Search Results (1,149)

The Sar-e-Sang lapis lazuli deposit has a mining history exceeding 5000 years, producing the world’s finest lapis lazuli. Recently, gem-quality forsterite has been discovered in the marble containing spinel, dolomite, and phlogopite at the periphery of the lapis lazuli ore body at the Pitawak mine, located east of the Sar-e-Sang deposit. The mineral assemblage indicates that the protolith of this marble is dolomite with aluminous and siliceous components. These forsterite crystals occur as colorless, transparent anhedral grains, exhibiting distinct red fluorescence under 365 nm ultraviolet light. To investigate the gemological and spectroscopic characteristics of the Pitawak mine forsterite, this study conducted and analyzed data from basic gemological analysis, electron probe microanalysis (EPMA), Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), ultraviolet–visible absorption spectroscopy (UV-VIS), Fourier-transform infrared spectroscopy (FTIR), laser Raman spectroscopy (RAMAN), and photoluminescence spectroscopy (PL) on four forsterite samples from the Pitawak mine. The analysis results reveal that the samples indicate a composition close to ideal forsterite with a crystal chemical formula of (Mg_2.00Fe_0.02)_Σ2.02Si_0.99O₄. The trace elements present include Fe, Mn, Ca, and minor amounts of Cr and Ni. The UV-VIS spectroscopy results show that the samples possess high transmittance across the visible light range with very weak absorption bands, contributing to the colorless and transparent appearance of Pitawak mine forsterite. This phenomenon is attributed to the extremely low content of chromophoric elements, which have a negligible effect on the forsterite’s color. PL spectroscopy indicates that the red fluorescence of the samples is caused by an emission peak near 642 nm. This emission peak arises from the spin-forbidden ⁴T₁ → ⁶A₁ transition of Mn²⁺ ions situated in octahedral sites within the forsterite structure. Full article

We developed an efficient and modular route to 2- and 6-(1,2,3-triazol-1-yl)azulenes to expand the synthetic accessibility and functional scope of azulene-based π-systems with stimulus-responsive photophysics. Readily accessible 2- and 6-azidoazulenes, prepared in excellent yields via S_NAr reactions of haloazulenes, were subjected to Cu(I)-catalyzed Huisgen [3 + 2] cycloaddition with a broad range of terminal alkynes to afford the corresponding triazolylazulenes in good to high yields, followed by acid-mediated decarboxylation and Staudinger reduction to enable further diversification to 2-azulenyltriazoles and a 6-aminoazulene derivative. Single-crystal X-ray diffraction analysis revealed substitution-position-dependent torsional arrangements and variations in π-conjugation between the azulene and triazole units. Photophysical characterization by UV/Vis absorption and fluorescence spectroscopy showed pronounced halochromism under acidic conditions, and selected derivatives displayed substantially enhanced fluorescence quantum yields. Overall, these results establish the azulene–1,2,3-triazole motif as a versatile building block for designing optoelectronic π-systems with acid-responsive emission properties. Full article

Cadmium sulfide is an important II-VI semiconductor known for its valuable photocatalytic properties ascribable to its band gap energy, which allows light absorption in the visible domain. Nonetheless, the application of cadmium sulfide in wastewater organic pollutant degradation is restricted due to its high toxicity to humans, soil, and marine life. To address this issue, we developed new composite materials by depositing CdS on a bentonite support in a 1:9 mass ratio to develop a photocatalyst with lower toxicity. In the first step, bentonite was activated using an aqueous HCl solution; for the deposition of CdS powder, we proposed the trituration method and compared it with chemical precipitation and hydrothermal synthesis, using thioacetamide as a sulfide ion source. The modified bentonite underwent characterization using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, UV-Vis, and FTIR spectroscopy. The photocatalytic activity was tested in the degradation of Congo red (CR), a persistent diazo dye. The efficiency of removing CR with CdS–bentonite composites depended on the deposition method of CdS, and it was higher than that of pristine CdS and of only adsorption onto acid-activated bentonite. The photocatalytic degradation mechanism was estimated by the scavenger test using ethylenediaminetetraacetic acid disodium salt, ascorbic acid, ethanol, and silver nitrate as radical scavengers. Full article

Vanadyl octa-(4-tert-butylphenyl)phthalocyanine (VOPc(t-BuPh)₈) and vanadyl octa-(4-tert-butylphenyl)tetrapyrazinoporphyrazine (VOTPyzPz(t-BuPh)₈) complexes were synthesized for the first time and confirmed by IR and UV-Vis spectroscopy and MALDI-TOF spectrometry. The method of synthesis of their precursors, 4,5-bis(4-tert-butylphenyl)phthalonitrile ((t-BuPh)₂PN) and 5,6-bis(4-tert-butylphenyl)pyrazine-2,3-dicarbonitrile ((t-BuPh)₂PDC), was modified, resulting in higher yields. For the vanadyl complexes, the basic properties were studied, and it was found that the red shift in the Q band in the first protonation step is approximately two times greater than that of previously known complexes. An electrochemical study showed the influence of aza-substitution on the redox properties and on the energies of the frontier orbitals of all the compounds presented. For all four considered compounds, quantum chemical calculations of the molecular structure, IR spectra, and electronic absorption spectra were carried out using density functional theory (DFT) and time-dependent density functional theory (TDDFT and simplified sTDDFT) approaches. According to the DFT calculations, vanadyl macrocyclic complexes have dome-shaped distorted structures. Experimental and theoretical IR and electronic absorption spectra were compared and interpreted. Full article

Photodynamic therapy is a cancer treatment that relies on a photosensitizer (PS) to generate reactive oxygen species upon light activation, thereby destroying cancer cells. The photophysical properties of porphyrins make them effective PSs, while nanoparticles (NPs) enhance their delivery and stability. The bioavailability and targeting efficiency of NPs-PS complexes may be improved through transport via human serum albumin (HSA). This study investigates the HSA binding affinity with 5,10,15,20-(Tetra-4-carboxyphenyl)porphyrin (TCPP) and with TiO₂-TCPP complexes. The interactions were analyzed using UV-Vis absorption, laser-induced fluorescence (LIF), and FTIR spectroscopy. Molecular docking was performed and provided consistent binding constant values for the TCPP–HSA complex with UV-Vis absorption measurements. LIF data revealed a slightly lower affinity when compare free porphyrin with TiO₂-TCPP, possibly due to competitive binding between TiO₂ and HSA. Docking simulations indicated that TCPP favorably interacts with amino acid residues located in subdomains IB and IIIA of HSA, supporting a preferential binding near Sudlow site I. FTIR measurements revealed conformational changes in HSA for both its interactions with TCPP and TiO₂-TCPP, including alterations in α-helical content and reorganization of the hydrogen bonding network within the polypeptide backbone. Full article

A novel series of benzoxazole-derived iminocoumarins was synthesized via a Knoevenagel condensation and fully characterized using NMR, UV–Vis spectroscopy, and computational methods. Their photophysical properties were systematically examined in solvents of varying polarity, revealing pronounced effects of both substituents and solvent environment on absorption maxima and intensity. Derivatives bearing electron-donating substituents on the coumarin core exhibited distinct and reversible pH-responsive spectral shifts, confirming their potential as optical pH probes. Experimental pK_a values derived from absorption titrations showed excellent agreement with DFT-calculated data, validating the proposed protonation-deprotonation equilibria and associated electronic structure changes. Structure–property relationships revealed that electron-donating groups enhance intramolecular charge transfer, while electron-withdrawing substituents modulate spectral response and stability. In parallel, the compounds were evaluated for antiproliferative, antiviral, and antifungal activities in vitro. Strong electron-donating substituents were associated with potent but non-selective cytotoxicity, whereas derivatives bearing electron-withdrawing groups displayed moderate and more selective antiproliferative effects against leukemia cell lines. Antifungal screening revealed moderate inhibition of phytopathogenic fungi, particularly for compounds with electron-withdrawing or methoxy substituents. Overall, these findings demonstrate that benzoxazole iminocoumarins represent a promising class of multifunctional heterocycles with potential applications as optical pH sensors and scaffolds for bioactive compound development. Full article

The compounds LiCo_1−xMn_xO₂ (x = 0.5, 0.7) were synthesized via the solid-state method and exhibited crystallization in the cubic spinel structure (space group Fd-3m). UV–Vis spectroscopy reveals strong visible-light absorption and a reduction in the indirect optical band gap from 1.85 eV (x = 0.5) to 1.60 eV (x = 0.7) with increasing Mn content, which is consistent with semiconducting behavior. This narrowing arises from Mn³⁺/Mn⁴⁺ mixed valence, which introduces mid-gap states and enhances Co/Mn 3d–O 2p orbital hybridization within the spinel framework. In contrast, the Urbach energy increases from 0.55 eV to 0.65 eV, indicating greater structural and energetic disorder in the Mn-rich composition which is attributed to the Jahn–Teller distortions and valence heterogeneity associated with Mn³⁺. Impedance and dielectric modulus analyses confirm two distinct non-Debye relaxation processes related to grains and grain boundaries. AC conductivity is governed by the Correlated Barrier Hopping (CBH) model, with bipolaron hopping identified as the dominant conduction mechanism. The x = 0.7 sample displays significantly enhanced conductivity due to increased Mn³⁺/Mn⁴⁺ mixed valence, lattice expansion, efficient 3D electronic connectivity of the spinel lattice, and reduced interfacial resistance. These findings highlight the potential of these two spinels compounds as narrow-gap semiconductors for optoelectronic applications including visible-light photodetectors, photocatalysts, and solar absorber layers extending their utility beyond conventional battery cathodes. Full article

CuO/TiO₂ is a highly active visible-light-driven photocatalyst. The precise structural regulation of TiO₂ and the quantum dot-scale loading strategy of CuO have long been researching hotspots and challenges. This work presents an ingenious synthetic strategy, leveraging the photoinduced superhydrophilicity and dark-induced reversible hydrophobicity of TiO₂, coupled with carbon quantum dots (CQDs) as “seeds” to induce the in situ synthesis of CuO quantum dots (CuO QDs). Specifically, CuO QDs with an average diameter of 5–10 nm were successfully anchored onto TiO₂ nanowire arrays (TNWAs) with a diameter of 10–15 nm. By adjusting the dosage of “seeds” (CQDs), the loading amount of CuO QDs can be effectively controlled. Corresponding characterizations were performed, including ultraviolet-visible-near-infrared (UV-Vis-NIR spectroscopy) for optical absorption properties, photoluminescence (PL) spectroscopy for photoluminescent behavior, electron paramagnetic resonance (EPR) spectroscopy for free radical generation capability, and bisphenol A (BPA) degradation assays for photocatalytic performance. Loading 4.78 wt% CuO QDs can effectively inhibit the recombination of electron–hole pairs in TNWAs. Simultaneously, it prolongs the lifetime of charge carriers (photoelectrons) and enhances the yields of hydroxyl radicals (•OH) and superoxide radicals (•O₂⁻). The BPA degradation efficiency of the CuO QDs/TNWA composite is 2.4 times higher than that of TNWAs. Furthermore, we found that the loading of CuO QDs significantly modulates the depletion layer width of the P–N heterojunction, and the underlying mechanism has been discussed in detail. Full article

Alkaline treatment in 0.2 and 0.4 M NaOH solutions successfully generated controlled mesoporosity into ZSM-5 (Zeolite Socony Mobil-5) zeolite, resulting in average mesopore diameters of approximately 15 and 25 nm, respectively, while preserving the crystalline structure of the zeolite framework. Parent ZSM-5 and its mesoporous derivatives obtained by desilication were used to prepare (Fe species)@(zeolite matrix) composites. The synthesis was carried out by co-precipitating Fe²⁺/Fe³⁺ ions onto both parent and desilicated ZSM-5 matrices under oxygen-free conditions. Comprehensive characterization by X-ray diffraction, scanning electron microscopy, N₂ adsorption, vibrating-sample magnetometry, ⁵⁷Fe Mössbauer spectroscopy, and diffuse reflectance UV–Vis spectroscopy revealed that the degree of introduced mesoporosity dramatically influences the size, dispersion, phase composition, and oxidation state of the iron-containing nanospecies. On purely microporous ZSM-5, relatively large (~15 nm) partially oxidized magnetite nanoparticles are formed predominantly on the external surface, exhibiting superparamagnetism at room temperature (Mₛ = 11 emu/g) and a band gap of 2.12 eV. Increasing mesoporosity leads to progressively smaller and more highly dispersed iron(III) oxo/hydroxo clusters with significantly lower blocking temperatures and reduced magnetization (down to 0.7 emu/g for Fe@ZSM-5_0.4). All composites display strong visible-light absorption confirming their potential as magnetically separable visible-light-driven photocatalysts for environmental remediation. Full article

Precise control over defect structures is essential for tuning the functional properties of lithium niobate (LiNbO₃) crystals. Although the threshold effect of Hf⁴⁺ doping is well recognized, its underlying atomic-scale mechanism, especially in systems co-doped with luminescent rare earth ions, remains unclear. In this study, we combine experimental and theoretical approaches to elucidate the Hf⁴⁺ concentration-driven threshold behavior in Dy: LiNbO₃ crystals. A series of crystals with Hf⁴⁺ concentrations of 2, 4, 6, and 8 mol% were grown using the Czochralski method. Characterization through XRD and IR spectroscopy identified a threshold near 4 mol%, evidenced by an inflection in lattice constants and a pronounced blue shift of the OH⁻ absorption peak. UV–Vis–NIR absorption spectra revealed a systematic enhancement of Dy³⁺f–f transition intensities, linking the global defect structure to the local crystal field of the optical activator. First-principles calculations showed that Hf⁴⁺ ions preferentially occupy Li sites, repairing antisite Nb defects ($\mathrm{N}{\mathrm{b}}_{\mathrm{Li}}^{4+}$) below the threshold, and incorporate into Nb sites beyond it, inducing structural reorganization. Electron Localization Function analysis visualized strengthened Hf-O covalent bonding in the post-threshold regime. This work establishes a complete atomic-scale picture connecting dopant site preference, chemical bonding, and macroscopic properties, providing a foundational framework for the rational design of advanced LiNbO₃-based materials. Full article

This study aimed to elucidate the impact of Persian Gum (PG; Amygdalus scoparia Spach) on the heat-induced aggregation and interfacial behavior of whey protein isolate (WPI). To achieve this, pure WPI and mixed WPI-PG systems were subjected to thermal treatments between 25 and 85 °C, and their structural and functional changes were characterized using fluorescence spectroscopy, UV-vis absorption, turbidity and bulk viscosity measurements, interfacial shear and dilatational rheology, and foaming assessments. The presence of PG altered the aggregation pathway of WPI in a temperature-dependent manner, producing smaller, more soluble complexes with lower turbidity, particularly at higher temperatures. Both pure WPI and WPI-PG mixtures exhibited increased surface hydrophobicity upon heating; however, PG generally reduced the dilatational elastic modulus except at 85 °C, where the mixed system showed a higher modulus than WPI alone. In contrast, the interfacial shear modulus increased over time in all samples, with consistently higher values observed for WPI-PG mixtures at both 25 °C and 85 °C. Notably, three complementary methods were employed to evaluate foaming properties and interfacial behavior in this study, revealing that factors such as concentration, measurement time, and methodological approach strongly influence the observed responses, highlighting the complexity of interpreting protein-polysaccharide interactions. The ability of PG to modulate WPI unfolding and limit the formation of large aggregates during heating demonstrates a previously unreported mechanism by which PG tailors heat-induced protein network formation. These findings underscore the potential of Persian Gum as a functional polysaccharide for designing heat-treated food systems with controlled aggregation behavior and optimized interfacial performance. Full article

Flavonoids, natural organic compounds from the polyphenolic group with broad bioactive and pharmaceutical properties, are strong ligands for many metal ions. This work describes the formation of the complex between Zn(II) and morin. The synthesized compound is characterized using three analytical techniques, i.e., ¹H NMR, IR, and thermal gravimetric analysis. Importantly, the complex was successfully obtained in the form of a solid, which enables its further physicochemical and structural characterization. Physicochemical characterization of the Morin-Zn complex was performed by steady-state and time-resolved spectroscopy. The absorption spectrum of the complex contains two main bands at ca. 407–415 nm and ca. 265 nm, and the complex emits yellow-green light with higher intensity than the free ligand. In the next step, morin and zinc complex were dispersed in a PMMA (poly (methyl methacrylate)) polymer matrix, and respective thin layers were produced. The studied thin films were deposited on silicon substrates by using the spin-coating method and characterized by X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM), Spectroscopic Ellipsometry (SE), UV-VIS spectroscopy, and photoluminescence (PL). The absorption of thin layers showed, similarly to solutions, the presence of two transitions: π→π* and n→π*, and a bathochromic shift for the morin-zinc complex compared to morin. The photoluminescence of the complex thin film showed two bands, the first in the range of 380–440 nm corresponding to PMMA, and the second with a maximum at 490 nm, derived from the synthesized compound. Full article

This study explores the sol–gel synthesis, structural characterization, and photocatalytic performance of Ho³⁺-doped TiO₂ nanopowders at two dopant levels (0.5 and 2 mol%). Transparent, homogeneous gels were prepared using titanium (IV) butoxide and holmium (III) nitrate pentahydrate in ethanol, followed by drying and optional annealing at 500 °C. X-ray diffraction confirmed anatase TiO₂ as the dominant crystalline phase, with Ho incorporation suppressing crystal growth and yielding smaller crystallite sizes than undoped TiO₂. FT-IR and UV-Vis spectroscopy verified complete hydrolysis–condensation during gel formation, while diffuse reflectance spectra revealed a red-shifted absorption edge, indicating reduced band gaps. SEM analysis showed nanoscale particles with agglomeration, which intensified after annealing. Photocatalytic activity was tested under UV irradiation using Crystal Violet (anionic dye) and Carmoisine (cationic dye). Annealed Ho-doped powders exhibited markedly higher degradation rates, with the 2 mol% sample achieving the greatest efficiency, particularly against Crystal Violet. These findings demonstrate that Ho³⁺ doping enhances TiO₂’s UV-driven photocatalytic activity by tailoring its structural and optical properties. Full article

Azulene-based chromophores are of growing interest due to their unique electronic structures and potential applications as pH-responsive optical materials. In this study, a series of azulene–1,3,6,8-tetraazapyrene (TAP) triads were successfully synthesized and characterized to systematically explore how connectivity between the TAP and azulene units influences their optical and redox properties. UV-Vis absorption spectroscopy and cyclic voltammetry measurements clearly show that the electronic properties depend heavily on the connectivity pattern, as the effective π-conjugation and molecular planarity vary considerably in triads. Remarkably, triads A₂₂ and A₂₆, in which the TAP core is directly connected through the electron-rich five-membered ring, exhibit enhanced π-conjugation and pronounced color changes upon protonation. In contrast, A₆₆, linked via the electron-deficient seven-membered ring, reveals weaker π-conjugation and less pronounced pH-responsiveness. These experimental findings are further supported by DFT calculations. This comprehensive structure–property relationship study provides valuable insights for the rational design of advanced optoelectronic and stimuli-responsive materials. Full article

Copper(II) complexes with 2,2′:6′,2″-terpyridines (terpys) are promising candidates for anticancer therapy and catalysis. Their structural and optical properties can be tuned by modifying the terpy backbone, including a substitution at the 4′ position or the replacement of peripheral pyridines with thiazole rings, forming 2,6-bis(thiazol-2-yl)pyridines (dtpys). dtpy-based copper(II) complexes (Cu-dtpys), despite their applicative potential, are barely characterized in the literature. Here, the series of Cu-dtpys (1–13) was synthesised and characterized by FT-IR, HRMS, X-ray diffraction, and UV-Vis spectroscopy. Their structural and optical features were compared to previously studied Cu-dtpys (14–24) and their terpy analogues (Cu-terpy-1 ÷ Cu-terpy-24). The detailed analysis revealed that five-coordinate Cu-dtpys complexes adopt a square pyramidal geometry comparable to that of Cu-terpys complexes but with markedly smaller deviations from the ideal square pyramid. Compared with Cu-terpys, Cu–Cl_apical bonds are shorter, while Cu–N_central bonds are elongated. The Cu-dtpy systems usually present the longest wavelength of the lowest energy absorption band in comparison to Cuterpys. The analysis of the relationship between Hammett’s constant and wavelength of absorption indicates that the most promising from the photophysical point of view are compounds 4–6, 10–13, 16–17, and 22, for which a newly formed intraligand charge transfer band is formed. Full article