Synthesis and characterization of platinum nano sized particles by laser ablation in C<Subscript>2</Subscript>H<Subscript>6</Subscript>O<Subscript>2</Subscript> solution

Platinum nano sized particles (Pt NPs) are superior catalysts for many intentions, such as glucose sensors, cancer therapy, gas sensors, etc. Here, Pt NPs were produced by pulsed laser ablation in C₂H₆O₂ solution using Q-switched Nd:YAG laser, for the first time. Then, the influence of the laser fluence during synthesis of them was investigated; and they were characterized by UV–vis spectroscopy, TEM, FE-SEM, XRD, FT-IR, and Raman spectroscopy. The results showed that with increasing laser fluence, the mean particle size of the spherical NPs enhanced. Meanwhile, they had a polycrystalline cubic structure. Correspondingly, the plasmon peak position of generated NPs in the absorption spectra shifted from 257 to 266 nm, with a rise of laser fluence. The IR and Raman spectroscopy was used to achieve the information about the surface state of Pt NPs. We propose that the optimum adjusted laser fluence is an important factor to increase the ablation efficiency.     

Gold nanoparticle production by laser ablation in liquid nitrogen medium followed by cryogenic medium substitution with ethanol

The use of liquid nitrogen as a medium for laser ablation made it possible to obtain Au particles shaped as cores, cores/hollow shells, and hollow shells by radiation of a picosecond Nd:YAG laser. In this case, the substitution of the cryogenic liquid medium of the colloid by evaporating on the surface of a room-temperature liquid causes the shift and broadening of the plasmon resonance peak of Au nanoparticles, which results from the formation of fractal nanoparticle aggregates.     

Linear optical absorption and photoluminescence emission properties of gold nanoparticles prepared by laser ablation technique

Gold nanoparticles of average size varying between 1.1 and 3.3?nm are prepared by 1064?nm Nd:YAG laser ablation of solid gold target kept in ethylene glycol medium. The measured UV-Visible absorption spectra showed the presence of sharp absorption peaks in the UV and in the visible regions due to the interband transition and surface plasmon resonance (SPR) oscillations in Au nanoparticles, respectively. The increase in linewidth of the SPR peaks with the reduction in particle sizes is observed due to intrinsic size effects. The prepared samples exhibit photoluminescence (PL) emissions in the UV-Visible region peaked at ??354?nm due to the recombination of electrons with holes from sp conduction band to d-band of Au. The peak PL intensity in the sample prepared with 60 minutes of laser ablation time is enhanced by a factor of ??2.5 compared to that obtained in the sample prepared with a laser-ablation time duration of 15 minutes.     

Pulsed-laser generation of gold nanoparticles with on-line surface plasmon resonance detection

Size of nanoparticles is an important parameter for their applications. The real-time monitoring is required for reliable and reproducible production of nanoparticles with controllable size. We present results of our research on development of the system for the online nanoparticle characterization during their production by a laser. The laser ablation chamber which allows measurements of surface plasmon resonance spectra during the nanoparticle generation process has been designed and fabricated. The online characterization system was tested by producing and modification of gold nanoparticles. Nanoparticles were generated by nanosecond-laser (wavelength 1064 nm) ablation of gold target in deionized water, and optimal conditions for the highest nanoparticle productivity were estimated. The mean diameter of nanoparticles was determined using their absorption spectra measured in the real-time during the ablation experiments and from the TEM images analysis, and it varied from 20 to 45 nm. The mismatch between nanoparticle diameters, estimated using these two methods, is due to the polydispersity of the generated nanoparticles. The further experiments of laser-induced modification of colloidal gold nanoparticles were carried out using second harmonic (wavelength 532 nm) of nanosecond Nd:YAG laser and alteration in nanoparticle size were acquired by the online measurement system.     

Laser based fabrication of chitosan mediated silver nanoparticles

We report fabrication of silver nanoparticles (Ag NPs) by laser ablation technique in different concentrations of aqueous chitosan solution. The ablation process of silver plate was carried out by using a nanosecond Q-switched Nd:YAG pulsed laser and the characterization of Ag NPs was done by Transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. UV-visible plasmon absorption spectra revealed that the formation efficiency as well as the stability of nanoparticles was increased by addition of chitosan. On the other hand, the size decrement of nanoparticles was more remarkable in the higher chitosan concentration.     

Nucleation and growth of silver nanoshells through copper vapor laser irradiation

Silica core–silver shell, silver nanoshells (NSs), have been synthesized by an innovative laser-based approach. The NSs’ nucleation and growth progressed upon the pulse strikes of a copper vapor laser on a colloidal solution containing silver and silica nanoparticles (NPs). The silver NPs were separately synthesized by ablation of a silver target in deionized water by a 1064 nm Q-switched Nd:YAG laser. The dependence of silver NSs’ growth on the laser exposure time has been systematically studied by UV–VIS absorption spectroscopy technique. Transmission electron microscopy was exploited as well to visually confirm the NSs’ evolution through the process.     

长短脉冲间自同步的光探针

一、引言 在六路激光系统中,我们采用从主激光输出中分出一部分进行喇曼频率变换和脉冲压缩,获得了最短脉宽为25ps的630nm的光,用此喇曼光我们进行了等离子体的阴影、纹影、干涉和磁场的测量,得到了一系列有用的信息。我们将此喇曼光用BBO晶体倍频,进一     

Laser-assisted shape selective fragmentation of nanoparticles

Experimental results are presented on laser-assisted fragmentation of gold-containing nanoparticles suspended in liquids (either ethanol or water). Two kinds of nanoparticles are considered: (i) elongated Au nanorods synthesized by laser ablation of a gold target immersed in liquid phase; (ii) gold-covered NiCo nanorods with high aspect ratio (θ ∼ 10) synthesized by wet chemistry processes. The shape selectivity induced by laser fragmentation of these nanorods is gained via tuning the wavelength of laser radiation into different parts of the spectrum of their plasmon resonance corresponding to different aspect ratios θ. Fragmentation is performed using three laser wavelengths, involving a Cu vapour laser (510 and 578 nm) and a Nd:YAG (1064 nm). Nanoparticles are characterized by UV-vis spectrometry, Transmission Electron Microscopy (TEM). The effect of laser pulse duration (nanosecond against picosecond range) is also studied in the case of fragmentation with an IR laser radiation.     

Synthesis of composite gold/tin-oxide nanoparticles by nano-soldering

Composite Au–SnO₂ nanoparticles (NPs) are synthesized by nano-soldering of pure Au and SnO₂ NPs. The multi-step process involves synthesis of pure Au and SnO₂ NPs separately by nanosecond pulse laser ablation of pure gold and pure tin targets in deionized water and post-ablation laser heating of mixed solution of Au colloidal and SnO₂ colloidal to form nanocomposite. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM) were used to study the effect of laser irradiation time on morphology of the composite Au–SnO₂ NPs. The spherical particles of 4 nm mean size were obtained for 5 min of post-laser heating. Increased mean size and elongated particles were observed on further laser heating. UV–vis spectra of Au–SnO₂ nanocomposites show red shift in the plasmon resonance absorption peak and line shape broadening with respect to pure Au NPs. The negative binding energy shift of Au 4f_7/2 peak observed in X-ray Photoelectron Spectra (XPS) indicates charge transfer in the nano-soldered Au–SnO₂ between gold and tin oxide and formation of soldered nanocomposite.     

Structural,optical, and nonlinear optical properties of indium nanoparticles prepared by laser ablation

A study of indium nanoparticles prepared by two laser ablation techniques is reported. The suspensions of indium nanoparticles were prepared using the laser ablation of bulk indium in liquids. The prepared suspensions of indium nanoparticles were analyzed by the X-ray fluorescence spectroscopy and absorption spectroscopy. The position of the surface plasmon resonance of In-containing suspensions (350 nm) was consistent with the estimations taking into account the average size of In nanoparticles (43 nm) measured using the X-ray fluorescence spectroscopy. The nonlinear optical parameters of indium nanoparticles-containing liquids were studied by the z-scan technique using a picosecond Nd:YAG laser. We compare the laser ablation in liquids with the laser ablation of indium in vacuum at the tight and weak focusing conditions of a Ti:sapphire laser and analyze the 60 nm indium nanoparticles synthesized in the latter case. PACS 42.65.An; 42.65.Hw; 42.65.Jx; 61.46.Df; 78.67.Bf     

Generation of Ag nanospikes via laser ablation in liquid environment and their activity in SERS of organic molecules

The formation of dense arrays of nanospikes occurs under laser ablation of bulk silver immersed in liquids such as water or ethanol. The average height of spikes is 50 nm and their density on the target amounts to 10¹⁰ cm^-2. This effect is observed with sufficiently short laser pulses. In particular, either a 350 ps or a 90 ps Nd:YAG lasers are used operating in their fundamental harmonics. These nanospikes are characterized by UV–visible reflection spectrometry and atomic force microscopy. The oscillations of electrons within Ag nanospikes results in a permanent coloration of the surface and a modification of the optical reflection spectra of the metal. Nanospikes show a peak of plasmon resonance around 380 nm, which shifts to the visible range upon oxidation in air. The initial spectrum may be restored by reduction of the oxidized Ag surface through processing in an ammonia aqueous solution. Scanning the laser beam along the metal surface allows its nanostructuring over extended areas (∼1 cm²). The nanostructured Ag surface shows enhanced Raman scattering of acridine molecules at a concentration of 10^-5 M/l, whereas initial Ag target do not show any signal within the accuracy of measurements. PACS 68.65.k; 64.70.Dv; 79.20.Ds; 42.62.Cf     

Effect of shape and interstice on surface enhanced Raman scattering (SERS) of molecules adsorbed on gold nanoparticles in the near‐dipole and quadrupole regions

Surface enhanced Raman scattering (SERS) of adsorbed molecule on colloidal gold nanoparticles of different shapes, namely nanospheres (NSs), nanorods (NRs), and nanoprisms (NPs) as well as the three NPs arrays of different interstice prepared by NS lithography, are studied with incident wavenumbers in the near‐dipole and near‐quadrpole regions of the nanoparticles. In the colloidal gold nanoparticles, the SERS enhancement is the largest for the sharp tip followed by the truncated tip NPs, then the NRs and least enhancement for the NSs. This decreasing order of enhancement occurs although the incident wavenumber was near the dipole resonance of NSs and the quadrupole resonance for the NPs. These varied enhancements are explained in part as due to the binding energies of the nanocrystal facets, but the larger contribution results from the plasmon electromagnetic fields. A parallel finite difference time domain (FDTD) calculations were carried out, which corporate the experimental results and show agreement with ratios of the SERS enhancement for the different shapes. The normalized SERS intensity for NPs of different interstice distances show a sharp rise with the decrease of the interstice distances because of interparticle dipolar and quadrupolar coupling as evidenced also by FDTD calculations. Furthermore, these calculations show that the enhancement is polarization independent for an incident wavelength near quadrupole resonance but polarization dependent for an incident wavelength near the plasmon dipole transition. In the last case, the enhancement is larger by an order of magnitude for a polarization parallel to the NPs bisector than for polarization normal to the bisector with no hot spots for the relatively large interstice dimensions used. Copyright © 2012 John Wiley & Sons, Ltd.     

Stimulated Raman scattering in light and heavy water under picosecond laser excitation

The spectra of stimulated Raman scattering in ordinary and heavy water under excitation by second harmonic of a picosecond Nd:YAG laser were compared. It was shown that when stimulated Raman scattering is excited in water in cavities of a photonic crystal (synthetic opal matrix constructed of silica nanoglobules) or a photonic glass in the form of close-packed monodimensional millimeter-size amorphous-quartz balls, the efficiency of stimulated Raman scattering increases significantly compared to a uniform liquid medium.     

Effect of picosecond laser induced cavitation bubbles generated on Au targets in a nanoparticle production set-up

This work is aimed at an analysis of the influence on the efficiency of nanoparticle production of a cavitation bubble (CB), which forms during the laser ablation process in high-fluence regime. The CB is produced on an Au metal target immersed in water by 1064 nm ps Nd:YAG laser pulses at different fluences. Its time–space evolution is monitored by a shadowgraphic set-up, while the Au nanoparticles production rate is tagged by the growth of the plasmon resonance, which is detected by measuring shot-by-shot the UV-Vis absorbance. We analyze the dependence of bubble size on the experimental parameters. Our results appear of interest to enhance the nanoparticle production efficiency in a liquid medium.     

Influence of size and surface capping on photoluminescence and cytotoxicity of gold nanoparticles

Hydrophilic and homogeneous sub-10 nm blue light-emitting gold nanoparticles (NPs) functionalized with different capping agents have been prepared by simple chemical routes. Structure, average, size, and surface characteristics of these NPs have been widely studied, and the stability of colloidal NP solutions at different pH values has been evaluated. Au NPs show blue PL emission, particularly in the GSH capped NPs, in which the thiol-metal core transference transitions considerably enhance the fluorescent emission. The influence of capping agent and NP size on cytotoxicity and on the fluorescent emission are analyzed and discussed in order to obtain Au NPs with suitable features for biomedical applications. Cytotoxicity of different types of gold NPs has been determined using NPs at high concentrations in both tumor cell lines and primary cells. All NPs used show high biocompatibility with low cytotoxicity even at high concentration, while Au-GSH NPs decrease viability and proliferation of both a tumor cell line and primary lymphocytes.     

Influence of processing time on nanoparticle generation during picosecond-pulsed fundamental and second harmonic laser ablation of metals in tetrahydrofuran

The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by Mie-scattering of dispersed nanoparticle clusters.     

皮秒激光瞬态受激喇曼散射的实验研究

本文采用对撞脉冲锁模Nd:YAG激光器输出10ps脉冲串,经KTP非线性晶体腔外倍频,泵浦喇曼介质为二甲亚砜(DMSO)液体.实验研究了不同透镜焦长、焦点位置及不同喇曼介质氏度对瞬态受激喇曼散射的影响,获得了能量转换效率分别为45.6%和10.5%的前、后向一阶斯托克斯-喇曼散射光,并对实验结果进行了讨论.     

Generation of nanospikes via laser ablation of metals in liquid environment and their activity in surface-enhanced Raman scattering of organic molecules

The formation of dense arrays of nanospikes occurs under laser ablation of bulk targets (Ag, Au, Ta, Ti) immersed in liquids such as water or ethanol. The average height of spikes is 50 nm and their density on the target amounts to 10¹⁰ cm⁻². The effect is observed with sufficiently short laser pulses. In particular, either a 350 ps or a 90 ps Nd:YAG lasers are used in their fundamental harmonics. The nanospikes are characterized by UV-Visible reflection spectrometry and atomic force microscopy. The oscillations of electrons within nanospikes result in a permanent coloration of the surface and a modification of the optical reflection spectra of the metal. Scanning the laser beam along the metal surface allows its nanostructuring over extended areas (∼1 cm²). The nanostructured Ag surface shows enhanced Raman scattering of acridine molecules at a concentration of 10⁻⁵ M/l, whereas the initial Ag targets do not show any signal within the accuracy of measurements.     

拉曼激发激光诱导电子荧光流场测量系统中标记过程的研究

研制了一套拉曼激光发激光诱导电子荧光空气流场测速系统,利用Nd:YAG激光器的二次谐波及其抽运的氧气受激拉曼散射作为标记光源,以ArF准分子激光作为荧光再现光源,并用像增强CCD摄像机（ICCD）记录荧光图像,成功地获得了纯氧及空气中的标记线的荧光图像,并进行了氧气喷流速度测量的初步研究。     

Generation and size classification of single-walled carbon nanotube aerosol using atmospheric pressure pulsed laser ablation (AP-PLA)

Gas suspended single-walled carbon nanotubes (SWCNTs) with single tube diameter smaller than 2 nm and length of longer than 500 nm were generated by simple and continuous system using laser ablation technique under atmospheric conditions. Graphite target containing 0.5 wt%-nickel and 0.5 wt%-cobalt was ablated by Nd:YAG laser in an electrical furnace under atmospheric pressure of nitrogen flow that allowed one step and continuous synthesis of the SWCNTs. Size distribution of the gas suspended SWCNTs aerosol was measured using size-classification by a differential mobility analyzer (DMA) coupled with a condensation particle counter (CPC) used as a detector. Characteristics of SWCNT aerosol generated under the different temperature were also investigated using scanning and transmission electron microscopes and Raman scattering. Mono-mobility SWCNT aerosol with mobility diameter of 100 and 200 nm was successfully prepared after the size separation using a DMA.