Synthesis and stability of chitosan gold nanocomposites: Effect of time of heating and concentration of reactant

Gold nanoparticles (AuNPs) exhibit red colour and is suitable for development of indicators based on colour change. This work investigated the influence of concentration of gold precursor and time of thermal treatment on the properties of chitosan gold nanocomposites. Three concentrations of gold, 5 mM, 10 mM, and 15 mM were used and the heating time studied were 5 min and 15 min. The UV–vis spectra, transmission electron microscopic characteristics, zeta potential, and visible colour were inspected. All the samples have shown distinct colour change and the characteristic surface plasmonic resonance peak at ~530 nm. The spectral properties, zeta potential, and particle dispersity were significantly affected by the concentration and time. Furthermore, the nanoparticles were exposed to frozen condition at −18 °C ± 2 °C. The absorbance maxima of surface plasmonic resonance peak have changed significantly in all the samples. The visible colour of chitosan gold nanocomposites has changed on freezing and the microscopic analysis demonstrated the clustering and change in shape of nanoparticles on freezing. The results suggest that the chitosan gold nanocomposites synthesised with 10 mM gold chloride and 5 min of heating can be efficiently used as freeze indicator.     

Corrosion protection of mild steel in hydrochloric acid up to 313 K using propyl benzimidazole: Electroanalytical,adsorption and quantum chemical studies

The inhibition efficiency of propyl benzimidazole for mild steel in hydrochloric acid in three different concentrations at 303, 308 & 313 K have been studied by polarization, electrochemical impedance spectroscopy, adsorption, surface studies and basic computational calculations. The inhibition efficiencies and the global chemical reactivity relate to total energy, E_HOMO, E_LUMO and gap energy (ΔE). Propyl benzimidazole interact with mild steel surface through adsorption and the process of adsorption follow Langmuir isotherm model. The inhibition efficiency increases with concentration and reaches maximum at 150 ppm. The increase in temperature have an inverse relationship with protection efficiency. The corrosion inhibition efficiencies and the global chemical reactivity relate to total energy, E_HOMO, E_LUMO and gap energy (ΔE).     

Sustainable transport and the modernisation of urban transport in Delhi and Stockholm

This article addresses issues of the development of transport systems taking its examples from Delhi and Stockholm. The introduction of the first bus rapid transport corridor in Delhi and the congestion tax in Stockholm is presented and discussed in terms of modernisation and sustainable transport. This paper explores the perceptions of politicians and examines some transport plans in the search for the driving forces for transport policies. The continuing presence of a high proportion of non-motorised modes of transport and use of public transport in Delhi over the past 50 years gives it a greater political opportunity for creating a more inclusive city than Stockholm. Whereas, in Stockholm, awareness of the influence of emissions on climate change makes the inhabitants more inclined to accept fees for the use of city streets where sustainable transport and modernisation of transport systems are seen as key activities, but are perceived and operationalised differently in Delhi and Stockholm. Despite all the differences, some similarities in the development of their urban transport projects have been found. This paper inquires into the planning and operationalisation of transport modernisation and the politics of sustainable transport.     

Electronic and spin configurations of Co3+ and Ni3+ ions in oxides of K2NiF4 structure: A magnetic susceptibility study

In La₄LiCoO₈, Li⁺ and Co³⁺ ions are ordered in two dimensions and Co³⁺ ions undergo transitions from the low-spin to the intermediate as well as the high-spin states. Both Sr₄TaCoO₈ and Sr₄NbCoO₈ exhibit low to intermediate-spin state transitions of Co³⁺ ions. In the system LaSr_1?xBa_xNiO₄, the e_g electrons are essentially in extended states forming a band. With increase in x, the band width decreases accompanying an increase in unit cell volume; high-spin Ni³⁺ ions are formed to a small extent with increasing x, but there is no spin-state transition. In LaSrAl_1?xNi_xO₄, at small x, there is a small proportion of high-spin Ni³⁺; when x ≈ 0.6, there is an abrupt decrease in the $\text{c}$/$\text{a}$ ratio, signalling the formation of the band. In LnSrNiO₄, the $\text{c}$/$\text{a}$ ratio decreases sharply between Ln = La and Nd; this is likely to be accompanied by a broadening of the band.     

Electrical properties of the system lanthanum lead cobalt titanium oxide

Measurements of DC electrical resistivity and Seebeck coefficient on the perovskite system La_1−x Pb _x−δ Co_1−x Ti _x O_3−δ for 0·2≤x≤0·9 have been made in the temperature range 300–800 K. AC conductivity,σ _a.c, of all the samples were measured as a function of temperature (300–573 K) and frequency (1 kHz-1 MHz). DC resistivity behaviour of all the samples is similar. However, the resistivity value, which varies over 5–6 orders of magnitude, depends on both the compositionx and the structure of the samples. All the samples exhibitp-type electronic conduction. The value of Seebeck coefficient,α, for samples withx≤0·5 initially increases with temperature up to a particular temperature. Above this temperature, the behaviour ofα for samples withx≤0·5 and for samples withx>0·5 over the entire temperature range is similar to that of La CoO₃. All the samples exhibit frequency-dependent a.c. conductivity at low temperatures.     

Dye sensitized solar cell based on platinum decorated multiwall carbon nanotubes as catalytic layer on the counter electrode

In this study we have employed multiwall carbon nanotubes (MWCNT), decorated with platinum as catalytic layer for the reduction of tri-iodide ions in dye sensitized solar cell (DSSC). MWCNTs have been prepared by a simple one step pyrolysis method using ferrocene as the catalyst and xylene as the carbon source. Platinum decorated MWCNTs have been prepared by chemical reduction method. The as prepared MWCNTs and Pt/MWCNTs have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In combination with a dye adsorbed TiO₂ photoanode and an organic liquid electrolyte, Pt/MWCNT composite showed an enhanced short circuit current density of 16.12 mA/cm² leading to a cell efficiency of 6.50% which is comparable to that of Platinum.     

Effective thermal conductivity and rheological characteristics of ethylene glycol-based nanofluids with single-walled carbon nanohorn inclusions

In this study, we report the effective thermal conductivity and rheological behavior of ethylene glycol with single-walled carbon nanohorn inclusions. The thermal conductivity and viscosity was found to increase with respect to nanohorn loading. Maximum thermal conductivity enhancement of ～11% at a nanohorn loading of 1.5 vol% was obtained in this study. The viscosity of nanofluids increase with respect to nanohorn loading and decreases with respect to shear rate which indicates the non-Newtonian shear thinning behavior at higher nanohorn loading. Finally, the effectiveness of nanofluids was calculated for laminar and turbulent regions to predict the heat transfer performance and favorability of these nanofluids. The present nanofluids are favorable upto 0.1 vol% in the laminar region. However, these nanofluids are not favorable for turbulent region and loadings beyond 0.1 vol% due to higher viscosity enhancement.