Optical properties of NiOOH films in formaldehyde solutions
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Films of nickel hydroxide have been obtained by electrodeposition. The analysis of interferograms, optical spectra, XRD analysis and the SEM of the obtained films showed that the deposition of films with ~ 10−5 mol/L PcNi(SO3Na)4 in the Ni(NO3)2 solution helps to control the formation of uniform Ni(OH)2 films with dominance structure of α-Ni(OH)2. The studies of the kinetics of optical changes of NiOOH films in aqueous formaldehyde solutions showed that due to the reaction of NiOOH with formaldehyde, its color changes. It was established that the dependence of the rate of change of light transmittance, ΔT/Δt, on the concentration of formaldehyde is linear in the range of 0.5–20 mmol/L. An analysis of cyclic plots of electrochemical oxidation of Ni(OH)2 to NiOOH and its reduction by the action of formaldehyde showed that the formaldehyde concentration of more than 22 mmol/L can be determined from the absolute value of light transmittance. It was established that an dominance of structure of α-Ni(OH)2 and decrease the thickness of the films to ~ 150 nm contributes by oxidation processes solutions of millimolar concentrations formaldehyde.
KeywordsNiOOH films Chemichromic effect Formaldehyde Kinetics decoloration Light transmittance Electrochromic properties
List of symbols
Optical density (arbitrary unit)
Additive concentration at Ni(OH)2 deposit surface (mol/cm2)
Time h (min)
Rate of change in light transmittance (s−1)
The authors are grateful to Dr. V. Ya Chernii for providing a sodium salt of nickel phthalocyanine PcNi(SO3Na)4 which was used in electrodeposition of Ni(OH)2.
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