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[资源] Advanced material 一篇最新关于纳米材料性质的综述

DOI: 10.1002/adma.200601173
When Small Is Different: Some RecentAdvances in Concepts and Applicationsof Nanoscale Phenomena**
By Gary Hodes*
Reduction in size often does more than simply make things smaller. There are manyproperties of materials that undergo qualitative, often sudden, changes below acertainsize scale. This Report first describes some of these size-dependent properties.Following this general description, recent developments in a number of selectedtopics innanoscience are covered. These topics are: luminescence from Au nanoparticles;Si (and related) nanoparticle luminescence; modification of opticalabsorption by surfaceadsorption on nanoparticles; and transistors (and some other devices) based on nanotubesand nanowires.

1. Introduction‘Nano’ has become almost a household word. Even thosewho do not know what it represents mathematically are invariablyaware that it refers to something ‘very small’. Inthescientific community, it is commonly used to designate structuresat least 1 nm but less (often much less) than 1 lm. However,semantics apart, there is another requirementthat iscommonly accepted for inclusion in the “nanoclub”; the structureshould be artificially made. Note that the word ‘structure’is deliberately used: macromolecules, forexample, can justifiablybe considered to be nanomaterials, yet they are notusually so classified.Having arrived at a working definition of ‘nano’ as appliedto materials, thenext question that the scientifically literatelayman might reasonably ask is: “what is so special aboutnanomaterials”? Of course, it does not require a great deal ofscientificliteracy to understand that the smaller ‘things’—forexample, electronic circuits—can be made, the smaller ourelectronic devices become and (for the slightly more literate)thefaster they become and the more they can store.Apart from this subject of increasing miniaturization, an importantquestion is: What properties or behavior cannanomaterialsexhibit that they would not do if they were not so small.This is the really scientifically interesting side of these materials/structures. The size at which materialsstart to show theseproperties depends upon the specific property or behaviorand can vary from a nanometer (and sometimes even less)and extend into the micrometerrange.This progress report reflects a clear bias towards nano- fromthe viewpoint of a chemist (nanoparticles prepared typicallyby using chemical means) rather than thetraditional sub-microelectronicstudies by physicists (structures deposited typicallyby using vacuum or gas-phase techniques followed byetching procedures). Thus, a broadfield of mesoscopic physicsdealing with the interference of electron waves is only brieflytreated.This report starts with a general introduction where differenttypes ofnanometer-size-determined phenomena are described.In this introduction, results from the past few yearsare not emphasized as they are for the rest of the report.Followingthis introduction, several specific fields are discussedthat represent some of these size-determined phenomena thathave exhibited rapid progress in the past fewyears. This sectionstarts with luminescence from gold clusters where emissionefficiencies can rival those of semiconductor quantumdots. Continuing with luminescence, therecent rapid progressin light emission from Si nanoparticles is discussed. FollowingPROGRESS REPORTAdv. Mater. 2007, 19, 639–655 . 2007 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim 639Reduction in size often does more than simply make things smaller. There are manyproperties of materials that undergo qualitative, often sudden,changes below acertain size scale. This Report first describes some of these size-dependent properties.Following this general description, recent developments in a numberof selectedtopics in nanoscience are covered. These topics are: luminescence from Au nanoparticles;Si (and related) nanoparticle luminescence; modification ofopticalabsorption by surface adsorption on nanoparticles; and transistors (and some other devices) based on nanotubesand nanowires.–

Prof. G. HodesDepartment ofMaterials and InterfacesWeizmann Institute of ScienceRehovot 76100 (Israel)E-mail: gary.hodes@weizmann.ac.il[**] I am grateful to Robert Dickson (Georgia Institute ofTechnology),Louis Brus (Columbia University), and Sidney Cohen and DavidCahen (both of the Weizmann Institute of Science) for reading partsof this Report and providingvaluable suggestions for improving it.Size quantizationtens nmDoping/defectstens nmCrystal phasetens nmSingle charge effectsca. 50 nm at room temperatureChargedepletiontypically 100 nmScattering/interference of lighthundreds nmBallistic transporthundreds nm

[ Last edited by popsheng on 2007-7-9 at 21:09 ]

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