Whispering Gallery Mode Biosensing – A Detailed Study on ZnO Microspheres

We demonstrate the potential of using ZnO microspheres (MS) for biosensing applications. ZnO MS with smooth surface exhibiting novel whispering gallery mode (WGM) in photoluminescence and spectroscopic imaging ellipsometry behavior were synthesized by hydrothermal techniques. Sharp resonance peaks covering the entire visible range could be excited not only by UV but also visible light. Moreover, the theoretical modeling was carried out. Essential information about the position, TE and TM modes of each resonance are precisely predicted. Such information is very important for the investigation of resonance shift caused by the attachment of foreign molecules. Both experimental and theoretical results support that ZnO spherical micro cavity can be a good candidate for biosensing applications.