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12 pages, 2238 KiB

Open AccessArticle

Enhancing the Photovoltaic Performance of Cd_(1−x)Zn_xS Thin Films Using Seed Assistance and EDTA Treatment

by Gayan W. C. Kumarage, Ruwan P. Wijesundera, Elisabetta Comini and Buddhika S. Dassanayake

Micro 2023, 3(4), 867-878; https://doi.org/10.3390/micro3040059 - 12 Nov 2023

Viewed by 986

Abstract

This research article provides a comprehensive investigation into the optoelectronic characteristics of three distinct types of cadmium sulfide (CdS) thin films, namely: (a) conventionally prepared CdS thin films using chemical bath deposition (CBD-CdS), (b) CdS thin films produced via chemical bath deposition with [...] Read more.

This research article provides a comprehensive investigation into the optoelectronic characteristics of three distinct types of cadmium sulfide (CdS) thin films, namely: (a) conventionally prepared CdS thin films using chemical bath deposition (CBD-CdS), (b) CdS thin films produced via chemical bath deposition with the inclusion of zinc (CBD-Cd_(1−x)Zn_xS, x = 0.3), and (c) CdS thin films synthesized using a seed-assisted approach, treated with ethylenediaminetetraacetic acid (EDTA), and incorporating zinc (ED/CBD + EDTA-Cd_(1−x)Zn_xS). The investigation reveals that the crystallite size of these thin films decreases upon the addition of EDTA to the reaction solution, leading to an increase in the inter-planar spacing and dislocation density. Furthermore, a blue shift in the transmittance edge of the ED/CBD + EDTA-Cd_(1−x)Zn_xS samples compared to CBD-CdS implies modifications in the band gaps of the deposited films. The incorporation of Zn²⁺ into the reaction solution results in an increased band gap value of up to 2.42 eV. This suggests that Cd_(1−x)Zn_xS thin films permit more efficient photon transmission compared to conventional CdS. Among the three types of films studied, ED/CBD + EDTA-Cd_(1−x)Zn_xS exhibits the highest optical band gap of 2.50 eV. This increase in the optical band gap is attributed to the smaller crystallite size and the splitting of the tail levels from the band structure. Additionally, the increment in the optical band gap leads to reduced light absorption at longer wavelengths, thereby enhancing the electrical properties. Notably, ED/CBD + EDTA-Cd_(1−x)Zn_xS thin films demonstrate improved photovoltaic performance in a photoelectrochemical (PEC) cell, characterized by enhanced open-circuit voltage (363 mV, V_OC), short-circuit current (35.35 μA, I_SC), and flat-band voltage (−692 mV, V_fb). These improvements are attributed to the better adhesion of CdS to the fluorine-doped tin oxide (FTO) substrate and improved inter-particle connectivity. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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10 pages, 11778 KiB

Open AccessCommunication

Improved Properties of Post-Deposition Annealed Ga₂O₃/SiC and Ga₂O₃/Al₂O₃/SiC Back-Gate Transistors Fabricated by Radio Frequency Sputtering

by Hee-Jae Lee, Geon-Hee Lee, Seung-Hwan Chung, Dong-Wook Byun, Michael A. Schweitz, Dae Hwan Chun, Nack Yong Joo, Minwho Lim, Tobias Erlbacher and Sang-Mo Koo

Micro 2023, 3(4), 775-784; https://doi.org/10.3390/micro3040055 - 30 Sep 2023

Viewed by 1690

Abstract

The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga₂O₃ demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga₂O₃ is lower [...] Read more.

The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga₂O₃ demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga₂O₃ is lower than that of other wide-bandgap materials, resulting in the degradation of the electrical performance and reduced reliability of devices. The heterostructure formation on substrates with high thermal conductivity has been noted to facilitate heat dissipation in devices. In this work, Ga₂O₃ thin films with an Al₂O₃ interlayer were deposited on SiC substrates by radio frequency sputtering. Post-deposition annealing was performed at 900 °C for 1 h to crystallize the Ga₂O₃ thin films. The Auger electron spectroscopy depth profiles revealed the interdiffusion of the Ga and Al atoms at the Ga₂O₃/Al₂O₃ interface after annealing. The X-ray diffraction (XRD) results displayed improved crystallinity after annealing and adding the Al₂O₃ interlayer. The crystallite size increased from 5.72 to 8.09 nm as calculated by the Scherrer equation using the full width at half maximum (FWHM). The carrier mobility was enhanced from 5.31 to 28.39 cm² V⁻¹ s⁻¹ in the annealed Ga₂O₃ thin films on Al₂O₃/SiC. The transfer and output characteristics of the Ga₂O₃/SiC and Ga₂O₃/Al₂O₃/SiC back-gate transistors reflect the trend of the XRD and Hall measurement results. Therefore, this work demonstrated that the physical and electrical properties of the Ga₂O₃/SiC back-gate transistors can be improved by post-deposition annealing and the introduction of an Al₂O₃ interlayer. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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13 pages, 5522 KiB

Open AccessArticle

Experimental Wear Analysis of Nano-Sized Titania Particles as Additives in Automotive Lubricants

by Ádám István Szabó, Álmos Dávid Tóth, Hebah Abdallah and Hajnalka Hargitai

Micro 2023, 3(3), 715-727; https://doi.org/10.3390/micro3030050 - 21 Aug 2023

Cited by 1 | Viewed by 1574

Abstract

This study focuses on the wear effects of nano-sized titania as a potential engine lubricant additive. Titanium dioxide nanoparticles have promising wear-reducing properties and significant tribological potential. In this article, titania nanoparticles were homogenized in Group III automotive oil at five different concentrations [...] Read more.

This study focuses on the wear effects of nano-sized titania as a potential engine lubricant additive. Titanium dioxide nanoparticles have promising wear-reducing properties and significant tribological potential. In this article, titania nanoparticles were homogenized in Group III automotive oil at five different concentrations (0.1; 0.2 … 0.5 wt%). The nanodoped oil samples were tested on a linear oscillating tribometer with oil circulation. Based on the tribological results, titania nanoparticles increased friction by 20–32% but can reduce the wear area by up to 32%. According to the confocal microscopic examination, wear volume can be reduced by up to 57% with titania nanoparticles. Titania nanoparticles improved the repeatability of tribological measurements. A scanning electron microscopy examination of the wear track revealed that the characteristic wear of the tribological system was abrasive, but a significant amount of adhesive wear was also observed. Energy dispersive X-ray spectroscopy analysis found that the nanoparticles fill the deeper trenches of the wear. The worn surface uniformly contains TiO₂ particles and the quantified normalized titanium concentration was between 0.56 and 0.62%. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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16 pages, 4976 KiB

Open AccessArticle

Matrix Effect of Properties of Au, ZnO and Eu₂O₃: Silica, Titania and Alumina Matrices

by Carlos Díaz, Olga Cifuentes-Vaca and María Luisa Valenzuela

Micro 2023, 3(3), 699-714; https://doi.org/10.3390/micro3030049 - 19 Aug 2023

Viewed by 987

Abstract

The composites Au/SiO₂, Au/TiO₂, Au/Al₂O₃, ZnO/TiO₂, ZnO/TiO₂, ZnO/Al₂O₃ and Eu₂O₃/SiO₂, Eu₂O₃/TiO₂ and Eu₂O₃/Al [...] Read more.

The composites Au/SiO₂, Au/TiO₂, Au/Al₂O₃, ZnO/TiO₂, ZnO/TiO₂, ZnO/Al₂O₃ and Eu₂O₃/SiO₂, Eu₂O₃/TiO₂ and Eu₂O₃/Al₂O₃ were prepared using a solid-state method. The effect of the polymer precursors was investigated using two precursor polymers, Chitosan and Poly(styrene-co-4vinylpyridine), (PS-co-4-PVP) in the M/M_xL_y•Chitosan//M’_xO’_y as well as M/M_xL_y•PS-co-4-PVP//M’_xO’_y with M’_xO’_y = SiO₂, TiO₂ and Al₂O₃. The effects on the particle size and morphology were observed. The new composites were characterized using X-ray powder diffraction, SEM-EDS mapping and HRTEM analysis. The distribution of the metallic nanoparticles as well as the metal oxide nanoparticles inside the matrices depend on the matrix. Marked optical and photocatalytic effects of the Au, ZnO and Eu₂O₃ inside the SiO₂, TiO₂ and Al₂O₃ matrices are expected. An experiment is in course. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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18 pages, 3398 KiB

Open AccessArticle

Extraction and Modification of Cellulose Microfibers Derived from Biomass of the Amazon Ochroma pyramidale Fruit

by Ana Luisa Farias Rocha, Bianca de Andrade Feitosa, Adriano de Souza Carolino, Ronald Zico de Aguiar Nunes, Célio Matias Airone Macalia, Kalil Araújo da Silva, Cleverton Oliveira Dias, Sérgio Michielon de Souza, Pedro Henrique Campelo, Jaqueline de Araújo Bezerra and Edgar Aparecido Sanches

Micro 2023, 3(3), 653-670; https://doi.org/10.3390/micro3030046 - 28 Jul 2023

Cited by 2 | Viewed by 2169

Abstract

Microfibers are important to several areas of human lifestyle, and the knowledge about their physicochemical characteristics allows for proposing new technological applications. The in natura microfiber of Ochroma pyramidale fruit (IN sample) and its extracted pulp (PU sample) were evaluated by X-ray Diffraction [...] Read more.

Microfibers are important to several areas of human lifestyle, and the knowledge about their physicochemical characteristics allows for proposing new technological applications. The in natura microfiber of Ochroma pyramidale fruit (IN sample) and its extracted pulp (PU sample) were evaluated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry and Differential Scanning Calorimetry (TG/dTG and DSC). Microfibers were composed mainly of (68 ± 1)% holocellulose, (35.8 ± 0.1)% cellulose, (32 ± 3)% lignin and (3.7 ± 0.3)% extractives. The XRD pattern of the PU sample revealed that the mercerization process resulted in the change of the cellulose crystal structure from Iα type (triclinic) to type II (monoclinic). The SEM technique showed that the IN sample presented regular cylindrical/hollow-shaped wire-like microfibers with diameters ranging from 5 µm to 25 µm. However, the mercerization process changed their natural morphology. A significant change in the FTIR spectra after the removal of hemicellulose and lignin components was observed: weak bands at 1739 cm⁻¹ (C=O stretching of lignin and hemicellulose fractions), 1463 cm⁻¹ (CH₃ of lignin) and 1246 cm⁻¹ (C-O of lignin) were still observed in the PU sample, indicating that the lignin was not completely removed due to the natural difficulty of isolating pure cellulose. The TG/dTG and DSC evaluation revealed a temperature increase of the second thermal event (starting at 235 °C) in the PU sample, which was assigned to the cellulose and residual hemicellulose degradation. Then, this work aimed to disseminate and characterize a microfiber with unusual characteristics still little explored by the scientific community, as well as its cellulosic pulp, providing information that may be useful in its application in different industries, enabling the positive development of new biocompatible, renewable and sustainable materials. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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10 pages, 5217 KiB

Open AccessArticle

Selective Hydrodeoxygenation of Guaiacol to Cyclohexane over Ru-Catalysts Based on MFI Nanosheets

by Dmitry Tsaplin, Alexey Sadovnikov, Dzhamalutdin Ramazanov, Dmitry Gorbunov, Valeriya Ryleeva, Anton Maximov, Kaige Wang and Evgeny Naranov

Micro 2023, 3(2), 610-619; https://doi.org/10.3390/micro3020042 - 20 Jun 2023

Cited by 2 | Viewed by 1418

Abstract

Bio-oils derived from the pyrolysis of lignin-based biomass often contain a variety of oxygenated compounds, which can compromise their usefulness as a fuel. To improve the quality of bio-oil, catalytic hydrodeoxygenation (HDO) is a crucial step that removes oxygen from the oil in [...] Read more.

Bio-oils derived from the pyrolysis of lignin-based biomass often contain a variety of oxygenated compounds, which can compromise their usefulness as a fuel. To improve the quality of bio-oil, catalytic hydrodeoxygenation (HDO) is a crucial step that removes oxygen from the oil in the form of water. In this study, we showed that MFI nanosheets are excellent supports for Ru-catalysts. We synthesized highly crystalline MFI nanosheets using a simple hydrothermal seeding procedure; the final material was obtained in 56 h of crystallization. We investigated the activity of Ru supported on different materials. Our findings indicated that Ru supported on hierarchical MFI demonstrated excellent activity in HDO of guaiacol. Our results demonstrated that Ru/ZNS-56 achieved nearly 100% selectivity towards cyclohexane under mild conditions (200 °C, 50 bar H₂, 1 h). Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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14 pages, 7348 KiB

Open AccessArticle

Tensile Behavior of [0/90]₇ Hemp/Elium Biocomposites after Water Aging: In-Situ Micro-CT Testing and Numerical Analysis

by Quentin Drouhet, Fabienne Touchard and Laurence Chocinski-Arnault

Micro 2023, 3(2), 496-509; https://doi.org/10.3390/micro3020033 - 2 May 2023

Cited by 2 | Viewed by 1561

Abstract

This paper aims to study the tensile behavior of a woven [0/90]₇ hemp/Elium composite after three different conditionings: “Ambient storage”, “Saturated at 60 °C” and “15 wet/dry cycles”. Instrumented repeated progressive tensile loading tests were carried out and showed an unexpected increase [...] Read more.

This paper aims to study the tensile behavior of a woven [0/90]₇ hemp/Elium composite after three different conditionings: “Ambient storage”, “Saturated at 60 °C” and “15 wet/dry cycles”. Instrumented repeated progressive tensile loading tests were carried out and showed an unexpected increase in the secant modulus for the aged samples at the end of the test. An in-situ micro-CT tensile test was then performed on a “15 wet/dry cycles” aged sample. The analysis of the tomographic images showed the damage development with interfacial debonding and matrix cracks in the specimen volume, and also the decrease in the curvature radius of the warp yarns during tensile loading facilitated by the plasticization of the resin. Finite element calculations were thus performed and demonstrated that the increase in the modulus is directly linked to the straightening of warp yarns, showing that the evolution of the modulus on a macroscopic scale can be explained by the deformations of the yarns on a microscopic level. These results allow us to better understand the mechanical behavior and the damage mechanisms that occur in biocomposites during tensile testing after water aging. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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12 pages, 2460 KiB

Open AccessArticle

Effect of CdSTe QDs’ Crystal Size on Viability and Cytochrome P450 Activity of CHO-K1 and HEP-G2 Cells

by Luis Alamo-Nole, Adriana Ponton-Almodovar and Ivan Ortiz-Laboy

Micro 2023, 3(1), 308-319; https://doi.org/10.3390/micro3010021 - 2 Mar 2023

Viewed by 1827

Abstract

In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study [...] Read more.

In the last few years, quantum dots (QDs) have attracted research interest in different fields of science and technology. Despite their applications, it is essential to understand how nanomaterials (with different crystal sizes) are metabolized inside organisms. Thus, the focus of this study was on an evaluation of how crystal sizes of CdSTe QDs affect the viability and response of the cytochrome P450 system in CHO-K1 and HEP-G2 cells. CdSTe QDs were synthesized using a microwave-assisted system at different reaction temperatures (60, 120, 150, and 180 °C) to obtain different crystal sizes. The optical and structural characterization confirmed four crystal sizes from 3 to 8 nm. Fluorescence microscopy confirmed that CdSTe QDs are incorporated into both cell lines. Viability studies suggested that CHO-K1 cells are more sensitive than HEP-G2 cells to CdSTe QDs and Cd⁺² ions. The responsible mechanisms for the toxicity of QDs and Cd⁺² are apoptosis followed by necrosis. The activity of CYP 1A1, 1A2, and 3A4 isoenzymes suggests that the smallest CdSTe crystals are recognized in a manner similar to that of Cd⁺². Furthermore, the largest CdSTe crystals can have different metabolic routes than Cd⁺². Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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8 pages, 1434 KiB

Open AccessArticle

Structural Consequences of Post-Synthetic Modification of Cu₂P₃I₂

by Gregory R. Schwenk, John T. Walters and Hai-Feng Ji

Micro 2023, 3(1), 256-263; https://doi.org/10.3390/micro3010018 - 1 Mar 2023

Viewed by 1837

Abstract

In an attempt to widen the family of Phosphorus Metal Halides (M_xP_yX_z) and enable new applications, post-synthetic modifications to the M_xP_yX_z, Cu₂P₃I₂ have been reported. While such [...] Read more.

In an attempt to widen the family of Phosphorus Metal Halides (M_xP_yX_z) and enable new applications, post-synthetic modifications to the M_xP_yX_z, Cu₂P₃I₂ have been reported. While such a technique suggests access to an entirely new family of M_xP_yX_z-based materials, we report, in this work, that the ion-exchange process seemingly influences important properties such as the crystallographic pattern and vibrational modes. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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17 pages, 80791 KiB

Open AccessArticle

Influence of the Chromium Content on the Characteristics of the Matrix, the Tantalum Carbides Population, and the Hardness of Cast Co(Cr)-0.4C-6Ta Alloys

by Patrice Berthod, Merzouk Bouaraba and Junfu Cai

Micro 2023, 3(1), 239-255; https://doi.org/10.3390/micro3010017 - 16 Feb 2023

Cited by 1 | Viewed by 1662

Abstract

The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences [...] Read more.

The mechanical and chemical behaviors of cast cobalt-base superalloys are governed by the carbides and by a reactive element, which is often chromium. The content of this later element, which is efficient in resisting hot oxidation and also hot corrosion, may have consequences on the melting temperature, microstructure, and mechanical properties at high temperatures and at room temperature. Seemingly, the effect of chromium content on the microstructure and properties of cast equi-axed Co-Cr-Ta-C superalloys containing TaC as single reinforcing carbide and in high-enough quantities to achieve a high level of creep resistance has not been the subject of previous investigations. The present work is devoted to the exploration of this influence of Cr content on the as-cast microstructure of a model alloy in this category, as well as on its microstructure transformations at high temperatures. The work aims to help rate the Cr content to achieve the best characteristics in machinability and high-temperature properties. This is of great importance for fabricability (production cost) and sustainability in service (long enough lifetime performance). A series of six alloys derived from a rather well-known alloy and presenting various Cr contents were thus elaborated by casting. Their microstructures were investigated in their as-cast state as well as in an aged state resulting from a 4-day stage at 1400 K. Vickers indentation was also carried out to study how hardness may evolve with Cr content. It was seen that the higher the Cr content, the lower the solidus temperature, the coarser the TaC population, the harder the alloy, and the higher the risk of brittleness. In order to reach the best compromise, the preferred Cr weight content range, as identified by this work, is 20–30%; indeed, for such Cr contents: (1) the matrix is austenitic, then dense, and then hard and not brittle, and thus is mechanically resistant and tough; (2) the TaC carbides are script-shaped and resistant against morphology changes at high temperatures, and thus efficiently preserve interdendritic cohesion for a long time, and, consequently, (3) the alloys are machinable, have expected good toughness, and can be resistant against creep deformation as well as oxidation and corrosion at high temperatures thanks to the Cr content, allowing for chromium-forming behavior. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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16 pages, 11185 KiB

Open AccessArticle

Barrier Performance of Spray Coated Cellulose Nanofibre Film

by Kirubanandan Shanmugam, Narendhar Chandrasekar and Ramachandran Balaji

Micro 2023, 3(1), 192-207; https://doi.org/10.3390/micro3010014 - 3 Feb 2023

Cited by 2 | Viewed by 2520

Abstract

Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication [...] Read more.

Cellulose nanofibre (CNF) is the sustainable nanomaterial used for developing high-performance barrier materials that are renewable, recyclable, and biodegradable. The CNF film has very low oxygen permeability; however, its water vapor permeability is significantly higher than that of conventional packaging plastics. The fabrication method influences their barrier properties of the film. A spray-coating CNF on a stainless-steel plate was developed to form a compact film with two unique surfaces, namely a smooth layer on the base side and rough layer on the free side. It improves both the ease of preparation of the film and reduces the water vapour permeability via tailoring the basis weight and thickness of the film through simple adjusting CNF content in the suspension. The air permanence of the film from 1.0 wt.% to 2.0 wt.% CNF suspension is less than 0.003 µm/Pa·S confirming that is an impermeable film and proves a good packaging material. SEM, optical profilometry, and AFM revealed that the spray-coated surface was smooth and glossy. For sprayed CNF films with basis weight between 86.26 ± 13.61 and 155.85 ± 18.01 g/m², WVP were ranged from 6.99 ± 1.17 × 10⁻¹¹ to 4.19 ± 1.45 × 10⁻¹¹ g/m·Pa·S. In comparison, the WVP of 100 g/m² vacuum filtered CNF film was 5.50 ± 0.84 × 10⁻¹¹ g/m·Pa·S, spray-coated film (of 96.6 g/m²) also show similar permeability at around 5.34 ± 0.603 × 10⁻¹¹ g/m·Pa·S. The best performance was achieved with spraying of 2.0 wt.% CNF and a water vapour permeability of 3.91 × 10⁻¹¹ g/m·s·Pa. Spray coated CNF film is impermeable against air and water vapour and a potential alternative to synthetic plastics. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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20 pages, 6490 KiB

Open AccessArticle

Polyaniline Hybrids with Biological Tissue, and Biological Polymers as Physiological—Electroactive Materials

by Mai Ichikawa, Masashi Otaki and Hiromasa Goto

Micro 2023, 3(1), 172-191; https://doi.org/10.3390/micro3010013 - 1 Feb 2023

Cited by 1 | Viewed by 1801

Abstract

A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. [...] Read more.

A sprout/polyaniline was synthesized via the chemical oxidative polymerization of aniline in the presence of natural sprout, based on a concept of cyborg plant composite. The composite consisted of both polyaniline and plants. The chemical structure was confirmed by infrared absorption spectroscopy measurements. Optical microscopy observation revealed that polyaniline was deposited into the micro-tissue of the sprout to form the conductive polymer bio-composite. Micro-optical fiber functions for the composite were visually confirmed. Furthermore, the sprout/polyaniline based organic diode exhibited an avalanche breakdown phenomenon. Next, a fucoidan/polyaniline composite as a physiological active material/conducting polymer composite was prepared. This composite showed good film-forming ability, electrochromism, and a micro-porous surface. This paper reports the preparation of conducting polymer composites with a combination of bio-tissue and bio-substance for the creation of bio-based electrically active organized architecture. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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16 pages, 5023 KiB

Open AccessArticle

In-Vitro Cell Response to Strontium/Magnesium-Doped Calcium Phosphate Nanoparticles

by Kathrin Kostka, Shabnam Hosseini and Matthias Epple

Micro 2023, 3(1), 156-171; https://doi.org/10.3390/micro3010012 - 1 Feb 2023

Cited by 3 | Viewed by 1951

Abstract

Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based [...] Read more.

Calcium phosphate nanoparticles are highly biocompatible and biodegradable in bone regeneration. On the other hand, strontium and magnesium enhance the formation of bone. The substitution of calcium by strontium and magnesium is an efficient way to improve the biological properties of calcium phosphate-based biomaterials. Strontium-doped calcium phosphate nanoparticles and magnesium-doped calcium phosphate nanoparticles with degrees of cation substitution of 5, 10, 15, and 20 mol% with respect to calcium were prepared by precipitation, followed by surface functionalization with polyethyleneimine (PEI, cationic) or carboxymethylcellulose (CMC, anionic). The nanoparticles were characterized by dynamic light scattering (DLS), zeta potential measurement, scanning electron microscopy (SEM), atomic absorption spectrometry (AAS), energy dispersive X-ray analysis (EDX), and X-ray powder diffraction (XRD). The particles were approximately spherical (diameter 40–70 nm). The addition of magnesium and strontium considerably decreased the internal crystallinity, i.e., the doped particles were almost X-ray amorphous. The cell-biological effects were assessed on three different cell lines, i.e., HeLa cells, MG63 cells, and MC3T3 cells. Cell viability tests (MTT) showed a low cytotoxicity, the alkaline phosphatase (ALP) activity was strongly increased, and the nanoparticles were taken up well by the three cell lines. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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13 pages, 10358 KiB

Open AccessArticle

Graphene Formation through Spontaneous Exfoliation of Graphite by Chlorosulfonic Acid: A DFT Study

by Alfredo Bol-Arreba, Isabel G. Ayala and Nicolás A. Cordero

Micro 2023, 3(1), 143-155; https://doi.org/10.3390/micro3010011 - 31 Jan 2023

Cited by 1 | Viewed by 1729

Abstract

Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield [...] Read more.

Using exfoliating agents is one of the most promising ways for large-scale production of liquid dispersed graphenic materials from graphite. Therefore, it is crucial to know the reason why some molecules have a larger exfoliating power than others. The highest reported experimental yield for the liquid phase single-surfactant spontaneous exfoliation of graphite, i.e., without sonication, has been obtained using chlorosulfonic acid. The ability of this acid to disperse graphite is studied within the framework of Density Functional Theory (DFT). Equilibrium configurations, electron transfers, binding energies, and densities of states are presented for two acid concentrations and for two situations: adsorption (on monolayer and bilayer graphene) and intercalation (in between simple hexagonal and Bernal-stacked bilayer graphene). Experimental exfoliation power and dispersion stability are explained in terms of charge transfer—the largest found among several studied exfoliating and surfactant agents—facilitated by the good geometrical matching of chlorosulfonic acid molecules to constituent carbon rings of graphene. This matching is in the origin of the tendency toward adsorption of chlorosulfonic acid molecules on graphene monolayers when they separate, originating the charging of the monolayers that precludes their reaggregation. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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25 pages, 4773 KiB

Open AccessArticle

Chitosan/Hydroxyapatite Scaffolds with P28 as a Promising Osteoinductive Scaffold for Bone Healing Applications

by Farah Alwani Azaman, Florence Daubiné, Amélie Lebatard, Margaret E. Brennan Fournet and Declan M. Devine

Micro 2023, 3(1), 118-142; https://doi.org/10.3390/micro3010010 - 31 Jan 2023

Cited by 5 | Viewed by 2205

Abstract

Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although [...] Read more.

Despite bone’s inherent ability to heal, large bone defects remain a major clinical concern. This study proposes an off-the-shelf treatment combining chitosan/hydroxyapatite (CS/HAp) scaffolds, covalently linked with either bone morphogenetic protein-2 (BMP-2) or its related peptide P28 via a UV crosslinking process. Although covalently binding the growth factors was reported as a great alternative to the conventionally physical adsorption and encapsulation methods, this method presents the risk of altering the molecular activity and interaction of the growth factors. Therefore, alkaline phosphatase (ALP) activity and alizarin red staining (ARS) with a quantitative cetylpyridinium chloride (CPC) assay were conducted to validate that our photo-crosslinking fabrication method did not interfere with the functionality of the growth factors. The ALP activity of C2C12 with 100 µg/mL P28 was found to be comparable to 0.5 µg/mL BMP-2 after two weeks, where 0.001 U/mL was recorded for both treatments. The C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds also showed an increased ALP activity compared to the negative control. ARS-CPC assay presented the highest optical density in 0.3 µg/mL BMP-2 and 50 µg/mL P28, while the highest intensity of ARS was observed in C2C12 cultured with CS/HAp/BMP-2 and CS/HAp/P28 scaffolds compared to the negative controls. The osteoconductive capability of this delivery system was then investigated through a rat femoral condyle defect model, where the new bone mineral density and the bone volume increased for all CS/HAp scaffolds compared to the collagen sponge control treatment. The histological assessment showed a favourable bone regeneration efficacy of the CS/HAp/P28 compared to the CS/HAp/BMP-2 treatment, thus showing the use of CS/HAp scaffolds with P28 as a promising osteoinductive scaffold for bone healing applications. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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Nanometals and Metal Ion Pollution from Dental Materials in Dental Environment

by Ana Carla B. C. J. Fernandes and Rodrigo França

Micro 2023, 3(2), 471-483; https://doi.org/10.3390/micro3020031 - 17 Apr 2023

Cited by 2 | Viewed by 2474

Abstract

The dental environment is being polluted with metals from dental materials in many ways, mainly due to aerosol-generating procedures; this could affect the long-term well-being of dentists, dental students, and dental personnel. The current dental pollution incorporates metallic nanoparticles, which are highly reactive [...] Read more.

The dental environment is being polluted with metals from dental materials in many ways, mainly due to aerosol-generating procedures; this could affect the long-term well-being of dentists, dental students, and dental personnel. The current dental pollution incorporates metallic nanoparticles, which are highly reactive and quickly become airborne, especially those particles that become unbound in the bulk composition. In addition, liquid mercury or mercury vapors may be released from dental amalgam, causing concerns in the dental community. In our study, we reviewed the behavior of metallic elements present in dental materials, their routes of exposure, and their potentially toxic effects on the dental team. This review found that skin and lung disorders are the most harmful effects of metallic exposure for dentists, dental students, and dental personnel. Therefore, chronic exposure to low concentrations of metals in the dental environment, especially in nanosized forms, should be further investigated to improve the environmental matrix, material choice, and safety protocols. Full article

(This article belongs to the Special Issue Feature Papers in Micro- or Nanoscale Materials Sciences and Technology)

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