Determination of bulk and surface transport properties by photocurrent spectral measurements

2000 ◽  
Vol 71 (3) ◽  
pp. 305-310 ◽  
Author(s):  
A. Castaldini ◽  
D. Cavalcoli ◽  
A. Cavallini
Keyword(s):  
Transport Properties ◽  
Spectral Measurements ◽  
Surface Transport

scholarly journals The Importance of Motions that Accompany Those Occurring Along the Reaction Coordinate

2015 ◽  
Vol 68 (8) ◽  
pp. 1202 ◽  
Author(s):  
Jeffrey R. Reimers
Keyword(s):  
Reaction Coordinate ◽  
Spectral Measurements ◽  
Visible Absorption ◽  
Photochemical Process ◽  
New Approach ◽  
Energy Devices ◽  
Adiabatic Theory ◽  
Core Theory ◽  
Basic Ideas

The reaction coordinate is a well known quantity used to define the motions critical to chemical reactions, but many other motions always accompany it. These other motions are typically ignored but this is not always possible. Sometimes it is not even clear as to which motions comprise the reaction coordinate: spectral measurements that one may assume are dominated by the reaction coordinate could instead be dominated by the accompanying modes. Examples of different scenarios are considered. The assignment of the visible absorption spectrum of chlorophyll-a was debated for 50 years, with profound consequences for the understanding of how light energy is transported and harvested in natural and artificial solar-energy devices. We recently introduced a new, comprehensive, assignment, the centrepiece of which was determination of the reaction coordinate for an unrecognized photochemical process. The notion that spectroscopy and reactivity are so closely connected comes directly from Hush’s adiabatic theory of electron-transfer reactions. Its basic ideas are reviewed, similarities to traditional chemical theories drawn, key analytical results described, and the importance of the accompanying modes stressed. Also highlighted are recent advances that allow this theory to be applied to general transformations including isomerization processes, hybridization, aromaticity, hydrogen bonding, and understanding why the properties of first-row molecules such as NH3 (bond angle 108°) are so different to those of PH3–BiH3 (bond angles 90–93°). Historically, the question of what is the reaction coordinate and what is just an accompanying motion has not commonly been at the forefront of attention. In our new approach in which all chemical processes are described using the same core theory, this question becomes thrust forward as always being the most important qualitative feature to determine.

scholarly journals FIELD DETERMINATION OF SOIL HYDRAULIC AND CHEMICAL TRANSPORT PROPERTIES 1

Soil Science ◽  
2002 ◽  
Vol 167 (6) ◽  
pp. 353-368 ◽  
Author(s):  
Salem A. Al-Jabri ◽  
Robert Horton ◽  
Dan B. Jaynes ◽  
Anju Gaur
Keyword(s):  
Transport Properties ◽  
Chemical Transport ◽  
Soil Hydraulic

scholarly journals Ionic Transport Properties of P2O5-SiO2 Glassy Protonic Composites Doped with Polymer and Inorganic Titanium-based Fillers

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3004
Author(s):  
Maciej Siekierski ◽  
Maja Mroczkowska-Szerszeń ◽  
Rafał Letmanowski ◽  
Dariusz Zabost ◽  
Michał Piszcz ◽  
...  
Keyword(s):  
Transport Properties ◽  
Continuous Wave ◽  
Electrochemical Impedance ◽  
Pore Space ◽  
Poly Vinyl Alcohol ◽  
Proton Mobility ◽  
Polymeric Additives ◽  
Wave Technique ◽  
Poly Ethylene

This paper is focused on the determination of the physicochemical properties of a composite inorganic–organic modified membrane. The electrical conductivity of a family of glassy protonic electrolytes defined by the general formula (P2O5)x(SiO2)y, where x/y is 3/7 are studied by Alternating Current electrochemical impedance spectroscopy (AC EIS) method. The reference glass was doped with polymeric additives—poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA), and additionally with a titanium-oxide-based filler. Special attention was paid to determination of the transport properties of the materials thus modified in relation to the charge transfer phenomena occurring within them. The electrical conductivities of the ‘dry’ material ranged from 10−4 to 10−9 S/cm, whereas for ‘wet’ samples the values were ~10−3 S/cm. The additives also modified the pore space of the samples. The pore distribution and specific surface of the modified glassy systems exhibited variation with changes in electrolyte chemical composition. The mechanical properties of the samples were also examined. The Young’s modulus and Poisson’s ratio were determined by the continuous wave technique (CWT). Based on analysis of the dispersion of the dielectric losses, it was found that the composite samples exhibit mixed-type proton mobility with contributions related to both the bulk of the material and the surface of the pore space.

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