Conformation-Dependent Coordination of Carboxylic Acids with Fe₃O₄ Nanoparticles Studied by ATR-FTIR Spectral Deconvolution

Abstract

The coordination of valeric acid (VA), glutaric acid (GA), and tricarballylic acid (TA) with Fe−OH on the Fe 3 O 4 nanoparticle surface has been systematically studied to elucidate the effects of COOH, molecular configuration, and ligand concentration on the coordination by the combined use of attenuated total reflectance Fourier transform infrared (ATR-FTIR) and thermogravimetric analysis (TGA). The results show that the binding ability of the acids increases with the increase in the COOH number. Multiple conformations coexist for the dicarboxylic and tricarboxylic acid coordinated on the iron oxide NPs. Saturated coordination formed with only a one-, two-, or three-COOH conformation for VA, GA, and TA, respectively, occurs under ligand-scarce conditions, while unsaturated coordination formed with the mixture of uncoordinated, one-, and/or two-COOH conformations for VA, GA, and TA, respectively, exists under ligand-abundant conditions. The maximum coordination numbers for monolayer adsorption for VA, GA, and TA on Fe 3 O 4 NPs are 9, 2.4, and 2.7 nm −2 , respectively. This study helps us to understand the fine coordination mechanism caused by the acid molecules with different configurations and elucidates, for the first time, the fine conformational variance incurred by the surrounding ligand with different concentrations and the way in which the ligand is added.

The Significant Influence of the pH Value on Citrate Coordination upon Modification of Superparamagnetic Iron Oxide Nanoparticles

“…This concentration level should be, on the one hand, sufficient to obtain a citrate monolayer with a high molecule density and, on the other hand, still low enough to keep the concentration‐related pressure to form different surface coordinations minimal. [ 12,19,47,48 ] (2)The second parameter is the base used for pH adjustment. Unfortunately, we are not aware of any appropriate study concerning its citrate adsorption‐related influence.…”

Dendritic Network Implementable Organic Neurofiber Transistors with Enhanced Memory Cyclic Endurance for Spatiotemporal Iterative Learning

“…These results provide strong evidence that carboxylic acid (COOH) groups were changed to carboxylate (COO − ) groups with resonance coupling between CO single bonds and CO double bonds. [ 32 ] Additionally, i) reduced absorption at the 3500–2500 cm −1 broad band corresponding to the OH stretching and hydrogen bonding of the dimer [ 33 ] and ii) appearance of strong absorption at 1300 cm –1 and 1398 cm –1 by (COO − ) group in FT‐IR [ 34 ] as well as (iii) X‐ray photoelectron spectroscopy analysis results support the removal of hydrogen from carboxylic acid groups in the oxidized P3CT (see Figures S8 and S9, Supporting Information). This behavior is consistent with previously reported results showing that the dissociation of protons in carboxylic acid groups induced a charge balance with the polarons under an applied oxidation potential, leading to a long‐term memory state.…”

The Simple Method of Preparation of Highly Carboxylated Bacterial Cellulose with Ni- and Mg-Ferrite-Based Versatile Magnetic Carrier for Enzyme Immobilization

“…This band appeared from the initial concentration of CA used for composite preparation above 0.5%, and the highest value was presented at the CA amount of 2.5% to 5.0%. The second band appeared only in spectra of modified BC at ≈ 1580 cm −1 assigned to the -O stretch of the deprotonated carboxylic group [32,33,34]. The changes in its intensity were well correlated with changes in the band's intensity at the range 1760 cm −1 to 1710 cm −1 .…”