激光蒸凝法制备氧化铜纳米粒子

以１５０Ｗ ＣＷ ＣＯ_２激光器为光源,Ｃｕ（ＡＣ）_２·Ｈ_２Ｏ为靶材,采用激光蒸凝法制备出了氧化铜纳米粒子．初步研究了反应参数对纳米粒子性能的影响,并用Ｘ射线衍射、电子衍射、透射电镜等技术对纳米粒子的性能进行了表征,同时对纳米粒子的形成机理进行了初步的探讨．实验结果表明;激光功率密度、反应压力、载气种类及流量等工艺参数对产品的粒度、晶型等性能均有影响．在惰性气氛下,产物主要是Ｃｕ和Ｃｕ_２Ｏ,粒径为１０～３０ｎｍ;在氧气气氛下,产物主要是Ｃｕ、Ｃｕ_２Ｏ和ＣｕＯ的混合物,粒径为１０～５０ｎｍ．     

Increase in the fluorescence intensity of ZnO nanoparticle by laser irradiation

We increased fluorescence intensity of ZnO nanoparticles by irradiation of laser to nanoparticles in solvent. The intensity of laser-irradiated nanoparticles became 1.4 times larger than that of non-irradiated one. The ZnO nanoparticles were synthesized by precipitation method. The laser for irradiation to ZnO nanoparticles was He-Cd cw laser. It was found that the average particle size was slightly increased during laser irradiation by red-shifted absorbance onset. These highly-fluorescent nanoparticles in solvent are useful for biomedical field such as biological imaging.     

Synthesis of ceramic nanoparticles by ultrafast laser ablation of solid targets in water

We report production of nanoparticles of several advanced ceramics (Si3N4, SiC, AlN, and Al2O3) by ablation with femtosecond laser pulses of solid targets submerged in deionized water. The products withstand comparison with commercial nanoparticle suspensions obtained by other techniques as they are analyzed by means of transmission electron microscopy. As compared with metal nanoparticles produced with the same technique, we have found that the overall dependence of mean sizes and distribution widths on the laser fluence is similar. We explain why it is difficult to synthetize very small (<5 nm) and monodisperse particles in terms of ablation mechanism and discuss the aplicability of the technique for industrial production.     

Co掺杂CeO2稀磁氧化物陶瓷和纳米颗粒的铁磁性能

分别采用固相烧结法及激光液相烧蚀(LAL)技术,成功制备出Co掺杂CeO_2稀磁氧化物陶瓷块体和纳米颗粒。XRD和SEM研究发现所制备的材料具有良好的结晶性和形貌。Co掺杂CeO_2稀磁氧化物陶瓷块体和纳米颗粒均为多晶立方结构,与纯立方相的CeO_2结构相同,说明Co掺杂未形成其他结构和杂相。磁性测量表明固相烧结法和激光烧蚀液相法制备的Co掺杂CeO_2样品均具有较高的室温铁磁性,且远高于文献中报道的结果。将陶瓷块材经激光烧蚀成纳米颗粒后,纳米颗粒的铁磁性与陶瓷块材保持一致。这说明激光烧蚀法制备的纳米材料可以很好地保持母材的特性,是一种很好的纳米颗粒制备方法。根据XRD和SEM研究结果,笔者认为Co掺杂CeO_2陶瓷块材及纳米颗粒的室温铁磁性是内禀性质;磁性产生的机理源于氧空位诱导的铁磁性耦合。     

自组装制备PEG接枝聚苯乙烯微球的粒径控制

用苯乙烯封端的聚乙二醇(St—PEG)大单体与苯乙烯(St)进行接枝共聚，将得到的双亲性接枝共聚物(PEG—g—PSt)逐步滴加到各种比例的甲醇／水的混合溶剂中，通过该聚合物在混合溶剂中的自组装，制得了PEG—g—PSt微球。用透射电子显微镜(TEM)和激光光散射(LLS)对微球的形态和粒径进行了表征。实验结果表明，改变接枝液组成、接枝液浓度、滴加速度以及混合溶剂组成等反应条件可有效地控制所得微球的粒径及其分布。     

Synthesis and characterization of Ag-Ni bimetallic nanoparticles by laser-induced plasma

We present an approach in which laser ablation deposition is used to synthesize silver-nickel bimetallic nanoparticles. A variety of techniques, including scanning electron microscopy, energy disperse spectroscopy and X-ray photoelectron spectroscopy have been used to characterize the morphology, composition and construction of synthesized bimetallic nanoparticles, respectively. The formation mechanism of bimetallic nanoparticles has been discussed. The Raman spectra of silver-nickel bimetallic nanoparticles have been analyzed. Time-of-flight mass spectrometry has been applied to directly measure intermediate species. The results indicate that diatomic AgNi is the most abundant species and suggest that the AgNi is the most stable intermediate which may play an important role in the synthesis process. Emission spectra demonstrate that the electron temperature is in the range of 6000-10000 K during the ablation process and increases with the laser power density.     

Continuous laser irradiation under ambient conditions: A simple way for the space-selective growth of gold nanoparticles inside a silica monolith

Thanks to the potential and various applications of metal-dielectric nanocomposites, their syntheses constitute an interesting subject in material research. In this work, we demonstrate the achievement of gold nanocrystals growth through a visible and continuous laser irradiation. The in situ and direct space-selective generation of metallic nanoparticles is localized under the surface within transparent silica monoliths. For that purpose, the porous silica monoliths are prepared using a sol-gel route and post-doped with gold precursors before the irradiation. The presence of Au nanoparticles inside the irradiated areas was evidenced using absorption spectroscopy, X-ray diffraction analysis and transmission electron microscopy. The comparison between the results obtained after a laser irradiation and by a simple heat-treatment reveals that the local precipitation of gold nanoparticles by continuous photo-irradiation occurs following a photo-thermal activated mechanism.     

Thermal formation mechanism and size control of spherical hematite nanoparticles

Hematite nanoparticles were prepared by a FeCl₂ solution. The whole thermal formation mechanism as well as the size and dispersity control of hematite nanoparticles was studied. It has been found that goethite nanoparticles were firstly produced through the mix and oxidation of 0.5 M ferrous salt and 2.1 M bicarbonate and then hematite nanoparticles were obtained directly by thermal transformation of the goethite samples. At higher temperatures, nanopores were observed in the goethite nanocrystals and then merged into slits due to the high water pressure in the nanopores. The morphology of hematite particles with regular texture was changed due to recrystallization and then spherical nanoparticles were formed in the end. The particle size and dispersity of hematite nanoparticles could be controlled by different charging rates. From the second particle size distribution diagrams measured by the laser dynamic scatter method, not only the hematite particle size became small but also the dispersity of hematite nanoparticles was improved as the charging rate increased.     

Optothermal escape of plasmonically coupled silver nanoparticles from a three-dimensional optical trap

We demonstrate that optical trapping of multiple silver nanoparticles is strongly influenced by plasmonic coupling of the nanoparticles. Employing dark-field Rayleigh scattering imaging and spectroscopy on multiple silver nanoparticles optically trapped in three dimensions, we experimentally investigate the time-evolution of the coupled plasmon resonance and its influence on the trapping stability. With time the coupling strengthens, which is observed as a gradual red shift of the coupled plasmon scattering. When the coupled plasmon becomes resonant with the trapping laser wavelength, the trap is destabilized and nanoparticles are released from the trap. Modeling of the trapping potential and its comparison to the plasmonic heating efficiency at various nanoparticle separation distances suggests a thermal mechanism of the trap destabilization. Our findings provide insight into the specificity of three-dimensional optical manipulation of plasmonic nanostructures suitable for field enhancement, for example for surface-enhanced Raman scattering.     

Synthesis and characterization of CdTe quantum dots embedded gelatin nanoparticles via a two-step desolvation method

Novel CdTe quantum dots (QDs) embedded gelatin nanoparticles (CdTe/gelatin nanoparticles) were synthesized via a two-step desolvation method. The morphology and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and laser particle size analyzer. They are presented spherically and relatively uniform with a diameter of 150 nm. The luminescent properties of the nanoparticles were investigated by using fluorescence spectrophotometry and fluorescence microscopy. The fluorescence stability of nanoparticles was tested in vitro. It was found that the nanoparticles were stable in water and phosphate-buffered saline (PBS) solution (pH 7.4) for at least 15 days. A possible formation mechanism of the CdTe/gelatin nanoparticles was also proposed. The inherent stability and biocompatibility indicate that the nanoparticles are expected to be promising candidates for in vivo biological imaging studies.     

Tat修饰Au-Au2S纳米颗粒的合成及其穿膜机制

为了实现对肿瘤的靶向性药物/基因治疗,通过化学还原法制备了细胞穿膜肽Tat修饰的Au-Au₂S纳米药物载体。采用透射电镜、表面增强拉曼光谱仪、紫外分光光度计对Tat/Au-Au₂S纳米粒子进行表征,采用流式细胞仪、激光共聚焦显微镜研究Tat/Au-Au₂S纳米粒子的穿细胞膜机制。理化分析结果表明,Tat可通过Au—S键接枝于Au-Au₂S纳米粒子表面, 直径约50 nm的Tat/Au-Au₂S纳米粒子具有近红外敏感性。细胞内化途径示踪物共定位分析和抑制剂阻断实验表明, Tat/Au-Au₂S纳米粒子以脂筏介导的巨胞饮途径进入Hela细胞, 而以受体和脂筏共介导的巨胞饮途径进入骨髓间充质干细胞（BMSCs）。      

Synthesis of Silver Nanoparticles by a Laser–Liquid–Solid Interaction Technique

Silver nanoparticles of high chemical homogeneity have been synthesized by a novel laser–liquid–solid interaction technique from a solution composed of silver nitrate, distilled water, ethylene glycol, and diethylene glycol. Rotating nickel, niobium, stainless steel, and ceramic Al₂O₃ substrates were irradiated using a continuous-wave CO₂ laser and Q-switched Nd–YAG laser ( = 1064 and 532 nm). The silver nanoparticles were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe x-ray microanalysis (EPMA). The shape of silver particles was dependent on the chemical composition and laser parameters. The synthesis mechanism of silver nanoparticles has been proposed to occur primarily at the laser–liquid–substrate interface by a nucleation and growth mechanism.     

Room temperature direct space-selective growth of gold nanoparticles inside a silica matrix based on a femtosecond laser irradiation

A one-step procedure without heat-treatment was carried out to yield the space-selective growth of gold nanoparticles inside a transparent silica matrix. A silica porous monolith was prepared via a sol-gel route and then post-doped with an aqueous solution of hydrogen tetrachloroaurate (HAuCl₄) as a gold precursor, in the presence of sodium carbonate as an additive. Direct and local precipitation of gold nanoparticles inside the deep volume of the silica matrix was induced by a femtosecond laser irradiation at room temperature. Gold nanoparticles with size of about 50-60 nm were evidenced by absorption spectroscopy and transmission electron microscopy. The additive is assumed to be involved in a photo-electrochemical mechanism including redox reactions, which is necessary to the formation of gold nanoparticles.     

Laser power effect on morphology and photoluminescence of ZnO nanostructures by laser ablation in water

The morphology and photoluminescence of ZnO nanostructures formed by laser ablation in water were found to be susceptible to the applied laser power. The products varied from nanoflakes to nanoparticles, then to short nanorods with the increase of laser power. Correspondingly, the relative intensity of violet emission decreased and that of green emission increased. The morphology formation mechanism and defect relaxation were analyzed from a view of laser power effect on the induced plasma states, which includes plasma intensity, lifetime, distribution, and thus on defect type. These results would be of great importance for understanding the growth dynamics of nanomaterials under extreme conditions.     

Amorphous boron nanoparticles and BN encapsulating boron nano-peanuts prepared by arc-decomposing diborane and nitriding

Amorphous boron nanoparticles were prepared by arc-decomposing diborane, which had ideal morphologies in comparison with that of those fabricated by furnace or laser heating diborane. Peanut-shaped boron nitride encapsulating boron nanocapsules were fabricated by nitridation of amorphous boron nanoparticles. Unique core/void/shell structure of the nanocapsules was observed by using a high-resolution transmission electron microscopy. The mechanism of growing the BN nanocapsules by a catalyst free process was distinctly different from the process of arc discharge or laser heating. The broadening of nonpolar intralayer Raman line of hexagonal BN at about 1370 cm^–1 was observed, which was attributed to the small crystal size of BN.     

Optically controlled thermal management on the nanometer length scale

The manipulation of polymers and biological molecules or the control of chemical reactions on a nanometer scale by means of laser pulses shows great promise for applications in modern nanotechnology, biotechnology, molecular medicine or chemistry. A controllable, parallel, highly efficient and very local heat conversion of the incident laser light into metal nanoparticles without ablation or fragmentation provides the means for a tool like a 'nanoreactor', a 'nanowelder', a 'nanocrystallizer' or a 'nanodesorber'. In this paper we explain theoretically and show experimentally the interaction of laser radiation with gold nanoparticles on a polymethylmethacrylate (PMMA) layer (one-photon excitation) by means of different laser pulse lengths, wavelengths and pulse repetition rates. To the best of our knowledge this is the first report showing the possibility of highly local (in a 40?nm range) regulated heat insertion into the nanoparticle and its surroundings without ablation of the gold nanoparticles. In an earlier paper we showed that near-infrared femtosecond irradiation can cut labeled DNA sequences in metaphase chromosomes below the diffraction-limited spot size. Now, we use gold as well as silver-enhanced gold nanoparticles on DNA (also within chromosomes) as energy coupling objects for femtosecond laser irradiation with single-and two-photon excitation. We show the results of highly localized destruction effects on DNA that occur only nearby the nanoparticles.     

Experimental study of interaction of laser radiation with silver nanoparticles in SiO2 matrix

Thin films of silica containing silver nanoparticles were deposited by magnetron co-sputtering followed by thermal annealing in air or Ar+2% H2. Laser fragmentation of the particles was carried out at two different wavelengths. The films were characterized by UV-VIS absorption spectroscopy and plasmon resonance numerical modeling based on the Mie theory, together with Rutherford backscattering elemental analysis, X-ray photoelectron spectroscopy chemical characterization, combined with statistical analysis of the transmission electron microscopy micrographs, and surface topography study by atomic force microscopy. It is demonstrated that the fragmentation is a result of a thermal process and its mechanism does not depend on the laser wavelength as long as the laser light is absorbed by the silver particles. Laser treatment with moderate fluences does not alter the precipitated metal content while fragmenting the particles. TEM study indicates that laser assisted silver particle modification can serve as a method for narrowing the particle size distribution.     

Laser-assisted production of spherical TiO2 nanoparticles in water

TiO(2) nanoparticles with controllable average diameter have been obtained by laser ablation in water. A monomode ytterbium doped fiber laser (YDFL) was used to ablate a metallic titanium target placed in deionized water. The resulting colloidal solutions were subjected to laser radiation to study the resizing effect. The crystalline phases, morphology and optical properties of the obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), x-ray energy dispersive spectroscopy (EDS) and UV-vis absorption spectroscopy. The colloidal suspensions produced consisting of titanium dioxide crystalline nanoparticles show almost perfect spherical shape with diameters ranging from 3 to 40 nm. The nanoparticles are polycrystalline and exhibit anatase as well as rutile phases.     

Cation-assisted laser desorption/ionization for matrix-free surface mass spectrometry of alkanethiolate self-assembled monolayers on gold substrates and nanoparticles

We propose a new scheme of matrix-free laser desorption/ionization with cation assistance for surface mass spectrometry of self-assembled monolayers (SAMs) of alkanethiolates on gold substrates and gold nanoparticles (NPs). In a proof-of-concept experiment, a simple treatment using an aqueous salt solution such as NaI(aq) was shown to lead to a significant laser desorption/ionization, producing the characteristic (disulfide) ions of alkanethiolate molecules from the monolayers. Further efforts to understand the mechanism were also given, including laser power and salt concentration dependence studies. In the power dependence study, the characteristic ions were found to be produced at low laser power where no gold substrate species was seen. At high laser power, the generation of gold species, Au(+)-Au5(+), resulted in a saturation behavior in the characteristic mass peak for alkanethiolate molecules. In addition, characteristic ions with gold adducts were not observed at any laser power. With increasing salt concentration, the characteristic mass peak was gradually increased. The results suggest that the adduct formation of a cation with alkanethiolates in the monolayers provide a facile pathway to supply a charge to UV laser-desorbed secondary neutrals for mass spectrometric detection. This cation-assisted laser desorption/ionization (CALDI) mass spectrometry was further examined with the SAMs and mixed SAMs with various terminals such as -OH, -OCH3, -NH2, -ethylene (-CH=CH2), and -acetylene (-C[triple bond]CH). The CALDI method was also successfully applied to surface mass spectrometry of monolayer-protected gold NPs (approximately 16 nm diameter) with OH- and COOH-terminated SAMs. The unique advantages of the matrix-free CALDI method may extend our capability in investigations of interfacial chemistry at SAMs as well as mass spectrometric applications using biochips and nanoparticles.     

Laser annealing induced melting of silver nanoparticles in a glass matrix

We have studied the effect of nanosecond-pulsed KrF excimer laser radiation on a composite metamaterial based on a soda-lime-silicate glass containing ion-synthesized silver nanoparticles, depending on the number of pulses. It is established that, as the number of laser pulses increases, the average size of silver nanoparticles in the ion-implanted layer monotonically decreases. In addition, the laser annealing is accompanied by the diffusion of silver inward the glass and by the partial evaporation of silver from the sample surface. The observed decrease in the size of silver nanoparticles is considered with allowance for the simultaneous melting of both the metal particles and glass matrix.