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Luminescent materials containing europium ions are investigated for different optical applications. They can be obtained using bio-macromolecules, which are promising alternatives to synthetic polymers based on the decreasing oil resources. This paper describes studies of the DNA- and Agar-europium triflate luminescent membranes and its potential technological applications are expanded to electroluminescent devices. Polarized optical microscopy demonstrated that the samples are birefringent with submicrometer anisotropy. The X-ray diffraction analysis revealed predominantly amorphous nature of the samples and the atomic force microscopy images showed a roughness of the membranes of 409.0 and 136.1 nm for the samples of DNA10Eu and Agar1.11Eu, respectively. The electron paramagnetic resonance spectra of the DNA(n)Eu membranes with the principal lines at g ≈ 2.0 and g ≈ 4.8 confirmed uniform distribution of rare earth ions in a disordered matrix. Moreover, these strong and narrow resonance lines for the samples of DNA(n)Eu when compared to the Agar(n)Eu suggested a presence of paramagnetic radicals arising from the DNA matrix. The emission spectra suggested that the Eu3+ ions occupy a single local environment in both matrices and the excitation spectra monitored around the Eu emission lines pointed out that the Eu3+ ions in the Agar host were mainly excited via the broad band component rather than by direct intra-4f(6) excitation, whereas the opposite case occurred for the DNA-based sample.

Biopolymer-based membranes have particular interest due to their biocompatibility, Biodegradability, easy extraction from natural resources and low cost. The incorporation of Er3+ ions into natural macromolecule hosts with the purpose of producing highly efficient emitting phosphors is of widespread interest in materials science, due to their important roles in display devices. Thus, biomembranes may be viewed as innovative materials for the area of optics. This paper describes studies of luminescent material DNA-based membranes doped with erbium triflate and demonstrates that their potential technological applications may be expanded to electrochromic devices. The sample that exhibits the highest ionic conductivity is DNA10Er, (1.17×10−5 and 7.76×10−4 S.cm−1 at 30 and 100°C, respectively). DSC, XRD and POM showed that the inclusion of the guest salt into DNA does not change significantly its amorphous nature. The overall redox stability was ca. 2.0V indicating that these materials have an acceptable stability window for applications in solid state electrochemical devices. The EPR analysis suggested that the Er3+ ions are distributed in various environments. A small ECD comprising a Er3+-doped DNA-based membrane was assembled and tested by cyclic voltammetry and chronoamperometry. These electrochemical analyses revealed a pale blue color to transparent color change and a decrease of the charge density from -4.0 to -1.2 mC.cm−2 during 4000 color/bleaching cycles. [ABSTRACT FROM AUTHOR]

Highlights: [•] DNA is investigated for several electrochemical applications. [•] Ln3+ make them well suited as luminescent groups, with applications in biotechnology. [•] Thermal and electrochemical stability of electrolytes is adequate for devices. [ABSTRACT FROM AUTHOR]