Breaking K+ Concentration Limit on Cu Nanoneedles for Acidic Electrocatalytic CO2 Reduction to Multi-Carbon Products

Electrocatalytic CO₂ reduction reaction (CO₂RR) to multi-carbon products (C₂₊) in acidic electrolyte is one of the most advanced routes for tackling our current climate and energy crisis. However, the competing hydrogen evolution reaction (HER) and the poor selectivity towards the valuable C₂₊ products are the major obstacles for the upscaling of these technologies. High local potassium ions (K⁺) concentration at the cathode's surface can inhibit proton-diffusion and accelerate the desirable carbon-carbon (C−C) coupling process. However, the solubility limit of potassium salts in bulk solution constrains the maximum achievable K⁺ concentration at the reaction sites and thus the overall acidic CO₂RR performance of most electrocatalysts. In this work, we demonstrate that Cu nanoneedles induce ultrahigh local K⁺ concentrations (4.22 M) – thus breaking the K⁺ solubility limit (3.5 M) – which enables a highly efficient CO₂RR in 3 M KCl at pH=1. As a result, a Faradaic efficiency of 90.69±2.15 % for C₂₊ (FE_C2+) can be achieved at 1400 mA.cm⁻², simultaneous with a single pass carbon efficiency (SPCE) of 25.49±0.82 % at a CO₂ flow rate of 7 sccm.     

Simultaneous voltammetric determination of acetylsalicylic acid,caffeine and paracetamol in pharmaceutical formulations using screen-printed carbon electrode

Electrochemical oxidation of Paracetamol (PAR), Acetylsalicylic acid (ASA) and Caffeine (CAF) was investigated employing square wave stripping voltammetry (SWSV) using screen–printed carbon electrodes (SPCE). Determinations were performed in 0.1 mol L⁻¹ BR buffer (pH 2.0) without accumulation step. SWV were obtained by scanning the potential from 0.00 to 1.40 V employing a scan increment of 4 mV, pulse amplitude 25 mV and frequency of 25 Hz. PAR, ASA and CAF presents oxidation signals at 0.45, 1.03 and 1.32 V. The detection limits were 1.2, 1.7 and 1.7 mg L⁻¹, respectively. The method was applied in the PAR-ASA-CAF determination on pharmaceutical formulations.     

Structural evolution: mechanism of olefin insertion in hydroformylation reaction

Hydroformylation is the transformation of an alkene to an aldehyde via the addition of both hydrogen and carbon monoxide. The final aldehyde has one more carbon atom than the precursor alkene. Two isomeric products can result. The regiochemistry of the hydroformylation reaction is believed to be controlled by the olefin insertion step. A reaction mechanism is usually studied by finding the reactants, products, intermediates, and transition states. Alternatively, a chemical reaction can be studied from the redistribution of the electron density along the reaction path connecting the stationary points. The aim of this work is to describe the reaction mechanism of the insertion process by the structural evolution defined by the changes in the electron density during the reaction.     

Comparison of two extraction methods for the determination of selective serotonin reuptake inhibitors in sewage sludge by hollow fiber liquid-phase microextraction

This paper presents two procedures for the determination of four selective serotonin reuptake inhibitors (citalopram, paroxetine, fluoxetine, and sertraline) and one metabolite (norfluoxetine) in sewage sludge utilizing three-phase hollow fiber liquid-phase microextraction (HF-LPME). First, direct HF-LPME was used for extraction, clean-up, and preconcentration. The pharmaceuticals were extracted from slurry samples into an organic phase and then back-extracted into an aqueous phase in the lumen of the hollow fiber. Second, a procedure combining pressurized hot water extraction and HF-LPME for clean-up and preconcentration was developed for the same analytes and matrix. The extracts were subsequently analyzed by liquid chromatography-mass spectrometry. For direct HF-LPME, limits of detection were between 1 and 12 ng g(-1) (dry weight) and the relative standard deviation (RSD) values were 3-12%. For the second method, limits of detection were approximately 6 ng g(-1) for all the compounds and RSD values were 8-12%. The methods were validated by comparison of results for the same samples. Sewage sludge from a Swedish wastewater treatment plant was analyzed by both methods; average concentrations were similar for citalopram, paroxetine, and fluoxetine with values of approximately 530, 40, and 200 ng g(-1) , respectively.     

Observation of a Mott insulating ground state for Sn/Ge(111) at low temperature

We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3x3) phase formed at approximately 200 K, reverts to a new ((square root 3)x(square root 3))R30 degrees phase below 30 K. The vertical distortion characteristic of the (3x3) phase is lost across the phase transition, which is fully reversible. Angle-resolved photoemission experiments show that, concomitantly with the structural phase transition, a metal-insulator phase transition takes place. The ((square root 3)x(square root 3))R30 degrees ground state is interpreted as the formation of a Mott insulator for a narrow half-filled band in a two-dimensional triangular lattice.     

3,5-Dimethyl and 3,5-di-tert-butylpyrazolato complexes with alkali metals: monomeric, dimeric, cluster, and 1D chain structures

The pyrazolato complexes [(Me(2)pz)(THF)Li] (1), [((t)Bu(2)pz)Li](4) (2), [((t)Bu(2)pzH)((t)()Bu(2)pz)Li](2) (2a), [(Me(2)pz)Na] (3), [((t)Bu(2)pz)Na](4), [((t)Bu(2)pz)(6)(OH)Na(7)] (4a), [((t)Bu(2)pz)(18-crown-6)Na] (4b), and [((t)Bu(2)pz)K] (5) were synthesized by metalation reactions between R(2)pzH (R = Me, (t)()Bu) and alkyllithium, elemental sodium, or potassium. All the complexes were characterized by spectroscopic methods and microanalysis, and in addition, the crystal structures of 2, 2a, 3, 4a, 4b, and 5 were obtained by single-crystal X-ray diffraction. They show monomeric, dimeric, cluster, and 1D chain structures in the solid state. Ab initio calculations on the structure and stabilities of the monomeric pzM complexes were performed at the MP2 level of theory showing good agreement with the coordination preferences of the pyrazolato ligand to a particular alkali ion.     

Morphology and thermal properties relationship in poly(p-dioxanone)/layered double hydroxides nanocomposites

Nanocomposites of poly(p-dioxanone) (PPDO) with unmodified and organically modified layered double hydroxide (LDH) have been prepared by melt extrusion method. Dodecyl sulfate was used as organic modifier. The morphology of nanocomposites was analyzed by X-ray diffraction and transmission electron microscopy and their thermal properties by differential scanning calorimetry and thermogravimetric analysis. It has been found that the organic modifier decisively influences the nanocomposite morphology, resulting in a higher level of exfoliation. In addition, the glass transition temperature of nanocomposites was slightly higher than in case of unfilled PPDO. Moreover, the crystallization was delayed by LDH incorporation. The above behavior was ascribed to interactions between carbonyl groups of polymer matrix and hydroxyl groups of LDH, as supported by Fourier transformed infrared analysis. Interestingly, two different crystallization processes have been observed in the nanocomposite of PPDO and organically modified LDH. Unmodified and organo-modified LDH, practically did not alter the final melting point of PPDO. However, the thermal decomposition behavior was clearly influenced by the morphology exhibited by nanocomposites.     

Subsurface Engineering Induced Fermi Level De-pinning in Metal Oxide Semiconductors for Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting is a promising approach for renewable solar light conversion. However, surface Fermi level pinning (FLP), caused by surface trap states, severely restricts the PEC activities. Theoretical calculations indicate subsurface oxygen vacancy (sub-O_v) could release the FLP and retain the active structure. A series of metal oxide semiconductors with sub-O_v were prepared through precisely regulated spin-coating and calcination. Etching X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and electron energy loss spectra (EELS) demonstrated O_v located at sub ∼2–5 nm region. Mott–Schottky and open circuit photovoltage results confirmed the surface trap states elimination and Fermi level de-pinning. Thus, superior PEC performances of 5.1, 3.4, and 2.1 mA cm⁻² at 1.23 V vs. RHE were achieved on BiVO₄, Bi₂O₃, TiO₂ with outstanding stability for 72 h, outperforming most reported works under the identical conditions.     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.     

Highly Efficient Decomposition of Perfluorocarbons for over 1000 Hours via Active Site Regeneration

Tetrafluoromethane (CF₄), the simplest perfluorocarbon (PFC), has the potential to exacerbate global warming. Catalytic hydrolysis is a viable method to degrade CF₄, but fluorine poisoning severely restricts both the catalytic performance and catalyst lifetime. In this study, Ga is introduced to effectively assists the defluorination of poisoned Al active sites, leading to highly efficient CF₄ decomposition at 600 °C with a catalytic lifetime exceeding 1,000 hours. ²⁷Al and ⁷¹Ga magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the introduced Ga exists as tetracoordinated Ga sites (Ga_IV), which readily dissociate water to form Ga−OH. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density function theory (DFT) calculations confirmed that Ga−OH assists the defluorination of poisoned Al active sites via a dehydration-like process. As a result, the Ga/Al₂O₃ catalyst achieved 100 % CF₄ decomposition keeping an ultra-long catalytic lifetime and outperforming reported results. This work proposes a new approach for efficient and long-term CF₄ decomposition by promoting the regeneration of active sites.