In a generic synthesis approach, all three CsPbX3 (X=Cl, Br and I) perovskite nanocrystals having near unity quantum yields is reported. This has been achieved by injecting the desired amount of ...preformed alkylammonium halide salts which acted as a dual source providing halide ions and the capping agent to an equimolar amount of non‐halide Pb and Cs precursors in a reaction flask at an optimized reaction temperature. The composition sensitivity of Pb to Cs ratio, high temperature reaction, and injection of ammonium halide remained the key parameters for obtaining the high quantum yields. Details of the reaction process, use of different reagents and setting up the reaction parameters are reported.
Three colors: A rational synthesis of CsPbX3 (X=Cl, Br, and I) nanocrystals gives all three perovskites with near unity photoluminescence quantum yield. Careful analysis of the reaction chemistry and the parameters allows a generic reaction to be developed.
High-energy-emitting CsPbCl3 nanocrystals have shown significant loss and enhancement of their emission intensity (∼40–50 folds) during purification and surface treatments, respectively. This ...confirms that the surfaces of these nanocrystals are very sensitive. In this Letter, physical insights of the interface bindings on the surface of these blue-emitting CsPbCl3 nanocrystals with different passivating agents and their consequential impact on purification are investigated. Using various metal chlorides irrespective of the charge and size of the metal ions, metal acetates, and nonmetal chloride, the predominant influence of chloride ions in helping retrieve/intensify the blue emission is established. The purification processes are observed to be very delicate, and successive purifications with introduction of polar nonsolvents led to the transformation of an emitting cubic CsPbCl3 phase to nonemitting tetragonal CsPb2Cl5 phase nanocrystals irreversibly. The impact of various salt additions only temporarily helped in enhancing the emission, but the phase change remained inevitable upon successive purification. However, as a remedy, by in situ use of alkylammonium chloride salt in high-temperature reactions, the surface binding was improved, and significant emission as well as the phase could be retained with successive purifications.
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•Safeguarding young maize plants from infestation by fall armyworm is of utmost importance.•Seed treatment with diamides was effective on early and mid-age caterpillars.•It is ...possible to protect the crop up to one month from emergence of seedlings through seed dressing with diamides.•Seed treatment may provide a more efficient and cost-effective alternative to foliar spray.
The fall armyworm, Spodoptera frugiperda (J. E. Smith) is one of the major pests of maize worldwide. Farmers apply multiple rounds of pesticides within a single cropping season to control the fall armyworm. This leads to increased costs for plant protection and accelerates the selection pressure for evolution of resistance to various insecticide molecules in a short period. Hence, it is crucial to minimize the frequency of insecticide sprays on the crop. In this study we assessed the efficacy of seed treatment chemicals viz.- cyantraniliprole 19.8 % + thiamethoxam 19.8 % FS, chlorantraniliprole 62.5 % FS, and thiamethoxam 70 % WS against neonates and third instar larvae of S. frugiperda. Lab bioassays using leaves from seed treated plants were conducted. Results showed that thiamethoxam 70 % WS was completely ineffective. It was thus presumed that only cyantraniliprole contributed to the observed larval mortality in the combination chemical tested here. Although both cyantraniliprole and chlorantraniliprole were effective for up to a month, the latter consistently recorded greater larval mortality. As seed treatment is easy to practice, poses lower risk and economical, we recommend this application method, especially using chlorantraniliprole 62.5 % FS, as a part of the integrated pest management strategy to combat the fall armyworm in maize.
The effect of fiber surface treatment on the structural, thermal, and tribological properties of sisal fibers and their epoxy composites were investigated in this research work. Sisal fibers were ...modified with alkali (NaOH), glutamic acid, and a combination of both alkali and glutamic acid. To analyze the effect of chemical modification on the properties of sisal fibers, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), and thermogravimetric analysis (TGA) were performed. It is observed from the experimental results that there is an improvement in the surface roughness, crystallinity, and thermal stability of chemically treated fibers in comparison to untreated fibers. Microhardness properties of chemically treated sisal fiber reinforced epoxy composites (SFREC) also showed minor improvement. The dry sliding wear experiments were carried out according to Taguchi design of experiment (DOE) methods. The results of the wear test showed an increase in the wear resistance of chemically modified SFREC relative to untreated SFREC. The best wear properties were demonstrated by alkali treated SFREC. It is also observed from the findings of ANOVA that the applied load and sliding distance have the most defining effect on wear volume loss of SFREC.
The spatio-temporal distribution of COVID-19 across India's states and union territories is not uniform, and the reasons for the heterogeneous spread are unclear. Identifying the space-time trends ...and underlying indicators influencing COVID-19 epidemiology at micro-administrative units (districts) will help guide public health strategies. The district-wise daily COVID-19 data of cases and deaths from February 2020 to August 2021 (COVID-19 waves-I and II) for the entire country were downloaded and curated from public databases. The COVID-19 data normalized with the projected population (2020) and used for space-time trend analysis shows the states/districts in southern India are the worst hit. Coastal districts and districts adjoining large urban regions of Mumbai, Chennai, Bengaluru, Goa, and New Delhi experienced > 50,001 cases per million population. Negative binomial regression analysis with 21 independent variables (identified through multicollinearity analysis, with VIF < 10) covering demography, socio-economic status, environment, and health was carried out for wave-I, wave-II, and total (wave-I and wave-II) cases and deaths. It shows wealth index, derived from household amenities datasets, has a high positive risk ratio (RR) with COVID-19 cases (RR: 3.577; 95% CI: 2.062-6.205) and deaths (RR: 2.477; 95% CI: 1.361-4.506) across the districts. Furthermore, socio-economic factors such as literacy rate, health services, other workers' rate, alcohol use in men, tobacco use in women, overweight/obese women, and rainfall have a positive RR and are significantly associated with COVID-19 cases/deaths at the district level. These positively associated variables are highly interconnected in COVID-19 hotspot districts. Among these, the wealth index, literacy rate, and health services, the key indices of socio-economic development within a state, are some of the significant indicators associated with COVID-19 epidemiology in India. The identification of district-level space-time trends and indicators associated with COVID-19 would help policymakers devise strategies and guidelines during public health emergencies.
Bright lead halide perovskite nanocrystals, which have been extensively studied in the past 5 years, are mostly confined to a six faceted hexahedron (cube/platelet) shape. With variations of ligand, ...precursor, reaction temperature, and surface modification, their brightness has been enhanced and phase became stable, but ultimate nanocrystals still retained the hexahedron cube or platelet shape in most of the hot injection reactions. In contrast, by exploration of α-halo ketone in amine as a halide precursor, different shaped nanocrystals without compromising the photoluminescence quantum yield (PLQY) are reported. Confining to orthorhombic CsPbBr3, the obtained nanocrystals are stabilized by 12 facets ({200}, {020}, {112}) and led to 12 faceted rhombic dodecahedrons. These facets are absolutely different from six ({110}, {002}) equivalent facets of widely reported orthorhombic cube shaped CsPbBr3 nanocrystals. These also retained the colloidal and phase stability, as well as showed near unity PLQY. With further annealing, these are transformed to 26 faceted rhombicuboctahedrons by dissolving all their vertices. Importantly, these 12 faceted nanocrystals showed wide area self-assembly in most of the reactions. It has also been concluded that primary ammonium ions led to six faceted nanocrystals, but tertiary ammonium ions obtained in this case stabilized different group of facets. While perovskite nanocrystals were broadly confined to only nanocubes, these new nanocrystals with intense emission would certainly provide a new avenue for continuing their further research.
Halide perovskite nanocrystals are the subject of in-depth research because of their bright color-tunable optical emissions. Synthesis of these nanocrystals and their phase stability in different ...halide compositions and reaction environments are also extensively studied. However, going beyond these nanocrystals, the chemistry of epitaxial growth of metallic crystals on selective facets of ionic crystals has not been largely established yet. For the formation of heteronucleations as well as retaining the epitaxial relation at the junction, a high reaction temperature remains a key factor. However, with an increase in temperature, there are possibilities for cross nucleations and also detachment of metal particles from the host. Keeping these in mind, herein, the thermal impacts on different structural combinations of Pd-CsPbBr3 nanocrystal heterostructures are reported. Following the high-temperature reaction protocol, two types of heterostructures, facet-directive epitaxial and nonepitaxial decorated Pd-CsPbBr3, are first obtained, and these are further explored to study the annealing impact. In these cases, smaller size Pd particles are first grown epitaxially and form a one-to-one heterostructure, and then with time, Pd cubes are observed to be decorated randomly. However, the formation and growth of Pd particles remained sensitive to both the reaction temperature and the time as these did not grow to beyond a certain size in the heterostructure, rather facilitated cross nucleation formation. This provides strong support that annealing does not hamper the epitaxial junction and it only helps the successive growth of nonepitaxially connected metal nanocrystals.
The pre- and post-scission neutron multiplicities are measured for the fission of 208Rn, populated with the reactions 30Si+178Hf and 48Ti+160Gd in the excitation energy range of 54.5 - 80.8 MeV. We ...found significant differences in the pre-scission neutron multiplicities of these two systems. Also, both the reactions exhibit an enhancement in the pre-scission multiplicity with respect to the existing data for the 16O+194Pt reaction populating 210Rn. The measured multiplicities are compared with the theoretical predictions obtained from the Langevin dynamical model for fission. Dynamical simulations are also performed to estimate the capture cross-sections. Contribution of the neutrons, emitted during the fusion process, is shown to be crucial in determining the neutron multiplicities for the present systems. Moreover, in case of the 48Ti+160Gd reaction, rapid quasi-fission dynamics prevents neutron emission from the thermalized target-projectile composite. The present measurement helps us to understand the relative importance of fusion and quasi-fission processes and their timescales depending on the entrance channel mass asymmetry.
In a generic synthesis approach, all three CsPbX
(X=Cl, Br and I) perovskite nanocrystals having near unity quantum yields is reported. This has been achieved by injecting the desired amount of ...preformed alkylammonium halide salts which acted as a dual source providing halide ions and the capping agent to an equimolar amount of non-halide Pb and Cs precursors in a reaction flask at an optimized reaction temperature. The composition sensitivity of Pb to Cs ratio, high temperature reaction, and injection of ammonium halide remained the key parameters for obtaining the high quantum yields. Details of the reaction process, use of different reagents and setting up the reaction parameters are reported.
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