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Science and Technology of Advanced Materials Applied to Society: Including Collections from the Latest Papers of KRIS 2023

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

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 15130

Special Issue Editor

Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA
Interests: synthesis-microstructure-property relations of ceramic bulk; thin-film and nano-heterostructures for electrochemical devices (sensors and fuel cells); biomedical applications.
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Humanity faces numerous challenges that have never been faced before. There are fears that if we continue on our current path, humanity will not be able to continue living on this planet. People from all fields around the world have discussed and established specific goals to be achieved by 2030: the Sustainable Development Goals (SDGs). Materials scientists around the world are researching and developing the advanced materials needed to achieve the SDGs. The developed materials are implemented in society and contribute greatly to its sustainable development. In this Special Issue, we welcome the submission of papers on the science and technology of advanced materials that contribute to achieving the SDGs.

National Institute of Technology (KOSEN), Japan’s largest higher education institution for science and technology, will host KRIS 2023: KOSEN Research International Symposium 2023 in March 2023. One of the major themes of this international conference is the SDGs. The advanced materials science papers to be discussed at this international conference will be published in this Special Issue. The Guest Editors of this Special Issue are looking forward to receiving submissions from colleagues around the world.

Prof. Dr. Sheikh A. Akbar
Guest Editor

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Novel materials
  • energy storage materials
  • drugs
  • tribology materials
  • functional polymer materials
  • superconducting devices
  • self-healing materials
  • biocompatible materials
  • superconducting devices
  • bio-inspired materials
  • ecology materials

Published Papers (16 papers)

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Research

13 pages, 6254 KiB  
Article
Solvent-Free Reaction for Unsymmetrical Organodisulfides with High Purity and Application as Cathode-Active Materials
Materials 2024, 17(3), 699; https://doi.org/10.3390/ma17030699 - 01 Feb 2024
Viewed by 396
Abstract
Unsymmetrical disulfides, in which different organic groups are bonded to disulfide bonds, have been synthesized by cross-coupling reactions using thiols as substrates. However, due to the low-binding energy of unsymmetrical disulfides, its disproportionation occurs based on the side reactions with nucleophilic thiols, resulting [...] Read more.
Unsymmetrical disulfides, in which different organic groups are bonded to disulfide bonds, have been synthesized by cross-coupling reactions using thiols as substrates. However, due to the low-binding energy of unsymmetrical disulfides, its disproportionation occurs based on the side reactions with nucleophilic thiols, resulting in the impurity of symmetric disulfides. In this study, we developed a solvent-free synthesis method for unsymmetrical disulfides using thiosulfonates, thiols, and a base. This synthetic method enabled us to obtain highly pure diaryl-substituted unsymmetrical disulfides with particularly low-binding energy without control over the nucleophilicity and elimination properties of the substrate. Furthermore, it was observed that the disproportionation of unsymmetrical disulfides occurred in the solvent. This means that solvent-free condition is one of the factors to obtain unsymmetrical disulfides. As a new application of unsymmetrical disulfides, we applied unsymmetrical disulfides to cathode active materials of lithium batteries based on the reversible multi-electron redox activity of S–S bonds. The batteries using unsymmetrical disulfide cathode-active materials with a carbon nanotube exhibited initial capacities of 127 and 158 Ah/kg, equal to 42 and 53% of their theoretical ones. We demonstrated that unsymmetrical disulfides could be used as cathode-active materials for rechargeable batteries. Full article
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10 pages, 3223 KiB  
Article
Fabrication of (Ge0.42Sn0.58)S Thin Films via Co-Evaporation and Their Solar Cell Applications
Materials 2024, 17(3), 692; https://doi.org/10.3390/ma17030692 - 01 Feb 2024
Viewed by 407
Abstract
In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in multi-junction solar cells. A (Ge0.42 Sn0.58)S thin film was prepared [...] Read more.
In this study, as a novel approach to thin-film solar cells based on tin sulfide, an environmentally friendly material, we attempted to fabricate (Ge, Sn)S thin films for application in multi-junction solar cells. A (Ge0.42 Sn0.58)S thin film was prepared via co-evaporation. The (Ge0.42 Sn0.58)S thin film formed a (Ge, Sn)S solid solution, as confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses. The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of (Ge0.42 Sn0.58)S thin-film solar cells were 0.29 V, 6.92 mA/cm2, 0.34, and 0.67%, respectively; moreover, the device showed a band gap of 1.42–1.52 eV. We showed that solar cells can be realized even in a composition range with a relatively higher Ge concentration than the (Ge, Sn)S solar cells reported to date. This result enhances the feasibility of multi-junction SnS-system thin-film solar cells. Full article
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10 pages, 3006 KiB  
Article
Synthesis and Characterization of Type II Ge-Si Clathrate Films for Optoelectronic Applications
Materials 2024, 17(2), 504; https://doi.org/10.3390/ma17020504 - 20 Jan 2024
Viewed by 471
Abstract
Type II inorganic clathrates consist of cage-like structures with open frameworks, and they are considered promising materials due to their unique properties. However, the difficulty of synthesizing phase-pure and continuous films has hindered their application in practical devices. In this report, we demonstrate [...] Read more.
Type II inorganic clathrates consist of cage-like structures with open frameworks, and they are considered promising materials due to their unique properties. However, the difficulty of synthesizing phase-pure and continuous films has hindered their application in practical devices. In this report, we demonstrate the synthesis of type II SiGe clathrate films through the thermal decomposition of a Na-deposited amorphous SiGe film on a sapphire substrate in a high vacuum. The as-prepared films of type II SiGe clathrates showed uniform growth and were evaluated for their structural and optical properties. Morphological studies conducted using a scanning electron microscope showed the presence of cracks on the film surface. Full article
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17 pages, 10157 KiB  
Article
Embrittlement Fracture Behavior and Mechanical Properties in Heat-Affected Zone of Welded Maraging Steel
Materials 2024, 17(2), 440; https://doi.org/10.3390/ma17020440 - 17 Jan 2024
Viewed by 443
Abstract
In welded maraging steels, mechanical properties, particularly ductility and toughness, are often compromised in the heat-affected zone (HAZ). This study focuses on 300-grade maraging steel bars, solution annealed at 1123 K for 1.5 h (5.4 ks) and welded using gas tungsten arc welding, [...] Read more.
In welded maraging steels, mechanical properties, particularly ductility and toughness, are often compromised in the heat-affected zone (HAZ). This study focuses on 300-grade maraging steel bars, solution annealed at 1123 K for 1.5 h (5.4 ks) and welded using gas tungsten arc welding, followed by a post-weld heat treatment at 753 K for 13.33 h (48 ks). In situ observations during three-point bending tests on HAZ samples featuring coarsened prior austenite grain sizes were conducted to examine damage behavior and the crack path near the crack tip. The main crack initiated at the peak applied load during the bending test and, upon further loading, exhibited significant deflection and extension accompanied by numerous microcracks and localized crack branching. Distinctive damage features, such as transgranular cracking across block regions, intense intergranular cracking along packet boundaries with a pronounced shear component, and crowding of microcracks ahead of the crack tip, were observed in the HAZ sample during the in situ test. The interaction between the main crack tip and microcracks and its influence on the local crack propagation driving force was discussed using fracture mechanics. Experimental results, including tensile fracture surface observations and in situ images, along with analysis of the stress anti-shielding effect by microcracks, suggest that the HAZ sample exhibits embrittlement fracture behavior with lower ductility and toughness compared to the base metal sample. Full article
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11 pages, 3240 KiB  
Communication
Hematite (α-Fe2O3) with Oxygen Defects: The Effect of Heating Rate for Photocatalytic Performance
Materials 2024, 17(2), 395; https://doi.org/10.3390/ma17020395 - 12 Jan 2024
Viewed by 599
Abstract
Hematite (α-Fe2O3) emerges as an enticing material for visible-light-driven photocatalysis owing to its remarkable stability, low toxicity, and abundance. However, its inherent shortcomings, such as a short hole diffusion length and high recombination rate, hinder its practical [...] Read more.
Hematite (α-Fe2O3) emerges as an enticing material for visible-light-driven photocatalysis owing to its remarkable stability, low toxicity, and abundance. However, its inherent shortcomings, such as a short hole diffusion length and high recombination rate, hinder its practical application. Recently, oxygen vacancies (Vo) within hematite have been demonstrated to modulate its photocatalytic attributes. The effects of Vo can be broadly categorized into two opposing aspects: (1) acting as electron donors, enhancing carrier conductivity, and improving photocatalytic performance and (2) acting as surface carrier traps, accelerating excited carrier recombination, and deteriorating performance. Critically, the generation rate, distribution, role, and behavior of Vo significantly differ for synthesis methods due to differences in formation mechanisms and oxygen diffusion. This complexity hampers simplified discussions of Vo, necessitating careful investigation and nuanced discussion tailored to the specific method and conditions employed. Among various approaches, hydrothermal synthesis offers a simple and cost-effective route. Here, we demonstrate a hydrothermal synthesis method for Vo introduction to hematite using a carbon source, where variations in the heating rate have not been previously explored in terms of their influence on Vo generation. The analyses revealed that the concentration of Vo was maximized at a heating rate of 16 °C/min, indicative of a high density of surface defects. With regard to photocatalytic performance, elevated heating rates (16 °C/min) fostered the formation of Vo primarily on the hematite surface. The photocatalytic activity was 7.1 times greater than that of the sample prepared at a low heating rate (2 °C/min). These findings highlight the crucial role of surface defects, as opposed to bulk defects, in promoting hematite photocatalysis. Furthermore, the facile control over Vo concentration achievable via manipulating the heating rate underscores the promising potential of this approach for optimizing hematite photocatalysts. Full article
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14 pages, 3098 KiB  
Article
The Influence of [110] Compressive Stress on Kinetically Arrested B2–R Transformation in Single-Crystalline Ti–44Ni–6Fe and Ti–42Ni–8Fe Shape-Memory Alloys
Materials 2024, 17(1), 51; https://doi.org/10.3390/ma17010051 - 22 Dec 2023
Viewed by 524
Abstract
Ti–(50−x)Ni–xFe alloys exhibit a thermally induced B2–R martensitic transformation (MT) when x is between 1.5% and 5.7%, whereas this transformation is suppressed when x is 6 at% and higher. We studied the reason for this suppression by applying compressive [...] Read more.
Ti–(50−x)Ni–xFe alloys exhibit a thermally induced B2–R martensitic transformation (MT) when x is between 1.5% and 5.7%, whereas this transformation is suppressed when x is 6 at% and higher. We studied the reason for this suppression by applying compressive stress in the [110]B2 direction to single-crystalline Ti–44Ni–6Fe and Ti–42Ni–8Fe (at%) alloys. Under stress, these alloys exhibit a B2–R MT with a large temperature hysteresis of ≥50 K. The B2–R MT in these alloys is probably thermally arrested, and a small entropy change is a possible reason for this arrest. The Young’s modulus E[110] of these alloys significantly decreases with decreasing temperature, and the B2–R MT under stress occurs at a temperature where E[110] is approximately 50 GPa. Presumably, lattice softening assists the B2–R MT. Full article
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14 pages, 4162 KiB  
Article
Antibiofilm Property and Biocompatibility of Siloxane-Based Polymer Coatings Applied to Biomaterials
Materials 2023, 16(23), 7399; https://doi.org/10.3390/ma16237399 - 28 Nov 2023
Viewed by 910
Abstract
Biofilm infections sometimes occur on biomaterials inserted into the body because biomaterials can block the attack of immune cells such as macrophages, promoting biofilm formation by invading bacteria. Owing to their use in antifouling applications, including biofilm formation, siloxane-based polymer coatings are considered [...] Read more.
Biofilm infections sometimes occur on biomaterials inserted into the body because biomaterials can block the attack of immune cells such as macrophages, promoting biofilm formation by invading bacteria. Owing to their use in antifouling applications, including biofilm formation, siloxane-based polymer coatings are considered a promising method to prevent biofilm formation on the surface of biomaterials. In this study, we explored the antibiofilm property and biocompatibility of siloxane-based polymer coatings. Biofilm formation and cytotoxicity tests were performed using Escherichia coli and Staphylococcus epidermidis to quantify the biofilms while U937 cells were used to measure the time course of viable cell concentration and viability, respectively. In both the biofilm formation and cytotoxicity tests, stainless steel SUS316L plates and titanium plates coated with the siloxane-based polymer and sterilized in an autoclave were used as the biomaterials. The amount of biofilm formed on the polymer-coated titanium plate was substantially higher than that on a noncoated titanium plate in the case of S. epidermidis. The viable cell concentration and viability of U937 cultured on the polymer-coated titanium plate were lower than those of U937 cultured on the noncoated titanium plate. The same trend was observed between polymer-coated and noncoated SUS316L plates. These results indicate that the siloxane-based polymer coatings need additional treatment to achieve a satisfactory antibiofilm property and that they are sensitive to autoclave treatment, resulting in cytotoxicity. Full article
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17 pages, 6839 KiB  
Article
AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect
Materials 2023, 16(21), 7051; https://doi.org/10.3390/ma16217051 - 06 Nov 2023
Viewed by 943
Abstract
Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials [...] Read more.
Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials’ specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz–12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface. Full article
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7 pages, 1325 KiB  
Communication
Development of Porous MoO2 Pellet Target for 99Mo/99mTc Generator
Materials 2023, 16(20), 6713; https://doi.org/10.3390/ma16206713 - 16 Oct 2023
Viewed by 555
Abstract
Technetium-99m(99mTc) is used worldwide in 85% of nuclear medicine diagnostic imaging procedures. We developed porous MoO2 pellets as an alternative to reactor-based targets in an (n,γ) reaction for producing Technetium-99m (99mTc) in nuclear medicine. The pellets, formed through [...] Read more.
Technetium-99m(99mTc) is used worldwide in 85% of nuclear medicine diagnostic imaging procedures. We developed porous MoO2 pellets as an alternative to reactor-based targets in an (n,γ) reaction for producing Technetium-99m (99mTc) in nuclear medicine. The pellets, formed through a manufacturing process involving mixing, sintering, eluting, and drying, offer advantages such as selective dissolution and improved yield. This research offers a potential solution for stable 99mTc production, focusing on porous molybdenum dioxide (MoO2) as a target material due to its insolubility in water. Using potassium molybdate (K2MoO4) as a pore former, we developed porous MoO2 pellets that facilitate efficient technetium extraction and target recycling. This approach offers control over pore formation and shows promise in addressing supply challenges and enhancing 99mTc production. Full article
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9 pages, 2481 KiB  
Communication
Stability Modification of Dye-sensitized Solar Cells by Ruthenium Dyes Embedded on Eggshell Membranes
Materials 2023, 16(20), 6654; https://doi.org/10.3390/ma16206654 - 11 Oct 2023
Viewed by 803
Abstract
Dye-sensitized solar cells (DSSCs) have been one of the most promising technologies to convert sunlight into electricity repeatedly based on the mechanism that dyes inject/accept electron into the metal oxides/from redox mediator. Specifically, N719 ([RuL2(NCS)2], L: 4,4′-dicarboxy-2,2′-bipyridine), immobilized on [...] Read more.
Dye-sensitized solar cells (DSSCs) have been one of the most promising technologies to convert sunlight into electricity repeatedly based on the mechanism that dyes inject/accept electron into the metal oxides/from redox mediator. Specifically, N719 ([RuL2(NCS)2], L: 4,4′-dicarboxy-2,2′-bipyridine), immobilized on TiO2 through the interaction between its ligands (-COO and -NCS) and the oxygen on the TiO2 surface, has been used as a conventional DSSC dye with high voltage. Nevertheless, -NCS ligands have been removed from Ru2+ in N719 due to UV irradiation and exchanged with H2O or OH in electrolyte, resulting in voltage drop. In this work, we developed the first DSSC using the N719-adsorbed Eggshell (ESM)-TiO2 composite to maintain the immobilization of N719 on TiO2 through electrostatic interaction between the protein of ESM and N719. The DSSC using the composite maintained the voltage even after 12 h light irradiation, although the voltage of DSSC without ESM dropped drastically. It means that the ESM contributed to stable photovoltaic performances of DSSCs through the protection of NCS ligands of N719. Full article
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11 pages, 17199 KiB  
Article
Optimization of Sulfide Annealing Conditions for Ag8SnS6 Thin Films
Materials 2023, 16(18), 6289; https://doi.org/10.3390/ma16186289 - 19 Sep 2023
Viewed by 696
Abstract
Ag8SnS6 (ATS) has been reported to have a band gap of 1.33 eV and is expected to be a suitable material for the light-absorbing layers of compound thin-film solar cells. However, studies on solar cells that use ATS are currently [...] Read more.
Ag8SnS6 (ATS) has been reported to have a band gap of 1.33 eV and is expected to be a suitable material for the light-absorbing layers of compound thin-film solar cells. However, studies on solar cells that use ATS are currently lacking. The objective of this study is to obtain high-quality ATS thin films for the realization of compound thin-film solar cells using vacuum deposition and sulfide annealing. First, glass/SnS/Ag stacked precursors are prepared by vacuum deposition. Subsequently, they are converted to the ATS phase via sulfide annealing, and various process conditions, namely, annealing time, annealing temperature, and number of steps, are studied. By setting the heat treatment temperature at 550 °C and the heat treatment time at 60 min, a high-quality ATS thin film could be obtained. Multi-step heat treatment also produces thin films with nearly no segregation or voids. Full article
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10 pages, 3449 KiB  
Article
Development of UV-Irradiated PADC and Improvement of Etching for Reducing Experimental Time
Materials 2023, 16(15), 5413; https://doi.org/10.3390/ma16155413 - 02 Aug 2023
Viewed by 582
Abstract
PADC is well known as a highly sensitive solid-state nuclear track detector. A proposal is for a radiation education method that utilizes these characteristics. A significant issue in the proposed educational method using PADC is the time-consuming etching process. This study attempted to [...] Read more.
PADC is well known as a highly sensitive solid-state nuclear track detector. A proposal is for a radiation education method that utilizes these characteristics. A significant issue in the proposed educational method using PADC is the time-consuming etching process. This study attempted to reduce etching time by using a homemade PADC. The experimental results have revealed that the homemade PADC achieves faster etch pit enlargement compared to BARYOTRAK (commercial PADC). An attempt was made to enlarge etch pit diameters rapidly by irradiating UV at a wavelength of 253.7 nm and etching with NaOHaq/ethanol solution. The results revealed that UV irradiation at a wavelength of 253.7 nm, after etching, resulted in etch pit diameters several times larger than those obtained in conventional methods within the same etching time. Therefore, UV irradiation and short-time etching with NaOHaq/ethanol solution proved to be effective. This study also investigated the effects of fading on the PADC during its storage period after UV irradiation. The experimental results confirmed that the etch pit diameters shrank by approximately 30% after 2 months of storage. However, considering the enlargement effect of the etch pit diameters due to UV irradiation, it can be concluded that UV irradiation is practical for radiation education experiments. Full article
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13 pages, 2105 KiB  
Article
Pd-Based Nano-Catalysts Promote Biomass Lignin Conversion into Value-Added Chemicals
Materials 2023, 16(14), 5198; https://doi.org/10.3390/ma16145198 - 24 Jul 2023
Viewed by 835
Abstract
Lignin, as a structurally complex biomaterial, offers a valuable resource for the production of aromatic chemicals; however, its selective conversion into desired products remains a challenging task. In this study, we prepared three types of Pd-based nano-catalysts and explored their application in the [...] Read more.
Lignin, as a structurally complex biomaterial, offers a valuable resource for the production of aromatic chemicals; however, its selective conversion into desired products remains a challenging task. In this study, we prepared three types of Pd-based nano-catalysts and explored their application in the depolymerization of alkali lignin, under both H2-free (hydrogen transfer) conditions and H2 atmosphere conditions. The materials were well characterized with TEM, XRD, and XPS and others, and the electronic interactions among Pd, Ni, and P were analyzed. The results of lignin depolymerization experiments revealed that the ternary Pd-Ni-P catalyst exhibited remarkable performance and guaiacols could be produced under H2 atmosphere conditions in 14.2 wt.% yield with a selectivity of 89%. In contrast, Pd-Ni and Pd-P catalysts resulted in a dispersed product distribution. Considering the incorporation of P and the Pd-Ni synergistic effect in the Pd-Ni-P catalyst, a possible water-involved transformation route of lignin depolymerization was proposed. This work indicates that metal phosphides could be promising catalysts for the conversion of lignin and lignin-derived feedstocks into value-added chemicals. Full article
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13 pages, 2831 KiB  
Article
RAFT Synthesis and Characterization of Poly(Butyl-co-2-(N,N-Dimethylamino)Ethyl Acrylates)-block-Poly(Polyethylene Glycol Monomethyl Ether Acrylate) as a Photosensitizer Carrier for Photodynamic Therapy
Materials 2023, 16(11), 4192; https://doi.org/10.3390/ma16114192 - 05 Jun 2023
Viewed by 873
Abstract
Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) [...] Read more.
Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) for zinc phthalocyanine (ZnPc) delivery. In this study, poly(butyl-co-2-(N,N-dimethylamino)ethyl acrylates)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(BA-co-DMAEA)-b-PPEGA) was synthesized via reversible addition and fragmentation chain transfer (RAFT) polymerization to explore the role of neutral hydrophobic units in photosensitizer delivery. The composition of DMAEA units in P(BA-co-DMAEA) was adjusted to 0.46, which is comparable to that of P(St-co-DMAEA)-b-PPEGA. The size distribution of the P(BA-co-DMAEA)-b-PPEGA micelles changed when the pH decreased from 7.4 to 5.0, indicating their pH-responsive ability. The photosensitizers, 5,10,15,20-tetrakis(pentafluorophenyl)chlorin (TFPC), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP), protoporphyrin IX (PPIX), and ZnPc were examined as payloads for the P(BA-co-DMAEA)-b-PPEGA micelles. The encapsulation efficiency depended on the nature of the photosensitizer. TFPC-loaded P(BA-co-DMAEA)-b-PPEGA micelles exhibited higher photocytotoxicity than free TFPC in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1), indicating their superiority for photosensitizer delivery. ZnPc-loaded P(BA-co-DMAEA)-b-PPEGA micelles also exhibited superior photocytotoxicity compared to free ZnPc. However, their photocytotoxicity was lower than that of P(St-co-DMAEA)-b-PPEGA. Therefore, neutral hydrophobic units, as well as pH-responsive units, must be designed for the encapsulation of photosensitizers. Full article
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11 pages, 2344 KiB  
Article
Study on Reversible Solubilization by Adjusting Surfactant Properties
Materials 2023, 16(9), 3550; https://doi.org/10.3390/ma16093550 - 05 May 2023
Cited by 1 | Viewed by 776
Abstract
Solubilization allows us to dissolve hydrophobic materials in water and to carry them to where they are needed. The purpose of this study is to control solubilization, especially the release of solubilized materials, via external stimulation. An amphoteric surfactant, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide inner salt [...] Read more.
Solubilization allows us to dissolve hydrophobic materials in water and to carry them to where they are needed. The purpose of this study is to control solubilization, especially the release of solubilized materials, via external stimulation. An amphoteric surfactant, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide inner salt (SB-12), was employed, and a pH change was chosen as the external stimulus. We measured the surface tension of an SB-12 solution via the Wilhelmy method, and the absorbance of a solubilized solution was determined using UV-Vis spectroscopy at various pH values. The surface tension was almost the same at any pH, contrary to our expectations. This result suggests that the adsorption behavior and micelle formation of SB-12 were not affected by pH very much. On the other hand, the solubilization behavior remarkably depended on the pH. In particular, the solubilization ability under the basic condition was much larger than that under the acidic and neutral conditions. Taking advantage of such a difference in solubilization ability under some pH conditions, the solubilized material could be completely removed from the solution. Thus, we clarified the mechanism of release for solubilized materials due to a pH change. Full article
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13 pages, 6704 KiB  
Article
Formation of Self-Healing Organic Coatings for Corrosion Protection of Al Alloys by Dispersion of Spherical and Fibrous Capsules
Materials 2023, 16(8), 3018; https://doi.org/10.3390/ma16083018 - 11 Apr 2023
Cited by 3 | Viewed by 3919
Abstract
In previous works, we developed a self-healing organic coating with dispersed spherical capsules for corrosion protection. The capsule consisted of a polyurethane shell and healing agent as the inner. When the coating was damaged physically, the capsules were broken, and the healing agent [...] Read more.
In previous works, we developed a self-healing organic coating with dispersed spherical capsules for corrosion protection. The capsule consisted of a polyurethane shell and healing agent as the inner. When the coating was damaged physically, the capsules were broken, and the healing agent was released from the broken capsules to the damaged area. The healing agent could react with moisture in the air to form the self-healing structure and cover the damaged area of coating. In the present investigation, a self-healing organic coating with spherical and fibrous capsules was formed on aluminum alloys. The corrosion behavior of the specimen coated with the self-healing coating was examined in a Cu2+/Cl solution after physical damage, and it was found that no corrosion occurred during the corrosion test. This is discussed in terms of the high healing ability of fibrous capsules as a result of the high projected area. Full article
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