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Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: closed (31 March 2021) | Viewed by 26023

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Special Issue Editor

Prof. Dr. Jae-Min Oh

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Guest Editor

Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul 04620, Korea
Interests: clay; layered double hydroxide; earth science; intercalation; two-dimensional materials; environment; nanocomposite; industry; nanomedicine
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Natural and engineered clays are widely studied in terms of exploring new industrial application fields as well as comprehending the fundamentals of their two-dimensional structures. Naturally occurring clays inherently have two-dimensional structures of which composition and physicochemical properties can be controlled variously. Engineered or synthesized clays could have more finely tuned physicochemical properties to load intended functionalities.

Due to the increasing interest in two-dimensional materials and their eco-friendly application, I am honored to present this Special Issue titled “Natural and Engineered Clays: Two-Dimensional Nano-Building Clocks for Functional Nanomaterials” under the expertized support of Nanomaterials and MDPI.

I would especially like to take advantage of the 4th Asian Clay Conference (ACC-2020), which will be held in Pattaya, Thailand, from June 7 to 10, 2020, to expand communication among clay scientists from various fields. The conference is mainly organized by the Vidyasirimedhi Institute of Science and Technology, Thailand. Not only distinguished scientists from China, Korea, Japan, and Thailand but also international clay scientists from Germany, Australia, the USA, Taiwan, Russia, Israel, Malaysia, and Cambodia are participating to strengthen the academic and industrial aspects of this conference. The aim of ACC-2020 is to support cooperation between scientists and to develop an international research network to facilitate open discussions between scientists, students, and industry representatives with an interest in academic and industrial studies on natural and engineered clays.

Therefore, considering academic comprehension and industrial applications, the main goal of this Special Issue can be strongly supported by conference participants. However, I do not limit the contributors to this Special Issue to conference participants. I invite all scientists in clay- and nanomaterials-related fields to be potential contributors, including those who research clays in earth sciences, clays in industry/civil engineering, clays for environments, clays for life/health/biology, clays for functional materials, etc.

Prof. Dr. Jae-Min Oh
Guest Editors

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Keywords

Clays
Nanomaterials
Two-dimensional nanostructures
Earth sciences
Environment
Health and biology
Industrial applications

Published Papers (10 papers)

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Research

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12 pages, 3781 KiB

Open AccessArticle

Preparation of MgGa Layered Double Hydroxides and Possible Compositional Variation

by Rattanawadee (Ploy) Wijitwongwan, Soontaree (Grace) Intasa-ard and Makoto Ogawa

Nanomaterials 2021, 11(5), 1206; https://doi.org/10.3390/nano11051206 - 1 May 2021

Cited by 4 | Viewed by 2159

Abstract

Layered double hydroxides (LDHs), shown as the general formula of [M²⁺_1−xM³⁺_x(OH)₂]^x+(Aⁿ⁻)_x/n∙yH₂O, are useful for various applications such as anion exchangers/adsorbents, catalysts and catalysts’ supports, and drug/gene carriers due to their structural, compositional and morphological characteristics and their variation. The x value (M³⁺/(M²⁺ + M³⁺) ratio) in layered double hydroxides (LDHs), corresponding to the layer charge density, is one of the important parameters for controlling the properties of LDHs. The x values in commonly available LDHs are limited (0.2 < x < 0.3). In order to obtain LDHs with x < 0.2, Mg²⁺ Ga³⁺–LDHs with interlayer iodide were examined. The linear correlation between lattice parameter a and x value in the products with x of 0.06–0.24 was seen, suggesting the successful substitution of Mg²⁺ in the brucite-like sheet with Ga³⁺. Carbonate and dodecyl sulfate types MgGa–LDH were prepared by ion exchange with carbonate anion and reconstruction in aqueous solution of sodium dodecyl sulfate. The products with x of 0.06 were dispersed in water and hexanol better than those with x of 0.24 for MgGa–LDHs containing carbonate and dodecyl sulfate, respectively, suggesting effects of the lower layer charge density on the dispersion. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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8 pages, 1943 KiB

Open AccessArticle

Photoluminescence Gas Sensing by Fluorescein-Dye Anions/1-Butanesulfonate/Layered Double Hydroxide Hybrid Materials under Humid Environment Conditions

by Ryo Sasai, Satoshi Yamamoto and Akane Naito

Nanomaterials 2021, 11(4), 914; https://doi.org/10.3390/nano11040914 - 3 Apr 2021

Cited by 3 | Viewed by 1750

Abstract

In this study, we investigated the photoluminous spectroscopic behavior of hybrid powder incorporating both anionic fluorescein dye (AFD) and 1-butanesulfonate (C4S) with layered double hydroxide (LDH) in the presence of NH₃ or NO₂ gas under various relative humidity conditions. In the presence of NH₃ gas, drastic photoluminescence enhancement from the LDH/AFD/C4S hybrid was observed at relative humidity (RH) ≥ 40% when the NH₃ reached a certain concentration. Meanwhile, the LDH/AFD/C4S hybrid was exposed to NO₂ gas at various relative humidity conditions, and the following behavior was observed: At RH ≥ 60%, the photoluminescence (PL) intensity from the hybrid gradually decreased as NO₂ concentration increased. Therefore, the LDH/AFD/C4S hybrid investigated in this study is inferred to be suitable for optical NH₃/NO₂ sensor devices, which can be used in humid air. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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13 pages, 3210 KiB

Open AccessArticle

Development of Mesopore Structure of Mixed Metal Oxide through Albumin-Templated Coprecipitation and Reconstruction of Layered Double Hydroxide

by Sang-Yong Jung, Bo-Kyung Kim, Hyoung-Jun Kim and Jae-Min Oh

Nanomaterials 2021, 11(3), 620; https://doi.org/10.3390/nano11030620 - 2 Mar 2021

Cited by 5 | Viewed by 2289

Abstract

Mixed metal oxide (MMO) with relatively homogeneous mesopores was successfully obtained by calcination and reconstruction of albumin-templated layered double hydroxide (LDH). The aggregation degree of albumin-template was controlled by adjusting two different synthesis routes, coprecipitation and reconstruction. X-ray diffraction patterns and scanning electron microscopic images indicated that crystal growth of LDH was fairly limited during albumin-templated coprecipitation due to the aggregation. On the hand, crystal growth along the lateral direction was facilitated in albumin-templated reconstruction due to the homogeneous distribution of proteins moiety. Different state of albumin during LDH synthesis influenced the local disorder and porous structure of calcination product, MMO. The N₂ adsorption-desorption isotherms demonstrated that calcination on reconstructed LDH produced MMO with large specific surface area and narrow distribution of mesopores compared with calcination of coprecipitated LDH. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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16 pages, 2941 KiB

Open AccessArticle

Controlled Growth of Silver Oxide Nanoparticles on the Surface of Citrate Anion Intercalated Layered Double Hydroxide

by Do-Gak Jeung, Minseop Lee, Seung-Min Paek and Jae-Min Oh

Nanomaterials 2021, 11(2), 455; https://doi.org/10.3390/nano11020455 - 11 Feb 2021

Cited by 16 | Viewed by 2348

Abstract

Silver oxide nanoparticles with controlled particle size were successfully obtained utilizing citrate-intercalated layered double hydroxide (LDH) as a substrate and Ag⁺ as a precursor. The lattice of LDH was partially dissolved during the reaction by Ag⁺. The released hydroxyl and citrate acted as a reactant in crystal growth and a size controlling capping agent, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and microscopic measurements clearly showed the development of nano-sized silver oxide particles on the LDH surface. The particle size, homogeneity and purity of silver oxide were influenced by the stoichiometric ratio of Ag/Al. At the lowest silver ratio, the particle size was the smallest, while the chemical purity was the highest. X-ray photoelectron spectroscopy and UV-vis spectroscopy results suggested that the high Ag/Al ratio tended to produce silver oxide with a complex silver environment. The small particle size and homogeneous distribution of silver oxide showed advantages in antibacterial efficacy compared with bulk silver oxide. LDH with an appropriate ratio could be utilized as a substrate to grow silver oxide nanoparticles with controlled size with effective antibacterial performance. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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15 pages, 3625 KiB

Open AccessArticle

Porous Hybrids Structure between Silver Nanoparticle and Layered Double Hydroxide for Surface-Enhanced Raman Spectroscopy

by Su-Bin Lee, Seung-Min Paek and Jae-Min Oh

Nanomaterials 2021, 11(2), 447; https://doi.org/10.3390/nano11020447 - 10 Feb 2021

Cited by 5 | Viewed by 2536

Abstract

Silver nanoparticle (AgNP), in terms of antibacterial, catalytic, electronic, and optical applications, is an attractive material. Especially, when prepared to furnish sharp edge and systematic particle orientation on the substrate, AgNPs can take advantage of surface-enhanced Raman spectroscopy (SERS). In this research, we suggested a synthetic method to immobilize the AgNP on metal oxide by utilizing Ag-thiolate and layered double hydroxide (LDH) as precursor and template, respectively. The layer-by-layer structure of LDH and Ag-thiolate transformed through reductive calcination to metal oxide and AgNP array. Physicochemical characterization, including powder X-ray diffraction, N₂ adsorption–desorption, microscopies, and X-ray photoelectron spectroscopy, revealed that the AgNP with sufficient crystallinity and particle gap was obtained at relatively high calcination temperature, ~600 °C. UV-vis diffusion reflectance spectroscopy showed that the calcination temperature affected particle size and electronic structure of AgNP. The prepared materials were subjected to SERS tests toward 4-nitrothiophenol (4-NTP). The sample obtained at 600 °C exhibited 50 times higher substrate enhancement factor (SEF) than the one obtained at 400 °C, suggesting that the calcination temperature was a determining parameter to enhance SERS activity in current synthetic condition. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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14 pages, 4726 KiB

Open AccessArticle

Porous Clay Heterostructure with Alginate Encapsulation for Toluene Removal

by Yeongkyun Son, Tae-Hyun Kim, Daekeun Kim and Yuhoon Hwang

Nanomaterials 2021, 11(2), 388; https://doi.org/10.3390/nano11020388 - 3 Feb 2021

Cited by 4 | Viewed by 2308

Abstract

A volatile organic compound adsorbent based on a porous clay heterostructure (PCH) with alginate biopolymer was successfully prepared. From N₂ adsorption–desorption analysis, the specific surface area, pore volume, and pore size of bentonite were dramatically increased after introducing the porous structure. Following complexation with alginate (Alg-PCH), the pore volume and pore size were not significantly affected by pore structure. The thermal stability of Alg-PCH shows enhanced thermal stability compared to alginate and alginate beads. The morphology layered structure of Alg-PCH was carried out by transmission electron microscopy (TEM), suggesting the disorder and re-order of the c-axis layer stacking by porous structure and complexation with alginate, respectively, which was well-matched with X-ray diffraction results. To optimize the preparation of Alg-PCH, various reaction conditions (alginate, CaCl₂ concentration, bead size, and weight ratio between alginate and PCH) were utilized. According to the toluene adsorption–desorption experiments, the preparation conditions for Alg-PCH were selected as a 2 mm extrusion tip, 0.5% of alginate, and 2% of CaCl₂ solution with a 1:50 alginate:PCH weight ratio. Additionally, it shows 61.63 mg/g adsorption capacity with around 49% desorption efficacy under atmospheric temperature and pressure. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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15 pages, 5689 KiB

Open AccessArticle

Microwave-Assisted Synthesis of Ge/GeO₂-Reduced Graphene Oxide Nanocomposite with Enhanced Discharge Capacity for Lithium-Ion Batteries

by Ji-Hye Koo and Seung-Min Paek

Nanomaterials 2021, 11(2), 319; https://doi.org/10.3390/nano11020319 - 27 Jan 2021

Cited by 18 | Viewed by 3358

Abstract

Germanium/germanium oxide nanoparticles with theoretically high discharge capacities of 1624 and 2152 mAh/g have attracted significant research interest for their potential application as anode materials in Li-ion batteries. However, these materials exhibit poor long-term performance due to the large volume change of 370% during charge/discharge cycles. In the present study, to overcome this shortcoming, a Ge/GeO₂/graphene composite material was synthesized. Ge/GeO₂ nanoparticles were trapped between matrices of graphene nanosheets to offset the volume expansion effect. Transmission electron microscopy images revealed that the Ge/GeO₂ nanoparticles were distributed on the graphene nanosheets. Discharge/charge experiments were performed to evaluate the Li storage properties of the samples. The discharge capacity of the bare Ge/GeO₂ nanoparticles in the first discharge cycle was considerably large; however, the value decreased rapidly with successive cycles. Conversely, the present Ge/GeO₂/graphene composite exhibited superior cycling stability. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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Graphical abstract

16 pages, 3418 KiB

Open AccessArticle

Changes in Optical Properties upon Dye–Clay Interaction: Experimental Evaluation and Applications

by Giorgia Giovannini, René M. Rossi and Luciano F. Boesel

Nanomaterials 2021, 11(1), 197; https://doi.org/10.3390/nano11010197 - 14 Jan 2021

Cited by 7 | Viewed by 2186

Abstract

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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Graphical abstract

13 pages, 2876 KiB

Open AccessArticle

Homogeneous Incorporation of Gallium into Layered Double Hydroxide Lattice for Potential Radiodiagnostics: Proof-of-Concept

by Do-Gak Jeung, Tae-Hyun Kim and Jae-Min Oh

Nanomaterials 2021, 11(1), 44; https://doi.org/10.3390/nano11010044 - 26 Dec 2020

Cited by 1 | Viewed by 2490

Abstract

Trivalent gallium ion was successfully incorporated into chemically well-defined MgAl-layered double hydroxide (LDH) frameworks through postsynthetic hydrothermal treatment. Quantitative analysis with inductively coupled plasma-mass spectroscopy exhibited that Ga³⁺ was first incorporated into LDH through partial dissolution-precipitation at the edge of LDH particle and homogeneously distributed throughout the particle by substitution of Ga³⁺ for Al³⁺ in LDH frame works. The powder X-ray diffraction patterns showed that the Ga³⁺ incorporation did not affect the crystal structure without evolution of unexpected impurities. The morphology and surface property of LDH evaluated by scanning electron microscopy and light scattering showed the preservation of physicochemical properties throughout 24 h of hydrothermal reaction. The distribution of incorporated Ga³⁺ was visualized with energy dispersive spectroscopy-assisted transmission electron microscopy, suggesting the homogeneous location of Ga³⁺ in an LDH particle. The X-ray absorption near-edge structure and extended X-ray absorption fine structure suggested that the Ga moiety was immobilized in LDH from 0.5 h and readily crystallized upon reaction time. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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Review

Jump to: Research

19 pages, 40361 KiB

Open AccessReview

Mixed Metal Oxide by Calcination of Layered Double Hydroxide: Parameters Affecting Specific Surface Area

by Su-Bin Lee, Eun-Hye Ko, Joo Y. Park and Jae-Min Oh

Nanomaterials 2021, 11(5), 1153; https://doi.org/10.3390/nano11051153 - 28 Apr 2021

Cited by 23 | Viewed by 3801

Abstract

Mixed metal oxide (MMO) is one of the widely utilized ceramic materials in various industries. In order to obtain high performance, the specific surface area of MMO should be controlled. Calcination of layered double hydroxide (LDH) is a versatile way to prepare MMO with homogeneous metal distribution and well-developed porosity. Although researchers found that the specific surface area of LDH-originated MMO was relatively high, it had not been systematically investigated how the surface area is controlled under a certain parameter. In this review, we summarized LDH-originated MMO with various starting composition, calcination temperature, and pore developing agent in terms of specific surface area and porosity. Briefly, it was represented that MMOs with Mg-Al components generally had higher specific surface area than Mg-Fe or Zn-Al components. Calcination temperature in the range 300–600 °C resulted in the high specific surface area, while upper or lower temperature reduced the values. Pore developing agent did not result in dramatic increase in MMO; however, the pore size distribution became narrower in the presence of pore developing agents. Full article

(This article belongs to the Special Issue Natural and Engineered Clays: Two-Dimensional Nano-Building Blocks for Functional Nanomaterials)

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