Florentina Monica Raduly

Scopus Publications

Influence of Cold Plasma Treatment on Cellulose Modification with Different Oxidizing Agents
Denis Mihaela Panaitescu, Sorin Ionuţ Vizireanu, Gabriela Mădălina Oprică, Cătălina Diana Uşurelu, Cristian Stancu, Veronica Sătulu, Marius Ghiurea, Cristian-Andi Nicolae, Monica Florentina Raduly, and Adriana Nicoleta Frone
MDPI AG
Cellulose is a versatile biopolymer increasingly applied in medicine and industry due to its biodegradability and biocompatibility, along with the renewability and large availability of source materials. However, finding simple, eco-friendly, and effective methods to modify cellulose to provide it with new functionalities remains a challenge. This work presents a new, inexpensive, and eco-friendly method to chemically modify microcrystalline cellulose (MCC) by the submerged cold plasma treatment of an aqueous suspension of MCC containing different oxidizing agents, such as hydrogen peroxide (H2O2), sodium hypochlorite (NaClO), or sodium periodate (NaIO4). Fourier-transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that plasma treatment intensified the oxidizing effect of H2O2, NaClO, and NaIO4, with plasma-assisted NaClO treatment yielding the highest MCC oxidation level. XPS indicated that the plasma-assisted oxidations also resulted in different degrees of chemical degradation of MCC, a finding further supported by the thermogravimetric analysis (TGA) results. X-ray diffraction (XRD) data revealed a different effect of the oxidizing agents on the crystalline and amorphous regions in MCC. Scanning electron microscopy (SEM) images showed that the combined treatment with plasma and chemical oxidizing agents led to MCC fragmentation and varying degrees of defibrillation into nanofibers.

De- and Re-Structuring of Starch to Control the Melt and Solid State Visco-Elasticity as Method for Getting New Multi Component Compounds with Scalable Properties
Doina Dimonie, Ramona-Marina Grigorescu, Bogdan Trică, Monica Raduly, Celina-Maria Damian, Roxana Trusca, Alina-Elena Mustatea, Stefan-Ovidiu Dima, and Florin Oancea
MDPI AG
The aim of the article was to design and develop new thermodynamically stable starch-based compounds, with scalable properties, that are melt-processable into finished products by classic or 3D printing methods. This is based on phenomena of de-structuring, entanglement compatibilization, and re-structuring of starch, along with the modification of the polymer, polyvinyl alcohol (PVA), by following an experimental sequence involving pre-treatment and melt compounding in two stages. The new compounds selection was made considering the dependence of viscoelastic properties on formulation and flowing conditions in both the melted and solid states. Starting from starch with 125 °C glass transition and PVA with a Tg at 85 °C, and following the mentioned experimental sequence, new starch-PVA compounds with a high macromolecular miscibility and proven thermodynamic stability for at least 10 years, with glass transitions ranging from −10 °C to 50 °C, optimal processability through both classical melt procedures (extrusion, injection) and 3D printing, as well as good scalability properties, were achieved. The results are connected to the approaches considering the relationship between miscibility and the lifetime of compounds with renewable-based polymer content. By deepening the understanding of the thermodynamic stability features characterizing these compounds, it can be possible to open the way for starch usage in medium-life compositions, not only for short-life applications, as until now.

Direct Hydrothermal Synthesis and Characterization of Zr–Ce-Incorporated SBA-15 Catalysts for the Pyrolysis Reaction of Algal Biomass
Simona-Bianca Ghimiș, Florin Oancea, Monica-Florentina Raduly, Andreea-Luiza Mîrț, Bogdan Trică, Mihaela Cîlțea-Udrescu, and Gabriel Vasilievici
MDPI AG
In recent years, algae have emerged as a promising feedstock for biofuel production, due to their eco-friendly, sustainable, and renewable nature. Various methods, including chemical, biochemical, and thermochemical processes, are used to convert algal biomass into biofuels. Pyrolysis, a widely recognized thermochemical technique, involves high temperature and pressure to generate biochar and bio-oil from diverse algal sources. Various pyrolytic processes transform algal biomass into biochar and bio-oil, including low pyrolysis, fast pyrolysis, catalytic pyrolysis, microwave-assisted pyrolysis, and hydropyrolysis. These methods are utilized to convert a range of microalgae and cyanobacteria into biochar and bio-oil. In this publication, we will discuss catalytic pyrolysis using mesoporous materials, such as SBA-15. Mesoporous catalysts have earned significant attention for catalytic reactions, due to their high surface area, facilitating the better distribution of impregnated metal. Pyrolysis conducted in the presence of a mesoporous catalyst is viewed more as efficient, compared to reactions occurring within the smaller microporous cavities of traditional zeolites. SBA-15 supports with incorporated Zr and/or Ce were synthesized using the direct hydrothermal synthesis method. The catalyst was characterized using structural and morphological technical analysis and utilized for the pyrolysis reaction of the algal biomass.

Functionalized Palygorskite as a Delivery Platforms for Bioactive Asymmetric Beta-Diketone Dyes
Florentina Monica Raduly, Valentin Raditoiu, Alina Raditoiu, Maria Grapin, Radu Claudiu Fierascu, Iuliana Raut, and Mariana Constantin
MDPI AG
Natural clay minerals are among the most versatile materials used in the biomedical field. Palygorskite has found various applications in this field, from the treatment of diarrheal diseases in the past to materials with antibacterial properties and platforms carrying bioactive compounds used in the treatment of diseases, cosmetic and healthcare products in the present. In this study, a possible delivery method of some bioactive asymmetric β-diketonic compounds is presented. Palygorskite modified with amphionic groups (P) and copper ions (PCu) was used as a platform to load bioactive curcumin derivatives (1 and 2). By varying the copper ions, the amounts of charged active compounds were monitored. Studies have shown that the hybrid materials resulting from the loading of 1 and 2 compounds on palygorskite with 30% copper ions (PCu30) can be used as delivery methods for these asymmetric curcumin derivatives, while palygorskite with 50% copper ions(PCu50) loaded with the same type of bioactive compounds has antibacterial properties.

Morphological, Thermal, and Mechanical Properties of Nanocomposites Based on Bio-Polyamide and Feather Keratin–Halloysite Nanohybrid
George Mihail Teodorescu, Zina Vuluga, Andreea Ioniță, Cristian Andi Nicolae, Marius Ghiurea, Augusta Raluca Gabor, Valentin Rădițoiu, Monica Raduly, Ioana Andreea Brezeştean, Daniel Marconi,et al.
MDPI AG
One solution to comply with the strict regulations of the European Commission and reduce the environmental footprint of composites is the use of composite materials based on bio-polymers and fillers from natural resources. The aim of our work was to obtain and analyze the properties of bio-polymer nanocomposites based on bio-PA (PA) and feather keratin–halloysite nanohybrid. Keratin (KC) was mixed with halloysite (H) as such or with the treated surface under dynamic conditions, resulting in two nanohybrids: KCHM and KCHE. The homogenization of PA with the two nanohybrids was conducted using the extrusion processing process. Two types of nanocomposites, PA–KCHM and PA–KCHE, with 5 wt.% KC and 1 wt.% H were obtained. The properties were analyzed using SEM, XRD, FTIR, RAMAN, TGA, DSC, tensile/impact tests, DMA, and nanomechanical tests. The best results were obtained for PA–KCHE due to the stronger interaction between the components and the uniform dispersion of the nanohybrid in the PA matrix. Improvements in the modulus of elasticity and of the surface hardness by approx. 75% and 30%, respectively, and the resistance to scratch were obtained. These results are promising and constitute a possible alternative to synthetic polymer composites for the automotive industry.

Half-Curcuminoids Encapsulated in Alginate–Glucosamine Hydrogel Matrices as Bioactive Delivery Systems
Florentina Monica Raduly, Valentin Raditoiu, Alina Raditoiu, Cristian Andi Nicolae, Maria Grapin, Miruna Silvia Stan, Ionela Cristina Voinea, Raluca-Ioana Vlasceanu, Cristina Doina Nitu, Dan F. Mihailescu,et al.
MDPI AG
The therapeutic effects of curcumin and its derivatives, based on research in recent years, are limited by their low bioavailability. To improve bioavailability and develop the medical field of application, different delivery systems have been developed that are adapted to certain environments or the proposed target type. This study presents some half-curcuminoids prepared by the condensation of acetylacetone with 4-hydroxybenzaldehyde (C1), 4-hydroxy-3-methoxybenzaldehyde (C2), 4-acetamidobenzaldehyde (C3), or 4-diethylaminobenzaldehyde (C4), at microwaves as a simple, solvent-free, and eco-friendly method. The four compounds obtained were characterized in terms of morphostructural and photophysical properties. Following the predictions of theoretical studies on the biological activities related to the molecular structure, in vitro tests were performed for compounds C1–C3 to evaluate the antitumor properties and for C4’s possible applications in the treatment of neurological diseases. The four compounds were encapsulated in two types of hydrogel matrices. First, the alginate–glucosamine network was generated and then the curcumin analogs were loaded (G1, G3, G5–G7, and G9). The second type of hydrogels was obtained by loading the active compound together with the generation of the hydrogel carrier matrices, by simply dissolving (G4 and G10) or by chemically binding half-curcuminoid derivatives to glucosamine (G2 and G8). Thus, two types of curcumin analog delivery systems were obtained, which could be applied in various types of medical treatments.

Clam Shell-Derived Hydroxyapatite: A Green Approach for the Photocatalytic Degradation of a Model Pollutant from the Textile Industry
Roxana Ioana Matei (Brazdis), Anda Maria Baroi, Toma Fistos, Irina Fierascu, Maria Grapin, Valentin Raditoiu, Florentina Monica Raduly, Cristian Andi Nicolae, and Radu Claudiu Fierascu
MDPI AG
This work aims to evaluate the potential use of natural wastes (in particular, clam shells) to synthesize one of the most well-known and versatile materials from the phosphate mineral group, hydroxyapatite (HAP). The obtained material was characterized in terms of morphology and composition using several analytical methods (scanning electron microscopy—SEM, X-ray diffraction—XRD, X-ray fluorescence—XRF, Fourier transform infrared spectroscopy—FTIR, thermal analysis—TGA, and evaluation of the porosity and specific surface characteristics by the Brunauer–Emmett–Teller—BET method) in order to confirm the successful synthesis of the material and to evaluate the presence of potential secondary phases. The developed material was further doped with iron oxide (HAP-Fe) using a microwave-assisted method, and both materials were evaluated in terms of photocatalytic activity determined by the photodecomposition of methylene blue (MB) which served as a contaminant model. The best results (approx. 33% MB degradation efficiency, after 120 min. of exposure) were obtained for the hydroxyapatite material, superior to the HAP-Fe composite (approx. 27%). The utilization of hydroxyapatite obtained from clam shells underscores the importance of sustainable and eco-friendly practices in materials syntheses. By repurposing waste materials from the seafood industry, we not only reduce environmental impact, but also create a valuable resource with diverse applications, contributing to advancements in both healthcare and environmental protection.

Ag<sup>0</sup>–Ginger Nanocomposites Integrated into Natural Hydrogelated Matrices Used as Antimicrobial Delivery Systems Deposited on Cellulose Fabrics
Florentina Monica Raduly, Valentin Raditoiu, Alina Raditoiu, Maria Grapin, Mariana Constantin, Iuliana Răut, Cristian Andi Nicolae, and Adriana Nicoleta Frone
MDPI AG
In the textile, medical, and food industries, many of the applications have targeted the use of textile fabrics with antimicrobial properties. Obtaining eco-friendly coatings is of wide interest, especially for applications related to wound dressing or to food packaging. In order to obtain coatings with antimicrobial properties through environmentally friendly methods, a series of experiments were carried out on the use of natural polymers loaded with silver nanoparticles. In this study, coatings with antimicrobial properties were obtained by depositing natural composites based on rice flour, carob flour, or alginate on cotton fabrics. These antimicrobial coatings were multicomponent systems, in which the host matrix was generated via hydration of natural polymers. The nanocomposite obtained from the phytosynthesis of silver particles in ginger extract was embedded in hydrogel matrices. The multicomponent gels obtained by embedding silver nanoparticles in natural polymer matrices were deposited on cotton fabric and were studied in relation to nanoparticles and the type of host matrix, and the antimicrobial activity was evaluated. Fabrics coated with such systems provide a hydrophilic surface with antimicrobial properties and can therefore be used in various areas where textiles provide antibacterial protection.

Biomedical Promise of Sustainable Microwave-Engineered Symmetric Curcumin Derivatives
Cristina Doina Niţu, Maria Mernea, Raluca Ioana Vlasceanu, Bianca Voicu-Balasea, Madalina Andreea Badea, Florentina Monica Raduly, Valentin Rădiţoiu, Alina Rădiţoiu, Speranta Avram, Dan F. Mihailescu,et al.
MDPI AG
Curcumin is a polyphenol of the Curcuma longa plant, which can be used for various medicinal purposes, such as inflammation and cancer treatment. In this context, two symmetric curcumin derivatives (D1—(1E,6E)-1,7-bis(4-acetamidophenyl)hepta-1,6-diene-3,5-dione and D2—p,p-dihydroxy di-cinnamoyl methane) were obtained by the microwave-based method and evaluated for their antitumoral effect on human cervix cancer in comparison with toxicity on non-tumoral cells, taking into account that they were predicted to act as apoptosis agonists or anti-inflammatory agents. The HeLa cell line was incubated for 24 and 72 h with a concentration of 50 μg/mL of derivatives that killed almost half of the cells compared to the control. In contrast, these compounds did not alter the viability of MRC-5 non-tumoral lung fibroblasts until 72 h of incubation. The nitric oxide level released by HeLa cells was higher compared to MRC-5 fibroblasts after the incubation with 100 μg/mL. Both derivatives induced the decrease of catalase activity and glutathione levels in cancer cells without targeting the same effect in non-tumoral cells. Furthermore, the Western blot showed an increased protein expression of HSP70 and a decreased expression of HSP60 and MCM2 in cells incubated with D2 compared to control cells. We noticed differences regarding the intensity of cell death between the tested derivatives, suggesting that the modified structure after synthesis can modulate their function, the most prominent effect being observed for sample D2. In conclusion, the outcomes of our in vitro study revealed that these microwave-engineered curcumin derivatives targeted tumor cells, much more specifically, inducing their death.

COMPOSITE MATERIAL WITH ANTIMICROBIAL EFFECT FOR THE PRESERVATION OF WATERLOGGED WOOD CULTURAL HERITAGE OBJECTS

REMOVAL OF PHENOL AND NON-STEROIDAL ANTI-INFLAMMATORY DRUGS FROM WATER MATRICES USING DOPED HYDROXYAPATITE

Cellulose Fabrics Functionalized with Sol–Gel Photocatalytic Coatings Based on Iron (III) Phthalocyanine Tetracarboxylic Acids–TiO<inf>2</inf>–Silica Hybrids
Alina Raditoiu, Valentin Raditoiu, Monica Florentina Raduly, Augusta Raluca Gabor, Adriana Nicoleta Frone, Maria Grapin, and Mihai Anastasescu
MDPI AG
Photocatalytic coatings are difficult to obtain on textile materials because of the sometimes contradictory properties that must be achieved. In order to obtain a high efficiency of a photocatalytic effect, the metal–oxide semiconductor must be found in the vicinity of the coating–air interface in order to come into direct contact with the contaminant species and allow light radiation access to its surface. Another necessary condition is related to the properties of the covering textile material as well as to the stability of the xerogel films to light and wet treatments. In this sense, we proposed a solution based on hybrid silica films generated by sol–gel processes, coatings that contain as a photocatalyst TiO2 sensitized with tetracarboxylic acid of iron (III) phthalocyanine (FeTCPc). The coatings were made by the pad–dry–cure process, using in the composition a bifunctional anchoring agent (3-glycidoxipropyltrimethoxysilane, GLYMO), a crosslinking agent (sodium tetraborate, BORAX), and a catalyst (N-methylimidazole, MIM) for the polymerization of epoxy groups. The photodegradation experiments performed on methylene blue (MB), utilized as a model contaminant, using LED or xenon arc as light sources, showed that the treatment with BORAX improves the resistance of the coatings to wet treatments but worsens their photocatalytic performances.

Thermal behavior and thermo-mechanical properties of biocompatible poly(lactic acid)/allyl-POSS nanohybrids
Adriana Nicoleta Frone, Dora Dominica Baciu, Marius Stelian Popa, Cristian Andi Nicolae, Augusta Raluca Gabor, Monica Florentina Raduly, Radu Claudiu Fierascu, and Denis Mihaela Panaitescu
Springer Science and Business Media LLC

Characterization of Two Types of Polylactic Acid Coating Loaded with Gentamicin Sulphate Deposed on AZ31 Alloy
Manuela Elena Voicu, Daniela Ionita, George-Octavian Buica, Doina Draganescu, Valentina Anuta, Florentina Monica Raduly, and Ioana Demetrescu
MDPI AG
This paper compares two types of polylactic acid (PLA) coating on AZ31 alloy obtained by dip coating and electrospinning. Both types of coating were loaded with gentamicin sulphate (GS) and the drug-loading efficiency and release were assessed. A higher encapsulation and release efficiency of GS was seen for dip coating (73% and 49.53%, respectively) compared to nanofiber coating (65% and 12.37%, respectively). Furthermore, the antibacterial effect of the samples with and without GS was assessed using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria, showing that the samples with the drug encapsulated are more resistant to bacteria than the other samples. The electrochemical data reveal a higher stability in the SBF of the surface obtained by dipping than that obtained by electrospinning. The PLA coating shows a porosity of 46% for the sample obtained through dip coating and 32% for nanofibers, which is in accordance with the BET analysis results. Moreover, a higher adhesion strength was obtained for AZ31-PLA-dip (4.99 MPa) than for the AZ31-PLA-nanofibers (1.66 MPa). All samples were structurally, morphologically, and topographically characterized.

Multifunctional Finishing of Cotton Fabric with Curcumin Derivatives Coatings Obtained by Sol–Gel Method
Florentina Monica Raduly, Valentin Rădițoiu, Alina Rădițoiu, Adriana Nicoleta Frone, Cristian Andi Nicolae, Iuliana Răut, Mariana Constantin, and Maria Grapin
MDPI AG
Textile materials with fluorescent, repellent, or antimicrobial properties are increasingly used in common applications. Obtaining multi-functional coatings is of wide interest, especially for applications related to signaling or to the medical field. In order to increase the performance (color properties, fluorescence lifetime, self-cleaning or antimicrobial properties) of textile materials with special uses, a series of research was carried out regarding the modification of surfaces with nanosols. In this study, coatings with multiple properties were obtained by depositing nanosols on cotton fabrics generated through sol–gel reactions. These multifunctional coatings are hybrid materials in which the host matrix is generated using tetraethylorthosilicate (TEOS) and network modifying organosilanes:dimethoxydimethylsilane (DMDMS) or dimethoxydiphenylsilane (DMDPS) in a 1:1 mass ratio. Two curcumin derivatives were embedded in siloxane matrices, a yellow one (CY) that is identical to bis-demethoxycurcumin (one of the natural constituents in turmeric) and a red dye (CR) that has a N,N-dimethylamino group grafted in position 4 of the dicinnamoylmethane skeleton of curcumin. The nanocomposites obtained by embedding curcumin derivatives in siloxane matrices were deposited on cotton fabric and studied in relation to the dye and the type of host matrix. Fabrics coated with such systems provide a hydrophobic surface, have fluorescent and antimicrobial properties, change color depending on the pH, and therefore can be used in various fields where textiles provide signaling properties, self-cleaning, or antibacterial protection. The coated fabrics maintained their good multifunctional properties even after several washing cycles.

Contribution of the Surface Treatment of Nanofibrillated Cellulose on the Properties of Bio-Based Epoxy Nanocomposites Intended for Flexible Electronics
Adriana Nicoleta Frone, Cătălina Diana Uşurelu, Gabriela Mădălina Oprică, Denis Mihaela Panaitescu, Augusta Raluca Gabor, Cristian-Andi Nicolae, Florin Ciuprina, Celina Maria Damian, and Florentina Monica Raduly
MDPI AG
The growing interest in materials derived from biomass has generated a multitude of solutions for the development of new sustainable materials with low environmental impact. We report here, for the first time, a strategy to obtain bio-based nanocomposites from epoxidized linseed oil (ELO), itaconic acid (IA), and surface-treated nanofibrillated cellulose (NC). The effect of nanofibrillated cellulose functionalized with silane (NC/S) and then grafted with methacrylic acid (NC/SM) on the properties of the resulted bio-based epoxy systems was thoroughly investigated. The differential scanning calorimetry (DSC) results showed that the addition of NCs did not influence the curing process and had a slight impact on the maximum peak temperature. Moreover, the NCs improved the onset degradation temperature of the epoxy-based nanocomposites by more than 30 °C, regardless of their treatment. The most important effect on the mechanical properties of bio-based epoxy nanocomposites, i.e., an increase in the storage modulus by more than 60% at room temperature was observed in the case of NC/SM addition. Therefore, NC’s treatment with silane and methacrylic acid improved the epoxy–nanofiber interface and led to a very good dispersion of the NC/SM in the epoxy network, as observed by the SEM investigation. The dielectric results proved the suitability of the obtained bio-based epoxy/NCs materials as substitutes for petroleum-based thermosets in the fabrication of flexible electronic devices.

New Biodegradable Materials for Re-Thought Packaging from Pre-Consumer Wastes by Controlling the Storage Time as Method to Increase the Mechanical Recycling Efficiency
Doina Dimonie, Mihail Dragne, Bogdan Trica, Cristian-Andi Nicolae, Monica Raduly, Sanda Doncea, Magda Ladaniuc, Alina Mustatea, Florentina Miu, Laurentiu Soare,et al.
MDPI AG
The influence of storage conditions on the mechanical recycling of pre-consumer waste (PRE-CW) from the manufacture of multilayer packaging films starting from starch compounds using a renewable-based polymer with PCL and PBAT, which are biodegradable conventional-based polyesters, was studied. It was found that, unlike materials based on conventional-origin polymers that accumulate in the environment for hundreds of years, the studied compounds degraded, even in the solid state, duringstorage in unventilated spaces and during the rainy hot summers with alternatingheat and rain. The degradation of the mechanically recycled compounds obtained from PRE-CW stored in such conditions was highlighted by the comparative analysis with the primary compounds, which proved the following: specific FTIR spectra changes; 2–3-times higher melt fluidity than for primary compounds; melting in successive processes over the entire positive temperatures range, up to 115 °C, such as in cases of compositional de-mixing of incompatible blends, faced to a single melting endotherm with a maximum at around 120 °C for the primar thermal degradation with the movement of the main destruction stages towards higher temperatures; a high quantity residue at 750 °C in air; dispersed mechanical resistance properties y compounds; crystallization at temperatures 10 °C–15 °C higher. The elimination of storage before the mechanical recycling of the pre-consumer waste from this type of polymeric compound fabrication is a way to increase the mechanical recycling efficiency while obtaining new materials with functional properties required by the applications.

Influence of Perfluorooctanoic Acid on Structural, Morphological, and Optical Properties of Hybrid Silica Coatings on Glass Substrates
Violeta Purcar, Valentin Rădiţoiu, Florentina Monica Raduly, Alina Rădiţoiu, Simona Căprărescu, Adriana Nicoleta Frone, Raluca Şomoghi, Mihai Anastasescu, Hermine Stroescu, and Cristian-Andi Nicolae
MDPI AG
In recent years, various coatings based on fluorinated materials, used in a commercial application, have been created through many preparation routes. However, the techniques utilized to realize these coatings required either expensive and complex equipment, imply multiple manufacturing steps, or are time- or cost-consuming. In this paper, the major target was to develop fluorinated hybrid coatings presenting sustainable hydrophobicity and good transparency simultaneously. The sol–gel method was proposed to obtain these fluorinated hybrid coatings because it does not require expensive equipment, or the existence of stabilizing agents that reduce the storage period, it consumes less energy, and it is easy to implement. The influence of perfluorooctanoic acid, utilized in the sol–gel processing of hybrid silica materials, on the structural, morphological, and optical properties of coatings deposited on glass substrates, was evaluated. Different silane precursors (tetraethyl orthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES)) were utilized to synthesize hybrid silica materials. The properties of the obtained materials were characterized by FTIR, UV–Vis, TEM, TGA, AFM, Ellipsometry, and Contact Angle analyses. FTIR spectroscopy shows the formation of a silica network tailored with organofunctional and fluoroalkyl groups. The fluorinated silica coatings presented smooth surfaces and good transparency, with a transmittance of ~90% in the visible range. It was found that the fluorinated silica materials improved the coating’s hydrophobicity (~110° in contact angle with water). These fluorinated silica materials can create multifunctional structures with antireflective and hydrophobic coatings for possible optical devices.

PHYSICOCHEMICAL AND OPTICAL PROPERTIES OF HYBRID FILMS CONTAINING TiO2-BASED SILICA MATERIALS

Highlighting Bacteria with Calcifying Abilities Suitable to Improve Mortar Properties
Iuliana Răut, Mariana Constantin, Ionela Petre, Monica Raduly, Nicoleta Radu, Ana-Maria Gurban, Mihaela Doni, Elvira Alexandrescu, Cristi-Andi Nicolae, and Luiza Jecu
MDPI AG
Biomineralization, the use of microorganisms to produce calcium carbonate, became a green solution for application in construction materials to improve their strength and durability. The calcifying abilities of several bacteria were investigated by culturing on a medium with urea and calcium ions. The characterization of the precipitates from bacterial cultures was performed using X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The formation of carbonate crystals was demonstrated by optical and scanning electron microscopy. Water absorption and compressive strength measurements were applied to mortars embedded with sporal suspension. The efficiency of the supplementation of mortar mixtures with bacterial cells was evaluated by properties, namely the compressive strength and the water absorption, which are in a relationship of direct dependence, the increase in compressive strength implying the decrease in water absorption. The results showed that Bacillus subtilis was the best-performing bacterium, its introduction into the mortar producing an increase in compressive strength by 11.81% and 9.50%, and a decrease in water absorption by 11.79% and 10.94%, after 28 and 56 days of curing, respectively, as compared to standards. The exploitation of B. subtilis as a calcifying agent can be an interesting prospect in construction materials.

Investigation of Hybrid Films Based on Fluorinated Silica Materials Prepared by Sol–Gel Processing
Violeta Purcar, Valentin Rădiţoiu, Florentina Monica Raduly, Alina Rădiţoiu, Simona Căprărescu, Adriana Nicoleta Frone, Cristian-Andi Nicolae, and Mihai Anastasescu
MDPI AG
In this research, fluorinated silica materials were prepared through sol–gel processing with tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), using a fluorinated solution (FS) under acidic medium. The fluorinated solution (FS) was obtained by diluting the perfluorooctanoic acid (PFOA) in 2-propanol. These fluorinated sol–gel silica materials were placed on the glass surfaces in order to achieve the antireflective and hydrophobic fluorinated hybrid films. The structure and surface properties of the final samples were investigated by Fourier transform infrared spectroscopy (FTIR), ultraviolet/visible spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) determinations. FTIR spectra demonstrated the presence of a silica network modified with alkyl and fluoroalkyl groups. Thermal analysis showed that the fluorinated sol–gel silica materials prepared with HDTMES have a good thermostability in comparison with other samples. Ultraviolet/visible spectra indicated that the fluorinated hybrid films present a reflectance of ~9.5%, measured at 550 nm. The water contact angle analysis found that the wettability of fluorinated hybrid films was changed from hydrophilic (64°) to hydrophobic (~104°). These hybrid films based on fluorinated sol–gel silica materials can be useful in various electronics and optics fields.

Bio-Based Poly(lactic acid)/Poly(butylene sebacate) Blends with Improved Toughness
Adriana Nicoleta Frone, Marius Stelian Popa, Cătălina Diana Uşurelu, Denis Mihaela Panaitescu, Augusta Raluca Gabor, Cristian Andi Nicolae, Monica Florentina Raduly, Anamaria Zaharia, and Elvira Alexandrescu
MDPI AG
A series of poly(butylene sebacate) (PBSe) aliphatic polyesters were successfully synthesized by the melt polycondensation of sebacic acid (Se) and 1,4-butanediol (BDO), two monomers manufactured on an industrial scale from biomass. The number average molecular weight (Mn) in the range from 6116 to 10,779 g/mol and the glass transition temperature (Tg) of the PBSe polyesters were tuned by adjusting the feed ratio between the two monomers. Polylactic acid (PLA)/PBSe blends with PBSe concentrations between 2.5 to 20 wt% were obtained by melt compounding. For the first time, PBSe’s effect on the flexibility and toughness of PLA was studied. As shown by the torque and melt flow index (MFI) values, the addition of PBSe endowed PLA with both enhanced melt processability and flexibility. The tensile tests and thermogravimetric analysis showed that PLA/PBSe blends containing 20 wt% PBSe obtained using a BDO molar excess of 50% reached an increase in elongation at break from 2.9 to 108%, with a negligible decrease in Young’s modulus from 2186 MPa to 1843 MPa, and a slight decrease in thermal performances. These results demonstrated the plasticizing efficiency of the synthesized bio-derived polyesters in overcoming PLA’s brittleness. Moreover, the tunable properties of the resulting PBSe can be of great industrial interest in the context of circular bioeconomy.

Hybrid Organic-Inorganic Materials Used to Improve the Environment and Human Health
Florentina Monica Raduly and Radu Claudiu Fierăscu
MDPI AG
The Special Issue on “Hybrid Organic-Inorganic Materials Used to Improve the Environment and Human Health” is a collection of 11 original articles (including one communication paper) dedicated to theoretical and experimental research works providing new insights and practical findings in the fields of the environmental protection and human health—related topics [...]

Influence of Organic-Modified Inorganic Matrices on the Optical Properties of Palygorskite–Curcumin-Type Hybrid Materials
Florentina Monica Raduly, Valentin Rădițoiu, Radu Claudiu Fierăscu, Alina Rădițoiu, Cristian Andi Nicolae, and Violeta Purcar
MDPI AG
Clays are very important from an economic and application point of view, as they are suitable hosts for organic compounds. In order to diversify the fields of application, they are structurally modified by physical or chemical methods with cationic species, and/or different bifunctional compounds, such as organosilanes. In this study, palygorskite was modified with (3-Aminopropyl) triethoxysilane, which was subsequently modified at the amino group by grafting an acetate residue. By using this strategy, two types of host hybrid materials were obtained on which curcumin derivatives were deposited. The composites obtained were structurally characterized and their photophysical properties were investigated in relation to the structure of the host matrices and interactions with curcumin-type visiting species. The hybrid composites have different colors (orange, yellow, pink), depending on the polarity of the inorganic matrices modulated by different organic groups grafted at the surface. Fluorescence emission in the visible range is characterized by the presence of two emission maxima, one belonging to the chromophore and the other influenced by the physical interactions between auxochromes and host matrices. These hybrid materials, compared to other composite structures, are obtained by a simple adsorption process. They are temperature stable in aggressive environments (acid/base) and render the fluorescent properties of dyes redundant, with improved luminescent performance compared to them.

Florentina Monica Raduly

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