Fig. 44.

Schematic diagram illustrating the fabrication of sensing layers on QCM. (a) ESN deposition of fibrous membranes onto the electrode of QCM. (b) Surface modification of NFN with diluted PEI solutions. (c) Illustration of PEI/PA-6 NFN on gold electrode and the reaction mechanism between formaldehyde and PEI. (d) Typical FE-SEM image of PA-6 NFN membranes. FE-SEM images of PA-6 NFN (e) and (g) PS fibrous membranes and their corresponding samples modified with PEI: (f) PEI/PA-6 and (h) PEI/PS. Reprinted with permission from [27]. © 2011 Royal Society of Chemistry.