Functionalization of MgZnO nanorod films and characterization by FTIR microscopic imaging

Metal organic chemical vapor deposition grown films consisting of Mg_xZn_1-xO (4% < x < 5%) nanorod arrays (MgZnO_nano) were functionalized with 11-azidoundecanoic acid (1). The MgZnO_nano was used instead of pure ZnO to take advantage of the etching resistance of the MgZnO_nano during the binding and subsequent sensing device fabrication processes of sensor devices, while the low Mg composition level ensures that selected ZnO properties useful for sensors development, such as piezoelectricity, are retained. Compound 1 was bound to the MgZnO_nano surface through the carboxylic acid group, leaving the azido group available for click chemistry and as a convenient infrared spectroscopy (IR) probe. The progress of the functionalization with 1 was characterized by FTIR microscopic imaging as a function of binding time, solvents employed, and MgZnO_nano morphology. Binding of 1 was most stable in solutions of 3-methoxypropionitrile (MPN), a non-protic polar solvent. This occurred first in μm-scale islands, then expanded to form a rather uniform layer after 22 h. Binding in alcohols resulted in less homogenous coverage, but the 1/MgZnO_nano films prepared from MPN were stable upon treatment with alcohols at room temperature. The binding behavior was significantly dependent on the surface morphology of MgZnO_nano. Graphical abstract The functionalization of MgZnO nanorod films with a click-ready linker and its dependence on bidning conditions and morphology has been studied by FTIR microscopic imaging using the azido group as the IR tag.