We investigated the structural and optical characteristics of nonpolar a-plane (11-20) GaN structure grown on TiO2 nanoparticles (NP)-coated r-plane sapphire by spin coating method. The surface morphology without any observable inverse pyramidal pits was observed by atomic force microscopy (AFM) measurement. Transmission electron microscopy (TEM) analysis revealed that the threading dislocations (TDs) and basal plane stacking faults (BSFs) densities were around 4.5 × 109 cm-2 and 3.1 × 10 5 cm-1, respectively. It was also found that the broadening of x-ray rocking curves (XRC) full width at a half maximum (FWHM) in Si-doped a-plane GaN on the TiO2 NP-coated r-plane sapphire was affected by the tilt and twist of mosaic crystals. The photoluminescence (PL) intensity of TiO2 NP-related MQWs sample at 295 K was approximately 18 % higher than that of the reference sample. This implied that the improved PL intensity was attributed to scattering of light by TiO2 NP and InGaN/GaN MQWs interface of high quality.