Comparison of the effectiveness of the most used chemicals against Tuta absoluta in Tunisia

Control failures with several chemicals have prompted research into the resistance status of Tuta absoluta and the effectiveness of certain active ingredients against this pest. In this context, a comparison was made of the effectiveness of the most widely used chemicals against T. absoluta in Tunisia. The results show that the L1 larval stage of Tuta absoluta is very sensitive to all of the chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%. Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants

Magnetocaloric properties of a novel ferromagnet Gd3Co4+xAl12-x (x = 0.50).

International audienceA novel gadolinium and cobalt based aluminide, namely Gd3Co4+xAl12-x (x = 0.50(3)) is shown to crystallize in the hexagonal Gd3Ru4Al12 structure-type (space-group P63/mmc, a = 8.6830(1) Å, c = 9.3164(2) Å at room temp.). The investigation of its magnetic properties revealed a reversible ferromagnetic ordering at TC ≈ 40 K but expanding in a wide temp. range, potentially due to the geometrical magnetic frustrations expected in this structure-type. The magnetocaloric properties of this intermetallic, detd. from both magnetization and sp. heat data, are dominated by a max. entropy variation of -3.28 J kg-1 K-1 at 39(1) K and an adiabatic temp. change of about 1.5 K extending from 20 to 40 K, highlighting some interest for low temp. applications

Comparison of the effectiveness of the most used chemicals against Tuta absoluta in Tunisia

Control failures with several chemicals have prompted research into the resistance status of Tuta absoluta and the effectiveness of certain active ingredients against this pest. In this context, a comparison was made of the effectiveness of the most widely used chemicals against T. absoluta in Tunisia. The results show that the L1 larval stage of Tuta absoluta is very sensitive to all of the chemicals tested. Stage L2 is sensitive to Spinosad, indoxacarb and emactin, while Bacillus thuringiensis, martine do not cause 50% mortality. L3 stage mortality fluctuates between 20% and 80% mortality. The L4 stage is more affected by the treatment with Bacillus thuringiensis which can go to 100%. Based on these results, chemical treatments should be directed according to the dominant larval stage in the plants

New p-type Al-substituted SrSnO 3 perovskites for TCO applications?

International audienceNovel p-type SrSn 1-x Al x O 3 (x=0, 0.2, 0.5) perovskites are presented as potential candidates for electro-optical applications. A combined experimental and theoretical study reveals that chemical substitutions can be used as a lever to stabilize oxygen holes in the valence band. Transparent conductive oxides (TCO) are an original class of materials combining two contrasting properties in one single compound that is, electrical conductivity and optical transparency in visible spectrum. TCOs are widely used in electro-optical devices such as flat-panels, organic light emitting diodes, photovoltaic devices, and plasma displays. 1-6 However, standard commercial TCOs are limited to post-transition metal oxides, e.g. ZnO, In 2 O 3 and SnO and derivatives. 7 These oxides are characterized by a band gap larger than 3eV between the O(2p) valence band maximum (VBM) and the metal (s,p) conduction band minimum (CBM). They display excellent n-type electronic conductivity when the donor, i.e. metal, is doped. In contrast, the development of high performant p-type TCOs is more challenging, 8-11 due to the strongly localized states of the acceptor, i.e. oxygen, which are at the origin of large hole effective mass (poor electronic conductivity). As a consequence, the probability is high that the newly created shallow acceptors are counterbalanced by the formation of native defects such as anion vacancies or cation interstice. 12 Up to now, n-type tin-doped indium oxide (ITO) shows the best performance. 1,13 Nevertheless and despite the remarkable properties of ITO, the relative high cost of In and its increasing scarcity appeals for alternative elements or materials. 14 ABO 3 perovskites are of great interest thanks to the use of mixed A and B cations capable of generating versatile structures and properties with high chemical stability. SrSnO 3 (SSO) is one of the most promising candidate due to its high visible light transmittance, high thermal stability and reasonable cost. 15 Pure SSO is a charge transfer insulator crystallizing in the orthorhombic GdFeO 3-type structure with lattice parameters a = 5.7113 Å, b = 8.0647 Å and c = 5.7042 Å. In this tri-dimensional structure, SnO 6 octahedra are corner-shared and Sr lies in the available vacant interstices. 16,17 To meet the industrial specifications of efficient TCOs, SSO must display high carrier concentration and mobility 18-21 which requires its doping. Attempts to develop n-type SSO candidates that could rival the electro-optical properties of ITO were intensively described and interesting performance were reported. 22-26 In contrast, p-type doping is still lacking for this class of materials. 27-29 Recently, Hautier et al. showed that the large difference in mobility between n-type and p-type materials is not inevitable and could be overcome by the investigation of alternative chemistries. Based on this statement and considering the high industrial stakes associated with the discovery of new p-type TCOs, we used chemical substitution to check the ability of SSO to behave as a performant p-type TCO. This concept was introduced for the first time by Hosono and coworkers 2 and is known as the "chemical modulation of the valence band" (CMVB). Based on the hypothesis that partial substitution of Sn(IV) for the smaller trivalent cation Al(III) can enhance electron delocalization (through a significant volume contraction of the perovskite structure) while concomitantly generate stable holes in the valence band, various Sn/Al-substituted SSO phases were synthesized. Using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDX), we here demonstrate the solubility of the Al element in the SSO perovskite structure for SrSn 1-x Al x O 3 (SSAO) compositions x = 0 to 0.5. UV-Vis-NIR spectroscopy is then used to show that the absorption profile of SSO is not altered by the chemical Sn/Al substitution while the low-energy absorption band (intra-band transitions) is enhanced. A thermodynamic study based on first-principles DFT (Density Functional Theory) calculations is then performed to determine the type of charge carriers in SSO and SSAOs (p-type) and combined with chemical bond analyses to rationalize the impact of Sn/Al substitution on the p-type performance of SSAOs. SrSn 1-x Al x O 3 (x= 0, 0.2, 0.5) perovskites were successfully obtained through solid state reaction. Details of the synthesis steps are given in ESI part. The impact of the Sn(IV)/Al(III) substitution ratio on the macroscopic properties of SrSn 1-x Al x O 3 was investigated through complementary XRD and SEM-EDX. The structural and morphological analyses of the synthesized samples are presented in Fig.1 and S1. From the XRD patterns of SSO and SrSn 1-x Al x O 3 (SSAO) the orthorhombic Pnma structure (JCPDS 10-6354) is confirmed. A slight shift towards higher angles is observed in agreement with the smaller Shannon ionic radius of Al 3+ (0.54 Å) compared to Sn 4+ (0.69 Å)