Photocatalytic activity of cerium-doped mesoporous TiO2 coated Fe3O4 magnetic composite under UV and visible light

A novel kind of magnetically separable photocatalyst of cerrium-doped mesoporous titanium dioxide coated magnetite (Ce/MTiO2/ Fe3O4) was prepared and its activities under UV and visible light were reported. The catalysts with Ce/MTiO2 shell and Fe3O4 core were pre-pared by coating photoactive Ce/MTiO2 onto a magnetic Fe3O4 core through the hydrolysis of tetrabutyltitanate (Ti(OBu)4, TBT) with pre-cursors of ammonium ceric nitrate and TBT in the presence of Fe3O4 particles. The MTiO2 shell was for photocatalysis, the Fe3O4 core was for separation by the magnetic field and the doped Ce was used to enhance the photocatalytic activity of MTiO2. The morphological, struc-tural and optical properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET) surface area, transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of cerrium-doped content on the photocatalytic activity was studied and the result revealed that 0.5 mol.% Ce/MTiO2/Fe3O4 exhibited highest photoactivity. The photocatalytic activities of obtained photocatalysts under UV and visible light were estimated by measuring the degradation rate of methylene blue (MB, 50 mg/L) in an aqueous solution. The results showed that the prepared photocatalyst was activated by visible light and used as effective catalyst in photooxi-dation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, Ce/MTiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by an external magnetic filed. So, the photocatalyst can be reused without any mass loss. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.     

Preparation and upconversion luminescence of monodisperse Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles

Y2O2S:Yb/Ho-silica/aminosilane core-shell nanoparticles were prepared by a solid-gas method in combination with polyvinylpyr-rolidone assisted one-step ammoniating method. The core was a single Y2O2S:Yb/Ho with 80 nm in diameter and the shell was silica/aminosilane with around 5 nm in thickness. The results of sedimentation experiment indicated that the nanoparticles could be well-dispersed in ethanol and water to form stable colloids. Since the coating weakened lattice vibration energies of the Y2O2S:Yb/Ho...     

Magnetic Field Effect on Critical Behavior of Perovskite Ferromagnet

The polycrystalline samples of La2/3Ca1/3MnO3 were prepared by a conventional solid state reaction method. The magnetizations （ZFC, FC and initial magnetization） of the polycrystalline La2/3Ca1/3MnO3 were measured with superconducting quantum interference device magnetometer. The scaling theory was employed to study the changes of critical behavior arising from the applied external field. The critical parameter β decreases with increasing the external magnetic field results in an increase in the magnitude of ferromagnetic ordering.     

Effect of Electromagnetic Frequency on Magnetic Flux Coupling by Traveling Magnetic Field

The effect of frequency on magnetic flux coupling field were analyzed with traveling-wave electromagnetic stirring system using a coupled model of magnetic induction and fluid dynamics.Simulations were performed to investigate the influences of the frequency on magnetic flux density,electromagnetic body force and flow field.The results showed that the magnetic flux density decreased with increasing frequency.The electromagnetic body force wavy moved along the same direction and increased with increasing the frequency when the traveling magnetic field is applied.The core area of the stirring was in the bottom of the alloy melt.A large circulation in the vertical section of the alloy melt can be produced by the electromagnetic body and the maximum flow rate first increased and then decreased with increasing frequency.     

Sonochemical synthesis and photoluminescence properties of rare-earth phosphate core/shell nanorods

Rare earth phosphate core/shell nanostructures were synthesized via facile ultrasound irradiation method.XRD and TEM were em-ployed to characterize the structure and morphology properties.The photoluminescence(PL) properties of TbPO4/CePO4 and CePO4/TbPO4 core/shell nanorods were studied to explore the energy transfers from Ce3+ to Tb3+.In the Ce0.9Tb0.1PO4/LaPO4 core/shell nanorods,the PL intensity of Ce0.9Tb0.1PO4 nanorods was enhanced when the LaPO4 shells were coated.     

Facile synthesis of Er3+/Tm3+co-doped magnetic/luminescent nanosystems for possible bioimaging and therapy applications

Manganese-zinc ferrite is a kind of very important magnetic ferrite material.The properties of wide absorption band,sensitivity to ultraviolet(UV)light and tumor H₂O₂ promise it to be possibly used as a photothermal therapy(PTT),photodynamic therapy(PDT)and chemodynamic therapy(CDT)agent.Based on the unique advantages of rare-earth doped nanoparticles,an Er³⁺,Tm³⁺co-doped upconversion-mediated nanosystem with manganese-zinc ferrite shell(named as UCNPS@M)was developed through a facile thermal co-decomposition method.The final nanosystems were surface-modified by using dopamine hydrochloride(DA)in order to warrant good biocompatibility(named as UCNPS@M@DA).Under irradiation of near-infrared(NIR)light,UCNPS emit both ultraviolet and visible light.The UV light is mostly abso rbed by manga nese-zinc ferrite shell to produce reactive oxygen species(ROS),which is essential to the potential PDT and CDT effect of nanosystems,and at the same time,Mn_0.5Zn_0.5Fe2O₄ can further react with H₂O₂ to promote the efficiency of OH-generation.It is expected that UCNPS@M@DA can act as upconversion luminescence imaging guidance due to the visible emission from UCNPS.In addition,the energy absorbed by the nanosystems can be transferred to heat to realize photothermal effect.Moreover,UCNPS@M@DA was successfully applied as a T₁/T₂-weighted magnetic resonance imaging(MRI)contrast agent due to the existence of Gd,Mn,and Fe elements.In light of the upconversion luminescence(UCL)imaging from the UCNPS as well as potential PTT,PDT,CDT effect mentioned above,this work provides a possibility to realize cancer multi-model bioimaging guided treatment by using an all-in-one diagnosis and therapy nanosystem through a simple yet powerful strategy.     

Effect of Magnetic Field on Synthesis of Nano-FeOOH by Low-Temperature Neutralization Method

Using XRD,TEM and VSM methods,the phase,morphology and magnetic property of iron hydroxide oxide(FeOOH)which has been prepared by low-temperature neutralization reaction under different magnetic fields were analyzed.It can be found that the magnetic field had a great influence on the product.Acicular goethite(α-FeOOH)was synthetized without magnetic field.When the magnetic flux density was increased to 0.1T,γ-FeOOH was obtained.If the magnetic field intensity was raised to 0.5T,the product was all composed ofσ-FeOOH.Moreover,the crystallization of FeOOH was greatly influenced by magnetic field as well.Thermodynamic calculation results show that the magnetic free energy of chemical reaction reached to more than hundreds KJ/mol when the magnetic field is applied.It meaned that the application of magnetic field was conducived to producing the products with higher susceptibility.Even under the low magnetic field,due to the stability of the reaction products was broken by the magnetic field,the magnetic free energy was also effective.     

Investigations on multi-photon emissions of Nd~(3+)-sensitized core/shell nanoparticles

The past few years witnessed extensive emergence of short-wavelength upconversion(UC) emission stimulated photoactivation studies. However, low efficiency of multi-photon process greatly limits further applications. Here, ultraviolet(UV) upconversion emissions originated from multi-photon process of Tm~(3+) were studied with Nd~(3+)-sensitized NaGdF_4:Yb,Tm@NaYF_4:Nd,Yb core/shell nanoparticles. Crucial factors, including the contents of sensitizers Nd~(3+), Yb~(3+) and activator Tm~(3+), as well as the excitation power density were investigated based on the UV emission. Spectral results showed that high contents of Nd~(3+) in shell region up to 50%(molar fraction hereafter) and Yb~(3+) of 10% were essential to mediate the energy transfer via the core/shell interface and facilitate multi-photon UV emissions. Compared with segregated activator and sensitizer, a core/shell strategy with isolated Nd~(3+) in the shell was important for higher UV emission. Although the upconverting process was initiated with Nd~(3+)→Yb~(3+), the short-wavelength emissions were intrinsically coming from four- and five-photon process. The optimized nanoparticles were found to be able to manipulate the configuration transition of azobenzene molecules, and it could be promising for near infrared(NIR) triggered optical switches applications.     

Effect of High Magnetic Field on Magnetostrictive Property of Tb-Fe Alloy During Heat Treatment

TbFe₂,as a typical magnetostrictive material,is ferrimagnetic.Its magnetostrictive property can be improved by an external magnetic field at a temperature below its Curie temperature.In this paper,the effects of high magnetic fields on the preferred orientation,phase composition and magnetostrictive property of Tb-Fe alloys during heat treatment process were investigated.It was found that the magnetostriction performance of the alloy annealed in an 11.5 T magnetic field was improved by 30%contrary to that without magnetic field.Such increase can be attributed to the increase in orientation degree of<113>caused by the high magnetic field during the heat treatment.     

Low-temperature electrochemical synthesis and characterization of ultrafine Y（OH）_3 and Y_2O_3 nanoparticles

Ultrafine Y(OH)3 nanoparticles were successfully deposited from an additive-free 0.005 mol/L YCl3 low-temperature bath on the steel cathode at the current density of 0.5 mA/cm2 and bath temperature of 10 oC. Heat treatment of the prepared Y(OH)3 nanoparticles at 600 oC in air led to the formation of Y2O3 nanoparticles. Thermal behavior and phase transformation during the heat treatment of Y(OH)3 were investigated by differential scanning calorimetry (DSC) and thermogramimetric analysis (TGA). The morphologies, crystal structures and compositions of the prepared materials were examined by means of scanning and transmission electron microscopy (SEM and TEM) as well as X-ray diffraction (XRD) and FT-IR spectroscopy. The results showed that the prepared Y(OH)3 nanoparticles was essentially amorphous and composed of well dispersed ultrafine particles with size of 4 nm. After heat treatment, the obtained oxide product was well crystallized cubic phase of Y2O3 nanoparticles with the grain size of around 5 nm. It was concluded that low-temperature cathodic electrodeposition offered a facile and feasible way for preparation of ultrafine Y(OH)3 and Y2O3 nanoparticles.     

Ultra-high sensitivity of rhodamine B sensing based on NaGdF4:Yb3+,Er3+@NaGdF4 core-shell upconversion nanoparticles

A series of mono-dispersed hexagon NaGdF_4:Yb~(3+),Er~(3+)@NaGdF_4 core-shell nanoparticles with different shell thickness were synthesized via a co-precipitation method. Nanoparticles with high upconversion fluorescent emissions result in large signal-to-noise ratio, which guarantees the accuracy of the sensitivity. Besides, the maximum sensitivity of these NPs as detection film increases first and then decreases with the shell thickness increasing. When the shell thickness is 2.3 nm(NaGdF_4-2), the maximum sensitivity(0.69959 ppm~(-1)) is reached. A large degree of overlap between the rhodamine B absorption band and the Er~(3+) green emission bands ensures that the NaGdF_4:Yb~(3+),Er~(3+)@NaGdF_4 nanoparticles can be used as fluorescent probe to detect the concentration of rhodamine B based on fluorescent intensity ratio technology. The linear relationship between the rhodamine B concentration and the intensity ratio(R) of green and red emission intensity(I_(S+H) and I_F) were studied systematically. The result shows that the maximum sensitivity can be obtained in low concentration rhodamine B(4 ppm), which is lower than the reported minimum detection concentration. Thus, the ultra-high sensitivity detection by NaGdF_4:Yb~(3+),Er~(3+)@NaGdF_4 core-shell upconversion nanoparticles in low concentration can be realized,which provides promising applications in bio-detection filed.     

Study on application of CeO2 and CaCO3 nanoparticles in lubricating oils

The ceria （CeO2） nanoparticles and calcium carbonate （CaCO3） nanoparticles were chosen as additives of anti-wear and extreme pressure for lubricating oils, and the morphology and sizes of nanoparticles were examined using Transmission Electron Microscope （TEM）. The tribological performance of lubricating oils containing combined nanoparticles were determined by four-ball friction and wear tester, and the chemical composition of steel ball with worn surface were analyzed by X-ray Photoelectron Spectrurn（XPS）. The results showed that the lubricating oils containing combined nanoparticles had good anti-wear and friction reducing effects, and the tribological properties were optimal when WCeO2＋CaCO3=0.6%, WCeO2：WCaCO3=1：1. The extreme pressure value increased by 40.25%, the wear spot diameter reduced by 33.5%, and friction coefficient reduced by 32% compared with 40CD oil. The coordinated action of big and small particles made anti-wear and friction reducing effective. Tribological chemical reactions resulting from the friction surface formed metal calcium, metal cerium and oxides film, and they could fill up the concave surface and protect the worn surface.     

Nd3+-sensitized upconversion nanoparticle coated with antimony shell for bioimaging and photothermal therapy in vitro using single laser irradiation

Combining treatment and diagnosis, called theranostics, which is achieved within single nanoparticle is an ultimate goal of many studies. Herein, we developed a new nanotheranostic agent ? Nd³⁺-sensitized upconversion nanoparticles core for dual modal imaging (i.e., upconversion luminescence imaging and magnetic resonance imaging) and antimony nanoshell for photothermal therapy (PTT). The core-shell-shell upconversion nanoparticles (NaYF₄:Yb,Er@NaYF₄:Yb,Nd@NaGdF₄:Nd, named as UCNP) were firstly synthesized using thermal decomposition method and then were coated by antimony shell over the surface of UCNP using simple cost and time effective new method. Furthermore, the surface of UCNP@Sb nanostructures was modified with DSPE-PEG in order to enhance the water solubility and biocompatibility. The final nanotheranostic agent, named as UCNP@Sb-PEG, exhibits very low toxicity, good biocompatibility, very good photothermal therapeutic effect, and efficient upconversion luminescence (UCL) imaging of HeLa cells under only one laser (808 nm) irradiation. The antimony shell is quenching the upconversion emission in pristine nanotheranostic agent, but interestingly, the UCL intensity of the agent recovers progressively under 808 nm laser irradiation due to light induced degradability of antimony shell. Besides, high longitudinal relaxivity (r₁) obtained from the experiment approves excellent potential of the nanotheranostic agent for T₁-weighted magnetic resonance imaging application.     

纳米结构Fe_3O_4制备与应用的研究进展

纳米结构的Fe3O4具有与生物组织的相容性以及与尺寸和形貌有关的电学和磁学性能,在磁流体、传感器和生物医药等领域具有广泛的应用前景。Fe3O4纳米结构的主要制备方法包括高温气相法、高温有机液相回流法、溶剂热法和水热法等;已经制备出各种纳米结构单元的Fe3O4,如:零维纳米颗粒,纳米颗粒组装的纳米链,纳米颗粒组装的微球,一维纳米线、棒,二维纳米片,以及三维的金字塔、八面体、核桃状球形纳米颗粒等。该文综合介绍这些制备方法的特点及其近期的研究进展,并对Fe3O4纳米结构的性质和应用进行综述。最后对Fe3O4纳米材料未来的发展进行展望。     

CeF_3纳米微粒的合成、结构及摩擦学行为研究

在溶液中化学合成了有机化合物表面修饰的油溶性 Ce F3纳米微粒 ,初步探讨了表面修饰 Ce F3纳米微粒的制备条件 ,并表征了表面修饰 Ce F3纳米微粒的结构和性能。结果表明 ,表面修饰 Ce F3纳米微粒添加剂具有良好的减摩抗磨性 ,并且可以有效地提高基础油的承载性能 ,其性能优于商品添加剂 T2 0 2 (ZDDP)。     

LaF3纳米微粒的摩擦学行为研究

本文在醇－水体系中采用共沉淀表面修饰法制备了磷酸烷基酯修饰的ＬａＦ３纳米微粒。利用多种分析手段表征了表面修饰ＬａＦ３纳米微粒的结构和润滑性能,结果表明形成了以ＬａＦ３为纳米核、有机磷化合物为表面修饰层在有机溶剂中具有良好分散性的ＬａＦ３纳米微粒,作为润滑油添加剂,具有良好的减摩、抗磨和承载性能。     

Photoluminescence properties of LaF3：Eu^3＋ nanoparticles prepared by refluxing method

The europium-doped LaF3 nanoparticles were prepared by refluxing method in glycerol/water mixture and characterized with X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), UV-vis diffuse reflectance spectrum, and photoluminescence spectra. The results of XRD indicated that the obtained LaF3: Eu3+ nanoparticles were well crystallized with a hexagonal structure. The FE-SEM image illustrated that the LaF3: Eu3+ nanoparticles were spherical with an average size around 30 nm. Under irradiation of UV light, the emission spectrum of LaF3: Eu3+ nanoparticles exhibited the characteristic line emissions arising from the 5D0→7FJ (J=1, 2, 3, 4) transitions of the Eu3+ ions, with the dominating emission centered at 590 nm. In addition, the emissions from the 5D1 level could be clearly observed due to the low phonon energies (-350 cm-1) of LaF3 matrix. The optimum doping concentration for LaF3: Eu3+ nanoparticles was determined to be 20mol.%.     

多晶壳NaYF4纳米颗粒的能量传递机理研究

以乙二醇（EG）为溶剂，聚乙烯亚胺（PEI）为表面活性剂，采用溶剂热法合成了多晶壳结构的上转换纳米颗粒NaYF₄: 18 %Yb, 20 %Gd, 2 % Er@NaYF₄: 10 %Yb, 40 %Nd.通过HAADF元素分析和HRTEM确认多晶壳层的存在，壳层厚度用HRTEM直接观测和TEM粒径统计分布进行计算.通过调节壳层反应物的加入量，实现对外延生长的NaYF₄: Yb, Nd活性壳层厚度的精确调控.研究发现，当多晶壳层厚度为1.7 nm时，上转换发光强度达到最大，与上转换发光强度随单晶壳层厚度的单调递增的规律不同.可能原因是多晶活性壳层中的大量晶界，导致Yb-Yb长程能量传递过程中的能量损失率增高.