Photocatalytic and bactericidal activities of hydrothermally and sonochemically prepared Fe2O3–SnO2 nanoparticles

Fe₂O₃–SnO₂ nanocomposites (NCs) were prepared by hydrothermal and sonochemical methods. Transmission electron micrographs confirmed that the composites comprise nanoparticles. Energy-dispersive X-ray analyses revealed compositions of 25 at.% Sn and 22 at.% Fe for hydrothermally prepared NC (HNC) and 4 at.% Sn and 56 at.% Fe for sonochemically prepared NC (SNC). X-Ray diffractograms revealed rutile SnO₂, γ-Fe₂O₃, and FeO(OH) as components of HNC, and rutile SnO₂, γ-Fe₂O₃, β-Fe₂O₃ and FeO(OH) of SNC. Both NCs absorb visible light and display red emission. The solid-state impedance spectrum for HNC is a half-semicircular arc and SNC exhibits a quasi-linear relationship between Z′′ and Z′. Both NCs are ferromagnetic. The saturation magnetization of HNC is much less than that of the SNC, which in turn is far less than that of the γ-Fe₂O₃ precursor. Both NCs display visible light photocatalysis and HNC is a better photocatalyst than SNC. Furthermore, both NCs exhibit bactericidal activity.     

AFM and XPS Study on the Surface and Interface States of CuPc and SiO2 Films

利用热生长工艺和热蒸发方法分别获得CuPc和SiO2薄膜层,通过原子力显微镜和X射线光电子能谱对其表面界面电子状态进行了研究,并采用高斯拟合方法对各谱进行了详细分析.结果表明,在氧原子的作用下,N1s,C1s,O1s 和Cu2p都经受了一定的化学位移,从而使得各原子间的相互作用强度有所改变,这是导致OFET性能劣化的重要原因之一.对OFET而言,采用溅射工艺制备的SiO2层应比热氧化生长的SiO2层更合适.     

Wireless Regional Area Networks and Cognitive Radio 2

The IEEE 802.22 Working Group hasbeen formed in November 2004with the task ofdeveloping astandard for the Wireless RegionalArea Network (WRAN) based onCognitive Radio (CR) technologies. Thestandard includes PhysicalLayer (PHY)and Media Access Control(MAC), usingthe already allocated fallow spectrums tobroadcast TVwith no interference. TheWRAN employs CR technologies tosense and estimate the televisionfrequencies and uses the dynamicspectrum management to find andallocate fallow …     

Processing and physical properties of single phase Tl2Ba2CaCu2O8 and (Tl0.5Pb0.5)Sr2−xBaxCa2Cu3O9 superconductors

Single phase Tl₂Ba₂CaCu₂O₈ (2212) superconductors with T_c of 97 K were obtained by a two-step synthesis. Prolonged annealing at 860°C in the second step of the synthesis resulted in a higher T_c, at the expense of the growth of an impurity trilayer 2223 phase in the form of stacking faults in the 2212 phase. Nearly single phase (Tl_0.5Pb_0.5)Sr_2−xBa_xCa₂Cu₃O₉) (1223) samples were obtained in a single air-sintering step. Replacement of Sr by Ba is necessary to grow the 1223 phase. Samples with x=0.75 displayed T_c as high as 117 K with a superconducting volume fraction over 50%.     

High Purity and Large-scale Preparation of β-Ga2O3 Nanowires and Nanosheets by CVD and Their Raman and Photoluminescence Characteristics

Ga2O3 nano-structures, nanowires and nanosheets are produced on Au pre coated（111） silicon substrates with chemical vapor deposition（CVD） technique. By evaporating pure Ga powder in the H2O atmosphere under ambient pressure the large-scale preparation of β-Ga2O3 with monoclinic crystalline structure is achieved. The crystalline structures and morphologies of produced Ga2O3 nano-structures are characterized by means of scanning electron microscope（SEM）, X-ray diffraction（XRD）, selected area electron diffraction （SAED） and transmission electron microscope（TEM）. Raman spectrum reveals the typical vibration modes of Ga2O3 The vibration mode shifts corresponding to Ga2O3 nano-structures are not found. Two distinguish photoluminescence（PL） emissions are found at about 399 nm and 469 nm owing to the VO-VGa excitation and VO-VGaO excitation, respectively. The growth mechanisms of Ga2O3 nanowires and nanosheets are discussed with vapor liquid-solid（VLS） and vapor-solid（VS） mechanisms.     

Mechanism and Development of TiO_2-Doped ZnO-Bi_2O_3-Based Varistors

This paper reviews the history of ZnO varistor,discribes its properties and recenttechnological status and forecasts its evolution.The future development trend is to produce the low-voltage high-energy multi-layer ZnO varistors.After the two additives are classified by their functions,the effect mechanism of Bi_2O_3 and TiO_2 additives are researched theoretically.TiO_2 will make ZnO graingrow bigger and V_ImA/mm be depressed down.Especially the colloid TiO_2 additive in the scale ofnanometer brings about a new method to realize the low voltage of ZnO varistor,which resolves theproblem of how to disturb nanometer powder evenly.Moreover the sintering temperature has prominenteffect on the electrical properties of ZnO varistors.Generally,the appropriate sintering temperature forlow-voltage ZnO varistor ceramics should not be more than 1 250℃.These provide an effective methodand rationale for studying low-voltage ZnO varistors.     

Synthesis and characterization of sol-processed α-MnO2 nanostructures

Nanostructure of α-MnO₂ was prepared by air oxidation of manganese chloride (MnCl₂) via sol processing by adding N, N-Dimethylformamide (DMF) as surface active material. The obtained material was conventionally annealed at 400 °C for 2 h. The product was characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The chemical reaction involved in the synthesis of α-MnO₂ nanostructure was proposed and discussed. From XRD pattern, the purity and crystallinity of final product was observed. The synthesized α-MnO₂ nanostructure showed an average crystallite size of 17 nm.     

Preparation and Photo—properties of Nanosize ZnS and Zn（en）2S

The precursore Zn(en)2 S (en=ethylenediamine) were prepared via a solvothermal process from elemental sulfur and zinc using ethylenediamine as a solvent. Detailed characterizations of the infrared (IR) absorption spectrum, powder X-- ray diffraction (XRD) and thermogravimetric analysis (TG) confirmed two en coordinated with Zn^2 to form a complex cation. The morphological property was also characterized by transmission electron microscopy (TEM) and electron diffraction analysis (ED). Phase—pure hexagonal wurtzite ZnS products were obtained by annealing the precursor in nitrogen stream at about 900 ℃ Zn(en)2S showed a nanosize of about 30 nm, and ZnS of about 60 nm. The fluorescence spectra were also studied. PL results showed that Zn(en)2S excited a fluorescence at 452 nm.     

Dielectric Spectroscopy and Mechanism of the Semiconductor–Metal Phase Transition in Doped VO2:Ge and VO2:Mg Films

Semiconductors - The frequency dependences of the dissipation factor tanδ(f) and the Cole–Cole diagrams for germanium- and magnesium-doped vanadium-dioxide films in the range of...     

Design and fabrication of compact 2 × 2 dual linear polarized wideband and high gain array for Ku-band satellite communication application

In this paper, the design of a planar array antenna for two-way satellite communication is presented. The antenna unit consists of four elements and two waveguide feeding networks used to connect the elements. The radiating elements are small horn apertures. Each element of the array includes two separate ports to radiate vertical and horizontal polarization, respectively. The feeding networks consist of power dividers and bends to connect the vertical and horizontal polarization ports of horns, separately. Radiating elements and feeding networks are designed to cover receive band (10.5–12.75 GHz) and transmit band (13.75–14.5 GHz) within Ku-band. The maximum gain for this type of antenna is 21 dBi.     

The Internet of Things and Ubiquitous Intelligence （2）

The traditional Internet is oriented towards person-to-person connection, whereas the Internet of Things (IoT) is oriented towards connections between inanimate objects. IoT covers a larger range of connections and involves more semantics. Traditional Internet and telecom networks focus on information transfer, but IoT focuses on information services. By combining sensor networks, Internet, telecom networks, and cloud computing platform, IoT can sense, recognize, affect, and control the physical world. The physical world can be unified with the virtual world and human perception. This lecture discusses IoT technology from three aspects: ubiquitous information sensing, ubiquitous network convergence, and intelligent information service. In this part, we discuss the architecture of sensor network and the status of the industry.     

Formation of the superconductor-semiconductor interface between Bi2Sr2CaCu2O8−x and indium-tin oxide

Planar heterostructures consisting of semiconducting highly textured indium-tin oxide (ITO) overlayers and c-axis oriented superconducting Bi₂Sr₂CaCu₂O_8−x (2212) underlayers have been formed onto MgO(100) substrates using dc magnetron sputtering. Annealing of the structures in air at 500 °C resulted in the appearance of both the interface resistivity anomaly at superconductive transition temperature—T_c and nonlinear current vs voltage behavior characteristics for a S-N junction. Meanwhile gradual change of the electrical properties towards S-I-N type behavior have been indicated with subsequent heat treatment in air at 50–100 °C. The origin of the insulating I-interlayer we associate with reversible oxygen removal in the 2212 compound at superconductor-semiconductor interface.     

Non——contact and Automatic Measurement of 2D Size with CCD Matrix and Computer System

A measurement system with the CCD matrix and computer system is designed to test the 2D size of any shape workpieces automatically. In addition, the system adopts the method of the relative measurement which increases the precision and the velocity. More importantly,the precision can‘t be changed with the conditions of the temperature and air pressure. The experiments show that the relative precision of 0. 002 9 and the absolute precision of 2.97 ttm are obtained. The instrument may be used in the product line and make the testing on line possible.     

Line positions and intensities in theν 2 band of D2O improvied pumped D2O laser frequencies

Using high resolution Fourier transform spectra, thev ₂ band of D₂O has been analysed leading to an extensive and precise set of rotational energy levels of the (0 1 0) vibrational state. These levels are reproduced very satisfactorily with a Watson type Hamiltonian and precise rotational constants as well as the band centerv ₂ = 1178.3789 ± 0.0005 cm^-1 are determined. A total of 61 line intensities were measured, much attention being paid to a possible contamination of the D₂O sample by HDO. A least squares fit of the intensity data has provided us with an expansion of the transition moment operator of thev ₂ band from which the first derivative \(\left( {\frac{{\partial ^x \mu }}{{\partial q_2 }}} \right)_e \) = 0.1690 ± 0.0030 D has been deduced. Finally the complete synthetic spectrum of this band has been computed. All these results have been used to derive improved frequencies for the known pumped and far-infrared laser lines of D₂O and to predict new possible coincidences with the available CO₂ laser lines.     

Scalable modeling and comparison for spiral inductors using enhanced 1-π and 2-π topologies

Two different scalable models developed based on enhanced 1-π and 2-π topologies are presented for onchip spiral inductor modeling.All elements used in the two topologies for accurately predicting the characteristics of spiral inductors at radio frequencies are constructed in geometry-dependent equations for scalable modeling.Then a comparison between the 1-π and 2-π scalable models is made from the following aspects:the complexity of equivalent circuit models and parameter-extraction procedures,scalable rules and the accuracy of scalable models.The two scalable models are further verified by the excellent match between the measured and simulated results on extracted parameters up to self-resonant frequency (SRF) for a set of spiral inductors with different L,R and N,which are fabricated by employing 0.18-μm 1P6M RF CMOS technology.     

Measurement and simulation of interfacial adhesion strength between SiO2 thin film and III–V material

Silicon oxide material, which has low-refractive index and high isolation characteristic, has been extensively adopted into high-brightness LED structures. However, the interfacial delamination problem between GaP and SiO₂ was observed in the high-brightness AlGalnP LED structure during fabrication process. It indicates that the weak adhesion strength of the GaP/SiO₂ interface is a significant issue for manufacturing of LEDs. Therefore, in this study, the interfacial adhesion strength between SiO₂ and III–V materials, such as GaP and GaAs, were measured by four-point bend test (4-PBT). In addition, the correspondence of the finite element models with the 4-PBT specimens was also established to predict the interfacial adhesion strength, G value, using the modified virtual crack closure technique (MVCCT) simulation technique. Comparing the predicted G value by MVCCT with experiment results of 4-PBT, the simulation results have good agreement with the experimental data.     

Scalable modeling and comparison for spiral inductors using enhanced 1-π and 2-π topologies

Two different scalable models developed based on enhanced 1-πand 2-πtopologies are presented for onchip spiral inductor modeling.All elements used in the two topologies for accurately predicting the characteristics of spiral inductors at radio frequencies are constructed in geometry-dependent equations for scalable modeling.Then a comparison between the 1-πand 2-πscalable models is made from the following aspects:the complexity of equivalent circuit models and parameter-extraction procedures,scalable rul...     

Ionic conductivity and dielectric relaxation in γ-irradiated TlGaTe2 crystals

The switching effect, field and temperature dependences of the permittivity and conductivity of TlGaTe₂ crystals subjected to various γ-irradiation doses are studied. Under rather low electric fields, the phenomenon of threshold switching with an S-shaped current-voltage characteristic containing a portion with negative differential resistance is observed in the crystals. In the region of critical voltages, current and voltage oscillations and imposed modulation are observed. Possible mechanisms of switching, ionic conductivity, disorder, and electrical instability in TlGaTe₂ crystals are discussed.     

Hydrothermal synthesis and characterization of α-Fe2O3 nanoparticles

Iron oxide (Fe₂O₃) nanoparticles were synthesized by a simple hydrothermal synthesis method using only Fe(NO₃)₃·9H₂O and NH₃·H₂O as raw materials. The effect of reaction temperature and time on the crystalline phase and morphology of Fe₂O₃ products was investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The XRD and TEM results show that reaction temperature and time play an important role in the formation of the crystalline phase and morphology of the products. With increasing reaction temperature and time, the diffraction peaks of α-Fe₂O₃ become stronger and sharper, and the morphologies of the samples have an obvious change from floccules to nanoparticles. FTIR peaks show that α-Fe₂O₃ nanoparticles have about a 25 cm^?1 shift to higher frequency compared with those of α-Fe₂O₃ with other morphologies.