In situ infrared study of formate reactivity on water–gas shift and methanol synthesis catalysts

In order to investigate the methanol synthesis reaction from CO₂/H₂, a comparative study of the reactivity of formate species on different types of catalysts and catalyst supports has been carried out. Formic acid was adsorbed on water–gas shift catalysts, Cu/ZnO/Al₂O₃ methanol synthesis catalyst and ZnO/Al₂O₃ support, Cu/ZnO/ZrO₂ and Cu/ZnO/CeO₂ methanol synthesis catalysts as well as their corresponding supports ZnO/ZrO₂ and ZnO/CeO₂. Superior reactivity and selectivity of dedicated methanol synthesis catalysts was evidenced by their behavior during the subsequent heating ramp, when these samples showed the simultaneous presence of formates and methoxy species and a higher stability of these reaction intermediates in the usual temperature range for the methanol synthesis reaction.     

Sorting out the value of spectroscopic tools to assess the Colletotrichum acutatum impact in olive cultivars with different susceptibilities

The olive tree (Olea europaea L.) can be affected by Colletotrichum acutatum, causing a loss of yield and quality of the final products, whilst the incidence of this fungal infection depends on several factors, including cultivar susceptibility. Thus, the effect of C. acutatum infection in cultivars displaying different susceptibilities to this fungal disease (‘Galega Vulgar’ ‐ susceptible, ‘Cobrançosa’ ‐ moderately susceptible, ‘Picual’ ‐ tolerant) has been assessed through spectrophotometric methods and HPLC, while the FTIR spectra of the cuticles have been concomitantly registered, resorting to the ATR accessory. With the support of multivariate analysis, these spectra allowed to discriminate olives with distinct infection times, besides retrieving evidences concerning the different susceptibility of each cultivar, while these observations were reinforced by the spectrophotometric and chromatographic methods. Furthermore, the assessment of the phenolic profile evidenced individual compounds in the distinct cultivars, so as their variations in response to the fungal infection.     

Effect of calcination temperature on structure and characteristics of calcium oxide powder derived from marine shell waste

Marine fishery wastes such as bivalve shells, crab shells and cuttlebone are rich in calcium. Calcium carbonate derived from these materials can be transformed into calcium oxide by calcination, which is used in a wide variety of applications (e.g., biomaterials for bone and teeth implants and drugs). In this study we analyze the effects of calcination temperatures (550 °C, 700 °C and 900 °C) on characteristics and elemental composition of calcium oxide derived from shells of four marine species collected in Thailand: oyster (Saccostrea cucullata), green mussel (Perna viridis), blue swimming crab (Portunus pelagicus), and cuttlefish (Sepia brevimana). The XRD patterns indicated the complete transformation of calcium carbonate into calcium oxide, observed by the changes of diffraction angles at 900 °C for all calcined samples, except cuttlebone, which was calcined successfully at 700 °C. Likewise, the FT-IR results revealed changes of functional groups at the same calcination temperatures. In addition, ICP-OES showed the effects of calcination temperature on elemental contents: major elements (Ca, P and K) increased in all samples, and some minor elements increased in blue swimming crab shell (Zn and Cu) and oyster shell (Fe) as a result of increasing the calcination temperature. This study demonstrates the optimum calcination temperature of calcium oxide production from four types of marine wastes that might be benefit for the chemical compound production industry.     

Operando XAFS on Hydrated Calcium Vanadium Bronze Cathode for Aqueous Zn-ion Storage

Multivalent ion storage and aqueous electrochemical systems continue to build interest for energy application. The Zn-ion system with 2 electron transfer and an ideal metal anode is a strong candidate but is still at the early stage of development. Using both in situ near-edge (XANES) and X-ray absorption fine structure spectroscopy, EXAFS, a nanostructured cathode material, Ca_xV₂O₅-H₂O (CVO), was probed at the V-K absorption edge. This operando study reveals the local electronic and geometric structure changes for CVO during galvanostatic cycling as the active material in an aqueous Zn-ion cell. The XANES data provides a fine resolution to track the evolution of the vanadium oxidative state and near-neighbor coordination sphere showing subtle shifts and delocalized charge. The Zn-ion influence on the V-K absorption edge is visualized using a difference technique called Δμ. Coupled with theoretical calculations and modelling, the extended region extracted local bonding information further confirms excellent electronic and structural reversibility of this vanadium oxide bronze in an aqueous Zn-ion electrochemical cell.     

Investigating Membrane-Mediated Antimicrobial Peptide Interactions with Synchrotron Radiation Far-Infrared Spectroscopy

Synchrotron radiation-based Fourier transform infrared spectroscopy enables access to vibrational information from mid over far infrared to even terahertz domains. This information may prove critical for the elucidation of fundamental bio-molecular phenomena including folding-mediated innate host defence mechanisms. Antimicrobial peptides (AMPs) represent one of such phenomena. These are major effector molecules of the innate immune system, which favour attack on microbial membranes. AMPs recognise and bind to the membranes whereupon they assemble into pores or channels destabilising the membranes leading to cell death. However, specific molecular interactions responsible for antimicrobial activities have yet to be fully understood. Herein we probe such interactions by assessing molecular specific variations in the near-THz 400–40 cm⁻¹ range for defined helical AMP templates in reconstituted phospholipid membranes. In particular, we show that a temperature-dependent spectroscopic analysis, supported by 2D correlative tools, provides direct evidence for the membrane-induced and folding-mediated activity of AMPs. The far-FTIR study offers a direct and information-rich probe of membrane-related antimicrobial interactions.     

Generation and Identification of the Linear OCBNO and OBNCO Molecules with 24 Valence Electrons

Two structural isomers containing five second-row element atoms with 24 valence electrons were generated and identified by matrix-isolation IR spectroscopy and quantum chemical calculations. The OCBNO complex, which is produced by the reaction of boron atoms with mixtures of carbon monoxide and nitric oxide in solid neon, rearranges to the more stable OBNCO isomer on UV excitation. Bonding analysis indicates that the OCBNO complex is best described by the bonding interactions between a triplet-state boron cation with an electron configuration of (2s)⁰(2p_σ)⁰(2p_π)² and the CO/NO⁻ ligands in the triplet state forming two degenerate electron-sharing π bonds and two ligand-to-boron dative σ bonds.     

A Comprehensive Study on the Full Series of Alkali-Metal Selenocyanates AI[SeCN] (AI=Li−Cs)

The full series of quasibinary alkali-metal selenocyanates was synthesized either by oxidation of the respective cyanides (A=Li−Rb) or by metathesis (A=Cs). For Li[SeCN] only ball-milling and subsequent annealing led to the isolation of the quasibinary selenocyanate. Their structures were refined from single-crystal and powder X-ray data. The respective solid-state IR and Raman spectra were interpreted with the aid of solid-state quantum-mechanical calculations and DSC-TGA measurements allowed for extraction of melting points. Only for Li[SeCN] a possible phase transition was observed that is discussed on the basis of VT-PXRD experiments. It is also the only quasibinary selenocyanate to form a hydrate (Li[SeCN] ⋅ 2H₂O).     

Pitfalls in X-ray absorption spectroscopy analysis and interpretation: A practical guide for general users

Despite the growing popularity of X-ray absorption spectroscopy (XAS) in scientific research, many researchers do not receive formalized training on this technique. Some of them learned from online resources, which only briefly introduce XAS and its applications. Here, this article aims to provide the overview of tips about the XAS analysis, general rules, as well as required information for presenting XAS data in publications, and some common mistakes in XAS data interpretations. Armed with these basics, the motivated aspiring XAS researchers will find existing resources more accessible and can progress much faster in understanding and using XAS.     

Recent Progress in the Simulation of Chiral Systems with Real Time Propagation Methods

In this brief review, an overview about recent efforts to simulate the spectroscopic signatures of chiral molecules is given with focus on real time propagation approaches to solve the time-dependent Schrödinger equation. In particular the simulation of electric circular dichroism spectra and vibrational Raman optical activity is discussed. In comparison to linear absorption spectra, where only the response of the electric dipole moment is necessary, the response of the magnetic dipole moment and electric quadrupole moment is more intricate. Issues such as gauge origin dependence, basis set dependence, non-local potentials and the dipole approximation are addressed.