Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy最新文献

The coupling effect between the element structures of the traditional Huygens metasurface is easy to cause the efficiency of the designed functional devices to be reduced. In order to eliminate or reduce the coupling effect between the element structures, a border-type Huygens metasurface element structure is proposed. In order to confirm that the bounding element structure can significantly reduce the coupling effect, the near-field distribution and far-field properties of two Huygens metasurfaces with and without bounding are compared. Through comparative analysis, we find that the bounding Huygens element structure can significantly reduce the coupling effect between the element structures, and the far-field scattering angle is more consistent with the theoretical calculation value. In order to realize the free regulation of the far-field scattering angle of THz waves, we introduce the Fourier convolution principle in digital signal processing, and operate the element sequence of Huygens metasurface on the addition principle to realize the free regulation of scattered beams. In addition, we performed functional addition operations on the bounding and unbounding coding sequences. The bounding code structure can accurately achieve the synthesis of functions.

Classical electromagnetic theory applied to infrared (IR) and vibrational circular dichroism (VCD) spectra of chiral compounds can provide useful insights, such as the fact that the area of all bands of wavenumber-normalized absorbance above zero must be the same as the area below zero. Additionally, dispersion analysis based on wave optics and dispersion theory, which was extended by Born and Kuhn to include chiral substances, can be used to quantitatively describe the dielectric function and the chiral admittance functions that shape IR and VCD spectra. For dispersion analysis, pairs of coupled oscillators, with five different kinds of parameters, namely oscillator strength, damping, oscillator position, vertical distance between coupled oscillators, and the coupling constant are used to model the dielectric functions and chiral admittance functions. We report the results of such an analysis for α-Pinene and Propylene oxide. For most bands, the oscillator model using two coupled oscillators is sufficient to achieve a good correspondence between experimental and modelled data.

A unique spectrofluorimetric protocol has been conceived for octreotide (a synthetic peptide drug) quantitation in both its authentic form and its application to dosage form. The protocol has been established simply upon condensation of octreotide by ninhydrin / phenyl acetaldehyde reagent in buffered media (pH 6.2). An intense fluorescence product has been formed and quantified at 463 nm (390 nm for excitation). After optimization for various experimental conditions, a wide linear interval (0.2-4.0 µg/ml) has been used to construct the calibration curve with a determination coefficient (r²) of 0.9994, a slope ± SD of 81.147 ± 0.7985, and a highly sensitive detection and quantitation limits nearly equal to 0.066 and 0.2 µg/ml, respectively. A proposed protocol has been checked in accordance with ICH validation guidelines, which indicate good accuracy and high precision of the proposed method. Furthermore, this protocol could be perfectly applied for the quantitative estimation of octreotide in its ampoules with a high degree of accuracy and precision. As a result, a developed protocol is ideally appropriate for fast and simple octreotide quantitative estimation in quality control laboratories.

Ionic liquids (ILs) are good candidates for azeotropy separation. Knowledge of the microstructure properties of azeotrope - IL mixtures is important because they could reveal the molecular intrinsic cause of the elimination of azeotropy and represent the basis for the practical process. In this work, the microstructures of ethyl acetate-acetonitrile azeotrope mixtures and a representative IL, 1‑butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf₂N], which could eliminate the azeotropy of the ethyl acetate-acetonitrile system, were studied by Fourier transform infrared spectroscopy with the assistance of quantum chemical calculations and excess spectra. The C≡N stretching vibrational region of acetonitrile was closely examined. The interaction complexes of ethyl acetate-acetonitrile and ion cluster/ion pair/ion - acetonitrile were identified. Weak strength hydrogen-bonds with electrostatically dominant and closed-shell interaction properties were found in these complexes. The interactions between [BMIM][Tf₂N] and acetonitrile were stronger than those between ethyl acetate and acetonitrile, which caused the addition of IL to easily destroy the ethyl acetate-acetonitrile interaction complex. The interactions between [BMIM][Tf₂N] and acetonitrile were stronger than those between [BMIM][Tf₂N] and ethyl acetate, which would influence the relative volatility of ethyl acetate and acetonitrile in the azeotrope system. When x(IL) was larger than 0.027, all the interaction complexes between acetonitrile and ethyl acetate were completely broken apart, and the azeotrope was eliminated.

In order to evaluate the structure-property relationships of Cu(II) complex by using DFT methods, the structure of the newly synthesized Cu(II) complex, [Cu(6-Brpic)₂(bpy)], was investigated by XRD, FTIR, UV-Vis, and fluorescence spectroscopic methods. In addition, Hirshfeld surface and NBO analyses were fulfilled to identify possible interactions in the intermolecular and coordination environment. The five different DFT methods (HCTH, M06L, TPSSTPSS, B3LYP, and CAM-B3LYP levels), having four different functionalities (the GGA, meta-GGA, hybrid-GGA, and range-separated hybrid), were carried out so as to investigate the structure-property relationship, considering the geometric parameters (bond lengths and angles), vibrational frequencies, electronic absorption wavelengths, electronic transitions, and linear and nonlinear optical parameters. The R² for structural and vibrational parameters, as well as MPD%, MAD, an optimal scaling factor (λ) and overall root mean square (RMS) deviation, were considered only at vibration frequencies. While it was determined that M06-L and TPSSTPSS levels gave the best results for the bond lengths and angles of the Cu(II) complex, the best results for vibrational frequencies were obtained in the HCTH method along with these methods. In NLO parameters, the static and dynamic first-order hyperpolarizability (<β(0;0,0)> and β(-ω;ω,0)/<β(-2ω;ω,ω)>) values, the largest values were obtained in the HCTH method (38.817 × 10^-30 and 437.86 × 10^-30/201.55 × 10^-30 esu), whereas the smallest values were found to be in the CAM-B3LYP/TPSSTPSS levels (6.118 × 10^-30 esu, 8.270 × 10^-30/11.730 × 10^-30 esu). By regarding the static γ (<γ(0;0,0,0)>) and dynamic (<γ(-ω;ω,0,0)> parameters, the largest values were calculated in the M06L (232.101 × 10^-36) and HCTH (1711.52 × 10^-36) methods and the smallest values were obtained in the CAM-B3LYP (43.281 × 10^-36 and 60.844 × 10^-36) method. In fact, it is obviously seen that the β and γ values obtained by the aforementioned DFT levels are many times higher than that of the standard molecule of urea. These results indicate that the Cu(II) complex may be used as a potential NLO material to evolve optoelectronic devices.

As gas signaling molecules in organisms, SO₂ derivatives and H₂S play crucial regulating roles in a series of physiological processes. Therefore, developing an assay that can accurately monitor the concentration of SO₂ derivatives and H₂S in cells is extremely important for the research and treatment of related illnesses. A bifunctional probe SN-F based on FRET mechanism for SO₂ derivatives and H₂S was designed. SN-F had a short response time to SO₂ (2 min), excellent anti-interference capability and selectivity in the non-organic solvent system (pH = 7.4), which was suitable for the determination of SO₂ derivatives in cells. SN-F had a wide linear range for H₂S. Moreover, SN-F was applied in cell imaging successfully with high targeting ability to endoplasmic reticulum (ER) and could monitor endogenous and exogenous H₂S in cells.

DFT and TDDFT approaches were used to design three (T_16,17,18) molecules based on 4,4'-dimethoxy-2,2'-bithiophene core to explore the influence of substitution of triphenylamine (TPA) fragment by methoxy groups, and introduction of azomethine π-bridges on the optoelectronic properties of hole transporting materials for perovskite solar cells (PSCs) or as donor for organic solar cells (OSCs). To shed light on the efficiency, stability, and solubility several physicochemical parameters were computed in dichloromethane solvent. All designed molecules show appropriate frontier molecular orbital levels, which facilitates effective hole transfer from the perovskite materials to the HTMs in the hole-transporting layer in PSC devices. They all show good efficiency and pore-fillings and are stable and soluble in dichloromethane. Electron-hole pairs can easily dissociate into free charge carriers, especially for T₁₆ and T₁₇; consequently, improve short-circuit current densities and facilitate hole transport. It is also advised to use T₁₈ which includes azomethine bridges as a donor with a non-fullerene Y6 acceptor to create effective OSCs because it exhibits high open circuit voltage, fill factor and low gap energy.

We have developed a simple, rapid and cost-effective Dual-channel "colorimetric and absorbance" sensor using polyvinylpyrrolidone (PVP) capped Rhodamine6g (Rh6G) dye composite. Dye-doped polymer composite probe (PVPRH) exhibit intense, narrow absorption properties and long-term stability than the bare Rh6G. The probe's colorimetric relationship with pH was demonstrated by absorption titration. The PVPRH provides a sensitive dual channel method for the determination of sulfide and bicarbonate with colorimetric response and absorption quenching. The synthesized probe, as a two-faced, exhibited remarkable colorimetric responses from orange to pale yellow in the presence of S^2- and orange to soft pink in the presence of HCO₃^- ion, which can be observed by the naked eye also. Under optimal conditions, the relative absorption intensity decreases with increasing ion concentration of sulfide and bicarbonate ions. This trend is observed within the probe solution concentration range of 5 mM to 50 mM. The Dye-doped polymer composite probe is easy, cost effective, rapid, and has real time detection capability for sulfide and bicarbonate ions. The composite probe is stable and optically modified and can be successfully used for detections of S^2- and HCO₃^- ions as strip senor.

Sulfur dioxide (SO₂) and its derivatives (SO₃^2- and HSO₃^-), are important active sulfur species that play significant roles in physiological processes. Fluorescence probe imaging technology, due to its high temporal and spatial resolution, real-time non-invasive and non-destructive detection, has emerged as a valuable tool for studying SO₂ in biological systems. In this study, we presented a colorimetric fluorescent probe for the detection of HSO₃^-. The structure of probe TPN-BP consists of a triphenylamine group and a benzopyrylium group that are connected by a vinyl double bond. The benzopyrylium group in probe TPN-BP, which carries a positive charge, serves two important functions: enhancing water solubility, allowing for its effective use in fully aqueous environments, and acting as a fluorescence quencher for the triphenylamine group. Upon interaction with HSO₃^-, probe TPN-BP exhibited significantly increase in fluorescence at 480 nm, causing the solution to change from blue to colorless. Spectral experiments showed that probe TPN-BP showed quick response time (10 s), high sensitivity (12.7 nM), and excellent selectivity towards HSO₃^-. It is worth noting that probe TPN-BP has been successfully used for fluorescence imaging and detection of HSO₃^- in plants and zebrafish. The results of this study indicated that probe TPN-BP can be used as a promising tool for the research and monitoring of SO₂ in living organisms.

The optical excitation effects offer an opportunity to gain insights into the structure and the function of K⁺ channel, contributing to the prediction of possible targets for drug design and precision therapy. Although there has been increasing research attention on the modulation of ion permeation in K+ channel by terahertz electromagnetic (THz-EM) stimuli, little exploration has been conducted regarding the dependence of ion permeation on frequencies. By using two-dimensional (2D) infrared excitation spectrum calculation for the K⁺ channel, we have discovered that the frequency of 53.60 THz serves as an optimal excitation modulation mode. This mode leads to an almost twofold enhancement in the rate of K⁺ ion permeation and a tenfold increase in selectivity efficiency. These improvements can be attributed to the coupling mode matching of the excited properties of CO groups in the K⁺ channel. Our findings propose a promising application of terahertz technology to improve the performance of ion channels, nanomembrane sieves, nanodevices, as well as neural therapy.