Abstract:Among the most reliable
techniques for exfoliation of two-dimensional
(2D) layered materials, sonication-assisted liquid-phase exfoliation
(LPE) is considered as a cost-effective and straightforward method
for preparing graphene and its 2D inorganic counterparts at reasonable
sizes and acceptable levels of defects. Although there were rapid
advances in this field, the effect and outcome of the sonication frequency
are poorly understood and often ignored, resulting in a low exfoliation
efficiency. Here, we demo… Show more
“…Detailed AFM statistical analysis of exfoliated GO and rGO flakes was performed to analyze the distribution of the lateral size and thickness of the synthesized flakes throughout the wafer. Bath sonication at 80 kHz frequency (100 W) was used to form thinner and larger lateral size flakes, applying a technique based on sonication-assisted LPE recently proposed by our group [ 32 ].…”
Section: Resultsmentioning
confidence: 99%
“…Next, the mixture was centrifuged (12,000 rpm for 1 h) and washed with 5% hydrochloric acid (HCl) solution 2 times. Then, the mixture was extensively rewashed with distilled water and centrifuged (12,000 rpm for 1 h) until the solution reached pH = 7, and finally was dried in a vacuum furnace for 24 h. Finally, the obtained graphite oxide (brownish solid) was exfoliated to GO flakes after 2 h of sonication-assisted liquid-phase exfoliation (LPE) (Elmasonic P, bath frequency: 80 kHz, 100 W) [ 32 ].…”
Section: Methodsmentioning
confidence: 99%
“…Chemical vapor deposition (CVD) was used to reduce GO to rGO (black solid) [ 32 ]. Dried GO was loaded into a quartz tube and inserted into a Lindberg Blue furnace preheated to 900 °C for 2 h, and reduced by hydrogen flow (400 sccm) under an argon (100 sccm) atmosphere.…”
Recently, graphene and its derivatives have been extensively investigated for their interesting properties in many biomedical fields, including tissue engineering and regenerative medicine. Nonetheless, graphene oxide (GO) and reduced GO (rGO) are still under investigation for improving their dispersibility in aqueous solutions and their safety in different cell types. This work explores the interaction of GO and rGO with different polymeric dispersants, such as glycol chitosan (GC), propylene glycol alginate (PGA), and polydopamine (PDA), and their effects on human chondrocytes. GO was synthesized using Hummer’s method, followed by a sonication-assisted liquid-phase exfoliation (LPE) process, drying, and thermal reduction to obtain rGO. The flakes of GO and rGO exhibited an average lateral size of 8.8 ± 4.6 and 18.3 ± 8.5 µm, respectively. Their dispersibility and colloidal stability were investigated in the presence of the polymeric surfactants, resulting in an improvement in the suspension stability in terms of average size and polydispersity index over 1 h, in particular for PDA. Furthermore, cytotoxic effects induced by coated and uncoated GO and rGO on human chondrocytes at different concentrations (12.5, 25, 50 and 100 µg/mL) were assessed through LDH assay. Results showed a concentration-dependent response, and the presence of PGA contributed to statistically decreasing the difference in the LDH activity with respect to the control. These results open the way to a potentially safer use of these nanomaterials in the fields of cartilage tissue engineering and regenerative medicine.
“…Detailed AFM statistical analysis of exfoliated GO and rGO flakes was performed to analyze the distribution of the lateral size and thickness of the synthesized flakes throughout the wafer. Bath sonication at 80 kHz frequency (100 W) was used to form thinner and larger lateral size flakes, applying a technique based on sonication-assisted LPE recently proposed by our group [ 32 ].…”
Section: Resultsmentioning
confidence: 99%
“…Next, the mixture was centrifuged (12,000 rpm for 1 h) and washed with 5% hydrochloric acid (HCl) solution 2 times. Then, the mixture was extensively rewashed with distilled water and centrifuged (12,000 rpm for 1 h) until the solution reached pH = 7, and finally was dried in a vacuum furnace for 24 h. Finally, the obtained graphite oxide (brownish solid) was exfoliated to GO flakes after 2 h of sonication-assisted liquid-phase exfoliation (LPE) (Elmasonic P, bath frequency: 80 kHz, 100 W) [ 32 ].…”
Section: Methodsmentioning
confidence: 99%
“…Chemical vapor deposition (CVD) was used to reduce GO to rGO (black solid) [ 32 ]. Dried GO was loaded into a quartz tube and inserted into a Lindberg Blue furnace preheated to 900 °C for 2 h, and reduced by hydrogen flow (400 sccm) under an argon (100 sccm) atmosphere.…”
Recently, graphene and its derivatives have been extensively investigated for their interesting properties in many biomedical fields, including tissue engineering and regenerative medicine. Nonetheless, graphene oxide (GO) and reduced GO (rGO) are still under investigation for improving their dispersibility in aqueous solutions and their safety in different cell types. This work explores the interaction of GO and rGO with different polymeric dispersants, such as glycol chitosan (GC), propylene glycol alginate (PGA), and polydopamine (PDA), and their effects on human chondrocytes. GO was synthesized using Hummer’s method, followed by a sonication-assisted liquid-phase exfoliation (LPE) process, drying, and thermal reduction to obtain rGO. The flakes of GO and rGO exhibited an average lateral size of 8.8 ± 4.6 and 18.3 ± 8.5 µm, respectively. Their dispersibility and colloidal stability were investigated in the presence of the polymeric surfactants, resulting in an improvement in the suspension stability in terms of average size and polydispersity index over 1 h, in particular for PDA. Furthermore, cytotoxic effects induced by coated and uncoated GO and rGO on human chondrocytes at different concentrations (12.5, 25, 50 and 100 µg/mL) were assessed through LDH assay. Results showed a concentration-dependent response, and the presence of PGA contributed to statistically decreasing the difference in the LDH activity with respect to the control. These results open the way to a potentially safer use of these nanomaterials in the fields of cartilage tissue engineering and regenerative medicine.
“…In contrast to the amplitude, higher frequencies positively impact the MXene stability. They cause a high number of small bubbles with uniform sizes, preventing violent interparticle collapses and promoting the weakening of the interlayer Van der Waals forces [55]. Papers report different frequencies: from 6 kHz [56] to 40 kHz [57][58][59].…”
Section: Strategies Of Mxene Synthesis 221 Top-down Approachmentioning
A new class of two-dimensional nanomaterials, MXenes, which are carbides/nitrides/carbonitrides of transition and refractory metals, has been critically analyzed. Since the synthesis of the first family member in 2011 by Yury Gogotsi and colleagues, MXenes have quickly become attractive for a variety of research fields due to their exceptional properties. Despite the fact that this new family of 2D materials was discovered only about ten years ago, the number of scientific publications related to MXene almost doubles every year. Thus, in 2021 alone, more than 2000 papers are expected to be published, which indicates the relevance and prospects of MXenes. The current paper critically analyzes the structural features, properties, and methods of synthesis of MXenes based on recent available research data. We demonstrate the recent trends of MXene applications in various fields, such as environmental pollution removal and water desalination, energy storage and harvesting, quantum dots, sensors, electrodes, and optical devices. We focus on the most important medical applications: photo-thermal cancer therapy, diagnostics, and antibacterial treatment. The first results on obtaining and studying the structure of high-entropy MXenes are also presented.
“…Then, we studied the effect of gradual thermal annealing under an inert or reducing atmosphere on the phase transitions in the copper sulfide system. Subsequently, as we reported recently, we thinned down the bulk copper sulfides into few-layer flakes using liquid exfoliation via sonication at higher frequencies . To overcome the limitations of solvents with high boiling points, we used ethanol, which is defined as an environmentally friendly liquid due to its low toxicity, low boiling point, and easy availability.…”
Sunlight-driven photocatalysis is an environmentally friendly approach to solve ecological issues. The development of simple yet sufficiently stable photocatalytic materials capable of responding to the full-spectrum light remains challenging. Here, we demonstrate the phase transformations of bulk copper sulfides from digenite (Cu 9 S 5 ) to djurleite (Cu 1.97 S) and low chalcocite (Cu 2 S) by the reactive thermal annealing during ambient pressure chemical vapor deposition, followed by their top-down exfoliation. Using multiple techniques, we confirm that monoclinic Cu 2 S is primarily formed at higher temperatures or greater reaction times and using a reducing atmosphere. We measured the average thickness to be approximately 4 nm for the exfoliated flakes with relatively large lateral sizes of up to 10 μm. We tested the three phases of bulk copper sulfides and their exfoliated forms as photocatalysts for dye degradation under simulated solar light irradiation. Exfoliated Cu 2 S flakes exhibited superior photocatalytic activity (0.007 min −1 ), roughly twice higher than that of bulk chalcocite, which could be predominantly attributed to their 2D structure and also 2D planar defects, which could serve as active centers for dye photodegradation. Our study paves the way for developing nextgeneration full-spectrum-responsive 2D copper sulfide photocatalysts for environmental decontamination.
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