Quantum dots luminescence spectroscopy

Robelek R, Stefani FD, Knoll W (2006) Oligonucleotide hybridization monitored by surface plasmon enhanced fluorescence spectroscopy with bio-conjugated core/shell quantum dots. Influence of luminescence blinking. Phys Status Solidi A-Appl Mater Sci 203 3468-3475... 

High surface density of quantum dots caused an ambiguity in assigning of these lines. In the later studies the emission from a single dot was resolved. This progress [4] has permitted the luminescence spectroscopy of individual dots with controllable exciton population determined by the excitation intensity. 

The facile synthesis of water soluble CdSe QDs capped by 2-mercap-toethanol was reported by Mahmoud and Yaghmour. The influence of different processing parameters such as synthesis temperature, pH, CdSe/2-mercaptoethanol (ME) molar ratio on the luminescence properties was investigated. The average particle size of the prepared samples increased as the relative CdSe/ME molar ratio increased with the pH of the solution also having and effect on the PL spectroscopy. An increase in the solution pH during synthesis enhanced the emission intensity of the obtained CdSe quantum dots. 

Fig. 1. Energy levels of trivaient lanthanides below 43000 cm (5.3 eV) arranged according to the number q of 4f electrons. Excited levels known frequently to luminesce are indicated by a black triangle. The excited levels corresponding to hypersensitive transitions from the ground state are marked with a square. For each lanthanide, J is given to the right (in the notation of atomic spectroscopy, ] is added to the Russell-Saunders terms as lower-right subscripts). When the quantum numbers S and L are reasonably well-defined, the terms are indicated to the left. It may be noted that the assignments and F< in thulium(lll) previously were inverted these two levels with 7 = 4 actually have above 60% of H and F character, respectively. Calculated 7-levels are shown as dotted lines. They are taken from Carnall et al. (1968) who also contributed decisively to the identification of numerous observed levels, mainly by using the Judd-Ofelt parametrization of band intensities.

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