Flow control of single quantum dot enables measurements with nanoscale accuracy at lower cost
COLLEGE PARK, Md., Feb. 11, 2013 /PRNewswire-USNewswire/ -- Finding ways to see, position, measure, and accurately manipulate nanoscale objects is an ongoing challenge for researchers developing the next generation of ultra-compact electronics, sensors and optical devices. Even the most advanced conventional microscopes are limited by diffraction of the shortest wavelength of visible light, about 400 nanometers, rendering them unable to produce images or measurements of objects that are significantly smaller than this threshold.
Researchers attempt to solve this problem by using "reporting probes." A near-field scanning optical microscope (NSOM), for example, is equipped with a probe attached to a fine mechanical tip that can scan a nanoscale object and create an image based on the electromagnetic field it generates. But NSOMs are complex, delicate and expensive pieces of equipment, and the presence of the tip disturbs the interaction between the probe and the sample, distorting the image.
A new study by University of Maryland (UMD) researchers, published in the Feb. 5, 2013 issue of the journal Nature Communications , describes a novel technique for imaging far below the diffraction limit by using a particle that is much smaller than the wavelength of light as an optical probe. The particle is manipulated with high precision using an inexpensive microfluidic device. The breakthrough has enabled the researchers to capture nanoscale measurements with a spatial accuracy of 12 nanometers.Quantum Dots: Nanoscopic Spotlights in a Microscopic River A quantum dot is a 3–6 nanometer-sized, semiconducting particle about 25 times the diameter of a single atom. At room temperature, quantum dots can emit single photons of light that can be tuned to a desired wavelength. This makes them ideal probes for examining nanostructures smaller than the visible light threshold. Positioned close to a nanoscale object, the quantum dot becomes a sort of spotlight that amplifies what the microscope alone cannot see.