Titanium dioxide (TiO₂) is a prototypical wide-band-gap oxide whose three main polymorphs—anatase, rutile, and brookite—exhibit distinct surface structures and electronic properties;[1] these differences underpin TiO₂’s roles in photocatalysis, coatings, sensors, and energy devices (anatase and rutile band gaps are ~3.2 and ~3.0 eV, respectively). In the last decade, “green” synthesis has gained traction as a safer, lower-toxicity alternative to conventional sol–gel or hydrothermal routes[2]: plant extracts and biopolymers furnish polyphenols, proteins, and polysaccharides that act as reducing and capping agents, regulating nucleation, crystallite growth, and aggregation while minimizing hazardous reagents [3]. Within this framework, potato (Solanum tuberosum) resources are especially attractive; potato peel extracts have been used directly to fabricate TiO₂ nanoparticles, and potato starch has served as a benign capping/templating matrix that stabilizes particles and can tune surface chemistry [4], [5].

Titanium dioxide (TiO₂) is a transition-metal oxide known for its outstanding chemical stability, non-toxicity, and polymorphic versatility, crystallizing predominantly in anatase, rutile, and brookite phases[6]. Among these, anatase is often preferred for nanostructured applications due to its higher surface area, superior charge carrier mobility, and enhanced photocatalytic activity [7]. The structural properties of TiO₂ nanoparticles—such as crystal phase, crystallite size, strain, and morphology—critically influence their optical, electronic, and catalytic behaviors[8]. These properties can be tailored by the synthesis route employed [9]. In green synthesis, plant-derived biomolecules serve as both reducing and capping agents, modulating the nucleation and growth processes and thereby influencing the final crystalline structure [10]. The use of natural extracts rich in polyphenols, flavonoids, and starches—such as potato (Solanum tuberosum) extract—not only enables an eco-friendly and cost-effective fabrication route but also facilitates the formation of uniform, nanocrystalline particles [11], [12].

Titanium dioxide nanoparticles were synthesized via a green route using potato peel extract as a reducing and stabilizing agent, and titanium tetrachloride (TiCl₄) as the titanium precursor. First, the potato peel extract was prepared by collecting fresh peels from Solanum tuberosum (approximately 50 g), thoroughly washing them with deionized water to remove surface impurities, and then boiling in 250 mL of deionized water at 80 °C for 30 minutes. The resultant solution was cooled to room temperature and filtered using Whatman filter paper to obtain a clear extract, which was stored at 4 °C until use. Separately,

A 1.0 M TiCl₄ solution was prepared by slowly adding 5.4 mL of TiCl₄ (density ≈ 1.73 g/mL, molar mass = 189.68 g/mol) to 50 mL of ice-cooled deionized water under a fume hood with constant stirring, due to the highly exothermic hydrolysis and corrosive nature of TiCl₄. The clear TiCl₄ solution was then added dropwise to 100 mL of the prepared potato peel extract under continuous magnetic stirring at room temperature. The mixture was stirred for 4 hours until a white precipitate began to form, indicating the formation of TiO₂ nanoparticles. The resulting suspension was aged for 12 hours, followed by centrifugation at 8000 rpm for 15 minutes to collect the solid product. The precipitate was washed repeatedly with deionized water and ethanol to remove unreacted organic components and then dried in a hot air oven at 80 °C for 6 hours. The dried powder was finally calcined at 450 °C for 2 hours in a muffle furnace to improve crystallinity and remove residual organics, yielding fine white TiO₂ nanopowder. Structural characterization was performed using X-ray diffraction (XRD) to determine crystalline phases and crystallite size, field-emission scanning electron microscopy (FESEM) to analyze morphology and particle size, and Fourier-transform infrared spectroscopy (FTIR) to confirm the presence of Ti–O bonds and assess any residual bio-organic functional groups.

The XRD diffractogram displays a set of sharp and well-resolved peaks in the 2θ range from 10° to 80°, confirming the crystalline nature of the synthesized titanium dioxide sample. The prominent diffraction peak at 2θ ≈ 25.27°, indexed as the (011) plane, is characteristic of the anatase phase of TiO₂, which is further confirmed by the presence of additional peaks indexed as (004), (020), (015), (121), (024), (116), and (125). These peaks match the standard diffraction pattern of anatase TiO₂ listed under JCPDS card number 96-500-0224, which provides crystallographic reference data for anatase TiO₂ with a tetragonal crystal structure [13].