Infrared Spectroscopy Research Articles

A modular approach to 3D-printed bilayer composite scaffolds for osteochondral tissue engineering

Prolonged osteochondral tissue engineering damage can result in osteoarthritis and decreased quality of life. Multiphasic scaffolds, where different layers model different microenvironments, are a promising treatment approach, yet stable joining between layers during fabrication remains challenging. To overcome this problem, in this study, a bilayer scaffold for osteochondral tissue regeneration was fabricated using 3D printing technology which containing a layer of PCL/hydroxyapatite (HA) nanoparticles and another layer of PCL/gelatin with various concentrations of fibrin (10, 20 and 30 wt.%). These printed scaffolds were evaluated with SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy) and mechanical properties. The results showed that the porous scaffolds fabricated with pore size of 210–255 µm. Following, the ductility increased with the further addition of fibrin in bilayer composites which showed these composites scaffolds are suitable for the cartilage part of osteochondral. Also, the contact angle results demonstrated the incorporation of fibrin in bilayer scaffolds based on PCL matrix, can lead to a decrease in contact angle and result in the improvement of hydrophilicity that confirmed by increasing the degradation rate of scaffolds containing further fibrin percentage. The bioactivity study of bilayer scaffolds indicated that both fibrin and hydroxyapatite can significantly improve the cell attachment on fabricated scaffolds. The MTT assay, DAPI and Alizarin red tests of bilayer composite scaffolds showed that samples containing 30% fibrin have the more biocompatibility than that of samples with 10 and 20% fibrin which indicated the potential of this bilayer scaffold for osteochondral tissue regeneration.Graphical

Effect of H<sub>3</sub>PO<sub>4</sub> and Phenol Additives on Gel Formation in Silica Fire Retardant Coatings for Building Materials

Increasing the fire resistance of wooden building structures is quite effectively ensured thanks to the development of fire-fighting compositions with aromatic components that contribute to the formation of a carbonized layer on the surface of the material during combustion. It is also known about the mutual positive influence of benzene fragments and phosphate-containing compounds on the fire-resistant characteristics of wood. The paper considers the possibility of complex use of phenol and orthophosphate acid to improve the flame retardant properties of SiO2-based coatings. The effect of modifying additives on the rheological properties of silicic acid sols was determined. Based on the results of IR spectroscopy, the influence of components on the nature of polycondensation in experimental SiO2 sols was evaluated. It is shown that the use of orthophosphate acid as a modifier leads to the initiation of predominantly linear polycondensation in experimental sols. It was established that small additions of phenol practically do not affect the course of polycondensation in experimental sols. Increasing the phenol content to 0.5% showed an effect on gel formation due to the possible addition of phenol to the skeletal silanol groups by the donor-acceptor mechanism, which makes it possible to have a synergistic effect of the complex additive of orthophosphate acid and phenol on the properties of the silica-containing flame retardant composition.

Where is the hidden intramolecular H-bonding vibrational signal in the proline matrix IR spectrum?

The assignment of the hydrogen bonded O-H stretch vibration in the proline matrix IR spectrum has sparked controversy. Employing constrained nuclear electronic orbital methods, we provide a clear assignment that the vibrational frequency drops to near 3000cm-1 as a result of the interplay between electronic effects, nuclear quantum effects, and matrix effects.

Atmospheric chemistry of (Z)‐CF2HCF=CHCl: Kinetics and products of reaction with Cl atoms and OH radicals

AbstractLong path length FTIR‐smog chamber techniques were used to study the title reactions in 650 Torr of N2, oxygen, or air diluent at 296 ± 3 K. Values of k(Cl + (Z)‐CF2HCF = CHCl)═(6.6 ± 0.7) × 10−11 and k(OH + (Z)‐CF2HCF═CHCl)═(4.1 ± 0.7) × 10−12 cm3 molecule−1 s−1 were measured. The IR spectrum of (Z)‐CF2HCF═CHCl is reported. The atmospheric lifetime of (Z)‐CF2HCF═CHCl is determined by the reaction with OH and is approximately 2.8 days. Reaction of (Z)‐CF2HCF═CHCl with Cl atoms gives HC(O)Cl and CF2HC(O)F as major primary products. Under environmental conditions, the OH radical initiated oxidation gives CF2HC(O)F and HC(O)Cl in yields of (98 ± 8)% and (100 ± 4)%, respectively. Accounting for non‐uniform horizontal and vertical mixing leads to a 100‐year time‐horizon global warming potential value for (Z)‐CF2HCF═CHCl of essentially zero.

Design and characterization of novel A2B2 porphyrins: Solar cell applications, antimicrobial properties, and molecular docking insights

We synthesized novel A2B2 porphyrin derivatives (5a-e, 7a,b) with yields of 60–73 %. Porphyrin 2 was prepared by reacting dipyrromethane 1 with p-bromobenzaldehyde. Porphyrin 2 was then treated with n-BuLi in DMF at -15 °C to produce porphyrin 3. The final compounds, 5a-e and 7a,b, were synthesized by reacting porphyrin 3 with activated nitriles (4a-e) and thiazolone derivatives (6a,b). The structures of the novel compounds were confirmed using infrared (IR) spectroscopy, proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), mass spectrometry (MS), and elemental analysis. DFT calculations were used to explore the electronic structures and energy levels of the synthesized compounds. Compounds 7a and 7b showed improved electron transfer efficiency compared to 5a-e, with HOMO and LUMO levels aligned for optimal DSSC performance. The HOMO levels are below the electrolyte's redox potential (-5.2 eV), and the LUMO levels are above TiO2's conduction band (-4.2 eV), facilitating efficient electron injection and dye regeneration. Key parameters such as open-circuit voltage (VOC), free energy of injection (ΔGinj), and regeneration (ΔGreg) were calculated, highlighting these compounds' potential for DSSC applications. The newly synthesized compounds were tested for antibacterial activity against C. albicans, B. subtilis, and E. coli. Compounds 5e (MIC50 3.125 µg/mL, with inhibition zone 45 mm against B. subtilis) and (MIC50 12.5 µg/mL, with inhibition zone 31 mm against E. coli) and 7a (MIC50 3.125 µg/mL, with inhibition zone 44 mm against B. subtilis) and (MIC50 12.5 µg/mL, with inhibition zone 30 mm against E. coli) showed the highest antimicrobial activity. Compound 5e's carboxylic acid group likely enhances activity through strong hydrogen bonding and improved solubility, aiding interaction with microbial enzymes or cell walls. Compound 7a's dimalononitrile groups, being highly electron-withdrawing, increase reactivity, while phenylthiazolidine rings offer additional binding sites through hydrogen bonding and pi-stacking interactions. Docking studies of the most potent antibacterial porphyrin analogues, 5e and 7a, against the target protein PDB: 1ECl showed promising results. Compound 5e achieved a docking score of ‐7.9559 kcal/mol with an RMSD of 1.9743 Å, while compound 7a had an even better score of ‐8.9174 kcal/mol. Compound 7a formed interactions with two H-acceptors from its cyano groups, binding to Arg136 and Lys488, and a Pi-H interaction between the thiazolone ring and Asn158, with distances of 3.19, 3.63, and 3.71 Å, respectively.

Synthesis and Performance Evaluation of Metallocene Polyalphaolefins (mPAO) Base Oil with Anti-Friction and Anti-Wear Properties

Anti-wear and anti-oxidation abilities are two key properties of lubricants that play a crucial role in ensuring long-term stable equipment operation. In this study, we aimed to develop a base oil with good anti-oxidation and anti-wear properties for use under extreme pressure. The as-prepared metallocene polyalphaolefin (mPAO) was chemically modified using the trifluoromethanesulfonic acid (TfOH) catalysis through an alkylating reaction with triphenyl phosphorothioate (TPPT). During the experiments, when the reaction temperature exceeded 70 °C or the concentration of TfOH exceeded 2.67%, the β-scission reaction in the alkylation process became significantly more pronounced. The physical and chemical properties of TPPT-modified mPAO (T-mPAO) were evaluated by nuclear magnetic resonance spectroscopy, Fourier trans-form infrared spectroscopy, gel–permeation chromatography, and ASTM standards. T-mPAO showed significantly improved antioxidant capacity, with the initial oxidation temperature increasing by 32 °C compared to the base oil, and it exhibited the slowest increase in acid number in the 96-h oven oxidation test. The tribological tests showed that T-mPAO had the lowest friction coefficient, wear track, and wear rate (72.7% lower than that of mPAO) as well as the highest PB (238 kg) and PD (250 kg) among all tested samples. Compared to mPAO, the average friction coefficient of TPPT-modified mPAO in the four-ball friction test was reduced by 30.5%, and by 16.4% in the TE77 reciprocating friction test. Based on the experimental results, T-mPAO had strong anti-oxidation ability and excellent lubricating performance.The successful synthesis of multifunctional mPAO has enabled lubricant base oil additization, making it possible to use it in more demanding work scenarios, greatly broadening its application scope and making lubricant formulation blending more flexible.

Amide groups in 3.7 billion years old liquid inclusions

Carbon with depleted d13C (down to − 25.6‰ VPDB) found in > 3.7 billion year old metamorphic sediments from the Isua Supracrustal Belt, Southwestern Greenland, has been proposed to represent the oldest remains of life on Earth. Graphitic inclusions within garnet porphyroblasts from this locality have been shown to associate with elements consistent with biogenic remains. In this report, we focus on certain liquid inclusions found in the Isua garnets, characterizing their chemical composition using atomic force microscopy, AFM-based infrared spectroscopy, optical photothermal infrared spectroscopy, Raman spectroscopy, and time-of-flight secondary ion mass spectrometry. Our results show that the liquid inclusions contain functional groups consisting of carbon, nitrogen, and oxygen in a configuration similar to amide functional groups. We suspect that the amide groups formed from N, O and C-containing volatile components that were released from the original kerogenous material enclosed in the garnets, as this was graphitized during thermal maturation. This is consistent with the observed inclusion assemblage of solid graphitic and viscous fluid inclusions alike. Our observations are compatible with the inclusions forming from biogenic precursor material, and when considered alongside previous reports on the carbonaceous material in the Isua metamorphic sediments, these and our study collectively indicate that the carbonaceous material in the Isua metasediments represents the oldest traces of life on Earth.

Repairing Noise-Contaminated Low-Frequency Vibrational Spectra with an Attention U-Net.

Low-frequency vibrational modes in infrared (IR) and Raman spectra, often termed molecular fingerprints, are sensitive probes of subtle structural changes and chemical interactions. However, their inherent weakness and susceptibility to environmental interference make them challenging to detect and analyze. To tackle this issue, we developed a deep learning denoising protocol based on an attention-enhanced U-net architecture. This model leverages the inherent correlations between high- and low-frequency vibrational modes within a molecule, effectively reconstructing low-frequency spectral features from their high-frequency counterparts. We demonstrate the effectiveness of this method by recovering low-frequency signals of trans-1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on an Ag surface, a representative system for surface enhancement Raman spectroscopy (SERS). Notably, the trained model exhibits promising transferability to SERS spectra acquired under different surface and external field conditions. Furthermore, we applied this method to experimental IR and Raman spectra of BPE, achieving high-quality, low-frequency spectral recovery.

Rapid discrimination and quantification of chemotypes in Perillae folium using FT-NIR spectroscopy and GC–MS combined with chemometrics

Perillae Folium (PF) is a well-known food and herb containing different chemotypes, which affect its quality. Herein, a method was proposed to classify and quantify PF chemotypes using gas chromatography–mass spectrometry (GC–MS) and Fourier transform-near infrared spectroscopy (FT-NIR). GC–MS results revealed that PF contains several chemotypes, including perilla ketone (PK) type, α-asarone (PP-as) type, and dillapiole (PP-dm) type, with the PK type being the predominant chemotype. Based on FT-NIR data, different chemotypes were accurately classified. The random forest algorithm achieved >90 % accuracy in chemotype classification. Furthermore, the main components of perilla ketone and isoegomaketone in PF were successfully quantified using partial least squares regression models, with prediction to deviation values of 3.76 and 2.59, respectively. This method provides valuable insights and references for the quality supervision of PF and other foods.

Diagnosis of systemic lupus erythematosus using cross-modal specific transfer fusion technology based on infrared spectra and metabolomics

BackgroundSystemic lupus erythematosus (SLE) is a chronic autoimmune disease. Currently, the medical diagnosis of SLE mainly relies on the clinical experience of physicians, and there is no universally accepted objective method for diagnosing SLE. Therefore, there is an urgent need to design an intelligent approach to accurately diagnose SLE to assist physicians in formulating appropriate treatment plans. With the rapid development of intelligent medical diagnostic technology, medical data is becoming increasingly multimodal. Multimodal data fusion can provide richer information than single-modal data, and the fusion of multiple modalities can effectively enhance the richness of data features to improve modeling performance. ResultsIn this paper, a cross-modal specific transfer fusion technique based on infrared spectra and metabolomics is proposed to effectively integrate infrared spectra and metabolomics by fully exploiting the intrinsic relationships between features across different modalities, thus achieving the diagnosis of SLE. In this research, a Decision Level Fusion module is also proposed to fuse the representations of two specific transfers further, obtaining the final prediction scores. Comprehensive experimental results demonstrate that the proposed method significantly improves the performance of SLE prediction, with accuracy and Area Under Curve (AUC) reaching 94.98 % and 97.13 %, respectively, outperforming existing methods. SignificanceOur framework effectively integrates infrared spectra and metabolomics to achieve a more accurate prediction of SLE. Our research indicates that prediction methods based on different modalities outperform those using single-modality data. The Cross-modal Specific Transfer Fusion module effectively captures the complex relationships within each single modality and models the complex relationships between different modalities.

Synthesis and Performance Evaluation of Zwitterionic C-N Bonded Triazole-Tetrazole-Based Primary Explosives.

Developing advanced metal-free nitrogen-enriched primary explosives is challenging due to the inherent risks associated with their synthesis and handling. However, there is an urgent need to develop novel lead-free, nitrogen-rich primary explosives that offer balanced energetic properties. C-N bonded bicyclic compound 3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-amine (4), its salts, and 3,5-diazido-1H-1,2,4-triazole (8) were synthesized from inexpensive starting materials resulting in a fine blend of sensitivity and stability. These compounds exhibit high nitrogen content (79.78 to 83.43%), good thermal stability (129-210 °C), excellent detonation performance (VOD: 8592-9361 ms-1, DP: 27.1-33.8 GPa), and acceptable sensitivity (IS: 2.5-30 J, FS: 72-288 N). The hot needle tests of compounds 4 and 8 exhibit excellent ignition performance. All of the newly synthesized compounds were fully characterized using infrared spectroscopy (IR), high-resolution mass spectroscopy (HRMS), multinuclear magnetic spectroscopy (NMR), elemental analysis (EA), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), and 2, 4, and 8 were confirmed by single-crystal X-ray crystallographic studies. The molecular electrostatic potential (ESP), noncovalent interactions reduced density gradient (NCI-RDG) method, and QTAIM analysis were performed to investigate the intermolecular interactions. Together with promising performance properties, ease of synthesis, and ignitability, they are highly suitable candidates to pave new avenues for future applications.

10-[(4-Cyanobenzylidene)]-Anthracen-9(10H)-One: syntheses, characterization and application in UV light detection

In this work, the compound 10-[(4-cyanobenzylidene)]-anthracen-9(10H)-one (1) has been synthesized from the corresponding anthrone and 4-cyanobenzaldehyde. It has been characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (IR), high-resolution mass spectroscopy (HRMS) and single-crystal X-ray diffraction (XRD) analysis. Moreover, square wave voltammetry (SWV) was performed to determine the HOMO and LUMO potential levels of the anthrone derivative 1, which indicates that sensitization of TiO2-based electrodes is thermodynamically feasible. Therefore, this characteristic of compound 1 allowed its incorporation in a Grätzel-type solar cell. Photocurrent density measurements under UV irradiation are proportional to the light source intensity, and the operational parameters of the photoelectrochemical cell are relatively stable over time. In fact, the sensitivity of the generated photocurrent normalized by the supplied irradiance for TiO2-1 (7.73 µA/mW) as a photoanode is higher than that of TiO2 alone (5.14 µA/mW), indicating the improvement that 1 provides to TiO2 with respect to UV light detection. The higher photocurrent and the improved stability due to the implementation of 1 are very promising for possible applications as a sensitizer for UV light intensity sensors in dye-sensitized solar cells (DSSC).

Soft Ca2+-induced pea protein gels through mild heating: Controlling elasticity and fracturing behavior

With the rising demand for plant-based protein, understanding the formation of pea protein gels induced by calcium is important for manufacturing of food products with appealing textural properties. Moreover, the moderate temperature processing is becoming of greater and greater interest, based on conditions used for food fermentation. The objective of this study is to understand the structural and rheology behaviour of calcium-induced pea protein aggregates at moderate plateau temperatures i.e. in the range 30–45 °C with holding times from 0 to 60,000s. Based on the combination of confocal fluorescence microscopy (CLSM) imaging, rheology and IR spectroscopy, our results show that despite the relatively low temperature range, thermal agitation not only allows for partial protein particle dissolution, but also induces interactions leading to soft gel formation. Within a shorter holding time (0–600s) range, higher Gʹ/Gʹ0 (t) were observed at 40 °C and 45 °C, the end elastic modulus reaching for any parameters tested at least 1000 Pa. As the holding time was extended to 60,000s, the effect of temperature became less pronounced, i.e., all gels reached similar high values of Gʹ even for the low temperature of 30 °C, which is nearly 3–4 times higher than that formed at 600s holding time (at the temperature plateau). IR spectroscopy measurements showed that the protein secondary structure remained stable within the holding time ranging from 0s to 6,000s, while significant but moderate changes were monitored when extending the holding time to 60,000s, which correlated with a more progressive yielding observed in rheology, pointing to the formation of apparently more fragile physical gels. The combination of the techniques shows that the gel formation and strengthening mainly originated from rearrangements at the colloidal level leading to a denser network, while molecular rearrangements only intervened at the longest holding times (i.e, 60,000s).

The radiative efficiency and global warming potential of HCFC-132b.

Hydro-chloro-fluoro-carbons (HCFCs) are potent greenhouse gases which strongly absorb the infrared (IR) radiation within the 8 - 12 μm atmospheric windows. Despite international policies schedule their phasing out by 2020 for developed countries and 2030 globally, HCFC-132b (CH2ClCClF2) has been recently detected with significant atmospheric concentration. In this scenario, detailed climate metrics are of paramount importance for understanding the capacity of anthropogenic pollutants to contribute to global warming. In this work, the radiative efficiency (RE) of HCFC-132b is experimentally measured for the first time and used to determine its global warming potential (GWP) over 20-, 100- and 500-year time horizon. Vibrational- and rotational-spectroscopic properties of this molecule are first characterized by exploiting a synergism between Fourier-transform IR (FTIR) spectroscopy experiments and quantum chemical calculations. Equilibrium geometry, rotational parameters and vibrational properties predicted theoretically beyond the double-harmonic approximation, are employed to assist the vibrational assignment of the experimental trace. Finally, FTIR spectra measured over a range of pressures are used to determine HCFC-132b absorption cross section spectrum from 150 to 3000 cm-1, from which istantaneous and effective REs are derived and, in turn, used for GWP evaluation.

One-Pot multicomponent synthesis of novel pyrazole-linked thiazolyl-pyrazolines: Molecular docking and cytotoxicity assessment on breast and lung cancer cell-lines

Cancer remains a foremost cause of mortality globally, with approximately 20 million new cases and nearly 10 million deaths reported in 2022. Lung and breast cancers are particularly prevalent and deadly, underscoring the critical need for novel therapeutic strategies. This study utilized a one-pot, multicomponent reaction (MCR) approach to synthesize a novel series of pyrazole-linked thiazolyl-pyrazolines. The optimal reaction conditions were determined by systematically varying bases, temperatures, reaction times, and solvents. The best yield was achieved using NaOH as the base at 50 °C with 2 h of stirring in ethanol. The synthesized compounds underwent thorough characterization through IR, mass spectrometry, and NMR spectroscopy. Molecular docking studies indicated strong binding affinities to the ErbB4 kinase, suggesting potential utility as kinase inhibitors. Compounds 5E, 5F, and 5G exhibited significant cytotoxicity against breast cancer cell lines, with IC50 values ranging from 15.79±1.272 to 28.38±1.520 µM. Meanwhile, compounds 5A, 5B, 5D, and 5G demonstrated potent effects against lung cancer cell lines, with IC50 values between 7.945±0.99 and 9.295±1.074 µM. Remarkably, compound 5G showed potent efficacy against both breast and lung cancers, with IC50 values of 28.38±1.520 µM and 9.02±1.07 µM, respectively. This study illuminates the critical role of pyrazole-linked thiazolyl-pyrazoline scaffolds in crafting powerful cancer therapeutics targeting ErbB4 (HER4) kinase. Unique in its dual functionality, ErbB4 can act as either an oncogene or a tumor suppressor in lung and breast cancers, contingent on specific cellular contexts and isoform variations. The dynamic expression of ErbB4 intricately modulates tumor growth and patient outcomes, marking it as a compelling therapeutic target for innovative treatments in both breast and lung cancer.

Aloebarbadensis - Assisted MgBiO/MgCuBiO/MgBaBiO nanocomposites as effective gamma shielding novel materials

For the first of its kind, MgO/Bi2O3 (1:1) (MBO), MgO/CuO/Bi2O3 (1:1:1) (MCBO) and MgO/BaO/Bi2O3 (1:1:1) (MBBO) binary/ternary nanocomposites (NCs) were synthesized by Aloe barbadensis (Aloe vera) mediated solution combustion method. The as-formed NCs are subjected to calcination for 3 h at 600oC.The Mg-based NCs acquired are subjected to various analytical characterization methodologies, including PXRD (Powder X-ray Diffraction), SEM (Scanning Electron Microscopy), EDS (Energy Dispersive X-ray Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), and Ultraviolet–Visible Spectroscopy (UV–Vis). The Bragg reflections confirm the formation of monoclinic phase BaO, Bi2O3, cubic MgO and tetragonal CuO nanoparticles. The surface morphology of MBO, MCBO and MBBO NCs consists of irregular sized, leafy and burrow like structured agglomerated NPs with hollows and voids/pores. The Eg (direct energy band gap) determined from W-H (Wood and Tauc's) plot was found to be 3.09, 3.19 and 3.12 eV for MBO, MCBO and MBBO NCs respectively. The evaluation of gamma radiation shielding properties was conducted using a NaI (Tl) detector connected to a multi-channel analyzer. Shielding parameters of MBO, MCBO and MBBO, such as μ/ρ (mass attenuation coefficient), λ (mean free path), HVL (half-value layer), TVL (tenth-value layer) are measured. Among the as-synthesized Mg-based NCs, MBO exhibits better shielding properties compared to MCBO and MBBO. Thus, the procured Mg-based NCs are suitable for applications where weight reduction is critical, such as aerospace or portable radiation shielding systems.

Hydrogen-Bonded Complexes of HPN• and HNP• Radicals with Carbon Monoxide.

Phosphorus mononitride (PN) is a carrier of phosphorus in the interstellar medium. As the simplest derivatives of PN, the radical species HPN• and HNP• have remained elusive. Herein, we report the generation, characterization, and photochemistry of HPN• and HNP• in N2-matrix at 3 K. Specifically, HPN• was formed as a weakly bonded complex with CO in the matrix by 254 nm photolysis of the novel phosphinyl radical HPNCO•. The •NPH-CO complex is extremely unstable, as it undergoes spontaneous isomerization to the lower-energy isomer •PNH-CO through fast quantum mechanical tunneling (QMT) with a half-life of 6.1 min at 3 K. Upon further irradiation at 254 nm, the reverse conversion of •PNH-CO to •NPH-CO along with dehydrogenation to yield PN was observed. The characterization •NPH-CO and •PNH-CO with matrix-isolation IR spectroscopy is supported by D, 15N, and 13C isotope labeling and quantum chemical calculations at the XYGJ-OS/AVTZ level of theory, and the mechanism by hydrogen atom tunneling is consistent with multidimensional instanton theory calculations.

Synthesis, vibrational, thermal, topological, electronic, electrochemical stability and DFT studies of new DABCO based ionic liquids

The design of new ILs with different anions could provide interesting physico-chemical properties and for these reasons, the knowledge about the synthesis, the thermal, vibrational, topological, electronic, electrochemical properties and interaction between the selected cation-anion in these ILs are important subjects. Therefore, the understanding about these properties of these compounds is an important subject of study. In this work, we studied three ionic liquids based on the 1-decyl-1,4-diazabicyclo[2.2.2]octane, DABCO-cation, where the corresponding anions were [Br]-, [PF6]-, and [N(SO₂CF₃)₂]-. The syntheses of these bicyclic DABCO ionic liquids are based on an alkylation reaction of 1,4-diazabicyclo[2.2.2] octane and 1-bromodecanefollowed by anion exchange. The obtained ILs are characterized by 1H, 13C, 19F and 31P-NMR spectroscopy. Vibrational spectroscopy studies are conducted by infrared (FTIR/ATR) and Raman spectroscopy in the wavenumber range 600–4000 cm-1 and 45–3500 cm-1, respectively. Furthermore, the thermal stabilities were investigated using the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. Results indicate that the thermal stability follow the order [C10DABCO][Br]<[C10DABCO][PF6]<[C10DABCO][N(SO₂CF₃)₂]. Additionally, the structural parameters, electrostatic potential (ESP) maps, interaction energies, non-covalent interaction (NCI), atoms in molecule (AIM) analysis, natural bond orbital (NBO), frontier molecular orbital (FMO) analysis and Electrochemical window (ECW) are studied and analyzed by means of DFT calculations at the M06–2X-GD3/AUG–cc–pVDZ level of theory.

Infrared Spectroscopy and Photochemistry of Ethyl Maltol in Low-Temperature Argon Matrix

Ethyl maltol was investigated using matrix isolation infrared spectroscopy and DFT calculations. In an argon matrix (14.5 K), the compound was found to exist in a single conformer (form I), characterized by an intramolecular hydrogen bond with an estimated energy of ~17 kJ mol−1. The IR spectrum of this conformer was assigned, and the molecule’s potential energy landscape was explored to understand the relative stability and isomerization dynamics of the conformers. Upon annealing the matrix to 41.5 K, ethyl maltol was found to predominantly aggregate into a centrosymmetric dimer (2× conformer I) bearing two intermolecular hydrogen bonds with an estimated energy of ca. 28 kJ mol−1 (per bond). The UV-induced (λ &gt; 235 nm) photochemistry of the matrix-isolated ethyl maltol was also investigated. After 1 min of irradiation, band markers of two rearrangement photoproducts formed through the photoinduced detachment-attachment (PIDA) mechanism, in which the ethyl maltol radical acts as an intermediate, were observed: 1-ethyl-3-hydroxy-6-oxibicyclo [3.1.0] hex-3-en-2-one and 2-ethyl-2H-pyran-3,4-dione. The first undergoes subsequent reactions, rearranging to 4-hydroxy-4-propanoylcyclobut-2-en-1-one and photofragmenting to cyclopropenone and 2-hydroxybut-1-en-1-one. Other final products were also observed, specifically acetylene and CO (the expected fragmentation products of cyclopropenone), and CO2. Overall, the study demonstrated ethyl maltol’s high reactivity under UV irradiation, with significant photochemical conversion occurring within minutes. The rapid photochemical conversion, with complete consumption of the compound in 20 min, should be taken into account in designing practical applications of ethyl maltol.

Mixed equilibrium/nonequilibrium effects govern surface mobility in polymer glasses

Using angle-resolved X-ray photoelectron spectroscopy, sum-frequency generation vibrational spectroscopy, contact angle measurements, and molecular dynamics simulations, we verify that the glass transition temperature (Tg) of polymer glass is lower near the free surface. However, the experimental Tg-gradients showed a linear variation with depth (z) from the free surface, while the simulated equilibrium Tg-gradients exhibited a double exponential z-dependence. In typical simulations, Tg is determined based on the relaxation time of the system reaching a prescribed threshold value at equilibrium. Conversely, the experiments determined Tg by observing the unfreezing of molecular mobility during heating from a kinetically arrested, nonequilibrium glassy state. To investigate the impact of nonequilibrium effects on the Tg-gradient, we reduced the thermal annealing time in simulations, allowing the system to fall out of equilibrium. We observe a decrease in the relaxation time and the emergence of a modified z-dependence consistent with a linear Tg-gradient near the free surface. We further validate the impact of nonequilibrium effects by studying the dependence of the Tg on the heating/cooling rate for polymer films of varying thickness (h). Our experimental results reveal significant variations in the Tg-heating/cooling rate dependence with h below the bulk Tg, which are also observed in simulation when the simulated system is not equilibrated. We explain our findings by the reduction in mass density within the inner region of the system under nonequilibrium conditions, as observed in simulation, and recent research indicating a decrease in the local Tg of a polymer when placed next to a softer material.