Partial PdAu nanoparticle embedding into TiO support accentuates catalytic contributions from the Au/TiO interface.

Despite the broad catalytic relevance of metal-support interfaces, controlling their chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently, their contributions to overall catalytic reactivity, remains challenging, as the nanoparticle and support characteristics are interdependent when catalysts are prepared by impregnation. Here, we decoupled both characteristics by using a raspberry-colloid-templating strategy that yields partially embedded PdAu nanoparticles within well-defined SiO or TiO supports, thereby increasing the metal-support interfacial contact compared to nonembedded catalysts that we prepared by attaching the same nanoparticles onto support surfaces. Between nonembedded PdAu/SiO and PdAu/TiO, we identified a support effect resulting in a 1.

analysis of gas dependent redistribution kinetics in bimetallic Au-Pd nanoparticles.

The catalytic and plasmonic properties of bimetallic gold-palladium (Au-Pd) nanoparticles (NPs) critically depend on the distribution of the Au and Pd atoms inside the nanoparticle bulk and at the surface. Under operating conditions, the atomic distribution is highly dynamic. Analyzing gas induced redistribution kinetics at operating temperatures is therefore key in designing and understanding the behavior of Au-Pd nanoparticles for applications in thermal and light-driven catalysis, but requires advanced characterization strategies.

Deconvoluting the Individual Effects of Nanoparticle Proximity and Size in Thermocatalysis.

Nanoparticle (NP) size and proximity are two physical descriptors applicable to practically all NP-supported catalysts. However, with conventional catalyst design, independent variation of these descriptors to investigate their individual effects on thermocatalysis remains challenging. Using a raspberry-colloid-templating approach, we synthesized a well-defined catalyst series comprising PdAu alloy NPs of three distinct sizes and at two different interparticle distances.

Iterative Bragg peak removal on X-ray absorption spectra with automatic intensity correction.

This study introduces a novel iterative Bragg peak removal with automatic intensity correction (IBR-AIC) methodology for X-ray absorption spectroscopy (XAS), specifically addressing the challenge of Bragg peak interference in the analysis of crystalline materials. The approach integrates experimental adjustments and sophisticated post-processing, including an iterative algorithm for robust calculation of the scaling factor of the absorption coefficients and efficient elimination of the Bragg peaks, a common obstacle in accurately interpreting XAS data, particularly in crystalline samples. The method was thoroughly evaluated on dilute catalysts and thin films, with fluorescence mode and large-angle rotation.

Interrogating site dependent kinetics over SiO-supported Pt nanoparticles.

A detailed knowledge of reaction kinetics is key to the development of new more efficient heterogeneous catalytic processes. However, the ability to resolve site dependent kinetics has been largely limited to surface science experiments on model systems. Herein, we can bypass the pressure, materials, and temperature gaps, resolving and quantifying two distinct pathways for CO oxidation over SiO-supported 2 nm Pt nanoparticles using transient pressure pulse experiments.

A transient flow reactor for rapid gas switching at atmospheric pressure.

Herein, we present a design for a transient flow reactor system with high detection sensitivity and minimal dead volume, such that it is capable of sub-second switching of the gas stream flowing through a catalytic bed. We demonstrate the reactor's capabilities for step transient, pulse, and stream oscillation experiments using the model system of CO oxidation over Pd catalysts, and we find that we are able to precisely model step transients for CO oxidation using a pseudo-homogenous-packed bed reactor model. The design principles leading to minimal gas hold-up time and increased sensitivity that are described in this paper can be implemented into existing flow reactor designs with minimal cost, providing a readily accessible alternative to the existing transient instrumentation.

Predicting a Sharp Decline in Selectivity for Catalytic Esterification of Alcohols from van der Waals Interactions.

Controlling the selectivity of catalytic reactions is a critical aspect of improving energy efficiency in the chemical industry; thus, predictive models are of key importance. Herein the performance of a heterogeneous, nanoporous Au catalyst is predicted for the complex catalytic self-coupling of the series of C -C alkyl alcohols, based solely on the known kinetics of the elementary steps of the catalytic cycle for methanol coupling, using scaling methods augmented by density functional theory. Notably, a sharp decrease in selectivity for ester formation with increasing molecular weight to favor the aldehyde due to van der Waals interactions of reaction intermediates with the surface was predicted and subsequently verified quantitatively by experiment.

New Architectures for Designed Catalysts: Selective Oxidation using AgAu Nanoparticles on Colloid-Templated Silica.

A highly modular synthesis of designed catalysts with controlled bimetallic nanoparticle size and composition and a well-defined structural hierarchy is demonstrated. Exemplary catalysts-bimetallic dilute Ag-in-Au nanoparticles partially embedded in a porous SiO matrix (SiO -Ag Au )-were synthesized by the decoration of polymeric colloids with the bimetallic nanoparticles followed by assembly into a colloidal crystal backfilled with the matrix precursor and subsequent removal of the polymeric template. This work reports that these new catalyst architectures are significantly better than nanoporous dilute AgAu alloy catalysts (nanoporous Ag Au ) while retaining a clear predictive relationship between their surface reactivity with that of single-crystal Au surfaces.

Gas phase stabiliser-free production of hydrogen peroxide using supported gold-palladium catalysts.

Hydrogen peroxide synthesis from hydrogen and oxygen in the gas phase is postulated to be a key reaction step in the gas phase epoxidation of propene using gold-titanium silicate catalysts. During this process HO is consumed in a secondary step to oxidise an organic molecule so is typically not observed as a reaction product. We demonstrate that using AuPd nanoparticles, which are known to have high HO synthesis rates in the liquid phase, it is possible to not only oxidise organic molecules in the gas phase but to detect HO for the first time as a reaction product in both a fixed bed reactor and a pulsed Temporal Analysis of Products (TAP) reactor without stabilisers present in the gas feed.

Modelling analysis of the structure and porosity of covalent triazine-based frameworks.

Varying degrees of order have been found experimentally for a series of covalent triazine-based frameworks (CTFs) when synthesised under different reaction conditions. Here, we use molecular modelling to discuss the potential origins of this structural order by analysis of the node and strut building blocks. We use a combination of small model structures based on DFT optimised monomer units and more extended simulations using automated structure growth and molecular dynamics to discuss the influence of the strut structure on the local crystallinity of these materials.

Apolipoprotein E epsilon4 and catechol-O-methyltransferase alleles in autopsy-proven Parkinson's disease: relationship to dementia and hallucinations.

We determined whether apolipoprotein E epsilon4 (ApoE4) or catechol-O-methyltransferase (COMT) genotypes were associated with dementia, hallucinations, Alzheimer's disease pathological findings (AP), or cortical Lewy bodies (CLBs) in autopsy-confirmed cases of Parkinson's disease (PD). Outcomes were obtained from medical records. Pathology reports identified AP and CLBs.

Induction of the early-late Ddc gene during Drosophila metamorphosis by the ecdysone receptor.

During Drosophila metamorphosis, the 'early-late' genes constitute a unique class regulated by the steroid hormone 20-hydroxyecdysone. Their induction is comprised of both a primary and a secondary response to ecdysone. Previous work has suggested that the epidermal expression of the dopa decarboxylase gene (Ddc) is likely that of a typical early-late gene.

Expression of tumor necrosis factor alpha and its mRNA in the spinal cord following a weight-drop injury.

The effect of traumatic spinal cord injury (SCI) on the expression of tumor necrosis factor (TNFalpha) and its mRNA was examined. Quantitative reverse transcription polymerase chain reaction assay showed TNFalpha mRNA level increased > 20-fold at the lesion site by 1 h after the injury compared to that in uninjured controls. The TNFalpha mRNA level was still significantly higher than in the controls 72 h after the injury.