Quantum yield excitation spectrum (UV-visible) of CdSe/ZnS core-shell quantum dots by thermal lens spectrometry

Abstract

A recently developed thermal lens spectrometry configuration has been used to study CdSe/ZnS core-shell quantum dots ͑QDs͒ suspended in toluene and tetrahydrofuran ͑THF͒ solvents. The special features of this configuration make it very attractive to measure fluorescence quantum yield ͑͒ excitation spectrum since it simplifies the measurement procedure and consequently improve the accuracy. Furthermore, the precision reached is much higher than in conventional photoluminescence ͑PL͒ technique. Two methods, called reference sample and multiwavelength have been applied to determine , varying excitation wavelength in the UV-visible region ͑between 335-543 nm͒. The and PL spectra are practically independent of the excitation wavelength. For CdSe/ZnS QDs suspended in toluene we have obtained =76Ϯ 2%. In addition, the aging effect on and PL has been studied over a 200 h period for QDs suspended in THF.

Optimum quantum dot size for highly efficient fluorescence bioimaging

“…4. [31][32][33] Basically, the QDs solution is locally heated by a time-modulated beam (the pump beam) that is partially absorbed by the CdTe QDs. In our case, this "pump beam" was provided by a slightly focused argon laser, and the heat delivered is due to the non-vanishing k nrad .…”

Photothermal Spectroscopic Characterization in CdSe/ZnS and CdSe/CdS Quantum Dots: A Review and New Applications

“…For PMMA-encapsulated CdSe/ZnS,  is dependent on concentration (Pilla et al, 2007), and the aging effect (Cruz et al, 2010). The value of  decreased by ~ 60% over a 200-hour interval of UV-vis TL measurements (Cruz et al, 2010). For CdSe/ZnS QDs, the  values were dependent on the core size and concentration (Pilla et al 2008); for CdSe/ZnS suspended in toluene, the  results were nearly independent of the pump wavelength (335-543) nm (Cruz et al, 2010).…”

“…4); the values obtained for < em > are 525 nm, 560 nm and 619 nm for  (at 514.5 nm) of 0.31, 0.199 and 0.35 cm -1 , respectively. < em > values are dependent on QD concentrations (Pilla et al, 2008), solvents (Pilla et al, 2007) and aging effect (Cruz et al, 2010). For CdSe/CdS MSNs synthesized and studied here, the absorbance and fluorescence spectra are present in (Pilla et al, 2008).…”

“…The  results are presented for core-shell PMMA-encapsulated CdSe/ZnS suspended in toluene, chloroform and THF, for CdSe/ZnS suspended in toluene, and for the aqueous colloidal suspension of CdSe/ZnS and CdSe/CdS, respectively. For PMMA-encapsulated CdSe/ZnS,  is dependent on concentration (Pilla et al, 2007), and the aging effect (Cruz et al, 2010). The value of  decreased by ~ 60% over a 200-hour interval of UV-vis TL measurements (Cruz et al, 2010).…”

“…The thermo-optical properties of core-shell nanoparticle solutions were investigated by the TL method (Cruz et al, 2010;Pilla et al, 2007Pilla et al, , 2008 and by TSPM (Pilla et al, 2009). TL transient measurements were performed in the mode-mismatched dual-beam (excitation and probe) configuration ( Fig.…”