# Free-Standing Nanopatterned Films of Silk Sericin and Gellan Gum and the Spectroscopy Studies from Eu3+-Doped Films

## TL;DR

Researchers created flexible, transparent hybrid films from silk sericin and gellan gum, enhancing their optical properties with Eu3+ ions for potential use in biophotonics.

## Contribution

The study introduces a novel hybrid film combining silk sericin and gellan gum with Eu3+ ions for tunable optical properties in biophotonics.

## Key findings

- SSGG composite films showed improved mechanical and optical performance compared to pristine SS films.
- Incorporating Eu3+ ions produced red-emissive optical films with modified spectroscopic profiles.
- The films' optical behavior can be tuned through material design and preparation methods.

## Abstract

In this study, we investigated the development of flexible
and
nanopatterned hybrid films composed of silk sericin (SS) and gellan
gum (GG) for photonic applications. GG is widely recognized for its
ability to form free-standing films with excellent transparency and
flexibility, whereas pristine SS films often exhibit limited mechanical
and optical performance. By combining SS and GG, we engineered composite
films with improved functionality while maintaining high transparency,
unlocking new possibilities for diverse applications in biophotonics.
Here, soft lithography was employed to fabricate transparent nanostructured
SSGG composite films with different geometries. Additionally, we successfully
fabricated high-quality, red-emissive optical SSGG composite films
by incorporating Eu3+ ions at low concentrations. A comprehensive
characterization of the composite film’s structure was achieved
through an integrative approach, combining scanning electron microscopy,
atomic force microscopy, vibrational spectroscopy, and thermogravimetric
analyses. The interaction between the biopolymer-based films and lanthanide
ions was explored, revealing significant modifications in their spectroscopic
profile, particularly in the excitation process. We present a possible
energy transfer mechanism from biopolymers to the Eu3+ ions
and discuss the 5
D
0 excited-state
lifetime, suggesting coordination within either hydrophilic or hydrophobic
environments. Our findings demonstrate that the spectroscopic behavior
of the films varies with the preparation method, highlighting the
potential for tuning optical properties through material design. These
results provide new insights for applications in sensors, smart materials,
and optical devices, expanding the scope of biobased photonics.