DIODE-LIKE PROPERTY OF PRUSSIAN BLUE FILMS CONTAINING CONCENTRATION GRADIENTS IN SERIAL MIXED-VALENT LAYERS

Solid-state diode-like current-voltage behavior is described for films of partially dried Prussian blue that contain serially arranged layer s of the mixed Valent states (FeFeIII)-Fe-III/(FeFeII)-Fe-III and (FeF eII)-Fe-III/(FeFeII)-Fe-II, that contain concentration gradients of th e two redox couples. The films were electrochemically grown and dispro portionated to prepare the mixed valent concentration gradient microst ructure. The diode-like behavior is based on the junction between the concentration gradients of the two redox couples, where the conductive reaction, (FeFeIII)-Fe-III + (FeFeII)-Fe-II --> 2Fe(III)Fe(II), occur s under forward bias, but its reverse is nonconductive under reverse v oltage bias. Unfortunately, apparently due to uncontrolled counterion migration, the junction is not stable under reverse bias, but the Prus sian blue microstructure does serve to illustrate the generality of th e principle that solid-state diode-like junctions can be assembled fro m two-couple redox materials.