Luminous LaAlO3 :Dy3+ perovskite nanomaterials: Synthesis, structural and luminescent characteristics for WLEDs

Single-phase perovskite LaAlO₃ :Dy³⁺ phosphor was synthesized via gel-combustion method at 600 °C utilization Hexamethylenetetramine (HMT) as a fuel. Further calcination of the samples was carried out (800 and 1000 °C) to investigate the resultant effect on the crystalline and luminescence behaviour. The crystal structure having cubic unit cell (space group Pm3̅m) was examined via Rietveld refinement using X-ray diffraction (XRD) data. Additionally, Debye-Scherrer's and Williamson-Hall equations were applied to determine other structural features. The particle size and morphology of phosphors were evaluated using Transmission electron microscope (TEM). Diffraction measurements were supported by the various metal-oxygen vibration modes studied with the help of Fourier transform infrared (FTIR) spectroscopy. Energy dispersive X-ray analysis (EDX) verified the chemical composition of synthesized sample. Luminescence spectra of LaAlO₃ :Dy³⁺ phosphors exhibited intense bands for ⁴ F_9/2 → ⁶ H_15/2 (482 nm, bluish region) and ⁴ F_9/2 → ⁶ H_13/2 (574 nm, yellowish region) transitions. Commission Internationale de L'Eclairage (CIE) and Correlated Color Temperature (CCT) data confirmed cool-white emission of samples under UV-excitation. The interesting and advantageous luminescence characteristics of LaAlO₃ :Dy³⁺ phosphors make them potential materials for WLEDs.

Upconversion Yb3+/Er3+:La2Ti2O7 phosphors for solid-state lighting and optical thermometry

The solid-state reaction was employed as a suitable method to produce orthorhombic Yb³⁺/Er³⁺ co-doped La₂Ti₂O₇ phosphors. The pump power and temperature dependencies of spectra of the Yb³⁺/Er³⁺ co-doped La₂Ti₂O₇ were studied for color tunability and optical thermometry. The pump power significantly affected the color coordinates of the phosphors. The upconversion green light transformed to the broad white light at higher pump power. A two-photon transition was proposed to explain the upconversion energy transfer process. The fluorescence intensity ratio technique was used to calculate the optical temperature sensor sensitivities. The ΔE energy difference obtained from the intensity ratios of the thermally coupled ²H_11/2 and ⁴I_15/2 energy levels of Er³⁺ are 763.64 ± 76.62 cm^-1, 777.77 ± 44.62 cm^-1, 640.71 ± 137.39 cm^-1 for La_1.95Yb_0.04Er_0.01Ti₂O₇, La_1.94Yb_0.04Er_0.02Ti₂O₇, and La_1.93Yb_0.04Er_0.03Ti₂O₇, respectively. Absolute temperature sensitivities of the phosphors decreased with increasing Er³⁺ concentration. The maximum absolute sensitivity was determined to be 0.51x10^-2 K^-1 at 553 K for La_1.95Yb_0.04Er_0.01Ti₂O₇, 0.64x10^-2 K^-1 at 571 K for La_1.94Yb_0.04Er_0.02Ti₂O₇, and 0.38x10^-2 K^-1 at 457 K for La_1.93Yb_0.04Er_0.03Ti₂O₇.

Environmental friendly sustainable application of plant-based mordants for cotton dyeing using Arjun bark-based natural colorant

Ecofriendly exploration of Arjun bark (Terminalia arjuna) is a herbal natural colorant for cotton dyeing. This is because the demand for natural dyes has been increased worldwide due to their therapeutic usage and other food, textiles, agriculture, engineering, and medical applications. Therefore, this study has been carried out due to the isolation of colorant from Arjun bark in an acidified methanolic medium after exposure to ultrasonic rays up to 60 min. Additionally, using bio-mordants, it has been found that the application of 10% of Zeera (Cuminum cyminum) extract as meta-bio-mordant, 3% of Ilaichi (Elettaria cardamomum) extract as meta-bio-mordant, and10 % of Harmal (Peganum harmala) and Neem (Azadirachta indica) extract as meta-bio-mordants has given excellent color strength. These bio-mordants have not only made the coloration process more eco-friendly, viable, and greener, but also improved color strength with various tonal effects from red to reddish brown shades. Thus, it has been found that ultrasonic treatment as an environment-friendly tool has not only enhanced the color strength of natural colorant isolated from Arjun bark onto the cotton fabric under mild conditions.

Color compatibility between dental structures and three different types of ceramic systems

BACKGROUND

To assess color compatibility between dental structures (human enamel and dentine) and three different types of ceramic systems.

METHODS

Samples (1 and 2 mm-thick) of extracted tooth (containing dentine and enamel areas) and three ceramic systems with different shades and opacities (HT-High Translucent, T-Translucent) were prepared for this study: Vita Suprinity-VS (HT, T; A1, A2, A3, A3.5, B2, C2, D2) (Vita Zahnfabrik); Vita Enamic-VE (HT, T; 1M1, 1M2, 2M2, 3M2) (Vita Zahnfabrik) and Noritake Super Porcelain EX-3-NKT (A1, A2, A3, A3.5, B2, C2, D2) (Kuraray Noritake Dental). Reflectance measurements of all samples were performed over black backgrounds using a non-contact spectroradiometer (SpectraScan PR-670, Photo Research) under a CIE 45°/0° geometry. CIE L*a*b* color parameters were measured and CIELAB/CIEDE2000 color differences (ΔE₀₀/ΔE^*_ab) and corresponding Coverage Error (CE) of ceramic system for dentine or enamel samples were calculated. Color data was analyzed using one-way ANOVA and post-hoc multiple comparisons tests. CE values were interpreted by comparisons with available 50:50% acceptability color threshold (AT) for dentistry.

RESULTS

Statistically significant differences in lightness were found among all ceramic systems and human dentine (p < 0.001), while no significant differences were registered between enamel and VSHT, T and VEHT. 1 mm dentine showed no statistical differences with VST and VSHT for a* coordinate, while 2 mm dentine showed no significant differences (p > 0.05) with VEHT. Thin samples (1 mm) of dentine and enamel showed significant statistical differences (p < 0.05) for b* coordinate with less translucent materials (NKT, VET and VST). For dentine samples, none of the ceramic materials provided a CE lower than AT. VSHT provided the best CE for 1 mm-thick (CE₀₀ = 1.7, CE_ab = 1.9) and for 2 mm-thick (CE₀₀ = 2.3; CE_ab = 2.5) enamel samples.

CONCLUSIONS

Color coordinates of evaluated esthetic ceramic systems were statistically different from those of human dentine in almost all cases. The evaluated ZrO₂ lithium silicate glass-ceramic (VS), with its two levels of translucency, provided lower CE values with human enamel samples while conventional feldspathic ceramic (NKT) and hybrid ceramic systems (VE) demonstrated a better color compatibility with dentin samples.

Surface modification of cotton fabrics for antibacterial application by coating with AgNPs-alginate composite

In recent years nano-sized particles have been focused on bacteriostasis. We investigated antimicrobial activities by applying AgNPs-alginate composite on cotton fabric, using a simple one-step rapid synthetic route by reduction of silver nitrate using alkali hydrolyzed alginate solution which acts as both reducing and capping agent. FTIR spectra, color coordinates, silver content, silver release percent and SEM images of treated fabric samples confirmed the successful physical deposition of AgNPs-alginate composite on the fabric. The treated fabrics demonstrated an excellent antibacterial activity against the tested bacteria, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. A slight decrease in the antibacterial feature of the cotton fabrics was observed after successive washings. However, an efficient antibacterial activity still remained on the fabrics.

Characterization of nanosilver coated cotton fabrics and evaluation of its antibacterial efficacy

An ecological and viable method for coating of cotton fabrics with silver nanoparticles (AgNPs) has been carried out. Nanocoated fabrics were characterized by scanning electron microscopy, energy dispersive X-ray and infrared spectroscopy. Color coordinates and silver release were assessed and the impact of repeated washings was evaluated. Silver contents were measured using atomic absorption spectroscopy and were 109.07 and 97.85 mg/kg for the fabrics treated with 100 ppm of AgNPs in presence and absence of binder respectively. Antibacterial activities of the cotton fabrics coated by AgNPs were evaluated qualitatively and quantatively, and the results explored that, regardless of the concentration of AgNPs used, the biocidability was always higher without washing. However, for all coated fabrics, a sufficient antibacterial action still observed after 20 washings. The results revealed that valuable antibacterial textiles which are required in different medical textile fields could be successfully produced.

Spectroscopic investigation and optical characterization of Eu3+ ions in K-Nb-Si glasses

This paper reports on the effect of concentration of Eu(3+) ions in K2O-Nb2O5-SiO2-Eu2O3 (KNbSiEu) glasses prepared by the melt quenching technique. By using the Judd-Ofelt (JO) theory, the intensity parameters Ωλ (λ=2, 4, 6) have been determined from the absorption and emission spectra of Eu(3+) ions under different constraints. The radiative properties of some of the excited states of Eu(3+) ions have been calculated. The decay curves of (5)D0 level exhibited single exponential for all the Eu(3+) ions concentrations. From these results, it is suggested that the strong red emission at 616 nm corresponding to the (5)D0→(7)F2 transition could be used for the development of optical display devices.