A dual surface roughening scheme to improve the sensitivity of pH sensors based on hydrothermally grown nickel oxide nanosheets on KOH-etched Si substrates

A dual surface roughening scheme using KOH etched Si (100) substrate for the hydrothermal growth (HTG) of NiO nanosheets (NSs) to improve the pH sensing performance was demonstrated. Effects of the KOH etching condition and the HTG time for the synthesis of NSs on the pH sensing response were discussed. The NiO NSs sensing electrode (SE) based on the KOH-etched Si substrate shows a near perfect linearity of 0.999 and a near Nernstian response of 56.5 mV/pH. As compared with the NS type SE based on planar Si (53.64 mV/pH) and the SE based on sputtering NiO on the KOH etched Si substrate (52.87 mV/pH), an enhancement in pH sensitivity of 5.33% and 6.87% were achieved, respectively. It is attributed to the dual surface roughening scheme greatly increases the sensing area and the number of surface sites for ion adsorption.