Intensity Of Absorption Peak Research Articles

Hydrolysis susceptibility and carbamate formation for a low moisture-absorbing, siloxane-modified cyanate ester resin matrix (TC410) material used for composite space applications

Siloxane-modified cyanate ester resins are ideal matrix materials for next-generation, high-precision composites used for radomes and satellite structures. They provide extremely low moisture uptake, excellent microcracking resistance, and protection from atomic radiation. However, cyanate ester resins have been shown to be susceptible to hydrolysis during cure, which may significantly impact both mechanical and thermal performance. In this investigation, we evaluate the cure kinetics and hydrolysis susceptibility of a siloxane-modified prepreg system (TC410/M55J). DSC tests verified that the Ea of polymerization for the TC410 system is 65 KJ/mol. Samples were also exposed to moisture during cure at several temperatures, and FTIR was used to follow changes in the carbonyl peak absorption intensity to compare the rate kinetics and activation energy for hydrolysis leading to carbamate formation (52 KJ/mol). DMA tests of composites exhibited significantly reduced Tg’s with increasing moisture levels during cure. TGA of these cured samples exhibited both a significant decrease in the onset of the thermal decomposition temperature as well as an increase in the relative degree of volatiles generated at low temperature. Flatwise tension strength tests showed a linear reduction in strength with decreasing Tg, at an equivalent trend to previous work on an M55J/RS3C system indicating a similar mechanism. However, the added margin provided from the higher initial FWT strength in the TC410 system allows for larger decreases in Tg before significant degradation occurs. Laminates manufactured on composite mandrels resulted in parts with larger decreases in the tool-side Tg of the part when compared to the bag-side Tg, with the differential depending on the initial moisture content of the tool. AFM was shown to selectively identify these carbamate-affected regions by showing that the recession behavior of these less cross-linked areas was greater than in areas where the resin was properly cured. Composites with increased carbamate formation resulted in increasing warpage of the part with elevated temperature exposure due to variations in stress relaxation. This effect should be considered when manufacturing precision, high-dimensional stability composite hardware.

The drip loss inhibitory mechanism of nanowarming in jumbo squid (Dosidicus gigas) mantles: protein structure and molecular dynamics simulation.

The magnetic nanoparticles plus microwave thawing (MNPMT), a new rewarming technology entitled 'nanowarming', can serve as an effective method to achieve rapid and uniform thawing, thus reducing drip loss. The purpose of this study was to decipher the drip loss inhibitory mechanism of MNPMT in jumbo squid (Dosidicus gigas) from the perspectives of protein structure and ice crystal recrystallization. A number of different techniques such as dynamic rheology, Raman spectra, intrinsic fluorescence measurement, and ultraviolet (UV) absorption spectra were conducted to analyze myofibrillar protein conformation and stability of jumbo squid. Scanning electron microscopy (SEM) and myofibrillar fragmentation index (MFI) were used to observe the growth of ice crystals. The interaction between magnetic nanoparticles (MNPs) and ice crystals was studied by using molecular dynamic (MD) simulation. MNPMT exhibited the highest storage modulus (G') value at 90 °C, suggesting the protein conformation was more stable. The increase in α-helices, fluorescence intensity and characteristic absorption peak of MNPMT illustrated that MNPMT can effectively maintain the secondary and tertiary structure of the protein. Compared with cold storage thawing (CST) and microwave thawing (MT), the MFI value of MNPMT was significantly decreased (P < 0.01). The result of MD simulation showed that MNPs displayed a tendency to gradually approach the surface of ice crystals, and induced a certain degree of damage to the ice crystal surface, thereby markedly inhibiting ice crystal recrystallization. MNPMT can reduce the drip loss by keeping the protein conformation stable and inhibiting the recrystallization of ice crystals during the thawing process. © 2022 Society of Chemical Industry.

Electromagnetic wave absorption properties of polymer-derived magnetic carbon-rich SiCN-based composite ceramics

In this paper, the mixture of Fe and Ni nanoparticles (abbreviated as FeNi) was added to liquid polysilazane (PSZ) as a magnetic source, to prepare a series of magnetic carbon-rich SiCN-based composite ceramics by adjusting the mass ratio of FeNi through the polymer derivation method. The phase composition, microstructure, conductivity, electromagnetic wave (EMW) absorption performance and mechanism of composite ceramics prepared were discussed. The analysis shows that the introduction of magnetism has adjusted the impedance matching and improved the magnetic loss performance of composite ceramics on the whole, and the dielectric loss ability of composite ceramics has been strengthened benefiting from the formation of conductive path of CNTs precipitated by FeNi catalysis in the matrix. Therefore, the addition of magnetic particles improves the EMW absorption peak intensity and effective absorption bandwidth (EAB) of composite ceramics. When the addition amount of FeNi was 5 wt%, the sample 5# exhibited the best comprehensive EMW absorption performance: Its minimum reflection loss (RLmin) was −18 dB and the EAB was 2.5 GHz when the thickness was 1 mm, the EAB covering the C, X and Ku bands can be obtained by adjusting the thickness from 1.0 mm to 4.0 mm. Through calculation, the EAB (EABtf) of 5# with a thickness of 1 mm and a filling rate of 1 wt% can reach 50, which is significantly higher than that of a series of SiCN-based composite ceramics previously reported. In addition, the density of 5# was 2.3 g/cm3, and its compressive strength (CS) can reach 337 MPa. The data shows that the composite ceramic 5# prepared in this experiment has the merits of light weight, excellent comprehensive EMW absorption performance and good compression resistance, and is expected to be one of the promising materials in the field of new-generation EMW absorbers.

Retarding performance of the vadose zone for nitrogen pollutants derived from municipal solid waste landfills in the red bed zone

Nitrogen pollutants such as ammonia and nitrates cause soil and groundwater contamination at municipal solid waste landfill (MSWL) sites due to leachate leakage. Here, the migration of nitrogen pollutants in the vadose zone of the red bed (VZRB) at a MSWL site was studied by static adsorption batch experiments and one-dimensional simulated migration experiments. The results indicated that the soil in the red bed did not adsorb nitrates. Chemical adsorption and monolayer adsorption of the soil played dominant roles during ammonia adsorption in the VZRB, which was best fitted by the pseudo-second-order kinetic equation (RNH4+2 = 0.99) and the Langmuir model. The ammonia adsorption capacity of the soil was the highest (Qm = 2.041 mg·g−1) at 318 K. It was due to the endothermic and non-spontaneous chemical adsorption of ammonia, whose enthalpy change (ΔH) reached 20.995 kJ·mol−1 and Gibbs free energy ranged from 8.469 to 8.706 kJ·mol−1. Chloride penetration tests indicated that the diffusion coefficient and migration speed reached 0.0515 cm2·h−1 and 0.0833 cm·h−1, respectively, in the clay layer under the MSWL sites. The average hysteresis diffusion coefficients of ammonia in the simulated soil columns leached by ammonium chloride solution (SSCAC) and by the leachate from MSWL (SSCL) were 1.129 and 1.400, respectively. After the leaching experiments, the clay pore structure was saturated, and the specific surface area decreased. The absorption peak intensities of clay functional groups, including carboxyl, alkyne, and hydroxyl groups, were reduced. The ammonia content in the soil of SSCAC decreased from the top (14.51 mg·kg−1) to the bottom (3.14 mg·kg−1) and in the SSCL from 24.96 mg·kg−1 to 5.05 mg·kg−1, respectively. Thus, the impermeable clay layer and VZRB helped in retardation of ammonia leakage from MSWL sites. This was due to the blockage of seepage, ammonia mechanical filtration, ammonia monolayer chemical adsorption, and the reaction between the functional groups and ammonia in the VZRB underneath the MSWL sites.

Effect of annealing on the structural and optical properties of pristine and cerium doped calcium tungstate nanoparticles synthesized via hydrothermal method

The work is an investigation of the effect of annealing temperature on pristine and rare earth doped CaWO4 nanoparticles with hydrothermal route. The sample was annealed at two varied temperatures 800 ºC and 1200 ºC for 5 h. The structural analysis reveals the reduction in the broadening of the peaks as a result of annealing. Surface morphology shows the formation of agglomerated structures. In Ce3+:CaWO4 nanoparticles the morphology is modified to dumbbell like and flake like structures after annealing. Raman shift observed at 909 cm−1 Ag modes confirms the presence of CaWO4 nanoparticles with its own rotational and vibrationalmodes. Increase in the absorption peak intensity and a double absorption edge appears as an intermediate energy level state after the inclusion of Ce3+ ion as dopant.

Mechanism of radar wave absorption and bandwidth for easy-plane Y&lt;sub&gt;2&lt;/sub&gt;Co&lt;sub&gt;17 &lt;/sub&gt;rare earth soft magnetic composites

Wave absorbing materials are widely used to prevent military equipment from being detected by radar wave and also serve as civil electromagnetic shielding. The absorbing properties of wave absorbing materials are determined by a combination of the electromagnetic parameters and the thickness of the composite material. In the actual case, the theoretically designed reflection loss peak intensity and the bandwidth of wave absorbing materials deviate from the engineered values. There are few reports on the mechanism about the variation of the intensity of the reflection loss absorption peak with thickness and the bandwidth of the reflection loss absorption peak. In this work, based on an interfacial reflection model, the reflective properties of radar wave at the air interface of the absorbing coating are investigated. The dependence of the matching impedance on the matching thickness of the absorbing material is determined, and the matching impedance parameters are further used to design the absorbing composites, which exhibit excellent microwave absorption properties, i.e. an average value of reflection loss is below –10 dB at 4–18 GHz in different thickness wave absorbing materials, and an average value of reflection loss is below –20 dB at 6–18 GHz in different thickness wave absorbing materials. The bandwidth of the reflection loss peak at the matched thickness is discussed in depth in principle based on the interface reflection model, and the theoretical calculations accord with the experimental results.

EFFECT OF METAL CONCENTRATION ON PHYSICOCHEMICAL PROPERTIES OF COBALT/REDUCED GRAPHENE OXIDE THROUGH ONE-POT GREENER CHEMICAL-THERMAL REDUCTION USING ULTRASONIC ACTIVATION

A combination of ultrasonically supported one-step chemical thermal reductions for synthesizing cobalt/reduced graphene oxide (Co/RGO) has been successfully carried out. This study aims to investigate the variation of Co concentration to GO (1, 5, and 10% w/w) on its physicochemical properties. GO precursor was prepared by the Tour method with an oxidizing agent:graphite weight ratio of 3.5. According to the findings of the investigation, in XRD spectra, the reduction treatment succeeded in shifting the diffraction peaks from 10° of GO to ~24° of Co/RGO. In FTIR spectra, the intensity of absorption peaks of O-H and C=O vibrations decreased after reduction. In SAA isotherm, Co-5/RGO material has the largest specific surface area of 109.753 m2 /g with a pore volume of 0.158 cc/g and a pore diameter of 3.469 nm. Thus, this ratio (5% w/w) is the most optimal Co concentration that can be loaded to GO material.

Steady/transient state spectral researches on the solvent-triggered and photo-induced novel properties of metal-coordinated phthalocyanines.

The large conjugated system and the d orbitals of metallic phthalocyanines (MPcs) are easily triggered by solvent molecules and light to cause variations in photo-physical and photo-chemical properties. To clarify the novel properties of photo-excited MPcs in solvents, the steady/transient state spectral data were collected to investigate four MPc templates, including FePc, ZnPc, CoPc and AlClPc. The Q bands of FePc and CoPc were prone to redshift, while the peaks of ZnPc and AlClPc tended to blueshift in various solvents compared with that in DMSO. With xenon lamp irradiation, the characteristic absorption peak intensity of FePc and ZnPc in DMSO decreased gradually and then increased after being subjected to dark condition. The transient absorption spectra and kinetic data illustrated that photo-excited FePc and CoPc produced relatively short lifetime transient intermediates. The positive absorption at 650 nm in the Q bands of FePc and CoPc could be assigned to the d–π* electron transition in transient intermediates with unpaired d-orbital electron in the open shell configuration of Fe2+ and Co2+. The above studies were of great significance for the application of solvent-triggered and photo-induced novel properties of MPcs.

Antifungal, Antibacterial, and Cytotoxic Activities of Silver Nanoparticles Synthesized from Aqueous Extracts of Mace-Arils of Myristica fragrans.

In the present study, mace-mediated silver nanoparticles (mace-AgNPs) were synthesized, characterized, and evaluated against an array of pathogenic microorganisms. Mace, the arils of Myristica fragrans, are a rich source of several bioactive compounds, including polyphenols and aromatic compounds. During nano synthesis, the bioactive compounds in mace aqueous extracts serve as excellent bio reductants, stabilizers, and capping agents. The UV-VIS spectroscopy of the synthesized NPs showed an intense and broad SPR absorption peak at 456 nm. Dynamic light scattering (DLS) analysis showed the size with a Z average of 50 nm, while transmission electron microscopy (TEM) studies depicted the round shape and small size of the NPs, which ranged between 5–28 nm. The peaks related to important functional groups, such as phenols, alcohols, carbonyl groups, amides, alkanes and alkenes, were obtained on a Fourier-transform infrared spectroscopy (FTIR) spectrum. The peak at 3 keV on the energy dispersive X-ray spectrum (EDX) validated the presence of silver (Ag). Mace-silver nanoparticles exhibited potent antifungal and antibacterial activity against several pathogenic microorganisms. Additionally, the synthesized mace-AgNPs displayed an excellent cytotoxic effect against the human cervical cancer cell line. The mace-AgNPs demonstrated robust antibacterial, antifungal, and cytotoxic activity, indicating that the mace-AgNPs might be used in the agrochemical industry, pharmaceutical industry, and biomedical applications. However, future studies to understand its mode of action are needed.

Interaction of Prion Peptides with DNA Structures.

Prion protein aggregation is known to be modulated by macromolecules including nucleic acids. To clarify the role of nucleic acids in PrP pathology, we investigated the interaction between nucleic acids and the prion peptide (PrP)—a synthetic prion protein model peptide resembling a portion of the human prion protein in structure and function spanning amino acid residues 106–126. We used synthetic DNA lattices and natural DNA duplexes extracted from salmon (sDNA) bound with PrP and studied their interaction using distinct physical measurements. The formation of DNA lattices with PrP was visualized by atomic force microscopy (AFM) to investigate the influence of the PrP. PrP inhibited the growth of the double-crossover (DX) lattices significantly compared to the control peptide (CoP). We also conducted optical measurements such as ultraviolet–visible (UV–Vis), circular dichroism (CD), and Fourier transform infrared (FTIR) spectroscopies to validate the interaction between PrP and DNA immediately (D0) and after a 30-day incubation (D30) period. UV–Vis spectra showed variation in the absorbance intensities, specific for the binding of CoP and PrP to DNA. The CD analysis revealed the presence of various secondary structures, such as α-helices and β-sheets, in PrP- and PrP-bound sDNA complexes. The PrP–sDNA interaction was confirmed using FTIR by the change and shift of the absorption peak intensity and the alteration of PrP secondary structures in the presence of DNA. The cytotoxic effects of the PrP-bound sDNA complexes were assessed by a cytotoxicity assay in human neuroblastoma cells in culture. It confirmed that PrP with sDNA was less cytotoxic than CoP. This study provides new applications for DNA molecules by investigating their effect in complex with aggregated proteins. Our study unequivocally showed the beneficial effect of the interaction between DNA and the pathological prion protein. It therefore provides valuable information to exploit this effect in the development of potential therapeutics. Moreover, our work might serve as a basis for further studies investigating the role of DNA interactions with other amyloidogenic proteins.

Structured vanadium dioxide metamaterial for tunable broadband terahertz absorption

A tunable broadband terahertz (THz) absorber based on vanadium dioxide (VO2) is proposed, which is composed of a structured VO2 metamaterial layer, a dielectric layer, and a metal layer. The simulation results show that the peak absorption intensity of the absorber can be dynamically adjusted from 3.6% to 100% by changing the conductivity of VO2. When the conductivity of VO2 is 2×105 S/m, an excellent broadband absorption phenomenon appears, and the bandwidth of absorption rate greater than 90% is as wide as 4.10 THz from 3.25 THz to 7.35 THz. The impedance matching theory and the electric field distribution are used to explain the physical mechanism of the proposed absorber. In addition, the absorber shows the advantages of polarization-insensitiveness and wide-angle absorption. It is expected that this absorber can have potential applications such as modulators and photoelectric switches.

Collective Resonances of a Twisted Plasmonic Array Pair

Plasmonic SLR (surface lattice resonance) has sharp and intense extinction or absorption peaks, which facilitates a variety of optical and spectral applications, e.g., optical filters, absorbers, reflectors, sensors, etc. In this work, we propose a plasmonic array pair structure composed of two stacked finite square array panels. By twisting it, its plasmonic SLR changes, since the break of periodicity alters the inter-layer plasmonic coupling. Numerical simulation is carried out using the DDA (discrete dipole approximation) method. Simulation results show that its optical properties such as extinction spectra/absorption spectra change dramatically when the two-layer structure is twisted by only a small angle. More interestingly, two resonance peaks at different wavelengths show an inverse trend while twisting, one gets lower and broader, while the other gets higher and narrower. Dipole mapping of amplitude and phase is checked to reveal the plasmonic coupling under twist. The influence of environment/material permittivity on spectra is also examined. Results introduced in this work may work as a scientific tool to reveal more properties of plasmonic SLR and can serve as an angle sensor, tunable optical filter, chiral sensor, etc.

Characterization of emulsion films prepared from soy protein isolate at different preheating temperatures

The effect of soy protein isolate (SPI) preheating temperature on the physicochemical properties of SPI-oil emulsion (SPI-OE) films was investigated. Tensile strength (TS) and elongation at break (EAB) of the SPI-OE films prepared from SPI preheated at 45 °C were 7.90 MPa and 59.30%, respectively. The TS of the SPI-OE films increased with the preheating temperature of SPI, whereas the EAB first increased and then decreased. Discrepancy between the contact angles in the upper and lower surfaces of the films gradually increased with preheating temperature. When the preheating temperature of SPI was higher than 75 °C, oil droplets accumulated on the upper surfaces of the SPI-OE films, as shown in the scanning electron micrographs, and the intensity of absorption peak (1744 cm−1) obtained through infrared spectroscopy decreased. No obvious change in protein molecular weight was found in the SPI-OE films with increasing preheating temperature, but the glass transition temperature increased.

TiO2 nanoparticles reagent based nonenzymatic label-free optical sensor for the rapid detection of L-lactate in apple juice

L-lactate is an essential organic chemical in food processing, clinical, chemical, and fermentation industries. Titanium oxide nanoparticles (TiO2 NPs) was synthesized by the green chemical method and structural, morphological, zeta potential characterization studies were performed for achieving lower limit of detection (LOD), stability, and sensor fabrication. First time reporting TiO2 NPs functionalized with 3-aminophenylboronic acid (3-APBA^TiO2 NPs) for L-lactate detection in apple puree (lab prepared) and commercial Tropicana (Indian local brand) apple juice samples. Nanocomposite in the aqueous phase (pH 7.4) shows a selective binding towards L-lactate that results in a blue shift of UV-VIS absorption wavelength from 300 nm to 288 nm as L-lactate binds to the boron atom of boronic acid and forms a tetragonal complex stabilized by the TiO2 NPs. The apple samples spiked with L-Lactate (1-10 mM) showed an absorption peak intensity increases as per lactate concentration with the LOD= 3.11 mM using the calibration graphs. The nanosensor data was validated with a commercial Megazyme kit and conventional High-performance liquid chromatography (HPLC) technique. L-lactate content in commercial Tropicana apple juice samples was detected as 6.1 mM with 93.5 % correlation. This method could be an alternative to conventional L-lactate detection techniques and can be interfaced with a smartphone for onsite detection device development.

First principles study on modulating electronic and optical properties with h-BN intercalation in AlN/MoS2 heterostructure

The van der Waals (vdW) heterostructures formed by stacking layered two-dimensional materials can improve the performance of materials and provide more applications. In our paper, six configurations of AlN/MoS2 vdW heterostructures were constructed, the most stable structure was obtained by calculating the binding energy. On this basis, the effect of external vertical strain on AlN/MoS2 heterostructure was analyzed, the calculated results show that the optimal interlayer distance was 3.593 Å and the band structure was modulated. Then the h-BN intercalation was inserted into the AlN/MoS2 heterostructure, by fixing the distance between h-BN and AlN or MoS2, two kinds of models were obtained. Furthermore, the electronic properties of AlN/MoS2 heterostructure can be regulated by adding h-BN intercalation layer and adjusting its position. Finally, the optical properties show that the absorption coefficient of AlN/MoS2 heterostructure exhibits enhancement characteristic compared with that of the individual monolayers. Meantime, compared with AlN/MoS2, the AlN/h-BN/MoS2 shows a redshift effect and the light absorption peak intensity increased, which indicated that h-BN intercalation layer can be used to regulate the electronic and optical properties of AlN/MoS2 heterostructure.

Properties and Sensing Performance of THz Metasurface Based on Carbon Nanotube and Microfluidic Channel

Carbon-based metamaterials are expected to lead to biological and chemical sensing because of their fast electron transfer rate, good biocompatibility, and high absorption ratios. In this work, we integrate carbon nanotubes metasurface (CM) and microfluidic channel (MC) for a composite terahertz (THz) metasurface (CMMC). The absorption properties and sensing performance of the proposed composite metasurface have been studied. It is observed that the absorption is nearly 71.8% at 0.96 THz and 92.4% at 1.65 THz, respectively. The variation of response with refractive index of the analytes for the proposed CMMC is investigated and it is found that the frequency and intensity of the resonance absorption peak at 0.96 THz f1 decrease obviously with the increase of the refractive index of the analytes. Owing to the coupling of the CM and MC in the microfluidic channel, the interaction between the incident THz wave and analytes has been enhanced, and the frequency and intensity sensitivities has achieved 254 GHz/RIU and 314/RIU, respectively. In addition, the influence of the structural parameters of the proposed CMMC on the absorption characteristics is also studied in detail. The results shown that the absorption properties of the CMMC can be adjusted by changing the structural parameters, which will provide a guideline for design. The proposed CMMC will facilitate the realization of carbon nanotube metamaterials sensing applications, and, when combined with microfluidic channel, will lead to large-area THz biological and chemical sensing.

Terahertz spectroscopy detection of lithium citrate tetrahydrate and its dehydration kinetics

Lithium citrate (LC) as a common food additive and also a psychiatric drug, usually in the form of tetrahydrate can gradually lose its crystalline water and convert into LC anhydrate at temperatures higher than the room temperature. In order to quickly distinguish the tetrahydrate from the anhydrate and to study the dehydration kinetics of the LC hydrates under the influence of the temperature, terahertz time-domain spectroscopy (THz-TDS) is utilized in this work. Experimental results show that the LC tetrahydrate at room temperature has an obvious absorption peak around 1.66 THz, while the LC anhydrate has no absorption peak at 0.5–3.0 THz. The absorption peak intensity of the LC tetrahydrate decreases continuously upon heating from 25 to 100 °C. Based on the normalized absorption peak area of the LC tetrahydrate around 1.66 THz, variation of its dehydration rate with the heating temperature is investigated and their relationship is fitted by the Arrhenius equation. The reaction activation energy of the LC tetrahydrate is derived to be 495.1 ± 17.8 J/g with a deviation of about 3.7% from the traditional difference scanning calorimetry (DSC) measurement. These results indicate that THz-TDS can provide an efficient method to detect crystalline hydrates and can be applied to study the dehydration kinetics of crystalline hydrates with advantages of being fast, label-free and accurate.

A terpyridine-based chemosensor for detection transition metal ions in aqueous solution: Synthesis and characterization

A hydrophilic terpyridine-based copolymer chemosensor containing acrylic acid and fluorescence fragments to detect transition metal ions in aqueous solution were synthesized and well characterized. Characteristic color changes, which were resulted from chelating with specific metal ions and visible to the naked eye under natural and ultraviolet light provided possibility for real-time monitoring. Absorption and luminescence properties were adopted for further study, which exhibited unique response when treated with various metal ions. Intensity of absorption peak at 284 nm decreased with the increase of all kinds of metal ions while the secondary absorption peak at 335 nm increased with a certain concentration range. Different metal ions bring fluorescence enhancement or quenching response to the copolymer in aqueous solution. The unique fluorescence enhancing resulting from coordination of terpyridine and Zn2+ endows the polymer excellent detection ability. In particular, owing to metal-ligand charge transfer (MLCT) process, a new absorption peak appeared at 570 nm with the addition of Fe2+, and the polymer showed obvious color change.

Analysis of Dynamic Changes of Lipid Composition and Structure of Deep‐Fried Pork Slices during Storage

AbstractTo understand the reasons for the quality deterioration of traditional battered and deep‐fried pork slices during storage, fried pork slices stored for 12 h at 0–40 °C are used as the research samples, and Fourier‐transform infrared spectroscopy （FTIR） and gas chromatography‐mass spectrometry （GC‐MS） are used as analytical methods. The oil migration mode, fatty acid composition change, and functional group changes in the meat slices are analyzed. The experimental results show that the unsaturated fatty acid (USFA) in the starch paste enters the meat slice in a single diffusion mode during storage, and the migration direction of the fatty acid is reversed after 7 h. Oxidation mainly occurs after 4 h of storage. At this time, the absorption peak intensities of the C═C, OH, CH2, and CH3 groups began to increase significantly. After 8 h, the characteristic peak of C═O narrowed and disappeared after 12 h, indicating that the oxidation has entered a decline period. The content of USFA and linoleic acid (C18:2) showed a downward trend in phospholipids. Therefore, the stability of phospholipids, especially linoleic acid, plays an important role in the edibility of meat slices during storage.Practical Applications: Many studies have demonstrated that the edible quality of fried meat products decreases gradually during storage and the change in lipid content is the main reason for this phenomenon. However, there is a lack of targeted studies on lipid migration and compositional and structural changes during the storage of deep‐fried foods. In this study, dynamic mobility, dynamic modeling, and changes in fatty acid composition and structure of lipids before and after storage provide data support for the implementation of targeted improvement measures to reduce oil migration, oxidation, and decomposition, and thus effectively extend the consumption cycle.

Influence of laser wavelength on the optical and structural properties of MoS2 nanoparticles prepared via laser irradiation in ethylene glycol

MoS2 nanoparticles (NPs) were prepared by nanosecond (ns) laser ablation in ethylene glycol using a Q-switched neodymium:ytterbium aluminum garnet laser at 1064 and 532 nm laser wavelengths. The influence of laser wavelengths in ns laser production of MoS2 NPs is not yet fully understood. The shape, structure, crystalline phase, stability, and optical and photoluminescence (PL) properties of NPs were studied using TEM, dynamic light scattering, scanning electron microscopy with energy-dispersive x-ray, x-ray diffraction (XRD), ultraviolet–visible (UV–Vis), PL, Fourier transform infrared, and Raman spectroscopy. The UV–Vis absorption spectroscopy showed that the optimum laser wavelength for preparing MoS2 NPs is 1064 nm. Also, the absorption peak intensity of MoS2 NPs prepared at 1064 nm was 3.95 times higher than that at a 532 nm wavelength. In the case of ablation with 1064 nm, the most of NPs had spherical shapes and well dispersed compared with 532 nm. While the samples had the same crystalline structure for both wavelengths, as the laser wavelength increased, the mean particle size decreased from 22 to 13 nm. This is because of a photofragmentation phenomenon.