RESUMEN
Nanostructured hematite materials for advanced applications are conventionally prepared with the presence of additives, tainting its purity with remnants of copolymer surfactants, active chelating molecules, stabilizing agents, or co-precipitating salts. Thus, preparing nanostructured hematite via additive-free and green synthesis methods remains a huge hurdle. This study presents an environmentally friendly and facile synthesis of spherical nanostructured hematite (Sp-HNP) using rice starch-assisted synthesis. The physicochemical properties of the Sp-HNP were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DR UV-Vis), and nitrogen adsorptionâ»desorption analysis. The Sp-HNP showed a well-crystallized structure of pure rhombohedral phase, having a spherical-shaped morphology from 24 to 48 nm, and a surface area of 20.04 m²/g. Moreover, the Sp-HNP exhibited enhanced photocatalytic degradation of methylene blue dye, owing to the large surface-to-volume ratio. The current work has provided a sustainable synthesis route to produce spherical nanostructured hematite without the use of any hazardous agents or toxic additives, in agreement with the principles of green chemistry for the degradation of dye contaminant.
RESUMEN
The conventional synthesis route of nanostructured titania-silica (Ti-SiNS) based on sol-gel requires the use of a surfactant-type template that suffers from hazardous risks, environmental concerns, and a tedious stepwise process. Alternatively, biomaterials have been introduced as an indirect template, but still required for pre-suspended scaffold structures, which hinder their practical application. Herein, we report an easy and industrially viable direct-continuous strategy for the preparation of Ti-SiNS from nanostructured-silica (SiNS) using a hydrolyzed rice starch template. This strategy fits into the conventional industrial process flow, as it allows starch to be used directly in time-effective and less complicated steps, with the potential to upscale. The formation of Ti-SiNS is mainly attributed to Ti attachment in the SiNS frameworks after the polycondensation of the sol-gel composition under acidic-media. The SiNS had pseudo-spherical morphology (nanoparticles with the size of 13 to 22 nm), short order crystal structure (amorphous) and high surface area (538.74 m²·g−1). The functionalized SiNS into Ti-SiNS delivered considerable catalytic activity for epoxidation of 1-naphtol into 1,4-naphthoquinone. The described direct-continuous preparation shows great promise for a cheap, green, and efficient synthesis of Ti-SiNS for advanced applications.