第四章一维纳米材料（课件）.ppt

第四章 一维纳米材料 one dimensional nanometer materials,4.1 纳米丝或纳米棒 4.2 纳米管 4.3同轴纳米电缆,定义：在两个维度上为纳米尺度的材料,,,,横截面：,长度：几百纳米至几毫米,结构：,,,,,,,,种类：,,nanobelt,一维纳米材料的制备策略,,A) Dictation by the anisotropic crystallographic structure of a solid,B) Confinement by a liquid droplet as in the vapor-liquid-solid process,C) Direction through the use of a template,D) Kinetic control provided by a capping reagent,E) self-assembly of 0D nanostructures,F) Size reduction of a 1D microstructure,4.1 纳米丝或纳米棒,纳米棒(nanorod)：纵横比(长度与直径的比率)小，1m,Si纳米线、铁镍合金纳米线 SiC、Si3N4、GaN MgO、ZnO GaAs、InAs、InP、GaP,,种类：,(nanowire, nanowhisker,nanofiber),4.1.1 制备方法,(1) 气相生长合成法,Supersaturation factor,低过饱和度：whisker,中过饱和度：bulk crystal,高过饱和度：powder,直接气相法,粉体(如Si3N4、SiC、Ga2O3、ZnO)直接加热气化生成相应的纳米线,间接合成法,在纳米线的形成过程中可能涉及到中间产物,,,优点：simplicity and accessibility,例① ： MgO纳米线的制备,MgO+C(H2, H2O),Mg(V)+CO,Transport to Growth zone,MgO(Al2O3, ZnO, SnO2),氧化,两步法有助于降低过饱和度,(1) 气相生长合成法,,,,Cu+O2,Cu2O,H2S 室温,Cu2S,Cu＋air,CuO nanowire,Cu2O,,中间产物的生成有助于降低制备纳米线的温度,MgB2,MgO,900℃,氧化 H2/Ar,MgO,1200℃ 直接蒸发,MgO nanowire,(1) 气相生长合成法,,例②: Cu2S 纳米线的制备,△,例③: MgO 纳米线的制备,,,,,Si+SiO2(S),热蒸发 或激光蒸发,SixO(V),Six-1+SiO,Si+SiO2,,,SixO液体，起催化剂作用，有助于Si原子吸收、扩散、沉积,SiO2壳层，由SiO分解而来，有助于阻止横向生长,,,,温度梯度的存在是纳米线生长的外部推动力,+SiO,(1) 气相生长合成法,,例④: Si纳米线的制备,,,,可能生长机理：,T,Adv. Mater. 2000, 12, No. 18, p1343,X>1,(1) 气相生长合成法,,例⑤: GaAs纳米线的制备,氧化物辅助纳米线生长方法优点： ①无需金属催化剂； ②消除了金属原子对纳米线的污染,GaAs+Ga2O3,GaAs纳米线,在[111]生长方向的GaAs结晶核外面包覆了一层Ga2O3,生长机理：,(2) 气-液-固方法(VLS方法）,原理,优点：可用于制备单晶纳米线；产量相对较大 缺点：不能用于制备金属纳米线；金属催化剂的存在会污染纳米线,激光蒸发、热挥发、电弧放电－物理法 Chemical vapor transport and deposition－化学法,纳米线的直径由Au团簇或粒子的尺寸决定,应用最广泛的方法，制备的纳米线包括：,Si、Ge、B－elemental semiconductor GaN、GaAs 、 GaP 、 InP 、 InAs－III-V semiconductor ZnS、ZnSe、CdS、CdSe－II-VI semiconductor ZnO、MgO、SiO2－oxides,,Vapor来源：,,Ge纳米线的生长过程,Au cluster,GeI2,700-900℃分解,Ge-Au(L)合金(～12％Ge),在固液界面生长,过饱和,Ge(V),,360℃,,,,(2) 气-液-固方法(VLS方法）,,(3) Solution-Liquid-Solid methods(SLS方法),产物为单晶纳米须或线，横向尺寸10～150nm，纵向几mm,催化剂：低熔点金属，如In、Sn、Bi等,,优点：操作温度可在普通芳香烃的沸点以下,例①：{tert-Bu2In[-P(SiMe3)2]}2,111~203℃ 芳香烃溶剂 In催化剂,,InP (10~100nm, 1000nm),,原理,156.6,231.9,271.3,,,,,,Organometallic precursor,例②,烷基硫醇稳定的Au纳米粒子,己烷,,加热加压,,超临界流体状态,,Si纳米线,(Au-Si合金液体组成，18.6mol%, 363℃),(3) Solution-Liquid-Solid methods(SLS方法),,bp: 100oC,,bp: 68.7oC,,(4) 溶剂化热合成(solvothermal Methods),原理：使溶剂处于高温高压(大于临界点)下，提高固体的溶解度，加速固体之间的反应。

前驱体＋(结晶生长调节剂(如胺))+溶剂,高温、高压,纳米线,例：,GeCl4 or phenyl-GeCl3,烷烃 275℃, 100atm,Ge纳米线(7~30nm,10m),,优点：大多数材料在适当的溶剂中提高压力和温度至临界点时可溶，即具有普适性 缺点：产率低、纯度低，尺寸、形态均匀性差，用到的芳烃溶剂环境不友好，体系复杂，反应机理研究困难5) Solution-Phase Methods Based on Capping Reagents,例①,CdSe前驱体,三辛基氧化膦 己基磷酸,CdSe nanorod,例②,AgNO3+乙二醇＋PVP(聚乙烯基吡咯烷酮),Pt纳米粒子,Ag纳米线,,,A) Formation of bimodal silver nanoparticles through heterogeneous nucleation on Pt seeds and homogeneous nucleation B) Evolution of rod-shaped Ag nanostructure as directed by the capping reagent, poly(vinyl pyrrolidone) C) Growth if the Ag nanorods into wires at the expense of small Ag nanoparticles,(6) 各向异性结晶生长法,M2Mo6X6 (M=Li, Na, X=Se, Te),,制备的纳米线种类有：,(SN)x (聚硝化硫)-金属及超导特性,K2[Pt(CN)4],酞菁金属,Structural model of (Mo3Se3)- molecular wires A TEM image of bundles assembled from (Mo6Se6)- molecular wires,Triangular planar (Mo3Se3)- 间距0.45nm 分子线直径约2nm,Molybdenum Chalcogenide 硫族化钼,Se、Te,H2SeO3+N2H4(肼),Se+N2+3H2O,2Te(OH)6+3N2H4,2Te+3N2+12H2O,(6) 各向异性结晶生长法,,A. An illustration of the crystal structure of t-Se composed of hexagonally packed, helical chains of Se atoms paralled to each other along the c-axis,B. SEM images of t-Se nanowires with a mean diameter of 32nm,SEM images of t-Te nanowires and nanorods,(7) 模板法,,Templating Against Features on Solid Substrates,Schematic illustrations of procedures that generated 1D nanostructures by (A) shadow evaporation; (B) reconstruction at the bottom of V-grooves; (C) cleaved-edge overgrowth on the cross-section of a multilayer film and (D) templating against step edges on the surface of a solid substrate.,介孔材料模板法,聚合物介孔膜 氧化铝介孔膜 金属介孔膜,分子自组装结构模板法,(7) 模板法,,nanowire,nanotube,nanowire,nanotube,一维纳米材料模板法,碳纳米管,先沉积Ti,,Au、Pd、Fe、Al、Pb纳米线,生物大分子法,利用大分子侧基与离子的作用先生成纳米粒子，通过纳米粒子的连接，生成纳米线,例：利用DNA分子AgNO3或PtNO3可制备Ag、Pt纳米线,纳米线法,(7) 模板法,,例如，AuCl4-、Ag+、PdCl42-、PtCl42-等离子在LiMo3Se3分子纳米线的还原作用下可分别制得Au、Ag、Pd、Pt纳米线,纳米碳管模板法普适反应模式,例：,（8）其它方法,,Self-Assembly of Nanoparticles,A,B) Structures that were assembled from 150nm polystyrene beads (A), and 50 nm Au colloids (B), by templating against 120nm-wide channels patterned in a thin photoresist film. C) An L-shaped chain of Au@SiO2 spheres assembled against a template patterned in a thin photoresist film. D) A spiral chain of polystyrene beads that were assembled by templating against a V-groove etched in the surface of a Si(100) wafer.,Size Reduction,Isotropic deformation of a polycrystalline or amorphous material Anisotropic etching of a single crystal Near-field optical lithography with a phase-shift mask,,4.1.2 纳米丝(或棒)的性质和用途,(1)热性能,块状Ge，熔点930℃,,650℃,848℃,两头先熔，再向中间延伸，直接越小，熔点越低,退火温度低 有利于无缺陷纳米线的制备(熔融－重结晶) 有利于在较低温度下进行纳米线之间的焊接、切割、连接，以制备功能器件及电路 在纳米线的横截面尺寸和长度下降到一定尺寸时，环境温度和残余应力变化对纳米线的稳定性影响很大，易发生断裂,,。