第三节 有机无机杂化膜材料

第三节有机/无机杂化膜材料(1)通过调节体系的pH值，使纳米微粒表面原子发生质子化或去质子化使微粒带上电荷。

如FeO、Fe2O3、Fe3O4@SiO2、Ag@SiO2、MoO（纳米簇）、石墨氧化物、黏土板(2)控制形成微粒的阴、阳离子的化学计量比偏离1:1，这种方法适用于沉淀溶度积较大的沉淀体系。

如表面带有负电荷的水溶性PbI2纳米微粒(3)通过吸附带有电荷的小分子使微粒表面带有电荷。

如Au、Ag、CdS等(4)使用双官能团分子修饰微粒表面，其中一个官能基团与纳米微粒表面结合为微粒提供稳定性，而另一个指向周围介质的官能基团为微粒提供表面电荷。

如CdS、CdSe、CdTe、HgTe等纳米微粒表面修饰上电荷。

如何使纳米微粒表面带有电荷Nanorainbows: Graded Semiconductor Films from Quantum DotsJ. Am. Chem. Soc. 2001, 123,7738-7739The graded NP films were assembledusing four different CdTe dispersionswith luminescence maxima at 495–505 (green), 530–545(yellow), 570–585(orange), and 605–620 nm(red) .Layer-by-layer assembly was carriedout on glass and plastic substrates andtypically 5–10 CdTe NP bilayers ofeach of four luminescent colors weredeposited.三基色：red, green , blueLuminescence spectra of (a) exemplary CdTe NPs used in this work and (b) thin films obtained after the sequential deposition of five bilayers of (1) “green”, (2) “yellow”(3) “orange”, and (4) “red”CdTe.Transmission electron microscopy images of cross-sections of a graded film made from five bilayers of “green”, “yellow”, and “red”(total 15) NPs with different magnification.”To evaluate the internal structure of the gradient CdTe film, it was assembled on a flexible cellulose acetate substrate as described in ref 11.A cross-sectional slice of the NP stack was analyzed by transmission electron microscopy (TEM). The asymmetryof the film could be seen in the difference of electron diffracting power of the “red”and “green”sides of the assembly (Figure 3a,b). The layers of bigger NPs appear noticeably darker in the TEM image due to the greater percentage of heavier elements on this side of the multiplayer stack.(a) Cross-sectional confocal microscopy image of the graded LBL film of CdTe NPs made of 10 bilayers of “green”, yellow”, “orange”, and “red”NPs (total 40). Small NPs are assembled in the lower part (green and yellow luminescence), while bigger NPs are assembled on top of them (orange and red luminescence). The total thickness of the film was estimated to be 220±20 nm by the same technique. (b) Schematic arrangement of the conduction and valence energy levels of the film in (a).Exciton Recycling in Graded Gap NanocrystalStructuresNano Lett., 2004, 4, 1599-1603cascaded energy transfer (CET)F örster resonantenergy transfer(FRET)Diagram of the excitonic energy levels in the REF (a) and the CET (b) sample. The thick lines represent the bottom of the exciton band, thin solid lines the vibronic progressions. The dotted lines symbolize trap states. (a) Most of the excitons in the REF sample are trapped in surface states, from where they decay nonradiatively. Only defect-poor NCs contribute significantly to the PL yield. Even defect-poor NCs may be affected via exciton transfer to defect-rich NCs. (b) Excitons in the six layers of smaller sized NCs are trapped in surface states similar to the trapping in the REF sample. However, the trapped excitons can be transferred very efficiently from layers with smaller NCs to layers with larger NCs. Most importantly, these recycled excitons finally reach the center layer of red-emitting NCs with only low excess energy which reduces the probability of being trapped.Nanostructured artificial nacre(i)T he material of seashell nacre and bones are well known for their hardness,strength and toughness—superior to many man-made ceramics andcomposites—complemented by unique biological/biomedical properties.Their distinctive mechanical qualities are attributed to a highly regular brick-and-mortar arrangement of organic and inorganic elements, which combines the elasticity of 10–50 nm protein layers (for example β-chitin and lustrins) and the strength of CaCO3 tablets 200–900 nm thick.(ii)The structure–function harmony of nacre and other hard biological tissues has inspired a large class of biomimetic advanced materials and organic/inorganic composites. The addition of inorganic components, such as clays,to organic polymers noticeably improves the mechanical, barrier and thermal properties of polymers and Rubbers.nature materials 2003, 2, 413.A glass slide was sequentially immersed in a 0.5% solution ofpoly(diallydimethylammonium) chloride polycation(PDDA;M w= 200,000) for 5 min and anionic montmorillonite clay (Aldrich) for 10 min at pH 4.2 and 8.3 for polyelectrolyte (P) and clay (C) dispersions respectively. Each P and C adsorption step was followed by a rinse in deionized water (18 MΩ) at pH 5.6 for 2 min. The film growth process was then immediately continued by depositing the partner compound. The deposition procedure was realized with a robotic manipulator (DR-1, R&K Technologies, Germany) programmed to carry out all the operations automatically for n=1–200.PREPARATION OF FREE-STANDING FILMSThe glass slide carrying (P/C)n was immersed into 0.5 wt% HF solution, which dissolved the thin layer of SiO2 coating silicon wafers supporting the (P/C)n stack. It also rendered glass surfaces more hydrophobic due to the formation of silicon fluoride. The free-standing (P/C)n film could then be easily delaminated. HF treatment resulted in the breakage of some platelets, their average AFM size decreased from 150–400 nm to 50–200 nm, whereas the overall structure remained undisturbed.Figure 1 Microscopic and macroscopic description of (P/C)n multilayers. a, Phase-contrast AFM image of a (P/C)1 film on Si substrate.b, Enlarged portion of the film in a showing overlapping clay platelets marked by arrows. c,The(P/C)n film structure.The thickness of each clay platelet is 0.9 nm. d, Photograph of free-standing (P/C)50 film after delamination. e, Close up photograph of the film in d under side illumination.Figure 2 Electron microscopy images of (P/C)n multilayers. a, Scanningelectron microscopy of an edge of a (P/C)100 film. b and c,Transmissionelectron micrographs of (P/C)200 free-standing film cross-sections embedded in epoxy resin at different magnifications.Scanning electron microscopy (SEM)examination (Fig. 2a) of the (P/C)100film cross-section revealed a layeredstructure which was conceptuallysimilar to that of nacre. The film wasdense and uniform in thickness. Thethickness of the film cross-sectionswas 1.2 ±0.1 μm, 2.4 ±0.15 μm,and 4.9 ±0.4 μm for (P/C)50,(P/C)100, and (P/C)200 respectively(see Methods).Young's modulus, E, can be calculated by dividing the tensile stress by the tensile strain:whereE is the Young's modulus (modulus of elasticity)F is the force applied to the object;A0is the original cross-sectional area through which the force is applied;ΔL is the amount by which the length of the object changes;L0is the original length of the object.Layer-by-Layer Assembly of Zeolite Crystals on Glass with Polyelectrolytes as Ionic LinkersKyung Byung Yoon, J. Am. Chem. Soc., 2001, 123,, 9771SEM images of the outermost layers of G+/(PSS-/PDDA+/PSS-/Z+) (A), G+/(PSS-/PDDA+/PSS-/Z+)2 (B), and G+/(PSS-/PDDA+/PSS-/Z+)3 (C), and the corresponding cross sections (D, E, and F).原位化学反应制备有机－无机杂化多层膜Metallodielectric Photonic Structures Based on Polyelectrolyte MultilayersAdv. Mater. 2002, 4, 1534Schematical Illustration of the Fabrication of AR andAntifogging CoatingsPDDA&silicate complexes (1:2 in molar ratio):size ~13.2 nm;ζ-potential: +40 mV at pH 4.0 aqueous solutionAlternative Deposition of the PDDA&Silicate Complexeswith Poly(acrylic acid)Net frequency decrease: 2337.9±301.6 Hz PAA (□)PDDA&silicate complexes (■)Fabry-Pérot fringes Ref: Zhang, Y. J.; Xu, J. J. Phys.Chem. B 2006, 110, 13484The Morphology of the AR and Antifogging Coating Quartz Substrate with Multilayer coating of(PAA/PDDA&Silicate)*12 before (a, c) andafter calcination(b, d) (PAA/PDDA&silicate)*12 film Rms: 8.9 and 3.3 nmThickness Dependence of (PDDA&silicate/PAA)*n Films Before and After CalcinationBefore calcination: 21.4 nm/cycleAfter calcination: 10.1 nm/cycleComposition Changes of the Coatings Before and After Calcination ProcessAntireflection PropertyUV-vis Region: maximumNIR region: 99.5% transmittance of 99.86 %Wetting and Antifogging Properties First Water Droplet (1µL)Second DropletWenzel’s equationcos θa = r cos θ3D porous structurer infinite θa 0°0.24 sWhy PDDA&silicate complexes ?Relative Rapid Fabrication; Large Porosity, High Transmittance (1)材料易得(2)较为快速的膜构筑(3)高度稳定(4)多功能。