表面效應

表(biao)(biao)(biao)面(mian)(mian)(mian)效應(ying)是指納(na)米微粒(li)表(biao)(biao)(biao)面(mian)(mian)(mian)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)與總原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)數(shu)之比，隨粒(li)徑(jing)的(de)(de)變(bian)(bian)小(xiao)而(er)急(ji)劇增(zeng)(zeng)大(da)后(hou)引起性(xing)質上的(de)(de)變(bian)(bian)化(hua)。納(na)米材(cai)料(liao)的(de)(de)顆粒(li)尺寸小(xiao)，位(wei)于表(biao)(biao)(biao)面(mian)(mian)(mian)的(de)(de)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)所(suo)占的(de)(de)體積(ji)分數(shu)很大(da)，產生相當大(da)的(de)(de)表(biao)(biao)(biao)面(mian)(mian)(mian)能。隨著(zhu)納(na)米粒(li)尺寸的(de)(de)減(jian)小(xiao)，比表(biao)(biao)(biao)面(mian)(mian)(mian)積(ji)急(ji)劇加大(da)，表(biao)(biao)(biao)面(mian)(mian)(mian)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)數(shu)及(ji)比例迅速增(zeng)(zeng)大(da)。由于表(biao)(biao)(biao)面(mian)(mian)(mian)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)數(shu)增(zeng)(zeng)多(duo)，比表(biao)(biao)(biao)面(mian)(mian)(mian)積(ji)大(da)，使得表(biao)(biao)(biao)面(mian)(mian)(mian)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)處于“裸露”狀態。周圍缺(que)少(shao)相鄰(lin)的(de)(de)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi),原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)配位(wei)數(shu)不(bu)足，存在(zai)未(wei)飽和(he)鍵，導致了納(na)米顆粒(li)表(biao)(biao)(biao)面(mian)(mian)(mian)存在(zai)許多(duo)缺(que)陷，使這(zhe)(zhe)些表(biao)(biao)(biao)面(mian)(mian)(mian)具有很高的(de)(de)活性(xing)，特別容(rong)易吸附其(qi)他原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)或與其(qi)他原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)發生化(hua)學反應(ying)。這(zhe)(zhe)種表(biao)(biao)(biao)面(mian)(mian)(mian)原(yuan)(yuan)子(zi)(zi)(zi)(zi)(zi)(zi)的(de)(de)活性(xing)不(bu)但引起納(na)米粒(li)子(zi)(zi)(zi)(zi)(zi)(zi)表(biao)(biao)(biao)面(mian)(mian)(mian)輸(shu)運和(he)構(gou)型的(de)(de)變(bian)(bian)化(hua)，同時(shi)也引起表(biao)(biao)(biao)面(mian)(mian)(mian)電子(zi)(zi)(zi)(zi)(zi)(zi)自(zi)旋、構(gou)象(xiang)、電子(zi)(zi)(zi)(zi)(zi)(zi)能譜的(de)(de)變(bian)(bian)化(hua)。它是納(na)米粒(li)子(zi)(zi)(zi)(zi)(zi)(zi)及(ji)其(qi)固體材(cai)料(liao)的(de)(de)*重要(yao)的(de)(de)效應(ying)之一。

小尺寸效應

隨著顆(ke)(ke)粒(li)(li)尺(chi)(chi)(chi)(chi)寸的(de)(de)量(liang)變(bian)(bian)，在(zai)一定(ding)條件(jian)下(xia)會引起(qi)(qi)顆(ke)(ke)粒(li)(li)性(xing)(xing)質(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)質(zhi)(zhi)(zhi)(zhi)(zhi)變(bian)(bian)。由于(yu)(yu)(yu)顆(ke)(ke)粒(li)(li)尺(chi)(chi)(chi)(chi)寸變(bian)(bian)小所(suo)引起(qi)(qi)的(de)(de)宏(hong)(hong)(hong)觀(guan)物(wu)(wu)(wu)理性(xing)(xing)質(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)變(bian)(bian)化稱為(wei)小尺(chi)(chi)(chi)(chi)寸效(xiao)應(ying)(ying)。對超微(wei)(wei)顆(ke)(ke)粒(li)(li)而(er)(er)言，尺(chi)(chi)(chi)(chi)寸變(bian)(bian)小，同時其比表(biao)面(mian)(mian)積亦顯(xian)著增加(jia)，從而(er)(er)產生如下(xia)一系列新(xin)奇的(de)(de)性(xing)(xing)質(zhi)(zhi)(zhi)(zhi)(zhi)。當超細微(wei)(wei)粒(li)(li)的(de)(de)尺(chi)(chi)(chi)(chi)寸與(yu)光波(bo)波(bo)長、德布(bu)羅意波(bo)長以及超導態的(de)(de)相干長度或透射深度等(deng)物(wu)(wu)(wu)理特征尺(chi)(chi)(chi)(chi)寸相當或更小時，晶(jing)體的(de)(de)周(zhou)期(qi)性(xing)(xing)的(de)(de)邊界條件(jian)將被(bei)破壞；在(zai)非(fei)晶(jing)態納(na)米微(wei)(wei)粒(li)(li)的(de)(de)顆(ke)(ke)粒(li)(li)表(biao)面(mian)(mian)層(ceng)附近(jin)原子(zi)(zi)(zi)密度減少(shao), 磁性(xing)(xing)、內壓、光吸收、熱(re)阻(zu)、化學活性(xing)(xing)、催化性(xing)(xing)及熔點(dian)等(deng)與(yu)普通(tong)粒(li)(li)子(zi)(zi)(zi)相比都有很大變(bian)(bian)化, 這(zhe)(zhe)就是納(na)米粒(li)(li)子(zi)(zi)(zi)的(de)(de)小尺(chi)(chi)(chi)(chi)寸效(xiao)應(ying)(ying)。納(na)米材(cai)料(liao)之所(suo)以具(ju)有這(zhe)(zhe)些(xie)奇特的(de)(de)宏(hong)(hong)(hong)觀(guan)結構特征, 是由于(yu)(yu)(yu)在(zai)納(na)米層(ceng)次上, 物(wu)(wu)(wu)質(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)尺(chi)(chi)(chi)(chi)寸不大不小, 所(suo)包含的(de)(de)原子(zi)(zi)(zi)、分子(zi)(zi)(zi)數不多不少(shao), 其運動速度不快不慢。而(er)(er)決定(ding)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)(zhi)(zhi)性(xing)(xing)質(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)正是這(zhe)(zhe)個層(ceng)次的(de)(de)由有限分子(zi)(zi)(zi)組裝起(qi)(qi)來的(de)(de)集合體, 而(er)(er)不再是傳統觀(guan)念上的(de)(de)材(cai)料(liao)性(xing)(xing)質(zhi)(zhi)(zhi)(zhi)(zhi)直(zhi)接(jie)決定(ding)于(yu)(yu)(yu)原子(zi)(zi)(zi)和分子(zi)(zi)(zi)。介于(yu)(yu)(yu)物(wu)(wu)(wu)質(zhi)(zhi)(zhi)(zhi)(zhi)的(de)(de)宏(hong)(hong)(hong)觀(guan)結構與(yu)微(wei)(wei)觀(guan)原子(zi)(zi)(zi)、分子(zi)(zi)(zi)結構之間的(de)(de)層(ceng)次(即小尺(chi)(chi)(chi)(chi)寸效(xiao)應(ying)(ying))對材(cai)料(liao)的(de)(de)物(wu)(wu)(wu)性(xing)(xing)起(qi)(qi)著決定(ding)性(xing)(xing)作用。

量子尺寸效應

當(dang)粒(li)子(zi)尺寸下降到某一值(zhi)時, 金屬費米能(neng)(neng)(neng)(neng)(neng)(neng)級附(fu)近的(de)電(dian)子(zi)能(neng)(neng)(neng)(neng)(neng)(neng)級由準(zhun)連續(xu)變為(wei)離散能(neng)(neng)(neng)(neng)(neng)(neng)級的(de)現(xian)(xian)象，納米半導體微粒(li)存在不(bu)連續(xu)的(de)*被(bei)占分(fen)子(zi)軌(gui)道和*低未被(bei)占分(fen)子(zi)軌(gui)道能(neng)(neng)(neng)(neng)(neng)(neng)級，能(neng)(neng)(neng)(neng)(neng)(neng)隙變寬的(de)現(xian)(xian)象均稱為(wei)量子(zi)尺寸效(xiao)應(ying)。當(dang)能(neng)(neng)(neng)(neng)(neng)(neng)級間距大于(yu)熱(re)(re)能(neng)(neng)(neng)(neng)(neng)(neng)、磁(ci)能(neng)(neng)(neng)(neng)(neng)(neng)、光(guang)子(zi)能(neng)(neng)(neng)(neng)(neng)(neng)量或超(chao)導態的(de)凝聚能(neng)(neng)(neng)(neng)(neng)(neng)時，則引起(qi)能(neng)(neng)(neng)(neng)(neng)(neng)級改變、能(neng)(neng)(neng)(neng)(neng)(neng)隙變寬, 使粒(li)子(zi)的(de)發射能(neng)(neng)(neng)(neng)(neng)(neng)量增加，光(guang)學(xue)吸收(shou)向(xiang)短(duan)波方(fang)向(xiang)移動，直觀(guan)上表現(xian)(xian)為(wei)樣(yang)品顏色(se)的(de)變化(hua)，這(zhe)些(xie)必導致納米晶體材料的(de)光(guang)、熱(re)(re)、磁(ci)、聲、電(dian)等與常規材料有顯(xian)著的(de)不(bu)同，如(ru)特(te)異的(de)光(guang)催化(hua)、較高的(de)非線性光(guang)學(xue)效(xiao)應(ying)等。

量子隧道效應

量(liang)(liang)子(zi)(zi)(zi)隧道效應是從量(liang)(liang)子(zi)(zi)(zi)力(li)(li)學(xue)的粒子(zi)(zi)(zi)具有(you)波(bo)粒二(er)象(xiang)性的觀點出發，解釋(shi)粒子(zi)(zi)(zi)能(neng)夠穿(chuan)越比總(zong)能(neng)量(liang)(liang)高的勢壘，這是一種微觀現象(xiang)。微觀粒子(zi)(zi)(zi)具有(you)貫穿(chuan)勢壘的能(neng)力(li)(li)稱為隧道效應。