Surface properties and dye loading behavior of Zn2SnO4 nanoparticles hydrothermally synthesized using different mineralizers

We present for the first time the influence of different mineralizers on the isoelectric point (IEP) of zinc stannate (Zn2SnO4) nanoparticles hydrothermally prepared using three different mineralizers, viz., Na2CO3, KOH and tert-butyl amine, and the effect of the IEPs on the dye loading behavior of Zn2SnO4 based photoelectrodes in dye sensitized solar cells (DSSCs). To produce highly crystalline, uniform sized Zn2SnO4 nanoparticles, hydrothermal processing parameters, such as reaction temperature, time, and the mineralizers used have been critically adjusted. The structural and morphological features of the as-synthesized Zn2SnO4 nanoparticles have been observed using both scanning and transmission electron microscopy. For the surface state characterization of shape- and size-controlled Zn2SnO4 nanoparticles, the IEPs of Zn2SnO4 surfaces were determined through zeta potential measurements. The IEPs were found to be 5.7, 7.4 and 8.1 for Zn2SnO4 nanoparticles formed using Na2CO3, KOH and tert-butyl amine, respectively, suggesting that the surface properties of Zn2SnO4 nanoparticles can be manipulated through the choice of the mineralizers used during the hydrothermal reaction. The amount of N719 dye loading on the surfaces of Zn2SnO4 electrodes having different IEPs was also evaluated. It was revealed that the higher the IEP, the higher the dye loading amount, which means that the IEP mainly affects the dye loading at the dye metal oxide interface. (C) 2011 Elsevier Inc. All rights reserved.