Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot

Individual InAs/GaAs quantum dots are studied by micro-photoluminescence. By varying the strength of an applied external magnetic field and/or the temperature, it is demonstrated that the charge state of a single quantum dot can be tuned. This tuning effect is shown to be related to the in-plane electron and hole transport, prior to capture into the quantum dot, since the photo-excited carriers are primarily generated in the barrier.     

Magnetic Field,Flow Field and Inclusion Collision Growth in a Continuous Caster with EMBR

A three‐dimension mathematical model has been developed to describe the magnetic field, fluid flow and inclusion transport in a continuous caster with electromagnetic brake (EMBR). According to the model, all the governing equations can be expressed as a general differential equation, so a general numerical method was developed to solve these equations. The numerical results agree well with the experimental result. In the continuous caster, the inclusion distributions have ‘M’ shape under the nozzle and ‘W’ shape at the exit, which come from the centrifugal effect and the collision and aggregation among inclusions. The three‐dimensional static magnetic field can effectively damp local flows and affect the inclusion transport in a continuous caster. If EMBR is installed under the nozzle, it can promote the inclusion removal and the inclusion ‘M’ distribution disappears.     

Multifunctional polyaniline–tin oxide (PANI–SnO2) nanocomposite: Synthesis,electrochemical, and field emission investigations

Synthesis of PANI–SnO₂ nanocomposite has been performed using a simple two step chemical oxidative polymerization route. The structural, morphological and chemical properties of the as‐synthesized PANI–SnO₂ nanocomposite have been revealed by various characterization techniques such as SEM, TEM, XRD, FTIR, and XPS. Interestingly the as‐synthesized PANI–SnO₂ nanocomposite exhibits supercapacitance value of 721 F g^?1 with energy density 64 Wh kg^?1, which is noticed to be higher than that of pristine SnO₂ and PANI nanostructures. Furthermore, the galvanostatic charge–discharge characteristics revealed pseudocapacitive nature of the PANI–SnO₂ nanocomposite. The estimated values of charge transfer resistance and series resistance estimated from the Nyquist plot are found to be lower. Along with the supercapacitive nature, PANI–SnO₂ nanocomposite showed promising field emission behavior. The threshold field, required to draw emission current density of 1 μA/cm², is observed to be 0.90 V/μm and emission current density of 1.2 mA/cm² has been drawn at applied field of ～2.6 V/μm. The emission current stability investigated at preset values of 0.02 and 0.1 mA/cm² is observed to be fairly stable over duration of more than 3 h. The enhanced supercapacitance values, as well as, the promising field emission characteristics are attributed to the synergic effect of SnO₂ nanoparticles and PANI nanotubes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41401.     

Novel temperature and pH dual-sensitive PNIPAM/CMCS/MWCNT semi-IPN nanohybrid hydrogels: Synthesis,characterization, and DOX drug release

Novel poly(N-isopropylacrylamide)/carboxymethyl chitosan/multiwalled carbon nanotube semi-interpenetrating nanohybrid hydrogels were prepared, and the chemical structure and morphology were characterized. The prepared hydrogels showed temperature and pH dual-responsiveness, and the one containing multiwalled carbon nanotubes (MWCNTs)–COOH possessed high maximal swelling ratios. The phase transition produced at pH of 6.8–7.4 and temperature of 35–40°C, hinging on the system compositions and charge ratios. The hydrogels were used to load hydrophilic anticancer drug, with high entrapped efficiency of about 44%. The drug release changed with temperature, pH, and MWCNTs–COOH contents. The designed hydrogels can be used for site-specific target delivery of protein or hydrophilic anticancer drug.     

Alternating phenylenevinylene copolymers with dithienbenzothiadiazole moieties: Synthesis,photophysical, and photovoltaic properties

Two new soluble alternating phenylenevinylene copolymers S and L which contained dithienbenzothiadiazole moieties were synthesized by Heck coupling. The repeating unit of L was longer than that of S and contained two additional phenylene rings and two cyano‐vinylene bonds. Both copolymers were stable up to about 350°C and afforded char yield of 52–66% at 800°C in N₂. Their absorption spectra were broad and extended up to about 600 nm with a longer wavelength maximum at 447–502 nm and optical band gap of ～ 2.0 eV. These copolymers emitted yellow light in solution with PL maximum at 551–580 nm and orange‐red light in thin film with PL maximum at 588–661 nm. The emission maximum of L was considerably red‐shifted relative to S . Photovoltaic cells based on S (or L ) as donor and [6,6]‐phenyl C61‐butyric acid methyl ester as acceptor were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Alternating copolymers of oligoarylenes and naphthalene bisimides as low band gap semiconductors: Synthesis, electrochemical and spectroelectrochemical behavior

Three novel electroactive copolymers, consisting of alternating naphthalene bisimide and oligoarylene segments have been synthesized and studied by cyclic voltammetry and UV–vis-NIR spectroelectrochemistry. These studies show that the conjugation between both copolymer segments is very weak and the reduction of the bisimide part is essentially uninfluenced by the oligoarylene segment. The oxidation of the oligoarylene segment strongly depends on its length but is not affected by the presence of the bisimide part. The HOMO levels, determined electrochemically are systematically below −5.0 eV with respect to the vacuum level, changing from −5.45 eV for poly[1,4-phenylene-(4,3′(4′),3″-trioctyl-2,2′,5′,2″-terthiophene-5,5″-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (6) to −5.50 eV in poly[1,4-phenylene-(4,4′-dioctyl-2,2′-bithiophene-5,5′-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (5) and −5.84 eV for poly[1,4-phenylene-(3,4-dioctylthiophene-2,5-diyl)-1,4-phenylene-1,4,5,8-naphthalenediimide-N,N′-diyl] (4). The LUMO levels in all three cases are close to −4.0 eV. The obtained results clearly indicate that 5 and 6 are good candidates for the fabrication of ambipolar transistors operating in air whereas 4 can be considered as an active component of n-channels FETs.     

Magnetic polymer microspheres with azidocarbonyl groups: Synthesis,characterization and application in protein immobilization

A novel magnetic polymer microsphere with amide groups and carboxyl groups was synthesized and reported here. The azidocarbonyl groups were derived from amide groups and linked to the proteins to investigate their immobilization capacity. The morphology, size, functional groups and magnetic properties of magnetic microspheres were characterized by optical microscopy, particle size analyzer, atom force microscopy, magnetic force microscopy, fourier transform infrared spectrometer, vibrating‐sample magnetometer and thermal gravimetric analysis. The results indicated that the magnetic polymer microspheres had a well spherical shape with the size ranging from 1 to 10 μm, highly reactive functional groups, superparamagnetism and strong magnetic responsibility with saturation magnetization of 18.443 emu/g and Fe₃O₄ content around 21%. The immobilization capacity (η) was over 70%. The novel azidocarbonyl magnetic polymer microspheres showed potentials to be a good magnetic support and promising applications in bioseparation and biomedical fields. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Biocompatibility of Maleic Anhydride Copolymers: 1. Maleic Anhydride–Vinyl Acetate,Maleic Anhydride–Methyl Methacrylate and Maleic Anhydride–Styrene

A series of maleic anhydride (MA)–vinyl acetate (VA), MA–methyl methacrylate (MM) and MA–styrene (S) copolymers were prepared and characterized. By employing various amounts of initiator, MA–VA, MA–MM and MA–S copolymers with molecular weights ranging between 18 000 and 219 000 were obtained. The ‘in vivo’ and ‘in vitro’ tests performed on K562 cellular cultures (human chronic myeloid leukaemia) and also on Westar rats (inoculated with the Walker 256 carcinosarcome) showed that, as a function of the molecular weight, the copolymers synthesized had a 50% in vitro cytotoxicity and a mean tumour regression of a maximum of 68%. © 1997 SCI.     

Magnetic Multi-Wall Carbon Nanotubes for Methyl Orange Removal from Aqueous Solutions: Equilibrium,Kinetic and Thermodynamic Studies

The magnetic iron oxide nanoparticles (SPION) were prepared using the co-precipitation method. The magnetically modified multi-wall carbon nanotubes (MWCNT) were obtained by the same method. The magnetic nanoparticles were used as adsorbents for methyl orange (MO) removal from aqueous solutions. The surface properties of adsorbents were analyzed by XRD, TGA, FTIR, and SEM. The adsorption was carried out on batch type. The kinetic, equilibrium and thermodynamics parameters were obtained by experimental results. The maximum adsorption capacity was obtained at pH 3 for both of the adsorbents. Theoretical adsorption capacities were found as 0.31 mg/g for SPION and 10.54 mg/g for MWCNT/SPION composites from Langmuir isotherm parameters. The MWCNT/SPION composites can adsorb 95% of methyl orange from water. The kinetic parameters and thermodynamic parameters were calculated.     

Magnetic phase transition and magneto-dielectric analysis of spinel chromites: MCr2O4 (M = Fe,Co and Ni)

In this work, we present magnetic phase transition temperatures and magneto-dielectric coupling in MCr₂O₄ (M = Fe, Co and Ni) ceramics, synthesized using sol–gel auto-combustion route. In order to develop their respective crystalline textures, all these chromites were calcined at 650?°C for 2?h. X-ray diffraction patterns confirmed that FeCr₂O₄ had a rhombohedral structure while NiCr₂O₄ and CoCr₂O₄ exhibited a spinel-type cubic structure. The presence of relevant elements in the specific stoichiometric ratios was confirmed using energy dispersive X-ray spectroscopy. The shapes and sizes of the grains for all the samples were determined using the images obtained from a field emission scanning electron microscope. Temperature dependent magnetic analysis have shown that FeCr₂O₄, CoCr₂O₄ and NiCr₂O₄ are ferromagnetic at 5?K and their magnetic phase transition temperatures were measured as 80, 83 and 90?K, respectively. Spin-orbit interference was also studied through magneto-dielectric coupling for these chromites using a modified impedance analyzer set-up.