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

The high thermal stability and chemical durability of amide-linked covalent organic frameworks (amide COFs) make them a promising material for a range of new applications. Nevertheless, the low reversibility of the amide bond presents a significant challenge to the direct synthesis of amide-bonded COFs. In this paper, we present a simple method for synthesizing amide COFs. The synthesis of imine-linked COFs was initially achieved through the reaction of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde. Subsequently, amide COFs were synthesized via the oxidation of the imine bond into an amide bond, utilizing ammonium persulfate as the oxidizing agent. Due to the difference of link bond, two COFs separately displayed distinct and significant fluorescence enhancement for Al³⁺ and Ce³⁺, which was highly sensitive and less affected by environmental factors. The strategy offers a novel approach to the convenient and environmentally benign synthesis of amide COFs, which may facilitate their wider applications.

The current study introduces the first micellar-enhanced spectrofluorimetric approach for the estimation of the commonly abused CNS antitussive, dextromethorphan (DXM) in its syrup and biological fluids. A micellar solution of sodium dodecyl sulfate (SDS) containing DXM showed high native fluorescence emission at 305 nm following excitation at 224 nm. Using SDS as a micellar system resulted in about a 2.5-fold increase in the drug's fluorescence intensity and quantum yield as well as the sensitivity of the approach. A thorough investigation was conducted into the experimental factors affecting the studied drug's spectrofluorimetric behavior. Additionally, the quantum yield of DXM was calculated, and it was found to reach up to 22 %. A calibration plot with a straight line was produced across the concentration range of 10.0-200.0 ng/mL. The suggested approach demonstrated excellent sensitivity down to the nanogram level, with 1.80 ng/mL for the detection limit and 5.47 ng/mL for the quantification limit. The drug under study was successfully analyzed in syrup using the designed approach, which yielded low %RSD values (≤0.882) and high %recoveries (99.20-101.00). The efficacy of the suggested fluorimetric technique in detecting DXM in human plasma and urine samples has been demonstrated with excellent recovery (98.12-101.35) and %RSD (≤1.39) values owing to its high sensitivity and selectivity. As DXM is one of the most commonly abused CNS antitussives, the capacity of the proposed method for its analysis in biological fluids can provide further insights for monitoring its potential abuse. The excellent greenness and eco-friendliness of the method were confirmed using GAPI and AGREE metrics, while the BAGI tool assessed its economy, practicality, and applicability. The method was fully validated according to ICH Q2 (R2) guidelines.

The preservation of paper-based archival documents is crucial for safeguarding historical and cultural heritage. Some records possess visually inaccessible text or images because of previous conservation measures, their method of construction, or historic damage. Micro-spatially Offset Raman Spectroscopy (micro-SORS) has emerged as a promising method for probing below or through opaque material substrates non-invasively. This study explores the potential of micro-SORS to image hidden text and figures in paper-based archival documents, utilizing Raman signals, fluorescence emissions, and overall spectral intensity reflecting also sample absorption. We present case studies involving sealed letters and playing cards from historical collections, demonstrating the efficacy of micro-SORS in identifying pigments and deciphering hidden ink writings. Results show the successful mapping of vermilion pigment in playing cards and reconstruction of hidden iron gall ink text in sealed letters. Chemometric analysis further enhances the visualization of hidden text. Despite challenges such as the absence of Raman signal of the target materials, micro-SORS proves to be a valuable tool for accessing hidden information in paper-based artifacts, aiding in preservation efforts and historical research.

The development of B-lymphoblastic leukemia is tightly associated with aberrant expression of Pax-5a. This work presented a novel dual signal amplification strategy-based Pax-5a detection method by combining the rolling circle amplification reaction (RCA) and the Entropy-driven toehold-mediated strand displacement (ETSD). Particularly noteworthy is the employed ETSD, which effectively improves the rate and stability of the reaction due to its unique entropy-driven principle. The uniqueness of this method is the combination of two amplification techniques, each utilizing its own strengths to achieve our intended purpose. This sensing method has been effectively used to determine the Pax-5a gene which with a reliable linear correlation for detection within a range and achieving a detection limit of 3.34 pM, calculated using the formula (3σ/S). Furthermore, even in 1 % of human serum samples, the biosensor can identify the target gene with exceptional sensitivity. The recovery rates fall within the range of 96.68-101.76 %, with a relative standard deviation (RSD) of 5.47 %. The method has a strong specificity based on sequence-specific hybridization of nucleic acids, thereby effectively preventing potential false-positive results. This fluorescent biosensor has a high detection capability for Pax-5a, and offers stable results. It provides a new way for early clinical diagnosis of acute lymphoblastic leukemia.

Sunlight-induced degradable squarazine based electron deficient receptor 3,4-bis((E)-2-((perfluorophenyl)methylene)hydrazinyl)cyclobut-3-ene-1,2-dione, L has been reported here. Naked-eye colorimetric analysis, UV-Vis, IR and ¹H, 19F, ³¹P-NMR spectrometric results show that this receptor L high affinity with cyanide anion. The strength of the receptor L towards colorimetrically responded anions are calculated by UV-Vis spectrometric titrations and it is found to be 9.9597 × 10³ for cyanide. Interestingly, upon exposure of those anionic complexes under sunlight, the colors of those respective anionic complexes are disappeared. From this result, it is clear that these anionic complexes are capable to discharge the bound anion via CN free rotation. As evidenced from spectroscopic and colorimetric results, it is also clear that this anionic complex is not only release the bound anion, but also undergone self-degradation upon sunlight exposure. To the best of our knowledge, this is the first example for cyanide sensing of anion accomplished with self-degradation of anion complex upon exposure on sunlight.

Aquatic systems with low zinc levels can experience a significant decrease in carbon dioxide uptake and limited growth of phytoplankton species. In this study, we describe the use of a new fluorescent sensor based on NH₂-MIL-53(Al), and modified with glutaraldehyde and sulfadoxine, for selectively detecting zinc ions in water and blood serum samples. Characterization of the synthesized material was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirming successful functionalization and preservation of the MOF structure. The sensor's performance for Zn²⁺ detection was evaluated by spectrofluorometry, demonstrating a significant fluorescence enhancement upon Zn²⁺ binding due to the interaction between Zn²⁺ ions and the sulfonamide groups. With a detection limit as low as 3.14 × 10^-2 ppm, the sensor demonstrates high selectivity for Zn²⁺ over other common metal ions. The sensor's response is rapid, stable, and reproducible, making it suitable for practical applications. Real sample analysis was conducted in tap water and blood serum samples, with the results compared to those obtained using ICP-OES and a colorimetric test with 5-bromo-PAPS. The comparison confirmed the high accuracy and reliability of the fluorescent sensor in detecting Zn²⁺ ions in complex matrices. NH₂-MIL-53(Al) modified with glutaraldehyde and sulfadoxine shows potential as a selective fluorescent sensor for Zn²⁺ detection, making it a valuable tool for monitoring the environment and biology.

In this study, simultaneous determination of levodopa (LEV) and carbidopa (CBD) in binary mixtures, pharmaceutical formulation, and biological sample was conducted using the application of simple, fast, sensitive, and accurate UV-spectrophotometry in combination with chemometrics methods. The first method is net analyte signal (NAS) based on the multivariate calibration methods. The limit of detection (LOD) and limit of quantification (LOQ) were 0.9758, 0.7633 µg/mL and 2.956, 2.313 µg/mL over the linear range of 5-40 and 0.5-20 µg/mL for LEV and CBD, respectively. In the NAS approach, the mean recovery values of mixtures were 100.12 % for LEV and 99.65 % for CBD, where root mean square error (RMSE) values were 0.0106 and 0.0141 for LEV and CBD, respectively. The second method is absorbance subtraction (AS) based on the absorption factor technique for analyzing the isosbestic point. This model was constructed at an isosbestic point of 261 nm in the range of 5-40 and 0.5-20 µg/mL with coefficient determination (R²) of 0.9985 and 0.9996 for LEV and CBD, respectively. AS method could estimate LEV and CBD with LOD values of 1.924 and 0.5657 μg/mL and LOQ values of 5.833 and 1.714 μg/mL, respectively. The recovery percentage was between 91.50 % to 104.60 % with RMSE of 0.1455 for LEV and 92.00 % to 106.66 % with RMSE of 0.2508 for CBD. The introduced approaches have the benefit of concurrent analysis of the mentioned components without any pretreatment. Statistical comparison of the results of real sample analysis with high-performance liquid chromatography (HPLC) did not show a significant difference. These methods can replace HPLC in quality control laboratories when fast, precise, and low-cost analysis is needed.

This study designed and developed an innovative online detection device based on Continuous Solid-Phase Extraction Spectroscopy (CSPES) for rapid quantitative analysis of environmental water pollutants. The device is highly automated, eliminating environmental interference. Leveraging CSPES technology and adsorption kinetics theory, an online quantitative analysis model between the spectrum and component concentrations was established, along with a concentration calculation method based on the least squares method. The quantitative analysis method was validated using single-component and binary-component sample systems containing Fluoranthene, Benzo[k]Fluoranthene, and Rhodamine 6G. The model exhibited excellent predictive performance, with overall prediction concentration relative errors (RE) ranging from 0.45 % to 8.75 % and relative standard deviations (RSD) of less than 3 %. In real sample applications, recovery rates ranged from 86.8 % to 124.4 %, with RSDs between 0.33 % and 2.22 %. This method provides a robust tool for water quality monitoring and environmental analysis, holding significant potential for application across various fields.

Selective imaging of superoxide anion is important for understanding its role in cell membrane biology, but is often a challenging task because of the lack of an effective fluorescence probe. In this study, a new near-infrared fluorescent probe (SHX-O) that can target cell membrane was developed for imaging superoxide anion. SHX-O was designed by simultaneously incorporating a sulfonated bis-indole and a diphenylphosphinyl recognition group into the hemicyanine moiety. The probe itself showed a rather weak fluorescence due to the hemicyanine's hydroxyl substitution; however, its reaction with superoxide anion caused a large enhancement of near-infrared fluorescence at 790 nm. Moreover, SHX-O exhibited not only high selectivity for superoxide anion over other reactive oxygen species, but also specific cell membrane localization, which may be attributed to the probe's amphiphilic structure. Using the probe, fluorescence imaging of cell membrane superoxide anion produced in the presence of xanthine oxidase and xanthine has been achieved in living cells. We believe that SHX-O may serve as a potential tool for imaging and investigating superoxide anion of cell membrane.

Antioxidant activity, as a topic of current interest, is discussed together with the excited state intramolecular proton transfer (ESIPT) process for three flavonoid derivatives, based on density functional theory (DFT)and time-dependent DFT (TD-DFT) methods, as well as DPPH free radical scavenging assay. The potential energy curves and transition states demonstrate that the three molecules can undergo only single proton transfer in the excited state, and all of them are ultrafast ESIPT processes. The absorption spectra of all the molecules show effective protection against UV radiation with low fluorescence intensity, especially Baicalein (Bai), which demonstrates their great potential for sunscreen applications. The density of states, HOMO energy values, global and local indices reveal that the antioxidant activity of the molecules after ESIPT process is enhanced, with Bai having the highest antioxidant activity, which is significantly attributed to the number and position of phenolic hydroxyl groups. Moreover, by comparing the DPPH free radical scavenging activity under the dark and UV radiation conditions, the radical scavenging activity (RSA) value in the UV radiation is remarkably higher than that in the dark condition, in which Bai achieves RSA value of 93.4%. Overall, the antioxidant activity of all three ESIPT-based flavonoid derivatives, especially Bai, is significantly elevated in the keto* form, which reinforces the significant relationship between antioxidant activity and ESIPT process, and provides new application prospects for molecules with ESIPT properties.