Study of luminescence properties of dysprosium‐doped CaAl12O19 phosphor for white light‐emitting diodes

Dy³⁺‐doped CaAl₁₂O₁₉ phosphors were synthesized utilizing a combustion method. Crystal structure and morphological examinations were performed respectively using X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques to identify the phase and morphology of the synthesized samples. Fourier transform infrared spectroscopy (FTIR) estimations were carried out using the KBr method. Photoluminescence properties (excitation and emission) were recorded at room temperature. CaAl₁₂O₁₉:Dy³⁺ phosphor showed two emission peaks respectively under a 350‐nm excitation wavelength, centered at 477 nm and 573 nm. Dipole–dipole interaction via nonradiative energy shifting has been considered as the major cause of concentration quenching when Dy³⁺ concentration was more than 3 mol%. The CIE chromaticity coordinates positioned at (0.3185, 0.3580) for the CaAl₁₂O₁₉:0.03Dy³⁺ phosphor had a correlated color temperature (CCT) of 6057 K, which is situated in the cool white area. Existing results point out that the CaAl₁₂O₁₉:0.03Dy³⁺ phosphor could be a favorable candidate for use in white light‐emitting diodes (WLEDs).     

Exogenous Nitric Oxide Delays Ripening and Maintains Postharvest Quality of Pointed Gourd During Storage

This study was aimed to assess the effect of nitric oxide (NO; 1 and 2 mM) on shelf life and quality of pointed gourd. Fruits were stored at 12 °C for 14 days with simulated ambient storage for 3 days (7 + 3 and 14 + 3) to mimic the marketing period. NO treatment significantly improved the postharvest shelf life as compared to control samples. The fruits underwent to the application of NO (2 mM) effectively maintained the chlorophyll, phenolics, antioxidant activity and membrane integrity. It suppressed weight loss, yellow color development, lignin formation, and electrolytic leakage. Activity of enzymes (PAL and LOX) was also influenced positively by NO application. Postharvest treatment of NO (2 mM) could be suggested as an eco-safe and effective technique for enhancing the shelf life without hampering quality of pointed gourd.

     

A statistical approach to the morphological variability of Androsace himalaica (Knuth) Handel-Mazetti (Primulaceae) in Pakistan

The species Androsace himalaica is found lo comprise two spatially separate populations. Statistical analysis of bract and hair length show that the tax in question can be distinguished morphologically and recognized as subspecies.