Sensitive Optical Sensors for Air Pollution

In the new sensor, gold nanodisks are arranged in squares. The arrangement causes the sensor to emit UV light. (Source: V. K Valev & D. C. Hooper)

The new sensor is made up of a series of gold disk-shaped nano­particles on a glass slide. The team at the Uni­versity of Bath disco­vered that when they shone an infrared laser at a precise arrange­ment of the particles, they started to emit unusual amounts of ultra­violet light. This mechanism for gene­rating UV light is affected by molecules binding to the surface of the nano­particles, providing a means of sensing a very small amount of material.

The researchers, from the Uni­versity of Bath’s Depart­ment of Physics, hope that in the future they can use the tech­nology to develop new ultra­sensitive sensors for air pollution or for medical diag­nostics. Vent­sislav Valev, Royal Society Research Fellow and Reader in Physics at the Univer­sity of Bath, led the work with Research Asso­ciate David Hooper. He explained: “This new mechanism has great poten­tial for detecting small molecules. It is 100 times more sensitive than current methods. The gold nano­particle disks are arranged on a glass slide in a very precise array – changing the thick­ness and sepa­ration of the disks completely changes the detected signal.”

When molecules bind to the surface of a gold nano­particle, they affect the electrons at the gold surface, causing them to change the amount of UV light they emit. “The amount of UV light emitted would depend on the type of mole­cules that bind to the surface. This technique could enable ultra-sensitive detec­tion of molecules in tiny volumes. It could in the future be used for detecting very low concen­trations of bio­logical markers for the early diag­nostic screening for diseases, such as cancer”, Valev said.

The study has demon­strated the proof of principle for this new sensing mechanism. The team would next like to test the sensing of various types of chemicals and expects the technique to be available to other scientists to use within five years. The nano­particles were fabricated by researchers at North­western Uni­versity, Illinois. (Source: U Bath)

Reference: D. C. Hooper et al.: Second Harmonic Spectroscopy of Surface Lattice Resonances, Nano Lett. 19165 (2019); DOI: 10.1021/acs.nanolett.8b03574

Link: Centre for Photonics and Photonic Materials, Dept. of Physics, University of Bath, Bath, UK

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