[show abstract][hide abstract] ABSTRACT: A bottom-up based photomediated strategy is presented to create single crystalline silver spherical particles by pulsed laser irradiation of silver nanoparticles in liquid, where the unique selective laser heating is responsible for the formation of spherical particles. The present approach is facile and flexible for the design of silver spherical particles with tunable sizes. Systematical studies reveal that the experimental parameters including laser fluence, laser irradiation time, dispersing liquid, and concentration of starting material are important factors that influence the formation of silver spherical particles. As a demonstration of the as-synthesized silver spheres for electrochemical applications, the performance of silver spherical particles as potential supercapacitors was investigated by cyclic voltammetry, and the results indicated a higher capacity of silver spherical particles compared to that of silver raw nanoparticles, which is considered to originate from the enhanced electronic conductivity due to the single crystalline feature of silver spherical particles. We believe that the photomediated method presented in this work can be set as a new alternative in creating a variety of noble metallic spherical particles.
[show abstract][hide abstract] ABSTRACT: A new one-step approach was developed to synthesize bimetallic alloy submicrometer spheres, which are immiscible under equilibrium, using AuCo as a model system. Uniform, single-phase AuCo alloy submicrometer particles (230 nm) with a well-defined spherical morphology were successfully formed via pulsed laser irradiation of Au and Co-oxides nanoparticles dispersed in ethanol and characterized with a combination of electron microscopy, diffraction and magnetization measurements.
[show abstract][hide abstract] ABSTRACT: Simple, mild, and area-specific calcium phosphate (CaP) coating techniques are useful for the production and surface modification of biomaterials. In this study, an area-specific CaP coating technique for polymer substrates was successfully developed using a liquid-phase laser process. In the proposed method, Nd-YAG laser light (355 nm, 30 Hz, and 1-3 W) irradiated an ethylene-vinyl alcohol copolymer (EVOH) substrate immersed in a supersaturated CaP solution for various periods of time (up to 30 min). The CaP-forming ability increased with an increase in the laser power and irradiation period. At the optimal laser power (3 W), a continuous CaP layer formed within 30 min on the laser-irradiated surface of the EVOH substrate. The formation of CaP was attributed to laser absorption by the EVOH substrate, which promoted the surface modification of EVOH and an increase in the temperature of the solution near the surface of the substrate. The resulting CaP coating showed better cell adhesion property than the naked EVOH substrate. The proposed CaP coating technique is simple (quick and single step) and area specific. Furthermore, the present process is carried out under mild conditions, that is, at normal pressures and temperatures in a safe aqueous medium. These are significant advantages of the proposed CaP coating technique.
Journal of Biomedical Materials Research Part A 04/2012; 100(10):2573-80. · 2.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report the synthesis of Au-based submicrometer-sized spherical particles with uniform morphology/size and integrated porosity-magnetic property in a single particles. The particles are synthesized by a two-step process: (a) selective pulsed laser heating of colloidal nanoparticles to form particles with Au-rich core and Fe-rich shell and (b) acid treatment which leads to formation of porous architecture on particle surface. The simple, fast, inexpensive technique that is proposed demonstrates very promising perspectives for synthesis of composite particles.
[show abstract][hide abstract] ABSTRACT: The development of a general method to fabricate spherical semiconductor and metal particles advances their promising electrical, optical, magnetic, plasmonic, thermoelectric, and optoelectric applications. Herein, by using CuO as an example, we systematically demonstrate a general bottom-up laser processing technique for the synthesis of submicrometer semiconductor and metal colloidal spheres, in which the unique selective pulsed heating assures the formation of spherical particles. Importantly, we can easily control the size and phase of resultant colloidal spheres by simply tuning the input laser fluence. The heating-melting-fusion mechanism is proposed to be responsible for the size evolution of the spherical particles. We have systematically investigated the influence of experimental parameters, including laser fluence, laser wavelength, laser irradiation time, dispersing liquid, and starting material concentration on the formation of colloidal spheres. We believe that this facile laser irradiation approach represents a major step not only for the fabrication of colloidal spheres but also in the practical application of laser processing for micro- and nanomaterial synthesis.
[show abstract][hide abstract] ABSTRACT: Spherical iron oxide nanocomposite particles composed of magnetite and wustite have been successfully synthesized using a novel method of pulsed laser irradiation in ethyl acetate. Both the size and the composition of nanocomposite particles are controlled by laser irradiation condition. Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated. This work presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical stability. The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems.
Nanoscale Research Letters 01/2011; 6(1):226. · 2.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: A simple approach to prepare carbon quantum dots is presented in this communication by laser rapid passivation of nano carbon particles in ordinary organic solvent. The as-prepared carbon dots exhibited visible, tunable and stable photoluminescence (PL). XPS analysis showed that the increased oxygen concentration might be concerned with the origin of PL.
Chemical Communications 11/2010; 47(3):932-4. · 6.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: Electronic structure of individual boron nanobelts, which supposedly have α-tetragonal boron structure, was studied with electron energy-loss spectroscopy (EELS) and soft X-ray emission spectroscopy (SXES) in a transmission electron microscope. A boron K-shell excitation spectrum by EELS and boron K-emission spectra by SXES correspond to partial density of states of the conduction and the valence bands, respectively. Experimental results reveal that boron nanobelts are either a semimetal or narrow-gap semiconductor.
Journal of Physics Conference Series 07/2009; 176(1):012029.
[show abstract][hide abstract] ABSTRACT: Two unique laser processes of 'PLA in low vacuum (PLALV)' and 'PLA in liquid (PLAL)' have been examined to fabricate FePt nanoparticles and the magnetic and structural properties were investigated. The particles as prepared by PLALV showed a superparamagnetic behavior with an fcc structure. The annealing temperature dependence of the transformation from fcc to fct structure was studied by the structural and magnetic properties. A large coercivity of 3.6 kOe at 300 K was obtained by the low temperature (500 C) annealing. Composition deviation due to Fe dissolution in PLAL process was successfully suppressed by Ar bubbling.
Journal of Nanoscience and Nanotechnology 03/2009; 9(2):1454-7. · 1.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: We developed a technique to prepare gold nanoparticles (AuNPs) by wire spraying employing a room-temperature atmospheric H2/Ar microplasma jet driven with pulsing ultrahigh frequency and to subsequently deposit the AuNPs on nonheat-resistant materials such as paper in ambient air without apparent damage. In this technique, the application of a pulse waveform with higher voltage but rather low duty cycle effectively lowered the time-averaged gas temperature and facilitated preparing AuNPs. The size, crystallinity, and optical absorption of the prepared AuNPs were characterized, and the derivation and size evolution mechanisms were simply discussed based on the characterizations.
[show abstract][hide abstract] ABSTRACT: Gold and magnetite (Fe3O4) composite nanoparticles were prepared by a combination of unique laser processes in water. Pulsed laser ablation in liquid (PLAL) was employed to produce high pure gold nanoparticles and the successful gold/magnetite composite nanoparticles formation by a ‘nano-soldering’ effect was confirmed. The irradiation effect on the magnetic properties of the magnetite nanoparticles was investigated.
Journal of Magnetism and Magnetic Materials 01/2007; 310(2):2369-2371. · 1.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: This letter describes the dependence of photocurrent of single-crystalline boron nanobelts on the atmosphere. In ambient air, slow photoresponse under blue light illumination was observed. Rise and decay times exceeded three days. The magnitude of photoresponse in ambient air and oxygen was greater than that in hydrogen and argon atmospheres. In vacuum, a photoresistivity effect consisting of the continuous decrease of conductance under blue light illumination was observed. Variation of band bending of the nanobelt surface by adsorption or desorption of oxygen and water molecules appeared to switch the photoconduction on and off by the respective trapping and recombination of photoexcited carriers at the nanobelt core and surface.
[show abstract][hide abstract] ABSTRACT: Gold and magnetite composite nanoparticles have been prepared by a unique laser process. Both source colloid solutions of gold and magnetite were mixed and irradiated by an Nd:YAG laser (532 nm). The composite formation by a “nanosoldering” effect was confirmed by microscope observations.
IEEE Transactions on Magnetics 11/2006; · 1.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: Fe–Pt alloy particles were prepared by pulsed laser ablation in degassed hexane and deionized water. The atomic composition of the obtained binary metal particles significantly depended on the liquid media. Fe 23 Pt 77 close to FePt 3 and Fe 38 Pt 62 which contributed to the L1 0 phase formation were produced in hexane, however only Fe 26 Pt 74 close to FePt 3 was produced in water. The absence of oxygen atoms in the molecule of the liquid medium was important because oxidation of iron species led to deviation from stoichiometric alloy-ing. As-prepared particles produced in hexane had a random phase that was changed to the L1 0 phase by heat treatment at temperatures higher than 773 K.
Chemical Physics Letters 09/2006; 428(s 4–6). · 2.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: We measured electrical conductance of single crystalline boron nanobelts having α-tetragonal crystalline structure. The doping experiment of Mg was carried out by vapor diffusion method. The pure boron nanobelt is a p-type semiconductor and its electrical conductivity was estimated to be on the order of 10–3 (Ω cm)−1 at room temperature. The carrier mobility of pure boron nanobelt was measured to be on the order of 10−3 (cm2 Vs−1) at room temperature and has an activation energy of ∼0.19 eV. The Mg-doped boron nanobelts have the same α-tetragonal crystalline structure as the pristine nanobelts. After Mg vapor diffusion, the nanobelts were still semiconductor, while the electrical conductance increased by a factor of 100–500. Transition to metal or superconductor by doping was not observed.Graphical abstractSEM micrographs of boron nanobelt after Ni/Au electrode fabrication by electron beam lithography.
Journal of Solid State Chemistry. 01/2006; 179(9):2799-2804.
[show abstract][hide abstract] ABSTRACT: A case of primary retroperitoneal mucinous cystic tumor of borderline malignancy is reported. A 36-year-old, nulliparous woman complained of abdominal fullness. Physical examination revealed a cystic mass 12-cm x 8-cm in size. At laparotomy, a cystic tumor was observed in the right retroperitoneal space. Both ovaries appeared normal and the uterus was almost normal except for small myomatous nodules. Removal of the retroperitoneal tumor, an appendectomy, and a myomectomy were performed. The histologic diagnosis was a primary retroperitoneal mucinous cystic tumor of borderline malignancy, similar to findings for ovarian tumor. There was no evidence of disease 6 months after the surgery.
International Journal of Gynecological Pathology 08/2005; 24(3):218-23. · 1.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: A superconducting MgB2 film with a superconducting transition temperature of ∼36 K was successfully prepared on an MgO substrate by pulsed-laser ablation from a stoichiometric MgB2 target. A multilayer deposition process involving interposed Mg-rich layers was performed at 200°C by controlling the laser energy density in order to maintain the correct stoichiometry, and followed by an in situ annealing process at temperature ranging from 700° to 900°C. It was found that smooth, fine-grained films with superconducting transition temperatures of 24–36 K could be obtained from in situ annealing of the as-deposited multilayer at 900°C without excess Mg addition.
Journal of the American Ceramic Society 06/2005; 88(9):2385 - 2390. · 2.11 Impact Factor