1、Group 14 : 李紹唐 黃立柱 杜萌 王煒 邵長偉 王彩路 王榮華 Add your text in here Add your text in here Add your text in here Add your text in here Add your text in here Background Kinds of methodsMethods without template Application CommentsOutlineBackgroundlWhat is a hollow structure?l Consist of either organic or inorg

2、anic core and coated with shellsl Selective dissolution or calcinations to obtain a hollow structurelWhat special properties could be observed? well-defined interior voids, low density, large surface area, stability, surface permeabilityBackground chemical nanoreactorsefficient catalysts drug-delive

3、ry carriersphotonic crystals energy-storage devicesoptoelectronic sensors What is it for?What is it for?Due to its special structure and attractive functional features, it could be used in: Add your text in here Add your text in here Add your text in here Add your text in here Add your text in here

4、Background Kinds of methodsMethods without template Application CommentsOutline Synthesis methods Template method Template and layer-by-layer method Surface chemical reaction and depositionTemplate free method Kirkendall effect Inside-out ostwald ripening mechanism Solvothermal synthesisUtilization

5、of various removable templatesSoft ones surfactants, emulsion droplets, micelles, vesicles, ionic solvents, gas bubblesHard ones polymers, silica, carbon, metal oxides, metallic coresTemplates Add your text in here Add your text in here Add your text in here Add your text in here Add your text in he

6、re Background Kinds of methodsMethods without template Application CommentsOutlinecase 1 Preparation via Kirkendall effect The specific geometry, diffusivity, and concentration profile do not satisfy Equation. The product phase is rich in defects, which may absorb vacancies without forming voids. It

7、 is a ternary mutual-diffusion system. The object is very small, which makes a hollow structure unstable in the given environment.Case 2 Preparation via Ostwald Ripening What is Ostwald Ripening?What is Ostwald Ripening? This ripening process involves “the growth of larger crystals from those of sma

8、ller size which have a higher solubility than the larger ones” (IUPAC Compendium of Chemical Terminology, 2nd edition,1997)Preparation via Ostwald RipeningGeneral process of OA. Various schemes of OA for spherical colloidal aggregates: 1) core hollowing process; 2) symmetric OA for formation of a ho

9、mogeneous coreshell structure; 3) asymmetric OA in formation of a semi-hollow coreshell structure; 4) a combination of 1 and 2. A rotating core.Mass center of a semi-hollow coreshell structure.Proposed model for the formation of the void space between core and shell in scheme 2 of (b). Hashed lines:

10、 the cross-sectional plane of a sphere. Darker areas: larger and/or closely packed crystallites. Lighter areas: smaller and/or loosely packed crystallites. White areas: void space. Note that the above area illustrationsare simplified, as actual transitions between two different areas should be much

11、more gradual.Preparation via Ostwald RipeningZnS coreshell nanospheres (scheme 2, Figure 1b)TEM investigation of surface nucleation on ZnS solidspheres: a) overall spheres formed at this stage, b) complete formation of surface shell, and c) partial formation of surface shell; dark areas (larger crys

12、tallites) are indicated with arrows。Preparation via Ostwald RipeningTEM/SAED investigation of formation process of semihollow Co3O4 coreshell structures with asymmetric Ostwald ripening:after a) 12 h and bf) 24 h at 100. g) SAED pattern of a semihollow Co3O4 coreshell sphere.TEM image of crystallite

13、 orientation and crystallite size of semi-hollow Co3O4 coreshell structuresPreparation via Ostwald RipeningTiO2 nanospheres via Ostwaldripening under hydrothermal conditions30mL of the TiF4 solution (1.33-2.67 mM) was added to a Teflon-lined autoclave, and the hydrothermal synthesis was conductedat

14、140-220 C for 1.5-100 h in an electric oven. A total of 37 experiments were carried out to examine various synthetic parameters.Preparation via Ostwald RipeningA TEM image of the anatase TiO2 nanospheres synthesized at a higher temperature. Note that a much shorter reaction time is needed at higher

15、temperatures.Sun flower like TEM images of TiO2 spheres with a less compact surface and a solid core: (A) overall appearance (scale bar1000 nm), and (B) a detailed view on the surface region (scale bar 200 nm).Case 3 Preparation via Oriented Attachment(a) Classical crystallization pathway(b) oriente

16、d attachment of primary nanoparticles forming an iso-oriented crystal upon fusing(c) mesocrystal formation via self-assembly of primary nanoparticles covered with organicsHollow SnO2 via Oriented Attachment1. Formation of triangular crystallite aggregates2. Planar coalescence leads to three-dimensio

17、nal construction of octahedra3. When two or more such initial sheets are close to each other under low-fluidity conditions, the chance of joining exists. the octahedra grow into each other, fabricating evenmore complex hollow polyhedra. Hollow SnO2 via Oriented Attachmenttypical experiment, SnF2 (0.

18、24 g) was added to deionized water(50 mL) with vigorous stirring; the pH value was 2.83. The fresh solution (12 mL, 0.03m), deionized water (36 g), 2-propanol (1315 g), and ethylenediamine (12 g) were added to a Teflon-lined stainless steel autoclave. The autoclave was kept at 180 for 6-50 hHollow N

19、anocubes of Cu2O via OA and OR(C) under a low water content condition, the formed Cu2O crystallites are smaller and the surfaces of Cu2O (100)are rougher, leading to more mismatches among the crystallites (D) with a higher content of water, the formed Cu2O crystallites are larger and surface of Cu2O

20、 (100) are smoother,resulting in a better oriented attachment among the crystallitesCase 4 Selective removal of MnCO3 by HCl Eassily to control thethickness of shell andthe morphology.a three-step processStep OnePreparation of MnCO3 precursors with controlled morphologiesLow-magnification SEM image

21、of a MnCO3 crystalline precursor;b) Higher-magnification SEM image of a single solid MnCO3 microsphere.by adding the (NH4)2SO4 solutionStep TwoOxidation of MnCO3 precursor crystals with 0.032 mol/L KMnO4 in aqueous solution at room temperature.KMnO4 and MnCO3 can react with each other readily and fo

22、rm a diffusion pair. (Kirkendall effect). The coupled reaction/diffusion at the crystal/solution interface might lead to the quick formation of a MnO2 shell around the outside surfaces of the MnCO3 crystals.MnCO3 precursor;MnCO3MnO2 after chemical reaction (1);MnCO3MnO2 after partially selective rem

23、oval of MnCO3;Step ThreeH2O2 can removal the MnO2 shell, so that the best time could be well defined.SEM images of the process of MnO2 hollow nanostructures formation after MnCO3 was added in the KMnO4 solution at different time intervals: a) 2; b) 6; c)10 min; and d) after the removal of the core o

24、f MnCO3 crystals with HCl. Selective removal of MnCO3 crystal template with HClCase 5 Controlled decompositiondissolution (CDD) processControlled decompositiondissolution (CDD) process based on a solid-state thermal decomposition process, followed by an acid-washing process. Where does the inspirati

25、on come from?The idea was inspired by examining the thermogravimetric analysis (TGA) curve of Manganese carbonate cubelike microcrystalsMnCO3 + 1/2 O2 MnO2 + CO2 Step1400oCMnO2 1/2 Mn2O3 + 1/4 O2 Step2550oCTo obtain the pure phase, thermal decomposition should be conducted at a temperature of either

26、 plateau (a) or (b);However, if the thermal decomposition process was stopped at halfway, what would happen?Reported Strategy partially decomposed or under-calcined lead to an oxidation layer (MnO2) on the surface, whereas the inner cores remain as the MnCO3 salt, forming a“coreshell” structure.Repo

27、rted StrategyAn excellent opportunity to further tailor the microstructureControlled DecompositionDissolution method a: partial thermal decomposition of metal salts (yellow), forming metal oxide outer layers (red); b: dissolution of the residual metal salt core by acid washing, leading to hollow por

28、ousmetal oxide shells; c: further calcination to form cage like hollow structuresExperimental SectionKMnO4 solution0.632g in 20ml H2OSucrose solution0.5g in 20ml H2Ostirred and hydrothermally treated150oC 24h Obtained MnCO3 was calcined at 320 for 2hObtained core-shell Acid-washing: in HCl solution

29、0.1 MAs-prepared hollow microbox materials were further calcined at higher T (500-800)abcResults and DiscussionsXRD patterns and B) FTIR spectra of samples at different perioda: as-prepared MnCO3b: calcined at 350 for 2hc: acid-washed materiald: further calcined at 500XRD and FTIR analyses provide e

30、vidence of the removal of the MnCO3core from the partially decomposed MnCO3 particles by acid washing. Results and DiscussionsSEM and TEM images of the samples prepared at different stagesa, b: as-prepared MnCO3c, d, e: acid-washed MnO2f: HRTEM nanoporousg: thither walls 350oC for 4hh: calcined at 6

31、00oCi: calcined at 800oCIt is worth noting that the wall thickness and specific surface area of the microboxes can be easily tailored by controlling the calcination t & T.To confirm the generality of our CDD strategy, transition metal salts with different morphologies and compositions were processed

32、.Results and Discussionsa-d: MnCO3 & MnO2 ellipsoidal particlese, f: FeCO3 & Fe2O3 faceted morphologiesThe advantages of the method lie in: Simple and cost-effective Controllable by varying t & T Easily scaled up Add your text in here Add your text in here Add your text in here Add your text in here

33、 Add your text in here Background Kinds of methodsMethods without template Application CommentsOutline Application 1 Catalysts for Fuel CellThe nanosphere catalyst was 30-40 nm in diameter and 3-4 nm shell PPy(聚吡咯聚吡咯)two main peaks for the formic acid oxidation at about 0.35 V in both the positive a

34、nd negative scan directions are observed in the two catalyst electrodes, and the corresponding peak current densities are both over 150 mA/cm2Application 2 Dye-Sensitized Solar CellslSnO2 MHSs were prepared bya chemically induced self-assembly reaction of aqueous sucrose/SnCl4 solution under hydrothermal condition. lThe second step was to coat TiO2 nanocrystallites onto the SnO2 MHSs by impregnating in and then hydrolyzing TiCl4 to form a surfac