Structure and electronic properties of zirconium- and hafnium-ion functionalized cellulose nanofibrils

Abstract This study investigates the functionalization of cellulose nanofibrils (CNFs) with zirconium (Zr 4+ ) and hafnium (Hf 4+ ) ions to tailor their structural, thermal, and mechanical properties. CNFs were initially activated with sodium hydroxide (NaOH) and subsequently treated with zirconium oxychloride octahydrate (ZrOCl 2 ·8H 2 O) or hafnium oxychloride octahydrate (HfOCl 2 ·8H 2 O) at two stoichiometric ratios (2:1 and 4:1, OH⁻:metal). Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS) revealed that the 2:1 ratio yielded a denser and more homogeneous surface coverage, with metals highly concentrated at the surface. X-ray diffraction (XRD) analysis indicated significant amorphization, particularly for Hf 4+ treated samples, where crystallinity indices decreased by over 30%. Fourier-transform infrared (FTIR) and Raman spectroscopies confirmed the preservation of the cellulose backbone integrity despite the induction of local structural disorder. While thermogravimetry (TG) and differential scanning calorimetry (DSC) evidenced reduced thermal stability, dynamic mechanical analysis (DMA) demonstrated that Hf 4+ -functionalized samples, especially at the 2:1 ratio, exhibited enhanced stiffness and damping. Additionally, ultraviolet–visible spectroscopy (UV–Vis) indicated a narrowing of the optical band gap following metal incorporation. These findings underscore the tunability of CNF-based materials via Zr 4+ and Hf 4+ functionalization, paving the way for applications in advanced composites, coatings, and sustainable technologies.Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Author 1 Given name: Lucas Repecka Last name Alves; Author 2 Given name: Giovanni Miraveti Last name Carriello; Author 3 Given name: Guilherme Manassés Last name Pegoraro; Author 4 Given name: Thaís de Agrella Last name Janolla; Author 5 Given name: Henrique Solowej Medeiros Last name Lopes; Author 6 Given name: Amanda Stefanie Jabur de Last name Assis; Author 7 Given name: Ahmed Amer Last name Flayeh; Author 8 Given name: Roberta Ranielle Matos de Last name Freitas; Author 9 Given name: Vagner Roberto Last name Botaro; Author 10 Given name: Maira de Last name Lourdes Rezende; Author 11 Given name: Giovanni Pimenta Last name Mambrini; Author 12 Given name: Aparecido Junior de Last name Menezes. Also, kindly confirm the details in the metadata are correct.We corrected the last name of Thaís de Agrella Janolla.