Search

CuInS2/ZnS (CIS/ZnS) quantum dots (QDs) with high photoluminescence (PL) were synthesized via a facile solvothermal approach. Gaussian deconvolution of PL spectra, transmission electron microscopy, and time-resolved PL spectroscopies were used to characterize the emission properties of the prepared CIS and CIS/ZnS QDs. It was found that the growth of ZnS can reduce the surface defect acting as traps to minimize donor-acceptor emissions, and the contribution of band to donor/acceptor transition becomes a dominating emission with the increase of shell growth time. The blue shift of PL emission wavelength of CIS/ZnS QDs underwent two steps: the dramatic blue shift originated from the decreased fraction donor-acceptor transition due to the reduction of surface defects at the beginning and the subsequently mild blue-shift with the time from the interdiffusion of CIS and ZnS. The effect of trioctylphosphine (TOP) and dodecanethiol (DDT) as ligands during shell growth on the optical properties of QDs were investigated and compared. The PL quantum yield (QY) of CIS core affects the final value of CIS/ZnS QDs, and the higher PL QY is achieved while using CIS core with higher PL QY. Based on the selected ligand DDT, the reaction parameters, such as CIS core reaction time, shell growth time, and Zn/Cu feed molar ratio, were further optimized. CIS/ZnS QDs with high PL QY can be obtained with a Zn/Cu feed molar ratio larger than 4, shell growth time of 30 to 90 min, and shell growth temperature 220°C–240°C, and the maximum value was up to about 80% by adjusting the above-mentioned parameters.

A reactor‐combustor recycling system is proposed for safe operation of a hydrocarbon‐ and O2‐rich reactor by catalytically combusting excess O2 and recycling generated CO2 for dilution. The Pt/Al2O3 catalysts are determined as active and stable, and the Mars van Krevelen mechanism is applied for the combustion kinetics. Modeling and simulation of the system involving reactor, heater, combustor, valve, and cooler are performed, where multitubular, monolith, and microstructured reactors are compared for addressing the strong exothermic combustion. The system is highly promising because 99.9 % O2 can be consumed and explosion risk be eliminated via CO2 dilution. The microstructured combustor exhibits the highest potential by considering heat management, pressure drop, and compactness. [ABSTRACT FROM AUTHOR]

The development of recipes for synthesis of quantum dots (QDs), a novel semiconductor material for application in optoelectronic devices, is currently purely based on experiments. Since the quality of QDs represented by quantum yield (QY) and emission peak strongly depends on a number of different parameters (route, precursors, conditions, etc), a large number of experiments is necessary. In this article, we show that data‐driven modeling can be used as a supporting tool for optimization and a better understanding of the synthesis process. By using the results collected during the development of CuInS2/ZnS (CIS/ZnS) QDs, a neural network model has been established. The model is able to predict the optical properties (QY and emission peak) of CIS/ZnS QDs as a function of the most important synthesis parameters, such as reaction temperature, time of CIS core formation and ZnS shell growth, feed molar ratio of Cu/In and Zn/Cu, various starting precursors, and types of ligands. Finally, a model analysis under various effects influencing the quality of QDs is performed. [ABSTRACT FROM AUTHOR]

CuInS2/ZnS (CIS/ZnS) quantum dots (QDs) with high photoluminescence (PL) were synthesized via a facile solvothermal approach. Gaussian deconvolution of PL spectra, transmission electron microscopy, and timeresolved PL spectroscopies were used to characterize the emission properties of the prepared CIS and CIS/ZnS QDs. It was found that the growth of ZnS can reduce the surface defect acting as traps to minimize donor-acceptor emissions, and the contribution of band to donor/acceptor transition becomes a dominating emission with the increase of shell growth time. The blue shift of PL emission wavelength of CIS/ZnS QDs underwent two steps: the dramatic blue shift originated from the decreased fraction donor-acceptor transition due to the reduction of surface defects at the beginning and the subsequently mild blueshift with the time from the interdiffusion of CIS and ZnS. The effect of trioctylphosphine (TOP) and dodecanethiol (DDT) as ligands during shell growth on the optical properties of QDs were investigated and compared. The PL quantum yield (QY) of CIS core affects the final value of CIS/ ZnS QDs, and the higher PL QY is achieved while using CIS core with higher PL QY. Based on the selected ligand DDT, the reaction parameters, such as CIS core reaction time, shell growth time, and Zn/Cu feed molar ratio, were further optimized. CIS/ZnS QDs with high PL QY can be obtained with a Zn/Cu feed molar ratio larger than 4, shell growth time of 30 to 90 min, and shell growth temperature 220°C-240°C, and the maximum value was up to about 80% by adjusting the above-mentioned parameters. [ABSTRACT FROM AUTHOR]

Industrial research targets the reduction of CO2 footprint by means of renewable feedstocks. Three different topics are addressed: the use of the biomass as feedstock for fuels and chemicals, utilization of carbon dioxide as feedstock in the polymer industry, and finally, a concept to apply renewable energy in combination with carbon dioxide to make intermediates for chemical synthesis. These examples have been selected in order to illustrate that the strategic change of feedstocks has to be addressed on different time scales, necessity for the multidisciplinary approach, and the enabling role of catalysis. [ABSTRACT FROM AUTHOR]

Highly photoluminescent core/shell CuInS2/ZnS (CIS/ZnS) nanocrystals were synthesized. Zinc acetate and dodecanethiol in octadecene solvent were used for shell growth. The structure and composition of QDs were investigated with inductively coupled plasma-optical emission spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The crystal phase of CIS was tetragonal chalcopyrite. Based on X-ray diffraction analysis, it has been concluded that the growth of the ZnS shell did not affect the phase structure of CuInS2 (CIS). Photoluminescence (PL) quantum yield (QY) of CIS increased to 80% after epitaxial growth of ZnS, and the PL emission wavelength can be feasibly tuned to be in the range of 560–710 nm by adjusting shell growth time. The superb photostability with high PL QY of CIS/ZnS nanocrystals is ascribed to the gradient of the chemical composition that has been formed between the core and the shell. [ABSTRACT FROM AUTHOR]