Time-resolved photoluminescence study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets

We used photoluminescence spectroscopy to resolve two emission features in CdSe/CdMnS/CdS and CdSe/CdS core/multi-shell nanoplatelet heterostructures. The photoluminescence from the magnetic sample has a positive circular polarization with a maximum centered at the position of the lower energy feature. The higher energy feature has a corresponding signature in the absorption spectrum; this is not the case for the low-energy feature. We have also studied the temporal evolution of these features using a pulsed-excitation/time-resolved photoluminescence technique to investigate their corresponding recombination channels. A model was used to analyze the temporal dynamics of the photoluminescence which yielded two distinct timescales associated with these recombination channels. The above results indicate that the low-energy feature is associated with recombination of electrons with holes localized at the core/shell interfaces; the high-energy feature, on the other hand, is excitonic in nature with the holes confined within the CdSe cores. © 2016 Author(s)

Time resolved photoluminescence study of magnetic CdSe/CdMnS/CdS core/multi-shell nanoplatelets

Colloidal semiconductor nanoplatelets (NPLs) are quasi 2D-nanostructures that are grown and processed inexpensively using a solution based method and thus have recently attracted considerable attention. We observe two features in the photoluminescence spectrum, suggesting two possible recombination channels. Their intensity ratio varies with temperature and two distinct temperature regions are identified; a low temperature region (10K < T < 90K) and a high temperature region (90K < T < 200K). This ratio increases with increasing temperature, suggesting that one recombination channel involves holes that are weakly localized with a localization energy of 0.043meV. A possible origin of these localized states are energy-variations in the xy-plane of the nanoplatelet. The presence of positive photoluminescence circular polarization in the magnetically-doped core/multi-shell NPLs indicates a hole-dopant exchange interaction and therefore the incorporated magnetic Manganese ions act as a marker that determines the location of the localized hole states.1 Time-resolved measurements show two distinct timescales (τfast and τslow) that can be modeled using a rate equation model. We identify these timescales as closely related to the corresponding recombination times for the channels. The stronger hole localization of one of these channels leads to a decreased electron-hole wave function overlap and thus a decreased oscillator strength and an increased lifetime. We show that we can model and understand the magnetic interaction of doped 2D-colloidal nanoplatelets which opens a pathway to solution processable spin controllable light sources. Copyright © 2017 SPIE

Magneto-optical studies of CdSe/CdMnS/CdS core/multi-shell colloidal nanoplatelets

We studied the photoluminescence (PL)) from CdSe/CdMnS/CdS core/multi-shell colloidal nanoplatelets, a versatile platform to study the interplay of optical properties and nanomagnetism. The photoluminescence (PL) exhibits σ+ polarization in the applied magnetic field. Our measurement detects the presence of even a single magnetic monolayer shell. The PLL consists of a higher and a lower energy component; the latter exhibits a circular polarization peak. The time-resolved PL (trPL) shows a red shift as function of time delay. At early (later) times the trPL spectra coincide with the high (low) energy PL component. A model is proposed to interpret these results. © 2016 SPIE

Tensile Properties of the Murine Ventral Vertical Midline Incision

In clinical surgery, the vertical midline abdominal incision is popular but associated with healing failures. A murine model of the ventral vertical midline incision was developed in order to study the healing of this incision type.The strength of the wild type murine ventral abdominal wall in the midline was contained within the dermis; the linea alba made a negligible contribution. Unwounded abdominal wall had a downward trend (nonsignificant) in maximal tension between 12 and 29 weeks of age. The incision attained 50% of its final strength by postoperative day 40. The maximal tension of the ventral vertical midline incision was nearly that of unwounded abdominal wall by postwounding day 60; there was no difference in unwounded vs. wounded maximal tension at postwounding day 120.After 120 days of healing, the ventral vertical midline incision in the wild type mouse was not significantly different from age-matched nonwounded controls. About half of the final incisional strength was attained after 6 weeks of healing. The significance of this work was to establish the kinetics of wild type incisional healing in a model for which numerous genotypes and genetic tools would be available for subsequent study

Time-resolved photoluminescence study of CdSe/CdMnS/CdS core/multi-shell nanoplatelets

We used photoluminescence spectroscopy to resolve two emission features in CdSe/CdMnS/CdS and CdSe/CdS core/multi-shell nanoplatelet heterostructures. The photoluminescence from the magnetic sample has a positive circular polarization with a maximum centered at the position of the lower energy feature. The higher energy feature has a corresponding signature in the absorption spectrum; this is not the case for the low-energy feature. We have also studied the temporal evolution of these features using a pulsed-excitation/time-resolved photoluminescence technique to investigate their corresponding recombination channels. A model was used to analyze the temporal dynamics of the photoluminescence which yielded two distinct timescales associated with these recombination channels. The above results indicate that the low-energy feature is associated with recombination of electrons with holes localized at the core/shell interfaces; the high-energy feature, on the other hand, is excitonic in nature with the holes confined within the CdSe cores.NRF (Natl Research Foundation, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)Published versio

Magneto-optical manipulation of surface plasmons in gold/ferromagnetic/gold multilayer films

Modulation of the surface plasmon wave vector in composite gold/cobalt/gold multilayer films due to periodic magnetization switching in cobalt is observed with a tilted slit-groove microinterferometer