• Journal of the Korean institute of surface engineering
• /
• v.53 no.3
• /
• pp.116-123
• /
• 2020

Ion beam irradiation induces self-organization of nanostructure on the surface of polymer film. We show that the incident angle of Ar ions on polyethylene naphthalate(PEN) film changes self-organized nanostructure. PEN film was irradiated by argon ion beams with the ion incident angle of 0°, 30°, 45°, 60°, and 80°. Nanostructure was altered from dimple to ripple structure as the angle increases. The ripple structure changed to pillar structure after 60°due to that the shallow incident angle increased the ion energy transfer per depth up to 50 eV/Å, which value could induce excessive surface heating and oligomer formation reacting as a physical mask for anisotropic etching. And quantitative analysis of the nanostructures was adapted by using ABC model and fractal dimension theory.

• Korean Chemical Engineering Research
• /
• v.55 no.1
• /
• pp.115-120
• /
• 2017

In recent, it is worldwide issued that nanoscale science and technology as a solution have supported to increase the sensing performance in carbon nanotube based biosensor system. Containing material chemistry in various nanostructures has formed their high potentials for stabilizing and activating biocatalyst as a bioreceptor for medical, food contaminants, and environmental detections using electrode modification technologies. Especially, the large surface area provides the attachment of biocatalysts increasing the biocatalyst loading. Therefore, nano-scale engineering of the biocatalysts have been suggested to be the next stage advancement of biosensors. Here, we would like to study the electrical mechanism depending on the exposure methods (soaking or dropping) to the sample solution to the assembled carbon nanotubes (CNTs) on the gold electrodes of biosensor for a simple and highly sensitive detection. We performed various experiments using polar and non-polar solutions as sampling tests and identified electrical response of assembled CNTs in those solutions.

• Korean Journal of Materials Research
• /
• v.23 no.11
• /
• pp.655-660
• /
• 2013

Photoelectrochemical cells have been used in photolysis of water to generate hydrogen as a clean energy source. A high efficiency electrode for photoelectrochemical cell systems was realized using a ZnO hierarchical nanostructure. A ZnO nanofiber mat structure was fabricated by electrospinning of Zn solution on the substrate, followed by oxidation; on this substrate, hydrothermal synthesis of ZnO nanorods on the ZnO nanofibers was carried out to form a ZnO hierarchical structure. The thickness of the nanofiber mat and the thermal annealing temperature were determined as the parameters for optimization. The morphology of the structures was examined by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The performance of the ZnO nanofiber mat and the potential of the ZnO hierarchical structures as photoelectrochemical cell electrodes were evaluated by measurement of the photoelectron conversion efficiencies under UV light. The highest photoconversion efficiency observed was 63 % with a ZnO hierarchical structure annealed at $400^{\circ}C$ in air. The morphology and the crystalline quality of the electrode materials greatly influenced the electrode performance. Therefore, the combination of the two fabrication methods, electrospinning and hydrothermal synthesis, was successfully applied to fabricate a high performance photoelectrochemical cell electrode.

• Journal of the Optical Society of Korea
• /
• v.9 no.1
• /
• pp.16-21
• /
• 2005

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

• Journal of Dairy Science and Biotechnology
• /
• v.23 no.1
• /
• pp.9-17
• /
• 2005

Nanotechnology has penetrated into the various branches of research and development and it is particularly of benefit to the particle size engineering. It has been widely known that the particle size of an active pharmaceutical ingredient (API) is critical in determining the bioavailability and processability of pharmaceutical formulation. However, the window of appropriate particle size has been limited mainly due to related processing difficulties. The windows have been widened by the recent development of nanotechnologies, resulting in diversified drug delivery systems. The impact of this development is far more fundamental than what can be expected from conventional particle size engineering. It is the case that the preparation and use of nanoparticles will soon be a common task in the particle engineering step of pharmaceutical unit operations. In this chapter, the basic principles of variouspreparation techniques will be discussed in detail. Regardless of processing details, the preparation methods of pharmaceutical nanoparticles mainly concern how to deal with the extra energy related with particle size. Depending on the ways of treating the e103 energy, preparation methods can be classified into two major classes, i.e.. thermodynamic and kinetic approaches. The recent progresses have shown the possibilities of much more complex combinations of different approaches and the use of new types of energy and nanostructures.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.461-461
• /
• 2013

Over the last decade, zinc oxide (ZnO) thin films have attracted considerable attention owing to large band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature [1-3]. Recent interest in ZnO related researches has been switched into the fabrication and characterization of low-dimensional nanostructures, such as nano-wires and nano-dots that can be applicable to manufacture the optoelectronic devices such as ultraviolet lasers, light-emitting-diodes and detectors. Since the optical properties of ZnO nano-structures might be distinct from those of bulk materials or thin films, the low-dimensional phenomena should be examined further. In order to utilize such advanced optoelectronic devices, one of the challenges is how to control the surface state related emissions that are drastically increased with increasing the density of the nano-structures and the surface-to-volume ratio. This paper reports the synthesis and characterization of self-assembled ZnO hexagonal nano-disks grown by radio-frequency magnetron sputtering. X-ray diffraction data and scanning electron microscopy data showed that ZnO hexagonal nano-disks were nucleated on top of the flat surfaces as the film thickness reached to 1.56 ${\mu}m$ and then the number of nano-disks increased with increasing the film thickness. The lateral size of hexagonal nano-disks was ~720 nm and height was ~74 nm. The strong photo luminescence spectra obtained at 10 K was also observed, which was assigned to a surface exciton emission at 3.3628 eV arising from the surface sites of hexagonal nano-disks.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.635-635
• /
• 2013

We report three-dimensional polycrystalline anatase TiO2 structures (3D a-TiO2) for environmental and bio-medical applications. The 3D a-TiO2 was synthesized without thermal treatment by the growth of rod-like polycrystals on Degussa P25 (P25) via low temperature (< $85^{\circ}C$) modified alkali hydrothermal processing. X-ray diffraction and high-resolution transmission electron microscopic results showed that the rod-like polycrystals of 3D a-TiO2 possessed the highly anatase nanostructures. The photocatalytic activity of 3D a-TiO2 was found to be 2.2 times higher than that of P25. The recyclability of the 3D a-TiO2 was found to be high: the decolorization rate was 94.8% of the initial value after fifteen cycles. In addition, 3D a-TiO2 exhibited excellent antibacterial activities for the sterilization of gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus). Even at the 10th recycled use, more than 98.4% of E. coli and S. aureus can be killed. These results indicated that 3D a-TiO2 might have utility in several promising applications such as photocatalytic water/air purification and bactericidal agents.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.636-636
• /
• 2013

Since first discovery of strong Raman spectrum of molecules adsorbed on rough noble metal, surface enhanced Raman scattering (SERS) has been widely used for detection of molecules with low concentration. Surface plasmons at noble metal can enhance Raman spectrum and using Au nanostructures as substrates of SERS has advantages due to it has chemical stability and biocompatibility. However, the photoluminescence (PL) background from Au remains a problem because of obtaining molecular vibration information. Recently, graphene, two-dimensional atomic layer of carbon atoms, is also well known as PL quenchers for electronic and vibrational excitation. In this study, we observed SERS of single layer graphene on or under monolayer of Au nanoparticles (NPs). Single layer graphene is grown by chemical vapor deposition and transferred onto or under the monolayer of Au NPs by using PMMA transfer method. Monolayer of Au NPs prepared using Langmuir-Blodgett method on or under graphene surface provides closed and well-packed monolayer of Au NPs. Scanning electron microscopy (SEM) and Raman spectroscopy (WItec, 532 nm) were performed in order to confirm effects of Au NPs on enhanced Raman spectrum. Highly enhanced Raman signal of graphene by Au NPs were observed due to many hot-spots at gap of closed well-packed Au NPs. The results showed that single layer graphene provides larger SERS effects compared to multilayer graphene and the enhancement of the G band was larger than that of 2D band. Moreover, we confirm the appearance of D band in this study that is not clear in normal Raman spectrum. In our study, D band appearance is ascribed to the SERS effect resulted from defects induced graphene on Au NPs. Monolayer film of Au NPs under the graphene provided more highly enhanced graphene Raman signal compared to that on the graphene. The Au NPs-graphene SERS substrate can be possibly applied to biochemical sensing applications requiring highly sensitive and selective assays.

• Journal of Powder Materials
• /
• v.20 no.3
• /
• pp.180-185
• /
• 2013

The iron oxides nanoparticles and iron oxide with other compounds are of importance in fields including biomedicine, clinical and bio-sensing applications, corrosion resistance, and magnetic properties of materials, catalyst, and geochemical processes etc. In this work we describe the preparation and investigation of the properties of coated magnetic nanoparticles consisting of the iron oxide core and organic modification of the residue. These fine iron oxide nanoparticles were prepared in air environment by the co-precipitation method using of $Fe^{2+}$: $Fe^{3+}$ where chemical precipitation was achieved by adding ammonia aqueous solution with vigorous stirring. During the synthesis of nanoparticles with a narrow size distribution, the techniques of separation and powdering of nanoparticles into rather monodisperse fractions are observed. This is done using controlled precipitation of particles from surfactant stabilized solutions in the form organic components. It is desirable to maintain the particle size within pH range, temperature, solution ratio wherein the particle growth is held at a minimum. The iron oxide nanoparticles can be well dispersed in an aqueous solution were prepared by the mentioned co-precipitation method. Besides the iron oxide nanowires were prepared by using similar method. These iron oxide nanoparticles and nanowires have controlled average size and the obtained products were investigated by X-ray diffraction, FESEM and other methods.

• Current Photovoltaic Research
• /
• v.1 no.1
• /
• pp.63-68
• /
• 2013

We investigated the effects of Au eutectic reaction on Si thin film growth by hot wire chemical vapor deposition. Small SiC and Si nano-particles fabricated through a wet etching process were coated and biased at 50 V on micro-textured Si p-n junction solar cells. Au thin film of 10 nm and a Si thin film of 100 nm were then deposited by an electron beam evaporator and hot wire chemical vapor deposition, respectively. The Si and SiC nano-particles and the Au thin film were structurally embedded in Si thin films. However, the Au thin film grew and eventually protruded from the Si thin film in the form of Au silicide nano-balls. This is attributed to the low eutectic bonding temperature ($363^{\circ}C$) of Au with Si, and the process was performed with a substrate that was pre-heated at a temperature of $450^{\circ}C$ during HWCVD. The nano-balls and structures showed various formations depending on the deposited metals and Si surface. Furthermore, the samples of Au nano-balls showed low reflectance due to surface plasmon and quantum confinement effects in a spectra range of short wavelength spectra range.