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

Water is a greatly convenient solvent in Raman spectroscopy. However, non-additive effects sometimes make its signal difficult to subtract. To understand these effects, spectra for clusters of model ions, including transition metal complexes and water molecules, were simulated and analyzed. A combined molecular mechanics/quantum mechanics approach was taken to reveal how relative Raman scattering intensities depend on the distance from the solute and the excitation wavelength. The computations indicate a big effect of solute charge; for example, the sodium cation affects Raman scattering by water to a lesser extent than the chlorine anion. The modeling was able to qualitatively reproduce the experimental observation that a solution of a simple salt may work as a baseline better than pure water in many Raman experiments. For absorbing species, an additional scattering boost occurs due to the resonance effect. Simulations thus provide useful insight into solute-solvent interactions and their effects on measured spectra.

This study explores the nonlinear optical (NLO) and photophysical properties of newly designed naphthyridine derivatives by density functional theory (DFT). The first hyperpolarizability (β_tot), a key indicator of NLO activity, varies significantly depending on the substituent groups. N-substituted compounds (IUB-N series) generally show lower β_tot values, while compounds with electron donor/acceptor groups (IUB-P series) demonstrate a broader range, with IUB-A-02 achieving the highest β_tot value of 16,362 a.u. due to the presence of two -NH₂ groups. TD-DFT analysis confirms key electronic transitions, mostly from HOMO to LUMO, with absorption wavelengths (λmax) ranging from 349.596 to 440.692 nm for the IUB-P series. The introduction of electron-donor groups considerably boosts absorption, particularly in IUB-P-06, with highest λ_max and oscillator strength (f_o) signifying excellent light absorption capabilities. The calculated light harvesting efficiency (LHE) correlates strongly with f_o values, IUB-N-01 to IUB-N-05 exhibiting higher LHE than the unsubstituted IUB. Additionally, lower radiative lifetimes (τ) for the modified compounds indicate faster decay, useful for applications in photodynamic therapy and fluorescence imaging. Lower transition energy (ΔE) and higher f_o values contributed to greater first hyperpolarizability (β_o). IUB-P-06, with two -NH₂ donor groups, shows the lowest ΔE (2.81 eV) and a correspondingly high β_o (60218.89 a.u.). Whereas IUB-A-02 exhibits the highest β_o (68907.84 a.u.) due to its large dipole moment change (Δμ = -6.37 D). Among N-substituted compounds, IUB-N-01 exhibits the highest charge density. IUB-P-06 has the highest charge density and electron-hole separation due to electron donor/acceptor groups, indicating a higher degree of internal atomic localization. This enhanced charge separation further confirms the superior performance of these compounds in NLO applications. In conclusion, this comprehensive analysis spanning ESP, TD-DFT, TLM, LHE, and TDM demonstrates that the studied naphthyridine derivatives possess promising NLO properties and exhibit strong potential for use in optoelectronics, photovoltaics, photodynamic therapy, and other advanced optical technologies.

Lead ion (Pb²⁺) is a common environmental contaminant, extremely toxic, persistent, and easily adsorbed, concentrated, and enriched by agricultural products. Ingestion of this ion can result in health problems for humans, including neurological disorders, heart disease, brain damage, and mental deficiency. In this research, a sensitive fluorescent biosensing method for detecting Pb²⁺ was developed using DNAzyme as the target recognition element and SYBR Green (SG) fluorescent dye as the signal indicator. Through catalytic action on a strand of DNA with ribo-adenine (rA), the DNAzyme was able to cut it in the presence of Pb²⁺. This led to the removal of intercalation sites for SG molecules, resulting in a decrease in fluorescence response. The newly developed biosensor was capable of identifying Pb²⁺ ions within a range of 0.1-600 µM with a detection limit of 0.018 µM. This label-free fluorescent biosensor proved to be both convenient and efficient in accurately measuring the levels of Pb²⁺ ions in blood serum and milk samples, yielding recovery rates between 96.81 % and 100.00 %. The DNAzyme-based biosensor offers an economical and easy-to-use sensing assay for Pb²⁺ ion.

Neutral radicals have the potential to construct pure organic light-emitting diodes (OLEDs) with internal quantum efficiencies reaching 100%. However, neutral radical luminescent materials with emission wavelengths in the second near-infrared (NIR-II) window are rare. Herein, a serial of neutral donor-bridge-acceptor (D-π-A) type radical derivatives are investigated. The dominant elements influencing the luminescent properties of neutral radicals, such as chemical stability, excited state characteristics, radiative decay rate (k_r) and internal conversion rate (k_IC) constants are taken into consideration. Theoretical calculations reveal that introducing heteroatomic fused-rings into neutral radicals can modulate the chemical stability and result in a red shift of the emission wavelength spectrum. In the presence of charge transfer characteristics, by increasing the effective overlap between the hole and electron wavefunctions, the k_r constants of the neutral D-π-A type radicals increase. In addition, avoiding the geometric relaxation between the lowest excited state (D₁) and the ground state (D₀), as well as reducing electron-vibration coupling and non-adiabatic coupling in the low-frequency region can effectively decrease the k_IC constants. Our study proposes an innovative design approach aiming to develop stable and efficient NIR-II window neutral radical luminescent materials utilizing heteroatomic fused-rings as key elements.

Development of a rapid and sensitive detection method for hazardous dyes attracts considerable research interest. In this work, L-Tryptophan-based Carbon dots were developed as a fluorescence sensor for the detection of Malachite green (MG). Green fluorescent L-Trp-C-dots were synthesized by a simple pyrolysis technique using L-Trp as the starting precursor. L-Trp-C-dots exhibited different quenching responses to MG, and other interfering species, consequently offering a selective strategy to detect MG. The proposed sensor shows a limit of detection (LOD) of 0.06 μM and a limit of quantification (LOQ) of 0.22 μM with in the linearity range of 0 to 60 µM concentration. Additionally, the relative standard deviation (RSD) was found to be below 1.7 %. Furthermore, the recovery of MG from the real-time samples (green peas) was investigated.

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.