Molecules

Editorial

Jump to: Research, Review

7 pages, 399 KiB

Open AccessEditorial

Sol-Gel Chemistry: From Molecule to Functional Materials

by Sébastien Clément and Ahmad Mehdi

Molecules 2020, 25(11), 2538; https://doi.org/10.3390/molecules25112538 - 29 May 2020

Cited by 9 | Viewed by 4050

Abstract

Through this Special Issue, you will discover the potentiality of inorganic polymerization (sol-gel process) which is a unique and versatile way for the preparation of materials [...] Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

Research

Jump to: Editorial, Review

16 pages, 8394 KiB

Open AccessArticle

Periodic Mesoporous Organosilica Nanoparticles with BOC Group, towards HIFU Responsive Agents

by Hao Li, Carolina Gascó, Anthony Delalande, Clarence Charnay, Laurence Raehm, Patrick Midoux, Chantal Pichon, Roser Pleixats and Jean-Olivier Durand

Molecules 2020, 25(4), 974; https://doi.org/10.3390/molecules25040974 - 21 Feb 2020

Cited by 11 | Viewed by 4017

Abstract

Periodic Mesoporous Organosilica Nanoparticles (PMONPs) are nanoparticles of high interest for nanomedicine applications. These nanoparticles are not composed of silica (SiO₂). They belong to hybrid organic–inorganic systems. We considered using these nanoparticles for CO₂ release as a contrast agent for [...] Read more.

Periodic Mesoporous Organosilica Nanoparticles (PMONPs) are nanoparticles of high interest for nanomedicine applications. These nanoparticles are not composed of silica (SiO₂). They belong to hybrid organic–inorganic systems. We considered using these nanoparticles for CO₂ release as a contrast agent for High Intensity Focused Ultrasounds (HIFU). Three molecules (P1–P3) possessing two to four triethoxysilyl groups were synthesized through click chemistry. These molecules possess a tert-butoxycarbonyl (BOC) group whose cleavage in water at 90–100 °C releases CO₂. Bis(triethoxysilyl)ethylene E was mixed with the molecules Pn (or not for P3) at a proportion of 90/10 to 75/25, and the polymerization triggered by the sol-gel procedure led to PMONPs. PMONPs were characterized by different techniques, and nanorods of 200–300 nm were obtained. These nanorods were porous at a proportion of 90/10, but non-porous at 75/25. Alternatively, molecules P3 alone led to mesoporous nanoparticles of 100 nm diameter. The BOC group was stable, but it was cleaved at pH 1 in boiling water. Molecules possessing a BOC group were successfully used for the preparation of nanoparticles for CO₂ release. The BOC group was stable and we did not observe release of CO₂ under HIFU at lysosomal pH of 5.5. The pH needed to be adjusted to 1 in boiling water to cleave the BOC group. Nevertheless, the concept is interesting for HIFU theranostic agents. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

20 pages, 3667 KiB

Open AccessArticle

In Depth Analysis of Photovoltaic Performance of Chlorophyll Derivative-Based “All Solid-State” Dye-Sensitized Solar Cells

by Michèle Chevrier, Alberto Fattori, Laurent Lasser, Clément Kotras, Clémence Rose, Michela Cangiotti, David Beljonne, Ahmad Mehdi, Mathieu Surin, Roberto Lazzaroni, Philippe Dubois, Maria Francesca Ottaviani, Sébastien Richeter, Johann Bouclé and Sébastien Clément

Molecules 2020, 25(1), 198; https://doi.org/10.3390/molecules25010198 - 3 Jan 2020

Cited by 11 | Viewed by 4407

Abstract

Chlorophyll a derivatives were integrated in “all solid-state” dye sensitized solar cells (DSSCs) with a mesoporous TiO₂ electrode and 2′,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin [...] Read more.

Chlorophyll a derivatives were integrated in “all solid-state” dye sensitized solar cells (DSSCs) with a mesoporous TiO₂ electrode and 2′,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption …) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO₂ surface were found to be the key parameters that govern their photovoltaic response. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

10 pages, 2601 KiB

Open AccessArticle

Encapsulation of Upconversion Nanoparticles in Periodic Mesoporous Organosilicas

by Saher Rahmani, Chiara Mauriello Jimenez, Dina Aggad, Daniel González-Mancebo, Manuel Ocaña, Lamiaa M. A. Ali, Christophe Nguyen, Ana Isabel Becerro Nieto, Nadège Francolon, Erwan Oliveiro, Damien Boyer, Rachid Mahiou, Laurence Raehm, Magali Gary-Bobo, Jean-Olivier Durand and Clarence Charnay

Molecules 2019, 24(22), 4054; https://doi.org/10.3390/molecules24224054 - 9 Nov 2019

Cited by 4 | Viewed by 3343

Abstract

(1) Background: Nanomedicine has recently emerged as a promising field, particularly for cancer theranostics. In this context, nanoparticles designed for imaging and therapeutic applications are of interest. We, therefore, studied the encapsulation of upconverting nanoparticles in mesoporous organosilica nanoparticles. Indeed, mesoporous organosilica nanoparticles [...] Read more.

(1) Background: Nanomedicine has recently emerged as a promising field, particularly for cancer theranostics. In this context, nanoparticles designed for imaging and therapeutic applications are of interest. We, therefore, studied the encapsulation of upconverting nanoparticles in mesoporous organosilica nanoparticles. Indeed, mesoporous organosilica nanoparticles have been shown to be very efficient for drug delivery, and upconverting nanoparticles are interesting for near-infrared and X-ray computed tomography imaging, depending on the matrix used. (2) Methods: Two different upconverting-based nanoparticles were synthesized with Yb³⁺-Er³⁺ as the upconverting system and NaYF₄ or BaLuF₅ as the matrix. The encapsulation of these nanoparticles was studied through the sol-gel procedure with bis(triethoxysilyl)ethylene and bis(triethoxysilyl)ethane in the presence of CTAB. (3) Results: with bis(triethoxysilyl)ethylene, BaLuF₅: Yb³⁺-Er³⁺, nanoparticles were not encapsulated, but anchored on the surface of the obtained mesoporous nanorods BaLuF₅: Yb³⁺-Er³⁺@Ethylene. With bis(triethoxysilyl)ethane, BaLuF₅: Yb³⁺-Er³⁺ and NaYF₄: Yb³⁺-Er³⁺nanoparticles were encapsulated in the mesoporous cubic structure leading to BaLuF₅: Yb³⁺-Er³⁺@Ethane and NaYF₄: Yb³⁺-Er³⁺@Ethane, respectively. (4) Conclusions: upconversion nanoparticles were located on the surface of mesoporous nanorods obtained by hydrolysis polycondensation of bis(triethoxysilyl)ethylene, whereas encapsulation occurred with bis(triethoxysilyl)ethane. The later nanoparticles NaYF₄: Yb³⁺-Er³⁺@Ethane or BaLuF₅: Yb³⁺-Er³⁺@Ethane were promising for applications with cancer cell imaging or X-ray-computed tomography respectively. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

17 pages, 4357 KiB

Open AccessArticle

Assessment of Antifouling Potential of Novel Transparent Sol Gel Coatings for Application in the Marine Environment

by Chloe Richards, Ciprian Briciu-Burghina, Matthew R. Jacobs, Alan Barrett and Fiona Regan

Molecules 2019, 24(16), 2983; https://doi.org/10.3390/molecules24162983 - 16 Aug 2019

Cited by 13 | Viewed by 4794

Abstract

In recent years, there has become a growing need for the development of antifouling technology for application in the marine environment. The accumulation of large quantities of biomass on these surfaces cause substantial economic burdens within the marine industry, or adversely impact the [...] Read more.

In recent years, there has become a growing need for the development of antifouling technology for application in the marine environment. The accumulation of large quantities of biomass on these surfaces cause substantial economic burdens within the marine industry, or adversely impact the performance of sensor technologies. Here, we present a study of transparent coatings with potential for applications on sensors or devices with optical windows. The focus of the study is on the abundance and diversity of biofouling organisms that accumulate on glass panels coated with novel transparent or opaque organically modified silicate (ORMOSIL) coatings. The diatom assessment was used to determine the effectiveness of the coatings against biofouling. Test panels were deployed in a marine environment in Galway Bay for durations of nine and thirteen months to examine differences in biofilm formation in both microfouling and macrofouling conditions. The most effective coating is one which consists of precursor, tetraethyl orthosilicate (HC006) that has a water contact angle > 100, without significant roughness (43.52 nm). However, improved roughness and wettability of a second coating, diethoxydimethylsilane (DMDEOS), showed real promise in relation to macrofouling reduction. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

14 pages, 4286 KiB

Open AccessArticle

Monitoring Silane Sol-Gel Kinetics with In-Situ Optical Turbidity Scanning and Dynamic Light Scattering

by Abul Bashar Mohammad Giasuddin and David W. Britt

Molecules 2019, 24(16), 2931; https://doi.org/10.3390/molecules24162931 - 13 Aug 2019

Cited by 9 | Viewed by 5414

Abstract

Organosilanes (e.g., R’-SiOR₃) provide hydrophobic functionality in thin-film coatings, porous gels, and particles. Compared with tetraalkoxysilanes (SiOR₄), organosilanes exhibit distinct reaction kinetics and assembly mechanisms arising from steric and electronic properties of the R’ group on the silicon atom. [...] Read more.

Organosilanes (e.g., R’-SiOR₃) provide hydrophobic functionality in thin-film coatings, porous gels, and particles. Compared with tetraalkoxysilanes (SiOR₄), organosilanes exhibit distinct reaction kinetics and assembly mechanisms arising from steric and electronic properties of the R’ group on the silicon atom. Here, the hydrolysis and condensation pathways of n-propyltrimethoxy silane (nPM) and a tri-fluorinated analog of nPM, 3,3,3-trifluoropropyl trimethoxy silane (3F), were investigated under aqueous conditions at pH 1.7, 2.0, 3.0, and 4.0. Prior to hydrolysis, 3F and nPM are insoluble in water and form a lens at the bottom (3F) or top (nPM) of the solutions. This phase separation was employed to follow reaction kinetics using a Turbiscan instrument to monitor hydrolysis through solubilization of the neat silane lens while simultaneously tracking condensation-induced turbidity throughout the bulk solution. Dynamic light scattering confirmed the silane condensation and particle aggregation processes reported by the turbidity scanning. Employing macroscopic phase separation of the starting reactants from the solvent further allows for control over the reaction kinetics, as the interfacial area can be readily controlled by reaction vessel geometry, namely by controlling the surface area to volume. In-situ turbidity scanning and dynamic light scattering revealed distinct reaction kinetics for nPM and 3F, attributable to the electron withdrawing and donating nature of the fluoro- and organo-side chains of 3F and nPM, respectively. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

9 pages, 4217 KiB

Open AccessArticle

Microwave Assisted Sol-Gel Synthesis of Silica-Spider Silk Composites

by Abul Bashar Mohammad Giasuddin and David W. Britt

Molecules 2019, 24(14), 2521; https://doi.org/10.3390/molecules24142521 - 10 Jul 2019

Cited by 7 | Viewed by 3927

Abstract

This study introduces a simple and environmentally friendly method to synthesize silica-protein nanocomposite materials using microwave energy to solubilize hydrophobic protein in an aqueous solution of pre-hydrolyzed organo- or fluoro-silane. Sol-gel functionality can be enhanced through biomacromolecule incorporation to tune mechanical properties, surface [...] Read more.

This study introduces a simple and environmentally friendly method to synthesize silica-protein nanocomposite materials using microwave energy to solubilize hydrophobic protein in an aqueous solution of pre-hydrolyzed organo- or fluoro-silane. Sol-gel functionality can be enhanced through biomacromolecule incorporation to tune mechanical properties, surface energy, and biocompatibility. Here, synthetic spider silk protein and organo- and fluoro-silane precursors were dissolved and mixed in weakly acidic aqueous solution using microwave technology. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) images revealed the formation of spherical nanoparticles with sizes ranging from 100 to 500 nm depending, in part, on silane fluoro- or organo-side chain chemistry. The silane-protein interaction in the nanocomposite was assessed through infrared spectroscopy. Deconvoluted ATR-FTIR (Attenuated total reflectance Fourier-transform infrared spectroscopy) spectra revealed silane chemistry-specific conformational changes in the protein-silane nanocomposites. Relative to microwave-solubilized spider silk protein, the β structure content increased by 14% in the spider silk-organo-silica nanocomposites, but decreased by a net 20% in the spider silk-fluoro-silica nanocomposites. Methods of tuning the secondary structures, and in particular β-sheets that are the cross-linking moieties in spider silks and other self-assembling fibrillar proteins, may provide a unique means to promote protein interactions, favor subsequent epitaxial growth process, and enhance the properties of the protein-silane nanocomposites. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

15 pages, 5577 KiB

Open AccessArticle

TiO₂-Based Hybrid Nanocomposites Modified by Phosphonate Molecules as Selective PAH Adsorbents

by Nadine Bou Orm, Quoc An Trieu and Stephane Daniele

Molecules 2018, 23(11), 3046; https://doi.org/10.3390/molecules23113046 - 21 Nov 2018

Cited by 11 | Viewed by 4244

Abstract

A robust sol-gel process was developed for the synthesis of surface-functionalized titania nanocrystallites bearing unsaturated groups starting from molecular heteroleptic single-source precursors. Molecules and nanomaterials were thoroughly characterized by multinuclear liquid and solid-state nuclear magnetic resonance (NMR), infra-red (FT-IR, DRIFT) spectroscopies. Nitrogen adsorption-desorption [...] Read more.

A robust sol-gel process was developed for the synthesis of surface-functionalized titania nanocrystallites bearing unsaturated groups starting from molecular heteroleptic single-source precursors. Molecules and nanomaterials were thoroughly characterized by multinuclear liquid and solid-state nuclear magnetic resonance (NMR), infra-red (FT-IR, DRIFT) spectroscopies. Nitrogen adsorption-desorption (BET), thermogravimetric (TG) and elemental analyses demonstrated the reliability and the fine tuning of the surface functionalization in terms of ratio TiO₂:ligand. The as-prepared materials were used as nano-adsorbents to remove mixture of 16 polycyclic aromatic hydrocarbon (PAHs) from aqueous solutions. Adsorption kinetic experiments were carried out for 24 h in solutions of one PAH [benzo(a)pyrene, 220 ppb] and of a mixture of sixteen ones [220 ppb for each PAH]. Most kinetic data best fitted the pseudo-second order model. However, in PAHs mixture, a competition process took place during the first hours leading to a remarkable high selectivity between light and heavy PAHs. This selectivity could be fine-tuned depending on the nature of the unsaturated group of the phosphonate framework and on the nanomaterial textures. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

11 pages, 3187 KiB

Open AccessArticle

Tuning Texture and Morphology of Mesoporous TiO₂ by Non-Hydrolytic Sol-Gel Syntheses

by Yanhui Wang, Maroua Bouchneb, Johan G. Alauzun and P. Hubert Mutin

Molecules 2018, 23(11), 3006; https://doi.org/10.3390/molecules23113006 - 17 Nov 2018

Cited by 6 | Viewed by 4566

Abstract

The development of powerful synthetic methodologies is paramount in the design of advanced nanostructured materials. Owing to its remarkable properties and low cost, nanostructured TiO₂ is widely investigated for applications such as photocatalysis, energy conversion or energy storage. In this article we [...] Read more.

The development of powerful synthetic methodologies is paramount in the design of advanced nanostructured materials. Owing to its remarkable properties and low cost, nanostructured TiO₂ is widely investigated for applications such as photocatalysis, energy conversion or energy storage. In this article we report the synthesis of mesoporous TiO₂ by three different non-hydrolytic sol-gel routes, and we investigate the influence of the synthetic route and of the presence and nature of the solvent on the structure, texture and morphology of the materials. The first route is the well-known ether route, based on the reaction of TiCl₄ with ⁱPr₂O. The second and third routes, which have not been previously described for the synthesis of mesoporous TiO₂, involve the reaction of Ti(OⁱPr)₄ with stoichiometric amounts of acetophenone and benzoic anhydride, respectively. All materials are characterized by XRD, N₂ physisorption and SEM. By playing with the non-hydrolytic route used and the reaction conditions (presence of a solvent, nature of the solvent, calcination), it is possible to tune the morphology and texture of the TiO₂. Depending on the reaction conditions, a large variety of mesoporous TiO₂ nanostructures could be obtained, resulting from the spontaneous aggregation of TiO₂ nanoparticles, either rounded nanoparticles, platelets or nanorods. These nanoparticle networks exhibited a specific surface area up to 250 m² g⁻¹ before calcination, or up to 110 m² g⁻¹ after calcination. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

15 pages, 4927 KiB

Open AccessArticle

Development of Zinc-Doped Hydroxyapatite by Sol-Gel Method for Medical Applications

by Catalin Constantin Negrila, Mihai Valentin Predoi, Simona Liliana Iconaru and Daniela Predoi

Molecules 2018, 23(11), 2986; https://doi.org/10.3390/molecules23112986 - 15 Nov 2018

Cited by 74 | Viewed by 5470

Abstract

Zinc- (Zn) doped hydroxyapatite (HAp) were prepared by sol-gel method. Zinc-doped hydroxyapatite (ZnHAp) and HAp were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Rietveld analysis revealed that the HAp and 7ZnHAp powders obtained by sol-gel method have a monophasic [...] Read more.

Zinc- (Zn) doped hydroxyapatite (HAp) were prepared by sol-gel method. Zinc-doped hydroxyapatite (ZnHAp) and HAp were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Rietveld analysis revealed that the HAp and 7ZnHAp powders obtained by sol-gel method have a monophasic hydroxyapatite structure belonging to the P6_3/m spatial group. The results obtained from the ultrasound characterization of HAp and ZnHAp are also presented in this study. The effect of zinc concentration on properties that were deduced from ultrasonic measurements are studied in the case of a significant zinc concentration (x_Zn = 0.07). From the values of the ultrasonic waves velocities were determined by the pairs of elastic coefficients of the suspensions (Young modulus E, Poisson coefficient ν), which have proven to be similar to those determined by other authors. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

13 pages, 1780 KiB

Open AccessFeature PaperArticle

New Layered Polythiophene-Silica Composite Through the Self-Assembly and Polymerization of Thiophene-Based Silylated Molecular Precursors

by Marie-José Zacca, Danielle Laurencin, Sébastien Richeter, Sébastien Clément and Ahmad Mehdi

Molecules 2018, 23(10), 2510; https://doi.org/10.3390/molecules23102510 - 30 Sep 2018

Cited by 7 | Viewed by 3665

Abstract

A new layered hybrid polythiophene-silica material was obtained directly by hydrolysis and polycondensation (sol-gel) of a silylated-thiophene bifunctional precursor, and its subsequent oxidative polymerization by FeCl₃. This precursor was judiciously designed to guarantee its self-assembly and the formation of a lamellar [...] Read more.

A new layered hybrid polythiophene-silica material was obtained directly by hydrolysis and polycondensation (sol-gel) of a silylated-thiophene bifunctional precursor, and its subsequent oxidative polymerization by FeCl₃. This precursor was judiciously designed to guarantee its self-assembly and the formation of a lamellar polymer-silica structure, exploiting the cooperative effect between the hydrogen bonding interactions, originating from the ureido groups and the π-stacking interactions between the thiophene units. The lamellar structure of the polythiophene-silica composite was confirmed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) analyses. The solid-state nuclear magnetic resonance (NMR), UV-Vis, and photoluminescence spectra unambiguously indicate the incorporation of polythiophene into the silica matrix. Our work demonstrates that using a polymerizable silylated-thiophene precursor is an efficient approach towards the formation of nanostructured conjugated polymer-based hybrid materials. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

15 pages, 6746 KiB

Open AccessArticle

Silica/Polyethylene Glycol Hybrid Materials Prepared by a Sol-Gel Method and Containing Chlorogenic Acid

by Michelina Catauro, Elisabetta Tranquillo, Alessia Salzillo, Lucia Capasso, Michela Illiano, Luigi Sapio and Silvio Naviglio

Molecules 2018, 23(10), 2447; https://doi.org/10.3390/molecules23102447 - 25 Sep 2018

Cited by 22 | Viewed by 4036

Abstract

Chlorogenic acid (CGA) is a very common dietary polyphenolic compound. CGA is becoming very attractive due to its potential use as preventive and therapeutic agent in many diseases, including cancer. Inorganic/organic hybrid materials are gaining considerable attention in the biomedical field. The sol-gel [...] Read more.

Chlorogenic acid (CGA) is a very common dietary polyphenolic compound. CGA is becoming very attractive due to its potential use as preventive and therapeutic agent in many diseases, including cancer. Inorganic/organic hybrid materials are gaining considerable attention in the biomedical field. The sol-gel process provides a useful way to obtain functional organic/inorganic hybrids. The aim of this study was to synthesize silica/polyethylene glycol (PEG) hybrids with different percentages of CGA by sol-gel technique and to investigate their impact on the cancer cell proliferation. Synthesized materials have been chemically characterized through the FTIR spectroscopy and their bioactivity evaluated looking by SEM at their ability to produce a hydroxyapatite layer on their surface upon incubation with simulated body fluid (SBF). Finally, their effects on cell proliferation were studied in cell lines by direct cell number counting, MTT, flow cytometry-based cell-cycle and cell death assays, and immunoblotting experiments. Notably, we found that SiO₂/PEG/CGA hybrids exhibit clear antiproliferative effects in different tumor, including breast cancer and osteosarcoma, cell lines in a CGA dependent manner, but not in normal cells. Overall, our results increase the evidence of CGA as a possible anticancer agent and illustrate the potential for clinical applications of sol-gel synthesized SiO₂/PEG/CGA materials. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

15 pages, 3739 KiB

Open AccessArticle

Antioxidant and Fluorescence Properties of Hydrogenolyzised Polymeric Proanthocyanidins Prepared Using SO₄²⁻/ZrO₂ Solid Superacids Catalyst

by Liwen Ni, Fanbin Zhao, Bolun Li, Tong Wei, Hang Guan and Shixue Ren

Molecules 2018, 23(10), 2445; https://doi.org/10.3390/molecules23102445 - 25 Sep 2018

Cited by 15 | Viewed by 3714

Abstract

Larix bark oligomeric proanthocyanidins (LOPC) were prepared from larix bark polymeric proanthocyanidins (LPPC) by catalytic hydrogenolysis using SO₄²⁻/ZrO₂ solid superacid as the catalyst. The catalyst to polymeric proanthocyanidins ratio was 0.2:1 (m/m). The LOPC, obtained [...] Read more.

Larix bark oligomeric proanthocyanidins (LOPC) were prepared from larix bark polymeric proanthocyanidins (LPPC) by catalytic hydrogenolysis using SO₄²⁻/ZrO₂ solid superacid as the catalyst. The catalyst to polymeric proanthocyanidins ratio was 0.2:1 (m/m). The LOPC, obtained after hydrogenolysis at 100 °C for 4 h under 3 MPa hydrogen pressure, retained the structural characteristics of proanthocyanidins. The average degree of polymerization was reduced from 9.50% to 4.76% and the depolymerization yield was 53.85%. LOPC has good antioxidant properties and, at the same concentration, the reducing ability of LOPC was much higher than that of LPPC. The IC₅₀ values of LOPC for scavenging DPPH^• and ABTS^•+ radicals were 0.046 mg/mL and 0.051 mg/mL, respectively. LOPC is biocompatible and has fluorescent properties that are affected by external factors, such as solvent polarity, pH and the presence of different metal ions. These features indicate that LOPC could be developed as a new biological fluorescent marker. The depolymerization of low-value polymeric proanthocyanidins to provide high-value oligomeric proanthocyanidins and the development of new applications for proanthocyanidins represent significant advances. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

13 pages, 1261 KiB

Open AccessFeature PaperArticle

Sol-Gel Immobilisation of Lipases: Towards Active and Stable Biocatalysts for the Esterification of Valeric Acid

by Soledad Cebrián-García, Alina M. Balu, Araceli García and Rafael Luque

Molecules 2018, 23(9), 2283; https://doi.org/10.3390/molecules23092283 - 6 Sep 2018

Cited by 22 | Viewed by 4072

Abstract

Alkyl esters are high added value products useful in a wide range of industrial sectors. A methodology based on a simple sol-gel approach (biosilicification) is herein proposed to encapsulate enzymes in order to design highly active and stable biocatalysts. Their performance was assessed [...] Read more.

Alkyl esters are high added value products useful in a wide range of industrial sectors. A methodology based on a simple sol-gel approach (biosilicification) is herein proposed to encapsulate enzymes in order to design highly active and stable biocatalysts. Their performance was assessed through the optimization of valeric acid esterification evaluating the effect of different parameters (biocatalyst load, presence of water, reaction temperature and stirring rate) in different alcoholic media, and comparing two different methodologies: conventional heating and microwave irradiation. Ethyl valerate yields were in the 80–85% range under optimum conditions (15 min, 12% m/v biocatalyst, molar ratio 1:2 of valeric acid to alcohol). Comparatively, the biocatalysts were slightly deactivated under microwave irradiation due to enzyme denaturalisation. Biocatalyst reuse was attempted to prove that good reusability of these sol-gel immobilised enzymes could be achieved under conventional heating. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

14 pages, 2200 KiB

Open AccessArticle

Europium-Doped Sol-Gel SiO₂-Based Glasses: Effect of the Europium Source and Content, Magnesium Addition and Thermal Treatment on Their Photoluminescence Properties

by Hussein Fneich, Nathalie Gaumer, Stéphane Chaussedent, Wilfried Blanc and Ahmad Mehdi

Molecules 2018, 23(7), 1768; https://doi.org/10.3390/molecules23071768 - 19 Jul 2018

Cited by 18 | Viewed by 4808

Abstract

Rare-earth doped silica-based glasses lead the optical materials due to their tailorable spectroscopic and optical properties. In this context, we took advantage of the sol-gel process to prepare various Eu-doped silica glasses to study their luminescent properties before and after annealing at 900 [...] Read more.

Rare-earth doped silica-based glasses lead the optical materials due to their tailorable spectroscopic and optical properties. In this context, we took advantage of the sol-gel process to prepare various Eu-doped silica glasses to study their luminescent properties before and after annealing at 900 °C. The effect of magnesium on these properties was studied in comparison with Mg-free-glass. Using TEM, nitrogen sorption, XRD and FT-IR, we confirmed that the magnesium modifies the glass structure and the thermal treatment eliminates the aqueous environment, modifying the structure ordering. The emission spectra and the decay time curves show the advantages of the Mg addition and the annealing on the photoluminescent properties. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

20 pages, 3568 KiB

Open AccessArticle

Photonic Band Gap and Bactericide Performance of Amorphous Sol-Gel Titania: An Alternative to Crystalline TiO₂

by M. Clara Gonçalves, José Carlos Pereira, Joana C. Matos and Helena Cristina Vasconcelos

Molecules 2018, 23(7), 1677; https://doi.org/10.3390/molecules23071677 - 10 Jul 2018

Cited by 43 | Viewed by 8115

Abstract

In addition to its traditional application in white pigments, nanocrystalline titania (TiO₂) has optoelectronic and photocatalytic properties (strongly dependent on crystallinity, particle size, and surface structure) that grant this naturally occurring oxide new technological applications. Sol-gel is one of the most [...] Read more.

In addition to its traditional application in white pigments, nanocrystalline titania (TiO₂) has optoelectronic and photocatalytic properties (strongly dependent on crystallinity, particle size, and surface structure) that grant this naturally occurring oxide new technological applications. Sol-gel is one of the most widely used methods to synthesize TiO₂ films and NPs, but the products obtained (mostly oxy-hydrated amorphous phases) require severe heat-treatments to promote crystallization, in which control over size and shape is difficult to achieve. In this work, we obtained new photocatalytic materials based on amorphous titania and measured their electronic band gap. Two case studies are reported that show the enormous potential of amorphous titania as bactericide or photocatalyst. In the first, amorphous sol-gel TiO₂ thin films doped with N (TiO_2−xN_x, x = 0.75) were designed to exhibit a photonic band gap in the visible region. The identification of Ti-O-N and N-Ti-O bindings was achieved by XPS. The photonic band gaps were found to be 3.18 eV for a-TiO₂ and 2.99 eV for N-doped a-TiO₂. In the second study, amorphous titania and amine-functionalized amorphous titania nanoparticles were synthetized using a novel base-catalysed sol-gel methodology. All the synthesized amorphous TiO₂ nanoparticles exhibit bactericide performance (E. coli, ASTME 2149-13). Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

18 pages, 6922 KiB

Open AccessArticle

Tubular and Spherical SiO₂ Obtained by Sol Gel Method for Lipase Immobilization and Enzymatic Activity

by Crina Anastasescu, Silviu Preda, Adriana Rusu, Dana Culita, Gabriel Plavan, Stefan Strungaru, Jose Maria Calderon-Moreno, Cornel Munteanu, Catalina Gifu, Mirela Enache, Radu Socoteanu, Daniel Angelescu, Mihai Anastasescu, Mariuca Gartner, Ioan Balint and Maria Zaharescu

Molecules 2018, 23(6), 1362; https://doi.org/10.3390/molecules23061362 - 5 Jun 2018

Cited by 16 | Viewed by 4589

Abstract

A wide range of hybrid biomaterials has been designed in order to sustain bioremediation processes by associating sol-gel SiO₂ matrices with various biologically active compounds (enzymes, antibodies). SiO₂ is a widespread, chemically stable and non-toxic material; thus, the immobilization of enzymes [...] Read more.

A wide range of hybrid biomaterials has been designed in order to sustain bioremediation processes by associating sol-gel SiO₂ matrices with various biologically active compounds (enzymes, antibodies). SiO₂ is a widespread, chemically stable and non-toxic material; thus, the immobilization of enzymes on silica may lead to improving the efficiency of biocatalysts in terms of endurance and economic costs. Our present work explores the potential of different hybrid morphologies, based on hollow tubes and solid spheres of amorphous SiO₂, for enzyme immobilization and the development of competitive biocatalysts. The synthesis protocol and structural characterization of spherical and tubular SiO₂ obtained by the sol gel method were fully investigated in connection with the subsequent immobilization of lipase from Rhizopus orizae. The immobilization is conducted at pH 6, lower than the isoelectric point of lipase and higher than the isoelectric point of silica, which is meant to sustain the physical interactions of the enzyme with the SiO₂ matrix. The morphological, textural and surface properties of spherical and tubular SiO₂ were investigated by SEM, nitrogen sorption, and electrokinetic potential measurements, while the formation and characterization of hybrid organic-inorganic complexes were studied by UV-VIS, FTIR-ATR and fluorescence spectroscopy. The highest degree of enzyme immobilization (as depicted from total organic carbon) was achieved for tubular morphology and the hydrolysis of p-nitrophenyl acetate was used as an enzymatic model reaction conducted in the presence of hybrid lipase–SiO₂ complex. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

10 pages, 1982 KiB

Open AccessArticle

Cast-In-Situ, Large-Sized Monolithic Silica Xerogel Prepared in Aqueous System

by Wenhui Ding, Xiaodong Wang, Dong Chen, Tiemin Li and Jun Shen

Molecules 2018, 23(5), 1178; https://doi.org/10.3390/molecules23051178 - 15 May 2018

Cited by 4 | Viewed by 4432

Abstract

This paper reports the preparation of cast-in-situ, large-sized monolithic silica xerogels by a two-step acid–base catalyzed approach under ambient pressure drying. Low-cost industrial silica sol and deionized water were used as the silicon source and the solvent, respectively. Hexadecetyltrimethylammonium bromide (CTAB) was used [...] Read more.

This paper reports the preparation of cast-in-situ, large-sized monolithic silica xerogels by a two-step acid–base catalyzed approach under ambient pressure drying. Low-cost industrial silica sol and deionized water were used as the silicon source and the solvent, respectively. Hexadecetyltrimethylammonium bromide (CTAB) was used as a modification agent. Different amounts of polyethylene glycol 400 (PEG400) was added as a pore-forming agent. The prepared silica xerogels under ambient pressure drying have a mesoporous structure with a low density of 221 mg·cm⁻³ and a thermal conductivity of 0.0428 W·m⁻¹·K⁻¹. The low-cost and facile preparation process, as well as the superior performance of the monolithic silica xerogels make it a promising candidate for industrial thermal insulation materials. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Graphical abstract

15 pages, 3595 KiB

Open AccessArticle

Innovative Formulation Combining Al, Zr and Si Precursors to Obtain Anticorrosion Hybrid Sol-Gel Coating

by Clément Genet, Marie-Joëlle Menu, Olivier Gavard, Florence Ansart, Marie Gressier and Robin Montpellaz

Molecules 2018, 23(5), 1135; https://doi.org/10.3390/molecules23051135 - 10 May 2018

Cited by 7 | Viewed by 5716

Abstract

The aim of our study is to improve the aluminium alloy corrosion resistance with Organic-Inorganic Hybrid (OIH) sol-gel coating. Coatings are obtained from unusual formulation with precursors mixing: glycidoxypropyltrimethoxysilane (GPTMS), zirconium (IV) propoxide (TPOZ) and aluminium tri-sec-butoxide (ASB). This formulation was characterized and [...] Read more.

The aim of our study is to improve the aluminium alloy corrosion resistance with Organic-Inorganic Hybrid (OIH) sol-gel coating. Coatings are obtained from unusual formulation with precursors mixing: glycidoxypropyltrimethoxysilane (GPTMS), zirconium (IV) propoxide (TPOZ) and aluminium tri-sec-butoxide (ASB). This formulation was characterized and compared with sol formulations GPTMS/TPOZ and GPTMS/ASB. In each formulation, a corrosion inhibitor, cerium (III) nitrate hexahydrate, is employed to improve the corrosion performance. Coatings obtained from sol based on GPTMS/TPOZ/ASB have good anti-corrosion performances with Natural Salt Spray (NSS) resistance of 500 h for a thickness lower than 4 µm. Contact angle measurement showed a coating hydrophobic behaviour. To understand these performances, nuclear magnetic resonance (NMR) analyses were performed, results make sol-gel coating condensation evident and are in very good agreement with previous results. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

9 pages, 3101 KiB

Open AccessArticle

Fabrication of Refractive Index Tunable Coating with Moisture-Resistant Function for High-Power Laser Systems Based on Homogeneous Embedding of Surface-Modified Nanoparticles

by Wei Yang, Xiangyang Lei, Haohao Hui, Qinghua Zhang and Xueran Deng

Molecules 2018, 23(5), 1105; https://doi.org/10.3390/molecules23051105 - 7 May 2018

Cited by 12 | Viewed by 3848

Abstract

Moisture-resistant silicone coatings were prepared on the surface of potassium dihydrogen phosphate (KDP) crystal by means of spin-coating, in which hydrophobic-modified SiO₂ nanoparticles were embedded in a certain proportion. The refractive index of such coating can be tuned arbitrarily in the range [...] Read more.

Moisture-resistant silicone coatings were prepared on the surface of potassium dihydrogen phosphate (KDP) crystal by means of spin-coating, in which hydrophobic-modified SiO₂ nanoparticles were embedded in a certain proportion. The refractive index of such coating can be tuned arbitrarily in the range of 1.21–1.44, which endows the KDP optical component with excellent transmission capability as well as the moisture proof effect. A dual-layer anti-reflective coating system was obtained by covering this silicone coating with a porous SiO₂ coating which is specially treated to enhance the moisture resistance. Transmittance of such a dual-layer coating system could reach 99.60% and 99.62% at 1064 nm and 532 nm, respectively, by precisely matching the refractive index of both layers. Furthermore, the long-term stability of this coating system has been verified at high humidity ambient of 80% RH for 27 weeks. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

13 pages, 4933 KiB

Open AccessArticle

Improvement of Adhesion Properties and Corrosion Resistance of Sol-Gel Coating on Zinc

by Pauline Savignac, Marie-Joëlle Menu, Marie Gressier, Bastien Denat, Yacine El Khadir, Stephan Manov and Florence Ansart

Molecules 2018, 23(5), 1079; https://doi.org/10.3390/molecules23051079 - 3 May 2018

Cited by 15 | Viewed by 4240

Abstract

Corrosion is a major problem for durability of many metals and alloys. Among the efficient classical surface treatments, chromate-based treatments must be banished from industrial use due to their toxicity. At the same time, sol-gel routes have demonstrated high potential to develop an [...] Read more.

Corrosion is a major problem for durability of many metals and alloys. Among the efficient classical surface treatments, chromate-based treatments must be banished from industrial use due to their toxicity. At the same time, sol-gel routes have demonstrated high potential to develop an efficient barrier effect against aggressive environments. By this process, the anti-corrosion property can be also associated to others in the case of the development of multi-functional hybrid coatings. In this paper, the main goal is precisely to improve both the corrosion resistance and the adhesion properties of phosphated zinc substrates by the deposition of a hybrid (organic-inorganic) sol-gel layer. To reach this double objective, a choice between two formulations 3-glycidoxypropyltrimethoxysilane (GPTMS)/aluminum-tri-sec-butoxide (ASB) and 3-(trimethoxysilyl)propylmethacrylate (MAP)/tetraethylorthosilicate (TEOS) was firstly made based on the results obtained by microstructural characterizations using SEM, optical analysis, and mechanical characterization such as shock and/or scratch tests (coupled to climatic chamber and salt spray exposure). Several investigations were performed in this study, and the best formulation and performances of the system were obtained by adding a new precursor (1-[3-(trimethoxysilyl)propyl]ureido-UPS) under controlled conditions, as detailed in this paper. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

12 pages, 2149 KiB

Open AccessReview

Recent Applications of Molecularly Imprinted Sol-Gel Methodology in Sample Preparation

by Mohammad Mahdi Moein, Abbi Abdel-Rehim and Mohamed Abdel-Rehim

Molecules 2019, 24(16), 2889; https://doi.org/10.3390/molecules24162889 - 9 Aug 2019

Cited by 63 | Viewed by 7350

Abstract

Due to their selectivity and chemical stability, molecularly imprinted polymers have attracted great interest in sample preparation. Imprinted polymers have been applied for the extraction and the enrichment of different sorts of trace analytes in biological and environmental samples before their analysis. Additionally, [...] Read more.

Due to their selectivity and chemical stability, molecularly imprinted polymers have attracted great interest in sample preparation. Imprinted polymers have been applied for the extraction and the enrichment of different sorts of trace analytes in biological and environmental samples before their analysis. Additionally, MIPs are utilized in various sample preparation techniques such as SPE, SPME, SBSE and MEPS. Nevertheless, molecularly imprinted polymers suffer from thermal (stable only up to 150 °C) and mechanical stability issues, improper porosity and poor capacity. The sol-gel methodology as a promising alternative to address these limitations allowing the production of sorbents with controlled porosity and higher surface area. Thus the combination of molecularly imprinted technology and sol-gel technology can create influential materials with high selectivity, high capacity and high thermal stability. This work aims to present an overview of molecularly imprinted sol-gel polymerization methods and their applications in analytical and bioanalytical fields. Full article

(This article belongs to the Special Issue Sol-Gel Chemistry. From Molecule to Functional Materials)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Sol-Gel Chemistry. From Molecule to Functional Materials

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Related Special Issue

Published Papers (22 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI