NOVELTY - Forming a metal-polyaniline (PANI) composite (C1) involves contacting a metal ion solution with a PANI porous asymmetric membrane, where the PANI porous asymmetric membrane is doped with an acidic dopant and the metal ion as its salt form having a reduction potential greater than that of the polyaniline, for a sufficient time to deposit the metal onto at least one surface of the membrane.    USE - For forming metal-polyaniline composite useful for catalyzing a hydrogenation reaction to obtain a hydrogenated product, and carrying out surface-enhanced Raman spectral analysis of an analyte (claimed). Also used in the selective hydrogenation of alkenes and alkynes, in surface processing, catalysis, in fuel cells or other chemical reactions, as modified surface electrodes, for anticorrosion and for biosensors.    ADVANTAGE - The method provides metal-PANI composite which is easily recoverable and reusable catalytic media for hydrogenation reactions; provides good catalytic activity to various organic reactions especially toward hydrogenation reactions. The metal is stably fixed to the PANI membrane, which can be easily recycled and reused where typical commercially available metal catalysts e.g. Pd on C can only be used once. The composite is prepared by electrodeless process. The metal of the composite have nanoscale structural features.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) catalyzing a hydrogenation reaction to obtain a hydrogenated product involving reacting an unsaturated organic compound with hydrogen in the presence of a metal-PANI composite (C1), where the PANI is a porous asymmetric membrane doped with an acidic dopant, and the metal is selected from platinum, and/or palladium; and recovering a hydrogenated product;    (2) a method of carrying out surface-enhanced Raman spectral analysis of an analyte involving providing metal-PANI composite (C1), where the metal is either silver or gold; bringing an analyte into effective contact with the composite (C1); illuminating the composite (C1) with radiation of at least one wavelength for causing elemental-state particles to produce a plasmon field and for causing the plasmon field to interact with molecules of the analyte in such a manner, such that to produce Raman photons; and collecting scatted radiation emitted from the composite (C1) for spectral analysis.