Special Issue "Layered Double Hydroxides"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Materials".

Deadline for manuscript submissions: closed (30 July 2019).

Special Issue Editors

Guest Editor
Dr. Giuseppe Prestopino

Università di Roma "Tor Vergata", Dipartimento di Ingegneria Industriale Via del Politecnico 1, I-00133 Roma, Italy
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Interests: thin film technology; chemical vapor deposition synthesis; synthetic diamond; self-assembled nanomaterials; layered double hydroxides; electrical and optical properties
Guest Editor
Dr. Giuseppe Arrabito

Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, V.le delle Scienze, 90128 Palermo, Italy
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Interests: wet-chemistry synthesis; biosensors; surface chemistry; zinc oxide; physical chemistry of interfaces

Special Issue Information

Dear Colleagues,

Two-dimensional (2D) materials constitute a versatile platform for the realization of a new class of functional systems showing unique enhanced surface effects and unprecedented tuneable confinement and geometry-related properties which can open up important applications in very different fields, namely surface chemistry and catalysis, band-gap engineering, photovoltaics, energy storage, harvesting and conversion, nanomedicine, spintronics and valleytronics. Many 2D materials with very different natures have been described in detail for these applications, such as graphene, silicene, phosphorene, hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDs), metal organic frameworks (MOFs), layered oxides and hydroxides, and DNA origami. Although the proof-of-principle for their outstanding functionality has been demonstrated, the ultimate hurdle for 2D materials to be implementable in technological applications is the ability to find reproducible, green-chemistry, environment friendly and low-cost approaches for their synthesis and subsequent functionalization at large scale and low cost. Among the up-to-date 2D materials, layered double hydroxides (LDHs) have attracted a huge research interest in the last years, with more than 2000 papers published in the last five years. LDHs are low-cost materials, and can be easily synthetized as self-assembled hierarchical nanosheet thin films and exfoliated up to the monolayer limit. LDHs are therefore a playground for exciting new research covering all of the most intriguing features of 2D materials and more.

The aim of this Special Issue is to provide a unique international platform that can enable scientists to publish the latest advancements on the following topics:

- Novel approaches to the controlled synthesis of inorganic, organic and biomolecular 2D materials (green chemistry, low temperature), with particular emphasis on the implementation of large-scale fabrication of devices, wet-chemistry and water-dispersible 2D material formulations.

- The synthesis, characterization, and functionalization of LDHs, including all contributions focusing on properties and applications of self-assembled hierarchical LDH nanosheet thin films and LDH exfoliation to monolayers, according to a multidisciplinary approach.

- Other 2D material monolayers, layered materials, Van der Waals heterostructures.

- Physical, chemical, and optical characterization of 2D materials and exploitation of their outstanding features for device fabrication and integration in complex systems.

Dr. Giuseppe Prestopino
Dr. Giuseppe Arrabito
Guest Editors

Manuscript Submission Information

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Keywords

  • green chemistry
  • surface chemistry
  • hydrothermal synthesis
  • catalysis
  • energy conversion
  • layered double hydroxides
  • LDHs
  • 2D materials
  • bottom-up, top-down, exfoliation
  • heterostructures and layered composites
  • quantum confinement
  • ionic conductivity

Published Papers (6 papers)

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Research

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Open AccessArticle
Antimonate Removal from Polluted Mining Water by Calcined Layered Double Hydroxides
Crystals 2019, 9(8), 410; https://doi.org/10.3390/cryst9080410
Received: 20 June 2019 / Revised: 31 July 2019 / Accepted: 1 August 2019 / Published: 6 August 2019
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Abstract
Calcined layered double hydroxides (LDHs) can be used to remove Sb(V), in the Sb(OH)6 form, from aqueous solutions. Sorption batch experiments showed that the mixed MgAlFe oxides, obtained from calcined hydrotalcite-like compound (3HT-cal), removed Sb(OH)6 through the formation of [...] Read more.
Calcined layered double hydroxides (LDHs) can be used to remove Sb(V), in the Sb(OH)6 form, from aqueous solutions. Sorption batch experiments showed that the mixed MgAlFe oxides, obtained from calcined hydrotalcite-like compound (3HT-cal), removed Sb(OH)6 through the formation of a non-LDH brandholzite-like compound, whereas the mixed ZnAl oxides, resulting from calcined zaccagnaite-like compound (2ZC-cal), trapped Sb(OH)6 in the interlayer during the formation of a Sb(V)-bearing LDH (the zincalstibite-like compound). The competition effect of coexistent anions on Sb(OH)6 removal was HAsO42 >> HCO3 ≥ SO42 for 2ZC-cal and HAsO42 >> HCO3 >> SO42 for 3HT-cal. Considering the importance of assessing the practical use of calcined LDHs, batch experiments were also carried out with a slag drainage affected by serious Sb(V) pollution (Sb = 9900 μg/L) sampled at the abandoned Su Suergiu mine (Sardinia, Italy). Results showed that, due to the complex chemical composition of the slag drainage, dissolved Sb(OH)6 was removed by intercalation in the interlayer of carbonate LDHs rather than through the formation of brandholzite-like or zincalstibite-like compounds. Both 2ZC-cal and 3HT-cal efficiently removed very high percentages (up to 90–99%) of Sb(V) from the Su Suergiu mine drainage, and thus can have a potential application for real polluted waters. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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Open AccessArticle
Mg-Fe Layered Double Hydroxides Enhance Surfactin Production in Bacterial Cells
Crystals 2019, 9(7), 355; https://doi.org/10.3390/cryst9070355
Received: 20 June 2019 / Revised: 11 July 2019 / Accepted: 11 July 2019 / Published: 12 July 2019
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Abstract
In this study, four additives—montmorillonite, activated carbon, and the layered double hydroxides (LDHs), Mg2Fe–LDH and Mg2Al–LDH—were tested for their ability to promote surfactin production in a Bacillus subtilis ATCC 21332 culture. Among these tested materials, the addition of 4 [...] Read more.
In this study, four additives—montmorillonite, activated carbon, and the layered double hydroxides (LDHs), Mg2Fe–LDH and Mg2Al–LDH—were tested for their ability to promote surfactin production in a Bacillus subtilis ATCC 21332 culture. Among these tested materials, the addition of 4 g/L of the Mg-Fe LDH, which featured an Mg/Fe molar ratio of 2:1, produced the highest surfactin yield of 5280 mg/L. During the time course of B. subtilis cultivation with the added LDH, two phases of cell growth were evident: Growth and decay. In the growth phase, the cells grew slowly and secreted a high amount of surfactin; in the decay phase, the cells degraded rapidly. The production in the presence of the Mg2Fe–LDH had three characteristics: (i) High surfactin production at low biomass, indicating a high specific surfactin yield of 3.19 g/g DCW; (ii) rapid surfactin production within 24 h, inferring remarkably high productivity (4660 mg/L/d); and (iii) a lower carbon source flux to biomass, suggesting an efficient carbon flux to surfactin, giving a high carbon yield of 52.8%. The addition of Mg2Fe–LDH is an effective means of enhancing surfactin production, with many potential applications and future industrial scale-up. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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Open AccessArticle
Rapid Removal and Efficient Recovery of Tetracycline Antibiotics in Aqueous Solution Using Layered Double Hydroxide Components in an In Situ-Adsorption Process
Crystals 2019, 9(7), 342; https://doi.org/10.3390/cryst9070342
Received: 9 June 2019 / Revised: 28 June 2019 / Accepted: 1 July 2019 / Published: 4 July 2019
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Abstract
This work demonstrates a simple approach for the efficient removal of tetracycline (TC) antibiotic from an aqueous solution. The in situ-adsorption removal method involved instant precipitation formation of mixed metal hydroxides (MMHs), which could immediately act as a sorbent for capturing TC from [...] Read more.
This work demonstrates a simple approach for the efficient removal of tetracycline (TC) antibiotic from an aqueous solution. The in situ-adsorption removal method involved instant precipitation formation of mixed metal hydroxides (MMHs), which could immediately act as a sorbent for capturing TC from an aqueous solution, by employing layered double hydroxide (LDH) components including magnesium and aluminum ions in alkaline conditions. By using this approach, 100% removal of TC can be accomplished within 4 min under optimized conditions. The fast removal possibly resulted from an instantaneous adsorption of TC molecules onto the charged surface of MMHs via hydrogen bonding and electrostatically induced attraction. The results revealed that our removal technique was superior to the use of LDH as a sorbent in terms of both removal kinetics and efficiency. Moreover, the recovery of captured TC was tested under the influence of various common anions. It was found that 98% recovery could be simply achieved by using phosphate, possibly due to its highly charged density. Furthermore, this method was successful for efficient removal of TC in real environmental water samples. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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Open AccessArticle
The Fabrication of Calcium Alginate Beads as a Green Sorbent for Selective Recovery of Cu(Ⅱ) from Metal Mixtures
Crystals 2019, 9(5), 255; https://doi.org/10.3390/cryst9050255
Received: 3 April 2019 / Revised: 13 May 2019 / Accepted: 13 May 2019 / Published: 17 May 2019
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Abstract
Calcium alginate (CA) beads as a green sorbent were easily fabricated in this study using sodium alginate crosslinking with CaCl2, and the crosslinking pathway was the exchange between the sodium ion of α-L-guluronic acid and Ca(II). The experimental study was conducted [...] Read more.
Calcium alginate (CA) beads as a green sorbent were easily fabricated in this study using sodium alginate crosslinking with CaCl2, and the crosslinking pathway was the exchange between the sodium ion of α-L-guluronic acid and Ca(II). The experimental study was conducted on Cu(II), Cd(II), Ni(II) and Zn(II) as the model heavy metals and the concentration was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The characterization and sorption behavior of the CA beads were analyzed in detail via using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The adsorption experiments demonstrated that the CA beads exhibited a high removal efficiency for the selective adsorption of Cu(II) from the tetra metallic mixture solution and an excellent adsorption capacity of the heavy metals separately. According to the isotherm studies, the maximum uptake of Cu(II) could reach 107.53 mg/g, which was significantly higher than the other three heavy metal ions in the tetra metallic mixture solution. Additionally, after five cycles of adsorption and desorption, the uptake rate of Cu(II) on CA beads was maintained at 92%. According to the properties mentioned above, this material was assumed to be applied to reduce heavy metal pollution or recover valuable metals from waste water. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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Open AccessArticle
Luminescent Layered Double Hydroxides Intercalated with an Anionic Photosensitizer via the Memory Effect
Crystals 2019, 9(3), 153; https://doi.org/10.3390/cryst9030153
Received: 12 February 2019 / Revised: 8 March 2019 / Accepted: 9 March 2019 / Published: 14 March 2019
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Abstract
Layered double hydroxides (LDHs) containing Eu3+ activators were synthesized by coprecipitation of Zn2+, Al3+, and Eu3+ in alkaline NO3-rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al [...] Read more.
Layered double hydroxides (LDHs) containing Eu3+ activators were synthesized by coprecipitation of Zn2+, Al3+, and Eu3+ in alkaline NO3-rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al and Eu. For suitably low calcination temperatures, this phase can be restored to LDH by rehydration in water, a feature known as the memory effect. During rehydration of an LDH, new anionic species can be intercalated and functionalized, obtaining desired physicochemical properties. This work explores the memory effect as a route to produce luminescent LDHs intercalated with 1,3,5-benzenetricarboxylic acid (BTC), a known anionic photosensitizer for Eu3+. Time-dependent hydration of calcined LDHs in a BTC-rich aqueous solution resulted in the recovery of the lamellar phase and in the intercalation with BTC. The interaction of this photosensitizer with Eu3+ in the recovered hydroxide layers gave rise to efficient energy transfer from the BTC antennae to the Eu3+ ions, providing a useful tool to monitor the rehydration process of the calcined LDHs. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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Review

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Open AccessReview
Layered Double Hydroxides: A Toolbox for Chemistry and Biology
Crystals 2019, 9(7), 361; https://doi.org/10.3390/cryst9070361
Received: 20 June 2019 / Revised: 10 July 2019 / Accepted: 13 July 2019 / Published: 15 July 2019
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Abstract
Layered double hydroxides (LDHs) are an emergent class of biocompatible inorganic lamellar nanomaterials that have attracted significant research interest owing to their high surface-to-volume ratio, the capability to accumulate specific molecules, and the timely release to targets. Their unique properties have been employed [...] Read more.
Layered double hydroxides (LDHs) are an emergent class of biocompatible inorganic lamellar nanomaterials that have attracted significant research interest owing to their high surface-to-volume ratio, the capability to accumulate specific molecules, and the timely release to targets. Their unique properties have been employed for applications in organic catalysis, photocatalysis, sensors, drug delivery, and cell biology. Given the widespread contemporary interest in these topics, time-to-time it urges to review the recent progresses. This review aims to summarize the most recent cutting-edge reports appearing in the last years. It firstly focuses on the application of LDHs as catalysts in relevant chemical reactions and as photocatalysts for organic molecule degradation, water splitting reaction, CO2 conversion, and reduction. Subsequently, the emerging role of these materials in biological applications is discussed, specifically focusing on their use as biosensors, DNA, RNA, and drug delivery, finally elucidating their suitability as contrast agents and for cellular differentiation. Concluding remarks and future prospects deal with future applications of LDHs, encouraging researches in better understanding the fundamental mechanisms involved in catalytic and photocatalytic processes, and the molecular pathways that are activated by the interaction of LDHs with cells in terms of both uptake mechanisms and nanotoxicology effects. Full article
(This article belongs to the Special Issue Layered Double Hydroxides)
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