Search Results (239)

With the increasing market demand for spinels of various colors, purple spinel—long regarded as a symbol of nobility—has attracted growing attention. In this study, pinkish-purple to purple spinels from the Mogok region of Myanmar were systematically examined using conventional gemological, spectroscopic, and chemical analytical techniques. Raman analysis reveals that these spinels commonly contain octahedral inclusions composed of calcite, dolomite, magnesite, and graphite. Chemically, the samples are primarily magnesia-alumina spinels. Color variation is influenced by trace elements: increasing Cr and V contents enhance the red hue, while higher Fe concentrations intensify the purple tone. UV–Vis spectra show that Cr³⁺ and V³⁺ jointly contribute to absorptions at 388 nm and 548 nm, with Fe²⁺ and Fe³⁺ responsible for the bands at 371 nm and 457 nm, respectively, together controlling the pink-to-purple color variation. Most samples display four Cr³⁺-related peaks near 700 nm; however, these are absent in deeply purple spinels. In contrast, light pink spinels show weaker absorption at 371 nm and 457 nm, attributed to Fe²⁺ and Fe³⁺. Fluorescence spectra confirm characteristic Cr³⁺ emission bands at 673 nm, 684 nm, 696 nm, 706 nm, and 716 nm, indicating a strong crystal field environment. Raman spectra have peaks mainly around 312 cm⁻¹, 406 cm⁻¹, 665 cm⁻¹, and 768 cm⁻¹. The peaks of the infrared spectrum mainly appear around 840 cm⁻¹, 729 cm⁻¹, 587 cm⁻¹, 545 cm⁻¹, and 473 cm⁻¹. Full article

Accumulation of ferrous sulfate residue (FSR) not only occupies land but also results in environmental pollution and waste of iron resource; thus, recycling of iron from FSR has attracted widespread concern. To this end, this article shows fabrication and system analysis of hematite (HM) nanoparticles from FSR via microwave-assisted reduction technology. Physicochemical properties of HM nanoparticles were investigated by multiple analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet visible (UV-Vis) spectrum, vibrating sample magnetometer (VSM), and the Brunauer–Emmett–Teller (BET) method. Analytic results indicated that the special surface area, pore volume, and pore size of HM nanoparticles with the average particle size of 45 nm were evaluated to be ca. 20.999 m²/g, 0.111 cm³/g, and 0.892 nm, respectively. Magnetization curve indicated that saturation magnetization Ms for as-synthesized HM nanoparticles was calculated to be approximately 1.71 emu/g and revealed weakly ferromagnetic features at room temperature. In addition, HM nanoparticles exhibited noticeable light absorption performance for potential applications in many fields such as electronics, optics, and catalysis. Hence, synthesis of HM nanoparticles via microwave-assisted reduction technology provides an effective way for utilizing FSR and easing environmental burden. Full article

The purpose of current study was the green synthesis of bioactive silver nanoparticles (AgNPs) using Brevibacillus sp. MAHUQ-41 and the exploration of their role in controlling drug-resistant bacterial pathogens Listeria monocytogenes and Yersinia enterocolitica. The culture supernatant of strain MAHUQ-41 was employed for a simple and eco-friendly synthesis of biofunctional silver nanoparticles (AgNPs). The resulting nanoparticles were analyzed using several techniques, including UV–Visible spectroscopy, XRD, FE-TEM, FTIR, and DLS. The UV–Vis spectral analysis of the AgNPs synthesized via Brevibacillus sp. MAHUQ-41 revealed a prominent absorption peak at 400 nm. FE-TEM results confirmed spherical-shaped 15–60 nm sized nanoparticles. XRD results indicated that the synthesized AgNPs were crystalline in nature. The FTIR spectrum determined various functional groups on the surface of synthesized nanoparticles. Potent antibacterial properties were observed in green-synthesized AgNPs against tested pathogens. The MIC value of extracellular synthesized AgNPs for both pathogenic bacteria was 6.2 µg/mL, and the MBCs were 25.0 µg/mL and 12.5 µg/mL for L. monocytogenes and Y. enterocolitica, respectively. Treatment by synthesized AgNPs resulted in morphological alterations and structural damages in both L. monocytogenes and Y. enterocolitica. These alterations can interfere with regular cellular activities, potentially resulting in cell death. This study is the first to report the antimicrobial properties of silver nanoparticles synthesized using Brevibacillus sp. MAHUQ-41. The findings obtained in the present study supported the role of Brevibacillus sp. MAHUQ-41-mediated synthesized AgNPs in controlling drug-resistant bacterial pathogens L. monocytogenes and Y. enterocolitica. Full article

Using optical spectroscopy methods including absorption in the UV-VIS, FTIR, Raman, and fluorescence, the spectra of 25 different Baltic amber samples were measured, and the ability of each method to distinguish between thermally modified and naturally aged material was analyzed. The natural ambers studied are characterized by a wide range of spectral properties: the position of the transmission edge in the UV-VIS spectra, the absorbance ratios of the C-H and C=O groups in the IR spectra, a difference of approximately 20% in the fluorescence intensity level, and differences in the band ratios in the C=C and C-H bonds in the Raman spectrum. Spectral studies were carried out on samples of natural and thermally modified amber at temperatures of 100, 150, and 200 °C for 2–8 h. Drastic changes occur at temperatures above 150 °C: the color changes to dark brown, the UV-VIS transmission edge shifts, the absorbance of the C=O group increases, the absorbance intensity of the C=C bond decreases, and fluorescence disappears. In some special cases, fluorescence methods allow for the unambiguous distinction of amber from different geographical regions (e.g., Baltic and Dominican). Spectroscopic methods can distinguish natural amber from thermally modified amber only for large changes in the spectrum at temperatures of 150–200; for smaller changes, the differences between individual samples of natural amber may be greater than in the case of thermal modification. Full article

IR-780 is a heptamethine cyanine dye that exhibits strong absorbance in the near-infrared region. Herein, we report IR-780 dye as a dual sensor for chromogenic cyanide detection and azide’s fluorogenic sensing in acetonitrile. Cyanide and hydroxide cause instant, dramatic color changes in the dye solution from green to yellow and dramatic spectral changes in the UV-Vis spectrum. The interaction of cyanide and hydroxide with the dye caused a dramatic decrease in the intensity of the strong absorption band at 780 nm and a concomitant band appearance at 435 nm. Other monovalent ions, including fluoride, chloride, bromide, iodide, dihydrogen phosphate, thiocyanate, acetate, and dihydrogen arsenate, caused no significant color or spectral changes. UV-Vis studies showed that the IR-780 dye is sensitive and selective to both ions. The detection limits for cyanide and azide are 0.39 µM and 0.50 µM, respectively. Interestingly, the IR-780 dye exhibited strong fluorescence at 535nm upon interaction with azide, while its initial emission at 809 nm was quenched. Both UV-Vis and fluorescence spectroscopy accomplished the detection of cyanide and azide using IR-780. Furthermore, the sensor’s effectiveness in fluorescence imaging of intracellular CN⁻ ions is demonstrated in live HeLa cells. Full article

Organic violet-blue fluorescent materials have garnered significant interest for a broad spectrum of applications. A series of triazine-based molecules, that is, 2,4,6-tri(9H-carbazol-9-yl)-1,3,5-triazine (TCZT), 2,4,6-tri(1H-indol-1-yl)-1,3,5-triazine (TIDT), and 2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,3,5-triazine (TDBCZT), exhibiting violet-blue emission were synthesized via a catalyst-free aromatic nucleophilic substitution reaction. These compounds possess a non-planar and twisted structure with favorable charge-transfer characteristics, demonstrating excellent thermal stability (decomposition temperatures of 370 °C, 384 °C, and 230 °C, respectively). Cyclic voltammetry analysis, combined with time-dependent density functional theory (TD-DFT) calculations at the B3LYP/6-31G(d) level, offered detailed insights into their electronic structures and electrochemical properties. Optical properties were systematically characterized using Ultraviolet–visible (UV–Vis) absorption and photoluminescence (PL) spectroscopy. The compounds exhibited violet-blue luminescence with emission peaks located at 397 nm, 383 nm, and 402 nm in toluene, respectively. In their respective films, the compounds exhibited varying degrees of spectral shifts, with emission peaks at 408 nm, 381 nm, and 369 nm. Moreover, the CIE (Commission Internationale de l’Éclairage) coordinates of TIDT in toluene were (0.155, 0.067), indicative of excellent violet purity. These compounds demonstrated significant two-photon absorption (TPA) properties, with cross-sections of 4.6 GM, 15.3 GM, and 7.4 GM, respectively. Notably, they exhibited large molar absorptivities and substantial photoluminescence quantum yields (PLQYs), suggesting their potential for practical applications as violet-blue fluorescent materials. Full article

In recent years, domestic research on the ion substitution behavior and chromaticity of the mineral composition of “Ya’an Green” remains insufficient, while there is almost no relevant research on “Ya’an Green” abroad. In this study, X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), infrared spectroscopy (IR), ultraviolet–visible spectroscopy (UV-Vis), and colorimetry were employed. The results indicate that the green and yellow matrices of “Ya’an Green” are primarily composed of muscovite, with rutile also present in the yellow matrix. In contrast, the white–green samples are mainly composed of quartz, with muscovite as a secondary mineral. Additionally, it was observed that the (004) crystal plane of muscovite exhibits a peak shift to lower 2θ angles, attributed to the substitution of Al³⁺ by ions with larger radii, such as Ba²⁺, Cr³⁺, and Fe²⁺, leading to an increase in unit cell parameters and a consequent shift in the peak to lower wavenumbers. The main elements of “Ya’an Green” are Al, Si, and K, with minor elements including Na, Fe, and Cr. Furthermore, Mg²⁺, Ca²⁺, Ti⁴⁺, Cr³⁺, and Fe²⁺ in the samples can substitute for Al³⁺ through isomorphic substitution. The infrared spectrum of muscovite in the ‘Ya’an Green’ sample shows three typical absorption peaks, 422 cm⁻¹ and 513 cm⁻¹ caused by Si-O bending vibration, 697 cm⁻¹ and 837 cm⁻¹ caused by Si-O-Al vibration, 948 cm⁻¹ caused by O-H bending vibration, and 3647 cm⁻¹ caused by O-H stretching vibration. The peak at 837 cm⁻¹ exhibits varying degrees of shift due to the substitution of Al³⁺ by ions with larger radii. The ultraviolet–visible spectra display two broad absorption bands at 422 nm and 615 nm, which are caused by Cr³⁺ transition, indicating that Cr is the chromogenic element responsible for the green color. A correlation was observed between the Cr³⁺ content and the hue angle h in “Ya’an Green” samples: the higher the Cr³⁺ content, the closer the hue angle is to 136^°, resulting in a darker green color, while lower Cr³⁺ content leads to a deviation from the dark green hue. This study establishes for the first time the correlation between the mineral composition of ‘Ya’an Green’ and its chromatic parameters and explores the linear relationship between its color and the number of color-causing elements and elemental substitution, which provide data support and theoretical models for the study of the color of seal stones. Full article

Two modifications of ZnMoO₄ were successfully obtained by mechanochemical treatment with two milling speeds applied at 500 and 850 rpm. The phase formation was monitored by XRD analysis. The metastable monoclinic ß-ZnMoO₄ was directly synthesized at room temperature using the higher milling speed of 850 rpm. The thermodynamically stable triclinic α-ZnMoO₄ was obtained by combining heat treatment t 600 °C and ball milling at the lower milling speed of 500 rpm. The IR spectra contain typical vibration bands and confirm the formation of both ZnMoO₄ polymorphs. UV-Vis absorption and photoluminescence (PL) spectroscopy are used to study the optical properties of the as-prepared samples. The calculated optical band gaps for α- and ß-ZnMoO₄ are 4.09 and 3.02 eV. The photoluminescence emission spectrum of both samples shows peaks with different maximum intensity at 615 and 403 nm for α and ß phase, respectively. CIE co-ordinates are located in the orange and blue range of the color diagram. Full article

This study explores the factors influencing the body color of kyanites and the chromogenic mechanism from a novel perspective of gemstone chromaticity. The gemological properties of 20 samples from Coronel Murta, Minas Gerais, Brazil, were characterized using a color spectrophotometer, Fourier-transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV–Vis). The results indicate that the Fe content in kyanites significantly affects the hue angle h°, chroma C*, and colorimetric coordinate b*, with higher Fe concentrations resulting in a deeper blue hue. Additionally, the Cr and Ti contents influence the body color of kyanites. As the Ti content increases, the lightness L* of kyanites decreases. In the UV–Vis spectrum, the lightness L* of natural samples is significantly related to the wavelength corresponding to the first peak in the orange-red region, and the absorption band at 600 nm also influences the hue angle h°. Full article

The synthesis of silver nanoparticles using phytochemical reducing agents is the most preferred technique because of its low cost and environmental friendliness. Consequently, there are several reports published on the synthesis of silver nanoparticles using extracts from leaves, barks, roots, and fruit peels. However, information on the use of fruit extracts for the synthesis of silver nanoparticles is limited. Thus, the green synthesis of silver nanoparticles (HAF-AgNPs) using phytochemicals extracted from Harrisonia abyssinica fruit (HAF) is reported in the current study. The silver nanoparticles were synthesized through chemical precipitation and characterized using UV-Vis spectrophotometry, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and X-ray diffraction analysis (XRD). The findings showed that fabricated HAF-AgNPs were crystalline and spherical, and exhibited a strong UV-absorption band at 420 nm. The appearance of a peak at 3 keV in the EDX spectrum indicated metallic silver atoms in the fabricated nanoparticles. The fabricated nanoparticles exhibited antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains. The antibacterial activity was stronger for Staphylococcus aureus (MIC = 5 µg/mL) compared to Escherichia coli (MIC = 10 µg/mL). The preliminary findings from the current study suggest that the nanoparticles prepared from the extract could serve as a potential antibacterial agent against Gram-positive and Gram-negative bacteria. Full article

Extensive research has already been conducted on sapphires, yet there remains a notable absence of methods available to identify the provenance of pink-purple sapphires, particularly those originating from Vietnam and Madagascar. This study examined pink-purple sapphires from Vietnam and Madagascar by conducting basic gemological tests, microscopic observations, infrared spectroscopy, Raman spectroscopy, UV–Vis–NIR spectroscopy, and LA ICP MS, while also drawing comparisons with pink-red corundum from other locations. In appearance, the Vietnamese samples have a foggy appearance and orange iridescence, while the Madagascan samples show a relatively strong purple hue. The color origin analysis reveals that the absorption peaks of the ultraviolet spectrum caused by Cr³⁺ in the yellow-green and blue-purple regions account for the pink color of the Vietnamese and Madagascan samples. The lower UV wavelength position of the two main peaks in the Madagascan samples, as compared to the Vietnamese ones, indicates that Fe³⁺ d–d transitions, as well as transitions between Fe²⁺—Ti⁴⁺ and Fe³⁺—Ti³⁺ ions, enhance blue light transmission and cause the samples to tend towards a purple hue. Regarding inclusions, the Vietnamese samples are characterized by white and blue bands, cloudy inclusions, and extensive yellow-orange staining, whereby the cloudy inclusions give them their special appearance, and their calcite and apatite inclusions indicate that they come from marble-type deposits. The presence of many small-grained zircon formations, especially clusters, in the Madagascan samples indicates that they come from alkaline basalt. Chemical analysis confirmed the origin of the samples from the two locations. Compared with the pink-red corundum of the same marble type (Myanmar and Yunnan, China), the Vietnamese samples have lower V, Mg, and Ga contents and a higher Fe content. Compared with the pink-red corundum of the high-iron type (Thailand, Cambodia, and Tanzania), the Madagascan samples have lower Fe and higher Ga contents overall. This study possesses considerable significance in tracing and identifying the origin of pink-purple sapphires. Full article

Plant-based preparation of nanomaterials has become a recent global research focus due to its cost-effectiveness, sustainability, and environmentally friendly approach. This study aims to synthesize silver nanoparticles (HAgNPs) using red lentil husk aqueous extract (LHE) and to assess its antibacterial activity. Synthesized HAgNPs were analyzed by ultraviolet-visible spectroscopy (UV-vis.), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX) analysis. The antibacterial efficacy of synthesized HAgNPs was investigated against Staphylococcus aureus (ATCC No: 25923), Enterococcus faecalis (ATCC No: 29212), Klebsiella pneumoniae (ATCC No: 700603), and Shigella sonnei (ATCC No: 25931) at varying concentrations via the agar well diffusion scheme. The UV-vis absorption maximum observed around 420 nm directed the creation of HAgNPs. The shifting of peak positions in the FTIR spectrum of the synthesized HAgNPs compared to the FTIR spectrum peak positions of LHE indicated the involvement of biomolecules present in LHE in reducing silver ions to metallic silver. XRD examination of the prepared sample suggested face-centred cubic crystals of the HAgNPs. The average particle dimension of prepared HAgNPs was 8.9 nm by the Debye–Scherer equation. An FESEM examination of the synthesized HAgNPs revealed spherical morphology, while the EDX study showed that silver (Ag⁰) was the predominant component, comprising 62.3% by weight. The synthesized HAgNPs displayed a higher DPPH radical scavenging capacity (IC₅₀ = 38.87 ± 3.52 µg/mL) than that of LHE (IC₅₀ = 65.27 ± 1.17 µg/mL). The prepared HAgNPs exhibited significant antibacterial efficacy against some human pathogen bacteria at lower concentrations. Hence, the present study highlights an environmentally benevolent and economical synthetic approach to the preparation of HAgNPs and its potential utility for the production of biomedical products. Full article

Vibrational circular dichroism (VCD) enhancement by low-lying electronic states (LLESs) is a fascinating phenomenon, but accounting for it theoretically remains a challenge despite significant research efforts over the past 20 years. In this article, we synthesized two transition metal complexes using the tetradentate Schiff base ligands (R,R)- and (S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine with Co(II) and Mn(III), referred to as Co(II)-salen-chxn and Mn(III)-Cl-salen-chxn, respectively. Their stereochemical properties were explored through a combined experimental chiroptical spectroscopic and theoretical approach, with a focus on Co(II)-salen-chxn. Extensive conformational searches in CDCl₃ for both high- and low-spin states were carried out and the associated infrared (IR), VCD, ultraviolet-visible (UV-Vis) absorption, and electronic circular dichroism (ECD) spectra were simulated. A good agreement between experimental and simulated data was achieved for IR, VCD, UV-Vis, and ECD, except in the case of VCD of Co(II)-salen-chxn which exhibits significant intensity enhancement and monosignate VCD bands, attributed to the LLESs. Interestingly, detailed comparisons with Mn(III)-Cl-salen-chxn and previously reported Ni(II)-salen-chxn and Cu(II)-salen-chxn complexes suggest that the enhancement factor is predicted by the current density functional theory simulations. However, the monosignate signatures observed in the experimental Co(II) VCD spectrum were not captured theoretically. Based on the experiment and theoretical VCD and ECD comparison, it is tentatively suggested that Co(II)-salen-chxn exists in both low- and high-spin states, with the former being dominant, while Mn(III)-Cl-salen-chxn in the high-spin state. The study indicates that VCD enhancement by LLESs is at least partially captured by the existing theoretical simulation, while the symmetry consideration in vibronic coupling provides further insight into the mechanisms behind the VCD sign-flip. Full article

Ultraviolet-visible (UV–Vis) absorption spectroscopy for in situ water quality sensing has garnered increasing attention. However, the selection of the characteristic wavelengths for water quality indicators has been underexplored in existing studies, resulting in surrogate monitoring models with low accuracy and high complexity. This research used field data from the Maozhou River in Shenzhen. The accuracy of the surrogate model based on the wavelength selection method is 134.8%, 52.5%, and 13.5% improvement in accuracy compared to the single wavelength method, the PCA method, and the full spectrum method, respectively. We investigate seven characteristic wavelength optimisation algorithms and five machine learning models for surrogate monitoring of five water quality indicators: TOC, BOD₅, COD, TN, and NO₃-N. The results indicate that the competitive adaptive reweighted sampling (CARS) method for wavelength selection, combined with ridge regression as a surrogate monitoring model, achieved the best performance in this study. The determination coefficient (R²) of the five water quality indicators were 0.80, 0.64, 0.82, 0.97, and 0.96, respectively. The study shows that for watersheds with relatively stable water chemical components, there is no need to use overly complex nonlinear models, and the regression model with characteristic wavelength selection can achieve good prediction results. This study provides detailed technical information on river water quality spectral surrogate monitoring, offering an important practice reference. Full article

Sulfonated indocyanines 3 and 5 (sCy3, sCy5) are widely used to label biomolecules. Their high molar absorption coefficients and lack of spectral overlap with biopolymers make them ideal as linker components for rapid assessment of bioconjugate stoichiometry. We recently found that the determination of the sCy3:sCy5 molar ratio in a conjugate from its optical absorption spectrum is not straightforward, as the sCy3:sCy5 absorbance ratio at the maxima tends to be larger than expected. In this work, we have investigated this phenomenon in detail by studying the spectral properties of a series of sCy3-sCy5 conjugates in which the dyes are separated by linkers of various lengths, including DNA duplexes. It was found that when sCy3 and sCy5 are located in close proximity, they consistently exhibit an “abnormal” absorbance ratio. However, when the two dyes are separated by long rigid DNA-based spacers, the absorbance ratio becomes consistent with their individual molar absorption coefficients. This phenomenon should be taken into account when assessing the molar ratio of the dyes by UV-Vis spectroscopy. Full article