  A preconcentrating surface-enhanced Raman scattering (SERS) sensor for the
analysis of liquid-soaked tissue, tiny liquid droplets and thin liquid films
without the necessity to collect the analyte is reported. The SERS sensor is
based on a blockcopolymer membrane containing a spongy-continuous pore system.
The sensor's upper side is an array of porous nanorods having tips
functionalized with Au nanoparticles. Capillarity in combination with
directional evaporation drives the analyte solution in contact with the flat
yet nanoporous underside of the SERS sensor through the continuous nanopore
system toward the nanorod tips where non-volatile components of the analyte
solution precipitate at the Au nanoparticles. The nanorod architecture
increases the sensor surface in the detection volume and facilitates analyte
preconcentration driven by directional solvent evaporation. The model analyte
5,5'-dithiobis(2-nitrobenzoic acid) can be detected in a 1 x 10-3 m solution
about 300 ms after the sensor is brought into contact with the solution.
Moreover, a sensitivity of 0.1 ppm for the detection of the dissolved model
analyte is achieved.
