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Organic and Carbon Gels: Properties and Application

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

Deadline for manuscript submissions: closed (1 September 2021) | Viewed by 20677

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Special Issue Editor

Dr. Ana Arenillas

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Guest Editor

CSIC - Instituto Nacional del Carbón (INCAR), Oviedo, Spain
Interests: carbon gels; polymer design; energy; microwave heating

Special Issue Information

Dear Colleagues,

Since the 1980s, when the first organic and carbon gels were synthetised, a lot of research work has been performed due to their properties and their great potential in a wide numer of applications. Their main advantage, compared to other porous carbon materials, is the possibility to control and design their final chemical, structural and porous properties. Thus, adjusting the different variables involved during their synthesis, a relatively narrow and defined pore size distribution in the range of mesopores, or macropores, can be obtained. This cannot be achieved as easily and directly with other porous materials with the sol-gel process. Furthermore, the selection of the monomers used, and the possibility to incorporate other components and nanoparticles to the polymeric structure also leads to a highly controlled chemical composition without impurities. Obviously, this ability to design the properties of the final organic or carbon gel creates the maximum range of possible applications for these materials: from adsorption and separation processes in the gas or liquid phase to support for catalysts, sensors and electrochemistry, but also thermal insulation, among others.

This Special Issue will provide a compendium of the latest advances in designing organic and carbon gels to obtain the optimum materials for different cutting-edge applications in fields as diverse as catalysis, separation, electrochemistry, biotechnology or clean and sustainable energy.

Dr. Ana Arenillas
Guest Editor

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Keywords

organic gels
carbon gels
porosity design
controlled chemistry
adsorption
separation processes
catalysis support
electrochemistry
photocatalysis
sensors

Published Papers (7 papers)

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Research

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14 pages, 4066 KiB

Open AccessArticle

Silver-Nanoparticles Embedded Pyridine-Cholesterol Xerogels as Highly Efficient Catalysts for 4-nitrophenol Reduction

by Ganesh Shimoga, Eun-Jae Shin and Sang-Youn Kim

Materials 2020, 13(7), 1486; https://doi.org/10.3390/ma13071486 - 25 Mar 2020

Cited by 1 | Viewed by 2080

Abstract

Two xerogels made of 4-pyridyl cholesterol (PC) and silver-nanocomposites (SNCs) thereof have been studied for their efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of aqueous sodium borohydride. Since in-situ silver doping will be effective in ethanol and acetone solvents with a PC gelator, two silver-loaded PC xerogels were prepared and successive SNCs were achieved by using an environmentally benign trisodium citrate dehydrate reducing agent. The formed PC xerogels and their SNCs were comprehensively investigated using different physico-chemical techniques, such as field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), powdered X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis). The FE-SEM results confirm that the shape of xerogel-covered silver nanoparticles (SNPs) are roughly spherical, with an average size in the range of 30–80 nm. Thermal degradation studies were analyzed via the sensitive graphical Broido’s method using a TGA technique. Both SNC-PC (SNC-PC-X1 and SNC-PC-X2) xerogels showed remarkable catalytic performances, with recyclable conversion efficiency of around 82% after the fourth consecutive run. The apparent rate constant (k_app) of SNC-PC-X1 and SNC-PC-X2 were found to be 6.120 × 10^-3 sec^-1 and 3.758 × 10^-3 sec^-1, respectively, at an ambient temperature. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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15 pages, 4585 KiB

Open AccessArticle

Carbon Black as Conductive Additive and Structural Director of Porous Carbon Gels

by Ana Casanova, Alicia Gomis-Berenguer, Aurelien Canizares, Patrick Simon, Dolores Calzada and Conchi O. Ania

Materials 2020, 13(1), 217; https://doi.org/10.3390/ma13010217 - 4 Jan 2020

Cited by 18 | Viewed by 3543

Abstract

This work investigates the impact of carbon black (CB) as a porogenic agent and conductive additive in the preparation of electrically conductive nanoporous carbon gels. For this, a series of materials were prepared by the polycondensation of resorcinol/formaldehyde mixtures in the presence of increasing amounts of carbon black. The conductivity of the carbon gel/CB composites increased considerably with the amount of CB, indicating a good dispersion of the additive within the carbon matrix. A percolation threshold of ca. 8 wt.% of conductive additive was found to achieve an adequate “point to point” conductive network. This value is higher than that reported for other additives, owing to the synthetic route chosen, as the additive was incorporated in the reactant’s mixture (pre-synthesis) rather than in the formulation of the electrodes ink (post-synthesis). The CB strongly influenced the development of the porous architecture of the gels that exhibited a multimodal mesopore structure comprised of two distinct pore networks. The microporosity and the primary mesopore structure remained rather unchanged. On the contrary, a secondary network of mesopores was formed in the presence of the additive. Furthermore, the average mesopore size and the volume of the secondary network increased with the amount of CB. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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15 pages, 3344 KiB

Open AccessArticle

Graphitized Carbon Xerogels for Lithium-Ion Batteries

by Maria Canal-Rodríguez, Ana Arenillas, Sara F. Villanueva, Miguel A. Montes-Morán and J. Angel Menénedez

Materials 2020, 13(1), 119; https://doi.org/10.3390/ma13010119 - 26 Dec 2019

Cited by 6 | Viewed by 2818

Abstract

Carbon xerogels with different macropore sizes and degrees of graphitization were evaluated as electrodes in lithium-ion batteries. It was found that pore structure of the xerogels has a marked effect on the degree of graphitization of the final carbons. Moreover, the incorporation of graphene oxide to the polymeric structure of the carbon xerogels also leads to a change in their carbonaceous structure and to a remarkable increase in the graphitic phase of the samples studied. The sample with the highest degree of graphitization (i.e., hybrid graphene-carbon xerogel) displayed the highest capacity and stability over 100 cycles, with values even higher than those of the commercial graphite SLP50 used as reference. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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10 pages, 2432 KiB

Open AccessFeature PaperArticle

Water-Ionic Liquid Binary Mixture Tailored Resorcinol-Formaldehyde Carbon Aerogels without Added Catalyst

by Balázs Nagy, István Bakos, Erik Geissler and Krisztina László

Materials 2019, 12(24), 4208; https://doi.org/10.3390/ma12244208 - 14 Dec 2019

Cited by 6 | Viewed by 1999

Abstract

The potential applications of mesoporous carbon aerogels are wide-ranging. These gels are often obtained from resorcinol-formaldehyde (RF) hydrogel precursors. The sol-gel method in this synthesis provides an efficient and versatile means of product control through systematic variation of process conditions, such as pH, stoichiometry, concentration, catalyst, further additives, etc., in addition to the drying and pyrolytic conditions. Here, a novel means of tuning the texture of carbon aerogels is proposed. Water-1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO₄] mixtures constitutes a polycondensation medium that requires no added catalyst, thus yielding an intrinsically metal-free carbon aerogel after pyrolysis. We also show that the carbon morphology is tailored by the supramolecular structure of the aqueous ionic liquid. The results of scanning electron micrographs, low-temperature nitrogen adsorption/desorption isotherms, and small-angle X-ray scattering (SAXS) confirm that changing the initial water concentration from 9 to 55 wt % gives rise to systematic alteration of the mesopore size and volume, as well as of the bead size. The pore structure becomes consolidated only when the water content exceeds 25 wt %. When the water content reaches 55 wt %, the bead size increases by two orders of magnitude. The electrocatalytic performance, however, is compromised, most probably by structural defects. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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22 pages, 11619 KiB

Open AccessArticle

Modification of Collagen Derivatives with Water-Soluble Polymers for the Development of Cross-Linked Hydrogels for Controlled Release

by Ioanna Tzoumani, Georgia Ch. Lainioti, Alexios J. Aletras, Gabriel Zainescu, Simina Stefan, Aurelia Meghea and Joannis K. Kallitsis

Materials 2019, 12(24), 4067; https://doi.org/10.3390/ma12244067 - 6 Dec 2019

Cited by 13 | Viewed by 3135

Abstract

Novel cross-linked hydrogels were synthesized as potential materials for the development of smart biofertilizers. For this purpose, hydrogels were prepared using collagen hydrolysate recovered from tannery waste. The water-soluble polymer poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMAx)) was among others used for the cross-linking reaction that combined hydrophilic nature with epoxide groups. The synthetic procedure was thoroughly investigated in order to ensure high percentage of epoxide groups in combination with water-soluble behavior. The copolymer did not show cytotoxicity against normal lung, skin fibroblasts, or nasal polyps fibroblasts. Through the present work, we also present the ability to control the properties of cross-linked hydrogels by altering copolymer’s composition and cross-linking parameters (curing temperature and time). Hydrogels were then studied in terms of water-uptake capacity for a period up to six days. The techniques Proton Nuclear Magnetic Resonance (¹H NMR), Thermogravimetric Analysis (TGA), Size Exclusion Chromatography (SEC), and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) were applied for the characterization of the synthesized copolymers and the cross-linked hydrogels. Three samples of biofertilizers based on collagen hydrolysate functionalized with P(SSNa-co-GMAx) and starch and having nutrients encapsulated (N, P, K) were prepared and characterized by physical–chemical analysis and Energy Dispersive X-ray analysis-Scanning Electron Microscope (EDAX-SEM) in terms of microstructure. Preliminary tests for application as fertilizers were performed including the release degree of oxidable organic compounds. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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15 pages, 3240 KiB

Open AccessArticle

DNA Adsorption Studies of Poly(4,4′-Cychlohexylidene Bisphenol Oxalate)/Silica Nanocomposites

by Aisha Nawaf Al balawi, Nor Azah Yusof, Sazlinda Kamaruzaman, Faruq Mohammad, Helmi Wasoh and Hamad A. Al-Lohedan

Materials 2019, 12(7), 1178; https://doi.org/10.3390/ma12071178 - 11 Apr 2019

Viewed by 3160

Abstract

The present study deals with the synthesis, characterization, and DNA extraction of poly(4,4′-cyclohexylidene bisphenol oxalate)/silica (Si) nanocomposites (NCs). The effects of varying the monomer/Si (3.7%, 7%, and 13%) ratio towards the size and morphology of the resulting NC and its DNA extraction capabilities have also been studied. For the NC synthesis, two different methods were followed, including the direct mixing of poly(4,4′-cyclohexylidene bisphenol oxalate) with fumed Si, and in situ polymerization of the 4,4′-cyclohexylidene bisphenol monomer in the presence of fumed silica (11 nm). The formed NCs were thoroughly investigated by using different techniques such as scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powdered X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) analysis where the results supported that there was the successful formation of poly(4,4′-cyclohexylidene bisphenol oxalate)/Si NC. Within the three different NC samples, the one with 13% Si was found to maintain a very high surface area of 12.237 m²/g, as compared to the other two samples consisting of 7% Si (3.362 m²/g) and 3.7% Si (1.788 m²/g). Further, the solid phase DNA extraction studies indicated that the efficiency is strongly influenced by the amount of polymer (0.2 g > 0.1 g > 0.02 g) and the type of binding buffer. Among the three binding buffers tested, the guanidine hydrochloride/EtOH buffer produced the most satisfactory results in terms of yield (1,348,000 ng) and extraction efficiency (3370 ng/mL) as compared to the other two buffers of NaCl (2 M) and phosphate buffered silane. Based on our results, it can be indicated that the developed poly(4,4′-cyclohexylidene bisphenol oxalate)/Si NC can serve as one of the suitable candidates for the extraction of DNA in high amounts as compared to other traditional solid phase approaches. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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Review

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15 pages, 5040 KiB

Open AccessReview

Carbon Gels-Modified TiO₂: Promising Materials for Photocatalysis Applications

by Dongge Ma, Jundan Li, Anan Liu and Chuncheng Chen

Materials 2020, 13(7), 1734; https://doi.org/10.3390/ma13071734 - 8 Apr 2020

Cited by 24 | Viewed by 3077

Abstract

Carbon gels are a kind of porous organic polymer, which play pivotal roles in electrode, supercapacitor, hydrogen storage, and catalysis. Carbon gels are commonly prepared by the condensation of resorcinol and formaldehyde. The as-prepared polymers are further aged and sintered at a high temperature in an inert atmosphere to form cross-linked and intertwined porous structures. Owing to its large specific area and narrow pore size distribution, this kind of material is very appropriate for mass transfer, substrate absorption, and product desorption from the pores. In recent years, carbon gels have been discovered to function as effective hybrid materials with TiO₂ for photocatalytic applications. They could act as efficient deep-traps for photo-induced holes, which decreases the recombination probability of photo-induced carriers and lengthens their lifetime. In this mini-review, we will discuss the state-of-the-art paragon examples of carbon gels/TiO₂ composite materials applied in photo(electro)catalysis. The major challenges and gaps of its application in this field will also be emphasized. Full article

(This article belongs to the Special Issue Organic and Carbon Gels: Properties and Application)

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