Infrared Vibrational Spectroscopy Research Articles

Dissociation of HBr in Water Clusters Based on a Hybrid Density Functional Approach.

The dissociation of acidic molecules within a microscopic water environment is crucial for understanding intermolecular interactions such as hydrogen bonding. This study explores the optimal configurations of HBr(H2O)n=1-7 using hybrid density functional theory. According to the different mixed cluster structures, the corresponding HBr bond lengths, single-point energies, and introduced proton-transfer parameters are computed and analyzed. The findings indicate that a minimum of three water molecules is necessary for the dissociation of HBr. Subsequently, this conclusion is reinforced through the decomposition of energy components between the acid molecule and water clusters, calculation of hydrogen bonding energies, and analysis of vibrational infrared spectroscopy.

Influence of smectite clays' pores volume on isoniazid adsorption and release

Clays have been extensively utilized in various fields due to their remarkable adsorption properties. In pharmaceutical and medical applications, they serve as potential excipients in pills. Emerging research demonstrated their effectiveness as vehicles for controlling drug release. Little has been elucidated, however, regarding the optimal clay characteristics for such applications. Therefore, this study aimed to investigate the influence of clay pores volume on the adsorption of isoniazid (INH), a key drug in tuberculosis treatments worldwide. To achieve this, seven clays were investigated to examine the impact of pores volume on the adsorption and release of INH. Chemical characterization of the clays was conducted using X-ray fluorescence (XRF) and Infrared vibrational spectroscopy (IR), while their mineralogical composition was determined through X-ray diffraction (XRD) and their pore volume by BET method via N2 adsorption/desorption isotherms. Additionally, the interaction between clay and INH was evaluated using FT-IR, XRD, and Thermogravimetric Analysis (TGA). Kinetic adsorption studies were performed to determine the time to reach the equilibrium saturation of the clay by the drug, which was found to be around three hours for all clays. By comparing the pore volume of the studied clays, it became apparent that the clay with an optimal pore volume of approximately 0.100 cm3/g exhibited superior adsorption/retention compared to those with lower or higher volumes. Furthermore, in vitro INH release curves were obtained mimicking release conditions in the intestine (pH 7.4) for a duration of 5 h. It was clearly shown that the release of INH from the clays depend on the pore volume. Our results provided valuable insights into the optimal clay characteristics which would enhance the adsorption and release of INH.

Substituent effect on photophysical properties and proton transfer process of HBQ derivatives

AbstractBackgroundIn view of the potential applications of 10‐hydroxybenzo [h] quinoline (HBQ) in biological probes and organic light‐emission devices, the excited state intramolecular proton transfer (ESIPT) mechanism of HBQ was investigated theoretically in the work.AimsIn order to give a detailed reaction mechanism, the ESIPT of molecular system with hydrogen bond is systematically studied using density functional theory and density functional theoryMethodsUsing density functional theory (DFT) and time‐dependent density functional theory (TDDFT), we investigate the photophysical properties and excited state proton transfer of 10‐hydroxybenzo [h] quinoline (HBQ)derivatives.ResultsThe optimized structure shows that HBQ1 and HBQ2 have no stable structure in S1 state. The analysis of bond length parameters and infrared vibration spectroscopy proved that the substituent groups regulated the hydrogen bond strength in the S0 state.ConclusionTherefore, substitution position will affect the excited state intramolecular proton transfer and the photophysical properties of the molecule.

Insights from computational analysis: Excited-state hydrogen-bonding interactions and ESIPT processes in phenothiazine derivatives

Organic materials with Mechanofluorochromism (MFC) properties have potential application value. Phenothiazine derivatives are a class of substances with MFC properties that have been synthesized and reported in experiments (Dyes and Pigments 172 (2020) 107835). Dual fluorescence of a series of phenothiazine derivatives is observed in the experiment, which proved that the ESIPT process is carried out. In this work, we choose phenothiazine derivatives (C2PAHN, C4PAHN, C8PAHN) as models to theoretically analyze the influence of different alkyl chain lengths on the excited state intramolecular proton transfer (ESIPT). In addition, the shift value of fluorescence spectrum is related to the length of alkyl chain. The fluorescence shift of C2PAHN is the largest (6.31 nm), and that of C8PAHN is the smallest (2.40 nm). The theory of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) are adopted to simulate the molecular dynamics in the ground state and excited state. The analysis of the optimized molecular geometry parameters and infrared vibrational spectroscopy (IR) illustrate the stronger hydrogen bonding of the excited state molecules, which is favorable for the progress of ESIPT. Fluorescence spectroscopy reveals that the appropriate increase or decrease of alkyl chains would change the photophysical properties of the molecules. Frontier molecular orbitals (FMOs) indicate that the rearrangement of electron density from electronic level to is the driving force of the ESIPT process. Reduction density gradient (RDG) surfaces and Natural Population Analysis (NPA) tentatively lead to the conclusion that alkyl chain length is inversely proportional to hydrogen bond strength. Finally, the data are qualitatively analyzed by scanning the potential energy curves, and it is concluded that the longer the alkyl chain, the weaker the hydrogen bonding effect and the more unfavorable the ESIPT process.

Effects of varying Alx moles on structure and luminescence properties of ZnAlxO1.5x+1:0.1 mol% Tb3+ nanophosphors prepared using citrate sol–gel method

Un-doped and ZnAlxO1.5x+1:0.1 mol% Tb3+ (ZAOT) nano-powders were synthesized via citrate sol-gel method. The Alx moles were varied in the range of 0.25 ≤ x ≤ 5.0. The X-ray powder diffraction (XRD) data reveal that for x < 1.5, the prepared samples crystal structure consists of mixed phases of the cubic ZnAl2O4 and hexagonal ZnO phases, while for x ≥ 1.5 the structure consists of single phase of cubic ZnAl2O4. The Raman and Fourier-transform infrared (FTIR) vibrational spectroscopy show the presence of vibrations emanating ZnAl2O4 spinel. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the presence of irregular sphere at x≥ 2.0 attributed to ZnAl2O4. The photoluminescence (PL) spectroscopy reveals emissions from both the host and Tb3+ transitions. Emissions from Tb3+ are observed at 382, 414, 439, 458 nm and 489, 545, 585, 621 nm, which were attributed to the 5D3 → 7F6,5,4,2 and 5D4 → 7F6,5,4,3, respectively. The results confirm that the Tb3+ occupation site depends on the Alx moles. The International Commission on Illumination (CIE) colour chromaticity shows that the emission colour can be tuned from blue to green by varying the Alx moles.

Measurement of Transport Number of Lithium in Glycerol Assisted by Fourier Transform Spectroscopy Analysis: Progress towards Elaboration of Optimal Electrolyte of Friendly Environmental Battery

Up to now, a great deal of research investigations on lithium ion conductors has been carried out, because they are potentially utilized in the solid electrolytes of the batteries and the electrochemical devices. However, in order to elaborate new ecological batteries of lithium, it becomes primordial to study and understand the properties of transport of the lithium electrolytes using eco-friendly solvents, with view perhaps to find out the best electrolyte for such devices. In fact, the electromotive forces (EMFs) of lithium chloride electrolyte in the hydrogen-bonded solvents glycerol, were measured using the concentration cells (CCs) 0.005/0.05 and 0.05/0.5. Then the transport numbers of the lithium-ion were deduced by means of the Nernst equation in combination with the Debye-Huckel limiting law. Whilst the activation energy values were calculated from the parameters of the fitting of the transference number data to the empirical power law, yielding a regression coefficient of 95.9% for the most concentrated concentration cell. The structure and interactions in the lithium electrolyte solution were studied by vibrational Infra-Red spectroscopy. The experimental data were discussed and compared to those obtained previously, using impedance spectroscopy of glass-forming glycerolate lithium electrolytes for the same purpose. Despite the enormous difference between their viscosities; glycerol shows similar activation energy (i.e. 31.40 kJ.mol–1) with water (i.e. 31.73 kJ.mol–1), in particular at very low concentration, confirming both solvents being hydrogen-bonded. Besides, this study suggests the utilization of the glycerol-lithium ion electrolyte for future conception of ecological lithium-ion battery, rather than those using ion electrolyte polymer currently on the market. Similarly to relaxation and conductivity, the transport number data suggests that the diffusion of conformational states is also monitoring the overall lithium ion transport mechanism.

Synthesis and Characterization of Azido Esters as Green Energetic Plasticizers

AbstractThree azido‐esters based green energetic plasticizers were synthesized from their chlorides including DEGBAA (diethyleneglycol bis(azidoacetate)), DPGBAA (dipropyleneglycol bis(azidoacetate)) and HETTAA (hexanetriol tris(azidoacetate)). The syntheses were carried out in a two‐step process: the first step was esterification of glycol or triol using chloroacetyl chloride, and the second step was substitution of chloracetate with sodium azide that yields corresponding azido derivatives. The parameters of synthesis such as molar ratio of hydroxyl and acyl groups, and amount and type of solvent (dimethyl sulfoxide and dimethyl formamide) were optimized to achieve maximal conversion and purity of the products. The obtained products were characterized by elemental analysis, nuclear magnetic resonance (NMR), and infrared vibrational spectroscopy (IR). Thermal and rheological properties were determined using DSC and Modular Compact Rheometer. Condensed phase heat of formation and several properties important for high‐energy materials were predicted from quantum chemical calculations using CBS‐4M method. Detonation and combustion performance of energetic compounds were calculated with the thermochemical computer code EXPLO5V06.05. using the predicted heats of formation and experimentally determined densities as input. The energetic and physical properties of the synthesized compounds were compared to the literature data for common plasticizers.

Harmonic and Anharmonic Oscillator Models for Pure Vibrational Infrared Spectroscopy of Diatomic Molecules

In molecular vibrational infrared spectroscopy, absorption spectra arise from molecular vibration and correspond to transitions between the vibrational energy levels associated with a given electronic state of the molecule. The vibrational transitions, which fall in the near infrared region, are induced through the interaction of the molecular electric dipole with the electric vector of the electromagnetic radiation. The near infrared region extends roughly from 1?m to ?10?^2 ?m. The article explains the pure vibrational absorption spectra of diatomic molecules such as HCl, HBr, HI, CO, … etc. In order to explain the vibrational spectra, diatomic molecules are treated as harmonic oscillator and anharmonic oscillator. In the harmonic oscillator model, we get only one absorption band at the wavenumber value? ?_osc corresponding to frequency of oscillation?_osc while in the actual experimental data, there are many absorption bands corresponding to wave numbers slightly lesser than ? ?_osc, 2? ?_osc, 3? ?_osc, ……..The occurrence of these additional bandsis attributed to the selection rule ?v=±2, ±3, ±4, ……The additional bands are having lesser intensity and are called overtone bands.

Unraveling the Physicochemical Determinants of Protein Liquid-liquid Phase Separation by Nanoscale Infrared Vibrational Spectroscopy.

The phenomenon of reversible liquid-liquid phase separation of proteins underlies the formation of membraneless organelles, which are crucial for cellular processes such as signalling and transport. In addition, it is also of great interest to uncover the mechanisms of further irreversible maturation of the functional dense liquid phase into aberrant insoluble assemblies due to its implication in human disease. Recent advances in methods based on atomic force microscopy (AFM) have made it possible to study protein condensates at the nanometer level, providing unprecedented information on the nature of the intermolecular interactions governing phase separation. Here, we provide an in-depth description of a protocol for the characterisation of the morphology, stiffness, and chemical properties of protein condensates using infrared nanospectroscopy (AFM-IR).

Tip- and Plasmon-Enhanced Infrared Nanoscopy for Ultrasensitive Molecular Characterizations

We propose a method for ultrasensitive infrared (IR) vibrational spectroscopy of molecules with nanoscale footprints by combining the tip enhancement of a scattering-type scanning near-field optical microscope (s-SNOM) and the plasmon enhancement of breathing-mode (BM) plasmon resonances of graphene nanodisks (GNDs). To demonstrate this, we develop a quantitative model that is capable of computing accurately the s-SNOM signals of nanoscale samples. With our modeling, we show that the s-SNOM tip can effectively excite gate-tunable BM plasmonic resonances in GNDs with strong field enhancement and sensitive dependence on the size of GND. Moreover, we demonstrate that the intense electric field of tip-excited plasmonic BMs can strongly enhance the IR vibrational modes of molecules. As a result, IR vibrational signatures of individual molecular particles with sizes down to 1--2 nm are readily observable by s-SNOM. Our study sheds light on future ultrasensitive IR biosensing that takes advantage of both the tip and plasmon enhancement.

Pyrazol-triazole energetic hybrid with high thermal stability and decreased sensitivity: facile synthesis, characterization and promising performance

The barrier in the development of energetic material is the material design and performance improvement based on it. Currently, creative design and preparation of novel nitrogen-rich compounds are significant for new generation of green energetic materials. At the present work, organic heterocyclic hybrid pyrazol-triazole was constructed, synthesized and applied as building blocks in the development of versatile thermally stable high-energy materials. All derivatives were fully characterized by vibrational infrared spectroscopy (IR), multinuclear NMR (1H, 13C) spectroscopy, elemental analysis, differential scanning calorimetry (DSC), impact and friction-sensitivity test. Additionally, the structures of 4–8 and 10–13 were further confirmed by single-crystal X-ray diffraction and their crystal packing characteristics were thoroughly analyzed. Compound 2 not only enchanced physical properties of its ionic derivatives obviously, but also showed good detonation performance (D: 9075 m s−1) exceeding that of RDX, excellent insensitivity (IS > 80 J, FS > 360 N) comparable to that of TATB and superior thermal stability (331 °C) to that of HNS. Its ionic salts (compounds 4–14) also exhibit reasonable properties, such as good experimental densities (1.75–2.10 g cm−3), high thermal stability (174289 °C), good safety properties, excellent detionation performance (Dv: 7745–8952 m s−1, P: 23.830.6 GPa), suggesting this new pyrazol-triazole hybrid is beneficial for improving their physical performance. This work is helpful for accelerating the discovery of insensitive, thermostable and high-energy green energetic materials.

Thermal analysis (TG–DSC, DSC–microscopy and EGA) and characterization of heavy trivalent lanthanides and yttrium isonicotinates

The trivalent lanthanide isonicotinates were synthesized to obtain stoichiometry Lu(IN)3 and Ln(IN)3·2H2O (Ln = Tb to Lu, and Y; IN = isonicotinate). A deep study of the thermal behavior in oxidant (air) and inert (N2) atmospheres was carried out using the following thermoanalytical techniques: simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), differential scanning calorimetry (DSC) and evolved gas analysis (EGA by TG–DSC–FTIR). From these results, it was possible to determine that dehydration occurs in a single step and the thermal decomposition of the anhydrous compounds occurs in one or two (air), and two or three steps (N2). The final residues of thermal decomposition were Tb4O7 and Ln2O3 (Ln = Dy to Lu, and Y) in air atmosphere, while in N2 atmosphere the mass loss is still being observed up to 1000 °C. The identified gaseous products evolved during the thermal decomposition in dynamic dry air and nitrogen atmospheres were water, CO2, pyridine and CO. From these thermoanalytical data, it was possible to propose a general equation of thermal decomposition of these compounds in the N2 atmosphere. DSC curves of Tb and Ho compounds presented endothermic peaks corresponding to a reversible phase transition, confirmed by powder X-ray diffractometry (XRD), not previously reported. In addition, infrared vibrational spectroscopy (IR) suggests the coordination through carboxylate as bridging bidentate ligand toward the heavy trivalent lanthanides metals. This paper is complementary to our previous study involving the series of light trivalent lanthanides isonicotinates.

The structure ofortho-(trifluoromethyl)phenol in comparison to its homologues – A combined experimental and theoretical study

AbstractThe molecular and crystal structure of commercially-availableortho-(trifluoromethyl)phenol were determined by means of single-crystal X-ray diffractometry (XRD) and represent the first structural characterization of anortho-substituted (trihalomethyl) phenol. The unexpected presence of a defined hydrate in the solid state was observed.Intermolecular contacts and hydrogen bonding were analyzed. The compound was further characterized by means of multi-nuclear nuclear magnetic resonance (NMR) spectroscopy (1H,13C{1H},19F) and Fourier-Transform infrared (FT-IR) vibrational spectroscopy. To assess the bonding situation as well as potential reaction sites for reactions with nucleophiles and electrophiles in the compound by means of natural bonding orbital (NBO) analyses, and density functional theory (DFT) calculations were performed for the title compound as well as its homologous chlorine, bromine and iodine compounds. As far as possible, experimental data were correlated to DFT data.

Thermal behavior study of palladium(II) complexes containing the iminic ligand N,N′-bis(3,4-dimethoxybenzaldehyde) ethane-1,2-diamine

This study describes the synthesis, characterization and thermal behavior study of the Schiff base N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine (C.1) and four new compounds of palladium(II) N,N-chelate coordination, with the general formula [Pd(X1)(X2)(3,4dm-1,2am)] where 3,4dm-1,2am=N,N′-bis(3,4-dimethoxybenzaldehyde)ethane-1,2-diamine, X1 = X2 = Cl− (C.2), X1 = X2 = Cl− and Br− (C.3), X1 = X2 = N3− (C.4) and X1 = X2 = NCO− (C.5). The compounds were characterized by elemental analysis, infrared vibrational spectroscopy (IR) and nuclear magnetic resonance (NMR) 1H and 13C. The TG/DTA curves showed that the thermal decomposition of the C2–C.5 complexes occurred in steps that involve the removal of both inorganic and organic ligand, and palladium oxidation steps forming palladium(II) oxide followed by the reduction of PdO into Pd(0), this being the constituent of the residual mass observed at the end of the TG curves, which have values consistent with the expected ones. The formed compounds can be ordered according to thermal stability considering the initial decomposition temperature (C.5 > C.2 > C.3 > C.4).

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals.

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Fourier Transform Fluorescence-Encoded Infrared Spectroscopy.

While time-resolved infrared (IR) vibrational spectroscopy provides insight on structural dynamics of solution-phase systems, current techniques are limited to high concentrations. Fluorescence-encoded infrared spectroscopy (FEIR) can be used to encode IR-driven vibrational excitations into excited electronic states that fluoresce, which can be detected at lower concentrations than a coherently detected IR signal. Here, we report on the development of Fourier transform FEIR as an alternate approach for high-sensitivity IR spectroscopy. Upon driving vibrational excitation with a pair of IR fields with a variable time delay, an interferometric component was observed in the encoded fluorescence. This signal can be Fourier transformed to obtain a vibrational spectrum. By additionally varying the time delay of the encoding pulse following the second IR pulse, we observed frequency-difference oscillations, allowing us to construct a 2D correlation spectrum of coupled vibrations. Response functions for this experiment have been modeled, which reproduce the observed spectral features and relate them to excitation pathways using diagrammatic perturbation theory. The pathways observed in a 2D FEIR spectrum arise from the excitation of vibrational populations and coherences between coupled vibrations.

Selenium biofortification ofPleurotusspecies and its effect on yield, phytochemical profiles, and protein chemistry of fruiting bodies

Selenium is considered an essential component of a balanced diet due to its antioncogenic and antioxidative properties. Highly popular edible mushrooms belonging to the genus Pleurotus (Oyster mushrooms) were biologically fortified with selenium by exploiting their saprophytic ability. Selenium-rich wheat straw, generally wasted or burned by farmers, was used for cultivation of three species of Pleurotus: P. florida, P. ostreatus, and P. sajor-caju. Atomic Absorption Spectroscopy of harvested fruiting bodies exhibited over a 100-fold increase in bio-accumulation of selenium compared to control samples. P. florida preferred selenium-rich substrate over the normal straw as exhibited by increased yield on selenium-rich straw. Total protein content and antioxidant profiles of Se-rich mushroom extracts also improved significantly. Vibrational Infra-Red Spectroscopy analysis confirmed alteration of flexibility and unfolding of proteins extracted from Se-rich fruit bodies compared to the control, indicating bond formations between selenium and amino acids. The extracts and proteins from selenium enriched as well as control Pleurotus species also showed inhibitory potential towards common pathogens. Practical applications The Se-rich wheat straw can be a useful though underutilized substrate for cultivation of Se-biofortified oyster mushrooms besides enhancing their protein content. The oyster mushrooms cultivated on Se-rich wheat straw vary in their Se-accumulation potentials. Thus, greater health benefits can be obtained by choosing specific Se-rich oyster mushroom species. The Se-proline can be one of the alternate Se-species besides Se-cysteine and Se-methionine. Se-biofortification of oyster mushrooms is feasible by cultivation on Se-rich agricultural waste such as wheat straw which otherwise is burnt by the farmers resulting in air pollution.

Synthesis and photoluminescence properties of [Eu(dbm)3·PX] and [Eu(acac)3·PX] complexes

Two novel luminescent europium tris(β-diketonate) complexes [Eu(dbm)3·PX] and [Eu(acac)3·PX] (dbm: dibenzoylmethane, acac: acetylacetonate and PX: piroxicam) were successfully synthesized. These coordination compounds were characterized by infrared vibrational spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and luminescence spectroscopy. The thermal behavior of the complexes was investigated by thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG) techniques. The optical results have shown that these complexes present a clear intra and inter-molecular energy transfer and corroborates the sensitivity of their emission efficiency to the excitation wavelength, multiphonon non-radiative decays and temperature dependence. These new complexes may act as efficient light converting molecular devices, suggesting that they can be used for controllable photonic applications.

Two-Photon-Excited Fluorescence-Encoded Infrared Spectroscopy.

We report on a method for performing ultrafast infrared (IR) vibrational spectroscopy using fluorescence detection. Vibrational dynamics on the ground electronic state driven by femtosecond mid-infrared pulses are detected by changes in fluorescence amplitude resulting from modulation of a two-photon visible transition by nuclear motion. We examine a series of coumarin dyes and study the signals as a function of solvent and excitation pulse parameters. The measured signal characterizes the relaxation of vibrational populations and coherences but yields different information than conventional IR transient absorption measurements. These differences result from the manner in which the ground-state dynamics are projected by the two-photon detection step. Extensions of this method can be adapted for a variety of increased-sensitivity IR measurements.

Boron as a promoter in the goethite (α-FeOOH) phase: Organic compound degradation by Fenton reaction

The aim of this study was to obtain iron oxides (goethite phase, α-FeOOH) to be used as Fenton catalysts in the catalytic oxidation of methylene blue (MB). Moreover surface modifications were attempted by treating the oxides with boric acid in order to improve the materials’ catalytic properties through the generation of more active groups on the surface of goethite. The types of structures formed on the surface were investigated through the following characterization techniques: vibrational infrared spectroscopy, Mössbauer spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and BET surface area measurements. The results of these characterization analyses the showed complexation of boric acid on the surface of goethites and the partial reduction of some Fe(III) to Fe(II) species, resulting of a hybrid material containing both goethite and magnetite phases. When tested in the oxidation of organic compounds, the new class of iron oxide showed high capacity for degradation of organic compounds present in the solution. The Gt-B catalyst exhibited enhanced catalytic activity in degradation of methylene blue compared with the pure goethite, especially Gt-B1×4 which, after 240min of reaction, was able to degrade about 80% of the MB in solution. The increase in the catalytic activity was assigned to the role of boron as a promoter in the transfer of electrons from iron to hydrogen peroxide, the increasing of surface area and the presence of Fe(II) species, which are kinetically more favourable for the Fenton’s reaction. In addition, theoretical calculations were carried out at the density functional theory (DFT) level in order to investigate the interaction between goethite and boric acid. The theoretical findings showed that the treatment with the H3BO3 significantly modifies the electron density of goethite (100).