共查询到20条相似文献,搜索用时 0 毫秒
1.
Laser irradiation of tungsten and gold nanoparticles in aqueous solutions of Th(NO3)4 was experimentally studied. Picosecond Nd:YAG lasers with a wavelength of 1.06 μm and a peak power from 1011 to 1013 W cm−2 were used. The composition of colloidal solutions before and after laser irradiation was analyzed using atomic absorption
and gamma spectrometry. It was found that laser irradiation initiates nuclear reactions involving thorium nuclei, occurring
via two different channels. Radioactive decay of thorium nuclei within its radioactive series is enhanced under laser irradiation
in D2O; one of the fission fragments is 137Cs. Possible mechanisms of the process are discussed. 相似文献
2.
3.
The recent experimental results on the acceleration of alpha decay under laser exposure of metallic nanoparticles in aqueous
solutions (D2O or H2O) of uranium salt UO2Cl2 are reviewed. It is demonstrated that the rate of the alpha decay of uranium branching depends on the laser wavelength and
laser peak power both under exposure of the solution of uranium salt in colloidal solutions of metallic nanoparticles and
under laser ablation of a bulk target in an aqueous solution. Tuning the laser wavelength to the plasmon resonance allows
observation of large deviations of the contents of radio-nuclides of 238U branching from their equilibrium values. The effect of laser exposure is characterized by high isotopic selectivity towards
the decay of different nuclides. Possible mechanisms of the laser-induced alpha decay of uranium isotopes and their potential
applications are discussed. 相似文献
4.
M. Samiul Islam Sarker Takahiro Nakamura Yuliati Herbani Shunichi Sato 《Applied Physics A: Materials Science & Processing》2013,110(1):145-152
Many late transition binary alloy nanoparticles (NPs) have been fabricated through a wide variety of techniques. Various steps are involved in the fabrication of such NPs. Here, we used a simple and green route to fabricate solid-solution Rh–Pd and Rh–Pt bimetallic alloy NPs through femtosecond laser irradiation in a solution without any chemicals like reducing agents. X-ray diffraction (XRD) peaks of NPs obtained in the solutions with different ratios of Rh–Pd and Rh–Pt ions monotonically varied from the position of pure Rh to those of Pd and to Pt which respectively indicated that these NPs were alloy. Composition of fabricated NPs was fully tuned over the entire range of Rh1?x –Pd x , and Rh1?x –Pt x with varying the mixing ratio of metal ions in the solution. Studies of Rh–Pd and Rh–Pt solid-solution system suggest that the alloy formation occurs through the nucleation of Rh and then followed by the diffusion of Rh, Pd and Rh, Pt to form a homogeneous alloy. The variety of average size of the alloy NPs for different compositions could be attributed to different reduction rate and surface energies of metal ions. Our result implies that femtosecond laser irradiation in aqueous solution is one of the potential methodologies to form multimetallic solid-solution alloy NPs with fully tunable composition. 相似文献
5.
6.
Composite Au/TiO2 nanoparticles were synthesized by laser ablation of gold plate in TiO2 sol. The nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction,
and atomic force microscopy. The peak of surface plasmon is at 550 nm with a red shift of 30 nm compared with that of Au nanoparticles
in water. Monolayers of composite Au/TiO2 nanoparticles were obtained by dip-coating technique. The XRD pattern of Au/TiO2 powders resembles a mixture of anatase TiO2 and gold. 相似文献
7.
Ultrafast temperature relaxation processes in Au film including two temperature relaxation and thermal diffusion relaxation with femtosecond laser pulse excitation were investigated numerically by Finite Element Method (FEM). With the temperature dependent thermal parameters, the full 2D temperature field evolution in picosecond and nanosecond domains were obtained. It is proposed that the heat transfer depth can be alternatively localized or enhanced by the distinct temperature relaxation mechanisms. Moreover, the effect of laser parameters and Au film thickness and surface reflectivity on the two temperature relaxation time were analysed. 相似文献
8.
Laser-induced accelerated alpha-decay of 232U nuclei under laser exposure of Au nanoparticles in aqueous solutions of uranium salt has been experimentally studied. It is demonstrated that the decrease in the alpha-activity depends strongly on the peak intensity of laser radiation in the liquid and reaches a maximum at 1012–1013Wcm?2. The decrease in the alpha-activity of the exposed solutions is accompanied by deviation of gamma-activities of daughter nuclides of 232U from their equilibrium values. Experimental data on the accelerated alpha-decay of 238U under similar experimental conditions are also presented. Possible mechanisms of laser effect on the alpha-activity are discussed in terms of the amplification of the electric field of laser wave on metallic nanoparticles. 相似文献
9.
Keisuke Kawabata Yasushi Nanai Seiji Kimura Tsuyoshi Okuno 《Applied Physics A: Materials Science & Processing》2012,107(1):213-220
Fabrication of ZnO nanoparticles by laser ablation in liquid medium is reported. The possibility of using a sintered ZnO target
for the ablation as well as a Zn plate is demonstrated. The appropriate aqueous solution of sodium dodecyl sulfate is found
to be 1 mM for ZnO growing. The shape of ZnO nanoparticles is sphere and its diameter is 30∼60 nm. Fourier transform infrared
spectra, Raman scattering spectra, and photoluminescence spectra reveal the optical properties of ZnO nanoparticles. Nanoparticles
obtained by using ZnO targets show a smaller defect density compared with those by using Zn targets. 相似文献
10.
Degradation of the antibiotics amoxicillin in aqueous solution using sulphate radicals under ultrasound irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with only oxone (2KHSO5·KHSO4·K2SO4), cobalt activated oxone (oxone/Co2+), oxone + ultrasonication (oxone/US) and cobalt activated oxone + ultrasonication (oxone/Co2+/US). The chemical oxygen demand (COD) removal efficiency were in the order of oxone < oxone/Co2+ < oxone/US < oxone/Co2+/US for the amoxicillin solution. The variables considered for the effect of degradation were the temperature, the power of ultrasound, the concentration of oxone, as well as catalyst and the initial amoxicillin concentration. More than 98% of COD removal was achieved within 60 min under optimum operational conditions. Comparative analysis revealed that the sulfate radicals had the high oxidation potential and the use of ultrasound irradiation reduced the energy barrier of the reaction and increased the COD removal efficiency of organic pollutants. The degradation of amoxicillin follows the first-order kinetics. 相似文献
11.
Gang Chang Yasuhiko Shimotsuma Masaaki Sakakura Toshirou Yuasa Hidekazu Homma Munetaka Oyama Kiyotaka Miura Jiarong Qiu Peter G. Kazansky Kazuyuki Hirao 《Applied Surface Science》2008,254(16):4992-4998
Metal nanowires with electric conductive properties can be useful for optical polarization control medium and electro-conductive nanomaterial. We report on metallic Cu nanowires with a length of 1.0 μm and a diameter of 85 nm which were successfully photo-converted from commercial scale-like Cu particles, dispersed in a methanol solution, by using femtosecond laser irradiation. The growth mechanism of Cu nanowires under laser irradiation was suggested to be a nucleation growth process. 相似文献
12.
H. G. Silva-Pereyra J. Arenas-Alatorre L. Rodriguez-Fernández A. Crespo-Sosa J. C. Cheang-Wong J. A. Reyes-Esqueda Alicia Oliver 《Journal of nanoparticle research》2010,12(5):1787-1795
Au nanoparticles (NPs) with a size in the 2–12 nm range have been grown in silica by 2 MeV Au-ion implantation and a subsequent
thermal annealing in air. The as-prepared Au NPs were irradiated with 10 MeV Si ions elongating some of them. From transmission
electron microscopy in Z-contrast mode, we observed a narrow size distribution of the minor axis of the deformed NPs, which
presents its higher frequency around 6–7 nm and have a saturation about 9 nm. This final result agrees well with the diameter
of the track formed by Si ions of 10 MeV in silica, supporting the thermal spike model, which would explain the deformation
of the NPs. In this model, the NP melts and creeps along the ion track. Our results show that the NP crystallization is in
the fcc structure. On the other hand, a 200 keV electron irradiation provoked roundness on the previously elongated nanoparticles.
This effect was observed in situ by high-resolution transmission electron microscopy, showing additionally that, during the
roundness process, the fcc structure, as well as its crystalline orientation, remain unchanged. Thus, this study shows how
Au NPs embedded in silica, within this size distribution, keep the fcc bulk structure under both ion and electron irradiations. 相似文献
13.
Takahiro Nakamura Kouichi Takasaki Akihiko Ito Shunichi Sato 《Applied Surface Science》2009,255(24):9630-9633
Platinum nano-particles were directly fabricated through molecular dissociation process induced by tightly focused femtosecond laser pluses in hydrogen hexachloroplatinate (IV) hexahydrate (H2PtCl6·6H2O) aqueous solution. After irradiation, it was found that UV-visible absorption spectrum of the solution was changed and a large number of small platinum particles were synthesized. The variation of absorbance in the spectrum and the yield the particle synthesis depended on the concentration of the solution. The most effective condition for particle synthesis was 0.1 wt%. Black precipitates of platinum particles were observed in the bottom of the vessel after irradiation in some cases. The dispersibility of the particles was greatly improved by the addition of polyvinylpyrrolidone (PVP) as a dispersant, and no precipitates were found in the solution with 1.0 × 10−2 wt% PVP. Consequently, highly monodispersed platinum nano-particles with the mean size of about 3 nm were successfully fabricated. 相似文献
14.
HODA MAHDIYAN MOMEN 《Pramana》2016,87(2):26
Laser energy absorption results in significant heating of metallic nanoparticles and controlling the heating of nanoparticles is one of the essential stages of selective cell targeting. It is necessary to note that the laser action should be done by laser pulses with a wavelength that is strongly absorbed by the particles and it is important to select wavelengths that are not absorbed by the medium. Laser pulse duration must be chosen sufficiently short to minimize heat flow emitted from absorbing particles. Numerical calculations based on Mie theory were used to obtain the effect of laser wavelength and particle size on absorption factor for colloidal silver nanoparticles with radii between 5 and 50 nm. Calculations for acquiring temperatures under irradiations of pulsed KrF laser and pulsed Nd:YAG laser were performed. We showed that for low wavelengths of the laser, smaller nanoparticles have larger absorption efficiency compared to larger nanoparticles and in high wavelengths, temperature of all particles increased in the same way. 相似文献
15.
《Ultrasonics sonochemistry》2014,21(2):572-575
Degradation of azo dye Acid Orange 7 (AO7) by zero-valent aluminum (ZVAl) in combination with ultrasonic irradiation was investigated. The preliminary studies of optimal degradation methodology were conducted with sole ultrasonic, sole ZVAl/air system, ultrasonication + ZVAl/air system (US-ZVAl). In ZVAl/air system, the degradation of AO7 could almost not be observed within 30 min. The degradation of AO7 by ZVAl/air system was obviously enhanced under ultrasound irradiation, and the enhancement is mainly attributed to that the production of hydroxyl radicals in ultrasound-ZVAl process was much higher than that in sole ultrasonic or in sole ZVAl/air system. The variables considered for the effect of degradation were the power of ultrasound, the initial concentration of AO7, as well as the initial pH value and the dosage of zero-valent aluminum. The results showed that the decolorization rate increased with the increase of power density and the dosage of ZVAl, but decreased with the increase of initial pH value and initial concentration of AO7. More than 96% of AO7 removal was achieved within 30 min under optimum operational conditions (AO7: 20 mg/L, ZVAl: 2 g/L, pH: 2.5, ultrasound: 20 kHz, 300 W). This study demonstrates that ultrasound-ZVAl process can effectively decolorize the azo dye AO7 in wastewater. 相似文献
16.
Bleaching experiments in some laser dyes under high power UV irradiation from a nitrogen laser are described. Very high bleaching quantum efficiencies, of the order of 10-3 molecules bleached/photon absorbed, and a dependence of this efficiency on intensity have been found. The diffusion coefficients for the dyes in ethyl alcohol were also measured. 相似文献
17.
N. Mizuno Y. Takeshita J. Kobayashi K. Esashika T. Saiki 《Applied Physics A: Materials Science & Processing》2014,115(1):75-78
Here we describe an ultrasensitive antigen-antibody immunoassay using gold nanoparticles (AuNPs). Polarization microscopy is used to discriminate individual AuNP dimers from isolated single AuNPs by means of their Brownian motion in aqueous solution. The optical anisotropy and rotational diffusion time were measured to provide accurate and robust discrimination. Since the size of a naked antibody is comparable to that of an AuNP, the distance between two AuNPs (inter-dimer distance) is rather large, and therefore the optical anisotropy is seriously degraded. To address this problem, we digested the antibody with the protease pepsin to reduce the distance. Autocorrelation analysis allowed discrimination of the difference in optical anisotropy and rotational diffusion time. Setting an appropriate threshold for the measurement enabled sufficient accuracy in the discrimination. 相似文献
18.
The ubiquity of naturally occurring nanoparticles in the aquatic environment is now widely accepted, but a better understanding
of the conditions that promote their formation and persistence is needed. Using cadmium sulfide (CdS) as a model metal sulfide
species, thiolate-capped CdS nanoparticles were prepared in the laboratory to evaluate how aquatic conditions influence metal
sulfide nanoparticle growth and stability. This work examines CdS nanoparticle growth directly in aqueous solution at room
temperature by utilizing the size-dependent spectroscopic properties of semiconductors detectable by UV/vis. CdS nanoparticle
growth was governed by oriented attachment, a non-classical mechanism of crystallization in which small precursor nanoparticles
coalesce to form larger nanoparticle products. Nanoparticle growth was slowed with increasing capping agent and decreasing
ionic strength. In addition to examining the short-term (hours) growth of the nanoparticles, a long-term study was conducted
in which cysteine-capped CdS nanoparticles were monitored over 3 weeks in solutions of various ionic strengths. The long-term
study revealed an apparent shift from small nanoparticles to nanoparticles twice their original size, suggesting nanoparticle
growth may continue through oriented attachment over longer time scales. High-ionic strength solutions resulted in salt-induced
aggregation and eventual settling of nanoparticles within days, whereas low-ionic strength solutions were stable against settling
over the course of the experiment. Sulfide recovery from cysteine-capped CdS nanoparticles as acid volatile sulfide was nearly
quantitative after 2 weeks in fully oxygenated water, demonstrating significantly slowed oxidation of sulfide when complexed
to Cd(II) within CdS nanoparticles. The nanoparticles were also shown to be resistant to oxidation by Fe(III) (hydr)oxide.
This study illustrates that aggregation, rather than chemical oxidation, is likely more important to the lifetime of many
metal sulfide nanoparticles in the aquatic environment. 相似文献
19.
T. Fukami 《Il Nuovo Cimento D》1993,15(5):771-773
Summary Thermal measurements of the aqueous solution of the Rochelle salt were carried out with slow evaporation. It is found that
the phase transition occurs from the transparent-solution state of strong viscosity to a white solid state with exothermic
peak. 相似文献
20.
M. Moussaoui R. Saoudi A.V. Tishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(11):1792-1795
We synthesized zinc sulfide (ZnS) nanopowders with size ranging from 2 to 100 nm by a simple, low-cost, and mass production chemical method. The nanoparticles (NPs) were characterized by X-ray powder diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and UV-vis absorption spectroscopy. Our study concerns also the change in the refractive index of deionized water in presence of ZnS nanospheres. We present experimental results on effective index variation of water dispersed ZnS NPs at different wavelengths in visible spectrum. 相似文献