XPS analysis of two-dimensional j-aggregate of cyanine dye self-assembled on bromide-covered Ag(111)

Abstract

An atomically flat Ag(111) film covered with a halide monolayer allows well‐ordered two‐dimensional (2D) aggregates of cyanine dyes to be easily self‐assembled from a dilute monomeric dye solution. The superior planarity of the sample carrying the self‐assembled monolayer makes the XPS method a powerful tool to illuminate the molecular orientation and arrangement of dye molecules in their 2D network. This is exemplified by analysing the 2D J‐aggregate of a typical cyanine dye, a particularly unique molecular assembly of both fundamental and practical interest. The collective Coulomb interaction involving the cationic dye chromophores and counter‐anions, as reflected upon a marked (∽1 eV) chemical shift in the relevant XPS signals, is likely to play a critical role in determining the 2D network structure characteristic of J‐aggregate. Copyright © 1999 John Wiley & Sons, Ltd.

Controlled Layering of Two-Dimensional J-Aggregate of Anionic Cyanine Dye on Self-Assembled Cysteamine Monolayer on Au(111)

“…Nevertheless, the LB method involves a delicate control over the surface pressure and other preparation conditions, and yet the mechanical monolayer translation from the air/water interface to the substrate surface gives no guarantee for preservation of the structure as initially formed at the air/water interface. Alternatively, we have shown elsewhere − that a similar J-aggregate monolayer but with a much higher level of structural perfection can be very easily self-assembled on an atomically flat Ag(111) precovered with a halide monolayer. This is particularly useful as a simple model of J-aggregate on the AgX surface, and its outstanding structural simplicity gave us the privilege to make a direct STM (scanning tunneling microscopy) observation of the J-aggregate monolayer 17 along with a series of XPS (X-ray photoelectron spectroscopy) analysis. , Yet the thus self-assembled J-aggregate monolayer also has one apparent shortcoming in that its dye chromophore is separated from the metal (Ag) surface only by the atomically thin halide monolayer.…”

“…Alternatively, we have shown elsewhere − that a similar J-aggregate monolayer but with a much higher level of structural perfection can be very easily self-assembled on an atomically flat Ag(111) precovered with a halide monolayer. This is particularly useful as a simple model of J-aggregate on the AgX surface, and its outstanding structural simplicity gave us the privilege to make a direct STM (scanning tunneling microscopy) observation of the J-aggregate monolayer 17 along with a series of XPS (X-ray photoelectron spectroscopy) analysis. , Yet the thus self-assembled J-aggregate monolayer also has one apparent shortcoming in that its dye chromophore is separated from the metal (Ag) surface only by the atomically thin halide monolayer. This poses a severe limitation in application of the photoexcitation energy, which either by energy transfer or electron transfer may dissipate too fast into the metal.…”