Carbon nanotubes (CNTs) are known as nano-architectured allotropes of carbon, having graphene sheets that are wrapped forming a cylindrical shape. Rolling of graphene sheets in different ways makes CNTs either metals or narrow-band semiconductors. Over the years, researchers have devoted much attention to understanding the intriguing properties CNTs. They exhibit some unusual properties like a high degree of stiffness, a large length-to-diameter ratio, and exceptional resilience, and for this reason, they are used in a variety of applications. These properties can be manipulated by controlling the diameter, chirality, wall nature, and length of CNTs which are in turn, synthesis procedure-dependent. In this review article, various synthesis methods for the production of CNTs are thoroughly elaborated. Several characterization methods are also described in the paper. The applications of CNTs in various technologically important fields are discussed in detail. Finally, future prospects of CNTs are outlined in view of their commercial applications.

Owing to its exciting physicochemical properties and doping–dedoping chemistry, polyaniline (PANI) has emerged as a potential adsorbent for removal of dyes and heavy metals from aqueous solution. Herein, we report on the synthesis of PANI composites with magnetic oxide (Fe₃O₄) for efficient removal of Basic Blue 3 (BB3) dye from aqueous solution. PANI, Fe₃O₄, and their composites were characterized with several techniques and subsequently applied for adsorption of BB3. Effect of contact time, initial concentration of dye, pH, and ionic strength on adsorption behavior were systematically investigated. The data obtained were fitted into Langmuir, Frundlich, Dubbanin-Rudiskavich (D-R), and Tempkin adsorption isotherm models for evaluation of adsorption parameters. Langmuir isotherm fits closely to the adsorption data with R² values of 0.9788, 0.9849, and 0.9985 for Fe₃O₄, PANI, and PANI/Fe₃O₄ composites, respectively. The maximum amount of dye adsorbed was 7.474, 47.977, and 78.13 mg/g for Fe₃O₄, PANI, and PANI/Fe₃O₄ composites, respectively. The enhanced adsorption capability of the composites is attributed to increase in surface area and pore volume of the hybrid materials. The adsorption followed pseudo second order kinetics with R² values of 0.873, 0.979, and 0.999 for Fe₃O₄, PANI, and PANI/Fe₃O₄ composites, respectively. The activation energy, enthalpy, Gibbs free energy changes, and entropy changes were found to be 11.14, −32.84, −04.05, and −0.095 kJ/mol for Fe₃O₄, 11.97, −62.93, −07.78, and −0.18 kJ/mol for PANI and 09.94, −74.26, −10.63, and −0.210 kJ/mol for PANI/Fe₃O₄ respectively, which indicate the spontaneous and exothermic nature of the adsorption process.

This work explores the opportunity to reduce the cost and enhance the stability of RuO₂ as an oxygen evolution reaction catalyst by coating RuO₂ on chemically stable SnO₂ support. Nano‐sized RuO₂/SnO₂ composites of different mass ratios of RuO₂ to SnO₂ (0.45:1, 0.67:1, and 1.07:1) were synthesized using solution‐based hydrothermal method. The physicochemical properties of the RuO₂/SnO₂ were studied by scanning electron microscopy, X‐ray diffraction, transmission electron microscopy, and N₂ adsorption–desorption isotherms. The electrochemical activity of RuO₂/SnO₂ as anode electrocatalyst was investigated in a proton exchange membrane (PEM) water electrolysis cell of Pt/C cathode and Nafion membrane. Experimental results showed that RuO₂/SnO₂ of ratio (1.07:1) exhibit higher electrochemical activity compared to pure RuO₂, resulting ~50% reduction of noble metal content. The extended life test of electrocatalysts for 240 h implied that RuO₂/SnO₂ (1.07:1) significantly improved the stability of electrode in comparison to pure RuO₂ in oxygen evolution processes. Copyright © 2013 John Wiley & Sons, Ltd.