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We present the behavior of multiple solid solutions within ternary (BaxCa1–x)B6 and (BaxSr1–x)B6 compounds and demonstrate that nanodomain formation is preferred over uniform solid solutions under certain processing conditions. Instead of the expected single solid solution of M1 and/or M2 atoms within the MB6 phase, we note separation into nanodomain regions rich in either M1 or M2. This phase separation has been observed from detailed analyses of the shapes of the peaks in X-ray diffraction data, where peak splitting and asymmetry are the result of multiple solid solutions with lattice parameters differing by up to 1.4%. High-resolution transmission electron microscopy confirms the presence of these nanodomains, which are about 2–3 nm in size, and reveals varying degrees of lattice misalignment. We also present X-ray diffraction analysis of (BaxCa1–x)B6 powders calcined from 1273 to 1973 K and document the enhancement in sample homogeneity as the separated phases merge into a uniform solid solution. As s...

In this study, tomato plants were grown in vitro with and without incorporation of TiO2 nanoparticles in Murashige and Skoog (MS) growth medium. The aim of this study was to describe the morphological (area and roundness cell) and mechanical (Young’s Modulus) change in the different tissue of tomato root, epidermis (Ep), parenchyma (Pa), and vascular bundles (Vb), when the whole plant was exposed to TiO2 nanoparticles (TiO2 NPs). light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), wavelength dispersive X-ray fluorescence (WDXRF) techniques were used to identify changes into the root cells when TiO2 NPs were incorporated. TiO2 NPs incorporation produces changes in the area, roundness, and Young’s Modulus of the tomato root. When tomato root is exposed to TiO2 NPs, the Ep and Vb area size decreases from 260.92 µm2 to 160.71 µm2 and, 103.08 µm2 to 52.13 µm2, respectively, compared with the control area, while in Pa tissue the area size was increased considerably from 337.72 mm2 to 892.96 mm2. Cellular roundness was evident in tomato root that was exposed to TiO2 NPs in the Ep (0.49 to 0.67), Pa (0.63 to 0.79), and Vb (0.76 to 0.71) area zones. Young’s Modulus in Pa zone showed a rigid mechanical behavior when tomato root is exposed to TiO2 NPs (0.48 to 4.98 MPa control and TiO2 NPs, respectively). Meanwhile, Ep and Vb were softer than the control sample (13.9 to 1.06 MPa and 6.37 to 4.41 MPa respectively). This means that the Pa zone was stiffer than Ep and Vb when the root is exposed to TiO2 NPs. Furthermore, TiO2 NPs were internalized in the root tissue of tomato, accumulating mainly in the cell wall and intercellular spaces, with a wide distribution throughout the tissue, as seen in TEM.

In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a unique frequency of microwave irradiation. The sphere sizes were controlled by the microwave power level and the concentration of dissolved precursor. Structural and morphological characterization was performed by SEM, HRTEM, EELS and XRD. The results demonstrated that rhombohedral zero valent Bi spheres were synthesized after microwave radiation at 600 and 1200 W. However, if the power level is decreased to 120W, a monoclinic phase of Bi2O3 is obtained with a flake-like morphology. In comparison with a conventional hydrothermal process, the microwave-assisted solvothermal approach provides many advantages such as shorter reaction time, optimum manipulation of morphologies and provides a specific chemical phase and avoids the mixture of structural phases and morphologies which is essential for further applications such as drug delivery or functionalization with organic materials, thanks to its biocompatibility.

Self-assembling systems of amphiphilic molecules display structures similar to those of biomineralization natural systems. This allows to somehow mimic nature to synthesize nanomaterials with low polidispersity and with diverse morphologies. In this work we describe the synthesis and characterization of gold-copper, silver-copper, and gold-silver bimetallic nanoparticles by chemical reduction in self-assembling systems of two surfactants. The nanoparticles were characterized by Transmission Electron Microscopy and UV-Vis spectroscopy. We have prepared a composite material using mesoporous silica as support of the AuAg bimetallic nanoparticles. The system was used in photocatalysis experiments for water remediation applications. Our results show that the AuAg/SBA15 composite material degrades methyl orange in water from 17 ppm to 4 ppm in 30 minutes.

This work shows the comparison of high-resolution electron energy loss spectra (HR-EELS) in the low loss region (0−15 eV) to investigate the electronic structure from koechilinite Bi 2 MoO 6 to rusellite Bi 2 WO 6 varying the stoichiometric relation Bi 2 Mo x W 1−x O 6 . The effect of the Mo to W ratio on the bandgap energy was evaluated on individual particles. Two approximations were considered in order to determine the band gap energy value, the first one was a linear fit and the second one was a mathematical fit. Both analyses are in agreement with those ones collected and analyzed by UV–Vis characterization. Our results suggest a direct electronic transition that increases from about 2.53 eV to about 3 eV as the W content increase from 0% to 100% wt. X-ray diffraction was used to corroborate the crystal structure and crystal size; transmission electron microscopy was used to monitor the morphology evolution and UV–Vis spectroscopy in diffuse reflectance mode to determine the Eg. These techniques complement the characterization of these materials.

Codoped Er 3+ and Yb 3+ nanocrystalline ZrO 2 –B 2 O 3 phosphor obtained by a modified sol–gel method is demonstrated. The addition of up to 2.5 mol% B 2 O 3 to nanocrystalline ZrO 2 :Yb(2%), Er(1%) keep the tetragonal rare-earth stabilized ZrO 2 phase; whereas higher B 2 O 3 content destabilize the tetragonal phase, leading to the tetragonal to monoclinic transition with no tetragonal ZrO 2 phase segregation. Visible upconversion of the luminescent active ions, Er 3+ and Yb 3+ , depend strongly on B 2 O 3 content. The PL intensity is strongly quenched for high B 2 O 3 content due to increasing multiphonon relaxation processes related to B O and B O B vibronic modes.

a b s t r a c t Wide band gap nanocrystalline bismuth doped barium zirconate is synthesized by a facile hydrother- mal method at 100 ◦C. The obtained cubic perovskites are characterized by powder X-ray diffraction (XRD), UV-VIS diffuse reflectance spectroscopy, photoluminescence (PL) spectroscopy, and photocat- alytic activity. The estimated band gap in the 2.4-4.9 eV range, depending on Bi concentration, suggests nanocrystalline BaZrO3:Bi as a useful visible-light activated photocatalyst under excitation wavelengths

The wet synthesis hydrothermal method at 100 °C was used to elaborate barium zirconate (BaZrO3) unpurified with 0.5 mol% of different rare earth ions (RE = Yb, Er, Dy, Eu, Ce). Morphological, structural and UV-photoluminescence properties depend on the substituted rare earth ionic radii. While the crystalline structure of RE doped BaZrO3 remains as a cubic perovskite for all substituted RE ions, its band gap changes between 4.65 and 4.93 eV. Under 267 nm excitation the intrinsic green photoluminescence of the as synthesized BaZrO3: RE samples is considerably improved by the substitution on RE ions. For 1000 °C annealed samples, under 267 nm, the photoluminescence is dominated by the intrinsic BZO emission. It is interesting to notice that Dy3+, Er3+ and Yb3+ doped samples present whitish emissions that might be useful for white light generation under 267 nm excitation. CIE color coordinates are reported for all samples.

Under NIR excitation at 967 intense blue and red photoluminescence (PL) emissions are observed at room temperature in codoped Tm 3+ –Yb 3+ barium zirconate (BaZrO 3 :Yb,Tm) powders. Powders were prepared by a simple hydrothermal method, and present a wide band gap that depends on the total rare earth content due to the degree of disorder induced in the BaZrO 3 lattice by the substitution of the rare earth ions. Rietveld refinements of the XRD patterns indicated the presence of primary nanocrystallites with sizes between 50 and 70 nm depending on the Tm 3+ content. Scanning transmission electron microscopy (STEM) shows that these primary particles self-aggregated in larger secondary particles which present a regular morphology with sizes around 1 μm. The intense blue and red PL emissions in BaZrO 3 powders under 967 nm excitation are governed by energy transfer processes from Yb 3+ ions to Tm 3+ ions and crossrelaxation among Tm 3+ ions.