Orderly Assembly Of Bio-macromolecules On Ni-In LDHs And Infrared Emissivity Study

Low infrared emissivity materials can reduce the infrared radiation performance of the targets, thus reducing the possibility to be found by the infrared imaging and thermal imaging system. Currently, researches concerning low infrared emissivity materials mainly focused on metal materials, semiconductor doping materials and nanocomposites. Supramolecular assembly materials with unique surface and interface effects and the synergestic effects between the host and guest species specially have potential application in low infrared emissivity materials. However, the reasonable regulation of the assembly process, the structure and composition of the materials at the nanometer scale, thereby controlling the infrared radiation properties of the materials is still a remaining challenge.Layered double hydroxides (LDHs) are a class of inorganic supramolecular structural materials composed of host and guest components. The special characteristics confined by interaction between the host and guest species and the two-dimensional (2D) structure make them have unique optical, electical, catalysis, adsorption and other physical or chemical properties. Multicomponents materials with special and ordered structure can be obtained by the combination of the LDHs host and different guest species by the assembly process. Then the infrared radiation property of a single component can be modulated and new physical and chemical properties may be generated by the construction of continous multicomponent interface. Accordingly, in this paper, a serious of bio-inorganic supramolecular structural materialshave been prepared by the assembly of LDHs and DNA biomolecular in order to modulate the infrared radiation property of the materials and the structure, properties and the infrared emissivity values of the hybird materials have been investigated.1. Based on the tunability of the components in the host layer of LDHs, Ni2+ and In3+ cation have been introduced into the host layer of LDHs and thepowder Ni-In LDHs with high crystallinity have been prepared. Then the LDHs-based thin films have been constructed to adjust the infrared emissivity values of the materials through the regulation of the surface condition. It was found that the incorporation of Ni2+ and In3+ in the host layer significantly reduced the infrared emissivity value and the value was further reduced by the fabrication of LDHs films. This study provide a good host materials for the host-guest assembly process and supplied theoretical basis for the application of supramolecular assembly in low infrared emissivity materials.2. Baed on the supramolecular assembly process, the layer structural Ni-In LDHs have been delaminated into 2D nanosheets. The acetate anions with weak binding force with the host layer have been intercalated into the gallery of LDHs and the delamination behavior of the acetate-intercalated LDHs has been studied. Nickel acetate and indium acetate are used as precursors in order to avoid the interferance of inorganic anions.The acetate-intercalated Ni-In LDHs were prepared by coprecipitation method followed by hydrothermal treatment. The two layer arrangement of the acetate anion in the gallery of LDHs layer was proposed with increased basal spacing and weaker interaction between the host layers, compared with acetate-intercalated Ni-In LDHs prepared by anion-exchange method. Thus the monodispered positive charged LDHs nanosheets were easily obtained by the delaminating of acetate-intercalated LDHs in water. This simple method did not need reflux at high temperature, overcoming the deficiency of using organic solvents, resulting in a steady colloidal suspension of 2D nanosheets. Finally, we have validated the suitability of these nanosheets as cationic macromolecular building blocks by re-assembling the carbonate intercalated LDHs in the presence of an excess of anions. Our data confirm that the intrinsic properties of the bulk material are retained by these segregated nanosheets, thus opening the door for their use in the development of layered multifunctional materials.3. We describe a facile approach to fabricate DNA/LDHs nanohybrid by coassembly of exfoliated Ni-In LDHs nanosheets with DNA. In the assembly progress, exfoliated LDHs nanosheets and DNA with different initial DNA/LDHs mass ratio were mixed together, and the DNA intercalated LDHs nanohybird was obtained only when the input DNA/LDHs mass ratio is< 0.3 mg/mg. The helix chain oriented parallel to the basal plane of host layer forming ordered sandwich structure. The infrared emissivity value of the DNA/LDHs nanohybird was then investigated. It was found that the infrared emissivity values were significantly reduced by coassembly of exfoliated LDHs nanosheets with DNA, which may be attributed to the synergistic effect and interfacial interaction between the DNA biomolecule and inorganic LDHs layers reinforced by the construction of ordered sandwich structure. The method for the fabrication of bio-inorganic hybird materials possesses several advantages such as component variability, low cost and easy manipulation. Therefore, this strategy provides a new way of fabrication of composites with low infrared emissivity.4. Core-shell structural SiO2@DNA-LDHs nanocomposite was prepared via Layer-by-Layer assembly of exfoliated LDHs nanosheets with DNA bio-molecules over the surface of SiO2 particles. Based on the special characteristic of the core-shell structure, the infrared radiation property can be adjusted by the mutual modification of the core and shell components. The nanocomposite presented well-defined hierarchical core-shell construction with momodispersed SiO2 core covered with layered structural DNA intercalated LDHs shell. The infrared emissivity value of the SiO2@DNA-LDHs nanocomposite was low, which may be attributed to the synergistic effect and the interfacial interaction strengthened by the construction of the DNA intercalated LDHs functional shell. This method overcomes the restriction of unitary shell composition and structure, which largely riched the structure and properties of the core-shell nanocomposites.5. We describe the bottom-up fabrication of a novel artificial designed hybrid film derived from negatively charged layered titanium oxide (LTO) nanosheets and DNA molecules assembled alternatively with positively charged LDHs nanosheets via sequentially electrostatic Layer-by-Layer deposition technique. The (LDHs/DNA/LDHs/LTO)n hybrid film possesses a long range stacking order in the normal direction of the substrate, with DNA molecules and LTO nanosheets accommodated in the LDH gallery respectively as monolayer arrangement. The film exhibits a continuous and uniform morphology. This new multilayered hybrid film possesses a low infrared emissivity value based on the synergistic effect of its multi-components, the interfacial interaction between different layers and the uniform and smooth surface. It can be expected that, by using such method, anion species with different characteristics can be assembled with LDHs simultaneously for desiging and fabricating mutifunctional materials, which largely expand the scope and applied fields for supramolecular assembly. This study is meaningful for the fabrication of advanced functional materials with muticomponents and sophisticated structure.