Cheap Nano Sensors Warn Against Hard to Detect Dangerous Chemicals

A number of chemicals widely used in industrial processes today are dangerous at very small concentrations, either to humans or the environment. These chemicals are currently difficult to detect at trace levels in complex mixtures. Commonly used chemicals are polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) such as benzene, toluene and xylene (BTX).

Conventional detection techniques require complex, expensive instrumentation in specialised laboratories. Scientists working on the EU funded project ''Innovative nanostructured optochemical sensors'' (INGENIOUS) are developing ultra sensitive, highly selective and portable (possibly disposable) sensors for the molecules of interest. They consist of arrays of nanoparticles whose core is formed by a fluorescent dye coupled to a metal and whose silica shell sports molecularly imprinted receptors (SNMIRs).

INGENIOUS is employing an emerging and powerful fluorescence tool, metal-enhanced fluorescence (MEF). MEF exploits the free electrons in nearby metals to dramatically enhance the emission intensity and stability of weakly fluorescent materials. By coupling a fluorescent dye to metal nanoparticles, thus forming the core of SNMIR and acting as the signal transducer (binding causes fluorescence), the technique promises to lower the detection limit of the INGENIOUS sensor. As such, extensive work was carried out in this period to produce dye-conjugated metals.

The team has also tested printing procedures to be used within the project. These include single and multi-array inkjet printing for deposition of metal particles and SNMIRs. Preliminary tests of the lithography technique using the colloidal nanoparticles to define the pattern on a flexible plastic foil showed similar characteristics to those obtained using rigid glass or silicon.

Finally, waveguiding features for efficient light transmission have been created using the imprint lithography technique. Hardware and controlling software have been developed and tested, verifying detection of gases. Sensitivity will be optimised during the next period.

PAHs and BTXs are commonly used toxic chemicals with far-reaching effects including cancer and neurological deficits. Thanks to technology developed by INGENIOUS, cost effective, mass produced sensors based on flexible processing technology to monitor and protect the workplace and environment may be just around the corner. -- © European Union, CORDIS