Journal of Applied Spectroscopy最新文献

Triple hybrid nanocomplexes based on selenium (Se⁰) nanoparticles, cellulose polymer carrier (CPC), and the photosensitizer fotoditazine (FD) were synthesized with different sequences of component addition and ratios. The spectral characteristics of these triple nanocomplexes were compared with analogous characteristics of FD and double complexes of variable composition (FD/Se⁰, CPC/FD, and CPC/Se⁰) using spectral methods. The synthesized triple hybrid Se-containing nanocomplexes could be promising for photodynamic therapy and diagnostics.

An advanced chemometric model based on ratiometric surface-enhanced Raman scattering (SERS) was developed for the quantification of glucose in serum samples. In the absence of glucose, it was mainly the SERS signal of silver nanoparticles (AgNPs)-o-phenylenediamine (OPD). When glucose was added, glucose oxidase catalyzed glucose to produce hydrogen peroxide (H₂O₂), which oxidized OPD to produce 2,3-diaminophenazine (DAP) in the presence of AgNPs. The generated DAP exhibited a new strong SERS signal and changed the Raman peak ratio between DAP and OPD. Without using any internal standard, the advanced chemometric model mitigated the fluctuations in SERS intensity and achieved accurate concentration predictions for glucose in serum samples with recoveries in the ranges of 92.8–104.8%. The accuracy of the quantitative results obtained using the proposed method is comparable with that of the reference method — glucometer. The proposed sensor showed high sensitivity and selectivity in detecting glucose with a limit of detection (LOD) of 0.28 μM. Additionally, the presented SERS sensor demonstrated great promise in determining H₂O₂-related metabolites in real serum samples.

The vibrational spectra of the natural ammonium sulfates tschermigite NH₄Al(SO₄)₂(H₂O)₁₂, lonecreekite NH₄Fe(SO₄)₂(H₂O)₁₂, ammoniovoltaite (NH₄)₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂(H₂O)₁₈, sabieite NH₄Fe(SO₄)₂, ammonioalunite NH₄Al₃(SO₄)₂(OH)₆, and ammoniojarosite NH₄Fe₃(SO₄)₂(OH)₆ were studied to determine the behavior of ammonium in symmetry-inappropriate positions. Disorder of the ammonium cation in salt crystals caused by the need to adjust the tetrahedral cation to the symmetry of the position to preserve the crystal symmetry was revealed. If the symmetry group of the position was not a subgroup of the tetrahedral symmetry group, the NH₄ tetrahedron was distorted by the subgroup Hʹ common for T_d and H, where H is the symmetry group of the position. Then, a polyhedron corresponding to the symmetry of the position was constructed from N = |H|/|Hʹ| (|H| and |Hʹ| are the orders of these groups) distorted tetrahedra. The disordered ammonium cation had several orientations (N), the superposition of which formally gave a polyhedron corresponding to the local symmetry. The maximum common subgroups for the given salts were C_3v and C₃. Distortion of ammonium led to activation of ν₁ and ν₂ [NH₄⁺ ] vibrations in the IR spectrum and splitting of ν₃ and ν₄ [NH₄⁺ ]. However, the effect was barely noticeable for ammonium in a centrosymmetric position, as in ammonioalunite and ammoniojarosite. The ν₄ [NH₄⁺] band was noticeably split and ν₁ and ν₂ [NH₄⁺ ] vibrations were clearly visible in spectra of the ammonium alums, ammoniovoltaite, and sabieite.

A series of Tb³⁺-doped Li₂CaSiO₄ phosphors were prepared by high-temperature solid-state reaction method. The structural studies were done using the X-ray diffraction (XRD) technique. The XRD patterns revealed that the sample was monophased and crystallizes in a cubic structure. Scanning electron microscopy (SEM) was used to obtain information about the morphology of the prepared samples. SEM micrographs clearly indicated that the particles crystallized in inhomogeneous morphology, with the particle size ranging from 1 μm to 100 nm. Also, photoluminescence (PL) analysis of the phosphor samples for different concentrations of doping ions with variable excitations were presented. The PL excitation spectrum of Tb³⁺ ion-doped Li₂CaSiO₄ has many sharp peaks, mainly at 418 nm (⁵D₃ → ⁷F₅), 436 nm (⁵D₃ → ⁷F₄), 456 nm (⁵D₃ → ⁷F₃), 472 nm (⁵D₃ → ⁷F_2,1,0), 487 nm (⁵D₄ → ⁷F₆), 550 nm (⁵D₄ → ⁷F₅), and 590 nm (⁵D₄ → ⁷F₄), assigned to the transitions of Tb- ion respectively (excited at 237 nm). The 1931 CIE (x, y) chromaticity coordinates showed the distribution of the spectral region calculated from PL emission spectra, and found to be (0.19, 0.22) in a bluish-green region of Tb³⁺ (0.01 wt (in grams)) Li₂CaSiO₄ phosphor. Our study shows that as-prepared phosphor may be useful for optical devices, mainly for LEDs, as a bluish-green component.

Aluminum is a widely distributed element and plays an indispensable role in our lives, but excessive intake of Al³⁺ can cause potential harm to human health. Highly selective methods for the rapid detection of Al³⁺ are urgently needed. Here, a novel "turn on" fluorescent probe L based on Schiff-base of 2-hydroxy-1-naphthaldehyde and 8-aminoquinoline was obtained in an excellent yield. Probe L presents significant properties such as rapid response, good stability, wide pH range, simple synthetic operation, and provides an efficient strategy for the highly selective detection of Al³⁺ in an aqueous solution of DMSO/H₂O (7:3, v:v). According to Job's curve and fluorescence titration, probe L with Al³⁺ forms a 2:1 ratio of complex, and the lowest limit of detection is 3.23 × 10⁻⁸ mol/L. The possible combination mode for probe L with Al³⁺ was proposed by comparison with the changes of 1H NMR and FTIR spectra of L and its complex. In addition, the potent applicants for probe L were also investigated, and indicated that it could conveniently be made into a series of sensor strips and applied to rapidly detect trace Al³⁺ in traditional Chinese medicine.

Ultraviolet-emitting phosphors with the formula K_2–xPb_xAl₂B₂O₇ (0.0025 ≤ x ≤ 0.03) were synthesized at 850°C for 6 h in air. The powder X-ray diffraction technique was used to analyze the phases of all prepared borates. The FTIR technique was used to examine the bond structure of K₂Al₂B₂O₇. At room temperature, a spectrofluorometer was used to examine the photoluminescence characteristics of the prepared phosphors. K₂Al₂B₂O₇:Pb²⁺ was found to have emission and excitation bands at 373 and 271 nm, respectively. An extensive investigation was conducted on the correlation between emission intensity and Pb²⁺ content for K_2–xPb_xAl₂B₂O₇. Consequently, 0.01 mol Pb²⁺ was found to be the optimal concentration in K₂Al₂B₂O₇. Eventually, it was found that the Stokes shift of the prepared material K₂Al₂B₂O₇:Pb²⁺ is 10,090 cm⁻¹ using the excitation band at 271 nm and the emission band at 373 nm. As a result of this investigation, a brand-new UVA radiation-emitting material has been established.

A detailed analysis of the previously discovered effect of the concentration of phosphotungstic acid (PTA) on its reduction within nanocomposite films with poly(vinyl alcohol) (PVA) induced by gamma radiation indicated that the molar absorption coefficient of the maximum of the PTA band due to intervalence charge transfer in reduced PTA heteropolyanions at low PTA concentrations is eight times higher than at high concentrations. Only 20% of this increase is attributed to the predominance of two- and one-electron-reduced heteropolyanions at low and high concentrations, respectively. We concluded that the main reason for the concentration effect is associated with a decrease in the size the PTA nanoparticles with decreasing PTA concentration in the films.

We present new aspects of erbium- or ytterbium-doped pure gadolinium oxide (Gd₂O₃:Er³⁺/Yb³⁺) as a suitable candidate for drug delivery and magnetic resonance (MR) applications. The samples were prepared using the conventional sol–gel synthesis technique. The structural studies revealed that the prepared sample was monophased and crystallizes in a cubic structure. FTIR measurements confirmed the creation of Gd₂O₃:Er³⁺/Yb³⁺ phosphor. SEM micrographs clearly indicated that the particles crystallized in uniform shape, exhibiting nano-rod formation, with the particle size ranging from 55 to 5 nm. TEM images revealed that Er³⁺- and Yb³⁺-co-doped Gd₂O₃ nanoparticles were the collection of the nano-rods 2–4 nm thick and 18–20 nm long. Also, photoluminescence analysis of the phosphor samples for variable concentrations of doping ions was presented. When doped with Er³⁺/Yb³⁺, nano-rod Gd₂O₃ emits intense green emission and some red emission peaks, under a 980-nm near-infrared laser. Our study shows that as-prepared samples may be useful for optical imaging systems and that nano-rod formation may be used as a major host carrier for drug delivery.

The photophysical properties and efficiency of photosensitized singlet oxygen formation by meso-tetrakis(4- N-methylpyridyl)porphyrin in a complex with hydroxyapatite nanoparticles were studied. At least three types of complexes characterized by different access of oxygen to porphyrin molecules were shown to form on the surface of the hydroxyapatite nanoparticles. Rotation of the pyridyl substituents of porphyrin in the complex with hydroxyapatite nanoparticles was found to be significantly hindered, while porphyrin molecules on the surface of the nanoparticles were in a less polar environment than in water. The quantum yield of photosensitized singlet oxygen formation was observed to decrease by at least nine times for porphyrin in the complex with hydroxyapatite nanoparticles. Porphyrin was released from hydroxyapatite nanoparticles and the efficiency of singlet oxygen formation increased although it did not reach the values characteristic for free porphyrin if the pH decreased to less than 5.0 (pH < 5.0).

A technique was developed to fabricate a new type of hybrid exciton-plasmonic nanostructures consisting of laterally oriented silver nanoplates electrostatically deposited on polymer films and capped with hydrophobic Zn_xCu_yIn_zS₂/ZnS quantum dot layers via a Langmuir–Blodgett technique. Pronounced photoluminescence quenching and a decrease in the average emission decay times indicated the presence of effective resonance energy transfer in the resulting hybrid plasmonic nanostructures. An approach based on a comparison of the polarization dependences of the photoluminescence bands from monolayers of quantum dots atop the quartz glass and monolayers of laterally oriented silver nanoplates was proposed to clarify the nature of the emission from these nanostructures. The data point toward a secondary emission mechanism due to scattering by transverse surface plasmons of the silver nanoplates excited through resonance energy transfer from the quantum dots.