الفهرس 
What is nanotechnology?Only 14 pages are availabe for public view
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Abstract
Summary
Gold nanoparticles show brilliant colors due to the surface plasmon resonance absorption. The examination of the surface plasmon resonance absorption is part of a large ongoing research field to investigate properties on the nanometer scale. The color of metal nanoparticles is found to depend on the shape and size of the nanoparticle and dielectric constant of the surrounding medium, leading to many studies on their synthesis and applications. Chemical reduction, photochemical reduction, electrochemical reduction, heat evaporation etc. chemical and physical methods are used for NPs synthesis, which are not environmentally friendly. This study interested in bio-synthesis of gold nanoparticles, AuNPs and using the synthesized nanogold as antimicrobial agent.
This study is divided into four chapters
Chapter I: 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 II: This chapter includes the different experimental techniques that have been employed to charctarize gold
nanoparticles that prepared using some medicinal plants. In this chapter, samples prepration for antimicrobial assay was discussed.
Chapter III: This chapter includes the biosynthesis of nanogold using Salvia Officinalis leaf extract as source of reducing agent (antioxidant) capable of converting Au3+ to Au nanoparticles. This plant extract has been chosen because of its value in the medicinal applications. Unlike chemical protocols, which demands expensive instruments and results in release of inimical chemicals, biological method is more facile, eco-friendly and results in more monodispersed nanoparticles. Gold salt when exposed to aqueous extracts of plant have resulted in formation of metal nanoparticles. The rate of formation for nanoparticles was followed using Uv-Vis spectrophotometer. The data showed that size of the nanoparticles could be manipulated by controlling parameters such as pH, temperature, substrate concentration, metal salt concentration and exposure time to the extract. The important results obtained can be summarized as follows:
a) Addition of different concentration of the sage leaf extract (from 0.02% to 0.32%) to the Au3+ solution (1.4x10-4M) leads to change in the color of the solution from yellow to violet, pink to dark pink and green color is characteristic for the
surface plasmon resonance (SPR) of different size of gold nanoparticles and prove the formation of gold nanoparticles.
b) Upon increasing the sage leaf extract (0.02-0.06%), the absorption spectra exhibit a gradual increase of the absorbance accompanied with a shift in the transverse, longitudinal SPR from 550, 1040 to 530,680 nm respectively, indicating a decrease in the particle size by increasing extract concentration. This result is supported by TEM measurements. The formed gold nanoparticles at low extract concentration (0.04%) were predominantly nanotriangle and nanohexagons in shape with diameters reach to 500 nm. When higher extract concentrations is used (0.06%), the AuNPs decrease in size reaching to about 20 nm and the predominant nearly spherical gold nanoparticles are formed.
c) The Uv-vis spectra of the AuCl4- solution after the addition of (0.06%) extract as a function of time showed no change in the absorption peak at about 540, 780 nm after 45 min indicating that this biosynthesis method is fast.
d) XRD pattern of the gold nanoparticles synthesized by the sage leaf extract exhibit number of Bragg reflections were present and indexed on the bases of the face centered cubic fcc structure of gold nanoparticles.
e) A pH of the extract solution has an important effect on the size and shape of the nanoparticles. The absorbance increased with increasing pH to 7 with blue shift whereas in the basic medium the absorbance decreased with increasing pH with blue shift. Increasing alkalinity of the surrounding media induced change in electron density on the surface so it was affected on surface plasmon band and band intensity decreased. This result was confirmed by TEM images. In acidic medium, the anisotropic and spherical AuNPs varied in size between large size reach to 392 nm and small size reach to 20 nm. In basic medium, only gold nanosphere presented in small size and there was no marked variation in size.
f) Absorbance spectra of AuNPs were recorded at different temperature. The higher temperature might increase the kinetic mobility of the nanoparticles and consequently decrease the possibility of aggregation. Therefore, various shaped AuNPs were expected to form at room temperature and at 40°C. While most of AuNPs tended to be spherical due to lesser secondary reduction at higher temperatures.
g) FTIR measurements were carried out to identify the potential biomolecules in sage leaf responsible for the reduction, capping of and efficient stabilization of the bio-reduced gold nanoparticles. The FTIR spectra of the AuNPs reveal the presence of different functional groups possibly of rosmarinic
acid, carnosic acid and essential oils as α-thujone, β-thujone and camphor.
h) TGA plot of the capped gold nanoparticles in the temperature range of 100°–550°C showed weight loss of 46.55% due to the desorption of bioorganic compounds capped AuNPs. This high value of adsorbed compounds on the surface suggests the high surface area of the nanoparticles.
i) This method for AuNP synthesis does not use any toxic reagent and thus has a great potential for the use in biomedical applications as antimicrobial agent. It was found that this synthesized gold nanoparticles improve the efficiency of the antimicrobial activity of sage leaf extract towards Gram Positive bacteria (Bacillus subtillus and Staphylococcus aureus), Gram negative bacteria (E.Coli and Pseudomonas Aeruginosa), Yeast (Candida albicans) and Fungi (Aspergillus niger).
Chapter IV: This chapter deals with the biosynthesis of nanogold using Foeniculum vulgare (fennel ) seeds extracts following the same green chemistry eco-friendly protocol used in the synthesis of the AuNPs by the sage extract. The high phenolic content of the hot water extract of the fennel seeds having strong anti-oxidant properties helped in the reduction of
gold cations to Au NPs. The phytochemicals present in the seeds extract served as effective reducing and capping agent.
TEM studies showed the particles to be of various shapes and sizes. The XRD patterns showed a (1 1 1) preferential orientation of the gold nanoparticles. Fourier transform infra-red spectroscopy (FTIR) measurements showed the GNPs having a coating of the extract compounds indicating a possible role of biomolecules responsible for capping and efficient stabilization of the gold nanoparticles. The influence of various reaction parameters such as extract concentration, pH and temperature of extract to the morphology and size of biosynthesized AuNps were also investigated. The results indicated that at higher extract concentration and high pH, spherical AuNPs could be obtained. The gold nanoparticles synthesized through using fennel seed extract active towards Gram Positive bacteria (Bacillus subtillus and Staphylococcus aureus), Gram negative bacteria (E.Coli and Pseudomonas Aeruginosa), Yeast (Candida albicans).