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RISS 인기검색어
- 검색키워드
- 저자 : Shinzawa, Hideyuki (검색결과 3 건)
- 무료
- 기관 내 무료
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Kim, Saetbyeol,Shinzawa, Hideyuki,Chung, Hoeil,Ozaki, Yukihiro The Royal Society of Chemistry 2015 The Analyst Vol.140 No.6
<P>A simple and effective strategy for improving the accuracy of the multivariate determination of polyethylene (PE) density using Raman spectroscopy has been demonstrated. This strategy is based on the possibility that varied polymeric structures of the PE samples, especially at a sub-zero temperature range, would enhance their spectral selectivity, thereby potentially improving the multivariate correlation with their pre-determined physical properties such as density. For the evaluation, Raman spectra were collected at regular intervals during continuous increase of the PE temperature from cryogenic to near room temperature. Then, using partial least squares (PLS) regression, calibration models were developed to correlate the Raman spectral features collected at each time period with the reference PE density values. Interestingly, the accuracy was improved when the temperature of the PE pellets was −35 °C, near the glass transition temperature (<I>T</I><SUB>g</SUB>). To explain the improved accuracy, a two-dimensional (2D) correlation analysis was employed to detail the spectral variation induced by temperature change. Diverse segmental chain motions (so called micro-Brownian motion) predominantly occurring in the amorphous section of the PEs around <I>T</I><SUB>g</SUB> greatly enhanced the spectral selectivity among PE samples. In addition, minor β-relaxation occurring around this temperature was an additional source of the enhanced spectral selectivity. In parallel, differential scanning calorimetry (DSC) curves of the samples were also examined to check the existence of the phase transitions.</P> <P>Graphic Abstract</P><P>A simple and effective strategy for improving the accuracy of the multivariate determination of polyethylene (PE) density using Raman spectroscopy has been demonstrated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4an02144d'> </P>
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Chang, Kyeol,Shinzawa, Hideyuki,Chung, Hoeil Academic Press 2018 Microchemical Journal Vol. No.
<P><B>Abstract</B></P> <P>When near-infrared (NIR) spectroscopy is employed to determine the concentrations of inorganic acids in etchant solutions, the perturbation of the water bands resulting from the interactions with these acids is the only information available for analysis, since inorganic acids do not directly absorb NIR radiation. The water bands perturbed by dissociated hydronium ions and respective anions of the acids are not highly component-specific; therefore, characterization of their different interactions with water is necessary to understand the results of the multivariate quantitative analysis. For this purpose, the variations in the water bands that occurred with the inclusion of HCl, H<SUB>2</SUB>SO<SUB>4</SUB>, H<SUB>3</SUB>PO<SUB>4</SUB>, and HNO<SUB>3</SUB> were initially examined with the aid of a two-dimensional (2D) correlation analysis. According to this analysis, components with higher acidity, such as HCl, perturbed the water hydrogen bonding network more strongly. Also, the interactions between each dissociated ionic species and water molecules were somewhat dissimilar. This dissimilarity enabled differentiation between the four acids, although the spectral specificity was not high owing to the absence of direct NIR absorption. The accuracy in the determination of concentrations was better for components with lower p<I>K</I> <SUB>a</SUB>s, such as HCl and H<SUB>2</SUB>SO<SUB>4</SUB>, owing to their stronger perturbation of the water bands. When multicomponent samples were measured, the resulting accuracies deteriorated due to the further degradation in component specificity. Acquisition of reproducible spectra and avoidance of model over-fitting are critical for reliable NIR analysis of these types of samples, as the analyte-induced spectral features are broad and rather specificity-insufficient.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Inorganic acids (HCl, H<SUB>2</SUB>SO<SUB>4</SUB>, H<SUB>3</SUB>PO<SUB>4</SUB>, and HNO<SUB>3</SUB>) do not directly absorb NIR radiation. </LI> <LI> Varied NIR water band by dissociated H<SUB>3</SUB>O<SUP>+</SUP> and anion was used to determine concentration. </LI> <LI> 2D correlation analysis revealed that interaction of each acid with water molecule differed. </LI> <LI> Acidity governing strength of acid-water interaction directly influenced on accuracy. </LI> <LI> Multiple PCs were required in PLS modeling since diverse acid-water interactions occurred. </LI> </UL> </P>
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Chan Park, Seok,Shinzawa, Hideyuki,Qian, Jue,Chung, Hoeil,Ozaki, Yukihiro,Arnold, Mark A. Royal Society of Chemistry 2011 The Analyst Vol.136 No.15
<P>A novel strategy is demonstrated to improve the accuracy for determination of polyethylene (PE) density using Raman spectroscopy by optimizing the temperature of sample measurement. Spectral features associated with the conformation change of the polymer induced by temperature may provide valuable information to quantify important polymer properties such as density. To evaluate possible existence of an optimal temperature providing improved quantitative accuracy, Raman spectra of PE pellets with different densities were collected at eight different temperatures from 30 to 100 °C at 10 °C intervals. Using the spectral datasets collected at each temperature, partial least squares (PLS) models were developed using the reference PE density values determined by a standard density gradient method at 23 °C. Interestingly, the most accurate determination of density was realized at 70 °C. Multiple perturbation two-dimensional (MP2D) correlation analysis and differential scanning calorimetry (DSC) were used to examine the origin of improved accuracy at 70 °C. From these analyses, the pre-melt behavior of the PE samples was identified below their melting temperatures. Structural variations induced at the pre-melt stages enhance Raman spectral selectivity among the samples, thereby providing more accurate determination of PE density. The MP2D correlation analysis revealed the unforeseen thermal behavior of PE samples and successfully explained the improved accuracy at 70 °C.</P> <P>Graphic Abstract</P><P>Optimization of Raman spectral collection temperature improved the accuracy for determination of polyethylene (PE) density. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1an15231a'> </P>
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