Parameter dependence of nickel oxide nanoparticles prepared by pulsed-laserablation

Naoto Koshizaki,Takeshi Sasaki,Leszek Zbroniec 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.2

Nickel oxide nanoparticles were fabricated by a laser ablation technique using the third harmonic of an Nd:YAG laser and sintered NiO targets in an on-axis configuration under argon pressures of 0.67, 1.33, and 2.00 Pa. The effects of the number of irradiating laser pulses, gas pressure, and target-to-substrate (T-S) distance on the average particle size, size distribution, and particle areal density were investigated. The nanoparticles obtained were always crystalline and 2 to 6 nm in diameter, irrespective of the preparation conditions as determined by high-resolution transmission electron microscopic (HRTEM) analysis. The average particle size increased with the number of laser pulses, indicating the particle growth on the substrate. The particle areal density was strongly affected by the target-to-substrate distance. The formation process of the nanoparticles is also discussed.

Highly Stable Au Nanoparticles with Tunable Spacing and Their Potential Application in Surface Plasmon Resonance Biosensors

Gao, Shuyan,Koshizaki, Naoto,Tokuhisa, Hideo,Koyama, Emiko,Sasaki, Takeshi,Kim, Jae-Kwan,Ryu, Joonghyun,Kim, Deok-Soo,Shimizu, Yoshiki WILEY-VCH Verlag 2010 Advanced Functional Materials Vol.20 No.1

<P>Colloidal Au-amplified surface plasmon resonance (SPR), like traditional SPR, is typically used to detect binding events on a thin noble metal film. The two major concerns in developing colloidal Au-amplified SPR lie in 1) the instability, manifested as a change in morphology following immersion in organic solvents and aqueous solutions, and 2) the uncontrollable interparticle distance, determining probe spacing and inducing steric hindrance between neighboring probe molecules. This may introduce uncertainties into such detecting techniques, degrade the sensitivity, and become the barricade hampering colloidal Au-based transducers from applications in sensing. In this paper, colloidal Au-amplified SPR transducers are produced by using ultrathin Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite films via a radio frequency magnetron co-sputtering method. Deposited Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite films exhibit superior stability, and average interparticle distances between Au nanoparticles with similar average sizes can be tuned by changing surface coverage. These characteristics are ascribed to the spacer function and rim confinement of dielectric Al<SUB>2</SUB>O<SUB>3</SUB> and highlight their advantages for application in optimal nanoparticle-amplified SPR, especially when the probe size is smaller than the target molecule size. This importance is demonstrated here for the binding of protein (streptavidin) targets to the probe (biotin) surface. In this case, the dielectric matrix Al<SUB>2</SUB>O<SUB>3</SUB> is a main contributor, behaving as a spacer, tuning the concentration of Au nanoparticles, and manipulating the average interparticle distance, and thus guaranteeing an appropriate number of biotin molecules and expected near-field coupling to obtain optimal sensing performance.</P> <B>Graphic Abstract</B> <P>An innovative colloidal Au-amplified surface plasmon resonance (SPR) transducer is achieved by a using remarkably stable and space-tunable Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite film. This study indicates that the Au/Al<SUB>2</SUB>O<SUB>3</SUB> nanocomposite film is very promising; it simultaneously overcomes the instability and uncontrollable interparticle distance, which are the current bottlenecks hampering the application of SPR sensors. <img src='wiley_img/1616301X-2010-20-1-ADFM200901232-content.gif' alt='wiley_img/1616301X-2010-20-1-ADFM200901232-content'> </P>

펄스 레이저 어블레이션을 이용한 비정질 GaN박막의 성장 및 특성분석

심승환,윤종원,심광보,Naoto Koshizaki 한국결정성장학회 2004 韓國結晶成長學會誌 Vol.14 No.1

고밀도 GaN 타겟의 레이저 어블레이션으로 상온에서 비정질 GaN 박막을 제조하였다. 다양한 Ar 압력 및 레이저 에너지로 증착된 박막의 표면미세구조 및 조성분석 결과, 10Pa의 압력하에 증착된 박막은 smooth한 표면을 갖는 비정질 GaN로 구성되었음을 확인하였으며, 특히 200mJ/pu1se로 증착된 박막은 저 에너지에서 증착된 박막과 비교하여 결정성의 증가 및 화학양론에 가까운 조성을 나타냈다. 상온 photoluminescence spectra로부터 비정질 GaN 박막은 약 2.8eV에서 강한 band gap발광특성이 관측되었으며, 200mJ/pu1se의 10 Pa에서 가장 높은 발광효율을 나타냈다. Amorphous GaN film was deposited using a laser ablation of the highly densified GaN target. Through the surface morphological and compositional analysis of films deposited under various laser energies and Ar gas pressures, the film deposited under the pressure of 10 Pa were found to be amorphous GaN with the smooth surface. In particular, the film at 200 mJ/pulse showed the enhanced crystallinity and stoichiometric composition, compared with those of the films at relatively lower laser energy. The strong band-gap emission at 2.8 eV was observed from amorphous GaN film in the room temperature photoluminescence spectra, showing the highest efficiency in the film at 200 mJ/pulse under 10 Pa.

Topological analysis of Au particles in Au/SiO₂ nanocomposite films designed for molecular conduction measurement through Voronoi diagram

Kim, Dae-Gun,Shimizu, Yoshiki,Sasaki, Takeshi,Koshizaki, Naoto,Lee, Byunghoon,Kim, Deok-Soo,Lee, Young Jung,Kim, Young Do IOP Pub 2007 Nanotechnology Vol.18 No.14

<P>Monolayered Au/SiO<SUB>2</SUB> nanocomposite films with a high Au particle number density and insulating property were prepared by radio frequency magnetron co-sputtering to develop a new substrate for molecular conduction measurement. The topologies of Au nanoparticles distributed in the SiO<SUB>2</SUB> matrix were statistically evaluated by morphology observation using a field emission scanning electron microscope (FE-SEM) and the Voronoi diagram of a circle set by regarding the Au nanoparticles as a circle generator. The mean Au particle size and the interparticle distance between neighbours increased with deposition time. However, the fraction of the neighbouring Au nanoparticle combinations having interparticle distance shorter than a certain length increased as the deposition time increased. The results also demonstrated that many conducting paths several tens of nanometres long can be created by attaching conductive molecules 2.4?nm long between the Au nanoparticle combinations. Thus this suggests that the nanocomposite substrate can provide a facile way to measure conducting properties of molecules.</P>

Fabrication and characterization of Au/SiO2 nanocomposite films grown by radio-frequency cosputtering

Kyung-Han Jung,윤종원,Young-Soo Kwon,Naoto Koshizaki 한국물리학회 2008 Current Applied Physics Vol.8 No.6

Au/SiO₂ nanocomposite films were prepared on Si wafers by cosputtering of SiO₂ and gold wires. Au/Si atomic ratios in Au/SiO₂ nanocomposite films were varied from 0.53 to 0.92 by controlling the length of gold wire to study the evolution of the crystallization of gold, the size of Au/SiO₂ nanocomposite particles, and the optical properties of as-deposited Au/SiO₂ nanocomposite films. An X-ray photoelectron spectroscopy reveals that Au exists as a metallic phase in the bulk of SiO2 matrix. Dome-shaped Au/SiO₂ nanocomposite particles and both Au (111) and (200) planes were observed in a field-emission scanning electron microscopy and X-ray diffraction studies respectively. With an ultraviolet-visible, absorption peaks of Au/SiO₂ nanocomposite films were observed at 525 nm. Au/SiO₂ nanocomposite films were prepared on Si wafers by cosputtering of SiO₂ and gold wires. Au/Si atomic ratios in Au/SiO₂ nanocomposite films were varied from 0.53 to 0.92 by controlling the length of gold wire to study the evolution of the crystallization of gold, the size of Au/SiO₂ nanocomposite particles, and the optical properties of as-deposited Au/SiO₂ nanocomposite films. An X-ray photoelectron spectroscopy reveals that Au exists as a metallic phase in the bulk of SiO2 matrix. Dome-shaped Au/SiO₂ nanocomposite particles and both Au (111) and (200) planes were observed in a field-emission scanning electron microscopy and X-ray diffraction studies respectively. With an ultraviolet-visible, absorption peaks of Au/SiO₂ nanocomposite films were observed at 525 nm.

Topological analysis for Au nanoparticles distributed in an Au/SiO₂composite film by co-sputtering

Dae-Gun Kim,Young Jung Lee,Naoto Koshizaki,Young Do Kim 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2

Various Au/SiO₂ nanocomposite films were prepared by a co-sputtering method while controlling the number of Au wires, sputtering power, and sputtering time for the Au nanoparticulate monolayer films. The Au area fractions, Au mean particle sizes, and number densities for the Au nanoparticles of each Au/SiO₂ nanocomposite film were measured by image analysis of FE-SEM micrographs. Interparticle distances of Au nanoparticles were calculated using geometrical relationships. Various Au/SiO₂ nanocomposite films were prepared by a co-sputtering method while controlling the number of Au wires, sputtering power, and sputtering time for the Au nanoparticulate monolayer films. The Au area fractions, Au mean particle sizes, and number densities for the Au nanoparticles of each Au/SiO₂ nanocomposite film were measured by image analysis of FE-SEM micrographs. Interparticle distances of Au nanoparticles were calculated using geometrical relationships.

Au/SiO₂ nanocomposite film substrates with a high number density of Au nanoparticles for molecular conductance measurement

Kim, Dae-Gun,Koyama, Emiko,Kikkawa, Yoshihiro,Kirihara, Kazuhiro,Naitoh, Yasuhisa,Kim, Deok-Soo,Tokuhisa, Hideo,Kanesato, Masatoshi,Koshizaki, Naoto IOP Pub 2007 Nanotechnology Vol.18 No.20

<P>Au/SiO<SUB>2</SUB> nanocomposite films consisting of an extremely high number density of Au nanoparticles dispersed in a SiO<SUB>2</SUB> matrix a few nanometres thick were deposited by a co-sputtering method, and employed for molecular conductance measurement by immobilizing and bridging conjugated biphenyl molecules on dispersed Au nanoparticles. The number density of Au nanoparticles in the insulating SiO<SUB>2</SUB> matrix was approximately 14 000 µm<SUP>−2</SUP>, and the average interparticle distance from their neighbours was about 8 nm. The current increased considerably up to the range of nanoamperes after the immobilization of the conjugated biphenyl molecules, 10<SUP>5</SUP> times larger than without molecules before immobilization. Although the Au nanoparticles can be connected to only 30% of all combinations of neighbouring Au nanoparticles by biphenyl molecules 2.4 nm long from the topological analysis, the biphenyl molecules can bridge most of the Au nanoparticles, and their bridging continuity is over 100 nm in length. Thus the measured current is suggested to come from the continuously bridged molecules between the Au nanoparticles. Furthermore the <I>I</I>–<I>V</I> data of the whole Au/SiO<SUB>2</SUB> nanocomposite film immobilized with conjugated molecules are confirmed to be in a reasonable range in comparison with the scanning tunnelling spectroscopy data of similar conjugated molecules.</P>

Pulsed-Laser-Induced Simple Synthetic Route for Tb ₃ Al ₅ O ₁₂ :Ce ³⁺ Colloidal Nanocrystals and Their Luminescent Properties

Mhin, SungWook,Ryu, JeongHo,Kim, KangMin,Park, GyeongSeon,Ryu, HanWool,Shim, KwangBo,Sasaki, Takeshi,Koshizaki, Naoto Springer 2009 NANOSCALE RESEARCH LETTERS Vol.4 No.8

<P>Cerium-doped Tb<SUB>3</SUB>Al<SUB>5</SUB>O<SUB>12</SUB>(TAG:Ce<SUP>3+</SUP>) colloidal nanocrystals were synthesized by pulsed laser ablation (PLA) in de-ionized water and lauryl dimethylaminoacetic acid betain (LDA) aqueous solution for luminescent bio-labeling application. The influence of LDA molecules on the crystallinity, crystal morphology, crystallite size, and luminescent properties of the prepared TAG:Ce<SUP>3+</SUP>colloidal nanocrystals was investigated in detail. When the LDA solution was used, smaller average crystallite size, narrower size distribution, and enhanced luminescence were observed. These characteristics were explained by the effective role of occupying the oxygen defects on the surface of TAG:Ce<SUP>3+</SUP>colloidal nanocrystal because the amphoteric LDA molecules were attached by positively charged TAG:Ce<SUP>3+</SUP>colloidal nanocrystals. The blue-shifted phenomena found in luminescent spectra of the TAG:Ce<SUP>3+</SUP>colloidal nanocrystals could not be explained by previous crystal field theory. We discuss the 5d energy level of Ce<SUP>3+</SUP>with decreased crystal size with a phenomenological model that explains the relationship between bond distance with 5d energy level of Ce<SUP>3+</SUP>based on the concept of crystal field theory modified by covalency contribution.</P>

Simple synthetic route for hydroxyapatite colloidal nanoparticles via a Nd:YAG laser ablation in liquid medium

Mhin, Sung Wook,Ryu, Jeong Ho,Kim, Kang Min,Park, Gyeong Seon,Ryu, Han Wool,Shim, Kwang Bo,Sasaki, Takeshi,Koshizaki, Naoto Springer-Verlag 2009 APPLIED PHYSICS A MATERIALS SCIENCE AND PROCESSING Vol.96 No.2