1、第34卷第2期河南師范大學學報(自然科學版V ol.34N o.2 2006年5月J our nal of H enan N or mal Univers ity(N atur al S cienceM ay.2006文章編號:1000-2367(200602-0061-04單分子膜模板法誘導無機晶體取向生長的研究進展高書燕1,2,鄭洪河1,趙揚1,逯樂慧2,張洪杰2應用化學研究所稀土化學與物理重點實驗室,長春130022摘要:近年來,受生物體內生物礦化現象和科學家對生物體內生物礦物沉積過程的深入研究結果的啟發而產生并發展起來的單分子膜誘導晶體生長方法引起了人們的極大關注.本文評述了該領域國際

2、研究的熱點:(1系統研究單分子膜誘導晶體生長的機理,找出特殊規律以發展和完善晶體學;(2利用規律開發新型晶體材料.關鍵詞:單分子膜;模板;無機晶體;生長中圖分類號:T B383文獻標識碼:A單分子膜誘導晶體生長是在化學、物理學與生物學多門學科相互交融的基礎上發展起來的新興學科,并逐漸成為仿生合成的重要分支.近年來,單分子膜誘導晶體生長方法引起了人們的極大關注,特別是國際著名期刊Science和Nature等對此進行的大量報道1-2使該領域的研究活躍起來.與經典的晶體生長方法不同,單分子膜誘導晶體生長的方法是受生物體內生物礦化現象和科學家對生物體內生物礦物沉積過程的深入研究結果的啟發而產生并發展

3、起來的.自然界中生物礦化的實例很多,如珍珠、貝殼、蛋殼、牙齒、珊瑚、象牙、魚骨、細菌中的磁性晶體等都是在特定細胞膜分泌的有機物誘導下生成的.在這個過程中,有機物起到模板的作用來調節無機相的取向成核和生長.生成的礦物具有獨特精美的結構、尺寸、形狀、取向、紋理及精確控制的組分,因而展示出特殊的性能.例如,藻類中的硫酸鋇可作為重力接受器,魚類中的三氧化二鐵可作為生物的磁羅盤,軟體動物中的碳酸鈣可形成珍珠等.為了合成可與自然礦物相媲美的高級材料,科學家采用簡易的表面活性劑分子組裝(如LB膜來模擬生物膜.有機LB膜是兩親性分子在空氣-水界面通過水平加壓使分子緊密有序排列而形成的有序單分子膜.這些兩親性分

4、子的親水基團指向水,疏水基團則伸出水面,親水基團在水面形成一個二維單晶生長平面,在親水基團與晶相之間存在靜電吸引、結構對應和立體化學匹配等關系,從而影響基團的形狀、結構、取向和性質等,這可指導晶體擇向成核,從而誘導無機晶體的取向生長.這對晶體工程學、無機納米材料、有機復合材料和陶瓷材料的合成以及生物礦化模擬研究等在理論和應用方面都具有重要的意義.過去的研究主要集中在利用兩親性分子的LB膜作為模板誘導晶體的取向生長3-5.例如英國貝茲大學的M ann6以及南京大學的唐瑞康7各自研究了氨基酸、碳酸鈣、硫酸鋇、硫酸銅、氟化鋇和氟化鈣等晶體的結晶現象.目前研究的熱點主要集中在兩方面:(1系統研究單分子

5、膜誘導晶體生長的機理,找出特殊規律以發展和完善晶體學.(2利用規律開發新型晶體材料8-12.下面分述這兩方面的研究進展及我們已開展的工作.1單分子膜誘導無機材料生長機理的研究有機單分子膜誘導晶體生長的機理是該領域的研究熱點之一,這方面的突破有助于揭密生物礦化現象.收稿日期:2005-10-12基金項目:國家高技術發展與規劃(863項目(2002A A324080;河南省自然科學基金項目(0511022000作者簡介:高書燕(1972-,女,河南南陽人,河南師范大學講師,中國科學院長春應用化學研究所在讀博士研究生,研究方向:納米材料的結構構筑和性能研究.62河南師范大學學報(自然科學版2006年

6、各國的科研工作者為此作了大量的工作,并且取得了可喜的進展13.在超飽和溶液中,晶體成核有兩種可能:一種是在超飽和溶液中發生均相成核;另一種則是在基底表面發生異相成核.單分子膜誘導晶體成核實際上就是促進異相成核而抑制均相成核14.根據晶體成核熱力學理論15:穩定成核活化能($G n同超飽和溶液中形成固相所克服的表面能($G I以及晶粒聚集成鍵所釋放的能量($G b密切相關,3者之間的關系可表示如下:$G n=16P($G I33$G b其中$G b=kT ln S也可用經典的晶體成核理論表示如下16:對于均相成核:$G n=-RT ln S+R A異相成核:$G n=-RT ln S+R c l

7、 A c l+(R s c-R s lA s c式中k為玻爾茲曼常數;S為溶液的超飽和度;T為溫度;R為氣體常數;R為界面能;A為表面積;c、s和l 分別代表晶粒、基底和液體.由上述公式可以看出:降低表面能壘或增加溶液的超飽和度都可促進成核;如果晶粒-基底表面之間相互作用所表示的凈界面能要比晶粒-溶液的界面能低,那么異相成核優先發生.在單分子膜存在下,晶體生長的機理發生了改變,一方面膜的存在使溶液表面成核物種濃度增加;另一方面膜-成核物種之間的分子識別導致膜親水基團和成核物種之間的精確匹配.膜壓大小也對晶體成核有著顯著的影響,一般認為在高的膜壓下(小于崩潰壓成核優先發生,因為在高的膜壓下,膜是

8、緊密有序堆積的,這種堆積方式應該更利于成核發生.但也有人對此提出異議,Cooper等人17在研究不同單分子膜下天冬氨酸、天冬酰胺-水合物的成核時發現:在中等或更低的膜壓下,成核更容易發生.所以膜壓究竟以什么樣的機理影響晶體的成核這個問題還需要進一步去考證.膜的相態也是影響晶體成核的一個重要因素.如南京大學的唐瑞康等人7對硫酸銅五水化合物晶體在不同單分子膜下的成核情況作了研究,他們發現:LB膜誘導晶體成核的能力并非都在氣態或液態條件下為最佳,有的(如9-hexadecykununo-4、5-diazafluo rene的LB膜卻在固-液態下表現出良好的誘導成核能力,這可能與膜-晶體之間的協同效應

9、有關.此外,膜的微觀結構決定了晶體成核的特性.近幾年研究顯示,改變膜表面可以達到控制晶體的成核形態、增長特性、取向甚至手性等目的6.2利用單分子膜制備無機材料近年來,隨著有序分子膜研究的不斷深入,利用單分子膜有序模板效應在膜中生長無機晶體已成為當前有序分子膜研究中非常活躍的新領域.單分子膜不僅具有特殊的物理-光學性質,而且膜界面具有局域化學控制和有序模板效應,因而可以誘導晶體定向生長,這就為晶體生長和化學反應提供了一種特殊媒介,并可在膜層間合成納米粒子,它們表現出增強的長程有序性和各向異性.利用單分子膜制備無機材料的方法大致可分為3類:第一類是利用成膜分子與已制得的無機材料之間靜電相互作用,通

10、過夾帶制其單分子膜,或者利用成膜分子與成核離子之間的靜電相互作用,將其轉移到固體基底上,然后將所得的單分子膜利用溶劑溶解或在程控烘箱中加熱除去有機部分則得到比較均勻的無機物薄膜.第二類是利用單分子膜作為模板來誘導無機材料的生成.第3類是把單分子膜層間作為納米空間反應器,通過氣相和液相擴散,在層間反應生成無機納米材料.2.1利用成膜分子與成核離子(或已制得的無機材料之間的靜電相互作用制其單層膜將花生酸氯仿溶液鋪展在510-5mol/L氯化鐵的亞相上,調節pH值為3.9,膜壓保持在30mN/m,以0.52mm/min的沉積速率可把花生酸鐵LB膜多層沉積到覆蓋有SiO2的硅片上.將所得到的LB膜在程

11、控烘箱中加熱到300e,保持30min,然后在3045m in內冷卻到室溫即得到均勻的氧化鐵薄膜18. Amm等人19將花生酸的氯仿溶液鋪展在YCl3(110-5mo l/L的亞相上(用NH4OH溶液調節pH為8.0,在疏水的N-型硅片上,以膜壓25mN/m、沉積速率1050mm/min的條件,沉積得到了轉移比達0.91.0的高質量Y-型花生酸釔LB膜.將所得到的花生酸釔LB膜于空氣中以10e/m in的速率加熱. 250e前無明顯的變化,溫度達250e時,膜的厚度開始很快變薄.在250350e之間,單分子膜的有機部分被除去.掃描電子顯微鏡顯示所得到的Y 2O 3膜完全均勻.最近,T alap

12、atr a 小組利用單分子LB 膜技術,將帶正電荷的銀納米粒子組裝到帶負電荷的十八酸單分子膜上,成功地實現了納米粒子的組裝10.2.2 單層膜誘導無機材料的生長和單分子膜層間反應制備無機材料Fendler 等人20以Pb(NO 32溶液為亞相,在上面鋪展二十烷基羧酸單分子膜,在一定表面壓下通入H 2S 氣體,得到(111取向的三角形PbS 晶體.此外還發現:當亞相條件不同時會得到不同類型的半導體.以Pb(NO 32溶液為亞相,在上面鋪展花生酸單分子膜,在一定表面壓下通入H 2S 氣體,得到n 型PbS 半導體;當亞相同時含有Pb(NO 32和硫脲時通入氨氣,在花生酸單分子膜下則得到了p 型的P

13、bS 半導體21.徐如人等人22采用單分子膜輔助電化學方法制備了CdS 納米晶體.他們將單分子膜覆蓋在金電極上,然后將其插入按一定比例混合的CdSO 4、Na 2S 2O 3等溶液中去,再插入另一鉑電極,將兩電極接在恒電位器上,一段時間后,在LB 膜表面便沉積一層均勻的CdS 薄膜.實驗分析發現,CdS 薄膜的類型可以通過改變單分子膜來控制,這對類似半導體納米材料的生長具有一定意義.最近,Golan 小組將聚丁二炔單分子膜置于空氣-硝酸銀界面處,而后通入H 2S 氣體制得了Ag 2S 納米晶體12.3 本實驗室已開展的相關工作由上述可見,利用有組織的有機分子作為模板誘導晶體取向生長已成為材料科

14、學的一個新的研究熱點.目前在該領域研究得較多的是無機氧化物和半導體材料,而鈣鈦礦結構的AM nF 3(A=NH 4,Na,K 、M g晶體具有有趣的結構、獨特的磁、壓電和發光性質,其特殊的物理化學性質激發起人們對其結構、形貌和取向隨意調控的需求,基于此,我們小組在有機膜模板下實現了它們的可控生長3-5,23.在室溫條件下,通過優化實驗條件以二十二烷基羧酸的有機單分子膜為模板制備了高質量的(100取向的立方三氟錳化銨和三氟錳化鉀以及(101取向的三氟錳化鈉無機晶體,探討了溶液種類、濃度、pH 值和M n:F 配比對所得到的晶體結構、形貌、取向和質量的影響.并且基于實驗結果和以前的研究對于3種不同

15、的晶體在單分子膜模板下的生長機理進行了討論.4 展 望以前的研究結果表明,單層膜的存在在一定程度上降低了表面能壘,在膜-水界面這一特殊的區域物理化學環境、幾何空間的限制及有限的反應質點下,可以很容易地制得所需大小和形態的無機材料.在該領域中,圖案化單分子膜在晶體取向生長的作用和應用以及手性有機分子形成的單分子膜在模擬手性礦物材料取向生長的應用研究這兩個方向存留很大的空間,有望成為該領域研究的主要發展方向.參 考 文 獻1Ber man A,A hn D J,L io A ,et a l.T o tal alignment of calcite at acidic po ly diacety l

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26、測題(時間:120分鐘滿分:150分第一部分聽力(共30分略第二部分英語知識運用(共兩節,滿分45分第一節單項填空(共15小題;每小題1分,滿分15分21.Do you know anything about that newly-opened hotel?It's _ five-star one and it is well-known for _ service it offers.A.a; theB.the; aC.a; /D.the; the22.I am sorry I broke the glass.Oh, _. It wasn't expensive.A.I

27、9;d rather you didn'tB.I'm afraid notC.that's all rightD.Don't mention it23.The fact is that they have _ evidence to prove you are guilty.24._in his work, he forgot to have lunch as well as breakfast.B.To buryD.Having buried25.It is said that only a few people have _ to information a

28、bout the case.26.I would like the project you are in charge of _ by the end of this month.A.being finishedB.to be finishedC.having finished27.He was not very well off, but he managed to _ something to the people in the earthquake-hit area.28.They will be finethey just need time to _their new surroun

29、dings.A.adjust toB.meet withC.test outD.participate in29.He was very active in the discussion yesterday, _ was a rare thing for him to do.30.After many years away, he finally returned to his hometown. _, one misses one's home when one is old.A.After allD.In addition31.After getting off the train

30、 in Beijing, he first went to look for _.32._ let his parents down again, he decided to do all he could _ harder and get better grades.A.In order to; studyB.In order not to; to studyC.So as to; to studyD.So as not to; study33.Jimmy liked_ to the beach for a holiday, which his parents usually did twi

31、ce a year.B.having been takenC.to be takingD.to be taken34.He _ a certain amount of time to exercise every day, from which he benefited a lot.A.set asideB.turned aroundC.reflected onD.kept up35.After we finish this task I wonder what is _next.A.to doB.to be doingC.to be doneD.to have done第二節完形填空(共20

32、小題;每小題1.5分,滿分30分My mother always amazes me. Whenever I have a question about something, I give her a call and she almost always has a(n 36 . My mother is my“Google”. She is nearly 70, but I find myself 37 her for advice more than I do on my favorite search engine.I 38 my mother every day, sometimes

33、just to chat, and sometimes to learn something new. For example, I called her one day to ask if I could 39 her food dehydrator(脫水器 to dehydrate some carrots for my daughter's pet pig.She 40 me she had got rid of the dehydraor years before, but that I could dehydrate the carrots 41 with my microw

34、ave(微波爐. She was right!There have also been 42 moments when I've called her about one of the kids being 43 . And she always offers me some 44 advice to make them feel better.My mother has been a mother for 45 years now. When you 45 the amount of knowledge she has gathered along the way, it's

35、 no 46 that she has the answers so frequently.When you 47 a job, you learn a specific set of skills. When you're mother, you 48 a little about almost everything. Think about how much mothers“dabble”(涉足 in 49 professions. Most 50 have learnt a thing or two about how to be: a(n 51 (constructing th

36、e most confusing toys, chef(廚師( 52 all kinds of food, artist (drawing with the kids, and so on. Of course, we, as mothers, aren't as knowledge as a library, 53 our great day to day experience makes up for that.I have been a mother for about 10 years. I can honestly say I have 54 an “expert” in c

37、ertain areas. And I have already been able to 55 some of this knowledge with others. If I keep going at this pace, maybe I can hope to be“Google”for my kids some day too.37.A.turning to B.making upC.insisting onD.looking into45.A.talk about B.worry aboutC.think aboutD.care about第三部分閱讀理解(共20小題;每小題2分,

38、滿分40分第一節(共15小題;每小題2分,滿分30分AAs a middle-school student in the 1980s, Lee Buono stayed after school one day to remove the brain and spinal cord (脊髓 from a frog. He did such a good job with the frog that his science teacher told him he might be a doctor some day.That is exactly what Buono did. Years la

39、ter, a patient with a tumor (腫瘤came to see Buono. The tumor was benign (良性的, but it interfered with the patient's speech. “He could get some words out,” Buono recalls. “But it was hard to understand them.”“I was talking to his wife, and I told his family I would try to help him,” he continues. “

40、They started asking me about myself.” They asked Buono who had inspired him to become a doctor, and he told them about his old teacher, Al Siedlecki, back at Medford Memorial Middle School in Medford, Nes Jersey.The operation was a success. The patient could speak freely again. He was excited and ha

41、ppy and crying and wanted to just hug Buono. “Call your teacher,” the patient said. “Make sure you thank him.”So Buono did. “I picked the phone up and heard, Hey, it's Lee Buono,” Siedlecki says to his former student. “Lee, what's going on? I haven't heard from you since you graduated,”

42、he said.“I want to thank you,” Buono replied.“I was very surprised,” Siedlecki says. “I said, Of all the people in your entire career, you want to thank me?Actually it was the same feeling I had when. when my kids were born. I started to cry. It made me feel really important that I had that influenc

43、e on you.”Lately, Siedlecki admits, “I am almost afraid to say that I'm a teacher to some people.”“Not any more,” he tells Buono, “because you called me. I'm a teacher, and I'm going to help as many people as I can to find their passion, too.”56.What made Buono become a doctor?A.The expe

44、rience of working on the frog.B.His science teacher' s encouragement.C.His conversation with the patient with a tumor.D.The success of the operation on a patient with a tumor.57.What can we learn about the patient from the text?A.He couldn't speak before the treatment.B.He knew Buono's t

45、eacher very well.C.He was crying due to the pain of his illness.D.He hoped Buono would thank his teacher.58.Why did Buono's teacher cry when Buono called him?A.He was moved by Buono's thanks.B.His children were born at that time.C.He was afraid to admit he was a teacher.D.He hadn't had a

46、 call for a long time.59.What is the text mainly about?A.How to become a good teacher.B.How to become a good doctor.C.How Buono did a good job in an operation.D.How Buono thanked the teacher who inspired him.BA friend asks you to be a volunteer. Your husband asks you to glance over an e-mail he is w

47、riting to his boss. You say you'd love to. Really! But. “I don' t have time.”It seems plausible(有道理的. We're all busy these days, right? But there are reasons not to use these four words, at least with yourself.Here's the big one: it is not true. You tell yourself “I don't have ti

48、me” to exercise, but we all have 168 hours a week. If someone offered to pay you $100,000 a week to go to the gym for 5 of those 168 hours, you would probably find the time to do it. Since that isn't going to happen, this is a more accurate statement:“It's not a priority(優先處理的事.”There are a

49、million things we could be doing with our time; some are priorities and some are not, even if it's wrong to say so. Try it. “I'm not going to read to you tonight, sweetie, because it's not a priority. Daddy's priority is to check his e-mails.”Using the words “I don't have time” k

50、eeps us from admitting to the fact that how we spend our time is a choice. It puts the responsibility for our lives on someone else: a boss, a client or a family member.Better to be truthful:“I have another volunteer job on which I am focusing my energy right now. It is the cause that is most import

51、ant to me.” Or, to your husband “I wish you had mentioned this earlier. Right now, my priority is to get our children dressed and out of the door for school. I will be available around lunch time if you would like talk.”60.What does the word “it” in the third paragraph refer to?A.Saying “I don't

52、 have time.”B.Saying “We are all busy today.”C.Checking your husband's e-mail.D.Telling your friend you won't volunteer.61.From the third paragraph we can learn that _.A.it is enough to exercise for five hours a weekB.we are too busy to exercise these daysC.we can earn $100,000 a week by exe

53、rcisingD.we don't often regard exercise as priority62.Which would be the best answer if your friend asks you to be a volunteer?A.I have to check my e-mails first.B.I already have a volunteer job that I enjoy.C.I cannot find any time to do it.D.I have a million things to do.63.What is the text ma

54、inly about?A.How to be responsible for our lives.B.How to get time to do exercise.C.How to say no to others without saying “I don't have time.”D.How we should spend our time reasonably these days.CWalking is good for people. In his book, The Lost Art of Walking, Geoff Nicholoson praises the bene

55、fits of walking and studies how and why we walk. Besides providing physical, psychological and social benefits, this simple, free activity can change your life, he suggests. From a health perspective(角度, walking is the key to managing weight, controlling blood pressure and reducing the risk of a str

56、oke, breast cancer, diabetes and many other health problems. A daily walk lengthens your life, decreases the risk of depression(沮喪 and improves your mood and sense of well-being. According to Beth Israel Medical Centre, walking lowers total cholesterol(膽固醇 and increases high-density, lipoproteins, o

57、r the “good cholesterol”.From a psychological viewpoint, walking offers an opportunity to clear one's thoughts, solve problems and reduce stress. If you set a rhythm that is relaxing and peaceful, walking can also become a form of meditation(沉思. Walking regularly with someone else enables a frie

58、ndship to blossom as the pair of you exercise. My husband and I enjoy our regular walk “dates”and use the time to discuss issues without being bothered.Also, the best way to explore some of the world's great citiessuch as New York, London, Paris and Romeis on foot. Walking stimulates(刺激 the senses and lets you enjoy a rich engageme