As contamination and environmental degradation increase nowadays, there is a huge demand for new eco-friendly materials. Despite its use for thousands of years, cellulose and its derivatives have gained renewed interest as favourable alternatives to conventional plastics, due to their abundance and lower environmental impact. We report the fabrication of photonic and plasmonic structures by moulding hydroxypropyl cellulose into sub-micrometric periodic lattices, using soft lithography. This is an alternative way to achieve structural colour in this material which is usually obtained exploiting its chiral nematic phase. Cellulose based photonic crystals are biocompatible and can be dissolved in water or not depending on the derivative employed. Patterned cellulose membranes exhibit tuneable colours and may be used to boost the photoluminescence of a host organic dye. Furthermore, we show how metal coating these cellulose photonic architectures leads to plasmonic crystals with excellent optical properties acting as disposable surface enhanced Raman spectroscopy substrates.

Hydroxypropyl cellulose is used as a nanoimprinting resist to fabricate photonic architectures with water as a solvent.

Micro- and nanoscale patterned monolayers of plasmonic nanoparticles were fabricated by combining concepts from colloidal chemistry, self-assembly, and subtractive soft lithography. Leveraging chemical interactions between the capping ligands of pre-synthesized gold colloids and a polydimethylsiloxane stamp, we demonstrated patterning gold nanoparticles over centimeter-scale areas with a variety of micro- and nanoscale geometries, including islands, lines, and chiral structures (e.g., square spirals). By successfully achieving nanoscale manipulation over a wide range of substrates and patterns, we established a powerful and straightforward strategy, nanoparticle chemical lift-off lithography (NP-CLL), for the economical and scalable fabrication of functional plasmonic materials with colloidal nanoparticles as building blocks, offering a transformative solution for designing next-generation plasmonic technologies.

crystal substrates when epitaxial growth is pursued. These requirements dramatically limit their applicability excluding the possibility to prepare many artificial multilayered architectures to investigate emergent phenomena that arise in thin films and at their interfaces, [2] as well as the fabrication of flexible devices and monolithic integration into silicon. [3-5] Many efforts have been devoted to develop procedures to detach the functional oxide film from the growth substrate in order to be able to freely manipulate it. They include mechanical exfoliation, [6] dry etching, [7,8] and wet-chemical etching. [9,10] Among the chemical etching procedures, the use of a sacrificial layer, which is incorporated between the substrate and the functional oxide, appears as a fast and relatively low-cost process. For this approach to be successful, the sacrificial layer should transfer the epitaxy from the substrate to the desired oxide, stand the deposition process of the functional oxide and be selectively removed by a chemical treatment, which allows to retrieve the original single-crystal substrate. (La,Sr)MnO 3 has been proved effective to be selectively etched by an acid blend allowing the transfer of single epitaxial Pb(Zr,Ti)O 3 layers [11] and more complex architectures such as SrRuO 3 /Pb(Zr,Ti)O 3 /SrRuO 3. [12] Recently, the use of water-soluble Sr 3 Al 2 O 6 (SAO) sacrificial layer enlarged the family of free-standing epitaxial perovskite oxide layers (SrTiO 3 , BiFeO 3 , BaTiO 3) [13-15] and multilayers (SrTiO 3 /(La,Sr) MnO 3) [16] that can be manipulated opening a whole new world of opportunities. [5,10,17] The deposition techniques to prepare such structures is also a key factor to be considered not only for film quality but also for process scalability. While high vacuum deposition techniques such as molecular beam epitaxy and pulsed laser deposition are well established techniques to produce high quality films, [1,18-20] alternate procedures that can deliver low-cost production such as solution processing and atomic layer deposition are gaining interest. [21,22] Chemical solution deposition (CSD) is considered a mature technique for the preparation of oxide films. The synthesis of ternary and quaternary oxides is not a trivial task but the pioneering work done in ferroelectric lead zirconate titanate inspired many researchers to extend it to other compositions and broaden the application fields. [23,24] Nonetheless, there is still a myriad of compositions to be explored, including SAO, The growth of epitaxial complex oxides has been essentially limited to specific substrates that can induce epitaxial growth and stand high temperature thermal treatments. These restrictions hinder the opportunity to manipulate and integrate such materials into new artificial heterostructures including the use of polymeric and silicon substrates and study emergent phenomena for novel applications. To tackle this bottleneck, herein, a facile chemical route to prepare water-soluble epitaxial Sr 3 Al 2 O 6 thin films to be ...