Langmuir−Blodgett Films of Known Layered Solids:  Preparation and Structural Properties of Octadecylphosphonate Bilayers with Divalent Metals and Characterization of a Magnetic Langmuir−Blodgett Film

Abstract

Langmuir-Blodgett (LB) films of a series of divalent metal octadecylphosphonates have been prepared and characterized. The films are each shown to be LB analogs of known solid-state metal phosphonates possessing 2-dimensional ionic-covalent metal phosphonate layers. The metal phosphonate layers crystallize during the LB deposition process. Films were characterized with XPS, X-ray diffraction, ellipsometry, attenuated total reflectance FTIR, and, in the case of the manganese film, SQUID magnetometry. Octadecylphosphonate films with Mn 2+ , Mg 2+ , and Cd 2+ form with the stoichiometry M(O 3 PC 17 H 37 )‚H 2 O and have metal phosphonate bonding consistent with the analogous M(O 3 PR)‚H 2 O layered solids. The Ca 2+ film forms as Ca(HO 3 PC 18 H 37 ) 2 , which is also a known solid-state phase. Magnetic measurements reveal that the manganese octadecylphosphonate film undergoes a magnetic ordering transition at 13.5 K resulting in a "weak ferromagnet". The behavior is similar to that of the known layered solid-state manganese alkylphosphonates which are also "weak ferromagnets". The magnetic ordering is antiferromagnetic where incomplete cancellation of the magnetic sublattices, due to low site symmetry, results in a spontaneous magnetization. A spin-flop transition is observed at 2.5 T in magnetization Vs applied field measurements of the ordered state. The film also exhibits magnetic memory, with a small remnant magnetization and a coercive field of 20 mT at 2 K. The results demonstrate that magnetic ordering phenomena can be incorporated into LB films and that LB film methods can be used to prepare monolayer and multilayer films of known solid-state materials.

Coatings against corrosion and microbial adhesion

“…The C-H stretching region (3000-2800 cm À1 ) intensively studied in the literature shows the position and shape of the n a (CH 2 ) and n s (CH 2 ) bands that reflect the conformational order and packing of aliphatic chains in monolayers [29]. When the alkyl chains are highly ordered (trans-zigzag conformation), the bands appear near to 2920 and 2950 cm À1 , respectively.…”

Hybrid Organic/Inorganic Langmuir-Blodgett Films. A Supramolecular Approach to Ultrathin Magnetic Films

“…However, from the chemical point of view this polymeric approach is strongly limited by the stability of the extended inorganic network compared to that of the molecular precursors, and by the templating effect of the organic surfactant. The first successful results in this context have been reported by Talham et al [19] They have based their work on well-known hybrid organic/inorganic layered solids, as for example the divalent metal organophosphonates of formula M(O 3 PR) (M 2+ = Mn, Cd, Mg; R = C 17 H 37 ) and Ca(HO 3 PR) 2 . The built-up LB films appear to be isostructural with their solidstate analogs.…”

Magnetic Langmuir–Blodgett films of ferritin with different iron loadings

“…The first one involves the preparation of structurally ordered monolayers of polymeric metal complexes in which the extended structure of the inorganic network facilitates the occurrence of cooperative magnetic phenomena. Some examples are LB films of divalent metal organophosphonates and cyanide-based extended networks [15][16][17]. The problem of this strategy is the difficulty to control the formation of extended networks at the water-air interface.…”