Dear Maroua Abdallaoui,

Layer-by-layer (LbL) self-assembly is an approach to develop an ultra-thin film on solid support by alternate exposure to positive and negative species with spontaneous deposition of the oppositely charged ions with wash steps in between. It is done by using various techniques such as immersion, spin, spray, electromagnetism, or fluidics. This method is used for formation of multilayer films. A variety of nanomaterials use it for the modification of films to enhance their resultant durability as well as strength. Studies have shown that many different types of materials can be used for fabrication of multilayers. Recently, the layer-by-layer selfassembly technique has also been used for fabrication of gas sensors, hydrogen sensors and solar-based cells. Various methods, such as spin deposition, calcinations, and dry-transfer printing are being used for fabrication of thin films

Its representation can be made by defining two oppositely charged polyions as + and -, and defining the wash step as W. To make an LbL film with 5 bilayers one would deposit W+W-W+W-W+W-W+W-W+W-W, which would lead to a film with 5 bilayers, specifically + - + - + - + - + - .

Representation of the LbL method as a multilayer build-up based solely on electrostatic attraction is a simplification. Multilayer build-up is enabled by multiple attractive forces acting cooperatively, typical for high-molecular weight building blocks, while electrostatic repulsion provides self-limitation of the absorption of individual layers.

Advantages over other thin film deposition methods:

1. LbL is simple and inexpensive method.

2. Wide variety of materials that can be deposited by LbL including polyions, metals, ceramics, nanoparticles, and biological molecules.

3. LbL has the high degree of control over thickness, which is due to the variable growth profile of the films, which directly correlates to the materials used, the number of bilayers, & the assembly method.

4. As each bilayer can be as thin as 1 nm, this method offers easy control over the thickness with 1 nm resolution.

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya

The assembly of multilayers by LbL (Layer by Layer) technique is a unique novel approach for the fabrication of ultrathin films on solid substrate. This technique has high flexibility over the selection of materials from small organic molecules, polymers, proteins, ceramic, colloids to bio active molecules. The organization of different molecular units in ordered Nanoscale range has potential towards device fabrication. As the films fabricated by LbL (Layer by Layer) process show dynamic change in photophysical properties from bulk or solution so future development of this technique will provide an envisioned up growth towards the understanding of anisotropy and other photophysical characteristics of electro-statically organized self assembled molecular assemblies, which could lead to remarkable progress in the arena of device fabrication as well as also fundamental research.

You can read this paper in order to know details.

With Best Regards

Md. Majibul Haque Babu

M.Sc student

Thank you all! That's very useful!