飞秒激光烧蚀Ag膜的研究

研究飞秒激光烧蚀Ag膜表面,采用扫描电镜(SEM)观测其表面烧蚀形貌,发现烧蚀点大致分为3个区域,烧蚀面积随着脉冲能量的增大而增大,脉冲数的增加而增大,但当脉冲数达到一定值后烧蚀面积变化不大.改变脉冲数在烧蚀点得到了周期为650和150nm的长短周期条纹结构.根据烧蚀区域面积与脉冲能量的关系算出单脉冲与多脉冲的烧蚀阈值...     

飞秒激光烧蚀制备纳米结构IT0薄膜

利用飞秒激光烧蚀ITO与ZnO双层薄膜的方法,制备具有大面积表面纳米结构的ITO薄膜.在激光频率lkHz、脉冲宽度130fs、波长775nm、能量20μJ时,在ITO薄膜表面,获得了大面积的周期为176nm左右的周期性平行条纹结构.通过改变激光能量,研究了大面积纳米结构与激光能量之间的关系,发现这种大面积纳米结构是在激...     

Au改性BaTiO_3纳米颗粒在模拟太阳光照射下的光催化降解性能

用聚丙烯酰胺凝胶法制备BaTiO_3纳米颗粒,然后用光还原法在其表面沉积Au颗粒,制备出Au/BaTiO_3复合光催化剂。使用X射线粉末衍射技术(XRD)、透射电子显微镜(TEM)、紫外-可见光漫反射光谱(UV-Vis DRS)和荧光光谱(PL)等手段对样品进行了表征。结果表明:Au修饰没有改变BaTiO_3的晶体结构;粒径分布在5~20 nm的Au纳米颗粒,附着在BaTiO_3颗粒表面(平均粒径约为55 nm);Au纳米颗粒的表面等离子体共振吸收效应(SPR)使Au/BaTiO_3对~560 nm处的可见光产生较强的吸收;与BaTiO_3单体相比,Au/BaTiO_3中光生电子和空穴的复合几率明显降低。同时,提出了Au纳米颗粒在BaTiO_3表面的形成机制。以偶氮染料亚甲基蓝(MB)作为目标降解物,在模拟太阳光的照射下研究了产物的光催化活性和光催化稳定性。结果表明:适量的Au修饰明显提高了BaTiO_3的光催化降解活性,且使Au/BaTiO_3具有良好的光催化稳定性。探讨了Au纳米颗粒改善BaTiO_3模拟太阳光光催化性能的机理。     

Au/Ag芯-壳复合结构纳米颗粒的制备和表征

利用二步液相还原法制备了 Au/Ag 芯 壳复合结构的纳米颗粒。用 TEM对反应液中金离子和银离子的摩尔比分别为1∶2和1∶1时所制备的 Au/Ag芯 壳复合结构的纳米颗粒的尺寸和形貌进行了表征。其紫外 可见吸收光谱具有 2 个可区分的吸收带,与纯金和纯银纳米颗粒的光学吸收特性对比后认为:随着反应液中银离子摩尔份数的增加,等离子体共振吸收峰始终位于 410nm附近的吸收带为银纳米颗粒的等离子体吸收带;另一个将随之产生蓝移的吸收带为Au/Ag芯 壳复合结构纳米颗粒的等离子体吸收带,蓝移是由于银壳厚度的增加而引起的。     

微波加热制备尺寸各向异性纳米金属钌颗粒

采用微波加热Polyol法以PVP作为稳定剂,首先快速合成了晶粒尺寸为2～6nm具有不同长宽比的各向异性的单分散金属钌胶体颗粒.以单分散胶体颗粒为晶种,获得不同团聚程度的纳米金属钌颗粒.高分辨电子显微镜(HRTEM)研究表明,树枝状纳米金属钌是由随机取向的金属钌单晶颗粒组成的.     

激光辐射法用于聚酰亚胺/纳米Ag复合膜的制备

在涂覆有PVP/AgNO3胶体的聚酰亚胺(PI)薄膜上,采用激光辐射法将Ag+还原成Ag纳米粒子并嵌入到PI表面,从而制备出聚酰亚胺/纳米Ag复合膜。通过XPS、AFM、SEM等表征手段研究了复合膜表面的化学成分、以及激光通量和PVP/AgNO3配比对纳米银粒子形貌的影响。结果表明,激光通量的提高可使聚酰亚胺/纳米Ag复合膜上的纳米Ag粒子产生一定程度的定向排列;调节PVP/AgNO3的配比,可大致控制Ag粒子尺寸在25～160nm间变化。     

金/银合金纳米颗粒的制备及光学吸收特性

以柠檬酸盐为还原剂,通过共还原氯金酸和硝酸银的混合溶液制备出Au／Ag合金纳米颗粒,用透射电子显微镜（TEM）对颗粒的形貌和尺寸进行了表征。300-800nm范围的吸收光谱研究发现,Au／Ag合金纳米颗粒具有单峰等离子体吸收特征,且随着反应液中氯化金和硝酸银的摩尔比的减少,吸收峰将产生蓝移。实验结果表明,Au-Ag合金纳米颗粒的光学吸收特性具有组分可裁剪性,使其在纳米尺度的光学领域具有潜在的应用价值。     

Co掺杂CeO2稀磁氧化物陶瓷和纳米颗粒的铁磁性能

分别采用固相烧结法及激光液相烧蚀(LAL)技术,成功制备出Co掺杂CeO_2稀磁氧化物陶瓷块体和纳米颗粒。XRD和SEM研究发现所制备的材料具有良好的结晶性和形貌。Co掺杂CeO_2稀磁氧化物陶瓷块体和纳米颗粒均为多晶立方结构,与纯立方相的CeO_2结构相同,说明Co掺杂未形成其他结构和杂相。磁性测量表明固相烧结法和激光烧蚀液相法制备的Co掺杂CeO_2样品均具有较高的室温铁磁性,且远高于文献中报道的结果。将陶瓷块材经激光烧蚀成纳米颗粒后,纳米颗粒的铁磁性与陶瓷块材保持一致。这说明激光烧蚀法制备的纳米材料可以很好地保持母材的特性,是一种很好的纳米颗粒制备方法。根据XRD和SEM研究结果,笔者认为Co掺杂CeO_2陶瓷块材及纳米颗粒的室温铁磁性是内禀性质;磁性产生的机理源于氧空位诱导的铁磁性耦合。     

原子层淀积Al_2O_3薄膜表面自组装Au纳米颗粒及其热稳定性

在原子层淀积的A12O3薄膜表面自组装生长Au纳米颗粒,研究了Au纳米颗粒的自组装过程和热稳定性,结果表明,原子层淀积的A12O3薄膜表面很容易吸附氨丙基三甲基硅烷(APTMS),有利于Au纳米颗粒的自组装,生长出的Au纳米颗粒尺寸为5-8 nm,密度约为4x1011cm-2,在300℃氮气中退火使Au纳米颗粒的尺寸增大,但是没有改变APTMS的吸附状态和Au的化学组成.当退火温度提高到450℃时,Au纳米颗粒发生明显的团聚,且分布变得极不均匀.     

玻璃微珠和ZrB2改性石英酚醛复合材料的耐烧蚀性能

在石英/酚醛防热复合材料中引入玻璃微珠和ZrB_2颗粒,旨在提高其耐冲刷、烧蚀性能。采用氧乙炔烧蚀试验测试所得石英/酚醛复合材料的耐烧蚀性能,对比分析了玻璃微珠和ZrB_2颗粒对低密度和全密度石英/酚醛材料烧蚀机理和烧蚀性能的影响。结果表明,在低密度石英酚醛复合材料中掺入适量的ZrB_2颗粒能使复合材料在烧蚀表面形成熔覆层,该熔覆层能有效保护碳化层及基体材料,降低线烧蚀率和质量烧蚀率。而表面熔覆层的形成与ZrO_2在硅系熔融物中产生的"钉锚效应"相关,同时也与B_2O_3降低硅系熔融物的表面能有关。在全密度石英酚醛复合材料中引入ZrB_2颗粒,可使其在烧蚀过程中形成多孔的ZrO_2层,有效地将碳化层和烧蚀环境隔离。然而,ZrO_2层没有熔融铺展,与碳化层结合力较弱,在烧蚀过程中容易剥落。     

Nano-scaled Pt/Ag/Ni/Au contacts on p-type GaN for low contact resistance and high reflectivity

We synthesized the vertical-structured LED (VLED) using nano-scaled Pt between p-type GaN and Ag-based reflector. The metallization scheme on p-type GaN for high reflectance and low was the nano-scaled Pt/Ag/Ni/Au. Nano-scaled Pt (5 A) on Ag/Ni/Au exhibited reasonably high reflectance of 86.2% at the wavelength of 460 nm due to high transmittance of light through nano-scaled Pt (5 A) onto Ag layer. Ohmic behavior of contact metal, Pt/Ag/Ni/Au, to p-type GaN was achieved using surface treatments of p-type GaN prior to the deposition of contact metals and the specific contact resistance was observed with decreasing Pt thickness of 5 A, resulting in 1.5 x 10(-4) ohms cm2. Forward voltages of Pt (5 A)/Ag/Ni contact to p-type GaN showed 4.19 V with the current injection of 350 mA. Output voltages with various thickness of Pt showed the highest value at the smallest thickness of Pt due to its high transmittance of light onto Ag, leading to high reflectance. Our results propose that nano-scaled Pt/Ag/Ni could act as a promising contact metal to p-type GaN for improving the performance of VLEDs.     

Magnesia supported Au and Ag catalysts for the preparation of few-layer graphene–metal nanocomposites: relationship between catalyst structure and the properties of graphene composites

Magnesia supported Au, Ag, and Au–Ag nanostructured catalysts were prepared, characterized, and used to synthesize few-layer graphene–metal nanoparticle (Gr–MeNP) composites. The catalysts have a mezoporous structure and a mixture of MgO and MgO·H₂O as support. The gold nanoparticles (AuNPs) are uniformly dispersed on the surface of the Au/MgO catalysts, and have a uniform round shape with a medium size of ~8 nm. On the other hand, the silver nanoparticles (AgNPs) present on the Ag/MgO catalyst have an irregular shape, larger diameters, and less uniform dispersion. The Au–Ag/MgO catalyst contains large Au–Ag bimetallic particles of ~20–30 nm surrounded by small (5 nm) AuNPs. Following the RF-CCVD process and the dissolution of the magnesia support, relative large, few-layer, wrinkled graphene sheets decorated with metal nanoparticles (MeNPs) are observed. Graphene–gold (Gr–Au) and graphene–silver (Gr–Ag) composites had 4–7 graphitic layers with a relatively large area and similar crystallinity for samples prepared in similar experimental conditions. Graphene–gold–silver composites (Gr–Au–Ag) presented graphitic rectangles with round, bent edges, higher crystallinity, and a higher number of layers (8–14). The MeNPs are encased in the graphitic layers of all the different samples. Their size, shape, and distribution depend on the nature of the catalyst. The AuNPs were uniformly distributed, had a size of about 15 nm, and a round shape similar to those from Au/MgO catalyst. In Gr–Ag, the AgNPs have a round shape, very different from that of the Ag/MgO catalyst, large size distribution and are not uniformly distributed on the surface. Agglomerations of AgNPs together with large areas of pristine few-layer graphene were observed. In Gr–Au–Ag composites, almost exclusively large bimetallic particles of about 25–30 nm, situated at the edge of graphene rectangles have been found.     

飞秒激光与金膜作用的脉冲累积效应

采用1kHz飞秒激光（脉宽148fs，中心波长775nm）对石英衬底的金膜的烧蚀过程进行了研究．单脉冲与多脉冲的烧蚀阈值可以通过烧蚀点的直径平方与所用的激光能流的关系曲线获得．通过累积能流和烧蚀脉冲数的关系，可以得到金膜的脉冲累积因子．采用飞秒激光加工材料的一些特点可以合理解释单脉冲阈值附近获得的一些实验现象．     

The Nanostructures Produced by Laser Ablation of Metals in Superfluid Helium

The coagulation of impurities in superfluid helium, in contrast to that in all other liquids where spherical colloid particles are usually produced, led to producing thin and long nanowires with regular internal structure. This is due to the presence in HeII of quasi one-dimensional quantized vortices serving as condensation nuclei and providing a catalyzing effect on the process of any impurities coagulation. The metal was introduced into superfluid helium by laser ablation of targets made of gold, copper, nickel, permalloy, indium, lead, tin and bismuth immersed in liquid HeII. For all of these metals, the formation of thin (about 8 nm in diameter), long high-quality nanowires was observed after laser ablation. The structure of nanowires as well as of micron-sized metallic spheres, appeared as products at high laser pulse energy, providing evidence that they were formed via molten state. The spheres are metastable, and under damage of their surface, thousands of nanoballs emerge from their interior. The hollow shells left after this event are similar to those found as the products of laser ablation in normal fluids. The metal ablation into HeII bulk from thin film was found much less effective then that from thick foils.     

Particle growth mechanisms in Ag-ZrO(2) and Au-ZrO(2) granular films obtained by pulsed laser deposition

Thin films consisting of Ag and Au nanoparticles embedded in amorphous ZrO(2) matrix were grown by pulsed laser deposition in a wide range of metal volume concentrations in the dielectric regime (0.08相似文献   

液相脉冲激光轰击石墨制备碳纳米材料研究进展

碳纳米材料具有特殊的力学、电学及物化性能,在微电子、航空航天、军用材料等领域具有广阔的应用前景,利用脉冲激光高效、可控制备新型碳纳米材料已成为研究热点。简要介绍了激光与碳材料的相互作用及纳米粒子的成形机理,详细阐述了液相脉冲激光制备纳米金刚石、碳纳米管、石墨烯等碳纳米材料的过程及其影响因素,并展望了激光轰击石墨制备碳纳米材料的主要研究方向。     

Formation of Amorphous Carbon Nanoparticles by the Laser Electrodispersion Method

Experimental results on the laser ablation of the highly oriented pyrolytic graphite by using light pulses of an Nd:YAG laser (pulse width 25 ns, pulse energy 220 mJ) are presented. Analysis of the surface profile of the carbon target shows that the target material melts in the course of the laser ablation. As a result of ablation, a coating consisting of carbon nanoparticles about 10 nm in size is formed on the substrate placed at a distance of 4 cm from the target. It is assumed that such particles are formed as a result of the electrodispersion of carbon droplets detached from the target surface and charged to an unstable state in the laser plasma plume. Raman spectra of the coatings indicate that the carbon nanoparticles being formed have an amorphous structure.     

Necklace-shaped Au-Ag nanoalloys: laser-assisted synthesis and nonlinear optical properties

Here in this paper, necklace-shaped Au-Ag nanoalloys (NAs) have been synthesized by a laser-based approach. A chain of Ag nanoparticles (NPs), which were joined together with Au junctions, was formed upon copper vapor laser (CVL) irradiation of a colloidal mixture of Ag and Au NPs; while the corresponding NPs were separately provided by laser ablation of gold and silver targets in deionized water by a 1064 nm Q-switched Nd:YAG laser. Dependence of the NAs development process on the CVL irradiation time in three distinct stages of as-mixed, nucleation and complete formation has been systematically studied by UV-vis optical absorption spectroscopy analysis as well as by transmission electron microscopy (TEM), which was exploited to visually confirm the NAs evolution through the process. Furthermore, the x-ray photoelectron spectroscopy (XPS) technique was accurately employed to determine the synthesized alloy content. On the other hand, using the open-and closed-aperture Z-scan technique, the nonlinear absorption (NLA) as well as nonlinear refraction (NLR) changes in Au-Ag NAs were investigated through their formation. The deduced results from the nonlinear optical properties of the colloidal NAs in the mentioned stages were interpreted considering the spectroscopic and microscopic observations. The total change of individual Au and Ag NPs saturable absorption (SA) into the reverse saturable absorption (RSA) behavior was concluded through the evolution into Au-Ag NAs.     

Reduced Aggregation and Cytotoxicity of Amyloid Peptides by Graphene Oxide/Gold Nanocomposites Prepared by Pulsed Laser Ablation in Water

A novel and convenient method to synthesize the nanocomposites combining graphene oxides (GO) with gold nanoparticles (AuNPs) is reported and their applications to modulate amyloid peptide aggregation are demonstrated. The nanocomposites produced by pulsed laser ablation (PLA) in water show good biocompatibility and solubility. The reduced aggregation of amyloid peptides by the nanocomposites is confirmed by Thioflavin T fluorescence and atomic force microscopy. The cell viability experiments reveals that the presence of the nanocomposites can significantly reduce the cytotoxicity of the amyloid peptides. Furthermore, the depolymerization of peptide fibrils and inhibition of their cellular cytotoxicity by GO/AuNPs is also observed. These observations suggest that the nanocomposites combining GO and AuNPs have a great potential for designing new therapeutic agents and are promising for future treatment of amyloid‐related diseases.     

Analysis and optimization of silver nanoparticles laser synthesis with emission spectroscopy of induced plasma

Emission spectroscopy of the laser induced plasma is used to characterize the laser synthesis of silver nanoparticles in water via attributing the thermodynamic parameters of the plasma plume to qualitative features of the synthesized nanoparticles. In this approach, effects of the pulse energy and frequency of a pulsedNd:YAGlaser on nanoparticles synthesis yield and size distribution is studied by an analysis on the behavior of electron temperature and total density of the plasma dominant species (neutral Ag atoms; AgI). Variation of these thermodynamic parameters obtained from the time-integrated emission spectroscopy of the induced plasma was found to be in a closed correlation with the mentioned characteristics of the synthesized nanoparticles. Assessment of the qualitative features of nanoparticles was performed by evaluating the particles concentration in liquid, optical absorption spectroscopy and transmission electron microscopy. Finally, the optimum operating conditions for the synthesis of silver nanoparticles in pure water is determined by summarizing the results of emission spectroscopy observations attributed to the mentioned characteristics of synthesized nanoparticles.