• Smart Structures and Systems
• /
• v.8 no.5
• /
• pp.471-486
• /
• 2011

Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite's strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.

• Applied Chemistry for Engineering
• /
• v.5 no.1
• /
• pp.37-43
• /
• 1994

Mononitrotoluenes were reduced to aminotoluenes using porphyrin as a catalyst in the presence of several types of reductants including hydrogen sulfide and 1, 4-dithiothreitol(DTT). Intermediates and final products of porphyrin-catalyzed reduction of mononitrotoluenes were identified and a pathway for the reduction of the nitro group to the corresponding amino group was proposed. The optimum pH for the reduction was determined. The catalytic activity of the porphyrin was confirmed by UV/VIS absorption spectra and basic kinetics of porphyrin-catalyzed reduction were studied. Of several types of reductants tested, DTT sodium hydrosulfite, and hydrogen sulfide were seen to give significant reduction of nitrobodies. When hydrogen sulfide was used as a reductant hydrogen sulfide and nitrotoluenes were removed simultaneously.

• Applied Chemistry for Engineering
• /
• v.20 no.1
• /
• pp.75-79
• /
• 2009

The ratio of aniline dimer (p-aminodiphenylamine), which is a nucleation site of chain growth in a chemical polymerization of aniline monomer, to aniline monomer was controlled to synthesize polyaniline with the molecular weight ($M_w$) between 10000 and 20000 g/mol. The result of OCP measurement showed that the reaction rate of polymerization was increased as the mole ratio of dimer was increased. The increase in the molar ratio of dimer resulted in the shift of absorption wavelength of polyaniline to the short wavelength region on measurement of UV/Vis and the decrease of molecular weight on the measurement of GPC.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.1
• /
• pp.169-174
• /
• 2011

The synthesis of new pyrazolyl and cyclopropyl derivatives of purpurin-18 methyl ester and purpurin-18-N-butylimide 1a, 1b, 2a, 2b and 8 is described. The new compounds were characterized by NMR, UV-vis spectroscopy and mass spectrometry. UV-vis spectra of the new compounds showed long wavelength absorption of ranges 692 - 708 nm ($\lambda_{max}$). Photodynamic effects of the chlorin derivatives 1a, 1b, 2a and 2b were investigated by WST-1 assay in A549 cells, and showed good photodynamic activities with high photocytotoxicity and low cytotoxicity in the dark. In comparison between pyrazolyl and cyclopropyl derivatives, purpurin-18 methyl ester compounds 1a and 1b showed comparable photocytotoxicity result of the cell viabilities, otherwise, pyrazolyl derivative of purpurin-18-N-butylimide 2a showed better cell viabilities than those of cyclopropyl derivative 2b. And cyclopropyl derivative of purpurin-18-N-butylimide 2b showed higher dark cytotoxicity than that of others.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.11
• /
• pp.3755-3760
• /
• 2012

Single crystals of lithium potassium phthalate (LiKP) were successfully grown from aqueous solution by solvent evaporation technique. The grown crystals were characterized by single crystal X-ray diffraction. The lithium potassium phthalate $C_{16}\;H_{12}\;K\;Li_3\;O_{11}$ belongs to triclinic system with the following unit-cell dimensions at 298(2) K;$a=7.405(5){\AA}$;$b=9.878(5){\AA}$;$c=13.396(5){\AA}$;${\alpha}=71.778(5)^{\circ}$;${\beta}=87.300(5)^{\circ}$;${\gamma}=85.405(5)^{\circ}$; having a space group P1. Mass spectrometric analysis provides the molecular weight of the compound and possible ways of fragmentations occurs in the compound. Thermal stability of the crystal was also studied by both simultaneous TGA/DTA analyses. The UV-Vis-NIR spectrum shows a good transparency in the whole of Visible and as well as in the near IR range. Third order nonlinear optical studies have also been studied by Z-scan technique. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also estimated. The results have been discussed in detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.153-153
• /
• 2008

Practical application of single-walled carbon nanotubes (SWCNTs) qualified as a promising material has been limited by either poor dispersion or their insolubility in aqueous or organic media due to formation of bundling by relatively high surface energy. Thus, major attention to overcome this issue has been paid at surface modification of CNTs by functionalization, but this introduces defects to the sidewall of CNTs, consequently perturbing the inherent electronic and optical properties. Therefore, using surfactants is a general approach to disperse SWCNTs with lower damages by which bundled nanotubes could be dispersed up to the level of individuals or small bundles. Here, we have investigated various surfactants for their efficiency in dissolving purified SWCNTs produced by arc discharge in deionized water. To compare the surfactants respectively, we have determined the least amount of each surfactant to suspend the nanotubes under optimized experimental conditions(CNT amount, sonication power, and centrifugation speed, etc.) set on the basis of the most common surfactant (sodium dodecyl sulfate, SDS) and discussed the qualitative and quantitative characterization of SWCNT dispersions by UV-Vis absorption spectroscopy. Quantitative aspect about nanotube dispersion was that in particular N-methyl-2-pyrrolidone (NMP) and sodium dodecylbenzene sulfonate (NaDDBS) were found to be effective in dispersing individual tubes.

• Korean Journal of Materials Research
• /
• v.24 no.1
• /
• pp.33-36
• /
• 2014

This study was aimed at synthesizing and characterizing cerium-doped titania. Cerium-doped anatase titania powders were prepared by sol-gel process, with ammonium (IV) nitrate and titanium (IV) butoxide as the raw materials. The characteristics of pure $TiO_2$ and cerium-doped $TiO_2$ were investigated by XRD, TG/DTA, FE-SEM, and UV-vis spectroscopy. The results of this study show that anatase type of $TiO_2$ was obtained in as-prepared and calcined $TiO_2$ and Ce-$TiO_2$ powder. A DTA curve was also observed as the crystallization temperature decreased with increasing cerium contents. We found that the crystallite size of the obtained anatase particles decreased from 55 nm to 25 nm and the particle size decreased with increasing cerium contents. Moreover, UV-vis spectra showed that anatase titania powders with various cerium contents effectively extend the light absorption properties to the visible region.

• Journal of Electrochemical Science and Technology
• /
• v.15 no.2
• /
• pp.268-275
• /
• 2024

The study examined the electrogeneration of hypochlorite ions (ClO^-) via electrolysis of aqueous NaCl solutions using a dimensionally stable anode-type (DSA-type) electrode based on platinum and palladium oxides supported on titanium mesh (Ti/PtPd(10%)O_x). The electrogenerated ClO^- was quantified on the basis of the absorption band at 292 nm (A_λ = 292) of the UV-Vis spectrum. The effect of initial pH, concentration of NaCl, cell potential difference and electrolysis time were investigated in this study. The results showed that the electrolysis of aqueous NaCl solutions increases the solution pH up to high values (≥ 8.0) that favor the formation of ClO^- over chlorine or hypochlorous acid. The hypochlorite concentration increases significantly at pH values > 7.0 and shows a linear trend with increasing NaCl concentration and with increasing cell potential difference. When the cell potential and NaCl concentration are held constant, the maximum hypochlorite value during electrolysis depends on both the cell potential and NaCl concentration. The Ti/PtPd(10%)O_x anode favors the production of hypochlorite ions, making this anode a promising material for use in electrochemical oxidation of wastewater via an indirect mechanism.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.20 no.4
• /
• pp.371-382
• /
• 2022

Carbonates are inorganic ligands that are abundant in natural groundwater. They strongly influence radionuclide mobility by forming strong complexes, thereby increasing solubility and reducing soil absorption rates. We characterized the spectroscopic properties of Am(III)-carbonate species using UV-Vis absorption and time-resolved laser-induced fluorescence spectroscopy. The deconvoluted absorption spectra of aqueous Am(CO₃)₂^- and Am(CO₃)₃^3- species were identified at red-shifted positions with lower molar absorption coefficients compared to the absorption spectrum of aqua Am³⁺. The luminescence spectrum of Am(CO₃)₃^3- was red-shifted from 688 nm for Am³⁺ to 695 nm with enhanced intensity and an extended lifetime. Colloidal Am(III)-carbonate compounds exhibited absorption at approximately 506 nm but had non-luminescent properties. Slow formation of colloidal particles was monitored based on the absorption spectral changes over the sample aging time. The experimental results showed that the solubility of Am(III) in carbonate solutions was higher than the predicted values from the thermodynamic constants in OECD-NEA reviews. These results emphasize the importance of kinetic parameters as well as thermodynamic constants to predict radionuclide migration. The identified spectroscopic properties of Am(III)-carbonate species enable monitoring time-dependent species evolution in addition to determining the thermodynamics of Am(III) in carbonate systems.

• Corrosion Science and Technology
• /
• v.19 no.1
• /
• pp.16-22
• /
• 2020

It is important to realize that benzoate was intercalated into hydrotalcite (HTC-Bz) by the co-precipitation method. In this case, acrylic coating with 0.5 wt% HTC-Bz was deposited on carbon steel using the spin coating method. Next, the HTC-Bz structure was characterized by Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). In fact, an ultraviolet vision spectroscopy (UV-Vis) was used to determine the benzoate content in HTC-Bz, and the UV absorption ability of HTC-Bz. Using electrochemical techniques, water contact angle measurement, and thermal-gravimetric analysis, we compared the protective properties before and after QUV test, hydrophobicity and the thermal stability of acrylic coating containing HTC-Bz. The obtained results showed that HTC-Bz with a plate-like structure was successfully synthesized; benzoate was intercalated into the interlayer of hydrotalcite with a concentration of 28 wt%. Additionally, it was noted that HTC-Bz has an UV absorption peak at 225 nm. In conclusion, the addition of HTC-Bz enhanced the UV stability, hydrophobicity and the thermal stability of acrylic coating.