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Special Issue "Green Chemistry - both precursors and processes - to Hierarchical Materials"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Biomaterials".

Deadline for manuscript submissions: closed (31 March 2017)

Special Issue Editors

Guest Editor
Dr. Francisco del Monte

Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, Madrid 28049, Spain
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Guest Editor
Dr. María Concepción Gutiérrez

Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, Madrid 28049, Spain
Website | E-Mail

Special Issue Information

Dear Colleagues,

Assembling nanoparticles into hierarchical porous materials is challenging because the resulting materials would offer a desirable combination of a high internal reactive surface area and straightforward molecular transport through broad “highways” leading to such a surface, which is of special relevance to any of the above applications. Therefore, materials chemists should be able, not only to make nanostructures of any size and shape, but also to assemble them in any form and to control their final structure at different space levels (e.g., hierarchically organized) so that their chemical natures and dimensions ensure accessibility to the inner interfaces.

In materials science and from a green chemistry point of view, progress in the preparation of advanced materials with controlled structure and/or unprecedented functionality de- pends largely on the core competence of materials chemists to design and develop new synthetic strategies that, at any stage of the synthesis, limit the use of chemical reagents—e.g., reducing and/or cross-linking agents, solvents or surfactants, among others—that may eventually be difficult to eliminate from the reaction batch. This issue has, lately, attracted a great deal of attention for preparation of nanoparticles and nanocomposites, useful in catalysis/biocatalysis and biomedicine. It is worth noting that the absence of undesired byproducts can be of help in either reducing nanoparticles poisoning in catalytic/biocatalytic reactions or preventing denaturation of biological entities (due to biocompatibility enhancement) in biomedical applications.

Moreover, besides the utilization of environmentally benign chemicals and solvents, the in situ preparation of nanocomposites into the required hierarchical structure (e.g., spheres, nanospheres, capsules, or scaffolds, among others) is another key issue that merits important consideration. This is because the reduction or full elimination of processing steps that may eventually give rise to contamination can also be of help for the final performance of any catalytic or biomedical device.

Based on this, the current Special Issue will include papers dealing with the “Application of Green Chemistry for the Design of Precursors and Processes of Potential Interest for the Preparation of Hierarchically Organized Materials”.

Dr. Francisco del Monte
Dr. María Concepción Gutiérrez
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. Materials 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 1500 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

  • green chemistry
  • sustainable reagents and processes
  • hierarchical materials
  • porous materials

Published Papers (5 papers)

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Research

Open AccessFeature PaperArticle Study of Superbase-Based Deep Eutectic Solvents as the Catalyst in the Chemical Fixation of CO2 into Cyclic Carbonates under Mild Conditions
Materials 2017, 10(7), 759; doi:10.3390/ma10070759
Received: 8 June 2017 / Revised: 28 June 2017 / Accepted: 29 June 2017 / Published: 7 July 2017
Cited by 1 | PDF Full-text (1995 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Superbases have shown high performance as catalysts in the chemical fixation of CO2 to epoxides. The proposed reaction mechanism typically assumes the formation of a superbase, the CO2 adduct as the intermediate, most likely because of the well-known affinity between superbases
[...] Read more.
Superbases have shown high performance as catalysts in the chemical fixation of CO2 to epoxides. The proposed reaction mechanism typically assumes the formation of a superbase, the CO2 adduct as the intermediate, most likely because of the well-known affinity between superbases and CO2, i.e., superbases have actually proven quite effective for CO2 absorption. In this latter use, concerns about the chemical stability upon successive absorption-desorption cycles also merits attention when using superbases as catalysts. In this work, 1H NMR spectroscopy was used to get further insights about (1) whether a superbase, the CO2 adduct, is formed as an intermediate and (2) the chemical stability of the catalyst after reaction. For this purpose, we proposed as a model system the chemical fixation of CO2 to epichlorohydrin (EP) using a deep eutectic solvent (DES) composed of a superbase, e.g., 2,3,4,6,7,8-hexahydro-1H-pyrimido[1,2-a]pyrimidine (TBD) or 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine (DBU), as a hydrogen acceptor and an alcohol as a hydrogen bond donor, e.g., benzyl alcohol (BA), ethylene glycol (EG), and methyldiethanolamine (MDEA), as the catalyst. The resulting carbonate was obtained with yields above 90% and selectivities approaching 100% after only two hours of reaction in pseudo-mild reaction conditions, e.g., 1.2 bars and 100 °C, and after 20 h if the reaction conditions of choice were even milder, e.g., 1.2 bars and 50 °C. These results were in agreement with previous works using bifunctional catalytic systems composed of a superbase and a hydrogen bond donor (HBD) also reporting good yields and selectivities, thus confirming the suitability of our choice to perform this study. Full article
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Open AccessFeature PaperArticle Macroporous Calcium Phosphate/Chitosan Composites Prepared via Unidirectional Ice Segregation and Subsequent Freeze-Drying
Materials 2017, 10(5), 516; doi:10.3390/ma10050516
Received: 16 March 2017 / Revised: 24 April 2017 / Accepted: 1 May 2017 / Published: 8 May 2017
Cited by 1 | PDF Full-text (4846 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Calcium phosphate chitosan-based composites have gained much interest in recent years for biomedical purposes. In this paper, three-dimensional calcium phosphate chitosan-based composites with different mineral contents were produced using a green method called ice segregation induced self-assembly (ISISA). In this methodology, ice crystals
[...] Read more.
Calcium phosphate chitosan-based composites have gained much interest in recent years for biomedical purposes. In this paper, three-dimensional calcium phosphate chitosan-based composites with different mineral contents were produced using a green method called ice segregation induced self-assembly (ISISA). In this methodology, ice crystals were used as a template to produce porous structures from an aqueous solution of chitosan (CS) and hydroxyapatite (Hap) also containing acetic acid (pH = 4.5). For better characterization of the nature of the inorganic matter entrapped within the resulting composite, we performed either oxygen plasma or calcination processes to remove the organic matter. The nature of the phosphate salts was studied by XRD and NMR studies. Amorphous calcium phosphate (ACP) was identified as the mineral phase in the composites submitted to oxygen plasma, whereas crystalline Hap was obtained after calcination. SEM microscopy revealed the formation of porous structures (porosity around 80–85%) in the original composites, as well as in the inorganic matrices obtained after calcination, with porous channels of up to 50 µm in diameter in the former case and of up to 20 µm in the latter. The biocompatibility of the composites was assessed using two different cell lines: C2C12GFP premyoblastic cells and MC3T3 preosteoblastic cells. Full article
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Open AccessArticle Photoactive Nanomaterials Inspired by Nature: LTL Zeolite Doped with Laser Dyes as Artificial Light Harvesting Systems
Materials 2017, 10(5), 495; doi:10.3390/ma10050495
Received: 30 March 2017 / Revised: 27 April 2017 / Accepted: 28 April 2017 / Published: 4 May 2017
Cited by 1 | PDF Full-text (3837 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The herein reported work describes the development of hierarchically-organized fluorescent nanomaterials inspired by plant antenna systems. These hybrid materials are based on nanostructured zeolitic materials (LTL zeolite) doped with laser dyes, which implies a synergism between organic and inorganic moieties. The non-interconnected channeled
[...] Read more.
The herein reported work describes the development of hierarchically-organized fluorescent nanomaterials inspired by plant antenna systems. These hybrid materials are based on nanostructured zeolitic materials (LTL zeolite) doped with laser dyes, which implies a synergism between organic and inorganic moieties. The non-interconnected channeled structure and pore dimensions (7.1 Å) of the inorganic host are ideal to order and align the allocated fluorophores inside, inferring also high thermal and chemical stability. These artificial antennae harvest a broad range of chromatic radiation and convert it into predominant red-edge or alternatively white-light emission, just choosing the right dye combination and concentration ratio to modulate the efficiency of the ongoing energy transfer hops. A further degree of organization can be achieved by functionalizing the channel entrances of LTL zeolite with specific tailor-made (stopcock) molecules via a covalent linkage. These molecules plug the channels to avoid the leakage of the guest molecules absorbed inside, as well as connect the inner space of the zeolite with the outside thanks to energy transfer processes, making the coupling of the material with external devices easier. Full article
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Open AccessFeature PaperArticle Ice as a Green-Structure-Directing Agent in the Synthesis of Macroporous MWCNTs and Chondroitin Sulphate Composites
Materials 2017, 10(4), 355; doi:10.3390/ma10040355
Received: 23 February 2017 / Revised: 21 March 2017 / Accepted: 24 March 2017 / Published: 28 March 2017
Cited by 1 | PDF Full-text (5060 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The incorporation of multi-walled carbon nanotubes (MWCNTs) into chondroitin sulphate-based scaffolds and the effect on the structural, mechanical, conductive, and thermal properties of the resulting scaffolds is investigated. Three-dimensional hierarchical materials are prepared upon the application of the ice segregation-induced self-assembly (ISISA) process.
[...] Read more.
The incorporation of multi-walled carbon nanotubes (MWCNTs) into chondroitin sulphate-based scaffolds and the effect on the structural, mechanical, conductive, and thermal properties of the resulting scaffolds is investigated. Three-dimensional hierarchical materials are prepared upon the application of the ice segregation-induced self-assembly (ISISA) process. The use of ice as structure-directing agents avoids chemicals typically used for this purpose (e.g., surfactants, block copolymers, etc.), hence, emphasising the green features of this soft-templating approach. We determine the critical parameters that control the morphology of the scaffolds formed upon ice-templating (i.e., MWCNTs type, freezing conditions, polymer and MWCNT concentration). MWCNTs are surface functionalized by acidic treatment. MWCNT functionalization is characterized by Raman, Fourier transfer infrared (FTIR) and X-ray Photoelectron (XPS) spectroscopies. Scanning electron microscopy (SEM) analysis and porosity studies reveal that MWCNT content modifies the morphology of the macroporous structure, which decreases by increasing MWCNT concentration. Differences in scaffold morphology should be translated into their conductivity and mechanical properties. As a general trend, the Young’s modulus and the electrical conductivity of the scaffolds increase with the MWCNT content. Preliminary biocompatibility tests with human osteoblast-like cells also reveal the capability of these structures to support cell growth. Full article
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Open AccessArticle Peanut Shell-Derived Carbon Solid Acid with Large Surface Area and Its Application for the Catalytic Hydrolysis of Cyclohexyl Acetate
Materials 2016, 9(10), 833; doi:10.3390/ma9100833
Received: 5 September 2016 / Revised: 29 September 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
PDF Full-text (2613 KB) | HTML Full-text | XML Full-text
Abstract
A carbon solid acid with large surface area (CSALA) was prepared by partial carbonization of H3PO4 pre-treated peanut shells followed by sulfonation with concentrated H2SO4. The structure and acidity of CSALA were characterized by N2
[...] Read more.
A carbon solid acid with large surface area (CSALA) was prepared by partial carbonization of H3PO4 pre-treated peanut shells followed by sulfonation with concentrated H2SO4. The structure and acidity of CSALA were characterized by N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), 13C cross polarization (CP)/magic angle spinning (MAS) nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), titration, and elemental analysis. The results demonstrated that the CSALA was an amorphous carbon material with a surface area of 387.4 m2/g. SO3H groups formed on the surface with a density of 0.46 mmol/g, with 1.11 mmol/g of COOH and 0.39 mmol/g of phenolic OH. Densities of the latter two groups were notably greater than those observed on a carbon solid acid (CSA) with a surface area of 10.1 m2/g. The CSALA catalyst showed better performance than the CSA for the hydrolysis of cyclohexyl acetate to cyclohexanol. Under optimal reaction conditions, cyclohexyl acetate conversion was 86.6% with 97.3% selectivity for cyclohexanol, while the results were 25.0% and 99.4%, respectively, catalyzed by CSA. The high activity of the CSALA could be attributed to its high density of COOH and large surface area. Moreover, the CSALA showed good reusability. Its catalytic activity decreased slightly during the first two cycles due to the leaching of polycyclic aromatic hydrocarbon-containing SO3H groups, and then remained constant during following uses. Full article
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