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1.
Gold catalysts have attracted attention for enabling sustainable chemical processes under ambient conditions. This reactivity is attributed to the small size of the catalysts (<5 nm); however, their size also creates difficulty when removing from product streams and often require rare-metal additives to enhance reaction rate kinetics, thereby limiting the environmental benefits of these catalysts. Comparatively, submicron gold catalysts are easier to separate but are much less reactive under ambient conditions. In this study, we synthesized submicron gas-stabilising gold nanocones (gs-AuNCs) that are acoustically responsive to afford greater reaction rates than other conventional gold catalysts. We explore the catalytic performance of acoustically responsive gs-AuNCs exposed to focussed ultrasound at 5.0 MPa peak negative pressure and 1.1 MHz center frequency. Cavitation nucleated from gs-AuNCs significantly increased the sonocatalytic degradation of water pollutants without the need for co-catalysts. The ability to amplify catalysis with ultrasound by tailoring the morphology of the catalyst to control cavitation opens new paths for future designs of sonocatalysts that may enable a sustainable chemical approach needed for a broad range of industrial processes. 相似文献
2.
Hassan M. BortehNicholas J. Ferrell Randall T. ButlerSusan V. Olesik Derek J. Hansford 《Applied Surface Science》2011,258(1):230-235
In this work, the use of patterned proteins and peptides for the deposition of gold nanoparticles on several substrates with different surface chemistries is presented. The patterned biomolecule on the surface acts as a catalyst to precipitate gold nanoparticles from a precursor solution of HAuCl4 onto the substrate. The peptide patterning on the surfaces was accomplished by physical adsorption or covalent attachment. It was shown that by using covalent attachment with a linker molecule, the influence of the surface properties from the different substrates on the biomolecule adsorption and subsequent nanoparticle deposition could be avoided. By adjusting the reaction conditions such as pH or HAuCl4 concentration, the sizes and morphologies of deposited gold nanoparticle agglomerates could be controlled. Two biomolecules were used for this experiment, 3XFLAG peptide and bovine serum albumin (BSA). A micro-transfer molding technique was used to pattern the peptides on the substrates, in which a pre-patterned poly(dimethylsiloxane) (PDMS) mold was used to deposit a lift-off pattern of polypropylmethacrylate (PPMA) on the various substrates. The proteins were either physically adsorbed or covalently attached to the substrates, and an aqueous HAuCl4 solution was applied on the substrates with the protein micropatterns, causing the precipitation of gold nanoparticles onto the patterns. SEM, AFM, and Electron Beam Induced Current (EBIC) were used for characterization. 相似文献
3.
Thin films of silicon nanoparticles (diameter 5-10 nm) were deposited on highly oriented pyrolytic graphite (HOPG) by low-pressure DC magnetron sputtering. The effect of different room-temperature oxidation techniques was investigated using XPS sputter-depth profiling. Both oxygen treatment during deposition (using an argon-oxygen mixture in the sputter gas) as well as post-deposition oxidation techniques (exposure to oxygen plasma beam, ambient air conditions) were studied. In all cases oxidation was found to involve the whole film down to the film/substrate interface, indicating a network of open pores. Depending on the type of oxidation between 15 and 25 at% of oxygen, mostly associated with low oxidation states of silicon, were detected in the interior of the film and attributed to oxidized surfaces of the individual silicon nanoparticles. The highest oxygen concentrations were found at the very film surface, reaching levels of 25-30% for films exposed to air or prepared by reactive magnetron sputtering. For the oxygen plasma-treated films even oxygen surface concentrations around 45% and fully oxidized silicon (i.e., SiO2) were achieved. At the Si/HOPG interface formation of silicon carbide was observed due to intermixing induced by Ar-ion beam used for sputter-depth profiling. 相似文献
4.
G. H. Wen R. K. Zheng K. K. Fung X. X. Zhang 《Journal of magnetism and magnetic materials》2004,270(3):1026-412
Co nanoparticle films were prepared by plasma–gas-condensation-type particle beam deposition system. High-resolution transmission electron microscopy images show that the Co nanoparticles have a very narrow size distribution with an average diameter of 20 nm, and each of the Co nanoparticles is covered with an 3 nm layer of CoO. Hysteresis loops of the films after field-cooling in a 5 T magnetic field are greatly shifted, which can be attributed to the exchange bias effect caused by the interfacial exchange coupling between the CoO shell and the Co core. The zero field cooled films show several prominent properties, such as a quite large coercive field, a small remanence and their abnormal dependences on temperature. All these observations can be attributed to the existence of an exchange bias effect within each single Co nanoparticle even without a field-cooling process. 相似文献
5.
It needs appropriately attractive forces to construct multilayer thin films by layer-by-layer (LBL) assembly technique. It is feasible to prepare multilayer thin films on glass slides with negatively charged gold nanoparticles and positively charged lysozyme through the electrostatic LBL assembly technique. The gold nanoparticles/lysozyme multilayer thin films are highly stable; immersion in 0.1 M HCl, NaOH, and surfactant sodium dodecyl sulfate aqueous solutions cannot destroy the films. The highly stable gold nanoparticles/lysozyme multilayer thin films have potential application in long-term antibacterial coating. 相似文献
6.
Nguyen Dang LuongJoonsuk Oh Youngkwan LeeJaehyun Huh Jong Jin ParkJong Min Kim Jae-Do Nam 《Applied Surface Science》2011,257(8):3233-3235
In this study, for the first time, electrically-conductive tetramethylbenzidine (TMB) nanofibers were synthesized and covered with gold nanoparticles via the in situ redox reaction of TMB and HAuCl4 in ethanol media. The gold nanoparticles were uniformly bound to the fiber surface through the coordination of the amine atoms in TMB molecules with gold nanoparticles. The conductivity of the composite fibrous membrane was found to be 2.1 × 10−3 S cm−1. The developed method described herein is simple and effective for the production of novel electrically-conductive TMB/Au nanofibers. We believed that the composite fibrous materials could be used in various fields such as optoelectronic or sensor applications. 相似文献
7.
We demonstrate that crystalline organic rubrene thin films can be obtained by a facile spin-coating method using gold (Au) nanoparticles (NPs). Dodecanethiol-functionalized Au NPs were dissolved with rubrene molecules in solvent and a thin film of Au/rubrene was prepared by a simple spin coating process. The results of confocal photoluminescence (PL) and absorption spectral mapping confirmed the local formation of orthorhombic crystalline structures of the Au/rubrene hybrid film, in contrast to the monoclinic structure of plain rubrene films. Further, the results of transmission electron microscopy (TEM) and X-ray diffraction analysis, as well as Raman spectroscopy measurements of the rubrene and Au/rubrene films suggested the formation of high crystalline Au/rubrene film. The molecular crystallization of the Au/rubrene hybrid film is attributed to the nucleation effect of the Au NPs. 相似文献
8.
Carbon films were grown on a Pt(1 1 1) single crystal by ethylene decomposition at elevated temperatures (1000-1300 K). Depending on the preparation conditions, different carbon structures formed on the metal surface such as flat and curved graphitic layers, carbon particles and carbon nanowires. Although these carbon films exhibited a high density of surface defects, gold interacted only weakly with the carbon surface. CO adsorption on the Au/carbon systems was very similar to that observed for various Au/oxide systems previously studied. This finding strongly indicates that CO adsorption on gold is essentially independent of the nature of support. 相似文献
9.
The specific antibody-antigen reaction was detected by taking advantage of the effect of surface enhanced infrared absorption (SEIRA). For the SEIRA active film, single Au nanoparticles (AuNP) deposited on the SiO2/Si wafer surface were used. After immobilizing specific antibodies onto the AuNP, these samples were then exposed to specific antigens (unspecific antigens, respectively); then the samples were investigated with infrared spectroscopy. In addition, the same kind of sample preparation was done using a 40 nm thick non-enhancing Au film, in order to compare the SEIRA transmission spectra to the infrared reflection absorption spectra (IRRAS) and therefore to determine the factor of the SEIRA enhancement. In both geometries, SEIRA transmission and IRRAS, the antibody-antigen coupling could clearly be detected; a comparison of the spectra showed, that the enhancement factor due to the Au nanoparticles is roughly 25. 相似文献
10.
The concentration of polyethylene glycol-300 was found to play a crucial role in the formation of nanoparticles in PbS-chemical bath deposition process. We report here an endeavor to set up a relation between the variation of lead sulfide (PbS) nanocrystalline thin film properties, grown by (CBD) process at room temperature on corning glass and Si(100) substrates, with amount fluctuations of polyethylene glycol-300 in the solution. The transmittance of the films, for a fixed reaction time, increased up to ∼ 80% with the increase of % polyethylene glycol-300 in the solution, indicating the formation of very thin films due to the decrease of reaction rate with the increase of the concentration of polyethylene glycol-300. The optical band gaps were found to strongly rely on the composition of the bath deposition and increase with the increase of the polyethylene glycol-300 amount in the solution. Particle sizes between 2.8 and 8.7 nm were obtained by varying the % of polyethylene glycol-300 from 0.2 to 1.5. The concentration of polyethylene glycol-300 not only affects the reaction rate but also the morphology of the obtained films. PbS nanoparticles were found to be oriented preferentially along the < 200> plane. The absorption shifts towards short wavelength indicating a blue-shifting as a consequence of quantum confinement. 相似文献
11.
V. Lavalley 《Surface science》2007,601(23):5424-5432
First and original results are reported regarding the surface evolution of two kinds of oxide film after covalent grafting and hybridization of hairpin oligonucleotide probes. These hairpin probes were monolabelled with a 1.4 nm gold nanoparticle. One kind of oxide film was rough Sb doped SnO2 oxide film and the other kind was smooth SiO2 film. Same process of covalent grafting, involving a silanization step, was performed on both oxide surfaces. Atomic force microscopy (AFM) was used to study the evolution of each oxide surface after different steps of the process: functionalization, probe grafting and hybridization. In the case of rough SnO2 films, a slight decrease of the roughness was observed after each step whereas in the case of smooth SiO2 films, a maximum of roughness was obtained after probe grafting. Step height measurements of grafted probes could be performed on SiO2 leading to an apparent thickness of around 3.7 ± 1.0 nm. After hybridization, on the granular surface of SnO2, by coupling AFM with SEM FEG analyses, dispersed and well-resolved groups of gold nanoparticles linked to DNA duplexes could be observed. Their density varied from 6.6 ± 0.3 × 1010 to 2.3 ± 0.3 × 1011 dots cm−2. On the contrary, on smooth SiO2 surface, the DNA duplexes behave like a dense carpet of globular structures with a density of 2.9 ± 0.5 × 1011 globular structures cm−2. 相似文献
12.
A combination Monte Carlo and equivalent-continuum simulation approach was used to investigate the structure-mechanical property
relationships of titania nanoparticle deposits. Films of titania composed of nanoparticle aggregates were simulated using
a Monte Carlo approach with diffusion-limited aggregation. Each aggregate in the simulation is fractal-like and random in
structure. In the film structure, it is assumed that bond strength is a function of distance with two limiting values for
the bond strengths: one representing the strong chemical bond between the particles at closest proximity in the aggregate
and the other representing the weak van der Waals bond between particles from different aggregates. The Young’s modulus of
the film is estimated using an equivalent-continuum modeling approach, and the influences of particle diameter (5–100 nm)
and aggregate size (3–400 particles per aggregate) on predicted Young’s modulus are investigated. The Young’s modulus is observed
to increase with a decrease in primary particle size and is independent of the size of the aggregates deposited. Decreasing
porosity resulted in an increase in Young’s modulus as expected from results reported previously in the literature. 相似文献
13.
采用直流磁控溅射的方法制备出Ir金属纳米粒子薄膜.利用扫描电子显微镜分析了纳米粒子的形态和分布以及不同工艺条件对粒子粒径及形貌的影响,表明纳米粒子的大小可通过调节溅射气体压强来控制.在25%孔度的W海绵基体内浸入6∶1∶2铝酸盐发射物质,然后在其表面沉积上厚度为200—500 nm的纳米粒子薄膜层,最后在H2气中1200℃烧结,即制成了新型纳米粒子薄膜阴极.利用阴极发射微观均匀性测试仪对纳米粒子薄膜阴极和传统覆膜阴极的热电子发射的均匀性进行了对比研究.采用飞行时间质谱仪测试了真空本底、纳米粒子薄膜阴极、传统覆膜阴极等各种阴极蒸发物的成分,研究了阴极蒸发速率与阴极温度的关系,比较了不同阴极蒸发速率的大小.研究了Ba-W阴极覆上纳米粒子薄膜后的发射特性.
关键词:
纳米粒子薄膜
热阴极
发射均匀性
蒸发 相似文献
14.
Zhen-guo An Jing-jie Zhang Shun-long Pan 《Journal of Physics and Chemistry of Solids》2009,70(7):1083-10223
Low-density (about 0.9 g/cm3) composite core-shell hollow microspheres with tunable magnetic properties were fabricated by Ni-Fe-P deposition on hollow glass microspheres (HGM) with modified electroless plating process. The effects of mole ratio of Fe2+/Ni2+, concentration of the reducer and pH value of the solution on the magnetic properties of the products were investigated. In conclusion, the increase in the mole ratio of Fe2+/Ni2+ and pH value of the solution could improve the soft magnetic properties of composite microspheres remarkably, while the increase in the concentration of NaH2PO2 had the opposite effect. The as-obtained metallic shells were amorphous and the crystallization got better with increased annealing temperature after plating. In addition, the saturation intensity of the composite microspheres was enhanced monotonically by increasing the annealing temperature. This work provided a facile and effective strategy to fabricate core-shell composite hollow microspheres with tailored magnetic properties. 相似文献
15.
Acoustic levitation supplies a containerless state to eliminate natural convection and heterogeneous crystal nucleation and thus provides a highly uniform and ultra clean condition in the confined levitating area. Herein, we attempt to make full use of these advantages to fabricate well dispersed metal nanoparticles. The gold nanoparticles, synthesized in an acoustically levitated droplet, exhibited a smaller size and improved catalytic performance in 4-nitrophenol reduction were synthesized in an acoustically levitated droplet. The sound field was simulated to understand the impact of acoustic levitation on gold nanoparticle growth with the aid of crystal growth theory. Chemical reducing reactions in the acoustic levitated space trend to occur in a better dispersed state because the sound field supplies continuous vibration energy. The bubble movement and the cavitation effect accelerate the nucleation, decrease the size, and the internal flow inside levitated droplet probably inhibit the particle fusion in the growth stage. These factors lead to a reduction in particle size compared with the normal wet chemical synthetic condition. The resultant higher surface area and more numerous active catalytic sites contribute to the improvement of the catalytic performance. 相似文献
16.
ITO/Au/ITO multilayer thin films on transparent polycarbonate with enhanced EMI shielding properties
《Current Applied Physics》2020,20(4):489-497
ITO/Au/ITO multilayer thin films were deposited onto polycarbonate substrate via magnetron sputtering technique without intentional heating. The deposition times of both ITO and Au layers were studied to optimize the overall transparency and conductivity. As-prepared thin films were characterized using X-ray diffraction analysis, secondary ion mass spectroscopy, scanning and transmission electron microscopy, atomic force microscopy and physical property measurement system. The optical measurement results revealed that the transmittance of the films were enhanced by increasing the gold deposition time up to 15 s. Beyond this point, further increasing the duration caused a decrease in optical transmittance. Upon optimization of the Au deposition time, the deposition duration of ITO layers was also studied to increase electromagnetic interference (EMI) shielding effectiveness (SE). Maximum EMI SE in this work was measured as 26.8 dB, yielding 99.8% power attenuation, which was verified by simulation results. 相似文献
17.
The effects of biaxial stress in ZnO:Ga thin films on different substrates, e.g., sapphire(0001), quartz, Si(001), and glass have been investigated by X-ray diffraction, atomic force microscopy, and electrical transport and ellipsometric measurements. A strong dependence of orientation, crystallite size, transport, and electronic properties upon the substrate-induced stress has been found. The structural properties indicate that a tensile stress exists in epitaxial ZnO:Ga films grown on sapphire, Si, and quartz, while a compressive stress appears in films grown on glass. The resistivity of the films decreased with increasing biaxial stress, which is inversely proportional to the product of the carrier concentration and Hall mobility. The refractive index n was found to decrease with increasing biaxial stress, while the optical band gap E0 increased with stress. These behaviors are attributed to lattice contraction and the increase in the carrier concentration that is induced by the stress. Our experimental data suggest that the mechanism of substrate-induced stress is important for understanding the properties of ZnO:Ga thin films and for the fabrication of devices which use these materials. 相似文献
18.
Characterization of BCN films synthesized by radiofrequency plasma enhanced chemical vapor deposition 总被引:1,自引:0,他引:1
Md. Abdul Mannan Masamitsu Nagano Norie Hirao 《Journal of Physics and Chemistry of Solids》2009,70(1):20-25
Boron carbonitride (BCN) films have been synthesized on Si(1 0 0) substrate by radio frequency plasma enhanced chemical vapor deposition using tris-(dimethylamino)borane (TDMAB) as a precursor. The deposition was performed at the different RF powers of 400-800 W, at the working pressure of 2×10−1 Torr. The formation of the sp2-bonded BCN phase was confirmed by Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy measurements showed that B atoms were bonded to C and N atoms to form the BCN atomic hybrid configurations with the chemical compositions of B52C12N36 (sample 1; prepared at the RF power of 400 W), B52C10N38 (sample 2; at 500 W) and B46C18N36 (sample 3; at 800 W), respectively. Near-edge X-ray absorption fine structure (NEXAFS) measurements indicated that B atoms were bonded not only to N atoms but also to C atoms to form various configurations of sp2-BCN atomic hybrids. The polarization dependence of NEXAFS suggested that the predominant hybrid configuration of sp2-BCN films oriented in the direction perpendicular to the Si substrate. 相似文献
19.
Takuya Kinoshita Satoshi Seino Yoshiteru Mizukoshi Takashi Nakagawa Takao A. Yamamoto 《Journal of magnetism and magnetic materials》2007
Magnetic composite nanoparticles of gold and iron-oxide synthesized with gamma-rays or ultrasonics were functionalized with thiol-modified oligonucleotides. The amount of oligonucleotides bound to the functionalized nanoparticle probes via hybridization was quantified with fluorescently-labeled target oligonucleotides. Our composite nanoparticles magnetically separated the specific target oligonucleotides without the non-specific adsorption. 相似文献
20.
J. Bartolomé L.M. García F. Bartolomé F. Luis F. Petroff C. Deranlot F. Wilhelm A. Rogalev 《Journal of magnetism and magnetic materials》2007
Magnetization and susceptibility measurements have been performed on Co granular (Al2O3/Co/Pt)25 multilayers. A cusp-like anomaly is present in the susceptibility, which together with magnetization measurements suggests that the samples behave as an amorphous Correlated-Super-Spin system. The presence of CoPt partial alloying is proven by the XANES spectra. The XMCD spectra show that the interfacial Pt atoms become magnetically polarized by hybridization of the Pt 5d and Co 3d electrons, and are ferromagnetically coupled to the Co particle moments. The Pt layer is effective in transmitting interparticle exchange coupling. 相似文献