Huihui Li

Magnetic force microscopy of magnetic domain structure in highly ordered Co nanowire arrays

Abstract Highly ordered anodic alumina oxide (AAO) membranes with a diameter of about 50 nm are prepared by two-step anodization. Cobalt nanowires were obtained by ac electro-deposition of Co2+ into the pore of AAO membranes. Vibrating sample magnetometer (VSM) results show that such a sample has highly perpendicular anisotropy properties. Here, we first use magnetic force microscopy (MFM) to obtain a fine image of magnetic domain structure in Co/AAO film successfully. MFM images show that each as-prepared nanowire in the membrane show single domain structure. The nearest neighbor bits have opposite magnetization. The magnetic moment was aligned in the same direction after the sample was magnetized under a 1 T external field. Due to its high bit density (up to 100 Gbits / in. 2 ), such a material may be used as high-density perpendicular recording quantum magnetic disks (QMD).

Structural evaluation of azobenzene-functionalized self-assembled monolayers on gold by reflectance FTIR spectroscopy

Abstract The end-group-dominated molecular orientation in azobenzene self-assembled monolayers (SAMs), C n AzoC 2 SH ( n = 1–4), on gold was evaluated by grazing incidence reflection absorption FTIR spectroscopy. All these azobenzene SAMs form highly organized and closely packed structures, with the molecule tilting gradually away from the surface normal direction with increasing end group alkyl length.

Preparation of γ-MnO2/carbon composite material by a wet chemical method

Abstract The gamma manganese dioxide was prepared with the sulfonated graphite carbon materials as the nucleation centers or the substrate for precipitate by a wet chemical method. The XRD patterns confirmed that the products were the composite of γ-MnO 2 and graphite. The SEM images showed that the manganese dioxide particles conglobulated on the surface of scalelike graphite carbon. The MnO 2 /C material gave the better deep discharge capacity than that of the EMD and can be used as the good dopant for EMD.

Effect of the molecular interaction on molecular packing and orientation in azobenzene-functionalized self-assembled monolayers on gold

The effect of van der Waals interaction between alkyl chains on the molecular packing density and orientation in the self-assembled monolayers (SAMs) of a series of novel functionalized azobenzene on gold has been studied by reflectance infrared spectroscopy and contact angle measurement. The aromatic interaction between the azobenzene groups and hydrogen bonding between the amide groups help to organize the molecules, forming a well-defined structure. Larger van der Waals interactions introduced by alkyl chains with longer length at the front of the azobenzene group lead to a higher packing density and a larger tilting angle of the molecules.

Enhanced Photocatalytic Performance of Luminescent g-C3N4 Photocatalyst in Darkroom

Graphitic-C3N4(g-C3N4), a low-cost visible-light-driven photocatalyst, was used for the photocatalytic oxidation of aqueous methylene blue (MB) in the dark with Sr4Al14O25:(Eu,Dy) assistance. The Sr4Al14O25:(Eu,Dy)/g-C3N4 photocatalysts were fabricated through the ultrasonic dispersion method. The commercial Sr4Al14O25:(Eu,Dy) phosphor was used as a long afterglow supplier for exciting g-C3N4 in the dark. The results demonstrated that the metal-free g-C3N4 photocatalyst could use the eye-visible long afterglow to photocatalytically decompose MB dyes in the dark. This work may expand the appealing application of g-C3N4 for the environmental cleanup.

Surface-enhanced infrared spectra of azobenzene LB monolayers on silver island film

Abstract Surface enhanced infrared spectra (SEIRS) of the azobenzene Langmuir–Blodgett monolayer on silver film with different thickness is studied. The roughness of the surface is found to be essential for SEIRS, and mutual electromagnetic coupling between the silver islands is evidenced through the different infrared absorption behaviour of COOH residing in the gap between the silver island and the COO − on the silver island.

Spy Must Be Spotted: A Multistimuli-Responsive Luminescent Material for Dynamic Multimodal Anticounterfeiting and Encryption

The development of luminescent materials for anticounterfeiting and encryption is of great importance. Herein, we develop a multistimuli-responsive luminescent material, Na2CaGe2O6:Pb2+/Er3+, and use it to print luminescent images. The photoluminescence and upconversion luminescence of these images show different patterns and colors under different stimuli. The photostimulated luminescence (PSL) of the printed images causes dynamic changes in appearance and is accordingly applied for dynamic multimodal anticounterfeiting on banknotes. The PSL of these luminescent images is also applied in a virtual war scenario to demonstrate that the dynamic PSL-encrypted information in the fabricated image is sufficiently safe even in extreme cases and that spies will be detected. These results can inspire us with more creative security designs based on this luminescent material.

A thermal-sensitizing and thermochromic phosphor

Phosphors are efficient luminescent materials that are being extensively used in lighting and displays in todays world. However, the serious emission loss at high temperatures due to thermal quenching effects is still one of the most significant challenges that limit the application of phosphors. Herein, we report a unique thermal sensitizing effect of the Na2CaGe6O14:Pr3+ phosphor, in which the red emission of Pr3+ is significantly enhanced with the increase in temperature, even upto 250 °C. Moreover, the emission of the phosphor still keeps increasing over time at high temperatures. This thermally induced emission increase originates from the generation of more defect levels and more efficient energy transfer from the defects to Pr3+ at higher temperatures. This significant discovery may enlighten a new strategy to minimize or even completely eliminate the serious thermally induced emission loss of the phosphors.

Effect of the status of Sm on the properties of Sm contained N doped TiO2 photocatalysts

Nitrogen-doped TiO2 (TiO2−xNy) nanoparticles with and without adding Sm3+ were synthesized by thermohydrolysis of TiCl3. The samples were characterized by X-ray diffraction, specific surface area determination, UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the sample was investigated by employing the oxidative destruction of nitric oxide as a probe reaction using a flow reactor. Although the doping of Sm3+ in the lattice of titania was not useful to improve the photocatalytic activity, loading of samarium oxides on the surface of titania resulted in an improvement of the photocatalytic activity of the nitrogen-doped TiO2. The beneficial effect was explained by an increased separation efficiency of the photogenerated electron–hole pairs.

Persistent photocatalysis effect of black peony-like BiOCl and its potential full-time photocatalytic applications

A new concept of a “Persistent Photocatalysis (PersP)” effect is defined for the first time according to the observation that the black peony-like BiOCl material is able to efficiently degrade Rhodamine B dye after removing visible light irradiation, just as in persistent luminescence of phosphors. The discovery of the PersP effect provides a potential solution to realize full-time photocatalytic applications. The PersP effect was justified through a series of decomposition experiments, and its potential prospect for full-time application was evaluated by experiments as well. On the basis of the results, a possible PersP mechanism of the black peony-like BiOCl material has been proposed.