Conservative dynamics in a novel class of 3D generalized thermostatted systems.

This paper reports a method to derive a novel class of 3D generalized thermostatted oscillators from a simple damped harmonic oscillator. Its detailed procedure is obtained through a mathematical derivation. Then, we propose an example system to show the effectiveness of the method. Furthermore, the numerical analysis is performed to investigate its rich conservative dynamics, including chaotic sea, hierarchical invariant tori, and the coexistence of chaotic seas and invariant tori with islands-around-islands hierarchy, even if there are three dissipative terms in the example system. To verify the existence of conservative chaos at the physical level, an analog circuit is presented to observe the existing conservative chaotic flows in National Instruments multisim. We finally provide two systems, which can produce conservative chaotic flows with more complicated topologies, and draw our conclusions.

Metal-Free [5 + 1] Cycloaddition-Aromatization of Benzotriazoles and Sulfur Ylides to Construct 1,2,4-Benzotriazines.

Reported herein is a novel [5 + 1] cycloaddition-aromatization of benzotriazoles and sulfur ylides to efficiently construct 1,2,4-benzotriazine derivates with good yield. This new protocol does not employ any transition metal reagent and enables the cycloaddition by cleavage of the N-N single bond. The use of inexpensive and readily available starting materials, a broad substrate scope, mild reaction conditions, metal-free, and versatile functionalization of the 1,2,4-benzotriazines make this strategy more attractive.

First-principles study on the initial decomposition process of CH3NH3PbI3.

Hybrid perovskites are promising materials for high-performance photovoltaics. Unfortunately, hybrid perovskites readily decompose in particular under humid conditions, and the mechanisms of this phenomenon have not yet been fully understood. In this work, we systematically studied the possible mechanisms and the structural properties during the initial decomposition process of MAPbI3 (MA = CH3NH3+) using first-principles calculations. The theoretical results show that it is energetically favorable for PbI2 to nucleate and crystalize from the MAPbI3 matrix ahead of other decomposition products. Additionally, the structural instability is an intrinsic property of MAPbI3, regardless of whether the system is exposed to humidity. We find that H2O could facilitate the desorption of gaseous components, acting as a catalyst to transfer the H+ ion. These results provide insight into the cause of the instability of MAPbI3 and may improve our understanding of the properties of hybrid perovskites.

Generation of highly reactive oxygen species on metal-supported MgO(100) thin films.

The formation of highly reactive oxygen species (ROS) on metal oxide surfaces has attracted considerable interest due to their diverse applications. In this work, we have performed density functional theory calculations to investigate the co-adsorption of oxygen and water on ultrathin MgO(100) films deposited on a Mo(100) substrate. We reveal that molecular oxygen can be completely decomposed stepwise with the assistance of water. Consequently, a series of highly ROS including superoxide, hydroperoxide, hydroxyl and single oxygen adatoms are formed on Mo(100) supported MgO(100) thin films. The reaction barriers accompanied by the generation of ROS are reported, and the influence of the thickness of MgO(100) films is also discussed. The promising routes to produce these species provide valuable information to understand the importance of synergy effects between the substrate, the co-adsorbed species, and the film thickness in multiphase catalyst design.

Surfactant-assisted alignment of ZnO nanocrystals to superstructures.

Self-organization of ZnO nanoparticles into various superstructures (sheet, platelet, ring) has been achieved with the assistance of micelles formed by surfactant cetyltrimethylammonium bromide (CTAB) under one-pot condition. The CTAB-modified zinc hydroxy double salt (Zn-HDS) mesocrystals act as intermediates to form ZnO hexagonal superstructures at temperatures as low as 50 degrees C. The decomposition temperature of Zn-HDS mesocrystals is much lower than that of the corresponding bulk crystals because the organic additive CTAB effectively decreases the degree of crystallinity. Taking advantage of temperature-induced phase transformation of micelles, two-stage self-organization can form ZnO platelets and ring mesocrystals, that is, ZnO ellipsoidal superstructures formed through vertical attachment on (0001) facets of basic units can further assemble to form ZnO platelets and rings through vertical attachment on (0001) facets of ZnO ellipsoidal superstructures. The structural transformation of micelles as shape templates can offer a new route for self-assembly of nonspherical colloids into three-dimensional photonic crystals. ZnO sheet, ring, and platelet mesocrystals with a high population of polar Zn-(0001) plane are expected to have high photocatalytic activity.

Single mullite nanoribbon as a glucose sensor.

Mullite (2SiO(2).3Al(2)O(3)) nanoribbons, millimetres in length and with a high width-to-thickness ratio, were synthesized at temperatures as low as 1150 degrees C. This high ratio made it easy to fabricate a single nanoribbon sensor. The I-V relation of the sensor versus concentration of glucose was recorded with a pico-ammeter. The sensor shows good reproducibility and long-term stability. This single nanoribbon sensor may be used as an in situ monitor. The nanoribbons were also characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and x-ray photoemission spectroscopy.