Chemically assembled heterojunctions of SnO2 nanorods with TiO2 nanoparticles via "click" chemistry

• Published in: Journal of materials chemistry Vol. 22; no. 23; pp. 11561 - 11567
• Main Authors: Shah, Sohil, Benson, Michelle C, Bishop, Lee M, Huhn, Alex M, Ruther, Rose E, Yeager, Joseph C, Tan, Yizheng, Louis, Kacie M, Hamers, Robert J
• Format: Journal Article
• Language: English
• Published: 01.01.2012
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm31227a

SnO 2 is a promising material for photovoltaic and photocatalytic applications because it exhibits high electron mobility, its conduction band lies at a convenient energy to act as an electron acceptor, and it can be easily grown in a variety of different nanostructures including nanoparticles, nanorods, and nanosheets. However, strategies for surface functionalization of SnO 2 are much less well developed than alternative oxides. Here, we demonstrate the growth and subsequent chemical functionalization of SnO 2 nanorods to enable the chemically directed assembly of SnO 2 nanorod-TiO 2 nanoparticle heterojunctions, and we characterize the charge-transfer properties using time-resolved surface photovoltage measurements. Vertically aligned SnO 2 nanorods were grown via a high-pressure chemical synthesis method. The SnO 2 nanorods were square in cross-section, exposing sidewalls consisting of {110}-type crystal planes. Functionalization via photochemical grafting with butenol yielded nanorods terminated with a high density of -OH groups that were converted to azide groups. The azide groups were linked with alkyne-modified TiO 2 nanoparticles via the Cu( i )-catalyzed Azide-Alkyne Cycloaddition (CuAAC) reaction, a form of "click" chemistry, thereby covalently grafting the TiO 2 nanoparticles to the SnO 2 nanorods. Time-resolved surface photovoltage measurements of the resulting adducts showed that the covalent bonding of TiO 2 nanoparticles to the SnO 2 nanorods enhances the interfacial charge transfer compared to the unmodified SnO 2 nanorods, leading to an increased accumulation of holes at the surface. Use of the Cu-catalyzed azide-alkyne cycloaddition "click" reaction enables chemical assembly of photoactive heterojunctions of SnO 2 nanorods and TiO 2 nanoparticles with enhanced charge transfer.