This Article describes the preparation of carbohydrate microarrays by the immobilization of carbohydrates via microcontact printing (microCP) on glass and silicon substrates. To this end, diene-modified carbohydrates (galactose, glucose, mannose, lactose, and maltose) were printed on maleimide-terminated self-assembled monolayers (SAMs). A Diels-Alder reaction occurred exclusively in the contact area between stamp and substrate and resulted in a carbohydrate pattern on the substrate. It was found that cyclopentadiene-functionalized carbohydrates could be printed within minutes at room temperature, whereas furan-functionalized carbohydrates required long printing times and high temperatures. By successive printing, microstructured arrays of up to three different carbohydrates could be produced. Immobilization and patterning of the carbohydrates on the surfaces was investigated with contact angle measurements, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and fluorescence microscopy. Furthermore, the lectins concanavalin A (ConA) and peanut agglutinin (PNA) bind to the microarrays, and the printed carbohydrates retain their characteristic selectivity toward these proteins.

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A model alkane molecule, triacontane, is used to assess the effects of condensed gold and silver nanoparticles on the molecular ion yields upon atomic (Ga(+) and In(+)) and polyatomic (C60(+) and Bi3(+)) ion bombardment in metal-assisted secondary ion mass spectrometry (MetA-SIMS). Molecular films spin-coated on silicon were metallized using a sputter-coater system, in order to deposit controlled quantities of gold and silver on the surface (from 0 to 15 nm equivalent thickness). The effects of gold and silver islets condensed on triacontane are also compared to the situation of thin triacontane overlayers on metallic substrates (gold and silver). The results focus primarily on the measured yields of quasi-molecular ions, such as (M - H)(+) and (2M - 2H)(+), and metal-cationized molecules, such as (M + Au)(+) and (M + Ag)(+), as a function of the quantity of metal on the surface. They confirm the absence of a simple rule to explain the secondary ion yield improvement in MetA-SIMS. The behavior is strongly dependent on the specific projectile/metal couple used for the experiment. Under atomic bombardment (Ga(+), In(+)), the characteristic ion yields an increase with the gold dose up to approximately 6 nm equivalent thickness. The yield enhancement factor between gold-metallized and pristine samples can be as large as approximately 70 (for (M - H)(+) under Ga(+) bombardment; 10 nm of Au). In contrast, with cluster projectiles such as Bi3(+) and C60(+), the presence of gold and silver leads to a dramatic molecular ion yield decrease. Cluster projectiles prove to be beneficial for triacontane overlayers spin-coated on silicon or metal substrates (Au, Ag) but not in the situation of MetA-SIMS. The fundamental difference of behavior between atomic and cluster primary ions is tentatively explained by arguments involving the different energy deposition mechanisms of these projectiles. Our results also show that Au and Ag nanoparticles do not induce the same behavior in MetA-SIMS of triacontane. The microstructures of the metallized layers are also different. While metallic substrates provide higher yields than metal islet overlayers in the case of silver, whatever the projectile used, the situation is reversed with gold.

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