Interfacial Charge-Transfer Transitions Between ZnO Nanoparticles and Aliphatic Thiols

Interfacial charge-transfer transitions (ICTTs) betweenorganiccompounds and inorganic semiconductors have recently gained increasinginterest for their potential applications in photoenergy conversionsand chemical/biological sensing. Particularly, ICTTs enable the absorptionof visible light even using colorless organic and inorganic substancesand efficient photoinduced charge separation between them. However,ICTTs have been limited to & pi;-conjugated molecules so far. Itis an important subject to expand the scope and utility of ICTTs toaliphatic compounds that are representative colorless organic compounds.Here, we report ICTTs between ZnO nanoparticles and alkanethiols.Despite the wide HOMO-LUMO gap of alkanethiols, the ZnO-alkanethiolcomplexes can absorb visible light due to ICTTs from the alkanethiolateadsorbates to ZnO. In addition, the absorption range is significantlyexpanded to longer wavelengths with increasing the alkyl-chain lengthand adsorption density via the interchain interactions.Our research opens up a novel way to the fundamental research andapplications of ICTTs with aliphatic compounds.