Journal of Applied Spectroscopy最新文献

Detection of nonstructural protein 1 (NS1) in saliva is a potential solution to noninvasive, early dengue detection. However, NS1 in saliva detected using enzyme-linked immunosorbent assay reports only 64.7% sensitivity and is undetectable using rapid test kits even in acute cases. Exploiting surface-enhanced Raman spectroscopy (SERS) and silicon (Si) as a low-cost, abundant material, a nano silver-coated porous silicon SERS substrate was developed for the novel detection of low-concentration NS1. The conventional wet lab electrochemical method was used to fabricate the PSi template, whereas the drop deposition method was used to deposit the AgNP on the PSi. Using rhodamine as the Raman marker, an enhancement factor of 53 was obtained, with a 0.01-mg/mL limit of detection (LOD), which is not spectacularly impressive. However, surprisingly, the SERS substrate surface functionalized with the dengue antibody resulted in the visibility of several peaks related to NS1 up to 0.001 mg/mL. Advanced lithography methods can further lower the LOD and enhance the performance of the PSi-based SERS substrate. Moreover, PSi-based SERS substrate fabrication allows for mass production and low costs. The study successfully developed the SERS substrate for its intended novel application: to detect low-concentration NS1.

The interaction of indotricarbocyanine dyes with lipid-transfer protein Ns-LTP1 in Dulbecco's phosphate-buffered saline (PBS) was studied. An orthophenylene bridge with a chlorine in the meso-position of the dye was shown to be ineffective as a linker for protein macromolecules without a free cysteine residue. The indotricarbocyanine dye was modified into the N-hydroxysuccinimide ester to obtain a complex of the indotricarbocyanine dye with the Ns-LTP1 protein. A complex of dye molecules with the Ns-LTP1 protein was obtained by mixing a two-phase system of the protein in PBS and the dye activated ester in 1,2-dichloroethane. The half-width of the absorption spectrum increased from 56 to 61 nm; the fluorescence decay time, from 0.3 to 0.5 ns; and the degree of polarization, from 27 to 31% upon formation of the complex. It was established that HCl at concentrations equivalent to its content in gastric juice (0.1–0.5%) led to irreversible destruction of the dye. Capsules that can withstand stomach acid and dissolve in the intestines could be used to treat erosive and ulcerative lesions with peroral administration of the complex.

A dynamic light-scattering method for qualitative analysis was developed and used in production and quality control of hydrolyzed collagen (HC). A semiquantitative analytical method based on ultrafiltration coupled with spectrophotometry was proposed for the peptide fraction with molecular mass <10 kDa, which determines the most significant properties of HC.

Herein, an accurate and simple spectrophotometric method for investigating cefixime in different formulations is reported. The proposed method elaborates on the complexation of cefixime with vanadyl sulfate in acidic media. The yellow color complexation product manifested its maximum absorbance peak at around 321 nm, and obeyed Beer's law in 2 × 10⁻⁶–1 × 10⁻⁴ M cefixime concentration. Obtained spectroscopic data were used to calculate standard deviation (S), limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation (RSD) as 6.5 × 10⁻⁵, 1.96 × 10⁻⁴, 6.5 × 10⁻⁴ M, and 0.057%, respectively. In addition, the formation constant associated with the complex obtained, calculated as 5.7 × 1016, indicates that the final complex was remarkably stable.

This paper is aimed at investigating the structure and luminescence properties of Sr₃Y₂Ge₃O₁₂ activated by Eu³⁺ (SYGO:Eu³⁺), which were synthesized by using the sol-gel method. The synthesis was conducted at 1200°C for 8 h, with an optimal doping concentration of 5 mol% Eu³⁺. Under near-ultraviolet excitations at 395 nm, SYGO:x mol.% Eu³⁺ phosphors showed the red emission of Eu³⁺ (⁵D₀–⁷F₁) at 612 nm, and the photoluminescence intensity was highest at 5 mol.% Eu³⁺ doping. X-ray diff raction analysis of SYGO materials displays a single-phase structure that belongs to the Ia3d (230) space group. The result showed that the Eu³⁺ ion substitutes the asymmetrical location in the SYGO host, particularly the Sr²⁺ position, by calculating the ionic radius. In addition, the investigated red phosphors show high luminescence intensity and deep red emission. Thus, they show application potential as redemitting phosphor materials in white LEDs under near-ultraviolet excitations.

Y₂Sr₃B₄O₁₂ phosphors doped with europium ions were synthesized by a modified conventional solid-state reaction method. Characterizations of the prepared samples, viz., X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and Commission Internationale de I’Eclairage were studied. The XRD analysis confirmed the formation of mixed phase due to polyborate and has a hexagonal crystalline yttrium orthoborate phosphor. SEM images showed the irregular morphology of the sample. The grain size distribution was broad and the average size was found to range from 2 μm to 100 nm. PL measurements showed excitation and emission characteristics of the prepared phosphor with different concentrations of the doping ion. From the emission spectra, it was clearly observed that the emission intensity of the magnetic dipole was higher than that of electric dipole transition owing to the Eu³⁺ ions occupying a higher symmetry site in the Y₂Sr₃B₄O₁₂ host. The intensity of PL increased with increasing concentration of the doping ion up to 2.0 mol.%; after that, the PL intensity decreased owing to the concentration-quenching phenomenon. The results indicated that Y₂Sr₃B₄O₁₂:Eu³⁺ phosphors can be selected as a potential candidate for solar cell/photovoltaic application.

Iron, as the most prevalent critical trace element in the human body, is crucial for many basic physiological functions and has many environmental applications. Therefore, excellent chemosensors with high sensitivity and good selectivity toward iron are highly desired. Three new fluorescent colorimetric chemosensors (CS1, CS2, and CS3) were synthesized and prepared through a one-step reaction to selectively detect Fe³⁺ in aqueous media. To effectively coordinate metal ions, the sensors contain rhodamine derivatives with different "N, O" donor atoms. Of these sensors, CS2 and CS3 demonstrated sensing behavior and colorimetric "off–on" sensing for Fe³⁺ over various biologically important metal ions, rendering good selectivity. Fluorescent imaging was performed to confirm the possibility of applying the sensors in living cells.

The removal of Cd(II) ions was investigated from various samples of water employing magnetic acrylamide nanocomposite. The effects of magnetic acrylamide nanocomposite dosage, pH extraction, and contact time on Cd(II) removal from sample water were monitored using spectrometry. In addition, adsorption isotherm models for the sorption of Cd(II) were studied in this research. The adsorption capacity of magnetic acrylamide nanocomposite for Cd(II) was achieved at 18.64 mg/g. The removal of Cd(II) using magnetic acrylamide nanocomposite was fitted with the model of the Freundlich isotherm. This removal process provides a value coefficient (R² = 0.98) for Cd²⁺ ions and a very excellent linear range of 0.4–22 mg/L. By using a signal-to-noise ratio of 3 (limit of detection, LOD = 2.04 μg/L), the LODs for Cd²⁺ ions adsorption by magnetic acrylamide nanocomposite were attained. According to these results, magnetic acrylamide nanocomposite is a suitable adsorbent for removing Cd(II) from various water samples.

Theoretically calculated IR absorption spectra of Ti/SiO₂/Si₃N4/n⁺-Si structures with an island surface layer were used to show that the absorption maximum broadened and shifted to longer wavelength as the n⁺-Si island size increased with a constant period of their placement on the surface. This peak was probably associated with excitation of plasmon oscillations in the surface island layer. A structure with an island size of 3 μm and a period of 6 μm was shown to absorb ~99% of the incident radiation at a wavelength practically equal to the period (6.2 μm). Other absorption bands at ~4 μm and 9.0–9.5 μm arose regardless of the island size and were associated with absorption in the SiO₂ layer. A layer of undoped silicon of thickness up to 200 nm located between the Ti substrate and SiO₂ layer slightly reduced the intensity and half-width of the plasmon absorption maximum.

The photooxidation process of aromatic hydrocarbons isolated from crude petroleum from the Zagly field by liquid chromatography was studied using modern spectroscopic methods (UV spectroscopy, IR spectroscopy, NMR spectroscopy, and luminescence) and changes in the chemical composition, spectral parameters, and spectral luminescent properties.