真空中聚乙烯膜在纳秒脉冲电压下的沿面闪络特性

 在高功率离子束二极管中，当利用阳极膜沿面闪络产生的等离子体作为离子束引出源时，其特性对产生离子束的大小和品质有着很大的影响，因此要深入研究阳极膜的沿面闪络特性。主要介绍了所研制的一套适用于沿面闪络特性研究的实验装置和测量诊断系统。对离子束二极管中使用的三种厚度聚乙烯薄膜在脉冲电压下的沿面闪络特性进行了实验研究，并对沿面闪络过程中薄膜表面的发光现象作了初步的诊断。     

Mass fabrication of size-controllable hydrogel microarrays by dip-pen nanolithography with viscosity-tunable ink

A method of mass fabricating poly(ethylene glycol) (PEG) hydrogel microarrays is demonstrated. Microarrays of poly(ethylene glycol) dimethacrylate (PEG-DMA) with photoinitiator were patterned by one-dimensional (1-D) parallel dip-pen nanolithography (DPN), and the microarrays were cross-linked to form PEG hydrogels by UV irradiation in N₂ air. As an ink material for DPN printing, solid and liquid phase of PEG-DMA were mixed and prepared to tune viscosity of the ink material by temperature. Thus, the diameter of the microarrays was able to be averagely controlled from 1.7 to 6.2 μm as temperature during printing was increased from 25 °C to 37 °C, respectively. The overall microarrays showed less than 16% coefficient of variation (C.V.). Moreover, small molecules, such as fluorescence dyes, were able to be embedded in the PEG hydrogel microarrays.     

表面等离子体激元的若干新应用

表面等离子体激元（SPPs）是在金属和介质界面传播的一种波动模式。本文首先叙述了SPPs的相关特性和激发方式,给出了一种基于表面等离子体激元共振（SPR）场增强原理产生相干极紫外辐射的方法,利用该方法可极大地提高光源的光子流量。分析了SPPs在生物及医疗领域的新应用,并对其在治疗癌症方面的技术原理进行了讨论。介绍了SPPs在新型光源和能源领域的发展和应用情况,综述了SPPs在太阳能电池、光子芯片以及集成电路方面的新工艺和新技术,包括最近几年来所取得的一些重要成果。最后讨论了SPPs在光存储方面的快速发展和巨大贡献。     

FTIR定量分析聚乙二醇/聚乙烯共混物组成

利用傅里叶转变红外光谱(FTIR)定量分析聚乙二醇/聚乙烯共混物组成,对特征谱带的选择,重叠峰的分离,数据的拟合处理作了详细讨论。采用1 378 cm-1处聚乙烯的复合峰与1 110 cm-1处聚乙二醇的复合峰强度比作为定量分析的基准,利用基于Beer-Lambert定律的理论拟合方程能较好的实现峰强度比与组分浓度的对应关系,可满足聚乙二醇/聚乙烯共混物组分的定量分析的要求。     

Uniformity analysis of dielectric barrier discharge (DBD) processed polyethylene terephthalate (PET) surface

A dielectric barrier discharge (DBD) plasma, operating in air at atmospheric pressure, has been used to induce changes in the surface properties of polyethylene terephthalate (PET) films. The effects that the key DBD operating parameters: discharge power, processing speed, processing duration, and electrode configurations, have on producing wettability changes in the PET surface region have been investigated. The approach taken involves the application of an Taguchi experimental design and robust analysis methodology. The various data sets obtained from these analyses have been used to studies the effect of the operating parameters on the surface uniformity and efficiency of the said treatment.In general, the results obtained indicate that DBD plasma processing is an effective method for the controlled surface modification of PET. Relatively short exposures to the atmospheric pressure discharge produces significant wettability changes at the polymer film surface, as indicted by pronounced reductions in the water contact angle measured. It was observed that the wettability of the resultant surface shows no significant differences in respect to orientation parallel (L-direction) or perpendicular (T-direction) to the electrode long axis. However, there was significant differences between the data obtained from these two orientations. Analysis of the role of each of the operating parameters concerned shows that they have a selective effectiveness with respect to resultant surface modification in terms of uniformity of modification and wettability. The number of treatment cycles and the electrode configuration used were found to have the most significant effects on the homogeneity of the resultant PET surface changes in L- and T-orientation, respectively. On the other hand, the applied power showed no significant role in this regard. The number of treatment cycles was found to be the dominant factor (at significance level of 0.05) in respect of water contact angle changes at the processed PET surface in both orientations. The driven metal electrodes (stainless steel or aluminium) were apparently superior to the driven dielectric electrode (ceramic or quartz) configurations. The grounded electrode in each case was a silicon rubber-covered aluminium plate (see later). The nature and scale of the surface changes that originate from the various processing conditions employed have been considered so as to determine the optimum treatment conditions in respect of processing outcomes, properties and any orientation dependence. Thus, it was revealed that higher processing speeds and longer processing durations are key for uniformity along the electrode axial orientation, while lower processing speeds and short exposure durations are key considerations, in the corresponding perpendicular orientation. In general, longer processing durations (low processing speeds and a high number of treatment cycles) and higher plasma powers induced greater changes in the surface wettability of the PET, as demonstrated by the observed water contact angles. This behaviour is taken to indicate that different combinations of DBD operating parameters and electrodes produce discharge conditions that can result in different plasma chemical processes in respect of uniformity, treatment efficiency and orientation dependence.     

Modification of polycarbonate surface properties by nano-, micro-, and hierarchical micro–nanostructuring

Polycarbonate surfaces were patterned with nanopillars, microbumps, or nanopillars superimposed on microbumps. Patterning was achieved by applying nanoporous anodized aluminum oxide (AAO) membranes, microstructured aluminum foil, or anodic alumina on microstructured aluminum as mold inserts in injection molding. The effect of the different-sized structures on properties of the polycarbonate surface was investigated in contact angle measurements with water and oleic acid. The water contact angle increased from 82° on the smooth surface to 139° on the hierarchical micro–nanostructure. The transmittance of the polycarbonate increased with nanopatterning, while the reflection properties of the polycarbonate surface decreased. Reflection was lowest for the nanostructure with 53 nm pillar diameter and 77 nm interpillar distance. Values ranged from 0.6 to 1.1% over the whole wavelength range of visible light, which was 4–5% units lower than the corresponding values for the smooth polycarbonate.     

Molecular dynamics simulation of gas diffusion behavior in polyethylene terephthalate/aluminium/polyethylene interface

Molecular dynamics (MD) simulations were performed to estimate the diffusion coefficients of O₂ and H₂O molecules in polyethylene terephthalate/aluminum/polyethylene interface at the temperature of 298 K. It came out that the diffusion coefficient of gasses in the interface is smaller than that of a single polymer, and the diffusion coefficients compare well with experimental data as well as previously published work. Furthermore, the diffusion coefficients of H₂O molecules in the interface are preferable to that of O₂ molecules. Interestingly, the largest diffusion coefficient was detected in the polyethylene terephthalate/aluminum(1 0 0)/polyethylene interface, while the smallest value of the diffusion coefficients was found in the polyethylene terephthalate/aluminum(1 1 1)/polyethylene interface. Calculation and analysis of the interaction between aluminum and polymers indicated that the interaction of polymer/aluminum(1 1 0) has the most interface strength, and crystal density of the metal surface has a definite effect on the planar interface energy. What’s more, the figure of gas molecule concentration is further resulted that the interface make contribution to adsorption of gas molecules. Moreover, the diffusion is belonging to the Einstein diffusion in the multilayer materials, and this work provides some key clues to improve the performance of polymer materials.     

Swelling and mechanical properties of radiation crosslinked Au/PVA hydrogel nanocomposites

Hydrogel nanocomposites of polyvinyl alcohol (PVA) filled with gold nanoparticles (Au NPs) were synthesised using gamma irradiation technique. Structural, optical, and morphological characterisation was performed using powder XRD, UV-vis, FESEM, and TEM techniques. Inclusion of Au NPs at the time of crosslinking may have reduced the binding sites of PVA matrix, which resulted in high-swelling capacity of Au/PVA hydrogel nanocomposites. The increase in mechanical stability of the Au/PVA hydrogel nanocomposites has been observed and it may be due to increase in the crystallinity percentage with increased Au NPs in PVA matrix. These nanocomposites may fulfil the increasing demand for multifunctional hydrogel with enhanced swelling and mechanical properties.     

Improvement of organic solar cells by flexible substrate and ITO surface treatments

In this paper, surface treatments on polyethylene terephthalate with polymeric hard coating (PET-HC) substrates are described. The effect of the contact angle on the treatment is first investigated. It has been observed that detergent is quite effective in removing organic contamination on the flexible PET-HC substrates. Next, using a DC-reactive magnetron sputter, indium tin oxide (ITO) thin films of 90 nm are grown on a substrate treated by detergent. Then, various ITO surface treatments are made for improving the performance of the finally developed organic solar cells with structure Al/P3HT:PCBM/PEDOT:PSS/ITO/PET. It is found that the parameters of the ITO including resistivity, carrier concentration, transmittance, surface morphology, and work function depended on the surface treatments and significantly influence the solar cell performance. With the optimal conditions for detergent treatment on flexible PET substrates, the ITO film with a resistivity of 5.6 × 10⁻⁴ Ω cm and average optical transmittance of 84.1% in the visible region are obtained. The optimal ITO surface treated by detergent for 5 min and then by UV ozone for 20 min exhibits the best WF value of 5.22 eV. This improves about 8.30% in the WF compared with that of the untreated ITO film. In the case of optimal treatment with the organic photovoltaic device, meanwhile, 36.6% enhancement in short circuit current density (J_sc) and 92.7% enhancement in conversion efficiency (η) over the untreated solar cell are obtained.     

Competition between surface reaction and diffusion of gold deposited onto ZrTe3

Surface reaction and diffusion of gold, deposited onto the (0 0 1) ZrTe₃ van der Waals (vdW) surface, is studied by transmission electron and scanning tunneling microscopy. It is shown that both processes compete at temperatures as low as room temperature. In case of diffusion the deposited gold mostly disappears from the surface and intercalates into the vdW gaps of the substrate. Residual unreacted gold agglomerates are rather mobile and are often displaced by the scanning tip along the [1 0 0] direction of the substrate. In case of reaction, which usually takes place at somewhat higher substrate temperatures, grains of Zr₃Te₂, AuTe₂ and/or Au₂Te₃ are formed. Contrary to unreacted gold, the reaction products are not mobile.     

Oxidation degree dependent adsorption of ssDNA onto graphene-based surface

DNA/GO composite plays a significant role in the research field of biotechnology and nanotechnology, and attracts a great deal of interest. However, it is still unclear how the oxidation degree of the graphene-based surface affects the adsorption process of single-strand DNA(ss DNA). In this paper, based on the molecular dynamics simulations, we find that ss DNA molecule is absorbed on the GO surface in the most stable state with the oxidation degree around 15%. The microscopic mechanism is attributed to the van Der Walls and the electrostatic interactions between the ss DNA molecule and the graphene-based surface, which is accompanied with the π–π stacking and hydrogen bond formation. The number of π–π stacking between ss DNA and GO reaches the maximum value when the oxidation degree is around 15% among all the GO surfaces. Our simulation results also reveal the coexistence of stretched and curved configurations as well as the adsorption orientation of ss DNA on the GO surface. Furthermore, it is found that the absorbed ss DNA molecules are more likely to move on the graphene-based surface of low oxidation degree, especially on pristine graphene. Our work provides the physics picture of ss DNA's physisorption dynamics onto graphene-based surface and it is helpful in designing DNA/GO nanomaterials.     

Hydrodynamical model for bulk and surface plasmons in cylindrical wires

In this paper, we study the electrostatic surface and volume modes of a cylindrical wire using the hydrodynamical model of plasmon excitation, which allows an analytical study of dispersion effects. We solve the hydrodynamical equations for a cylindrical wire geometry, obtaining new analytical expressions for the bulk and surface modes. New dispersion relations are obtained for each type of mode and numerical solutions are given. We analyze in detail the characteristics of the solutions and their differences with previous treatments based on non-dispersive models. These differences become important for wires of small radii, particularly in the range of few nanometers.     

Direct observation of surface and internal phase-separated structure of the active layer buried in organic photovoltaic cells

A phase-separated structure of the active layer, of variable thickness, buried in organic thin film solar cells (OTSC) was directly observed by scanning force microscopy (SFM) with the aid of a surface and interface cutting analysis system (SAICAS). This deals with SFM observation to both the surface and the internal regions of the OTSCs, leading to discussion about the formation of the overlayer in the active layer.     

Surface potential decay of DC-corona-charged PET films on humid electrodes

Surface potential decay measurement is a widely used tool to test the electrical properties of insulation materials. The aim of the present paper is to evaluate the effect of a humid electrode on the surface potential decay process. The experiments are performed on 1-mm thick samples of PET films (50 mm × 50 mm) in ambient air (temperature: 25 °C–29 °C; relative humidity: 42%–48%). The samples are placed on a grounded humid electrode (aluminum plate covered by a humid textile: 52 mm × 52 mm), and are charged by exposing them for 10 s to the negative DC corona discharge generated by a high-voltage wire-type dual electrode.The results show that the humid electrode has a significant influence on the surface potential evolution during the first moments after corona charging. Bipolar charge injection is the main physical mechanism that explains this potential decay.     

Pressed waves: Surface-bulk electromagnetic eigenmodes of metal surface

We discovered that in the infrared in conditions of surface electromagnetic waves (SEW) excitiation on finite grating coupler a wave packet consisted of evanescent and bulk waves is generated. This wave packet is conventionally called pressed wave by us. The wave packet is demonstrated to satisfy Maxwell equations and boundary conditions on smooth part of a surface outside the grating coupler. Thus the wave packet is a new type of surface-bulk electro-magnetic eigenmodes of metal surface.     

Investigation of the surface properties of gold nanowire arrays

Gold nanowire arrays with diameters ranging from 45 to 200 nm were obtained via electrochemical deposition within the ion-track templates. The morphology of gold nanowires was imaged by scanning electron microscopy (SEM). The surface properties were investigated by surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS). The SPR peaks were observed as the gold nanowire arrays embedded in the templates and their intensity decreased after the sample exposed to the air for a certain time due to the formation of chemisorbed oxygen on nanowire surface. The positive binding energy shifts in Au core level was found when the gold nanowire arrays embodied in template and the initial- and finial-state effects were introduced to explain this phenomenon.     

Electronic modifications and surface reactivity of an ion bombarded graphite surface

The first steps of structural and electronic modifications of a graphite surface bombarded with argon, hydrogen and deuterium ions were investigated using high resolution electron energy loss spectroscopy (HREELS). The energy and the damping of the low energy plasmon mode of graphite (E//C mode) were studied with respect to the bombardment settings. We show that argon bombardment affects the energy of the plasmon mode, while no similar change is observed after hydrogen (deuterium) bombardments. This can be related to the variation of inter-planar distance between two graphene layers. Moreover, the damping of the plasmon mode can be correlated with the interstitial defect concentration. Concerning the reactivity of the bombarded surfaces, we demonstrate that deuterium bombardment produce a non-deuterated surface. This last is very reactive to a further atomic deuterium exposure, as it is shown by the formation of C-D bondings. The deuterated sites can be removed after thermal annealings between 473 and 783 K. The occurrence of a chemical erosion mechanism accompanying this deuteration is discussed.     

Propagation of surface plasmon polaritons in anisotropic MIM and IMI structures

Electromagnetic wave propagation through waveguide structures consisting of anisotropic dielectric layers, assisted by surface plasmon-polaritons (SPPs) is theoretically studied. Dispersion relations corresponding to both short range and long range coupled SPP modes in metal/insulator/metal (MIM) and insulator/metal/insulator (IMI) structures, taking into consideration the anisotropy of the insulator, are derived and numerically solved. The dispersion has a prominent dependence on the anisotropy of the dielectric environment. The dependence of propagation on the misalignments of the optic axes of the insulator has also been investigated.     

Modification of cycloolefin copolymer and poly(vinyl chloride) surfaces by superimposition of nano- and microstructures

Cycloolefin copolymer (COC) and poly(vinyl chloride) (PVC) surfaces were patterned with nanopillars or with microbumps on which nanopillars were superimposed. The area of patterned surfaces was several square centimeters. Patterning was achieved by applying nanoporous anodized aluminum oxide (AAO) membrane as a mask in injection molding or imprinting. Nanostructures superimposed on microstructures were achieved by patterning the AAO mask with microstructures before anodization. Micro- and nanometer-sized structures could then be transferred simultaneously to polymer surfaces. Structures were characterized by SEM, AFM, and contact profilometry. The effect of different-sized structures on properties of the polymer surface was studied by contact angle measurements. Relative to the smooth surface, the increase in water contact angle on a COC surface with nanostructures superimposed on microstructures was up to 50°.     

Chemical surface composition of the polyethylene implanted by Ag ions studied by phase imaging atomic force microscopy

High density polyethylene (HDPE) has been modified by Ag⁺ ion implantation with the energy of 60 keV. The total amount of implanted silver ions was 1, 5 and 12 × 10¹⁵ ions/cm². The surface topography was observed by atomic force microscopy (AFM), while the surface composition changes were detected using phase imaging AFM. Surface topography changes were studied in detail using 3D surface parameters analyses. The average roughness decreased for the implanted HDPE indicating the flattening of the surface. Phase AFM images indicated the homogenization of the polyethylene during ion implantation, while histogram analyses confirmed the change in surface composition.