Tunable Multicolor Emission in Oligo(4-hydroxyquinoline)

The results on the chemical oxidative polymerization of 4-hydroxyquinoline (HQ) are reported. The treatment of HQ with ammonium peroxydisulphate in an acidic aqueous medium afforded a conjugated quinoline oligomer (OHQ). The spectral analysis results suggested that the polymerization of HQ occurred mainly at C3 and C8 positions. The obtained oligomer exhibited an uncommon multicolor emission behavior. Although a wide range of emission colors by using various conjugated oligomer/polymers has been reported in literature many times, quinoline oligomer reported here emitted multicolor when irradiated at different wavelengths. Moreover, a linear relationship was observed between the excitation energy and emission maxima obtained (lambda(Em) = -108.82(Ex) = +819.07, R-2 = 0.986). This allows us to effectively tune the photoluminescence colors between blue and orange-red.