While single compound semiconductors were initially used for photocatalysis, combining
two compounds to form a heterojunction significantly increases the photocatalysis
performance. This review will outline how heterojunctions are superior, explain the
different heterostructure architectures assembled from nanoparticles, and discuss
the importance of achieving a large and quality contact in the junction, the heterojunction.
Reference is made to methods for increasing the charge carrier performance and reducing
recombination. Solution-based synthesis approaches, have been selected as the preferred
route of manufacture, for the low cost scalability, and ability to combine a larger
number of compounds. The main objective of this review article is to provide insight
to the range of chemical solution-based methods for forming chemically bonded junction
in nanoheterostructures for photocatalysis. Methods include chemical precipitation,
impregnation, chemical bath deposition, hot injection, solvothermal, photo-deposition,
electrochemical deposition, cation exchange and linker assisted assembly. The synthesis
of different photocatalysts is addressed for each synthesis method. Solution synthesis
is offered for coupling oxide semiconductors (i.e. TiO2, ZnO, WO3, Fe2O3, BiVO4) with
other oxides or metal chalcogenide quantum dots or metallic plasmonic nanoparticles.