Nanodiamond based sponges with entrapped enzyme: a novel electrochemical probe for hydrogen peroxide.

A "modular approach" has been demonstrated for the preparation of nanodiamond (ND) based sponges (NS) with entrapped enzyme (horseradish peroxidase, HRP) (ND-NS(HRP)) and utilization as an electrochemical probe for detection of hydrogen peroxide (H₂O₂). ND-NS comprises ND, porous poly(aniline)-poly(2-acrylamido 2-methyl propane sulfonic acid) (PANI-PAMPSA) network and entrapped HRP. Field emission scanning electron microscope image of ND-NS(HRP) reveals sponge like suprastructure comprising interconnected nanospheres with numerous openings/pinholes/cavities. The entrapped HRP in ND-NS exhibits effective direct electron transfer with an electron transfer rate constant of 1.85 s(-1). ND-NS(HRP) exhibited excellent bioelectrocatalytic reduction of hydrogen peroxide (H₂O₂) with a wide linear concentration range (1-45 mM), quick response (5s), high sensitivity (129.6 μAM(-1)) and low detection limit 59 μM (S/N=3).