Cyclic voltammetric methodwas used for the electrodeposion of Prussian blue on ITO electrode. The scanning range was set between 0.2 V and 1.2 V with a scan rate of 0.05 V/s. Before use,
the ITO electrode was ultrasonicated in ultrapure water for 5 min,
and then it was ultrasonicated in ethanol for 5 min.
The electrodeposition experiment was conducted with a freshly prepared solution containing 5.0 mmol/L FeCl3,
5.0 mmol/L K3Fe (CN) 6, and 10 mmol/L HCl.
After scanning for 10 cycles, a desirable PB filmwas obtained on the ITO plate. The fingerprint collection experiments
were conducted in a fume cupboard, where the relative humidity
and temperature were monitored and controlled. When the ITO
plate was connected to an electric power of an appropriate voltage,
the fingerprint images can be obtained by rolling the finger on the
ITO film.