Effect of surface passivating ligand on structural and optoelectronic properties of polymer : CdSe quantum dot composites

Abstract

We demonstrate the effect of surface passivation of cadmium selenide quantum dots (CdSe QDs) (∼5–7 nm) by tri-n-octylphosphene-oxide (TOPO) and oleic acid (OA) on the structural and optoelectronic properties of their respective polymer : CdSe composites by dispersing them in poly(2-methoxy-5(2-ethylhexyloxy)-1,4-phenylinevinylene) and poly(3-hexylthiophene) polymers. It has been found that OA passivated-QDs (∼7 nm), as compared with TOPO passivated CdSe QDs (∼5 nm), are of (i) high quality that provide better steric stability against coagulation, homogeneity and photostability to their respective polymer : CdSe composites, (ii) show low value of Stern–Volmer quenching constant (KSV) calculated from photoluminescence quenching measurements. These effects have been attributed to (i) CdSe(OA) (∼7 nm) particles having relatively smaller surface energies compared with CdSe(TOPO) (∼5 nm) particles thus showing lesser quenching capabilities (ii) dominance of respective processes of photoinduced Förster energy transfer between host polymer (donors) and guest CdSe nanocrystals (acceptors) in polymer : CdSe(OA) composites and charge transfer in polymer : CdSe(TOPO) composites.

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

“…For this purpose, the passivation of the surface of the QDs has been carefully studied in order to minimize the traps and to provide a barrier with the surrounding medium [27], and hence to provide an enhancement of the emission efficiency [28]. Indeed, colloidal nanocrystals are usually characterized by temperature-insensitive emission, because the barriers are so high that thermal energy losses are inhibited.…”

Controlling the self-assembly of magnetic nanoparticles by competing dipolar and isotropic particle interactions

“…These are balanced by the stabilizing repulsive interactions that originate from i) the steric stabilization layer consisting of the PS-COOH 20 surfactant on each particle, and ii) the TOPO coordinating stabilizer. Since the molar mass and the grafting density of the sterically dominating PS-COOH surfactant are similar for all samples, it is reasonable to conclude that the steric repulsion by the polymer is not responsible for the observed differences in 25 self-assembled structures. While the contour length of a TOPO layer is about 1 nm, 22 the thickness of a grafted PS-COOH layer can be estimated according to the blob-based model of Biver 23 for polymer brushes on curved surfaces as approximately 8 -10 nm.…”

“…No indication is found for the presence of a crystalline CoO phase neither in X-ray diffraction nor in electron diffraction experiments. 25 In order to get a better insight into the dynamic nature of the 30 chain formation and the structures present in dispersion, we perform static (SLS) and dynamic light scattering (DLS) experiments on particle dispersions in toluene. Light scattering experiments for magnetic nanoparticles are scarce due to their high absorption, and in order to reduce this effect measurements 35 are carried out at very low sample concentrations (~ 3 x 10 -3 wt.-%).…”

“…The particles are washed several times with hexane and redispersed in toluene. The resulting black particle dispersions are highly stable 25 against precipitation for several months. The sample denotation (Co-xTOPO) indicates the TOPO concentration during synthesis (x) expressed in mmol·L -1 (s. Table 1).…”

Effect of Nanoparticles Shape on the Efficiency of Hybrid Solar Cells

“…The CdSe QDs had diameters between 3.1 and 3.9 nm with a deviations ± 0.2 nm, and an optical absorption spectral of about 450 nm. Kumari et al [23] have demonstrated that CdSe QDs (5 ~ 7 nm) with TOPO and oleic acid (OA) have a good surface passivation and optoelectronic properties.…”