Stage 1/2020 - Development of cellulosic materials containing CeO₂ nanoparticles with catalytic activity under the action of UV light

Activity 1.1 - Preparation of hybrid composite materials by immobilization of CeO₂ NPs (commercial, synthesized in our laboratory or organically modified) in native cellulose (avicel, fibers, cotton foil, cellulose acetate) or oxidized cellulose.

Activity 1.2 - Investigation of the catalytic performance of the prepared hybrid materials under UV irradiation

CeO₂ nanoparticles were synthesized by two different methods. The prepared nanoparticles (NPs) and some commercial ones were functionalized on the surface with organic groups to be immobilized in a cellulose template, in order to obtain an improved dispersion of them and a better connectivity between NPs and the polymer matrix. Simple or organically modified CeO₂ NPs were characterized by appropriate techniques (UV-vis, fluorescence, FTIR, ATG, X-rays, TEM). CeO₂ NPs were immobilized in cellulose acetate, resulting in semi-transparent films. The photocatalytic activity of the films was investigated following the photodegradation of methyl-orange dye.

Schematic representation of the reaction pathways used for the preparation of CeO₂ nanoparticles in the presence of (a) NaOH (pH = 5-6) or (b) NH₄OH (pH = 8-9) and their corresponding TEM images.

• M.E. Culica, A.L. Chibac-Scutaru, V. Melinte, S. Coseri - Stabilization of cerium oxide nanoparticles by natural derived polymeric matrices - MacroYouth 2020, Iasi, Romania, 19 November 2020 (oral presentation)

• M.E. Culica, A.L. Chibac-Scutaru, V. Melinte, S. Coseri - Novel support based on renewable resources doped with cerium oxide nanoparticles with technical applications - SICHEM 2020, Bucharest, Romania, 17– 18 September 2020 (oral presentation)

• A.L. Chibac-Scutaru, V. Melinte, M. Culica, S. Coseri - Synthesis, organic functionalization and immobilization of CeO₂ nanoparticles in cellulose matrix. Evaluation of their photocatalytic efficiency  - SICHEM 2020, Bucharest, Romania, 17– 18 September 2020 (oral presentation)

Stage 2/2021 - Preparation, characterization and evaluation of photocatalytic efficiency of some hybrid materials containing CeO₂ NPs immobilized in oxidized cellulose matrices or cellulose-based mixtures

Activity 2.1 - Preparation of hybrid composite materials by immobilizing CeO₂ NPs (commercial, synthesized in our laboratory or organically modified) within native cellulose (avicel, fibers, cotton linters, cellulose acetate) or oxidized cellulose.

Activity 2.2 - Synthesis of hybrid composite materials by immobilization of CeO₂ nanoparticles (synthesized in our laboratory or organically modified) within cellulose-based mixtures.

Activity 2.3 - Testing the catalytic performance of hybrid materials containing oxidized cellulose / cellulose-based mixtures - CeO₂ NPs under UV irradiation.

In this stage, we continued the activities started in the previous step by preparing hybrid composites based on cellulose acetate and CeO₂ nanoparticles with various concentrations (C2-F). The resulting films were thoroughly characterized (FTIR, SEM, EDX), and the photocatalytic performance was investigated by following the degradation of different contaminants (Congo red, methyl-orange, 4-nitrophenol). It has been observed that by modifying the cellulosic substrate after regeneration and oxidation reactions, active photocatalysts were succesfully used on the photoreduction of 4-nitrophenol to 4-aminophenol. The photocatalytic activity under UV irradiation was very good, while the results obtained under visible irradiation were very encouraging, too. In this stage, six types of CeO₂ NPs were synthesized and characterized by FTIR, XRD, SEM and TEM techiques. Their optical properties (UV-Vis spectroscopy) evidenced that two of the samples have lower values of the forbidden band energy (Eg), and are expected to have photocatalytic activity in the visible range. For this reason, they were immobilized in various gravimetric proportions of oxidized cellulose / polyvinyl alcohol blends, and were preliminarily characterized by FTIR and SEM images.

SEM micrographs of hybrid films recorded (A) on the surface and (B) in cross section: (a) CelA_C2-F-5% , (b) Cel_reg_C2 F-5% and (c) Cel_ox_C2-F-5% 

Various types of 4 – NPh transformation reactions in the presence of catalyst films containing 5 wt% CeO2 NPs (C2-F) and various cellulosic substrates on the surface: cellulose acetate (CelA_C2 – F-5%), regenerated cellulose (Celreg_C2 – F -5%) or oxidized cellulose (Celox_C2 – F-5%)

UV-Vis absorption spectrum of aqueous 4-nitrophenol solution in the presence of 5% C2-F hybrid films embedded in different cellulosic matrices: (a) cellulose acetate, (b) regenerated cellulose and (c) oxidized cellulose 

• V. Melinte, A.L. Chibac-Scutaru, M.E. Culica, S. Coseri, Mineralization versus photoreduction of 4-nitrophenol under the influence of surface functionalized CeO₂ nanoparticles, hosted by versatile cellulose supports, Applied Surface Science 565, 150494 (2021) IF = 6.707.
• A.L. Chibac-Scutaru, C. Cojocaru, G. Roman, P. Samoila, G. Sacarescu, M. Simionescu, L. Sacarescu, Synthesis of benzaldehyde-grafted polysilane: A highly stable and selective "turn-on" fluorescent sensor for cytosine, Journal of Molecular Liquids 326, 115300 (2021) IF = 6.165.
• L. Sacarescu, C. Cojocaru, G. Roman, G. Sacarescu, M. Simionescu, P. Samoila, A.L. Chibac-Scutaru, Nano-assembly and optical properties of difluoroboron dibenzoylmethane-polysilane, Polymer 232, 124188 (2021) IF = 4.43.
• A.L. Chibac-Scutaru, V. Podasca, A.I. Dascalu, V. Melinte, Tuning the optical properties of CeO₂ NPs by varying the synthesis parameters (under publication on Surfaces and Interfaces)

• A.L. Chibac-Scutaru, V. Melinte, CeO₂ nanoparticles embedded in different cellulosic substrates: photocatalytic materials for pollutant removal or organic reactions, The 10th Global Conference on Materials Science and Engineering CMSE 2021, August 1-4, 2021 (invited conference)
• M.E. Culica, A.L. Chibac-Scutaru, V. Melinte, S. Coseri, Cellulose - derived matrices for functionalized CeO₂ nanoparticles immobilization, and their photocatalytic behaviour, 2nd Bucharest Polymer Conference, Bucharest, Romania, June 9-11, 2021 (oral presentation)
• L. Stroea, A.L. Chibac-Scutaru, V. Melinte, UV-Shielding ability of aliphatic polyurethane – silane-functionalized TiO₂ nanoparticle elastomeric coatings, 2nd Bucharest Polymer Conference, Bucharest, Romania, June 9-11, 2021 (oral presentation)
• A.L. Chibac-Scutaru, V. Melinte, M.E. Culica, S. Coseri, Versatility of cellulosic matrix used for immobilization of synthesized CeO₂ nanoparticles in tailoring the photocatalytic properties of hybrid composites, The 3rd International Workshop Advances on Photocatalysis AdvPhotoCat-EE2021, Online, June 28-29, 2021 (oral presentation)
• L. Stroea, A.L. Chibac-Scutaru, V. Melinte, Surface functionalization of inorganic nanoparticles for covalent immobilization in polymer matrices, 13th International Conference on Physics of Advanced Materials, Sant Feliu de Guixols, Spain, September 24-30, 2021 (oral presentation)
• V. Melinte, A.L. Chibac–Scutaru, V. Podasca, Comparative structural, morphological and optical characterization of CeO₂/doped-CeO₂ nanoparticles, 13th International Conference on Physics of Advanced Materials, Sant Feliu de Guixols, Spain, September 24-30, 2021 (poster)