Wisely Designed Phthalocyanine Derivative for Convenient Molecular Fabrication on a Substrate

An axial-substituted silicon phthalocyanine derivative, SiPc­(OR)₂ (R = C₄H₉), that is soluble in organic solvent is conveniently synthesized. This silicon phthalocyanine derivative reacts with a hydroxyl group on a substrate and then with another phthalocyanine derivative under mild conditions. The accumulation number of the phthalocyanine molecules on the substrates is easily controlled by the immersion time. On the basis of AFM (atomic force microscopy) images, the surface of the phthalocyanine-modified glass substrate has uneven structures on the nanometer scale. ITO electrodes modified with the composition of the phthalocyanine derivative and PCBM show stable cathodic photocurrent generation upon light irradiation

Surfactant-Assisted Hydrothermal Synthesis of Water-Dispersible Hafnium Oxide Nanoparticles in Highly Alkaline Media

Hafnium oxide nanoparticles were synthesized via a short-duration (10 min) hydrothermal reaction. The reaction was found to produce three differently shaped nanoparticles: flower-like nanostructures (20 nm diameter), polycrystalline nanoagglomerates (25 nm diameter), and water-dispersible single nanoparticles (4 nm diameter). The mechanisms by which these different shapes form were then investigated by examining the effects of precursor alkalinity and the presence of an organic capping agent. The synthesized water-dispersible nanoparticles showed a very high affinity for water-soluble polymers, thus demonstrating their potential for fabrication of transparent nanocomposite films

Nanoepitaxy of Anatase-type TiO₂ on CeO₂ Nanocubes Self-Assembled on a Si Substrate for Fabricating Well-Aligned Nanoscale Heterogeneous Interfaces

Nanoscale epitaxy or nanoepitaxy for fabricating macroscopically well-aligned nanoscale heterogeneous interfaces on a Si substrate is demonstrated, combining bottom-up and top-down processes efficiently. TiO₂ sputtered in vacuum was selectively nucleated on the atomically flat surfaces of individual CeO₂ nanocubes prefabricated by self-assembly in solution on the substrate, and anatase-type TiO₂ was grown after a heat treatment by solid-phase epitaxy to produce tandem nanocrystals with heterogeneous interfaces. The atomic configurations of the tandem nanocrystals fabricated after sputtering and subsequent annealing were determined using high-resolution scanning transmission electron microscopy to characterize the nanoscale heterogeneous interfaces. Sharp heterogeneous interfaces were observed between the anatase TiO₂(001) and the CeO₂(001) nanocubes, with the TiO₂ [110] directions being parallel to the CeO₂ [100] directions. This unique nanoepitaxial growth technique will contribute to the development of devices and catalytic materials incorporating functional tandem nanocrystals with nanoscale heterogeneous interfaces

Highly Efficient Electrocatalysis and Mechanistic Investigation of Intermediate IrO_<i>x</i>(OH)_<i>y</i> Nanoparticle Films for Water Oxidation

A new transparent iridium oxide (IrO_<i>x</i>) film on fluorine-doped tin oxide (FTO) electrodes were achieved from a homogeneous precursor complex solution by employing a facile spin-coating technique. The composition of the nanostructure and crystallinity of the IrO_<i>x</i> film is tunable by a simple annealing treatment of a compact complex layer, which is responsible for their significantly different electrocatalytic performances for water oxidation. Transmission electron microscopy (TEM) observations showed uniformly dispersed small IrO_<i>x</i> nanoparticles of dimensions ca. 2–5 nm for the film annealed at 300 °C, and the nanoparticles gradually agglomerated to form relatively large particles at higher temperatures (400 and 500 °C). The IrO_<i>x</i> films prepared at different annealing temperatures are characterized by Raman spectroscopic data to reveal intermediate IrO_<i>x</i>(OH)_<i>y</i> nanoparticles with two oxygen binding motifs: terminal hydroxo and bridging oxo at 300 and 350 °C annealing, via amorphous IrO_<i>x</i> at 400 °C, transforming ultimately to crystalline IrO₂ nanoparticles at 500 °C. Cyclic voltammetry suggests that the intrinsic activity of catalytic Ir sites in intermediate IrO_<i>x</i>(OH)_<i>y</i> nanoparticles formed at 300 °C annealing is higher in comparison with amorphous and crystalline IrO_<i>x</i> nanoparticles. Electrochemical impedance data showed that the charge transfer resistance (<i>R</i>_ct = 232 Ω) for the IrO_<i>x</i>(OH)_<i>y</i> film annealed at 300 °C is lower relative to that of films annealed at higher temperatures. This is ascribable to the facilitated electron transfer in grain boundaries between smaller IrO_<i>x</i> particles to lead the efficient electron transport in the film. The high intrinsic activity of catalytic Ir sites and efficient electron transport are responsible for the high electrocatalytic performance observed for the intermediate IrO_<i>x</i>(OH)_<i>y</i> film annealed at 300 °C; it provides the lowest overpotential (η) of 0.24 V and Tafel slope of 42 mV dec^–1 for water oxidation at neutral pH, which are comparable with values for amorphous IrO_<i>x</i>·<i>n</i>H₂O nanoparticle films (40–50 mV dec^–1) reported as some of the most efficient electrocatalysts so far

Potential Tuning of Nanoarchitectures Based on Phthalocyanine Nanopillars: Construction of Effective Photocurrent Generation Systems

Nanopillars composed of a photoresponsive phthalocyanine derivative have been conveniently fabricated using a continuous silane coupling reaction on a substrate. The chemical potentials of phthalocyanine nanopillars (PNs) are precisely controlled by changing the number of phthalocyanine derivatives on the substrate. In addition, photocurrent generation efficiencies have been strongly influenced by the number of phthalocyanine derivatives. High photocurrent conversion cells in a solid state have been obtained by the combination of PNs and a fullerene derivative