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All inorganic CsPbX3 (X is Cl, Br, or I) perovskite nanocrystals (CPX NCs) have become one of the most promising materials which can be integrated into high performance optoelectronic devices such as light emitting diodes, sensors, and solar cells. However, poor thermal stability seriously hampers successful demonstration of commercially available optoelectronic devices based on CPX NCs. In this study, we demonstrate strikingly enhanced thermal stability of CPX NCs by employing impurity metal halides during synthesis. Thermal stability of CPX NCs were investigated by microscopic and spectroscopic characterizations, and it turned out that various metal halides are effective for enhancement of thermal stability of CPX NCs. CPX NCs maintains their original structures and properties with little sign of instability such as merging and phase transformations when the NCs were synthesized by adding impurity metal halides. We finally propose plausible mechanisms on enhanced thermal stability of CPB NCs synthesized under the presence of impurity metal halides.

Post-synthetic surface redesign significantly enhances the stability of perovskite nanocrystals.

Strain engineering of perovskite quantum dots (pQDs) enables widely tunable photonic device applications. However, manipulation at the single-emitter level has never been attempted. Here, we present a tip-induced control approach combined with tip-enhanced photoluminescence (TEPL) spectroscopy to engineer strain, bandgap, and the emission quantum yield of a single pQD. Single CsPbBrxI3-x pQDs are clearly resolved through hyperspectral TEPL imaging with ∼10 nm spatial resolution. The plasmonic tip then directly applies pressure to a single pQD to facilitate a bandgap shift up to ∼62 meV with Purcell-enhanced PL increase as high as ∼105 for the strain-induced pQD. Furthermore, by systematically modulating the tip-induced compressive strain of a single pQD, we achieve dynamical bandgap engineering in a reversible manner. In addition, we facilitate the quantum dot coupling for a pQD ensemble with ∼0.8 GPa tip pressure at the nanoscale estimated theoretically. Our approach presents a strategy to tune the nano-opto-electro-mechanical properties of pQDs at the single-crystal level.

The technique of Brightness Temperature Difference (BTD) between 11 and separates yellow sand dust from clouds according to the difference in absorptive characteristics between the channels. However, this method causes consistent false alarms in many cases, especially over the desert. In order to reduce these false alarms, we should eliminate the background noise originated from surface. We adopted the Background BTD (BBTD), which stands for surface characteristics on clear sky condition without any dust or cloud. We took an average of brightness temperatures of 11 and channels during the previous 15 days from a target date and then calculated BTD of averaged ones to obtain decontaminated pixels from dust. After defining the BBTD, we subtracted this index from BTD for the Yellow Sand Index (YSI). In the previous study, this method was already verified using the geostationary satellite, MTSAT. In this study, we applied this to the polar orbiting satellite, MODIS, to detect yellow sand dust over Northeast Asia. Products of yellow sand dust from OMI and MTSAT were used to verify MODIS YSI. The coefficient of determination between MODIS YSI and MTSAT YSI was 0.61, and MODIS YSI and OMI AI was also 0.61. As a result of comparing two products, significantly enhanced signals of dust aerosols were detected by removing the false alarms over the desert. Furthermore, the discontinuity between land and ocean on BTD was removed. This was even effective on the case of fall. This study illustrates that the proposed algorithm can provide the reliable distribution of dust aerosols over the desert even at night.

Design creativity can be enhanced by identifying the underlying cognitive capabilities used by expert designers and training novice designers for those capabilities specifically. It has been identified by Goel that designers use the Limited Commitment Mode (LCM) control strategy in design problem solving. In this work, we conducted a study to confirm that LCM control strategy is used in solving a design problem and to see whether there is a difference in the level of LCM control strategy between expert and student designers. We devised a quantitative measure that can indicate the level of LCM control strategy usage as well as a visual representation for LCM control strategy usage. As a result, through these methods, we concluded that expert designers used more LCM control strategy than student designers. Also, we compared LCM control strategy usage with how soon critical idea decision is made.