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

Ascorbic acid (AA) plays an important role in many life processes. The chronic nutritional deficiency of AA will lead to the symptoms of scurvy. Therefore, the sensitive quantitative detection of AA is most important in the pharmaceutical analysis, food industry and diagnostic application. In this study, a dual-functional magnetic metal-organic frameworks (Fe₃O₄@SiO₂@UiO-PBA) nanoparticles was synthesized by modifying phenylboronic acid to the surface of magnetic UiO-66-NH₂ via postsynthetic modification for selectively and sensitively florescent detection of AA. Due to the abundant amino groups and grafted phenylboronic acid, the proposed nanoparticles have the dual properties of hydrophilicity and boronate affinity. Under optimum conditions, the obtained Fe₃O₄@SiO₂@UiO-PBA nanoparticles can detect AA within 30 s, and has a good linear relationship with the concentration of AA in the range of 5.0-60 μM with a detection limit of 2.5 μM (S/N = 3). In addition, the prepared Fe₃O₄@SiO₂@UiO-PBA nanoparticles showed excellent selectivity and great potential application in the highly efficient determination of trace AA in vitamin C tablets. These results indicated that a convenient method was proposed to develop fluorescent probes for rapid and sensitive detection of trace AA in real samples.

Two novel click derived sensory systems for different derivatives connected via a triazole linkage have been developed as a component of a chemosensor with sensitive towards Fe³⁺ ions. The 1-octyl-4-carboxyl-1,2,3-triazole (TR1) system demonstrated sensitivity to calcium ion. The 1,3-bis(4-hydroxycarbamoyl-1,2,3-triazol-1-yl)xylylene (TR2) system was shown to possess a preferential detection capability as a colorimetric probe for Fe³⁺ ions by exhibiting an obvious pH-dependent color change from colorless to pink. Complexation of the ligands with Fe³⁺ ions was studied. The 1:1 stoichiometry and bonding sites of TR1_-Fe³⁺, and TR2_-Fe³⁺ complexes were elucidated by analyzing the Job plot. The association constants of 5.35 × 10⁵ M¹ for TR1_- Fe³⁺ and 3.58 × 10⁴ M¹ for TR2_-Fe³⁺ and detection limits 1.68 × 10^-8 and 2.52 × 10^-7 were determined from standard deviation and linear fittings.

A benzimidazole-based probe, BIPMA (2-(1H-benzo[d]imidazol-2-yl)-N-(pyridin-2-ylmethyl)aniline), was designed and synthesized to detect Cu²⁺ ions. BIPMA exhibited a fluorescent "turn-on" mechanism when bound to Cu²⁺ ions in an acetonitrile/water mixture (5:5, v/v, HEPES 10 mM, pH 7.4) owing to the synergistic effect of the chelation-enhanced fluorescence and internal charge-transfer mechanisms. Moreover, the BIPMA probe effectively detected nanomolar-range concentrations (0-400 nM) of Cu²⁺ ions in an aqueous system with a detection limit of 4.80 nM; this value is significantly lower than that set by the U.S. Environmental Protection Agency (≈20 μM). Additionally, BIPMA showed an ultrafast response to Cu²⁺ ions, with a maximum intensity achieved 25 s after adding Cu²⁺. Furthermore, BIPMA detected Cu²⁺ ions in solutions with a pH range of 5-11, without being influenced by pH, underscoring its applicability under various physiological conditions. Density functional theory studies revealed that internal charge transfer was responsible for emission. Finally, BIPMA effectively detected Cu²⁺ ions in real water samples and living cells.

Four spectrophotometric approaches had been established and optimized for the simultaneous estimation of two anti-diabetic drugs; linagliptin (LIN) and empagliflozin (EMP) in their bulk and tablet dosage form. LIN concentration could be first determined from the zero order spectra at its λ_max (293 nm) without interference from EMP as at this wavelength EMP showed zero absorbance. The LIN and EMP zero order absorption spectra displayed considerable overlap which hindered the direct determination of EMP. Thus, four indirect spectrophotometric approaches were established and optimized for the determination and quantification of EMP concentrations in presence of LIN. Method (I) was ratio difference method (RD) which depended on the determination of difference amplitudes in the ratio spectra (ΔP) at 236 nm and 227 nm; ΔP_(236-227) was directly proportional to EMP concentration. Method (II) was ratio derivative method (¹DD) based on the measuring of the amplitude of first derivative of ratio spectra at 243 nm which was directly proportional to EMP concentration. For determination of EMP concentration using both method (I) and (II); LIN 7 µg/mL was used as the divisor. Method (III) was area under curve method (AUC) which depended on the measurement of area confined between 220 and 230 nm and 273-290 nm. Method (IV) was dual wavelength method (DWL) which based on measurement of absorbance difference (ΔA) in zero order spectra between 239.8 and 282.6 nm which was directly proportional to EMP concentration. The four developed methods were optimized and entirely validated regarding to ICH guidelines. The proposed spectrophotometric approaches were used for the quantification of LIN and EMP simultaneously in their tablet dosage form. F-test and t-test were applied for statistical comparison between the results obtained by the proposed approaches and that obtained by the reported method. There was no significant difference concerning to precision and accuracy.

Raman and Raman Optical Activity (ROA) signals are amply affected by solvent effects, especially in the presence of strongly solute-solvent interactions such as Hydrogen Bonding (HB). In this work, we extend the fully atomistic polarizable Quantum Mechanics/Molecular Mechanics approach, based on the Fluctuating Charges and Fluctuating Dipoles force field to the calculation of Raman and ROA spectra. Such an approach is able to accurately describe specific HB interactions, by also accounting for anisotropic contributions due to the inclusion of fluctuating dipoles. To highlight the potentiality of the novel approach, Raman and ROA spectra of L-Serine and L-Cysteine dissolved in aqueous solution are computed and compared both with alternative theoretical approaches and experimental measurements.

Understanding the structural properties of ionic liquids (ILs) in azeotrope mixtures is crucial for designing and synthesizing IL entrainers tailored for extractive distillation. While extensive research has been conducted to comprehend the molecular properties of IL systems, much of this work has been limited to IL-cosolvent binary mixtures and fails to fully capture the essence of breaking azeotropy. In this study, we utilized Fourier-transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations to study the microstructure of the IL-azeotropic system. Leveraging the high resolution of excess spectroscopy and employing the methanol hydroxyl group as an effective probe, our research focused on the IL-acetonitrile-methanol mixtures. This approach enabled us to pinpoint species transformations during the mixing process, revealing the nature of phase equilibrium changes within the azeotrope. Consequently, our findings offer valuable insights into the microstructures of multicomponent solutions.

In this study, N-doped fluorescent carbon dots with aggregation enhanced emission (N-CDs) were synthesized by a simple and rapid microwave-assisted method using o-phenylenediamine (OPD) and urea as raw materials and water as solvent. The fluorescence quantum yield of N-CDs was 20.64 %. N-CDs can be applied as invisible inks for message encryption. Furthermore, the fluorescence intensity of N-CDs can be quenched by Fe³⁺ and enhanced by tetracycline (TC). Therefore, two fluorescent probes were simultaneously designed in this study. Namely, "turn-off" fluorescence probe for Fe³⁺ and "turn-on" fluorescence probe for TC. The linear detection range of Fe³⁺ is from 1 to 70 μM, and detection limit is 0.1011 μM; the linear detection range of TC is from 0.1 to 10 μM, and the detection limit can be as low as 0.0555 μM. In this paper, the mutual interference between Fe³⁺ and TC was investigated for the first time. The detection of Fe³⁺ and TC was made more accurate by optimizing pH conditions and adding masking agent.

Rice flour is a raw material for various foods and is used as a substitute for wheat flour. However, some merchants adulterate rice flour with the illegal additive Rongalite to extend the shelf life and earn illegal profits. Rongalite is highly carcinogenic, and ingestion of more than 10 g can even cause death. high-performance liquid chromatography (HPLC) and mass spectrometry (MS) are currently the main methods for detecting food adulteration, however, the existing methods have many limitations, complex operation, expensive instrumentation, etc. Raman spectroscopy has the advantages of convenience and non-destructive samples, but Raman spectroscopy can be affected by interference such as fluorescence background that affects detection, in addition to the problem of difficult quantitative analysis due to nonlinear bias. In this article, we used the preprocessing method of Savitzky-Golay smoothing filtering and VTPspline to improve the quality of the spectra and proposed the SARNet, which combines autoencoder and residual network to achieve the quantitative analysis of Rongalite content in rice flour. The new model combines a linear model with a nonlinear model, which can solve the nonlinear problem effectively. Experiments showed that the new SARNet model achieved state-of-the-art results, achieving the best R² of 0.9703 and RMSEP of 0.0075. The lowest Rongalite concentration detected by the portable Raman spectrometer was 0.49%. In summary, the proposed method using portable Raman spectroscopy combined with machine learning has low detection bias and high accuracy, which can realize quantitative analyses of adulterated Rongalite in rice flour quickly. The method provides an accurate and nondestructive analytical tool in the field of food detection.

Researchers have become increasingly interested in solar energy based on semiconductor photocatalysts to remove hazardous pollutants and clean the environment. In this work, an efficient MoS₂-Bi₂Te₃-V₂O₅ nanocomposite has been prepared through wet impregnation method. MoS₂-Bi₂Te₃-V₂O₅ photocatalyst was utilized to decompose the MB and Rh B dyes. The photocatalytic efficiency (Rh B) of MoS₂-Bi₂Te₃-V₂O₅ nanocomposite (95.19 %) was higher than 2.70 times of Bi₂Te₃ nanorods, 1.55 times of V₂O₅ nanoparticles, 1.68 times of MoS₂ nanosheets, 1.50 times of MoS₂-Bi₂Te_3, and 1.21 times of MoS₂-V₂O₅ nanocomposite, respectively. Recycling tests conducted on the MoS₂-Bi₂Te₃-V₂O₅ nanocomposite revealed its high stability and durability. The outcomes obtained from the scavenger test suggest that the photogenerated hydroxyl radicals play a chief role in the photocatalytic performance of Rh B dye in the MoS₂-Bi₂Te₃-V₂O₅ nanocomposite, respectively. The enhanced photocatalytic performance of the MoS₂-Bi₂Te₃-V₂O₅ nanocomposite is ascribed to the strong hybrid formation of Bi₂Te₃, V₂O₅, and MoS₂ nanosheets, respectively. Consequently, the straightforward and readily synthesized MoS₂-Bi₂Te₃-V₂O₅ nanocomposite can serve as an economical, highly effective material for environmental applications.

Lead (Pb²⁺) is one of the most toxic heavy metals, and its environmental pollution and serious damages is a global concern. Therefore, it is necessary to develop effective sensing methods. This study describes a new strategy for the design of label-free competitive time-resolved fluorescent (TRF) aptasensor for detecting Pb²⁺ ions. The sensing principle of this aptasensor is the competition between Pb²⁺ and Tb³⁺ ions to bind to the guanine/thymine-rich sequence (lead aptamer) and the sensitized luminescence of Tb³⁺ by this sequence. The developed TRF aptasensor demonstrated a good linear detection range from 2.5 nM to 150 nM and a limit of detection (LOD) of 645 pM. In addition, the proposed TRF aptasensor has a high selectivity towards Pb²⁺, and it has also been successfully utilized to detect this ion in milk and human serum samples. This TRF aptasensor offers advantages such as short analysis time, simple operation, low cost, being label-free, and surpassing the interference of background fluorescence of biological samples due to its TRF characteristic. In this paper, we propose a Tb³⁺/guanine/thymine-rich sequence system for designing different aptasensors against diverse targets by applying a proper guanine-rich sequence.