Amorphous interface oxide formed due to high amount of Sm doping (5-20 mol%) stabilizes finer size anatase and lowers indirect band gap

In this study, we have synthesized Ti(1-x)SmxO2 (x = 0–20%) nanocomposites by adopting an aqueous sol-gel route. A two or multi-phase mixture of titania and samarium oxide could be expected as samarium added >5% may exceed its solubility limit in anatase. Surface and high-resolution characterization found Sm forming a predominantly thin amorphous layer that is not discernible in conventional transmission electron microscopy. The addition of Sm in such a high amount stabilizes formation of anatase phase of TiO2. Importantly, we observe that the incorporation of such high amount of Sm in titania leads to a grain growth inhibition of anatase. Sm can also be reduced from a trivalent state to a bivalent state. The addition of Sm thus results in very thin amorphous layer around the nanocrystalline anatase, inhibits the growth of this anatase and lowers the indirect band gap from 3.0 eV to 2.47 eV. That such lowering happens along with a lowering of size and a resulting increase in surface area means that doping of titania by more than 5% Sm can make better a photocatalyst either for the purpose of photodegradation of industrial organic water-pollutants and microorganisms under the visible light irradiation than a pristine anatase

Phosphine free synthesis of copper telluride nanocrystals in 1D and 2D shapes using dipehylditelluride (DPDTe) as an air-stable source

In this paper, we have developed a 'phosphine-free' method for synthesising copper telluride nanocrystals using diphenyl ditelluride as an air-stable tellurium source. The diphenyl ditelluride is shown to have optimal reactivity for the colloidal synthesis of Cu2Te, allowing optimal control over the phase and morphology. Using this unexplored Te precursor for copper telluride synthesis, 1D nanorods of hexagonal phase (Cu2Te) were synthesised at a moderate temperature of 180 °C. The precise control over key parameters for this system results in Cu2−xTe nanocrystals forming with varied shapes (1D nanorods and 2D nanoplates), sizes, and crystal phases (hexagonal Cu2Te and orthorhombic Cu1.43Te).</p

Amorphization driven Na-Alloying in SixGe1-x alloy nanowires for Na-ion batteries

Here we report the use of 1D SixGe1−x (x = 0.25, 0.5, 0.75) alloy nanowires (NWs) as anode materials for Na-ion batteries (NIBs). The strategy involves the synthesis of crystalline SixGe1−x NWs via the solution–liquid–solid (SLS) mechanism, followed by amorphization to activate the material for Na-ion cycling within a NIB. This study demonstrates the successful activation of SixGe1−x amorphous NW alloys, with a-Si0.5Ge0.5 delivering 250 mA h g−1 as compared to a-Ge NWs delivering only 107 mA h g−1 after 100 cycles. Also, amorphization proved to be a critical step, since crystalline NWs failed to activate in NIBs. However, Si NWs performed poorly during Na-ion cycling even after amorphization, and this behavior was explained by poor comparative Na-ion diffusivity. Further investigations on the impact of the relative content of Ge within the amorphized SixGe1−x NWs, Na-ion diffusivity and electrode degradation during cycling were also performed. Notably, the incorporation of Ge in the a-SixGe1−x alloy boosted Na ion diffusivity in the amorphized alloy, resulting in improved cycling performance and rate capability as compared to parent a-Si and a-Ge NWs.</p

Foam-like Ce–Fe–O-based nanocomposites as catalytic platforms for efficient hydrogen oxidation in air

Foam-like nanocomposites of the Ce–Fe–O system with two (c-CeO2, am-F2O3), three (c-CeO2, o-CeFeO3, α-F2O3), or four phases (c-CeO2, o-CeFeO3, α-F2O3, am-Fe2O3) were synthesized using the RedOx reaction of glycine-nitrate combustion. The glycine/nitrate ratio (G/N) varied from deficient (0.2, 0.4) and stoichiometric (0.6) to excess ratios of glycine (0.8, 1.0, 1.2, 1.4). PXRD, 57Fe Mössbauer spectroscopy, N2-physisorption, TEM, H2-TPD, O2-TPD, and H2-TPR were used to examine the characteristics of the obtained samples. The average crystallite size of the obtained composites was in the range of 1.3–31.3 nm, 33.4–50.7 nm, and 10.1–33.9 nm for c-CeO2, o-CeFeO3, and α-Fe2O3, respectively. The lowest SBET (1.5 m2/g) belonged to the case of stoichiometric G/N, while the highest value (49.2 m2/g) was found in the case of the highest amount of glycine (G/N = 1.4); the latter case also had the largest total pore volume (Vp = 0.182 cm3/g) when compared to the others. Moreover, the advanced catalytic performance of foamy Ce–Fe–O-based nanocomposites toward H2 combustion in air was found with t10 = 275 °C, t50 = 345 °C, and Ea = 76.9 kJ/mol for sample G/N = 1.2. The higher activity of sample G/N = 1.2 in catalysis was attributed to different properties of the composite, including an appropriate component phase ratio, the smaller size of crystallites, higher specific surface area, higher reducibility,oxygen capacity, etc. The findings make it possible to carry out the directed synthesis of catalysts based on the Ce–Fe–O system with specific phases, dispersion, and morphological composition for efficient hydrogen oxidation at moderate temperatures.</p

Colloidal synthesis of the mixed ionic–electronic conducting NaSbS2 nanocrystals

Solution-based synthesis of mixed ionic and electronic conductors (MIECs) has enabled the development of novel inorganic materials with implications for a wide range of energy storage applications. However, many technologically relevant MIECs contain toxic elements (Pb) or are prepared by using traditional high-temperature solid-state synthesis. Here, we provide a simple, low-temperature and size-tunable (50–90 nm) colloidal hot injection approach for the synthesis of NaSbS2 based MIECs using widely available and non-toxic precursors. Key synthetic parameters (cationic precursor, reaction temperature, and ligand) are examined to regulate the shape and size of the NaSbS2 nanocrystals (NCs). FTIR studies revealed that ligands with carboxylate functionality are coordinated to the surface of the synthesized NaSbS2 NCs. The synthesized NaSbS2 nanocrystals have electronic and ionic conductivities of 3.31 × 10−10 (e−) and 1.9 × 10−5 (Na+) S cm−1 respectively, which are competitive with the ionic and electrical conductivities of perovskite materials generated by solid-state reactions. This research gives a mechanistic understanding and post-synthetic evaluation of parameters influencing the formation of sodium antimony chalcogenides materials.</p

WS2 nanotubes dressed in gold and silver: synthesis, optoelectronic properties, and NO2 sensing

This conference contribution is focused on decoration of WS2 nanotubes (NT-WS2) with gold and silver nanoparticles via facile routes implying direct reaction of tungsten disulfide with water-soluble AuIII and AgI species at 100oC. The underlying mechanism of these interactions will be discussed in details based on extensive studies of reaction mixtures and resulting metal–NT-WS2 nanocomposites, including thorough X-ray photoelectron spectroscopy (XPS) analysis. Surprising features in optical spectra of the designed nanocomposites would be reported, including suppression of plasmon resonance in tiny noble metal nanoparticles (< 10 nm in diameter) grown onto NT-WS2. The plasmonic features of individual gold nanoparticles on the surface of disulfide nanotube were also characterized by electron energy loss spectroscopy in scanning transmission electron microscopy mode (STEM-EELS). Photoresistive NO2-sensing response of NT-WS2 under green light illumination (Ȝmax = 530 nm) and its enhancement by plasmonic gold “nanoantennas” will be reported as well

Subsuming the metal seed to transform binary metal chalcogenide nanocrystals into multinary compositions

Direct colloidal synthesis of multinary metal chalcogenide nanocrystals typically develops dynamically from the binary metal chalcogenide nanocrystals with the subsequent incorporation of additional metal cations from solution during the growth process. Metal seeding of binary and multinary chalcogenides is also established, although the seed is solely a catalyst for nanocrystal nucleation and the metal from the seed has never been exploited as active alloying nuclei. Here we form colloidal Cu–Bi–Zn–S nanorods (NRs) from Bi-seeded Cu2–xS heterostructures. The evolution of these homogeneously alloyed NRs is driven by the dissolution of the Bi-rich seed and recrystallization of the Cu-rich stem into a transitional segment, followed by the incorporation of Zn2+ to form the quaternary Cu–Bi–Zn–S composition. The present study also reveals that the variation of Zn concentration in the NRs modulates the aspect ratio and affects the nature of the majority charge carriers. The NRs exhibit promising thermoelectric properties with very low thermal conductivity values of 0.45 and 0.65 W/mK at 775 and 605 K, respectively, for Zn-poor and Zn-rich NRs. This study highlights the potential of metal seed alloying as a direct growth route to achieving homogeneously alloyed NRs compositions that are not possible by conventional direct methods or by postsynthetic transformations.</p

Synthesis of sandwiched composite nanomagnets by epitaxial growth of Fe3O4 layers on SrFe10Cr2O19 nanoplates in high-boiling organic solvent

Herein, we demonstrate the synthesis of sandwiched composite nanomagnets, which consist of hard magnetic Cr-substituted hexaferrite cores and magnetite outer layers. The hexaferrite plate-like nanoparticles, with average dimensions of 36.3 nm × 5.2 nm, were prepared via a glass crystallization method and were covered by spinel-type iron oxide via thermal decomposition of iron acetylacetonate in a hexadecane solution. The hexaferrite nanoplates act as seeds for the epitaxial growth of the magnetite, which results in uniform continuous outer layers on both sides. The thickness of the layers can be adjusted by controlling the concentration of metal ions. In this way, layers with an average thickness of 3.7 and 4.9 nm were obtained. Due to an atomically smooth interface, the magnetic composites demonstrate the exchange coupling effect, acting as single phases during remagnetization. The developed approach can be applied to any spinel-type material with matching lattice parameters and opens the way to expand the performance of hexaferrite nanomagnets due to a combination of various functional properties.</p