Direct Evidence of Clay-Mediated Charge Transfer

Abstract

The charge transfer (CT) from montmorillonite K10 (iron-containing clay) was studied by monitoring the reaction of halides (Cl-, Br-, and I-) with the intercalated photosensitizer, 10-methylacridinium (AcH+). The electrodes, which were fabricated by the AcH+-intercalated clays (denoted clay/AcH+), showed no current responses to bromide and chloride. However, there was a significant current response corresponding to the reduction of iodine and this response was enhanced by light irradiation. These differences in the electrochemical behavior suggested the electron transfer on the clay/AcH+ surface was regulated by the electrochemically active iron species in the clay. The lifetime of AcH+ is ca. 36 ns, whereas for AcH+ (clay), it is as fast as the instrumental response (<10 ns), indicating the clay can efficiently quench the excited acridinium, AcH+*. Moreover, a long-lived species, attributed to I2 -•, was recorded in KI solutions (pH 4) containing either AcH+ or clay/AcH+. In contrast, the transient species, presumed to be Br2 -•, was only observed in the solutions containing free AcH+. Both electrochemical and laser spectroscopic results indicated that the electron transfer between AcH+* and I- is mediated by the iron species in montmorillonite K10.

Can clay emit light? Ru(bpy)32+-modified clay colloids and their application in the detection of glucose

“…Recently we reported several photocatalytic systems based on the iron-containing clay colloids (montmorillonite K10) and photosensitizers, like 10-methylacridinium and cyanoanthracenes. These heterogeneous photochemical systems may induce electron transfer between the adsorbed photosensitizer and the electron donors in solutions [16] and also reveal application potentials in image recording [17] and photooxygenation [18]. During these studies, we also wanted to consider the possibility: can clay colloids be made to emit light?…”

Glucose sensing based on an effective conversion of O2 and H2O2 into superoxide anion radical with clay minerals

“…According to literature reports, most naturally occurring clay minerals contain a variety of metal ions, such as Fe II and Fe III , in their layer-structured frameworks due to the isomorphous substitution reactions with low valence transition-metal cations [54]. The contained iron species are effective mediators for a variety of reactions, such as the oxidation of aromatic compounds [55], the reduction of H 2 O 2 [56], the oxidation of ascorbic acid [57], and the photo-induced electron transfer across the clay|electro-lyte interface [58]. In view of this, we attribute the catalytic effect displayed by Mont.…”

Reviews of Environmental Contamination and Toxicology

“…A similar photoinduced electron transfer to laponite, silica gel, and silica-alumina was reported for pyrene (Liu et al 1994). There is also evidence that ferric ion included in montmorillonite clay as an impurity acts as an electron mediator between excited lO-methylacridinium hexafluorophosphate and iodide as an acceptor (Theng et al 1997). There is also evidence that ferric ion included in montmorillonite clay as an impurity acts as an electron mediator between excited lO-methylacridinium hexafluorophosphate and iodide as an acceptor (Theng et al 1997).…”