Photoconductivity of complexes of chrysotile with tetra (4-sulfonatophenyl) porphyrins created via ionic self-assembly

Tetrakis(4-sulfonatophenyl) porphine (TPPS4) molecules form complexes with chrysotile nanotubes in a chloroform-methanol solvent; the self-assembly is driven by Coulombic attractions. The UV/vis absorption spectrum indicates J-aggregation. In AFM, the complexes appear as straight, long tubes when deposited onto oxidized silicon substrates. Preliminary experiments conducted in a dry nitrogen atmosphere (0.2% oxygen concentration) show that the aggregates are photoconductive. When illuminated for long periods at 428 nm, the photoconductivity grows slowly, and there is also a growth of persistent photoconductivity. These observations are similar to those for nanorods self-assembled from TPPS4 (without chrysotile),2 though the current levels are much lower in the chrysotile complexes.