Visible Light Induced Photocatalysis of Cerium Ion Modified Titania Sol and Nanocrystallites

The cerium ion(Ce4+) doped titania sol and nanocrystallites were prepared by chemical coprecipitation-peptization and hydrothermal synthesis methods, respectively. The X-ray diffraction pattern shows that Ce4+-TiO2 xerogel powder has semicrystalline structure and thermal sintering sample has crystalline structure. Ce4+-TiO2 nanocrystallites are composed of the major anatase phase titania (88.82 wt pct) and a small amount of crystalline cerium titanate. AFM micrograph shows that primary particle size of well-dispersed ultrafine sol particles is below 15 nm in diameter. The particle sizes are 30 nm for xerogel sample and 70 nm for nanocrystallites sample, which is different from the estimated values (2.41 nm and 4.53 nm) by XRD Scherrer's formula. The difference is mainly due to aggregation of nanocrystallites. The experimental results exhibit that photocatalysts of Ce4+-TiO2 sol and nanocrystallites have the ability to photodegrade reactive brilliant red dye (X-3B ) under visible light irradiation with the ion-TiO2/VIS/dye system. Moreover, Ce4+ doped titania sol has shown higher efficiency than the nanocrystallites sample in respect of potocatalytic activity. Meanwhile, dye photodegradation mechanisms are proposed to different photocatalytic reaction systems, which are dye photosensitization, ion-dye photosensitization and interband photocatalysis & dye photosensitization with respect to TiO2 nanocrystallites, Ce4+-TiO2 sol and Ce4+-TiO2 nanocrystallites system.

Hydrothermal Synthesis and Characterization of Europium-doped Barium Titanate Nanocrystallites

Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO_3 consisting of spherical particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900 was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu^(3+)was used as a structural probe, and the luminescence properties recorded from Ba TiO_3 :Eu^(3+)and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles.

Cathodoluminescent properties of Tb^(3+)-doped yttria nanocrystallites

The Tb3＋-doped Y2O3 nanopowders were synthesized using the modified Pechini method. The average size of nanocrystaUites was controlled by different sintering temperatures. The structure and morphology of obtained nanopowders were examined using the XRD and SEM analyses. The Cr：Al2O3 was mixed with Th3＋：Y2O3 powders and its normalized emission was used. to measure a relative intensity of Tb3＋：Y2O3. The mixtures were electrophoretically deposited on ITO-glass slides. The cathodoluminescence spectra of obtained layers were recorded and analysed. The discussion over an influence of average grains size on phosphor efficiency was presented.

Synthesis and Characterization of Zirconia Nanocrystallites by Cationic Surfactant and Anionic Surfactant

Study on nanomaterials has attracted great interests in recent years. In this article, zirconia nanocrystallites of different structures have been successfully synthesized via hydrothermal methods with cationic surfactant （CTAB） and anionic surfactant （SDS）, respectively. Differential Scanning Calorimeter （DSC-TG）, X-ray Diffractometer （XRD）, Transmission Electron Microscope （TEM）, Ultraviolet-Visible （UV-vis） and N2 adsorption-desorption analyses are used for their structure characteristics. The results show that the cationic surfactant has a distinctive direction effect on the formation of zirconia nanocrystallites, while the anionic surfactant has a self-assembly synergistic effect on them. The sample synthesized with the cationic surfactant presents good dispersion with the main phase of tetragonal zirconia, and the average nanocrystal size is around 15 nm after calcination at 500 ℃. While the sample synthesized with the anionic surfactant exhibits a worm-like mesoporous structure with pure tetragonal phase after calcination at 500 ℃ and with good thermal stability.

The charge storage characteristics of ZrO_2 nanocrystallite-based charge trap nonvolatile memory

ZrO2 nanocrystallite-based charge trap flash memory capacitors incorporating a （ZrO2）0.6（SiO2）0.4 pseudobinary high-k oxide film as the charge trapping layer were prepared and investigated. The precipitation reaction in the charge trapping layer, forming ZrO2 nanocrystallites during rapid thermal annealing, was investigated by transmission electron microscopy and X-ray diffraction. It was observed that a ZrO2 nanocrystallite-based memory capacitor after post-annealing at 850 ℃ for 60 s exhibits a maximum memory window of about 6.8 V, good endurance and a low charge loss of -25% over a period of 10 years （determined by extrapolating the charge loss curve measured experimentally）, even at 85 ℃. Such 850 ℃-annealed memory capacitors appear to be candidates for future nonvolatile flash memory device applications.

Phonon Confinement Effect in Two-dimensional Nanocrystallites of Monolayer MoS_2 to Probe Phonon Dispersion Trends Away from Brillouin-Zone Center

The fundamental momentum conservation requirement q - 0 for the Raman process is relaxed in the nanocrystal- lites （NCs）, and phonons away from the Brillouin-zone center will be involved in the Raman scattering, which is well-known as the phonon confinement effect in NCs. This usually gives a downshift and asymmetric broadening of the Raman peak in various NCs. Recently, the A1 mode of 1L MoS2 NCs is found to exhibit a blue shift and asymmetric broadening toward the high-frequency side [Chem. Soc. Rev. 44 （2015） 2757 and Phys. Rev. B 91 （2015） 195411]. In this work, we carefully check this issue by studying Raman spectra of lL MoS2 NCs prepared by the ion implantation technique in a wide range of ion-implanted dosage. The same confinement coefficient is used for both E＇ and A＇1 modes in 1L MoS2 NCs since the phonon uncertainty in an NC is mainly determined by its domain size. The asymmetrical broadening near the A＇1 and E＇ modes is attributed to the appearance of defect-activated phonons at the zone edge and the intrinsic asymmetrical broadening of the two modes, where the anisotropy of phonon dispersion curves along Г-K and Г- M is also considered. The photoluminescence spectra confirm the formation of small domain size of 1L MoS2 nanocrystallites in the ion-implanted 1L MoS2. This study provides not only an approach to quickly probe phonon dispersion trends of 2D materials away from Г by the Raman scattering of the corresponding NCs, but also a reference to completely understand the confinement effect of different modes in various nanomaterials.

The effect of Fe doping on structural and magnetic properties of nanocrystallite Co_2Cr_(1-x)Fe_xAl Heusler alloys prepared by mechanical alloying

Mechanical alloying has been used to produce nanocrystallite Co2Crl-xFexAl （x = 0, 0.4, 0.6, 1） Heusler alloys. The formation of the L21 phase of Co2Cr1-xFexAl by the mechanical alloying method was investigated. The effect of Fe doping on the structural and magnetic properties of the samples was also studied. The results were compared with the Slater Pauling prediction. A comparison between these samples and those prepared by the arc-melting method in the literature was made. An increase of the coercivity Hc with the increasing Fe doping level was observed. This phenomenon was explained by the increases of lattice strain and magnetic anisotropy with the increasing Fe content.

Hydrothermal Synthesis of Pb_(1-1.5x)La_xZr_(0.5)Ti_(0.5)O_3 (x = 0.01-0.06) Nanocrystallites

Nanocrystalline Pb1-1.5xLaZr0.5Ti0.5O3 (x = 0.01-0.06, PLZT) powders with particle size from 30 to 150 nm were hydrothermally synthesized from the gets under mild conditions. The reaction conditions such as La content, reaction temperature and time were studied in detail and optimal conditions were established for synthesizing PLZT powders with different La contents. The effects of La content, alkali concentration, reaction temperature and time on the particle size were studied.

Preparation and 1.06μm Fluorescence Decay of Nd3+-Doped Glass Ceramics Containing NaYF4 Nanocrystallites

Considered to be a candidate for large-size bulk materials used in lasers and other fields,Nd3+-doped glass ceramics containing NaYF4 nanocrystallites are prepared.Using x-ray diffraction and transmission electron microscopy,we show that pure cubic NaYF4 is well precipitated in the glass matrix.To obtain the optical property of this material at 1.06 μm,the fluorescence decay of 4F3/2 energy levels is measured and analyzed.It is found that the fluorescence lifetime decreases first and then increases with the increasing dopant concentration due to the existing but finally weakening energy dissipation.As a result,a long radiation lifetime of about 191-444μs is obtained at 1.06μm in the prepared material.It is thus revealed that Nd3+-doped glass ceramic containing NaYF4 nanocrystallites is a potential candidate as a near-infrared laser material.

Predicting Nanocrystallites Development in Cement Pastes

Cement nanocrystallites constitute the binding phase in concrete, a material that has been around for more than two thousand years and remains the most widely used of manufactured materials. Thanks to their size, their disordered nature, their reprecipitation after combination with water, and their rapid evolution when the concrete sets, these nanostructures have only been subjected to careful investigation quite recently. Nanotechnology is now able to control their formation and exploit their evolution (shrinking and swelling) during the setting phase to produce a concrete with a strength and ductility close to those of steels. Furthermore, the analysis of basic nanoscopic reactions occurring during setting, and their modification by polymer additives acting at the interfaces, numerical modelling techniques are potentially able to predict big evolutions and properties of nanocrystallites. Here we discuss the future of these nanocrystallites in new applications.

Influence of concentration and sintering temperature on luminescence properties of Eu^(3+):SnO_2 nanocrystallites

The nanopowders of SnO2 doped with different Eu^3＋ concentrations were synthesized using the modified Pechini method. The Eu^3＋ concentrations were high above solubility limit. The average size of crystallites was controlled by the sintering temperatures. The structure and the morphology of obtained powders were examined using the XRD （X-ray diffraction） and TEM （transmission electron microscopy） analyses. The Eu2Sn2O7 phase separation was observed at relatively high concentration of Eu^3＋ ions. The ZnS：Ag micropowders were mixed with the Eu^3＋：SnO2 powders and their normalized emission was used to measure a relative efficiency of Eu3＋：SnO〉 The photoluminescence spectra of mixed powders were measured in function of Eu^3＋ concentration and average size of nanocrystallites. The reference peak method was used for comparison of intensities of the samples and selection of optimal one. The influence of the average grain size and Eu^3＋ concentration on the phosphor＇s efficiency was discussed. The presented results confirmed the rightness of synthesis of the Eu^3＋：SnO2 in form of nanocrystalites with relatively high Eu^3＋ concentration.

Growth kinetics of MgH2 nanocrystallites prepared by ball milling

MgH2 is one of promising hydrogen storage materials due to its high hydrogen capacity of 7.6 wt%.However,MgH2 nanocrystallites easilygrow up during hydrogen absorption-desorption cycling,leading to deterioration of hydrogen storage properties.To clarify the growth kinetics of MgH2 crystallites,the growth characteristics of MgH2 nanocrystallites are investigated in this work.The growth exponents of MgH2 nanocrystallites in pure MgH2 and MgH2-10 wt% Pr3 Al11 samples are evaluated to be n=5 and n=6,respectively.Meanwhile,their activation energies for crystallite growth are also determined to be109.2 and 144.2 kJ/mol,respectively.The increase of growth exponent and rise of activation energy for crystallite growth in MgH2-10 wt% Pr3 Al11 composite are ascribed to the presence of nano-sized Pr3 Al11phase.

Enhanced electroluminescence from nanocrystallite Si based MOSLED by interfacial Si nanopyramids

The interracial Si nano-pyralnid-enhanced electroluminescence （EL） of an ITO/SiOx/p-Si/Al metal-oxidesemiconductor （MOS） diode with turn-on voltage of 50 V, threshold current of 1.23 mA/cm^2, output power of 16 nW, and lifetime of 10 h is reported.

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A novel architecture of CdS/ZnO nanorods with plasmonic silver(Ag) nanoparticles deposited at the interface of ZnO nanorods and CdS nanocrystallites,was designed as a photoanode for solar hydrogen generation,with photocurrent density achieving 4.7 mA/cm^2 at 1.6 V(vs.RHE),which is 8 and 1.7 times as high as those of pure ZnO and CdS/ZnO nanorod films,respectively.Additionally,with optical absorption onset extended to^660 nm,CdS/Ag/ZnO nanorod film exhibits significantly increased incident photo-tocurrent efficiency(IPCE) in the whole optical absorption region,reaching 23.1% and 9.8% at 400 nm and500 nm,respectively.The PEC enhancement can be attributed to the one-dimensional ZnO nanorod structure maintained for superior charge transfer,and the extended visible-light absorption of CdS nanocrystallites.Moreover,the incorporated plasmonic Ag nanoparticles could further promote the interfacial charge carrier transfer process and enhance the optical absorption ability,due to its excellent plasmon resonance effect.

Multiscale frictional behaviors of sp^(2) nanocrystallited carbon films with different ion irradiation densities

sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil current in an electron cyclotron resonance plasma sputtering system.Their multiscale frictional behaviors were investigated with macro pin‐on‐disk tribo‐tests and micro nanoscratch tests.The results revealed that,at an ion irradiation density of 16 mA/cm^(2),sp^(2) nanocrystallited carbon film exhibits the lowest friction coefficient and good wear resistant properties at both the macroscale and microscale.The film sliding against a Si_(3)N_(4) ball under a contact pressure of 0.57 GPa exhibited a low friction coefficient of 0.09 and a long wear life at the macroscale.Furthermore,the film sliding against a diamond tip under a contact pressure of 4.9 GPa exhibited a stable low friction coefficient of 0.08 with a shallow scratch depth at the microscale.It is suggested that sp^(2) nanocrystallites affect the frictional behaviors in the cases described differently.At the macroscale,the contact interface via the small real contact area and the sp^(2) nanocrystallited transfer layer dominated the frictional behavior,while the sp^(2) nanocrystallited structure in the film with low shear strength and high plastic resistivity,as well as the smooth surface morphology,decided the steady low nanoscratch properties at the microscale.These findings expand multiscale tribological applications of sp^(2) nanocrystallited carbon films.

Improving contrast and sectioning power in confocal imaging by third harmonic generation in SiOx nanocrystallites

We present a new optical microscope in which the light transmitted by a sample-scanned transmission confocal microscope is frequency-tripled by SiOx nanocrystallites in lieu of being transmitted by a confocal pinhole. This imaging technique offers an increased contrast and a high scattered light rejection. It is demonstrated that the contrast close to the Sparrow resolution limit is enhanced and the sectioning power are increased with respect to the linear confocal detection mode. An experimental implementation is presented and compared with the conventional linear confocal mode.

Mechanical and Wear Properties of Nanostructured Surface Layer in Iron Induced by Surface Mechanical Attrition Treatment

A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic moduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.

Hydrothermal synthesis and catalytic performance of bulky titanium silicalite-1 aggregates assembled by bridged organosilane

A facile and effective method to synthesize TS‐1zeolite aggregates has been presented.The crystallization of silanized seeds and nanocrystallites led to large and irregular TS‐1zeolite aggregates ranging from5to40μm in size,based on the special sol‐gel chemistry of bridged organosilane.Epoxidation of1‐hexene and cyclohexene was used as a probe reaction to investigate the catalytic performance of the resulting materials.These TS‐1zeolite aggregates possessed both the conventional nanoparticle properties of TS‐1zeolites and variable surface hydrophilic/hydrophobic features,which enhanced the catalytic properties of hydroperoxides for alkene epoxidation.Moreover,the large aggregates effectively simplified the separation procedure during preparation and catalytic reactions.

Effect of Ni^(+2)-substituted Fe_2TiO_5 on the H_2-reduction and CO_2 Catalytic Decomposition Reactions at 500℃

CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas, high activity nanosized Ni＋2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method. The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 （iron titanate） phase that has a nanocrystallite size of -80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases （-80 nm） NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only. Samples with Ni^＋2=0 shows the lowest reduction extent （20%）; as the extent of Ni＋2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis （TGA） experiments. The oxidation of the H2-reduced Ni＋2 substituted Fe2TiO5 at 500℃ was investigated. As Ni^＋2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction （XRD） and transmission electron microscopy （TEM） of oxidized samples show also the presence of carbon in the sample containing Ni＋2〉0, which appears in the form of nanotubes （25 nm）.