Direct synthesis of highly conductive poly（3,4- ethylenedioxythiophene）：poly（4-styrenesulfonate） （PEDOT：PSS）/graphene composites and their applications in energy harvesting systems

We report for the first time highly conductive poly（3,4-ethylenedioxythiophene）： poly（4-styrenesulfonate） （PEDOT：PSS）/graphene composites fabricated by in situ polymerization and their applications in a thermoelectric device and a platinum （Pt）-free dye-sensitized solar cell （DSSC） as energy harvesting systems. Graphene was dispersed in a solution of poly（4-styrenesulfonate） （PSS） and polymerization was directly carried out by addition of 3,4-ethylenedioxythiophene （EDOT） monomer to the dispersion. The content of the graphene was varied and optimized to give the highest electrical conductivity. The composite solution was ready to use without any reduction process because reduced graphene oxide was used. The fabricated film had a conductivity of 637 S.cm-1, corresponding to an enhancement of 41%, after the introduction of 3 wt.% graphene without any further complicated reduction processes of graphene being required. The highly conductive composite films were employed in an organic thermoelectric device, and the device showed a power factor of 45.7 μW·m^-1K^-2 which is 93% higher than a device based on pristine PEDOT：PSS. In addition, the highly conductive composite films were used in Pt-free DSSCs, showing an energy conversion efficiency of 5.4%, which is 21% higher than that of a DSSC based on PEDOT：PSS.     

Development of Molybdenum Trioxide （MoO3） by Spin Coating Method for Photovoltaic Application

Molybdenum trioxide （MOO3）, thin films have been deposited on glass substrates by spin-coating method using ammonium heptamolybdate tetrahydrate （（NH4）6Mo7O24·4H2O） as a single source precursor of Mo and O. They were subjected to atmospheric heat treatment at different temperatures （200, 400 and 500 ℃）. MoQ thin films obtained were characterized using X-ray diffraction techniques （XRD）, scanning electron microscopy （SEM）, energy dispersed spectroscopy （EDS） and integrating sphere. The XRD patterns of annealed films show the formation of MoO3 in a polycrystalline phase, formation of MoO3 was also confirmed by EDS. The SEM photographs show that the thin films obtained are in layer-type structure and their grains size increases with increasing of annealing temperatures. The measurement results of integrating sphere show that the MoO3 thin film prepared at 500 ~C transmit about 72% and reflect about 12% of the visible spectrum.     

Effects of Power Density and Post Annealing Process on the Microstructure and Wettability of TiO2 Films Deposited by Mid-frequency Magnetron Reactive Sputtering

The relationship of ＂preparation parameters-microstructures-wettability＂ of TiO2 films was reported. In this work, TiO2 films were deposited onto glass and silicon substrates by using mid-frequency dual magnetron sputtering technique at ambient temperature with various power densities and deposition time. After deposition, the films were heat treated at different annealing temperatures. X-ray diffraction （XRD）, Raman spectroscopy, and field-emission scanning electron microscopy （FE-SEM） were utilized to characterize TiO2 films. The wettability of the films was evaluated by water contact angle measurement. The phase transition temperature of TiO2 films depended on the power density. It was demonstrated that wettability was strongly structure dependent and the film with the thickness of 610 nm （the power density was 2.22 W/cm^2） showed the lowest contact angle （8°）. It can be concluded that smaller crystallite size, the rutile phase with （110） face being parallel to the surface, and tensile stress favored the hydrophilicity of the TiO2 films.     

Controlled Microstructure and Photochromism of Inorganic-organic Thin Films by Ultrasound

A series of inorganic-organic thin films based on uniformly dispersed nanoparticles of polyoxometalates （POM）entrapped in polyacrylamide （PAM） matrix were prepared by ultrasonic method with different irradiation time.The microstructure, photochromic behavior and mechanism of the films were studied by transmission electron microscopy （TEM）, ultraviolet-visible spectra （UV-VIS） and Fourier transform-infrared spectroscopy （FT-IR）.The microstructure and photochromic properties of the hybrid thin films could be controlled by ultrasound.TEM image revealed that the average size of phosphotungstic acid （PWA） nanoparticles decreased from 20 to 10 nm with the ultrasound irradiation time from 30 to 60 min. After irradiated with ultraviolet light,the transparent films changed from colorless to blue and showed reversible photochromism. The hybrid film, with ultrasound irradiation for 60 min had higher photochromic efficiency and faster bleaching reaction than the one with ultrasound irradiation for 30 min. FT-IR spectra showed that the Keggin geometry of heteropolyoxometalate was still preserved inside the composites, and the interactions between polyanions and polymer matrix increased as the ultrasound time prolonged. It is suggested that the mechanism of the different photochromic properties for the inorganic-organic thin films is the variation of the microstructure and interfacial interactions induced by ultrasound.     

The Inhibitive Effect of para-Amino Benzoic Acid and Its Polymer on Corrosion of Iron in 1 mol/L HCl Solution

Poly p-aminobenzoic acid has been synthesized by chemical oxidation method. The inhibitive effect of poly p-aminobenzoic acid on iron in 1 mol/L HCI solution was investigated by polarization and electrochemical impedance spectroscopy and compared with that of monomer p-aminobenzoic acid. The effectiveness of poly p-aminobenzoic acid is very high in comparison with that of monomer. The results show that both cathodic and anodic processes were suppressed by p-aminobenzoic acid and poly p-aminobenzoic acid of iron dissolution in 1 mol/L HCI by their adsorption on the iron surface. The inhibition efficiency of both p-aminobenzoic acid and poly p-aminobenzoic acid were found to increase with the inhibitor concentrations. Ultraviolet （UV） reflectance studies of the iron surface after exposure to inhibitor acid show that poly p-aminobenzoic acid is strongly adsorbed on iron surface.     

Effect of Low Molecule Polyamide and Nano-SiO2 on Properties of the Poly （MMA/BA/MAA）

Effects of low molecule polyamide （LMPA） and namometer SiO2 particles on the properties of the poly （MMA/ BA/MAA） adhesive for wearable and nonskid PVC （polyvinyl carbazole） materials were investigated. The experimental results show that the shear strength of poly （MMA/BA/MAA）/LMPA is increased, when the LMPA is added into poly （MMA/BA/MAA）. The optimum addition of LMPA is about 4 wt pct. By adding 3 wt pct nano-SiO2 into poly （MMA/BA/MAA）/LMPA adhesive, its properties such as the shear strength, thermal stability, wear resistance and sea waterproof resistance are increased too.     

Structural Morphological and Optical Properties of SnSb2S4 Thin Films Grown by Vacuum Evaporation Method

SnSb2S4 thin films were prepared from powder by thermal evaporation under vacuum of 1.33 × 10^-4 Pa （ 10^-6 Torr） on unheated glass substrates. The effect of thickness on the structural, morphological and optical properties of SnSb2S4 thin films was investigated. Films thickness measured by interference fringes method varied from 50 to 700 nm. X-ray diffraction analysis revealed that all the SnSb2S4 films were polycrystalline in spite without heating the substrates and the crystallinity was improved with increasing film thickness. The microstructure parameters： crystallite size, strain and dislocation density were calculated. It was observed that the crystallite size increased and the crystal defects decreased with increasing film thickness. In addition, by increasing the film thickness, an enhancement in the surface roughness root-mean-square （RMS） increased from 2.0 to 6.6 nm. The fundamental optical parameters like band gap, absorption and extinction coefficient were calculated in the strong absorption region of transmittance and reflectance spectrum. The optical absorption measurements indicated that the band （Eg） gap of the thin films decreased from 2.10 to 1.65 eV with increasing film thickness. The refractive indexes were evaluated in transparent region in terms of envelope method, which was suggested by Swanepoul. It was observed that the refractive index increased with increasing film thickness.     

XRD and XPS Analysis of TiO2 Thin Films Annealed in Different Environments

Undoped and Nb-doped TiO2 thin films have been fabricated on glass substrate by RF magnetron sputtering. The morphologic, structural and surface composition of these films before and after annealing in different environments were investigated by atomic force microscopy （AFM） imaging, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The XRD data reveal that the crystallinity is improved when the films are Nb-doped and annealed in H2 environment. The TiO2 thin films annealed in H2 environment exhibit only the anatase phase. The XPS analysis of TiO2 with Nb indicates the maximum shift in binding energy of the Ti 2p peak. A mechanism for the incorporation of Nb in the TiO2 lattice has been proposed.     

Structure and Optical Behavior of Nanocomposite Hybrid Films of Well Monodispersed ZnO Nanoparticles into Poly （vinylpyrrolidone）

We fabricated an inorganic-polymeric photoluminescent thin film based on ZnO nanoparticles, which were grown directly in the poly（vinylpyrrolidone） （PVP） matrix. The microstructure, composition, thermal stability, and the temperature-dependent photoluminescence of the thin film were investigated. X-ray diffraction （XRD） and transmission electron microscopy （TEM） results indicated that all the ZnO nanoparticles with a polycrys talline hexagonal wurzite structure were well separated from each other and were dispersed in the polymeric matrix homogeneously and randomly. Raman spectrum （Raman） showed a typical resonant multi-phonon process within the hybrid thin film. The shifts of infrared bands for PVP in the hybrid film should be attributed to strong coulombic interaction between ZnO and polymeric matrix. The stability of the hybrid film and the effect of the perturbation of ZnO on the stability were determined by means of the thermogravimetric analysis （TG） and differential thermal analysis （DTA）. The ultraviolet-visible adsorption （UV-vis） showed distinct excitonic features. The photoluminescent spectrum （PL） of the ZnO nanoparticles modified by PVP molecules showed markedly enhanced ultraviolet emission and significantly reduced green emission, which was due to the Perfect surface passivation of ZnO nanoparticles. Temperature dependent photoluminescent spectrum studies suggested that the ultraviolet emission was associated with bound exciton recombination.     

Effect of Deposition Temperature on Some Properties of MOCVD Molybdenum Sulphide Thin Films

Molybdenum sulphide thin films were deposited on sodalime glass, silicon Wafer and stainless steel （AISI 304L） substrates using Metal Organic Chemical Vapour Deposition （MOCVD） technique at temperatures ranging from 360 ℃ to 450 ℃. The films were characterized using Rutherford Backscattering Spectroscopy （RBS）, Ultraviolet-Visible Spectroscopy, Four point probe technique, Scanning Electron Microscopy （SEM） and Atomic Force Microscopy （AFM）. Elemental analysis showed that the S/Mo ratio increases from 1.22 to 2.33 with increasing temperature. The optical band gap varies from 1.69 eV to 1.79 eV as deposition temperature increases. The electrical conductivity ranging from 0.5 Ω-1 cm-1 to 1.30 Ω-1 also depends on deposition temperature. SEM micrographs of the films showed the layered structure of the film with an estimated grain size that increases from 1.6 μm to 2.4 μm as the deposition temperature increases. This study demonstrates that the properties of the films depend on the deposition temperature.     

Degradation and miscibility of poly(DL-lactic acid)/poly(glycolic acid) composite films: Effect of poly(DL-lactic-co-glycolic acid)

The in vitro degradation behaviour of poly(glycolic acid) (PGA) and its composite films containing poly(DL-lactic acid) (PDLLA) and poly(DL-lactic-co-glycolic acid) (PDLGA) were investigated via mass loss, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). All the films were prepared by solution casting, using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the solvent. Since the degradation rate of PDLLA is lower than that of PGA, those of the PDLLA/PGA composite films decreased. As a compatibilizer, PDLGA improved the compatibility and hydrolytic stability of PDLLA/PGA composite films. Changes in the composite films indicate that this kind of PGA-based composite biomaterial may be applicable to device design for clinical application in the future.     

Polysaccharide surface engineering of poly(D, L-lactic acid) via electrostatic self-assembly technique and its effects on osteoblast growth behaviours

The objective of this study was to surface modify the poly (D, L-lactic acid) (PDLLA) films and assess the effects of the modified surfaces on the functions of osteoblasts cultured in vitro. A layer-by-layer (LBL) self assembly technique, was used leading to the formation of multilayers on the PDLLA film surfaces. Chitosan (Chi) and poly (styrene sulfonate, sodium salt) (PSS) were utilized as polycation and polyanion in this study, respectively. The layer structure was investigated by using X-ray photoelectron spectroscopy (XPS) and water contact angle measurement, respectively. XPS analysis displayed the presence of chitosan on PDLLA surface. A full coverage of coating with PSS/Chi layers was achieved on the PDLLA surface only after the deposition layers of PEI/(PSS/Chi)₂. These results showed that PDLLA films could be modified with PSS/Chi pairs which may affect the biocompatibility of the modified PDLLA films. To confirm this hypothesis, cell proliferation, cell viability as well as alkaline phosphtase activity of osteoblasts on layer-by-layer modified PDLLA films as well as control samples were investigated in vitro. The proliferation of osteoblasts on modified PDLLA films was found to be greater than that on control (p < 0.05 and p < 0.01) after 1, 4 and 7 days culture, respectively. Cell viability measurement showed that the PSS/Chi modified PDLLA films have higher cell viability (p < 0.01) than control. Osteoblast differentiation function (ALP) on LBL-modified PDLLA film was found significantly higher (p < 0.01) than that of virgin PDLLA films. These data suggests that PSS/Chi pair was successfully employed to surface modify PDLLA film via a layer-by-layer technique, and enhanced its cell biocompatibility.     

HECS-g-PDLLA共聚物的微波合成及与聚乳酸的相容性

在微波作用下,以辛酸亚锡为催化剂,羟乙基壳聚糖（HECS）为大分子引发剂引发D,L-丙交酯（D,L-LA）开环聚合制备羟乙基壳聚糖-g-聚乳酸（HECS-g-PDLLA）,通过红外（IR）、元素分析（EA）、氢核磁共振（1H-NMR）、X射线衍射（XRD）和差示扫描量热分析（DSC）对产物进行了表征。然后采用溶液共混法...     

In vitro degradation and drug release from polymer blends based on poly(<Emphasis Type="SmallCaps">dl</Emphasis>-lactide), poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide-glycolide) and poly(ε-caprolactone)

Bioresorbable materials are extensively used for a wide range of biomedical applications. Accurately modifying and evaluating the degradation rate of these materials is critical to their performance and the controlled release of bioactive agents. The aim of this work was to modify the physical properties, degradation rate and drug delivery characteristics of thin films for medical applications by blending poly(dl-lactic acid) (PDLLA), poly(l-lactide-co-glycolide) (PLGA) and poly(ε-caprolactone) (PCL). The thin films were prepared using solvent casting and compression moulding and the in vitro degradation study was performed by immersing the films in a phosphate-buffered saline at elevated temperature for a period of 4 weeks. The degradation rate of the materials was analysed by differential scanning calorimetry, tensile testing and weight loss studies. The thermal analysis of the blends indicated that the presence of PLGA or PDLLA in the film resulted in increased degradation of the amorphous regions of PCL. It was observed that the samples consisting of PDLLA with PCL demonstrated the greatest weight loss. The decrease in mechanical properties observed for both sets of polymer blends proved to be similar. The solvent cast technique was selected as the most appropriate for the formation of the polymer/drug matrices, due to the potentially adverse thermal processing effects associated with compression moulding. It was found that modulation of drug release was achievable by altering the ratio of PCL to PDLLA or PLGA in the thin film blends.     

Time-dependent effects of pre-aging polymer films in cell culture medium on cell adhesion and spreading

We have tested the hypothesis that cell adhesion and spreading on polymer films are influenced by the amount of time that the polymer films are pre-aged in cell culture medium. Cell adhesion and spreading were assessed after a 6-h culture on poly(d,l-lactic acid) (PDLLA) films that had been pre-aged in cell culture medium for 30 min, 1, 3 or 7 d. Cell adhesion and spread area were enhanced as the duration of pre-aging PDLLA films in cell culture medium was increased. Materials characterization showed that the hydrophobicity and surface morphology of the PDLLA films changed with increasing length of pre-aging time. These results suggest that cell adhesion and spreading are sensitive to the time-dependent changes in PDLLA hydrophobicity and surface morphology that occur during exposure of the polymer to cell medium for different lengths of time. These results demonstrate that cell response to a degradable, biomedical polymer can change as a function of the amount of time that the polymer is exposed to physiological medium. This article, a contribution of the National Institute of Standards and Technology, is not subject to US copyright.     

Effects of baicalin-modified poly(D,L-lactic acid) surface on the behavior of osteoblasts

In the present study, the functions of rat calvaria osteoblasts on baicalin-modified poly(D,L-lactic acid) (PDLLA) films were investigated in vitro. The surface characteristics of surfaces (both modified and control) were investigated by water contact angle measurement and electron spectroscopy for chemical analysis (ESCA). Cell morphologies on these surfaces were examined by scanning electron microscopy (SEM). Cell adhesion and proliferation were used to assess cell growth on the modified and control surfaces. The MTT assay was used to determine cell viability and alkaline phosphatase (ALP) activity was performed to evaluate differentiated cell function. Compared to control films, cell attachment of osteoblasts on baicalin-modified PDLLA film was significantly higher (P<0.05 and P<0.01) after 6 h and 8 h culture, and cell proliferation was also significantly greater (P<0.05 and P<0.01) at the end of 4th and 7th day, respectively. The MTT assay suggested that the cell viability of osteoblasts cultured on baicalin-modified PDLLA film was significantly higher (P<0.05) than that seeded on the control. Meanwhile, the ALP activity of osteoblasts cultured on modified films was also considerably enhanced (P<0.01) compared to that found on control. These results revealed that the biocompatibility PDLLA could be improved by surface modification with baicalin.     

Characterization of Combinatorial Polymer Blend Composition Gradients by FTIR Microspectroscopy

A new FTIR technique was developed for characterizing thin polymer films used in combinatorial materials science. Fourier transform infrared microspectroscopy mapping technique was used to determine the composition of polymer blend gradients. Composition gradients were made from poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid) (PDLLA) in the form of thin films (6 cm × 2 cm) deposited on IR reflective substrates. Three composition gradient films were prepared and characterized. The results demonstrate the reproducibility and feasibility of a new, high-throughput approach for preparing and characterizing polymer composition gradients. The combination of composition gradient film technology and automated nondestructive FTIR microspectroscopy makes it possible to rapidly and quantitatively characterize polymer composition gradients for use in combinatorial materials science.     

等离子体处理偶联胶原提高聚乳酸材料的细胞相容性

本研究通过结合氨气等离子体处理以及胶原改性的方法来改善聚乳酸材料的细胞相容性。水接触角分析表明氨气等离子体处理可以改善聚乳酸材料的亲水性,促进细胞的粘附。光学显微镜以及扫描电镜的分析结果表明,氨气等离子体处理后通过胶原改性可以进一步促进细胞在聚乳酸材料表面的生长。并且,与涂覆胶原相比,偶联胶原可以更好地使胶原蛋白固定在聚乳酸材料表面,从而表现出更好的细胞相容性。     

磷脂胆碱仿生修饰聚乳酸及其生物学评价

通过自由基聚合反应将马来酸酐接枝到聚(D,L-乳酸)(PDLLA)侧链上,然后通过引入的活性反应基团马来酸酐与甘油磷脂胆碱反应,实现磷脂胆碱对聚乳酸的整体仿生修饰。采用红外光谱和核磁共振碳谱对磷脂胆碱修饰聚乳酸进行了表征。生物降解实验表明,该功能化聚乳酸具有明显抑制酸致降解作用。体外细胞形貌观察证实磷脂胆碱修饰的聚乳酸具有良好的细胞相容性。同时,蛋白吸附和血小板粘附实验表明,该聚合物具有良好的血液相容性。该改性聚乳酸可望用作组织工程支架及血液接触类植入体。     

Spatio-temporal release of NGF and GDNF from multi-layered nanofibrous bicomponent electrospun scaffolds

Scaffolds capable of providing dual neurotrophic factor (NTF) delivery with different release kinetics, spatial delivery of NTFs at different loci and topographical guidance are promising for enhanced peripheral nerve regeneration. In this study, we have designed and fabricated multi-layered aligned-fiber scaffolds through combining emulsion electrospinning, sequential electrospinning and high-speed electrospinning (HS-ES) to modulate the release behavior of glial cell line-derived growth factor(GDNF) and nerve growth factor (NGF). GDNF and NGF were incorporated into poly(lactic-co-glycolic acid) (PLGA) fibers and poly(D,L-lactic acid) (PDLLA) fibers, respectively. Aligned fibers were obtained in each layer of multi-layered scaffolds and relatively thick tri-layered and tetra-layered scaffolds with controlled layer thickness were obtained. Their morphology, structure, properties, and the in vitro release of growth factors were examined. Dual and spatio-temporal release of GDNF and NGF with different release kinetics from multi-layered scaffolds was successfully demonstrated. High separation efficiency by PDLLA fibrous barrier layer for spatial neurotrophic factor delivery from both tri-layered scaffolds and tetra-layered scaffolds was achieved.