Synergy between iono-covalent bonds and van der Waals interactions in SAMs formation: A first-principles study of adsorption of carboxylic acids on the Zn–ZnO(0001) surface

Immobilization of 4-MBA & Cu2+ on Au nanoparticles modified screen-printed electrode for glyphosate detection

This study introduces an innovative electrochemical biosensor, engineered through the functionalization screen-printed electrode (SPE) with a coordination complex comprised of 4-mercaptobenzoic acid (4-MBA) and copper ions (Cu2+), achieving precise quantitative determination of glyphosate. Electrodepositing gold nanoparticles (AuNPs) onto the electrode surface, forming a self-assembled monolayer (SAM) of 4-MBA via thiol-gold interactions, and immobilizing Cu2+ via coordination bonding with the monolayer, finalizing the electrochemical biosensor construction as Cu2+/4-MBA/AuNPs/SPE. The successful modification of the biosensor interface is confirmed through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical characterization. Through parameter optimization, critical metrics for the biosensor preparation process have been determined. Using square wave voltammetry (SWV), a linear relationship between the glyphosate concentration and the peak current inhibition ratio at the electrode surface is established. Additionally, the repeatability and anti-interference capabilities of the fabricated biosensors are evaluated. The experimental outcomes affirm the biosensor's capability for quantitative glyphosate detection across a 5-100 nM range, boasting a 1.65 nM limit of detection (LOD). Testing on tap water samples verifies a robust recovery rate for glyphosate residues, spanning 89.84 %-107.48 %. The proposed biosensor holds significant promise for glyphosate detection, offering substantial applicability and this study provides a valuable reference for the advancement of biosensors geared toward the quantitative assessment of organophosphate pesticides (OPs).

Examination of the Corrosion Behavior of Shape Memory NiTi Material for Biomedical Applications

In this study, corrosion and wear tests of NiTi alloy (Ni 55%-Ti 45%) samples, known as shape memory alloy, which offer a shape recovery memory effect between memory temperatures ranging from 25 to 35 °C, have been carried out. The standard metallographically prepared samples' microstructure images were obtained using an optical microscope device and SEM with an EDS analyzer. For the corrosion test, the samples are immersed with a net into the beaker of synthetic body fluid, whose contact with the standard air is cut off. Electrochemical corrosion analyses were performed after potentiodynamic testing in synthetic body fluid and at room temperature. The wear tests of the investigated NiTi superalloy were carried out by performing reciprocal wear tests under 20 N and 40 N loads in a dry environment and body fluid. During wear, a 100CR6-quality steel ball of the counter material was rubbed on the sample surface for a total of 300 m with a unit line length of 13 mm and a sliding speed of 0.04 m/s. As a result of both the potentiodynamic polarization and immersion corrosion tests in the body fluid, an average of 50% thickness reduction in the samples was observed in proportion to the change in the corrosion current values. In addition, the weight loss of the samples in corrosive wear is 20% less than that in dry wear. This can be attributed to the protective effect of the oxide film on the surface at high loads and the effect of reducing the friction coefficient of the body fluid.

Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH₃, R' = -CH₃), inh2 (R = -CH₃, R' = -CH₂CH₂NH₂), and inh3 (R = -C₆H₃(NH₂)₂, R' = -CH₂CH₂NH₂). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (∼182.38 kJ/mol) strongly interacts with ZnO(101̅0) compared to inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and O_surf (of the surface), respectively, creating N-Zn and H-O_surf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on O_surf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101̅0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel.

Modelling the Interaction between Carboxylic Acids and Zinc Oxide: Insight into Degradation of ZnO Pigments

Computational modelling applied to cultural heritage can assist the characterization of painting materials and help to understand their intrinsic and external degradation processes. The degradation of the widely employed zinc oxide (ZnO)—a white pigment mostly used in oil paints—leads to the formation of metal soaps, complexes of Zn ions and long-chain fatty acids coming from the degradation of the oil binder. Being a serious problem affecting the appearance and the structural integrity of many oil paintings, it is relevant to characterize the structure of these complexes and to understand the reaction pathways associated with this degradation process. Density functional theory (DFT) calculations were performed to investigate the adsorption of the acetate and acetic acid on relatively large ZnO clusters and the formation of Zn–acetate complexes. Carboxylic acids with longer alkyl chains were then investigated as more realistic models of the fatty acids present in the oil medium. In addition, DFT calculations using a periodic ZnO slab were performed in order to compare the obtained results at different levels of theory. Optimization calculations as well as the formation energies of the ZnO@carboxylate coupled systems and the thermodynamics leading to possible degradation products were computed. Our results highlight the potential for DFT calculations to provide a better understanding of oil paint degradation, with the aim of contributing to the development of strengthening and conservation strategies of paintings.

Colloidal CdS sensitized nano-ZnO/chitosan hydrogel with fast and efficient photocatalytic removal of congo red under solar light irradiation

Colloidal CdS sensitized nano-ZnO/chitosan (CdS@n-ZnO/CS) hydrogel was prepared and characterized extensively by XRD, SEM-EDS, TEM, UV-Vis DRS, FT-IR and TGA. The photocatalytic activity of CdS@n-ZnO/CS was evaluated with the photodegradation of congo red (CR) as an organic pollutant under solar light irradiation. The influences of initial dye concentration, catalyst dosage, recycling runs, and radical scavenger on decolorization of CR by CdS@n-ZnO/CS were investigated. 95% of CR was removed in just 1 min for 5.0 mg L^-1 and 94.34% of CR was removed in 30 min for 100 mg L^-1. CdS@n-ZnO/CS exhibited an excellent and ultra-fast performance toward CR removal under solar light due to the synergistic effect of adsorption by chitosan and photocatalysis by ZnO and CdS in CdS@n-ZnO/CS hydrogel. Radical trapping control experiments indicated that h⁺ and O₂^- played the major role for CR decolorization. The high performance of CdS@n-ZnO/CS hydrogel was also demonstrated under natural solar light irradiation, suggesting that CdS@n-ZnO/CS hydrogel could be used in practical wastewater treatment.

Corrosion protection of Al(111) by 8-hydroxyquinoline: a comprehensive DFT study

The corrosion protective 8HQ monolayer on Al(111).

Interactions of the Calcite {10.4} Surface with Organic Compounds: Structure and Behaviour at Mineral - Organic Interfaces

The structure and the strength of organic compound adsorption on mineral surfaces are of interest for a number of industrial and environmental applications, oil recovery, CO₂ storage and contamination remediation. Biomineralised calcite plays an essential role in the function of many organisms that control crystal growth with organic macromolecules. Carbonate rocks, composed almost exclusively of calcite, host drinking water aquifers and oil reservoirs. In this study, we examined the ordering behaviour of several organic compounds and the thickness of the adsorbed layers formed on calcite {10.4} surfaces. We used X-ray reflectivity (XRR) to study calcite {10.4} surfaces that were prepared in three alcohols: methanol, isopropanol and pentanol and one carboxylic acid: octanoic acid. All molecules adsorbed in self-assembled layers, where thickness depended on the density and the length of the molecule. For methanol and isopropanol, molecular dynamic simulations (MD) provided complementary information, which allowed us to develop a surface model. Branching in isopropanol induced slightly less ordering because of the additional degree of freedom. Pentanol and octanoic acid adsorbed as single monolayers. The results of this work indicate that adhered organic compounds from the surrounding environment can affect the surface behaviour, depending on properties of the organic compound.

The interaction of propionic and butyric acids with ice and HNO₃-doped ice surfaces at 195-212 K

The interaction of propionic and butyric acids on ice and HNO3-doped ice were studied between 195 and 212 K and low concentrations, using a Knudsen flow reactor coupled with a quadrupole mass spectrometer. The initial uptake coefficients (γ0) of propionic and butyric acids on ice as a function of temperature are given by the expressions: γ0(T) = (7.30 ± 1.0) × 10(-10) exp[(3216 ± 478)/T] and γ0(T) = (6.36 ± 0.76) × 10(-11) exp[(3810 ± 434)/T], respectively; the quoted error limits are at 95% level of confidence. Similarly, γ0 of propionic acid on 1.96 wt % (A) and 7.69 wt % (B) HNO3-doped ice with temperature are given as γ(0,A)(T) = (2.89 ± 0.26) × 10(-8) exp[(2517 ± 266)/T] and γ(0,B)(T) = (2.77 ± 0.29) × 10(-7) exp[(2126 ± 206)/T], respectively. The results show that γ0 of C1 to C4 n-carboxylic acids on ice increase with the alkyl-group length, due to lateral interactions between alkyl-groups that favor a more perpendicular orientation and well packing of H-bonded monomers on ice. The high uptakes (>10(15) molecules cm(-2)) and long recovery signals indicate efficient growth of random multilayers above the first monolayer driven by significant van der Waals interactions. The heterogeneous loss of both acids on ice and HNO3-doped ice particles in dense cirrus clouds is estimated to take a few minutes, signifying rapid local heterogeneous removal by dense cirrus clouds.