Terahertz Time-domain Spectra of Aromatic Carboxylic Acids Incorporated in Nano-sized Pores of Mesoporous Silicate

NTT Basic Research Laboratories, Atsugi, Kanagawa, Japan.
Analytical Sciences (Impact Factor: 1.39). 08/2007; 23(7):803-7. DOI: 10.2116/analsci.23.803
Source: PubMed


Terahertz time-domain spectroscopy (THz-TDS) is used to study the intra- and intermolecular vibrational modes of aromatic carboxylic acids, for example, o-phthalic acid, benzoic acid, and salicylic acid, which form either intra- or intermolecular hydrogen bond(s) in different ways. Incorporating the target molecules in nano-sized spaces in mesoporous silicate (SBA-16) is found to be effective for the separate detection of intramolecular hydrogen bonding modes and intermolecular modes. The results are supported by an analysis of the differences in the peak shifts, which depend on temperature, caused by the different nature of the THz absorption. Raman spectra revealed that incorporating the molecules in the nano-sized pores of SBA-16 slightly changes the molecular structures. In the future, THz-TDS using nanoporous materials will be used to analyze the intra- and intermolecular vibrational modes of molecules with larger hydrogen bonding networks such as proteins or DNA.

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    • "It has been known for some time that the resonant frequencies of these molecular networks are in the THz range, which is one of the very important targets to be revealed by THz spectroscopy and imaging techniques. THz spectroscopy is a powerful tool for identifying inter-molecular hydrogen bonds in biological samples, such as organic acids [4], amino acids [5], [6], sugars [7], pharmaceuticals [8], polypeptides [9], [10], DNA [11], [12] proteins [13], and cancer cells [14], [15]. Amino acids and pharmaceuticals have hydrogen bonds, which show several peaks in THz spectra and make quantitative analyses possible [16], [17]. "
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    ABSTRACT: THz spectroscopy is advantageous in analytical chemistry because it can detect and identify intermolecular interactions in chemical compounds, such as hydrogen bonds and hydrations, and molecular networks. Recent advances in THz components, such as ultrashort pulsed lasers and photoconductive antennas, have improved the sensitivity of THz time-domain (TDS) spectroscopy and have made the THz chemical imaging possible. THz chemical imaging can reveal hydrogen bond distributions and will be a very powerful tool in biology, pharmacology, and life sciences. THz-TDS is also promising for the quantitative chemical analysis and detection of molecules and clusters in nanospace and ice.
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    • "On the other hand, Ueno et al. [73] incorporated aromatic carboxylic acid molecules in SBA-16 and Sujandi et al. [74] studied chloropropyl-functionalized mesoporous silica with cage-type cubic Im3m phases. "
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    ABSTRACT: The aim of this article is to review current knowledge related to the synthesis and characterization of sol gel-derived SBA-16 mesoporous silicas, as well as a review of the state of the art in this issue, to take stock of knowledge about current and future applications. The ease of the method of preparation, the orderly structure, size and shape of their pores and control, all these achievable through simple changes in the method of synthesis, makes SBA-16 a very versatile material, potentially applicable in many areas of science and molecular engineering of materials.
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    ABSTRACT: Recent progress in analytical terahertz (THz) spectroscopy is reviewed with illustrative examples showing that it is an effective method for detecting and identifying intermolecular interactions in chemical compounds, such as hydrogen bonds. The unique and characteristic properties of THz waves, their significance to both science and industry, and the bases of one of the successful fields of analytical THz spectroscopy, namely THz time-domain spectroscopy and THz imaging for chemical analysis, are described. Preliminary quantitative studies are presented to show the potential of THz spectroscopy for the detection and identification of intermolecular hydrogen bonds in unknown mixture samples. The selective detection of intramolecular hydrogen bonds and the detection of intramolecular interactions in ice are also introduced. Some brief remarks are provided on future developments, the main issues, and the prospects for analytical THz spectroscopy.
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