Ceramic magnetic ferrite nanoribbons: Eco-friendly synthesis and their antifungal and parasiticidal activity

Ceramic nanostructures with their unique morphologies have attractive properties and various biomedical and medical applications. The production of nanoparticles (NPs) with a special morphology has been strongly influenced by lab-scale synthesis conditions and the type of reducing agents. Generally, the production of NPs with unique shapes and sizes can be adjusted by changing and optimizing the reaction mixture conditions and parameters. The formation of ceramic nanostructures during synthesis process contained the nucleation, seeding, and growth steps. By altering the kinetics and thermodynamics of synthesis process (at each stage), the shape of the produced nanostructures can be controlled. In this study, nickel ferrite ceramic nanoribbons were produced through a green and environmentally-friendly method based on the bioethical principles of preventing environmental damage, without using any other chemical composition, and only by applying plant extracts as reducing and stabilizing agents. The prepared ceramic nanoribbons were evaluated by XRD, SEM, FTIR, VSM, and HR-TEM. The results confirmed that the calcination could significantly affect the size and shape of the resulting ceramic nanostructures. The calcination could lead to the deformation of thin and hair-like ceramic nanoribbons into spherical NPs (～20 nm). Additionally, the antiparasitic properties of these nanoribbons were evaluated using MTT method, and the antifungal effects were analyzed against Aspergillus ustus. The obtained results illustrated that these nanostructures had significant toxicity against Leishmania tropica and A. ustus.     

四氧化三钴@石墨烯纳米带材料储锂性能研究

针对Co3O4导电性差、离子迁移率低和体积膨胀过大的缺点,本研究利用GNRs比表面积大、纵宽比高和含氧基团多的特点,通过与GNRs复合的方式制备纳米级复合材料对Co3O4进行了改性,采用了一步沉淀法制备纳米级复合材料Co3O4@GNRs提高电化学性能。将钴源用氨水进行沉淀一步得制备复合材料Co3O4@GNRs。针对复合材料并采用SEM、XRD、TEM、Raman、XPS对其微观形貌和晶体结构进行表征。结果表明：纳米复合材料中Co3O4颗粒大小约为5-8 nm,附着在GNRs的边缘及表面;所得Co3O4@GNRs材料碳含量约为10.41%,电化学性能较好。组装成锂离子半电池得到电化学性能,循环95圈容量保持787.1mAh·g-1,当电流密度为8000 mA·g-1时,放电容量可达到151.1mAh·g-1。电化学性能的提高主要归因于复合材料Co3O4@GNRs独特的纳米结构。在转化型反应中,Co3O4在充放电过程中通常形成金属单质,引起材料体积膨胀问题,本研究利用GNRs比表面积大、纵宽比高、含氧基团多能够负载更多Co3O4颗粒,提高材料的导电率和离子迁移率,缓和体积膨胀效应,从而增加材料传输能力,有利于提高负极材料的储能性能。     

Photoresponse Properties of CdSe Single‐Nanoribbon Photodetectors

Photodetectors are fabricated from individual single‐crystal CdSe nanoribbons, and the photoresponse properties of the devices are studied systematically. The photodetector shows a high sensitivity towards excitation wavelength with a sharp cut‐off at 710 nm, corresponding to the bandgap of CdSe. The device exhibits a high photo‐to‐dark current ratio of five orders of magnitude at 650 nm, and can function with excellent stability, reproducibility, and high response speed (< 1 ms) in a wide range of switching frequency (up to 300 Hz). The photocurrent of the device shows a power‐law dependence on light intensity. This finding together with the analysis of the light intensity‐dependent response speed reveals the existence of various traps at different energy levels (shallow and deep) in the bandgap. Coating with a thin SiO₂ isolating layer increases the photocurrent but decreases the response speed of the CdSe nanoribbon, which is attributed to reduction of recombination centers on ribbon surface.     

Preparation and characterization of graphene nanoribbons

Graphene nanoribbons(GNRs) have been synthesized by unzipping oxidized multiwalled carbon nanotubes.The thickness of the GNRs synthesized is ranged from mono-layer to four layers.The morphology of prepared GNRs is strongly dependent on structure and defects of the MWCNTs.The synchrotron radiation X-ray diffractions show the d(002) spacing of the GNRs decreases with the increase of the annealing temperature.This may be caused by the removing of water molecules and oxygen-containing functional groups in the GNRs.     

Designing the Width and Texture of Vanadium Oxide Macroscopic Fibers: Towards Tuning Mechanical Properties and Alcohol‐Sensing Performance

Macroscopic vanadium oxide fibers have been fabricated by an extrusion process. By varying the shear rate associated with the gel extrusion process we have been able to tune the diameter and transversal geometry of the fibers at macroscopic length scales. At the mesoscopic length scale, small‐angle X‐ray scattering (SAXS) analysis provides evidence for the possibility of fine tuning the degree of alignment of the V₂O₅ ribbons inside the fibers; this alignment is clearly improved upon increasing the shear rate. Nitrogen physisorption measurements (Brunauer–Emmett–Teller (BET)) indicate that the as‐synthesized fibers exhibit poor mesoporosity, largely due to the presence of remaining poly(vinyl alcohol) (PVA) entities. Microscopically, from XRD measurements, the fiber structure appears to be semi‐crystalline. ⁵¹V magic angle spinning NMR (MAS NMR) spectroscopy reveals that the local environment of ⁵¹V is typical of the structure of a V₂O₅·1.8 H₂O xerogel. We demonstrate here that the alignment of the nanoribbon subunits can be tuned via the shear rate applied during the extrusion process, which provides a good handle for tuning the mechanical and sensing properties of the as‐synthesized fibers.