Luminescence of colloidal CdSe/ZnS nanoparticles: high sensitivity to solvent phase transitions

Abstract

We investigate nanosecond photoluminescence processes in colloidal core/shell CdSe/ZnS nanoparticles dissolved in water and found strong sensitivity of luminescence to the solvent state. Several pronounced changes have been observed in the narrow temperature interval near the water melting point. First of all, the luminescence intensity substantially (approximately 50%) increases near the transition. In a large temperature scale, the energy peak of the photoluminescence decreases with temperature due to temperature dependence of the energy gap. Near the melting point, the peak shows N-type dependence with the maximal changes of approximately 30 meV. The line width increases with temperature and also shows N-type dependence near the melting point. The observed effects are associated with the reconstruction of ligands near the ice/water phase transition.

Observations of unusual temperature dependent photoluminescence anti-quenching in two-dimensional nanosheets of ZnS/ZnO composites and polarization dependent photoluminescence enhancement in fungi-like ZnO nanostructures

“…13 The increase in PL intensity with increasing temperature in the core/shell QDs with a thick CdS monoshell and a CdS/ZnCdS/ZnS multishell has been reported recently by Jing et al 2 and the PL enhancement has been considered to come from delocalization of charge carriers localized at the CdSe/CdS interface. Peculiarities in the PL emission behavior of in-liquid colloidal CdSe/ZnS nanoparticles near the water phase transition temperature (T ¼ 273 K) has been reported by Antipov et al 6 LTAQ effect has also been observed for surface modified CdS QDs and ZnS-CdS alloy QDs and are explained by using a three levels energy model including a triplet origin exciton state, the so called dark exciton state. 7 Anomalous PL emission behavior in isoelectronic ZnSe 1Àx O x semiconductors have been reported very recently and the complex decay profiles induced by O traps had been shown to play the important role.…”

“…[2][3][4]11,12 In the low temperature region, interesting results such as prolonged lifetime below 20 K related to bright-dark exciton splitting, thermally activated quenching due to surface defect states, and luminescence temperature antiquenching (LTAQ) assigned to a phase transition in the capping layer, etc., have been reported by various researchers. 6,[12][13][14] The LTAQ effect has been reported previously by Wuister et al in capped CdSe QDs. 13 The increase in PL intensity with increasing temperature in the core/shell QDs with a thick CdS monoshell and a CdS/ZnCdS/ZnS multishell has been reported recently by Jing et al 2 and the PL enhancement has been considered to come from delocalization of charge carriers localized at the CdSe/CdS interface.…”

“…Such organicinorganic hybrid materials has attracted a lot of attention, recently, due to their potential applications in optoelectronic devices, solar cells etc. [1][2][3][4][5][6] In addition to that highly lattice mismatched ZnS/ZnO composite or isoelectronic ZnM 1Àx O x semiconductors (M ¼ S, Se, Te, etc.) have also attracted a continued interest due to their oxygen-induced peculiar optical properties.…”

Temperature and Phase Transition Sensing in Liquids with Fluorescent Probes

“…Recently it has been demonstrated, that number of quantum emitters exhibit sensitivity to phase transitions occurring in solvents. In the case of CdSe/ZnS quantum dots [21] it has been reported, that photoluminescence intensity demonstrates significant growth close to a phase transition point, and accompanied by shift and linewidth increase of the emission peak. Quantum dots also demonstrate a drop in lifetime at the transition point.…”

Effect of Retrapping on Thermoluminescence Peak Intensities of Small Amorphous Silicon Quantum Dots

“…TL continues to be an active area of research because of its immense contribution in the fields of personal and environmental dosimetry, dating of archaeological artifacts, sediments and study of defects in solids [1]. In particular, light emission from silicon quantum dots has got recent attention because of its potential applications in the silicon-based optoelectronic devices [6][7][8][9][10]. There are different mechanisms of increasing the efficiency of the light emitting device.…”