Spectroscopic characterizations of the mixed Langmuir-Blodgett (LB) films of 2,2'-biquinoline molecules: evidence of dimer formation

TL;DR

This study investigates the spectroscopic properties and molecular organization of mixed Langmuir-Blodgett films of 2,2'-biquinoline, revealing evidence of dimer formation and microcrystalline aggregates through various spectroscopic and microscopic techniques.

Contribution

It provides new insights into the molecular aggregation and dimer formation in mixed LB films of 2,2'-biquinoline with different matrices, using comprehensive spectroscopic and microscopic analysis.

Findings

Complete immiscibility of BQ with PMMA and SA matrices.

Formation of microcrystalline aggregates of BQ molecules.

Evidence of dimer or higher order n-mers at higher surface pressures.

Abstract

This communication reports the -A isotherms and spectroscopic characterizations of mixed Langmuir and Langmuir-Blodgett (LB) films of nonamphiphilic 2, -biquinoline (BQ) molecules, mixed with polymethyl methacrylate (PMMA) and stearic acid (SA). The pi-A isotherms and molefraction versus area per molecule studies indicate complete immiscibility of sample (BQ) and matrix (PMMA or SA) molecules. This immiscibility may lead to the formation of microcrystalline aggregates of BQ molecules in the mixed LB films. The scanning electron micrograph gives the visual evidence of microcrystalline aggregates of BQ molecules in the mixed LB films. UV-Vis absorption, fluorescence and excitation spectroscopic studies reveal the nature of these microcrystalline aggregates. LB films lifted at higher surface pressure indicate the formation of dimer or higher order n-mers.