A simple approach of template growth of graphitic-carbon nitride (g-CN), a polymeric unit consisting of C, N, O, and H elements derived from extracts of green plant Aloe vera , which are rich in several chemical constituents, has been successfully experimented in this work. Comparing several other methods used for synthesizing g-CN involving a large amount of toxic components, here, we propose the simplest route economically and environmentally highly viable for near future. Green plants are highly rich in natural carbon and nitrogen compounds, such as acemannan, glucose, aloin, protein, etc. Way before g-CN research, many carbon-based materials have been synthesized for multifunctional properties, but g-CN has much benefit over them due to the presence of elements such as C, N, O, and H, thus making it electron-rich. Multifunctional properties of graphitic-carbon nitride interface bonding as a supercapacitor or as a metal-free catalyst thus help degrade dyes. Violet-blue broad band emission was even noticed when excited at 240 nm via C–C bonding (π–π* transition) in the absorption band with an extinction coefficient of ∼10 4 M –1 cm –1 . With our research, we want to pave new ways of synthesizing such materials present in our nature in a biological form, which can protect our environment, thus causing less harm to mankind.

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The Eu3+ doped CaIn2O4 is a novel oxide phosphor useful for multifunctional applications such as display systems, lasers, energy-converters, photocatalysts, optical imaging, medical tools, and several others. Here, a natural aloe-vera gel is explored to obtain a precursor gel bridging Eu3+, Ca2+ and In3+ cations in a network so that it yields Eu3+:CaIn2O4 of small crystallites bonding over a grafted C-sp2 surface layer. The Eu3+ in varied from 0.1 to 2 mol% promptly promotes blue and red light-emissions in two major bands over 300-580 nm and 600-900 nm in 5DJ → 7FJ′ (J = 3, 2, 1 and J′ = 4 →1) and 5D0 → 7F1→ 4 transitions in the Eu3+ species, what is it is required in many optical and catalytic devices. The novel results are described in correlation to the light absorption and core-shell nanostructure.

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A natural aloe-vera gel is promptly bridging the Eu 3+ , Ca 2+ and In 3+ species in a bio-complex of a polymer network, so as it yields a sample Eu 3+ :CaIn 2 O 4 of small crystallites bonding over a grafted C-sp 2 surface layer when it is burnt in a selfpropagating combustion in air. The Eu 3+ doped C-CaIn 2 O 4 sample appears in a core-shell structure in part of the carbon forming a conjoint surface layer (shell) thereon of the individual crystallites in a hybrid nanostructure. The results are analyzed in terms of XRD patterns, phonon bands (in IR and Raman spectra), XPS bands, and hierarchical microstructure in the samples prepared with different Eu 3+ dosages in finely tuning the microstructure and optical properties as useful for an efficient phosphor, optical display system, visible lasers, energy-converters, photocatalysts, optical imaging, medical tools, and several others. A partial Eu 3+ → In 3+ doping in a crystal lattice CaIn 2 O 4 clearly reflects in a marked expansion of the lattice, as much as 2.2% found in the Eu 3+ content progressively raised to 2.0 mol% in a tailored hybrid composite structure. An inbuilt C-sp 2 shell structure of the crystallites is characterized in terms of its characteristic phonon bands in a conjoint polymer network, which are accounted well in modified XPS bands in the surface species.* Barkha Tiwari, barkha@matsc.iitkgp.ernet.in | Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.