Processing of leather has an historical reputation as a chemically and energetically intensive process which produces large volumes of aqueous waste. Saline pollution combined with heavy-metal, dyes and acid and base streams make leather production an ecologically sensitive industry. The current study shows that a variety of deep eutectic solvents, DESs may be used for the tanning, fatliquoring and dyeing of animal hides, being particularly useful for mineral (chromium) and vegetable tanning processes. The tanning agents are able to penetrate rapidly into the hide, driven by lyotropic swelling due to their high ionic strength. The samples are shown to have similar tanning agent content to the currently used aqueous chromium (III) sulfate solution, however the waste metal content is shown to be significantly reduced. Incorporation of the DES Ethaline into the leather significantly alters the swelling properties of the leather increasing the flexibility and ductility of the material, therefore acting in the same manner as a fatliquor which lubricates or plasticises the fibrous structure of the collagen. Ethaline was also used to transport a lysochromic dye throughout the cross-section of the leather, and the hydrophobicity of the dye prevents leaching into the aqueous wash solution. Physical measurements show that leather processed using DESs have similar mechanical properties to that processed using conventional aqueous systems.

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Nacre structure has aragonite polygonal tablets, tessellated to generate separate layers, and exhibits adjacent layers and tablets within a layer bonded by a biopolymer. Here, we report the development of a nacre‐like organic/inorganic hybrid nanocomposite coating consisting of epoxy tablets as well as rare‐earth‐activated aluminate and graphene oxide tablet/tablet interfaces. The lanthanide‐activated aluminate was prepared using a high temperature solid‐state approach followed by top‐down technology to provide the phosphor nanoparticles (PNPs). Graphene oxide nanosheets were prepared from graphite. The prepared epoxy/graphene/phosphor nanocomposites were applied onto mild steel. Covalent bonds were formed between epoxy polymer chains resin and the graphene oxide nanosheets. These interface interactions resulted in a tough surface, high tensile strength, and excellent durability. The use of phosphor in the nanoparticle form guaranteed that no agglomerations were produced throughout the hardening procedure by allowing better distribution of PNPs in the nacre‐like matrix. The generated nacre‐like substrates displayed reversible fluorescence. The excitation of the white coloured nacre‐like coats at 367 nm resulted in a green emission band at 518 nm as designated by the Commission Internationale de l'éclairage (CIE) Laboratory and photoluminescence spectra. Various analysis methods were utilized to inspect the surface structure and elemental composition of the nacre‐like coats. An improved hydrophobicity and mechanical characteristics were detected when increasing the phosphor concentration. Due to the astonishing characteristics of the prepared nacre‐like composite paint, both ceramics and metals can benefit from the current simple strategy.

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