Tuning the Aggregates of Thiophene-based Trimers by Methyl Side-chain Engineering for Photocatalytic Hydrogen Evolution
Résumé
Organic π-conjugated semiconductors (OCSs) have recently emerged as a promising alternative to traditional inorganic materials for photocatalysis. However, the aggregation of OCSs in photocatalytic aqueous solution caused by self-assembly, which closely relates to the photocatalytic activity, has not yet been studied. Here, the relationship between the aggregation of 4,7-Bis(thiophen-2yl) benzothiadiazole (TBT) and the photocatalytic activity was systematically investigated by introducing 2 and varying the position of methyl side chains on the two peripheral thiophene units. Experimental and theoretical results indicated that the introduction of-CH3 group at the 3-position of TBT resulted in the smallest size and best crystallinity of aggregates compared to that of TBT, 4-and 5-positions. As a result, TBT-3 exhibited an excellent photocatalytic activity towards H2 evolution, ascribed to the shorten charge carrier transport distance and solid long-range order. These results suggest the important role of aggregation behavior of OCSs for efficient photocatalysis.
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