Application of fractal geometry for studies of heterogeneity properties of nanomaterials

Calculations based on the fractal geometry in the estimation of surface heterogeneity are superior compared with conventional calculation methods (e.g. from the data of gas adsorption or X-ray radiation scattering) as they can be applied without limitation as far as the range of surface sizes of the studied structures is concerned. This paper presents structural characteristics of carbon and carbon- free nanomaterials based on the determined surface and volumetric fractal coefficients. Fractal coefficients were determined from the data obtained by means of two independent methods: sorptometry and atomic force microscopy (AFM). Correlation between porosity parameters and fractal coefficients is presented.     

NiMoO4纳米线@ZnCo MOF(350)核壳结构复合材料的制备及其析氧电催化性能

采用液相合成法成功合成了一种新型的ZnCo金属有机骨架（MOF）纳米晶原位生长于NiMoO₄纳米线（NWs）表面的复合材料NiMoO₄ NWs@ZnCo MOF。经350 ℃低温热处理（所得产物命名为NiMoO₄ NWs@ZnCo MOF（350））后,仍旧较好地保持了前驱体的结构和形貌,但在ZnCo MOF内部出现了极少量的Co₃O₄相,证明发生了轻微热解。化学键C—O—Mo和相异质界面处产生的大量氧空位可以成为活性位点的来源。新的Co₃O₄相的形成也导致异相界面的进一步增加。此外,少量的热解使核壳结构表面更加粗糙、疏松和多孔,产生更高的比表面积、更快的离子扩散路径和更好的导电性。因此经惰性玻碳电极测试,在10 mA·cm^-2电流密度下电催化剂表现出360 mV的低过电位,并保持了30 000 s的长期催化稳定性。     

Enhanced Electrocatalytic Detection of Choline Based on CNTs and Metal Oxide Nanomaterials

Choline is an officially established essential nutrient and precursor of the neurotransmitter acetylcholine. It is employed as a cholinergic activity marker in the early diagnosis of brain disorders such as Alzheimer’s and Parkinson’s disease. Low levels of choline in diets and biological fluids, such as blood plasma, urine, cerebrospinal and amniotic fluid, could be an indication of neurological disorder, fatty liver disease, neural tube defects and hemorrhagic kidney necrosis. Meanwhile, it is known that choline metabolism involves oxidation, which frees its methyl groups for entrance into single-C metabolism occurring in three phases: choline oxidase, betaine synthesis and transfer of methyl groups to homocysteine. Electrocatalytic detection of choline is of physiological and pathological significance because choline is involved in the physiological processes in the mammalian central and peripheral nervous systems and thus requires a more reliable assay for its determination in biological, food and pharmaceutical samples. Despite the use of several methods for choline determination, the superior sensitivity, high selectivity and fast analysis response time of bioanalytical-based sensors invariably have a comparative advantage over conventional analytical techniques. This review focuses on the electrocatalytic activity of nanomaterials, specifically carbon nanotubes (CNTs), CNT nanocomposites and metal/metal oxide-modified electrodes, towards choline detection using electrochemical sensors (enzyme and non-enzyme based), and various electrochemical techniques. From the survey, the electrochemical performance of the choline sensors investigated, in terms of sensitivity, selectivity and stability, is ascribed to the presence of these nanomaterials.     

Iron Oxychloride/Bovine Serum Albumin Nanosheets as Chemodynamic Therapy Agents

Iron oxychloride (FeOCl) is known for reactive oxygen species (ROS) generation through Fenton chemistry. The activity of FeOCl is preserved in the slightly acidic pH value of the tumor microenvironment (pH 6.5−6.9). Such property can be advantageous in biobased systems, where ROS generation can be modulated in slightly acidic conditions, which is characteristic of the solid tumor microenvironment. In the present study, BSA-stabilized FeOCl nanosheets (NSs) are synthesized and characterized by transmission electron microscope, Fourier transform infrared spectroscopy, zeta potential analysis, dynamic light scattering, and UV–vis spectroscopy. The morphology of the nanoparticles is flake-like, and their hydrodynamic diameter is around 200 nm. MTT, apoptosis assay, and trypan blue staining evaluate the toxicity of FeOCl NSs toward the 4T1 cell line. It is found that the toxicity of the NSs is higher in physiological conditions of solid tumors (pH 6.5, H₂O₂ 100 × 10⁻⁶ m ) than in the conditions of healthy organs (pH 7.4). Specifically, cancer cells are in their late apoptotic stage by more than eight times higher at pH 6.5 than pH 7.4. The toxicity results are in agreement with the in vitro catalytic assay of the NSs. Therefore, the FeOCl NSs can be the building blocks for constructing chemodynamic therapy agents.     

Impact of Extracellular Polymeric Substance in the Inactivation of Harmful Algae by Ag2O/g-C3N4 under Visible Light

Photocatalysis has attracted much attention as an emerging algae removal technology, but the inactivation performance is inevitably affected by the extracellular polymeric substance (EPS) produced by algae. In this study, a photocatalyst (Ag₂O/g-C₃N₄) with efficient algae inactivation is adopted to investigate the interactions with EPS, and the impact of EPS on photocatalytic algae removal is studied. The results show that EPS can adhere to the surface of Ag₂O/g-C₃N₄ by electrostatic force. The interaction with EPS decreases the surface zeta potential of the Ag₂O/g-C₃N₄ from 7.71 to −22.3 mV with the increase in EPS concentration, and the maximum ratio of particle size increases from 825 to 1281 nm. In addition, the interaction with EPS inhibits the release of Ag⁺ in Ag₂O/g-C₃N₄ by half, thus, the toxicity of metal ions will be alleviated. Meanwhile, EPS can also be degraded by Ag₂O/g-C₃N₄, indicating that EPS can work as a radical scavenger to protect the algae cells. Without the protection of EPS, 97.8% of algae cells are inactivated after 5 h photocatalysis. Therefore, more attention should be given to the interaction between EPS and photocatalyst to promote the design and application of the photocatalytic.     

Au Nanowire–Au Nanoparticles Conjugated System which Provides Micrometer Size Molecular Sensors

We report a new type of molecular sensor using a Au nanowire (NW)–Au nanoparticles (NPs) conjugated system. The Au NW–NPs structure is fabricated by the self‐assembly of biotinylated Au NPs on a biotinylated Au NW through avidin; this creates hot spots between NW and NPs that strongly enhance the Raman signal. The number of the Au NPs attached to the NW is reproducibly proportional to the concentration of the avidin, and is also proportional to the measured surface‐enhanced Raman scattering (SERS) signals. Since this well‐defined NW–NPs conjugated sensor is only a few micrometer long, we expect that development of multiplex nanobiosensor of a few tens micrometer size would become feasible by combining individually modified multiple Au NWs together on one substrate.     

Cement Composites with Carbon-Based Nanomaterials for 3D Concrete Printing Applications – A Review

3D concrete printing (3DCP) is an emerging additive manufacturing technology in the construction industry. Its challenges lie in the development of high-performance printable materials and printing processes. Recently developed carbon-based nanomaterials (CBNs) such as graphene, graphene oxide, graphene nanoplatelets, and carbon nanotubes, have various applications due to their exceptional mechanical, chemical, thermal, and electrical characteristics. CBNs also have found potential applications as a concrete ingredient as they enhance the microstructure and modify concrete properties at the molecular level. This paper focuses on state-of-the-art studies on CBNs, 3DCP technology, and CBNs in conventional and 3D printable cement-based composites including CBN dispersion techniques, concrete mixing methods, and fresh and hardened properties of concrete. Furthermore, the current limitations and future perspectives of 3DCP using CBNs to produce high-quality composite mixtures are discussed.     

Functional Nanomaterial-Modified Anodes in Microbial Fuel Cells: Advances and Perspectives

Microbial fuel cell (MFC) is a promising approach that could utilize microorganisms to oxidize biodegradable pollutants in wastewater and generate electrical power simultaneously. Introducing advanced anode nanomaterials is generally considered as an effective way to enhance MFC performance by increasing bacterial adhesion and facilitating extracellular electron transfer (EET). This review focuses on the key advances of recent anode modification materials, as well as the current understanding of the microbial EET process occurring at the bacteria-electrode interface. Based on the difference in combination mode of the exoelectrogens and nanomaterials, anode surface modification, hybrid biofilm construction and single-bacterial surface modification strategies are elucidated exhaustively. The inherent mechanisms may help to break through the performance output bottleneck of MFCs by rational design of EET-related nanomaterials, and lead to the widespread application of microbial electrochemical systems.