Low molecular weight two-component gels were obtained from naphthalene diimide undecanoic acid mixed with several aliphatic and aromatic diamines. The gelation properties, structural characteristics and fluorescence of these two-component gels were studied via scanning electron microscopy, X-ray diffraction and spectroscopy. Specifically, the gel containing diaminoanthraquinone (DAQ) was sensitive to nitrite anions. The absorbance and emission intensity of the gel in the visible range obviously decreased upon addition of an aqueous solution of sodium nitrite. The faded gel collapsed and changed to a sediment after detection and the organic acid could be recycled. Te NO₂⁻ detection with the gel provides a convenient method of nitrite analysis that is visible to the “naked eye”.