There is a growing need for technologies that can detect and characterize nanoparticles in gaseous and liquid environments, due to their relevance to areas such as drug delivery, atmospheric pollution, and biodefense. Optical whispering gallery mode resonators enable parallel label free detection of nanoparticle mass, refractive index, and size. Their strong spatial and temporal optical confinement provides, in principle, ultrahigh sensitivity in an on-chip platform in both liquid and gaseous environments. In this talk I will discuss progress towards the development of the whispering gallery mode sensors at the University of Queensland. This includes an interferometric technique to characterise particle size and refractive index, insensitive to laser frequency noise and many sources of environmental noise; plasmonic enhancement of the sensors response, in principle enabling sensing at the level of a single BSA protein; and the possibility of mass sensing with attogram precision by regenerative excitation of mechanical vibrations within the resonator.BIOGRAPHY: Dr. Warwick Bowen leads the QueenslandQuntum optics Group at the University of Queensland, and is a prgramme manager in the ARC Centre of Excellence in Engineered Quentum Systems. His groups research is primarily focused on applications of silitcon chip based optical microresonators in fundamental science, photonics and sensing.