Abstract
The authors produced novel radical-trapping sheets mainly from an environmentally friendly material, natural bentonite clay. Using two identical radical-trapping reagents, their effectiveness was confirmed for high performance in active radical trapping. Radical-trapping sheets were prepared using casting from dispersion pastes including clay and radical-trapping reagents. Purified natural bentonite clay that had been treated by quaternary ammonium ions was used along with one of two radical-trapping reagents, a spin-trap reagent (α-phenyl-N-tert-butyl nitrone; PBN) or a radical-scavenging reagent (4-Oxo-2, 2, 6, 6-tetramethylpiperidine 1-Oxyl; 4-Oxo-TEMPO), yielding 40-üm-thick flexible self-standing sheets. The sheets' radical-trapping performance was investigated using electron spin resonance (ESR). Results confirmed the radical-trapping sheets' capability for capturing active radical species that were observed neither in the original radical trap reagents nor in the clay. The PBN spin-trapping sheet trapped hydroxyl radicals and hydroxyethyl radicals. The sheet provides long-term stabilization of radical species. The trapped radicals remained active more than one month after the trapping experiment. The 4-Oxo-TEMPO radical scavenging sheet also trapped both radicals. New basal-plane reflection was observed in the X-ray diffraction (XRD) pattern of the radical-trapping sheets, suggesting intercalation of radical-trapping reagents between the clay platelet crystals. These radical-trapping sheets might be applicable to packaging, catalytic sheets for radical reactions, and environmental analyses.
