pH determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p -and n -type) and plane n -type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1-10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D=300 nm and L=10 μm, to 58 mV/pH for D=50 nm and L=1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n -Si substrate as compared to plane n -Si at room temperature for pH ranging from 4 to 12 in buffer and NaCl solutions.
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The authors gratefully acknowledge financial support from the Swedish Research Council.