• 통합자연과학논문집
• /
• 제1권3호
• /
• pp.250-253
• /
• 2008

New issues arise as to surface characterization, quantification and interface formation. Surface and interface control of CdSe nanocrystal systems, one of the most studied and useful nanostructures. Semiconductor quantum dots (QDs) have been the subject of much interest for both fundamental reseach and technical applications in recent years, due mainly to their strong size dependent properties and excellent chemical processibility. In this dissertation, the synthesis of CdSe quantum dots were synthesized by pyrolysis of high-temperature organometallic reagents. In order to modify the size and quality of quantum dots, we controlled the growth temperature and the relative amount of precursors to be injected into the coordinating solvent. Moreover, an effective surface passivation of monodisperse nanocrystals was achieved by overcoating them with a higher-band-gap material. Synthesized CdSe quantum dots were studied to evaluate the optical, electronic and structural properties using UV-absorption, and photoluminescence measurement.

• Bulletin of the Korean Chemical Society
• /
• 제33권2호
• /
• pp.393-397
• /
• 2012

We report a new route to synthesize high quality zinc blende CdS and ZnS nanocrystals in noncoordinating solvent 1-octadecene, using dodecanethiol (DDT) molecules as both the sulfur source and surface capping ligands. Different reaction temperatures and Cd(Zn)/DDT molar ratios were tested to optimize the synthesis conditions. Absorption photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) pattern, and transmission electron microscopy (TEM) were used to characterize assynthesized nanocrystals. The narrow half width at the half-maximum on the long wavelength side of the firstexcitonic absorption peak and TEM images demonstrated nearly monodisperse size distributions of asprepared CdS, ZnS, and CdS/ZnS core/shell nanocrystals. Only trap emissions of the nanocrystals were detected when the amount of DDT was excessive, this came from the strong quenching effect of thiol groups on the nanocrystal surfaces. After overcoating with ZnS shells, band-gap emissions of CdS nanocrystals were partially recovered.

• Journal of Electrochemical Science and Technology
• /
• 제2권3호
• /
• pp.163-167
• /
• 2011

Nicotinamide adenine dinucleotide, $NAD^+$, and its reduced form, NADH, play important roles as coenzymes in many enzymatic reactions. Electrochemical methods for $NAD^+$ or NADH detection or generation are drawn attention because it can provide the simple and low cost platform with fairly good sensitivity. In this study, the polysiloxane viologen polymer/diaphorase/hydrophilic polyurethane (PSV/DI/HPU) modified electrodes were simply prepared and demonstrated for bio-electrocatalytic $NAD^+$ sensors. The electrodes were co-immobilized with diaphorase and polysiloxane viologen polymer as an electron mediator followed by the overcoating with HPU membrane. The mixture of the enzyme and the electron mediator was well stabilized within HPU membrane and exhibited good reversibility and stability. The sensitivity was 0.2 $nA{\cdot}{\mu}M^{-1}$ and the detection limit was 28 ${\mu}M$ with a response time of 50 s ($t_{90%}$). The capability for NADH sensor was also observed on the PSV/DI/HPU electrode.

• Corrosion Science and Technology
• /
• 제23권3호
• /
• pp.228-234
• /
• 2024

Zinc wiping is a phenomenon used to control zinc-coating thickness on steel substrate during hot dip galvanizing by equipment called air knife. Uniformity of zinc coating weight in length and width profile along with surface quality are most critical quality parameters of galvanized steel. Deviation from tolerance level of coating thickness causes issues like overcoating (excess consumption of costly zinc) or undercoating leading to rejections due to non-compliance of customer requirement. Main contributor of deviation from target coating weight is dynamic change in air knives equipment setup when thickness, width, and type of substrate changes. Additionally, cold coating measurement gauge measure coating weight after solidification but are installed down the line from air knife resulting in delayed feedback. This study presents a coating weight control model (Galvantage) predicting critical air knife parameters air pressure, knife distance from strip and line speed for coating control. A reverse engineering approach is adopted to design a predictive, prescriptive, and descriptive model recommending air knife setups that estimate air knife distance and expected coating weight in real time. Implementation of this model eliminates feedback lag experienced due to location of coating gauge and achieving setup without trial-error by operator.