**1. Introduction**

Dimensionalityisoneofthemostfundamentalmaterialparametersbecauseitdefinestheatomic structure of materials and determines its main properties. Thus, one chemical element or compound can exhibit different properties in different dimensions. Some interesting exam‐ ples about size effect are surface plasmon resonance in metal nanoparticles, quantum confine‐ ment in semiconductor particles, and superparamagnetism in magnetic nanomaterials.

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If one dimension is restricted, we have two‐dimensional (2D) or layered shape material. An interesting example of this kind of materials is graphene. This material is a monolayer of carbon atoms tightly packed into 2D honeycomb lattice that has attracted worldwide attention since it was discovered in 2004 [1, 2]. This new material has emerged with a promising future due to its amazing properties such as transparency, high‐charge mobility, thermal conductivity, and mechanical resistance. Due to these unique properties, graphene has been proposed as a good candidate for manufacturing transparent‐conducting electrodes, transistors, hydrogen‐ storage devices, and gas sensors [3, 4]. The growing interest on graphene has highlighted the importance of another 2D material in technological applications such as transition metal chalcogenides (TMC) and layered ionic solids.

Several 2D materials can be obtained by exfoliation of a layered bulk crystal. However, this procedure is often difficult because the van der Waals interactions between adjacent layers must be overcome. Mechanical exfoliation provides good results, but mostly applied for fundamental research because it is arduous and expensive to produce the material at industrial scale by this way. Other methodologies such as solvent‐assisted ultrasound exfoliation [5] or chemical synthesis [6] allow obtaining large amounts of materials at low cost, although they present several disadvantages against mechanical exfoliation. One important disadvantage is related with the deposition of materials onto solids. Hence, for several technological applica‐ tions, it is necessary to support 2D materials onto solid substrates [7, 8] and since the properties of 2D materials deposited onto solids are strongly affected by the film morphology, a deposi‐ tion methodology becomes necessary, which allows a great control of the material density and packing. Several techniques such as drop casting [9] or spin coating [10] have been used to integrate these materials onto novel devices; however, they often lead to nonuniform films or films with aggregated materials due to uncontrolled capillary flow and dewetting processes during solvent evaporation. These aggregates decrease the specific properties of each material [2, 11]. An illustrative example of the aggregation produced by solvent evaporation can be seen in **Figure 1**. The figure shows a field emission scanning electron microscopy (FESEM) image of a graphene oxide (GO) film deposited onto silicon by drop casting.

**Figure 1.** FESEM image of graphene oxide deposited onto silicon by drop casting.

An alternative technique is the Langmuir‐Blodgett (LB) methodology. This method consists on the transfer process of a water‐insoluble material from the air‐water interface onto a solid substrate by vertical dipping of the solid in the Langmuir monolayer [12]. This technique allows continuous variation of material density, packing, and arrangement by compressing or expanding the film using barriers. Consequently, it offers the possibility of preparing films with the control of interparticle distance necessary to exploit the 2D materials in technological applications. Despite this methodology being successfully used for transferring water‐ insoluble molecules [12–14] and nanoparticles [15], it has been less employed to transfer graphene derivatives [16–19] or TMC materials onto solid substrates.

This chapter reviews some strategies to build 2D material films by means of the LB method‐ ology. The content is organized into three main sections. The first one introduces the LB methodology. The second one summarizes the production of thin films of graphene oxide derivatives by using this methodology [17–20]. The last section describes some representative results concerning thin films of Quantum Dots (QDs) of transition metal chalcogenides [21– 26] and silver nanowires (AgNWs) [27]. All sections are focused on the possibility of tuning the morphology of the 2D material by modifying the surface composition of the Langmuir monolayer and the deposition methodology.
