LBL与PBL双轨教学模式在Access数据库课程中的应用

针对目前数据库应用技术课程在教学中存在的问题,结合工作实际对数据库应用技术课程的教学模式,提出PBL和LBL双轨教学模式,指出采用该模式可以提高学生解决问题、团队协作、综合思考等能力。     

Flexible H2 sensor fabricated by layer-by-layer self-assembly of thin films of polypyrrole and modified in situ with Pt nanoparticles

A novel flexible H₂ gas sensor was fabricated by the layer-by-layer (LBL) self-assembly of a polypyrrole (PPy) thin film on a polyester (PET) substrate. A Pt-based complex was self-assembled in situ on the as-prepared PPy thin film, which was reduced to form a Pt-PPy thin film. Microstructural observations revealed that Pt nanoparticles formed on the surface of the PPy film. The sensitivity of the PPy thin film was improved by the Pt nanoparticles, providing catalytically active sites for H₂ gas molecules. The interfering gas NH₃ affected the limit of detection (LOD) of a targeted H₂ gas in a real-world binary gas mixture. A plausible H₂ gas sensing mechanism involves catalytic effects of Pt particles and the formation of charge carriers in the PPy thin film. The flexible H₂ gas sensor exhibited a strong sensitivity that was greater than that of sensors that were made of Pd-MWCNTs at room temperature.     

Self-assembly of polyelectrolytic multilayer thin films of polyelectrolytes on quartz crystal microbalance for detecting low humidity

Low-humidity sensors were made by layer-by-layer (LBL) self-assembly of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) or poly(styrenesulfonic acid) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) into multilayer thin films on a gold electrode of quartz crystal microbalance (QCM). The thin films were characterized by QCM and atomic force microscopy (AFM). The effects of maleic acid (MA) in PSSMA, the number of layers and the ionic strength on the low-humidity sensing properties (sensitivity) were compared with those of PSS. The sensitivity of the PSSMA/PAH multilayer thin film exceeded that of the PSS/PAH multilayer thin film when the multilayered thin films of polyelectrolytes were prepared from solutions without NaCl. The sensitivity of both PSSMA/PAH and PSS/PAH multilayered thin films was increased by increasing the number of layers and by adding salt to the deposition solution. The PSS/PAH multilayered thin film that was prepared from the solutions with NaCl had the highest sensitivity (1.923 −ΔHz/Δppm_v at 27.5 ppm_v) and a short response time. Spin-coating was also adopted to fabricate PSS-based low-humidity sensors for comparison.     

Cu2SnS3薄膜的制备及性能研究

采用LBL(layer-by-layer)法制备了Cu2SnS3薄膜.即首先采用电化学方法在SnO2衬底上制备SnS薄膜,然后又在其上用化学沉积法制备CuS薄膜,最后进行退火处理得到厚度约为960 nm的Cu2SnS3薄膜.探讨了薄膜的制备机理、生长速度、结构和光学特性.制备的薄膜为多晶(Cu2SnS3)72z(三斜或假单斜晶系)结构,其直接光学带隙约为1.05 eV.     

氧化铟纳米立方块的合成及其自组装膜

以乙酰丙酮铟为前驱体,在不同的有机溶剂中进行溶剂热反应,得到棱角规则清晰、尺寸可控的立方相氧化铟纳米立方块,通过X射线粉末衍射（XRD）、透射电子显微镜（TEM）等对产品进行详细表征,采用层层自组装技术,将氧化铟纳米立方块自组装戍厚度可控的薄膜,UV-vis吸收光谱强度的线性增长为多层膜组装提供了证据,且对氧化铟纳米立方块及其自组装薄膜的光致发光光谱进行了测试。     

Multilayer membranes via layer-by-layer deposition of PDDA and DNA with Au nanoparticles as tags for DNA biosensing

A novel Au nanoparticles (Au-NPs)-based protocol for DNA hybridization detection based on assembly of alternating DNA and poly(dimethyldiallylammonium chloride) (PDDA) multilayer films by layer-by-layer (LBL) electrostatic adsorption has been studied. Electrochemical impedance spectroscopy (EIS) and UV-vis absorbance measurements were used to study the film assembly. All the results indicate that the uniform multilayer can be obtained on the polypyrrole (PPy) coated electrode surface and the hybridization reaction can be amplified by the layer-by-layer progress. The hybridization was detected by the reductive signal of Au-NPs and nonspecific adsorption was greatly eliminated by an unrelated DNA sequence to the target DNA. Under optimum conditions, a significant sensitivity enhancement had been obtained, and the detection limit was down to 3.20 × 10⁻¹⁴ M when 6 layers assembled. The DNA biosensor has good stability and reproducibility.     

层层自组装可食性涂层在蓝莓常温保鲜中的应用

目的为了延长蓝莓常温保鲜期,优化层层自组装可食性涂层的构建工艺。方法以“绿宝石”蓝莓(Vaccinium rhododendraceae)为试验原料,以糖酸比为单因素的评价指标,考察不同浓度壳聚糖(CS)、羧甲基纤维素钠(CMC)、甘油以及晾干时间对层层自组装可食性涂层保鲜蓝莓的效果,并采用正交试验设计获得层层自组装可食性涂层对蓝莓采后常温保鲜效果最佳的参数。结果层层自组装可食性涂层最佳的构建工艺为CS浓度为6 mg/mL、CMC浓度为10 mg/mL、甘油浓度为0.06 mL/mL、晾干时间40 min。蓝莓常温保鲜期可以达到12 d,测得蓝莓失重率为(23.97±2.64)%,糖酸比为(20.39±0.26)%,明显优于对照组(失重率为(33.04±3.39)%,糖酸比为(25.63±0.29)%(p<0.05)。结论经层层自组装可食性涂层处理的蓝莓,在贮藏期内,失重率、糖酸比下降速率显著放缓,有利于蓝莓的常温保鲜。本研究为层层自组装可食性涂层技术在果蔬保鲜中的实践应用提供了理论依据。     

Optical properties and crystallinity of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by rf-PECVD

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared in a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system have been studied. The rf powers were fixed in the range of 5 W-80 W. The optical properties and crystallinity of the films were studied by X-ray diffraction (XRD), Micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM), and optical transmission and reflection spectroscopy. The XRD and Micro-Raman scattering spectra were used to investigate the evidence of crystallinity in order to determine the crystallite sizes and crystalline volume fraction in the films. The HRTEM image of the film was used to correlate with the crystallinity that was determined from XRD and Micro-Raman scattering spectra. Optical constants such as refractive index, optical energy gap, Tauc slope, Urbach energy and ionic constants were obtained from the optical transmission and reflectance spectra. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of rf power. Also, the ionic constants of the films showed an indication of the degree of crystallinity in the films. The variation of the optical energy gap with the rf power based on structure disorder and the quantum confinement effect is discussed.     

An α-K3PMo3W9O40 film loaded with silver nanoparticles: Fabrication, characterization and properties

A composite film consisting of the mixed-addenda Keggin-type polyoxometalate α-K₃PMo₃W₉O₄₀ (PMo₃W₉) and silver nanoparticles (AgNPs) was fabricated on quartz, silicon, and ITO by the layer-by-layer self-assembly method. The regular growth of the multilayer film was monitored by UV–vis spectroscopy, and the morphology was measured by atomic force microscopy (AFM). The multilayer film embedded by AgNPs exhibited the photo-luminescence ascribed to electronic transitions from excited states to d levels of the silver nanoparticles. The composite film also showed electrocatalytic activity towards reduction of NO₂⁻, H₂O₂, ClO₃⁻, BrO₃⁻, and IO₃⁻ attributed to tungsten-centered and molybdenum-centered redox processes of PMo₃W₉.