CO2 is selectively hydrogenated to HCO2H or hydrocarbons (HCs) by RuFe nanoparticles (NPs) in ionic liquids (ILs) under mild reaction conditions. The generation of HCO2H occurs in ILs containing ...basic anions, whereas heavy HCs (up to C21 at 150 °C) are formed in the presence of ILs containing nonbasic anions. Remarkably, high values of TONs (400) and a TOF value of 23.52 h–1 for formic acid with a molar ratio of 2.03 per BMI·OAc IL were obtained. Moreover, these NPs exhibited outstanding abilities in the formation of long-chain HCs with efficient catalytic activity (12% conversion) in a BMI·NTf2 hydrophobic IL. The IL forms a cage around the NPs that controls the diffusion/residence time of the substrates, intermediates, and products. The distinct CO2 hydrogenation pathways (HCO2H or FT via RWGS) catalyzed by the RuFe alloy are directly related to the basicity and hydrophobicity of the IL ion pair (mainly imposed by the anion) and the composition of the metal alloy. The presence of Fe in the RuFe alloy provides enhanced catalytic performance via a metal dilution effect for the formation of HCO2H and via a synergistic effect for the generation of heavy HCs.
A redox-active hybrid organic-inorganic polyoxometalate surfactant showed solvent-dependent self-assembly to form nano-scale architectures. The supramolecular assemblies exhibited contrasting ...electronic structure and redox activity to their molecular building units, and were found to be stable under electrochemical reduction and re-oxidation.
Crystallographically preferred oriented porous Ta3N5 nanotubes (NTs) were synthesized by thermal nitridation of vertically oriented, thick-walled Ta2O5 NTs, strongly adhered to the substrate. The ...adherence on the substrate and the wall thickness of the Ta2O5 NTs were fine-tuned by anodization, thereby helping to preserve their tubular morphology for nitridation at higher temperatures. Samples were studied by scanning electron microscopy, high-resolution electron microscopy, X-ray diffraction, Rietveld refinements, ultraviolet–visible spectrophotometry, X-ray photoelectron spectroscopy, photoluminescence spectra, and electrochemical techniques. Oxygen content in the structure of porous Ta3N5 NTs strongly influenced their photoelectrochemical activity. Structural analyses revealed that the nitridation temperature has crystallographically controlled the preferential orientation along the (110) direction, reduced the oxygen content in the crystalline structure and the tubular matrix, and increased the grain size. The preferred oriented porous Ta3N5 NTs optimized by the nitridation temperature presented an enhanced photocurrent of 7.4 mA cm–2 at 1.23 V vs RHE under AM 1.5 (1 Sun) illumination. Hydrogen production was evaluated by gas chromatography, resulting in 32.8 μmol of H2 in 1 h from the pristine porous Ta3N5 NTs. Electrochemical impedance spectroscopy has shown an effect of nitridation temperature on the interfacial charge transport resistance at the semiconductor–liquid interface; however, the flat band of Ta3N5 NTs remained unchanged.
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.
A question of the IL: Carbon nanodots (C‐dots) produced by laser ablation in imidazolium ionic liquids (ILs) showed a tuneable broadband fluorescence emission under ultraviolet/visible excitation. The formation, stabilisation and photophysics of the nanoparticles depend on the nature of the ionic liquid (see figure).
In(OH)3/In2O3 nano-objects (plates and tubes) were prepared under controlled mild reaction conditions by simple basic thermal hydrolysis of 1-(2-methoxy-ethyl)-3-methyl imidazolium tetrachloro-indate ...(BMIOMe·InCl4) ionic liquid (IL). As the reaction temperature increased from 10 °C to 80 °C, there was not only an increase in concentration of In2O3 but the growth of nano-tubes (NTs) also increased. At 10 °C, 30 °C, 50 °C, and 80 °C, 25.2 ± 7 nm sized nanoplates (NPls), small nanotubes (26.6 ± 6 nm in length and 8 ± 2 nm in width), NTs with a length of 25.9 ± 6 nm, and larger nanotubes (49.2 ± 18 nm) were obtained, respectively. The surface concentration of In(OH)3 decreased with the augmentation of the reaction temperature (from 100% at 10 °C to 5.1% at 80 °C). The nano-objects displayed a band gap of 5.4 eV, which is in the range expected for photo-catalytic activity to generate hydrogen from alcoholic solutions. Remarkably, In(OH)3/In2O3 catalyst prepared at 30 °C revealed 3.72 μmol h−1 of rate of hydrogen with apparent quantum yield of 16.3%, yielding a total H2 productivity of 57.6 μmol (5.76 mmol/g) after 32 h. This is the most active semiconductor photocatalysts reported so far of bare indium-based. The presence of In2O3 inside the nano-tubes is also important for the photacatalytic activity of the In(OH)3 based semiconductor. The presence of the IL layer not only acts as a template to control the structure of the nano-objects, but its presence also induces H2 generation.
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•In(OH)3/In2O3 nano -plates and -tubes were prepared by thermal hydrolysis of indate ionic liquid.•Photoreforming by small sized In(OH)3/In2O3 (1:1) nanotubes yields H2 up to 3.72 μmol h−1.•Presence of IL on the nano-objects surface is the driving force for enhancing of the H2 generation.
Surface-clean Au nanoparticles (NPs) confined in films of ionic liquids (ILs) can be easily fabricated by sputtering deposition. A silicon wafer coated with films of both hydrophobic ...(bis((trifluoromethyl)sulfonyl)amide, NTf
) and hydrophilic (tetrafluoroborate, BF
) imidazolium-based ILs forms an 'ionic carpet-like' structure that can be easily decorated with Au NPs of 5.1 and 6.5 nm mean diameter, respectively. The depth profile distribution of the Au NPs depends on the arrangement of the IL, which is controlled mainly by the anion volume. Higher concentrations of Au NPs are found closer to the IL surface for the system containing a larger anion (NTf
) whereas Au NPs are located deeper in the IL for the system containing a smaller anion (BF
). The Au NPs are well distributed over the IL/Si support and are strictly confined in a single layer of the IL. This method is among the most simple and versatile for the generation of liquid layers containing surface-clean, stable and confined Au NPs.
In this work, we show the effect of the thermal treatment temperature on the photoelectrochemical (PEC) activity of CdSe/TiO
2
nanocomposites. TiO
2
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 TiO
2
NTs at different temperatures prior to CdSe deposition and further heating the CdSe/TiO
2
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/TiO
2
nanocomposites and pristine TiO
2
NTs, linear sweep voltammetry (LSV) curves were obtained under visible light and under 1 sun illumination. It was observed that CdSe incorporation into the TiO
2
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/TiO
2
nanocomposites are dependent on the thermal treatment temperature of the TiO
2
nanotubular substrate, prior to CdSe deposition. Moreover, a three-fold improvement in photocurrent was observed upon further thermal treatment of the obtained nanocomposite.
Effect of the thermal treatment temperature on the photoelectrochemical (PEC) activity of CdSe/TiO
2
nanocomposites.
Reversible addition–fragmentation chain transfer (RAFT) mediated dispersion polymerisation in supercritical carbon dioxide (scCO2) is an efficient and green method for synthesising block copolymer ...microparticles with internal nanostructures. Here we report for the first time the synthesis of phase separated poly(methyl methacrylate-block-styrene-block-4-vinylpyridine) (PMMA-b-PS-b-P4VP) triblock terpolymer microparticles using a simple two-pot sequential synthesis procedure in scCO2, with high monomer conversions and no purification steps. The microparticles, produced directly and without further processing, show a complex internal nanostructure, appearing as a “lamellar with spheres” L + S(II) type morphology. The P4VP block is then exploited as a structure-directing agent for the fabrication of TiO2 microparticles. Through a simple and scalable sol–gel and calcination process we produce hollow TiO2 microparticles with a mesoporous outer shell. When directly compared to porous TiO2 particles fabricated using an equivalent PMMA-b-P4VP diblock copolymer, increased surface area and enhanced photocatalytic efficiencies are observed.
Highly ordered TiO
2
NT arrays were easily decorated with CdSe
via
RF magnetron sputtering. After deposition thermal annealing at different temperatures was performed to obtain an improved TiO
2
.../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 TiO
2
NTs under 1 sun and under visible light illumination, respectively. IES results confirmed the improved charge transfer across the TiO
2
/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.
Highly ordered TiO
2
NT arrays were easily decorated with CdSe
via
RF magnetron sputtering.
Carbon Nanodots The fabrication of fluorescent C‐dots by laser ablation from graphite powder dispersed in ionic liquids is described. The final luminescent solution illuminated by a violet laser is ...shown in inset. For more details, see the Full Paper by J. D. Scholten, J. Dupont, R. R. B. Correia et al. on page 138 ff.
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