Smrutiranjan Parida

Encapsulating 8-hydroxyquinoline in graphene oxide-stabilized polystyrene containers and its anticorrosion performance

We report the formation of encapsulated graphene oxide/polystyrene (GO/PS) containers via Pickering emulsion polymerization of oil-in-water emulsions stabilized by GO sheets. Without further functionalization, the as-synthesized GO sheets were used for emulsion stabilization to minimize the process step. A one-step process was developed to encapsulate 8-Hydroxyquinoline (8-HQ) in GO/PS containers. FT-IR study confirmed the encapsulation. The inhibiting effect of 8-HQ was found to affect the kinetics of the emulsion polymerization and shift the polymerization temperature to a higher value. A detailed study of stability, size, and morphology of encapsulated containers (PS/GO) was carried out as a function of GO-to-oil ratio and oil volume fraction in the formulation, to optimize the process parameters. A possible mechanism for the formation of GO/PS containers at various GO-to-oil ratios was discussed. The corrosion inhibition performance of 8-HQ-encapsulated containers was studied in an epoxy coating. These encapsulated containers induced long-term anticorrosive property to the coating. The use of cost-effective materials and a scalable method used in this work can be utilized to prepare environmentally friendly coatings for large-area applications.

One step eco-friendly synthesis of Ag–reduced graphene oxide nanocomposite by phytoreduction for sensitive nitrite determination

We report a facile, ecofriendly, surfactant-free one step green synthesis of a silver–reduced graphene oxide nanocomposite (Ag–RGO) using a Justicia adhatoda (adulsa) leaf extract as green reducing agent and its application to construct a nitrite (NO2−) sensor. The crystallinity, size, morphology and composition of as prepared Ag–RGO nanocomposite were studied using a range of techniques. TEM results showed that ultrasmall silver nanoparticles (2–4 nm) were well dispersed on RGO sheets with C/O ratio of 4.4 and 63.8% of sp2 carbon, obtained from XPS analysis. These results confirmed that adulsa leaf extract not only simultaneously reduce silver ion and graphene oxide but also act as effective capping agent. Electrochemical investigations indicated that Ag–RGO nanocomposite had excellent catalytic activity towards nitrite oxidation with sensitive nitrite detection below 1 ppm. The sensor exhibited two linear ranges; one from 10 nM to 1000 nM with a sensitivity of 3.0 × 104 μA mM−1 cm−2 (R = 0.999) and another from 10 μM to 1000 μM with a sensitivity of 373.46 μA mM−1 cm−2 (R = 0.978). These values are superior to other previously reported NO2− sensors.

Designing binder-free, flexible electrodes for high-performance supercapacitors based on pristine carbon nano-onions and their composite with CuO nanoparticles

The increasing demand for energy has triggered tremendous research efforts for the development of light-weight and durable energy storage devices. This requires exploring simple and economical methods to prepare the active materials and to design lightweight, flexible, free-standing supercapacitor electrodes in an inexpensive binder-free process. Herein, we try to address both these critical issues using CNOs and their composite with CuO as the active material. Active materials were supported on cotton wipes by a simple “sonication and drying” process to obtain light-weight, flexible and free-standing binder-free electrodes. In a symmetrical two-electrode cell, a pristine CNO electrode delivers a specific capacitance of 102.16 F g−1 (20 mV s−1), an energy density of 14.18 W h kg−1 and a power density of 2448 W kg−1, which are the highest values reported so far for CNO-based materials. CNO–CuO nanocomposites demonstrate a very significant specific capacitance of 420 F g−1 (10 mV s−1) with deliverable energy and power density at 58.33 W h kg−1 and 4228 W kg−1, respectively. Electrodes of both the active materials show an excellent cyclic performance and stability, retaining up to 90–95% of their initial capacitance after 5000 charge–discharge cycles at a current density of 5 A g−1. A simple cost estimation indicates that our device can deliver an energy density of 58.33 W h kg−1 at an estimated cost of less than 1

Nanoporous gold–copper oxide based all-solid-state micro-supercapacitors

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Facile sonochemical synthesis of highly dispersed ultrafine Pd nanoparticle decorated carbon nano-onions with high metal loading and enhanced electrocatalytic activity

The rapid growth of miniaturized electronic devices has increased the demand for energy storage devices with small dimensions. Micro-supercapacitors have great potential to supplement or replace batteries and electrolytic capacitors for a wide range of applications. Micro-supercapacitor can be fabricated with micro-electronic devices for efficient energy storage unit. However, the lower energy densities of micro-supercapacitors are still a bigger challenge to its application in micro devices. In this paper, we report all-solid-state nanoporous gold (NPG)–copper oxide (CuO) based micro-supercapacitor prepared using a simple fabrication process. In this process, first NPG interdigital patterns were developed by using a simple annealing and dealloying procedure, and then CuO was electrodeposited on NPG interdigital microelectrodes. The nanoporous gold substrate provides good electronic/ionic conductivity with high intrinsic surface area for the electrodeposition of CuO, which forms a novel hybrid electrode. The NPG–CuO micro-supercapacitor exhibits maximum areal capacitance 26 mF cm−2, maximum specific energy 3.6 μW h cm−2 and maximum specific power 646 μW cm−2. NPG–CuO micro-supercapacitors show excellent cyclic stability with 98% capacitance retention after 10 000 cycles.

Structural Evolution during Milling, Annealing, and Rapid Consolidation of Nanocrystalline Fe–10Cr–3Al Powder

Highly dispersed, ultrafine Pd nanoparticle decorated carbon nano-onions (CNO) were prepared by a facile, one-step sonochemical method. The presence of surface functional groups and the mesoporosity of the as-prepared CNO helped achieve high nanoparticle dispersion at a high Pd loading with a marginal effect on the particle size under the sonochemical conditions. The Pd loading in the catalyst was varied as 18, 28 and 60 weight percent (wt%). The average size of Pd nanoparticles was around 2 nm up to 28 wt% loading and increases to 4 nm at 60 wt% loading. The electrocatalytic performance of Pd decorated CNOs were evaluated using formaldehyde oxidation in alkaline media. The electrochemically active surface area and the peak current density for formaldehyde electrooxidation increased with Pd loading up to 28 wt%. This suggests that the effect of metal loading dominates the particle size effect in CNO supported electrocatalysts if a high metal loading is achieved with a high degree of nanoparticle dispersion and better size control. The study also demonstrates that by selecting a suitable support material and controlling the synthesis conditions, the particle size and dispersion can be controlled while achieving high mass loading in an electrocatalyst.

A facile method for high yield synthesis of carbon nano onions for designing binder-free flexible supercapacitor

Structural changes during the deformation-induced synthesis of nanocrystalline Fe–10Cr–3Al alloy powder via high-energy ball milling followed by annealing and rapid consolidation by spark plasma sintering were investigated. Reduction in crystallite size was observed during the synthesis, which was associated with the lattice expansion and rise in dislocation density, reflecting the generation of the excess grain boundary interfacial energy and the excess free volume. Subsequent annealing led to the exponential growth of the crystallites with a concomitant drop in the dislocation density. The rapid consolidation of the as-synthesized nanocrystalline alloy powder by the spark plasma sintering, on the other hand, showed only a limited grain growth due to the reduction of processing time for the consolidation by about 95% when compared to annealing at the same temperature.

Facile wick-and-oil flame synthesis of high-quality hydrophilic onion-like carbon nanoparticles

Carbon nano onion (CNO) is a promising material for diverse application areas such as energy devices, catalysis, lubrication, biology and gas storage, etc. However, its implementation is fraught with the production of high-quality powders in bulk quantity. Herein, we report a facile scalable and one-step “wick-and-oil” flame synthesis of pure and water dispersible CNO nanopowder. Other forms of carbon did not contaminate the as-prepared CNO; hence, a post processing purification procedure was not necessary. Brunauer Emmett Teller (BET) specific surface area of as-prepared CNO was 218 m2/g, which is higher as compared to other reported flame synthesis methods. Locally available daily used cotton wipe has been used for fabrication of such an ideal electrode by “dipping and drying” process providing outstanding strechability and mechanical flexibility with strong adhesion between CNOs and porous wipe. The specific capacitance 102.16 F/g, energy density 14.18 Wh/kg and power density 2448 W/kg at 20 mV/s scan ...