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Special Issue "Sol-Gel Chemistry. From Molecule to Functional Materials"

A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: 31 July 2018

Special Issue Editors

Guest Editor
Prof. Ahmad Mehdi

Institut Charles Gerhardt Montpellier, Montpellier, France
Website | E-Mail
Interests: molecular chemistry; hybrid materials; sol-gel; surface modification; materials for health
Guest Editor
Dr. Sébastien Clément

Institut Charles Gerhardt Montpellier, Montpellier, France
Website | E-Mail
Interests: conjugated materials; hybrid materials; organic electronics; sensing; therapy

Special Issue Information

Dear Colleagues,

One of the main challenges in materials science is to find effective strategies to organize the matter in terms of properties: Chemical, physical, etc. In this respect, bottom up approaches based on the self-assembly of molecules at the nanometric scale to form larger structures need to be considered. In particular, the sol-gel process (called inorganic polymerization) has emerged as one of the most important routes for preparing organized materials. It is, thus, important for Molecules to dedicate a Special Issue to this process, since it is perfectly compatible with all kinds of chemistry. This Special Issue will contain contributions discussing all the aspects that are broadly indicated by the keywords. Reviews articles by experts in the field of sol-gel, organosilica, porous hybrid materials and self-assembly will be welcome.

Prof. Ahmad Mehdi
Dr. Sébastien Clément
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Sol-gel
  • Functional oxide
  • Nanoparticles
  • Hybrid materials

Published Papers (4 papers)

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Research

Open AccessArticle Cast-In-Situ, Large-Sized Monolithic Silica Xerogel Prepared in Aqueous System
Molecules 2018, 23(5), 1178; https://doi.org/10.3390/molecules23051178
Received: 21 April 2018 / Revised: 12 May 2018 / Accepted: 12 May 2018 / Published: 15 May 2018
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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)
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Graphical abstract

Open AccessArticle Innovative Formulation Combining Al, Zr and Si Precursors to Obtain Anticorrosion Hybrid Sol-Gel Coating
Molecules 2018, 23(5), 1135; https://doi.org/10.3390/molecules23051135
Received: 25 April 2018 / Revised: 4 May 2018 / Accepted: 6 May 2018 / Published: 10 May 2018
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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)
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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
Molecules 2018, 23(5), 1105; https://doi.org/10.3390/molecules23051105
Received: 23 April 2018 / Revised: 4 May 2018 / Accepted: 4 May 2018 / Published: 7 May 2018
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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)
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Open AccessArticle Improvement of Adhesion Properties and Corrosion Resistance of Sol-Gel Coating on Zinc
Molecules 2018, 23(5), 1079; https://doi.org/10.3390/molecules23051079
Received: 3 April 2018 / Revised: 26 April 2018 / Accepted: 28 April 2018 / Published: 3 May 2018
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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)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Author: Xue-Ran Deng
Affiliation: University of Electronic Science and Technology of China | UESTC · Department of Electronic Science and Technology
Tentative title: Fabrication of refractive index tunable coating with moisture-resistant function based on the homogeneous embedding structure

Author: Malgorzata Adamczyk,
Affiliation: Prodziekan ds. Dydaktycznych Kierunków Mechatronika i Inżynieria Materiałowa, Poland
Tentative title: Electric and magnetic properties of PFN ceramics

Author: Rafael Luque
Affiliation: Departamento de Quimica Organica,Universidad de Cordoba
Campus de Rabanales Edificio Marie Curie (C-3) Ctra Nnal IV, Km. 396E-14014 Cordoba (Spain)
Tentative title: Sol-gel synthesis of encapsulated lipases/laccases/peroxidases for the esterification of valeric acid: towards novel biofuels

Author: Andrea S. S. de Camar
Affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, Brazil
Tentative title: Host-guest luminescent materials based on highly emissive species loaded into versatile sol-gel hosts

Author: Parola Stéphane
Affiliation: Laboratoire de Chimie UMR ENS-CNRS-UCBL 5182, University of Lyon (France)
Tentative title: Functional materials by entrapment of nanoparticles in composite xerogels or aerogels

Author: M. Clara Gonçalves1,2*, H Cristina Vasconcelos
Affiliation:
1 Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
2 CQE, Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Universidade dos Açores, Ponta Delgada, Portugal.
Abstract: In addition to its traditional application in white pigments, nanocrystlline titania optoelectronic and photocatalytic properties grant new technological applications. Its wide band gap (~3.2 eV) enables its use in photochemical degradation of toxic chemicals, as a bactericide / anti-fungicide agent, in energy conversion in solar cells, or as an electrode material in lithium batteries. All the properties performance is, nevertheless, strongly dependent on crystallinity, particle size, and surface structure. Sol-gel method is one of the most widely used to synthesise TiO2 films and NPs. However, sol-gel products are mostly oxy-hydrated amorphous phases, being severe heat-treatments (T  400ºC) needed to promote crystallization, where the control over size and shape are difficult to achieve.
Photocatalytic performance of amorphous TiO2 thin films doped with N is studied. Films of TiO2-xNx compositions, with N concentrations up to x = 0,75 (25 at.%), are prepared by sol-gel processing followed by spin-coating onto Si(100) wafers, glass slides and CaF2 substrates. The identification and quantification of different Ti-O-Ti, N-Ti-O and Ti-N-Ti bondings is achieved by X-ray photoemission spectroscopy (XPS) and Vacuum ultraviolet (VUV) light scattering. Photoabsorption spectra of oxynitride thin films is observed in the energy range 3.9–10.8 eV (320–115 nm), changing the amorphous titania films paradigm in photocatalysis.
Amorphous titania nanoparticles are synthetized by a novel, eco-friendly, base-catalysed sol-gel methodology. Cotton and polyester textile matrixes are impregnated with amorphous titania nanoparticles, aiming bactericide hospital applications. Titania nanoparticles functionalization with amine groups and bioconjugation with chitosan polymer favour textile impregnation efficiency and bactericide performance. All synthesized nanoparticles (titania, titania functionalized and titania bioconjugated) and all impregnated textiles (cotton and polyester matrices) exhibit bactericide performance, being a promising tool in hospital infections combat, and changing the amorphous titania nanoparticle paradigm as bactericide.

Author: M. Clara Gonçalves
Affiliation: Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
Abstract: Silica (SiO2) is one of the most abundant minerals in the earth crust (~75%), making it a favorite raw material ever since; furthermore, its presence in human body allows its use as a biomaterial, where its presence in dentistry, orthopedics, and dermatology become a commonplace. Recently sol-gel SiO2 nanoparticles (NPs) appear as new promising applications in a wide range of biomedical and pharmaceutical applications, namely as drug/target delivery, gene and imaging therapies or even theranosis, where they stand out for their high biocompatibility, hydrophilicity, enormous flexibility for surface modification with a high payload capacity, and prolonged blood circulation time. The sol-gel process is an extremely versatile bottom-up methodology, offering a wide range of chemical possibilities, namely full scale pH processing.
In situ NPs silica functionalization, by introducing organic functional groups during the sol-gel process (forming an ORganically MOdified SILica matrix, known as ORMOSIL), allows easy chemical conjugation/decoration of biomolecules at the ORMOSIL NPs surface and/or the load with either hydrophilic or hydrophobic drugs/dyes.
But sol-gel silica NPs found technological applications in wide range of fields beyond medicine and pharmacy. Areas such technical textiles, drinking and waste water treatment, catalysis, adsorption, chromatography, sensor technology, gas storage, optics and photonics, magnetism and electronics are familiar with silica chemistry. Actually, sol-gel hybrid silica matrices were taken further by the in situ co-polymerization of silanol groups and cellulose acetate polymers, aiming new hybrid cellulose acetate-silica ultrafiltration membranes for water treatment or artificial organs in near future.
This review surveys some of the emerging approaches in the field of sol-gel silica NPs aiming biomedical applications.

Author: Leda Maria Saragiotto Colpini
Title: Photocatalytic degradation of textile dye orange-122 via electrospray mass spectrometry
Abstract: This work attend with the study of the application potential of catalytic materials (Zn/TiO2) obtained by the sol gel method, in environmental decontamination processes through photodegradation reactions of textile dyes, monitored by electrospray mass spectrometry. The synthesis of the catalysts was performed according to a 2² factorial design with repetition at the central point, where the calcination temperatures and the zinc metallic load were varied. The catalysts were characterized by determination of the zero point of charge, specific surface area, X-ray diffraction and scanning electron microscopy with energy dispersive X-ray and the photocatalytic tests were carried out in batch in the presence of sunlight.

Author: Clément GENET, Marie-Joëlle MENU, Marie GRESSIER, Florence ANSART
Affiliation: CIRIMAT, Université de Toulouse, CNRS INPT UPS, UMR 5085, 118 Route de Narbonne - 31062 Toulouse Cedex 09, France
Title: Innovative sol formulations to develop anticorrosion hybrid sol-gel coatings
Abstract: The aim is to improve the aluminium alloy corrosion resistance by Organic-Inorganic Hybrid (OIH) sol-gel coatings. Coatings are obtained from unusual formulations with precursors mixing: glycidoxypropyltrimethoxysilane (GPTMS), zirconium propoxide (TPOZ) and aluminium tri-sec-butoxide (ASB) before been compared to more classical sol formulations. In each case, a corrosion inhibitor is also incorporated to improve the anti-corrosion performances.
Coatings from sols based on GPTMS/TPOZ/ASB exhibit anti-corrosion properties even for a thickness lower than 4 µm. Furthermore, contact angle measurements showed hydrophobic properties of these coatings. To understand these phenomena, NMR analyses were performed and correlations have been established between microstructure and working properties.

Author: Pauline SAVIGNAC, Marie-Joëlle MENU, Marie GRESSIER, Bastien DENAT ,
Y. EL KHADIR, Stephan MANOV, Florence ANSART
Affiliation: 1 VM Building Solutions, « Les Mercuriales » Tour du Ponant, 40 rue Jean Jaurès, 93170 Bagnolet, France; 2 CIRIMAT, Université de Toulouse, CNRS INPT UPS, UMR 5085, 118 Route de Narbonne - 31062 Toulouse Cedex 09, France
Title: Improvement of adhesion properties and corrosion resistance of sol-gel coatings on zinc
Abstract: The main goal of this study was to improve both the corrosion resistance and the adhesion properties of preweathered zinc substrates by the deposit of a hybrid sol–gel layer. To reach this double objective, a choice between two formulations (TEOS-MAP or GPTMS-ASB) was firstly made from the results obtained by microstructural characterizations (after climatic chamber test, salt spray test, shock test and/or scratch test).
Several analyses were performed and the best formulation was obtained by adding a new precursor (UPS) in controlled conditions, detailed in this paper

Author: Crina Anastasescu 1, Silviu Preda1, Radu Socoteanu 1, Daniel Angelescu 1, Jose Maria Calderon-Moreno 1, Adriana Rusu 1, Gabriel Plavan 2, Stefan Strungaru 2, Mariuca Gartner 1, Mihai Anastasescu 1, Ioan Balint 1, Maria Zaharescu 1
Affiliation: 1 “Ilie Murgulescu” Institute of Physical Chemistry of the Romanian Academy, 202 Spl. Independentei, 060021, Bucharest, Romania
2 “Alexandru Ioan Cuza” University of Iasi, 11 Carol I Blvd., 700506 Iași, Romania
Title: Tubular and spherical SiO2 obtained by sol gel method for enzyme immobilization
Abstract: A wide range of hybrid biomaterials has been designed in order to sustain various industrial and bioremediation processes, by associating the sol gel SiO2 matrix with various biologically active compounds (enzymes, antibodies). The immobilization of enzymes on silica is looking for an improving of the biocatalysts efficiency in terms of endurance and economic costs, the SiO2 being a widespread, chemical stable and non-toxic material.
Our present work is meant to disclose the significant potential of amorphous SiO2 displaying different morphologies for enzymes immobilization and competitive biocatalysts developing. The synthesis protocol and structural characterization of spherical and tubular SiO2 obtained by sol gel method are deeply investigated in connection with the subsequent immobilization of lipase from Rhizopus orizae. The immobilization is led 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. In this sense, the morphological, textural and surface properties of spherical and tubular SiO2 were investigated by SEM, Nitrogen sorption, PZC measurement, while the formation and characterization of hybrid organic inorganic complex was followed by UV-VIS, FTIR-ATR and Fluorescence Spectroscopy. The degree of enzymes immobilization on SiO2 with different morphologies as depicted from TOC measurements is here discussed

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