Sulfur poisoning critically limits the activity and durability of Pt catalysts, yet the nanoscale structure-reactivity relationships that govern sulfate adsorption and its thermal desorption remain poorly resolved. Using infrared nanospectroscopy,...

Polyhydroxyalkanoates (PHAs) hold significant potential as sustainable alternatives to fossil-based plastics because of their bio-based origin and inherent biodegradability. Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) is a well-known commercial member of the PHA family characterized by good mechanical resistance and thermal behavior similar to that of some conventional polymers, such as polypropylene. However, its high crystallinity and fragility limit its application. Poly3-hydroxybutyrate-co-4-hydroxybutyrate (P(3HB-co-4HB)) is a new commercial copolymer containing a 4-hydroxybutyrate (4HB) segment that provides increased flexibility because of its amorphous phase. In this study, PHBV and P(3HB-co-4HB) were blended by extrusion, varying the percentage of P(3HB-co-4HB) to improve the PHBV properties without losing the PHA assets and potentializing the insertion of this biopolymer in the market. The results indicate that the impact energy required for fracture was increased in the polymer blends. These blends exhibited greater thermal stability than pure PHBV, with no significant changes observed in the melting and crystallization temperatures. Furthermore, blending was found to reduce shrinkage in injection-molded samples. The degradation in the soil increased with the highest P(3HB-co-4HB) content. Through 3D printing, it was observed that the blends led to an increase in the melt flow index and a reduction in warpage in the printed objects, thereby facilitating the processing of these materials. Consequently, incorporating P(3HB-co-4HB) into PHBV has emerged as a promising strategy to address the inherent limitations of PHBV. This approach not only enhances the mechanical properties and thermal stability but also improves the overall processability, thereby expanding the potential applications of this biopolymer blend.

Resonant catalysis theory predicts that applying an intermittent stimulus, such as charge, strain, heat or light, at frequencies on a timescale higher than the catalytic turnover frequency, can enhance activity by orders of magnitude and improve selectivity. However, experimental evidence of resonant catalysis is unfortunately lacking. This is partly due to the fact that the effect of intermittent stimulation on catalysts and reaction intermediates is not well understood. To address this challenge, time-resolved "stimulando" spectroscopic methods are needed to observe catalysts under operating conditions and during stimulation. Here, we use diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) to study the effect of intermittent light stimulation on the catalytic hydrogenation of CO2 over Ni-Ga-based catalyst materials as a model reaction. Previous research has shown that light can cause CO desorption and change the reactivity of formate intermediates during reaction. Since CO and formate species are believed to be active intermediates in CO2 hydrogenation, understanding how intermittent light affects their binding energy and surface coverage can provide insights into how to effectively stimulate catalysts to possibly achieve resonant catalysis. Ni3-Ga/SrTiO3 catalysts were synthesized using incipient wetness impregnation and tested under CO2 hydrogenation reaction conditions. Stimulando DRIFTS measurements were performed using both steady-state and rapid-scan DRIFTS to study the effect of continuous and intermittent ultraviolet (UV) light stimulation. Steady-state DRIFTS revealed that the surface coverage of CO, formate, and carbonate intermediates decreased reversibly upon UV illumination, with each species exhibiting distinct timescales to reach steady state (ranging from seconds to minutes). Furthermore, rapid-scan DRIFTS with millisecond time resolution demonstrated that spectral changes generally occurred faster when switching the UV light on compared to when switching it off in steady-state experiments. However, when using intermittent light at a 1 Hz on/off frequency, the rates of change for spectral features upon light switching on and off became comparable. This showcases the need to study catalyst stimulation under intermittent stimulation to capture the dynamic response of the system at the limit cycle. Despite the observed changes in the coverage of surface species, the CO2 hydrogenation performance of the catalyst was not significantly affected under the conditions studied herein. The stimulando spectroscopy method showcased here provides valuable insights for adjusting light stimulation parameters, such as intensity, duty cycle and light wavelength, paving the way to more effective catalyst stimulation.

While electrostatic interactions often drive protein adsorption at biointerfaces, the influence of the underlying secondary structure of the scaffold remains poorly understood. In this study, we compare the adsorption of photoactive yellow protein (PYP) onto three positively charged model protein surfaces: a rigid, planar β-sheet scaffold, a three-dimensional α-helical scaffold, and their (αβ) mixture, by using controlled pH and temperature adjustments to impose distinct secondary structures of poly-L-lysine. Using chiral and achiral vibrational sum-frequency generation (VSFG) and nano-FTIR spectroscopy, we demonstrate that the β-sheet surface promotes the formation of a well-defined monolayer with a signature β-scaffold peak at 1627 and 1680 cm-1. In contrast, the α-helical surface induces a multilayering effect, resulting in a five-fold enhancement of the chiral signal and the emergence of a prominent broad feature at 1654 cm-1, assigned to a chiral hydration network trapped within the protein assembly. Our results reveal that the 3D 'brush-like' topography of the helical surface provides superior orientational templating compared to the planar β-sheet, forcing the PYP molecules into a near-perfect vertical alignment. This work highlights that the conformational architecture of a biointerface is as critical as its chemical functionality in governing protein orientation and hydration at the nanoscale.

Lignin-carbohydrate complexes, in which lignin and polysaccharides are directly connected, have been identified and extensively analyzed. To date, however, the origin of these structures has not been unequivocally established. That notwithstanding, it has been found that delignification, whether by conventional pulping and bleaching processes or in the biorefinery context, is effected by the presence of lignin-carbohydrate complexes. Using density functional theory calculations, the current work has evaluated the thermodynamics of bond dissociation as a function of structure and chemical composition. Among the lignin-carbohydrate complexes that have been identified, the homolytic bond dissociation energy is highest for the α-benzyl ethers and γ-ester, with phenyl glycosides being markedly less endothermic. This is consistent with observations on the recalcitrance of these compounds. Heterolytic cleavage reactions of the α-benzyl ethers are less endothermic, due to water solvation of the ions. The latter observation may provide support for the proposed homolytic cleavage reaction, since if heterolysis were operative, the α-benzyl ethers would not exhibit the level of recalcitrance that is observed experimentally.

Selective separation of rare earth elements (REEs) in nanoporous media is very challenging due to the similar physicochemical properties of lanthanide ions. In this work, we systematically investigate the transport and selectivity of REE3+ ions through two model nanofluidic channels: 1.5 nm diameter carbon nanotube porins (wCNTPs) and 2.1 nm diameter boron nitride nanotube porins (BNNTPs). Using a fluorescence-based vesicle assay, we find that wCNTPs show almost no differential selectivity across the lanthanide series, a behavior consistent with bulk-dominant transport through their moderately-confined channels with chemically inert, hydrophobic walls. In contrast, BNNTPs exhibit nearly an order of magnitude higher permeability and mild differential selectivity, following a volcano-shaped trend with Eu3+ ions showing the highest permeability. We attribute this enhanced performance to the high negative surface charge of BNNTPs, which facilitates a surface-dominated transport mechanism where ion migration within the electric double layer becomes the primary contributor to ion transport. These results elucidate the distinct roles of surface charge in nanoscale confinement and provide critical design rules for the development of future membranes tailored for efficient REE separations.

We present a highly interpretable and efficient machine learning framework for predictive and generative modeling of adsorption energies on surfaces using subgraph isomorphic decision trees (SIDTs). Extracting graph representations of...

There has been a great amount of interest in nanopores as the basis for sensors and templates for preparation of biomimetic channels as well as model systems to understand transport properties at the nanoscale. The presence of surface charges on the pore walls has been shown to induce ion selectivity as well as enhance ionic conductance compared to uncharged pores. Here, using three-dimensional continuum modeling, we examine the role of the length of charged nanopores as well as applied voltage for controlling ion selectivity and ionic conductance of single nanopores and small nanopore arrays. First, we present conditions where the ion current and ion selectivity of nanopores with homogeneous surface charges remain unchanged, even if the pore length decreases by a factor of 6. This length-independent conductance is explained through the effect of ion concentration polarization (ICP), which modifies local ionic concentrations, not only at the pore entrances but also in the pore in a voltage-dependent manner. We describe how voltage controls the ion selectivity of nanopores with different lengths and present the conditions when charged nanopores conduct less current than uncharged pores of the same geometrical characteristics. The manuscript provides different measures of the extent of the depletion zone induced by ICP in single pores and nanopore arrays, including systems with ionic diodes. The modeling shown here will help design selective nanopores for a variety of applications where single nanopores and nanopore arrays are used.