Reduction of Cu sup 2+ sub (aq) by CO sub 2 sup minus : First steps and the formation of colloidal copper. [Accelerated electrons]

Journal Article · Thu Oct 31 00:00:00 EST 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100175a104· OSTI ID:6998579

Ershov, B G; Janata, E; Michaelis, M; Henglein, A ^[1]

---

1. Hahn-Meitner-Inst. Berlin GmbH (Germany)

Aqueous solutions of Cu(ClO{sub 4}){sub 2} and HCOONa were pulse-radiolyzed and the changes in optical absorption and conductivity recorded. CO{sub 2}{sup {minus}} reduces Cu{sup 2+} to yield Cu{sup +} (k = 2 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}). Cu{sup +} reacts with CO{sub 2}{sup {minus}} to yield CuCO{sub 2} (absorption at 480 nm (pH = 7.3); k = several 10{sup 10} M{sup {minus}1} s{sup {minus}1}). CuCO{sub 2} exists in two forms depending on the pH of the solution (385 nm at lower pH's). CuCO{sub 2} reacts with Cu{sup 2+} to form 2Cu{sup +} + CO{sub 2} (k = 5 {times} 10{sup 8} M{sup {minus}1} s{sup {minus}1}) and with Cu{sup +} to form Cu{sub 2}{sup +} (350 nm; k {approximately} 10{sup 8} M{sup {minus}1} s{sup {minus}1}). Cu{sub 2}{sup +} and Cu{sup +} are the precursors to the formation of colloidal copper particles. Three distinct time periods during the reduction of Cu{sup 2+} to copper metal can be distinguished: (1) formation and disappearance of the first intermediates, i.e., CuCO{sub 2} and Cu{sub 2}{sup +}, within about 100 {mu}s; (2) formation of nuclei within milliseconds to seconds; and (3) rather sudden formation of larger aggregates within seconds. At the beginning of this sudden formation, the particles absorb in the UV; they are probably oligomers of nonmetallic character. In the later stages of formation, larger metallic particles absorbing in the UV and visible are present.

• OSTI ID: 6998579
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 95:22; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
COPPER
FLOCCULATION
REDUCTION
ABSORPTION SPECTROSCOPY
AQUEOUS SOLUTIONS
CATIONS
ELECTRIC CONDUCTIVITY
FORMATES
PH VALUE
RADIOLYSIS
TIME RESOLUTION
CARBOXYLIC ACID SALTS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
DECOMPOSITION
DISPERSIONS
ELECTRICAL PROPERTIES
ELEMENTS
IONS
METALS
MIXTURES
PHYSICAL PROPERTIES
PRECIPITATION
RADIATION EFFECTS
RESOLUTION
SEPARATION PROCESSES
SOLUTIONS
SPECTROSCOPY
TIMING PROPERTIES
TRANSITION ELEMENTS
400600* - Radiation Chemistry