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15 pages, 4176 KiB

Open AccessArticle

Effects of Charge Compensation on Colossal Permittivity and Electrical Properties of Grain Boundary of CaCu₃Ti₄O₁₂ Ceramics Substituted by Al³⁺ and Ta⁵⁺/Nb⁵⁺

by Jakkree Boonlakhorn, Jedsada Manyam, Pornjuk Srepusharawoot, Sriprajak Krongsuk and Prasit Thongbai

Molecules 2021, 26(11), 3294; https://doi.org/10.3390/molecules26113294 - 30 May 2021

Cited by 6 | Viewed by 1974

Abstract

The effects of charge compensation on dielectric and electrical properties of CaCu₃Ti_4-x(Al_1/2Ta_1/4Nb_1/4)_xO₁₂ ceramics (x = 0−0.05) prepared by a solid-state reaction method were studied based on the configuration [...] Read more.

The effects of charge compensation on dielectric and electrical properties of CaCu₃Ti_4-x(Al_1/2Ta_1/4Nb_1/4)_xO₁₂ ceramics (x = 0−0.05) prepared by a solid-state reaction method were studied based on the configuration of defect dipoles. A single phase of CaCu₃Ti₄O₁₂ was observed in all ceramics with a slight change in lattice parameters. The mean grain size of CaCu₃Ti_4-x(Al_1/2Ta_1/4Nb_1/4)_xO₁₂ ceramics was slightly smaller than that of the undoped ceramic. The dielectric loss tangent can be reduced by a factor of 13 (tanδ ~0.017), while the dielectric permittivity was higher than 10⁴ over a wide frequency range. Impedance spectroscopy showed that the significant decrease in tanδ was attributed to the highly increased resistance of the grain boundary by two orders of magnitude. The DFT calculation showed that the preferential sites of Al and Nb/Ta were closed together in the Ti sites, forming self-charge compensation, and resulting in the enhanced potential barrier height at the grain boundary. Therefore, the improved dielectric properties of CaCu₃Ti_4-x(Al_1/2Ta_1/4Nb_1/4)_xO₁₂ ceramics associated with the enhanced electrical properties of grain boundaries. In addition, the non-Ohmic properties were also improved. Characterization of the grain boundaries under a DC bias showed the reduction of potential barrier height at the grain boundary. The overall results indicated that the origin of the colossal dielectric properties was caused by the internal barrier layer capacitor structure, in which the Schottky barriers at the grain boundaries were formed. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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12 pages, 3088 KiB

Open AccessArticle

The Primary Origin of Excellent Dielectric Properties of (Co, Nb) Co-Doped TiO₂ Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

by Theeranuch Nachaithong, Narong Chanlek, Pairot Moontragoon and Prasit Thongbai

Molecules 2021, 26(11), 3230; https://doi.org/10.3390/molecules26113230 - 27 May 2021

Cited by 15 | Viewed by 2093

Abstract

(Co, Nb) co-doped rutile TiO₂ (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO₂ phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO₂ with [...] Read more.

(Co, Nb) co-doped rutile TiO₂ (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO₂ phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO₂ with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ ≈ 36,105 and a low loss tangent of tanδ ≈ 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoV_oTi complex defect. On the other hand, the substitution of TiO₂ with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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Review

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29 pages, 12394 KiB

Open AccessReview

High Calorific Values Boron Powder: Ignition and Combustion Mechanism, Surface Modification Strategies and Properties

by Yang Liu, Yinglei Wang, Yuezhou Liu, Baodong Zhao, Weixiao Liu, Qilong Yan and Xiaolong Fu

Molecules 2023, 28(7), 3209; https://doi.org/10.3390/molecules28073209 - 04 Apr 2023

Cited by 2 | Viewed by 2012

Abstract

Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants, high-energy explosives, and pyrotechnics. However, the easily formed liquid oxide layer can adhere to the surface [...] Read more.

Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants, high-energy explosives, and pyrotechnics. However, the easily formed liquid oxide layer can adhere to the surface of boron powder and react with the hydroxyl (-OH) group of hydroxyl-terminated polybutadiene (HTPB) binder to form a gel layer that is detrimental to propellant processing and restricts the complete oxidation of boron powder. Therefore, to improve the combustion efficiency of boron powder, the ignition and combustion mechanisms of boron powder have been studied, and surface coating modification strategies have been developed by researchers worldwide, aiming to optimize the surface properties, improve the reaction activity, and promote the energy release of boron powder. In this review, recent studies on the ignition and combustion mechanisms of boron powder are discussed. Moreover, the reported boron powder coating materials are classified according to the chemical structure and reaction mechanism. Additionally, the mechanisms and characteristics of different coating materials are summarized, and the mechanism diagrams of fluoride and metal oxide are provided. Furthermore, promising directions for modification methods and the potential application prospects of boron powder are also proposed. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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25 pages, 6969 KiB

Open AccessReview

Localized Therapeutic Approaches Based on Micro/Nanofibers for Cancer Treatment

by Diana Alves, Joana C. Araújo, Raul Fangueiro and Diana P. Ferreira

Molecules 2023, 28(7), 3053; https://doi.org/10.3390/molecules28073053 - 29 Mar 2023

Cited by 2 | Viewed by 2258

Abstract

Cancer remains one of the most challenging health problems worldwide, and localized therapeutic approaches based on micro/nanofibers have shown potential for its treatment. Micro/nanofibers offer several advantages as a drug delivery system, such as high surface area, tunable pore size, and sustained release [...] Read more.

Cancer remains one of the most challenging health problems worldwide, and localized therapeutic approaches based on micro/nanofibers have shown potential for its treatment. Micro/nanofibers offer several advantages as a drug delivery system, such as high surface area, tunable pore size, and sustained release properties, which can improve drug efficacy and reduce side effects. In addition, functionalization of these fibers with nanoparticles can enhance their targeting and therapeutic capabilities. Localized delivery of drugs and/or other therapeutic agents via micro/nanofibers can also help to overcome the limitations of systemic administration, such as poor bioavailability and off-target effects. Several studies have shown promising results in preclinical models of cancer, including inhibition of tumor growth and improved survival rates. However, more research is needed to overcome technical and regulatory challenges to bring these approaches to clinical use. Localized therapeutic approaches based on micro/nanofibers hold great promise for the future of cancer treatment, providing a targeted, effective, and minimally invasive alternative to traditional treatments. The main focus of this review is to explore the current treatments utilizing micro/nanofibers, as well as localized drug delivery systems that rely on fibrous structures to deliver and release drugs for the treatment of cancer in a specific area. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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20 pages, 3170 KiB

Open AccessReview

Recent Advances in Cancer Therapeutic Copper-Based Nanomaterials for Antitumor Therapy

by Reyida Aishajiang, Zhongshan Liu, Tiejun Wang, Liang Zhou and Duo Yu

Molecules 2023, 28(5), 2303; https://doi.org/10.3390/molecules28052303 - 01 Mar 2023

Cited by 16 | Viewed by 2971

Abstract

Copper serves as a vital microelement which is widely present in the biosystem, functioning as multi-enzyme active site, including oxidative stress, lipid oxidation and energy metabolism, where oxidation and reduction characteristics are both beneficial and lethal to cells. Since tumor tissue has a [...] Read more.

Copper serves as a vital microelement which is widely present in the biosystem, functioning as multi-enzyme active site, including oxidative stress, lipid oxidation and energy metabolism, where oxidation and reduction characteristics are both beneficial and lethal to cells. Since tumor tissue has a higher demand for copper and is more susceptible to copper homeostasis, copper may modulate cancer cell survival through reactive oxygen species (ROS) excessive accumulation, proteasome inhibition and anti-angiogenesis. Therefore, intracellular copper has attracted great interest that multifunctional copper-based nanomaterials can be exploited in cancer diagnostics and antitumor therapy. Therefore, this review explains the potential mechanisms of copper-associated cell death and investigates the effectiveness of multifunctional copper-based biomaterials in the field of antitumor therapy. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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21 pages, 4311 KiB

Open AccessReview

Chitosan Based Materials in Cosmetic Applications: A Review

by Karolina Kulka and Alina Sionkowska

Molecules 2023, 28(4), 1817; https://doi.org/10.3390/molecules28041817 - 15 Feb 2023

Cited by 24 | Viewed by 4817

Abstract

This review provides a report on the properties and recent advances in the application of chitosan and chitosan-based materials in cosmetics. Chitosan is a polysaccharide that can be obtained from chitin via the deacetylation process. Chitin most commonly is extracted from cell walls [...] Read more.

This review provides a report on the properties and recent advances in the application of chitosan and chitosan-based materials in cosmetics. Chitosan is a polysaccharide that can be obtained from chitin via the deacetylation process. Chitin most commonly is extracted from cell walls in fungi and the exoskeletons of arthropods, such as crustaceans and insects. Chitosan has attracted significant academic interest, as well as the attention of the cosmetic industry, due to its interesting properties, which include being a natural humectant and moisturizer for the skin and a rheology modifier. This review paper covers the structure of chitosan, the sources of chitosan used in the cosmetic industry, and the role played by this polysaccharide in cosmetics. Future aspects regarding applications of chitosan-based materials in cosmetics are also mentioned. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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41 pages, 7961 KiB

Open AccessReview

Cyclo- and Polyphosphazenes for Biomedical Applications

by Girolamo Casella, Silvia Carlotto, Francesco Lanero, Mirto Mozzon, Paolo Sgarbossa and Roberta Bertani

Molecules 2022, 27(23), 8117; https://doi.org/10.3390/molecules27238117 - 22 Nov 2022

Cited by 9 | Viewed by 2756

Abstract

Cyclic and polyphosphazenes are extremely interesting and versatile substrates characterized by the presence of -P=N- repeating units. The chlorine atoms on the P atoms in the starting materials can be easily substituted with a variety of organic substituents, thus giving rise to a [...] Read more.

Cyclic and polyphosphazenes are extremely interesting and versatile substrates characterized by the presence of -P=N- repeating units. The chlorine atoms on the P atoms in the starting materials can be easily substituted with a variety of organic substituents, thus giving rise to a huge number of new materials for industrial applications. Their properties can be designed considering the number of repetitive units and the nature of the substituent groups, opening up to a number of peculiar properties, including the ability to give rise to supramolecular arrangements. We focused our attention on the extensive scientific literature concerning their biomedical applications: as antimicrobial agents in drug delivery, as immunoadjuvants in tissue engineering, in innovative anticancer therapies, and treatments for cardiovascular diseases. The promising perspectives for their biomedical use rise from the opportunity to combine the benefits of the inorganic backbone and the wide variety of organic side groups that can lead to the formation of nanoparticles, polymersomes, or scaffolds for cell proliferation. In this review, some aspects of the preparation of phosphazene-based systems and their characterization, together with some of the most relevant chemical strategies to obtain biomaterials, have been described. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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21 pages, 6637 KiB

Open AccessReview

Recent Advances in the Synthesis and Application of Three-Dimensional Graphene-Based Aerogels

by Jingyun Jing, Xiaodong Qian, Yan Si, Guolin Liu and Congling Shi

Molecules 2022, 27(3), 924; https://doi.org/10.3390/molecules27030924 - 29 Jan 2022

Cited by 14 | Viewed by 3210

Abstract

Three-dimensional graphene-based aerogels (3D GAs), combining the intrinsic properties of graphene and 3D porous structure, have attracted increasing research interest in varied fields with potential application. Some related reviews focusing on applications in photoredox catalysis, biomedicine, energy storage, supercapacitor or other single aspect [...] Read more.

Three-dimensional graphene-based aerogels (3D GAs), combining the intrinsic properties of graphene and 3D porous structure, have attracted increasing research interest in varied fields with potential application. Some related reviews focusing on applications in photoredox catalysis, biomedicine, energy storage, supercapacitor or other single aspect have provided valuable insights into the current status of Gas. However, systematic reviews concentrating on the diverse applications of 3D GAs are still scarce. Herein, we intend to afford a comprehensive summary to the recent progress in the preparation method (template-free and template-directed method) summarized in Preparation Strategies and the application fields (absorbent, anode material, mechanical device, fire-warning material and catalyst) illustrated in Application of 3D GAs with varied morphologies, structures, and properties. Meanwhile, some unsettled issues, existing challenges, and potential opportunities have also been proposed in Future Perspectives to spur further research interest into synthesizing finer 3D GAs and exploring wider and closer practical applications. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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31 pages, 1952 KiB

Open AccessReview

Enhancement of the Detection Performance of Paper-Based Analytical Devices by Nanomaterials

by Renzhu Pang, Qunyan Zhu, Jia Wei, Xianying Meng and Zhenxin Wang

Molecules 2022, 27(2), 508; https://doi.org/10.3390/molecules27020508 - 14 Jan 2022

Cited by 10 | Viewed by 2858

Abstract

Paper-based analytical devices (PADs), including lateral flow assays (LFAs), dipstick assays and microfluidic PADs (μPADs), have a great impact on the healthcare realm and environmental monitoring. This is especially evident in developing countries because PADs-based point-of-care testing (POCT) enables to rapidly determine various [...] Read more.

Paper-based analytical devices (PADs), including lateral flow assays (LFAs), dipstick assays and microfluidic PADs (μPADs), have a great impact on the healthcare realm and environmental monitoring. This is especially evident in developing countries because PADs-based point-of-care testing (POCT) enables to rapidly determine various (bio)chemical analytes in a miniaturized, cost-effective and user-friendly manner. Low sensitivity and poor specificity are the main bottlenecks associated with PADs, which limit the entry of PADs into the real-life applications. The application of nanomaterials in PADs is showing great improvement in their detection performance in terms of sensitivity, selectivity and accuracy since the nanomaterials have unique physicochemical properties. In this review, the research progress on the nanomaterial-based PADs is summarized by highlighting representative recent publications. We mainly focus on the detection principles, the sensing mechanisms of how they work and applications in disease diagnosis, environmental monitoring and food safety management. In addition, the limitations and challenges associated with the development of nanomaterial-based PADs are discussed, and further directions in this research field are proposed. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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31 pages, 43054 KiB

Open AccessReview

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications

by Jan Ozimek and Krzysztof Pielichowski

Molecules 2022, 27(1), 40; https://doi.org/10.3390/molecules27010040 - 22 Dec 2021

Cited by 20 | Viewed by 4734

Abstract

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties [...] Read more.

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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21 pages, 5156 KiB

Open AccessReview

An Overview of Linear Dielectric Polymers and Their Nanocomposites for Energy Storage

by Lvye Dou, Yuan-Hua Lin and Ce-Wen Nan

Molecules 2021, 26(20), 6148; https://doi.org/10.3390/molecules26206148 - 12 Oct 2021

Cited by 18 | Viewed by 3247

Abstract

As one of the most important energy storage devices, dielectric capacitors have attracted increasing attention because of their ultrahigh power density, which allows them to play a critical role in many high-power electrical systems. To date, four typical dielectric materials have been widely [...] Read more.

As one of the most important energy storage devices, dielectric capacitors have attracted increasing attention because of their ultrahigh power density, which allows them to play a critical role in many high-power electrical systems. To date, four typical dielectric materials have been widely studied, including ferroelectrics, relaxor ferroelectrics, anti-ferroelectrics, and linear dielectrics. Among these materials, linear dielectric polymers are attractive due to their significant advantages in breakdown strength and efficiency. However, the practical application of linear dielectrics is usually severely hindered by their low energy density, which is caused by their relatively low dielectric constant. This review summarizes some typical studies on linear dielectric polymers and their nanocomposites, including linear dielectric polymer blends, ferroelectric/linear dielectric polymer blends, and linear polymer nanocomposites with various nanofillers. Moreover, through a detailed analysis of this research, we summarize several existing challenges and future perspectives in the research area of linear dielectric polymers, which may propel the development of linear dielectric polymers and realize their practical application. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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23 pages, 6520 KiB

Open AccessReview

Advances in the Synthesis of Crystalline Metallosilicate Zeolites via Interlayer Expansion

by Chaoqun Bian, Yichang Yang, Xiaohui Luo, Wenxia Zhang, Jie Zhang, Longfeng Zhu and Jianping Qiu

Molecules 2021, 26(19), 5916; https://doi.org/10.3390/molecules26195916 - 29 Sep 2021

Cited by 5 | Viewed by 1765

Abstract

Given the numerous industrial applications of zeolites as adsorbents, catalysts, and ion-exchangers, the development of new zeolite structures is highly desired to expand their practical applications. Currently, a general route to develop new zeolite structures is to use interlayer expansion agents to connect [...] Read more.

Given the numerous industrial applications of zeolites as adsorbents, catalysts, and ion-exchangers, the development of new zeolite structures is highly desired to expand their practical applications. Currently, a general route to develop new zeolite structures is to use interlayer expansion agents to connect layered silicates. In this review, we briefly summarize the novel zeolite structures constructed from the lamellar precursor zeolites MWW, RUB-36, PREFER, Nu-6(1), COK-5, and PLS-1 via interlayer expansion. The contents of the summary contain detailed experiments, physicochemical characterizations, possible expansion mechanisms, and catalytic properties. In addition, the insertion of metal heteroatoms (such as Ti, Fe, Sn) into the layered zeolite precursor through interlayer expansion, which could be helpful to modify the catalytic function, is discussed. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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28 pages, 5947 KiB

Open AccessReview

The Art of Framework Construction: Core–Shell Structured Micro-Energetic Materials

by Binghui Duan, Jiankang Li, Hongchang Mo, Xianming Lu, Minghui Xu, Bozhou Wang and Ning Liu

Molecules 2021, 26(18), 5650; https://doi.org/10.3390/molecules26185650 - 17 Sep 2021

Cited by 6 | Viewed by 2512

Abstract

Weak interfacial interactions remain a bottleneck for composite materials due to their weakened performance and restricted applications. The development of core–shell engineering shed light on the preparation of compact and intact composites with improved interfacial interactions. This review addresses how core–shell engineering has [...] Read more.

Weak interfacial interactions remain a bottleneck for composite materials due to their weakened performance and restricted applications. The development of core–shell engineering shed light on the preparation of compact and intact composites with improved interfacial interactions. This review addresses how core–shell engineering has been applied to energetic materials, with emphasis upon how micro-energetic materials, the most widely used particles in the military field, can be generated in a rational way. The preparation methods of core–shell structured explosives (CSEs) developed in the past few decades are summarized herein. Case studies on polymer-, explosive- and novel materials-based CSEs are presented in terms of their compositions and physical properties (e.g., thermal stability, mechanical properties and sensitivity). The mechanisms behind the dramatic and divergent properties of CSEs are also clarified. A glimpse of the future in this area is given to show the potential for CSEs and some suggestions regarding the future research directions are proposed. Full article

(This article belongs to the Special Issue Review Papers in Materials Chemistry)

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