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The size of a quantum-confined nanocrystal determines the energies of its excitonic transitions. Previous work has correlated the diameters of PbS nanocrystals to their excitonic absorption; however, we observe that PbS quantum dots synthesized in saturated dispersions of PbCl can deviate from the previous 1S-1S energy vs. diameter curve by 0.8 nm. In addition, their surface differs chemically from that of PbS quantum dots produced via other syntheses. We find that these nanocrystals are coated in a shell that is measurable in transmission electron micrographs and contains lead and chlorine, beyond the monoatomic chlorine termination previously proposed. This finding has implications for understanding the growth mechanism of this reaction, the linewidth of these quantum dots' photoluminescence, and electronic transport within films of these nanocrystals. Such fundamental knowledge is critical to applications of PbS quantum dots such as single-photon sources, photodetectors, solar cells, light-emitting diodes, lasers, and biological labels.
This article was published in the following journal.
Name: The journal of physical chemistry letters
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Nanometer sized fragments (the dots) of semiconductor crystalline material which emit PHOTONS. The wavelength is based on the quantum confinement size of the dot. They are brighter and more persistent than organic chemical INDICATORS. They can be embedded in MICROBEADS for high throughput ANALYTICAL CHEMISTRY.
Injury to the nervous system secondary to exposure to lead compounds. Two distinct clinical patterns occur in children (LEAD POISONING, NERVOUS SYSTEM, CHILDHOOD) and adults (LEAD POISONING, NERVOUS SYSTEM, ADULT). In children, lead poisoning typically produces an encephalopathy. In adults, exposure to toxic levels of lead is associated with a peripheral neuropathy.
Poisoning that results from chronic or acute ingestion, injection, inhalation, or skin absorption of LEAD or lead compounds.
Unstable isotopes of lead that decay or disintegrate emitting radiation. Pb atoms with atomic weights 194-203, 205, and 209-214 are radioactive lead isotopes.
Neurologic disorders occurring in children following lead exposure. The most frequent manifestation of childhood lead toxicity is an encephalopathy associated with chronic ingestion of lead that usually presents between the ages of 1 and 3 years. Clinical manifestations include behavioral changes followed by lethargy; CONVULSIONS; HALLUCINATIONS; DELIRIUM; ATAXIA; and vomiting. Elevated intracranial pressure (HYPERTENSION, INTRACRANIAL) and CEREBRAL EDEMA may occur. (From Adams et al., Principles of Neurology, 6th ed, p1210-2)
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