GREEN SYNTHESIS OF COPPER OXIDE NANOPARTICLES

Nanoparticles of metal and metallic oxides have be come a very active research area in the field of material chemistry. The surfac e effect is mainly responsible for deviation of the properties of nano-materials from that of the bulk. Nanosize copper oxide was synthesized by hydrolysi s of copper salts in basic medium using biodegradable non-ionic polymer polyethylene glycol (PEG) as surface active agent The X-ray powder diffraction p atterns (XRD) present typical peaks of copper oxides formed. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images determined the shape and the nanosizes of th e particles of about 10-30nm. The results exhibited the role of intermediate nanosize copper hydroxide species on the formation of copper oxide nanoparticles. The influence of synthesis temperatu re, reaction time, calcination temperature, etc. wa s studied.


INTRODUCTION
In recent years, copper oxide has been interested in fundamental research as well as in various applications.It has been widely used as industrial materials such as gas sensor, magnetic storage, solar energy converter, inorganic dyes… In the field of adsorption and catalysis, CuO is a traditional oxidation catalyst for treatment of carbon monoxide in gas phase in place of precious metals.Carbon monoxide, emitted from many industrial processes and transportation activities, is considered as an important class of air pollutions.Catalytic oxidation is an efficient way to convert CO to (PEG) is one of the most extensively studied bio-polymers due to its biocompatibility and its good solubility in both organic solvents and water [10].In this work we focused on the solgel synthesis of CuO nanoparticles via a green pathway using non-ionic low molecular biodegradable polyethyleneglycol (PEG) in water.It was also found that the presence of PEG dispersant and its content have great effects on the shape and size of nanocopper oxides... [11][12][13].The influence of reaction chemical compositions, drying temperature and calcination temperatures on morphology and structure of CuO nanoparticle as well as its intermediate copper hydroxide was studied.

Preparation of CuO nanoparticles
The reaction was processed in a thermostat.
The temperature was adjusted in the range of

RESULTS AND DISCUSSION
In basic medium copper sulphate quickly converts into its hydroxide form and then the copper oxide obtained after drying as the following reaction equations: In other words, the sol-gel route for synthesis    TAÏ P CHÍ PHAÙ T TRIEÅ N KH&CN, TAÄ P 14, SOÁ K3 -2011 Trang 69 ever known as result of their nanosize and great surface/volume ratio.These characteristics permit them to easily access the bacterial membranes along with electronic effects.Furthermore the CuO nanoparticles could combine with the polymers or cover on other surfaces without difficulty.This feature increases their antibacterial effect [1-5].Some methods have been suggested for the preparation of CuO nanoparticles: liquids, liquid and supercritical carbon dioxide, and water.Water is particularly attractive because it is inexpensive and environmentally benign.Poly(ethylene glycol) 5406 Å), the operation voltage and current were 40 kV and 60 mA, respectively, with the rate of 1.0 o C/min.The morphology of nanoparticles was observed on a JEOL-JSM-6500F (FESEM) with Schottky emitter of acceleration potential of 2 kV.The surface morphology was performed on a Transmission Electron Microscope (TEM) (JEM-1400, JEOL, Japan), operating at an acceleration voltage of 200 kV; for these observations, the sample was prepared by dropping the CuO nanoparticles ethanol dispersion on carbon-coated Cu grids.
10 to 30 o C, and distilled water was used as medium in the bath.The solution of CuSO 4 .5H 2 O with a given ratio (x 1 ) with NaOH was added into the round-bottom flask set in the thermostat in 4h.A quantity of PEG 400 surfactant of given ratios (x 2 )with CuSO 4 and the solution of NaOH were respectively added into the flask under violent mixing.The reaction time was maintained in about 40 minutes.The precipitate was then centrifuged, TAÏ P CHÍ PHAÙ T TRIEÅ N KH&CN, TAÄ P 14, SOÁ K3 -2011 Trang 63 washed once with distilled water, then three times with absolute ethanol.The intermediate product was characterised by XRD patterns and TEM image before drying in air at room temperature or various temperatures in oven.The final products were collected for other characterizations as XRD, SEM, TEM images… The influence of chemical composition (x 1 , x 2 ), reaction temperature and drying condition (time, temperature) on CuO particle size was studied.

Fig. 1 .
Fig. 1 .XRD patterns of Cu(OH) 2 (left) and CuO (right) obtained by drying The size and morphology of the products were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).The TEM image (Fig. 2a) reveals that the product consists of spherical particles with a regular morphology and narrow size distribution.Typical TEM image of the asprepared Cu(OH) 2 nanoparticles is presented in Fig. 2, showing that the intermediate product

Fig. 6 .Fig. 7 .
Fig.6.XRD patterns of intermediate products in various condition of treatment of products