The First International Palestinian Conference on Nanotechnology for Advanced Material and Devices

In order to solve water contamination problems several procedures are commonly used. Each procedure has its shortcomings, (such as DBPs production and cost. Photo- degradation of microorganisms using photo-catalysts (such as ZnO) could be a good alternative. Photodegradation of microorganisms has been examined in water disinfection. TiO2 and ZnO photocatalysts have been examined for inactivation of Escherichia coli and some other types of bacteria by photodegradation. ZnO has a wide band gap (3.2 ev), with limited photo-catalytic applications to shorter wavelengths, UV. Because only about 4% of the solar spectrum falls in the UV region, ZnO semiconductor is sensitized by to function in the visible solar light. In this work, ZnO semiconductor particles were sensitized with safe a low cost sensitizer, anthocyanin. The ZnO/anthocyanin was used to disinfect water from bacteria by photodegradation, using solar simulator light. Nano sized ZnO particles were investigated here.
Key Words: photo-degradation, ZnO, anthocyanin, bacteria.

Nano-sized CdS films were deposited onto FTO/glass substrates by different techniques, namely: electrochemical (EC), chemical bath (CB) and electrochemical followed by chemical bath (EC/CB) deposition techniques. The latter technique is examined here for the first time. Scanning electron microscopy (SEM), X-Ray diffraction (XRD), photoluminescence spectra (PL) and electronic absorption spectra were studied for different films. Photo-electrochemical (PEC) characteristics of different films, such as photo (J-V) plots, dark (J-V) plots, conversion efficiency and stability, were all investigated. Films prepared by different methods showed different SEM images. Electronic absorption spectra for different films were not much different except in PL intensity values. PEC characteristics for different films showed different behaviors. The EC/CBD films showed higher light-to-electricity conversion efficiency than EC films, but lower efficiency than CBD counterparts. Moreover, the EC/CBD films showed higher values of JSC with time, than either EC or CBD counterparts, which give an idea about the advantage of the new described films. The deposited films were modified by annealing at 250oC under N2. Cooling of pre- heated films to room temperature was performed by a gradual slow process. The effect of annealing & slow cooling on film characteristics, such as XRD, SEM, PL, electronic absorption spectra were all measured for different films. Photo-electrochemical characteristics of different films, such as: open-circuit voltage (Voc), current density (Jsc), photo (J-V) plots, efficiency and stability, were studied. Films treated by annealing & slow cooling showed higher conversion efficiency than their un-treated counterparts. SEM images showed that annealing increased the grain size of CdS nano particle in cases of CBD, EC and EC/CBD. XRD measurements showed that annealing lowered the crystallite size for EC-CdS films, whereas annealing enhanced the crystallite size for both CBD-CdS and EC/CBD-CdS films. Photoluminescence spectra were not af- fected by annealing except in PL intensity values. In each prepared CdS film, annealing enhanced PEC characteristics, by increasing conversion efficiency and stability. On the other hand, the annealed EC/CBD showed higher conversion efficiency and stability than either the annealed EC or CBD films. On the other hand, the higher conversion efficiency of both annealed CBD-CdS and EC/CBD-CdS films than non-annealed counterparts coincided with SEM topography, XRD spectra and PL intensity results. XRD patterns showed enhancement in crystal- lite size for both annealed CBD-CdS and EC/CBD-CdS films. SEM images showed homogenized layers with more ordered and uniformly packed coagulates for annealed films. In addition, PL spectra for annealed films exhibited higher emission values than non-annealed films. This is because annealing enhances the particle characteristics, giving more uniform and compact surface and consequently higher PL intensity. The results indicate that the new CdS nano-films, prepared by EC/CBD technique, are advantageous over other earlier known types.

In recent years, polycrystalline CdS thin films have received intensive attention due their major role in the photovoltaic technology and optoelectronic devices. They have been used as partner of several types of thin film solar cells, such as, Cu2S, CuInSe2, and CdTe. Specifically, CdTe/CdS heterojunction solar cells with efficiency of about 16% have been reported. CdS thin films can be prepared by several methods, such as, electrodeposition, vacuum evaporation, screen printing, photochemical deposition, CBD, spray pyrolysis, and sputtering. Among all these, chemical bath deposition and electrodeposition techniques are con- venient low-cost processes and useful for large area industrial application. FTO/CdS nano-films prepared by electrochemical (EC) and chemical bath (CBD), separately and combined together have been described by Sahar Khudruj in this lab. The target was to produce a new type of CdS solar cells with high efficiency and high stability. In this work, a new strategy has been developed to modify the resulting films using annealing, cooling rate control and then coverage with electro-active materials imbedded inside polymer matrices. CdS film annealing enhanced the solar cell effi ciency, while the polymer matrix coating enhanced its stability Characterization of the prepared thin films was achieved by UV-visible spectrophotometry, photoluminescence, AFM, SEM and XRD.

Researchers are active in finding ways to combine advantages of both homogeneous and heterogeneous catalysts together, by supporting the homogeneous catalysts onto insoluble supports. Such a technique would give a catalyst system that is highly active (like homogeneous systems) and easy to recover (like heterogeneous systems). This work describes how homogeneous catalysts, such as metalloporphyrins, has been interclated into nano-and micro-scale clays particles to produce a new type of supported catalyst system. We examined the two techniques, metalloporphyrin intercalation between layers and metalloporphyrin encapsulation inside spongy structure of treated nano-clay particles. The supported catalyst was then used in hydrosilylation reactions of terminal olefins. Such reactions are important in glass and sensor industries. Details of our catalyst efficiency results will be presented together with catalyst characterization results. Reaction kinetics and catalyst stability will also be presented.
Key Words: Clay; metalloporphyrin; supported catalysts; nano-and micro-sized particles.

Widely spread of chemically industry producing many types of environmentally pollutants ( e.g dyes, herbicides, pesticides, insecticides, drugs, and others), most of these pollutants reaches our drinking water resources, different strategies have been followed to purify contaminated water, one of the low-cost technology is using semiconductors as catalyst for photodegradation of water organic contaminants, TiO2 is widely studies for water treatment, however, the wide band gab TiO2 limits its use in the UV range, which is less than 4% of our reaching-in solar spectrum. Therefore, sensitization of TiO2 has been studied in order to activate the photodegradation processes by the visible light. our previous work was used CdS (~2.3 eV) to sensitized TiO2, the prepared catalyst TiO2/CdS shows catalytic efficiency in visible light toward photodegradation of organic water contaminants (Methyl Orange & Phenazopyridine), during the photodegradation process the CdS observed decom- position producing Cd+2 ions in the treated water. A save, economic, nontoxic natural dye (Anthocyanin) is being used to sensitized TiO2 nanoparticles, the produced catalyst TiO2/Anth and AC/TiO2/Anth were tested for photodegradation of both Methyl Orange and Phenazopyridine under visible light, the prepared catalysts show an observable efficiency towered photodegradation water organic contaminants. The efficient degradation was observed in photodegradation Methyl Orange using AC/TiO2/Anth under acidic condition. Complete mineralization of contaminants was confirmed by the potential increasing of menial ions like NO-3, SO4-2 and S2O3-2 .Results of photodegradation study, Kinetics, effect of temperature, and effect of pH will be represented.