We report a solution-based synthetic method to produce shapetunable iron pyrite (FeS 2 ) nanocrystals using iron oxy-hydroxide (β-FeOOH) as a precursor and their application for selective reduction of functionalized nitroarenes to aniline derivatives with formic acid-triethylamine (HCOOH− Et 3 N) as a hydrogen donor system.

Nanowires and nanorods of magnetite (Fe 3 O 4 ) are of interest due to their varied biological applications but most importantly for their use as magnetic resonance imaging contrast agents. One-dimensional (1D) structures of magnetite, however, are more challenging to synthesize because the surface energy favors the formation of isotropic structures. Synthetic protocols can be dichotomous, producing either the 1D structure or the magnetite phase but not both. Here, superparamagnetic Fe 3 O 4 nanorods were prepared in solution by the reduction of iron oxy-hydroxide (β-FeOOH) nanoneedles with hydrazine (N 2 H 4 ). The amount of hydrazine and the reaction time affected the phase and morphology of the resulting iron oxide nanoparticles. One-dimensional nanostructures of Fe 3 O 4 could be produced consistently from various aspect ratios of β-FeOOH nanoneedles, although the length of the template was not retained. Fe 3 O 4 nanorods were characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and SQUID magnetometry.

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Perovskite materials possess diversified structures, with a virtue of customizable chemical compositions to generate versatile chemical, mechanical, and physical properties. Traditional lead halide perovskites with the general formula APbX 3 , where A is an organic (CH 3 NH 3 + , CH(NH 2 ) 2 + ) or inorganic cation (Cs + ), and X is a halide (I − , Br − , or Cl − ), [1] have received much research as solar cells and optical materials. [2][3][4] However, the facts of toxicity and low stability of these materials have urged researchers to quest for other perovskite systems.Cs 2 HfCl 6 (CHC) is a type of Pb-free material with a vacancy-ordered double perovskite structure, with a space group of 3 Fm m (No. 225). [5] Compared with other double perovskites such as Cs 2 AgBiX 6 (X = Cl, Br) without vacancy, [6][7][8] the CHC in a 2:1:6 atomic ratio contains unoccupied B′ sites when expressed as A 2 BB′X 6 , with a low mass density of 3.56 g cm -3 . [9] This type of material with a vacancy-ordered double perovskite structure has received increasingly renewed attention in the past years. [10][11][12][13] Burger et al. have grown CHC single crystals, which were nonhygroscopic but could give high light yield by γ-rays without any intentional doping. [14] The scintillation was centered at 400 nm, with a principal decay time of 4.37 µs. Through first-principles calculations, Kang and Biswas found that although its bandgap is large (6.34 eV), the luminescence is originated from self-trapped excitons (STEs) that are caused by (HfCl 6 ) 2octahedra trapping localized carries. [15] Further, using undoped CHC single crystals, Král et al. identified photoluminescence (PL) emission bands at 380 nm by STEs, and 460 nm by defects. [16] The emissions could be tuned through dopants. [17][18][19] The CHC material has been widely studied as scintillators [14,[20][21][22][23][24][25][26][27] and light-emitting diodes (LEDs) applications. [17] Besides, other halides in this family, Cs 2 HfBr 6 (CHB) [28] and Cs 2 HfI 6 (CHI), [29,30] have also been reported as scintillators.However, the research on Cs 2 HfF 6 (CHF), the first member of the halide Cs 2 HfX 6 family, is much limited compared to other members. Unlike CHC, CHB, and CHI with a double perovskite structure, CHF crystalized as a hexagonal Bravais Compared to halides Cs 2 HfX 6 (X = Cl, Br, I) with a vacancy-ordered cubic double perovskite structure, the halide Cs 2 HfF 6 (CHF), with a hexagonal Bravais lattice, possesses a higher mass density and chemical stability for radiation detection. Luminescence properties and energy transfer mechanisms of rare-earths-doped CHF materials are studied here. The structure of CHF is identified as a new type of vacancy-ordered hexagonal perovskite, with the same type of building blocks of the double perovskite but stacked with single layers. Density-functional theory calculations reveal a large bandgap of CHF. A broad emission is observed from the pristine CHF host, which is suggested to be associated with self-trapped excitons (STEs). A series of...

Glucose biosensors are widely used for clinical, industrial, and environmental applications. Nonenzymatic electrochemical glucose biosensors based on metal oxides with a perovskite structure have exhibited high sensitivity, excellent stability, and...