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Silica nanoparticles (SNPs) are produced on an industrial scale and are an addition to a growing number of commercial products. SNPs also have great potential for a variety of diagnostic and therapeutic applications in medicine. Contrary to the well-studied crystalline micron-sized silica, relatively little information exists on the toxicity of its amorphous and nano-size forms. Because nanoparticles possess novel properties, kinetics and unusual bioactivity, their potential biological effects may differ greatly from those of micron-size bulk materials. In this review, we summarize the physico-chemical properties of the different nano-sized silica materials that can affect their interaction with biological systems, with a specific emphasis on inhalation exposure. We discuss recent in vitro and in vivo investigations into the toxicity of nanosilica, both crystalline and amorphous. Most of the in vitro studies of SNPs report results of cellular uptake, size- and dose-dependent cytotoxicity, increased reactive oxygen species levels and pro-inflammatory stimulation. Evidence from a limited number of in vivo studies demonstrates largely reversible lung inflammation, granuloma formation and focal emphysema, with no progressive lung fibrosis. Clearly, more research with standardized materials is needed to enable comparison of experimental data for the different forms of nanosilicas and to establish which physico-chemical properties are responsible for the observed toxicity of SNPs.

The conversion of hydrocarbons to produce high-quality diesel fuel can be catalysed by bifunctional materials that contain a metal site and an acid site; it has been assumed that these sites should be as close as possible in order to enhance catalysis, but it is now shown that having them too close together can be detrimental to selectivity. Improved prospects for diesel fuel production New generations of monofunctional catalysts increasingly benefit from precisely controlled and optimized nanoscale features. Jovana Zečević et al . now show that optimization at the nanoscale can also improve the performance of the bifunctional hydrocracking catalysts widely used for the production of high-quality diesel fuels. These catalysts contain a metal site and an acid site, and for many years the received wisdom was that these sites should be as close as possible for optimum performance. But Zečević et al . find that having them too close together can be detrimental to selectivity, and that the sites should be positioned at nanometre-scale separations. This work may lead to more effective diesel production from alternative sources such as natural gas, vegetable oil and algal oil. The ability to control nanoscale features precisely is increasingly being exploited to develop and improve monofunctional catalysts 1 , 2 , 3 , 4 . Striking effects might also be expected in the case of bifunctional catalysts, which are important in the hydrocracking of fossil and renewable hydrocarbon sources to provide high-quality diesel fuel 5 , 6 , 7 . Such bifunctional hydrocracking catalysts contain metal sites and acid sites, and for more than 50 years the so-called intimacy criterion 8 has dictated the maximum distance between the two types of site, beyond which catalytic activity decreases. A lack of synthesis and material-characterization methods with nanometre precision has long prevented in-depth exploration of the intimacy criterion, which has often been interpreted simply as ‘the closer the better’ for positioning metal and acid sites 8 , 9 , 10 , 11 . Here we show for a bifunctional catalyst—comprising an intimate mixture of zeolite Y and alumina binder, and with platinum metal controllably deposited on either the zeolite or the binder—that closest proximity between metal and zeolite acid sites can be detrimental. Specifically, the selectivity when cracking large hydrocarbon feedstock molecules for high-quality diesel production is optimized with the catalyst that contains platinum on the binder, that is, with a nanoscale rather than closest intimacy of the metal and acid sites. Thus, cracking of the large and complex hydrocarbon molecules that are typically derived from alternative sources, such as gas-to-liquid technology, vegetable oil or algal oil 6 , 7 , should benefit especially from bifunctional catalysts that avoid locating platinum on the zeolite (the traditionally assumed optimal location). More generally, we anticipate that the ability demonstrated here to spatially organize different active sites at the nanoscale will benefit the further development and optimization of the emerging generation of multifunctional catalysts 12 , 13 , 14 , 15 .

Background Increasing environmental and occupational exposures to nanoparticles (NPs) warrant deeper insight into the toxicological mechanisms induced by these materials. The present study was designed to characterize the cell death induced by carbon black (CB) and titanium dioxide (TiO 2 ) NPs in bronchial epithelial cells (16HBE14o- cell line and primary cells) and to investigate the implicated molecular pathways. Results Detailed time course studies revealed that both CB (13 nm) and TiO 2 (15 nm) NP exposed cells exhibit typical morphological (decreased cell size, membrane blebbing, peripheral chromatin condensation, apoptotic body formation) and biochemical (caspase activation and DNA fragmentation) features of apoptotic cell death. A decrease in mitochondrial membrane potential, activation of Bax and release of cytochrome c from mitochondria were only observed in case of CB NPs whereas lipid peroxidation, lysosomal membrane destabilization and cathepsin B release were observed during the apoptotic process induced by TiO 2 NPs. Furthermore, ROS production was observed after exposure to CB and TiO 2 but hydrogen peroxide (H 2 O 2 ) production was only involved in apoptosis induction by CB NPs. Conclusions Both CB and TiO 2 NPs induce apoptotic cell death in bronchial epithelial cells. CB NPs induce apoptosis by a ROS dependent mitochondrial pathway whereas TiO 2 NPs induce cell death through lysosomal membrane destabilization and lipid peroxidation. Although the final outcome is similar (apoptosis), the molecular pathways activated by NPs differ depending upon the chemical nature of the NPs.

Synthetic methods that allow for the controlled design of well-defined Pt nanoparticles are highly desirable for fundamental catalysis research. In this work, we propose a strategy that allows precise and independent control of the Pt particle size and coverage. Our approach exploits the versatility of the atomic layer deposition (ALD) technique by combining two ALD processes for Pt using different reactants. The particle areal density is controlled by tailoring the number of ALD cycles using trimethyl(methylcyclopentadienyl)platinum and oxygen, while subsequent growth using the same Pt precursor in combination with nitrogen plasma allows for tuning of the particle size at the atomic level. The excellent control over the particle morphology is clearly demonstrated by means of in situ and ex situ X-ray fluorescence and grazing incidence small angle X-ray scattering experiments, providing information about the Pt loading, average particle dimensions, and mean center-to-center particle distance. The performance of supported nanoparticle catalysts is closely related to their size, shape and interparticle distance. Here, the authors introduce an atomic layer deposition-based strategy to independently tune the size and coverage of platinum nanoparticles with atomic-level precision.

A bstract We propose magnetic quivers for the complex-symplectic contraction spaces, which are related to implosions and have a natural interpretation in terms of the Moore-Tachikawa category. We use 3-d mirrors to provide computational checks.

This perspective outlines recent developments in the field of NMR spectroscopy, enabling new opportunities for in situ studies on bulk and confined clathrate hydrates. These hydrates are crystalline ice-like materials, built up from hydrogen-bonded water molecules, forming cages occluding non-polar gaseous guest molecules, including CH4, CO2 and even H2 and He gas. In nature, they are found in low-temperature and high-pressure conditions. Synthetic confined versions hold immense potential for energy storage and transportation, as well as for carbon capture and storage. Using previous studies, this report highlights static and magic angle spinning NMR hardware and strategies enabling the study of clathrate hydrate formation in situ, in bulk and in nano-confinement. The information obtained from such studies includes phase identification, dynamics, gas exchange processes, mechanistic studies and the molecular-level elucidation of the interactions between water, guest molecules and confining interfaces.

Safe storage and utilisation of hydrogen is an ongoing area of research, showing potential to enable hydrogen becoming an effective fuel, substituting current carbon-based sources. Hydrogen storage is associated with a high energy cost due to its low density and boiling point, which drives a high price. Clathrates (gas hydrates) are water-based (ice-like) structures incorporating small non-polar compounds such as H 2 in cages formed by hydrogen bonded water molecules. Since only water is required to construct the cages, clathrates have been identified as a potential solution for safe storage of hydrogen. In bulk, pure hydrogen clathrate (H 2 O-H 2 ) only forms in harsh conditions, but confined in nanospaces the properties of water are altered and hydrogen storage at mild pressure and temperature could become possible. Here, specifically a hydrophobic mesoporous silica is proposed as a host material, providing a suitable nano-confinement for ice-like clathrate hydrate. The hybrid silica material shows an important decrease of the pressure required for clathrate formation (approx. 20%) compared to the pure H 2 O-H 2 system. In-situ inelastic neutron scattering (INS) and neutron diffraction (ND) provided unique insights into the interaction of hydrogen with the complex surface of the hybrid material and demonstrated the stability of nano-confined hydrogen clathrate hydrate. This work focuses on clathrates, ice-like structures incorporating H 2 molecules in their cages. In bulk, pure H 2 clathrates only form in harsh conditions. Here, the formation of pure H 2 clathrate hydrate in confined space of a porous silica is demonstrated at much reduced pressures compared to the bulk H 2 clathrate.

Transitioning to a fossil fuel free society requires an increase in solar energy production. However, expanding solar power to farmland competes with food production. Additionally, climate change threatens food security and leads increasingly to yield losses. Agrivoltaic systems produce solar energy and food on the same field, while sheltering crops. In agrivoltaic systems, crops grow in a protected environment with reduced solar irradiance, a modified microclimate, and a potential physical cover protecting against hail damage. The agrivoltaic system may help safeguard crop yields from extreme weather events such as frost during flowering or sunburn during heat waves. Studies on agrivoltaic fruit production have previously focused on raspberry or apple. However, multiyear field trials are often lacking, and no study has described agrivoltaic pear cultivation. This research describes the multiyear effect of agrivoltaics on pear fruit, revealing that a predictable fruit yield and quality can be attained under solar panels in a temperate maritime climate. Tree rows were fitted with semi-transparent monofacial c-Si photovoltaic modules at a ground coverage ratio of 25.45%. Across three growing seasons, we recorded a 24% light reduction at canopy level. Agrivoltaic pear trees yielded 15% less than the reference control plots in 3 consecutive years. Flowering and fruit-set were unchanged, while agrivoltaics reduced leaf flavonoid levels. The leaf photosynthetic performance was identical, yet delayed leaf senescence under agrivoltaics suggests an adaptation to the modified environment. Agrivoltaics impacted fruit shape, as there was an increase in the number of bottle-shaped pears and a reduction in caliber. Other fruit quality traits were unaffected, including postharvest ethylene production. A land equivalent ratio of 1.44 was reached in the agrivoltaics orchard. This study demonstrates that agrivoltaics hold potential for pear production under temperate climates and highlights how pear productivity and quality is predictable when compared with conventional cultivation methods.

This work describes the synthesis of ordered 3D siloxane-silsesquioxane reticular materials with silicate D4R cubes (Si8O208−), harvested from a sacrificial tetrabutylammonium cyclosilicate hydrate (TBA-CySH) precursor, interlinked with octyl and dicyclopentyl (Cp2) hydrocarbon functionalities in a one-step synthesis with organodichlorosilanes. Advanced solid-state NMR spectroscopy allowed us to unravel the molecular order of the nodes and their interconnection by the silicone linkers. In the case of octyl-methyl silicone linkers, changing the silane-to-silicate ratio in the synthesis allowed for tuning the length of the linker between the nodes. With dicyclopentyl linkers, the addition of dimethyldichlorosilane was essential to enable the formation of a reticular network. The resulting materials contained mixed, dimeric silicone linkers, i.e., Si8-O-Si(Me2)-O-Si(Cp2)-O-Si8.

Despite the intense research efforts directed to electrocatalytic nitrogen reduction reaction (eNRR), the NH 3 yield and selectivity are still not up to the standard of practical application. Here, high-entropy perovskite oxides with composition Ba x (FeCoNiZrY) 0.2 O 3− δ (B x (FCNZY) 0.2 ( x = 0.9, 1) are reported as eNRR catalysts. The eNRR activity of high-entropy perovskite oxide is enhanced by changing the nonstoichiometric metal elements at the A-site, thus generating additional oxygen vacancies. The NH 3 yield and Faraday efficiency for B 0.9 (FCNZY) 0.2 are 1.51 and 1.95 times higher than those for B(FCNZY) 0.2 , respectively. The d-band center theory is used to theoretically predict the catalytically active center at the B-site, and as a result, nickel was identified as the catalytic site. The free energy values of the intermediate states in the optimal distal pathway show that the third protonation step (*NNH 2 → *NNH 3 ) is the rate-determining step and that the increase in oxygen vacancies in the high-entropy perovskite contributes to nitrogen adsorption and reduction. This work provides a framework for applying high-entropy structures with active site diversity for electrocatalytic nitrogen fixation.