SURFACE MASS-SPECTROMETRY - APPLICATION TO BIOSENSOR CHARACTERIZATION

In order to allow a detailed control and specific tailoring of interfa ces a surface analytical tool is required that localizes, identifies, and quantifies the molecular structures of interest. Surface mass spec trometry techniques (secondary ion mass spectrometry (SIMS) and laser postionization of sputtered neutrals (SNMS) as well as matrix assisted laser desorption (MALDI)) are such analytical tools. SIMS is the meth od of choice for a detailed characterization of the uppermost monolaye r. With time-of-flight analysers (TOF-SIMS) elements as well as molecu les up to 15,000 u can be identified with a sensitivity down to the pp b and fmol range, respectively. Larger molecules can be investigated b y their characteristic fragments in so called fingerprint spectra. By rastering the ion beam across the surface ion images with a lateral re solution of <100 nm (elements) and about 1 mu m (molecules) can be obt ained. The additional use of lasers for the postionization of sputtere d neutrals (laser-SNMS) allows the quanitification of the results. By means of MALDI molecules up to several 100,000 u can be desorbed witho ut fragmentation. In particular, proteins, saccharides and polymer mol ecules can uniquely be analyzed by this technique.