Gold nanoparticle embedded hydrogel matrices as catalysts: Better dispersibility of nanoparticles in the gel matrix upon addition of N-bromosuccinimide leading to increased catalytic efficiency

A simple and convenient method for generating and immobilizing gold NPs into polyethylene glycol-polyurethane (PEGPU) matrices is presented. The gold NP immobilized PEGPU (Au NP-PEGPU) hydrogel matrices are easy to handle and can be used as catalysts. The efficiency, reusability and durability of the Au NP-PEGPU catalyst matrices were investigated using the reduction of 4-nitroaniline (4NA) to p-phenylenediamine (p-PDA) by sodium borohydride in the presence of the catalyst as a test reaction. The Au NPs in the PEGPU matrix got aggregated after 3 cycles of catalysis but dispersion could be regenerated by the addition of N-bromosuccinimide (NBS). After this regeneration process the Au NPs-PEGPU matrix showed excellent efficiency without any aggregation, leaching or degradation. The reusability of the catalyst for 28 cycles yielding a total turnover number of 3220 and turn over frequency of 0.152 s−1 is demonstrated.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Gold NPs were immobilized on polyethylene glycol-polyurethane (PEGPU) hydrogels. ► Such immobilized NPs can be used as catalysts. ► This is a generic method and can be extended to other metals as well. ► Gold NP catalyzed 4-nitroaniline reduction with NaBH4 was used as the test reaction. ► These catalysts are re-usable with appreciable turnover numbers and frequencies.