Monolayer And Its Application In The Synthesis Of Nanocomposite

The monolayer and LB films are used as the simple model of biological membrane because of their similar structures and properties to the membrane, excellent biological miscibility and placing the functional molecules in the established location. When the monolayer is in solid state, the rigid packed molecules can control the growth of crystal. The results are helpful to understand the formation mechanism of biology mineralization. Otherwise, the exceed crystal lattice structure of surfactant-capped nanoparticles has been fabricated by spreading the particles onto the air/water interface and transferring the monolayer onto substrate.Based on these considerations, the dissertation consists of four parts, which include the preparation and properties of bilirubin/cholesterol mixed monolayer and DPPC/bilirubin mixed monolayer, the preparation of monolayer and LB film of the surfactant-capped Ag₂S particles, and the biomimetic synthesis of AgxCdyS particlesunder arachidic acid monolayer.1. From a detail analysis of surface pressure-area isotherms of mixed bilirubin/cholesterol monolayers, it is concluded that the miscibility of bilirubin and cholesterol decreased with the increase of the concentration of Ca²⁺ in subphase. The non-ideality of mixed monolayers is evident in the mean area-composition and the collapse pressure-composition figures. The mixed monolayers exhibited noticeable negative deviation on pure water and positive deviation on Ca²⁺ subphase. It suggests that the attractive interactions between bilirubin and cholesterol should be displaced by the multi-interaction among Ca²⁺, bilirubin and cholesterol. So the molecular packing of bilirubin/cholesterol monolayers is hindered on Ca²⁺ subphase because of the coordination between Ca²⁺ and the components. Furthermore, curves of the free energy of mixing and the excess free energy of mixing to composition indicate that the mixed monolayers become less stable as the concentration of Ca²⁺ increased in subphase.2. In order to get an insight into the mechanism of action between lipid and bilirubin, we undertake the study on the DPPC/BR binary system at the air/water interface. The interactions between DPPC and BR within the monolayer arecharacterized by n-A isotherms, compressibility modulus, mixed free energy, etc.. The conclusions are as listed below:DPPC and BR were miscible and formed non-ideal monolayers at the air/water interface; the attractive interaction between hydrophilic groups is dominant in the molecular packing of mixing monolayers. Owing to the strong hydrogen bonds between the polar groups of DPPC and BR, the stable 1:2 stoichiometry complex (MD_B) can be organized self-assembly at the air/water interface. In addition, the properties of DPPC/BR mixed monolayers were nearly correlative to the subphase pH and calcium ions in subphase. DPPC monolayer becomes condensable on acid aqueous subphase, but its monolayer on alkali aqueous subphase is no difference comparing with it on pure water; the BR monolayer has no apparently change on acid aqueous subphase, but the BR molecules nearly can't form stable monolayer on basic aqueous solution. Thanks to the hydrogen bonds between DPPC and BR, the mixed monolayer is affected more conspicuously by OH" than by H+. On Ca2+ subphase, pure DPPC and pure BR monolayers became condensed comparing with that on pure water. However, the mixed DPPC/BR monolayer became a little expanded.3. The NDM-capped Ag2S nanoparticles are synthesized in the microemulsion, the size of the spherical particles is about 53nm. FTIR spectra indicate that the Ag2S nanoparticles are capped by the NDM and the particles become hydrophobic. The NDM-capped Ag2S nanoparticles monolayer is prepared successfully by spreading the particles onto the water. The particles arrange more orderly in monolayer with the increase of surface pressure. In addition, the multiplayer film containing surfactant-capped Ag2S nanoparticles has been fabricated by the Langmuir-Blodgett technique. The Uv spectra show that the LB film has notable quantum-size domino-offect.4. AgxCdyS nanoparticles are obtained beneath arachidic acid monolayer, floating on aqueous solution containing Ag+ and Cd2+, by inputting H2S over the monolayer. The arachidic acid/ AgxCdyS LB films are prepared by transferring their monolayer onto substrate. The small angle X-ray diffraction identified obvious period structure of the LB films. The molar ratio of Ag and Cd in AgxCdyS is 0.16:0.84, measured bythe XPS. The formation mechanism of the AgxCdyS nanoparticles induced and controlled by the headgroups of arachidic acid in the monolayer in terms of lattice matching was discussed.