Characterization of laser-ablated and chemically reduced silver colloids in aqueous solution by UV/VIS spectroscopy and STM/SEM microscopy |
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Authors: | R Brause H Möltgen K Kleinermanns |
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Institution: | Institut für Physikalische Chemie und Elektrochemie I, Heinrich-Heine-Universit?t Düsseldorf, 40225 Düsseldorf, Germany, DE
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Abstract: | Silver colloids in aqueous solution were studied by different scanning microscopy techniques and UV/VIS spectroscopy. The
silver colloids were produced either by chemical reduction or by nanosecond laser ablation from a solid silver foil in water.
Variation of laser power and ablation time leads to solutions of metal clusters of different sizes in water. We characterized
the electronic absorption of the clusters by UV/VIS spectroscopy. STM (scanning tunneling microscope) imaging of the metal
colloids shows atomic resolution of rod- or tenon-like silver clusters up to 10-nm length formed by laser ablation. Our scanning
electron microscope measurements, however, show that much larger silver colloids up to 5-μm length are also formed, which
are not visible in the STM due to their roughness. We correlate them with the long-wavelength tail of the multimodal UV/VIS
spectrum. The silver colloids obtained by chemical reduction are generally larger and their electronic spectra are red-shifted
compared to the laser-ablated clusters. Irradiation of the colloid solution with nanosecond laser pulses of appropriate fluence
at 532 nm and 355 nm initially reduced the colloid size. Longer irradiation at 355 nm, however, leads to the formation of
larger colloids again. There seems to be a critical lower particle size, where silver clusters in aqueous solution become
unstable and start to coagulate.
Received: 24 June 2002 / Revised version: 25 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"This work is part of the thesis of H. M?ltgen
RID="**"
ID="**"Corresponding author. Fax: +49-211/811-5195, E-mail: kleinermanns@uni-duesseldorf.de |
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Keywords: | PACS: 82 70 Dd 82 80 Ch 61 16 Ch |
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