Z.F. Liu

A novel photoelectrochemical hybrid one-way process observed in the azobenzene system

Abstract The photoelectrochemical behaviour of an azobenzene derivative Langmuir-Blodgett monolayer film has been studied on a transparent SnO2 glass electrode. The trans and cis isomers of the azobenzene derivative were found to have significantly different electrochemical reduction potentials. The reduction product hydrazobenzene derivative was oxidized exclusively to the energetically more stable trans isomer. On the basis of these experimental observations, a novel hybrid “one-way” process is obtained. This hybrid process suggests a number of unique applications in “photoelectrochemical memories” and “photon counters”, etc.

Difference between the electrochemical reductivities of trans and cis isomers of an azo compound in the assembled monolayer film

Abstract The difference between the electrochemical reductivities of trans and cis isomers of an amphiphilic azo compound in the assembled monolayer film has been evaluated quantitatively. The reduction kinetics of two isomers were found to be distinctly different, with the trans isomer being more irreversible than the cis isomer. Both the redox potentials and the reductivity difference of the two isomers were pH dependent, and the dependences in all cases changed drastically when the pH value exceeded ca. 7.0. The observed pH effects can be explained by two different protonation mechanisms involved in the electrode reaction.

New applications of electrochemical techniques

Abstract Two novel applications of electrochemical techniques are discussed based on the photochemical/elctrochemical hybridized reaction of azobenzene species. The first is photoelectrochemical information storage. This new recording technique has advantages of ultrahigh storage density (up to 1012 bits cm−2), non-destructive optical readout and rewritability. The second is electrochemical actinometry, in which the trans—cis photoisomerization of 4-octyl-4′-(5-carboxy-pentamethylene-oxy)-azobenzene (ABD) in an assembled monolayer film is used to detect incident light, and the quantification of the cis-ABD thus produced is performed through its selective electrochemical reduction, leading to an instantaneous evaluation of the irradiation intensity.

Electrochemical counting of photon number using the assembled monolayer film of azo compound

Abstract A chemical actinometer using an assembled monolayer film of amphiphilic azo compound is proposed. It is based on the distinct difference in electrochemical reduction potential of trans - and cis -azo isomers. This novel actinometry does not require any sophisticated mathematical treatment, since the light intensity is directly obtained from its linear relationship to the current of faradaic charge in the electrochemical reduction process. This enables simple and nearly instantaneous counting of photon number in photochemical and photoelectrochemical experiments.

Photoelectrochemical memory system using azo compound LB film

A photoelectrochemical memory system is created by combining the photochemical trans‐cis isomerization and the electrochemical reduction‐oxidation of azo compounds in LB film. This novel system has the advantages of storge density up to 1012bits/cm2, non‐destructive readout, multiple memory function, rewritability and room‐temperature working condition.

INFORMATION STORAGE USING PHOTOELECTROCHEMICAL HYBRID SYSTEMS

Photoelectrochemical behavior of an azobenzene derivative monolayer film has been investigated on a transparent SnO 2 glass electrode. A novel hybrid one-way phenomenon was observed due to the following two experimental results: the first is that the cis form of the azobenzene derivative was reduced to a hydrazobenzene species at substantially more anodic potential than the trans form; the second is that the hydrazobenzene derivative subsequently produced was exclusively oxidized to the energetically stable trans form. On the basis of this hybrid effect, a new type of photon-mode storage technique has been developed, which leads to a photoelectrochemical memory device with an ultra-high storage density and multiple functions being created.