Electrochemical sensing with carbon nanotubes

In this chapter we aim at reviewing the most relevant contributions in the development of electrochemical sensors and biosensors based on carbon nanotubes (CNTs). Particular attention will be focused on the different strategies to modified the electrodes for sensing application. First, we will discuss about the electrochemical properties of nanotubes, their peculiar physical-chemical features that make them very useful for sensing. For instance, CNTs have been incorporated in electrochemical sensors to decrease overpotential and to improve sensitivity. In addition, concerning biosensing, the use of nanotubes enhancing the electrochemical reactivity of important biomolecules by promoting the electron-transfer reactions of biomolecules with catalytic activity. Different ways of integrating nanotubes and electrodes will be presented: from a bulk modification to a more sensible surface one. After a survey of bulk modification strategies, we will show an in-depth study of the surface modification technique developing the random and oriented choice to modify the surface, especially focusing on the vertical alignment. A structured methodological point of view will be given in this latter section. We will review the state of the art of sensing and biosensing with CNTs. In the first part of this section we will present how CNTs modified electrodes can act as sensors without any further modification of their structure. In the latter we will first focalize the attention to the functionalization techniques required in order to make CNTs able to detect biological substrates. Therefore we will review how CNTs modified electrodes will detect biological species such as neurotransmitters, proteins, enzymes and proteins enhancing the detection limits obtained using other techniques. Finally a future perspectives section is provided in which we will analyze the possibility to integrate the CNTs electrochemical devices in microfluidic platforms in order to diminish the average dimensions of the substrates, to enhance the selectivity and other appreciable advantages.