Nanotechnologists' new plastic can see in the dark (Jan 10/05): U of Toronto Professor Ted Sargent and his team used quantum dots trapped in lead and sulfur. "“We made particles from semiconductor crystals which were exactly two, three or four nanometres in size. The nanoparticles were so small they remained dispersed in everyday solvents just like the particles in paint,” explains Sargent. Then, they tuned the tiny nanocrystals to catch light at very long wavelengths. The result – a sprayable infrared detector. ..
The discovery may also help in the quest for renewable energy sources. Flexible, roller-processed solar cells have the potential to harness the sun’s power, but efficiency, flexibility and cost are going to determine how that potential becomes practice, says Josh Wolfe [of Lux Capital]. “These flexible photovoltaics could harness half of the sun’s spectrum not previously accessed.” .. Professor Peter Peumans of Stanford University, reviewed the U of T team’s research.. “Our calculations show that, with further improvements in efficiency, combining infrared and visible photovoltaics could allow up to 30 per cent of the sun’s radiant energy to be harnessed, compared to six per cent in today’s best plastic solar cells.”
U of T graduate student Steve MacDonald carried out many of the experiments .. “The key was finding the right molecules to wrap around our nanoparticles,” he explains. “Too long and the particles couldn’t deliver their electrical energy to our circuit; too short, and they clumped up, losing their nanoscale properties. It turned out that one nanometer – eight carbon atoms strung together in a chain – was ‘just right’.” 12:14:10 AM