Iron Formate Research Articles

Direct detection of acetylcholinesterase by Fe(HCOO)2.6(OH)0.3. H2O nanosheets with oxidase-like activity on a smartphone platform

Monitoring acetylcholinesterase (AChE) is crucial in clinical diagnosis and drug screening. Traditional methods for detecting AChE usually require the addition of intermediates like acetylthiocholine, which complicates the detection process and introduces interference risks. Herein, we develop a direct colorimetric assay based on alkaline iron formate nanosheets (Fe(HCOO)2.6(OH)0.3·H2O NSs, Fef NSs) for the detection of AChE without any intermediates. The as-prepared Fef NSs exhibit oxidase-like activity, catalyzing the generation of O2·-, 1O2 and ·OH, which leads to a color change from colorless to blue when exposed to 3,3′,5,5′-tetramethylbenzidine. AChE directly inhibits the oxidase-like activity of Fef NSs, resulting in a hindered color reaction, enabling the detection of AChE. The biosensor has a linear detection range of 0.1–30 mU/mL, with a minimum detection limit of 0.0083 mU/mL (S/N = 3), representing a 100-fold improvement in detection sensitivity over the traditional Ellman's method. Satisfactory results were obtained when analyzing real AChE samples. Attractively, a method for the quantitative detection of AChE by a smartphone is established based on the Fef NSs. This method enables instant acquisition of AChE concentrations, achieving real-time visualized detection.

Co–Fe–oxide nanoparticles supported on the various highly dispersed matrices: the effect of the carrier on structural and magnetic properties

sA series of mixed oxides was synthesized by deposition of the guest phase on the highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65–91 m2/g were selected as highly dispersed matrices. Co–Fe mixed oxides with the general formula Co4xFexOy (Co: Fe = 4: 1) were deposited as the guest oxides using the two-step method: (i) solvate-stimulated modification of the surface of fumed nanocarriers with the mixture of cobalt nitrate (II) and iron (III) formate and (ii) subsequent heat treatment up to 600 °C to form Co4xFexOy. The aim of this paper was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the morphology of the resulting composites in the gaseous and aqueous media using the XRD, XPS, FTIR, nitrogen adsorption and SEM/EDX, as well as quasi-elastic light scattering (QELS) methods. The low-temperature nitrogen adsorption isotherms have a sigmoidal shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area (SBET) of the composites varies from 48 to 82 m2/g, showing a tendency towards a decrease in the SBET values by 10–26% in comparison with the initial nanocarriers. The SEM data show the denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30–60 nm range and the EDX data confirm the formation of a guest phase on the mixed aluminosilicate carriers, mainly in the surface patches corresponding to the alumina structure. According to the QELS data, there is a tendency to form aggregates of 100–10 μm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of Co3O4 with the crystallites of 25–26 nm in size for the individual SiO2 and Al2O3 nanocarriers and 34–37 for the mixed ones, but the iron oxide reflections were not identified for the composites. XPS observation demonstrates the signal of Fe 2p electrons as the form of Fe2O3 oxide in the surface layer of nanocomposites as well as Co 2p as the Co3O4 and Co(OH)2.

An iron formate framework with mixed-valence metal active sites as a promising anode material for stable Li-storage

Metal organic frameworks (MOFs) with metal active sites of mixed-valence are still less studied for Li-storage, especially for the anode. We present the Li-storage performance of a formate framework with both Fe(II) and Fe(III) as active sites. It delivered an impressive reversible capacity of ≈920 mAh/g at 50 mA g−1, good rate performance of 683 mAh/g at 500 mA g−1, and long-term cycling stability of 500 cycles with 73% capacity retention. Reversible structure conversion accompanying self-nano-crystallization at certain crystal directions accounts for the good cycling stability and progressively improved rate performance.

Effect of Formic and Acetic Acids on Corrosion of 410 Stainless Steel in Bio-Oils

Biomass derived oils, made from decomposition and conversion of biomass feedstocks, are proposed as alternative sustainable fuels and potential precursors to valuable chemicals. Bio-oils are produced using different approaches including hydrothermal liquefaction and fast pyrolysis of biomass feedstocks. The composition of bio-oils varies depending on the biomass source as well as on the production method. Bio-oils also contain various functional groups including carboxyl, ketone, aldehyde, phenol etc. Among the functional groups, compounds containing oxygenated species such as carboxyl, phenol and ketone groups can be particularly corrosive to metallic and polymeric materials used for transportation, production, and storage of bio-oils. Formic and acetic acids are some of the most prevalent carboxylic acids present in fast-pyrolysis bio-oils and pose a concern for corrosion of metal alloys. In the present study, we varied the amounts of carboxylic acids in a forest residue fast pyrolysis bio-oil to assess their effects on corrosion of type 410 stainless steel (410SS). To study the effect of formic and acetic acids on corrosion in bio-oils, we exposed 410SS specimens in FR3 (forest residue, fast pyrolysis bio-oil) in short term (48 hour), mild temperature (50 °C) exposures. 410SS specimens were polished, weighed and exposed to fast pyrolysis bio-oil (FR3) with baseline modified total acid number (AMTAN) value of 50.1 mg of KOH per gram of bio-oil. Using a piece of Teflon string, specimens were suspended in approximately 25 g of bio-oil at 50 °C for 48 hours. The oil samples were then spiked with either formic or acetic acids. Capillary electrophoresis was used to quantify formic and acetic acids present in the bio-oil. The area under the curves were determined and correlated to concentration of each specie using standards. Electrochemical Impedance Spectroscopy (EIS) was also performed to investigate corrosion behavior of 410SS in FR3 bio-oil at room temperature. A miniature glass cell & Luggin capillary to minimize ohmic drop within the bio-oil phase was utilized. Reference mercury sulfate electrode and platinum mesh counter electrode were used for EIS measurements.The results of short-term (48 hour, 50°C) exposures of 410SS coupons in bio-oils with addition of small carboxylic acids are shown in Figure 1. Mass change plot vs the concentration of formic acid is shown in the left graph. We observed linear increase in mass loss of 410SS with increasing formic acid concentration in the bio-oil. This is expected given our previous results that showed corrosivity of formic acid towards low chromium alloys. Iron formate was the main corrosion product that formed on the surface. However, acetic acid shows the opposite effect on mass change data as shown in the graph on the right in Figure 1. Increasing addition of acetic acid resulted in decreased mass loss. This result is intriguing because acetic acid unexpectedly behaves as a corrosion inhibitor. We are currently performing more experiments to study this effect and to understand the reason for seemingly inhibitory effect of acetic acid on corrosion of 410 stainless steel. Mass changes and cross-sectional examination of post-exposure SS410 specimens, using scanning electron microscopy equipped with energy dispersive x-ray spectroscopy, will also be presented. Impedance data from EIS measurements were analyzed as another means to assess corrosion performance of SS410 in the bio-oil and used for comprehensive corrosion assessment along with other results. Funding provided by DOE Bioenergy Technologies Office. Figure 1

Local structure study of the Fe ions in mixed-valence iron(II)-iron(III) metal formate frameworks

X-ray Absorption Spectroscopy (XAS) methods have been used to study the mixed-valence iron(II)-iron(III) metal–organic frameworks (MOFs) that undergo order–disorder phase transitions. In particular, this paper reports X-ray Absorption Fine Structure (XAFS) study of the electronic and local structure at the Fe K-edge (7 keV) for three mixed-valence iron(II)-iron(III) formate frameworks, namely dietylammonium ((C2H5)2NH2[FeIIIFeII(HCOO)6], DEtAFeFe), dimethylammonium ((CH3)2NH2[FeIIIFeII(HCOO)6], DMAFeFe) and N-etylmethylammonium (CH3NH2C2H5[FeIIIFeII(HCOO)6], EtMeAFeFe) analogues. DMAFeFe (DEtAFeFe) was studied at 140 K and 155 K (240 K and 250 K) in detail to obtain information on the structural changes during the phase transitions. The near-edge x-ray absorption fine structure (XANES) analysis confirms the octahedrally coordinated Fe in the studied samples and the electron transfer from divalent to trivalent iron ions. A slight variation was found in the Fe-O bond lengths and quantified the order in the bond length distribution measured by the Debye-Waller factor (σ2) around the phase transition temperature. The Fe2+/Fe3+ ions are homogeneously distributed in the order–disorder phase transition samples. The slight variation in the local structure defines the nature of the phase transition.

Static disorder in a perovskite mixed-valence metal–organic framework

Effects of A-site and M-site substitutions on the structural properties of perovskite dimethylammonium iron formate.

Construction, Magnetic and Dielectric Properties of Mixed-Valence Iron Formate with Methylammonium Guest

Construction, Magnetic and Dielectric Properties of Mixed-Valence Iron Formate with Methylammonium Guest

Determination of Mercury in Sediments by Slurry Sampling Electrothermal Atomic Absorption Spectrometry

The concentration of mercury in suspensions of sediments is determined by electrothermal atomic absorption spectrometry (ET-AAS) using a novel chemical modifier (ChM) based on activated carbon treated by iron(II) formate. The efficiency of chemical modifiers based on activated carbon, also modified by Ag(I), Au(III), Pd(II), Co(II), and Ni(II) compounds is studied. The optimum conditions are found for the temperature and time program of the atomizer; they prevent mercury losses at the stage of drying sample suspensions and also exclude spectral interferences at the stage of atomization and measurement of the analytical signals. The minimum characteristic mass of mercury (52 pg) is reached using an iron-containing chemical modifier based on activated carbon. The conditions of ET-AAS analysis using this ChM are tested on certified reference materials of sediments and a sample selected near the sea port of Temryuk (Sea of Azov). The limit of detection found by the 3s-test was 0.05 mg/kg and the relative standard deviation was 5% at the concentration of mercury in the sample 149 mg/kg.

First-principles study of the structural, electronic, magnetic, and ferroelectric properties of a charge-ordered iron(ii)-iron(iii) formate framework.

Density functional theory calculations have been performed for the structural, electronic, magnetic, and ferroelectric properties of a mixed-valence Fe(ii)-Fe(iii) formate framework [NH2(CH3)2][FeiiiFeii(HCOO)6]. Recent experiments report a spontaneous electric polarization, and our calculations are in agreement with the reported experimental value. Furthermore, we shed light onto the microscopic mechanism leading to the observed value, as well as on how to possibly enhance the polarization. The interplay between charge ordering, dipolar ordering of DMA+ cations, and the induced structural distortions suggest new interesting directions to explore in these complex multifunctional hybrid perovskites.

Local Structure of Ferroic Iron Formates at Low Temperature and High Pressure Studied by Mössbauer Spectroscopy

Mossbauer spectroscopy (MS) measurements were conducted on ammonium iron formate, [NH4][Fe(HCOO)3] (AFeF), and dimethylammonium iron formate, [(CH3)2NH2][Fe(HCOO)3] (DMAFeF), under non-ambient cond...

Environment-Controlled Postsynthetic Modifications of Iron Formate Frameworks.

New, hybrid iron-formate perovskites have been obtained in high-pressure reactions. In addition to the pressure range, the liquid environment of the sample also regulates the course of transformations. Formate α-DmaFe2+Fe3+For6 (Dma = (CH3)2NH2+, For = HCOO-), when compressed in oil or in isopropanol at 1.40 GPa, transforms to a new phase γ, different than that obtained at low-temperature (phase β). In glycerol, phase α can be compressed to 1.40 GPa, but then it reacts to DmaFe2+For3, with all Fe(III) cations reduced, surrounded by amorphous iron formate devoid of Dma cations. Another mixed-valence framework Dma3Fe2+3Fe3+For12·CO2 can be produced from phase α incubated in methanol and ethanol at 1.15 GPa. These pressure-induced environment-sensitive modifications have been rationalized by the volume effects in transforming structures, their different chemical composition, voids, ligands, and cation oxidation states switching between Fe(II), Fe(III), their high- and low-spin states, as well as solubility, molecular size, and the chemical and physical properties of the pressure transmitting media. The topochemical redox paths controlled by pressure and the liquid environment offer new highly efficient, safe, and environment-friendly reactions leading to new advanced materials and their postsynthetic modifications.

Thermal and Magnetic Properties of Maghemite γ-Fe2O3 Synthesized by a Precursor Method

Low-dimension ferromagnetic maghemite γ-Fe2O3 was synthesized through a precursor route, using basic iron formate Fe(OH)(HCOO)2 as a precursor. Conditions of formation of γ-Fe2O3 and the temperature range of its existence on heating in air were determined. The saturation magnetization of γ-Fe2O3 produced through heating the precursor at 350°C 57.5 (T = 4.2 K) and 43.8 emu/g (T = 300 K).

Transformations of Iron (III) Precursors in a Wave of Flameless RDX Combustion

Flameless combustion of 40% Fe2O3 – 40% RDX – 20% HDI (mix I) and 30% CoCO3 – 15% iron formate – 40% RDX – 15% HDI (mix II) systems was explored by time-resolved X-ray diffraction (TRXRD). In case of mix I, the reaction was found to proceed via the formation of FeO intermediate: Fe2O3 → FeO → Fe3O4. Variation in the extent of iron reduction was associated with dynamic temperature change and a reductant content of the reaction zone. The reduction proceeded as a solid-state reaction, without amorphization of the structure. The process in system II involved the formation of CoO and FeO intermediates. Further reduction – up to metals – takes place behind the combustion front and yields a mixture of nanosized Co, Fe, and Co0.7Fe0.3 particles. Exposure of hot reaction products – nano-sized Co and Fe – to the air leads to their self-ignition and formation of Co3O4 and Fe3O4, respectively.

Synthesis, magnetic and vibrational properties of two novel mixed-valence iron(II)-iron(III) formate frameworks

We report synthesis of two novel mixed-valence iron(II)-iron(III) formate frameworks templated by N-ethylmethylammonium (EtMeA+) and 2-Hydroxyethylammonium (HEA+) cations. X-ray diffraction shows that these compounds crystallize in the P3¯1c niccolite-type structures. Optical studies confirm mixed-valence character of these compounds. Magnetic investigation reveals that both N-ethylmethylammonium iron formate (EtMeAFeFe) and 2-Hydroxyethylammonium iron formate (HEAFeFe) exhibit magnetic order at 36.5 and 37.0K, respectively. EtMeAFeFe also exhibits large negative magnetization below 31.0K indicating that this compound is an N-type ferrimagnet. We also present Raman and IR data for both compounds. In order to help assignment of modes corresponding to the EtMeA+ cation, we also performed quantum chemical calculations to derive the harmonic and anharmonic vibrational wavenumbers. The performed calculations revealed that protonation should affect most strongly modes related to vibrations of the N–H bonds as well as the stretching modes of the CH2 and CH3 groups attached to the N atom.

Conversion of ferrous compounds in a flameless combustion wave of hexogen-based systems filled with iron formate and other additives

The thermal decomposition of the energetic component and chemical reactions occurring at elevated temperatures in a flameless combustion wave of systems based on hexogen (filled with iron(II) formate and polyisocyanurate binding agent) afford a mixture of iron oxides and iron nitride as nanosized particles. The purposeful change in the ratio of the indicated basis components can provide individual Fe2O3, Fe3O4, or FeO in the conversion products. Additives of anthracene and hydroquinone to the initial composition can result in the formation of predominantly iron carbide in the products, whereas mainly iron nitrides are formed upon the addition of guanidine nitrate or 5-aminotetrazole. The addition of aluminum hydride components to the initial mixture results in the reduction of iron to the zero-valence state in the form of iron—aluminum intermetallic compounds.

Cationic Effect on Pressure Driven Spin-State Transition and Cooperativity in Hybrid Perovskites

Hybrid or metal–organic framework (MOF) perovskites of general composition, ABX3, are known to show interesting properties that can lead to a variety of technological applications. Our first-principles study shows they are also potential candidates for exhibiting cooperative spin-state transitions upon application of external stimuli. We demonstrate this by considering two specific Fe-based MOF perovskites, namely dimethylammonium iron formate, [CH3NH2CH3][Fe(HCOO)3], and hydroxylammonium iron formate, [NH3OH][Fe(HCOO)3]. Both the compounds are found to undergo high-spin (S = 2) to low-spin (S = 0) transition at Fe(II) site upon application of moderate strength of hydrostatic pressure, along with large hysteresis. This spin-state transition is signaled by the changes in electronic, magnetic, and optical properties. We find both the transition pressure and the width of the hysteresis to be strongly dependent on the choice of A-site cation, dimethylammonium or hydroxylammonium, implying that tuning of spin-...

Activation of CO2, CS2, and Dehydrogenation of Formic Acid Catalyzed by Iron(II) Hydride Complexes

Fluoroarylimine‐stabilized iron(II) hydrides were used for the activation of CO2. The resulting iron(II) formate complex 6, which was obtained by formal CO2 insertion into the Fe–H bond, turned out to be unstable in solution. CO was suitable for the formation of stable analogues of complex 6. From the three‐component reaction of CO, CO2, and iron hydride, a series of stable carbonyl formate iron(II) complexes 7–9 were generated. Iron(II) formate complex 6 could also be obtained from the reaction of the iron(II) hydride complex with formic acid. On the basis of this result, the dehydrogenation of formic acid catalyzed by iron(II) hydrides was explored. The reaction was monitored by in situ 1H NMR spectroscopy, and a possible mechanism was proposed. In addition, iron(II) hydrides also reacted with CS2 to generate thiocarboxy iron(II) complexes 12, 13, 14, and 16. Unexpected complex 17 was produced from the three‐component reaction of CS2, complex 4, and compound 15. The possible mechanism of the three‐component reaction was also studied by operando IR spectroscopy.

Structural, magnetic and dielectric properties of two novel mixed-valence iron(ii)–iron(iii) metal formate frameworks

Mixed-valence iron(ii)–iron(iii) formate framework templated by diethylammonium cations exhibit structural and magnetic phase transitions near 240 and 39 K, respectively.

Base-free non-noble-metal-catalyzed hydrogen generation from formic acid: scope and mechanistic insights.

The iron-catalyzed dehydrogenation of formic acid has been studied both experimentally and mechanistically. The most active catalysts were generated in situ from cationic Fe(II) /Fe(III) precursors and tris[2-(diphenylphosphino)ethyl]phosphine (1, PP3 ). In contrast to most known noble-metal catalysts used for this transformation, no additional base was necessary. The activity of the iron catalyst depended highly on the solvent used, the presence of halide ions, the water content, and the ligand-to-metal ratio. The optimal catalytic performance was achieved by using [FeH(PP3 )]BF4 /PP3 in propylene carbonate in the presence of traces of water. With the exception of fluoride, the presence of halide ions in solution inhibited the catalytic activity. IR, Raman, UV/Vis, and EXAFS/XANES analyses gave detailed insights into the mechanism of hydrogen generation from formic acid at low temperature, supported by DFT calculations. In situ transmission FTIR measurements revealed the formation of an active iron formate species by the band observed at 1543 cm(-1) , which could be correlated with the evolution of gas. This active species was deactivated in the presence of chloride ions due to the formation of a chloro species (UV/Vis, Raman, IR, and XAS). In addition, XAS measurements demonstrated the importance of the solvent for the coordination of the PP3 ligand.

Lewis acid-assisted formic acid dehydrogenation using a pincer-supported iron catalyst.

Formic acid (FA) is an attractive compound for H2 storage. Currently, the most active catalysts for FA dehydrogenation use precious metals. Here, we report a homogeneous iron catalyst that, when used with a Lewis acid (LA) co-catalyst, gives approximately 1,000,000 turnovers for FA dehydrogenation. To date, this is the highest turnover number reported for a first-row transition metal catalyst. Preliminary studies suggest that the LA assists in the decarboxylation of a key iron formate intermediate and can also be used to enhance the reverse process of CO2 hydrogenation.