2014-11-場誘導化學反應

1、,,場誘導化學合成與制備材料Materials Induce-synthesized & Prepared by Fields,管自生,南京工業(yè)大學材料科學與工程學院,,,包括：1）尋找新合成與制備方法的科學問題New Strategy；2）以適當?shù)臄?shù)量和形態(tài)合成材料的技術問題；3）已有材料的新合成方法（如Sol-gel）及其新形態(tài)（如Fiber、Film、Hierarchical Structures）的合成。,合成與制備(

2、synthesize & Prepare),合成： 指促使原子、分子結合而構成材料的化學與物理過程。制備:研究如何控制原子與分子使之構成有用的材料。,場：包括磁場；電場；微波；等離子體；光；聲場；重力場包括加熱等；為材料的合成與制備針對反應提供反應能量或者提高反應速度或者改變反應途徑等,,,5.電場合成 靜電合成-靜紡Electric-field induced Synthesize &Electrospinning

3、,主要內容(Main contents)：,1.光誘導合成 Light-induced Synthesize & Prepare,2. 微波等離子合成 Microwave & Plasma,3. 聲波合成 Acoustic wave Synthesize,4. 重力場(Gravity field)在材料合成中的應用,,,Electromagnetic spectra,1. Introduction Lights,,,電磁

4、波的范圍,,,,分子光譜,,Molecular Spectra,,,2. 光與物質作用理論基礎Theories of Light-excited Materials,2.1原子分子受光激發(fā) Excited Atom & Molecules 原子分子軌道；電子躍遷與輻射；分子能級圖；原子分子受光激發(fā)后變化過程 2.2半導體受激光激發(fā)Excited Semicondutors半導體躍遷；半導體受光激發(fā)的變化過程2.3

5、 金屬受激光激發(fā) Excited Metals,,,,,,,,,Figure Excitation and deexcitation process in molecule,Absorption~ 10-15 s,S0,S2,Internal conversion10-14-10-13 s,S1,T1,Fluorescence10-9-10-5,,,Internal and External radiationless con

6、version,Intersystem crossing 10-6 s,Chemical reaction,Singlet excited state,Triplet excited state,Electron transfer（ms),Phosphorescence10-5-10-3,Ground state,2.1原子分子受光激發(fā),,,當基態(tài)分子的一個成對電子吸收光輻射后，被激發(fā)躍遷到能較高的軌道上，通常它的自旋方向spinni

7、ng direction不改變，即?S=0，則激發(fā)態(tài)仍是單線態(tài)，即“單線(重)激發(fā)態(tài)”；    如果電子在躍遷過程中，還伴隨著自旋方向的改變，這時便具有兩個自旋不配對的電子，電子凈自旋不等于零，而等于1： S=1/2+1/2=1 其多重性： M=2S+1=3    即分子在磁場中受到影響而產(chǎn)生能級分裂，這種受激態(tài)稱為“三線(重)激發(fā)態(tài)”；,,,原子核外電子受不同能量光子激發(fā)

8、后，輻射過程,,,1)平動-平動轉移 Translation-Translation2)平動-轉動轉移 Translation-Rotation3)轉動-轉動轉移 Rotation-Vibration4)振動-平動轉動轉移Vibration-Translation5) 振動-振動轉移 Vibration-Vibration6)電子-振動轉移 Electron-Vibration7)電子-電子轉移Electron-Electr

9、on,能量轉移 Energy Transfer ：,Molecule orbits & Energy Levels 分子軌道與能級,2.1原子分子受光激發(fā),,,Illumination of Electron Levels、 Vabriation Levels、 Rotation Levels,Electron Levels,Vabriation Levels,Rotation Levels,

10、2.1原子分子受光激發(fā),,,量子力學理論，分子的振 – 轉躍遷也是量子化的或者說將產(chǎn)生非連續(xù)譜。因此，分子的能量變化 ΔE 為各種形式能量變化的總和：,運動的分子外層電子Outlayer Electrons - 吸收外來輻射 - 產(chǎn)生電子能級躍遷 – 分子吸收譜Molecular absorption spectra。,其中?Ee 最大： 1-20 eV; ?Ev 次之： 0.05-1 eV; ?Er 最小： <0.05 eV

11、,2.1原子分子受光激發(fā),,,光源簡介:普通光源;激光光源,太陽光模擬光源,,,,鹵素燈,,,氙燈,紫外燈高壓汞燈,,,(一)光誘導合成法 Light-induced Synthesize,5. 其它光與材料合成,4.激光與材料化學合成,2. 光與物質作用理論基礎 Principles,1.光與激光laser簡介,3. 激光誘導化學反應Laser-induced Chemical Reactions,,,1.激光簡介Introd

12、uction of Laser,近幾十年來，隨著激光技術的應用與發(fā)展，出現(xiàn)了一門嶄新的邊緣學科——激光化學Laser chemistry 。 它和經(jīng)典的光化學反應(Photochemistry )一樣，是研究在光子Photon與物質相互作剛的過程中，物質激發(fā)態(tài)Exited States 的產(chǎn)生、結構、性能及其相互轉化的一門學科。,,,特點: 1)具有亮度高、單色性好homochromatism、方向性好 Orien

13、tation ;2) 高亮度，可以成為一種特殊熱源; 利用這種熱源:直接加熱Heating蒸發(fā)Evaporation解離Ionization 化學物質使許多繁雜、艱難的化學操作變得簡單可行；3) 激光對原子、分子選擇性相互作用Selective Reactions 提供了必要條件；4)利用激光的方向性，可實現(xiàn)微區(qū)域Microarea的高溫化學反應High-temperature Reactions。,,,激

14、光器類型,1 CO2激光器 Carbon Dioxide Laser2 He-Ne激光器 Helium-neon3氬激光器:Argon laser4 準分子激光器 excimer laser5 固體激光器:釹激光器:neodymium laser/Nd laser6 自由電子激光器 Free Electron Laser,,,CO2 Laser,屬于氣體激光器，分子激光器molecular laserWavelength

15、 9-11?m，最常見10.6 ?m效率高 High efficiency光束質量好 High Quality功率范圍大 （幾瓦～幾兆瓦）運行方式多樣結構多樣,,,,He-Ne Laser,氣體原子激光器 Gas Atomic LaserOutput 輸出譜線Spectrum line ：632.8nm，1.15 ?m，3.39 ?m，以632.8 nm為最常見 功率在mW級，最大1W光束質量好，發(fā)散角可小于1mrad

16、單色性好Homochromatism ，帶寬Bandwidth可小于20HzHigh stability,,,準分子激光器Excimer laser,準分子指在激發(fā)態(tài)能夠暫時結合成的不穩(wěn)定分子高重復率 可調諧 量子效率高、波長短，紫外到可見區(qū),主要的準分子激光器,Excimer laser是一種紫外線化學激光器Ultraviolet Chemical Laser，常用于眼科手術及半導體工藝上。,,,YAG Solid Laser

17、Yttrium Aluminum Garnet石榴石,Nd: YAG固體脈沖激光器主要性能指標：Wavelength：213、266、355、532、1064 nm Repeat Frequency：1-50 Hz（可調） Energy：連續(xù)可調，Max 300 mJ （瞬間可融化、氣 化多種材料及其表面） 脈寬Pulse width：3-5 ns,Energy Levels,(1) Changes of Atoms o

18、r Molecules Excited by Laser,Coulomb explosion 庫侖裂解Relativistic regime 相對論區(qū)間,Timescales of various electron and lattice processes in laser-excited solids. Each green bar represents an approximate range of characteristi

19、c times over a range of carrier densities from1017 to 1022cm–3.The triangles at the top show the current state-of the-art in the generation of short pulses of electromagnetic radiation: 1. 5 fs, 2. 120 fs (X-ray), 3. 0.5

20、 fs (far ultraviolet).,Time Scales,碰撞電離,Figure Electron and lattice excitation and relaxation processes in a laser-excited direct gap semiconductor. CB is the conduction band and VB the valence band. d, Carrier distribut

21、ion before scattering. e, Carrier–carrier scattering. f, Carrier–phonon scattering. g, Radiative recombination. h,Auger recombination. i, Diffusion of excited carriers.j,Thermal diffusion. k,Ablation. l, Resolidification

22、 or condensation.,a, Multiphoton absorption.b, Free-carrier absorption. c, Impact ionization.,,,中國“低空衛(wèi)士”激光系統(tǒng),,,,鋁背鈍化的太陽能電池,,,3.2,,用各種波長激光（紅外、可見、紫外）誘發(fā)的化學反應大約有幾百種。根據(jù)波長的不同，激光誘發(fā)化學反應的機理也不相同: 例如：紅外激光Infrared Laser誘導化學反應:

23、 紅外敏化反應Infrared sensitized Reactions; 振動異構化反應Isomerization reaction; 紅外異相催化反應Heterocatalysis; 紅外誘導鏈反應Chain reaction; 紅外光解范德華分子反應Photolysis Van der Waals Molecules; 紅外多光子離解反應Multiphoton dissociation; 紅外多光子離解反應要求激光

24、必須有足夠高的強度（至少108瓦/平方厘米）。,3. 激光如何誘導化學反應,1). 激光誘導化學反應是指在常溫常壓下不能進行但在激光的照射下可被誘發(fā)的化學反應。激光具有單色性、高強度和短脈寬等優(yōu)越性能，是誘發(fā)光化學反應最理想的光源。,2) 激光誘導化學反應主要是指激光光解反應Laser-induced Photolysis以及由光解碎片splinter引起的后續(xù)化學反應，例如，自由基Free radical或原子Atom，所產(chǎn)生的自由

25、基又可以誘發(fā)鏈鎖反應Chain reaction。,,,紅外激光誘導化學反應中，激光的作用不是簡單的熱作用，而是紅外光子同分子內的特定鍵或振動膜之間發(fā)生共振耦合。 紅外激光誘導化學反應是一種定向的Orientation、低反應活化能Low activation energy的快速過程，具有高度的選擇性Selectivity。以三氯化硼分子為例，該分子的反對稱伸縮振動v3(955cm-1) 。當用低功率的二氧化碳紅外激光（λ＝10.

26、55微米)輻照含有BCl3分子的混合氣體時，將誘發(fā)化學反應。如混合氣體為BCl3＋H2S，常溫常壓下不發(fā)生反應。在激光輻照時，使B-Cl鍵被激發(fā)，并發(fā)生以下反應過程：,,3BCl2SH→（BClS）3＋3HCl   （BClS）3→B2S3＋BCl3,,,反應物分子被激發(fā)至電子激發(fā)態(tài)excited electronic state絕大多數(shù)分子的離解能Dissociation energy在60～752.

27、4 kJ.mol-1或3～7eV之間，這就需要波長為400～140 nm的紫外光輻照才行。原則上講，只要選擇合適波長的激光，任何分子都能被光解，對同一分子來說，不同波長的激光輻照時有可能按不同的方式光解。例如，激光法生產(chǎn)氯乙烯（C2H3Cl）：,C2H4Cl·＋Cl·,C2H3Cl＋Cl·這是一個紫外激光誘導的自由基鏈反應radical chain reaction，關鍵是二氯乙烷被準分子激光光解所引發(fā)。

28、激光誘導化學反應已用于10余種同位素的分離。,C2H4Cl2,,hv,C2H4Cl2＋Cl·→C2H3Cl2·＋HCl C2H3Cl2· → C2H3Cl＋Cl·,紫外或可見激光光解反應Ultraviolet & Visible Laser-induced Reactions,,,,,光電離 Photoionization,1）光直接電離 Directly Photoion

29、ization分子電子直接被激發(fā)出2) 自電電離分子被激發(fā)到高于電離能的超激發(fā)態(tài)superexcited states，然后被微擾Disturbance電離一個離子ion和電子electron的狀態(tài),,,4.激光與材料制備Materials of Laser-induced Synthesise,4.1激光催化化學反應 Laser-induced Catalytic Chemical Reactions4.2激光誘導化學反應

30、Laser-induced Chemical Reactions4.3激光選擇化學反應Laser-induced Selective ChemicalReactions 4.4激光顯微化學反應 Laser-induced Microarea Chemical Reactions4.5激光合成陶瓷粉體 Ceramic Powder of Laser-induced Synthesis 4.6 脈沖激光沉積鍍膜

31、 Pulse Laser-induced Deposition Films4.7其它高能射線High Energy Rays在材料合成中的應用,1. Laser-induced Catalytic Chemical Reactions,激光催化加快化學反應速度表1列舉了一些激光催化反應的效果。,,,4.2 Laser-induced Chemical Reactions,,,,,,,,,,,,光解制備氧化物半導體,Fast Sy

32、nthesis of ZnO Nanostructures byLaser-Induced Decomposition of Zinc Acetylacetonate,Presenting very attractive engineering properties like large exciton binding energy, photoluminescence, and piezoelectricity while bein

33、g easily synthesizable in a plenty of different morphologies in single-crystal form, nanostructured zinc oxide has become one of the most studied semiconductor nanomaterials of the beginning of the 21st century.,Because

34、of their great potential for the fabrication of new devices, in particular for optoelectronic and gassensing applications, 1D ZnO nanostructures have attracted much attention，oriented ZnO microtube arrays have been grown

35、 by solution chemistry for bio-/gas sensors by the selective UV light response.,Figure . Schematic depiction of the synthesis process. (A) Laser-induced decomposition of precursor solution. (B) Detail of the reaction zon

36、e with the different nanostructures obtained.,Solution Preparation. A quantity of 0.4 g of zinc acetylacetonate hydrate [æsiti'læsit?u,neit]乙酰丙酮 (Zn(C5H7O2)2?H2O, >95% purity) was manually mixed with

37、2 mL of deionized water and 2 mL of denatured ethanol (EtOH 85.47%, MeOH 13.68%, EtOAc 0.85%) for 5 min, forming a slurry of 0.355 M of Zn(AcAc)2?H2O. The pH of the solution was measured to be 8.25. A few drops of the

38、 solution was then transferred to a fused quartz substrate,Laser Decomposition. A CO2 laser ?=10.6 ?m,,Figure (A) Low-magnification view of deposit grown at 20 W, 2 s; (B) nanoparticle film; (C) nanowires; (D) nanoro

39、ds grown at the same parameters.,Only a few seconds of irradiation, various zinc oxide (ZnO) nanostructures including nanorods and nanowires are formed near the center of the irradiated zone, surrounded by a porous thin

40、film of ZnO nanoparticles,indeterminate shape with a very rough surface in the center.,nanoparticle aggregates,Ridges: nanowires nanorods,Different Zone,,,Figure . Influence of laser power on deposit morphology at a cons

41、tant irradiation time of 10 s: (A) 5 W, 40 W/cm2; (B) 10 W, 80 W/cm2; (C) 15 W, 119 W/cm2; (D) 20 W, 159 W/cm2.,The type of structures produced and their localization on the substrate can be varied by selecting adequate

42、irradiation time and laser power ranges.,crystalline whiskersan average length: 1.3um an average width of 167 nm,more randomly grown ZnO whiskers can be seen,,,Figure . SEM images of nanowires and nanonails grown with

43、different laser irradiation parameters: (A and B) 20 W, 5 s; (C and D) 20 W, 2 s.,The type of structures produced and their localization on the substrate can be varied by selecting adequate irradiation time and laser pow

44、er ranges.,UV lasing has been observed from ZnO whiskers and gas-sensing devices, and UV photodiodes were made from multipod-shaped nanorods.,Nanowires: 4.4 um further away from the center of the reaction zone,width of 4

45、7 nm,Nanoplates and nanonails with hexagonal tips between 100 and 300 nm wide,an assortment ofnanowire,,,Laser-Induced Mutual Transposition of the Core and the Shell of a Au@Pt Nanosphere,Noble-metal clusters and colloi

46、ds with nanometer dimensions, exhibiting new optical and physical properties, have attracted a great deal of interest.,光誘導制備納米晶金屬,The design and controlled fabrication of nanostructured materials with functional properti

47、es have been extensively studied recently.,Nanostructured metals attract considerable attention scientifically as well as industrially because they can be used in diverse applications such as catalysts, magnetic devices,

48、 single electron transistors, and optoelectronics.,,,Figure. Illustration of processes taking place in a platinum-topped gold nanosphere during irradiation with 1064-nm laser pulses of 30 ps. The black indicates gold, wh

49、ile the gray indicates platinum. 1)The thermalized photon energy of platinum-plasmon resonances melts small platinum nanoparticles surrounding the core gold to convert the topped nanosphere into a smooth Au@Pt core-shell

50、 nanosphere. 2)Gold having the lower melting point melts and soaks out to the surface with further irradiation to produce a reversed core/shell Pt@Au core-shell nanosphere.,The optical properties of platinum, palladium,

51、silver, and gold colloidal nanoparticles have received considerable attention because of this plasmon band.,Figure . TEM (A) and HRTEM images (B) of platinum-topped gold nanoparticles before (left) and after irradiation

52、(right) with 1064-nm laser pulses of 30 ps for 120 min. Note that the actual particles transformed into the particles of the right are different from those of the left.,1) Aqueous 15-nm gold colloids of 50 mL having sur

53、factant-free gold nanospheres a gold atomic concentration of 1.0 mM were prepared by the citrate檸檬酸 reduction of HAuCl4。 2) platinum-topped gold nanoparticles were prepared by adding 21 mL of a 10 mM 2-day-aged

54、H2PtCl6 aqueous solution and 8 mL of a 100 mL-ascorbic acid抗壞血酸 aqueous solution to 30 mL of the above-prepared gold colloids under vigorous stirring.,Experimental Sections,Citratic Acid,ascorbic acid,2-nm Pt,,,Figure 1.

55、 (A) Pictures of dried film 1 20, 40, and 60 min after the 355 nm laser irradiation. (B) Picture of formic acid-doped film (degree of doping 6 wt %) containing BP and HAuCl4 5 min afterthe 355 nm laser irradiation.,Accel

56、eration of Laser-Induced Formation ofGold Nanoparticles in a Poly(vinyl alcohol) Film,PVA (Mw ) (8.9-9.8)x104), BP, 2-mercaptoethane sulfonate, 2-巰乙基磺酸,Polyvinyl alcohol,,,反應歷程：Reaction mechanism,formic acid-doped,BPH?

57、 radical,PVA radical,,,Laser-Induced Self-Assembly of Pseudoisocyanine J-Aggregates Yoshito Tanaka isocyanine [ais?u'sai?ni:n]異花青 Pseudo [‘psju:d?u]偽-,Laser-Induced Organic Molecules Self-Assembly,A 1064 nm near

58、-infrared (NIR) laser beam from a continuous waveNd-YAG laser was introduced into an inverted microscope and focused on a 520 nm spot by a 100 Plan-Neofluar objective lens,光誘導異構化反應,花青,,,4.3.激光選擇化學反應Laser-induced select

59、ive chemical reaction2,有些化學反應(熱反應、經(jīng)典光化學反應等)在通常條件下是一種方向，而在激光的作用下則會改變反應方向?；蚴窃诨旌衔镏校蚴峭凰刂?，激光能激發(fā)某些原于、分子或同位素，而其余則不被激發(fā)，這種反應稱之為定向反應或選擇化學反應。激光選擇化學反應已成了無機物分離提純的全新技術手段。,,,激光選擇分離稀土元素 稀土元素的化學性質是非常近似的。用化學方法分離，不但工藝繁雜，而且效率低，成

60、本高。美國海軍研究所Donohue等人用準分子激光器的紫外輸出引發(fā)液相中的稀土元素反應，成功地分離了銪和鈰。,,氧化態(tài)的變化會引起溶解度、可萃取性或反應性的變化，再用適當?shù)幕瘜W方法就可達到分離之目的。例如，用氟化氬激光器193nm的紫外光輸出激光激發(fā)Eu3+的水溶液，可使Eu3+還原為Eu2+，再用SO42-沉淀，而鈰留在溶液之中。反應為： 在0.01mol/L的Ce稀土溶液中進行實驗，用250nm的激光照

61、射稀土溶液，就會發(fā)生光氧化反應，再用IO3-沉淀，反應為：,,,,,4,,,利用激光的方向性可實現(xiàn)顯微化學反應，這在集成電路和半導體器件的生產(chǎn)中可用于修補、掃描無掩膜光刻、歐姆接觸及局部摻雜等。,4.4 激光顯微化學反應,（a)激光化學沉積（LCVD） 化學氣相沉積(CVD)是晶體生長和薄膜生長的一種有效技術， 它是通過加熱置于氧化或還原氣氛中的基板進行氣相沉積，通常在整個基板表面上都有沉積發(fā)生。CVD特點：基板進行長時間

62、的高溫加熱，因此不能避免雜質的遷移和來自基板的自摻。 LCVD優(yōu)點：不用直接加熱整塊基板，可按照需要進行沉積?？臻g選擇性好，甚至可使薄膜生長限制在基板的任意微區(qū)上。局部可控沉積,,,激光沉積與化學氣相沉積相比具有很多優(yōu)點：(1)激光學沉積面積只有10-4 cm2，而化學氣相沉積則是數(shù)個cm2。(2) SiH4的壓力比化學氣相沉積高2-3數(shù)量級。沉積速率比化學氣相沉積快2-3數(shù)量級。,SiH4/Ar,CO2激光作用熱源,,石英片作基

63、板,1000-1200℃,硅沉積在石英片,Si-SiO2,美國南加利福尼亞大學Christensen,,,4.5 激光合成精細陶瓷粉末,,?m,美國麻省理工學院的能量及材料加工實驗室的J.Haggar等人,CO2激光器(10.6?m),SiH4和NH3混合氣體(強吸收10.6 ?m光子),,在同樣條件下也可合成SiC粉末：,?m,氮化硅是一種重要的結構陶瓷材料。它是一種超硬物質，本身具有潤滑性，并且耐磨損，為原子晶體；高溫時抗氧化。而

64、且它還能抵抗冷熱沖擊，在空氣中加熱到1000℃以上，急劇冷卻再急劇加熱，也不會碎裂。,,,激光合成精細陶瓷粉末的基本原理：1）利用了反應物對激光的強吸收性，用吸收的能量引發(fā)氣相化學反應，生成固態(tài)精細粉末。2）生成物最好對激光不吸收或很少吸收。 特點：a.反應區(qū)界限很分明，而且范圍小； b. 具有反應氣體均勻快速的加熱率； c. 具有生成物的快速冷卻率；

65、 d. 具有反應溫度的閾值； 當溫度高于這一值時，反應快速進行，均勻成核。,,綜上所述：激光在無機化學中的應用是非常廣泛的。隨著現(xiàn)代科學技術的進步和激光技術的發(fā)展，光技術一定會在無機化學中得到更廣泛的應用。,,,4.6 脈沖激光沉積鍍膜Pulse Laser-induced Deposition Films,Pulse Excimer laser所產(chǎn)生的高功率脈沖激光束聚焦作用于靶材料表面，使靶材料表面產(chǎn)生高溫及熔蝕

66、，并進一步產(chǎn)生高溫高壓等離子體（T≥104K）High Temperature and High Pressure Plasma, 這種等離子體定向Orientation局域膨脹發(fā)射并在襯底上沉積而形成薄膜。,,脈沖激光沉積鍍膜示意圖,優(yōu)點：,①易于保證鍍膜后化學計量比的穩(wěn)定②反應迅速，生長快。③定向性強、薄膜分辯率高，能實現(xiàn)微區(qū)沉積 ④生長過程中可原位引入多種氣體 ⑤易制多層膜和異質膜 ⑥易于在較低溫度下原位生長取向一致的結

67、構和外延單晶膜,Scanning electron microscopy micrographs of the deposited films revealed that PTFE grains were uniformly grown on the cotton surface with an average grain size of about 50–70 nm.,using a KrF 248 nm excimer laser,

68、The laser energy was fixed at 1 J/cm2,Pulsed laser deposition (PLD) was utilized to deposit polytetrafluoroethylene (PTFE) thin films on cellulosic cotton substrates at room temperature.,a cellulosic cotton fiber,PTFE de