| fifth General Session |
Nanostructures & Thin FILMS APPLICATIONS
|
Prof. M. Sherif El-Eskandarany
Nanostructures for Photochemical and Thermoelectric Applications
Clemens Burda
Case Western Reserve University
Cleveland, OH 44106, USA
This presentation will summarize recent work from the Burda group. A variety of semiconductor nanoparticles and nanostructures will be discussed, as they were synthesized and optimized for photochemical and optoelectronic applications. Femtosecond measurements of the electron-hole relaxation dynamics are presented, as well as thermoelectric measurements and measurements of defect dynamics. The talk will discuss the effects on chemical structure, energetics, and dynamics as space and time become confined to the nanometer and sub-nanosecond regimes, respectively.
Examples of presented nanoscale systems with optically enhanced properties will include a) erbium-doped Silicon nanoparticles, in which the relaxation dynamics is dependent on the doping sites, b) copper oxide and copper sulfide nanoparticles, which might become potential substitutes for the ubiquitous II-VI semiconductor quantum dots, as well as nitrogen-doped titania nanoparticles, which absorb visible light up to 550 nm compared to the 390 nm of pure TiO2.
A further example of nanoscale enabled properties, is the strong length dependent scaling of the thermoelectric figure of merit. Only for materials below 10 nm an efficient thermoelectric effect can be expected. We have recently achieved nanowires and nanorods in this interesting size regime. Materials composed of such building units will be exciting to investigate for nano-enhanced figures of merit. On such examples we demonstrate that control over the initial dynamics of the charge carrier and phonon dynamics allows to enhance nanostructured materials for applications in photocatalysis, photovoltaics and thermoelectrics. Thin films of this materials are being immobilized on varying substrates and property measurements are being currently carried out. Latest results will be discussed.
refrences:
(1) Samia, A. C. S.; Lou, Y.; Burda, C.; Senter, R. A.; Coffer, J. L. “Effect of the erbium dopant architecture on the femtosecond relaxation dynamics of silicon nanocrystals”. J. of Chem. Phys. (2004), 120(18), 8716-8723.
(2) Yin, M.; Wu, C.-K.; Lou, Y.; Burda, C.; Koberstein, J.T.; Zhu, Y.; O'Brien, S. “Copper Oxide Nanocrystals. “ J. Am. Chem. Soc. (2005), 127(26), 9506-9511.
(3) Lou, Y.; Chen, X.; Burda, C. “The Femtosecond Spectroscopic Investigation of the Carrier Lifetimes in Digenite Quantum Dots: Discrimination of the Electron and Hole Dynamics via Ultrafast Interfacial Electron Transfer” J. Phys. Chem. B (2003), 107(45), 12431-12437.
(5) Liu, Y.; Chen, X.; Li, J.; Burda, C. “Photocatalytic degradation of azo dyes by nitrogen doped TiO2 nanocatalysts.” Chemosphere, (2005), 61(1), 11-18.
(4) Chen, X.; Lou, Y.; Samia, A. C. S.; Burda, C.; Gole, J. L. “Formation of oxynitride as the photocatalytic enhancing site in nitrogen-doped titania nanocatalysts: comparison to a commercial nanopowder” Adv. Func. Mat. (2005), 15(1), 41-49.
(6) Qiu, X.; Burda, C.; Fu, Ruiling; Pu, Lin; Chen, Hongyuan; Zhu, Junjie. “Heterostructured Bi2Se3 Nanowires with Periodic Phase Boundaries” J. Am. Chem. Soc. (2004), 126(50),16276-16277.
(7) Qui, X.; Lou, Y.; Samia, A.C.S.; Anandos, H.; Burgess, J.; Dayal, S.; Burda, C.* “PbTe Nanorods via Sonoelectrochemistry” Angew. Chem. Intl. Ed., (2005), 44(36), 5855 5857.
Photocatalytic activity of zinc oxide thin films
O. A. Fouad *, A. A. Ismail, Z. I. Zaki, R. M. Mohamed
Central Metallurgical Research and Development Institute (CMRDI),
P.O. Box: 87 Helwan 11421, Cairo, Egypt
Abstract
Thin zinc oxide (ZnO) films have been grown on silicon substrates by thermal physical vapor deposition approach. X-ray diffraction (XRD) analyses reveal that the deposited films are polycrystalline ZnO phase. Atomic force microscopy images (AFM) show needle-like shape highly oriented ZnO crystals. Thin film thickness ranges from 10 to 80 nm. X-ray photoelectron spectroscopy (XPS) results declare that the films compose mainly of Zn and O. Nevertheless, Si is not detected in the films and consequently no possibility of any silicide formation as is confirmed by XRD analysis. Photocatalytic decomposition of azo-reactive dye on ZnO films is tested. The results show that the dye decomposition efficiency increases with decreasing pH. Maximum photodecomposition, 99.6% is obtained at pH = 2 with 10 mg/l dye concentration.
Keywords: ZnO thin films, vapor deposition, azo-reactive dye, photocatalytic activity
Mechanically-Induced Solid-State Reaction for Synthesizing of Nanocrystalline Nacl-Type Tic Powders and Subsequent Consolidation
M. Sherif El-Eskandarany, Prof. Dr. Eng. a, b
a)Mining, Metallurgy and Petroleum Engineering Department, Faculty of Engineering, Al Azhar University, Nasr City, 11371 Cairo, Egypt
b)Institute of New Materials and Advanced Technologies, Mubarak City for Scientific Research and Technology Applications, Alexandria,Egypt.
Abstract
Carbides, especially those of the transition-metal carbides of IV and V groups in the periodic table possess unusual properties that make them desirable and useful engineering materials for many industrial applications. The cubic form of TiC (NaCl-structure) with its extremely high melting point (3373 K) is a refractory material with certain of the characteristic properties of metals (luster, metallic conductivity, etc.) and, in addition, extraordinary hardness and toughness, excellent resistance to wear and abrasion and infusibility. TiC has received much attention due to its powerful usage as a hard coating to protect the surface of cutting tools from wear and erosion, extending the tool life.
In the present study, room-temperature ball milling technique was employed for synthesizing nanocrystalline of Ti44C56 powders by milling the reactant starting powders of Ti and C under an argon gas atmosphere. The progress of the mechanically-induced solid state reaction has been monitored by means of X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy and/or high resolution transmission electron microscopy after several stages of the milling times.
