Dynamic aspects of films prepared by a sequential deposition of species: perspectives for smart and responsive materials

The deposition of surface coatings using a step-by-step approach from mutually interacting species allows the fabrication of so called "multilayered films". These coatings are very versatile and easy to produce in environmentally friendly conditions, mostly from aqueous solution. They find more and more applications in many hot topic areas, such as in biomaterials and nanoelectronics but also in stimuli-responsive films. We aim to review the most recent developments in such stimuli-responsive coatings based on layer-by-layer (LBL) depositions in relationship to the properties of these coatings. The most investigated stimuli are based on changes in ionic strength, temperature, exposure to light, and mechanical forces. The possibility to induce a transition from linear to exponential growth in thickness and to change the charge compensation from "intrinsic" to "extrinsic" by controlling parameters such as temperature, pH, and ionic strength are the ways to confer their responsiveness to the films. Chemical post-modifications also allow to significantly modify the film properties.     

非平衡行星大气发射与透射的Line—by—Line计算模式

导出了非局域热力学平衡（ＮＬＴＥ）行星大气发射与透射的基本公式，假设转动能级是热力学平衡（ＬＴＥ）的，建立了一个精确的Ｌｉｎｅ－ｂｙ－Ｌｉｎｅ（ＬＢＬ）ＮＬＴＥ发射与透射的有效算法计算较高层行星大气红外活跃样品的辐射强度．用本算法计算了地球大气１２Ｃ１６Ｏ２４．３μｍ和１５μｍ带在白天、夜晚和ＮＬＴＥ、ＬＴＥ条件下的临边辐射强度，揭示了ＮＬＴＥ辐射强度对ＬＴＥ辐射强度有显著而重要的偏离．     

用生长/氢等离子体交替处理堆积层表面技术制备微晶硅薄膜

利用HW-MWECR CVD系统,用氢等离子体处理间隙生长堆积层表面技术,制备了一系列不同厚度的μc-Si:H薄膜.发现,当薄膜厚度在0.55μm以下时,样品具有较为典型的非晶硅特征,光电导衰退率很大;当薄膜厚度为0.60～0.70μm之间时,样品兼备非晶和微晶的特点,在这一厚度范围内,光电导随薄膜厚度变化非常敏感,光电导衰退率较小;当薄膜厚度为0.80μm以上时,薄膜表现为明显的微晶硅性质,其光电导衰退率很小,通过模拟光照53.5h,其光电导几乎不变化.     

肝素/壳聚糖微胶囊的制备及其抗凝血性能

采用层层自组装(LbL)技术制备了肝素/壳聚糖(HEP/CHI)5微胶囊,并研究了其抗凝血性能、胃肠道稳定性和毒副作用等。结果表明:该微胶囊具有球形结构;在p H 5.0、7.4中肝素能够缓慢可控地释放;在p H 5.0、7.4以及模拟胃液、肠液条件下具有稳定性;APTT法和全凝固实验验证了它在体外具有良好的抗凝血效果;并且对内皮细胞无细胞毒性。因此,该微胶囊有望作为口服剂型,用于临床肝素给药。     

LBL法制备Cu3SbS4薄膜

针对水溶液化学沉积法沉积过程复杂且难于控制的缺点,利用LBL(layer-by-layer)法,在玻璃基片上制备出了Cu3SbS4薄膜。即首先在玻璃基片上沉积Sb2S3薄膜,然后再在其上制备CuS薄膜,最后进行退火处理。探讨了薄膜的制备机理、生长速度、结构特性和光学特性。制备的薄膜为多晶Cu3SbS4(四方晶系)结构,厚度为344nm,直接光学带隙约为0.47eV。     

PBL和LBL教学模式中二表法的体验

在“电路理论”课程中,三相电路功率测量的二表法是其中的一个难点。本文以学生的角度介绍在PBL与LBL教学模式下,对该内容的学习体会及对难题案例解决的自主学习探索。通过案例问题及伴随的新问题的解决,进一步加深了对课堂知识的理解,结合课堂外知识的学习,提高了学生应用知识综合解决问题的能力。     

Covalently attached metalloporphyrins in LBL self-assembled redox polyelectrolyte thin films

A formylporphyrin has been covalently bound to Poly (Allylamine Hydrochloride) (PAH) and electrostatically self-assembled polyelectrolyte films, containing the attached metalloporphyrin, have been constructed. The UV-vis absorption band at 390 nm has been followed as core porphyrin marker. The reflection-absorption IR spectra of the gold films modified with layer-by-layer (LBL) polyelectrolytes were recorded after 6 and 12 layers. Characteristic infrared absorbance bands of porphyrin, PAH and PVS became more evident on increasing the number of bilayers. The absorption bands at 750, 1214 and 2960 cm⁻¹, attributed at ν(S-O), ν_s(SO₃⁻) and ν(NH₂⁺), respectively, showed a linear growth (R² > 0.99) with the number of adsorbed layers. A lower correlation coefficient was observed for the band at 1585 cm⁻¹ attributed to Fe-protoporphyrin. In order to evaluate the electron transfer (ET) rate, the ΔE_p of the [Fe(CN)₆]⁴⁻/[Fe(CN)₆]³⁻ couple in solution was measured after covering the electrode. A proportional increase of the ΔE_p with the number of layers is observed up to the 4th layer. After the second bilayer, the magnitude of the peak separation is highly related to the charge of the topmost layer. The method allowed controlling the film thickness via the number of deposited layers (LBL). The electrode described, resulted in a good catalyst for O₂ reduction and sulfite oxidation.     

Fabrication and biocompatibility of polyethyleneimine/heparin self-assembly coating on NiTi alloy

NiTi alloy has been used widely as biomaterials. But because of toxic effects possibly caused by excess Ni ions released during the corrosion process in the physiological environment, it is still a controversial material. Fabricating medicine-loaded coating, which is expected to decrease the release of Ni ions and improve the biocompatibility of the materials, is a potential way to solve the problem. In this paper, NiTi alloy is coated by polyethyleneimine/heparin films via layer-by-layer (LBL) self-assembly method. UV-Vis, FT-IR, atomic force microscopy (AFM) and contact angle measurements are used to characterize the microstructure of coatings and select the best fabrication conditions. Potentiodynamic polarization researches in sodium chloride and dynamic clotting time experiment are utilized to study its corrosion resistance capability and biocompatibility of coatings, respectively. The results indicate that PEI/heparin multilayer coating can improve the biocompatibility of NiTi alloy surface.     

动态LBL组装聚离子膜对乙醇/水体系的渗透汽化性能

采用动态层-层吸附成膜法(动态LBL),以聚醚砜超滤膜为基膜,以聚丙烯酸(PAA)、聚乙烯亚胺(PEI)为聚离子制备了聚离子复合膜.考察了动态成膜与静态吸附成膜的膜性能比较,研究了动态过滤时间、聚离子浓度、进料浓度、温度等因素对该复合膜渗透汽化性能的影响;并对复合膜表面和截面做了扫描电镜分析.在40℃时,该复合膜对乙醇/水体系的分离因子可达1300,渗透通量约150 g/(m2.h),体现了较好的渗透汽化分离性能.