pH measurements using two kind of samples, namely zinc oxide (ZnO) nanorods of 300nm in diameter and 10µm in length grown on 2D macro-porous periodic structures (2DMPPS) and plane n-Si substrates and ZnO nanorods of 60nm in diameter and 500nm in length grown on the silver coated tip of glass capillary (D=0.7µm). We found that the sensitivity of ZnO nanorods increases with reductions in size from (35mV/pH for D=300nm and L=10µm) to (58mV/pH for D=50nm and L=1µm) using the site binding model. The potential difference for the ZnO nanorods electrode vs. Ag/AgCl electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si, as compared to plane n-Si, and had a sensitivity equal to 51.88mV/pH at 22oC for the ZnO on the capillary tip for pH (4-12) in buffer solutions. Vertically nanoelectrodes of this type can be applied to penetrate a single living cell without causing cell apoptosis
