Showing papers by "Nanchang Hangkong University published in 2011"

Novel Benzo[1,2‐b:4,5‐b′]dithiophene–Benzothiadiazole Derivatives with Variable Side Chains for High‐Performance Solar Cells

Abstract: Polymer solar cells (PSCs) have attracted considerable attention because of their advantages of low cost, light weight, and fl exibility in large area applications by ink-jet printing and rollto-roll solution processes. [ 1 ] The concept of bulk heterojunction (BHJ) has improved the power conversion effi ciencies (PCEs) of the PSCs signifi cantly by blending electron-donating conjugated polymers and electron-accepting fullerene derivatives (such as [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM)). [ 2 ] In the past few years, regioregular poly(3-hexylthiophene) (P3HT) and PC 61 BM based PSCs were taken as standard BHJ devices with high effi ciencies of 4–5%. [ 3 ] However, the improvement of PCEs was limited in these devices by their low open circuit voltages ( V oc ) and narrow absorption spectra. Aiming at achieving broader absorption, higher hole mobility, and more suitable energy levels, low bandgap (LBG) conjugated polymers were developed rapidly to be the alternatives of P3HT with effi ciency values over 7%. [ 1c , 1d , 4 ]

Fabrication of PbS Nanoparticle-Sensitized TiO2 Nanotube Arrays and Their Photoelectrochemical Properties

Abstract: TiO2 nanotube arrays (NTAs) are modified with PbS nanoparticles by successive ionic layer adsorption and reaction (SILAR) or electrodeposition, with an aim towards tuning the photoelectrochemical cell to the visible region. The PbS modification of the TiO2 NTAs results in an increase in the visible light adsorption, however the increase in photocurrent is dependent on the modification method. PbS/TiO2 NTAs prepared by SILAR and electrodeposition show, respectively, photocurrents of 11.02 and 5.72 mA/cm2. The increase in photocurrent is attributed to enhanced charge separation efficiency and improved electron transport.

Sensitive determination of dopamine in the presence of uric acid and ascorbic acid using TiO2 nanotubes modified with Pd, Pt and Au nanoparticles

Abstract: A simple modified TiO2 nanotubes electrode was fabricated by electrodeposition of Pd, Pt and Au nanoparticles. The TiO2 nanotubes electrode was prepared using the anodizing method, followed by modifying Pd nanoparticles onto the tubes surface, offering a uniform conductive surface for electrodeposition of Pt and Au. The performance of the modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The Au/Pt/Pd/TiO2 NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. In both case, electro-oxidation peak currents of dopamine were linearly related to accumulated concentration over a wide concentration range of 5.0 × 10−8 to 3.0 × 10−5 M. However in the same range of dopamine concentration, the sensitivity had a significant loss at Pt/Pd/TiO2 NTs electrode, suggesting the necessity for Au nanoparticles in modified electrode. The limit of the detection was determined as 3 × 10−8 M for dopamine at signal-to-noise ratio equal to 3. Furthermore, the Au/Pt/Pd/TiO2 NTs modified electrode was able to distinguish the oxidation response of dopamine, uric acid and ascorbic acid in mixture solution of different acidity. It was shown that the modified electrode possessed a very good reproducibility and long-term stability. The method was also successfully applied for determination of DA in human urine samples with satisfactory results.

Self-Assembly of Octadecyltrichlorosilane on Graphene Oxide and the Tribological Performances of the Resultant Film

Abstract: Taking advantage of the condensation between Si–OH of the hydroxylated octadecyltrichlorosilane (OTS) and C–OH on graphene oxide (GO) surface, we grafted OTS onto the GO-based dual-layer film, which was composed of GO outerlayer and (3-aminopropyl)triethoxysilane (APTES) self-assembled underlayer, on a Si substrate. Thus, a hydrophobic trilayer film coded as APTES-GO-OTS was prepared successfully. To confirm the chemical composition, structure, and morphology of the trilayer film, various means including water contact angle measurement, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were performed. Moreover, to investigate the tribological performances, the micro- and macrotribological experiments were conducted with AFM and a UMT tribometer. The results showed that the as-prepared trilayer film exhibited low adhesion and greatly reduced the friction force in both the micro- and macroscale. Therefor...

Isolation and characterization of endophytic bacterium LRE07 from cadmium hyperaccumulator Solanum nigrum L. and its potential for remediation

Abstract: Valuable endophytic strains facilitating plants growth and detoxification of heavy metals are required because the application of plant–endophyte symbiotic system is a promising potential technique to improve efficiency of phytoremediation. In this study, endophytic bacterium LRE07 was isolated from cadmium hyperaccumulator Solanum nigrum L. It was identified as Serratia sp. by 16S rRNA sequence analysis. The endophytic bacterium LRE07 was resistant to the toxic effects of heavy metals, solubilized mineral phosphate, and produced indoleacetic acid and siderophore. The heavy metal detoxification was studied in growing LRE07 cells. The strain bound over 65% of cadmium and 35% of zinc in its growing cells from single metal solutions 72 h after inoculation. Besides the high removal efficiencies in single-ion system, an analogous removal phenomenon was also observed in multi-ions system, indicating that the endophyte possesses specific and remarkable heavy metal remediation abilities.

Selective Separation of Cu(II) from Aqueous Solution with a Novel Cu(II) Surface Magnetic Ion-Imprinted Polymer

Abstract: A novel Cu(II) magnetic ion-imprinted polymer (MIIP) was prepared via the sol−gel method. The Cu(II)-MIIP exhibited good magnetic property and thermal stability. The binding characteristics of Cu(II)-MIIP were studied by adopting both static and dynamic adsorption experiments. The maximum adsorptions calculated from the Langmuir isotherm are 58.20 and 23.10 mg/g for Cu(II)-MIIP and magnetic nonimprinted polymer (MNIP), respectively. The kinetics studies showed that the adsorption process obeyed a pseudo-second-order kinetic model. The selectivity coefficients of the Cu(II)-MIIP for Cu(II) in the presence of Zn(II) and Ni(II) are 49.44 and 50.38, respectively. The relative selectivity coefficients of Cu(II)-MIIP for Cu(II)/Zn(II) and Cu(II)/Ni(II) are 12.36 and 8.73, respectively. Moreover, Cu(II)-MIIP could be used five times without obvious deterioration in their adsorption capacities.

Morphological Multiscale Enhancement, Fuzzy Filter and Watershed for Vascular Tree Extraction in Angiogram

Abstract: This paper presented an automatic morphological method to extract a vascular tree using an angiogram. Under the assumption that vessels are connected in a local linear pattern in a noisy environment, the algorithm decomposes the vessel extraction problem into several consecutive morphological operators, aiming to characterize and distinguish different patterns on the angiogram: background, approximate vessel region and the boundary. It started with a contrast enhancement and background suppression process implemented by subtracting the background from the original angiogram. The background was estimated using multiscale morphology opening operators by varying the size of structuring element on each pixel. Subsequently, the algorithm simplified the enhanced angiogram with a combined fuzzy morphological opening operation, with linear rotating structuring element, in order to fit the vessel pattern. This filtering process was then followed by simply setting a threshold to produce approximate vessel region. Finally, the vessel boundaries were detected using watershed techniques with the obtained approximate vessel centerline, thinned result of the obtained vessel region, as prior marker for vessel structure. Experimental results using clinical digitized vascular angiogram and some comparative performance of the proposed algorithm were reported.

An item-oriented recommendation algorithm on cold-start problem

Abstract: Based on a hybrid algorithm incorporating the heat conduction and probability spreading processes (Proc. Natl. Acad. Sci. U.S.A., 107 (2010) 4511), in this letter, we propose an improved method by introducing an item-oriented function, focusing on solving the dilemma of the recommendation accuracy between the cold and popular items. Differently from previous works, the present algorithm does not require any additional information (e.g., tags). Further experimental results obtained in three real datasets, RYM, Netflix and MovieLens, show that, compared with the original hybrid method, the proposed algorithm significantly enhances the recommendation accuracy of the cold items, while it keeps the recommendation accuracy of the overall and the popular items. This work might shed some light on both understanding and designing effective methods for long-tailed online applications of recommender systems.

A simple two-step electrochemical synthesis of graphene sheets film on the ITO electrode as supercapacitors

Abstract: In this study, a simple and controllable two-step electrochemical process is described for the synthesis of graphene sheets (GS) film on a cleaned indium tin oxide (ITO) sheet electrode. Namely, the main procedures involve the electrophoretic deposition (EPD) of graphene oxide (GO) film onto ITO electrode and the subsequent in situ electrochemical reduction (ECR) of GO to generate GS film. X-ray photoelectron spectroscopy (XPS) measurement demonstrates that most of the oxygen-containing functional groups in GO film have been removed after ECR. By electrochemical measurements, the maximum specific capacitance of the prepared GS film electrode was calculated to be 156 F g−1, besides, the capacitance retention of the material remained 78% after 400 times of cycling, showing a promising prospect as supercapacitor materials.

Pyrazino[2,3-g]quinoxaline-based conjugated copolymers with indolocarbazole coplanar moieties designed for efficient photovoltaic applications

Abstract: A series of low band gap copolymers consisting of electron-accepting pyrazino[2,3-g]quinoxaline (PQx) and an electron-donating indolo[3,2-b]carbazole and thiophene units have been designed and synthesized by Stille coupling polymerization. Their optical and electrical properties could also be facilely fine-modulated for photovoltaic application by adjusting the donor/acceptor ratios. UV-vis measurements showed that increasing the content of PQx units led to enhanced absorption. The band gaps obtained from UV-vis spectra, CV scanning, and DFT modeling all indicated a narrowing band gap with increasing the PQx content in the copolymer structure. The photovoltaic solar cells (PSCs) based on these copolymers were fabricated and tested with a structure of ITO/PEDOT:PSS/copolymer:PCBM/Ca/Al under the illumination of AM 1.5G, 100 mW cm−12. The best performance was achieved using P3/[70]PCBM blend (1 : 3) with Jsc = 9.55 mA cm−2, Voc = 0.81 V, FF = 0.42, and PCE = 3.24%, which is the highest efficiency for the PQx and indolo[3,2-b]carbazole based devices. The present results also indicate that the efficient photovoltaic materials with suitable electronic and optical properties can be achieved by just fine-tuning the ratios of the strong electron-deficient accepters and large-π planar donors.

BaTiO3–polyethersulfone nanocomposites with high dielectric constant and excellent thermal stability

Abstract: BaTiO3–polyethersulfone (PES) nanocomposites were prepared using the simple ultrasonic dispersion and hot-pressing method. The dielectric properties and thermal properties of the obtained composites were investigated using a LCR digital meter, a thermal gravimetric analyzer (TGA), and a differential scanning calorimeter (DSC). The results indicated that the BaTiO3–PES composites possessed desirable properties, such as high dielectric constant, low loss tangent, high thermal stability, as well as good processability. Furthermore, the dielectric constants of the composites were weak frequency dependent from 10 kHz to 100 kHz and weak temperature dependent from 20 °C to 150 °C. In addition, most loss tangents of the composites were less than 0.05. Furthermore, the composites exhibited high glass transition temperature (>225 °C) and high 5.0% weight loss temperature (>500 °C). The present work indicated that the BaTiO3–PES composites could be a candidate for embedded capacitors under the high temperature environment.

Analytical modeling and experimental investigation of laser induction hybrid rapid cladding for Ni-based WC composite coatings

Abstract: Laser induction hybrid rapid cladding (LIHRC) cannot only increase the cladding efficiency, but can also eliminate porosity and cracking of ceramic–metal composite coatings. In order to obtain a deep understanding of LIHRC with rapid cladding speed and high powder deposition rate, an analytical model of LIHRC for Ni-based WC composite coatings is proposed in the paper. The predictions of cladding height and powder efficiency obtained with this model are in good agreement with experimental results. Injection angles at which the attenuation rate of laser power is relatively low are identified and crack-free composite coatings with smooth surface, good profile and metallurgical bonding to substrate can be obtained. The calculated results for the temperature of the powder particles are compared to experimental data of the microhardness profiles and show a similar trend.

A novel route for the synthesis of poly(2-hydroxyethyl methacrylate- co -methyl methacrylate) grafted titania nanoparticles via ATRP

Abstract: A new method is presented for grafting poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (P(HEMA-co-MMA)) chains from the surface of TiO2 nanoparticles via atom transfer radical polymerization (ATRP). First, the ATRP initiators were immobilized onto the TiO2 surface by using 3-aminopropyltriethoxysilane coupling agent and 2-bromoisobutyryl bromide. Then the copolymerization of 2-hydroxyethyl methacrylate with methyl methacrylate was initiated and propagated on the TiO2 surface by ATRP. The resulting composite nanoparticles were characterized by means of XPS, FT-IR, 1H NMR, GPC and TGA. The results indicated that the grafting of copolymer chains from the TiO2 surface was successful. This method opens up new avenues for the preparation of TiO2-polymer nanocomposites.

Surface structural evolution in iron oxide thin films.

Abstract: Ordered iron oxide ultrathin films were fabricated on a single-crystal Mo(110) substrate under ultrahigh vacuum conditions by either depositing Fe in ambient oxygen or oxidizing preprepared Fe(110) films. The surface structure and electronic structure of the iron oxide films were investigated by various surface analytical techniques. The results indicate surface structural transformations from metastable FeO(111) and O-terminated Fe(2)O(3)(0001) to Fe(3)O(4)(111) films, respectively. The former depends strongly on the oxygen pressure and substrate temperature, and the latter relies mostly upon the annealing temperature. Our experimental observations are helpful in understanding the mechanisms of surface structural evolution in iron oxides. The model surfaces of Fe-oxide films, particularly O-terminated surfaces, can be used for further investigation in chemical reactions (e.g., in catalysis).

Fringe projection profilometry based on a novel phase shift method.

Abstract: Fringe projection profilometry is generally used to measure the 3D shape of an object. In oblique-angle projection, the grating fringe cycle is broadened on the reference surface. A well-fitted, convenient, and quick cycle correction method is proposed in this study. Based on the proposed method, an accurate four-step phase shift method is developed. Comparative experiments show that the fringe projection profilometry based on the novel phase shift method can eliminate cycle error and significantly improve measurement accuracy. The relative error of the measurement is less than 1.5%. This method can be widely employed for measuring large objects.

Effects of substrate curvature radius, deposition temperature and coating thickness on the residual stress field of cylindrical thermal barrier coatings

Abstract: In a thermal barrier coating (TBC) system with cylindrical geometry, the position of coating plays an important role in the distribution of residual stress. In this paper, the residual stress field in three different types of TBCs with cylindrical geometry has been analyzed. The main focus is on the effects of substrate curvature radius, deposition temperature and coating thickness on the residual stress distribution during a deposition process. The results show that the substrate curvature radius significantly affects the distributions of radial and hoop residual stresses, which are in good agreement with experimental measurements by photo-stimulated luminescence piezospectroscopy (Wang et al., Acta Mater., 2009, 57(1):182–195). The maximum radial residual stress locates closely to the coating/thermal grown oxide interface. However, the maximum hoop residual stress lies in the thermal grown oxide layer, which is much more than other three layers and presents a strong stress singularity along the thickness direction.