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Substituted ALPO-5 Zeolites as Promising O 2 Sorption Pump Materials: A Density Functional Theory Study
Many chemical processes depend on having an environment that is low in oxygen partial pressure (P O2 < 100 Pa); sorption pumps are a promising route to establishing that environment by either oxygen pumping or oxygen separation from an inert gas. Near ambient sorption-based processes rely on either pressure or thermal swings, requiring no moving parts, no electricity, and neither very high nor very low temperatures. In this work, we use ab initio calculations to explore zeolites as a class of materials for sorption based oxygen pumping/separation. Our calculations indicate that while the neat ALPO-5 zeolite does not adsorb O 2 , O 2 does adsorb on zeolites selectively substituted with transition metals and metalloids and hence, can enable separation and pumping. ALPO-5 substituted with Si, Ge, Sn, Pd, Pt, Ti, V, Cr, Mn, Zr, Mo, Hf, W, Ce, and Pr provides adsorption energies ranging from -0.19 to -3.92 eV, (-) indicates exothermic process. Additionally, we provide a comprehensive understanding of what controls the adsorption energy: 1) the substi-tutions must be able to adopt an oxidation state that is more positive than the cation it replaces, and 2) the size of the pore into which the O 2 adsorbs to the wall. Additionally, we conduct a ther-modynamic analysis of a thermal swing cycle to approximate the optimal O 2 binding energy for 2 low energy O 2 pumping/separation. We find that the minimum energy cost likely occurs when the adsorption energy is in the range of 0.75 – 1.00 eV (72 – 97 kJ·mol -1 ), which corresponds to Ge, V, Pt, or Ce substituted ALPO-5.
Creating Functional Oxynitride–Silicon Interfaces and SrNbO 2 N Thin Films for Photoelectrochemical Applications
Photoelectrochemical performance dependence upon absorption length, carrier diffusion length, and surface area of an oxynitride photoabsorber is investigated. How best to fabricate optical-quality thin films of bandgap-tunable oxynitrides is also discussed. We targeted the stoichiometric compound SrNbO 2 N as an optimal wide-bandgap photoabsorber (1.9 eV) for use with silicon (1.1 eV) in a tandem structure photoelectrochemical cell. Preparation of perovskite oxynitrides at high-temperature as isolated powders is often straightforward, but it is difficult to integrate them as thin films in tandem junction devices with low-temperature materials. Here we develop the first method to prepare optical-quality SrNbO 2 N thin-films of tunable thickness and roughness on single-crystal silicon substrate. This achievement required an interfacial layer of ultra-thin TaN to be used as a barrier to reduce the inter-diffusion of silicon and oxygen during oxynitride syn-thesis. We produced a variety of SrNbO 2 N film thicknesses (20-440 nm) on n + -Si(100) surfaces. Roughness factor (0.14-21) scaled with thickness. The intrinsic photoelectrochemical activity of these devices was evaluated using a low-barrier sacrificial electron donor. Photocurrent density and photovoltage revealed a significant (and non-linear) dependence on film thickness and roughness. Furthermore, absorption length, carrier diffusion length, and surface area were each found to play key roles. Balancing these is required for optimally performing devices.
Optical Cycling Functionalization of Arenes
Closed, laser-induced optical transitions (“optical cycling transitions”) of molecules can be used for state preparation and measurement in quantum information science and quantum sensing. Increasingly complex molecular species supporting optical cycling can provide new capabilities for quantum science, and it is not clear if there is a limit on their size or complexity. We explore Ca–O–L molecular constructs to support the optical cycling center, Ca, with ligands, L, being arenes. We find that L can be as large as coronene (i.e., CaOC 24 H 11 ) without losing the diagonality of the Franck–Condon factor (FCF). Furthermore, L can be substituted with electron-withdrawing groups to improve the FCF. Larger L, beyond ~7 rings, can disrupt the diagonality of the FCF by closing the HOMO–LUMO ligand electronic state gap and reordering with the local states on the cycling center. Altogether, we find that optical cycling can be retained for arenes, and we offer a principle for their design.
Effect of Polymer Chain Length on the Superlattice Assembly of Functionalized Gold Nanoparticles
We report on the assembly of gold nanoparticle (AuNPs) superlattices at the liquid/vapor interface and in the bulk of their suspensions. Interparticle distances in the assemblies are achieved on multiple length scales by varying chain lengths of surface grafted AuNPs by polyethylene glycol (PEG) with molecular weights in the range 2000–40,000 Da. Crystal structures and lattice constants in both 2D and 3D assemblies are determined by synchrotron-based surface-sensitive and small-angle X-ray scattering. Here, assuming knowledge of grafting density, we show that experimentally determined interparticle distances are adequately modeled by spherical brushes close to the θ point (Flory–Huggins parameter, x ≈ 1/2) for 2D superlattices at a liquid interface and a nonsolvent (χ = ∞) for the 3D dry superlattices.
Covalent Functionalization of Silicon with Plasma-Grown “Fuzzy” Graphene: Robust Aqueous Photoelectrodes for CO 2 Reduction by Molecular Catalysts
Carbon electrodes are ideal for electrochemistry with molecular catalysts, exhibiting facile charge transfer and good stability. Yet for solar-driven catalysis with semiconductor light absorbers, stable semiconductor/carbon interfaces can be difficult to achieve, and carbon’s high optical extinction means it can only be used in ultrathin layers. Here, we demonstrate a plasma-enhanced chemical vapor deposition process that achieves well-controlled deposition of out-of-plane “fuzzy” graphene (FG) on thermally oxidized Si substrates. The resulting Si|FG interfaces possess a silicon oxycarbide (SiOC) interfacial layer, implying covalent bonding between Si and the FG film that is consistent with the mechanical robustness observed from the films. The FG layer is uniform and tunable in thickness and optical transparency by deposition time. Using p-type Si|FG substrates, noncovalent immobilization of cobalt phthalocyanine (CoPc) molecular catalysts was employed for the photoelectrochemical reduction of CO 2 in aqueous solution. The Si|FG|CoPc photocathodes exhibited good catalytic activity, yielding a current density of ∼1 mA/cm 2 , Faradaic efficiency for CO of ∼70% (balance H 2 ), and stable photocurrent for at least 30 h at −1.5 V vs Ag/AgCl under 1-sun illumination. Furthermore, the results suggest that plasma-deposited FG is a robust carbon electrode for molecular catalysts and suitable for further development of aqueous-stable Si photocathodes for CO 2 reduction.
Solution-Phase Activation and Functionalization of Colloidal WS[subscript 2] Nanosheets with Ni Single Atoms
Abstract not provided
Efficient electrochemical synthesis of robust, densely functionalized water soluble quinones
Robust, highly water-soluble quinone derivatives are efficiently prepared by a scalable electrosynthetic protocol employing low-cost commercially available precursors.
Design of functional composite and all-inorganic nanostructured materials via infiltration of polymer templates with inorganic precursors
Robust and efficient approaches for the synthesis of materials with structure, porosity, and composition controlled at the nanoscale are highly important for a wide range of applications. Polymer templates are promising platforms to achieve such control. The self-assembly process of polymers provides access to diverse structures that can serve as templates for the deposition of inorganic materials. By infiltrating metal precursors from gas or liquid phases, using sequential infiltration synthesis (SIS) or swelling-based infiltration (SBI), respectively, into the polymer templates, one can create finely-tuned texturing of the surface films and bulk materials. In this review, we outline the specifics and dynamics of the polymer infiltration process and characterize the structure and properties of the synthesized materials. Finally, we highlight recent progress in implementing polymer infiltration-based nanoporous ceramics for many applications, including sensors, antireflective coatings, oil-absorbing foams, nanolithographic patterns, and catalytic materials.
Structural and functional conservation of the programmed -1 ribosomal frameshift signal of SARS coronavirus 2 (SARS-CoV-2)
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Aspects of thermal one-point functions and response functions in AdS black holes
Not Available
Structure and Function of the Cytochrome P450 Monooxygenase Cinnamate 4-hydroxylase from Sorghum bicolor
Not provided.
Thermal Properties of Sodium Borosilicate Glasses as a Function of Sulfur Content
SO3 additions, up to 3.0 wt%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2-10Al2O3-12B2O3-21Na2O-7CaO (wt%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.5 wt% SO3. It was found that sulfur (here as sulfate) in this glass increased the glass transition temperature, thermal diffusivity, heat capacity, and thermal conductivity, and decreased the mass density. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased crosslinking of the borosilicate backbone lead to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.
Functional and structural characterization of AntR, an Sb(III) responsive transcriptional repressor
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Structural and functional ramifications of antigenic drift in recent SARS-CoV-2 variants
Defenses against SARS-CoV-2 variants Our key defense against the COVID-19 pandemic is neutralizing antibodies against the SARS-CoV-2 virus elicited by natural infection or vaccination. Recent emerging viral variants have raised concern because of their potential to escape antibody neutralization. Wang et al . identified four antibodies from early-outbreak convalescent donors that are potent against 23 variants, including variants of concern, and characterized their binding to the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Yuan et al . examined the impact of emerging mutations in the receptor-binding domain of the spike protein on binding to the host receptor ACE2 and to a range of antibodies. These studies may be helpful for developing more broadly effective vaccines and therapeutic antibodies. —VV