In situ and ex situ functionalization of nanostructured gallium oxy-hydroxide with a porphyrin dye

The surface attachment of a porphyrin dye to nanocrystalline GaOOH was performed using two routes of solution-based functionalization. The first method of functionalization utilized an in situ incorporation of dissolved porphyrin salt in solution during the microwave synthesis step. Additionally, synthesized GaOOH nanorods were mixed in porphyrin solution after the microwave process to make an ex situ GaOOH/TTP-PO-₃ . X-ray photoelectron spectroscopy confirmed the presence of expected surface species and provided evidence of increased surface coverage of TTP-PO₃ on GaOOH in the ex situ- GaOOH/TTP-PO₃ as compared to the in situ one. Size and morphology changes were investigated using SEM and, along with analysis of XRD, the in situ samples showed larger crystallite sizes. This was confirmed with PL due to the higher bandgap energy evident in the ex situ GaOOH/TTP-PO₃ compared to the in situ sample. A stability study was performed using fluorescence spectroscopy which indicated no leaching of porphyrin from the in situ GaOOH/TTP-PO₃ . However, porphyrin leaching was evident from the ex situ GaOOH/TTP-PO₃ sample. The stability of the in situ GaOOH/TTP-PO₃ makes it attractive for a number of interfacial applications. SCANNING 38:671-683, 2016. © 2016 Wiley Periodicals, Inc.