Low-cost Fluorescence Sensors Powered by Nano-antenna Arrays Help Detect Poor Water Quality

A series of new plasmonic nano-antenna arrays can lead to the development of a new generation of ultrasensitive and low-cost fluorescence sensors. The sensors can then be used to monitor water quality in sensitive environments. The plasmonic nanoantenna arrays series was designed and tested by a group of researchers from the Universities of Bristol and Bedfordshire in collaboration with multinational company ABB.

The arrays, designed and tested by researcher Dr. Neciah Dorh during his PhD at the University of Bristol, are made from aluminum nanorods fabricated using electron beam lithography by commercial partner Kelvin Nanotechnologies. The nanorods, 50 nm wide and 158 nm long, are designed to resonantly enhance fluorescence emission from a range of contaminants in water such as diesel or tryptophan.

The work, published in Applied Optics, shows a six-fold increase in measured fluorescence emission from a dye. The research also shows that by correctly designing the array element spacing, strongly directional fluorescent emission can be obtained which would allow for highly integrated multi-wavelength sensors to be designed.

The work was carried out in Professor Martin Cryan's research group, which is part of the Photonics Research group in the Department of Electrical and Electronic Engineering. The project was in collaboration with Dr. Andrei Sarua from the School of Physics at Bristol and Dr. Tahmina Ajmal from the University of Bedfordshire, who had previously worked on the Aquatest project at Bristol. Together they developed a prototype low-cost, LED based sensor system, which they plan to develop further into a hand-held field deployable system for performing water quality monitoring.

The nano-antenna arrays, which can be fabricated by lower cost production techniques such as nanoimprint lithography, can bring significant sensitivity enhancement so that laboratory quality measurements could be carried out in the field. This would allow for deployment of remote wireless sensor networks for early warning of pollution or continuous monitoring of water quality in sensitive environments.

Dr. Dorh, now a Fellow within Bristol's QTEC programme, has co-founded a start-up, FluoretiQ, developing quantum enhanced fluorescence sensors which will help identify bacteria within minutes rather than days. Professor Cryan's group is developing systems that could combine the power of nanoantennas with quantum enhanced sensors to produce yet further sensitivity enhancements.