Ferrite nanoparticles synthesized by co-precipitation method depend mostly on parameters such as synthesis temperature, pH of the suspension, and initial molar concentration. We reported the size and ...morphology of nanoparticles magnetite (Fe3O4) synthesized by co- precipitation method with variation of temperature in the range between 25°C and 80°C in order to investigate the effect of synthesis temperature to its size and morphology. The nanoparticle forms are spherical, with band-gap values were 1.76 eV, 1.20 eV, 1.27 eV and 1.14 eV at synthesis temperatures of 25°C, 40°C 60°C and 80°C respectively. It was found that the smallest of magnetite nanoparticles was 10.14 nm for the sample synthesized at 25°C.
In the last decade, experiment and theory have expanded our vision of non‐covalent interactions (NCIs), shifting the focus from the conventional hydrogen bond to new bridging interactions involving a ...variety of weak donor/acceptor partners. Whereas most experimental data originate from condensed phases, the introduction of broadband (chirped‐pulse) microwave fast‐passage techniques has revolutionized the field of rotational spectroscopy, offering unexplored avenues for high‐resolution studies in the gas phase. We present an outlook of hot topics for rotational investigations on isolated intermolecular clusters generated in supersonic jet expansions. Rotational spectra offer very detailed structural data, easily discriminating the isomeric or isotopic composition and effectively cancelling any solvent, crystal, or matrix bias. The direct comparison with quantum mechanical predictions provides insight into the origin of the inter‐ and intramolecular interactions with much greater precision than any other spectroscopic technique, simultaneously serving as test‐bed for fine‐tuning of theoretical methods. We present recent examples of rotational investigations around three topics: oligomer formation, chiral recognition, and identification of halogen, chalcogen, pnicogen, or tetrel bonds. The selected examples illustrate the benefits of rotational spectroscopy for the structural and energetic assessment of inter‐/intramolecular interactions, which may help to move from fundamental research to applications in supramolecular chemistry and crystal engineering.
Rotating molecules: The role of rotational spectroscopy to investigate non‐covalent interactions by using mass‐ and interaction‐specific molecular aggregates generated and isolated in a supersonic jet expansion is reviewed and examples of recent investigations with halogens, chalcogens, and pnicogens as electrophile partners in R−A⋅⋅⋅B interactions are provided.
The charge‐transport properties of the spiro‐linked compounds 2,2′,7,7′‐tetrakis(diphenylamino)‐9,9′‐spirobifluorene, 2,2′,7,7′‐tetrakis(N,N′‐di‐p‐methylphenylamino)‐9,9′‐spirobifluorene, ...2,2′,7,7′‐tetra(m‐tolyl‐phenylamino)‐9,9′‐spirobifluorene, and 2,2′,7,7′‐tetra(N‐phenyl‐1‐naphthylamine)‐9,9′‐spirobifluorene, and their corresponding parent compounds, N,N,N′,N′‐tetraphenylbenzidine, N,N,N′,N′‐tetrakis(4‐methylphenyl)benzidine, and N,N′‐bis(3‐methylphenyl)‐(1,1′‐biphenyl)‐4,4′‐diamine, N,N′‐diphenyl‐N,N′‐bis(1‐naphthyl)‐1,1′‐biphenyl‐4,4′‐diamine, are investigated. The field‐effect mobilities of charge carriers in thin films of the parent compounds are slightly higher than those of the spiro‐linked compounds. However, the transistor action of the parent‐compound thin films vanishes because the films crystallize after being stored in ambient atmosphere for a few days. In contrast, the hole mobilities in thin films of the spiro‐linked compounds do not change significantly after the samples are stored in ambient atmosphere for up to nine months. Also discussed is the temperature dependency of the mobilities of charge carriers, which is presented using two models, namely the Arrhenius and the Gaussian disorder models.
Charge‐carrier transport in thin films of spiro‐linked compounds is compared to that of the corresponding parent compounds. The performance of films of spiro‐linked compounds is maintained, in contrast to that of the parent compounds, which is reduced in a matter of hours, even if the sample is kept in a continuously evacuated chamber (see figure).
Superconductors are materials with the unique characteristics when the temperature of the material is below its critical temperature, namely zero resistivity. There are many superconducting phenomena ...that need to be explained theoretically. One of them is the effect of addition of impurities on the physical properties of superconducting materials. In this study, the addition of 0.01 Ni magnetic impurities in the Eu2-xCexCuO4+α-δ material has been carried out to form the structure Eu2-xCexCu0.99Ni0.01O4+α-δ, in an under-doped area with a concentration of Ce (x) = 0.09 and 0.10. Material synthesis was carried out by the solid reaction method with prefire at 900 °C for 20 hours, sintering at 1,000 °C for 16 hours, and annealing at 900 °C for 10 hours by flowing argon (Ar) gas. The XRD measurements were carried out to investigate the crystal structure, while the magnetic properties were carried out by SQUID measurement at temperature of 2 K to 30 K. From the XRD measurements, it was found that the crystals formed had a tetragonal crystal structure T’ which was indicated by the appearance of two main peaks with Miller indices (103) and (110), lattice parameter a is 3,904 Å in both samples, lattice c is 11.8752 Å and 11.9738 Å for the concentrations of Ce (x) = 0.09 and 0.10. The volume of unit cells obtained were 181.0178 Å3 and 181.0244 Å3 with the bond distance between Cu-O of 1.9521 Å and 1.9523 Å. It was also obtained that the crystal size were 86.2604 nm and 91.6735 nm. From the SQUID measurement, it was found that the material Eu2-xCexCu0.99Ni0.01O4+α-δ has paramagnetic properties. The value of the effective magnetic moment was decreased by reducing the addition of Ni impurities of 0.0057 and 0.0051.
Electron-doped superconductor Eu1.85Ce0.15CuO4+α-δ has been synthesized using solid state reaction method. The purpose of this research is to study the effect of heating process with and without ...annealing treatment to its superconductivity. The sample without annealing treatment was covered by CuO to prevent the excess of oxygen in sample during heating process. All samples were characterized by XRD, resistivity and susceptibility measurement to study structure, electrical and magnetic properties of Eu1.85Ce0.15CuO4+α-δ samples with different heating process. From XRD measurement, it is found that all samples have tetragonal crystal with T' structure. From magnetic susceptibility and resistivity measurement, superconductivity was observed only in the sample with annealing treatment. The absence of superconductivity in sample without annealing was probably due to the existence of excess oxygen.
Ferrite nanoparticles synthesized by coprecipitation method depend mostly on parameters synthesis such as reaction temperature, pH of the suspension, and initial molar concentration. Here, we ...reported the physical properties of nanoparticles magnetite (Fe3O4) synthesized by coprecipitation method with variation of pH in the range between 8 and 11, in order to investigated the effect of pH treatment to its optical properties, particles size, and phase changes after sintering treatment. The band gap parameters of magnetite nanoparticles and crystal structure of magnetite powder are determined. From UV-Vis measurement, it is found that the band gap of magnetite nanoparticles was in the range of 1.3 eV to 1.5 eV with the smallest size of nanoparticles was 9.69 nm obtained at condition of pH = 10. From XRD characterization, it was found that all samples sintered at 100°C for 4h have magnetite phase of Fe3O4 with cubic structure, while all samples sintered at 1100°C for 4 h have hematite phase of a-Fe2O3 with hexagonal structure.
Scherrer formula and Williamson-Hall plot or WH-plot are the common methods to determine microstructure information from diffraction pattern, a technique with the expenses of the physical meaning of ...the result. Eventually a Whole Powder Pattern Modeling (WPPM) has been proposed, allowing physical information to be extracted from the diffraction data with the one-step refinement of the experimental pattern. In this paper, we reported the comparison between Williamson-Hall plot and Whole Powder Pattern Modeling to determine the crystallite size of nanoparticle barium hexaferrites which prepared by mechanical alloying and direct ultrasonic destruction.
Superconductivity is a phenomenon when the resistivity becomes zero below the critical temperature (Tc). The appearance of superconductivity in undoped bulk samples of T'-La1.8-xEu0.2MxCuO4 (M = Sr, ...Ca; x = 0.05, 0.10, 0.15) has altered the existing phase diagram in superconducting cuprates and raised big questions about the mechanism of superconductivity. Here, new materials of T'-La2-yYyCuO4 with y = 0.05, 0.10, 0.15 have been synthesized by the low-temperature synthesis method in order to grow undoped superconductors with the single phase of the T'-structure. The powder x-ray diffraction analysis was performed to identify of the crystal structure, while magnetic susceptibility measurements were carried out using a SQUID magnetometer at low temperature down to 2 K. It has been found that the T'-structure is stabilized when it was annealed at 500 - 600°C. The c-axis length decreases with increasing Yttrium-concentration. For y = 0.10, the single phase of the T'-structure was obtained by the oxidation annealing at 300°C and the succeeding reduction annealing at 500°C for 24 hours. From magnetic susceptibility measurements, it has been found that no trace superconductivity is observed in all samples, which is probably due to the remaining excess oxygen suppressing the appearance of superconductivity in the sample.
Partially Zn-substituted for Cu in electron-doped superconducting cuprates of Eu1.85Ce0.15Cu1-yZny4+α-δ (ECCZO) with y = 0, 0.01, 0.02, 0.05 and various δ values have been studied in order to ...elucidate the effect of nonmagnetic impurity of Zn to their structure and resistivity properties in the electron-doped cuprates. It has been found that the main peaks of T' structures are clearly observed in all samples. Superconductivity disappeared with Zn substitution for Cu in electron-doped system of ECCZO.
The conformational landscape of the cyclohexanol⋯SO2 cluster was revealed in the gas phase using chirped-pulsed broadband rotational spectroscopy and quantum chemical calculations. Four isomers ...stabilized by a dominant S⋯O chalcogen bond and cooperative C–H⋯O=S and O–H⋯O=S secondary weak hydrogen bonds were observed, with a near-parallel orientation of the S=O and O–H bonds. Isomers formed by equatorial-gauche cyclohexanol are more stable than the isomers containing axial cyclohexanol. The multiple conformations of cyclohexanol and the versatile binding properties of SO2, simultaneously operating as nucleophile and electrophile through its π-holes and non-bonding electrons lead to a complex conformational behavior when the cluster is formed. The long (2.64–2.85 Å) attractive S⋯O interaction between SO2 and cyclohexanol is mainly electrostatic and the contribution of charge transfer is obvious, with an NBO analysis suggesting that the strength of the S⋯O interaction is nearly two orders of magnitude larger than the hydrogen bonds. This study provides molecular insights into the structural and energetic characteristics that determine the formation of pre-nucleation clusters between SO2 and a volatile organic compound like cyclohexanol.
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