**4. Techniques to Probe the Redox Enzymes in Carbon Nanomaterials**

Although electrochemical investigations (e.g., rotating disk electrodes) coupled with computational simulations [66,76] and a theoretical analysis of current–potential curves [77,78] for an investigation into DET-type bioelectrocatalysis have been well studied during the past 10 years, techniques to directly probe the behavior of redox enzymes in carbon nanomaterials are still highly desired [79]. Several techniques, particularly a quartz crystal microbalance (QCM) and infrared (IR) spectroscopy, used to analyze the enzyme adsorption, conformation, and orientation of redox enzymes in carbon nanomaterials have been proposed and developed during the past decades.
