【作者】 刘爱萍；

【导师】 韩杰才；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2008， 博士

【摘要】 新型生物电极材料是目前材料科学和电化学领域研究开发的重点和热点之一。四面体非晶碳(ta-C)以其优异的机械性能、良好的生物相容性、高耐磨损能力、长期的稳定性和化学惰性、低成膜温度等特性成为制备生物电极的优选材料。但是ta-C薄膜的电阻率高、内应力大,限制了其作为半导体薄膜电极材料的使用。本文在ta-C沉积过程中掺入磷元素,通过控制工艺参数研究薄膜中磷含量的变化对薄膜的结构、机械性能、应力、光电性能、电化学性能、生物相容和耐腐蚀性能的影响,并研究其对生化物质的催化检测能力。采用过滤阴极真空电弧技术以磷烷(PH3)为掺杂气体,通过调整磷烷流量和基底负偏压制备了不同磷含量的掺磷四面体非晶碳(ta-C:P)薄膜。利用X射线光电子谱、拉曼光谱、红外吸收光谱、原子力显微镜研究了ta-C:P薄膜的成分和微观结构。XPS分析表明ta-C:P薄膜中磷主要以C-P和C=P形式与碳结合,二者随着磷含量的增加而增加。Raman结果显示磷的掺入增加了薄膜中sp2杂化含量和sp2团簇尺寸,随着磷含量的增加sp2杂化构型由链状向芳香环状转化,拟合的G峰峰位下移,半高宽减小,D峰和G峰强度比增大。红外吸收光谱分析表明,在1000~1800 cm-1之间的吸收带是CP伸缩振动与CC骨架振动共同作用的结果,2800~3100 cm-1的区域为CH的伸缩振动带。H的含量随着PH3流量的增加而增加,H能增加薄膜中sp3-C的含量并饱和=C键为=CHx基团,从而增加了荧光效率。原子力显微镜的观察证实ta-C:P薄膜表面出现不规则分布的纳米团簇,高能量等离子体的撞击也增大了薄膜的表面粗糙度,薄膜更加疏松多孔。利用纳米压痕和基底曲率法研究了ta-C:P薄膜的机械性能和内应力。磷的引入降低了碳的配位数,局部键长和键角的变形减小,导致杨氏模量和压应力降低。sp2含量的增加和sp3含量的减小使薄膜硬度降低。ta-C:P薄膜中磷含量从0增加到6.8 at.%时,薄膜的硬度从50 GPa下降至22 GPa,杨氏模量从400 GPa下降为230 GPa。通过对ta-C:P薄膜光电性能参数的测定,较低磷含量的ta-C:P薄膜E04带隙减小,表现出大量“n型”带尾态的电子结构,薄膜中磷含量达到6.8 at. %时导电性最好。较高磷含量的ta-C:P薄膜中H的饱和作用使E04带隙增加,定域态距离增大,薄膜导电能力降低。在293 K到573 K的温度范围内ta-C:P薄膜中的载流子表现出跳跃式传导和热激活传导两种导电机制。利用接触角实验和血液相容性实验研究ta-C:P薄膜在生物环境下的表面、界面行为和血液相容性。ta-C:P薄膜表面亲水性提高,表面能和极化分量与色散分量的比值增大,薄膜与水之间的界面张力减小。ta-C:P薄膜对红细胞几乎没有破坏作用,溶血率小于1 %。白蛋白和纤维蛋白原在ta-C:P薄膜表面的吸附能力降低,且白蛋白择优吸附于ta-C:P薄膜表面。ta-C:P薄膜表面吸附血小板的数量少于钛合金和ta-C薄膜,血小板团聚、变形情况减弱,抗凝血能力提高。借助动电位极化实验研究ta-C:P薄膜的化学稳定性和耐腐蚀性。ta-C:P薄膜在含有氯离子的生物体液中具有高的腐蚀电势和低的腐蚀电流密度。磷使ta-C薄膜的腐蚀电阻增大,孔隙率降低,对钛合金的保护效率提高。采用电化学工作站研究ta-C:P薄膜电极的电化学活性,ta-C:P薄膜在硫酸溶液中的电势窗口为~2 V,背景电流密度为~1μAcm-2。硫酸的预处理暴露了ta-C:P电极表面的CP活性点,加快了电极表面电荷的传输速度,扩宽了ta-C:P电极的电势窗口,改善了电极的可逆性。ta-C:P表面金纳米粒子的修饰进一步提高了ta-C:P电极的催化活性。金在ta-C:P表面的成核生长符合渐近成核和扩散控制的生长过程。金核的存在减小了能量势垒,利于金核的逐渐长大。通过控制金粒子在电极表面的沉积时间可有效的调节金纳米粒子的尺寸和分布,从而调节ta-C:P/Au电极的催化行为。通过循环伏安和差分脉冲伏安法研究ta-C:P薄膜作为生物电极的检测能力。ta-C:P可以对铜、铅、镉重金属离子共存体系进行检测,溶出曲线在约-0.9、-0.6和-0.2 V处先后出现镉、铅和铜的溶出峰且不互相干扰。金纳米粒子修饰的ta-C:P/Au电极对H2O2有很高的催化活性,电极表面H2O2氧化信号和H2O2浓度在0.2μM~1 mM范围内满足线性关系,信噪比为3时的检测限为0.08±0.01μM,比相同条件下ta-C:P电极的检测限低1个数量级。ta-C:P/Au电极对神经递质多巴胺和抗坏血酸有催化活性,二者的氧化峰信号明显分离0.2 V,可以在大量抗坏血酸存在的条件下有效的检测多巴胺的浓度。磷和金纳米粒子提高了ta-C薄膜的导电性,促进了带正电的多巴胺的氧化而限制了带负电的抗坏血酸的氧化。更多还原

【Abstract】 Great attention has been given to the development of new bioelectrode materials in the field of material and electrochemistry sciences. Tetrahedral amorphous carbon (ta-C) is suggested to be a preponderant material due to its excellent mechanical properties, good biocompatibility, high wear resistant, long-term stability, chemical inertness against aggressive media and ambient temperature growth on virtually any substrate. However, the high resistance and intrinsic compressive stress of ta-C film limit its practical application as a semiconductor electrode. In this paper, phosphorus impurity was incorporated into the carbon network during ta-C film preparation. The effect of phosphorus content in the film on the microstructure, mechanical properties, compressive stress, photoelectrical and electrochemical behaviors, haemocompatibility and corrosion resistance was investigated, and the catalytic and analytical abilities of the resulted film towards biochemical matters were estimated.Phosphorus incorporated tetrahedral amorphous carbon (ta-C:P) films were deposited on conductive silicon wafers by filtered cathodic vacuum arc system with PH3 gas as the dopant source at varying flow rate of PH3 and substrate bias. The chemical compositions and microstructures of ta-C:P films were examined by the analyses of X-ray photoemission spectroscopy (XPS), Raman spectroscopy, Fourier Transform infrared (FTIR) spectrometer and atomic force spectroscope. The XPS results show that phosphorus is bonded with carbon as C-P and C=P forms and the contents of these bonds increase with phosphorus level in ta-C:P films. Phosphorus incorporation results in an increased content of sp2-hybridized carbon atoms in the film and the clustering of sp2 groups, especially, an evolution of sp2 configurations from olefinic groups to rings. The downshift of G peak, the fall in the full width at half maximum of G peak and the increase of the intensity ratio of D and G peaks, ID/IG, are related to the increase of phosphorus fraction in ta-C:P films. The IR absorption band in the range of 1000-1800 cm-1 contains both CC skeleton modes and CP stretching species, and the spectrum at 2800-3100 cm-1 is attributed to C-H stretching modes. Hydrogen content increases with PH3 flow rate varying from 3 to 30 sccm, which modifies the carbon network by saturating isolated sp3 dangling bonds and =C bonds as =CHx groups. This contributes to the increase in photoluminescence efficiency of ta-C:P film. Some isolated and irregular nanoclusters induced by phosphorus impurities are dispersed on the film surfaces. High bombardment energy (-2000 V bias) increases the surface roughness of ta-C:P films, which makes the films more loose and porous.The mechanical properties and intrinsic stress of ta-C:P films were investigated by nanoindentation and substrate curvature measurements. Phosphorus incorporation results in a decreased coordination number of carbon and a released local distortion, which reduces the Young’s modulus and compressive stress of the films. The increase of sp2 content and the decrease of sp3 content lead to the loss of hardness of ta-C:P films. When phosphorus content of ta-C:P films increases from 0 to 6.8 at.%, the hardness of the films varies from 50 GPa to 22 GPa, and Young’s modulus from 400 GPa to 230 GPa.By measuring the photoelectricial performances of ta-C:P films, the results show that low-phosphorus ta-C:P films have smaller E04 and represent an electronic structure with a large number of‘n-type’band tail states. The film with 6.8 at.% phosphorus shows the best conductive ability. Progressive saturation of sp2 sites by excessive H induced by high flow rate of PH3 is responsible for the slight narrowing of E04 and the loss of conductivity for the high-phosphorus ta-C:P films. The carriers represent hopping conduction and thermally activated conduction mechanisms in the temperature range from 293 to 573 K.The surface and interface behaviors, and the haemocompatibility of ta-C:P films in the biological environment were evaluated using contact angle and blood compatibility measurements. ta-C:P films represent more hydrophilic surfaces, and the interfacial tensions between the films and water are more closer to the cell-medium interface tension (1-3 mJ/m2). Phosphorus incorporation also increases the surface energy and the ratio of the polar component to dispersive component. There is little destruction action of ta-C:P films to red blood cells and the haemolytic effect is lower than 1 %. The adsorption of albumin and fibrinogen on ta-C:P surfaces is weak and the adsorption ability of albumin is stronger than that of fibrinogen. The numbers of adhered platelets on ta-C:P films are significantly lower than those attached to Ti alloy and ta-C surfaces. Platelet adhesion tests show that ta-C:P films with less spreading area and circularity index represent lower adhesion and activation of platelets, and therefore lower thrombosis risk. The stability and corrosion resistance of ta-C:P films were studied via potentiodynamic polarization experiments. ta-C:P films in 0.89 wt. % NaCl solution have high corrosion potential and low corrosion current density. Phosphorus incorporation increases the polarization resistance, decreases the porosity of ta-C film and provides efficient protection to Ti alloy.The electrochemical activity of ta-C:P films was investigated by an electrochemical workstation. ta-C:P electrodes show a wide potential window around 2.0 V and low background current density of 1μAcm-2 in H2SO4 solution. Acid pre-treatments with different concentrations develop active CP sites and remove inactive PO sites, accelerate the electron exchange between ta-C:P electrode and aqueous solution, widen the potential window of ta-C:P electrodes, and improve the reversibility of the electrodes. The modification of gold nanoparticles to ta-C:P surfaces further favors the electrochemical reaction on ta-C:P electrodes. The progressive nucleation and diffusion-controlled growth of Au on ta-C:P surface are confirmed. The existed Au sites decrease the energy barrier and favor the growth of Au nuclei. The size and coverage of Au nanoparticles can be adjusted by controlling the deposition time, which dominates the electrochemical properties of ta-C:P/Au electrodes.The detection capability of ta-C:P films as bioelectrodes was evaluated by cyclic voltammetry and differential pulse voltammetry. ta-C:P electrodes can determine Cu2+, Pb2+ and Cd2+ simultaneously. The stripping peak positions of these three ions are about -0.9, -0.6 and -0.2 V, respectively, with no interference. ta-C:P/Au electrode reveals high electrocatalytic ability towards the electrooxidation of hydrogen peroxide because the three-dimensional Au nanoparticles accelerate the electron exchange between ta-C:P electrode and H2O2 in aqueous solution. The current of H2O2 at ta-C:P/Au electrode is linear within a wider concentration range from 0.2μM to 1 mM with a sensitivity of 20.0±0.2 nA/μM (n=6). The detection limit at signal-to-noise ratio of 3 to 1 is calculated to be 0.08±0.01μM. The value is one order lower than that obtained at ta-C:P electrode under the same conditions. The neurotransmitter of dopamine (DA) and ascorbic acid (AA) can be oxidized on ta-C:P/Au electrodes and the oxidation peaks of those are separated by 0.2 V. Therefore, ta-C:P/Au electrodes can provide effective detection to DA in the presence of large amount of AA. Phosphorus and Au nanoparticles increase the conductivity of ta-C, which attracts positive DA and repulses negative AA due to the electrostatic repulsion.更多还原