• Journal of Electrochemical Science and Technology
• /
• v.15 no.2
• /
• pp.261-267
• /
• 2024

An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm² has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.

• Journal of the Korean Ceramic Society
• /
• v.41 no.4
• /
• pp.297-301
• /
• 2004

Nano-sized mullite (3Al$_2$O$_3$$.$2SiO$_2$) colloids were prepared by use of the spray combustion method. For combustion reaction, Al(NO$_3$)$_3$$.$9$H_2O$, and CH$_{6}$N$_4$O were used as an oxidizer and a fuel respectively, and then colloidal silica was also added as 2SiO$_2$source for mullite. The temperature of the reaction chamber was kept at 80$0^{\circ}C$ to initiate the ignition of droplets of the mixed precursors. For preventing droplet coagulation, the droplet number concentration was reduced using the metal screen filter, and the residence time of aerosol was kept at 2.5 seconds for laminar flow. The synthesized colloidal particles had an uniform spherical shape with 130 nanometer size and the crystalline phase showed the mullite with stoichiometry in the observations of XRD and TEM.

• Journal of the Korean Ceramic Society
• /
• v.41 no.1
• /
• pp.76-80
• /
• 2004

Nano-sized ZnO colloids were prepared by use of spray combustion method. for combustion reaction, $Zn(NO_3)_2{\cdot}6H_2O$ and $CH_6N_4O$ were employed as an oxidizer and a fuel. Exothermic peak was shown at $230^{\circ}C$ by DTA/TGA, and it was considered as a combustion reaction followed by ignition of the precursor mixture. In case of spray combustion method, because insufficient contents of molecules and radicals generated from precursor droplets may lead an incomplete igmition, the ignition temperature of combustion chamber was chosen at $500^{\circ}C$. For diminishing aerosol coagulation, the droplet number concentration was reduced by filter media. The fluid was laminar with 2.5 seconds of aerosol residence time. The synthesized colloids had spherical shape with 180 nanometer size, and the crystalline phase was ZnO with hexagonal structure.

• Korean Journal of Materials Research
• /
• v.15 no.11
• /
• pp.705-710
• /
• 2005

NIL (nanoimprint lithography) technique has demonstrated a high potential for wafer size definition of nanometer as well as micrometer size patterns. During the replication process by NIL, the stiction between the stamp and the polymer is one of major problems. This stiction problem is moi·e important in small sized patterns. An antistiction layer prevents this stiction ana insures a clean demolding process. In this paper, we were using a TCP (transfer coupled plasma) equipment and $C_4F_8$ as a precursor to make a Teflon-like antistiction layer. This antistiction layer was deposited on a 6 inch silicon wafer to have nanometer scale thicknesses. The thickness of deposited antistiction layer was measured by ellipsometry. To optimize the process factor such as table height (TH), substrate temperature (ST), working pressure (WP) and plasma power (PP), we were using a design of experimental (DOE) method. The table of full factorial arrays was set by the 4 factors and 2 levels. Using this table, experiments were organized to achieve 2 responses such as deposition rate and non-uniformity. It was investigated that the main effects and interaction effects between parameters. Deposition rate was in proportion to table height, working pressure and plasma power. Non-uniformity was in proportion to substrate temperature and working pressure. Using a response optimization, we were able to get the optimized deposition condition at desired deposition rate and an experimental deposition rate showed similar results.

• Clean Technology
• /
• v.17 no.1
• /
• pp.78-82
• /
• 2011

For effectively photochemical hydrogen production, P (negative semiconductor) and B (positive semiconductor) ions (0.1, 0.2, 0.5, and 1.0 mol%) incorporated $TiO_2$ (P- and B-$TiO_2$) nanometer sized particles were prepared using a solvothermal method as a photocatalyst. The characteristics of the synthesized P- and B-$TiO_2$ photocatalysts were analyzed by X-ray Diffraction (XRD), Transmission electron microscopy (TEM), W-visible spectroscopy (UV-Vis), and Photoluminescence spectra (PL). The evolution of $H_2$ from methanol/water (1:1) photo-splitting over B-$TiO_2$ photocatalysts was enhanced compared to those over pure $TiO_2$ and P-$TiO_2$ photocatalysts; 0.42 mL of $H_2$ gas was evolved after 10 h when 0.5 g of a 1.0 mol% B-$TiO_2$ catalyst was used.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.581-588
• /
• 2007

To enhance the photodecomposition of concentrated ammonia into N2, Pt/V-TiO2 photocatalysts were prepared using solvothermal and impregnation methods. Nanometer-sized particles of 0.1, 0.5 and 1.0 mol% V-TiO2 were prepared solvothermally, and then impregnated with 1.0 wt% Pt. The X-ray diffraction (XRD) peaks assigned to V2O5 at 30.20 (010) and Pt metal at 39.80 (111) and 46.20 (200) were seen in the 1.0 wt% Pt/ 10.0 mol% V-TiO2. The particle size increased in the order: pure TiO2, V-TiO2 and Pt/V-TiO2 after thermal treatment at 500 °C, while their surface areas were in the reverse order. On X-ray photoelectron spectroscopy (XPS), the bands assigned to the Ti2p3/2 and Ti2p1/2 of Ti4+-O were seen in all the photocatalysts, and the binding energies increased in the order: TiO2 < Pt/V-TiO2 < V-TiO2. The XPS bands assigned to the V2p3/2 (517.85, 519.35, and 520.55 eV) and V2p1/2 (524.90 eV) in the V3+, V4+ and V5+ oxides appeared over V-TiO2, respectively, while the band shifted to a lower binding energy with Pt impregnation. The Pt components of Pt/ V-TiO2 were identified at 71.60, 73.80, 75.00 and 76.90 eV, which were assigned to metallic Pt 4f7/2, PtO 4f7/2, PtO2 4f7/2, and PtO 4f5/2, respectively. The UV-visible absorption band shifted closer towards the visible region of the spectrum in V-TiO2 than in pure TiO2 and; surprisingly, the Pt/V-TiO2 absorbed at all wavelengths from 200 to 800 nm. The addition of vanadium generated a new acid site in the framework of TiO2, and the medium acidic site increased with Pt impregnation. The NH3 decomposition increased with the amount of vanadium compared to pure TiO2, and was enhanced with Pt impregnation. NH3 decomposition of 100% was attained over 1.0 wt% Pt/1.0 mol% V-TiO2 after 80 min under illumination with 365 nm light, although about 10% of the ammonia was converted into undesirable NO2 and NO. Various intermediates, such as NO2, -NH2, -NH and NO, were also identified in the Fourier transform infrared (FT-IR) spectra. From the gas chromatography (GC), FT-IR and GC/mass spectroscopy (GC/MS) analyses, partially oxidized NO and NO2 were found to predominate over V-TiO2 and pure TiO2, respectively, while both molecules were reduced over Pt/V-TiO2.

• Clean Technology
• /
• v.19 no.1
• /
• pp.22-29
• /
• 2013

A comparison of photo-efficiency on dye-sensitized solar cells (DSCs) assembled by using $TiO_2$ materials with different structures and crystallite sizes were investigated in this study. The size and structure of $TiO_2$ have been controlled by pHs and calcination temperatures using solvothermal and sol-gel methods, respectively. Six types of $TiO_2$ samples are obtained; 8.9, 12.8, and 20.2 nm sized $TiO_2$ particles, and the other types using sol-gel method were anatase-rutile mixtures on the structure. The highest photo-efficiency which is remarkable result reached to 8.6% over DSC assembled by anatase $TiO_2$ with 20.2 nm particle size.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.8
• /
• pp.2295-2298
• /
• 2014

To effectively destruct 2-chlorophenol, a representative sterile preservative, nanometer-sized Mn (0.5, 1.0, 3.0 mol %)-incorporated $TiO_2$ powders were synthesized by a solvothermal method. XRD result demonstrated that the Mn ingredients were perfectly inserted into $TiO_2$ framework. The Mn-$TiO_2$ particles exhibited an anatase structure with a particle size of below 20 nm. The absorbance was shifted to the higher wavelength on Mn-$TiO_2$ compared to that of $TiO_2$. Otherwise, the PL intensities which has a close relationship for recombination between holes and electrons significantly decreased on Mn-$TiO_2$. The photodecomposition for 2-chlorophenol in a liquid system was enhanced over Mn-doped $TiO_2$ compared with pure $TiO_2$: 2-chlorophenol of 50 ppm was completely decomposed after 12 h when 1.0 mol % Mn-$TiO_2$ was used. Consequently, the core of this paper is as follows. introducing Mn into $TiO_2$ framework reduced the band-gap, moreover, it played as an electron capture resulted to lower recombination between electrons and holes during photocatalytic reaction for removal of 2-cholophenol.

• Korean Journal of Materials Research
• /
• v.12 no.12
• /
• pp.941-946
• /
• 2002

Both Cu and Cu-oxide nanopowders have great potential as conductive paste, solid lubricant, effective catalysts and super conducting materials because of their unique properties compared with those of commercial micro-sized ones. In this study, Cu and Cu-oxide nanopowders were prepared by Pulsed Wire Evaporation (PWE) method which has been very useful for producing nanometer-sized metal, alloy and ceramic powders. In this process, the metal wire is explosively converted into ultrafine particles under high electric pulse current (between $10^4$ and $10^{ 6}$ $A/mm^2$) within a micro second time. To prevent full oxidations of Cu powder, the surface of powder has been slightly passivated with thin CuO layer. X-ray diffraction analysis has shown that pure Cu nanopowders were obtained at $N_2$ atmosphere. As the oxygen partial pressure increased in $N_2$ atmosphere, the gradual phase transformation occurred from Cu to $Cu_2$O and finally CuO nanopowders. The spherical Cu nanopowders had a uniform size distribution of about 100nm in diameter. The Cu-oxide nanopowders were less than 70nm with sphere-like shape and their mean particle size was 54nm. Smaller size of Cu-oxide nanopowders compared with that of the Cu nanopowders results from the secondary explosion of Cu nanopowders at oxygen atmosphere. Thin passivated oxygen layer on the Cu surface has been proved by XPS and HRPD.

• Macromolecular Research
• /
• v.12 no.6
• /
• pp.598-603
• /
• 2004

Cellulose nitrate (CN) composite membranes, containing cobalt porphyrin (CoP) complexes self-assembled within nanometer-sized rhenium clusters (ReCoP), have been prepared and their oxygen and nitrogen gas perme­abilities were analyzed. The solubility of ReCoP and the characteristics of the corresponding composite membranes were analyzed using a Cahn microbalance, FT-IR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry. The nitrogen permeability through the CN composite membranes decreased upon addition of ReCoP and CoP, which implies that the presence of these oxygen carrier complexes affects the structure of the polymer matrix. The oxygen permeability through the composite membranes containing small quantities of ReCoP decreased, but it increased upon increasing the concentration. The oxygen gas transport was affected by the matrix at low ReCoP concentrations, but higher concentrations of ReCoP increased the oxygen permeability as a result of its reversible and specific interactions with oxygen, effectively realizing ReCoP carrier-mediated oxygen transport.