A Molecular Adsorption Concept for Increasing Energy Density of Hybrid Supercapacitors.

In this report, we demonstrate that high-capacity hybrid supercapacitors can be realized by utilizing iron azaphthalocyanine (FeAzPc-4N) adsorbed activated carbons (ACs) as an electrode due to the combination of the electric double layer of activated carbon surfaces and redox reactions of FeAzPc-4N molecules. By increasing the mixing ratio of FeAzPc-4N with ACs, a maximum capacity of 907 F/gAC is achieved, also enabling rapid charging and discharging at 20 A/g. The revelation of the capacitor electrode's durability through 20 000 cycles of charging and discharging is realized, and the capacitor cell had sufficient output power to illuminate LEDs. This concept illustrates the potential for enhancing capacitor performance by immobilizing redox-active species.

Benchmarking pH-field coupled microkinetic modeling against oxygen reduction in large-scale Fe-azaphthalocyanine catalysts.

Molecular metal-nitrogen-carbon (M-N-C) catalysts with well-defined structures and metal-coordination environments exhibit distinct structural properties and excellent electrocatalytic performance, notably in the oxygen reduction reaction (ORR) for fuel cells. Metal-doped azaphthalocyanine (AzPc) catalysts, a variant of molecular M-N-Cs, can be structured with unique long stretching functional groups, which make them have a geometry far from a two-dimensional geometry when loaded onto a carbon substrate, similar to a "dancer" on a stage, and this significantly affects their ORR efficiency at different pH levels. However, linking structural properties to performance is challenging, requiring comprehensive microkinetic modeling, substantial computational resources, and a combination of theoretical and experimental validation. Herein, we conducted pH-dependent microkinetic modeling based upon ab initio calculations and electric field-pH coupled simulations to analyze the pH-dependent ORR performance of carbon-supported Fe-AzPcs with varying surrounding functional groups. In particular, this study incorporates large molecular structures with complex long-chain "dancing patterns", each featuring >650 atoms, to analyze their performance in the ORR. Comparison with experimental ORR data shows that pH-field coupled microkinetic modeling closely matches the observed ORR efficiency at various pH levels in Fe-AzPc catalysts. Our results also indicate that assessing charge transfer at the Fe-site, where the Fe atom typically loses around 1.3 electrons, could be a practical approach for screening appropriate surrounding functional groups for the ORR. This study provides a direct benchmarking analysis for the microkinetic model to identify effective M-N-C catalysts for the ORR under various pH conditions.

Controlling the Formation of Polyhedral Block Copolymer Nanoparticles: Insights from Process Variables and Dynamic Modeling.

This study delves into the formation of nanoscale polyhedral block copolymer particles (PBCPs) exhibiting cubic, octahedral, and variant geometries. These structures represent a pioneering class that has never been fabricated previously. PBCP features distinct variations in curvature on the outer surface, aligning with the edges and corners of polyhedral shapes. This characteristic sharply contrasts with previous block copolymers (BCPs), which displayed a smooth spherical surface. The emergence of these cornered morphologies presents an intriguing and counterintuitive phenomenon and is linked to process parameters, such as evaporation rates and initial concentration, while keeping other variables constant. Using a system of coupled Cahn-Hillard (CCH) equations, we uncover the mechanisms driving polyhedral particle formation, emphasizing the importance of controlling relaxation parameters for shape variable u and microphase separation v. This unconventional approach, differing from traditional steepest descent method, allows for precise control and diverse polyhedral particle generation. Accelerating the shape variable u proves crucial for expediting precipitation and aligns with experimental observations. Employing the above theoretical model, we achieve shape predictions for particles and the microphase separation within them, which overcomes the limitations of ab initio computations. Additionally, a numerical stability analysis discerns the transient nature versus local minimizer characteristics. Overall, our findings contribute to understanding the complex interplay between process variables and the morphology of polyhedral BCP nanoparticles.

Low Friction of Graphene Oxide Aggregates in Lubricant Oil between a Steel Ball and Glass Disk under Boundary Lubrication.

Previously, isolated nanocarbons in lubricating oils were considered essential for good lubrication. However, we observed that graphene oxide (GO) aggregates in lubricating oil have lower frictional properties than isolated dispersed GO. The GO was dispersed in polyα-olefin (PAO) using alkylamine at different ratios of GO and alkylamine, or it was heated at different temperatures to synthesize high- and low-dispersible GO-dispersed PAO. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy measurements showed that low-dispersible modified GOs retained many of the original GO chemical and structural features. Macrotribological tests between a steel ball and glass disk in GO-dispersed oil were conducted with a load of 5 N under boundary lubrication. The friction interface was observed in situ using an optical microscope. In the low-dispersible GO-dispersed PAO, many GO aggregates were observed through optical microscopy. Surprisingly, the friction coefficients decreased when the GO aggregates entered the friction interface and covered the contact area. The low-dispersible GO-dispersed PAO using alkylamine had the lowest friction coefficient of 0.05, as the GO aggregates covered the contact area. From microtribological tests with a load of 0.8 mN as well, it is assumed that the low friction of the GO aggregates originates due to the sliding between the weakest shear layers in the aligned multiple GO layers.

Preparation of Hierarchic Porous Films of α-MnO2 Nanoparticles by Using the Breath Figure Technique and Application for Hybrid Capacitor Electrodes.

The honeycomb-structured film has advantages such as high wettability and high surface area. This structure and properties are suitable for the capacitor electrode. In this study, the electrode structure is controlled by the synthesis of MnO2 nanoparticles using the breath figure method. The electrode performance was calculated by electrochemical measurements. As a result, the capacitance value was 100.5 F/g at 1 mV s-1, which was improved 2.7 times as compared with that without structure control.

Ashura Particles: Experimental and Theoretical Approaches for Creating Phase-Separated Structures of Ternary Blended Polymers in Three-Dimensionally Confined Spaces.

Unique morphologies were found in binary and ternary polymer blended particles, including Ashura-type phase separation, which has three different polymer components on the particle surface. The morphologies of phase-separated structures in the binary polymer blended particles are discussed in terms of the surface tensions of the blended polymers. Structural control of ternary polymer blended particles was achieved based on the combination of polymers by examining binary polymer blended particles. A theoretical approach based on the Cahn-Hilliard equations gives identical morphologies with the experimental results. This work opens the way to creating polymer particles with sophisticated nanostructures by controlling their morphologies as predicted by theoretical simulations.

Self-assembled microrings of Au nanoparticle and Au nanorod clusters formed at the equators of Janus particles.

A method for fabricating polymer Janus particles with microring structures at their equators has been developed. This method allows gold nanoparticles and nanorods to be aligned and densely packed along the microrings.

A Fluorescence Indicator at Extreme Low pH Region Based on Dissolution of Zn Tetra-2,3-Pyridoporphyradine (TPP) Nanocrystal Suspension.

Conventional organic pH indicators are widely used for chemical synthesis and analysis based on change of π conjugation length depending on pH values. However, there are a few organic pH indicators for strong acid conditions, because organic compounds are usually decomposed at extreme low pH. Tetra-2,3-pyridoporphyradine (TPP) has high chemical stability and crystallinity, and its nano-crystal is widely used as stable pigments. ZnTPP exhibits red fluorescence, but ZnTPP crystals don't exhibit fluorescence due to concentration quenching. In this paper, we show a UV-assisted synthesis of ZnTPP nano-crystals and application for fluorescence pH indicator at extreme low pH condition by quaternization of ZnTPP nano-crystals. ZnTPP crystals were successfully synthesized and then dispersed into 1 to 10 M HCl aq. UV-Vis and fluorescence spectroscopy revealed that absorption and fluorescence change were observed depending on HCl concentrations at extreme low pH conditions due to quarternization of ZnTPP and dissolution of ZnTPP nano-crystals. These results indicate that ZnTPP nano-crystals can be used for fluorescence pH indicators at extreme low pH.