Novel 3D-flower shaped KTaO3 perovskite for highly efficient photocatalytic and H2 generation ability.

Treatment of industrial wastewater is one of the biggest challenges that mankind is facing today to prevent environmental pollution and its associated adverse effects on human health. Environmentalists across the world have given a clarion call for dye degradation, wastewater treatment and their effective management in our surrounding habitats. Despite significant progress in the development of new water treatment technologies, new materials haven't matured enough for large scale industrial applications. Hence, the development of new scalable and sustainable multifunctional materials having the potential to treat wastewater and generate energy is the need of the hour. In this direction, novel 3D-flower shaped KTaO3 (3D-F-KT) material has been synthesized using areca seed powder as a green fuel. This new material has been successfully applied for the treatment of industrial wastewater contaminated with Rose Bengal. The efficiency of the material was analysed using several parameters like catalytic loading, dye concentration, kinetic and scavenging experiments, photostability, effect of co-existing ions and recyclability. In addition, the material was subjected to optical studies and H2 generation, making it a highly versatile multifunctional material, exhibiting a degradation efficiency of 94.12% in a short span of 150 min and a photocatalytic H2 generation efficiency of 374 µmol g-1 through water splitting. With an immense potential, KTaO3 presents itself as a multifunctional catalyst that can be scaled up for a variety of industrial applications ranging from wastewater treatment to energy generation and storage.

Templated Growth of Pd Nanoparticles Using Sputtering Deposition Process and Its Catalytic Activities.

A simple method based on sputtering deposition of Pd onto mesoporous SiO2 (SBA-15) was employed to produce supported Pd nanoparticles (NPs) that can be used as hydrogenation catalysts. The use of sputtering deposition eliminates contaminants and avoids additional drawbacks of traditional chemical methods applied to prepare heterogeneous supported metal catalysts. A mechanical resonant stirrer was used to revolve the SBA-15 powder and ensure homogeneous distribution of the Pd NPs over the support. The SBA-15 pores act as templates for Pd NPs and drive nanostructure growth. Consequently, the NPs obtained have the same diameter as that of the SBA-15 channels (~5 nm) and elongated particles are formed as sputtering deposition increases. The SBA-15 supported Pd NPs (Pd NPs/SBA-15) were tested in a probe hydrogenation of cyclohexene reaction to evaluate the catalytic activity of the Pd NPs. Turnover frequency (TOF) of 2000 min-1 were achieved with the lower Pd NPs concentration (0.15 wt%) catalyst.

Pristine Ta3 N5 Nanotubes: Trap-Driven High External Biasing Perspective in Semiconductor/Electrolyte Interfaces.

Ta3 N5 is a promising photoelectrode for solar hydrogen production; however, to date pristine Ta3 N5 electrodes without loading co-catalysts have presented limited photoelectrochemical (PEC) performance. In particular, large external biasing has been required to run water oxidation, the origin of which is investigated herein. Ta3 N5 nanotubes (NTs) prepared by nitridation were characterized by a wide range of techniques. The bandgap was confirmed by a novel PEC technique. Nondestructive synchrotron-excited XPS has shown the presence of reduced Ta species deeper in the Ta3 N5 surface. Lower photocurrent and transient spikes that were intense at lower applied biasing were observed under water oxidation; however, spikes were inhibited in the presence of a sacrificial agent and photocurrent was improved even at low biasing. It was observed for the first time that the lower PEC performance under water oxidation can be attributed to the presence of interband trapping states associated with pristine Ta3 N5 NTs/electrolyte junction. These states correspond to the structural defects in Ta3 N5 , devastate PEC performance, and present the necessity to apply higher biasing. The key to circumvent them is to use a sacrificial agent in the electrolyte or to load a suitable co-catalyst to avoid hole accumulation under water oxidation, thereby improving the phootocurrent. The findings on the interband states could also provide guidance for the investigation of PEC properties of new types of semiconducting devices.

Synergizing nanocomposites of CdSe/TiO2 nanotubes for improved photoelectrochemical activity via thermal treatment.

In this work, we show the effect of the thermal treatment temperature on the photoelectrochemical (PEC) activity of CdSe/TiO2 nanocomposites. TiO2 nanotubes (NTs) were synthesized by anodization and the nanocomposites were obtained by depositing CdSe clusters via magnetron sputtering. A two-step thermal treatment was performed: heating the TiO2 NTs at different temperatures prior to CdSe deposition and further heating the CdSe/TiO2 nanocomposites. The nanocomposites were characterized by Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV-Vis spectrophotometry, and electrochemical impedance spectroscopy (EIS). To compare the PEC performance of the CdSe/TiO2 nanocomposites and pristine TiO2 NTs, linear sweep voltammetry (LSV) curves were obtained under visible light and under 1 sun illumination. It was observed that CdSe incorporation into the TiO2 template enhances the visible light absorbance thereby improving the PEC performance of the nanocomposites. We have found that the optical, structural and PEC properties of the CdSe/TiO2 nanocomposites are dependent on the thermal treatment temperature of the TiO2 nanotubular substrate, prior to CdSe deposition. Moreover, a three-fold improvement in photocurrent was observed upon further thermal treatment of the obtained nanocomposite.

Synthesis and Characterisation of Fluorescent Carbon Nanodots Produced in Ionic Liquids by Laser Ablation.

Carbon nanodots (C-dots) with an average size of 1.5 and 3.0 nm were produced by laser ablation in different imidazolium ionic liquids (ILs), namely, 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4 ), 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2 ) and 1-n-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (OMI.NTf2 ). The mean size of the nanoparticles is influenced by the imidazolium alkyl side chain but not by the nature of the anion. However, by varying the anion (BF4 vs. NTf2 ) it was possible to detect a significant modification of the fluorescence properties. The C-dots are much probably stabilised by an electrostatic layer of the IL and this interaction has played an important role with regard to the formation, stabilisation and photoluminescence properties of the nanodots. A tuneable broadband fluorescence emission from the colloidal suspension was observed under ultraviolet/visible excitation with fluorescence lifetimes fitted by a multi-exponential decay with average values around 7 ns.

Mesoporous Foam TiO2 Nanomaterials for Effective Hydrogen Production.

Hydrolysis of TiCl4 in a diether-functionalized imidazolium ionic liquid (IL), namely 1-methyl-3-[2-(2-methoxy(ethoxy)ethyl]imidazolium methane sulfonate (M(MEE)I⋅CH3 SO3 ), results in a heterostructured organic/inorganic and sponge-like porous TiO2 material. The thermal treatment (300 °C) followed by calcination (500 °C) affords highly porous TiO2 . The characterization of the obtained samples (with and without IL, before and after calcination) by XRD, SEM, and TEM reveals TiO2 anatase crystalline phases and irregular-shaped particles with different porous structures. These hierarchical-structured mesoporous TiO2 nanomaterials were employed as efficient photocatalysts in the water-splitting process, yielding up to 1304 µmol g(-1) on hydrogen production.

How Sorbitan Monostearate Can Increase Drug-Loading Capacity of Lipid-Core Polymeric Nanocapsules.

Lipid-core polymeric nanocapsules are innovative devices that present distinguished characteristics due to the presence of sorbitan monostearate into the oily-core. This component acted as low-molecular-mass organic gelator for the oil (medium chain triglycerides). The organogel-structured core influenced the polymeric wall characteristics disfavoring the formation of more stable polymer crystallites. This probably occurred due to interpenetration of these pseudo-phases. Sorbitan monostearate dispersed in the oily-core was also able to interact by non-covalent bonding with the drugs increasing the drug loading capacity more than 40 times compared to conventional nanocapsules. We demonstrated that the drug-models quercetin and quercetin pentaacetate stabilized the organogel network probably due to interactions of the drug molecules with the sorbitan monostearate headgroups by hydrogen bonding.

Structural, optical and photoelectrochemical characterizations of monoclinic Ta3N5 thin films.

Monoclinic Ta3N5 thin films were synthesized by thermal nitridation of amorphous Ta2O5 films directly sputtered by radio frequency magnetron sputtering. The samples were studied by high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis-NIR spectrophotometry, rietveld refinements, spectroscopic ellipsometry and electrochemical techniques. The surface composition of Ta3N5 thin film was found to be different than the underlying film, affecting the optical properties of the material. Rietveld refinement has confirmed that the nitridation process results in Schottky and oxygen substitutional defects within the crystalline structure of monoclinic Ta3N5 thin film. The optical constants of the film were obtained by spectroscopic ellipsometry within a spectral range of 4.60-0.54 eV, i.e. 270-2300 nm. The suitable parameterization was found to consist of three Tauc-Lorentz and one Lorentz oscillators. The conduction band, valence band and the flat band positions were determined by photoelectrochemical techniques, presenting a strong dependence on pH of the eletrolyte. Improved photocurrent was obtained in alkaline conditions and attributed to the shorter depletion region width measured by Mott-Schottky and the lower recombination life time measured by open circuit potential decay analyses.

Easy Access to Metallic Copper Nanoparticles with High Activity and Stability for CO Oxidation.

Copper catalysts are very promising, affordable alternatives for noble metals in CO oxidation; however, the nature of the active species remains unclear and differs throughout previous reports. Here, we report the preparation of 8 nm copper nanoparticles (Cu NPs), with high metallic content, directly deposited onto the surface of silica nanopowders by magnetron sputtering deposition. The as-prepared Cu/SiO2 contains 85% Cu0 and 15% Cu2+ and was enriched in the Cu0 phase by H2 soft pretreatment (96% Cu0 and 4% Cu2+) or further oxidized after treatment with O2 (33% Cu0 and 67% Cu2+). These catalysts were studied in the catalytic oxidation of CO under dry and humid conditions. Higher activity was observed for the sample previously reduced with H2, suggesting that the presence of Cu-metal species enhances CO oxidation performance. Inversely, a poorer performance was observed for the sample previously oxidized with O2. The presence of water vapor caused only a small increase in the temperature require for the reaction to reach 100% conversion. Under dry conditions, the Cu NP catalyst was able to maintain full conversion for up to 45 h at 350 °C, but it deactivated with time on stream in the presence of water vapor.

Sputtering-deposition of Ru nanoparticles onto Al2O3 modified with imidazolium ionic liquids: synthesis, characterisation and catalysis.

Well-distributed Ru nanoparticles (Ru-NPs) were produced over Al(2)O(3) supports modified with covalently anchored imidazolium ionic liquids (ILs) containing different anions and cation lateral alkyl chain lengths by simple sputtering from a Ru foil. These Ru-NPs were active catalysts for the hydrogenation of benzene. Furthermore, depending on the nature of the IL used to modify the support (hydrophilic or hydrophobic), different catalytic behaviours were observed. Turnover numbers (TON) as high as 27 000 with a turnover frequency (TOF) of 2.73 s(-1) were achieved with Ru-NPs of 6.4 nm supported in Al(2)O(3) modified with an IL containing the N(SO(2)CF(3))2(-) anion, whereas higher initial cyclohexene selectivities (ca. 20% at 1% benzene conversion) were attained for Ru-NPs of 6.6 nm in the case where Cl(-) and BF(4)(-) anions were used. Such observations strongly suggest that thin layers of ILs surround the NP surface, modifying the reactivity of these catalytic systems. These findings open a new window of opportunity in the development of size-controlled Ru-NPs with tuneable reactivity.

Hydrophobic effects on supported ionic liquid phase Pd nanoparticle hydrogenation catalysts.

Hybrid organosilicas prepared by sol-gel processes using 1-n-butyl-3-(3-trimethoxysilylpropyl)-imidazolium cations associated with hydrophilic and hydrophobic anions can be easily decorated with well dispersed and similar size (1.8-2.1 nm) Pd nanoparticles (Pd-NPs) by simple sputtering-deposition. Higher Pd concentration at the surface compared to the deeper region is obtained in the supports with smaller pore diameter (containing hydrophobic ILs) than in supports with the largest pore diameter (containing hydrophilic ILs). The IL hydrophobicity plays a central role in the hydrogenation of dienes by controlling the diene access to NP surface active sites.

TiO2 nanotubes sensitized with CdSe via RF magnetron sputtering for photoelectrochemical applications under visible light irradiation.

Highly ordered TiO2 NT arrays were easily decorated with CdSe via RF magnetron sputtering. After deposition thermal annealing at different temperatures was performed to obtain an improved TiO2/CdSe interface. The heterostructures were characterized by RBS, SEM, XRD, HRTEM, UV-Vis, EIS, IPCE and current versus voltage curves. The sensitized semiconducting electrodes display an enhanced photocurrent density of ca. 2 mA cm(-2) at 0.6 V (vs. Ag/AgCl) under visible light (λ > 400 nm). The sensitized photoelectrodes displayed 3 and 535-fold enhanced photocurrent when compared to bare TiO2 NTs under 1 sun and under visible light illumination, respectively. IES results confirmed the improved charge transfer across the TiO2/CdSe/electrolyte interface after annealing at 400 °C. Incident photon-to-electron conversion efficiency measurements confirmed the efficient sensitization by allowing photoresponse in the visible range.

Insights into the active surface species formed on Ta2O5 nanotubes in the catalytic oxidation of CO.

Freestanding Ta2O5 nanotubes were prepared by an anodizing method. As-anodized amorphous nanotubes were calcined at high temperature to obtain a crystalline phase. All materials were studied by means of BET analysis, XRD, TEM, SEM, XPS, and FTIR and were evaluated in the catalytic oxidation of CO. An XPS study confirmed the formation of different tantalum surface species after high temperature treatment of amorphous Ta2O5 nanotubes. Calcination at 800 °C generated Ta(4+) while higher temperature (1000 °C) treatment led to the formation of Ta(3+) species. These materials also showed significant differences in catalytic activity. Higher activity was observed for samples calcined at 800 °C than at 1000 °C, suggesting that Ta(4+) species are active sites for CO oxidation.

Photocatalytic hydrogen production of Co(OH)2 nanoparticle-coated α-Fe2O3 nanorings.

The production of hydrogen from water using only a catalyst and solar energy is one of the most challenging and promising outlets for the generation of clean and renewable energy. Semiconductor photocatalysts for solar hydrogen production by water photolysis must employ stable, non-toxic, abundant and inexpensive visible-light absorbers capable of harvesting light photons with adequate potential to reduce water. Here, we show that α-Fe2O3 can meet these requirements by means of using hydrothermally prepared nanorings. These iron oxide nanoring photocatalysts proved capable of producing hydrogen efficiently without application of an external bias. In addition, Co(OH)2 nanoparticles were shown to be efficient co-catalysts on the nanoring surface by improving the efficiency of hydrogen generation. Both nanoparticle-coated and uncoated nanorings displayed superior photocatalytic activity for hydrogen evolution when compared with TiO2 nanoparticles, showing themselves to be promising materials for water-splitting using only solar light.

Controlled synthesis of Mn3O4 nanoparticles in ionic liquids.

This work describes a simple one-step synthesis of Mn3O4 nanoparticles by thermal decomposition of [Mn(acac)2] (acac = acetylacetonate) using imidazolium ionic liquids (ILs) and a conventional solvent, oleylamine, for comparison. The Mn3O4 nanoparticles were characterized by XRD, ATR-FTIR, TEM, Raman, UV/VIS and magnetometry techniques. The addition of 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide IL (BMI·NTf2) yielded a smaller particle size (9.9 ± 1.8 nm) with better dispersion and more regular sizes than synthesis using oleylamine as the solvent (12.1 ± 3.0 nm). The complete conversion of the precursor to Mn3O4 nanoparticles occurred after 96 h at 180 °C for the reaction performed in BMI·NTf2. However, under these reaction conditions in oleylamine, no precursor was detected, but two different phases were observed: a major phase corresponding to Mn3O4 and a minor phase corresponding to MnO2. Magnetometry revealed that Mn3O4 nanoparticles synthesized in either oleylamine or BMI·NTf2 exhibited ferrimagnetic behavior at low temperatures, whereas they were paramagnetic at room temperature. As expected, the blocking temperature and the coercivity decreased with the size of nanoparticles. Our results demonstrate that reaction conditions such as time, and the nature of the ionic liquid play important roles in determining the size of Mn3O4 nanoparticles.

Sputtering deposition of magnetic Ni nanoparticles directly onto an enzyme surface: a novel method to obtain a magnetic biocatalyst.

A simple one-step method based on the sputtering deposition of Ni nanoparticles (NP) has been developed for the production of magnetic biocatalysts, avoiding the complications and drawbacks of methods based on chemical functionalisation or coating of magnetic NP. This new technique provided high levels of recovery, reusability and catalytic activity for the lipase-Ni biocatalyst.

Micro and nano-texturization of intermetallic oxide alloys by a single anodization step: preparation of artificial self-cleaning surfaces.

Micro- and nanostructures of Ti-γCu (γ = 0, 30, 50, 70, and 100 wt %) intermetallic alloys were produced through a single anodization step. It was found that the original alloy composition influences the final oxide morphology obtained after anodization which presented formation of a microstructure with nanotubes, nanoparticles or nanopillars on the surface. Pure Ti and Cu oxide metals and their alloys presented hydrophilic or superhydrophilic properties immediately after anodization. When the anodized pure metal and/or Ti-γCu surfaces were functionalized with trimethoxypropylsilane (TPMSi), by dipping and coating with a thin perfluorinated layer, the treated substrates became in all cases superhydrophobic (water contact angles in the range of 152-166°), showing excellent self-cleaning properties with hysteresis below 3°. These results can be explained by a combination of nanomicro morphologies with low surface energy compounds in the topmost monolayers. The decrease in hysteresis was associated with a higher M-OH bond concentration on the anodized surfaces, which allowed for more complete TMPSi coating coverage. This study also indicates that easy and effective fabrication of superhydrophobic surfaces in pure metals and alloys is possible without involving traditional multistep processes.

On the formation of anisotropic gold nanoparticles by sputtering onto a nitrile functionalised ionic liquid.

Sputtering deposition of gold onto the 1-(butyronitrile)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BCN)MI·N(Tf)(2) ionic liquid (IL) has generated colloidal and stable gold nanospheres (AuNS) and gold nanodisks (AuND) in a bimodal size distribution. Upon increasing the sputtering discharge voltage, three distinct phenomena were observed: (i) the mean diameter of both AuNS and AuND decreased; (ii) the population with lower diameters increased and (iii) the formation of AuND disappeared at voltages higher than 340 V. By dissolving the colloidal gold nanoparticles (AuNPs) in isopropanol and dropping the product onto carbon-coated Cu grids, 2D and 3D superlattices tended to be formed, as observed by transmission electron microscopy (TEM). Therefore, the formation of AuND is probably related to a strong interaction between sputtered Au atoms of low kinetic energy and the nitrile groups orientated to the vacuum phase of the IL surface, which drives the preferential anisotropic lateral growth.

From alumina nanopores to nanotubes: dependence on the geometry of anodization system.

The Conventional anodization of commercial aluminum sheets with a phosphoric acid electrolyte was employed for the preparation of alumina nanopore and/or nanotube structures. Modifying the system geometry (the ratio of platinum to aluminum electrode areas) controlled the nature of the anodization process (mild to hard). Nanotube formation was observed after low temperature preferential chemical etching of the defective corners of the hexagonal alumina cells using the same solution from the anodization process. Electrode geometry can be used to combine mild and hard anodization with low temperature etching to tune the alumina morphology from 100% nanopores to 100% nanotubos coverage.

Self-organized TiO2 nanotube arrays: synthesis by anodization in an ionic liquid and assessment of photocatalytic properties.

Self-organized TiO(2) nanotube (NT) arrays were produced by anodization in ethylene glycol (EG) electrolytes containing 1-n-butyl-3-methyl-imidazolium tetrafluoroborate (BMI.BF(4)) ionic liquid and water. The morphology of the as-formed NTs was considerably affected by changing the anodization time, voltage, and water and ionic liquid electrolyte concentrations. In general, a nanoporous layer was formed on the top surface of the TiO(2) NTs, except for anodization at 100 V with 1 vol % of BMI.BF(4), where the NT's mouth was revealed. The length and bottom diameter of the NTs as well as the pore diameter of the top layer showed a linear relationship with increased anodization voltage. These TiO(2) NTs were tested as photocatalysts for methyl orange photodegradation and hydrogen evolution from water/methanol solutions by UV light irradiation. The results show that the TiO(2) NTs obtained by anodization in EG/H(2)O/BMI.BF(4) electrolytes are active and efficient for both applications.