Fig. 1: Nanofluidic diodes functionalized with Azo-NH2 exhibit bidirectional rectification behavior.
From: A universal tunable nanofluidic diode via photoresponsive host–guest interactions
a I–V curves of the single asymmetrical nanochannel modified with Azo-NH2 under different pH conditions, exhibiting bidirectional rectification depending on the pH: a backward rectification is observed below pH 4, whereas a forward rectification is observed above pH 7. b Schematic illustration of the bidirectional rectification behavior (blue circle: -COOH, red circle: Azo-NH2). The -COOH groups and modified -NH2 groups on the side of the channel surface act as pH-responsive functional groups, and their protonation or deprotonation results in a sensitive and reversible pH-responsive device. c The contour plot of the pR value at asymmetric pH values (pHTip = 2, 3, 5, 7, 9, 11; pHBase = 2, 3, 5, 7, 9, 11)
