299 research outputs found
Temperature dependent photoluminescence of single CdS nanowires
Temperature dependent photoluminescence (PL) is used to study the electronic
properties of single CdS nanowires. At low temperatures, both near-band edge
(NBE) photoluminescence (PL) and spatially-localized defect-related PL are
observed in many nanowires. The intensity of the defect states is a sensitive
tool to judge the character and structural uniformity of nanowires. As the
temperature is raised, the defect states rapidly quench at varying rates
leaving the NBE PL which dominates up to room temperature. All PL lines from
nanowires follow closely the temperature-dependent band edge, similar to that
observed in bulk CdS.Comment: 11 pages, 4 figure
Low temperature photoluminescence imaging and time-resolved spectroscopy of single CdS nanowires
Time-resolved photoluminescence (PL) and micro-PL imaging were used to study
single CdS nanowires at 10 K. The low-temperature PL of all CdS nanowires
exhibit spectral features near energies associated with free and bound exciton
transitions, with the transition energies and emission intensities varying
along the length of the nanowire. In addition, several nanowires show spatially
localized PL at lower energies which are associated with morphological
irregularities in the nanowires. Time-resolved PL measurements indicate that
exciton recombination in all CdS nanowires is dominated by non-radiative
recombination at the surface of the nanowires.Comment: 9 pages, 3 figures, to be published in Applied Physics Letter
Dengue epidemic in southern Vietnam, 1998.
A widespread epidemic of dengue hemorrhagic fever (DHF) occurred in southern Vietnam in 1998, with 438.98 cases/100,000 population and 342 deaths. The number of DHF cases and deaths per 100,000 population increased 152.4% and 151.8%, respectively, over a 1997 epidemic. Dengue viruses were isolated from 143 patient blood samples; DEN-3 virus was identified as the predominant serotype, although a resurgence of DEN-4 was noted
- …