Amine‐Free Synthesis of Cesium Lead Halide Perovskite Quantum Dots for Efficient Light‐Emitting Diodes

Cesium lead halide perovskite quantum dots (PQDs) have attracted significant interest for optoelectronic applications in view of their high brightness and narrow emission linewidth at visible wavelengths. A remaining challenge is the degradation of PQDs during purification from the synthesis solution. This is attributed to proton transfer between oleic acid and oleylamine surface capping agents that leads to facile ligand loss. Here, a new synthetic method is reported that enhances the colloidal stability of PQDs by capping them solely using oleic acid (OA). Quaternary alkylammonium halides are used as precursors, eliminating the need for oleylamine. This strategy enhances the colloidal stability of OA capped PQDs during purification, allowing us to remove excess organic content in thin films. Inverted red, green, and blue PQD light‐emitting diodes (LED) are fabricated for the first time with solution‐processed polymer‐based hole transport layers due to higher robustness of OA capped PQDs to solution processing. The blue and green LEDs exhibit threefold and tenfold improved external quantum efficiency (EQE), respectively, compared to prior related reports for amine/ammonium capped cross‐linked PQDs. The brightest blue LED based on all inorganic CsPb(Br_1?xCl_x)₃ PQDs is also reported.     

Production of a high concentration of ethanol from potato tuber by high gravity fermentation

To produce a high concentration of ethanol from viscous potato tuber mash, potato tuber mash containing high contents of solids (28%) was prepared by grinding the potato tuber without the addition of water. The viscosity of the potato mash was reduced by using Viscozyme (0.1%) at 50°C for 30 min. The potato mash was then liquefied using Liquozyme (0.1%) at 90°C for 30 min and optimal conditions for the simultaneous saccharification and fermentation (SSF) of the potato mash for ethanol production were investigated using statistical methods. Using 2⁴ factorial design, saccharifying-enzyme and incubation temperature were found to be important factors. Using response surface methodology, the optimal saccharifying-enzyme dosage and incubation temperature were determined to be 1.45 AGU/g dry matter and 31.3°C, respectively. Under these optimal conditions for SSF, 14.92%(v/v) ethanol with 91.0% of theoretical yield was produced after 60 h, and all the starch was completely used up.     

The influence of hydrogen-enriched gas on the performance of lean NOx trap catalyst for a light-duty diesel engine

Modern diesel engines have improved engine fuel economy and significantly reduced nitrogen oxides (NO_x) and particulate matter (PM) emissions achieved by advances in both combustion and exhaust aftertreatment technologies. Recently, it has been shown that the vehicle emissions can be further improved by several catalytic systems including fuel reformers and aftertreatment systems, such as the Lean NO_x Trap (LNT). This NO_x removal system, called LNT, absorbs NO_x under lean exhaust gas conditions and releases NO_x under rich conditions. This technology can provide high NO_x conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter under appropriate conditions.     

Numerical prediction of morphological change of straight trapezoidal open-channel

This paper presents a numerical model that is capable of simulating the morphological process of the trapezoidal open-channel. The fact that particles on the sloped side bank do not move in the same direction as the flow adds the difficulty in modeling. The lateral distribution model, which distributes the unit discharge over the width, is used for the flow analysis. Vectorial bedload formula by Kovacs and Parker (1994) is used and channel topography is calculated by solving Exner’s equation with the help of sliding algorithm proposed by Menendez et al. (2008). Values of roughness coefficient and lateral eddy viscosity are calibrated using laboratory data sets. Finally, the proposed model is applied to laboratory experiments of Ikeda (1981) and Izumi et al. (1991). Time evolutions of channel cross section and dimensionless shear stress are provided and discussed.     

Improved size distribution of AgBiS2 colloidal nanocrystals by optimized synthetic route enhances photovoltaic performance

Ternary silver bismuth sulfide (AgBiS₂) colloidal nanocrystals (NCs) have been recognized as a photovoltaic absorber for environmentally-friendly and low-temperature-processed thin film solar cells. However, previous synthetic methods involving hot injection of sulfur precursors into metal oleate precursor solutions do not provide a balance between nucleation and growth, leading to AgBiS₂ NCs with broad size distributions. Here, we demonstrate the modified synthetic route that size distribution of AgBiS₂ NCs can be improved by pre-adding the non-coordinating 1-octadecene (ODE) solvent into metal precursor solutions, leading to controlled concentration of coordinating oleic acid with improved hot-injection synthetic conditions. The addition of ODE as a non-coordinating solvent to metal precursor/oleic acid solution significantly suppresses variations in the concentration of coordinating oleic acid after injection of the sulfur precursor solution, leading to a homogenous reaction between the metal and sulfur precursors. For photovoltaic devices fabricated using the resultant AgBiS₂ NCs, the champion device shows power conversion efficiency (PCE) of 5.94% with an open-circuit voltage (V_OC) of 0.52 V. This performance is better than that a control device (PCE of 5.50% and V_OC of 0.49 V) because of the reduced energetic disorder and band tail broadening originating from the uniformly-sized AgBiS₂ NCs.     

Extraction and prioritization of product attributes using an explainable neural network

Pattern Analysis and Applications - Identification of product attributes is an important matter in real-world business environments because customers generally make purchase decisions based on...     

Leakage analysis of helical grooved pump seal using CFD

Journal of Mechanical Science and Technology - The helical grooved seal, which is a non-contact sealing device using the viscosity of the fluid, prevents leakage by reducing fluid pressure...