Coherent-interface-induced strain in large lattice-mismatched materials: A new approach for modeling Raman shift.

Strain engineering as one of the most powerful techniques for tuning optical and electronic properties of Ill-nitrides requires reliable methods for strain investigation. In this work, we reveal, that the linear model based on the experimental data limited to within a small range of biaxial strains (< 0.2%), which is widely used for the non-destructive Raman study of strain with nanometer-scale spatial resolution is not valid for the binary wurtzite-structure group-III nitrides GaN and AlN. Importantly, we found that the discrepancy between the experimental values of strain and those calculated via Raman spectroscopy increases as the strain in both GaN and AlN increases. Herein, a new model has been developed to describe the strain-induced Raman frequency shift in GaN and AlN for a wide range of biaxial strains (up to 2.5%). Finally, we proposed a new approach to correlate the Raman frequency shift and strain, which is based on the lattice coherency in the epitaxial layers of superlattice structures and can be used for a wide range of materials. Electronic Supplementary Material: Supplementary material (Table S1: Values of bulk phonon deformation potentials and elastic constants for GaN and AlN from each reference used in Table 1, Fig. S1: Lattice parameters of SL layers using Eq. (8), and Fig. S2: Raman mapping using Eq. (7)) is available in the online version of this article at 10.1007/s12274-021-3855-4.

Larvicidal activity of 94 extracts from ten plant species of northeastern of Brazil against Aedes aegypti L. (Diptera: Culicidae).

In an effort to find effective and affordable ways to control of Aedes aegypti L. (Diptera: Culicidae), the larvicidal activities of 94 extracts from ten plant species belonging to eight families [Guettarda grazielae and Spermacoce verticillata (Rubiaceae), Coccoloba mollis and Triplaris americana (Polygonaceae), Eschweilera ovata (Lecytidaceae), Merremia aegyptia (Convolvulaceae), Ouratea nitida (Ochnnaceae), Protium heptaphyllum (Burseraceae), Rourea doniana (Connaraceae), and Tovomita brevistaminea (Guttiferae)], widely found in the northeast of Brazil, were initially screened at 250 microg/mL. Nineteen of the 94 extracts from six plant species (C. mollis, G. grazielae, M. aegyptia, R. doniana, S. verticillata, and T. americana) showed significant activity (>75% mortality) against the fourth instar larvae. Some of these extracts showed 100% mosquito larvae mortality, with LD(50) values lower 200 microg/mL. When compared to synthetic insecticide Temephos (LD(50) 8.7 microg/mL), two of them, hexane (LD(50) 12.1 microg/mL) and ethyl acetate (LD(50) 51.6 microg/mL) extracts from stems of R. doniana and G. grazielae, respectively, were the most effective. The isolation and purification of these extracts are in progress and evaluation of these compounds will be needed to identify the active component.