BOOK OF ABSTRACTS 39 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Monday, 24 August 2026 / Hall B+C Analysis and Characterization Em. = 290/310 nm, and the intensity of fluorescence maximum at Ex./Em. = 495/575nm, which was also observed in the blank sample, increased. This increase was also observed when the complex was formed with other organic substances even without fluorescent structure. Fluorescence maxima close to this Ex./Em. wavelength were also typically seen in SPF-EEM spectra of soils [1,2]. On the other hand, in the case of the complex of kaolinite or muscovite with an organic substance, the increase in the fluorescence maximum intensity that was originally observed in the blank sample was not significant. Even organic substances that originally do not have a fluorescent structure can emit new fluorescence when they are concentrated or when they form aggregates, which is called clustering-triggered emission (CTE) [4]. The fluorescence maximum at Ex./Em. = 495/575nm observed in this study may be caused by the specific arrangement of functional groups in the structure of clay minerals regardless of the type of organic matter. References 1. Y. Nakaya, S. Nakashima, M. Moriizumi, M. Oguchi, S. Kashiwagi, N. Naka, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 233(5) (2020) 118188. 2. Y. Nakaya, T. Hirose, R. Tamori, N. Fujitake, S. Nakashima, H. Yamamura, H. Satoh, Environmental Research 279(2) (2025) 121900. 3. Y. Nakaya, T. Hirose, R. Tamori, N. Fujitake, S. Nakashima, H. Yamamura, H. Satoh, Analytical Sciences 42 (2026) 131-140. 4. P. Liao, J. Huang, Y. Yan, B.Z. Tang, Materials Chemistry Frontiers 5 (2021), 6693-6717. Acknowledgement This work was supported by JSPS KAKENHI (grant number 24K21328) and the JSPS Program for Forming Japan’s Peak Research Universities (J-PEAKS) (grant number JPJS00420230001). The authors thank Kunimine Industries Co., Ltd. for supplying montmorillonite, Kunipia-F.
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