BIO-SENSING SENSITIVITY OF A NANOPARTICLE BASED ULTRAVIOLET PHOTODETECTOR

Abstract

Bio-sensing sensitivity of a spectrally selective nanoparticle based ultraviolet (UV) photodetector is characterized in comparison to a silicon photodiode and a photomultiplier tube (PMT). The nanoparticle based photodetector is comprised of poly-vinyl alcohol (PVA) coated zinc-oxide ( ZnO ) nanoparticles deposited on an aluminum-gallium-nitride ( AlGaN ) epitaxially grown substrate. The sensitivity was determined by measuring the fluorescence intensity of the native fluorophore, tryptophan, in Escherichia coli (E-coli, ATCC-25922) cells. Tryptophan intrinsically fluoresces with a peak at 340 nm under 280 nm UV light illumination. It is shown that this detector can sense the concentration of E-coli to 2.5 × 108 cfu/mL while the silicon photodiode cannot detect the intrinsic fluorescence at all. Nevertheless, the PMT outperformed the ZnO nanoparticle- AlGaN substrate based photodetector with the ability to sense E-coli concentrations to 3.91 × 106 cfu/mL. However, because PMT based systems are commonly limited by high dark current, susceptible to environmental changes, sensitive to ambient light, are not spectrally selective and have high power consumption, biological detection systems comprised of these ZnO nanoparticle- AlGaN substrate based photodetectors can be more effective for near real time characterization of potential bacterial contamination.