Fenton Reaction for Enhancing Polishing Rate and Protonated Amine Functional Group Polymer for Inhibiting Corrosion in Ge1Sb4Te5 Film Surface Chemical–Mechanical-Planarization

A Fenton reaction and a corrosion inhibition strategy were designed for enhancing the polishing rate and achieving a corrosion-free Ge1Sb4Te5 film surface during chemical–mechanical planarization (CMP) of three-dimensional (3D) cross-point phase-change random-access memory (PCRAM) cells and 3D cross-point synaptic arrays. The Fenton reaction was conducted with 1,3-propylenediamine tetraacetic acid, ferric ammonium salt (PDTA–Fe) and H2O2. The chemical oxidation degree of GeO2, Sb2O3, and TeO2 evidently increased with the PDTA–Fe concentration in the CMP slurry, such that the polishing rate of the Ge1Sb4Te5 film surface linearly increased with the PDTA–Fe concentration. The addition of a corrosion inhibitor having protonated amine functional groups in the CMP slurry remarkably suppressed the corrosion degree of the Ge1Sb4Te5 film surface after CMP; i.e., the corrosion current of the Ge1Sb4Te5 film surface linearly decreased as the corrosion inhibitor concentration increased. Thus, the proposed Fenton reaction and corrosion inhibitor in the Ge1Sb4Te5 film surface CMP slurry could achieve an almost recess-free Ge1Sb4Te5 film surface of the confined-PCRAM cells, having an aspect ratio of 60-nm-height to 4-nm-diameter after CMP.

Surface adsorption and survival of SARS-CoV-2 on frozen meat

The first case of a severe acute respiratory syndrome caused by coronavirus-2 was reported in December 2019 in China. The disease spread globally quickly, causing the 2019–2021 COVID-19 pandemic. The meat industry became concerned over the possibility of transmitting the virus in the slaughterhouse environment. The level of air exchange strongly affects the distribution of SARS-CoV-2 aerosols within the slaughterhouses. The adsorption of the SARS-CoV-2 virus on the surface of the frozen meat is dictated mainly by the interplay of electrostatic forces between the virion and tissue (pH) and environmental conditions (temperature and humidity) in the vicinity of adsorption micro-location. Suppose the virus contaminates the meat surface, whereby pH is 5.5 or less. In that case, it firmly adsorbs due to bonds established by protonated amine group and a hydrogen bond between the COOH group of the viral protein and oxygen in hydroxyl groups present on meat surfaces. The meat surface, coated with a thin water film, interacts with the SARS-CoV-2 virions by establishing strong hydrogen bonds. Although there is no proof of COVID-19 contraction by food consumption, the strong surface adsorption and ability of SARS-CoV-2 to survive meat freezing indicate a potential risk of virus transmission by meat.

Spectroscopic Investigations of 316L Stainless Steel under Simulated Inflammatory Conditions for Implant Applications: The Effect of Tryptophan as Corrosion Inhibitor/Hydrophobicity Marker

In this paper, the conformational changes of tryptophan (Trp) on the corroded 316 L stainless steel (SS) surface obtained under controlled simulated inflammatory conditions have been studied by Raman (RS) and Fourier-transform infrared (FT-IR) spectroscopy methods. The corrosion behavior and protective efficiency of the investigated samples were performed using the potentiodynamic polarization (PDP) technique in phosphate-buffered saline (PBS) solution acidified to pH 3.0 at 37 °C in the presence and absence of 10−2 M Trp, with different immersion times (2 h and 24 h). The amino acid is adsorbed onto the corroded SS surface mainly through the lone electron pair of the nitrogen atom of the indole ring, which adopts a more/less tilted orientation, and the protonated amine group. The visible differences in the intensity of the Fermi doublet upon adsorption of Trp onto the corroded SS surface, which is a sensitive marker of the local environment, suggested that a stronger hydrophobic environment is observed. This may result in an improvement of the corrosion resistance, after 2 h than 24 h of exposure time. The electrochemical results confirm this statement—the inhibition efficiency of Trp, acting as a mixed-type inhibitor, is made drastically higher after a short period of immersion.

Micro- and Nanoscale Spectroscopic Investigations of Threonine Influence on the Corrosion Process of the Modified Fe Surface by Cu Nanoparticles

The work presents a comprehensive vibrational analysis of the process of adsorption of threonine (Thr) onto an Fe surface with deposited Cu nanoparticles (NPs) (of about 4–5 nm in size) in a corrosive environment. The application of surface-enhanced Raman spectroscopy (SERS) and surface-enhanced infrared absorption spectroscopy (SEIRA) provides the opportunity for detailed description of adsorption geometry of amino acid onto a metal surface. The combination of conventional infrared spectroscopy (IR) with atomic force microscopy (AFM) resulted in a nano-SEIRA technique which made it possible to provide a precise description of adsorbate binding to the metal surface. The studies presented confirmed that there is a very good correlation between the spectra recorded by the SERS, SEIRA, and nano-SEIRA techniques. Threonine significantly influenced the process of corrosion of the investigated surface due to the existing strong interaction between the protonated amine and carboxylate groups and the CuNPs deposited onto the Fe surface. In addition, the application of two polarization modulations (s and p) in nano-SEIRA allows subtle changes to be observed in the molecule geometry upon adsorption, with the carboxylate group of Thr being almost horizontally oriented onto the metal surface; whereas the amine group that contains nitrogen is oriented perpendicular to this surface.

Quaternization of Composite Algal/PEI Beads for Enhanced Uranium Sorption—Application to Ore Acidic Leachate

The necessity to recover uranium from dilute solutions (for environmental/safety and resource management) is driving research towards developing new sorbents. This study focuses on the enhancement of U(VI) sorption properties of composite algal/Polyethylenimine beads through the quaternization of the support (by reaction with glycidyltrimethylammonium chloride). The sorbent is fully characterized by FTIR, XPS for confirming the contribution of protonated amine and quaternary ammonium groups on U(VI) binding (with possible contribution of hydroxyl and carboxyl groups, depending on the pH). The sorption properties are investigated in batch with reference to pH effect (optimum value: pH 4), uptake kinetics (equilibrium: 40 min) and sorption isotherms (maximum sorption capacity: 0.86 mmol U g−1). Metal desorption (with 0.5 M NaCl/0.5 M HCl) is highly efficient and the sorbent can be reused for five cycles with limited decrease in performance. The sorbent is successfully applied to the selective recovery of U(VI) from acidic leachate of uranium ore, after pre-treatment (cementation of copper, precipitation of rare earth elements with oxalate, and precipitation of iron). A pure yellow cake is obtained after precipitation of the eluate.

Complexes of antitubercular antibiotics with cellulose sulfate acetate

Water-insoluble complexes of antituberculosis antibiotics (AB) kanamycin (CNMC), amikacin (AMCC) and capreomycin (CPRMC), traditionally used parenterally, with cellulose acetate sulphate in the form of sodium salt (Na-SAC) were obtained. The possibility of their immobilization on the activated carbon (AC) to create a tablet form of AB was demonstrated. The composition of the complexes was determined depending on the medium pH and the order of solutions components mixing. It was shown that with decreasing pH from 6 to 1 due to an increase in the number of protonated amine groups in AB molecules, the number of contacts with polymer macromolecules increases and the amount of cellobiosic units in the complex’s composition increases as well: in the case of CNMC and AMCC from one to three and to four in the case of CPRMC. The electrostatic nature of the complexation is confirmed by the corresponding bands’ shifts in the IR spectra: Na-SAC sulfate groups and the antibiotic amino groups. It was established in vitro that the Na-SAC–CNMC complexes and their compositions with activated carbon are not only equivalent, but also have the double activity of the standard (injectable) form of CNMC in the relation to tuberculosis mycobacterium. The resulting compositions can be recommended for in vivo testing as a new form of aminoglycoside antibiotics for oral administration.

Tuning Mechanism through Buffer Dependence of Hydrogen Evolution Catalyzed by a Cobalt Mini-enzyme

Cobalt-mimochrome VI*a (CoMC6*a) is a synthetic mini-protein that catalyzes aqueous proton reduction to hydrogen (H₂). In buffered water, there are multiple possible proton donors, complicating the elucidation of mechanism. We have found that buffer pKa and sterics have significant effects on activity, evaluated through cyclic voltammetry (CV). Protonated buffer is proposed to act as the primary proton donor to the catalyst, specifically through the protonated amine of the buffers that were tested. At a constant pH of 6.5, catalytic H₂ evolution in the presence of buffer acids of pK_a ranging from 5.8 to 11.6 was investigated, giving rise to a potential-pK_a relationship that can be divided into two regions. For acids of pK_a ≤ 8.7, the half-wave catalytic potential (E_h) changes as a function of pKa with a slope of –128 mV/pK_a unit, and for acids of pK_a ≥ 8.7, Eh changes as a function of pKa with a slope of –39 mV/pKa unit. In addition, a series of buffer acids was synthesized to explore the influence of steric bulk around the acidic proton on catalysis. The catalytic current in CV shows a significant decrease in the presence of the sterically hindered buffer acids compared to their parent compounds, also consistent with the added buffer acid acting as the primary proton donor to the catalyst and showing that acid structure in addition to pK_a impacts activity. These results demonstrate that buffer acidity and structure are important considerations when optimizing and evaluating systems for proton-dependent catalysis in water.

Tuning Mechanism through Buffer Dependence of Hydrogen Evolution Catalyzed by a Cobalt Mini-enzyme

Cobalt-mimochrome VI*a (CoMC6*a) is a synthetic mini-protein that catalyzes aqueous proton reduction to hydrogen (H₂). In buffered water, there are multiple possible proton donors, complicating the elucidation of mechanism. We have found that buffer pKa and sterics have significant effects on activity, evaluated through cyclic voltammetry (CV). Protonated buffer is proposed to act as the primary proton donor to the catalyst, specifically through the protonated amine of the buffers that were tested. At a constant pH of 6.5, catalytic H₂ evolution in the presence of buffer acids of pK_a ranging from 5.8 to 11.6 was investigated, giving rise to a potential-pK_a relationship that can be divided into two regions. For acids of pK_a ≤ 8.7, the half-wave catalytic potential (E_h) changes as a function of pKa with a slope of –128 mV/pK_a unit, and for acids of pK_a ≥ 8.7, Eh changes as a function of pKa with a slope of –39 mV/pKa unit. In addition, a series of buffer acids was synthesized to explore the influence of steric bulk around the acidic proton on catalysis. The catalytic current in CV shows a significant decrease in the presence of the sterically hindered buffer acids compared to their parent compounds, also consistent with the added buffer acid acting as the primary proton donor to the catalyst and showing that acid structure in addition to pK_a impacts activity. These results demonstrate that buffer acidity and structure are important considerations when optimizing and evaluating systems for proton-dependent catalysis in water.

Vibrational spectroscopy of protonated amine–water clusters: tuning Fermi resonance and lighting up dark states

The H-bonded NH stretching fundamentals of protonated amine–water clusters pass through the “Fermi resonance window” formed by bending overtones, generating split bands due to anharmonic couplings.