Gadolinium-doped CoFe 2 O 4 semi-crystalline nanoparticles with designed morphology: The effect of synthesis parameters on microstructure and magnetic characteristics

APT2012 Symposium 2-5 July 2012, Singapore Effect of [Cu]/[Cu+In] molar ratios on the growth and physical properties of CuInS2 nano-particles using nan-vacuum method Lin-Ya, Yeh, Kong-Wei Cheng*,Wen-Chun Pan Department of Chemical & Material Engineering,Chang Gung University,Taoyuan, Taiwan, ROC Chung-Shan Institute of Science and Technology, Taoyaun, Taiwan, ROC *e-mail: kwcheng@mail.cgu.edu.tw Abstract In this study, CuInS2 nano-particles were prepared in an ultrasonic bath using the non-vacuum method. The X-ray diffraction (XRD) patterns of samples revealed that the samples are the tetragonal CuInS2 phase with a highly (112) preferential orientation. With an increase in [Cu]/[Cu+In] molar ratio in precursor solution, the XRD patterns of the samples indicates that the samples are tetragonal CuInS2 phase, except that the diffraction peaks were slightly shifted to higher angles. The [Cu]/[Cu+In] molar ratio of samples increased with an increase in [Cu]/[Cu+In] molar ratio in precursor solution. No apparent sulfur deficits were observed in samples using energy dispersive analysis of X-ray (EDAX). With [Cu]/[Cu+In] molar ratio in samples of greater than 0.50, the samples are p-type semiconductors while with [Cu]/[Cu+In] molar ratio in samples of less than 0.47, the samples are n-type semiconductors. CuInS2 samples with an average diameter of 20 nm were observed using transmission electron microscope (TEM). The direct energy band gaps of samples were in the ranges of 1.33-1.57 eV obtained using UV-vis-NIR spectrophotometer.

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO ₂ Reduction

In this study hydrothermal method was used to synthesize MIL-53(Al) (MIL stands for Materials Institute of Lavoisier). Plackett–Burman (P–B) as an experimental design method was applied to investigate the effect of synthesis and activation conditions on specific surface area, relative crystallinity, and production yield of MIL-53(Al) synthesis. Some parameters such as ligand-to-metal molar ratio, synthesis time, synthesis temperature, calcination temperature, and calcination time were selected as the variables. The Brunauer–Emmett–Teller (BET) technique was used in order to estimate the specific surface area of samples while the relative crystallinity of the samples was estimated by comparing their X-Ray Diffraction (XRD) pattern. The morphology of the samples was investigated by field emission scanning electron microscopy. The yield of final products was determined based on organic ligands. The results revealed the significant effect of synthesis temperature on BET surface area, particle size, yield, and crystallinity. The calcination temperature has significant positive effect on BET and crystallinity. Also, the negative significant effect of molar ratio on yield was concluded from the results. However, negligible effect of synthesis and calcination time on the properties of prepared materials were observed. Furthermore, separation capability of a selected sample for carbon dioxide (CO2) and methane (CH4) was measured. Pure gas adsorption data were successfully fitted to Langmuir, Sips, and Toth models. The selected sample provided high adsorption capacity for both gases. The binary adsorption of gases was also investigated based on extended Langmuir equations and the ideal adsorbed solution theory (IAST) models. Comparing the experimental and models data indicated good agreement between the IAST model and experiments. Finally, high CO2/CH4 selectivity of 7.6 was obtained experimentally for the CO2/CH4 molar ratio of 0.2/0.8.

Influence of synthesis temperature and reaction time on the structural and optical properties of ZnO nanoparticles synthesized by the hydrothermal method was investigated using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray, Fourier transform infra-red spectroscopy, and UV–visible and fluorescence spectroscopy. The XRD pattern and HR-TEM images confirmed the presence of crystalline hexagonal wurtzite ZnO nanoparticles with average crystallite size in the range 30–40 nm. Their energy gap determined by fluorescence was found to depend on the synthesis temperature and reaction time with values in the range 2.90–3.78 eV. Thermal analysis, thermogravimetric and the differential scanning calorimetry were used to study the thermal reactions and weight loss with heat of the prepared ZnO nanoparticles.

In this work, TiO(2) nanoparticles in anatase phase was prepared by sol-gel low temperature method from titanium tetra-isopropoxide (TTIP) as titanium precursor in the presence of acetic acid (AcOH). The effects of synthesis parameters such as AcOH and water ratios, sol formation time, synthesis and calcination temperature on the photocatalytic activity of TiO(2) nanoparticles were evaluated. The resulting nanoparticles were characterized by X-ray diffraction, UV-Vis reflectance spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller techniques. Photocatalytic activity of anatase TiO(2) nanoparticles determined in the removal of C. I. Acid Red 27 (AR27) under UV light irradiation. Results indicate that with increasing AcOH/TTIP molar ratio from 1 to 10, sol formation time from 1 to 3 h and synthesis temperature from 0 to 25°C, increases crystallite size of synthesized nanoparticles. It was found that optimal conditions for low temperature preparation of anatase-type TiO(2) nanoparticles with high photocatalytic activity were as follows: TTIP:AcOH:water molar ratio 1:1:200, sol formation time 1 h, synthesis temperature 0°C and calcination temperature 450°C.

Recently, Prussian blue analogues (PBAs) have been reported to exhibit a low voltage charge/discharge behavior with high capacity (300–545 mAh/g) in lithium-ion secondary batteries (LIBs) [...]

Ti-based metal-organic frameworks (MOFs) are demonstrated as promising photosensitizers for photoelectrochemical (PEC) water splitting. Photocurrents of TiO2 nano wire photoelectrodes can be improved under visible light through sensitization with aminated Ti-based MOFs. As a host, other sensitizers or catalysts such as Au nanoparticles can be incorporated into the MOF layer thus further improving the PEC water splitting efficiency.

ABSTRACTSemiconductor quantum dots are considered very promising candidates for bio-imaging and diagnosis applications because of their tunable optical properties and good optical stability in aqueous phase. Any practical application of these materials will rely on the viability of their simple and direct synthesis in aqueous phase with no need for toxic and unstable organic media. The optical properties of CdSe quantum dots and CuS nanoparticles are desirable in bio-imaging and cell sorting applications because of their tunable photoluminescence at the visible range. The present work addresses the synthesis of CdSe quantum dots and CuS nanoparticles via an optimized, simple and scalable aqueous processing route at low temperatures. The tunability of the optical properties was achieved by a suitable control of the citrate/Cd mole ratio, temperature of synthesis (20-90°C) and reaction time (0-1 hour). In the case of CuS, the strong plasmonic absorption offers the opportunity to investigate this material as a photothermal coupling agent for photothermal therapy. The intensity of the plasmonic absorption was enhanced by selecting an appropriate sulfide precursor (Na2S, Thioglycolic acid), temperature of synthesis (90-120°C) and reaction time. Nanocrystals were characterized by x-ray diffraction, UV-VIS, photoluminescence (PL) spectroscopy techniques and electron microscopy. The effects of the synthesis conditions on the crystal size and the corresponding functional properties of synthesized quantum dots are presented and discussed.

Ti(IV) incorporated layered stacking MWW zeolites with containing similar porous structure of ERB-1 and MCM-22 precursors (Ti-MCM-22 and Ti-ERB-1) and ERB-1 precursor as starting material subsequently further prepared micro-/mesoporous silica MCM-36 by silicates pillars (Ti-MCM-36) through a simple grafting method using different titanium alkoxides, including Ti(OEt)4, Ti(OiPr)4 and Ti(OBu)4 onto the post-treated calcined MWW. The X-ray diffraction patterns and N2 sorption isotherms confirmed the retention of basal MWW layer structure in Ti-MCM-22. The Si/Ti molar ratios analyzed by ICP-MS increased with the size of titanium alkoxides and varied in the order of Ti(OEt)4 < Ti(OiPr)4 < Ti(OBu)4 based on the same amounts of titanium alkoxides used in the grafting solutions. The UV-Vis and X-ray absorption spectra revealed that both tetrahedrally and octahedrally coordinated Ti(IV) species were present on Ti-MCM-22 prepared by grafting. However, the amount of octahedral Ti(IV) decreased with the decrease in Ti content. After acidizing with 2 M HNO3 concentration on Ti-MCM-22 due to the purpose of removed extra-framework TiO2 species, UV-Vis observation presents that 1-butanol has a well-retained Ti-anchored activity rather than ethanol as grafting solvent. Solid state 29Si NMR spectra indicated that most Ti(IV) were incorporated near the T-sites on the open bottom of the supercage, which were easily accessed by grafting agent. When applied in epoxidation of cycloalkenes, Ti-MCM-22 prepared by grafting with Ti(OEt)4 demonstrated better catalytic activities than Ti-YNU-1 or those grafting with Ti(OiPr)4 and Ti(OBu)4. The best catalytic performances were obtained over Ti-MCM-22 with Si/Ti molar ratio of ca. 100 prepared by grafting with Ti(OEt)4. The conversions were very high and epoxide selectivities were close to 100% in cyclohexene and cyclooctane oxidation using t-butylhydrogen peroxide as the oxidant. ERB-1 precursor as initial material follows the step-by-step experimental procedure to derive micro-/mesoporous silica MCM-36. Ti(IV)-incorporated MCM-36 (Ti-MCM-36) was prepared by a simple grafting method using different titanium alkoxides, including Ti(OEt)4, Ti(OiPr)4 and Ti(OBu)4 in various solvents, including ethanol, 1-butanol, and toluene. The X-ray diffraction patterns and N2 sorption isotherms confirmed the retention of the basal MWW layer structure in Ti-MCM-36. The Si/Ti molar ratios analyzed by ICP-MS increased with the size of titanium alkoxides and varied in the order of Ti(OEt)4 < Ti(OiPr)4 < Ti(OBu)4 based on the same amounts of titanium alkoxides used in the grafting solutions, while the solvent had little influence on the Ti loading. UV–vis and XANES spectra showed that titanium species were mainly tetrahedral coordinated Ti(IV) and small amount of titania clusters when grafting in ethanol and 1-butanol, while large bulky titania crystallites were formed in toluene. Ti-MCM-36 prepared by grafting with Ti(OEt)4 in 1-butanol demonstrated better catalytic activities in epoxidation of olefins, including cyclohexene, cyclooctene and dicyclopentadiene (DCPD) than Ti-YNU-1 or those grafted with Ti(OiPr)4 and Ti(OBu)4. In DCPD oxidation using t-butylhydrogen peroxide (TBHP) as the oxidant, about 100% DCPD conversionand 95% diepoxide selectivity could be achieved using TBHP/DCPD molar ratio of 3.5.

2H-MoS ₂ Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

Effect of [Al] and [In] molar ratio in solutions on the growth and microstructure of electrodeposition Cu(In,Al)Se2 films

A kaolinite-tetrabutylphosphonium bromide intercalation compound as an effective intermediate for intercalation of bulky organophosphonium salts

Mechano-thermal reduction of molybdenite (MoS2) in the presence of Sulfur scavenger: New method for production of molybdenum carbide

Different photoluminescent properties of binary and ternary europium chelates doped in PMMA

At present, operating temperature of solid oxide fuel cells (SOFCs) is as high as 800-1000 ° C due to requirement of sufficient oxide ion conductivity of electrolyte material. Under such high temperature operation, there remain problems of reliability, durability and limitation of materials. Development of electrolyte oxide which exhibits enough ionic conductivity at temperatures between 400-600 ºC should be required to solve the problems, resulting in development of so-called intermediate temperature SOFC (IT-SOFC). One of the probable methods to decrease the operation temperature is employing proton conducting oxide as electrolyte instead of oxide ion conducting oxide since lower energy is required for light proton transportation. Among proton conducting oxides, BaCe1−x Y x O3-δ shows the highest proton conductivity. Not only for practical application but also for elucidation of high proton conduction mechanism, information on accurate crystal structure of BaCe1−x Y x O3-δ is essential. So far, it has been reported that crystal structures of BaCe1-x Y x O3-δ are orthorhombic distorted perovskite and monoclinic distorted one for x=0.00-0.10 and x=0.15-0.20, respectively, at room temperature. The crystal structures have mainly been analyzed with Rietveld analyses of powder X-ray diffraction or neutron diffraction patterns. However, space groups employed for Rietveld analyses were not experimentally evidenced ones but assumed to be Pnma (No. 62) and I2/m (No. 12) for orthorhombic and monoclinic phase, respectively, in the most studies reported so far. In this study, we have clarified the space group of BaCe0.80Y0.20O3- δ by convergent beam electron diffraction. In addition, Rietveld analyses of powder X-ray diffraction and neutron diffraction patterns of BaCe0.80Y0.20O3- δ have been examined to elucidate minute crystal structure. BaCe0.80Y0.20O3-δ was prepared with Pechini method, with starting materials of BaCO3, CeO2 and Y2O3. BaCO3 was dissolved with citric acid. CeO2 and Y2O3 were dissolved with dilute HNO3 containing H2O2. After addition of ethylene glycol to mixed solution with stoichiometric cation composition, the solution was heated at 300 °C and burned to resin. The resin was calcined at 700 °C for 24 hour in air, followed by uniaxially pressing into pellets. The pellets were sintered at 1300~1400 °C for 10 hour in air. The obtained phase was revealed to be a single phase of monoclinic distorted perovskite structure with a=6.239 Å, b=8.740 Å, c=6.249 Å and β=91.06 º by X-ray diffraction measurement. Convergent beam electron diffraction (CBED) patterns were obtained at room temperature by using energy filtered TEM (JEOL Co., Ltd.: JEM-2010FEF) with operating voltage of 100 kV. X-ray diffraction pattern was obtained with RINT-2500 (Rigaku Co., Ltd.: CuKα, 50 kV, 250 mA). TOF neutron diffraction measurement was carried out using superHRPD at J-PARC. The Rietveld refinements for X-ray diffraction pattern and neutron diffraction one were carried out using RIETAN-FP [1] and Z-Rietveld [2], respectively. Figure attached shows zero-order Laue zone reflections of CBED pattern of BaCe0.80Y0.20O3-δ from [001] azimuth. The observation of the disc identified as 0k0 with odd k denied I-lattice. Space group of I2/m was also denied from A2-type dynamical extinction indicated by arrows, indicating existence of screw axis or glide plane. Combining various CBED patterns from various azimuths, space group of BaCe0.80Y0.20O3-δ was concluded to be P21/m (No. 11), which was a subgroup of Pnma (No. 62) of BaCeO3 [3]. It can be explained that substitution of Y and/or generation of oxide ion vacancy decreased crystal symmetry of BaCeO3. The both X-ray diffraction pattern and the neutron diffraction pattern could successfully be refined by Rietveld analysis with structure model of both I2/m and P21/m. This indicates that accurate space group cannot be clarified by only Rietveld analysis of powder diffraction patterns. The tilts of octahedrons of perovskite were represented as “a + b - c -“ and “a 0 b - c -“ for P21/m and I2/m, respectively [3]. It can be speculated that tilt angle according to a-axis in P21/m phase is so small that diffraction patterns of BaCe0.80Y0.20O3- δ can be refined by Rietveld analysis with space group of both I2/m and P21/m. [1] F. Izumi and K. Momma, Solid State Phenom., 130 (2007) 15. [2] R. O-Tomiyasu et. al. J. Appl. Cryst., 45 (2012) 299. [3] C. J. Howard and H. T. Stokes, Acta Cryst. B54 (1998) 782. Figure 1