An optically improved fluid filter for localization and microscopic imaging was prepared by electroless deposition of nickel-boron (Ni-B) nanoparticle structures in the approximately 0.2 um channel walls of alumina-based Anopore(TM) fluid filter membranes. The relatively simple, two-step membrane modification process of Pd catalyst addition followed by aqueous Ni-B deposition increases filter optical absorption by more than three orders of magnitude. The resulting black membrane retains its original flow properties but has approximately 98% less autofluorescence compared with the unmodified membrane (dark field illuminated at 488 nm) and has a significant reduction in fluorescence signal from non-specifically bound species. (C) 2004 Elsevier B.V. All rights reserved.