Mar 13, 2014 |
Colloidal silicon quantum dots: synthesis and luminescence tuning from the near-UV to the near-IR range
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(Nanowerk News) In 1990, scientists reported that nanostructured silicon can emit visible light. This report opened a new frontier for photoelectronics in information technology, called “silicon photonics”. Furthermore, the continuous tuning of electromagnetic emission from near-UV to near-infrared wavelengths has been achieved by controlling silicon nanostructures.
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The quantum yield (QY) of this radiation may exceed 70%, and the use of silicon as the emitting material is advantageous because of its abundance and low toxicity to the human body and environment.
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Photographs (top) and emission spectra (bottom) of silicon quantum dots suspended in methanol. Emission spectra gradually shift from near-infrared to red with decreasing particle size, which is achieved simply by annealing the as-prepared material at different temperatures. (© American Chemical Society)
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These advantages have been expected to stimulate the use of luminescent silicon in various fields; however, commercial applications are still lacking.
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In this paper ("Colloidal silicon quantum dots: synthesis and luminescence tuning from the near-UV to the near-IR range"), Ghosh and Shirahata focus on high-QY silicon nanoparticles. It summarizes the peculiarities of their emission, which depends on the preparation method and surface chemistry.
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In particular, there are two spectral ranges separated by green light, which can not be smoothly covered using a single synthesis approach. This green boundary is discussed to provide a better understanding of the emission mechanisms.
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Those mechanisms are summarized to ascertain the future challenges in the industrial use of silicon-based light emitters. The authors believe that silicon nanophotonics is still in its infancy.
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They predict that with high-quality materials of narrow size distribution and controlled surface chemistry in hand, novel photonic structures will be realized in the near future, including biomedical imaging devices, optical amplifiers, sensors, high-efficiency LEDs, and possibly a silicon-based laser.
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