Electrochemical Characterisation of Sol-Gel Derived SnO2 for Supercapacitor Application

Pseudocapacitive properties of SnO2 and Sb-doped SnO2 were determined in 0.5 mol dm–3 KCl solution. The samples were prepared by sol-gel method and analysed by X-ray powder diffraction (XRPD) and field emission scanning electron microscopy (FE SEM). Rietveld refinement of XRPD data showed the changes in unit cell parameters due to the incorporation of Sb3+ into the host SnO2 lattice, while FE SEM pointed out the differences in morphology caused by doping. Specific capacitance values of 3.67 and 6.89 F g–1 were obtained for SnO2 and Sb-doped SnO2, respectively. Reaction mechanism of SnO2 that corresponds to the obtained mass change was proposed. It was shown that redox reactions of SnO2 and Sb-doped SnO2 are dependent on structural changes since different mass change properties were obtained in comparison to the previous reports carried out for other metal oxides. This work is licensed under a Creative Commons Attribution 4.0 International License

Crystal structure prediction of (quasi-)two-dimensional lead halide perovskites

Two-dimensional lead halide perovskites are promising materials for optoelectronics due to the tunability of their properties with the number of lead halide layers and the choice of an organic spacer. Physical understanding for the rational design of materials primarily requires knowledge of crystal structure. 2D lead halide perovskites are usually prepared in the form of films complicating the experimental determination of structure. To enable theoretical studies of experimentally unresolvable structures as well as high-throughput virtual screening, we present an algorithm for crystal structure prediction of lead halide perovskites. Using automatically prepared classical potential we show that our algorithm enables fast access to a structure that can be used for further first-principles studies

Outbreak of West Nile virus infection among humans in Serbia, August to October 2012

We describe the first reported outbreak of West Nile virus (WNV) infection in humans in Serbia in August to October 2012 and examine the association of various variables with encephalitis and fatal outcome. Enzyme-linked immunosorbent assay (ELISA) was used for detection of WNV-specific IgM and IgG antibodies in sera and cerebrospinal fluid. A total of 58 patients (mean age: 61 years; standard deviation: 15) were analysed: 44 were from Belgrade and its suburbs; 52 had neuroinvasive disease, of whom 8 had meningitis, while 44 had encephalitis. Acute flaccid paralysis developed in 13 of the patients with encephalitis. Age over 60 years and immunosuppression (including diabetes) were independently associated with the development of encephalitis in a multivariate analysis: odds ratio (OR): 44.8 (95% confidence interval (CI): 4.93-408.59); p=0.001 (age over 60 years); OR: 10.76 (95% CI: 1.06-109.65); p=0.045 (immunosuppression including diabetes). Respiratory failure requiring mechanical ventilation developed in 13 patients with encephalitis. A total of 35 patients had completely recovered by the time they were discharged; nine patients died. The presence of acute flaccid paralysis, consciousness impairment, respiratory failure and immunosuppression (without diabetes) were found to be associated with death in hospital in a univariate analysis (p lt 0.001, p=0.007, p lt 0.001 and p=0.010, respectively)

Bioaccumulation potential of 'Meeker' and 'Willamette' raspberry (Rubus idaeus L.) fruits towards macro- and microelements and their nutritional evaluation

Raspberry (Rubus idaeus L.) is the most important type of berry fruit in the Republic of Serbia. The bioaccumulation factor (BF) for the elements detected in the fruits of the raspberry cultivars 'Willamette' and 'Meeker' was calculated to determine their bioaccumulation potential. In addition, the nutritional quality of fruits in relation to nutritionally essential elements was evaluated and compared with the recommended daily intake. For determining the concentrations of 19 macro- and microelements in fruits and the soil, the analytical technique of optical emission spectrometry with inductively coupled plasma was used. Among the analyzed elements, As, Cd, Co, Cr, Li and Mo were below the limit of detection in the fruits of both raspberry cultivars, whereas Na and Ni were detected only in fruits of the 'Meeker' cultivar. All analyzed elements were detected in the soil. The results of the work indicated the high potential of the studied cultivars to accumulate nutritional elements K and Ca. In both raspberry cultivars, there were no substantial differences in the bioaccumulation of most elements. However, two elements (B and Mn) can be singled out; the BF for B in the 'Willamette' fruit was 3 times lower compared to the BF in the 'Meeker' fruit, whereas, the BF value for Mn in the 'Willamette' fruit was almost 8 times higher compared to the BF value for the 'Meeker' fruit. Furthermore, the cultivars did not tend to accumulate potentially toxic elements such as Ba, Co, Cu and Ni. The nutritional evaluation revealed that the studied raspberry fruits are a good source of K, Ca, Mg, Fe, Mn and Cu. Based on the BF values, differences observed in the accumulation of B, Ba, Na, Ni and Mn may be attributed to the characteristics of the cultivars

Long cycle life of CoMn2O4 lithium ion battery anodes with high crystallinity

CoMn2O4 nanomaterials are prepared by a low temperature precipitation route employing metal acetates and NaOH. Structural changes, induced by different annealing temperatures, are comprehensively analyzed by X-ray powder diffraction and Raman spectroscopy. With rising annealing temperature the crystal lattice of CoMn2O4 undergoes changes ; AO4 tetrahedra expand due to thermally induced substitution of Co2+ by larger Mn2+ metal ions on the A-site of the spinel structure, while in contrast, BO6 octahedra shrink since the B-site becomes partially occupied by smaller Co3+ metal ions on account of the migrated Mn ions. CoMn2O4 particle sizes are easily fine-tuned by applying different annealing temperatures ; the particle size increases with increasing annealing temperature. During the battery operation, pulverization and reduction of particle sizes occurs regardless of the initial size of the particles, but the degree of division of the particles during the operation is dependent on the initial particle properties. Thus, contrary to the common assumption that nanostructuring of the anode material improves the battery performance, samples with the largest particle sizes exhibit excellent performance with a capacity retention of 104% after 1000 cycles (compared to the 2nd cycle)

Sodium-Ion Conductivity and Humidity-Sensing Properties of Na2O-MoO3-P2O5 Glass-Ceramics

A series of glass-ceramics were prepared by heat- treatments of 40Na2O-30MoO3-30P2O5 (in mol%) glass in a temperature range from 380 (Tg) to 490 °C (Tc) and for 1–24 h. The prepared glass-ceramics contain from 2 to 25 wt.% of crystalline NaMoO2PO4. The sodium-ion conductivity in these materials decreases up to one order of magnitude with an increase in the degree of crystallization due to the immobilization of sodium ions in crystalline NaMoO2PO4. The transport of sodium ions in these materials occurs primarily through the dominant continuous glassy phase, and it is weakly affected by the sporadically distributed crystalline grains. However, the prepared glassceramics exhibit high proton conductivity in a humid atmosphere and remarkable humidity-sensing properties ; this could be related to crystalline NaMoO2PO4, which provides sites for water adsorption. The glass-ceramic prepared at 450 °C for 24 h shows the best humidity-sensing performance among all samples, showing an increase in proton conductivity for more than seven orders of magnitude with the increase in relative humidity from 0% to 95%. Under a highly humid atmosphere (95% relative humidity and 25 °C), the proton conductivity of this glass-ceramic reaches 5.2 ×10−3 (Ω cm)−1. Moreover, the electrical response of these materials on the change in the relative humidity is linear and reversible in the entire range of the relative humidity, which indicates that they are novel promising candidates for application as humidity sensors