Calorimetric Investigation Research Articles

Probing the Interactions of Perfluorocarboxylic Acids of Various Chain Lengths with Human Serum Albumin: Calorimetric and Spectroscopic Investigations.

Despite an exponential increase in PFAS research over the past two decades, the mechanisms behind how PFAS cause adverse health effects are still poorly understood. Protein interactions are considered a significant driver of bioaccumulation and subsequent toxicity from re-exposure; however, most of the available literature is limited to legacy PFAS. We utilized microcalorimetric and spectroscopic methods to systematically investigate the binding between human serum albumin (HSA) and perfluorocarboxylic acids (PFCAs) of varying chain lengths and their nonfluorinated fatty acid (FA) counterparts. The results reveal the optimal chain length for significant PFCA-HSA binding and some fundamental interactions, i.e., the polar carboxylic head of PFCA is countered by ionizable amino acids such as arginine, and the fluorocarbon tails stabilized by hydrophobic residues like leucine and valine. Additionally, fluorine's unique polarizability contributes to PFCA's stronger binding affinities relative to the corresponding fatty acids. Based on these observations, we posit that PFCAs likely bind to HSA in a "cavity-filling" manner, provided they have an appropriate size and shape to accommodate the electrostatic interactions. The results reported herein widen the pool of structural information to explain PFAS bioaccumulation patterns and toxicity and support the development of more accurate computational modeling of protein-PFAS interactions. TOC graphic created with Biorender.com.

Investigation of the mechanism of nickel hydroxide formation from nickel nitrate

Nickel hydroxides are widely used as electrochemically active substances in alkaline batteries and hybrid supercapacitors; they can be used for electrocatalysis, in electrochemical sensors, and as pigments. Knowledge of the formation mechanism of nickel hydroxides is necessary for developing and optimizing targeted synthesis methods. The thermal effects of processes in the formation of nickel hydroxide from nitrate were studied by the calorimetry method. The mechanism of precipitate formation was investigated by the method of simultaneous potentiometric (with a glass universal electrode) and conductometric titration. The nickel content in the samples obtained at the determined NaOH/Ni2+ ratios was investigated by the chemical method of trilonometry after preliminary dissolution. Calorimetric investigations showed that the reaction of nickel nitrate with NaOH was exothermic with ΔНreaction=‒28328.5 J/mol. The exothermic nature of the NaOH dilution process was revealed with ΔНdilution =‒2454 J/mol. According to the results of potentiometric titration, the formation of a basic salt of the NiOHNO3 type was not detected. Analysis of the results of conductometric titration revealed a two-stage chemical mechanism for the formation of nickel hydroxide from nitrate. At the first stage, which had a high rate, due to the liquid-phase reaction of the nickel cation with the hydroxyl anion, a primary precipitate of the composition Ni(OH)1.87(NO3)0.13 was formed. In the second stage, as a result of a slow topochemical reaction of the primary precipitate with hydroxyl anions, nitrate ions were displaced from the precipitate to form nickel hydroxide. These data are confirmed by the analysis of precipitate obtained at NaOH/Ni2+ ratios of 1.87 and 2.2: the Ni content was 52.95 % and 55.63 %, corresponding to the formulas Ni(OH)1.87(NO3)0.13∙0.68H2O and Ni(OH)2∙0.71H2O. This clearly indicated that the primary precipitate was nitrate-doped α-Ni(OH)2 and the final precipitate corresponded to the α-modification of nickel hydroxide

Combined calorimetric, spectroscopic and microscopic investigation on the inclusion complex from cyclocurcumin and sulfobutylether-β-cyclodextrin in aqueous solution and Kinetics of thermal cis-trans isomerization

The complexation reaction between cyclocurcumin (CyCur), a natural curcuminoid with bioactive effects, and sulfobutylether-β-cyclodextrin (SBE-βCD), one of the more versatile and tolerate β-cyclodextrin derivates, was investigated in aqueous solution at 298 K. The UV–vis spectral changes of CyCur in the presence of SBE-βCD indicate the formation of the host-guest inclusion complex according to a 1:1 stoichiometry. The binding constant (Kb) determined by applying the Benesi-Hildebrand model was comparable to the value obtained by Isothermal Titration Calorimetry (ITC) measurements. Moreover, the thermodynamic parameters of the SBE-βCD/CyCur interactions demonstrate that the complexation process is enthalpically driven. Interestingly, microscopy analysis highlights the tendency of cyclocurcumin to aggregate into spherical fluorescent structures able to change their aspect and morphology in the presence of SBE-βCD. Finally, the thermal cis-trans isomerization rates of CyCur in the temperature range 294–314 K and the energetic parameters calculated by Arrhenius and Eyring plots were spectroscopically determined in SBE-βCD aqueous solution.

The curious case of the second/end peak in the heat release rate of wood: A cone calorimeter investigation

AbstractThe reasons behind the occurrence of a second/end peak heat release rate (PHRR) during wood combustion under radiative heating were determined. Effects of the type of rear material, wood thickness, char progression, and its microstructure, as well as moisture content/transport in spruce wood, were studied. Rear materials used were insulating Kaowool, conducting steel, and the same wood but physically separated from test specimen by aluminium foil. The intensity of the second/end PHRR with Kaowool was almost 50% more than that of the sample with steel. Thus, the second/end peak is governed by the boundary condition defined by the rear material, which determines the heat losses at the rear side of the specimen and consequently the temperature of the specimen. Higher specimen temperature enhances the pyrolysis rate, thereby causing the second/end PHRR. The appearance times and values of the second/end PHRR for 30, 20, and 10 mm wood were 1740 s/78 kWm−2, 685 s/134 kWm−2, and 450 s/160 kWm−2, respectively. Char progressed to the rear of the samples even with a thin (8 mm) conductive steel substrate. Cracks in char grew almost three times wider during the second/end PHRR compared to the sample with no second/end peak. Char cracking had no significance on the time of occurrence of the second/end PHRR but affected the overall heat release. High moisture content reduced the charring rate and delayed the time of occurrence of the second/end PHRR as more water was needed to undergo a phase change, requiring a higher amount of energy.

Mechanism and design of fluid catalytic cracking ash-blended cementitious composites for high performance printing

As a common waste in the oil refinery industry, fluid catalytic cracking (FCC) ash is used to partially replace cement for high-performance high-speed 3D concrete printing (3DCP). Effects of FCC ash on hydration, rheology, and compressive strength were evaluated systematically, and the optimal substitution rate was determined as 20 wt. % of cement. A cylinder with 240 mm diameter and 500 mm height was successfully printed at a high speed of 100 mm/s with the optimal mixture in 5 min 53 s only. Moreover, the optimal mixture shows good leaching performance, and it also reduces CO2 emission by 21.45 % and materials’ cost by 17.98 % compared with the control. In addition to material optimization, the contributions of FCC ash to the early hydration and static yield stress were extensively analyzed. Complementary calorimetric and mineralogical investigations show that FCC ash accelerates the initial hydrolysis of cement and hydration of C3A and C3S. On the other hand, the quantitative analyses of static yield stress reveal the contributions of FCC ash on the colloidal force, volume fractions, particle size distribution, and ultimately static yield stress evolution. The developed 3D printable cementitious material possesses multiple advantages, including high-speed printing compatibility, enhanced sustainability, and high commercial values for oil refinery and construction industries. Based on the mineralogical property of FCC ash, the study also enlightens potential research and application of zeolite in 3D concrete printing in the future.

Synthesis of Pyridine Heterocyclic Low-Melting-Point Phthalonitrile Monomer and the Effects of Different Curing Agents on Resin Properties.

A phthalonitrile monomer (DPTP) containing pyridine with sulfide bonds was prepared and cured into polymers using different curing agents under the same temperature-programmed process. We characterized and comprehensively evaluated the effects of different curing agents on the thermal and thermomechanical properties of phthalonitrile resin, showing that the DPTP monomer cured with naphthalene-containing curing agent exhibited the best performance among the three polymers. Differential scanning calorimetric (DSC) investigation manifested that the melting point of the DPTP monomer was 61 °C, with a processing window of about 170 °C, suggesting the presence of a wide processing range. Thermogravimetric analysis (TGA) demonstrated the outstanding heat resistance, T5%, of 460 °C in nitrogen, at the same time demonstrating superior long-term stability compared with other commonly used polymer materials, which proves the long-term usage under high temperatures of 300 °C. Dynamic mechanical analysis (DMA) revealed that the storage modulus at 50 °C was 3315 MPa, and the glass transition temperature (Tg) of the polymer was more than 350 °C. Therefore, DPTP resins have favorable thermal stability as well as prominent thermomechanical properties.

Spectroscopic and calorimetric investigation of cyclohexanol in different orientational states

The thermal analysis and infrared (IR) spectroscopy were used to study cyclohexanol irreversible transformations from an orientationally disordered plastic state to metastable III and then to a stable II crystalline phase. It was found that the orientational glass transition in cyclohexanol occurs at Tg ∼ 163.5 K. Solid–solid transition from orientationally disordered phase I to metastable phase III occurs at 195 K. Crystal phase III nucleates at Ta = 203 K and converts into phase I at T = 233.7 K. The stable crystal phase II is formed by nucleation at 213 K. It converts into phase I at T = 250 K. It is shown by IR spectroscopy that the phase transitions in solid cyclohexanol are correlated with conformational changes in the cyclohexanol molecule.

Energetics of hydroxylbastnäsite solid solutions, La1−xNdxCO3OH

Bastnäsites (LnCO3(F,OH)) are a group of common rare earth elements (REE)-bearing minerals and are one of the primary global sources of REE. Due to the chemical similarities among REE, bastnӓsites tend to occur as solid solutions instead of end members in REE containing ores. To better understand the processes and the mechanisms of formation of such deposits, it is essential to determine the thermodynamic properties of bastnӓsites, including hydroxylbastnӓsite (LnCO3OH) solid solutions. In this work, we performed detailed structural and calorimetric investigations on synthetic hexagonal La–Nd hydroxylbastnӓsite (La1–xNdxCO3OH, x = 0, 0.25, 0.5, 0.75, 1) solid solutions. X-ray diffraction confirms the crystal structure of the solid solution series in the P6¯ space group, and pair distribution function (PDF) analysis reveals local bonding environments characterized by three different types of 9-coordinated metal-oxygen polyhedra. Unit cell parameters of La1–xNdxCO3OH exhibit a nearly linear relation with the Nd content x, suggesting a random distribution of La and Nd in the structure. Their standard enthalpies of formation (ΔH°f) were determined by high temperature oxide melt drop solution calorimetry, from which the enthalpies of mixing (ΔHmix) were derived. The ΔHmix can be fitted by a regular solution model with an interaction parameter of 12.58 ± 0.16 kJ/mol, suggesting enthalpic metastability of La1–xNdxCO3OH relative to the two endmembers. Combining entropy and enthalpy, we further estimated the Gibbs free energies of mixing (ΔGmix) at relevant temperatures, revealing favorable temperatures under which the intermediate La1–xNdxCO3OH phases can be stabilized. Such entropy-driven stabilization, as is consistent with our geochemical modeling results, may explain the enhancement of thermal stability of the solid solutions in nature. Additionally, the temperature range constrained from this study may be used to estimate the thermal history of REE bastnӓsite deposit.

Thermal and Calorimetric Investigations of Some Phosphorus-Modified Chain Growth Polymers 1: Polymethyl Methacrylate.

The thermal and calorimetric characterizations of polymethyl methacrylate-based polymers are reported in this paper. The modifying groups incorporated the phosphorus atom in various chemical environments, including oxidation states of III, or V. Both additive and reactive strategies were employed, where the loading of phosphorus was kept at 2 wt% in all cases. The plaques, obtained through the bulk polymerization route, were subjected to a variety of spectroscopic, thermal and combustion techniques. The results showed that the different modifying groups exerted varying nature, degrees and modes of combustion behaviors, which also included in some cases an additive, and even an antagonistic effect. In the case of covalently-bound phosphonate groups, early cracking of the pendent ester moieties was shown to produce phosphoric acid species, which in turn can act in the condensed phase. For the additives, such as phosphine and phosphine oxide, limited vapor-phase inhibition can be assumed to be operative.

Calorimetric investigation of the binary Cu–In system

Abstract Although some investigations of the integral enthalpy of mixing of the binary Cu–In system have already been done, there is a lack of conformity of these data within the literature. Therefore the integral enthalpy of mixing was determined with a Calvet-type calorimeter. The measurements were performed at four different temperatures to determine the temperature dependence of the integral enthalpy of mixing.

Detailed Calorimetric Analysis of Mixed Micelle Formation from Aqueous Binary Surfactants for Design of Nanoscale Drug Carriers.

While numerous papers have been published according to the binary surfactant mixtures, only a few articles provide deeper information on the composition dependence of the micellization, and even less work attempts to apply the enhanced feature of the mixed micelles. The most important parameter of the self-assembled surfactants is the critical micelle concentration (cmc), which quantifies the tendency to associate, and provides the Gibbs energy of micellization. Several techniques are known for determining the cmc, but the isothermal titration calorimetry (ITC) can be used to measure both cmc and enthalpy change (ΔmicH) accompanying micelle formation. Outcomes of our calorimetric investigations were evaluated using a self-developed routine for handling ITC data and the thermodynamic parameters of mixed micelle formation were obtained from the nonlinear modelling of temperature- and composition- dependent enthalpograms. In the investigated temperature and micelle mole fractions interval, we observed some intervals where the cmc is lower than the ideal mixing model predicted value. These equimolar binary surfactant mixtures showed higher solubilization ability for poorly water-soluble model drugs than their individual compounds. Thus, the rapid and fairly accurate calorimetric analysis of mixed micelles can lead to the successful design of a nanoscale drug carrier.

Metabolic heat responses of Kluyveromyces marxianus and Saccharomyces cerevisiae during Carboxypeptidase Y Enzyme production

Kluyveromyces marxianus and Saccharomyces cerevisiae yeasts were compared for the production of Carboxypeptidase Y, a serine class glycoprotein exopeptidase (CPD-Y) using Bio calorimetry and Respirometric devices. The production medium components were optimized by Response Surface Methodology-based design of experiments. Bio calorimetric investigation combined with Respirometric studies suggested that the rate of heat evolution and respiration rate was directly linked to Dry Cell Weight (DCW), enzyme activity, and the consumption rate of the substrate. The Maximum yield obtained for K. marxianus and S. cerevisiae was 14 IU/mL and 8 IU/mL respectively which were threefold higher than the shake flask experiment. Yeast growth and nature of growth predicted using calorespirometric data fitted well with measured experimental results.

Calorimetric Investigation of the Relaxation Phenomena in Amorphous Lyophilized Solids.

Studying the thermal history and relaxation of solid amorphous drug product matrices by calorimetry is a well-known approach, particularly in the context of correlating the matrix parameters with the long-term stability of freeze-dried protein drug products. Such calorimetric investigations are even more relevant today, as the application of new process techniques in freeze-drying (which strongly influence the thermal history of the products) has recently gained more interest. To revive the application of calorimetric methods, the widely scattered knowledge on this matter is condensed into a review and completed with new experimental data. The calorimetric methods are applied to recent techniques in lyophilization, such as controlled nucleation and aggressive/collapse drying. Phenomena such as pre-Tg events in differential scanning calorimetry and aging shoulders in isothermal microcalorimetry are critically reviewed and supplemented with data of freeze-dried products that have not been characterized with these methods before.

Host-Guest Complexation Between Cyclodextrins and Hybrid Hexavanadates: What are the Driving Forces?

Host-guest complexes between native cyclodextrins (α-, β- and γ-CD) and hybrid Lindqvist-type polyoxovanadates (POVs) [V6 O13 ((OCH2 )3 C-R)2 ]2- with R = CH2 CH3 , NO2 , CH2 OH and NH(BOC) (BOC = N-tert-butoxycarbonyl) were studied in aqueous solution. Six crystal structures determined by single-crystal X-ray diffraction analysis revealed the nature of the functional R group strongly influences the host-guest conformation and also the crystal packing. In all systems isolated in the solid-state, the organic groups R are embedded within the cyclodextrin cavities, involving only a few weak supramolecular contacts. The interaction between hybrid POVs and the macrocyclic organic hosts have been deeply studied in solution using ITC, cyclic voltammetry and NMR methods (1D 1 H NMR, and 2D DOSY, and ROESY). This set of complementary techniques provides clear insights about the strength of interactions and the binding host-guest modes occurring in aqueous solution, highlighting a dramatic influence of the functional group R on the supramolecular properties of the hexavanadate polyoxoanions (association constant K1:1 vary from 0 to 2 000 M-1 ) while isolated functional organic groups exhibit only very weak intrinsic affinity with CDs. Electrochemical and calorimetric investigations suggest that the driving force of the host-guest association involving larger CDs (β- and γ-CD) is mainly related to the chaotropic effect. In contrast, the hydrophobic effect supported by weak attractive forces appears as the main contributor for the formation of α-CD-containing host-guest complexes. In any cases, the origin of driving forces is clearly related to the ability of the macrocyclic host to desolvate the exposed moieties of the hybrid POVs.

Differential scanning calorimetric investigations of three rotary nickel-titanium instrument systems before and after simulated clinical uses

BackgroundThe transformation temperatures were important values, influencing the mechanical properties and clinical performance of nickel-titanium instruments. The aim of this study was to determine the transformation temperatures of three rotary nickel-titanium (NiTi) instruments: Reciproc, HyFlex CM Pro, and Neoniti before and after simulated clinical uses.MethodsNinety new NiTi instruments of three single-file instruments: Reciproc, HyFlex CM Pro, and Neoniti were divided into three groups. Thirty instruments of each group were divided into 3 subgroups (10 instruments for each subgroup): new, one-time simulated clinical used and sterilised, and three times simulated clinical used and sterilized subgroups. The instruments were in the as-received condition for the new subgroups, one time used in the plastic endo-training blocks and sterilised for the one-time subgroups, and three times used in the plastic endo-training blocks and sterilised for the three times subgroups. Each instrument in subgroups was cut into four small segments of 4–5 mm. All segments of instruments were analysed using Differential Scanning Calorimetry (DSC). Data was collected and analysed using SPSS version 20.0 with ANOVA test or Kruskal–Wallis test at the significant level of 0.05.ResultsThere was not significant difference between before and after simulated clinical use with sterilised procedure in three NiTi instrument systems. The austenite-finish (Af) temperatures of three instrument systems were higher than that of the human body (37 °C), of these, the Af temperature of Neoniti was highest and that of HyFlex CM Pro was lowest.ConclusionsThe austenite-finish (Af) temperatures of three NiTi instruments were higher than that of human body temperature, therefore, material was in the phase transformation from martensite to austenite, gives the instruments more flexibility when used in the clinical situation.

A calorimetric and thermodynamic investigation of strontium fluorapatite [formula omitted

A calorimetric and thermodynamic investigation of one of the representatives of full-substituted fluorapatites, strontium-substituted fluorapatite {Sr10PO46F2}, was undertaken. The phase was synthesized according to the technique developed by the authors of the article based on the classical sol–gel process. The synthetic product was characterized by X-ray powder diffraction (XRD), X-ray fluorescence analysis (XRF), Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and Differential thermal/gravimetric analysis (DTA-TG). The enthalpy of formation of the phase was determined using HNO3-solution calorimetry giving ΔfHmo(T=298.15K,Sr10PO46F2,cr)=(-13721±8)kJ∙mol-1. The low-temperature heat capacity, Cp,mo, was measured using adiabatic calorimetry from T = (6.8 to 307.0) K. The high-temperature heat capacity, Cp,mo, was measured using DSC calorimetry from T = (306.7 to 651.7) K. Using these Cp,mo(T) data, the third law entropy at T = 298.15 K, Smo, is calculated as (938.7 ± 3.8) J∙K−1∙mol−1. This new experimental result, together with literature data, are used to calculate the Gibbs energy of formation, ΔfGmo, giving: ΔfGmo(T=298.15K,Sr10PO46F2,cr)=(-13000±9)kJ∙mol-1. Smoothed Cp,moT values between T → 0 K and T = 650 K are presented, along with values for Smo and the functions [HmoT-Hmo0] and [GmoT-Gmo0]. Thermodynamic stability of cation-substituted fluorapatites, M10PO46F2 with M = Ca, Ba, Sr, Mg, was analyzed based on literature and experimental data.

Calorimetric investigations on lithium based ceramics

Lithium based ceramics namely lithium titanate, lithium zirconate, and lithium aluminate are proposed materials for tritium breeding in a D-T based fusion reactor. Thermodynamic stability of these materials is important for their use under extreme conditions. In this paper, the thermodynamic stability analysis of lithium titanate, lithium zirconate, and lithium aluminate ceramics is reported. The standard molar enthalpy of formation Li2TiO3(s), Li2ZrO3(s), and LiAlO2(s) compounds have been determined for the first time employing an isoperibol room temperature solution calorimeter. The standard molar enthalpy of formation of Li2TiO3(s), Li2ZrO3(s), and LiAlO2(s) at 298.15 K are found to be – (1632.4 ± 9.7), – (1776.7 ± 6.7), and – (1188.2 ± 5.2) kJ·mol−1, respectively. The isobaric heat capacity of these compounds has been measured over the temperature range 300 K to 770 K employing Differential Scanning Calorimeter (DSC). Using the above experimental results the standard molar Gibbs energy of formation and other thermodynamic functions for these compounds have been derived and compared with the literature values.

Selective recognition of bisphenol S isomers in water by β-cyclodextrin

ABSTRACT The two isomers 4,4´-dihydroxydiphenyl sulphone and 2,4´-dihydroxydiphenyl sulphone (bisphenol S, BPS) form inclusion complexes with β-CD in solution, in the gas phase, and in the solid state. The complexes 4,4´-BPS@β-CD and 2,4´-BPS@β-CD were studied in solution by 1D and 2D NMR experiments. Calorimetric investigation by ITC evidenced that the β-CD host shows a greater affinity for 4,4´-BPS, with a 4,4´-BPS/2,4´-BPS selectivity ratio of 6.3. In the gas phase, CID MS experiments indicate that 4,4´-BPS has a higher kinetic barrier to escape from the β-CD cavity than the isomeric 2,4´-BPS. In the solid state, the 4,4´-BPS@β-CD and 2,4´-BPS@β-CD complexes form head-to-head dimers constituted by two β-CD macrocycles, with each β-CD hosting one BPS guest. The dimers of β-CD are sealed by H-bonding interactions involving exclusively the secondary OH groups. Finally, the formation of inclusion complexes between 4,4´-BPS or 2,4´-BPS and β-CD was also followed by FT-IR, DSC, and TGA analysis.

Calorimetric and Dielectric Investigations of Epoxy-Based Nanocomposites with Halloysite Nanotubes as Nanofillers

Epoxy nanocomposites are promising materials for industrial applications (i.e., aerospace, marine and automotive industry) due to their extraordinary mechanical and thermal properties. Here, the effect of hollow halloysite nanotubes (HNT) on an epoxy matrix (Ep) was the focus of the study. The structure and molecular mobility of the nanocomposites were investigated using a combination of X-ray scattering, calorimetry (differential (DSC) and fast scanning calorimetry (FSC)) and dielectric spectroscopy. Additionally, the effect of surface modification of HNT (polydopamine (PDA) and Fe(OH)3 nanodots) was considered. For Ep/HNT, the glass transition temperature (Tg) was decreased due to a nanoparticle-related decrease of the crosslinking density. For the modified system, Ep/m-HNT, the surface modification resulted in enhanced filler–matrix interactions leading to higher Tg values than the pure epoxy in some cases. For Ep/m-HNT, the amount of interface formed between the nanoparticles and the matrix ranged from 5% to 15%. Through BDS measurements, localized fluctuations were detected as a β- and γ-relaxation, related to rotational fluctuations of phenyl rings and local reorientations of unreacted components. A combination of calorimetry and dielectric spectroscopy revealed a dynamic and structural heterogeneity of the matrix, as confirmed by two glassy dynamics in both systems, related to regions with different crosslinking densities.

Calorimetric, spectroscopic and computational investigation of morin binding effect on bovine serum albumin stability

The interaction of morin (Mor) with bovine serum albumin (BSA) was investigated using calorimetric, spectroscopic and computational methods. The ligand binding to protein has been studied under physiological conditions at various temperatures using isothermal titration calorimetry (ITC). Furthermore, the enthalpy (ΔH), entropy (ΔS) and heat capacity (ΔCp) changes of ligand-protein complex formation were also calculated. The results indicated two sites for Mor binding with BSA. The presence of Mor in higher concentration caused an increased thermal stability of protein proved by differential scanning calorimetry (DSC) measurements. Molecular docking and dynamics simulations supported Sudlow’s sites I and II of BSA as binding receptors for Mor. The dual action of ligand binding was demonstrated: stabilizer of the native protein structure up to the denaturation temperature and promoter of aggregation above this temperature.