Dielectric behavior of adsorbed water. 4. Measurement at low temperatures on zinc oxide

Abstract

This suggests the existence of the sites which strongly promote the surface conduction of ZnO on physisorption of small amounts of H20. Though it is difficult to know what kinds of sites are effective for such an enhancement of the surface conduction, it is reasonable to infer that the conduction will be accelerated when the terminal points of hydrogen-bonded hydroxyl chains are connected with each other through the bridging H20 molecules.Acknowledgment. The present work was partly supported by a Grant-in-Aid for Scientific Research, No. 57470007, from the Ministry of Education, Science, and Culture of the Japanese Government.

Characterization of the State of Two-Dimensionally Condensed Water on Hydroxylated Chromium(III) Oxide Surface through FT-IR, Quasielastic Neutron Scattering, and Dielectric Relaxation Measurements

“…The observed relaxation at about 300 Hz and at 298 K for the present system may be attributable to the dipolar relaxation of the adsorbed water. [36][37][38] Such a shoulder has not been observed, of course, at around 298 K in the SrF 2and Y 2 O 3 -H 2 O systems. Comparing the present result with that for the bulk systems, 39,40 i.e., the dipolar relaxation frequencies for ice and liquid water of 2.5 kHz at 273 K and 18 GHz at 293 K, respectively, we can say that the adsorbed water on Cr 2 O 3 adopts the restricted motion of ice by mutual hydrogen bonding among the adsorbed water molecules.…”

“…Here, the relaxation times, τ N , determined in these temperature regions by quasielastic neutron scattering of the water molecules on Cr 2 O 3 are situated just above that of the liquid water. It is quite interesting to compare this with τ N values for the adsorbed water molecules on ZnO in which dynamical properties determined by dielectric measurements 36 lie on the extended line of neutron scattering. 51 In addition, correlation times for water molecules adsorbed on ZnO are smaller than those on Cr 2 O 3 .…”

“…The temperature dependence of the relaxation times, τ D and τ N , for the monolayer water on the Cr 2 O 3 surface is depicted in Figure 13. In this figure, τ D and τ N values for bulk water-ice and water-amorphous ice systems 39,42,[48][49][50] and also ZnO-H 2 O system assessed by dielectric 36 and quasielastic neutron scattering 51 measurements, respectively, are indicated. The change of the dynamic properties of water from liquid to amorphous ice is continuous.…”

Electrochemical and spectroelectrochemical characterization of lipid organization in an electric field

“…This addition was used to describe the exchange of water molecules at the interface. Fitting the data to this circuit yielded a relaxation time of 10 À3 -10 À4 s. Typically for water molecules in ice, the water relaxation is 10 À5 s while many reports of much longer relaxation times (10 À2 s) were measured for adsorbed water on glass or clay type materials [118][119][120][121][122][123][124][125]. This suggests that the Hg interface with desorbed DOPC present in a region close but not on the electrode surface must act to create an environment of strongly constrained water, such that the relaxation is very slow.…”

On the impedance of a lipid-modified Hg|electrolyte interface

“…The relaxation of water adsorbed or near surfaces has been studied by dielectric spectroscopy for glasses, minerals and a variety of oxides [39][40][41][42][43][44][45]. In a number of reports, the relaxation of adsorbed water, even up to a few monolayers, was characterized by relaxation times that varied from 100 Hz up to 10 kHz.…”