VEGF‐Functionalized Polyelectrolyte Multilayers as Proangiogenic Prosthetic Coatings

Stimulation of transprosthetic vascularization represents an interesting strategy in implantology to allow rapid tissue integration and finally to avoid prosthetic rejection. To achieve this goal, we modified the surface of porous titanium implants with polyelectrolyte multilayer (PEM) films functionalized with vascular endothelial growth factor (VEGF). Among the two PEM systems investigated, poly(L‐lysine)/poly(L‐glutamic acid) (PLL/PGA) and poly(allylamine hydrochloride)/poly(sodium 4‐styrenesulfonate) (PAH/PSS), the (PAH/PSS)₄ architecture was selected to functionalize porous titanium, both for its high efficiency to adsorb VEGF and for its biocompatibility toward endothelial cells. In an original way, we unambiguously demonstrated that VEGF adsorbed on (PAH/PSS)₄ maintains its bioactivity in vitro and stimulates endothelial cells proliferation. This effect was correlated with specific activation of intracellular signaling pathways induced by successive phosphorylation of the endothelial VEGF receptor VEGFR2 and mitogen‐activated protein kinases (MAPK) ERK1/2. By clearly demonstrating the proangiogenic activity of the VEGF‐PEM coating in vitro, the present study constitutes a first step toward in vivo application.     

LEED and Optical Spectroscopy Study of an Organic Epitaxial Multilayer Film

Epitaxial multilayers of 2,9‐di(2‐hydroxyethyl)‐anthra[2,1,9‐def:6,5,10‐d′e′f′]diisoquinoline‐1,3,8,10‐tetrone (DMe‐PTCDI) were prepared on epitaxially grown phthalocyanine copper(II ) complex (CuPc) multilayers on Ag(110) by molecular beam epitaxy. This work presents LEED and photoluminescence investigations of a highly ordered organic heterosystem. Four different mono‐ and multilayer structures are presented. LEED images taken during preparation of the monolayer structures show a dose‐dependent structural phase transition. Photoluminescence measurements on the heterosystem show a temperature‐dependent transition in the fluorescence spectrum, resulting in a significant intensity increase. The results are compared to a previous study of DMe‐PTCDI on Ag(110).     

Perpendicular magnetic anisotropy of Co_(85)Cr_(50)/Pt multilayers

The CoCr/Pt bilayers and (CoCr/Pt)20 multilayers with Pt underlayer were prepared by DC magnetron sputtering. The effects of prepared condition on perpendicular magnetic anisotropy were investigated. The results show that the thickness of Pt under-layer has a great effect on the microstructure and perpendicular magnetic anisotropy of CoCr/Pt bilayers and (CoCr/Pt)20 multilayers. When the thickness of Pt underlayer increases, Pt(111) and CoCr(002) peaks of both CoCr/Pt bilayers and (CoCr/Pt)20 multilayers increase and the bilayer periodicity of the multilayers is improved. The effective magnetic anisotropy of (CoCr/Pt)20 multilayers with Pt underlayer was much larger than that of CoCr/Pt bilayers. The (CoCr/Pt)20 multilayers has a stronger perpendicular magnetic anisotropy than that of CoCr/Pt bilayers. This is ascribed to the interface magnetic anisotropy of the multilayers.     

Si/SiO2和SiNx/SiO2多层膜的室温光致发光

采用射频磁控溅射法,制备了纳米Si/SiO2和SiNx/SiO2多层膜,得到强的可见光致发光,利用傅里叶红外吸收(FTIR)谱和光致发光(PL)谱,对其发光特性进行了研究,在374 nm和712 nm左右观察到强发光峰.用量子限制-发光中心(QCLC)模型解释了其可能的发光机制,认为发光可能源自于SiOx界面处的缺陷发光中心.建立了发光的能隙态(EGS)模型,认为440 nm和485 nm的发光源于N-Si-O和Si-O-Si缺陷态能级.     

磁控溅射技术制备硅纳米晶多层膜及微观结构表征

在室温下,分别利用常规磁控溅射和反应磁控溅射技术交替沉积Si薄膜和Si1-xNx薄膜在单晶硅基体上制备了Si/Si1-xNx纳米多层膜。接下来,在高温下对Si/Si1-xNx多层膜进行退火诱发各层中形成硅纳米晶。研究了Si1-xNx层厚度和N2流量沉积对Si/Si1-xNx多层膜中Si量子点形成的影响。TEM检测结果表明,N2流量为2.5mL/min时沉积的多层膜退火后形成了尺寸为20～30nm的等轴Si3N4纳米晶;N2流量为5.0mL/min时沉积的多层膜退火后在Si层和Si1-xNx多层中均形成了硅纳米晶,而在7.5mL/min N2流量下沉积的Si/Si1-xNx多层膜退火后仅在Si层中形成了硅纳米晶。     

Properties of exchange biased Co/Co3O4 bilayer films

Co/Co₃O₄ bilayer films were fabricated by RF sputtering with Co and Co₃O₄ targets. Exchange bias effect in the bilayer films was observed at 80 K by vibrating sample magnetometer. The bias effect disappeared about 240 K slightly lower than the Néel point of CoO and much higher than the Néel temperature of Co₃O₄ about 40 K. To clarify the origin of the exchange bias effect, Auger and X-ray photoelectron spectroscopy were employed and CoO was found at a transition region from Co₃O₄ layer to Co layer due to oxygen diffusion during sputtering. The angular dependence of exchange bias field H_E was obtained to obey function of H_E(θ)=18.06 (kA/m)[−cos θ+0.22 cos 3θ+0.03 cos 5θ−0.01 cos 7θ+].     

复合离子束制备氮化物多层膜的抗冲蚀性能

为了在TC4钛合金上获得抗冲蚀性能优良的膜层,利用金属蒸发真空多弧(Metal evaporation vacuum arc,MEVVA)离子源和阴极真空磁过滤弧复合离子束沉积技术在TC4钛合金基材表面制备Cr/Cr-N、Ti/Ti-N、Cr-Ti/Cr-Ti-N、Ti-Al/Ti-Al-N 4种体系的多层膜。采用努普显微硬度计、划痕仪、微粒喷浆冲蚀试验机、场发射扫描电子显微镜(FESEM)、体式显微镜等仪器对不同体系膜层的力学性能及形貌进行测试表征,对比研究各膜层体系抗冲蚀性能的机理。结果表明:该技术制备的膜层致密、交替层结构明显;不同膜层体系的抗冲蚀性能差异较大,尤以二元金属及其氮化物交替复合多层膜具有较好的抗冲蚀性能,其中CrTi/Cr-Ti-N体系的膜层抗冲蚀性能相比基体提高10.1倍以上,其次为Ti-Al/Ti-Al-N、Ti/Ti-N、Cr/Cr-N,分别提高6.1倍、4.1倍和2.3倍。     

E‐field Control of the RKKY Interaction in FeCoB/Ru/FeCoB/PMN‐PT (011) Multiferroic Heterostructures

E‐field control of antiferromagnetic (AFM) orders is promising for the realization of fast, compact, and energy‐efficient AFM applications. However, as the AFM spins are strongly pinned, the E‐field control process is mainly based on the exchange bias regulation that usually confines at a low temperature. Here, a new magnetoelectric (ME) coupling mechanism for the modulation of AFM orders at room temperature is explored. Based on the FeCoB/Ru/FeCoB/(011) Pb(Mg_1/3Nb_2/3)O₃‐PbTiO₃ (PMN‐PT) synthetic antiferromagnetic (SAF) heterostructures, the external E‐field generates relative magnetization switching in the two ferromagnetic (FM) layers, leading the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction tuning. This voltage‐induced switching behavior can be repeated in a stable and reversible manner for various SAFs, which is a key challenge in the E‐field control of AFM coupling and is not resolved yet. The voltage‐induced RKKY interaction changes by analyzing the dynamic optical and acoustic modes is quantified, and with first‐principles calculations, it is found that the distortion of the Fermi surface by the lattice reconstruction is the key of the relative magnetization switching and RKKY interaction modulation. This voltage control of the RKKY interaction in ME heterostructures provides an easy way to achieve the next generation of AFM/FM spintronic applications.     

Study of copper electrodeposition mechanism from a strike alkaline bath prepared with 1-hydroxyethane-1,1-diphosphonic acid through cyclic voltammetry technique

Copper strike baths are extensively used in metal plating industry as they present the ability to plate adherent copper layers on less-noble metal substrates such as steel and zinc die castings. However, in the last few years, due to environmental controls and safety policies for operators, the plating industry has been interested in replacing the toxic cyanide copper strike baths with environmentally friendly baths. A broad bibliographic review showed that the published papers, referring to the new nontoxic copper strike baths, are patents, having little or no emphasis focused on electrodeposition mechanisms. Therefore, it was decided to study the copper electrodeposition mechanism from a strike alkaline bath prepared with one of the most nontoxic chelating agents cited in many patents which is the 1-hydroxyethane-1,1-diphosphonic acid, known as HEDP. This acid forms very stable water soluble complexes with Cu²⁺ ions, thus cupric sulfate was used for preparing the plating bath. The results obtained through a cyclic voltammetry technique showed that Cu²⁺ ion reduction to Cu from an HEDP electrodeposition bath occurs via a direct reduction reaction without a formation of Cu⁺ intermediates.