Water-repelling behavior of the 1-D hematite nano-network.

Hematite is an attractive material used as electron transport layer in perovskite-based solar cells. Being hydrophilic in nature it attracts moisture, which can be damaging for perovskite layers. Therefore, it is important to make hematite moisture repelling, which can be beneficial for applications in solar cells or for protecting iron surfaces from further rust formation. In this work, we demonstrate that the systematic irradiation of nanostructured hematite with low-energy argon ions (Ar+) at various ion fluences can change the surface wettability as well as promote the formation of junctions between nanorods. The nano-welded network of the irradiated hematite turns out to be hydrophobic. Using TRI3DYN simulations, ion-induced surface roughening, the presence of surface oxygen vacancies, and joining between adjacent nanorods are predicted. Furthermore, the water-repelling behavior of the irradiated nano-network is evaluated using density functional theory (DFT) simulations by determining the interaction of water molecules with the surface. The interconnected hematite nano-network also shows a notable improvement in electrical conductivity.

Role of polymer template in crystal structure and photoactivity of Cu-TiO2 heterojunction nanostructures towards environmental remediation.

Exploring porous heterojunction nanomaterials as a photocatalyst for water depollution strategies towards environmental restoration is exceedingly difficult in the perspective of sustainable chemistry. Herein, we first report a porous Cu-TiO2 (TC40) heterojunction by using microphase separation of a novel penta-block copolymer (PLGA-PEO-PPO-PEO-PLGA) as a template through an evaporation induced self-assembly (EISA) method having nanorod-like particle shape. Furthermore, two types of photocatalyst were made with or without polymer template to clarify the function of that template precursor on the surface and morphology, as well as which variables are the most critical for a photocatalyst. TC40 heterojunction nanomaterial displayed higher BET surface area along with lower band gap value viz.2.98 eV compared to the other and these features make it a robust photocatalyst for wastewater treatment. In order to improve water quality, we have carried out experiments on the photodegradation of methyl orange (MO), highly toxic pollutants that cause health hazards and bioaccumulate in the environment. Our catalyst, TC40 exhibits the 100% photocatalytic efficiency towards MO dye degradation in 40 and 360 min at a rate constant of 0.104 ± 0.007 min-1 and 0.440 ± 0.03 h-1 under UV + Vis and visible light irradiation, respectively.

Alteration of Wettability of Copper-Copper Oxide Nanocomposites through Cu-O Bond Breaking Swayed by Ultraviolet and Electron Irradiation.

Converting a nonwetting surface to a highly wetting one, aided by ultraviolet radiation, is well explored. Here, in this work, we show just the reverse behavior of a copper-copper oxide nanocomposite surface where ultraviolet radiation turned the superhydrophilic surface to a superhydrophobic one. This observation is explained both experimentally and theoretically using first-principles density functional theory-based calculations considering the metal-oxygen (Cu-O) bond breaking and related change in surface chemistry. This observation has further been corroborated with electron irradiation on the same nanocomposite material. To the best of our knowledge, for the first time, we show that the radiation-induced breaking of the copper-oxygen bond makes the nanostructure surface energetically unfavorable for water adsorption.

Adhesive hydrophobicity of Cu2O nano-columnar arrays induced by nitrogen ion irradiation.

Low energy nitrogen ions are used in this work to manipulate wetting properties of the surface of the array of Cu2O nano-columns, which yields remarkable results. The nano-columnar thin films were grown on a highly conductive silicon surface by a sputter deposition technique. The films were irradiated at two different fluences of 5 × 10(15) and 1 × 10(16) ions per cm(2), respectively. With increasing fluence the shape of column tip changes, columns are bent and porous channels between columns are clogged up. While the surface of the pristine sample is hydrophilic, the irradiated surface turns into hydrophobic but having adhesion properties. We have analysed the structural and chemical properties of the surface in detail to understand the initial and modified wetting properties. Furthermore, the temporal evolutions of different droplet parameters are investigated to realize the interactions between the water droplet, the sample surface and the atmosphere. We envisage that such modified surfaces can be beneficial for transport of a small volume of liquids with minimum loss and spectroscopic studies, where a small amount of water droplet is available for measurements.

Conjugation of cytochrome c with hydrogen titanate nanotubes: novel conformational state with implications for apoptosis.

We show that hydrogen titanate (H(2)Ti(3)O(7)) nanotubes form strongly associated reversible nano-bio-conjugates with the vital respiratory protein, cytochrome c. Resonance Raman spectroscopy along with direct electrochemical studies indicate that in this nano-bio-conjugate, cytochrome c exists in an equilibrium of two conformational states with distinctly different formal redox potentials and coordination geometries of the heme center. The nanotube-conjugated cytochrome c also showed enhanced peroxidase activity similar to the membrane-bound protein that is believed to be an apoptosis initiator. This suggests that such a nanotube-cytochrome c conjugate may be a good candidate for cancer therapy applications.

Growth of aligned ZnO nanorod arrays from an aqueous solution: effect of additives and substrates.

We report a simple, versatile, low cost fabrication technique for synthesizing nanorod arrays whose architecture is suited for many applications spanning the nanometer to micrometer range. Specifically, we have covered the range of nanorod diameter from 50 to 1200 nm. From a detailed study of the growth parameters involved in the synthesis of the ZnO nanorod arrays from an aqueous solution, we report, in particular, the effects of varying the capping agent, substrate and substrate-seeding. We find that seeding the substrate and selecting the appropriate capping agent play the most crucial roles in the alignment of nanorod arrays. Our study on the use of different precursor materials and varied substrates for the growth of ZnO nanorod arrays should lead to an enhanced understanding of the controllable growth of ZnO crystals and nanostructures.

Optimization of the morphology of ZnO nanorods grown by an electrochemical process.

Zinc oxide nanorods were synthesized by a direct electrodeposition technique on indium tin oxide plates. The effect of a systematic variation of the deposition potential and the inter-electrode distance on the morphology of ZnO nanorods was investigated. X-ray diffraction studies indicated that the nanorods are highly c-axis oriented. The diameter of the nanorods depends mainly on the deposition potential and the electrode separation. Our detailed study of the synthesis-morphology correlations provide the optimal electrochemical conditions required for oriented ZnO nanorods with minimum diameter.

Surfactant-assisted synthesis of ceria-titania-rich mesoporous silica materials and their catalytic activity towards photodegradation of organic dyes.

Ceria-titania doped highly ordered hexagonal and cubic mesoporous silica composite samples with varying amounts of Ce and Ti have been synthesized using hexadecyltrimethylammonium bromide (CTAB) surfactant as a template under basic conditions in the presence of ammonia. The removal of the template resulted in the formation of mesoporous composites doped with Ce and Ti, which were thoroughly characterized via small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXRD), N2 adsorption, scanning and transmission electron microscopy analysis with energy-dispersive spectrometry mapping (SEM-TEM-EDS), inductively coupled plasma atomic emission spectrophotometry (ICP-AES), and ultraviolet-visible diffuse reflectance spectrometry (UV-visible). The electronic states of Ti and Ce species present on the surface of silica were also investigated by X-ray photoelectron spectroscopy (XPS). The catalytic activity of these Ti-modified ceria-silica samples for the photodecomposition of rhodamine B under visible-light irradiation was investigated. The results revealed that a sample with a higher Ti content, as well as equal amounts of Ce and Ti, displayed higher catalytic activity for the photodegradation of the organic dye rhodamine B.