After 45 minutes of continuous exposure by the high-power laser, ASE decreased in intensity to roughly half its initial value however, the presence of ASE over such a long time period and after nearly 2.7 × 106 laser shots demonstrates the good photostability of the NC-silica film. The ASE spectral widths were on the order of 5 to 7 nm. The films were then excited by the frequency-doubled output of a regeneratively amplified Ti:sapphire laser centered at 400 nm with a pulse width of 100 fs and a repetition rate of 1 kHz. To create a thin film of material for ASE testing, the CdS/ZnS NCs were dispersed in ethanol, added to a silica precursor that resulted in a slightly viscous liquid that was spin-coated onto a glass slide to form a thin clear film, and then annealed. By creating a CdS/ZnS NC-silica composite whereby CdS/ZnS core-shell NCs are chemically modified and incorporated into a sol-gel-derived silica film, the ZnS shell efficiently passivates the surface of the CdS NCs and eliminates deep-trap emission. Deep-trap emission, or the emission from the recombination of trapped electrons and holes with broad energy distributions because of surface irregularities such as missing atoms, uncommon oxidation states, or adsorbed impurities, leads to a broadened emission-spectrum profile that is undesirable for optical applications that rely on the narrow emission profiles of NCs. Recent experiments using CdS NCs that are embedded in a host matrix result in significant deep-trap emission because of surfaces that are not well passivated. However, by using core-shell cadmium sulfide/zinc sulfide (CdS/ZnS) NCs as an alternative gain material, researchers in the Department of Chemistry at the Massachusetts Institute of Technology (MIT Cambridge, MA) have demonstrated both room-temperature ASE and lasing at blue wavelengths. Although amplified spontaneous emission (ASE) and lasing at room temperature have been achieved for cadmium selenide (CdSe) NCs, ASE and lasing at blue wavelengths has never been achieved-possibly because of highly efficient nonradiative Auger relaxation processes that become dominant as the size of the NC decreases. doi: 10.1021/am300232z.Their size-dependent color tunability and chemical flexibility make semiconductor nanocrystals (NCs) unique as optical gain media. One-Pot Noninjection Route to CdS Quantum Dots via Hydrothermal Synthesis. doi: 10.1021/jacs.0c07274.Īboulaich A., Billaud D., Abyan M., Balan L., Gaumet J.-J., Medjadhi G., Ghanbaja J., Schneider R. An aqueous route synthesis of transition-metal-ions-doped quantum dots by bimetallic cluster building blocks. Zhang H., Yu J., Sun C., Xu W., Chen J., Sun H., Zong C., Liu Z., Tang Y., Zhao D. Quantum dots and their multimodal applications: A review. Doped quantum dots for white-light-emitting diodes without reabsorption of multiphase phosphors. Core-Shell quantum dots: Properties and applications. Vasudevan D., Gaddam R.R., Trinchi A., Cole I. Our developed core/shells are highly appropriate for the development of efficient light-emitting diodes.Ĭadmium sulfide copper doping nanocrystals optical properties photoluminescence quantum dots (QDs) zinc sulfide. Consequently, this minimized lattice mismatch and offered better passivation to any surface defects, resulting in increased photoluminescence. Our experimental results revealed that Cu-doped ZnS shells adopted the crystal structure of CdS due to its larger bandgap. Studying fluorescence, we witnessed a sharp emission peak at a wavelength of 440 nm and another emission peak at a wavelength of 620 nm, related to the fabricated Cu-doped CdS/ZnS core/shell QDs. The developed nanostructures were examined with relevant characterization techniques such as transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) emission/absorption spectroscopy. The objective was to materialize the Cu-doped CdS/ZnS shells by the adaptation of a two-stage high-temperature doping technique. In this work, novel Cu-doped CdS/ZnS shell structures were developed to enhance the photoluminescence properties. Controlling the fluorescence lifetime of QDs shells is imperative for various applications, including light-emitting diodes and single-photon sources. Recently, quantum-dot-based core/shell structures have gained significance due to their optical, optoelectronic, and magnetic attributes.
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