The one step synthesis scheme of copper
nanoparticles initiates with dissolving copper chloride
dihydrate (0.02 mol/L) in deionized water to obtain a
blue solution. L-ascorbic acid (0.1 mol/L) was dropwise
added to the aqueous solution of copper salt with
vigorous stirring at 353 K in oil bath. With the passage of
time, the color of dispersion gradually changed from
white, yellow, orange, brown finally to dark brown with
a number of intermediate stages. The appearance of
yellow color followed by orange color indicated the
formation of fine nanoscale copper particles from
L-ascorbic acid assisted reduction. The resulting
dispersion was centrifuged for 15 min. The supernatant
was placed under ambient conditions for two months.
The studies were performed at different concentrations of
ascorbic acid to investigate the size and shapes of copper
nanoparticles.
2.3 Characterization
UV-Visible spectroscopy from a double beam
spectrophotometer (UV 3000+ LABINDIA, path length 1.0 cm, spectral range from 200 nm to 800 nm) was used
for preliminary estimation of copper nanoparticles
synthesis. FTIR (ALPHA-T, Bruker) provided
information about the binding interactions of L-ascorbic
acid with zero valent copper particles. Morphological
study of the copper nanoparticles was carried out with
SEM (EVO 18, Carl Zeiss) image analysis. These
dispersed nanoparticles were centrifuged and ultrasonicated
for 40 min. 30 μL aliquots were then extracted
and deposited on stub for SEM analysis. Ultrasonicated
dispersed suspension was mounted on carbon coated
copper grid and TEM (FEI Techni G2S2 Twin) images
were recorded to confirm size distribution and shape
homogeneity of synthesized copper nanoparticles.