Optical Polarimatic Characterization of Zinc Oxide Nanorods as a Photosensitizer for Photodynamic Therapy

Abstract

The role of nanoparticles in diagnostic and treatment of cancer and other malignant diseases is gaining much research attention. The zinc oxide nanorods (ZnO NRs) are one of the most studied and promising semiconductor materials for applications in materials and medical sciences. In this study, we present optical properties of ZnO nanorods using Mueller matrix polarimetry to be suitable for its application in photodynamic therapy (PDT). Mueller matrix spectroscopic system capable of acquiring complete polarization information from single nanoparticle to nanostructure in term of transmittance, depolarization, retardance, and polarizance.The polarization properties measured from 400 to 800nm wavelength of light described decreasing trend of transmission at a wavelength range of 400nm to 530nm. This behavior of light describes Rayleigh scattering in the region and shows ZnO nanorods of relatively smaller diameter to excitation wavelength. Depolarization index decreases from 0.98 to 0.84 on 400nm to 650nm showing bulk scattering of light from randomly distributed ZnO nanorods. Slight change in retardance from 445nm to 550nm shows that light having low frequency and high wavelength passes readily than the high frequency light presenting that ZnO nanorods are strong, compact and composite material. Diattenuation magnitude increases with the increase in wavelength from 400nm to 750nm and changes abruptly at a wavelength range from 750nm to 800nm. This irregular trend indicates that ZnO nanorods are birefringent and anisotropic. These measured polarized properties proved that ZnO NRs are suitable to use as photosensitizer in PDT for diagnostic and treatment of cancer and other malignant diseases.