On the Shape-Selected, Ligand-Free Preparation of Hybrid Perovskite (CH3NH3PbBr3) Microcrystals and Their Suitability as Model-System for Single-Crystal Studies of Optoelectronic Properties

Hybrid perovskite materials are one of the most promising candidates for optoelectronic applications, e.g., solar cells and LEDs, which can be produced at low cost compared to established materials. Although this field of research has seen a huge upsurge in the past decade, there is a major lack in understanding the underlying processes, such as shape-property relationships and the role of defects. Our aerosol-assisted synthesis pathway offers the possibility to obtain methylammonium lead bromide (MAPbBr3) microcrystals from a liquid single source precursor. The differently shaped particles are aligned on several substrates, without using a directing agent or other additives. The obtained particles show good stability under dry conditions. This allows us to characterize these materials and their pure surfaces at the single-crystal level using time- and spatially resolved methods, without any influences of size-dependent effects. By optimizing the precursor for the aerosol process, we were able to eliminate any purification steps and use the materials as processed. In addition, we performed theoretical simulations to deepen the understanding of the underlying processes in the formation of the different crystal facets and their specific properties. The model system presented provides insights into the shape-related properties of MAPbBr3 single crystals and their directed but ligand-free synthesis.

Retrieval of process rate parameters in the general dynamic equation for aerosols using Bayesian state estimation: BAYROSOL1.0

The uncertainty in the radiative forcing caused by aerosols and its effect on climate change calls for research to improve knowledge of the aerosol particle formation and growth processes. While experimental research has provided a large amount of high-quality data on aerosols over the last 2 decades, the inference of the process rates is still inadequate, mainly due to limitations in the analysis of data. This paper focuses on developing computational methods to infer aerosol process rates from size distribution measurements. In the proposed approach, the temporal evolution of aerosol size distributions is modeled with the general dynamic equation (GDE) equipped with stochastic terms that account for the uncertainties of the process rates. The time-dependent particle size distribution and the rates of the underlying formation and growth processes are reconstructed based on time series of particle analyzer data using Bayesian state estimation – which not only provides (point) estimates for the process rates but also enables quantification of their uncertainties. The feasibility of the proposed computational framework is demonstrated by a set of numerical simulation studies.

The role of aerosol process representation in uncertainty in the North Atlantic region in CMIP6

<p>Previous studies have shown that anthropogenic aerosol emissions drive a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in CMIP6 historical simulations that was not simulated in the CMIP5 multi-model mean. The strength of the CMIP6 AMOC trend has been linked to the strength of the aerosol forcing, with the inclusion of aerosol-cloud interactions accounting for a large proportion of the difference between CMIP5 and CMIP6. However, there is large uncertainty in the magnitude and distribution of aerosol effective radiative forcing in CMIP6. Understanding this uncertainty is important for the interpretation of simulated AMOC variability.</p><p> </p><p>We present an evaluation of the atmospheric variables with the potential to influence AMOC changes in CMIP6 historical and AMIP simulations, including downwelling shortwave radiation, surface heat fluxes, surface air temperature, and precipitation. We examine the links between aerosol effective radiative forcing, the magnitude and pattern of biases in the mean and trends in modelled quantities, and the complexity of the representation of aerosol chemistry and aerosol-cloud interactions. Using these results, we highlight areas where model diversity in the representation of aerosol process may be particularly important for uncertainty in simulations of North Atlantic climate. </p>

Retrieval of process rate parameters in the general dynamic equation for aerosols using Bayesian state estimation

The uncertainty in the radiative forcing caused by aerosols and its effect on the climate change calls for research to improve knowledge of the aerosol particle formation and growth processes. While the experimental research has provided large amount of high quality data on aerosols in the last two decades, the inference of the process rates is still inadequate, mainly due to limitations in the analysis of data. This paper focuses on developing computational methods to infer aerosol process rates from size distribution measurements. In the proposed approach, the temporal evolution of aerosol size distributions is modeled with the general dynamic equation equipped with stochastic terms that account for the uncertainties of the process rates. The time-dependent particle size distribution and the rates of the underlying formation and growth processes are reconstructed based on time series of particle analyzer data using Bayesian state estimation – which not only provides (point) estimates for the process rates but also enables quantifying their uncertainties. The feasibility of the proposed computational framework is demonstrated by a set of numerical simulation studies.

Antimicrobial Air Filters Using Natural Sea Salt Particles for Deactivating Airborne Bacterial Particles

We developed an antimicrobial air filter using natural sea salt (NSS) particles. Airborne NSS particles were produced via an aerosol process and were continuously coated onto the surface of an air filter under various deposition times. The filtration efficiency and bactericidal performance of the NSS-coated filter against aerosolized bacterial particles (Staphylococcus epidermidis, Escherichia coli) were evaluated quantitatively. The filtration efficiency of the tested filter ranged from 95% to 99% depending on the deposition time, and the bactericidal performance demonstrated efficiencies of more than 98% against both tested bacterial bioaerosols when the NSS deposition ratio was more than 500 μg/cm2. The experimental results indicated that the NSS-coated filters have the potential to be used as effective antimicrobial air filters for decreasing environmental exposure to microbial contaminants.

Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts for chemo-enzymatic cascade reactions

<div> <p>Integrating enzymatic and heterogeneous catalysis can pave the way to new and performing cascade chemical processes. In this perspective, the preparation of bifunctional structures combining both an active inorganic catalyst and an enzyme is a key. However, such combinations are not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization would be restricted to the external surface. We overcame this challenge by developing a new kind of hybrid catalysts based on hollow zeolite microspheres. The method leverages on the aerosol-assisted assembly of TS-1 nanocrystals to form hollow zeolite microspheres with tailored hierarchical texture and high epoxidation activity in water. The latter spheres were subsequently loaded with glucose oxidase enzymes which were then cross-linked to secure their entrapment. This controlled design allows to combine all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite microsphere is used both as a nest for the enzyme and as an efficient inorganic heterogeneous catalyst. The enzyme ensures the <i>in situ</i> production of H₂O₂ subsequently utilized by the zeolite for the epoxidation of allylic alcohol. We anticipate our method will open up new perspectives in the field of hybrid catalysis. Starting from various catalytic nano-building blocks, hollow microspheres with open entry ways could be prepared using the aerosol process and could be used as vessels for enzymes or even multi-enzymatic systems, thereby giving access to a multitude of new heterogeneous chemo-biocatalysts. <br></p> </div>

Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts for chemo-enzymatic cascade reactions

<div> <p>Integrating enzymatic and heterogeneous catalysis can pave the way to new and performing cascade chemical processes. In this perspective, the preparation of bifunctional structures combining both an active inorganic catalyst and an enzyme is a key. However, such combinations are not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization would be restricted to the external surface. We overcame this challenge by developing a new kind of hybrid catalysts based on hollow zeolite microspheres. The method leverages on the aerosol-assisted assembly of TS-1 nanocrystals to form hollow zeolite microspheres with tailored hierarchical texture and high epoxidation activity in water. The latter spheres were subsequently loaded with glucose oxidase enzymes which were then cross-linked to secure their entrapment. This controlled design allows to combine all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite microsphere is used both as a nest for the enzyme and as an efficient inorganic heterogeneous catalyst. The enzyme ensures the <i>in situ</i> production of H₂O₂ subsequently utilized by the zeolite for the epoxidation of allylic alcohol. We anticipate our method will open up new perspectives in the field of hybrid catalysis. Starting from various catalytic nano-building blocks, hollow microspheres with open entry ways could be prepared using the aerosol process and could be used as vessels for enzymes or even multi-enzymatic systems, thereby giving access to a multitude of new heterogeneous chemo-biocatalysts. <br></p> </div>

Aerosol-Assisted Sol-Gel Synthesis of Mesoporous TiO2 Materials, and Their Use as Support for Ru-Based Methanation Catalysts

<div>Mesoporous TiO₂ materials have been prepared by an aerosol process, which leverages on the acetic acid-mediated sol-gel chemistry and on the evaporation-induced self-assembly phenomenon to obtain materials with high specific surface area and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when the calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions lead to the progressive destruction of the mesostructured, concomitant with a progressive drop of textural properties and with the crystallization of larger anatase domains. The mesoporous TiO₂ material calcined at 350°C (specific surface area = 260 m².g^-1; pore volume = 0.36 cm³.^-1; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO₂ nanoparticles, and subsequently annealed in air. It is shown that the presence of RuO₂ nanoparticles and subsequent annealing provoke further intense modification of the texture and crystallinity of the TiO₂ materials. In addition to a drop in the textural parameters, a RuO₂-mediated crystallization of rutile TiO₂ is highlighted at temperature as low as 250°C. After an in situ reduction in H₂, the catalysts containing TiO₂ rutile and relatively small RuO₂ crystals showed the highest activity in the methanation of CO₂. </div>

Aerosol-Assisted Sol-Gel Synthesis of Mesoporous TiO2 Materials, and Their Use as Support for Ru-Based Methanation Catalysts

<div>Mesoporous TiO₂ materials have been prepared by an aerosol process, which leverages on the acetic acid-mediated sol-gel chemistry and on the evaporation-induced self-assembly phenomenon to obtain materials with high specific surface area and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when the calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions lead to the progressive destruction of the mesostructured, concomitant with a progressive drop of textural properties and with the crystallization of larger anatase domains. The mesoporous TiO₂ material calcined at 350°C (specific surface area = 260 m².g^-1; pore volume = 0.36 cm³.^-1; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO₂ nanoparticles, and subsequently annealed in air. It is shown that the presence of RuO₂ nanoparticles and subsequent annealing provoke further intense modification of the texture and crystallinity of the TiO₂ materials. In addition to a drop in the textural parameters, a RuO₂-mediated crystallization of rutile TiO₂ is highlighted at temperature as low as 250°C. After an in situ reduction in H₂, the catalysts containing TiO₂ rutile and relatively small RuO₂ crystals showed the highest activity in the methanation of CO₂. </div>