Patterning of Magnetic Bimetallic Coordination Nanoparticles of Prussian Blue Derivatives by the Langmuir–Blodgett Technique

We report a novel method to prepare patterns of nanoparticles over large areas of the substrate. This method is based on the adsorption of the negatively charged nanoparticles dispersed in an aqueous subphase onto a monolayer of the phospholipid dipalmitoyl-l-α-phosphatidylcholine (DPPC) at the air–water interface. It has been used to prepare patterns of nanoparticles of Prussian blue analogues (PBA) of different size (K_0.25Ni­[Fe­(CN)₆]_0.75 (NiFe), K_0.25Ni­[Cr­(CN)₆]_0.75 (NiCr), K_0.25Ni­[Co­(CN)₆]_0.75 (NiCo), Cs_0.4Co­[Cr­(CN)₆]_0.8 (CsCoCr), and Cs_0.4Co­[Fe­(CN)₆]_0.9 (CsCoFe)). The behavior of DPPC monolayer at the air–water interface in the presence of the subphase of PBA nanoparticles has been studied by the compression isotherms and Brewster angle microscopy (BAM) images. Atomic force microscopy (AFM) of the transferred films on mica substrates shows that patterns of the nanoparticles are observed for a 10^–4 M concentration of the subphase, based on the nanoparticle precursors, at surface pressures between 1 and 6 mN/m and transfer velocities from 10 to 80 mm/min. Vertical, horizontal, or tilted fringes of the nanoparticles with respect to the transfer direction can be obtained depending on the transfer velocity and surface pressure

White Light-Emitting Electrochemical Cells Based on the Langmuir–Blodgett Technique

Light-emitting electrochemical cells (LECs) showing a white emission have been prepared with Langmuir–Blodgett (LB) films of the metallosurfactant bis­[2-(2,4-difluorophenyl)­pyridine]­[2-(1-hexadecyl-1<i>H</i>-1,2,3-triazol-4-yl)­pyridine]­iridium­(III) chloride (<b>1</b>), which work with an air-stable Al electrode. They were prepared by depositing a LB film of <b>1</b> on top of a layer of poly­(<i>N</i>,<i>N</i>′-diphenyl-<i>N</i>,<i>N</i>′-bis­(4-hexylphenyl)-[1,1′-biphenyl]-4,4′-diamine (pTPD) spin-coated on indium tin oxide (ITO). The white color of the electroluminescence of the device contrasts with the blue color of the photoluminescence of <b>1</b> in solution and within the LB films. Furthermore, the crystal structure of <b>1</b> is reported together with the preparation and characterization of the Langmuir monolayers (π–<i>A</i> compression isotherms and Brewster angle microscopy (BAM)) and LB films of <b>1</b> (IR, UV–vis and emission spectroscopy, X-ray photoelectron spectroscopy (XPS), specular X-ray reflectivity (SXR), and atomic force microscopy (AFM))