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

It is essential for luminescent materials to be compatible with complex bioenvironments when used for probing biological events. Förster resonance energy transfer (FRET) is a common process in gaining enhanced luminescence signals, in which the interaction between the donor and acceptor plays a decisive role in the optical properties of heterostructured bioprobes. Yet systematic investigations on the gradient amphiphilic and electrostatic interaction effect on luminescence in a complex environment are scarce. Heteronanostructures of Tb(C12H8N2)2(NO3)3 nanocrystals and Eu3+-doped oxide nanosheets in various solutions with varied double electric layers and amphiphilic capacities are chosen for the investigation. It is found that a complex redox process takes place and an interfacial Tb–O bond is formed during preparation of the heteronanostructures. According to the decay dynamics of Tb3+ and Eu3+ emission of the heteronanostructures in various amphiphilic alcohol solvents, the interfacial Tb3+ → Eu3+ energy transfer efficiency apparently displays an extraordinary dependence on alkyl chain length after excluding the refractive index effect, while the zeta potential data suggest that the interfacial electrostatic force on the heteronanostructures should be dominant via the electric double layer in alcohol solvents with short alkyl chain. As the length of alkyl chain increases, the amphiphilic force on the heteronanostructures with amphiphilic Tb(phen)2(NO3)3 and hydrophilic Eu3+-doped nanosheets tends to be overwhelming. These competitive forces strengthen the interaction between Tb3+ and Eu3+ and result in enhancement of the interfacial Tb3+ → Eu3+ energy transfer efficiency. The research helps design potential new bioprobes concerning the interfacial interaction in amphiphilic and salty biosystems.