OLD-fashioned 鈥渟pring鈥� thermometers are notoriously inaccurate. So would a nanoscale version be any better?
Yes, according to Nicholas Kotov at the University of Michigan, Ann Arbor. His team has built thermometers just 30 nanometres wide that function much like their larger cousins and can indicate temperatures to within 3 掳C over the range 20 掳C to 80 掳C. Spring thermometers, which rely on a coil made up of two different metals that winds and unwinds as the temperature changes, can be out by 10 掳C.
In the nanoscale version heat-sensitive springs composed of polyethylene glycol chains are attached at one end to a gold sphere 20 nanometres across. At the other end, each polymer spring carries a speck of cadmium telluride. The cadmium telluride glows when struck by laser light 鈥� and the closer to the gold it is, the more brightly it glows. At low temperatures the springs are coiled tightly, keeping the cadmium telluride close to the gold ball so that it glows brightly. As the temperature rises, the springs stretch out and the glow dims (Angewandte Chemie, DOI: 10.1002/anie.200501264).
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The nanothermometers are designed to be used with microfluidic devices. They could be used to monitor enzymatic and blood reactions, which can be very sensitive to temperature changes.
