Nanocrystallite Size Research Articles

Nanocrystalization effects on the structural, electrical and thermoelectric properties of 10KNbO3-10Fe2O3-50B2O3-30V2O5 glass for non-volatile electronic-memory devices

AbstractThe composition: 10KNbO3-10Fe2O3-50B2O3-30V2O5 (in mol%) is produced using the conventional melt quenching method and their corresponding glass–ceramic nanocomposites were studied. The structural properties of the as-quenched sample and its heat-treated samples were investigated using X-ray diffraction and differential thermal analysis. Density (ρ) was found to decrease with increasing average nanocrystallite size as the molar volume increases. Studies on thermoelectric power have been carried out. The glass–ceramic nanocomposite after 2 h of heating exhibits significant improvement of electrical conductivity. The activation energy (W), polaron radius (rp) and other parameters have been estimated in the non-adiabatic region. The current–voltage (I–V) curve of each sample was measured. A temporal analysis of current & voltage in nonlinear I–V curves show pinched hysteresis loop, which is the memristor’s fingerprint. The glass–ceramic nanocomposite after 2 h of heating exhibits a large switching window. The results of the study enable us to predict that they will be helpful for future applications of non-volatile electronic-memory devices.

Studies of Phase Transformation Kinetics in the System of Nanocrystalline Iron/Ammonia/Hydrogen at the Temperature of 350 °C by Means of Magnetic Permeability In Situ Measurement

The kinetics of phase transformations in the nitriding process α-Fe → γ’-Fe4N → ε-Fe3-2N of the pre-reduced iron ammonia synthesis catalyst was investigated under in situ conditions (atmospheric pressure, 350 °C) by measuring changes of mass, gas phase composition, and magnetic permeability in a differential tubular reactor. The iron nanocrystallite size distribution according to their specific active surface areas was measured, and it was found that the catalyst is bimodal as the sum of two Gaussian distributions, also differing in the value of the relative magnetic permeability. Relative magnetic permeability of small α-Fe crystals in relation to large crystals is higher by 0.02. In the area of α → γ’ transformation, the magnetic permeability dependencies change, proving the existence of two mechanisms of the α-Fe structure change in the α-Fe → γ’-Fe4N transformation. In the first area, a solution of α-Fe (N) is formed with a continuous and insignificant change of the crystal lattice parameters of the iron lattice. In the second area, there is a step, oscillatory change in the parameters of the iron crystal lattice in FexN (x = 0.15, 0.20, 0.25 mol/mol). In the range of γ’-Fe4N → ε-Fe3-2N transformation, a solution is formed, with nitrogen concentration varying from 0.25–0.45 mol/mol. During the final stage of the nitriding process, at a constant value of the relative magnetic permeability, only the concentration of nitrogen in the solution εr increases. The rate of the phenomenon studied is limited by a diffusion rate through the top layer of atoms on the surface of iron nanocrystallite. The estimated value of the nitrogen diffusion coefficient varied exponentially with the degree of nitriding. In the area of the solution, the diffusion coefficient is approximately constant and amounts to 5 nm2/s. In the area of oscillatory changes, the average diffusion coefficient changes in the range of 3–11 nm2/s, and is inversely proportional to the nitrogen content degree. The advantage of the research method proposed in this paper is the possibility of simultaneously recording, under reaction conditions, changes in the values of several process parameters necessary to describe the process. The research results obtained in this way can be used to develop such fields of knowledge as heterogeneous catalysis, materials engineering, sensorics, etc.

Stable low friction of sp2 nanocrystallited carbon films in different vacuum pressures

This study reported the stable low friction of sp2 nanocrystallited carbon films in vacuum environment. Carbon film with larger sp2 nanocrystallites size demonstrated consistently low friction in different vacuum pressures. The lowest friction coefficient arrived 0.018 at 10–6 Pa with a long stable sliding cycles. The mechanisms were ascribed to the stable contact interfaces formed by the rapidly transferred sp2 nanocrystallites and the oxidation passivation layer. The low shear force at the nanocrystallited interface reduced the friction and the oxidation passivation promised the stabilization of interface. Carbon film with smaller sp2 nanocrystallite size only achieved low friction of 0.023 at 10–6 Pa, and the film exhibited high friction at 10-1∼10-3 Pa due to the insufficient passivation and large dangling bonds. As pure carbon film, sp2 nanocrystallited carbon films offer broadly application possibilities for vacuum micro-/nano- devices.

Atomic layer deposition, mechanical, wear resistance, and optical properties of (Cr1-xAlx)2O3 films on Si (100)

This study presents the comparison of microstructure, mechanical, tribological, and optical properties of the ternary chromium-aluminum oxide films ((Cr1-xAlx)2O3) with binary Cr2O3 and Al2O3 films, deposited by atomic layer deposition at 275 °C. The atomic growth per cycle of the Al atoms increased from 3.1 to 8.5 atoms/nm2 on chromium oxide film. The Al2O3 films were X-ray amorphous. The Cr2O3 films contained crystallites of the eskolaite phase. Nano-size (diameter from 3 to 5 nm) crystallites with cubic symmetry and matching with that of cubic γ-Al2O3 or η-Al2O3 phases were observed in (Cr1-xAlx)2O3 films. The ternary film with Al/(Al + Cr) of 0.40 showed the highest hardness (18.4 GPa) and elastic modulus (169.4 GPa), whereas the wear rate of this film decreased by ∼80 % compared with Cr2O3 films. Optical band gap energy values corresponding to the indirect transition model decreased from 2.93 eV for the Cr2O3 film to 2.58 eV for the Cr-Al-O films.

Modifications of some physical properties of nanostructured indium doped Co3O4 thin films

Using the chemical spray pyrolysis (CSP) technique, nanostructured undoped and Co3O4:In thin films are deposited. The effect of indium doping content in Cobalt ranged from 1% to 3% on optical, structural, and topographical properties of Co3O4 nanostructured thin films. No new peaks belonging to the In phase were seen, according to X-ray diffraction research, which revealed that pure and Co3O4: In thin films are polycrystalline in and cubic phase with (111), (311), (400), and (511) preferable orientation for all filmsThe Scherrer formula computation of average crystallite size shows that the size of Nano crystallites grows when doping is enhanced. AFM micrographs demonstrated how the surface shape of the films was discovered to be influenced by the inclusion of indium in the Co3O4 location.SEM images of Undoped Co3O4 and Co3O4:In films (CSP technique), showing separate semi-spherical blocks (120-200 nm) of nanoparticles (<30 nm). Band gap values for pure and doped were 2.52 to 2.38 eV. Resistance increases with increases Indium-doping, indicating more charge carriers and potential surface roughness influence. Sensitivity decreases with higher Indium concentrations, attributing to enhanced crystallinity and nano-crystalline size.

Modifications of some physical properties of nanostructured indium doped Co3O4 thin films

Using the chemical spray pyrolysis (CSP) technique, nanostructured undoped and Co3O4:In thin films are deposited. The effect of indium doping content in Cobalt ranged from 1% to 3% on optical, structural, and topographical properties of Co3O4 nanostructured thin films. No new peaks belonging to the In phase were seen, according to X-ray diffraction research, which revealed that pure and Co3O4: In thin films are polycrystalline in and cubic phase with (111), (311), (400), and (511) preferable orientation for all filmsThe Scherrer formula computation of average crystallite size shows that the size of Nano crystallites grows when doping is enhanced. AFM micrographs demonstrated how the surface shape of the films was discovered to be influenced by the inclusion of indium in the Co3O4 location.SEM images of Undoped Co3O4 and Co3O4:In films (CSP technique), showing separate semi-spherical blocks (120-200 nm) of nanoparticles (<30 nm). Band gap values for pure and doped were 2.52 to 2.38 eV. Resistance increases with increases Indium-doping, indicating more charge carriers and potential surface roughness influence. Sensitivity decreases with higher Indium concentrations, attributing to enhanced crystallinity and nano-crystalline size.

Ultra-sensitive CuAl2O4 Nanoflakes for ppb level detection of Isopropanol

Trace-level detection of isopropanol is important for human health monitoring and air quality surveillance. In this work, we report synthesis of high surface area two-dimensional (2D) nanoflakes of CuAl2O4 using surfactant-assisted hydrothermal process and its application in ppb level detection of isopropanol. X-ray diffraction revealed the polycrystalline nature of the spinel and a nano crystallite size of 42 nm. The 2D morphology of CuAl2O4 was confirmed using field emission scanning electron microscope whereas BET revealed the mesoporous nature and a high surface area of 41.8 m2g-1. The surface oxidation states of the material were found through X-ray photoelectron spectroscopy. The 2D CuAl2O4 demonstrated excellent sensing towards isopropanol with its response varying from 11.8 to 84.5 % (500 ppb–10 ppm) at 300 °C. The limit of detection of the spinel was found to be 56 ppb at its optimum operating temperature of 300 °C. In addition, the sensing layer was found to have response times in range 1101 s for 500 ppb to 168 s for 10 ppm and recovery times in the range 300 s for 500 ppb to 570 s for 10 ppm.

Annealing Effect on Structural, Optical and Electrophysical Properties of ZnSe Nanocrystals Synthesized into SiO2/Si Ion Track Template.

We report the results of synthesis of zinc selenide (ZnSe) nanocrystals into SiO2/Si track templates formed by irradiation with 200 MeV Xe ions up to a fluence of 107 ions/cm2. Zinc selenide nanocrystals were obtained by chemical deposition from the alkaline aqueous solution. Scanning electron microscopy, X-ray diffractometry, Raman and photoluminescence spectroscopy, and electrical measurements were used for characterization of synthesized ZnSe/SiO2nanoporous/Si nanocomposites. XRD data for as-deposited precipitates revealed the formation of ZnSe nanocrystals with cubic crystal structure, spatial syngony F-43m (216). According to non-empirical calculations using GGA-PBE and HSE06 functionals, ZnSe crystal is a direct-zone crystal with a minimum bandgap width of 2.36 eV and anisotropic electronic distribution. It was found that a thermal treatment of synthesized nanocomposites at 800 °C results in an increase in ZnSe nanocrystallites size as well as an increase in emission intensity of created precipitates in a broad UV-VIS spectra range. However, vacuum conditions of annealing still do not completely prevent the oxidation of zinc selenide, and a formation of hexagonal ZnO phase is registered in the annealed samples. The current-voltage characteristics of the synthesized nanocomposites proved to have n-type conductivity, as well as increased conductivity after annealing.

Spectroscopic properties of Pr3+-doped Titania-Silicate glass ceramic for photonic applications

Silicate-Titania (SiTi) glass-ceramics doped with Pr3+ (0.6, 1.6, 2.4 and 3.6 mol%) ions were prepared by sol-gel technique. The materials were characterized by powder XRD, FTIR, TEM, EDX, Optical absorption and Photoluminescence spectroscopy. The identification of non-bridging oxygen (NBO) formation and the removal of OH groups are validated through analysis of the FTIR spectra. Additionally, measurements using XRD and TEM showed that the samples contain nano-sized crystallites. The three phenomenological Judd–Ofelt (J–O) intensity parameters Ω2, Ω4, and Ω6 were obtained and used to analyze different radiative characteristics for the fluorescence levels of Pr3+ in the glass ceramic, including radiative lifetime, branching ratio, radiative transition probability and stimulated emission cross-section. Several emissions were observed in the visible region, among which the 1D2→3H4 in the orange-red region is the most intense. All of these reported branching ratios, stimulated emission cross-sections, and visible emission spectra point to the possibility of employing them as red region lasers. The CIE chromaticity coordinates from all of the emission spectra were also assessed to determine if these materials are suitable for orange-red phosphors. According to CIE chromaticity investigations, 1.6 mol% of Pr3+ ion concentration is ideal for SiTiPr glass-ceramic for use as red phosphors and possibly red lasers.

Electrochemical and statistical study of Nickel ion assessment in daily children intake samples relying on magnesium aluminate spinel nanoparticles

Lately, children's daily consumption of some products, such as cereals and candies, has been rising, which provides a compelling rationale for determining any metallic substances that may be present. Monitoring the concentration of certain metals, like nickel, in these products is necessary due to medical issues in humans when consumed regularly. So, in this work, a novel and highly selective carbon paste as a Ni(II) ion-selective sensor was prepared and investigated using ceramic magnesium aluminum spinel nanoparticles as the ionophore and tritolyl phosphate (TOCP) as a plasticizer. A modified co-precipitation method was used to synthesize the spinel nanoparticles. X-ray diffraction, scanning electron microscope with EDAX, transmission electron microscope, and BET surface area were used to determine the phase composition, microstructure, pores size, particle size, and surface area of the synthesized nanoparticles. The spinel nanoparticle was found to have a nano crystallite size with a cubic crystal system, a particle size ranging from 17.2 to 51.52 nm, mesoporous nature (average pore size = 8.72 nm), and a large surface area (61.75 m2/g). The composition ratio of graphite carbon as a base: TOCP as binder: spinal as ionophore was 67.3:30.0:2.7 (wt%) based on potentiometric detections over concentrations from 5.0 × 10−8 to 1.0 × 10−2 mol L−1 with LOD of 5.0 × 10−8 mol L−1. A measurement of 29.22 ± 0.12 mV decade−1 over pH 2.0–7.0 was made for the Nernstian slope. This sensor demonstrated good repeatability over nine weeks and a rapid response of 8 s. A good selectivity was shown for Ni(II) ions across many interferents, tri-, di-, and monovalent cations. The Ni(II) content in spiked real samples, including cocaine, sweets, coca, chocolate, carbonated drinks, cereals, and packages, were measured. The results obtained indicated no significant difference between the proposed potentiometric method and the officially reported ICP method according to the F- and t-test data. In addition to utilizing ANOVA statistical analysis, validation procedures have been implemented, and the results exceed the ICP-MS methodology.

Enhancing electrical properties through in-situ controlled nanocrystallization of V2O5–TeO2 glass

V2O5–TeO2 glass–ceramics (VTGC) were prepared by controlled annealing of the V2O5–TeO2 glass (VTG), which illustrates a parent glass matrix with a single charge carrier. The annealing proceeded at six temperatures selected between the glass transition and the maximum of the first crystallization process to obtain various nanocrystallite sizes. Heat treatment caused an increase in DC conductivity by 2.5–3.5 (250–285 °C) order of magnitude. Using thermal analysis, the crystal growth process was determined to be 1D. Structural studies show that the obtained materials are partially amorphous and polycrystalline with nanometer-sized crystallites. Subtle thread-like structures were observed using conductive AFM. The activation energy of the conduction process decreased from 0.38 eV in VTG to 0.18–0.11 eV (250–285 °C) in VTGC. The radii of crystallites were calculated based on the theoretical model of electron hopping between connected semiconducting nanocrystallites and vary between 1.7 and 2.8 nm (250–285 °C). Thermoelectric studies indicate constant carrier concentration. Features characteristic of small polaron hopping-governed materials were observed. We suggest V3O7 nanocrystals as conductive media in VTGC.Graphical abstract

A novel electroactive biopolymer-graphene oxide nanocomposite membrane for high-performance electrochemical sensing of ethylene

This study focuses on formulating an electroactive composite membrane using polyvinyl alcohol (PVA), chitosan (CHT), and graphene oxide (GO), specifically emphasizing its application in electrochemical ethylene detection. Through the surface functionalization of the PVA-CHT-GO membrane via GO activation, the nanocrystallite GO-based composite, when incorporated into a microelectrode chip, exhibited a transformative enhancement in electrochemical ethylene sensing. Comprehensive characterizations of both the synthesized GO and the PVA-CHT-GO composite membranes were conducted by employing X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Raman spectroscopy, Energy Dispersive X-ray spectroscopy (EDS), Field emission scanning electron microscopy (FE-SEM), and Thermal gravimetric analysis (TGA). The XRD pattern provides insights into the stacking height, interplanar spacing, and the number of layers along the (002) direction. The synthesized GO's average nano-crystallite size was determined to be 10.38 nm. The Raman spectrum revealed prominent D and G bands at 1353 and 1591 cm-1, respectively. FE-SEM images depicted the overlapping of GO nanolayers, each layer having a thickness in the range of 20–30 nm. Following surface activation, thin layers developed on the membrane surface, with numerous folds accumulating, exhibiting thickness in the range of 20–50 nm. The intricate characterization underscored the structural and morphological features of the membrane, enhancing our understanding of its surface properties. The effectiveness of ethylene detection using the GO-activated PVA-CHT-GO membrane was evaluated via cyclic voltammetry (CV) measurements. These measurements confirmed the membrane's efficiency, demonstrating ultra-sensitive ethylene detection, even upon initial exposure to ethylene.

Nanocrystalline Iron Oxides with Various Average Crystallite Size Investigated Using Magnetic Resonance Method

A series of nanocrystalline iron oxide samples (M1–M5) which differ from each other in average crystallite size (from 26 to 37 nm) was studied. The raw material was nanocrystalline iron with an average crystallite size equal to 21 nm promoted with hardly reducible oxides: Al2O3, CaO, K2O (in total, max. 10 wt%). Nanocrystalline iron was subjected to oxidation with water vapor to achieve different oxidation degrees (α = 0.16–1.00). Metallic iron remaining in the samples after the oxidizing step was removed by etching. Magnetic resonance spectra of all samples were obtained at room temperature. All resonance lines were asymmetric and intense. These spectra were fitted by Lorentzian and Gaussian functions. All spectral parameters depend on the preparation method of the nanoparticles. We suppose that the Lorentz fit gives us a spectrum from larger agglomerated sizes whereas the Gaussian fit comes from much smaller magnetic centers. For the nanocrystalline samples with the largest size of iron oxide nanocrystallites, the highest value of total integrated intensity was obtained, indicating that at smaller sizes, they are more mobile in reorientation processes resulting in more settings of anti-parallel magnetic moments. The magnetic anisotropy should also increase with the increase in size of nanocrystallites.

Evidence of local structural distortions and subtle thermal disorder in transparent photochromic yttrium oxyhydride

The structural properties of photochromic yttrium oxyhydride powder in its transparent state were examined using x-ray diffraction and temperature-dependent extended x-ray absorption fine structure spectroscopy (EXAFS) combined with reverse Monte Carlo (RMC) simulations. The refinement of the x-ray powder diffraction pattern, employing the Rietveld method, indicates that yttrium oxyhydride crystallizes in the nanocrystalline phase with the cubic space group Fm-3m (225), at room temperature. The lattice parameter was determined as a = 5.404(3) Å, and the nanocrystallite size was estimated at d = 16(2) nm. The partial radial distribution functions (RDFs) g(r) for Y–O, O–O, and Y–Y atom pairs were obtained from the results of the RMC simulations of the Y K-edge EXAFS spectra measured at three temperatures (10, 150, and 300 K). The analysis of the RDFs reveals a subtle impact of the thermal disorder and splitting of the second coordination shell of yttrium atoms (the Y–Y RDF), remaining at all temperatures. This observation, also supported by our density functional theory calculations, suggests the presence of local structural distortions associated with yttrium sites, which do not affect the long-range crystal order.

Assessing microbially mediated vivianite as a novel phosphorus and iron fertilizer

BackgroundMicroorganisms can transform phosphorus (P)-enriched iron (Fe)-oxide sludge into products with higher P concentration or can directly promote the precipitation of P-rich compounds from water. However, there is no evidence of these products’ efficiency as fertilizers. This study aimed to assess the effectiveness of microbially mediated vivianite (biovivianite) as P and Fe fertilizer for durum wheat and white lupin, respectively.ResultsTo this end, two completely randomized block experiments were conducted with wheat (phosphorus (P) experiment) and white lupin (iron (Fe) experiment). The P and Fe sources used included biovivianite produced by microbial reduction of P-containing ferrihydrite at pH 6.5 (VivInsol6.5) and pH 7.0 (VivInsol7.0), biovivianite produced with soluble Fe(III) citrate (C6H5FeO7) in the presence of soluble phosphate at pH 7 (VivSol), and vivianite from a commercial company (ComViv). Potassium dihydrogen phosphate (KH2PO4) was used as a reference fertilizer in the P experiment, and Fe-EDDHA and Fe(II)-sulfate (FeSO4.7H2O) were used in the Fe experiment. Total P uptake by wheat plants from the product dominated by vivianite and phosphate-green rust (VivSol) was not significantly different from KH2PO4. The relative P use efficiency, i.e., the equivalence in terms of P recovery of VivSol was 74% of KH2PO4, making VivSol the effective P source for durum wheat among the products tested (aside from KH2PO4). For Fe uptake, product dominated by vivianite and metavivianite (VivInsol7.0), was the most effective Fe source for white lupin followed by Fe-EDDHA, ComViv, and VivSol with VivInsol6.5 as the least effective but without significant differences with Fe(II)-sulfate. The average crystallite sizes of the biovivianite were 59 nm, 63 nm, and 66 nm for VivSol, VivInsol7.0, and VivInsol6.5, respectively.ConclusionsThe mineral constituents of the biovivianite coupled with their nano-crystallite sizes explained its effectiveness as P and Fe fertilizers. The results reveal that biovivianite production is a novel way of producing efficient P and Fe fertilizers from P-enriched Fe sludge or P-rich water. Thus, it can be used for producing fertilizers with high P and Fe concentrations from water purification, providing new tools for a circular economy approach in the use of a non-renewable resource such as P.Graphical

Skew scattering dominated anomalous Hall effect in Si/Ni multilayers containing varying number of bilayers

A systematic study of the skew scattering dominated anomalous Hall effect (AHE) in Si/Ni multilayers has been carried out on several samples containing different number of bilayers. The investigation is performed by preparing a series of Si10Å/Ni30ÅN multilayers. When the number of bilayers (N) is decreased, structural analysis showed that the size of Ni nanocrystallites and the distance between them decreases whereas their count rises. As a result, the saturation magnetization lowers with N. Furthermore, the perpendicular magnetic anisotropy of the multilayers improves as N is reduced. The saturated AHE resistance (RHSA) is also found to decrease as N increases due to the decreases of the Si/Ni interface area and scattering effect from the Ni nanocrystallites. A maximum of about 28 times enhancement in RHSA is observed for the sample with N = 1 when compared with that for N = 24. It is seen that the skew scattering is the dominant mechanism which is responsible for the AHE in the Si/Ni multilayers.

Sonochemical synthesis of SnS and SnS2 quantum dots from aqueous solutions, and their photo- and sonocatalytic activity

Our study reports the ultrasound-assisted synthesis of SnS and SnS2 in the form of nanoparticles using aqueous solutions of respective tin chloride and thioacetamide varying sonication time. The presence of both compounds is confirmed by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, as well as Raman and FT-IR spectroscopic techniques. The existence of nanoparticles is proven by powder X-ray diffraction investigation and by high resolution transmission electron microscopy observations. The size of nanocrystallites are in the range of 3–8 nm and 30 50 nm for SnS, and 1.5–10 nm for SnS2. X-ray photoelectron spectroscopy measurements, used to investigate the chemical state of tin and sulphur atoms on the surface of nanoparticles, reveal that they are typically covered with tin on the same oxidation degree as respective bulk compound. Values of optical bandgaps of synthesized nanoparticles, according to the Tauc method, were 2.31, 1.47 and 1.05 eV for SnS (60, 90 and 120 min long synthesis, respectively), and 2.81, 2.78 and 2.70 eV for SnS2 (60, 90 and 120 min long synthesis, respectively). Obtained nanoparticles were utilized as photo- and sonocatalysts in the process of degradation of model azo-dye molecules by UV-C light or ultrasound. Quantum dots of SnS2 obtained under sonication lasting 120 min were the best photocatalyst (66.9 % color removal), while quantum dots of SnS obtained under similar sonication time were the best sonocatalyst (85.2 % color removal).

Glassy-like Transients in Semiconductor Nanomaterials.

Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs.

Irradiation Time Optimization on Photocatalytic Activity of Nanoparticles MgO from Dolomite Bangkalan

Dolomite is a type of sedimentary rock material that is often found in the Bangkalan Madura area. This dolomite has a higher MgO compound content than in the other areas, namely 40 %, but its utilization has only been as fertilizer and building materials. For this reason, this research aims to determine the characteristics of MgO nanoparticles and their application in photocatalytic with visible light irradiation. The synthesis of MgO nanoparticles used the hydrochloric acid leaching method, and the results were characterized by X-ray diffraction, Fourier transform infrared, Scanning electron microscopy, Transmission electron microscopy, Raman spectroscopy, Photoluminescence, and Ultraviolet-visible spectroscopy. The results showed that the synthesized MgO nanoparticles had a periclase phase and were shaped like a spherical cube with an average nanoparticle size of 27 nm and an energy gap of 3.9 eV. The optical properties of the MgO nanoparticles showed quite strong luminescence at a Raman shift of 1,087.36 cm−1, which was associated with the type of vibrational waves in the atomic lattice, and there were surface defects on the surface of the MgO nanoparticles, namely in the emission spectra of 720.06 and 740.39 nm originating from oxygen vacancies (F-center) and Mg vacancies (V-center). The photocatalytic activity of MgO nanoparticles in visible light showed the optimum time to degrade 30 ppm methylene blue dye in 360 min and yielded a degradation percentage of 99 %. Therefore, MgO nanoparticles could be used for processing industrial dye waste using visible light. HIGHLIGHTS The synthesis of MgO Nanoparticles from Bangkalan dolomite used the hydrochloric acid leaching method The presence of nanocrystallite size, crystal defects, and oxygen vacancies in MgO nanoparticles can increase photocatalytic activity MgO nanoparticles can degrade methylene blue dye with an optimum time of 360 minutes under visible light irradiation GRAPHICAL ABSTRACT

Impedance spectroscopy, ferroelectric and ferromagnetic properties of 60Bi2O3–10SrO–30Fe2O3 glass-ceramic nano-composites for energy storage applications

The glass of composition 60Bi2O3–10SrO–30Fe2O3 (BSFO) (in mol%) was prepared by conventional melt quenching technique. Heat treatment process was applied to the glass samples at temperature close to crystallization temperature (600 °C) for different time intervals of 0, 2, 4 and 8, respectively, to obtain glass ceramic nano-composites. X-ray diffraction (XRD) patterns displayed the formation of a cubic Bi3.43Fe0.57O6 for BSFO glass-ceramic nano-composites. The average nanocrystallite size (D) was determined to be between 13.48 and 17.26 nm. The values of D of the present samples were increased with an increment of heat treatment time. The high resolution-transmission electron microscope (HRTEM) images of a BSFO glass sample that was heat treated at 600 °C for 4 h show the nanocrystallites dispersed in the glass matrix with particle size in the range of 17 nm. The real part of permittivity (ε′) of BSFO decreased sharply with the increment in frequency for all samples. The decrement in the magnitude of the real part of impedance (Z′) with the increment in both frequency and temperature suggests an increase in ac conductivity σac. The correlated barrier hopping (CBH) model can explain the exponent S and temperature behavior we observed throughout all samples. For all glass–ceramic nano-composites, with an increase in the electric field, remnant polarization Pr increases. This confirms its ferroelectric nature. The energy storage density (Wr) is found to be maximum for the HT 8 h sample and equal to 34.3 mJ/cm3. The efficiency (η) of the HT 8 h sample was 65 %. The (M − H) loops of the glass–ceramic nano-composites displayed an antiferromagnetic trend. These observations suggest that the present samples might be a promising option for producing energy storage devices.