Highly efficient band-edge emission from InP quantum dots

Abstract

High quality InP quantum dots with diameters ranging from 25 to 45 Å, have been prepared; these quantum dots (QDs) show high quantum yields for band-edge photoluminescence (lowest energy HOMO-LUMO transition). The wavelength of the blue-shifted band-edge emission ranges from about 575 to 730 nm depending on QD size. The quantum yield for photoluminescence is 30% at 300 K and 60% at 10 K; the multiexponential decay of this emission exhibits lifetimes ranging from 5 to 50 ns. Deep red-shifted emission due to trapping of carriers in defect states on the QD surface which exhibits lifetimes above 500 ns, has been eliminated by treating the QDs with a dilute solution of HF or NH4F.

Spectroscopic Properties of Colloidal Indium Phosphide Quantum Wires

“…We describe efforts to enhance quantum-wire PL by photochemical etching with HF, which has proven successful for InP quantum dots. 1,2 We show that with InP quantum wires the method affords only photochemical wire thinning or photo-oxidation. The PL enhancements ultimately obtained are due to residual quantum-dot and quantum-rod domains left in the wires after photo-oxidation.…”

“…1,2 Therefore, a detailed analysis of the band gaps and PL behavior exhibited by InP quantum wires is provided. We describe efforts to enhance quantum-wire PL by photochemical etching with HF, which has proven successful for InP quantum dots.…”

Optical Properties of Afterglow Nanoparticles : , Capped with Polyethylene Glycol

“…The addition of PEG to the solution in which the nanoparticles were dispersed caused capping nanoparticles [33,34]. Surface passivation by polymer coating would be effective to prevent such a reduction of afterglow properties [19][20][21]. In this study, the addition of PEG increased the quantum yield, as shown in Figure 5.…”

“…Therefore, the florescence intensity and the quantum yield are decreased in the case of nanoparticles. There were many reports that passivation of fluorescent nanoparticles by polymers increased the fluorescence intensity [19][20][21]. Capping nanoparticles with PEG is also important for minimizing the nonspecific adsorption of proteins related to the immune system [25,26].…”

“…The advantages of capping are as follows: ( 1 ) the passivation of surface defects, which decreases the nonradiative recombination center and increases fluorescence intensity [19][20][21]; ( 2 ) the aggregation inhibition of nanoparticles by steric rather than electrostatic effects; ( 3 ) the ability to utilize nanoparticles for a drug delivery system (DDS) because of the improvement in immunoaffinity, especially in the case of capping nanoparticles with polyethylene glycol (PEG).…”