Vertically-aligned graphene flakes on nanoporous templates: morphology,thickness, and defect level control by pre-treatment

Various morphologies of the vertically-aligned graphene flakes were fabricated on the nanoporous templates treated with metal ions in solutions, as well as coated with a thin gold layer and activated in the low-temperature Ar plasma. The thickness and level of structural defects in the graphene flakes could be effectively controlled by a proper selection of the pre-treatment method. We have also demonstrated that various combinations of the flake thickness and defect levels can be obtained, and the morphology and density of the graphene pattern can be effectively controlled. The result obtained could be of interest for various applications requiring fabrication of large graphene networks with controllable properties.     

“Effect of nano-ZnO particles on the corrosion behavior of alkyd-based waterborne coatings”

A nano-composite was formed by incorporating nano-ZnO in a specially developed alkyd-based waterborne coating to different loading levels. The nano-ZnO based composite coatings were applied on mild steel substrate by dipping. The coated panels were subjected to various test environments like salt-spray, humidity, UV and mechanical tests like scratch and abrasion. The improvement in electrochemical performance and mechanical properties of the composite coatings were evaluated using various analytical techniques. FTIR technique was used to investigate the interaction between nano-ZnO particles and the polymer functionalities. Differential scanning calorimetry (DSC) was done to study the curing behavior of nano-composite coatings. SEM and AFM were used to investigate dispersion of nano-ZnO particles and the changes in the surface behavior of the coatings before and after exposure to the test environment. The result showed that, with increase in the concentration of nano-ZnO there was an improvement in the corrosion resistance, UV resistance and mechanical properties of the coatings indicating the positive effect of addition of nano-ZnO particles in the coatings.     

Controlled modification of Pt/Al2O3 for the preferential oxidation of CO in hydrogen: A comparative study of modifying element

The catalytic performance of a series of Pt/Al₂O₃ catalysts, modified with Cr, Mn, Fe, Co, Ni, Cu and Sn, has been tested for the preferential oxidation of CO in hydrogen. The promoters were deposited onto the surface of a 5 wt.% monometallic Pt/Al₂O₃ catalyst using a controlled surface approach, to give a nominal promoter:Pt surface atomic ratio of 1:2 (corresponding to typically 0.15–0.25 wt.% of the promoting metal). The aim of this approach was to selectively create the Pt-promoter oxide interfacial sites considered to be important for the non-competitive dual-site mechanism proposed for such promoted catalysts. In this mechanism the promoting oxide is believed to act as an active oxygen provider, providing oxygen for the oxidation of the CO on the Pt. The catalysts were characterised using TEM, EDX, ICP-AES and CO chemisorption and results suggest that the promoter was successfully deposited on to the Pt surface. Even at the low loadings of promoter used, significant enhancement was observed in the catalytic performance of the PROX reaction in a simulated reformate mixture, for the Fe- and Co-promoted catalysts in particular (and to a lesser extent the Mn, Sn, Cu- and Ni-promoted catalysts), highlighting the successful preparation of the Pt-promoting metal oxide interfacial sites. The Mn-promoted catalyst, however showed no enhancement in the absence of water suggesting that the form of the promoting metal oxide may be particularly important for promotion of Pt for the PROX reaction.     

Palladium‐Catalyzed C?H Functionalization of Ferrocenecarboxylic Acid by using 8‐Aminoquinoline as a Removable Directing Group

A mild and efficient palladium‐catalyzed synthetic method for the C H functionalization of N‐(quinolin‐8‐yl)ferrocenecarboxamide has been developed. Various aryl iodides containing I, NO₂, CN, COMe, CO₂Et, and NH functionalities and also alkyl iodides underwent the Pd‐catalyzed intermolecular carbon‐carbon bond forming reaction with ferrocenecarboxamide successfully which led to a diverse array of bis(aryl/alkyl)ferrocenecarboxamides in 34–92% yields. Cross‐coupling of the ferrocenyl C H bond with aryl iodides can also be achieved utilizing an economical Ni catalyst. Additionally, selective monoalkylation of ferrocenecarboxamide was studied using sodium bicarbonate as base and dibenzylphosphoric acid as additive under Pd‐catalyzed reaction conditions. Subsequently, removal of the directing group, 8‐aminoquinoline, from bis(aryl)ferrocenecarboxamides led to bis(aryl)ferrocenes bearing versatile methyl ester and carboxaldehyde functional groups.

     

Electrochemical behavior of nano-iron oxide modified alkyd based waterborne coatings

A nano-composite coating was formed using nano-Fe₂O₃ as pigments in different concentrations, to a specially developed alkyd based waterborne coating. The nano-Fe₂O₃ based composite coatings were applied on mild steel substrate by dipping. The dispersion of nano-Fe₂O₃ particles in coating system was investigated by SEM and AFM techniques. The effect of addition of these nano-pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy (EIS). Coating modified with higher concentration of nano-Fe₂O₃ particles showed comparatively better performance as it was evident from R_po and C_c values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano-particle modified coatings as compared to the neat coating, confirming the positive effect of nano-particle addition in coatings.     

Study on electrochemical behavior of Nano‐ZnO modified alkyd‐based waterborne coatings

A nano‐composite coating was formed using nano‐ZnO as pigment in different concentrations, to a specially developed alkyd‐based waterborne coating. The nano‐ZnO modified composite coatings were applied on mild steel substrate by dipping. The dispersion of nano‐ZnO particles in coating system was investigated by scanning electron microscopic and atomic force microscopic techniques. The effect of the addition of these nano‐pigments on the electrochemical behavior of the coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy. Coating modified with higher concentration of nano‐ZnO particles showed comparatively better performance as was evident from the pore resistance (R_po) and coating capacitance (C_c) values after 30 days of exposure. In general, the study showed an improvement in the corrosion resistance of the nano‐particle modified coatings as compared with the neat coating, confirming the positive effect of nano‐particle addition in coatings. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of interfacial pretreatment on the properties of montmorillonite/poly(vinyl alcohol) nanocomposites

This work explores the factors that control the dispersion of exfoliated montmorillonite (MMT) in poly(vinyl alcohol) (PVOH) during solution blending and solvent evaporation. Nanocomposite films were prepared by solution blending of aqueous PVOH solutions with dilute suspensions of fully exfoliated MMT platelets (as confirmed by AFM). Dynamic light scattering (DLS) indicates that addition of MMT suspensions to PVOH solutions results in undesired particle aggregation and thus poor MMT dispersion in cast films (as evidenced by transmission electron microscopic images and gas permeation measurements). We believe that PVOH bridging induces MMT platelet aggregation. To counteract bridging aggregation, we explore the novel idea of pretreating the MMT surface with a small amount of compatible polymer prior to solution blending with PVOH. We hypothesize that “pretreating” the MMT platelet surfaces with adsorbed polymer in dilute suspensions will protect the platelets from bridging aggregation during solution blending and solvent evaporation. MMT/PVOH composite films have been prepared using low‐molecular‐weight PVOH as the pretreatment polymer; and low‐, medium‐, and high‐molecular‐weight PVOH as the matrix polymer. A PEO‐PPO‐PEO triblock copolymer (F108 from the Pluronics^® family) was also evaluated as the pretreatment polymer. DLS shows that pretreated MMT platelets are less susceptible to aggregation during blending with PVOH solutions. Results compare the crystalline structure, thermal properties, dynamic mechanical properties, gas permeability, and dissolution behavior of MMT/PVOH films incorporating untreated versus pretreated MMT. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41867.     

Adaptive general perfectly periodic scheduling

We propose an adaptive algorithm Adaptmin to create perfectly periodic schedules. A perfectly periodic schedule schedules a client regularly after a predefined amount of time known as the period of the client. The periodicity of such schedules can be used to save battery life of nodes in a wireless network. The quality of a perfectly periodic schedule is a function of the ratio between the granted and requested periods. We find a worst case performance bound on the quality of schedules produced by Adaptmin. We compare our algorithm to previously proposed algorithm A in [Z. Brakerski, A. Nisgav, B. Patt-Shamir, General perfectly periodic scheduling, in: Proc. 21st Annual Symp. on Principles of Distributed Computing, 2002, pp. 163-172], and show families of input instances where either Adaptmin does no worse than A, or always outperforms A. The better performance of the proposed algorithm is also confirmed by simulations results for randomly generated input instances. Adaptmin produces 25% more efficient schedules as compared to A in our experiments. We also propose a variant of Adaptmin which is computationally much less demanding compared to A, but is very close to Adaptmin in terms of efficiency. Finally, we compare our algorithms to exponential-time optimal scheduling. Our simulation results indicate that the performance of the proposed algorithms is close to that of optimal scheduling.     

Plasma-enabled,catalyst-free growth of carbon nanotubes on mechanically-written Si features with arbitrary shape

Simple, rapid, catalyst-free synthesis of complex patterns of long, vertically aligned multiwalled carbon nanotubes, strictly confined within mechanically-written features on a Si(1 0 0) surface is reported. It is shown that dense arrays of the nanotubes can nucleate and fully fill the features when the low-temperature microwave plasma is in a direct contact with the surface. This eliminates additional nanofabrication steps and inevitable contact losses in applications associated with carbon nanotube patterns.     

Surface modification of CdSe quantum dots for biosensing applications: Role of ligands

For an optimum performance of colloidal nanocrystal devices for a variety of applications such as photonic devices, solar cells and biological labelling, the determining factors are the nanocrystal surface and size. In this work, these two factors have been tuned via wet chemistry to tailor the material properties: The absorption and emission spectra have been tailored by choice of the nanocrystal size; nanocrystal shape by surface modification and photoluminescence (PL) efficiency determined by surface traps, has been tuned via appropriate selection of the nanocrystal capping ligands. Here, we have shown that through ligand-exchange process, the surface of the CdSe quantum dots (QDs) can be modified by replacing the longer-chain ligands of conventional trioctyl phosphine oxide (TOPO) or oleic acid (OA) with shorter-chain ligand of butyl amine. This imparts colloidal stability and water solubility to CdSe QDs for its potential applications in biosensors and biological imaging. It is conjectured that crystallite sizes, oxidation potential of CdSe QDs and stereochemical compatibility of ligands (TOPO, oleic acid and butyl amine) greatly influences the photophysics and photochemistry of CdSe QDs.