Lithium inserted ZnSnN2 thin films for solar absorber: n to p-type conversion

ZnSnN₂ is a non-toxic and earth-abundant photoabsorber material for flexible photovoltaic devices because of its excellent optoelectronic behavior. However, theoretical studies show that the alkaline-earth metallic (Li, Na, K, Rb, Cs, and Fr) dopants in ZnSnN₂, particularly lithium (Li), display shallow-acceptor behavior and improve the performance of ZnSnN₂ semiconductors. Orthorhombic phase structure with (002) preferred orientation was observed for Li-doped films and the lattice parameters agree well with reported standards. Secondary ion mass spectroscopy (SIMS) analysis revealed the incorporation of Li in Li:ZnSnN₂ films. XPS, the density of states, and Born effective charge analysis revealed the chemical bonding states of Li–ZnSnN₂. In contrast to the pristine n-type ZnSnN₂, Li:ZnSnN₂ thin films showed conductivity with p-type hole concentrations varying between 1.14 × 10²⁰–9.47 × 10¹⁹ cm^?3 and the highest mobility of 20.03 cm²V^?1s^?1. Therefore, we obtained p-type conductivity by substituting an organolithium reagent (C?H?Li) on the Zn site, which highlights that Li:ZnSnN₂ can be effectively used as the photoanode layer for next-generation thin-film solar cell devices.     

Green synthesis and characterization of novel 1,2,4,5-tetrasubstituted imidazole derivatives with eco-friendly red brick clay as efficacious catalyst

Use of cheaper and recyclable materials contributes positively to economic growth with environmental sustainability. We report the prospect of utilizing red brick clay as catalyst, which exhibited excellent activity in rapid one-pot four-component condensation of 1,2,4,5-tetrasubstituted imidazoles with high conversion and yields (91–96%) in aqueous medium at 60 °C in short reaction times (25–40 min). The red brick clay material was fully characterized by XRD, FT-IR, SEM, TEM, EDX and BET analyses. Red brick clay consisted of oxides of Si (20.38%), Fe (19.55%), Al (14.30%) and minor amounts of Ca (3.60%) and Mg (1.68%). The slate-like-shaped structure morphology and flaky appearance of inexpensive solid clay material proved competent material for the synthesis of 15 novel 1,2,4,5-tetrasubstituted imidazole derivatives. In addition, the advantages of the eco-friendly method are non-toxicity and re-usability of the catalyst. Reaction offers 78% atom economy and 84% carbon capture.

     

Programmed Photodegradation of Polymeric/Oligomeric Materials Derived from Renewable Bioresources

Renewable polymeric materials derived from biomass with built‐in phototriggers were synthesized and evaluated for degradation under irradiation of UV light. Complete decomposition of the polymeric materials was observed with recovery of the monomer that was used to resynthesize the polymers.     

Dynamics of entangled polymer chains with nanoparticle attachment under large amplitude oscillatory shear

This paper presents a nonlinear viscoelastic model for polymer nanocomposites and the computed model response to large amplitude oscillatory shear flow. The model predicts the stress in a mixture of entangled polymer chains, with different convective constraint release (CCR) rates for free chains and nanoparticle‐attached chains, through an averaging scheme which is consistent with double reptation in the Marrucci–Ianniruberto constitutive equation. The nonlinear response of the mixture is evaluated both numerically in terms of Q and by an asymptotic analysis in terms of four frequency dependent parameters of medium amplitude oscillatory shear (MAOS) as well as the intrinsic nonlinearity parameter Q₀ . In the case of free polymer chains alone, the MAOS signatures are comparable to those of the Giesekus model with the notable difference of a minimum in the elastic parameter [e₁] at De >1. The viscous nonlinear parameters of the mixture model depart significantly from those of the free chains, especially in mixtures where the CCR parameter for attached chains is larger than that for the free chains: [v₁] has a prominent minimum and [v₃] has a prominent maximum near De = 2/c, the low frequency plateau region, along with a higher Q₀ compared to the matrix at all Deborah numbers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 62–76     

Plant-Derived Antiviral Compounds as Potential Entry Inhibitors against Spike Protein of SARS-CoV-2 Wild-Type and Delta Variant: An Integrative in SilicoApproach

The wild-type SARS-CoV-2 has continuously evolved into several variants with increased transmissibility and virulence. The Delta variant which was initially identified in India created a devastating impact throughout the country during the second wave. While the efficacy of the existing vaccines against the latest SARS-CoV-2 variants remains unclear, extensive research is being carried out to develop potential antiviral drugs through approaches like in silico screening and drug-repurposing. This study aimed to conduct the docking-based virtual screening of 50 potential phytochemical compounds against a Spike glycoprotein of the wild-type and the Delta SARS-CoV-2 variant. Subsequently, molecular docking was performed for the five best compounds, such as Lupeol, Betulin, Hypericin, Corilagin, and Geraniin, along with synthetic controls. From the results obtained, it was evident that Lupeol exhibited a remarkable binding affinity towards the wild-type Spike protein (−8.54 kcal/mol), while Betulin showed significant binding interactions with the mutated Spike protein (−8.83 kcal/mol), respectively. The binding energy values of the selected plant compounds were slightly higher than that of the controls. Key hydrogen bonding and hydrophobic interactions of the resulting complexes were visualized, which explained their greater binding affinity against the target proteins—the Delta S protein of SARS-CoV-2, in particular. The lower RMSD, the RMSF values of the complexes and the ligands, Rg, H-bonds, and the binding free energies of the complexes together revealed the stability of the complexes and significant binding affinities of the ligands towards the target proteins. Our study suggests that Lupeol and Betulin could be considered as potential ligands for SARS-CoV-2 spike antagonists. Further experimental validations might provide new insights for the possible antiviral therapeutic interventions of the identified lead compounds and their analogs against COVID-19 infection.     

High Tg polyimide nanofoams derived from pyromellitic dianhydride and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane

New routes for the synthesis of high T_g thermally stable polymer foams with pore sizes in the nanometer regime have been developed. Foams were prepared by casting well-defined microphase-separated block copolymers comprised of a thermally stable block and a thermally labile material. At properly designed volume fractions the morphology provides a matrix of the thermally stable material with the thermally labile material as the dispersed phase. Upon thermal treatment, the thermally unstable block undergoes thermolysis generating pores, the size and shape of which are dictated by the initial copolymer morphology. Triblock copolymers comprised of a high T_g, amorphous polyimide matrix with poly(propylene oxide) as the thermally decomposable coblock, were prepared. The copolymer synthesis was conducted through the poly(amic acid) precursor and subsequent cyclodehydration to the polyimide by either thermal or chemical means. Dynamic mechanical analysis confirmed microphase separated morphologies for all copolymers, irrespective of the propylene oxide block lengths investigated. Upon decomposition of the thermally labile coblock, a 9–18% reduction in density was observed, consistent with the generation of a foam which was stable to 400°C. © 1996 John Wiley & Sons, Inc.     

Deciphering the Role of MicroRNAs in Neuroblastoma

Neuroblastoma (NB) is a type of peripheral sympathetic nervous system cancer that most commonly affects children. It is caused by the improper differentiation of primitive neural crest cells during embryonic development. Although NB occurs for 8% of paediatric cancers, it accounts for 15% of cancer-related deaths. Despite a considerable increase in cytotoxic chemo- and radiotherapy, patients in advanced stages remain virtually incurable. Therefore, there is a desperate necessity for new treatment strategies to be investigated. Accumulating evidence suggested that microRNAs (miRNAs) are a class of non-coding RNAs with 19–25 nucleotides lengths and play a central role in the development of NB carcinogenesis. Fascinatingly, miRNA inhibitors have an antisense property that can inhibit miRNA function and suppress the activity of mature miRNA. However, many studies have addressed miRNA inhibition in the treatment of NB, but their molecular mechanisms and signalling pathways are yet to be analysed. In this study, we impart the current state of knowledge about the role of miRNA inhibition in the aetiology of NB.     

Wigner crystallization of quadratically dispersing electrons in graphene

The graphene surface with the unpaired π electrons presents an ideal two‐dimensional electron system. Although the effective massless Dirac fermions are important, they are not the only carriers that describe the quantum transport in graphene. Above zero energy, the current carrying carriers in graphene are the usual electrons. This electron density may vary depending on the surface defects and π–σ interaction, and this may lead to a possible Wigner crystallization on the surface of graphene. Calculations for nonmagnetic, ferromagnetic, and antiferromagnetic Wigner crystals are carried out based on the Koster–Kohn variational principle for direct calculation of Wannier functions. The effect of positive background due to the carbon ions is suitably treated. From our results, we find that Wigner crystallization is possible in grapheme, if we consider the electrons on the surface, which obey quadratic dispersion relation. The electron crystal with ferromagnetic phase and face centered square lattice structure has the lowest energy. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Evolution of crystalline orientation and texture during solid phase die‐drawing of PP‐Talc composites

The objective of the present work was to examine the development of crystalline orientation and texture in the polypropylene matrix of talc‐filled i‐PP and in unfilled i‐PP with increasing draw ratio during solid‐phase die‐drawing at high strain rates (～1 s^?1) and a die temperature of 145 °C. After drawing, the entire billet was cooled rapidly “under tension” to room temperature before releasing the billet and cutting specimens from different axial locations for analysis. Orientation distributions of the three crystal axes for increasing axial strains have been presented as pole figures in the MD‐TD plane with the direction of draw (MD) as the reference direction. While disruption of spherulites was noticed within the die for neat PP at a draw ratio of 1.5, transcrystalline domains within the composite persisted even at a draw ratio of 3.5 in the free draw region outside the die. The transformation to fibrillar crystal morphology was complete in both materials at a draw ratio of 4.5 but the texture continued to develop beyond this stage. While the (110)[001] texture component was found to be dominant at all draw ratios for neat PP, the (010)[001] texture component was dominant at the higher draw ratios in the drawn composite. This may be attributed to the (010)[001] slip system being more active as the transverse spacing between elongated voids encasing the particles was decreased. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1528–1538