Spin Texture Sensitive Photodetection by Dion-Jacobson Tin Halide Perovskites.

The organic spacer molecule is known to regulate the optoelectronic properties of two-dimensional (2D) perovskites. We show that the spacer layer thickness determines the nature of optical transitions, direct or indirect, by controlling the structural properties of the inorganic layer. The spin-orbit interactions lead to different electron spin orientations for the states associated with the conduction band minimum (CBM) and the valence band maximum (VBM). This leads to a direct as well as an indirect component of the transitions, despite them being direct in momentum space. The shorter chains have a larger direct component, leading to a better optoelectronic performance. The mixed halide Sn2+ Dion-Jacobson (DJ) perovskite with the shortest 4-C diammonium spacer outshines the photodetection parameters of those having longer (6-C and 8-C) spacers and the corresponding Ruddlesden-Popper (RP) phases. The DJ system with a 4-C spacer and equimolar Br/I embodies an unprecedentedly high responsivity of 78.1 A W-1 under 3 V potential bias at 485 nm wavelength, among the DJ perovskites. Without any potential bias, this phase manifests the self-powered photodetection parameters of 0.085 A W-1 and 9.9 × 1010 jones. The unusual role of electron spin texture in these high-performance photodetectors of the lead-free DJ perovskites provides an avenue to exploit the information coded in spins for semiconductor devices without any ferromagnetic supplement or magnetic field.

In-depth evaluation of nutritive, chemical constituents and anti-glycemic properties of jackfruit (Artocarpus heterophyllus Lam) clonal accessions with flake colour diversity from Eastern Sub-Himalayan plains of India.

The study was designed to elucidate the potential of jackfruit clonal accessions having diverse flake colours from nutritional and medicinal perspectives. Jack fruit accessions with deep yellow flakes were found to contain the highest flavonoids, antioxidant activity, ascorbic acid, and α-glucosidase inhibition whereas, orange-red flakes exhibited the highest ß-carotene, phenol, minerals (iron and zinc) and better inhibition of α-amylase and ß-glucosidase enzymes. Phenolic compounds profiling revealed the presence of higher sinapic acid, ferulic acid and quercetin contents in the orange-red-coloured flakes. Metabolite analysis revealed presence of anti-diabetic compounds (n-Hexadecanoic acid, tridecane, 2-Heptadecenal etc.) in deep yellow and orange-red coloured jack flakes with lower glycemic load. Considering the abundant health benefits as evident from the present study, orange-red and deep yellow-coloured flakes may be recommended for consumption to manage the hyperglycemic condition.

Transformation of Metal Halides to Facet-Modulated Lead Halide Perovskite Platelet Nanostructures on A-Site Cs-Sublattice Platform.

The conversion of metal halides to lead halide perovskites with B-site metal ion diffusion has remained a convenient approach for obtaining shape-modulated perovskite nanocrystals. These transformations are typically observed for materials having a common A-site Cs-sublattice platform. However, due to the fast reactions, trapping the interconversion process has been difficult. In an exploration of the tetragonal phase of Cs7Cd3Br13 platelets as the parent material, herein, a slower diffusion of Pb(II) leading to facet-modulated CsPbBr3 platelets is reported. This was expected due to the presence of Cd(II) halide octahedra along with Cd(II) halide tetrahedra in the parent material. This helped in microscopically monitoring their phase transformation via an epitaxially related core/shell intermediate heterostructure. The transformation was also derived and predicted by density functional theory calculations. Further, when the reaction chemistry was tuned, core/shell platelets were transformed to different facet-modulated and hollow CsPbBr3 platelet nanostructures. These platelets having different facets were also explored for catalytic CO2 reduction, and their catalytic rates were compared.

Light-Emitting Metal-Organic Halide 1D and 2D Structures: Near-Unity Quantum Efficiency, Low-Loss Optical Waveguide and Highly Polarized Emission.

Organic-inorganic metal-halide materials (OIMMs) with zero-dimensional (0D) structures offer useful optical properties with a wide range of applications. However, successful examples of 0D structural OIMMs with well-defined optical performance at the micro-/nanometer scale are limited. We prepared one-dimensional (1D) (DTA)2 SbCl5 ⋅DTAC (DTAC=dodecyl trimethyl ammonium chloride) single-crystal microrods and 2D microplates with a 0D structure in which individual (SbCl5 )2- quadrangular units are completely isolated and surrounded by the organic cation DTA+ . The organic molecular unit with a long alkyl chain (C12 ) and three methyl groups enables microrod and -plate formation. The single-crystal microrods/-plates exhibit a broadband orange emission peak at 610 nm with a photoluminescence quantum yield (PLQY) of ca. 90 % and a large Stokes shift of 260 nm under photoexcitation. The broad emission originates from self-trapping excitons. Spatially resolved PL spectra confirm that these microrods exhibit an optical waveguide effect with a low loss coefficient (0.0019 dB µm-1 ) during propagation, and linear polarized photoemission with a polarization contrast (0.57).

Evaluation of indigenous aromatic rice cultivars from sub-Himalayan Terai region of India for nutritional attributes and blast resistance.

Indigenous folk rice cultivars often possess remarkable but unrevealed potential in terms of nutritional attributes and biotic stress tolerance. The unique cooking qualities and blissful aroma of many of these landraces make it an attractive low-cost alternative to high priced Basmati rice. Sub-Himalayan Terai region is bestowed with great agrobiodiversity in traditional heirloom rice cultivars. In the present study, ninety-nine folk rice cultivars from these regions were collected, purified and characterized for morphological and yield traits. Based on traditional importance and presence of aroma, thirty-five genotypes were selected and analyzed for genetic diversity using micro-satellite marker system. The genotypes were found to be genetically distinct and of high nutritive value. The resistant starch content, amylose content, glycemic index and antioxidant potential of these genotypes represented wide variability and 'Kataribhog', 'Sadanunia', 'Chakhao' etc. were identified as promising genotypes in terms of different nutritional attributes. These cultivars were screened further for resistance against blast disease in field trials and cultivars like 'Sadanunia', 'T4M-3-5', 'Chakhao Sampark' were found to be highly resistant to the blast disease whereas 'Kalonunia', 'Gobindabhog', 'Konkanijoha' were found to be highly susceptible. Principal Component analysis divided the genotypes in distinct groups for nutritional potential and blast tolerance. The resistant and susceptible genotypes were screened for the presence of the blast resistant pi genes and association analysis was performed with disease tolerance. Finally, a logistic model based on phenotypic traits for prediction of the blast susceptibility of the genotypes is proposed with more than 80% accuracy.

Arm Growth and Facet Modulation in Perovskite Nanocrystals.

Highly emissive isotropic CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals are typically observed in a six-faceted cube shape. When a unique approach is adopted and the reaction medium is enriched with halides, arm growth on all six facets was carried out and reported. Analysis suggested that these armed nanostructures were obtained from intermediate polyhedron shaped structures having 26 facets, and these were formed under halide-deficient conditions. Surface energy calculations further supported the possible existence of all facets for both of these structures under different halide composition environments. The entire study was first explored for CsPbBr3 and then extended to CsPbCl3; however, for CsPbI3 nanocrystals, Sr(II) dopant was used for obtaining stable emission. Arm lengths could also be tuned with a function of reaction temperature for CsPbBr3. Formation of stable facets in polyhedron shaped nanostructures and their transformation to respective hexapods under halide-deficient and halide-rich conditions add new fundamental concepts for these nanostructures and their shape evolutions.

Genome wide molecular evolution analysis of begomoviruses reveals unique diversification pattern in coat protein gene of Old World and New World viruses.

Begomoviruses (Family-Geminiviridae) are plant infecting single stranded DNA viruses known to evolve very fast. Here, we have analysed the DNA-A sequences of 302 begomoviruses reported as 'type isolates' from different countries following the list of International Committee on Taxonomy of Viruses till 2017. Phylogenetic analysis was performed which revealed two major evolutionarily distinct groups namely Old World (OW) and New World (NW) viruses. Our work present evidence that cp gene has varied degree of diversification among the viruses reported from NW and OW. The NW viruses are more conserved in their cp gene sequences than that of OW viruses irrespective of host plant families. Further analysis reveals that cp gene differs in its recombination pattern among OW and NW viruses whereas rep gene is highly recombination prone in both OW and NW viruses. The sequence conservation in cp gene in NW viruses is a result of meagre recombination and subsequent low substitution rate in comparison to OW viruses. Our results demonstrated that the cp gene in NW viruses is less likely to possess nuclear localisation sequences than OW cp gene. Further we present evidence that the NW-cp is under the influence of strong purifying selection. We propose that the precoat protein (pcp) gene present exclusively in the 5' of cp gene in OW viruses is highly diversified and strong positive selection working on pcp gene might be attributing largely to the diversity of OW-cp gene.