共查询到20条相似文献,搜索用时 31 毫秒
1.
A. O. Dikovska M. T. Alexandrov G. B. Atanasova N. T. Tsankov P. K. Stefanov 《Applied Physics A: Materials Science & Processing》2013,113(1):83-88
In this work we report the results of investigation of silver (Ag) nanoparticles prepared on a silica substrate by laser ablation. Our attention was focused on the mean diameter, size distribution and optical absorption properties of nanoparticles prepared in vacuum by using different laser wavelengths. The fundamental wavelength and the second, third, and fourth harmonics of a nanosecond Nd:YAG laser were used for nanoparticles fabrication. The corresponding values of the laser fluence for each wavelength were: 0.6 J/cm2 at 266 nm, 0.8 J/cm2 at 355 nm, 2.8 J/cm2 at 532 nm, and 2 J/cm2 at 1064 nm. The Ag nanoparticles produced have mean diameters in the range from 2 nm to 12 nm as the nanoparticles’ size decreases with the decrease of the wavelength used. The presence of the Ag nanoparticles was also evidenced by the appearance of a strong optical absorption band in the measured UV-VIS spectra associated with surface plasmon resonance (SPR). A redshift and widening of the absorption peak were observed as the laser wavelength was increased. Some additional investigations were performed in order to clarify the structure of the Ag nanoparticles. 相似文献
2.
碳纳米粒子悬浮液具有良好的光限幅性质,是一种优良的宽波段光限幅材料。通过热传导方程和米氏散射理论建立了微气泡半径与入射光能量、碳纳米粒子悬浮液散射系数和透过率的理论模型。采用Matlab数值模拟了散射系数随微气泡尺寸因子的变化关系,碳纳米粒子悬浮液光限幅性能随入射光能量的变化规律。研究了气泡尺寸因子、入射激光能量以及波长对碳纳米粒子悬浮液光限幅特性的影响。研究发现当激光能量达到一定值时,微气泡的半径保持恒定,不再随入射激光能量的增加而增加。微气泡尺寸的增大对碳纳米粒子悬浮液的透过率有着显著的影响。同时,碳纳米粒子悬浮液对不同入射光波长和光能表现出不同的光限幅性能。研究结果为实验研究提供了理论指导。 相似文献
3.
N.V. Tarasenko A.V. Butsen E.A. Nevar N.A. Savastenko 《Applied Surface Science》2006,252(13):4439-4444
In this paper we report the formation of gold nanoparticles during laser ablation of gold target in water in the absence of any additives. The experiments were carried out by using the radiation of the pulsed Nd:YAG laser, operating at the second (532 nm, 10 ns, 10 Hz), or the fourth harmonic (266 nm) wavelengths. The properties of the nanoparticles were found to be susceptible to the additional 532 and 266 nm laser irradiation. It has been established that both the mean size of the nanoparticles and their stability could be varied by proper selection of the parameters of laser ablation and postirradiation such as laser fluence and wavelength combinations. 相似文献
4.
P. Šmejkal J. Pfleger K. Šišková B. Vlčková O. Dammer M. Šlouf 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1307-1309
The results of in-situ monitoring of a laser fragmentation process of a largely polydisperse and morphologically heterogeneous citrate-reduced Ag hydrosol containing a fraction of Ag nanowires are presented. The laser fragmentation was performed using several wavelengths of the incident laser pulses (1064, 532 and 355 nm). Surface plasmon extinction spectra monitoring the nanoparticle fragmentation process were acquired pulse by pulse and related to transmission electron microscopy (TEM) images and statistical TEM image analysis of Ag nanoparticles collected in selected stages of the fragmentation. It was found that, due to different interactions of the laser pulses of various wavelengths with a specific fraction of the Ag nanoparticles in the hydrosol, the course of the fragmentation process depends on the wavelength, leading to different size distributions of the nanoparticles in the resulting hydrosol. The laser pulses of 532 nm wavelength are the most effective for the fragmentation process of the citrate-reduced Ag hydrosol, yielding the narrowest size distribution and the smallest mean radius of the Ag nanoparticles. PACS 81.07.-b; 73.21.-b; 81.16.-c 相似文献
5.
6.
A.S. Nikolov N.N. NedyalkovR.G. Nikov P.A. AtanasovM.T. Alexandrov 《Applied Surface Science》2011,257(12):5278-5282
Pulsed laser ablation of Ag and Au targets, immersed in double-distilled water is used to synthesize metallic nanoparticles (NPs). The targets are irradiated for 20 min by laser pulses at different wavelengths—the fundamental and the second harmonic (SHG) (λ = 1064 and 532 nm, respectively) of a Nd:YAG laser system. The ablation process is performed at a repetition rate of 10 Hz and with pulse duration of 15 ns. Two boundary values of the laser fluence for each wavelength under the experimental conditions chosen were used—it varied from several J/cm2 to tens of J/cm2. Only as-prepared samples were measured not later than two hours after fabrication. The NPs shape and size distribution were evaluated from transmission electron microscopy (TEM) images. The suspensions obtained were investigated by optical transmission spectroscopy in the near UV and in the visible region in order to get information about these parameters. Spherical shape of the NPs at the low laser fluence and appearance of aggregation and building of nanowires at the SHG and high laser fluence was seen. Dependence of the mean particle size at the SHG on the laser fluence was established. Comments on the results obtained have been also presented. 相似文献
7.
Y.-F. Chau Y.-S. Sun D.P. Tsai T.-J. Yang 《Applied Physics A: Materials Science & Processing》2007,89(2):381-385
The deformation and plasmon effects of collective localized surface plasmons between incident light and bubble-pit AgOx-type super-RENS structure have been studied using finite-difference time-domain (FDTD) method. We find that the polarization,
wavelength of incident light, and particle sizes of Ag nanoparticles are sensitive to the plasma resonance. The Ag nanoparticles
inside the bubble-pit AgOx-type super-RENS structure give the additional outer boundaries to the motion of the Ag nanoparticles, and excite more evanescent
field which located in the far edge of the bubble from the optical axis of the incident beam. The optical properties between
active layer and incident light with polarization direction, different wavelengths, and varied particle sizes of Ag nanoparticles
exhibits nonlinear optical behavior in the near field. The far-field signals of different wavelength of incident light confirm
the relation between highly localized near-field distributions and enhanced resolution of far-field signals. The subwavelength
recording marks smaller than the diffraction limit were distinguishable since the Ag nanoparticles with high localized fields
transferred evanescent waves to detectable signals in the far field.
PACS 42.79.Vb; 71.15.Rn; 72.15.Rn; 73.22.-f; 73.22.Lp; 78.67.Bf; 73.20.Mf 相似文献
8.
Petr Šmejkal Jiří Pfleger Blanka Vlčková 《Applied Physics A: Materials Science & Processing》2008,93(4):973-976
Laser fragmentation of Ag nanoparticles in Ag hydrosol was studied by simultaneous measurements of the transmitted fluence
of the incident laser beam and the time evolution of the surface plasmon extinction (SPE) spectra. The experiments showed
that the laser fragmentation in a small volume of hydrosol proceeds during first 20 pulses and then reaches saturation. The
value of the transmitted fluence corresponding to saturation increases with incident pulse fluence, but the impact of the
first pulse applied to the hydrosols shows an optical limitation. Fluences above 303 mJ/cm2 cause the formation of less stable, aggregating nanoparticles, while fluences below 90 mJ/cm2 do not provide sufficient energy for efficient fragmentation. The interval of fluences between 90–303 mJ/cm2 is optimal for fragmentation, since stable hydrosols constituted by small, non-aggregated nanoparticles are formed. 相似文献
9.
THEORETICAL DEPENDENCE OF LONG WAVELENGTH PHOTOEMISSION UPON THE SIZE OF Ag NANOPARTICLES EMBEDDED IN BaO SEMICONDUCTOR THIN FILM 总被引:1,自引:0,他引:1 下载免费PDF全文
The dependence of long wavelength photoemission upon the size of Ag nanoparticles embedded in a BaO semiconductor is predicted and discussed theoretically. The calculated results show that the increase in the diameter of the Ag nanoparticle, in the range from 1.5 to 37.0nm, leads to the emergence of a roughly Gaussian form of the photoemission spectra and the peaks become markedly narrower. The results also show that the increase in the diameter of the Ag nanoparticle leads to the decrease of the long wavelength threshold. The incident light wavelength corresponding to the peak value of the photoemission gets bigger with the increase of the size of Ag nanoparticles, thus showing a redshift. 相似文献
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11.
不同波长脉冲激光液相制备Ag纳米颗粒在Raman光谱学中的应用 总被引:3,自引:2,他引:1
利用Nd:YAG(1064nm)和准分子(KrF,248nm)两种不同波长的脉冲激光器对处于去离子水中的Ag片进行激光烧蚀,得到了不同尺寸的Ag纳米颗粒,同时,这些Ag纳米颗粒与去离子水形成了Ag纳米胶体体系。由于制备这种Ag纳米胶体的是一种物理过程,所以具有较高的纯净性。通过透射电子显微镜(TEM)对两种不同激光器制备的Ag纳米胶体的观测发现,虽然这两种Ag纳米颗粒大小尺寸不同,但都具有较好的分散性和均匀性。同时,在Raman光谱学应用方面,由于这两种Ag纳米胶体中无任何氧化剂或还原剂等外来杂质的干扰,具有非常好的纯净性,可以作为非常好的表面增强拉曼散射的增强基底,并对这两种Ag纳米颗粒与探针对羟基苯甲酸(PHBA)的吸附行为做了简要的分析。 相似文献
12.
S. Barcikowski A. Hahn A.V. Kabashin B.N. Chichkov 《Applied Physics A: Materials Science & Processing》2007,87(1):47-55
Femtosecond laser ablation is used to generate nanoparticle aerosols and colloids from solid targets of various materials
(Ti, Ag, Au, Co, etc.) in air and water ambience. We determine the influence of different laser parameters (pulse energy,
pulse overlap) and properties of media (air, airbrush, water) on the rate of production and size distribution of the laser-generated
nanoparticles. It is shown that the pulse overlap and laser fluence are the parameters determining the nanoparticle size.
At optimum conditions the nanoparticle productivity can be increased by 150–300%. The generation of multimaterial nanoparticle
dispersions is demonstrated. Being free of toxic impurities, the laser-produced nanoparticles may be promising for biomedical
applications.
PACS 79.20.Ds; 81.16.Mk; 81.16.-c; 52.38.Ph; 06.60.Jn 相似文献
13.
Nonlinear optical limiting materials have attracted much research interest in recent years. Carbon nanoparticles suspended
in liquids show a strong nonlinear optical limiting function. It is important to investigate the nonlinear optical limiting
process of carbon nanoparticles for further improving their nonlinear optical limiting performance. In this study, carbon
nanoparticles were prepared by laser ablation of a carbon target in tetrahydrofuran (THF). Optical limiting properties of
the samples were studied with 532-nm laser light, which is in the most sensitive wavelength band for human eyes. The shape
of the laser pulse plays an important role for initializing the nonlinear optical limiting effect. Time-resolved analysis
of laser pulses discovered 3 fluence stages of optical limiting. Theoretical simulation indicates that the optical limiting
is initialized by a near-field optical enhancement effect. 相似文献
14.
E. D. Aluker N. L. Aluker G. M. Belokurov A. G. Krechetov B. G. Loboiko D. R. Nurmukhametov A. V. Tupitsyn V. P. Filin 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(1):63-65
A comparative study of the efficiency of the laser initiation of PETN by the first and second harmonics (1060 and 530 nm)
of a neodymium-doped phosphate glass laser was performed. A significant difference in the efficiency of PETN initiation by
the different harmonics was revealed: as the initial temperature of the sample increased from 373 to 450 K, the threshold
initiation fluence decreased from 3.0 to 0.5 J/cm2; at the same time, the second harmonic failed to initiate PETN even at a fluence of 10 J/cm2. The absorption spectrum of PETN was found to have a weak absorption band with a maximum at λ
m
= 1020 nm. It was assumed that the high efficiency of initiation by the first harmonic is associated with light absorption
(photo-initiation) by this band 相似文献
15.
A.V. Simakin V.V. Voronov N.A. Kirichenko G.A. Shafeev 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1127-1132
A review of results on nanoparticles formation is presented under laser ablation of Ag, Au, and Ti solids targets in liquid environments (H2O, C2H5OH, C2H4Cl2, etc.). X-ray diffractometry (XRD), UV-Vis optical transmission spectrometry, and high-resolution transmission electron microscopy (HRTEM) characterise the nanoparticles. The morphology of nanoparticles is studied as a function of both laser fluence and nature of the liquid. The evidence of an intermediate phase of Au-Ag alloy is presented under exposure of a mixture of individual nanoparticles to laser radiation. Self-influence of the beam of a femtosecond laser is discussed under the ablation of the Ag target in liquids under Ti:sapphire laser. The factors are discussed that determine the distribution function of particle size under laser ablation. The influence of laser parameters as well as the nature on the liquid on the properties of nanoparticles is elucidated. PACS 42.62.-b; 61.46.+w; 78.66.-w 相似文献
16.
Ireneusz Piwoński Kinga K?dzio?aAneta Kisielewska Katarzyna SoliwodaMarian Wolszczak Katarzyna LisowskaNatalia Wrońska Aleksandra Felczak 《Applied Surface Science》2011,257(16):7076-7082
Controlled photodeposition of silver nanoparticles (AgNP) on titania coatings using two different sources of UV light is described. Titania (anatase) thin films were prepared by the sol-gel dip-coating method on silicon wafers. AgNPs were grown on the titania surface as a result of UV illumination of titania films immersed in aqueous solutions of silver nitrate. UV xenon lamp or excimer laser, both operating at the wavelength 351 ± 5 nm, was used as illumination sources. The AFM topography of AgNP/TiO2 nanocomposites revealed that silver nanoparticles could be synthesized by both sources of illumination, however the photocatalysis carried out by UV light from xenon lamp illumination leads to larger AgNP than those synthesized using the laser beam. It was found that the increasing concentration of silver ions in the initial solution increases the number of Ag nanoparticles on the titania surface, while longer time of irradiation results the growth of larger size nanoparticles. Antibacterial tests performed on TiO2 covered by Ag nanoparticles revealed that increasing density of nanoparticles enhances the inhibition of bacterial growth. It was also found that antibacterial activity drops by only 10-15% after 6 cycles compared to the initial use. 相似文献
17.
P.V. Kazakevich 《Applied Surface Science》2006,252(13):4373-4380
The review of results on nanoparticles formation is presented under laser ablation of Ag, Au, and Cu-containing solid targets in liquid environments (H2O, C2H5OH, C2H4Cl2, etc.). X-ray diffractometry (XRD), UV-vis optical transmission spectrometry, and high resolution transmission electron microscopy (HRTEM) characterize the nanoparticles. The morphology of nanoparticles is studied as the function of both laser fluence and nature of the liquid. The possibility to control the shape of nanoparticles by ablation of an Au target by an interference pattern of two laser beams is demonstrated. Formation of alloyed Au-Ag and Ag-Cu nanoparticles is reported under laser exposure of a mixture of individual nanoparticles. The effect of internal segregation of brass nanoparticles is discussed due to their small lateral dimensions. The factors are discussed that determine the distribution function of particles size under laser ablation. The influence of laser parameters as well as the nature on the liquid on the properties of nanoparticles is elucidated. 相似文献
18.
Yuji Utsunomiya Takashi Kajiwara Takashi Nishiyama Kunihito Nagayama Shiro Kubota 《Applied Physics A: Materials Science & Processing》2010,99(3):641-649
We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the
refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that
laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is
focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present
study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media
with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film
was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon
on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the
splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000
m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid
jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy,
and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led
to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal
behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history. 相似文献
19.
F. Vidal S. Laville C. Goueguel H. Loudyi K. Rifai M. Chaker M. Sabsabi 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(17-18):2528-2533
A simple model is worked out to investigate laser-induced fluorescence in media of arbitrary optical thicknesses at the excitation wavelength. Close-form expressions are obtained for laser fluence, absorbed energy density and emitted fluorescence signal as a function of optical thickness and incident laser fluence. It is shown that in optically thick media saturation curves are not proportional to density of the species excited by the laser, except at saturation, and that the saturation fluence increases with optical thickness. Experimental saturation curves of lead in laser-produced plasmas of brass are discussed in the light of this model. 相似文献
20.
Experimental results are presented on ablation of metals (W, Cu, brass and bronze) in a liquid environment (e.g., ethanol or water) by irradiation with either a pulsed copper vapor laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The target material is ejected into surrounding liquid in the form of nanoparticles. In a certain range of laser parameters (fluence and number of laser shots) the surface of the solid target is composed of micro-cones having a regular structure. The distance between neighboring micro-cones in the structure depends on the laser spot size. The structures allow the observation of up-conversion of the laser frequency due to generation of the second harmonics in the eye retina. 相似文献