Langmuir-Blodgett (LB) Film Forming Reagents
Introduction
Langmuir-Blodgett (LB) film is an ultrathin organic film with a monolayer thickness of nanometer scale. LB film technology is a technique for precise control of film thickness and molecular structure, which can utilize the amphiphilic characteristic of the film-forming reagents to obtain densely arranged single molecule films and transfer them from the liquid surface to the solid substrate under the action of an external force field, thus achieving a multilayer ordered film structure. This enables the assembly of a multilayer ordered film structure and the uniform arrangement of catalyst molecules on the substrate.
Forming reagents
The film-forming reagents for LB films are usually amphiphilic molecules with polar hydrophilic groups such as carboxyl (-COOH) and hydroxyl (-OH) at one end and non-polar hydrophobic groups such as long-chain alkyl groups at the other end. The early film-forming reagents were mainly organic small molecules such as long-chain fatty acids and their salts, which were easy to synthesize, but the drawback was the poor mechanical strength and thermal stability of the LB films produced. The most typical organic compound is stearic acid, as it forms LB films more easily, but instability limits its application. Therefore, researchers have turned their attention to organic polymers with strong intermolecular forces. For example, LB films consisting of phospholipids are single molecule films and can be used not only for chemical or biological sensors, but also for simulating cell membranes to study the interaction of small molecules with cell membranes. Other film-forming reagents: fluorescent compounds, polymers and catalyst molecules that are soluble in organic solvents, etc. In addition, LB films can be prepared by non-classical amphiphiles, thus expanding their application.
Application
LB technology has been applied to the surface modification of protein molecules, organic polymer nanotubes, and ceramic flake materials, and its application areas have been further expanded to include two-dimensional dielectric materials and molecular probes. For example, the antimicrobial properties of 2D graphene oxide can be investigated by using LB technology, and the antimicrobial properties of 2D graphene oxide originate from its chemical properties, and the antimicrobial films formed by using LB technology are not easily peeled off and are highly stable.
Reference
- Oliveira Jr, Osvaldo N., Luciano Caseli, and Katsuhiko Ariga. The past and the future of Langmuir and Langmuir–Blodgett films. Chemical Reviews, 2022, 122.6: 6459-6513.