Intensity Of Absorption Peak Research Articles

Synthesis, characterization, and study of linear and non-linear optical properties of some newly thieno[2,3-b]thiophene analogs

Abstract Newly 3,4-Diaminothieno[2,3-b]thiophene derivatives were synthesized by attaching with different aromatic have rich electron. The resulted compounds have been investigated by FT-IR, NMR, elemental analysis, and optical absorption spectra. Comparison between these resulted compounds revealed oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene has the highest absorption peak intensity at ~ 696nm, thin films have been prepared by thermal evaporation technique and characterized by UV-Visible-NIR spectroscopy as well as the allied absorption, dielectric and dispersion parameters have been investigated and compared with other reported results. Obtained results indicated diethyl 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarboxylate and 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarbonitrile have manifested small band energy gap energy 1.95, 1.66 eV; respectively as a result of increasing conjugation and high absorption coefficient, make these compounds ideal for use in solar cell. The high nonlinear parameters such as refractive index and third-order nonlinear susceptibility of these organic compound thin films are significantly asymptotic compared with chalcogenide and oxide materials, making them suitable for nonlinear optical devices.

Single-layer black phosphorus-enhanced narrowband perfect absorber in the terahertz range

In this paper, a narrowband absorber based on black phosphorus (BP) is proposed. By utilizing a single-layer BP, a Si structure with four etched holes, and a perfectly electrically conductive (PEC) plate, multi-band absorption can be achieved in the range of 3.8 THz to 5.0 THz. The location and absorbance of the three peaks are 4.32 THz (99.7 %), 4.53 THz (95.6 %), and 4.69 THz (56.7 %), respectively. The anisotropy of the BP structure leads to different absorption spectra when illuminated by TE and TM polarized light sources. Altering the electron doping in BP allows control over the position and intensity of absorption peaks. Upon examining the electric field distribution of the absorber, it is evident that the dominant physical mechanism is the localized surface plasmon resonance (LSPR). Overall, the monolayer BP absorber designed in this study can be utilized to construct a polarimetric sensor for infrared wavelengths. Additionally, it provides a valuable reference for 2D anisotropic plasma devices.

Effects of indigenous microorganisms on the CO2 adsorption capacity of coal

The adsorption capacity of coal is a crucial criterion for CO2 sequestration in deep unminable coal seams. Previous studies have documented how indigenous microorganisms interact with supercritical carbon dioxide (ScCO2) in coal. But how these interactions affect the adsorption capacity were rarely investigated. In this study, we treated bituminous coal samples with ScCO2-H2O and ScCO2-H2O-microorganism interactions in high-pressure reactors for 120 days at 35 °C and 10 MPa, respectively. After the treatments, we characterized both coal pore types and structures. The comparisons between two different post-treatments indicate that no significant change in coal pore types but notable alterations in pore structures are observed. Specifically, the treated coal with microorganisms exhibits a significant increase in micropore specific surface area (SSA) and surface roughness than the one without them. However, changes in meso/macropore structures and overall pore complexity of the coal sample treated with microorganisms were less pronounced than in coal sample treated with ScCO2-H2O alone. FTIR spectra analysis indicated that the absorption peak intensity of oxygen-containing groups and aliphatic functional groups in the sample treated with microorganisms decreased much more significantly than the sample treated without microorganisms. The CO2 adsorption capacity slightly increased in all treated samples at equilibrium pressures below 2.5 MPa. Above this pressure, the coal sample treated with microorganisms maintained a higher CO2 adsorption capacity, while the sample treated without microorganisms exhibited lower CO2 adsorption capacity compared to untreated coal sample. The increased SSA and the reduced oxygen-containing functional groups of coal after the treatment exerted antagonistic effects on CO2 adsorption. These findings suggest that indigenous microorganisms in coal seams affect CO2 adsorption through antagonistic effects, necessitating site-specific microbial assessments.

Electronic and Optical Properties of 2D Heterostructure Bilayers of Graphene, Borophene and 2D Boron Carbides from First Principles.

In the present work the atomic, electronic and optical properties of two-dimensional graphene, borophene, and boron carbide heterojunction bilayer systems (Graphene-BC3, Graphene-Borophene and Graphene-B4C3) as well as their constituent monolayers are investigated on the basis of first-principles calculations using the HSE06 hybrid functional. Our calculations show that while borophene is metallic, both monolayer BC3 and B4C3 are indirect semiconductors, with band-gaps of 1.822 eV and 2.381 eV as obtained using HSE06. The Graphene-BC3 and Graphene-B4C3 bilayer heterojunction systems maintain the Dirac point-like character of graphene at the K-point with the opening of a very small gap (20-50 meV) and are essentially semi-metals, while Graphene-Borophene is metallic. All bilayer heterostructure systems possess absorbance in the visible region where the resonance frequency and resonance absorption peak intensity vary between structures. Remarkably, all heterojunctions support plasmons within the range 16.5-18.5 eV, while Graphene-B4C3 and Graphene-Borophene exhibit a π-type plasmon within the region 4-6 eV, with the latter possessing an additional plasmon at the lower energy of 1.5-3 eV. The dielectric tensor for Graphene-B4C3 exhibits complex off-diagonal elements due to the lower P3 space group symmetry indicating it has anisotropic dielectric properties and could exhibit optically active (chiral) effects. Our study shows that the two-dimensional heterostructures have desirable optical properties broadening the potential applications of the constituent monolayers.

Efficient photocatalytic degradation of microplastics by constructing a novel Z-scheme Fe-doped BiO2−x/BiOI heterojunction with full-spectrum response: Mechanistic insights and theory calculations

Recently, microplastics (MPs) have garnered significant attention as a challenging emerging pollutant to address. Here, a full-spectrum light-driven Fe-doping BiO2−x/BiOI (FBI) Z-scheme heterojunction was constructed for efficiently degrading MPs in waters. Compared with BiO2−x, Fe doping BiO2−x, and BiOI, the optimal photocatalyst (40-FBI) can cause deep cracks in the polyethylene terephthalate (PET) within 10 h under the irradiation of full-spectrum light. Meanwhile, FT-IR characterization revealed that the absorption peak intensities of the C-O group, CO group, -CH stretching vibration, and -OH group on the MPs surface gradually increased with degradation time. A series of experiments and theory calculations revealed that the introduction of Fe creates impurity levels, accelerating the separation of photo-generated carriers and reducing the work function of BiO2−x, thereby enhancing the transport of photo-generated carriers between Z-scheme heterojunctions. This study offers a valuable idea for designing an efficient photocatalyst by simultaneously introducing ion doping and constructing heterojunctions for enhancing MPs degradation.

Particle Properties and Flotation Characteristics of Difficult-to-Float Lean Coal

The flotation effect of lean coal is crucial for its clean utilization. Therefore, the flotation characteristics of difficult-to-float lean coal were studied. The analysis results of the feed properties showed that the ash content of the feed was high and the particle size was very fine. The minerals in the gangue mainly included sericite, kaolinite, quartz, white mica, and other substances. After flotation, the functional groups of the coal particles in the tailings decreased, and the absorption peak intensity weakened. Furthermore, the results of multi-factor flotation experiments showed that the dosages of the collector and the frother were significant factors affecting the yield of clean coal. The clean coal yield gradually increased with an increase in the two factors. The ash content of the clean coal increased with an increase in the frother dosage. Within the range of feed concentrations used in this work, the feed concentration was not a significant factor affecting the clean coal’s yield and ash content. Prediction models for the clean coal yield and ash content were proposed. Under optimized experimental conditions, the clean coal yield and the flotation perfection index were 72.15% and 46.63%, respectively, indicating a good flotation effect.

Comparative study on physicochemical properties and hypoglycemic activities of intracellular and extracellular polysaccharides from submerged fermentation of Morchella esculenta

The structural characteristic, physicochemical properties and structure-hypoglycemic activity relationship of intracellular (IPS) and extracellular (EPS) from submerged fermentation of Morchella esculenta were systematically compared and assessed. Both IPS and EPS were neutral, with a triple-helical conformation, and composed of galactose, glucose and mannose monosaccharides in different molar ratios. The molecular weight and particle size of IPS were higher than those of EPS. FTIR and SEM showed that the main functional group absorption peak intensity, glycosidic bond type and surface morphology of the two polysaccharides differed. Analysis of rheological and thermal properties revealed that the viscosity of IPS was higher than that of EPS, while thermal stability of EPS was greater than that of IPS. Hypoglycemic activity analysis in vitro showed that both IPS and EPS were non-competitive inhibitors of α-amylase and α-glucosidase. EPS showed strong digestive enzyme inhibitory activity due to its higher sulphate content and molar ratio of galactose, lower Mw and particle size. Meanwhile, with its higher Mw and apparent viscosity, IPS showed stronger glucose adsorption capacity and glucose diffusion retardation. These results indicate that IPS and EPS differed considerably in structure and physicochemical properties, which ultimately led to differences in hypoglycemic activity. These results not only suggested that IPS and EPS has the potential to be functional foods or hypoglycemic drugs, but also provided a new target for the prevention and treatment of diabetes with natural polysaccharides.

Polyvinyl alcohol-modified β-cyclodextrin incorporated forward osmosis membranes with good chlorine resistance

The applications of β-cyclodextrin (β-CD) in chlorine-resistant membranes have always faced the challenge of agglomeration at high concentrations. In this study, polyvinyl alcohol (PVA) modified β-CD was used as a monomer to prepare forward osmosis (FO) membranes with high chlorine resistance. Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), automated contact angle meter (CAM), electrodynamic analyzer (EA), X-ray photoelectron spectroscopy (XPS), and true color confocal microscopy (CSM) have been used to characterize the physicochemical properties of the FO membrane. The agglomerated β-CD affected the formation of the selective layer, resulting in reduced water fluxes ranging from 12.4 L m−2 h−1 to 1.75 L m−2 h−1. The modified TFC-PVA-β-CD FO membrane had a complete, defect-free selective layer, and water flux of 16.75 L m−2 h−1 at 1 M NaCl as a draw solution. FTIR spectra showed that the absorption peak intensity of the carbonyl (CO) group generated from β-CD and 1,3,5-Benzene tricarbonyl trichloride (TMC) increased after PVA modification. After 6 hours of chlorination, the reverse salt flux of the thin film composite (TFC) FO membranes abided by the following order: TFC (80.35 g m−2 h−1) > TFC-β-CD (60.95 g m−2 h−1) > TFC-PVA-β-CD (12.45 g m−2 h−1). The results indicated that the PVA effectively promotes uniform dispersion of β-CD. More chlorine-resistant ester bonds (-COO-) were formed in the TFC-PVA-β-CD FO membrane, so it possessed good chlorine resistance. This study provides a green, simple, and environmentally economical method for the preparation of chlorine-resistant FO membranes.

Tannic acid/non-covalent interaction-mediated modification of hemp seed proteins: Focused on binding mechanisms, oil-water interface behavior, and rheological properties

In this study, hemp seed protein (HSP) was treated to prepare a hemp seed protein-tannic acid non-covalent complex (Nov-HSP). To obtain an emulsifier with excellent properties at the oil-water interface and to propose a potential mechanism of action. The results showed that the α-helix and β-sheet content of Nov-HSP decreased and the intensity of the UV absorption peak increased, respectively, compared with that of HSP. The positions of the maximum fluorescence emission peaks of the synchronized fluorescence spectra were red-shifted to 301.8 nm and 340.6 nm, respectively. Fluorescence quench analysis revealed that static quench occurred between tannins and HSP, with ΔH of −16.138 kJ/mol and ΔS of −0.1073 kJ/mol. The physicochemical and functional properties of HSP and Nov-HSP were analyzed, and it was found that the volume mean diameter of Nov-HSP was 449.28 nm, the absolute value of zeta potential was 20.52 mV, and the solubility was 33.42% at a tannic acid concentration of 1.0 mg/mL. Focusing on the oil-water interfacial properties of Nov-HSP as an emulsifier, it was found that having non-covalent binding effectively increased the diffusion rate of HSP at the interface, thus enhancing the rheological properties of the emulsion. And the emulsification activity index and emulsion stability index were improved to 71.67 m2/g and 32.01 min. These findings provide new perspectives for the phenolic compound-mediated structural remodeling of HSP, expanding its application in emulsion food production.

Using terahertz spectroscopy to quantify bioactive flavonoids in Moxa Wool as predictor of rheumatoid arthritis treatment outcomes

BackgroundMoxibustion, a traditional Chinese medicine practice, employs Moxa Wool, derived from Artemisia argyi. Flavonoids, the key pharmacological constituents in Moxa Wool, are known for their anti-inflammatory and analgesic properties. The purity of Moxa Wool, particularly its flavonoid content, directly influences the efficacy of moxibustion treatments. However, quantifying these bioactive flavonoids accurately and non-destructively has been a challenge. PurposeThis study introduces terahertz spectroscopy as a non-destructive optical detection method for qualitative detection and quantitative analysis of flavonoids in Moxa Wool. By establishing a mathematical model between spectral signals and clinical efficacy, a reliable correlation between flavonoid concentration and the therapeutic effect of moxibustion can be established, providing a potential predictive model for the treatment outcomes of rheumatoid arthritis. Study DesignWe adopted terahertz spectroscopy technology and combined it with terahertz metamaterial biosensors to achieve rapid, efficient, and non-destructive testing of the quality of Moxa Wool. This method reduces the detection time from hours to minutes while lowering the sample detection limit, overcoming the limitations of traditional detection methods in pharmacological research. MethodsThrough terahertz metamaterial biosensors, rapid detection of the purity of Moxa Wool has been achieved. A combination of molecular simulation and terahertz spectroscopy was used to quantitatively analyze the flavonoid content in different purities of Moxa Wool. To ensure accuracy, the quantitative results of flavonoids obtained by terahertz spectroscopy were validated using high-performance liquid chromatography (HPLC). In addition, moxibustion treatment was performed on rats with rheumatoid arthritis using Moxa Wool, and medical indicator information was recorded. A mathematical analysis model was established to evaluate the correlation between flavonoid content and analgesic and anti-inflammatory effects. ResultsTerahertz spectroscopy analysis shows that there is a direct correlation between the flavonoid content in moxibustion and the absorption peak intensity. The maximum R2 in the model analysis is 0.98, indicating a high accuracy in predicting the purity of Moxa Wool. These results were also validated by HPLC. In a rat model, the purity of 30:1 Moxa Wool samples showed a 50 % decrease in TNF-α, IL-1β, and IL-6 levels during treatment compared to low-purity samples, significantly reducing inflammation markers and pain symptoms. Meanwhile, The PLS prediction model established a correlation between terahertz-detected flavonoid levels and treatment outcomes (PWL and IL-1β). The maximum R2 in the model is 0.91, indicating a high correlation between flavonoid levels and the anti-inflammatory and analgesic effects of moxibustion treatment. ConclusionThis study not only demonstrates the effectiveness of terahertz spectroscopy in the pharmacological quantification of bioactive compounds but also establishes a novel predictive model for the efficacy of moxibustion in rheumatoid arthritis treatment. It underscores the potential of integrating traditional medicine insights with advanced technology to enhance therapeutic strategies in pharmacology.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications.

This study focuses on the geometrical, electronic, and optical properties of the γ-graphyne-like novel γ-SiC nanoflake of the γ-silicon carbide (SiC) monolayer using density functional theory calculations. γ-SiC was revealed to be a stable semiconducting nanoflake confirmed by a negative cohesive energy, real vibrational frequencies, and a 1.749 eV energy gap. The adsorption of COCl2, HCN, PH3, AsH3, CNCl, and C2N2 toxic gases on the γ-SiC nanoflake is also studied, which revealed an attractive gas-nanoflake interaction with the adsorption energy ranging from -0.21 to -0.38 eV. The adsorption results in a significant charge transfer between gas-adsorbent complexes. A significant variation in the energy gap and electrical conductivity was observed due to gas adsorption. γ-SiC showed maximum sensitivity at room temperature for CNCl gas. The entire process of adsorption is exothermic and thermodynamically stable. γ-SiC showed a high absorption coefficient over 104 orders with a significant variation in the absorption peak intensity and blue peak shifting. According to the quantum theory and reduced density gradient analysis, all of the gases are physisorbed on the γ-SiC nanoflake due to van der Waals interactions. The obtained results signify the usability of γ-SiC as a potential toxic gas sensor.

A novel multi-model estimation of phosphorus in coal and its ash using FTIR spectroscopy

The level of phosphorus must be carefully monitored for proper and effective utilization of coal and coal ash. The phosphorus content needs to be assessed to optimize combustion efficiency and maintenance costs of power plants, ensure quality, and minimize the environmental impact of coal and coal ash. The detection of low levels of phosphorus in coal and coal ash is a significant challenge due to its complex chemical composition and low concentration levels. Effective monitoring requires accurate and sensitive equipment for the detection of phosphorus in coal and coal ash. X-ray fluorescence (XRF) is a commonly used analytical technique for the determination of phosphorus content in coal and coal ash samples but proves challenging due to their comparatively weak fluorescence intensity. Fourier Transform Infrared spectroscopy (FTIR) emerges as a promising alternative that is simple, rapid, and cost-effective. However, research in this area has been limited. Until now, only a limited number of research studies have outlined the estimation of major elements in coal, predominantly relying on FTIR spectroscopy. In this article, we explore the potential of FTIR spectroscopy combined with machine learning models (piecewise linear regression—PLR, partial least square regression—PLSR, random forest—RF, and support vector regression—SVR) for quantifying the phosphorus content in coal and coal ash. For model development, the methodology employs the mid-infrared absorption peak intensity levels of phosphorus-specific functional groups and anionic groups of phosphate minerals at various working concentration ranges of coal and coal ash. This paper proposes a multi-model estimation (using PLR, PLSR, and RF) approach based on FTIR spectral data to detect and rapidly estimate low levels of phosphorus in coal and its ash (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} of 0.836, RMSE of 0.735 ppm, RMSE (%) of 34.801, MBE of − 0.077 ppm, MBE (%) of 5.499, and MAE of 0.528 ppm in coal samples and R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^2$$\\end{document} of 0.803, RMSE of 0.676 ppm, RMSE (%) of 38.050, MBE of − 0.118 ppm, MBE (%) of 4.501, and MAE of 0.474 ppm in coal ash samples). Our findings suggest that FTIR combined with the multi-model approach combining PLR, PLSR, and RF regression models is a reliable tool for rapid and near-real-time measurement of phosphorus in coal and coal ash and can be suitably modified to model phosphorus content in other natural samples such as soil, shale, etc.

Nanofibrillated cellulose derived from rice bran, wheat bran, okara as novel dietary fibers: Structural, physicochemical, and functional properties

The structural, physicochemical, and functional properties of nanofibrillated cellulose (NFC) derived from rice bran (RB), wheat bran (WB), and okara were investigated and explored its potential as novel dietary fibers (DF). Cellulose microfibers (CMF) with cellulose purity of 87.4 % (RB), 92.1 % (WB), and 95.1 % (okara) were prepared by alkali and bleaching treatment, respectively. Subsequently, cellulose microfibers were prepared into NFCs with nanoscale diameters by dynamic high-pressure microjet treatment. Fourier transform infrared (FTIR) spectroscopy demonstrated a significant decrease in the intensity of characteristic absorption peaks of lignin and hemicellulose after chemical treatment. X-ray diffraction results indicated the order of relative crystallinity is: NFC (56.9 %) > CMF (50.8 %) > DF (26.1 %). Moreover, NFC exhibits higher water/oil holding capacity, swelling capability, nitrite/cholesterol/sodium cholate adsorption capacity than CMF and DF. Besides, NFC exhibited superior ability to inhibit starch and lipid digestion compared to DF. Consequently, NFC holds great promise as a novel dietary additive in the food industry. [Display omitted]

Design of ultra-thin multi-band sub-terahertz metamaterial absorber using three concentric ring resonators with same opening direction

In this paper, an ultra-thin sub-terahertz multi-band terahertz metamaterial absorber is proposed, its cell consists of three concentric ring resonators with the same opening direction, which can realize three discrete absorption peaks in the sub-terahertz frequency domain. The absorption peaks are mainly formed when the three open circular resonators interact with each other, and the superposition of the three discrete peaks creates a three-band absorption. The physical mechanisms of three-band absorption are illustrated by the electric fields and surface current distributions of three absorption peaks. Adjustment of the absorption effect could be obtained by altering the dimensions of the cleft circular resonator. By fixing the dimensions and changing the opening direction, these resonators will couple to each other and play an important role in regulating the frequency, intensity, and number of absorption peaks. Moreover, the multi-band metamaterial structure could be combined with vanadium dioxide, a phase change material, to actively modulate the absorption. In addition, the three-band metamaterial absorber has the characteristics of polarization-sensitive and wide-angle, which has extensive applications in the domains of security detection, biomedicine and communication.

Enhanced UV protection in silk fibroin based electrospun fabrics realized via orientation induced high efficiency of azobenzene isomerization

Due to the poor UV protection capability, natural silk fabrics not only suffer from easy damage by sunshine but also induce possible sunburn in the human body. Efficient azobenzene isomerization and enhanced UV shielding are realized by replacing the natural silk with natural protein silk fibroin (SF) and electrospinning together with light-responsive copolymer P(MEO2-co-OEG300-co-AHMA). Compared to a solution cast film, the absorption peak intensity at 355 nm is 60 % higher in UV–Vis spectra of the electropsun SF/P(MEO2-co-OEG300-co-AHMA) fabrics. This improvement is related to the highly oriented chains, inducing more space and higher efficiency for azobenzene isomerization. Only exposure to visible light for 20 min, the absorption peak corresponding to the trans- state at 355 nm recovers to 92.5 % in the electrospun fabrics, which is at least 100 % faster than that in the solution cast film (50 min). It is related to the zip effect of the isomerization in the oriented chain structure. Thus, not only the absorption of UV radiation, but also the isomerization rate is enhanced. Based on these unique absorption and recovery capabilities, the SF based electrospun fabrics can be used to replace the natural silk fabrics for UV shielding in summer, especially for cyclic use.

Multiparameter gas sensor based on UV-SFR combined with wavelet transform-neural network at ppb level

Abnormal concentrations of nitric oxide (NO), ammonia (NH3), carbon disulfide (CS2) and sulphur dioxide (SO2) in exhaled breath are closely associated with diseases in specific organs of the body. Meanwhile, the above gases are also common pollutants in the atmosphere, and effective online detection of them plays a key role in disease prevention and environmental pollution prevention. This study reports a multiparameter gas sensor system based on the combination of ultraviolet segmented fitting reduction (UV-SFR) and wavelet transform-neural network (WT-NN) model for simultaneous online detection of the concentrations of NO, NH3, CS2 and SO2. Firstly, to avoid the occurrence of spectral baseline drift and absorption peak intensity reduction, a UV-SFR method is proposed for the discrete single peak type absorption spectra contained in the UV spectra. Our method can remove the slow change absorption induced by other factors, and ultimately obtain the differential absorption spectra of the gas mixtures. Then, the WT is used to denoise the differential absorption spectra of the gas mixtures. Next, for the presence of severe spectral line overlap in gas mixtures, the NN model is built based on the denoised spectral data. Finally, transfer learning is introduced into NN to improve the detection accuracy. The experimental results show that the sensor system can reliably achieve simultaneous online detection of NO, NH3, CS2, and SO2 at ppb level, and the average absolute errors of their measurements are 0.96 ppb, 1.27 ppb, 0.76 ppb and 0.97 ppb, with measurement accuracies of 3.5 %, 0.8 %, 0.5 % and 0.9 %, respectively.

Cerium Oxide Nanoparticle-Papain Enzyme Bioconjugate: Synthesis, Characterization and Optical Absorption Study for Biomedical Applications

Objective: Here, we synthesize cerium oxide nanoparticles, successfully characterize them, and study the interaction between enzymes and cerium oxide nanoparticles (CeO2 NPs) using a simple optical spectroscopic technique. Method: CeO2 was fabricated by chemical method. Characterizations were done using UV-Vis absorption spectra, FESEM images, and XRD data. For the biomolecular study, papain was used as a model enzyme. Two different concentrations of CeO2, namely a small concentration range (0.05810 to 0.40670 mM) and a large concentration range (0.58100 to 0.92961 mM), were taken to study the interaction with the papain. UV-Vis absorption spectra were recorded to study bioconjugate formation. Findings: The CeO2 NPs have an intense absorption peak at 352 nm and a band gap of 3.78 eV. The XRD pattern showed the unit cell is cubic with an average particle size of 41.36 nm. The binding of papain with CeO2 NPs resulted in a red shift in its absorption peak. The apparent association constant (Kapp) was calculated for the bioconjugate and found to be 0.747 × 103 M-1 for small concentrations and 0.278 × 103 M-1 for large concentrations. In large concentrations, aggregation occurs instead of corona formation. Novelty: To the best of our knowledge, this may be the first study of the interaction of papain enzyme with CeO2 NPs. This study contributes to the application of NPs in the field of biomedicine. Keywords: Cerium oxide, Papaya proteinase (PP), Absorption spectra, Bioconjugate, Association constant

Effect of VO2/Graphene Heterojunction on Terahertz Wave Electromagnetic Absorption

In the past two decades, metamaterial design has been applied to terahertz wave detection research, which is very important because metamaterial has the advantages of high absorption, ultra-thin device thickness, design flexibility and frequency selectivity. In this paper, the VO2/Graphene heterostructures were designed on the silicon dioxide layer, and the terahertz wave absorption bandwidth was tuned by adjusting the size and conductivity of VO2 and the Fermi level of graphene. According to the simulation results, the VO2/Graphene heterostructures has a substantial absorption bandwidth of more than 7 THz and an absorption peak intensity that is continuously tuned between 2.8% and 98% by adjusting temperature change the conductivity of VO2. Meanwhile, the heterojunctions also have high absorption ability for terahertz waves incident at different polarization angles. The new idea is provided by our research results for the design of heterojunction terahertz absorption devices.

Intense charge transfer plasmons in golden nanoparticle dimers connected by conductive molecular linkers.

Golden nanoparticle dimers connected by conjugated molecular linkers 1,2-bis(2-pyridyl)ethylene are produced. The formation of stable dimers with 22nm diameter nanoparticles is confirmed by transmission electron microphotography. The possibility of charge transfer through the linkers between the particles in the dimers is shown by the density functional theory calculations. In addition to localized plasmon resonance of solitary nanoparticles with a wavelength of 530nm, the optical spectra exhibit a new intense absorption peak in the near-infrared range with a wavelength of ∼780nm. The emergent absorption peak is attributed to the charge-transfer plasmon (CTP) mode; the spectra simulated within the CTP developed model agree with the experimental ones. This resonant absorption may be of interest to biomedical applications due to its position in the so-called transmission window of biological tissues. The invitro heating of CTP dimer solution by a laser diode with a wavelength of 792nm proved the efficiency of CTP dimers for achieving a temperature increase of ΔT = 6 °C, which is sufficient for hyperthermia treatment of malignant tumors. This indicates the possibility of using hyperthermia to treat malignant tumors using the material we synthesized.

Kinetic Study of the Diels-Alder Reaction between Maleimide and Furan-Containing Polystyrene Using Infrared Spectroscopy.

The Diels-Alder (D-A) reaction between furan and maleimide is a thermally reversible reaction that has become a vital chemical technique for designing polymer structures and functions. The kinetics of this reaction, particularly in polymer bulk states, have significant practical implications. In this study, we investigated the feasibility of utilizing infrared spectroscopy to measure the D-A reaction kinetics in bulk-state polymer. Specifically, we synthesized furan-functionalized polystyrene and added a maleimide small-molecule compound to form a D-A adduct. The intensity of the characteristic absorption peak of the D-A adduct was quantitatively measured by infrared spectroscopy, and the dependence of conversion of the D-A reaction on time was obtained at different temperatures. Subsequently, the D-A reaction apparent kinetic coefficient kapp and the Arrhenius activation energy Ea,D-A were calculated. These results were compared with those determined from 1H-NMR in the polymer solution states.