibers. The immobilization of silver nanoparticles on the surface of polymetaphenylene isophthamide (PMIA) fibers was carried out by the functionalization of the PMIA fibers with poly(dopamine), followed by electroless silver plating. The poly(dopamine) (PDA) layer was deposited on the PMIA surface by simply dipping the PMIA substrate into an alkaline dopamine solution. The silver ions can be chemically bound to the catechol and indole functional groups in PDA. The silver ions were reduced into silver nanoparticles by using glucose as the reducing agent, resulting in a distinct silver layer on the PMIA surface. The obtained silver deposit was homogeneous and compact. The chemical composition of the modified PMIA fibers was studied by X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS), and the crystalline structure of the silver-coated PMIA fibers was characterized by powder X-ray diffraction (XRD). The topography of the modified PMIA fibers was investigated by scanning electron microscopy (SEM). The four-point probe resistivity meter was used to study the electrical resistivity of the silver-coated PMIA fibers, the results indicated that the electrical resistivity could be as low as 0.61 mΩ·cm, with a controllable silver content, and a satisfactory stability by ultrasonic treatment. © 2013 American Chemical Society. Source


Zhao C.,Key Laboratory of Carbon Fiber and Functional Polymers | Yao X.,Key Laboratory of Carbon Fiber and Functional Polymers | Ma Y.,Key Laboratory of Carbon Fiber and Functional Polymers | Yuan P.,Key Laboratory of Carbon Fiber and Functional Polymers | And 2 more authors.
Applied Surface Science | Year: 2012

First a SiO x layer, as a barrier layer between a photo active anatase TiO 2 layer and BOPP substrate, was coated on hydroxylated BOPP film by a sol-gel process. Then, TiO 2 layer was formed on SiO x surface through liquid phase deposition. Thus a flexible BOPP/SiO x/TiO 2 multilayer film which has photocatalytic activity was fabricated. The coating processes were monitored by FT-IR and UV-vis spectroscopy, scanning electron microscopy, atom force microscopy and water contact angle (CA) measurements. The thickness of SiO x and TiO 2 layer was about 600 nm and 135 nm, respectively. Root mean square (RMS) roughness of the SiO x layer was about 2-3 nm while the surface of TiO 2 layer was much coarse with RMS roughness about 30 nm which offered the large surface area. The TiO 2 layer endowed multilayer film photoinduced hydrophilic conversion property evidenced by the fact that its surface water contact angle could reduce to about 5° after 1 h of UV irradiation. The photocatalytic degradation ability of multilayer film was evaluated using methyl orange as model contamination and the results indicating that the degradation is efficient. © 2012 Elsevier B.V. All rights reserved. Source


Li C.Y.,Beijing University of Chemical Technology | Wang W.C.,Key Laboratory of Carbon Fiber and Functional Polymers | Wang W.C.,Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials | Xu F.J.,Beijing University of Chemical Technology | And 3 more authors.
Journal of Membrane Science | Year: 2011

A facile method to immobilize the initiators onto the substrate is desirable for surface initiated atom transfer radical polymerization (ATRP). In this work, a two-step process was first developed for covalent immobilization of ATRP initiators on the outside and inside surfaces of the porous nylon membrane. The nylon membrane was functionalized with poly(dopamine), and the bromoalkyl initiators were then immobilized on the poly(dopamine) functionalized nylon membrane surfaces in a two-step solid-phase reaction, followed by ATRP of acrylic acid (AAc), which was deprotonated by the addition of NaOH in an aqueous solution. The resulting nylon membranes with grafted poly(acrylic acid) (PAAc) side chains were characterized by X-ray photoelectron spectroscopy (XPS). The morphology of the nylon membranes was studied by scanning electron microscopy (SEM). The results indicated that the grafted PAAc polymers formed uniformly inside the pores throughout the entire membrane. With the increase of the polymerizing time, the average diameter of the pores became smaller. A kinetics study revealed that the chain growth from the membranes was consistent with a " controlled" process. The nylon-g-PAAc membranes exhibit rapid and reversible responses of the flux to the environmental pH varied from 3 to 8. Between pH 3.5 and 5.5, the membranes demonstrated a pH-valve function as the carboxyl group changed from neutral to charged states with a corresponding variation of chain configuration. © 2010 Elsevier B.V. Source

Discover hidden collaborations