The Stability Study Of Nano-silver Colloids

As an important noble metal nanometer material, nano-silver has been widelyused in catalytic, microelectronics, biology, medicine and other fields due to its hugespecific surface area which is different from macro block. And its stability is one ofthe important indexes affecting its application. But the stability research of nano silveris rare and characterization methods are limited. So it is meaningful to study ofstability of nano silver by a new method.Firstly, we synthesized nano-silver through chemical reduction method. Toevaluate the stability of solutions, Turbiscan optical analyzer has been employed inthis research. We studied the stabilities of nano-silver colloid at different temperature,concentration, PEG2000concentration, alkalinity and ionic strength. Results showedthat the intensity of transmission light of nano silver colloids changed significantlywith the increase of temperature, which indicated the solution was unstable; And it ishelpful to maintain the stability of nano silver colloids at lower concentration; It isbeneficial to maintain the stability of colloids at low concentration of PEG2000, butcolloids became unstable when the concentration of PEG2000was too high; Colloidsstayed stable under the suitable amount of alkaline, but excess NaOH will result indamage of colloid structure and the unstable of solutions; And the addition of NaClcan cause the flocculation of colloids.Then, high concentrations of nano-silver was prepared though chemicalreduction method and redundant reactants were removed through centrifugation andwashing. We dispersed nano-silver particles in different phase by ultrasonic dispersionmethod with different concentration. Its stabilities were monitored by Turbiscanoptical analyzer. Results showed that the nano-silver colloid dispersed in ethyleneglycol phase the most stable system, compared with these dispersed in water andethanol; And nano-silver colloids became unstable with the increase of theconcentration; In water and ethanol co-solvents, the colloid was the most stable whenmass ratio of water and ethanol was7:3; and in water and ethylene glycol co-solvents,the colloid became more stable with the increase of mass fraction of ethylene glycol.