The LUMIVOCS proof-of-concept project concerns the design, engineering, testing and optimisation of a portable optical sensing device for detection of volatile organic compounds (VOCs) at very low concentration levels. The portable device developed in this work integrates a novel light-emitting composite material, called “Guest@MOF”. This VOC sensor employs a periodic framework of nanoscale pores comprising metal-organic frameworks (MOFs) as a crystalline “host”, for incarcerating luminescent “guest” molecules. The resultant materials tested were highly emissive and selective to part-per-million (ppm) detection of important VOC analytes, such as acetone vapour. This concept can be harnessed to engineer luminescent sensing applications, where a fast response time of milliseconds to seconds is critical. For instance, the precise detection of acetone at ppm-level from human breath could pave the way to non-invasive diabetic diagnostics in medical and healthcare monitoring sectors. Likewise in manufacturing and commercial sectors, VOCs are difficult to detect at low concentration levels, and yet are most hazardous to human health and the environment. The results derived from the LUMIVOCS project can be summarised below. Notably, the systematic data obtained by this feasibility study allowed for the de-risking of the technology for future engineering of portable VOC sensors targeting the aforementioned applications.
• A compact luminescent sensor prototype with UV excitation source, Guest@MOF photoactive film, and optical fibre detection had been designed, built, and tested successfully. The small form factor presents an opportunity for further miniaturisation, but this will need additional product design and engineering research.
• Promising candidate Guest@MOF systems exhibiting either a turn-off or a turn-on type luminescent response were tested under low concentration VOC dosing studies. Sensitivity and selectivity towards ppm-level acetone vapour were confirmed, calibration curves and calibration protocol were established.
• Sensor stability was interrogated under a prolonged UV excitation, combined with humidity and VOC exposures. Enhanced sensor stability to external stimuli was determined for the Guest@MOF/Polymer composite fibres compared with a sensor film built from pristine Guest@MOF powder. The mechanical resilience of the polymer composite was improved, with only a negligible impact on its sensitivity. This area will require further research.
• General findings and non-confidential information about the portable VOC sensor and its engineering potential had been disseminated through presentations in workshops and conferences attended by academics as well as industry, and in science events open to the general public. Further, wider dissemination was achieved through the MMC Lab’s Twitter page (~3,000 subscribers) and via the research group’s website.
