RESUMEN
High-concentration (2-10 wt %) ZnCdSeS/ZnS alloyed quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared via ultraviolet (UV) curing. The QD-PDLC morphology and resonance characteristics of a coherent random laser were investigated. The doping concentration of the liquid crystal and quantum dots was varied to investigate its effect on the lasing threshold, line width, and stability with respect to the density and grain size of the liquid crystal droplets inside the PDLC structure. Furthermore, the QD-PDLC laser performance was influenced by the pump position and area because of spatial localization of the random resonators. Moreover, the QD-PDLC showed good long-term stability; after 15 days of laser excitation (3 h/day), the laser output was maintained at 92% of the original emission intensity. The random laser threshold was as low as 50 µJ/cm2 with the optimized preparation process, which suggested strong potential for applications in polymer random fiber lasers, sensors, and displays.
RESUMEN
We present a backlight module (BLM) employing a photoluminescent quantum-dot microstructure array for flexible/curved liquid crystal displays (LCDs). Differently sized quantum-dot (QD) BLMs were prepared based on the theoretical spectral model and microstructure fabrication process. A 27-inch curved prototype showed a wide color gamut of 122.79% under the National Television Systems Committee standard while achieving high brightness of over 4000 cd/m2 and brightness/color uniformity of 85.21%/9.2 × 10-3. An LCD monitor prototype equipped with the proposed BLM was also assembled and tested, which showed higher visual performance when compared with a common commercial monitor. This method produces QD BLMs without the need of additional optical elements, and has good compatibility with traditional processes.
RESUMEN
The fabrication of hexapod-like ternary PbSexS1-x nanostructures has been reported via an alternative organometallic route from reaction of Pb(II) salt with triphenylphosphine selenide (Ph3PSe) and dibenzyl disulfide (DBDS) in dibenzylamine (DBA) with addition of oleic acid (OA) at 260 °C. The shape, structure, and composition of the nanostructured hexapods are investigated and determined by techniques of XRD, SEM, TEM, Raman, HRTEM, SAED, XPS, EDX, and HAADF-STEM, and the obtained ternary nanostructured hexapods are of typical rock salt phase with Pb-rich features without phase separation, and their compositions could be systematically regulated by facile variations of reaction parameters. Investigations reveal that the successful fabrication of the ternary hexapods with tunable compositions is resulted from the effective selection of Se and S sources of Ph3PSe and DBDS that have similar reactivity in the current reaction system along with small lattice mismatch between the two end members of PbSe and PbS. Generally, the relations between the composition and lattice parameters for the ternary nanostructures obtained in DBA with varied addition of OA exhibit linear slops that are consistent well with Vegard's law. Interestingly, intensive investigations show that the nanostructures are mainly gradiently alloyed nanostructures with somewhat chalcogen-element segregations or disorders rather than homogeneously alloyed solid-state solutions due to kinetic limitation for short reaction time even though thermodynamics is feasible in the system, and also, high concentration of S element in the feedstocks tends to relative high density of disorders in the ternary nanostructures. Based on the revealing of the formation mechanism for the nanostructures with varied microstructures, the ternary PbSexS1-x hexapods can be tuned from gradient alloys with segregations to approximately homogeneous via enlongating reaction time. In addition, the photolysis of the nanostructures to lead oxysulfate and oxyselenate species is evidenced at ambient condition via Raman detection although they are stable at -190 °C.
RESUMEN
Lead selenide (PbSe) nanostructures with well-defined star-shaped morphology are successfully fabricated via a facile organometallic synthetic route from the reaction of tetraphenyl lead (Ph4Pb) with triphenylphosphine selenide (Ph3PSe) in dibenzylamine (DBA) with the assistance of oleic acid (OA) and oleylamine (OAm) at 220 °C for 30 min. The structure and shape of the nanocrystals are investigated by techniques of XRD, SEM, TEM, HRTEM, SAED, and EDX, and it is interesting that the obtained PbSe nanostars present Pb-rich features, although the PbSe nanostars are still in typical rock salt phase. Experimental investigations and ATR-FTIR studies demonstrate that the media of DBA, OA, and OAm with an order OA > DAB > OAm play important roles in the growth of the PbSe nanostars with well-defined shapes because the media not only serve as solvents but capping materials. The synergetic effects of the media are also favorable for the growth of PbSe nanocrystals with the well-defined star-shaped morphologies in the current reaction system. Meanwhile, varied PbSe nanostructures with cubic, side-cut cubic, and octahedral shapes can be fabricated by regulating the relevant reaction conditions, and all of these nanostructures prepared in the procedures demonstrate Pb-rich features due to the selective capping effects of the media to the exposed Pb(II) ions. It is confirmed that the specific shape and geometry of the nanostructures can be tuned by controlling the exposed crystal surfaces and/or the corresponding compositions via the variation of reaction conditions in the media.