Cluster ion beam generation from a wetted needle emitter for organic secondary ion mass spectrometry (organic SIMS) using a protic ionic liquid, propylammonium nitrate
Cluster ion beam generation from a wetted needle emitter for organic secondary ion mass spectrometry (organic SIMS) using a protic ionic liquid, propylammonium nitrate
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使用质子离子液体、硝酸丙铵从湿针发射器产生簇离子束，用于有机二次离子质谱（有机 SIMS）
DOI：
10.1002/rcm.8256
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Naoaki Saito
中科院分区：
文献类型：
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作者：
Yukio Fujiwara ;Naoaki Saito
硝酸丙基铵（PAN, [C3H7NH3][NO3]）是一种质子离子液体，其分子结构中有一个活性质子，因此能促进质子化。此外，PAN具有高聚集性，因此易于形成大的聚集（或簇）离子。这些特征将是有机材料二次离子质谱（SIMS）中的簇离子束所需要的。这种可聚集性使我们能够在真空中通过电喷雾从沾有聚丙烯腈的针尖产生簇状离子束。基于这些原因，使用外部湿润针状发射器研究了簇离子束的产生。方法采用磨尖玻璃棒作为射针器。利用针射器对聚丙烯腈进行真空电喷涂，产生簇状离子束。用测量束流电流瞬态响应的装置研究了束流的特性。用簇束离子束作为主离子束进行了SIMS实验；精氨酸和聚乙二醇（PEG300）进行分析。结果经聚丙烯腈浸湿的针射器产生了稳定的簇状离子束。离子束由混合的簇离子组成，其大小从180到5000不等，甚至更高。簇离子束成功地产生了质子化分子[M + H]+（M表示精氨酸和聚乙二醇分子），碎片化程度相对较小。还检测了丙基铵-附着反应形成的加合离子[M + C3H7NH3]+。结论用聚丙烯腈浸湿针状发射器可以产生包含大量簇离子的簇离子束。结果表明，簇状离子束有利于分子二次离子的产生，适合作为有机SIMS中的一次离子束。
RationalePropylammonium nitrate (PAN, [C3H7NH3][NO3]), a protic ionic liquid, has an active proton in its molecular structure, so that it can promote protonation. In addition, PAN has high aggregability, so that it tends to form large aggregated (or cluster) ions. These features will be desirable for cluster ion beams in secondary ion mass spectrometry (SIMS) of organic materials. The aggregability may enable us to generate a cluster ion beam from a needle tip wetted with PAN by electrospray in vacuum. For these reasons, cluster ion beam generation was investigated using an externally wetted needle emitter.MethodsA sharpened glass rod was used as a needle emitter. PAN was electrosprayed in vacuum using the needle emitter to generate a cluster ion beam. Beam characteristics were investigated with an apparatus for measuring transient responses of a beam current. SIMS experiments were also performed using the cluster ion beam as a primary ion beam; arginine and polyethylene glycol (PEG300) were analyzed.ResultsA stable cluster ion beam was generated from the needle emitter wetted with PAN. The ion beam consisted of mixed cluster ions whosem/zranged from about 180 to 5000 or higher. The cluster ion beam successfully produced protonated molecules [M + H]+(M denotes arginine and PEG molecules) with relatively little fragmentation. Adduct ions [M + C3H7NH3]+formed by propylammonium‐attachment reaction were also detected for PEG.ConclusionsIt has been demonstrated that a needle emitter wetted with PAN can generate a cluster ion beam that includes massive cluster ions. The cluster ion beam proved to be helpful in producing molecular secondary ions and suitable for a primary ion beam in organic SIMS.