Fabrication of three-dimensional platinum microstructures with laser irradiation and electrochemical technique

Three-dimensional (3D) platinum microstructures were fabricated by successive procedures: aluminum anodizing, laser irradiation, nickel/platinum electroplating, and removal of the aluminum substrate, the oxide films, and the nickel metal layer. Aluminum plates and rods were anodized in an oxalic acid solution to form porous type oxide films. The anodized specimens were immersed in a nickel electroplating solution, and then irradiated with a pulsed Nd-yttrium aluminum garnet (YAG) laser beam to remove the anodic oxide film with a three-dimensional XYZθ stage. The specimens were cathodically polarized in the nickel and a platinum electroplating solution to form the metal micropattern at the laser-irradiated area. The electroplated specimens were immersed in NaOH solution to dissolve the aluminum substrate and the oxide films, and then immersed in HCl solution to dissolve the nickel deposits. A platinum grid-shaped microstructure, a microspring, and a cylindrical network microstructure with 50-100 μm line width were obtained successfully.     

Nanofabrication of hybrid nanomaterials: Macroscopically aligned nanoparticles pattern via directed self-assembly of block copolymers

Periodic hybrid nanostructured materials based on aligned inorganic nanoparticles within self-assembled copolymer matrixes aimed to harness the collective properties of generated functional nanomaterials. The nanoparticles are desirable for their useful magnetic, optical, catalytic, and electronic properties owed to the quantum confinement effect. For instance, gold, palladium and platinum as nanoparticles, have shown significant change in the physiochemical properties in comparison to their bulk materials. If the nanoparticles are aligned into well-defined macroscopic periodic nanostructures in diverse of morphologies, the unique collective properties are significantly enhanced. These unique properties can be transformed to improve the performance of storage media, multi-contact tracks solar panels and optoelectronic devices. Within this review, the nanofabrication tools will be presented as an alternative route to conventional top-down methods for the fabrication of periodic nanostructured hybrid materials. A simple approach is reviewed to fabricate periodic nanostructured hybrid systems based on the directed assembly of inorganic nanoparticles into well-defined periodic three-dimensional nanostructures provided by the self-assembling ability of block copolymers. The fabrications of varieties morphologies and the formation mechanism at different dimensions will be discussed as well as the characterization techniques. Finally, several applications of the proposed hybrid nanostructures are highlighted for the next generation of miniaturized devices.     

The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH)

Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica microparticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique.     

A review of recent developments in tin dioxide nanostructured materials for gas sensors

Gas sensors based on SnO₂ nanostructures have been extensively investigated in recent years. Many recent investigations have focused on synthesizing 0D, 1D, 2D and 3D SnO₂ nanostructures with high sensing capacity. This work presents a review of the recent developments in pure, doped and metal oxide functionalized SnO₂ nanostructured gas sensors, emphasizing the main SnO₂ preparation methods and the working principle of SnO₂ gas sensors. Most studies have shown that doping, coupled with a high surface area, can significantly improve SnO₂ sensing properties. Sensing response, response/recovery times, and operating temperature can be modulated by the synergistic effect between these two factors. In general, fine nanoparticles, mesoporous materials, hollow and 3D nanostructures combined with additives such as Pt, Pd, Cu, Ni, Ag and Al have shown the best improvements in gas sensing.     

脉冲激光法制备修饰纳米(ZnO-Eu_2O_3)/聚苯胺杂化薄膜材料

采用聚焦脉冲激光法(PLA-IT/SFL)制备修饰纳米(ZnO-Eu2O3)/聚苯胺有机溶胶及其杂化薄膜材料。TEM显示金属氧化物粒子粒径约为15nm且其在聚苯胺中有较高的稳定性。荧光光谱表明该杂化薄膜材料在紫外光照射下发出强烈的黄光。热分析表明该杂化薄膜比导电性聚苯胺(PAN-HCSA)薄膜具有更好的热稳定性。该杂化薄膜材料可望用于电致发光领域。     

Selective laser induced autocatalytic metallization of NiO and Cr2O3 doped alumina zirconia ceramic substrates

In this study slip cast alumina-zirconia materials were doped with nickel oxide and chromium oxide and sintered in air. Chromium oxide forms a solid solution while nickel oxide forms spinel with alumina. The sintered substrates were selectively irradiated with a green, ps pulsed Nd:YVO₄ laser. During subsequent autocatalytic plating, copper was deposited selectively on laser-irradiated surfaces. It is assumed that under the irradiation influence at very high temperatures metal or lower valence oxides are produced which initiate the growth of copper crystallites during the plating process. The process offers the opportunity to manufacture 3D integrated circuit carriers with ceramic substrates, which offer superior strength, thermal stability and heat conductivity compared to polymers. Single dopant or co-dopant contents of < 2 wt% are sufficient to induce a reliable laser activation at a broad range of laser parameters which enables the application of very narrow continuous conductor paths.     

Adsorption,catalysis, and reactions on the surfaces of metal nano-oxides

Nanomaterials based on metal oxides are considered. Special attention is given to adsorption, because this step determines physicochemical properties of nanostructured materials. The main processes are considered that occur on the surface of metal nano-oxides in the course of adsorption and the nature of chemoresistance. A model is presented that explains the increasing sensitivity of semiconductor sensor materials with a decrease in the grain size. The potential of the use of metal and metal oxide nanoparticles in catalysis and photocatalysis is discussed. Examples are given for the selective synthesis of α-mercaptopyridine on the surface of TiO₂ with supported silver nanoparticles with a diameter of <1 nm. Possible problems that might appear when nanoparticles are used in large-scale manufactures are discussed. Promising examples of the use of magnesium and calcium oxide nanoparticles for the destruction of toxic substances, specifically 3,3-dimethyl-2-butylmethylphosphoxofluoride and dichloroethyl sulfide at room temperature are analyzed. The method of cryoformation is considered that makes it possible to create new nanomaterials for use in catalysis, in gas sensors, and for modifying pharmaceuticals to reach a higher biological activity.     

Fundamental studies of sonoelectrochemical nanomaterials preparation

The coupling of electrochemical processes and ultrasound has found a larger number of applications during the past years. Especially in the field of materials science and energy technology its potential for the production of nanomaterials, improved metals, alloys and composites is noteworthy. In this paper the focus is on fundamental studies applying the electrochemical quartz crystal microbalance technique in order to improve understanding of these sonoelectrochemical processes. Three examples from the work of the authors in the area are presented: A study of the modification of the electrodeposition of Cu from chloride-based electrolytes by ultrasound, the deposition of metal/ceria composites from electrolytes low in ceria content, and the deposition of metal nanoparticles for decoration of solid oxide fuel cell anode powders. In the first two examples the electrochemical quartz crystal microbalance technique is applied in situ, whereas in the latter example it was used to study the electrochemistry of the systems involved.     

Embedded metal nanoparticles as localized heat sources: An alternative processing approach for complex polymeric materials

Metal nanoparticles were utilized as heating elements within nanofibers to demonstrate an alternative approach to thermally process nanostructured polymeric materials. In the photothermal process, resonant light excites the surface plasmon of the nanoparticle and the absorbed energy is converted into heat due to electron-phonon collisions. This heating is efficient and strongly localized, generated from the nanometer-sized metal particles embedded within the polymer. Composite polyethylene oxide (PEO) nanofibers, containing differing concentrations and types of nanoparticles, were fabricated by electrospinning and irradiated by a low intensity laser tuned specifically to the metal nanoparticle surface plasmon absorbance; aggregation of fibers, loss of fibrous structure, and ultimately, complete melting were observed. The photothermal response to irradiation increased with nanoparticle concentration as long as particle aggregation was avoided. Pure PEO nanofibers, or those containing metal nanoparticles possessing a non-resonant surface plasmon, were also irradiated but no melting occurred, demonstrating the controllable specificity of this approach.     

State-of-the-art technology: Recent investigations on laser-mediated synthesis of nanocomposites for environmental remediation

In both developing and industrialized/developed countries, various hazardous/toxic environmental pollutants are entering water bodies from organic and inorganic compounds (heavy metals and specifically dyes). The global population is growing whereas the accessibility of clean, potable and safe drinking water is decreasing, leading to world deterioration in human health and limitation of agricultural and/or economic development. Treatment of water/wastewater (mainly industrial water) via catalytic reduction/degradation of environmental pollutants is extremely critical and is a major concern/issue for public health. Light and/or laser ablation induced photocatalytic processes have attracted much attention during recent years for water treatment due to their good (photo)catalytic efficiencies in the reduction/degradation of organic/inorganic pollutants. Pulsed laser ablation (PLA) is a rather novel catalyst fabrication approach for the generation of nanostructures with special morphologies (nanoparticles (NPs), nanocrystals, nanocomposites, nanowires, etc.) and different compositions (metals, alloys, oxides, core-shell, etc.). Laser ablation in liquid (LAL) is generally considered a quickly growing approach for the synthesis and modification of nanomaterials for practical applications in diverse fields. LAL-synthesized nanomaterials have been identified as attractive nanocatalysts or valuable photocatalysts in (photo)catalytic reduction/degradation reactions. In this review, the laser ablation/irradiation strategies based on LAL are systematically described and the applications of LAL synthesized metal/metal oxide nanocatalysts with highly controlled nanostructures in the degradation/reduction of organic/inorganic water pollutants are highlighted along with their degradation/reduction mechanisms.     

Next generation of aircraft coatings systems

The current generation of aircraft coatings had its basis in the polymer technologies of the 1970s and the use of chromate-based metal pretreatments and primers. There have been some incremental improvements in the epoxy and polyamide oligomers used in the primers as well as the isocyanates and flexible polyols used in topcoats, plus increases in the volume solids of the coatings to continue minimally meeting environmental requirements, but no truly new technologies have been developed and applied to aircraft coatings since that time. However, because of increasing economic and environmental pressures, this situation will soon change. Also, the U.S. Air Force is seeking a coating system that will have an ultimate lifetime of 30 years for maintenance cost control and fleet sustainability. The first change in the present coatings system will be in the pretreatments plus primers that currently constitute the metal protection system for the high strength Al alloys used for aircraft. For military aircraft, these alloys will continue to be Al 2024 T-3 and Al 7075-T6, heat-treated metals that have phase-separated regions rich in reactive metals such as Cu, Mg, and Zn. There are several new technologies now under consideration for such metal protection including conductive polymers as primers without Cr-based metal pretreatments, sol-gel based pretreatments and primers, plasma polymer metal pretreatments, and organo-modified aluminum oxide particles. Each of these technologies has shown some promise for Cr replacement, but each presently has a weakness that needs to be corrected for immediate usage. For the topcoat system, fluorinated polyols and improved use of UV-absorbers and light stabilizers will probably be the first changes implemented, with ceramer and other new crosslinking systems the most likely next polymer matrix candidates. The target for the entire coatings system is to have drastically improved wet-adhesion due to a covalently bonded system that has a gradient in composition that goes continuously from metal to metal oxide to mixed metal oxide/organic polymer to high-performance UV-stable organic polymer. The materials cost for such a system may be quite high, but the maintenance cost savings will much more than offset these costs. Presented at the 25th FATIPEC Congress, Sept. 19–22, 2000, in Turin, Italy. Department of Polymers & Coatings, Fargo, ND 58105.     

Green synthesis of copper-doped nickel oxide nanoparticles using okra plant extract for the evaluation of their cytotoxicity and photocatalytic properties

Considering the significant role of metal nanoparticles in the detection and removal of pollutants from the environment, metal oxides stand as inexpensive materials at the scale of nanometers that are capable of participating in photocatalytic and decontamination procedures. Meanwhile, nickel nanoparticles have been applied as a new approach for removing the existing pollution from the environment. In this paper, we have synthesized copper doping nickel oxide nanoparticles (Cu-doped NiO-NPs) by a sol-gel method that involved the application of okra plant extract and had investigated their photocatalytic properties and cytotoxicity effects. The obtained Cu-doped NiO-NPs have been characterized through FT-IR, UV–Vis, XRD, FESEM/EDAX/PSA, and VSM analyses in different concentrations (1, 3, and 5%) of copper at an optimum temperature of 400 °C. According to the XRD results, the size of nanoparticles under optimal conditions (at the temperature of 400 °C and % 3 Cu-doped) has been observed to be 10.66 nm while containing a face-centered cubic (fcc) structure. Furthermore, the obtained FESEM outcomes have been indicative of the good dispersion of these nanoparticles. Also, photocatalytic activity of Cu-doped NiO-NPs through the degradation of methylene blue (MB) pigment studied under UV-A light and had detected 78% of degradation throughout 105 min. To complete the characterization process, the cytotoxicity of nanoparticles in inhibiting the cancer CT26 cells has been determined using of MTT assay.     

Solution combustion synthesis of metal nanopowders: Nickel—Reaction pathways

Nanopowders of pure nickel were directly synthesized for the first time by conventional solution combustion synthesis (SCS) method. In this article, a specific reaction pathway is suggested to describe the metallic phase formation during SCS. It is proposed that the exothermic reaction between NH₃ and HNO₃ species formed during the decomposition of glycine and nickel nitrate acts as the source of energy required to achieve the self‐sustained reaction regime. A thermodynamic analysis of the combustion synthesis reaction indicates that increasing glycine concentration leads to establishing a hydrogen rich reducing environment in the combustion wave that in turn results in the formation of pure metals and metal alloys. TGA of reaction systems and XRD analysis of products in the quenched combustion wave show that the formation of oxide phases occurs in the reaction front, followed by gradual reduction of oxide to pure metallic phases in the postcombustion zone. A methodology for SCS of pure metals and metal alloys nanoparticles can be inferred from the results presented. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Corrosion protection of aluminum alloy substrate with nano-silica reinforced organic–inorganic hybrid coatings

Organic–inorganic hybrid (OIH) thin films derived from the sol–gel process have emerged as sustainable metal pretreatment alternatives to toxic heavy metal-based systems. In recent years, such OIH systems based on Si, Zr, and Ti have been successfully developed and commercialized for pretreatment of aluminum alloys, galvanized steel, cold-rolled steel, and many other metals and alloys, for improving adhesion and corrosion resistance performance. A variety of approaches are being used to further enhance performance of such OIH systems to match or surpass that obtained from chromate-based systems. In the present study, a novel bis-silane compound has been synthesized and used as a primary sol–gel precursor for OIH coatings. In order to further improve their mechanical and corrosion resistance performance, colloidal nanoparticles have been incorporated. The microstructure of the deposited films as a function of their composition and formation of Si–O–Si structural network has been studied by Confocal Raman spectroscopic technique. The chemical structure of the OIH films has been characterized by FTIR analysis. Electrochemical impedance spectroscopy, DC polarization measurements, and accelerated neutral salt-fog test (ASTM B117) have been used to evaluate corrosion resistance performance of coatings on industrial aluminum alloy AA 3003 H14. Nano-indentation tests of these OIH films have been performed to study the effect of colloidal nanoparticles on coating micro/nano structure and their mechanical properties. The study reveals that colloidal nanoparticles improve the corrosion resistance of OIH coatings by formation of a protective barrier to diffusion of corrosive species to the metal surface. The optimum content of colloidal nanoparticles that can provide best corrosion protection has been determined. Electrochemical study provides useful insight into the significance of interaction between the sol–gel hybrid and silica particles in the corrosion protection mechanism.     

Fabrication of crescent-shaped ceramic microparticles based on single emulsion microfluidics

Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology.     

相变关系到化工设备材料的合理设计与应用

金属与舍金经热处理与焊接等热加工,以及设备经受不同的操作温度,材料发生相变,析出金属间相及晶界沉淀或偏析,对材料强度、韧性以及耐蚀性等有很大影响.通过对不锈钢、碳钢、低舍金钢、Ni-P、镍、铝、铜、钛与锆等合金具体分析,说明相变对化工设备材料的设计、制作、维修与应用有重大意义.     

Li ion battery materials with core-shell nanostructures

Nanomaterials have some disadvantages in application as Li ion battery materials, such as low density, poor electronic conductivity and high risk of surface side reactions. In recent years, materials with core-shell nanostructures, which was initially a common concept in semiconductors, have been introduced to the field of Li ion batteries in order to overcome the disadvantages of nanomaterials, and increase their general performances in Li ion batteries. Many efforts have been made to exploit core-shell Li ion battery materials, including cathode materials, such as lithium transition metal oxides with varied core and shell compositions, and lithium transition metal phosphates with carbon shells; and anode materials, such as metals, alloys, Si and transition metal oxides with carbon shells. More recently, graphene has also been proposed as a shell material. All these core-shell nanostructured materials presented enhanced electrochemical capacity and cyclic stability. In this review, we summarize the preparation, electrochemical performances, and structural stability of core-shell nanostructured materials for lithium ion batteries, and we also discuss the problems and prospects of this kind of materials.     

Organometallic Derivatives of Polyphosphazenes as Precursors for Metallic Nanostructured Materials

Co-polyphosphazenes containing anchored organometallic fragments are useful precursors for nanostructured metallic materials. Pyrolysis in air at 800°C yields metallic nanoparticles of the type, M°/M _x O _y /M _z (P _x O _y )/P₄O₇, depending on the metal used; i.e., M° when the metal is a noble metal, metal oxide when the metal is Cr, W and Ru, metallic pyrophosphate when M = Mn and Fe. The organic spacer of the polyphosphazene influences strongly the morphology of the pyrolytic product. The mechanism of formation of the nanostructured materials involves carbonization of the organic matter, which produces holes where the nanoparticles are grown. Reaction of the phosphorus polymeric chain with O₂ yield phosphorus oxide units, which act as a P₄O₇ matrix to stabilize the nanoparticles and/or P _x O _y ⁻ⁿ for the formation of metallic pyrophosphates. The method appears to be a general and versatile new route to metallic nanostructured materials. Dedicated to Professor Harry Allcock for his pioneering and persevering work on Polyphosphazene and their projection in another field as materials and recently nanomaterials.     

Nanofabrication with Pulsed Lasers

An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.     

New Non Phyto‐ and Eco‐Toxic Alumina‐Stabilized Silver and Praseodymium Nanoparticles

In the present study, we examined how the active aluminum nano‐oxide in the gamma form used as a neutral carrier for the nanoparticles of various metals (as Ag, Pr) affected their toxic behavior. Our experiments have shown that exposure to metal nanoparticles can be reduced by binding the nanoparticles to alumina nanoparticles and the aluminum nano‐oxide is suitable to function as the nano‐stabilizer for the Ag and Pr nanoparticles. We have managed to manufacture new alumina‐stabilized silver and praseodymium nanoparticles using dry sol‐gel method that are not phyto‐ and eco‐toxic.