Molecules

Research

15 pages, 2290 KiB

Open AccessArticle

Sequential Diffusion Spectra as a Tool for Studying Time-Dependent Translational Molecular Dynamics: A Cement Hydration Study

by Igor Serša

Molecules 2020, 25(1), 68; https://doi.org/10.3390/molecules25010068 - 24 Dec 2019

Cited by 2 | Viewed by 2318

Abstract

The translational molecular dynamics in porous materials are affected by the presence of the porous structure that presents an obstacle for diffusing molecules in longer time scales, but not as much in shorter time scales. The characteristic time scales have equivalent frequency ranges [...] Read more.

The translational molecular dynamics in porous materials are affected by the presence of the porous structure that presents an obstacle for diffusing molecules in longer time scales, but not as much in shorter time scales. The characteristic time scales have equivalent frequency ranges of molecular dynamics, where longer time scales correspond to lower frequencies while the shorter time scales correspond to higher frequencies of molecular dynamics. In this study, a novel method for direct measurement of diffusion at a given frequency of translational molecular dynamics is exploited to measure the diffusion spectra, i.e., distribution of diffusion in a wide range of frequencies. This method utilizes NMR modulated gradient spin-echo (MGSE) pulse sequence to measure the signal attenuation during the train of spin-echoes formed in the presence of a constant gradient. From attenuation, the diffusion coefficient at the frequency equal to the inverse double inter-echo time is calculated. The method was employed to study the white cement hydration process by the sequential acquisition of the diffusion spectra. The measured spectra were also analyzed by the diffusion spectra model to obtain the time-dependence of the best-fit model parameters. The presented method can also be applied to study other similar systems with the time evolution of porous structure. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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13 pages, 3227 KiB

Open AccessFeature PaperArticle

Magnetic Behavior of Carbon Materials Made from Biomass by Fe-Assisted Hydrothermal Carbonization

by Mara Olivares, Silvia Román, Beatriz Ledesma and Alfredo Álvarez

Molecules 2019, 24(21), 3996; https://doi.org/10.3390/molecules24213996 - 5 Nov 2019

Cited by 7 | Viewed by 3355

Abstract

Biomass magnetic materials were synthesized by several hydrothermal carbonization methods, by which iron was provided in different ways: as FeCl₃ prior to or during hydrothermal carbonization, as pure Fe particles, or as magnetic ferrofluid, followed or not by pyrolysis processes. The materials [...] Read more.

Biomass magnetic materials were synthesized by several hydrothermal carbonization methods, by which iron was provided in different ways: as FeCl₃ prior to or during hydrothermal carbonization, as pure Fe particles, or as magnetic ferrofluid, followed or not by pyrolysis processes. The materials were thoughtfully characterized in terms of elemental composition, thermal degradation, porosity (N₂ adsorption, SEM micrography), surface chemistry (FTIR spectroscopy, XRD diffraction), and magnetization curves on a self-made installation. The results indicated that the process design can significantly improve the structure and chemistry of the material, as well as the magnetization effect induced on the adsorbent. Fe as FeCl₃ was more interesting in regards to the development of porosity, mainly creating micropores, although it did not provide magnetism to the material unless a further pyrolysis was applied. Thermal treatment at 600 °C did not only increase the BET-specific surface (S_BET) (262 m² g⁻¹) of the hydrochar, but also involved the transformation of Fe into magnetite, providing magnetic behavior of the hydrochar. Increasing pyrolyisis temperature to 800 °C even enhanced a better development of porosity (S_BET of 424 m² g⁻¹) and also increased the specific magnetic susceptibility of the hydrochar as a result of the further transition of Fe into wustite and hydroxi-ferrite. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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17 pages, 5895 KiB

Open AccessArticle

Experimental Design Modeling of the Effect of Hexagonal Wurtzite—ZnO Synthesis Conditions on Its Characteristics and Performance as a Cationic and Anionic Adsorbent

by Mai M. Khalaf, Enshirah Da’na, Kawther Al-Amer and Manal Hessien

Molecules 2019, 24(21), 3884; https://doi.org/10.3390/molecules24213884 - 28 Oct 2019

Cited by 14 | Viewed by 2530

Abstract

Surface composite design was used to study the effect of the ZnO synthesis conditions on its adsorption of methyl orange (MO) and methylene blue (MB). The ZnO was prepared via hydrothermal treatment under different conditions including temperature (T), precursor concentration (C), pH, and [...] Read more.

Surface composite design was used to study the effect of the ZnO synthesis conditions on its adsorption of methyl orange (MO) and methylene blue (MB). The ZnO was prepared via hydrothermal treatment under different conditions including temperature (T), precursor concentration (C), pH, and reaction time (t). Models were built using four Design expert-11 software-based responses: the point of zero charge (pHzc), MO and MB removal efficiencies (R_MO, R_MB), MO and MB adsorption capacities (q_MO, q_MB), and hydrodynamic diameter of ZnO particles (D_h). ZnO was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, UV/VIS spectroscopy, thermal gravimetric analysis (TGA), and dynamic light scattering (DLS). The formation of ZnO was confirmed by the XRD, UV, and FTIR spectra. Results showed a very high efficiency for most of the samples for adsorption of MB, and more than 90% removal efficiency was achieved by 8 samples among 33 samples. For MO, more than 90% removal efficiency was achieved by 2 samples among 33 samples. Overall, 26 of 31 samples showed higher MB adsorption capacity than that of MO. R_MB was found to depend only on the synthesis temperature while R_MO depends on temperature, pH, and reaction time. pHzc was found to be affected by the synthesis pH only while D_h depends on the synthesis pH and precursor concentration. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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11 pages, 2317 KiB

Open AccessArticle

Electrical Characteristics and Reliability of Nitrogen-Stuffed Porous Low-k SiOCH/Mn₂O_3−xN/Cu Integration

by Yi-Lung Cheng, Yu-Lu Lin, Chih-Yen Lee, Giin-Shan Chen and Jau-Shiung Fang

Molecules 2019, 24(21), 3882; https://doi.org/10.3390/molecules24213882 - 28 Oct 2019

Cited by 6 | Viewed by 2682

Abstract

In our previous study, a novel barrier processing on a porous low-dielectric constant (low-k) film was developed: an ultrathin Mn oxide on a nitrogen-stuffed porous carbon-doped organosilica film (p-SiOCH(N)) as a barrier of the Cu film was fabricated. To form a [...] Read more.

In our previous study, a novel barrier processing on a porous low-dielectric constant (low-k) film was developed: an ultrathin Mn oxide on a nitrogen-stuffed porous carbon-doped organosilica film (p-SiOCH(N)) as a barrier of the Cu film was fabricated. To form a better barrier Mn₂O_3−xN film, additional annealing at 450 °C was implemented. In this study, the electrical characteristics and reliability of this integrated Cu/Mn₂O_3−xN/p-SiOCH(N)/Si structure were investigated. The proposed Cu/Mn₂O_3−xN/p-SiOCH(N)/Si capacitors exhibited poor dielectric breakdown characteristics in the as-fabricated stage, although, less degradation was found after thermal stress. Moreover, its time-dependence-dielectric-breakdown electric-field acceleration factor slightly increased after thermal stress, leading to a larger dielectric lifetime in a low electric-field as compared to other metal-insulator-silicon (MIS) capacitors. Furthermore, its Cu barrier ability under electrical or thermal stress was improved. As a consequence, the proposed Cu/Mn₂O_3−xN/p-SiCOH(N) scheme is promising integrity for back-end-of-line interconnects. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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13 pages, 936 KiB

Open AccessFeature PaperArticle

Advances in the Interpretation of Frequency-Dependent Nuclear Magnetic Resonance Measurements from Porous Material

by David Faux, Rémi Kogon, Villiam Bortolotti and Peter McDonald

Molecules 2019, 24(20), 3688; https://doi.org/10.3390/molecules24203688 - 14 Oct 2019

Cited by 12 | Viewed by 3510

Abstract

Fast-field-cycling nuclear magnetic resonance (FFC-NMR) is a powerful technique for non-destructively probing the properties of fluids contained within the pores of porous materials. FFC-NMR measures the spin–lattice relaxation rate

R_{1} (f)

as a function of NMR frequency f over the [...] Read more.

Fast-field-cycling nuclear magnetic resonance (FFC-NMR) is a powerful technique for non-destructively probing the properties of fluids contained within the pores of porous materials. FFC-NMR measures the spin–lattice relaxation rate

R_{1} (f)

as a function of NMR frequency f over the kHz to MHz range. The shape and magnitude of the

R_{1} (f)

dispersion curve is exquisitely sensitive to the relative motion of pairs of spins over time scales of picoseconds to microseconds. To extract information on the nano-scale dynamics of spins, it is necessary to identify a model that describes the relative motion of pairs of spins, to translate the model dynamics to a prediction of

R_{1} (f)

and then to fit to the experimental dispersion. The principles underpinning one such model, the 3

τ

model, are described here. We present a new fitting package using the 3

τ

model, called 3TM, that allows users to achieve excellent fits to experimental relaxation rates over the full frequency range to yield five material properties and much additional derived information. 3TM is demonstrated on historic data for mortar and plaster paste samples. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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14 pages, 2404 KiB

Open AccessArticle

Water in Mesoporous Confinement: Glass-To-Liquid Transition or Freezing of Molecular Reorientation Dynamics?

by Wilfried Schranz and Viktor Soprunyuk

Molecules 2019, 24(19), 3563; https://doi.org/10.3390/molecules24193563 - 1 Oct 2019

Cited by 2 | Viewed by 2856

Abstract

The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called “capillary transition” (here denoted as P3) of water in the core of the pores and [...] Read more.

The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called “capillary transition” (here denoted as P3) of water in the core of the pores and a second one at a lower temperature, which they called the “adsorbate transition” (P1 in present work) related to water near the surface of the pores. The capillary transition was identified with the freezing of water in the centre of the pores. However, even 40 years later, the origin of the adsorbate transition is not yet clear. One study relates it to the liquid-to-glass transition of the supercooled water in the pores, and another study to the freezing of the proton reorientations at the lattice defects. The present work shows the data from extensive dynamic mechanical analysis (DMA) measurements (f = 0.1 Hz–70 Hz) of water confined in mesoporous silica (d = 2.5, 5 and 10 nm), which are in favour of a liquid-to-glass scenario. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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16 pages, 8871 KiB

Open AccessArticle

Combining Soft Polysilazanes with Melt-Shear Organization of Core–Shell Particles: On the Road to Polymer-Templated Porous Ceramics

by Anna K. Boehm, Emanuel Ionescu, Marcus Koch and Markus Gallei

Molecules 2019, 24(19), 3553; https://doi.org/10.3390/molecules24193553 - 30 Sep 2019

Cited by 16 | Viewed by 4932

Abstract

The preparation of ordered macroporous SiCN ceramics has attracted significant interest and is an attractive area for various applications, e.g., in the fields of catalysis, gas adsorption, or membranes. Non-oxidic ceramics, such as SiCN, own a great stability based on the covalent bonds [...] Read more.

The preparation of ordered macroporous SiCN ceramics has attracted significant interest and is an attractive area for various applications, e.g., in the fields of catalysis, gas adsorption, or membranes. Non-oxidic ceramics, such as SiCN, own a great stability based on the covalent bonds between the containing elements, which leads to interesting properties concerning resistance and stability at high temperature. Their peculiar properties have become more and more important for a manifold of applications, like catalysis or separation processes, at high temperatures. Within this work, a feasible approach for the preparation of ordered porous materials by taking advantage of polymer-derived ceramics is presented. To gain access to free-standing films consisting of porous ceramic materials, the combination of monodisperse organic polymer-based colloids with diameters of 130 nm and 180 nm featuring a processable preceramic polymer is essential. For this purpose, the tailored design of hybrid organic/inorganic particles featuring anchoring sites for a preceramic polymer in the soft shell material is developed. Moreover, polymer-based core particles are used as sacrificial template for the generation of pores, while the preceramic shell polymer can be converted to the ceramic matrix after thermal treatment. Two different routes for the polymer particles, which can be obtained by emulsion polymerization, are followed for covalently linking the preceramic polysilazane Durazane1800 (Merck, Germany): (i) Free radical polymerization and (ii) atom transfer radical polymerization (ATRP) conditions. These hybrid hard core/soft shell particles can be processed via the so-called melt-shear organization for the one-step preparation of free-standing particle films. A major advantage of this technique is the absence of any solvent or dispersion medium, enabling the core particles to merge into ordered particle stacks based on the soft preceramic shell. Subsequent ceramization of the colloidal crystal films leads to core particle degradation and transformation into porous ceramics with ceramic yields of 18–54%. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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9 pages, 2025 KiB

Open AccessArticle

Hydroxyl-Group Identification Using O K-Edge XAFS in Porous Glass Fabricated by Hydrothermal Reaction and Low-Temperature Foaming

by Masanori Suzuki, Shigehiro Maruyama, Norimasa Umesaki and Toshihiro Tanaka

Molecules 2019, 24(19), 3488; https://doi.org/10.3390/molecules24193488 - 26 Sep 2019

Cited by 8 | Viewed by 3781

Abstract

Porous glass was prepared by the hydrothermal reaction of sodium borosilicate glass, and oxygen-ion characterization was used to identify the hydroxyl groups in its surface area. A substantial amount of “water” was introduced into the ionic structure as either OH⁻ groups or [...] Read more.

Porous glass was prepared by the hydrothermal reaction of sodium borosilicate glass, and oxygen-ion characterization was used to identify the hydroxyl groups in its surface area. A substantial amount of “water” was introduced into the ionic structure as either OH⁻ groups or H₂O molecules through the hydrothermal reaction. When the hydrothermally treated glass was reheated at normal pressures, a porous structure was formed due to the low-temperature foaming resulting from the evaporation of H₂O molecules and softening of the glass. Although it was expected that the OH⁻ groups would remain in the porous glass, their distribution required clarification. Oxygen K-edge X-ray absorption fine structure (XAFS) spectroscopy enables the bonding states of oxygen ions in the surface area and interior to be characterized using the electron yield (EY) and fluorescence yield (FY) mode, respectively. The presence of OH⁻ groups was detected in the O K-edge XAFS spectrum of the porous glass prepared by hydrothermal reaction with a corresponding pre-edge peak energy of 533.1 eV. In addition, comparison of the XAFS spectra obtained in the EY and FY modes revealed that the OH⁻ groups were mainly distributed in the surface area (depths of several tens of nanometers). Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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13 pages, 3313 KiB

Open AccessArticle

Nitrogen Self-Doped Activated Carbons Derived from Bamboo Shoots as Adsorbent for Methylene Blue Adsorption

by Bingbing Mi, Jingxin Wang, Hongzhong Xiang, Fang Liang, Jianfei Yang, Zixing Feng, Tao Zhang, Wanhe Hu, Xianmiao Liu, Zhijia Liu and Benhua Fei

Molecules 2019, 24(16), 3012; https://doi.org/10.3390/molecules24163012 - 20 Aug 2019

Cited by 24 | Viewed by 4934

Abstract

Bamboo shoots, a promising renewable biomass, mainly consist of carbohydrates and other nitrogen-related compounds, such as proteins, amino acids and nucleotides. In this work, nitrogen self-doped activated carbons derived from bamboo shoots were prepared via a simultaneous carbonization and activation process. The adsorption [...] Read more.

Bamboo shoots, a promising renewable biomass, mainly consist of carbohydrates and other nitrogen-related compounds, such as proteins, amino acids and nucleotides. In this work, nitrogen self-doped activated carbons derived from bamboo shoots were prepared via a simultaneous carbonization and activation process. The adsorption properties of the prepared samples were evaluated by removing methylene blue from waste water. The factors that affect the adsorption process were examined, including initial concentration, contact time and pH of methylene blue solution. The resulting that BSNC-800-4 performed better in methylene blue removal from waste water, due to its high specific surface area (2270.9 m² g⁻¹), proper pore size (2.19 nm) and relatively high nitrogen content (1.06%). Its equilibrium data were well fitted to Langmuir isotherm model with a maximum monolayer adsorption capacity of 458 mg g⁻¹ and a removal efficiency of 91.7% at methylene blue concentration of 500 mg L⁻¹. The pseudo-second-order kinetic model could be used to accurately estimate the carbon material’s (BSNC-800-4) adsorption process. The adsorption mechanism between methylene blue solution and BSNC-800-4 was controlled by film diffusion. This study provides an alternative way to develop nitrogen self-doped activated carbons to better meet the needs of the adsorption applications. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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13 pages, 3750 KiB

Open AccessArticle

Bread-Derived Bioactive Porous Scaffolds: An Innovative and Sustainable Approach to Bone Tissue Engineering

by Elisa Fiume, Gianpaolo Serino, Cristina Bignardi, Enrica Verné and Francesco Baino

Molecules 2019, 24(16), 2954; https://doi.org/10.3390/molecules24162954 - 14 Aug 2019

Cited by 36 | Viewed by 3554

Abstract

In recent years, bioactive glasses gained increasing scientific interest in bone tissue engineering due to their capability to chemically bond with the host tissue and to induce osteogenesis. As a result, several efforts have been addressed to use bioactive glasses in the production [...] Read more.

In recent years, bioactive glasses gained increasing scientific interest in bone tissue engineering due to their capability to chemically bond with the host tissue and to induce osteogenesis. As a result, several efforts have been addressed to use bioactive glasses in the production of three-dimensional (3D) porous scaffolds for bone regeneration. In this work, we creatively combine typical concepts of porous glass processing with those of waste management and propose, for the first time, the use of bread as a new sacrificial template for the fabrication of bioactive scaffolds. Preliminary SEM investigations performed on stale bread from industrial wastes revealed a suitable morphology characterized by an open-cell 3D architecture, which is potentially able to allow tissue ingrowth and vascularization. Morphological features, mechanical performances and in vitro bioactivity tests were performed in order to evaluate the properties of these new “sustainable” scaffolds for bone replacement and regeneration. Scaffolds with total porosity ranging from 70 to 85 vol% and mechanical strength comparable to cancellous bone were obtained. Globular hydroxyapatite was observed to form on the surface of the scaffolds after just 48-h immersion in simulated body fluid. The results show great promise and suggest the possibility to use bread as an innovative and inexpensive template for the development of highly-sustainable bone tissue engineering approaches. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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14 pages, 3759 KiB

Open AccessArticle

Gas Permeability of Cellulose Aerogels with a Designed Dual Pore Space System

by Kathirvel Ganesan, Adam Barowski and Lorenz Ratke

Molecules 2019, 24(15), 2688; https://doi.org/10.3390/molecules24152688 - 24 Jul 2019

Cited by 13 | Viewed by 4004

Abstract

The gas permeability of a porous material is a key property determining the impact of the material in an application such as filter/separation techniques. In the present study, aerogels of cellulose scaffolds were designed with a dual pore space system consisting of macropores [...] Read more.

The gas permeability of a porous material is a key property determining the impact of the material in an application such as filter/separation techniques. In the present study, aerogels of cellulose scaffolds were designed with a dual pore space system consisting of macropores with cell walls composing of mesopores and a nanofibrillar network. The gas permeability properties of these dual porous materials were compared with classical cellulose aerogels. Emulsifying the oil droplets in the hot salt–hydrate melt with a fixed amount of cellulose was performed in the presence of surfactants. The surfactants varied in physical, chemical and structural properties and a range of hydrophilic–lipophilic balance (HLB) values, 13.5 to 18. A wide range of hierarchical dual pore space systems were produced and analysed using nitrogen adsorption–desorption analysis and scanning electron microscopy. The microstructures of the dual pore system of aerogels were quantitatively characterized using image analysis methods. The gas permeability was measured and discussed with respect to the well-known model of Carman–Kozeny for open porous materials. The gas permeability values implied that the kind of the macropore channel’s size, shape, their connectivity through the neck parts and the mesoporous structures on the cell walls are significantly controlling the flow resistance of air. Adaption of this new design route for cellulose-based aerogels can be suitable for advanced filters/membranes production and also biological or catalytic supporting materials since the emulsion template method allows the tailoring of the gas permeability while the nanopores of the cell walls can act simultaneously as absorbers. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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21 pages, 4391 KiB

Open AccessArticle

Combined Minimum-Run Resolution IV and Central Composite Design for Optimized Removal of the Tetracycline Drug Over Metal–Organic Framework-Templated Porous Carbon

by Thuan Van Tran, Duyen Thi Cam Nguyen, Hanh T. N. Le, Long Giang Bach, Dai-Viet N. Vo, Kwon Taek Lim, Linh Xuan Nong and Trinh Duy Nguyen

Molecules 2019, 24(10), 1887; https://doi.org/10.3390/molecules24101887 - 16 May 2019

Cited by 34 | Viewed by 4434

Abstract

In this study, a minimum-run resolution IV and central composite design have been developed to optimize tetracycline removal efficiency over mesoporous carbon derived from the metal-organic framework MIL-53 (Fe) as a self-sacrificial template. Firstly, minimum-run resolution IV, powered by the Design–Expert program, was [...] Read more.

In this study, a minimum-run resolution IV and central composite design have been developed to optimize tetracycline removal efficiency over mesoporous carbon derived from the metal-organic framework MIL-53 (Fe) as a self-sacrificial template. Firstly, minimum-run resolution IV, powered by the Design–Expert program, was used as an efficient and reliable screening study for investigating a set of seven factors, these were: tetracycline concentration (A: 5–15 mg/g), dose of mesoporous carbons (MPC) (B: 0.05–0.15 g/L), initial pH level (C: 2–10), contact time (D: 1–3 h), temperature (E: 20–40 °C), shaking speed (F: 150–250 rpm), and Na⁺ ionic strength (G: 10–90 mM) at both low (−1) and high (+1) levels, for investigation of the data ranges. The 20-trial model was analyzed and assessed by Analysis of Variance (ANOVA) data, and diagnostic plots (e.g., the Pareto chart, and half-normal and normal probability plots). Based on minimum-run resolution IV, three factors, including tetracycline concentration (A), dose of MPC (B), and initial pH (C), were selected to carry out the optimization study using a central composite design. The proposed quadratic model was found to be statistically significant at the 95% confidence level due to a low P-value (<0.05), high R² (0.9078), and the AP ratio (11.4), along with an abundance of diagnostic plots (3D response surfaces, Cook’s distance, Box-Cox, DFFITS, Leverage versus run, residuals versus runs, and actual versus predicted). Under response surface methodology-optimized conditions (e.g., tetracycline concentration of 1.9 mg/g, MPC dose of 0.15 g/L, and pH level of 3.9), the highest tetracycline removal efficiency via confirmation tests reached up to 98.0%–99.7%. Also, kinetic intraparticle diffusion and isotherm models were systematically studied to interpret how tetracycline molecules were absorbed on an MPC structure. In particular, the adsorption mechanisms including “electrostatic attraction” and “π–π interaction” were proposed. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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11 pages, 2173 KiB

Open AccessArticle

Ethylene Adsorption Using Cobalt Oxide-Loaded Polymer-Derived Nanoporous Carbon and Its Application to Extend Shelf Life of Fruit

by Imam Prasetyo, Nur Indah Fajar Mukti and Teguh Ariyanto

Molecules 2019, 24(8), 1507; https://doi.org/10.3390/molecules24081507 - 17 Apr 2019

Cited by 9 | Viewed by 4084

Abstract

Suppressing the amount of ethylene during storage has been of interest as a method to enhance shelf life of fruit. In this work, ethylene removal by adsorption using cobalt oxide-impregnated nanoporous carbon has been studied. Nanoporous carbon with a high surface area up [...] Read more.

Suppressing the amount of ethylene during storage has been of interest as a method to enhance shelf life of fruit. In this work, ethylene removal by adsorption using cobalt oxide-impregnated nanoporous carbon has been studied. Nanoporous carbon with a high surface area up to 2400 m² g⁻¹ was prepared by carbonization process biomass and synthetic polymer at 850 °C. Dispersion of cobalt oxide on porous carbon surface was carried out by an incipient wetness procedure followed by calcination process at 200 °C. Ethylene adsorption test was performed using a volumetric method in an ultrahigh vacuum rig constructed by Swagelok VCR® fittings. The results showed that the cobalt oxide/carbon system had significant ethylene adsorption capacity. Ethylene uptake increases with the increasing cobalt oxide loading on the carbon. The highest ethylene capacity of 16 mol kg⁻¹ adsorbent was obtained by using 30 wt.% (weight percentage) of cobalt oxide dispersed in polymer-derived carbon. In closed storage, the ratio of 15 g adsorbent/kg fruit may extend the storage life up to 12 d, higher than that without adsorbent (3 d). Therefore, the results demonstrate the great potential use of cobalt oxide-impregnated nanoporous carbon as an adsorbent for ethylene removal during storage of fruit. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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11 pages, 10734 KiB

Open AccessArticle

Peel and Penetration Resistance of Porous Polyethylene Terephthalate Material Produced by CO₂-Assisted Polymer Compression

by Takafumi Aizawa

Molecules 2019, 24(7), 1384; https://doi.org/10.3390/molecules24071384 - 9 Apr 2019

Cited by 9 | Viewed by 2844

Abstract

CO₂-assisted polymer compression (CAPC) involves adhering fiber sheets without impurities at room temperature and producing porous materials suitable for use in medical and skin-contactable products. The mechanical strength of the resultant porous material has not yet been reported. The penetration resistance [...] Read more.

CO₂-assisted polymer compression (CAPC) involves adhering fiber sheets without impurities at room temperature and producing porous materials suitable for use in medical and skin-contactable products. The mechanical strength of the resultant porous material has not yet been reported. The penetration resistance of the CAPC material, which is a laminated material comprising fibrous polymer sheets, was measured, and this increased gradually with the density. Additionally, a T-type peel test was performed on the CAPC material, and the peel resistance increased rapidly with the density. The peel resistance enhancement is effectively explained by the cross-sectional analysis model. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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8 pages, 3069 KiB

Open AccessCommunication

Ginger Straw Waste-Derived Porous Carbons as Effective Adsorbents toward Methylene Blue

by Wenlin Zhang, Huihe Li, Jianmin Tang, Hongjia Lu and Yiqing Liu

Molecules 2019, 24(3), 469; https://doi.org/10.3390/molecules24030469 - 28 Jan 2019

Cited by 24 | Viewed by 3761

Abstract

In this work, ginger straw waste-derived porous carbons, with high adsorption capacity, high adsorption rate, and good reusability for removing the toxic dye of methylene blue from wastewater, were prepared by a facile method under oxygen-limiting conditions. This study opens a new approach [...] Read more.

In this work, ginger straw waste-derived porous carbons, with high adsorption capacity, high adsorption rate, and good reusability for removing the toxic dye of methylene blue from wastewater, were prepared by a facile method under oxygen-limiting conditions. This study opens a new approach for the utilization of ginger straw waste, and the porous materials can be employed as great potential adsorbents for treating dye wastewater. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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17 pages, 4246 KiB

Open AccessArticle

Dual Functional S-Doped g-C₃N₄ Pinhole Porous Nanosheets for Selective Fluorescence Sensing of Ag⁺ and Visible-Light Photocatalysis of Dyes

by Abhijit N. Kadam, Md. Moniruzzaman and Sang-Wha Lee

Molecules 2019, 24(3), 450; https://doi.org/10.3390/molecules24030450 - 27 Jan 2019

Cited by 60 | Viewed by 6114

Abstract

This study explores the facile, template-free synthesis of S-doped g-C₃N₄ pinhole nanosheets (SCNPNS) with porous structure for fluorescence sensing of Ag⁺ ions and visible-light photocatalysis of dyes. As-synthesized SCNPNS samples were characterized by various analytical tools such as XRD, [...] Read more.

This study explores the facile, template-free synthesis of S-doped g-C₃N₄ pinhole nanosheets (SCNPNS) with porous structure for fluorescence sensing of Ag⁺ ions and visible-light photocatalysis of dyes. As-synthesized SCNPNS samples were characterized by various analytical tools such as XRD, FT-IR, TEM, BET, XPS, and UV–vis spectroscopy. At optimal conditions, the detection linear range for Ag⁺ was found to be from 0 to 1000 nM, showing the limit of detection (LOD) of 57 nM. The SCNPNS exhibited highly sensitive and selective detection of Ag⁺ due to a significant fluorescence quenching via photo-induced electron transfer through Ag⁺–SCNPNS complex. Moreover, the SCNPNS exhibited 90% degradation for cationic methylene blue (MB) dye within 180 min under visible light. The enhanced photocatalytic activity of the SCNPNS was attributed to its negative zeta potential for electrostatic interaction with cationic dyes, and the pinhole porous structure can provide more active sites which can induce faster transport of the charge carrier over the surface. Our SCNPNS is proposed as an environmental safety tool due to several advantages, such as low cost, facile preparation, selective recognition of Ag⁺ ions, and efficient photocatalytic degradation of cationic dyes under visible light. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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21 pages, 2171 KiB

Open AccessArticle

Mechanisms of Methylparaben Adsorption onto Activated Carbons: Removal Tests Supported by a Calorimetric Study of the Adsorbent–Adsorbate Interactions

by Valentina Bernal, Liliana Giraldo, Juan Carlos Moreno-Piraján, Marco Balsamo and Alessandro Erto

Molecules 2019, 24(3), 413; https://doi.org/10.3390/molecules24030413 - 23 Jan 2019

Cited by 39 | Viewed by 5094

Abstract

In this study, the mechanisms of methylparaben adsorption onto activated carbon (AC) are elucidated starting from equilibrium and thermodynamic data. Adsorption tests are carried out on three ACs with different surface chemistry, in different pH and ionic strength aqueous solutions. Experimental results show [...] Read more.

In this study, the mechanisms of methylparaben adsorption onto activated carbon (AC) are elucidated starting from equilibrium and thermodynamic data. Adsorption tests are carried out on three ACs with different surface chemistry, in different pH and ionic strength aqueous solutions. Experimental results show that the methylparaben adsorption capacity is slightly affected by pH changes, while it is significantly reduced in the presence of high ionic strength. In particular, methylparaben adsorption is directly dependent on the micropore volume of the ACs and the π- stacking interactions, the latter representing the main interaction mechanism of methylparaben adsorption from liquid phase. The equilibrium adsorption data are complemented with novel calorimetric data that allow calculation of the enthalpy change associated with the interactions between solvent-adsorbent, adsorbent-adsorbate and the contribution of the ester functional group (in the methylparaben structure) to the adsorbate–adsorbent interactions, in different pH and ionic strength conditions. It was determined that the interaction enthalpy of methylparaben-AC in water increases (absolute value) slightly with the basicity of the activated carbons, due to the formation of interactions with π- electrons and basic functional groups of ACs. The contribution of the ester group to the adsorbate-adsorbent interactions occurs only in the presence of phenol groups on AC by the formation of Brønsted–Lowry acid–base interactions. Full article

(This article belongs to the Special Issue Advances in Porous Materials)

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