As a newly developed material, carbon gels have been receiving considerable attention due to their multifunctional properties. Herein, we present a facile, green, and template-free route toward sponge-like carbonaceous hydrogels and aerogels by using crude biomass, watermelon as the carbon source. The obtained three-dimensional (3D) flexible carbonaceous gels are made of both carbonaceous nanofibers and nanospheres. The porous carbonaceous gels (CGs) are highly chemically active and show excellent mechanical flexibility which enable them to be a good scaffold for the synthesis of 3D composite materials. We synthesized the carbonaceous gel-based composite materials by incorporating Fe3O4 nanoparticles into the networks of the carbonaceous gels. The Fe3O4/CGs composites further transform into magnetite carbon aerogels (MCAs) by calcination. The MCAs keep the porous structure of the original CGs, which allows the sustained and stable transport of both electrolyte ions and electrons to the electrode surface, leading to excellent electrochemical performance. The MCAs exhibit an excellent capacitance of 333.1 F·g(-1) at a current density of 1 A·g(-1) within a potential window of -1.0 to 0 V in 6 M KOH solution. Meanwhile, the MCAs also show outstanding cycling stability with 96% of the capacitance retention after 1000 cycles of charge/discharge. These findings open up the use of low-cost elastic carbon gels for the synthesis of other 3D composite materials and show the possibility for the application in energy storage.

The ultrafast dynamics of photoexcited charge carriers in condensed matter systems play an important role in optoelectronics and solar energy conversion. Yet it is challenging to understand such multidimensional dynamics at the atomic scale. Combining the real‐time time‐dependent density functional theory with fewest‐switches surface hopping scheme, we develop time‐dependent ab initio nonadiabatic molecular dynamics (NAMD) code Hefei‐NAMD to simulate the excited carrier dynamics in condensed matter systems. Using this method, we have investigated the interfacial charge transfer dynamics, the electron–hole recombination dynamics, and the excited spin‐polarized hole dynamics in different condensed matter systems. The time‐dependent dynamics of excited carriers are studied in energy, real and momentum spaces. In addition, the coupling of the excited carriers with phonons, defects and molecular adsorptions are investigated. The state‐of‐art NAMD studies provide unique insights to understand the ultrafast dynamics of the excited carriers in different condensed matter systems at the atomic scale. This article is categorized under: Structure and Mechanism > Computational Materials Science Molecular and Statistical Mechanics > Molecular Dynamics and Monte‐Carlo Methods Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Simulation Methods

Adsorption behavior of iron(II) phthalocyanine (FePc) on Au(111) surface at submonolayer coverage has been investigated using low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At the initial adsorption stage, FePc molecules prefer to adsorb on terrace dispersedly as isolated adsorbates because of the stronger molecule−substrate interaction than the lateral intermolecular interaction. Two different configurations of FePc on Au(111) surface are resolved on the basis of STM image analysis and are further identified by DFT calculations. When increasing molecule coverage, the intermolecular interaction becomes more important. The FePc molecules assemble to dimers, trimers, and short chains and even peculiar porous hexamers with two configurations. At a saturated coverage, highly ordered FePc monolayer with only one configuration of FePc is observed. The results indicate that the adsorption behavior of FePc on Au(111) is governed by a coverage-dependent competition between molecule−substrate and intermolecular interactions.

Two-dimensional (2D) materials have been studied extensively as monolayers, vertical or lateral heterostructures. To achieve functionalization, monolayers are often patterned using soft lithography and selectively decorated with molecules. Here we demonstrate the growth of a family of 2D materials that are intrinsically patterned. We demonstrate that a monolayer of PtSe can be grown on a Pt substrate in the form of a triangular pattern of alternating 1T and 1H phases. Moreover, we show that, in a monolayer of CuSe grown on a Cu substrate, strain relaxation leads to periodic patterns of triangular nanopores with uniform size. Adsorption of different species at preferred pattern sites is also achieved, demonstrating that these materials can serve as templates for selective self-assembly of molecules or nanoclusters, as well as for the functionalization of the same substrate with two different species.

Zinc oxide is one of the most important wide-band-gap (3.2 eV) materials with versatile properties, however, it can not be excited by visible light. In this work, we have developed an exquisite and simple way to prepare oxygen-deficient ZnO 1-x nanosheets with a gray-colored appearance and excellent visible light photocatalytic activity. Detailed analysis based on UV-Vis absorption spectra, X-band electron paramagnetic resonance (EPR) spectra, and photoluminescence (PL) spectra confirms the existence of oxygen vacancies in ZnO 1-x. The incorporation of oxygen defects could effectively extend the light absorption of ZnO 1-x into the visible-light region due to the fact that the energy of the localized state is located in the forbidden gap. Thus, our obtained ZnO 1-x shows a higher photodegradation of methyl orange (MO) compared to defect-free ZnO under visible light illumination. Additionally, the high content of ˙OH radicals with a strong photo-oxidation capability over the ZnO 1-x nanosheets significantly contributes to the improvement in the photocatalytic performance. Our oxygen deficient ZnO 1-x sample shows a very high photocatalytic activity for the degradation of MO even after 5 cycles without any obvious decline. The results demonstrate that defect engineering is a powerful tool to enhance the optoelectronic and photocatalytic performances of nanomaterials.

SignificanceFerromagnetic insulators are highly needed as the necessary components in developing next-generation dissipationless quantum-spintronic devices. Such materials are rare, and those high symmetric ones without chemical doping available so far only work below 16 K. Here we demonstrate a tensile-strained LaCoO3 film to be a strain-induced high-temperature ferromagnetic insulator. Both experiments and first-principles calculations demonstrated that the tensile-strain–supported ferromagnetism reaches its strongest when the composition is nearly stoichiometric. It disappears when the Co2+ defect concentration reaches around 10%. The discovery represents a chance for the availability of such materials, a high operation temperature, and a high epitaxial integration potential for making future devices.

A novel ternary plasmonic Ag 3 VO 4 /AgBr/Ag hybrid photocatalyst was successfully fabricated via an in situ anion-exchange reaction between Ag 3 VO 4 and KBr, followed by light reduction. The obtained samples were characterized by X-ray diffraction, scanning electron microscopy, energydispersive X-ray spectroscopy, UV−visible diffuse-reflectance spectroscopy (UV−vis DRS), and X-ray photoelectron spectroscopy. The photocatalytic activities of obtained photocatalysts were measured by the degradation of Rhodamine B and methylene blue under visible-light irradiation (λ ≥ 400 nm). As-prepared Ag 3 VO 4 /AgBr/Ag plasmonic photocatalysts exhibit wide absorption in the visible-light region and display superior visible-light-driven photocatalytic activities in degradation of organic contamination compared with pristine Ag 3 VO 4 , Ag 3 VO 4 /AgBr, and AgBr/Ag. This enhanced photocatalytic activity is attributed to the synergistic effects between Ag 3 VO 4 /AgBr-based heterostructured semiconductor photocatalysis and the surface plasmon resonance (SPR) of Ag nanoparticles (NPs). On the basis of UV−vis DRS and valence band X-ray photoelectron spectroscopy, a possible mechanism of enhanced photocatalytic activity of Ag 3 VO 4 /AgBr/Ag is proposed; the vectorial electron transfer driven by the matching band potentials of AgBr and Ag 3 VO 4 and the SPR of Ag NPs contribute to its high photocatalytic activity and the improved stability. Therefore, the present study provides helpful insight into the design of novel and highly efficient visible-light photocatalysts in the future.

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