Organic dyes show strong absorption bands in UV-visible spectral region. In organicdyes, excited electrons generated by an incident radiation return to the initial groundstates without emitting any light. On the other hand, rare earth metal ions displayphotoluminescence when their electrons are excited, though their quantum efficiencies arerather small. Interestingly, it we could hybridize organic dyes with rare metal ions thenthe photoluminescent intensity will be significantly enhanced, in which the energygenerated by the photoexcitation of a dye will be transferred to the rare metal ion.Furthermore, if we could introduce noncentrosymmetry in the molecular assemblies andfabricate a cavity with a mirror and a grating mirror at both edges of a device, theluminescent light will be amplified in the cavity to permitting laser light. Therefore, asecond harmonic light is then generated due to the noncentrosymmetric molecularassembly in the cavity. The second harmonic light can be emitted through the gratingmirror. We can classify this newly designed laser emitting device as one of the intelligentmaterials because it manifests simultaneously three fundamental functions: as a sensorresponding luminescent intensity, and an actuator for emitting shorter laser light.Therefore, this hybridization of organic dyes with rare metal ions offers multifunctionalnew devices.
|