Review Synthesis And Biomedical Applications Of Hollow-Books Pdf

REVIEW Synthesis and biomedical applications of hollow
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Table 1 Synthetic strategies for the hollow nanomaterials. Applied methods Hollow materials Initial materials templates Shape Ref. Co3 S4 Co9 S8 CoSe Co Sphere 21 33, Pt CoO Pt Co Yolk shell 21. Fe3 O4 Fe Fe3 O4 Sphere 34, Fe2 O3 Fe Sphere 35 44. ZnAl2 O4 ZnO Al2 O3 Tube 36 37, CoSe2 Co3 S4 CoTe Co Necklace 38. Ni2 P Co2 P Ni Co Sphere 39 40, CeO2 ZrO2 CeO2 ZrO2 Sphere box 41. FePt CoS2 FePt Co Yolk shell 98, FePt Fe2 O3 FePt Fe2 O3 Yolk shell 99.
Nanoscale Kirkendall effect, Au Fe2 O3 Au Fe2 O3 Yolk shell 42. Pt Cu Pt Cu Core shell 45, Cu2 x Se Cu2 O Sphere 46. CuO Cu Tube 47, Ag Ag2 Se Ag2 Se Ag Sphere tube 48 49. PbS Pb PbS Pb Ag Pb Sphere 50, CdS Cd Sphere 43, Co3 S4 Co CO3 0 35 Cl0 20 OH 1 10 Tube 51. ZnS ZnO Sphere 52, ZnO Zn Sphere 53, Fe Fe Box frame 54.
Fe phosphide Fe3 O4 Fe2 O3 Sphere box 22, Mn phosphide MnO Sphere multi pods 22. Mn Fe phosphide MnFe2 O4 Sphere 22, Chemical etching. ZnO Au ZnO Pt ZnO Au Pt ZnO ZnO Sphere 57, Co Co Box frame 55. Pd Pd Box frame 56, Cu2 O Cu2 O Dodecahedral frame 58. Au Ag Box cage triangular ring prism shaped box tubes 3 4 62 68. multiple walled shell or tube, Galvanic replacement Pd Ag Pt Ag Ag Box frame 69.
Au Ag Pt AuPt CoPt Co Sphere 70 75, AuPt Co Necklace 71. Au Pt Pd Co Necklace 76, Fe2 O3 Fe3 O4 FeOOH Capsule 23. K An T Hyeon, Fe2 O3 Silica Sphere 77, Nanotemplate Silica Fe3 O4 Sphere 78. FeOOH Organics Tube 80, Co CoO Parallelepiped 81, Applications of hollow nanostructures 361. tructures 1 Usually the hollow structures obtained via a sulfur dissolved in organic solution resulted in the forma. template mediated approach using silica or polymer parti tion of hollow cobalt sul de nanocrystals of either Co3 S4 or. cles as the templates are often larger than 200 nm because Co9 S8 depending on the molar ratio of sulfur and cobalt. it is hard to make smaller sized template particles In addi 21 33 During the transformation cobalt nanocrystals are. tion to this size limitation the template mediated method rst covered with a cobalt sul de shell Next the diffusion. has other disadvantages the post treatment necessary to of cobalt and sulfur atoms in opposite directions takes place. remove the templates adds complexity to the whole syn at the surface of cobalt and cobalt sul de As the reac. thetic process and increases the chance of the structural tion proceeds voids form in the cobalt side of the interface. deformation as well as the introduction of impurities In because the outward diffusion of cobalt atoms is faster than. order to overcome these limitations simple and novel the inward diffusion of sulfur atoms Similar intermediate. strategies are highly desired In this review we will focus. on the colloidal synthesis of high quality hollow nanostruc. tures with their sizes smaller than 200 nm The structures. of our interest encompass nanoframes and nanocages with. porous walls as well as those with solid walls The synthetic. approaches are categorized into four main types according. to how the hollow nanostructures are formed the Kirkendall. effect 2 21 chemical etching 22 galvanic replacement. 3 4 and template mediated approach see Table 1 All. of these approaches exploit nanoparticles as starting mate. rials except for the nanotemplate mediated approaches. where these starting nanomaterials play the role of the. sacri cial templates that are dissolved or transformed to. generate hollow nanostructures Hollow nanostructures can. nd various biomedical applications including simultaneous. diagnosis and therapy The large pore volume inside the hol. low nanostructures can be used to incorporate various drugs. and biomolecules and release them in a controlled manner. At the same time the surface of the hollow nanostructures. can be readily functionalized with optical labels and tar. geting agents 3 4 This review covers the recent progress. on the synthesis and biomedical applications of various hol. low nanostructures 23 30 The rst four sections describe. the synthesis of hollow nanostructures using four different. synthetic approaches followed by their various biomedical. applications, Nanoscale Kirkendall effect, In 1942 Kirkendall reported that net mass transport.
occurred across the interface between two different metal. species upon annealing and vacancy assisted hopping was. proposed as the main mode of atomic transport 31 At. the interface two metal species in contact have differ. ent diffusion rates resulting in the net ux of atoms from. one side of the interface to the other As atoms diffuse. through the interface vacancies move in the opposite direc. tion and accumulate to form voids The stress originated Figure 1 a f TEM images showing the shape evolution of. from an increase in the void volume during diffusion induces Fe Fe3 O4 core shell nanoparticle a via Kirkendall effect. the porosity in the solid This phenomenon is now known Core shell void intermediates obtained by the reaction for 1 h. as the Kirkendall Effect In 1947 Smigelkas and Kirkendall b and 2 h at 130 C c and 40 min d and 80 min at 210 C. demonstrated that at an elevated temperature the differ e Hollow Fe3 O4 nanoparticles from the reaction for 120 min. ence between the diffusion rates of copper and zinc in brass at 210 C f g Schematic illustration showing the shape evo. led to the formation of pores in the species 32 In 2004 lution from the core shell to the hollow structure reproduced. Alivisatos and his co workers reported exploiting the Kirk with permission from 34 copyright 2007 Wiley VCH h m. endall effect at the nanometer scale for the fabrication of TEM images showing the shape evolution of hollow iron iron. hollow nanostructures 21 In their report cobalt nanocrys oxide nanoparticles exposed to dry 20 oxygen for 1 min at room. tals were transformed to hollow chalcogenide nanocrystals temperature h 1 h i and 12 h at 80 C j 5 min k and 1 h at. by introducing either oxygen sulfur or selenium into the 150 C l Fully oxidized iron oxide nanocrystals were obtained. hot dispersion of cobalt nanocrystals For example the sul by oxidation for 1 h at 350 C m reproduced with permission. dation of cobalt nanocrystals by the addition of elemental from 35 copyright 2007 American Chemical Society. 362 K An T Hyeon, structures were observed in many other hollow nanomateri by the controlled oxidation under O2 atmosphere adopting. als Peng and Sun observed a core shell void intermediate the nanoscale Kirkendall effect 35 The reaction temper. structure during the synthesis of hollow Fe3 O4 nanocrystals ature and oxidation time allowed for precise tuning of the. 34 In their report they synthesized amorphous Fe Fe3 O4 thickness of the oxide shell as shown in Fig 1h m. nanoparticles Fig 1a via thermal decomposition of Fe CO 5 The Kirkendall effect can also be applied to fabricate. in a hot organic solution and subsequent air oxidation 1 dimensional 1 D hollow nanomaterials Fan and their. The controlled oxidation of Fe Fe3 O4 nanoparticles in the co workers fabricated single crystalline ZnAl2 O4 spinel nan. presence of an oxygen transfer reagent trimethylamine otubes Fig 2a and b with a diameter of 40 nm and a wall. N oxide yielded monodisperse hollow Fe3 O4 nanoparticles thickness of 10 nm using ZnO Al2 O3 core shell nanowires. with controlled sizes via the nanoscale Kirkendall effect It as the starting material 36 37 They proposed a model. was observed that when the reaction was quenched by low explaining the formation mechanism of their 1 D hollow. ering the temperature in the middle of the reaction process structures the so called Kirkendall effect surface diffu. multiple voids were formed in the particle By adjusting the sion process 37 According to the proposed model the. reaction temperature and time it was possible to obtain a surface diffusion process is a dominant mass ow mode. series of intermediate structures from the solid particle to responsible for the enlargement of interior pores after their. the core shell void the yolk shell and nally the hol formation induced by the Kirkendall effect Fig 2c illus. low structures which is a good evidence for the Kirkendall trates the different diffusion processes in the growth of. effect Fig 1a f show that the shape of the nanoparti hollow nanostructures At the early stage small Kirkendall. cles evolved from the core shell to the hollow ones as the voids are generated via bulk diffusion at the interface When. reaction time was increased and as the temperature was large numbers of voids contact the inner surface of the. raised which is also illustrated in Fig 1g The Alivisatos shell the surface diffusion of the atoms of the core material. group also synthesized a series of monodisperse iron iron becomes dominant along the skeletal bridges Through the. oxide core void shell and hollow iron oxide nanoparticles channels of the shell layer the material exchange proceeds. Figure 2 TEM images of a and b the ZnAl2 O4 spinel nanotubes reproduced with permission from 36 Copyright 2006 Nature. Publishing Group and b Schematic illustration showing the different diffusion processes in the growth of the hollow nanostructure. reproduced with permission from 2 copyright 2007 Wiley VCH. Applications of hollow nanostructures 363, Figure 3 a TEM HRTEM inset and b SEM image of the wires of hollow CoSe2 nanocrystals c Schematic illustration showing. the formation of hollow CoSe2 nanocrystals from cobalt nanoparticles in the 1 absence and 2 presence of an alternating magnetic. eld reproduced with permission from 38 copyright 2006 Wiley VCH. via direct dissolution in the solution phase or evaporation partial hollow structures in which the unreacted Cd core. in the gas phase generating the hollow nanostructure and the coalesced vacancies were separated into two dis. Xu et al applied the nanoscale Kirkendall process to tinct spherical caps It was attributed to the faster diffusion. magnetically assembled 1 D hollow nanostructures of cobalt of cadmium atoms through the polycrystalline shells com. chalcogenides 38 First they assembled cobalt nanocrys pared to sulfur atoms 43 They further extended the. tals with the size of 20 nm into necklace like structures synthetic method of the hollow core shell void nanopar. by the magnetic dipolar interactions Then the cobalt ticles to generate various quasi ternary superlattices 44. nanocrystal assemblies were transformed to CoSe2 hollow Recently Fan and co workers reviewed the fabrication of. nanostructures retaining the chain like shape via the Kirk nanotubes and hollow nanoparticles based on the Kirkendall. endall process Fig 3 During the synthesis by exerting effect and summarized various kinds of hollow nano and. an alternating magnetic eld a small number of individ micro materials 2. ual hollow CoSe2 nanocrystals were obtained which were. fractured from the chain because the applied vibrational. magnetic torque disrupted the dipolar interactions between Chemical etching. the particles, Several hollow nanostructures of oxides sul des Etching or partial dissolution of the interior of nanopar. selenides and phosphides have been synthesized by many ticles is another approach to synthesize hollow or. researchers via the nanoscale Kirkendall effect 39 53 porous nanomaterials Several kinds of hollow nanomate. For example the Schaak and Chiang groups indepen rials synthesized via the selective etching process have. dently reported hollow Ni2 P nanoparticles synthesized from been reported The Hyeon group synthesized hollow iron. oleylamine stabilized Ni nanoparticles in the presence of nanoframes by thermal decomposition of a Fe II stearate. trioctylphosphine TOP 39 40 The Li group fabricated complex in the presence of sodium oleate and oleic acid at. CeO2 ZrO2 nanocages by reacting ceria nanospheres with 380 C Fig 4a 54 In this process solid iron nanocubes. zirconium IV in a glycol medium 41 The Alivisatos group are initially generated from the thermal decomposition of. synthesized gold iron oxide core hollow shell nanopar Fe II stearate complex and subsequent reduction by the. ticles in which the formation of the hollow oxide shell byproducts from the decomposition of oleic acid These solid. resulted from the oxidation of the iron shell by oxygen nanocubes were subsequently transformed into nanoframes. 42 The same group also reported asymmetric Cd CdS with a hollow core This transformation was attributed to. 364 K An T Hyeon, Figure 4 a TEM and HRTEM inset images of the Fe nanoframes and the overall shape evolution of the Fe nanoparticles in the. lower panel reproduced with permission from 54 copyright 2007 American Chemical Society b and c TEM images of ZnO hollow. nanoparticles and the corresponding diameter distribution and electron diffraction pattern in the insets Schematic illustration of. the selective etching strategy for ZnO hollow nanoparticles using a sacri cial template is shown in the lower reproduced with. permission from 57 copyright 2008 American Chemical Society. sodium molten salt derived from sodium oleate in the solu cobalt nanocages and skeletons through NaF assisted etch. tion during the aging process at 380 C The molten salt ing of cobalt nanocube aggregates 55 Xiong et al reported. corrosion is a well known etching process of metal and corrosion based synthesis of palladium nanoboxes 56 They. it was suggested that in situ generated sodium salts in reported that the local corrosion of the surface of the. REVIEW Synthesis and biomedical applications of hollow nanostructures Kwangjin An Taeghwan Hyeon National Creative Research Initiative Center for Oxide Nanocrystalline Materials and School of Chemical and Biological Engineering Seoul National University Seoul 151 744 Republic of Korea

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