Figure 1

(Color online) (a) Comparison of normalized PL spectra of QDs in toluene and in NLC matrix. The emission for the latter is redshifted by $\Delta \lambda =37\text{nm}$. The schematics represent the arrangement of QDs for both these cases. Schlieren texture of the nematic phase imaged with polarization optical microscopy for (b) unaligned pure NLC, (c) unaligned NLC with QDs 30:1 by volume confirming the presence of the nematic phase in the mixture. (d) Particle size distribution from DLS characterization of QDs in toluene (dark gray) and in NLC (light gray).Reuse & Permissions

Figure 2

(Color online) (a) (Left) Spatially resolved PL map of the QD-NLC sample showing emission in the range of 500–515 nm when the NLC is unaligned. (Center) Emission from the same sample redshifts to 520–530 nm when the NLC has a well-defined director axis $\mathbf{n}$ (coordinate system shown in B) but no applied $E$. (Right) A scan of the same area at $E=0.8\text{V}/\mu \text{m}$ with $E\parallel \mathbf{n}$ showing further redshift. (b) (Left) Reference coordinate system used in the text. The director $\mathbf{n}$ is identified as the $x$ axis while the $z$ axis is the optical axis showing the direction of the excitation/collection beams. (Right) A schematic of the cell. The interdigitated electrodes allow an application of $E\perp \mathbf{n}$ along the $y$ axis. Cells with electrodes without the interdigitated extensions are used for applying $E$ along $\mathbf{n}$. (c) Normalized PL intensity as functions of applied $E$ and incident polarization angle $\theta$ for the QD-NLC sample where $E\perp \mathbf{n}$. (d) Line cuts of (c) at different values of $E$ (dashed lines), showing maximum emission intensity occurring at different $\theta$ with varying electric field. Lines are fits (see text).Reuse & Permissions

Figure 3

(Color online) (a) Time-resolved PL for isolated QDs in toluene and in NLC matrix. (b) (Top) PL lifetime obtained from exponential fits to time-resolved traces for different $E\perp \mathbf{n}$ for QD-NLC sample, shown for the two collection geometries, $\varphi =0°$ and $90°$ under copolarized conditions. (Bottom) Energy-transfer rate $K$ can be enhanced by the application of $E$ until $0.8\text{V}/\mu \text{m}$, which is almost equal to the threshold field for NLC realignment (indicated by the dotted red line).Reuse & Permissions

Figure 4

(Color online) PL collected in (a) $\varphi =0°\left(\perp E\right)$ and (b) $\varphi =90°\left(\parallel E\right)$ collection geometries showing ${\lambda }_{PEAK}$ varying with $\theta$ at $E=0$ and $1.5\text{V}/\mu \text{m}$. Spatial scans of ${\lambda }_{PEAK}$ are shown beside the plots. These are performed over a representative $100\mu \text{m}\times 100\mu \text{m}$ area of the sample at $E=0$ and $1.5\text{V}/\mu \text{m}$ at excitation and polarization marked by circles. The color scheme used for all scans is represented by the color bar on top. Lines are guide to the eyes.Reuse & Permissions