الفهرس 
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Abstract
Nanotechnology is an important field of modern research dealing with design, synthesis, and manipulation of particles structure ranging from approximately 1-100 nm. Tremendous growth in this emerging technology has opened novel fundamental and applied frontiers, including the synthesis of nanoscale materials and exploration or utilization of their exotic physicochemical and optoelectronic properties. Nanotechnology is rapidly gaining importance in a number of areas such as health care, cosmetics, food and feed, environmental health, mechanics, optics, biomedical sciences, chemical industries, electronics, space industries, drug-gene delivery, energy science, optoelectronics, catalysis, single electron transistors, light emitters, nonlinear optical devices, and photo-electrochemical applications. Chemical reduction, photochemical reduction, electrochemical reduction, heat evaporation and many other chemical and physical methods are used for NPs synthesis, which are not environmentally friendly and cost effective. This study interested in bio-synthesis of platinum nanoparticles
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(PtNPs) and bimetallic platinum-gold nanoparticles (PtAuNps) and using the synthesized PtNPs and PtAuNPs as a catalyst in a photo-catalytic degradation process.
This study divided into four chapters, these are:
Chapter one: Introduction and literature review: This chapter includes a general introduction on nanoparticles and nanotechnology. The chemical and biological methods especially the methods using plant extract for preparations are reviewed.
Chapter two: This chapter includes the different experimental techniques that have been employed to characterize platinum and bimetallic platinum-gold nanoparticles that have been prepared using some medicinal plants. In this chapter, samples preparation for PtNPs synthesis, PtAuNPs synthesis and photo-catalytic degradation assay were discussed.
Chapter three: This chapter includes four sections, these are:
i. The first section deals with the biosynthesis of PtNPs and PtAuNPs using green tea (Camellia
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sinensis) leaves extract as source of reducing agent (antioxidant) capable of converting Pt4+ to Pt0 and Au3+ to Au0 nanoparticles . This plant extract has been chosen because it contains large amounts of tannins or phenolic substances (5–27%), which easily donate the electrons to reduce free radicals, which interrupt the oxidation chain reaction. Exposing platinum and platinum-gold salts to green tea leaves extract with heating in water bath at 100 0C leads to formation of PtNPs and Pt-AuNPs respectively. The rate of formation for nanoparticles was followed using UV-Vis spectrophotometer and spectro-fluorometer. The important results obtained can be summarized as follows:
A) The change in solution color to black and deep violet in case of PtNPs and PtAuNPs respectively, was a physical parameter that characterized for Pt and PtAu nanoparticles formation. The color variations arose from
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changes in the composition, size, and shape of nanoparticles.
B) In aqueous solution, there is no specific wavelength that could be used to accurately determine their concentration. The peak at 330 nm can be taken as indication for Pt0 formation its UV–vis spectrum and 536 nm for Au0 respectively.
C) The TEM results indicate that 2 nm Pt nanoparticles were produced and the formed platinum- gold nanoparticles were predominantly spherical with some triangular and hexagonal shaped, with diameters ranging from 10 to 50 nm.
D) XRD pattern of the platinum and bimetallic platinum-gold nanoparticles synthesized by the green tea leaves extract exhibit number of Bragg reflections and indexed on the bases of the face centered cubic fcc structure of both PtNPs and PtAuNPs.
E) FTIR measurements were carried out to identify the potential biomolecules in green tea leaves responsible for the reduction,
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capping of and efficient stabilization of the bio-reduced Pt and PtAu nanoparticles. The FTIR spectra of the NPs reveal the presence of different functional groups possibly of caffeine, catechin (flavanol), gallic acid units and phenolic substances that have a strong antioxidant activity.
F) TGA plot of the capped Pt and PtAu nanoparticles in the temperature range of 100°–700°C showed weight loss of 48.40% and 50.07% respectively due to the desorption of bioorganic compounds capped on surface of PtNPs and PtAuNPs respectively. This high value of adsorbed compounds on the surface suggests the high surface area of the nanoparticles.
G) The EDX peaks of both Au and Pt peaks are clearly visible. The EDX spectra of single nanoparticles, however, immediately demonstrated that the metal nanoparticles consist of an alloy.
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ii. The second section deals with synthesis of both PtNPs and PtAuNPs using Mentha leaves extracts following the same green chemistry eco-friendly protocol used in the synthesis of the nanoparticles by the green tea extract. Mentha species are cited as favorable free radical scavengers as well as primary anti-oxidants that may react with free radicals and limit ROS attack on biological and food systems. The high phenolic content (mainly menthol) of the mint leaves hot water extract which have a strong anti-oxidant and capping properties, helped in the reduction of both Pt4+ to Pt0 and Au3+ to Au0 NPs. UV-vis spectroscopy showed, in case of PtNPs formation, that the absence of peaks at 378 and 460 nm indicates the reduction of Pt (IV). For bimetallic PtAuNPs, the maximum absorption of AuNPs appeared at 545 nm indicating the stabilization and saturation in the bio-reduction of Au3+. TEM studies showed the nanoparticles to be of various shapes and sizes. Fourier transform infra-red
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spectroscopy (FTIR) measurements showed that both PtNPs and PtAuNPs have been coated with the extract compounds which indicates for a possible role of biomolecules for capping and efficient stabilization of both platinum and bimetallic platinum-gold nanoparticles. TGA plots of the capped PtNPs and PtAuNPs in the temperature range of 100°–600°C showed weight losses of 45.29% and 40.90% respectively. This indicated the high ability of PtNPs and Pt-AuNPs for adsorption of the bioactive materials in the extract.
iii. The third section deals with the biosynthesis of PtNPs and PTAUNPs using Thymus vulgaris leaves extracts following the same green chemistry eco-friendly protocol used in the previous two sections. Thyme oil (common as Thymus) with a pungent odor and medical benefit has more than 44% of phenols which acts as a strong antioxidant. TEM images of the synthesized nanoparticles showed that the increase in size of formed nanoparticles in case
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of bimetallic PtAuNps compared to PtNPs may be due to core-shell formation where PtNPs formed firstly and be the nucleus around which AuNPs deposit. FTIR bands show that thymol oil present in the thyme leaves extract is mainly responsible for capping and stabilizing the formed NPs.
iv. The fourth section deals with the photocatalytic activity of the Pt and PtAu nanoparticles by photocatalytic degradation of the methylene blue. The degradation rate using different catalysts follow the order: Pt-TiO2 at 500 0C> PtAu-TiO2 at 500 0C> PtAu TiO2 at 100 0C > Pt TiO2 at 100 0C> TiO2 alone at 100 0C > Pt alone at 100 0C > PtAu alone at 100 0C this indicates that Pt/TiO2 is more effective than TiO2 alone for the removal of the organic pollutant such as methylene blue and upon heating the modified TiO2/PtNps or TiO2/PtAuNps; where all the organic molecules coating the nanoparticles are evaporated and removed, the rate of degradation increased.