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Size-selecting effect of water on fluorescent silicon clusters

机译：水对荧光硅团簇的尺寸选择作用

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Silicon clusters were produced by gas aggregation in vacuum and co-deposited with water vapour onto a cold target where the water vapour froze. Melting of the ice yielded fluorescent silicon nanoparticles suspended in water which were investigated by photoluminescence spectroscopy (PL) and atomic force microscopy (AFM). The PL spectrum showed a prominent band at 420nm and other, less intense bands at shorter wavelengths. No fluorescence was observed below 275nm. The shortest wavelength observed was related to a silicon cluster diameter of 0.9nm using a simple particle-in-a-box model. Drops of the suspension were also deposited on freshly cleaved HOPG and investigated by AFM. The images showed single and agglomerated clusters with heights of typically 0.6 up to 2nm. The sizes displayed by our measurements are not correlated to the average sizes that result from gas aggregation, indicating a size-selecting effect of the water suspension. The cluster-cluster interaction in water is governed by repulsion due to thermal energy and attraction due to van der Waals forces. For very small clusters repulsion dominates; at 3nm diameter the two forces are balanced. We identify this stable phase of small clusters as the origin of exceptionally stable fluorescence
机译：硅团簇是通过真空中的气体聚集产生的，并与水蒸气共沉积到冷的靶材上，水蒸气在那里冻结。冰的融化产生悬浮在水中的荧光硅纳米颗粒，其通过光致发光光谱法（PL）和原子力显微镜（AFM）研究。 PL光谱显示在420nm处有一个显着的谱带，而在较短波长下显示了其他强度较低的谱带。在275nm以下未观察到荧光。使用简单的盒中粒子模型，观察到的最短波长与0.9nm的硅团簇直径有关。悬浮液的液滴也沉积在新鲜裂解的HOPG上，并通过AFM研究。图像显示单个簇集簇，高度通常为0.6到2nm。我们的测量结果显示的尺寸与气体聚集产生的平均尺寸无关，表明水悬浮液的尺寸选择效果。水中的团簇相互作用受热能排斥和范德华力吸引。对于很小的星团，排斥力占主导地位。直径为3nm时，两个力是平衡的。我们将小簇的稳定相识别为异常稳定的荧光的起源

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