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The applicability of triangular silver nanoplates (TNPs) as a spectrophotometric reagent for the determination of mercury(II) in an aqueous solution was estimated. The method is based on the oxidation of TNPs with a mean edge length of 52 nm and thickness of 4 nm by mercury(II) ions, which is accompanied by a decrease in the surface plasmon resonance of nanoparticles. The effect of reaction time, pH of solution, and TNP concentration on the sensitivity of mercury(II) determination was studied. The limit of mercury(II) detection under the selected conditions was 0.022 [micro]g/mL. Keywords: silver nanoparticles, triangular silver nanoplates, mercury(II), spectrophotometry, surface plasmon resonance, Silver nanoparticles (NPs) find increasingly wider application as an alternative to spectrophotometric reagents because of unique optical properties and nonstandard methods for analytical signal generation in nanoanalytical systems [1, 2]. [...]

Ultrafine La0.7Sr0.3MnO3 powders were prepared via homogenization in chelate solutions, followed by the calcination of solid precursors at 700°C in air or oxygen, and their phase composition and average par- ficle size were determined. The solid precursors were obtained from a solution of polynuclear La, Sr, and Mn chelates (diethylenetriaminepentaacetates) by three procedures: (1) gelation of the solution, followed by air drying of the resultant gel; (2) gelation followed by microwave dehydration; and (3) microwave dehydration of the solution. The results demonstrate that the way in which the chelate solution is converted into solid foams has little effect on the phase composition and particle size of the powders. At the same time, the phase composition and particle size of the reaction products depend on the calcination atmosphere (air or oxygen). Calcination in oxygen (700°C, 10 h) ensures the preparation of phase-pure La0.7Sr0.3MnO3 powders, with an average particle size of ... 30 nm, from the three precursors. [ABSTRACT FROM AUTHOR]

The magnetic ordering of Mo 2 NiB 2 -type {Gd, Tb, Dy} 2 Co 2 Al ( Immm , No. 71, oI 10) compounds has been established using bulk magnetic measurements and neutron diffraction study. Polycrystalline Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al undergo ferrimagnetic transitions (T C ) at 78 K, 98 K and 58 K, respectively, and low-temperature field induced transition (T m ) around 15 K, 20 K and 15 K, respectively. Between T m and T C Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al are soft ferrimagnets. Below T m Gd 2 Co 2 Al is soft ferrimagnet, whereas Tb 2 Co 2 Al and Dy 2 Co 2 Al exhibit permanent magnet properties with residual magnetization per rare earth of 4.95 B and 4.8 B , respectively, and large coercive field of 72 kOe and 22 kOe, respectively, at 2 K. The magnetocaloric effects of Gd 2 Co 2 Al, Tb 2 Co 2 Al and Dy 2 Co 2 Al were calculated in terms of isothermal magnetic entropy change and they reach maximum values of −10.4 J/kg K, −7.6 J/kg K and −6.6 J/kg K for a field change of 50 kOe near 75 K, 98 K and 58 K, respectively. Low-temperature transition of Gd 2 Co 2 Al is followed by the magnetic entropy change of −2.9 J/kg K in a field change of 50 kOe at 15 K. Low temperature magnetic ordering with enhanced anisotropic effects in Tb 2 Co 2 Al and Dy 2 Co 2 Al is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +19.9 J/kg K at 20 K (field change 0–50 kOe) and +2.7 J/kg K at 15 K (field change 0–10 kOe), respectively. Neutron diffraction study shows that, in zero applied field, Tb 2 Co 2 Al exhibits c -axis ferrimagnetic ordering with magnetic space group Immm ′ and propagation vector K 0 = [0, 0, 0] below T C ND ∼ 111 K with M Tb = 8.86(15) B and M Co = 0.26(2) B at 2 K. [ABSTRACT FROM AUTHOR]

Novel RNi6Si6 compounds adopt the new CeNi6Si6-type structure for R=La–Ce (tP52, space group P4/nbm N 125-1) and new YNi6Si6-type structure for R=Y, Sm, Gd–Yb (tP52, space group N 117) that are tetragonal derivative of NaZn13-type structure, like LaCo9Si4-type. The CeNi6Si6, GdNi6Si6, TbNi6Si6, DyNi6Si6 and HoNi6Si6 compounds are Curie–Weiss paramagnets down to ~30K, and do not order magnetically down to 5K. However, the inverse paramagnetic susceptibility of LaNi6Si6 does not follow Curie–Weiss law. The DyNi6Si6 shows ferromagnetic-like saturation behaviour at 5K in applied fields of 50kOe, giving rise to a magnetic moment value of 6.5μB/f.u. in 50kOe. The powder neutron diffraction study in zero applied filed indicates square modulated the c-collinear antiferromagnetic ordering of TbNi6Si6 with K=[±1/4, ±1/4, 0] wave vector below ~10K. [ABSTRACT FROM AUTHOR]

The magnetic and magnetocaloric properties of the intermetallic family (Gd,Tb) 6 (Fe,Mn)Bi 2 have been studied from 2 K to temperatures above the respective Curie temperatures T C. The substitution of Gd by Tb (Gd 6 FeBi 2 , Gd 3 Tb 3 FeBi 2 , Tb 6 FeBi 2) tunes T C in the range 350-250 K and favors the apparition of a metamagnetic transition at very low temperature (below 10 K) from a complex magnetic state to a ferromagnetic one, as well as a spin reorientation transition below T m = 72 K. As a consequence, an important inverse magnetocaloric effect (IMCE) appears below 20 K and an interesting direct magnetocaloric effect (DMCE) appears over a wide temperature span between T C and T m with maxima at those temperatures. The partial substitution of Fe by Mn in Tb 6 Fe 0.5 Mn 0.5 Bi 2 shifts these effects upwards in temperature while expanding the region of the direct magnetocaloric effect between 70 and 400 K. The combination of adjoint IMCE and DMCE as well as the wide span of the latter shows that tuning this family allows to locate the magnetocaloric effect in different regions of interest. The critical behavior of the PM-FM transitions has been studied obtaining the critical exponents α, β, γ, δ and checking that the respective magnetocaloric effects also scale with the critical parameters n and δ. The transition in Gd 6 FeBi 2 belongs to the Heisenberg universality class with deviations due to magnetocrystalline anisotropies; the critical exponents for Gd 3 Tb 3 FeBi 2 (in agreement with the Mean Field model) suggest the presence of long range order magnetic interactions, while Tb 6 FeBi 2 and Tb 6 Fe 0.5 Mn 0.5 Bi 2 present an unconventional critical behavior aligned with long range order interactions. • Gd by Tb substitution tunes T C and improves the magnetocaloric properties. • Tb samples present two main transitions and extended temperature working range. • Adjoint inverse and direct magnetocaloric effects in Td-doped compounds. • Critical exponents α, β, γ, δ found for the PM-FM transition. [ABSTRACT FROM AUTHOR]