UV-Vis reflection spectroscopy under variable angle incidence at the air–liquid interface

Abstract

The UV-Vis reflection spectroscopy (UV-Vis-RS) in situ at the air-liquid interface provides information about tilt and aggregation of chromophores in Langmuir monolayers. This information is particularly important given in most cases the chromophore is located at the polar region of the Langmuir monolayer. This region of the Langmuir monolayers has been hardly accessible by other experimental techniques. In spite of its enormous potential, the application of UV-Vis-RS has been limited mainly to reflection measurements under light normal incidence or at lower incidence angles than the Brewster angle. Remarkably, this technique is quite sensitive to the tilt of the chromophores at values of incidence angles close to or larger than the Brewster angle. Therefore, a novel method to obtain the order parameter of the chromophores at the air-liquid interface by using s- and p-polarized radiation at different incidence angles is proposed. This method allowed for the first time the experimental observation of the two components with different polarization properties of a single UV-Vis band at the air-liquid interface. The method of UV-Vis spectroscopy under variable angle incidence is presented as a new tool for obtaining rich detailed information on Langmuir monolayers.

Spectroscopy of Retinoic Acid at the Air–Water Interface

“…The literature on UV–Vis-RAS spectroscopy is sparse, and the UV–Vis-RAS instrument is new to our laboratory; however, there are a handful of studies that cover the theory and application of the technique to different organic molecules, though none involve studying ATRA. − The theory of UV–Vis-RAS is principally the same as the theory of IR-RAS, and we refer to the studies cited here and cited in the IR-RAS section for details about the theory of RAS.…”

2D self-assembly ofo-OPE foldamers for chiroptical barcoding

“…2C). 53 Computer simulations under in vacuo conditions predicted five UV-vis bands at 356.9, 317.1, 311.3, 293.5 and 284.1 nm (Fig. S4, ESI †).…”

Langmuir–Blodgett Films of Diketopyrrolopyrroles with Tunable Amphiphilicity

“…While the UV−vis spectra of the LB films of A and B are virtually independent of the LB deposition pressure II LB , the monomer absorption peak of C can be slightly suppressed upon increasing the LB deposition pressures (Figure 4), typically causing higher supramolecular order. 36,39,45,52 The independence of Π LB is attributed to the above-mentioned πaggregation-induced, two-dimensional crystallization of A and B at the air−water interface. This π-aggregation was less dominant in the case of C, thus enabling smaller molecular inclination angles with respect to the air−water interface and explaining the weak dependence of the spectra of C on Π LB .…”