Abstract
A novel hybrid material comprising of two β-diketonate complexes, Tb(ASA)3Phen (TAP) and Eu(TTA)3Phen (ETP), has been synthesized and studied its photo-physics, energy transfer and optical thermometry applications. Using XRD and FTIR spectra, it has been demonstrated that both the complexes maintain their core entity and show weak interaction between them in the hybrid complex (HC). The TEM images show the coating of ETP layers over nano-fibrous TAP and further, embedded with Ag nanoparticles over HC. It has been observed that ligands (Phen, TTA as well as ASA) absorb the UV radiation and undergoes single to triplet via intersystem crossing transitions by transferring its excitation energy to central lanthanide ions (Eu3+ and Tb3+). In this strategy, an efficient energy transfer between two different species i.e. ASA to Tb3+ (in TAP complex) to Eu+3 ions (of ETP complex) has also been observed. To probe and verify the energy transfer mechanism, life time measurements have been carried out. The life time of Tb3+ decreases in HC as compared with TAP, whereas the life time of Eu3+ increases in HC as compared with ETP. The addition of silver nanoparticles (AgNPs) again enhances the fluorescence intensity of Eu3+ emission band. The prepared HC has further been demonstrated for ambient range temperature (295-365 K) sensing and the sensitivity of the material is found to be 6.8% change in signal per K. The strong optical property and non-toxic nature of this HC is useful in biomedical, bio-imaging and energy harvesting applications.
Highlights
Parola et al have given a detailed overview on different types of lanthanide based hybrid nanomaterials and demonstrated that, controlled coupling between plasmonics and luminescence opens a wide field of intense research.[15]
In our previous report we have demonstrated the multi-functionality of red emitting Eu(TTA)3Phen (ETP) complexes, in which TTA molecules absorbed the UV-A as well as UV-B part of the radiation and transfer its energy to central Eu3+ ion, whereas Phen protect it from the interaction with water molecules and provides stability to the complex.[6,28]
To confirm the possible interaction between the two complexes, we have carried out the x-ray diffraction (XRD) and infrared spectroscopic (FTIR) measurements
Summary
Lanthanide compounds specially organic-inorganic hybrid fluorophores have become a very wide, active and attractive field of intense research due to their multifunctional and versatile properties as well as wide range of practical applications in day-to-day life.[1,2,3,4,5] Their excellent optical properties such as large Stokes’ shifted emission, high quantum yield, narrow bandwidth, long lived decay profile and mechanical flexibility offer promising applications in many fields such as sensors, in medical diagnostics, optical and electronic devices etc.[1,2,3,4,5,6,7,8,9,10] Lanthanide complexes are basically organo-metallic complexes, in which organic ligands and the rare-earth ion are bonded either through covalent or co-ordinate bonds. Li et al successfully synthesized the Au nanoparticle@mSiO2@PABI-Eu nanocomposite and their spectroscopic results revealed that the emission intensity of the Au nanoparticle@mSiO2@PABI-Eu nanocomposite is highly dependent on the thickness of silica layer.[33] Sudheendra et al prepared a photonic material with plasmonic and up-converting properties by coating gold onto the surface of a fluoride matrix to see the plasmonic effect.[34] Fang et al observed luminescence enhancement and quenching in Eu(TTA)[3].H2O complex in the presence of silver nanoparticles depending on the concentration of Ag nanoparticles as well as complex molecule.[35] The Ag nanoparticles increase the electronic-dipole transition rate due to enhanced local field surrounding Eu3+ ions, while the nonradiative transition rate decreased owing to decreased resonant energy transfer among europium complex molecules. This material shows high-temperature sensitivity (295-365K), photostability and excellent brightness
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