Direct evidence of inter-molecular vibrations by THz spectroscopy

Nagai, Naoto; Kumazawa, Ryoichi; Fukasawa, Ryoichi

doi:10.1016/j.cplett.2005.08.023

Cited by 59 publications

(35 citation statements)

References 10 publications

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“…Likewise, Δκ is described as Equation (4) The difference between calculated and measured Δn 0.4 may be attributed to free and bound water in the specimen because THz radiation is sensitive to both water states [18][19][20][21][22][23][24][25][26]. Since amine cured EP resins have some hydrophilic groups such as hydroxyl groups and amine groups, water becomes bound to such groups to some extent.…”

Section: Discussionmentioning

confidence: 99%

“…The main advantages of THz-TDS for NDT studies are the high penetration of THz electromagnetic waves into polymers [13][14][15][16][17][18], high sensitivity to the inter/intra molecular vibrations (especially for water) [18][19][20][21][22][23][24][25][26], and ability to estimate the materials dielectric properties without direct contact [27][28][29]. The THz spectra of various thermoplastics [13][14][15] and thermosets [16,17] measured by THz-TDS were reported.…”

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confidence: 99%

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Non-destructive evaluation by terahertz spectroscopy for penetration of acid solutions into epoxy resin

Kusano¹,

Kubouchi²,

Bulgarevich³

et al. 2016

Express Polym. Lett.

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Abstract. Epoxy resins are used as high-performance thermosetting linings to protect substrates under corrosive environments. However, in a severe corrosive chemical solution, such protective layers may degrade with long time due to penetrations of solvent and solute molecules into resin network. In this regard, the terahertz time-domain spectroscopy (THz-TDS) is a promising tool for non-destructive evaluation of the penetrant amounts due to high transparency of such plastic materials and high sensitivity to the molecular vibrations in terahertz spectral range. In this work, the complex refractive indexes n and κ of epoxy specimens were measured after immersion into sulfuric acid solutions and compared with penetrated mass fractions of water and acid ions. It was found that n and κ depended linearly with water and sulfuric acid mass fraction in specimens, and κ of sulfuric acid immersed specimens was lager at higher frequency. While the calculated Δκ agreed well with THz-TDS measurement by THz-TDS, the calculated Δn was higher than the measurement. The difference may be attributed to the water and sulfuric states in the specimen.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Non-destructive evaluation by terahertz spectroscopy for penetration of acid solutions into epoxy resin

Kusano¹,

Kubouchi²,

Bulgarevich³

et al. 2016

Express Polym. Lett.

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“…Using this convenient room-temperature technique, noncovalent interactions between several smalland medium-sized molecules have been investigated, including nucleobases and nucleosides, [2][3][4] short-chain polypeptides, [5] cystine and glutathione, [6] retinal, [7] and saccharides. [8] Chen et al [9] and Nagai et al [10] could clearly distinguish between intramolecular and intermolecular modes by comparing crystalline structures and solvated molecules. Furthermore, it was shown that different isomers [7] as well as diverse crystalline forms [11] show distinctively different terahertz spectra.…”

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confidence: 98%

Probing Noncovalent Interactions in Biomolecular Crystals with Terahertz Spectroscopy

et al. 2008

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The far-infrared vibrational spectra of molecular crystals are dominated by intramolecular (internal) modes, which are also present in the isolated molecule, and noncovalent intermolecular modes, which arise from the interaction of the nearest neighbours (external modes). Conceptually this has long been understood and early experiments [1] using Fourier transform infrared (FTIR) spectroscopy confirmed the existence of a rich vibrational spectrum in polypeptides in the low-energy region. Yet, the assignment of the experimentally observed peaks in the low-energy region is often unsatisfying. Recently, the advent of terahertz time-domain spectroscopy (THz TDS) has revitalized the field. Using this convenient room-temperature technique, noncovalent interactions between several smalland medium-sized molecules have been investigated, including nucleobases and nucleosides, [2][3][4] short-chain polypeptides, [5] cystine and glutathione, [6] retinal, [7] and saccharides.

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“…1, in the ZDDP-Russia150 system, the concentration dependence of α follows the Beer's law in the concentration range from 0.18% to 6.78%. The intensity changes of molecular interaction at THz frequency region are thought of as peak shifts in intramolecular vibrations and/or the generation and disappearance of the peaks in direct intermolecular vibrations [12] . Thus, the peak shift in our case is due to the intramolecular vibrations of alkanes and aromatics in LBOs.…”

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confidence: 99%

Diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate content in lube base oils in terahertz regime

Tian¹,

Zhao²,

Zhou³

et al. 2011

中国光学快报

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We investigate the diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate (ZDDP) mixed with lube base oil (LBO) at different concentrations using terahertz time-domain spectroscopy (THz-TDS). When the concentration exceeds 6.78%, the characteristic absorption peaks exhibit significantly shift, and the absorption coefficient peak value is nonlinear against concentration. Moreover, the absorption coefficients of mixed samples follow the Beer's law at a concentration below 6.78%. The quantitative analysis enables a strategy for monitoring the formulation of lubricating oil in real time.OCIS codes: 070.4340, 160.4760, 190.4400, 300.6495. doi: 10.3788/COL201109.110010. Zinc dialkyldithiophosphate (ZDDP), as a multifunctional additive and inhibitor in petroleum industry, works mainly as antiwear, antioxidant, and anticorrosion agent [1,2] . ZDDP mixed with lube base oils (LBOs) has been used to study the effect of concentration on lubrication boundary and tribological properties [3] . The concentration of ZDDP in LBOs plays a crucial role in formulation, which is a balance of many different aspects of performance. Lubricating formulation generally results from a molecular diffusion mechanism due to the relative motion of molecules. Molecular diffusion in a steady-state and nonequilibrium system is divided into molecular motion and interaction. Molecular motion, containing the electronic motion, molecular vibration, and molecular rotation, is complicated and multibody. The intermolecular and intramolecular modes of ZDDP and LBO determine the ability of the reactants to approach each other and products to separate from each other. The intermolecular and intramolecular interactions often have their characteristic frequencies in the region lower than 100 cm −1 . Two major strategies can be used to investigate lowfrequency diffusion between ZDDP and LBO. Femtosecond optical Kerr-effect (OKE) spectroscopy has been used over past decades to investigate molecular motion in liquids and liquid mixtures [4] . The second technique is terahertz time-domain spectroscopy (THz-TDS) [5,6] , which is a promising and nondestructive analysis method for petroleum products. A unique attribute of THz-TDS is its ability to sensitively measure the induced molecular dipole moments of many petroleum products. Furthermore, the low photon energy of radiation allows propagation through flammable liquids without any danger of combustion. The past few years have witnessed a remarkable effort in employing THz-TDS for investigating the properties of petroleum products, including gasoline, diesel, lubricating oil, lube base oil, water-oil complexes, and organic solvents [7−9] . The absorption spectra of petroleum products show collective modes in the THz region.In this letter, we described the interaction between ZDDP and LBO using THz-TDS. First, we measured the THz-TDS of polar liquid of ZDDP at different concentrations in LBO from Russia and calculated their absorption coefficients. We then investigated the usefulness of...

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Direct evidence of inter-molecular vibrations by THz spectroscopy

Cited by 59 publications

References 10 publications

Non-destructive evaluation by terahertz spectroscopy for penetration of acid solutions into epoxy resin

Non-destructive evaluation by terahertz spectroscopy for penetration of acid solutions into epoxy resin

Probing Noncovalent Interactions in Biomolecular Crystals with Terahertz Spectroscopy

Diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate content in lube base oils in terahertz regime

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