Sr2+doped CsPbBrI2perovskite nanocrystals coated with ZrO2for applications as white LEDs.

Perovskite nanocrystals (NCs) feature adjustable bandgap, wide absorption range, and great color purity for robust perovskite optoelectronic applications. Nevertheless, the absence of lasting stability under continues energization, is still a major hurdle to the widespread use of NCs in commercial applications. In particular, the reactivity of red-emitting perovskites to environmental surroundings is more sensitive than that of their green counterparts. Here, we present a simple synthesis of ultrathin ZrO2coated, Sr2+doped CsPbBrI2NCs. Introducing divalent Sr2+may significantly eliminate Pb° surface traps, whereas ZrO2encapsulation greatly improves environmental stability. The photoluminescence quantum yield of the Sr2+-doped CsPbBrI2/ZrO2NCs was increased from 50.2% to 87.2% as a direct consequence of the efficient elimination of Pb° surface defects. Moreover, the thickness of the ZrO2thin coating gives remarkable heat resistance and improved water stability. Combining CsPbSr0.3BrI2/ZrO2NCs in a white light emitting diode (LED) with an excellent optical efficiency (100.08 lm W-1), high and a broad gamut 141% (NTSC) standard. This work offers a potential method to suppress Pb° traps by doping with Sr2+and improves the performance of perovskite NCs by ultrathin coating structured ZrO2, consequently enabling their applicability in commercial optical displays.

Phytochemical screening and enzymatic and antioxidant activities of Erythrina suberosa (Roxb) bark.

BACKGROUND: This study aimed to evaluate the phytochemicals screening of Erythrina suberosa (Roxb) bark and to analyze the enzymatic activities of its various organic fractions. MATERIALS AND METHODS: Crude methanolic fraction of E. suberosa (Roxb) bark and its respective fractions were screened for the presence of different phytochemicals with different reagents. On the basis of increasing order of polarity, different organic solvents were used to obtain different fractions. Enzymatic studies were performed on crude methanolic extract of the plant. All the assays were performed under standard in vitro conditions. RESULTS: The phytochemical analysis shows the presence of alkaloids, phenols, triterpenoids, phytosterols, and flavonoids. Phenolic compounds and flavonoids are the major constituents of the plant. In anticholinesterase assay, the percent inhibition of standard drug (eserine) was 91.27 ± 1.17 and the half maximal inhibitory concentration (IC50) was 0.04 ± 0.0001. For α-glucosidase inhibition, the IC50 value for Dichloromethane fraction was 8.45 ± 0.13, for Methanol fraction it was 64.24 ± 0.15, and for aqueous fraction it was 42.62 ± 0.17 as compared with standard IC50 that is 37.42 (acarbose). Furthermore, results show that all fractions have potential against anti-urease enzyme, but DCM fraction of crude aqueous extract has significant IC50 value (45.26 ± 0.13) than other fractions. CONCLUSION: Keeping in view all the results, it is evident that the plant can be used in future for formulating effective drugs against many ailments. Secondary metabolites and their derivatives possess different biological activities, for example, .g. flavonoids in cancer, asthma, and Alzheimer. Furthermore, the extracts of this plant can be used in their crude form, which is an addition to the complementary and alternative treatment strategies.

Fe-doped mayenite electride composite with 2D reduced Graphene Oxide: As a non-platinum based, highly durable electrocatalyst for Oxygen Reduction Reaction.

Since the last decades, non-precious metal catalysts (NPMC), especially iron based electrocatalysts show sufficient activity, potentially applicant in oxygen reduction reaction (ORR), however they only withstand considerable current densities at low operating potentials. On the other hand iron based electrocatalysts are not stable at elevated cathode potentials, which is essential for high energy competence, and its remains difficult to deal. Therefore, via this research a simple approach is demonstrated that allows synthesis of nanosize Fe-doped mayenite electride, [Ca24Al28O64]4+·(e-)4 (can also write as, C12A7-xFex:e-, where doping level, x = 1) (thereafter, Fe-doped C12A7:e-), consist of abundantly available elements with gram level powder material production, based on simple citrate sol-gel method. The maximum achieved conductivity of this first time synthesized Fe-doped C12A7:e- composite materials was 249 S/cm. Consequently, Fe-doped C12A7:e- composite is cost-effective, more active and highly durable precious-metal free electrocatalyst, with 1.03 V onset potential, 0.89 V (RHE) half-wave potential, and ~5.9 mA/cm2 current density, which is higher than benchmark 20% Pt/C (5.65 mA/cm2, and 0.84 V). The Fe-doped C12A7:e- has also higher selectivity for desired 4e- pathway, and more stable than 20 wt% Pt/C electrode with higher immunity towards methanol poisoning. Fe-doped C12A7:e- loses was almost zero of its original activity after passing 11 h compared to the absence of methanol case, indicates that to introduce methanol has almost negligible consequence for ORR performance, which makes it highly desirable, precious-metal free electrocatalyst in ORR. This is primarily described due to coexistence of Fe-doped C12A7:e- related active sites with reduced graphene oxide (rGO) with pyridinic-nitrogen, and their strong coupling consequence along their porous morphology textures. These textures assist rapid diffusion of molecules to catalyst active sites quickly. In real system maximum power densities reached to 243 and 275 mW/cm2 for Pt/C and Fe-doped C12A7:e- composite, respectively.

The crystal structure and luminescence properties of a novel green-yellow emitting Ca1.5Mg0.5Si1-xLixO4-δ:Ce3+ phosphor with high quantum efficiency and thermal stability.

A novel green-yellow emitting Ca1.5Mg0.5Si1-xLixO4-δ:Ce3+ phosphor with high quantum efficiency and thermal stability was discovered for applications in near ultraviolet pumped white light-emitting diodes. Its crystal structure was determined with a single-particle diagnosis approach. The Si sites in the SiO4 tetrahedra are reported for the first time to accommodate Li+ ions. This substitution, confirmed by 6Li solid-state NMR and T.O.F. neutron powder diffraction, causes a disordered occupation of Ca/Mg in the Ca3MgSi2O8 host and favors a phase transformation at ∼330 °C, which results in the formation of the novel phosphor. The produced phosphor was efficiently excited by near UV light peaking at 365 and 410 nm and produced broad green-yellow emission with peaks at 500 and 560 nm, respectively. Its quantum efficiency reached 88.4% (internal) and 55.7% (external) under excitation at 365 nm, and 80.5% (internal) and 42.7% (external) under excitation at 410 nm, while the decrease of luminescence intensity at 200 °C was small (∼26%). A WLED lamp with a high color rendering index of Ra = 92.8 was produced with the combination of a 365 nm emitting chip with blue emitting BaMgAl10O17:Eu2+, green-yellow emitting CMSL:0.01Ce, and red emitting Sr2Si5N8:Eu2+ phosphors.