Immobilization of TiO2nanoparticles onto paper modification through bioconjugation

Abstract

TiO₂ is commonly used as a brightening agent for paper, but may also be used on paper as a photocatalyst. The TiO₂ aggregates that typically form in/on paper are inefficient both for brightening or photooxidation. We describe, for the first time, the preparation of homogeneously distributed, non-aggregated TiO₂ particles on cellulose fibers using explicit bioconjugation with the fusion protein of CBM2a-Strep-tag II/streptavidin/biotinylated TiO₂. The maximum absorption of proteins and nanoparticles onto paper were determined to be ca. 6.22 × 10⁻² nm⁻² for CBM2a-Strep-tag II, 1.93 × 10⁻² nm⁻² for streptavidin, and 58 µm⁻² for TiO₂nanoparticles, respectively. The efficiency of photocatalysis of the TiO₂-containing paper prepared by this bioconjugation method was demonstrated by the decolorization of UV sensitive dye (reactive black dye 5). Immobilized TiO₂ efficiently degraded the dye within about 10 hours. Only after extensive photolysis (12 hours) did sufficient degradation of the bioconjugating linkers occur such that free TiO₂ particles and cellulose fibers were found in the supernatant. These experiments demonstrate that bioconjugation of TiO₂ to paper leads to an effective, supported photocatalyst system.