美國德隆公司所開發(fā)的LVEM5 和LVEM25 便是專門針對(duì)低電壓所開發(fā)的透射電鏡，如圖1所示。這種設(shè)備只需要很少的空間和資源就將其他成像模式，如掃描電子顯微鏡( SEM )、掃描透射電子顯微鏡( STEM )或電子衍射( ED )結(jié)合在一個(gè)設(shè)備中。另外，所使用的肖特基場(chǎng)發(fā)射槍與低電壓電子加速相結(jié)合，對(duì)于有機(jī)物來說又十分的友善。能夠很好地避免重金染色屬對(duì)組織、蛋白、基因、藥物、聚合物等有機(jī)物的污染和損害，同時(shí)保持合理的分辨率（<2 nm）。而這一點(diǎn)在許多文獻(xiàn)的報(bào)道中也均有體現(xiàn)，如圖2a-c所示，而即使5-10 nm的微小金顆粒在使用LVEM5時(shí)也能夠被順利的觀測(cè)，如圖2d所示。那么究竟低壓透射電鏡和傳統(tǒng)大電鏡相比有多大區(qū)別這個(gè)問題，今年C. Dazon等發(fā)表文獻(xiàn)就此問題進(jìn)行了專門的對(duì)比，如圖3所示。他們將幾種典型納米顆粒分別使用LVEM5（5 kV）和CM200（200 kV）進(jìn)行拍照并比較認(rèn)為兩者的圖像質(zhì)量并無明顯差別。

 

Claudel Mickael等使用LVEM5對(duì)CDs與bPEI600衍生物的納米TEM結(jié)構(gòu)表征。

 

 

Claudia Melissa等對(duì)冰川假單胞菌BNF20的形態(tài)使用LVEM5 SEM模式進(jìn)行觀測(cè)的圖像。

 

Adolfo Marican等使用LVEM5對(duì)環(huán)糊精衍生物凝膠CDHSA1（a-b）

和包裹有PDN（c-d）的CDHSA1進(jìn)行SEM圖像表征。

 

 

Hadi Ranji-Burachaloo等使用LVEM5拍攝TEM模式下的
有機(jī)聚合材料MOF（a）和rMOF（b）的納米結(jié)構(gòu)圖像。

 

總結(jié)

     低壓透射電鏡具有體積小、易操作、高襯度、良好的成像質(zhì)量等特性。在近幾年中，使用這種電鏡進(jìn)行結(jié)構(gòu)表征的文章也越來越多。相信隨著生物分子機(jī)制研究的深入和納米材料、藥物的發(fā)展，這種小巧而靈活的低壓透射電鏡將會(huì)有更加寬廣的應(yīng)用前景。


參考文獻(xiàn)

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