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The role of polymer in precipitation has been examined by studying the effect of poly(ethylene glycol) (PEG) on the formation of calcium carbonate particles. Absence of polymer led to the formation of calcite crystals. Introduction of poly (ethylene glycol) molecules reduced the rate of crystallization process, and the effect is dependent on molecular weight and concentration. In the presence of 0.01 mol L-1 PEG, after 3 h of precipitation initiation, aragonite, vaterite phase appeared in the system. The calcium carbonate obtained with PEG was characterized by smaller sized particles in comparison with the ones without polymer. The CaCO 3 particles were characterized by several techniques, such as FTIR, XRD, SEM, and particle size distribution analysis. Graphical Abstract

The object of the study is lignite. Analytical testing techniques, such as elemental analysis, 13C nuclear magnetic resonance (13C NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM), were used to acquire information on the structural parameters of lignite. The aromaticity of Xianfeng lignite is 43.57%, and the aromatic carbon structure is mainly naphthalene and anthracene/phenanthrene. The aliphatic carbon structure is dominated by cycloalkanes, alkyl side chains, and hydrogenated aromatics. Oxygen is mainly present in ether oxygen, carboxyl, and carbonyl groups. Nitrogen is mainly in the form of pyrrole nitrogen and quaternary nitrogen. Sulfur is mainly thiophene sulfur. According to the analysis results, the molecular structure model of XF lignite was constructed. The molecular formula is C184H172O39N6S2. The 2D structure was converted to a 3D structure using computer simulation software and optimized. The optimized model has a remarkable stereoconfiguration, and the aromatic lamellae are irregularly arranged in space. The aromatic rings were mainly connected by methylene, hypomethylene, methoxy, and aliphatic rings. In addition, the simulated 13C NMR spectra are in good agreement with the experimental spectra. This shows the rationality of the 3D chemical structure model.

The deformation of interatomic distances with respect to those of the perfect crystal generates atomic-level strain. In nanoalloys, strain can arise because of finite size, morphology, domain structure and lattice mismatch between their atomic compounds. Strain can strongly affect the functional properties of nanoalloys, as it alters their electronic energy levels. Moreover, atomic-level strain generates atomic-level stress, which in turn results in distortions induced by strain. When the stress accumulated in a nanoalloy exceeds a certain level, the particle can relax that stress by undergoing structural transitions such as shape and/or chemical ordering transitions. Atomic-level strain is then a powerful tool to control and manipulate the structural and functional properties of nanoalloys. This requires a combined theoretical and experimental approach both to deeply understand the physical origin of strain, and to characterize it with a sub-angstrom resolution. Here, we present a theoretical analysis of the main sources of strain in nanoalloys, we analyse how atomic-level strain can be experimentally measured with transmission electron microscopy, we discuss its effect on the functional properties of nanoalloys, finally we describe how atomic-level stress arises from atomic-level strain, and how stress can induce structural transformations at the nanoscale.

For the purpose of humidity sensing, the rGO/Fe 2 O 3 nanocomposite was synthesized through precipitation technique that is followed by lyophilization process to enhance the surface area of the prepared nanocomposite. In order to investigate the sensor preparation quality, its activity and efficiency, the prepared nanocomposite has undergone different characterization techniques such as; high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermo-gravimetric analysis (TGA), BET surface area and BJH pore diameter distribution. The study showed that Fe 2 O 3 nanoparticles are densely and homogeneously loaded over rGO sheets. The porosity and surface area play an important role on humidity sensing property. In addition, the BET surface area and BJH pore radius of the rGO/Fe 2 O 3 are found to be 2002.09 m 2 g −1 and 1.68 nm, respectively. Furthermore, the humidity-sensing performances were investigated in a wide range of working humidity (11–97% RH) and frequency (100 Hz–100 kHz). The obtained results confirmed that the optimum measuring frequency is 1 kHz, due to in inability of water molecule to be polarized at higher frequency. The humidity sensing performance of rGO/Fe 2 O 3 nanocomposite shows a parabola relationship with the RH value from 11 to 97%. The incorporation of Fe 2 O 3 into rGO creates more active sites, such as vacancies and defects which promote the adsorption of water molecule thereby increasing the sensitivity of the sensor. Molecular models of graphene; graphene/2Fe 2 O 3 , graphene/2Fe 2 O 3 /2H 2 O were built. The model suggested that decorating the graphene with 2Fe 2 O 3 enable it to be sensitive for humidity.

We have prepared graphene quantum dot-europium(III) complex composites by noncovalently connecting chelating ligands dibenzoylmethane (DBM) and 1,10-phenanthroline (Phen) with graphene quantum dots (GQDs) first, followed by coordination to Eu(III). The resulting composites are well water-soluble and display red fluorescence of high color purity. The composites were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Aqueous solutions of the composites under 365 nm excitation display fluorescence with a peak at 613 nm and a quantum yield as high as 15.5 %. The good water solubility and stable photoluminescence make the composites very different from other Eu(III)-based coordination complexes. The composites are cell viable and can be used to label both the cell membrane and the cytoplasm of MCF-7 cells. They are also shown to act as bioprobes for in-vivo localization of tumorous tissue. In our perception, such composites are expected to possess wide scope because of the many functionalizations that are possible with GQDs. Graphical abstract Synthesis of red fluorescent graphene quantum dot-europium complex composites for use in bioimaging.

Glauconite must be assessed as mica-rich mica-smectite R3 interstratified mineral, with the pure end-member mica also having intrinsic K-deficient chemical characteristics (K ~ 0.8 apfu). This assertion is in accordance with our X‑ray diffraction (XRD) and high-resolution tranmission electron microscopy (HRTEM) studies and chemical analyses by electron probe microanalysis (EPMA) of mature glauconites in Cenozoic Antarctic sediments that indicate that: (1) It consists of a glauconite-smectite (R3 ordered) mixed-layer silicate, composed mainly of mica-type layers (>90%), but displaying slightly different proportions of Fe(III)-smectite layers (<10%). (2) More mature glaucony grains are characterized by major K and Fe (mica layers) and minor Fe (smectite layers) content in the interstratified glauconite-smectite. (3) Potassium is stabilized at the interlayer site by the octahedrally coordinated Fe . (4) Microtexture of the glauconite crystals are comparable with those of other micas and illite minerals, with straight, defect-free lattice fringes of ~10 Å spacings glauconite packets characteristic of mica with minor interstratified poorly crystalline smectite layers. In addition, our new findings give insights into the glauconitization process and at the same time investigate the potassium-deficient character of the dioctahedral mica “ .” These findings show that glauconite crystallizes by a layer-growth mechanism at the expense of a poorly crystalline smectite precursor and that smectite-to-glauconite transformations are accompanied by a gradually higher octahedral charge deficiency (Fe /Fe ) stabilized by K uptake into the interlayer sheet.

Wet-chemical co-precipitation was used to create Co 0.5 Mg x Cu 0.5−x Fe 2 O 4 nano-ferrites (x = 0.0, 0.2, 0.3, and 0.4). XRD, FT-IR, HRTEM, and EDX analyses were used to confirm each sample’s single-phase spinel cubic crystal structure. The crystallite size was calculated from the XRD data and determined to be between (11.1570 and 16.1457 nm), with a lattice constant between (8.359 to 8.387Å). The two absorption bands found in the FTIR data were utilized to show metal cation and oxygen bond stretching at tetrahedral and octahedral positions, as well as to calculate the elastic moduli. The elemental composition and structural behavior of every sample were examined using FE-SEM and EDS. The magnetic parameters were also estimated based on the VSM data, the contribution of magnetic anisotropy (K), and the magnetic interaction by Neel’s and Y-K-type magnetism modify as the Mg 2+ ion substitution increases, thus we must consider how this variation in cation distribution affects all of these factors. As per the ferromagnet theory, ions originating from the magnetic tetrahedral A and octahedral B sites engage in super-exchange interactions with one another. Anti-ferromagnetic alignment occurs as a result (M B -M A ). Magnetization occurs as a result.

Although much effort has been directed towards the separation of single-walled carbon nanotube mixtures, chiral-selective growth is required for scalable production and applications. The chiral distribution of carbon nanotubes can now be altered by varying the composition of nickel–iron nanocatalysts. Chirally pure single-walled carbon nanotubes (SWCNTs) are required for various applications ranging from nanoelectronics to nanomedicine 1 . Although significant efforts have been directed towards separation of SWCNT mixtures, including density-gradient ultracentrifugation  2 , chromatography 3 and electrophoresis 4 , the initial chirality distribution is determined during growth and must be controlled for non-destructive, scalable and economical production. Here, we show that the chirality distribution of as-grown SWCNTs can be altered by varying the composition of Ni x Fe 1− x nanocatalysts. Precise tuning of the nanocatalyst composition at constant size is achieved by a new gas-phase synthesis route based on an atmospheric-pressure microplasma. The link between the composition-dependent crystal structure of the nanocatalysts and the resulting nanotube chirality supports epitaxial models and is a step towards chiral-selective growth of SWCNTs.