Pseudomorphic Transformation\nin Nanostructured Thiophene-Based\nMaterials

This study reveals the capability of nanostructured organic\nmaterials\nto undergo pseudomorphic transformations, a ubiquitous phenomenon\noccurring in the mineral kingdom that involves the replacement of\na mineral phase with a new one while retaining the original shape\nand volume. Specifically, it is demonstrated that the postoxidation\nprocess induced by HOF·CH<sub>3</sub>CN on preformed thiophene-based\n1D nanostructures preserves their macro/microscopic morphology while\nremarkably altering their electro-optical properties by forming a\nnew oxygenated phase. Experimental evidence proves that this transformation\nproceeds via an interface-coupled dissolution–precipitation\nmechanism, leading to the growth of a porous oxidized shell that varies\nin thickness with exposure time, enveloping the pristine smooth core.\nThe oxygenated species exhibits stronger electron-acceptor characteristics\nthan the core material, promoting charge transfer state formation,\nas confirmed by microspectroscopy and DFT calculations. This enables\n(i) precise modulation of the nanostructure’s surface potential,\nallowing for the formation of entirely organic heterojunctions with\nprecise spatial resolution via wet chemical processing; (ii) effective\ndoping of the nanostructure, resulting in a strong change of the conductivity\ntemperature dependence and a switch between a low and high conduction\nstate depending on the applied bias. Overall, this work showcases\nan approach to engineering “impossible” composite architectures\nwith pre-established morphology and tailored chemical-physical properties.