Synthesis and Analysis of Tm^(3+) Doped YF_3 Upconversion Luminescent Nano-materials

Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation, and impact of different grain sizes and morphology on the UC luminescence intensity was discussed. The fluorescence decay lifetime was calculated by Multi-exponential function fitting method. Results show that UC emission intensity was enhanced with the reduction of grain size, and the decay lifetime is 0.60 us.

Hydrothermal Synthesis and Structure Analysis of Indium Vanadate (InVO_4)

In this article, hydrothermal process is applied to synthesize nanometer InVO4. Influences of different experimental conditions （including mixing ratio of raw materials, reaction temperature, reaction time and so on） upon the synthetic products＇ purity and crystallite size are discussed to determine the best synthetic condition. The structure of nanometer InVO4 is analyzed, which helps to further understand the structure characteristics of InVO4 synthesized by applying hydrothermal process and lays foundation for further research.

Mechanism study on UV-induced photodegradation of nonylphenol ethoxylates by intermediate products analysis

Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate products including aldehydic compounds, carboxylic compounds and cyclohexanyl compounds were identified. Five main degradation routes involving the oxidation of the alkyl chain and ethoxylate unit, shortening of the alkyl chain and ethoxylate unit, hydrogenation of the benzene ring were proposed.

Ultrathin, Lightweight, and Flexible CNT Buckypaper Enhanced Using MXenes for Electromagnetic Interference Shielding

Lightweight,flexibility,and low thickness are urgent requirements for next-generation high-performance electromagnetic interference(EMI)shielding materials for catering to the demand for smart and wearable electronic devices.Although several efforts have focused on constructing porous and flexible conductive films or aerogels,few studies have achieved a balance in terms of density,thickness,flexibility,and EMI shielding effectiveness(SE).Herein,an ultrathin,lightweight,and flexible carbon nanotube(CNT)buckypaper enhanced using MXenes(Ti3C2Tx)for high-performance EMI shielding is synthesized through a facile electrophoretic deposition process.The obtained Ti3C2Tx@CNT hybrid buckypaper exhibits an outstanding EMI SE of 60.5 dB in the X-band at 100μm.The hybrid buckypaper with an MXene content of 49.4 wt%exhibits an EMI SE of 50.4 dB in the X-band with a thickness of only 15μm,which is 105%higher than that of pristine CNT buckypaper.Furthermore,an average specific SE value of 5.7×10^(4) dB cm^(2) g^(−1) is exhibited in the 5-μm hybrid buckypaper.Thus,this assembly process proves promising for the construction of ultrathin,flexible,and high-performance EMI shielding films for application in electronic devices and wireless communications.

Structure and Raman Spectroscopy of Nanocrystalline TiO_(2) Powder Derived by Sol-Gel Process

Nanocrystalline TiO_(2) powder was prepared by sol-gel process.The structures of the as-prepared and the TiO_(2) powder heat-treated at different temperatures were studied by thermogravimetric analyzer,differential thermal analysis,x-ray diffraction,and Raman spectra.As the powder was heat-treated at 350℃,it turned into tetragonal anatase structure.A structural transformation from anatase to rutile type occurred and the grains of the powder grew drastically when the powder was heat-treated at above 550℃.The structural transformation from anatase to rutile type completed at 750℃.The Raman spectra of TiO_(2) nanocrystalline powder were also studied.

Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots

Size-dependence of optical properties and energy relaxation in CdSe/ZnS quantum dots （QDs） were investigated by two-colour femtosecond （fs） pump-probe （400/800 nm） and picosecond time-resolved photoluminescence （ps TRPL） experiments. Pump-probe measurement results show that there are two components for the excited carriers relaxation, the fast one with a time constant of several ps arises from the Auger-type recombination, which shows almost particle sizeindependence. The slow relaxation component with a time constant of several decades of ns can be clearly determined with ps TRPL spectroscopy in which the slow relaxation process shows strong particle size-dependence. The decay time constants increase from 21 to 34 ns with the decrease of particle size from 3.2 to 2.1 nm. The room-temperature decay lifetime is due to the thermal mixing of bright and dark excitons, and the size-dependence of slow relaxation process can be explained very well in terms of simple three-level model.

A New Duplex Reverse Transcription PCR for Simultaneous Detection of Viable Cryptosporidium parvum Oocysts and Giardia duodenalis Cysts

Objective To simultaneously detect viable Cryptosporidium parvum oocysts and Giardia duodenalis cysts for the purpose of reducing time and cost spent. Methods A duplex reverse transcription polymerase chain reaction （RT-PCR） method was newly developed. Results Using duplex RT-PCR method for the hsp70 gene, viable （oo）cyst concentrations of 10^1 and l0^3 （oo）cysts/100 I.tL could be detected for C. parvum and G duodenalis, respectively. However, after heat-shock stimulation the expression of hsp70 mRNAs was detectable at 10^0 and 10^1 （oo）cysts/100 μL concentrations of C. parvum and G. duodenalis, respectively. Thus, the detection sensitivity was significantly increased when the viable （oo）cysts were exposed to heat shock. Conclusion This study describes a new duplex RT-PCR method for hsp70 gene to detect the viable （oo）cysts of the C. parvum and G duodenalis with less time consumed and at a lower cost. This newly developed duplex RT-PCR method may be used to detect these parasites not only in aquatic environments but also in clinical samples.

Detection and Molecular Characterization of Enteroviruses in Korean Surface Water by Using Integrated Cell Culture Multiplex RT-PCR

Objective To identify waterborne enteric viruses in Korean surface water. Methods Integrated cell culture（ICC）multiplex reverse transcription-polymerase chain reaction （RT-PCR） was simultaneously designed to detect coxsackieviruses （CV）, polioviruses （PV）, and reoviruses （RV）. ICC-multiplex RT-PCR and phylogenetic analysis were conducted using 21 total culturable virus assay （TCVA）-positive sample-inoculated cell cultures. Results CV and RV were detected in 9 samples each, and 3 samples were positive for both CV and RV. PV was not detected in any sample. Molecular phylogenetic analysis of the VP1 gene sequences revealed that CV types B2 and B4 predominated in Korean surface water, and the nucleotide sequences of CV type B2 were clustered with those of CVs isolated from China and Japan. The results suggested that the evolution of these viruses occurred in a region-specific manner. Conclusion CV and RV are detectable in Korean surface water, with a predominance of CV type B2, and the evolution of CV type B2 occur in a region-specific manner.

Microstructure and Magnetic Properties of Nd_(8.5)Fe_(77.1)B_(6.4)Co_4Zr_3Nb_(0.5)V_(0.5) Ribbons

Microstructure and magnetic properties of Nd8.5Fe77.1B6.4Co4Zr3Nb0.5V0.5 nanocomposite ribbons were investigated. A fine and uniform grain with 30 nm in average size was achieved for the ribbons annealed at 710 ℃ for 4 min, which enhanced the interaction coupling between grains and improved the magnetic properties. The results of three-dimensional atom probe (3DAP) revealed that V-enriched intergranular phase existed at the grain boundaries, suppressing the grain growth during crystallization process. The remanence and coercivity for annealed ribbons reached to 80 emu·g-1 and 567 kA·m-1, respectively.

Variation of passivation behavior induced by sputtered energetic particles and thermal annealing for ITO/SiO_x/Si system

The damage on the atomic bonding and electronic state in a SiO_x（1.4-2.3 nm）/c-Si（150 μm） interface has been investigated.This occurred in the process of depositing indium tin oxide（ITO） film onto the silicon substrate by magnetron sputtering.We observe that this damage is caused by energetic particles produced in the plasma（atoms,ions,and UV light）.The passivation quality and the variation on interface states of the SiO_x/c-Si system were mainly studied by using effective minority carrier lifetime（τ_（eff）） measurement as a potential evaluation.The results showed that the samples＇ τ_（eff）was reduced by more than 90%after ITO formation,declined from 107 μs to 5 μs.Following vacuum annealing at 200 ℃,the τ_（eff） can be restored to 30 μs.The components of Si to O bonding states at the SiO_x/c-Si interface were analyzed by x-ray photoelectron spectroscopy（XPS） coupled with depth profiling.The amorphous phase of the SiO_x layer and the ＂atomistic interleaving structure＂ at the SiO_x/c-Si interface was observed by a transmission electron microscope（TEM）.The chemical configuration of the Si-O fraction within the intermediate region is the main reason for inducing the variation of Si dangling bonds（or interface states） and effective minority carrier lifetime.After an appropriate annealing,the reduction of the Si dangling bonds between SiO_x and near the c-Si surface is helpful to improve the passivation effect.

Synthesis and Crystal Structure of Diethyl-2,6-dimethyl-3,5-diyl-(1-(2-chlorobenzoyl)-1H- pyrazole-3-diethyl-carboxylate)-pyridine

The reaction of hydrazine hydrate with a new α,γ-diketone ester 3, derived from the reaction of 2,6-dimethyl-3,5-diacetyl-pyridine 2 with diethyl oxalate in the presence of sodium ethoxide, afforded the pyrazole derivative 4. Treatment of 4 with 2-chlorobenzoyl chloride gave diethyl 2,6-dimethyl-3,5-diyl-（1-2（chlorobenzoyl）-1H-pyrazole-3-diethyl-carboxylate） pyridine 5. Fine crystal of 5 suitable for XRD analysis was obtained form recrystalization in ethyl acetate. The crystal belongs to the triclinic system, space group P1^-, with a = 1.0342（11）, b = 1.2211（12）, c = 1.5013（15） nm, α = 82.5190（10）,β = 85.7960（10）,γ = 85.3150（10）°, V= 1.8697（3） nm^3, Dc= 1.173 g/cm^3, μ = 0.219 mm^-1, F（000） = 684, Z = 2, the final R = 0.0720 and wR = 0.2211.

Crystal and electronic structure of a quasi-two-dimensional semiconductor Mg_(3)Si_(2)Te_(6)

We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions.Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure.The experimentally determined direct band gap is 1.39 eV,consistent with the value of the density function theory calculations.Our results reveal that Mg_(3)Si_(2)Te_(6)is a direct gap semiconductor,which is a potential candidate for near-infrared optoelectronic devices.

New 1222-Type Thallium-Indium Layered Cuprates(Tl,In)Sr_(2)(Nd,Ce)_(2)Cu_(2)O_(z) and Their Superconductivity

A new series of 1222-type thallium-indium layered cuprate compounds(Tl,In)Sr_(2)(Nd,Ce)_(2)Cu_(2)O_(z)have been successfully synthesized in the pure or nearly pure form and identified by powder x-ray diffraction analyses.The structure of the compounds is directly related to that of Nb-1222 NbSr_(2)(Nd,Ce)_(2)Cu_(2)O_(z),with a tetragonal body-center lattice.The lattice parameters are a=3.85Å,c=29.56Åfor(Tl_(0.7)ln_(0.3))Srz(Nd_(0.5)Ce_(0.5))_(2)Cu_(2)O_(z),and a=3.85Å,c=29.28Åfor lnSr_(2)(Nd_(0.75)Ce_(0.25))_(2)Cu_(2)O_(z).Resistance measurements showed that(T1_(1-x)In_(x))Sr_(2)(Nd_(0.75)Ce_(0.25))_(2)Cu_(2)O_(z)(x≤0.8)are superconducting with Tc(onset)=30-40K.

Femtosecond pulse laser-induced self-organized nanostructures on the surface of ZnO crystal

This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti：sapphire laser with a repetition rate of 250kHz. For a linearly polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was promoted. The period of self-organization structures is about 180 nm. The grating orientation is adjusted by the laser polarization direction. A long range Bragglike grating is formed by moving the sample at a speed of 10μm/s. For a circularly polarized laser beam, uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal.

Measurement of conversion efficiency of soft X-ray from 0.35μm laser-irradiated aluminum planar targets

Conversion efficiency of soft X-ray from 0.35μm pulse laser-irradiated aluminium planar target at laser intensities 10^13- 10^15 W/cm^2 on the Xingguang-Ⅱ facility （laser energy 5 - 90 J, focal spot - Φ 200μm full width of half maximun （FWHM） 400 - 800 ps） was measured. A simple model was given to explain soft X-ray conversion efficiency. In this model, because of the heat conduction from the laser-heated spot, the conversion was very small at lower irradiance limit, while at higher limit it was bounded by the energy lost in blow off plasma. Consequently, at the laser intensity around 2×10^14 W/cm^2 , the X-ray conversion efficiency reaches a maximum.

Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3^＋-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm^3＋-doped BaO-TiO2-SiO2 glass by a focused 800hm, 250 kHz and 150fs femtosecond laser irradiation. No apparent blue and red emissions are observed at the beginning, while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm^3＋ are observed near the focal point of the laser beam after irradiation for 25s. Micro-Raman spectra confirm that Ba2 TiSi2O8 crystalline dots and lines are formed after laser irradiation. The mechanism of the phenomenon is discussed.

Salt-induced Electron Transfer Photooxidation of Cholesterol in Nonpolar Solvents

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Diameter-Controlled Growth of Carbon Nanotubes Through Pyrolysis of Acetylene Using Rare Earth Alloy as Catalyst in Hydrogen

High-purity carbon nanotubes(CNTs)were synthesized in hydrogen ambience by CVD method by (using) rare earth alloy MlM_(5-1.35)(CoAlMn)_(1.35) as catalyst, acetylene as carbon source. The influence of hydrogen flow rate on the diameter, shape, purity, graphitization degree and output of carbon nanotubes was systematically studied by scanning selectronic microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD)and Raman technique. The results indicate that the size of MlM alloy particles changed from μm order into nm order during the process of hydrogen reduction. While no introducing hydrogen in the reaction of acetylene and catalyst, CNTs can also be synthesized on the catalyst. The CNTs are short and thick with average diameter of about 97.8 nm, and the wall of CNTs is also thick and rough. With increasing of hydrogen flow rate, the diameter of CNTs first decrease and then increase, while the output, purity, and graphitization degree first increase and then decrease. The optimized conditions are: CNTs reach its narrowest size with diameter of 49.1 nm when hydrogen flow rate is 50 ml·min^(-1). The purity, graphitization degree, and output of CNTs reach highest and largest when hydrogren flow rate is 75 ml·min^(-1). It has the most uniform tube size of 97.38 nm when hydrogen flow rate is 100 (ml·min^(-1).)

STUDY ON THE CONFORMATIONAL PROPERTIES OF RIGID POLYELECTROLYTE SPU IN SOLUTION

The conformation and dimension of SPU polyanion have been studied by viscosity and quasi-elastic light scattering methods. The rigidity of SPU is somewhat similar to CMC and its hydrodynamic radius decreases only slowly with increasing concentration of NaCl.

Polarization Raman spectra of graphene nanoribbons

The on-surface synthesis method allows the fabrication of atomically precise narrow graphene nanoribbons(GNRs),which bears great potential in electronic applications.Here,we synthesize armchair graphene nanoribbons(AGNRs)and chevron-type graphene nanoribbons(CGNRs)array on a vicinal Au(111112)surface using 10,10′-dibromo-9,9′-bianthracene(DBBA)and 6,12-dibromochrysene(DBCh)as precursors,respectively.This process creates spatially wellaligned GNRs,as characterized by scanning tunneling microscopy.AGNRs show strong Raman linear polarizability for application in optical modulation devices.Different from the distinct polarization of AGNRs,only weak polarization exists in CGNRs polarized Raman spectrum,which suggests that the presence of the zigzag boundary in the nanoribbon attenuates the polarization rate as an important factor affecting the polarization.We analyze the Raman activation mode of CGNRs using the peak polarization to expand the application of the polarization Raman spectroscopy in nanoarray analysis.