Highly efficient synthesis of aldehydes by layer by layer multi-walled carbon nanotubes (MWCNTs) laccase mediator systems

Laccase from Trametes versicolor was immobilized on multi-walled carbon nanotubes MWCNTs) applyingtwo different strategies based on the layer by layer (LbL) procedure: (i) the direct adsorption on pristineMWCNTs followed by coating with PDDA and a second layer of enzyme (catalyst II), and (ii) the adsorptionon modified MWCNTs and PDDA (catalyst III). The new catalysts were characterized by microscopy (SEM,AFM and HRTEM) and electrochemical (cyclic voltammograms) analyses, confirming the deposition ofenzyme and polyelectrolyte layers, and the role of polyelectrolyte to enhance the electron transfer rate.Kinetic, storage and reusability data showed a good activity and higher stability than the system obtainedby simple deposition of laccase on MWCNTs (catalyst I). Catalysts I–III were applied in the selective andefficient synthesis of aldehydes in the presence of redox mediators (TEMPO and ABTS). Catalyst II andTEMPO were more active (quantitative conversion of substrate and yield of prod