Changes In Molecular Structure Research Articles

Synergistic effect of thermal oxygen and UV aging on natural rubber

Abstract The oxidation of natural rubber (NR) leads to a decrease in mechanical properties, even resulting in failure of NR products. Many studies focusing on this single factor have failed to fully elucidate the impact of tropical island environment on NR properties. Based on this concern, the synergistic effect of thermal oxygen and ultraviolet (UV) aging on NR was systematically studied. The results revealed that thermal oxygenation can promote UV aging, which leads to the appearance of surface cracks and deepening of color. With the extension of aging time, the mechanical properties of NR correspondingly decreased. Besides, to deeply understand the mechanism of the synergistic effect of thermal oxygen and UV aging on NR, we selected squalene to simulate and analyze the molecular structure changes in NR. Based on these results, a possible synergistic effect of thermal oxygen and UV aging mechanisms on NR could be proposed.

Intrinsic-group-contribution PC-SAFT and its application in performance analysis of high-temperature organic Rankine cycle with siloxanes and alkanes

Thermodynamic property prediction of working fluids is of great importance on the performance analysis of high-temperature organic Rankine cycles (ORCs) for utilizing low-grade heat sources. In this study, an intrinsic-group-contribution perturbed-chain statistical associating fluid theory (iGC-PC-SAFT) is proposed for the high-temperature ORC performance analysis with 8 siloxanes and 10 alkanes. By adjusting the initial values and corresponding value ranges of PC-SAFT parameters repeatedly according to the changes in molecular structures, the PC-SAFT parameters were fitted to determine the initial iGC-PC-SAFT parameters. Afterwards, the final iGC-PC-SAFT parameters for each working fluid were obtained based on a global optimization algorithm. Furthermore, the iGC-PC-SAFT equation of state (EoS) was used to calculate the thermodynamic properties of working fluids. Compared with the results from Coolprop database, maximum relative deviations for the saturated liquid density and the compressibility factor in the superheated region are 0.95% for MM, and 0.84% for MD2M, respectively. Besides, the average absolute relative deviations of ORC performance parameters calculated by the iGC-PC-SAFT EoS at different input pressures of turbine, including the thermal efficiency, turbine power output, pump power consumption, heat rejection, mass flow, and exergy efficiency are less than 2.04% for siloxanes (except for MM) and 6.09% for alkanes, respectively.

Disclose effect and mechanism of external electric field on RP-1 fuel pyrolysis

To explore the combustion efficiency of aviation fuel in an electric field, a ReaxFF molecular dynamics and density functional theory calculation was performed to study the electric field effect on 3-component RP-1 (methylcyclohexane, n-dodecane, and isododecane) pyrolysis. The electrostatic potential, charge natural population analysis and molecular structure were discussed under electric fields of various directions and strengths. The chemical reaction kinetics and species were analyzed under a wide range of electrostatic fields and temperatures. The key reaction energy of RP-1 components and motion statistics were discussed. The analysis revealed significant changes in molecular charge density and structure, which predicted possible cracking sites. Cyclohexane and chain alkanes exhibited opposite trends of decomposition rates depending on the field strength and temperature. The different trends were detail analyzed by reaction pathways and product distribution. Newly cracking way appeared under electric field. The decomposition reaction barrier was reduced by the electric field overall. While the motion of molecules was inhibited with the field increasing, which decrease the molecular potential energy. This work conducted a comprehensive analysis about effect of external electric field on the RP-1 mixture fuel pyrolysis. offering a potential solution for improving combustion efficiency.

Pressure-induced hydrogen bonds reconstruction of energetic material 3,6-dihydrazino-1,2,4,5-tetrazine: A DFT study

Pressure-induced changes in molecular structure can result in the reconstruction of hydrogen bonds. The structure and vibrational properties of hydrogen-bonded material 3,6-dihydrazino-1,2,4,5-tetrazine were calculated to 50 GPa. When compression, the compressibility displays anisotropy. At 37 GPa, the N-H length increases abruptly to 1.51 Å, suggesting that N-H has broken. The discontinuous changes indicate that 37 GPa is a critical point for structural changes. The hydrogen bond network becomes strengthened, resulting in a decrease in the vibrational activity of NH/NH2. At 37 GPa, the direction of NH correlated vibration modes change. In Hirshfeld analysis, the strengthening of N…H interactions was confirmed.

Formulation and phase change mechanism of Capric acid/Octadecanol binary composite phase change materials

Fatty acids and fatty alcohols have the advantages of high latent heat of phase change, good thermal stability, no corrosion, no supercooling and phase separation. They can be used as phase change energy storage materials for passive temperature control. However, their popularization and application are limited because of their high phase transition temperature and narrow phase transition range. This study develops a novel binary composite phase change materials (PCMs) of Capric acid (CA) and Octadecanol (OD) by a melt blending method. The theoretical calculation and hot melt-step cooling were carried out to generate an optimal molar ratio, followed by DSC thermal characterization. ATR-FTIR and XRD were performed to determine the phase transformation and chemical and structure changes. The results showed the binary CA-OD binary composite PCMs has a high latent heat of fusion, a melting temperature Tm = 26.48 °C and △H = 181.06 J/g at optimal mass ratio of 85.15:14.86 (CA:OD), which is higher than the theoretically predicted latent heat of phase transition, indicating a good synergistic effect beneficial to energy storage. Solid CA exists in the form of dimer and –OH in solid OD exists in form of association, and intermolecular hydrogen bonds weakens in liquid. There are hydrogen bonds in the CA-OD binary composite PCMs, and the molecular structure changes before and after the phase transformation were similar to that of a single component CA or OD. The crystal structures of the two compounds also change and the latent heat of phase transformation is improved. Finally, through TG and high and low temperature cycle test, CA-OD binary PCMs demonstrates good thermal stability and practicability in the field of building energy conservation.

Improving tyrosol production efficiency through shortening the allosteric signal transmission distance of pyruvate decarboxylase.

Tyrosol is an important chemical in medicine and chemical industries, which can be synthesized by a four-enzyme cascade pathway constructed in our previous study. However, the low catalytic efficiency of pyruvate decarboxylase from Candida tropicalis (CtPDC) in this cascade is a rate-limiting step. In this study, we resolved the crystal structure of CtPDC and investigated the mechanism of allosteric substrate activation and decarboxylation of this enzyme toward 4-hydroxyphenylpyruvate (4-HPP). In addition, based on the molecular mechanism and structural dynamic changes, we conducted protein engineering of CtPDC to improve decarboxylation efficiency. The conversion of the best mutant, CtPDCQ112G/Q162H/G415S/I417V (CtPDCMu5), had over two-fold improvement compared to the wild-type. Molecular dynamic (MD) simulation revealed that the key catalytic distances and allosteric transmission pathways were shorter in CtPDCMu5 than in the wild type. Furthermore, when CtPDC in the tyrosol production cascade was replaced with CtPDCMu5, the tyrosol yield reached 38 g·L-1 with 99.6% conversion and 1.58 g·L-1·h-1 space-time yield in 24 h through further optimization of the conditions. Our study demonstrates that protein engineering of the rate-limiting enzyme in the tyrosol synthesis cascade provides an industrial-scale platform for the biocatalytic production of tyrosol. KEY POINTS: • Protein engineering of CtPDC based on allosteric regulation improved the catalytic efficiency of decarboxylation. • The application of the optimum mutant of CtPDC removed the rate-limiting bottleneck in the cascade. • The final titer of tyrosol reached 38 g·L-1 in 24 h in 3 L bioreactor.

FTIR Study of Enriched Bituminous Ukhaa-Khudag Coal

In the present work we pay an attention to the molecular structural changes between raw coal and its enriched, dense productions. Bituminous Ukhaa-Khudag coal in the form of an enriched, dense coal product is currently used as an energy source by Mongolian consumers for everyday need. There are three types of samples from one source: it is a raw coal (sample 1) and two of industrial prod- ucts as an enriched, dopant (organic based) added coal (sample 2) and simply enriched coal (sample 3). The raw coal general characterization is given through the elemental analysis, thermogravimetry analysis, moreover functional groups were identified by Fourier Transform infrared spectroscopy. The differences in the FTIR spectra of the samples were done.Some details are as follows: hydroxyl group vibrations are existing, rather weak in agreement of TG result; vibrations of aliphatic group were rarely in the long wave near region, carbonate minerals in the region of 1300-900 cm−1 are visible but overlapped, and an isolated out-of-plane deformational vibration (around 800 cm−1) or two-adjacent (800-750 cm−1) or three-adjacent (around 700 cm−1) of sp2-hybrid bonded aromatic CHx-groups were still presenting.After the processing hydroxyl group bands were affected in enriched coals, sample 2 and 3. In the spectrum of the sample 2 the long wave bands were intensively blurred.Industry processing retains an amount of water in the productions. Water excess influenced absorbance bands were able to be removed via the drying processing, however, the affection to the spectral struc- ture in sample 2 was unrecoverable.

Unraveling the role of the external electric field on the photo-physical properties of thermally activated delayed fluorescence

Density functional theory (DFT) calculations were performed to understand the effect of the external electric field (EEF) on the essential photo-physical properties of phenozazine-triphenyltriazine (PXZ-TRZ) emitter. Interestingly, the increases in ΔEST values were equally observed under EEFx/y/z = 5.0 × 106 V/cm due to the significant changes in molecular and electronic structures in T1 state. Moreover, spin-orbit couplings (SOCs) under EEFz = 5.0 × 105 V/cm and EEFy/z = 5.0 × 106 V/cm were tremendously augmented, whereas the SOC extremely decreased in the presence of EEFy = 5.0 × 105 V/cm and EEFx = 5.0 × 106 V/cm. Correspondingly, the calculated reverse intersystem crossing rate (kRISC) values are drastically improved in the presence of the EEFy/z = 5.0 × 106 V/cm. On the other hand, the effects of the EEFx = 5.0 × 106 V/cm and EEFy = 5.0 × 105 V/cm on the kRISC were determined to be disadvantageous. Consequently, our theoretical study clearly informs that the role of EEF on the photo-physical properties of TADF materials should be importantly considered as one of the determinants for characterizing TADF materials in the solid-state device.

Study on the Aging Mechanism of Down Fiber Under the Daily Washing and Drying Conditions

ABSTRACT In order to clarify the aging mechanism of down fiber under the daily washing and drying conditions, fluffiness, whiteness, microscopic morphology, crystallinity and molecular structure of down fiber after different washing and drying treatments were observed. Results showed that the daily washing conditions of weak acid or alkali (pH = 5–9) and drying conditions of low temperature drying (55°C and sunlight) only slightly affected fluffiness, whiteness, and microscopic morphology of down fiber. However, the addition of short-term mechanical agitation reduced damage and even improved fluffiness, whiteness. Additionally, down fiber did not experience chemical damage in the above environment. However, the strong alkali (pH = 10, pH = 12) washing environment and high temperature (105°C,155°C) drying treatment not only caused the decline of fluffiness, whiteness, microscopic morphology but also caused the change of crystallinity and molecular structure. Additionally, the stronger the alkalinity, the longer the time, the higher the drying temperature, the more obvious the performance decline. Moreover, regardless of the washing and drying conditions, mechanical agitation for a long time easily led to performance degradation. Therefore, down fibers were suitable for the daily washing conditions of weak acid and alkali (pH = 5–9) and drying conditions of low temperature drying (55°C or sunlight) with slightly mechanical agitation.

Asynchronous piezochromic fluorescence and phosphorescence behavior observed in an organic dual emission crystal

Mechanochromic luminescence (MCL) is attracting much attention due to its promising applications and academic importance. However, the present studies mainly focus on fluorescent dyes, and investigations on organic phosphorescent materials are still lack. In the current work, a new organic room temperature phosphorescence‒fluorescence dual emission crystal with well-separated emission peaks is used to investigate the MCL behaviors by the diamond anvil cell technique in conjunction with the spectroscopic measurements. The results demonstrate the remarkably asynchronous piezochromic fluorescence and phosphorescence behavior in both emission colors and intensities. The theoretical analyses and calculations indicate that the high pressure induced molecular conformation and stacking structure changes can differently influence the energy levels and distributions of singlet and triplet excited states, which is responsible for the interesting photo-physical properties. This work provides a new perspective of understanding the effect of molecular confined environments on organic light emitting properties.

Removal of neonicotinoid insecticide clothianidin from water by ozone-based oxidation: Kinetics and transformation products

In this paper, reaction kinetics, degradation mechanisms and associated toxicity have been assessed in detail concerning the abatement of neonicotinoid insecticide clothianidin (CLO) by ozone-based oxidation in water. The second-order rate constants for the reaction of CLO with molecular ozone (O3) and hydroxyl radical (OH) were determined by the direct and competition kinetics (with UV/H2O2 system as the radical source) methods, respectively, and estimated to be 103 M−1 s−1 and 3.7·109 M−1 s−1. This suggested a (potential) higher contribution of the indirect mechanism rather than the direct degradative pathway in the CLO ozonation process. Additionally, CLO oxidation was studied through an O3 and O3/H2O2 system for three complex real water matrices with distinct characteristics. DOC content was found to be the main parameter responsible for making difficult the achievement of high CLO degradations, whereas carbonate alkalinity did not exert a great impact on the process efficiency. Results indicated that typical ozone doses (up to 1 mg O3/mg DOC) were not enough for the complete removal of this micropollutant, ranging only from 50 to 80%. The study concerning the transformation products (TPs), performed by means of high-resolution mass spectrometry, allowed to suggest potential degradation routes based on the five major CLO-TPs identified. It was inferred that OH was involved in the formation of all TPs, whereas O3 was only involved in the formation of two of them. A preliminary toxicity assessment concerning CLO and its TPs during ozonation was conducted at three different trophic levels via the ECOSAR software. Results showed that none of the compounds was classified as very toxic for aquatic organisms, and all TPs exhibited minor toxicity than the parent compound. Changes in molecular structure, such as chlorothiazole ring breakdown, could be the main reason for this considerable decrease in toxicity. Overall, the present study demonstrates that ozonation can be considered a suitable technology alternative for CLO (and associated toxicity) abatement from aqueous matrices.

The Lifetime Prediction and Insulation Failure Mechanism of XLPE for High-Voltage Cable

The performance parameters and service life of the insulation layer of high-voltage cables are the key to ensure safe cable operation. Through extracting the mechanical parameters of high voltage cable insulation layer under different thermal aging temperatures, a normal linear regression model is established to predict the service life of high voltage cables. Meanwhile, the physicochemical characteristics such as microscopic morphology and molecular structure changes of the cable insulation layer are analyzed, the dielectric properties and breakdown field strength under ac condition are tested and the macroscopic electrical properties of the insulation layer are studied, and the insulation failure mechanism is further analyzed. The experimental results show that the elongation at break retention rate of cross-linked polyethylene (XLPE) increases slowly with the aging time, and then decreases rapidly when it reaches 50% of the initial elongation at break retention rate. The normal linear regression prediction model is established based on the Arrhenius formula, and it can be obtained the life endpoint of XLPE high voltage cable about 65 years at an operating temperature of 70 °C. Further analysis, under the action of heat and oxygen, the crystal zone structure of cable insulation is seriously damaged, and the carbonyl index is significantly increased. Accordingly, when the aging failure point is reached, the dielectric permittivity and dielectric loss of insulation are significantly increased, and the breakdown performance is significantly decreased. The work has an important guiding significance for insulation condition assessment and life prediction of high voltage cable.

Spectroscopic characterisation of acidified milk powders

The production of acidified milk powders by spray drying is challenging due to particle deposition on the dryer surface, which reduces yield, and may impair product quality. The composition, especially lactic acid concentration, and powder particle surface properties, are important in this context. This study explored the possibility of monitoring the drying process using vibrational spectroscopy techniques such as near-infrared (NIR), attenuated total reflection (ATR) and Raman imaging. The results showed that these techniques provide complementary qualitative measurements regarding the composition of acidified milk powders that are useful for understanding and controlling their production. Raman imaging revealed lactic acid surface composition providing better understanding of wall deposition during spray drying. NIR and ATR provided information about the composition and molecular structural changes in powders occurring during the prolonged exposure of powder to the high drying temperature, which may be applicable for on-line and at-line process control, respectively.

Determination of Nutritional and Antioxidant Properties of Maya Nut Flour (Brosimum alicastrum) for Development of Functional Foods.

Maya nut (Brosimum alicastrum) is a novel food with high nutritional value. This research aimed to evaluate the nutritional and antioxidant properties of Maya nut flour (MNF) made from seeds dried by different methods (sun-dried and using hot air at 45 °C and 60 °C) to explore its incorporation into cookies and evaluate its nutritional and functional properties. The naturally sun-dried flour (NF) had the highest content of ash (3.64 ± 0.11 g/100 g), protein (6.35 ± 0.44 g/100 g), crude fiber (6.75 ± 0.29 g/100 g), and functional properties (water and oil absorption). The color of the flour was affected by the different drying methods. While the drying methods influenced the total polyphenolic content (TPC) and antioxidant activity (AA) of MNF, they did not affect the morphology of the native starch or generated important molecular-structural changes. The substitution of 60% of wheat flour with NF in the cookie's formula increased the protein and fiber content, whereas 20% substitution increased its AA. MNF is a source of protein, dietary fiber, micronutrients, and functional compounds that can enrich cookie formulations.

Mechanism of the Impact-Sensitivity Reduction of Energetic CL-20/TNT Cocrystals: A Nonequilibrium Molecular Dynamics Study

High-energy low-sensitivity explosives are research objectives in the field of energetic materials, and the formation of cocrystals is an important method to improve the safety of explosives. However, the sensitivity reduction mechanism of cocrystal explosives is still unclear. In this study, CL-20/TNT, CL-20 and TNT crystals were taken as research objects. On the basis of the ReaxFF-lg reactive force field, the propagation process of the wave front in the crystals at different impact velocities was simulated. The molecular dynamics data were used to analyze the molecular structure changes and initial chemical reactions, and to explore the sensitivity reduction mechanism of the CL-20/TNT cocrystal. The results showed that the chemical reaction of the CL-20/TNT cocrystal, compared with the CL-20 single crystal, is different under different impact velocities. At an impact velocity of 2 km/s, polymerization and separation of the component molecules weakened the decomposition of CL-20. At an impact velocity of 3 km/s, the decay rates of CL-20 and TNT in the cocrystal decreased, and the intermediate products were enhanced, such as nitrogen oxides. At an impact velocity of 4 km/s, the cocrystal had little effect on the decay rates of the molecules and formation of CO2, but it enhanced formation of N2 and H2O. This may explain the reason for the impact-sensitivity reduction of the CL-20/TNT cocrystal.

Cation-responsive food polysaccharides and their usage in food and pharmaceutical products for improved quality of life

Demand for reduction of complication risks encountered in feeding of thin enteral nutrition including gastroesophageal reflux, dumping, and leakage from gastrostomy has increased in recent aged society, where people with eating difficulty has been increasing. In addition, control of satiety and caloric intake is demanded for long and healthy life. To realize these social demands, texture modification of liquid foods, particularly through semi-solidification (i.e. gelation and thickening) in the stomach, can be expected as a solution not to alter human natural feeding. In the stomach, foods encounter dramatic pH decrease, which can be used as a trigger for semi-solidification of liquid foods, and usage of polysaccharides whose molecular structure changes upon pH and accompanying cation concentration should be a practical option. With this background, this review refers to the basic technologies for the usage of alginate and pectin as cation-responsive polysaccharides in food and pharmaceutical products, followed by comprehensive overview of product development and clinical effects using them. In addition, solution to improve storage stability of the products will be mentioned when these polysaccharides are used. Information provided by this review is expected to facilitate the product development of high-value added and to contribute to improved quality of life for people.

Photoexcitation-Induced Assembly: A Bottom-Up Physical Strategy for Driving Molecular Motion and Phase Evolution

ConspectusIn the field of molecular assembly, photodriven self-assembly is a smart and crucial strategy to regulate the molecular orderliness, multiscale structure, and optoelectronic properties. Traditionally, photodriven self-assembly is based on photochemical processes, through molecular structural change induced by photoreactions. Despite great progress in the photochemical self-assembly, there still exists disadvantages (e.g., the photoconversion rate never reaches 100% with the possible side reactions). Therefore, the photoinduced nanostructure and morphology are often difficult to predict due to insufficient phase transition or defects. In contrast, the physical processes based on photoexcitation are straightforward and can fully utilize photons to avoid the drawbacks of photochemistry. The photoexcitation strategy excludes the change of molecular structure, only utilizing the molecular conformational change from the ground state to excited state. Then, the excited state conformation is employed to drive molecular movement and aggregation, further promoting the synergistic assembly or phase transition of the entire material system. The regulation and exploration of molecular assembly upon photoexcitation can open up a new paradigm to deal with the "bottom-up" behavior and develop unprecedented optoelectronic functional materials.This Account starts with a brief introduction to the problems faced by photocontrolled self-assembly and presents the photoexcitation-induced assembly (PEIA) strategy. Then, we focus on exploring PEIA strategy based on persulfurated arenes as the prototype. The molecular conformational transition of persulfurated arenes from the ground state to the excited state is conducive to the formation of intermolecular interactions, successively driving molecular motion, aggregation, and assembly. Next, we describe our progress in exploring PEIA of persulfurated arenes at the molecular level and then demonstrate that the PEIA of persulfurated arenes can synergistically drive molecular motion and phase transition in various block copolymer systems. Moreover, we provide the potential applications of PEIA in dynamic visual imaging, information encryption, and surface property regulation. Finally, an outlook on further development of PEIA is prospected.

The Physical vs. Mathematical Problem of Navier-Stokes Equations (NSE)

The Navier-Stokes equations describing the motion of viscous/real fluids in Rn (n = 2 or 3) depend on a positive coefficient (the viscosity, ν) via the Reynolds number. The key of NSE problem is the Reynolds number, mathematically considered a simple small perturbation parameter without any physical explanation, or a vague physical Newtonian ratio of inertial to viscous forces, 𝑅𝑅𝑅𝑅=𝑈𝑈𝑈𝑈𝜈𝜈, in spite of its quantic physical meaning as the initial excitation to response ratio, at the beginning of motion (IC at t = 0). The paper deals with the thixotropic property of real viscosity which softens (ν ↓) when strained (Re↑), but it doesn’t tend to zero (ν → 0) as much as the Reynolds number increases, holding a finite value, corresponding to the new thermodynamic equilibrium state. The (ν → 0 for Re → ∞) false physical condition renders the NSE problem to a unique solution less one beyond a critical Reynolds number, Recr. The understanding of the wall-bounded viscous flows, at both small-scales (slow motion, small Re) and larger scale (turbulent motion, large Re) must be in conjunction with the more-subtle torsional buckling effect of the “wall” lag concept that the wall has on the inherent fluid dynamics during the starting phase. The limitations of the diathermal wall associated with the starting accelerations at the onset of motion, of the order of acr/g ≥ 2/3, create the physical conditions (thermomolecular changes) for the loss of the mathematical uniqueness of the NSE solutions. The physical limitations in conjunction with the validity area of NSE model are considered in the sequel. Because of the nonlinearity of the PDE differential equations, the variation of geometrical and physical properties can lead to bifurcations in the solution and thus, to multiple solutions. Considerations relative to laminar-turbulent transition as the main bifurcation source for the more complex structure of a solution, engendered by molecular structure changes of a flowing fluid in more or less contact with the walls, are given and illustrated for the canonical flows on flat plates and viscous decay of a starting/contact vortex (“vortex eye”).

Monitoring Molecular Structure Changes of Cow and Camel Milk Mixtures during Coagulation: A Study Based on TPA and 2DCOS-MIR Spectroscopy

The aim of the present study is to evaluate the potential of mid-infrared spectroscopy in combination with two-dimensional correlation spectroscopy (2DCOS) and partial least squares discriminant analysis (PLS-DA) to monitor molecular structure evolution of milk mixtures of two species (cow and camel) during enzymatic coagulation. Molecular structure changes and texture characteristics were investigated on five different milk formulations by mixing camel milk (CaM) and cow milk (CM) (i.e., CaM, CaM3:CM1, CaM1:CM1, CaM1:CM3, and CM, (v/v)). Regarding MIR spectroscopy, two spectral regions were considered to monitor milk coagulation, the fatty acid acyl-chain region (3000–2800 cm−1) and the protein region (1700–1500 cm−1). Different formulation dissimilarities were revealed through the synchronous 2DCOS spectra and their respective auto-peaks. Moreover, using the cross-peak symbols of the synchronous and asynchronous spectra helps to establish the sequence of molecular structure modifications during coagulation. Finally, the analysis of the 2DCOS-MIR synchronous and asynchronous maps by PLS-DA gave good discriminant accuracy (88 to 100%) between each formulation. Those results highlighted that different synchronous and asynchronous chemical phenomena occurred during milk coagulation depending on the milk formulation. Texture attributes were influenced by camel milk ratio in mixtures based on the initial composition of milks. Samples containing more than 50% of CM showed significantly higher hardness compared to pure CaM and CaM3:CM; however, CM gel displayed lower springiness contrary to CaM. Textural characteristics of the resulted gels also confirmed that 2DCOS MIR observations are consistent with textural observations of the gels obtained after milk mixtures coagulation.

Theoretical study on the aggregation‐induced emission mechanism of anthryl‐tetraphenylethene

AbstractSince the concept of aggregation‐induced emission (AIE) was proposed by Benzhong Tang's research group in 2001, the exploration of the mechanism of AIE and the development of new high‐performance AIE materials have been the focus and goal of this field. On the basis of a large number of experiment results, AIE mechanism has been well explained by lots of works, such as restricted intramolecular motion (RIM), J‐aggregate et al. As tetraphenylethlene (TPE) molecules are stacked, the rotation of the benzene ring rotor is blocked, and the energy attenuation is released in the form of radiation, showing the AIE effect. In order to further explore the AIE effect of TPE, we performed electronic structure, spectrum simulation, and AIE mechanism calculations of the anthryl‐tetraphenylethene (TPE‐an) monomer and dimer in the gas phase, tetrahydrofuran (THF), and aqueous solutions at the B3LYP/6‐31G** level. The calculation results show that TPE‐an molecule is in a propeller‐like configuration, and its fluorescence intensity is weak; compared with the monomer, the fluorescence intensity of the dimer increases by 87% in aqueous solution; the fluorescence intensity in the gas phase, THF solution, and aqueous solution gradually enhances with the increase of the degree of aggregation, which are consistent with the experimental results. The enhancement of fluorescence intensity is caused by the change of molecular structure caused by aggregation. This detailed AIE luminescence mechanism will provide theoretical guidance for AIE material design.