Interfacial Interaction in Colloidal Heteronanostructures of Tb3+-Complex and Eu3+-Doped Nanosheets: Implications for Bioprobes

It is essential for luminescent materials to be compatiblewithcomplex bioenvironments when used for probing biological events. Fo''rsterresonance energy transfer (FRET) is a common process in gaining enhancedluminescence signals, in which the interaction between the donor andacceptor plays a decisive role in the optical properties of heterostructuredbioprobes. Yet systematic investigations on the gradient amphiphilicand electrostatic interaction effect on luminescence in a complexenvironment are scarce. Heteronanostructures of Tb(C12H8N2)(2)(NO3)(3) nanocrystalsand Eu3+-doped oxide nanosheets in various solutions withvaried double electric layers and amphiphilic capacities are chosenfor the investigation. It is found that a complex redox process takesplace and an interfacial Tb-O bond is formed during preparationof the heteronanostructures. According to the decay dynamics of Tb3+ and Eu3+ emission of the heteronanostructuresin various amphiphilic alcohol solvents, the interfacial Tb3+ -> Eu3+ energy transfer efficiency apparently displaysan extraordinary dependence on alkyl chain length after excludingthe refractive index effect, while the zeta potential data suggestthat the interfacial electrostatic force on the heteronanostructuresshould be dominant via the electric double layer in alcohol solventswith short alkyl chain. As the length of alkyl chain increases, theamphiphilic force on the heteronanostructures with amphiphilic Tb(phen)(2)(NO3)(3) and hydrophilic Eu3+-doped nanosheets tends to be overwhelming. These competitive forcesstrengthen the interaction between Tb3+ and Eu3+ and result in enhancement of the interfacial Tb3+ -> Eu3+ energy transfer efficiency. The research helps designpotential new bioprobes concerning the interfacial interaction inamphiphilic and salty biosystems.