Molecules

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32 pages, 9427 KiB

Open AccessArticle

2,5-Dimethylfuran Production by Catalytic Hydrogenation of 5-Hydroxymethylfurfural Using Ni Supported on Al₂O₃-TiO₂-ZrO₂ Prepared by Sol-Gel Method: The Effect of Hydrogen Donors

by Jorge Cortez-Elizalde, Gerardo E. Córdova-Pérez, Adib Abiu Silahua-Pavón, Hermicenda Pérez-Vidal, Adrián Cervantes-Uribe, Adrián Cordero-García, Juan Carlos Arévalo-Pérez, Norma Leticia Becerril-Altamirano, Nayi Cristel Castillo-Gallegos, María Antonia Lunagómez-Rocha, Jorge Noe Díaz de León, Zenaida Guerra-Que, Alejandra E. Espinosa de los Monteros and José Gilberto Torres-Torres

Molecules 2022, 27(13), 4187; https://doi.org/10.3390/molecules27134187 - 29 Jun 2022

Cited by 2 | Viewed by 2570

Abstract

5-Hydroxymethylfurfural (5-HMF) has been described as one of the 12 key platform molecules derived from biomass by the US Department of Energy, and its hydrogenation reaction produces versatile liquid biofuels such as 2,5-dimethylfuran (2,5-DMF). Catalytic hydrogenation from 5-HMF to 2,5-DMF was thoroughly studied [...] Read more.

5-Hydroxymethylfurfural (5-HMF) has been described as one of the 12 key platform molecules derived from biomass by the US Department of Energy, and its hydrogenation reaction produces versatile liquid biofuels such as 2,5-dimethylfuran (2,5-DMF). Catalytic hydrogenation from 5-HMF to 2,5-DMF was thoroughly studied on the metal nickel catalysts supported on Al₂O₃-TiO₂-ZrO₂ (Ni/ATZ) mixed oxides using isopropanol and formic acid (FA) as hydrogen donors to find the best conditions of the reaction and hydrogen donor. The influence of metal content (wt%), Ni particle size (nm), Nickel Ni⁰, Ni⁰/NiO and NiO species, metal active sites and acid-based sites on the catalyst surface, and the effect of the hydrogen donor (isopropanol and formic acid) were systematically studied. The structural characteristics of the materials were studied using different physicochemical methods, including N₂ physisorption, XRD, Raman, DRS UV-Vis, FT-IR, SEM, FT-IR Py_ad, H₂-TPD, CO₂-TPD, H₂-TPR, TEM and XPS. Second-generation 2,5-DMF biofuel and 5-HMF conversion by-products were analyzed and elucidated using ¹H NMR. It was found that the Ni⁰NiO/ATZ3_WI catalyst synthesized by the impregnation method (WI) generated a good synergistic effect between the species, showing the best catalytic hydrogenation of 5-HMF to 2,5-DMF using formic acid as a hydrogen donor for 24 h of reaction and temperature of 210 °C with 20 bar pressure of Argon (Ar). Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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12 pages, 5069 KiB

Open AccessArticle

Antibacterial and Chemical Characterization of Silica-Quercetin-PEG Hybrid Materials Synthesized by Sol–Gel Route

by Ignazio Blanco, Alberta Latteri, Gianluca Cicala, Antonio D’Angelo, Veronica Viola, Vincenzo Arconati and Michelina Catauro

Molecules 2022, 27(3), 979; https://doi.org/10.3390/molecules27030979 - 1 Feb 2022

Cited by 13 | Viewed by 2511

Abstract

This paper aims to synthesize, via the sol–gel method, a biomaterial usable in the medical field. Here, the silica-PEG-quercetin system was evaluated in relation to the different concentrations of PEG (0, 6, 12, 24, 50 wt%) and quercetin (0, 5, 10, 15 wt%), [...] Read more.

This paper aims to synthesize, via the sol–gel method, a biomaterial usable in the medical field. Here, the silica-PEG-quercetin system was evaluated in relation to the different concentrations of PEG (0, 6, 12, 24, 50 wt%) and quercetin (0, 5, 10, 15 wt%), respectively. In addition, Fourier Transform-Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and Kirby–Bauer analyses were performed. FT-IR was used to evaluate the hybrid formation and the influence of both PEG and Quercetin in the hybrid synthesized materials, SEM was used to evaluate the morphological properties, while the Kirby–Bauer test was used to understand the ability of the materials to inhibit the growth of the assayed bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus). Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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11 pages, 3077 KiB

Open AccessArticle

Sol-Gel Composites-Based Flexible and Transparent Amorphous Indium Gallium Zinc Oxide Thin-Film Synaptic Transistors for Wearable Intelligent Electronics

by Jin-Gi Min and Won-Ju Cho

Molecules 2021, 26(23), 7233; https://doi.org/10.3390/molecules26237233 - 29 Nov 2021

Cited by 2 | Viewed by 2122

Abstract

In this study, we propose the fabrication of sol-gel composite-based flexible and transparent synaptic transistors on polyimide (PI) substrates. Because a low thermal budget process is essential for the implementation of high-performance synaptic transistors on flexible PI substrates, microwave annealing (MWA) as a [...] Read more.

In this study, we propose the fabrication of sol-gel composite-based flexible and transparent synaptic transistors on polyimide (PI) substrates. Because a low thermal budget process is essential for the implementation of high-performance synaptic transistors on flexible PI substrates, microwave annealing (MWA) as a heat treatment process suitable for thermally vulnerable substrates was employed and compared to conventional thermal annealing (CTA). In addition, a solution-processed wide-bandgap amorphous In-Ga-Zn (2:1:1) oxide (a-IGZO) channel, an organic polymer chitosan electrolyte-based electric double layer (EDL), and a high-k Ta₂O₅ thin-film dielectric layer were applied to achieve high flexibility and transparency. The essential synaptic plasticity of the flexible and transparent synaptic transistors fabricated with the MWA process was demonstrated by single spike, paired-pulse facilitation, multi-spike facilitation excitatory post-synaptic current (EPSC), and three-cycle evaluation of potentiation and depression behaviors. Furthermore, we verified the mechanical robustness of the fabricated device through repeated bending tests and demonstrated that the electrical properties were stably maintained. As a result, the proposed sol-gel composite-based synaptic transistors are expected to serve as transparent and flexible intelligent electronic devices capable of stable neural operation. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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13 pages, 4090 KiB

Open AccessArticle

Highly Porous Hydroxyapatite/Graphene Oxide/Chitosan Beads as an Efficient Adsorbent for Dyes and Heavy Metal Ions Removal

by Nguyen Van Hoa, Nguyen Cong Minh, Hoang Ngoc Cuong, Pham Anh Dat, Pham Viet Nam, Pham Hau Thanh Viet, Pham Thi Dan Phuong and Trang Si Trung

Molecules 2021, 26(20), 6127; https://doi.org/10.3390/molecules26206127 - 11 Oct 2021

Cited by 25 | Viewed by 2915

Abstract

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared [...] Read more.

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g⁻¹ for MB and copper ions removal, respectively. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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12 pages, 3911 KiB

Open AccessArticle

Photocatalytic Crystalline and Amorphous TiO₂ Nanotubes Prepared by Electrospinning and Atomic Layer Deposition

by Orsolya Kéri, Eszter Kocsis, Dániel Attila Karajz, Zsombor Kristóf Nagy, Bence Parditka, Zoltán Erdélyi, Anna Szabó, Klára Hernádi and Imre Miklós Szilágyi

Molecules 2021, 26(19), 5917; https://doi.org/10.3390/molecules26195917 - 29 Sep 2021

Cited by 16 | Viewed by 2315

Abstract

In this work core/shell composite polymer/TiO₂ nanofibers and from those TiO₂ nanotubes were prepared. First, poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) fibers were synthetized by electrospinning. They were covered with a 100 nm thick amorphous TiO₂ layer by atomic layer [...] Read more.

In this work core/shell composite polymer/TiO₂ nanofibers and from those TiO₂ nanotubes were prepared. First, poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) fibers were synthetized by electrospinning. They were covered with a 100 nm thick amorphous TiO₂ layer by atomic layer deposition at 50 °C. Later the polymer core was removed by two different methods: dissolution and annealing. In the case of dissolution in water, the as-prepared TiO₂ nanotubes remained amorphous, while when annealing was used to remove the polymers, the TiO₂ crystallized in anatase form. Due to this, the properties of amorphous and crystalline TiO₂ nanotubes with exactly the same structure and morphology could be compared. The samples were investigated by SEM-EDX, ATR-IR, UV-Vis, XRD and TG/DTA-MS. Finally, the photocatalytic properties of the TiO₂ nanotubes were studied by decomposing methyl-orange dye under UV light. According to the results, crystalline anatase TiO₂ nanotubes reached the photocatalytic performance of P25, while amorphous TiO₂ nanotubes had observable photocatalytic activity. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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16 pages, 4699 KiB

Open AccessArticle

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO₂ Aerogel’s Structure

by Jolanta Doneliene, Egle Fataraite-Urboniene, Matas Rudzikas, Saulius Pakalka, Nina Danchova and Juras Ulbikas

Molecules 2021, 26(16), 5090; https://doi.org/10.3390/molecules26165090 - 22 Aug 2021

Cited by 7 | Viewed by 2626

Abstract

The aim of this investigation was to synthesize high porosity TiO₂ aerogel by applying sol-gel and subcritical drying methods and to identify the influence of reagent’s nature and synthesis conditions on their structural and optical properties. Methods of XRD, FT-IR, BET, STA, [...] Read more.

The aim of this investigation was to synthesize high porosity TiO₂ aerogel by applying sol-gel and subcritical drying methods and to identify the influence of reagent’s nature and synthesis conditions on their structural and optical properties. Methods of XRD, FT-IR, BET, STA, SEM, and UV-vis were applied to investigate and compare the properties of synthesized TiO₂ aerogels and to determine the most effective synthesis route. The structural parameters of the synthesized materials can be varied by changing the precursor type (titanium (IV), isopropoxide (TIP), or tetrabutylorthotitanate (TBOT)) and the nature of the solvent used for additional exchange (n-hexane (nH), cyclohexane (CH), or diethyl ether (DE)). All of the subcritical dried samples show the amorphous structure, which tends to crystallize into the anatase phase after calcination. The number of micro and mesopores and the specific surface area depends on the synthesis conditions. The pores with the highest diameter have been found for additionally nH exchanged and aged aerogel synthesized from precursor TIP. Despite the imperfections in the structure, the produced aerogels show structural and optical properties typical of the TiO₂ structures mentioned in the literature. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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16 pages, 3668 KiB

Open AccessArticle

The Influence of Nd and Sm on the Structure and Properties of Sol-Gel-Derived TiO₂ Powders

by Albena Bachvarova-Nedelcheva, Stancho Yordanov, Reni Iordanova, Irina Stambolova, Angelina Stoyanova, Nelly Georgieva and Veronica Nemska

Molecules 2021, 26(13), 3824; https://doi.org/10.3390/molecules26133824 - 23 Jun 2021

Cited by 11 | Viewed by 2134

Abstract

TiO₂ nanopowders modified by Nd and Sm were prepared using the sol-gel technique. It was found by XRD analysis that the samples containing Sm are amorphous up to 300 °C, while those with Nd preserve a mixed organic-inorganic amorphous structure at higher [...] Read more.

TiO₂ nanopowders modified by Nd and Sm were prepared using the sol-gel technique. It was found by XRD analysis that the samples containing Sm are amorphous up to 300 °C, while those with Nd preserve a mixed organic-inorganic amorphous structure at higher temperatures (400 °C). The TiO₂ (rutile) was not detected up to 700 °C in the presence of both modified oxides. TiO₂ (anatase) crystals found at about 400 °C in the Sm-modified sample exhibited an average crystallite size of about 25–30 nm, while doping with Nd resulted in particles of a lower size—5–10 nm. It was established by DTA that organic decomposition is accompanied by significant weight loss occurring in the temperature range 240–350 °C. Photocatalytic tests showed that the samples heated at 500 °C possess photocatalytic activity under UV irradiation toward Malachite green organic dye. Selected compositions exhibited good antimicrobial activity against E. coli K12 and B. subtilis. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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12 pages, 2829 KiB

Open AccessArticle

Spectral and Texture Properties of Hydrophobic Aerogel Powders Obtained from Room Temperature Drying

by Dimitar Shandurkov, Petar Ignatov, Ivanka Spassova and Stoyan Gutzov

Molecules 2021, 26(6), 1796; https://doi.org/10.3390/molecules26061796 - 23 Mar 2021

Cited by 6 | Viewed by 2372

Abstract

Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy and texture measurements based on nitrogen adsorption-desorption isotherms are combined to characterize silica aerogel granules with different degrees of hydrophobicity. The aerogels were prepared from tetraethoxysilane via a room temperature hydrolysis-gelation process, solvent exchange, hydrophobization, and drying [...] Read more.

Attenuated Total Reflectance Infrared (ATR-IR) spectroscopy and texture measurements based on nitrogen adsorption-desorption isotherms are combined to characterize silica aerogel granules with different degrees of hydrophobicity. The aerogels were prepared from tetraethoxysilane via a room temperature hydrolysis-gelation process, solvent exchange, hydrophobization, and drying at subcritical conditions. The dependencies between the texture properties, pore architectures, surface fractal dimensions, and degree of hydrophobicity of the samples are extracted from the ATR-IR spectra and the adsorption-desorption isotherms. The IR absorption in the region of the Si-O-Si and Si-OH vibrations is used for a description of the structural and chemical changes in aerogel powders connected with their surface hydrophobization. The Frenkel–Halsey–Hill (FHH) theory is applied to determine the surface fractal dimension of the powder species. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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