For PbS quantum dot (QD)-based optoelectronic devices, gold is the most frequently used electrode material. In most device architectures, gold is in direct contact with the QD solid. To better ...understand the formation of the interface between gold and a close-packed QD layer at an early stage, in situ grazing-incidence small-angle X-ray scattering is used to observe the gold sputter deposition on a 1,2-ethanedithiol (EDT)-treated PbS QD solid. In the kinetics of gold layer growth, the forming and merging of small gold clusters (radius less than 1.6 nm) are observed at the early stages. The thereby formed medium gold clusters (radius between 1.9–2.4 nm) are influenced by the QDs’ templating effect. Furthermore, simulations suggest that the medium gold clusters grow preferably along the QDs’ boundaries rather than as a top coating of the QDs. When the thickness of the sputtered gold layer reaches 6.25 nm, larger gold clusters with a radius of 5.3 nm form. Simultaneously, a percolation layer with a thickness of 2.5 nm is established underneath the gold clusters. This fundamental understanding of the QD–gold interface formation will help to control the implementation of sputtered gold electrodes on close-packed QD solids in device manufacturing processes.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
The unconstrained demand forecast for car rentals has become a difficult problem for revenue management due to the need to cope with a variety of rental vehicles, the strong subjective desires and ...requests of customers, and the high probability of upgrading and downgrading circumstances. The unconstrained demand forecast mainly includes repairing of constrained historical demand and forecasting of future demand. In this work, a new methodology is developed based on multiple discrete choice models to obtain customer choice preference probabilities and improve a known spill model, including a repair process of the unconstrained demand. In addition, the linear Holt–Winters model and the nonlinear backpropagation neural network are combined to predict future demand and avoid excessive errors caused by a single method. In a case study, we take advantage of a stated preference and a revealed preference survey and use the variable precision rough set to obtain factors and weights that affect customer choices. In this case study and based on a numerical example, three forecasting methods are compared to determine the car rental demand of the next time cycle. The comparison with real demand verifies the feasibility and effectiveness of the hybrid forecasting model with a resulting average error of only 3.06%.
SiO2 encapsulated SnZnCu microspheres (several micrometers to about 30 μm in diameter) with very low undercooling, narrow freezing/melting range, and high thermal cycling stability have been produced ...and used as the temperature stabilizer of the packed bed in highly exothermic Fischer–Tropsch reaction. The core–shell structured SnZnCu@SiO2 microspheres are prepared in a two-step way, namely SnZnCu microspheres are firstly produced via a molten LiCl–KCl–CsCl eutectic-based metal emulsion method, and then a sol–gel approach is employed to coat them with a uniform, anti-leakage SiO2 layer. It is found that raising the amount of Zn to 4.0 at.% is critical for achieving a very low undercooling (<5 °C for SnZn0.04Cux@SiO2 vs. about 84 °C for Sn@SiO2) and a narrow freezing/melting peak width, and both undercooling and peak width are almost unchanged as the Cu content (x) increases from 1.5 to 3.0 at.%. However, their thermal cycling stability depends positively on the amount of Cu and can be remarkably improved when 3.0 at.% Cu is added. The results also show that low undercooling and narrow freezing/melting peak width are associated with the formation of Sn–Zn–Cu ternary eutectic and metastable phase Cu5Zn8, and poor thermal cycling stability of SnZn0.04Cux@SiO2 microspheres with low Cu content is related to the decomposition of Cu5Zn8 during thermal cycling. By embedding thermally stable SnZn0.04Cu0.03@SiO2 microspheres into the Co/SiO2 catalyst for Fischer–Tropsch synthesis, the temperature gradient in the catalyst bed can be significantly reduced by suppressing the formation of hot spots or thermal runaway and thus rapid deactivation of Co catalyst that occurs in the SnZn0.04Cux@SiO2-absent Co/SiO2 catalyst can be avoided.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Integrin subunit alpha 3 (ITGA3) expression correlates with the development and prognosis of human cancers. This study aimed to investigate the association of ITGA3 expression with pancreatic cancer ...(PCa) prognosis. The ITGA3 gene expression data were extracted from The Cancer Genome Atlas (TCGA) pancreatic adenocarcinoma (PAAD) cohort and 14 Gene Expression Omnibus microarray datasets. The differences in ITGA3 expression levels between tumor and non-tumor tissues were compared using the Mann–Whitney
test. Cox regression analysis and meta-analysis were performed to detect the association of ITGA3 expression with PCa prognosis. ITGA3 expression was higher in tumors than in controls. Tumors with advanced grades (3/4) had higher ITGA3 levels compared with early-grade tumors (1/2). The meta-analysis of the TCGA PAAD cohort and seven microarray datasets (GSE28735, GSE62452, GSE79668, GSE71729, GSE57495, GSE78229, and GSE21501) showed that ITGA3 was a prognostic biomarker in PCa (hazard ratio (HR) = 1.38, 95% confidence interval (CI) 1.26–1.51,
< 0.00001). Five ITGA3-related genes, including ITGB1 (HR = 1.6), ITGB5 (HR = 1.6), ITGB6 (HR = 1.6), LAMA3 (HR = 2.1), and CD9 (HR = 2.3), correlated with PCa prognosis significantly (
< 0.05). Functional enrichment analysis showed that ITGA3 was related to “hsa04151: PI3K-Akt signaling pathway” and “hsa04510: Focal adhesion.” We concluded that high ITGA3 expression was a potential prognostic biomarker in PCa.
Chip-scale package (CSP) light-emitting diodes (LEDs) are considered as the next generation of highly efficient package LED. However, they suffer from total internal reflection that limits their ...light extraction efficiency (LEE). In this letter, surface patterning, in terms of microstructures, as a well-controlled surface roughness method is designed and applied on CSP-LED to improve the LEE. Based on simulation results, pyramid and flat top pyramid structures have been designed and optimized. Four types of layouts, including tightly, interlaced, distant and chessboard layout, are also compared. A LEE enhancement of more than 20% is achieved. Furthermore, the four layouts with pyramid structures are fabricated using nano-imprint technology. The experimental results match the simulated results well with only a mismatch of 2.9%. The fabricated layout shows an enhancement of 20.31% when pyramid structures are fully filling the surface. Surface patterned CSP-LED, therefore, exhibits a great potential for high efficient LED.
One series of Cu-Zn and two series of Cu-Zn-Al hydroxycarbonate precursors with varying metal molar ratios were prepared via co-precipitation or multi-precipitation method, and the mixed metal oxides ...obtained by calcination of the precursor materials were used as adsorbents for H2S removal in the range of 25-100A degree C. The results of H2S adsorption tests showed that these mixed oxides, especially two series of Cu-Zn-Al mixed metal oxides exhibited markedly high breakthrough sulfur capacities (ranging from 4.4 to 25.7gS/100g-sorbent with increase of Cu/Zn molar ratio) at 40A degree C. Incorporation Cu and/or Al decreased the mean crystalline sizes of ZnO and CuO species in the Cu-Zn and Cu-Zn-Al mixed metal oxide adsorbents by decreasing of mean crystalline sizes of hydroxycarbanate phases mainly including hydrozincite, aurichalcite and malachite, segregation of Al phase, etc. Higher breakthrough sulfur capacity of each adsorbent in two ternary series than that of the corresponding adsorbent in binary series should be ascribed to the enhancement of the dispersion of ZnO and/or CuO species with incorporation of aluminum, thereby increasing the overall rate of reaction between the adsorbent and H2S by reducing the thickness of potential sulfide shell on the outer layer of the oxide crystalline grains and increasing the area of the interface for the exchange of HSa degree /S2a degree and O2a degree . For each series of adsorbents, the breakthrough sulfur capacity increased with the increase of Cu/Zn molar ratio regardless of changes of the dispersion of CuO and/or ZnO. This phenomenon might be mainly attributed to faster rate of the lattice diffusion of HSa degree , S2a degree and O2a degree or exchange of HSa degree /S2a degree and O2a degree during the sulfidation of CuO than that during the sulfidation of ZnO due to less rearrangement of the anion lattice.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The emergence of optical Internet of Things (optical-IoT) for sixth-generation (6G) networks has been envisaged to relieve the bandwidth congestion in the conventional radio frequency (RF) channel, ...and to support the ever-increasing number of smart devices. Among the plethora of device innovations deemed essential for fortifying the development, herein we report on the visible-to-near-infrared color-conversion luminescent-dyes based on lead sulphide quantum dots (PbS QDs), so as to achieve an eye-safe high-speed optical link. The solution-processed PbS QDs exhibited strong absorption in the visible range, radiative recombination lifetime of 6.4 <inline-formula><tex-math notation="LaTeX">\mu</tex-math></inline-formula>s, as well as high photoluminescence quantum yield of up to 88%. Our proof-of-principle demonstration based on an orthogonal frequency-division multiplexing (OFDM) modulation scheme established an infrared data transmission of 0.27 Mbit/s, readily supporting an indoor optical-IoT system, and shed light on the possibility for PbS-integrated transceivers in supporting remote access control of multiple nodes. We further envisaged that our investigations could find applications in future development of solution-processable PbS-integrated luminescent fibers, concentrators, and waveguides for high-speed optical receivers.
BaClxFy as well as BaF2 and BaClF catalysts were prepared by solid-state reaction at room temperature with Ba(OH)2 as the precursor and NH4F/NH4Cl as the F and Cl sources. The catalysts were applied ...for the dehydrochlorination of 1-chloro-1,1-difluoroethane to vinylidene fluoride at 350 °C. The industrial manufacture of vinylidene fluoride (VDF) is carried out at 600–700 °C, whereas the BaClxFy catalysts provided a promising pathway to produce VDF at much lower temperatures. Unfortunately, the selectivity of VDF over BaF2 decreased from 94% to 84% along with the deactivation of the BaF2 catalyst monotonically. In the presence of small amounts of Cl in BaF2, stabilized selectivity was achieved. Over BaCl0.05F0.95, BaCl0.1F0.9 and BaCl0.25F0.75, no decrease in VDF selectivity was observed. Clearly, the presence of small amounts Cl during solid-state preparation inhibited the growth of BaF2 crystalline significantly. Far smaller particles were achieved. The particle size, or more precisely, the crystal size of the barium catalyst played a major role in the catalytic performance. In addition to the crystal growth, the presence of small amounts of Cl during catalyst preparation changed the chemical state of Ba, and therefore the adsorption and activation of the C–Cl bond for HCFC-142b were altered.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Colloidal PbS quantum dots (QDs) are attractive for solution-processed thin-film optoelectronic applications. In particular, directly achieving QD thin-films by printing is a very promising method ...for low-cost and large-scale fabrication. The kinetics of QD particles during the deposition process play an important role in the QD film quality and their respective optoelectronic performance. In this work, the particle self-organization behavior of small-sized QDs with an average diameter of 2.88 ± 0.36 nm is investigated for the first time in situ during printing by grazing-incidence small-angle X-ray scattering (GISAXS). The time-dependent changes in peak intensities suggest that the structure formation and phase transition of QD films happen within 30 seconds. The stacking of QDs is initialized by a templating effect, and a face-centered cubic (FCC) film forms in which a superlattice distortion is also found. A body-centered cubic nested FCC stacking is the final QD assembly layout. The small size of the inorganic QDs and the ligand collapse during the solvent evaporation can well explain this stacking behavior. These results provide important fundamental understanding of structure formation of small-sized QD based films prepared via large-scale deposition with printing with a slot die coater.
Near infrared to visible up-conversion devices have every growing demand in a myriad of industrial sectors including photovoltaics, energy harvesting, medicine and imaging. Here we have demonstrated ...an up-conversion device which utilizes quantum dots for both infrared absorption and visible emission. The band structure of the device is designed and optimized with well-constructed carrier transport and blocking layers. The achieved up-conversion device exhibits an impressive conversion efficiency of over 6 %, with a high near infrared on-off ratio of over 104. The device demonstrates a potential new approach for an up-conversion device designed solely on quantum dots with high efficiency.
PDF
