Improvement of the Heat Resistance of Prussian Blue Nanoparticles in a Clay Film Composed of Smectite Clay and ε‑Caprolactam

Prussian blue (PB) is limited in its application by its breakdown at elevated temperatures. To improve the heat resistance of PB, we prepared a composite film comprising PB nanoparticles (NPs), smectite clay, and an organic compound. The composite film had a microstructure in which PB NPs were intercalated between smectite/organic compound layers. The predominant oxidation temperature of the PB NPs in the composite film was around 500 °C in air, higher than the oxidation temperature of bulk PB in air (250 °C). This improvement in the oxidation temperature may be due to the composite film acting as a barrier to oxygen gas. These results indicate the effectiveness of clay materials for the improvement of heat resistance for low-temperature decomposition compounds, not only PB but also other porous coordination polymers

Trace Alcohol Adsorption by Metal Hexacyanocobaltate Nanoparticles and the Adsorption Mechanism

Adsorption of alkyl chain alcohols, ranging from methanol to <i>n</i>-hexanol, on manganese hexacyanocobaltate (MnHCCo) and copper hexacyanocobaltate (CuHCCo) nanoparticles was evaluated. The equilibrium adsorption capacity at low pressure was found to be larger than previously published results using other kinds of adsorbents, metal organic frameworks, zeolites, and activated carbons. For example, MnHCCo adsorbed 5 mmol/g of methanol at only 8.9 Pa, less than 1/10 of the lowest pressures used in previous studies. The adsorption can be understood using a two-step process: initial adsorption into the crystal (intra-nanoparticle adsorption) followed by that among the nanoparticles (inter-nanoparticle adsorption). The suggested mechanism was supported by the analysis of the adsorption isotherm with the dual-site Langmuir equation, and the entropy loss in the adsorption process. The highest adsorption amount at low pressure was caused by a combination of coordination bonding between alcohol molecules at the high-density open metal sites in the adsorbent and by the intermolecular interaction between the framework of the adsorbent and the alkyl chain of alcohols

A solvent-compatible filter-transfer method of semi-transparent carbon-nanotube electrodes stacked with silver nanowires

Low-density films of single-walled carbon nanotubes (SWNTs) can be used as a semi-transparent top electrode for all-solution-processed film devices; however, their semiconductor characteristics vary depending on the experimental factors in their dispersion into solvents, and the sublayers are damaged as a result of solvent incompatibility. In this study, we report a solvent-compatible filter-transfer method for SWNT films stacked with silver nanowires (AgNWs), and evaluate the semiconductor characteristics through the p/n heterojunction with a Si wafer (SWNT/Si). AgNWs and SWNTs were successively filtrated through their aqueous dispersion solutions using a membrane filter. The stacked semi-transparent films (AgNW/SWNT films with controlled densities) were successfully transferred onto glass plates and Si wafers. The transmittance at 550 nm revealed a window between 60% and 80% with a narrow sheet resistance range between 11 and 23 Ω □−1. The power conversion efficiency (PCE) of SWNT/Si was improved to 11.2% in a junction area of 0.031 cm2 through the use of spin-coated Nafion resins; however, the accumulated resistance of SWNTs drastically reduced the PCE to 2% as the area increased to ≥0.5 cm2. AgNWs maintained the PCE within a range of 10.7% to 8.6% for an area ranging from 0.031 cm2 to 1.13 cm2. All of the photovoltaic parameters were dependent on the junction areas, suggesting that AgNWs function as an effective current-collector layer on the semiconductor layer of SWNTs without direct contact of AgNWs with the Si surface. In addition, we report a solvent-compatible experiment for transferring AgNW/SWNT films onto a solvent-sensitive perovskite material (CH3NH3PbI3).</p

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

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