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Polyphenols (catechins) are vital biomolecules in tea plants (Camellia sinensis), which are well-known as typical Al accumulators. However, the interaction between Al and catechin remains obscured. The objective of the present study was to investigate the effect of Al on the transformation of (+)-catechin. Solutions with OH/Al molar ratios of 2.5 (pH 5.5) and 3.0 (pH 7.0) prepared at Al/catechin molar ratios (R) of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 were aged for 7 and 30 days, respectively. The precipitates were collected and examined by wet chemistry, X-ray diffraction, transmission electron microscopy, electron spin resonance (ESR), cross-polarization magic angle (CPMAS) 13C nuclear magnetic resonance (13C NMR) analyses, and Fourier transformation infrared absorption spectrometry (FT-IR). The weight of the precipitates increased with increasing Al/catechin molar ratios and with prolonged aging. The molar ratios of Al/catechin in the precipitates increased with increasing initial Al/catechin molar ratios and were close to the initial solution Al/catechin molar ratios. The chemical analysis and spectroscopic studies indicated that Al was bonded with catechin, forming a 1:1 type complex. The reaction of crystalline catechin with Al resulted in the formation of X-ray noncrystalline precipitates. The solid-state CPMAS 13C NMR spectra of the precipitates show the change in chemical shifts of catechin as a result of catechin complexation with Al. The FT-IR spectra of the Al-catechin precipitates also show the loss of absorption bands of several functional groups compared with catechin. The FT-IR data substantiate this reasoning. The ESR spectra of the precipitates show a single symmetrical line devoid of any fine splitting, indicating the presence of free radicals of semiquinones, which are commonly present in humified materials.

The Al concentration in tea plants indeed increases catechin concentrations and plays an important role in the growth of tea plants.

Information on the nature, physicochemical properties, and environmental fate of nanoparticles is severely lacking.Zeohte A was used to demonstrate its structural transformation from well crystalline to short-range-ordered (SRO) particles, including nanoparticles with size fractions in the range of 450 to 2000, 100 to 450, 25 to 100, and 1 to 25 nm. The chemical properties of a zeolite are dependent on its framework structure, which is formed by connecting truncated octahedra (sodalite) through the simple double four rings (D4-R) with external linkage in each sodalite. With decreasing particle size, the T(Si, Al)-0 asymmetric and symmetric stretching vibrations shift:ed toward higher frequencies and the SI to Al molar ratio increased consistently from 1.8 to 5.2. The chemical shift of''Al and ^'Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra was related to its structural transformation from well crystalline to SRO particles, which was attributed to the loss of external linkage D4-R units in the structure. Comparing the various particle-size fractions (PSFs) showed significant differences in surface area, Si/Al molar ratio, morphology, crystallinity, framework structure, and surface atomic structure of nanoparticles from those of the bulk sample (i.e.,<2000 nm) before particle-size fractionations. Formation of these mosr reactive nanoparticles were caused by physicochemical weathering merits increasing attention with reference to their nature and properties, and their importance in ecosystem integrity.

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