Nanomaterials

11 pages, 3770 KiB

Open AccessArticle

TiO₂ Nanowires with Doped g-C₃N₄ Nanoparticles for Enhanced H₂ Production and Photodegradation of Pollutants

by Liushan Jiang, Fanshan Zeng, Rong Zhong, Yu Xie, Jianli Wang, Hao Ye, Yun Ling, Ruobin Guo, Jinsheng Zhao, Shiqian Li and Yuying Hu

Nanomaterials 2021, 11(1), 254; https://doi.org/10.3390/nano11010254 - 19 Jan 2021

Cited by 6 | Viewed by 3985

Abstract

With the rapid consumption of fossil fuels, along with the ever-increasing environmental pollution, it is becoming a top priority to explore efficient photocatalysts for the production of renewable hydrogen and degradation of pollutants. Here, we fabricated a composite of g-C₃N₄ [...] Read more.

With the rapid consumption of fossil fuels, along with the ever-increasing environmental pollution, it is becoming a top priority to explore efficient photocatalysts for the production of renewable hydrogen and degradation of pollutants. Here, we fabricated a composite of g-C₃N₄/TiO₂ via an in situ growth method under the conditions of high-temperature calcination. In this method, TiO₂ nanowires with a large specific surface area could provide enough space for loading more g-C₃N₄ nanoparticles to obtain C₃N₄/TiO₂ composites. Of note, the g-C₃N₄/TiO₂ composite could effectively photocatalyze both the degradation of several pollutants and production of hydrogen, both of which are essential for environmental governance. Combining multiple characterizations and experiments, we found that the heterojunction constructed by the TiO₂ and g-C₃N₄ could increase the photocatalytic ability of materials by prompting the separation of photogenerated carriers. Furthermore, the photocatalytic mechanism of the g-C₃N₄/TiO₂ composite was also clarified in detail. Full article

(This article belongs to the Special Issue Application of Nanomaterials in Photocatalysis)

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17 pages, 4854 KiB

Open AccessArticle

Assessment of the Influence of Crystalline Form on Cyto-Genotoxic and Inflammatory Effects Induced by TiO₂ Nanoparticles on Human Bronchial and Alveolar Cells

by Anna Maria Fresegna, Cinzia Lucia Ursini, Aureliano Ciervo, Raffaele Maiello, Stefano Casciardi, Sergio Iavicoli and Delia Cavallo

Nanomaterials 2021, 11(1), 253; https://doi.org/10.3390/nano11010253 - 19 Jan 2021

Cited by 19 | Viewed by 3266

Abstract

Titanium dioxide nanoparticles (TiO₂NPs) are increasingly used in consumer products, industrial and medical applications, raising concerns on their potential toxicity. The available in vitro and in vivo studies on these NPs show controversial results. Crystalline structure is the physicochemical characteristic that [...] Read more.

Titanium dioxide nanoparticles (TiO₂NPs) are increasingly used in consumer products, industrial and medical applications, raising concerns on their potential toxicity. The available in vitro and in vivo studies on these NPs show controversial results. Crystalline structure is the physicochemical characteristic that seems to influence mainly TiO₂NPs toxicity, so its effect needs to be further studied. We aimed to study whether and how crystalline form influences potential cyto-genotoxic and inflammatory effects induced by two commercial TiO₂NPs (TiO₂-A, mainly anatase; TiO₂-B, mainly rutile) in human alveolar A549 and bronchial BEAS-2B cells exposed to 1–40 µg/mL. Cell viability (WST-1), membrane damage (LDH release), IL-6, IL-8 and TNF-α release (ELISA) and direct/oxidative DNA damage (fpg-comet assay) were evaluated. Physicochemical characterization included analysis of crystalline form (TEM and XRD), specific surface area (BET), agglomeration (DLS) and Z-potential (ELS). Our results show that TiO₂-A NPs induce in BEAS-2B cytotoxicity and a slight inflammation and in A549 slight oxidative effects, whereas TiO₂-B NPs induce genotoxic/oxidative effects in both cell lines, revealing different toxicity mechanisms for the two tested NPs. In conclusion, our study confirms the influence of crystalline form on cellular response, also demonstrating the suitability of our in vitro model to screen early TiO₂NPs effects. Full article

(This article belongs to the Special Issue Advances in Toxicity of Nanoparticles)

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62 pages, 11396 KiB

Open AccessReview

Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules

by Álvaro Terán-Alcocer, Francisco Bravo-Plascencia, Carlos Cevallos-Morillo and Alex Palma-Cando

Nanomaterials 2021, 11(1), 252; https://doi.org/10.3390/nano11010252 - 19 Jan 2021

Cited by 62 | Viewed by 9245

Abstract

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability [...] Read more.

Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers. Full article

(This article belongs to the Special Issue Functional Nanomaterials for Sensor Applications)

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14 pages, 5235 KiB

Open AccessArticle

Magnetic and Electronic Properties of Weyl Semimetal Co₂MnGa Thin Films

by Peter Swekis, Aleksandr S. Sukhanov, Yi-Cheng Chen, Andrei Gloskovskii, Gerhard H. Fecher, Ioannis Panagiotopoulos, Jörg Sichelschmidt, Victor Ukleev, Anton Devishvili, Alexei Vorobiev, Dmytro S. Inosov, Sebastian T. B. Goennenwein, Claudia Felser and Anastasios Markou

Nanomaterials 2021, 11(1), 251; https://doi.org/10.3390/nano11010251 - 19 Jan 2021

Cited by 27 | Viewed by 6611

Abstract

Magnetic Weyl semimetals are newly discovered quantum materials with the potential for use in spintronic applications. Of particular interest is the cubic Heusler compound Co₂MnGa due to its inherent magnetic and topological properties. This work presents the structural, magnetic and electronic [...] Read more.

Magnetic Weyl semimetals are newly discovered quantum materials with the potential for use in spintronic applications. Of particular interest is the cubic Heusler compound Co₂MnGa due to its inherent magnetic and topological properties. This work presents the structural, magnetic and electronic properties of magnetron co-sputtered Co₂MnGa thin films, with thicknesses ranging from 10 to 80 nm. Polarized neutron reflectometry confirmed a uniform magnetization through the films. Hard x-ray photoelectron spectroscopy revealed a high degree of spin polarization and localized (itinerant) character of the Mn d (Co d) valence electrons and accompanying magnetic moments. Further, broadband and field orientation-dependent ferromagnetic resonance measurements indicated a relation between the thickness-dependent structural and magnetic properties. The increase of the tensile strain-induced tetragonal distortion in the thinner films was reflected in an increase of the cubic anisotropy term and a decrease of the perpendicular uniaxial term. The lattice distortion led to a reduction of the Gilbert damping parameter and the thickness-dependent film quality affected the inhomogeneous linewidth broadening. These experimental findings will enrich the understanding of the electronic and magnetic properties of magnetic Weyl semimetal thin films. Full article

(This article belongs to the Special Issue Synthesis, Development and Characterization of Magnetic Nanomaterials)

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(a) XRD patterns of Co2MnGa films with different thicknesses. The inset shows the asymmetric 113 reflections. (b) Lattice parameters of Co2MnGa films as a function of thickness. Full article ">Figure 2
(a–d) AFM topographic images of the Co2MnGa films with different thicknesses. Full article ">Figure 3
(a) PNR measurements of an 80-nm-thick Co2MnGa film. The solid lines are the fitted curves. (b) Nuclear and magnetic SLD profiles obtained from fitting the PNR data. The right axis shows the magnetization corresponding to the magnetic SLD profile. Full article ">Figure 4
(a) Co 2p and (b) Mn 2p HAXPES spectra of Co2MnGa film on MgO(001). Shown are spectra taken with σ+ and σ− polarization of the photons. The insets show the difference spectra, that is the dichroism. Full article ">Figure 5
Magnetization hysteresis loops with H applied along the: (a) IP and (b) OOP film directions at 300 K for Co2MnGa films of various thicknesses. Full article ">Figure 6
(a–d) Resonance fields µ0Hres with H applied perpendicular to the film plane for the Co2MnGa films with various thicknesses; and (e–h) linewidths of the respective FMR modes, including linear fits for the damping parameters. Full article ">Figure 7
Resonance fields Hres and simulated resonance conditions (solid lines, see main text) at 300 K and 9.4 GHz of Co2MnGa films with different thicknesses: (a–d) H rotated in the (001) plane, i.e., IP rotation; and (e–h) H rotated in the (110) plane, i.e., IP to OOP rotation. The dashed lines indicate the crystallographic directions of the film at the respective angles. Inset in (h): Cartesian and polar coordinate system, where the crystallographic directions refer to the Co2MnGa film and the angles to the direction of H. Full article ">

16 pages, 1792 KiB

Open AccessArticle

In Vitro Interactions of TiO₂ Nanoparticles with Earthworm Coelomocytes: Immunotoxicity Assessment

by Natividad Isabel Navarro Pacheco, Radka Roubalova, Jaroslav Semerad, Alena Grasserova, Oldrich Benada, Olga Kofronova, Tomas Cajthaml, Jiri Dvorak, Martin Bilej and Petra Prochazkova

Nanomaterials 2021, 11(1), 250; https://doi.org/10.3390/nano11010250 - 19 Jan 2021

Cited by 10 | Viewed by 4100

Abstract

Titanium dioxide nanoparticles (TiO₂ NPs) are manufactured worldwide. Once they arrive in the soil environment, they can endanger living organisms. Hence, monitoring and assessing the effects of these nanoparticles is required. We focus on the Eisenia andrei earthworm immune cells exposed to [...] Read more.

Titanium dioxide nanoparticles (TiO₂ NPs) are manufactured worldwide. Once they arrive in the soil environment, they can endanger living organisms. Hence, monitoring and assessing the effects of these nanoparticles is required. We focus on the Eisenia andrei earthworm immune cells exposed to sublethal concentrations of TiO₂ NPs (1, 10, and 100 µg/mL) for 2, 6, and 24 h. TiO₂ NPs at all concentrations did not affect cell viability. Further, TiO₂ NPs did not cause changes in reactive oxygen species (ROS) production, malondialdehyde (MDA) production, and phagocytic activity. Similarly, they did not elicit DNA damage. Overall, we did not detect any toxic effects of TiO₂ NPs at the cellular level. At the gene expression level, slight changes were detected. Metallothionein, fetidin/lysenin, lumbricin and MEK kinase I were upregulated in coelomocytes after exposure to 10 µg/mL TiO₂ NPs for 6 h. Antioxidant enzyme expression was similar in exposed and control cells. TiO₂ NPs were detected on coelomocyte membranes. However, our results do not show any strong effects of these nanoparticles on coelomocytes at both the cellular and molecular levels. Full article

(This article belongs to the Special Issue An Evolutionary and Environmental Perspective of the Interaction of Nanomaterials with the Immune System-The Outcomes of the EU Project PANDORA)

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18 pages, 5591 KiB

Open AccessArticle

Conformation of Polyethylene Glycol inside Confined Space: Simulation and Experimental Approaches

by Tianji Ma, Nicolas Arroyo, Jean Marc Janot, Fabien Picaud and Sebastien Balme

Nanomaterials 2021, 11(1), 244; https://doi.org/10.3390/nano11010244 - 19 Jan 2021

Cited by 8 | Viewed by 3217

Abstract

The modification of the inner nanopore wall by polymers is currently used to change the specific properties of the nanosystem. Among them, the polyethylene glycol (PEG) is the most used to prevent the fouling and ensure the wettability. However, its properties depend mainly [...] Read more.

The modification of the inner nanopore wall by polymers is currently used to change the specific properties of the nanosystem. Among them, the polyethylene glycol (PEG) is the most used to prevent the fouling and ensure the wettability. However, its properties depend mainly on the chain structure that is very difficult to estimate inside this confined space. Combining experimental and simulation approaches, we provide an insight to the consequence of the PEG presence inside the nanopore on the nanopore properties. We show, in particular, that the cation type in the electrolyte, together with the type of electrolyte (water or urea), is at the origin of the ion transport modification in the nanopore. Full article

(This article belongs to the Special Issue Confinement Effect on the Stability of Different Molecular Species inside Nanostructures)

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13 pages, 1750 KiB

Open AccessArticle

Mechanical Properties and Bioactivity of Poly(Lactic Acid) Composites Containing Poly(Glycolic Acid) Fiber and Hydroxyapatite Particles

by Han-Seung Ko, Sangwoon Lee, Doyoung Lee and Jae Young Jho

Nanomaterials 2021, 11(1), 249; https://doi.org/10.3390/nano11010249 - 18 Jan 2021

Cited by 43 | Viewed by 4008

Abstract

To enhance the mechanical strength and bioactivity of poly(lactic acid) (PLA) to the level that can be used as a material for spinal implants, poly(glycolic acid) (PGA) fibers and hydroxyapatite (HA) were introduced as fillers to PLA composites. To improve the poor interface [...] Read more.

To enhance the mechanical strength and bioactivity of poly(lactic acid) (PLA) to the level that can be used as a material for spinal implants, poly(glycolic acid) (PGA) fibers and hydroxyapatite (HA) were introduced as fillers to PLA composites. To improve the poor interface between HA and PLA, HA was grafted by PLA to form HA-g-PLA through coupling reactions, and mixed with PLA. The size of the HA particles in the PLA matrix was observed to be reduced from several micrometers to sub-micrometer by grafting PLA onto HA. The tensile and flexural strength of PLA/HA-g-PLA composites were increased compared with those of PLA/HA, apparently due to the better dispersion of HA and stronger interfacial adhesion between the HA and PLA matrix. We also examined the effects of the length and frequency of grafted PLA chains on the tensile strength of the composites. By the addition of unidirectionally aligned PGA fibers, the flexural strength of the composites was greatly improved to a level comparable with human compact bone. In the bioactivity tests, the growth of apatite on the surface was fastest and most uniform in the PLA/PGA fiber/HA-g-PLA composite. Full article

(This article belongs to the Section Nanocomposite Materials)

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(a) FT-IR, (b,c) XPS for N1s, and (d) TGA of surface-grafted hydroxyapatite (HA): (b) HA-Hexamethylene diisocyanate (HMDI); (c) HA-HMDI-ethylene glycol (EG). Full article ">Figure 2
SEM images of fracture surface of (a) PLA/HA5, (b) PLA/HA10, (c) PLA/HA15, (d) PLA/HA-g-PLA(m)5, (e) PLA/HA-g-PLA(m)10, (f) PLA/HA-g-PLA(m)15, (g) PLA/PGA fiber10, (h) PLA/PGA fiber20, and (i) PLA/PGA fiber30. Full article ">Figure 3
(a) Flexural stress–strain curves, (b) flexural modulus, and (c) flexural strength of PLA and its composites: PLA (black solid line); PLA/PGA fiber30 (black dash line); PLA/PGA fiber30/HA10 (gray solid line); PLA/PGA fiber30/HA-g-PLA(m)10 (gray dash line). Full article ">Figure 4
(a) Weight loss by phosphate buffer saline (PBS) and (b) weight increase by simulated body fluid (SBF) solution of the composites: ■ PLA/PGA fiber30; ● PLA/PGA fiber30/HA10; ▲ PLA/PGA fiber30/HA-g-PLA(m)10. Full article ">Figure 5
Surface SEM images of the composites before and after apatite growth by immersing PLA/PGA fiber30 (A), PLA/PGA fiber30/HA10 (B), and PLA/PGA fiber30/HA-g-PLA(m)10 (C) in SBF solution. The subscript number represents the immersing days of the composites. Full article ">

10 pages, 2439 KiB

Open AccessArticle

Reduction of the Diazo Functionality of ?-Diazocarbonyl Compounds into a Methylene Group by NH₃BH₃ or NaBH₄ Catalyzed by Au Nanoparticles

by Marios Kidonakis and Manolis Stratakis

Nanomaterials 2021, 11(1), 248; https://doi.org/10.3390/nano11010248 - 18 Jan 2021

Cited by 3 | Viewed by 2980

Abstract

Supported Au nanoparticles on TiO₂ (1 mol%) are capable of catalyzing the reduction of the carbene-like diazo functionality of α-diazocarbonyl compounds into a methylene group [C=(N₂) → CH₂] by NH₃BH₃ or NaBH₄ in methanol [...] Read more.

Supported Au nanoparticles on TiO₂ (1 mol%) are capable of catalyzing the reduction of the carbene-like diazo functionality of α-diazocarbonyl compounds into a methylene group [C=(N₂) → CH₂] by NH₃BH₃ or NaBH₄ in methanol as solvent. The Au-catalyzed reduction that occurs within a few minutes at room temperature formally requires one hydride equivalent (B-H) and one proton that originates from the protic solvent. This pathway is in contrast to the Pt/CeO₂-catalyzed reaction of α-diazocarbonyl compounds with NH₃BH₃ in methanol, which leads to the corresponding hydrazones instead. Under our stoichiometric Au-catalyzed reaction conditions, the ketone-type carbonyls remain intact, which is in contrast to the uncatalyzed conditions where they are selectively reduced by the boron hydride reagent. It is proposed that the transformation occurs via the formation of chemisorbed carbenes on Au nanoparticles, having proximally activated the boron hydride reagent. This protocol is the first general example of catalytic transfer hydrogenation of the carbene-like α -ketodiazo functionality. Full article

(This article belongs to the Special Issue Nano Au Materials for Catalysis of Organic Transformations)

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Graphical abstract

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Full article ">Figure 1
Reduction of α-diazocarbonyl compounds by NH3BH3 or NaBH4 catalyzed by Au/TiO2. a With one additional B-H equivalent, the corresponding alcohols of the ketones 3j–l were isolated in >90% yield. b In this case, the corresponding hydrazone (Ε/Ζ = 85/15) was formed in 15% relative yield using NH3BH3 and in 25% with NaBH4. The isolated yield refers to the reaction with NH3BH3. Full article ">Scheme 1
Hydrosilylation of α-diazo carbonyl compounds catalyzed by Au/TiO2; reversal of chemoselectivity of the attempted hydrosilylation of diazo compound 1a in the presence of 0.5 equivalents of H2O. Full article ">Scheme 2
Reduction of α-diazocarbonyl compound 1a by boron hydride reagents in methanol catalyzed by Au/TiO2, and D-labeling experiments in the reduction of compound 1b. Full article ">Scheme 3
The reaction of α-diazocarbonyl compounds with NH3BH3 in methanol under different catalytic conditions. Full article ">Scheme 4
Au/TiO2-catalyzed reaction of 1a with excess of NaBH4 or NH3BH3, and a proof that hydrazones are not reaction intermediates. Full article ">Scheme 5
Mechanistic considerations in the reduction of α-diazocarbonyl compounds with NH3BH3 catalyzed by Au/TiO2 (the catalytic sites of nanoparticles are indicated as Aun). Full article ">

16 pages, 6842 KiB

Open AccessFeature PaperArticle

Cellulose Nanocrystals and Corn Zein Oxygen and Water Vapor Barrier Biocomposite Films

by Tal Ben Shalom, Shylee Belsey, Michael Chasnitsky and Oded Shoseyov

Nanomaterials 2021, 11(1), 247; https://doi.org/10.3390/nano11010247 - 18 Jan 2021

Cited by 26 | Viewed by 4243

Abstract

Cellulose nanocrystals (CNC) are well-suited to the preparation of biocomposite films and packaging material due to its abundance, renewability, biodegradability, and favorable film-forming capacity. In this study, different CNC and corn zein (CZ) composite films were prepared by adding CZ to the CNC [...] Read more.

Cellulose nanocrystals (CNC) are well-suited to the preparation of biocomposite films and packaging material due to its abundance, renewability, biodegradability, and favorable film-forming capacity. In this study, different CNC and corn zein (CZ) composite films were prepared by adding CZ to the CNC suspension prior to drying, in order to change internal structure of resulting films. Films were developed to examine their performance as an alternative water vapor and oxygen-barrier for flexible packaging industry. Water vapor permeability (WVP) and oxygen transmission rate (OTR) of the biocomposite films decreased significantly in a specific ratio between CNC and CZ combined with 1,2,3,4-butane tetracarboxylic acid (BTCA), a nontoxic cross linker. In addition to the improved barrier properties, the incorporation of CZ benefitted the flexibility and thermal stability of the CNC/CZ composite films. The toughness increased by 358%, and Young’s modulus decreased by 32% compared with the pristine CNC film. The maximum degradation temperature increased by 26 °C, compared with that of CNC film. These results can be attributed to the incorporation of a hydrophobic protein into the matrix creating hydrophobic interactions among the biocomposite components. SEM and AFM analysis indicated that CZ could significantly affect the CNC arrangement, and the film surface topography, due to the mechanical bundling and physical adsorption effect of CZ to CNC. The presented results indicate that CNC/CZ biocomposite films may find applications in packaging, and in multi-functionalization materials. Full article

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33 pages, 8793 KiB

Open AccessFeature PaperReview

Recent Advance in the Fabrication of 2D and 3D Metal Carbides-Based Nanomaterials for Energy and Environmental Applications

by Keming Wan, Yalin Li, Yan Wang and Gang Wei

Nanomaterials 2021, 11(1), 246; https://doi.org/10.3390/nano11010246 - 18 Jan 2021

Cited by 48 | Viewed by 5841

Abstract

Two-dimensional (2D) nanomaterials have attracted increased interest and exhibited extended applications from nanotechnology to materials science, biomedicine, tissue engineering, as well as energy storage and environmental science. With the development of the synthesis and fabrication of 2D materials, a new family of 2D [...] Read more.

Two-dimensional (2D) nanomaterials have attracted increased interest and exhibited extended applications from nanotechnology to materials science, biomedicine, tissue engineering, as well as energy storage and environmental science. With the development of the synthesis and fabrication of 2D materials, a new family of 2D materials, metal carbides (MCs), revealed promising applications in recent years, and have been utilized for the fabrication of various functional 2D and three-dimensional (3D) nanomaterials for energy and environmental applications, ascribing to the unique physical and chemical properties of MCs. In this review, we present recent advance in the synthesis, fabrication, and applications of 2D and 3D MC-based nanomaterials. For this aim, we first summarize typical synthesis methods of MCs, and then demonstrate the progress on the fabrication of 2D and 3D MC-based nanomaterials. To the end, the applications of MC-based 2D and 3D materials for chemical batteries, supercapacitors, water splitting, photodegradation, removal of heavy metals, and electromagnetic shielding are introduced and discussed. This work provides useful information on the preparation, hybridization, structural tailoring, and applications of MC-based materials, and is expected to inspire the design and fabrication of novel and functional MXene materials with improved performance. Full article

(This article belongs to the Special Issue Functionalization of 2D Carbides and Nitrides for Biomedical, Energy, and Environmental Applications)

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17 pages, 10561 KiB

Open AccessArticle

Modification of Surface Bond Au Nanospheres by Chemically and Plasmonically Induced Pd Deposition

by Heike Lisa Kerstin Stephanie Stolle, Andrea Csáki, Jan Dellith and Wolfgang Fritzsche

Nanomaterials 2021, 11(1), 245; https://doi.org/10.3390/nano11010245 - 18 Jan 2021

Cited by 2 | Viewed by 2781

Abstract

In this work we investigated methods of modifying gold nanospheres bound to a silicon surface by depositing palladium onto the surfaces of single nanoparticles. Bimetallic Au-Pd nanoparticles can thus be gained for use in catalysis or sensor technology. For Pd deposition, two methods [...] Read more.

In this work we investigated methods of modifying gold nanospheres bound to a silicon surface by depositing palladium onto the surfaces of single nanoparticles. Bimetallic Au-Pd nanoparticles can thus be gained for use in catalysis or sensor technology. For Pd deposition, two methods were chosen. The first method was the reduction of palladium acetate by ascorbic acid, in which the amounts of palladium acetate and ascorbic acid were varied. In the second method we utilized light-induced metal deposition by making use of the plasmonic effect. Through this method, the surface bond nanoparticles were irradiated with light of wavelengths capable of inducing plasmon resonance. The generation of hot electrons on the particle surface then reduced the palladium acetate in the vicinity of the gold nanoparticle, resulting in palladium-covered gold nanospheres. In our studies we demonstrated the effect of both enhancement methods by monitoring the particle heights over enhancement time by atomic force microscopy (AFM), and investigated the influence of ascorbic acid/Pd acetate concentration as well as the impact of the irradiated wavelengths on the enhancement effect. It could thus be proven that both methods were valid for obtaining a deposition of Pd on the surface of the gold nanoparticles. Deposition of Pd on the gold particles using the light-assisted method could be observed, indicating the impact of the plasmonic effect and hot electron for Pd acetate reduction on the gold particle surface. In the case of the reduction method with ascorbic acid, in addition to Pd deposition on the gold nanoparticle surface, larger pure Pd particles and extended clusters were also generated. The reduction with ascorbic acid however led to a considerably thicker Pd layer of up to 54 nm in comparison to up to 11 nm for the light-induced metal deposition with light resonant to the particle absorption wavelength. Likewise, it could be demonstrated that light of non-resonant wavelengths was not capable of initiating Pd deposition, since a growth of only 1.6 nm (maximum) was observed for the Pd layer. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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9 pages, 1308 KiB

Open AccessCommunication

Quantification of Nitric Oxide Concentration Using Single-Walled Carbon Nanotube Sensors

by Jakob Meier, Joseph Stapleton, Eric Hofferber, Abigail Haworth, Stephen Kachman and Nicole M. Iverson

Nanomaterials 2021, 11(1), 243; https://doi.org/10.3390/nano11010243 - 18 Jan 2021

Cited by 26 | Viewed by 3816

Abstract

Nitric oxide (NO), a free radical present in biological systems, can have many detrimental effects on the body, from inflammation to cancer. Due to NO’s short half-life, detection and quantification is difficult. The inability to quantify NO has hindered researchers’ understanding of its [...] Read more.

Nitric oxide (NO), a free radical present in biological systems, can have many detrimental effects on the body, from inflammation to cancer. Due to NO’s short half-life, detection and quantification is difficult. The inability to quantify NO has hindered researchers’ understanding of its impact in healthy and diseased conditions. Single-walled carbon nanotubes (SWNTs), when wrapped in a specific single-stranded DNA chain, becomes selective to NO, creating a fluorescence sensor. Unfortunately, the correlation between NO concentration and the SWNT’s fluorescence intensity has been difficult to determine due to an inability to immobilize the sensor without altering its properties. Through the use of a recently developed sensor platform, systematic studies can now be conducted to determine the correlation between SWNT fluorescence and NO concentration. This paper explains the methods used to determine the equations that can be used to convert SWNT fluorescence into NO concentration. Through the use of the equations developed in this paper, an easy method for NO quantification is provided. The methods outlined in this paper will also enable researchers to develop equations to determine the concentration of other reactive species through the use of SWNT sensors. Full article

(This article belongs to the Special Issue Multifunctional Nanomaterials and Hybrid Structures for Sensors, Actuators and Smart Technologies)

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Schematic of testing process. (A) Sensor-coated slide was placed into a heated slide holder and then bathed in saline (25 °C). The slide/slide holder was placed on the upright microscope and imaged before and after the addition of various NO concentrations. With the addition of increasing concentrations of NO, there is a decrease in the fluorescent signal emitted by the SWNT. (B) A schematic showing the change in fluorescence emission with the addition of NO. Full article ">Figure 2
Fluorescence quenching curves. (A) An example quenching curve before and after the addition of 10 µM NO. (B) Signal intensity over time, forming quenching curves that display the average response of the SWNT sensors to different concentrations of NO. Full article ">Figure 3
Difference in signal intensity for different NO concentrations. (A) The change in fluorescence intensity of the SWNT compared to NO concentration, with individual data points in red and averaged data points in black and (B) concentration curve (x = (y − 28.59)/3.73, with x = NO concentration in µM and y = difference in fluorescence intensity) that can be used to convert SWNT fluorescence changes into NO concentration. R2 value = 0.99. Full article ">Figure 4
Slope of signal intensity after the addition of different concentrations of NO. (A) The slope of the fluorescence intensity of the SWNT compared to NO concentration, with individual data points in blue and averaged data points in black and (B) concentration curve (x = −(y + 0.21)/0.42, with x = NO concentration in µM and y = slope of signal intensity) that can be used to convert SWNT fluorescence changes into NO concentration. R2 value = 0.99. Full article ">

15 pages, 4297 KiB

Open AccessArticle

High-Performance Humidity Sensor Based on the Graphene Flower/Zinc Oxide Composite

by Muhammad Saqib, Shenawar Ali Khan, Hafiz Mohammad Mutee Ur Rehman, Yunsook Yang, Seongwan Kim, Muhammad Muqeet Rehman and Woo Young Kim

Nanomaterials 2021, 11(1), 242; https://doi.org/10.3390/nano11010242 - 18 Jan 2021

Cited by 36 | Viewed by 4527

Abstract

Performance of an electronic device relies heavily on the availability of a suitable functional material. One of the simple, easy, and cost-effective ways to obtain novel functional materials with improved properties for desired applications is to make composites of selected materials. In this [...] Read more.

Performance of an electronic device relies heavily on the availability of a suitable functional material. One of the simple, easy, and cost-effective ways to obtain novel functional materials with improved properties for desired applications is to make composites of selected materials. In this work, a novel composite of transparent n-type zinc oxide (ZnO) with a wide bandgap and a unique structure of graphene in the form of a graphene flower (GrF) is synthesized and used as the functional layer of a humidity sensor. The (GrF/ZnO) composite was synthesized by a simple sol–gel method. Morphological, elemental, and structural characterizations of GrF/ZnO composite were performed by a field emission scanning electron microscope (FESEM), energy-dispersive spectroscopy (EDS), and an x-ray diffractometer (XRD), respectively, to fully understand the properties of this newly synthesized functional material. The proposed humidity sensor was tested in the relative humidity (RH) range of 15% RH% to 86% RH%. The demonstrated sensor illustrated a highly sensitive response to humidity with an average current change of 7.77 μA/RH%. Other prominent characteristics shown by this device include but were not limited to high stability, repeatable results, fast response, and quick recovery time. The proposed humidity sensor was highly sensitive to human breathing, thus making it a promising candidate for various applications related to health monitoring. Full article

(This article belongs to the Special Issue Nanomaterials and Devices)

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24 pages, 5782 KiB

Open AccessReview

Construction of Inorganic Bulks through Coalescence of Particle Precursors

by Zhao Mu, Ruikang Tang and Zhaoming Liu

Nanomaterials 2021, 11(1), 241; https://doi.org/10.3390/nano11010241 - 18 Jan 2021

Cited by 12 | Viewed by 4178

Abstract

Bulk inorganic materials play important roles in human society, and their construction is commonly achieved by the coalescence of inorganic nano- or micro-sized particles. Understanding the coalescence process promotes the elimination of particle interfaces, leading to continuous bulk phases with improved functions. In [...] Read more.

Bulk inorganic materials play important roles in human society, and their construction is commonly achieved by the coalescence of inorganic nano- or micro-sized particles. Understanding the coalescence process promotes the elimination of particle interfaces, leading to continuous bulk phases with improved functions. In this review, we mainly focus on the coalescence of ceramic and metal materials for bulk construction. The basic knowledge of coalescent mechanism on inorganic materials is briefly introduced. Then, the properties of the inorganic precursors, which determine the coalescent behaviors of inorganic phases, are discussed from the views of particle interface, size, crystallinity, and orientation. The relationships between fundamental discoveries and industrial applications are emphasized. Based upon the understandings, the applications of inorganic bulk materials produced by the coalescence of their particle precursors are further presented. In conclusion, the challenges of particle coalescence for bulk material construction are presented, and the connection between recent fundamental findings and industrial applications is highlighted, aiming to provide an insightful outlook for the future development of functional inorganic materials. Full article

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16 pages, 6800 KiB

Open AccessArticle

High Current Field Emission from Large-Area Indium Doped ZnO Nanowire Field Emitter Arrays for Flat-Panel X-ray Source Application

by Yangyang Zhao, Yicong Chen, Guofu Zhang, Runze Zhan, Juncong She, Shaozhi Deng and Jun Chen

Nanomaterials 2021, 11(1), 240; https://doi.org/10.3390/nano11010240 - 18 Jan 2021

Cited by 23 | Viewed by 3286

Abstract

Large-area zinc oxide (ZnO) nanowire arrays have important applications in flat-panel X-ray sources and detectors. Doping is an effective way to enhance the emission current by changing the nanowire conductivity and the lattice structure. In this paper, large-area indium-doped ZnO nanowire arrays were [...] Read more.

Large-area zinc oxide (ZnO) nanowire arrays have important applications in flat-panel X-ray sources and detectors. Doping is an effective way to enhance the emission current by changing the nanowire conductivity and the lattice structure. In this paper, large-area indium-doped ZnO nanowire arrays were prepared on indium-tin-oxide-coated glass substrates by the thermal oxidation method. Doping with indium concentrations up to 1 at% was achieved by directly oxidizing the In-Zn alloy thin film. The growth process was subsequently explained using a self-catalytic vapor-liquid-solid growth mechanism. The field emission measurements show that a high emission current of ~20 mA could be obtained from large-area In-doped sample with a 4.8 × 4.8 cm² area. This high emission current was attributed to the high crystallinity and conductivity change induced by the indium dopants. Furthermore, the application of these In-doped ZnO nanowire arrays in a flat-panel X-ray source was realized and distinct X-ray imaging was demonstrated. Full article

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12 pages, 3100 KiB

Open AccessArticle

A TiO₂ Coated Carbon Aerogel Derived from Bamboo Pulp Fibers for Enhanced Visible Light Photo-Catalytic Degradation of Methylene Blue

by Jian Zhang, Wei Yuan, Tian Xia, Chenghong Ao, Jiangqi Zhao, Bingxue Huang, Qunhao Wang, Wei Zhang and Canhui Lu

Nanomaterials 2021, 11(1), 239; https://doi.org/10.3390/nano11010239 - 18 Jan 2021

Cited by 27 | Viewed by 3472

Abstract

Carbon aerogels (CA) derived from bamboo cellulose fibers were coupled with TiO₂ to form CA/TiO₂ hybrids, which exhibited extraordinary performance on the photo-catalytic degradation of methylene blue (MB). The structure and morphology of CA/TiO₂ were characterized by field emission scanning [...] Read more.

Carbon aerogels (CA) derived from bamboo cellulose fibers were coupled with TiO₂ to form CA/TiO₂ hybrids, which exhibited extraordinary performance on the photo-catalytic degradation of methylene blue (MB). The structure and morphology of CA/TiO₂ were characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectrum. The CA displayed a highly porous and interconnected three-dimensional framework structure, while introducing the catalytic active sites of TiO₂ onto the aerogel scaffold could remarkably enhance its photo-catalytic activity. The adsorption and photo-catalytic degradation of MB by the CA/TiO₂ hybrid were investigated. The maximum adsorption capacity of CA/TiO₂ for MB was 18.5 mg/g, which outperformed many similar materials reported in the literature. In addition, compared with other photo-catalysts, the present CA/TiO₂ demonstrated superior photo-catalytic performance. Almost 85% of MB in 50 mL solution with a MB concentration of 10 mg/L could be effectively degraded by 15 mg CA/TiO₂ in 300 min. Full article

(This article belongs to the Special Issue Recent Advances in Nano-Hybrids of Cellulose and Carbon-Based Materials)

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12 pages, 2162 KiB

Open AccessArticle

Solvent-Free Mechanochemical Synthesis of ZnO Nanoparticles by High-Energy Ball Milling of ?-Zn(OH)₂ Crystals

by Gil Otis, Michal Ejgenberg and Yitzhak Mastai

Nanomaterials 2021, 11(1), 238; https://doi.org/10.3390/nano11010238 - 18 Jan 2021

Cited by 39 | Viewed by 5712

Abstract

A detailed investigation is presented for the solvent-free mechanochemical synthesis of zinc oxide nanoparticles from ε-Zn(OH)₂ crystals by high-energy ball milling. Only a few works have ever explored the dry synthetic route from ε-Zn(OH)₂ to ZnO. The milling process of ε-Zn(OH) [...] Read more.

A detailed investigation is presented for the solvent-free mechanochemical synthesis of zinc oxide nanoparticles from ε-Zn(OH)₂ crystals by high-energy ball milling. Only a few works have ever explored the dry synthetic route from ε-Zn(OH)₂ to ZnO. The milling process of ε-Zn(OH)₂ was done in ambient conditions with a 1:100 powder/ball mass ratio, and it produced uniform ZnO nanoparticles with sizes of 10–30 nm, based on the milling duration. The process was carefully monitored and the effect of the milling duration on the powder composition, nanoparticle size and strain, optical properties, aggregate size, and material activity was examined using XRD, TEM, DLS, UV-Vis, and FTIR. The mechanism for the transformation of ε-Zn(OH)₂ to ZnO was studied by TGA and XPS analysis. The study gave proof for a reaction mechanism starting with a phase transition of crystalline ε-Zn(OH)₂ to amorphous Zn(OH)₂, followed by decomposition to ZnO and water. To the best of our knowledge, this mechanochemical approach for synthesizing ZnO from ε-Zn(OH)₂ is completely novel. ε-Zn(OH)₂ crystals are very easy to obtain, and the milling process is done in ambient conditions; therefore, this work provides a simple, cheap, and solvent-free way to produce ZnO nanoparticles in dry conditions. We believe that this study could help to shed some light on the solvent-free transition from ε-Zn(OH)₂ to ZnO and that it could offer a new synthetic route for synthesizing ZnO nanoparticles. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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Graphical abstract

Graphical abstract
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Powder diffraction patterns of zinc oxides: (A) XRD spectra of ε-Zn(OH)2 (before milling) and milled products with different cycles; (1,0,0), (0,0,2), and (1,0,1) characteristic ZnO peaks are indicated. (B) Peak broadening and shifting of the (1,0,1) characteristic peak of ZnO. (C) Comparison of crystallite size calculated by the Scherrer and Williamson–Hall (WH) methods and lattice strain. Full article ">Figure 2
HRTEM images after 10 cycles indicating ZnO nanoparticle aggregates: (A) Large-scale image showing an aggregate consisting of small ZnO crystallites. (B) Small-scale image of nanocrystallites highlighting a crystallite with d-spacing of 2.81 angstrom fitting the (1,0,0) plane of ZnO (bottom right inset), and a SAED pattern of nanocrystalline aggregates (upper right inset). Full article ">Figure 3
Thermal gravimetric analysis of ZnO milled powders—a detailed analysis of the decomposition steps of samples after 2 (A), 5 (B), 8 (C), and 10 (D) cycles. Full article ">Figure 4
X-ray photoelectron spectroscopy (XPS) analysis of ZnO milled powders—0 1s XPS spectra of ε-Zn(OH)2 and milled powders examining the oxygen–zinc binding energy. Full article ">Figure 5
Methyl orange (MO) degradation assay. (A) Absorbance spectra of MO before and after exposure to UV radiation for 30 min (purple and yellow lines) and in the presence of powders after 2 (red), 5 (green), 8 (blue), and 10 (orange) cycles. (B) Degradation percentage of MO compared to the dye before UV exposure. Dye concentrations were calculated using the Beer–Lambert law. Full article ">

29 pages, 14653 KiB

Open AccessEditor’s ChoiceArticle

Investigations of Shape, Material and Excitation Wavelength Effects on Field Enhancement in SERS Advanced Tips

by Yaakov Mandelbaum, Raz Mottes, Zeev Zalevsky, David Zitoun and Avi Karsenty

Nanomaterials 2021, 11(1), 237; https://doi.org/10.3390/nano11010237 - 18 Jan 2021

Cited by 8 | Viewed by 3418

Abstract

This article, a part of the larger research project of Surface-Enhanced Raman Scattering (SERS), describes an advanced study focusing on the shapes and materials of Tip-Enhanced Raman Scattering (TERS) designated to serve as part of a novel imager device. The initial aim was [...] Read more.

This article, a part of the larger research project of Surface-Enhanced Raman Scattering (SERS), describes an advanced study focusing on the shapes and materials of Tip-Enhanced Raman Scattering (TERS) designated to serve as part of a novel imager device. The initial aim was to define the optimal shape of the “probe”: tip or cavity, round or sharp. The investigations focused on the effect of shape (hemi-sphere, hemispheroid, ellipsoidal cavity, ellipsoidal rod, nano-cone), and the effect of material (Ag, Au, Al) on enhancement, as well as the effect of excitation wavelengths on the electric field. Complementary results were collected: numerical simulations consolidated with analytical models, based on solid assumptions. Preliminary experimental results of fabrication and structural characterization are also presented. Thorough analyses were performed around critical parameters, such as the plasmonic metal—Silver, Aluminium or Gold—using Rakic model, the tip geometry—sphere, spheroid, ellipsoid, nano-cone, nano-shell, rod, cavity—and the geometry of the plasmonic array: cross-talk in multiple nanostructures. These combined outcomes result in an optimized TERS design for a large number of applications. Full article

(This article belongs to the Special Issue Application of SERS for Nanomaterials)

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22 pages, 6456 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Theoretical Studies on Sustainable Synthesis of Gold Sol Displaying Dichroic Effect

by Anshuman Jakhmola, Raffaele Vecchione, Valentina Onesto, Francesco Gentile, Maurizio Celentano and Paolo Antonio Netti

Nanomaterials 2021, 11(1), 236; https://doi.org/10.3390/nano11010236 - 18 Jan 2021

Cited by 19 | Viewed by 4084

Abstract

Gold nanoparticles depending on their shape and mixtures of multiple shapes can exhibit peculiar optical properties, including the dichroic effect typical of the Lycurgus cup, which has puzzled scientists for a long time. Such optical properties have been recently exploited in several fields [...] Read more.

Gold nanoparticles depending on their shape and mixtures of multiple shapes can exhibit peculiar optical properties, including the dichroic effect typical of the Lycurgus cup, which has puzzled scientists for a long time. Such optical properties have been recently exploited in several fields such as paint technology, sensors, dichroic polarizers, display (LCD) devices, laser applications, solar cells and photothermal therapy among others. In this article, we have demonstrated a simple room temperature one-pot synthesis of gold sol displaying a dichroic effect using a slow reduction protocol involving only trisodium citrate as a reducing agent. We found that the dichroic gold sol can be easily formed at room temperature by reducing gold salt by trisodium citrate below a certain critical concentration. The sol displayed an orangish-brown color in scattered/reflected light and violet/blue/indigo/purple/red/pink in transmitted light, depending on the experimental conditions. With minor changes such as the introduction of a third molecule or replacing a small amount of water in the reaction mixture with ethanol, the color of the gold sol under transmitted light changed and a variety of shades of red, pink, cobalt blue, violet, magenta and purple were obtained. The main advantage of the proposed method lies in its simplicity, which involves the identification of the right ratio of the reactants, and simple mixing of reactants at room temperature with no other requirements. TEM micrographs displayed the formation of two main types of particles viz. single crystal gold nanoplates and polycrystalline faceted polyhedron nanoparticles. The mechanism of growth of the nanoplates and faceted polyhedron particles have been described by an enhanced diffusion limited aggregation numerical scheme, where it was assumed that both trisodium citrate and the gold ions in solution undergo a stochastic Brownian motion, and that the evolution of the entire system is regulated by a principle of energy minimization. The predictions of the model matched with the experiments with a good accuracy, indicating that the initial hypothesis is correct. Full article

(This article belongs to the Special Issue Computational Modeling and Simulation for Nanomaterials, Nanotechnology, and Nanoscience)

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17 pages, 8854 KiB

Open AccessArticle

Stabilization of Calcium Oxalate Precursors during the Pre- and Post-Nucleation Stages with Poly(acrylic acid)

by Felipe Díaz-Soler, Carlos Rodriguez-Navarro, Encarnación Ruiz-Agudo and Andrónico Neira-Carrillo

Nanomaterials 2021, 11(1), 235; https://doi.org/10.3390/nano11010235 - 18 Jan 2021

Cited by 8 | Viewed by 2698

Abstract

In this work, calcium oxalate (CaOx) precursors were stabilized by poly(acrylic acid) (PAA) as an additive under in vitro crystallization assays involving the formation of pre-nucleation clusters of CaOx via a non-classical crystallization (NCC) pathway. The in vitro crystallization of CaOx was carried [...] Read more.

In this work, calcium oxalate (CaOx) precursors were stabilized by poly(acrylic acid) (PAA) as an additive under in vitro crystallization assays involving the formation of pre-nucleation clusters of CaOx via a non-classical crystallization (NCC) pathway. The in vitro crystallization of CaOx was carried out in the presence of 10, 50 and 100 mg/L PAA by using automatic calcium potentiometric titration experiments at a constant pH of 6.7 at 20 °C. The results confirmed the successful stabilization of amorphous calcium oxalate II and III (ACOII and ACO III) nanoparticles formed after PNC in the presence of PAA and suggest the participation and stabilization of polymer-induced liquid-precursor (PILP) in the presence of PAA. We demonstrated that PAA stabilizes CaOx precursors with size in the range of 20–400 nm. PAA additive plays a key role in the in vitro crystallization of CaOx stabilizing multi-ion complexes in the pre-nucleation stage, thereby delaying the nucleation of ACO nanoparticles. Indeed, PAA additive favors the formation of more hydrated and soluble phase of ACO nanoparticles that are bound by electrostatic interactions to carboxylic acid groups of PAA during the post-nucleation stage. These findings may help to a better understanding of the pathological mineralization resulting in urolithiasis in mammals. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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18 pages, 6779 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synthesis of Nanoparticles by Spark Discharge as a Facile and Versatile Technique of Preparing Highly Conductive Pt Nano-Ink for Printed Electronics

by Alexey A. Efimov, Pavel V. Arsenov, Vladislav I. Borisov, Arseny I. Buchnev, Anna A. Lizunova, Denis V. Kornyushin, Sergey S. Tikhonov, Andrey G. Musaev, Maxim N. Urazov, Mikhail I. Shcherbakov, Denis V. Spirin and Victor V. Ivanov

Nanomaterials 2021, 11(1), 234; https://doi.org/10.3390/nano11010234 - 18 Jan 2021

Cited by 29 | Viewed by 5660

Abstract

A cost-effective, scalable and versatile method of preparing nano-ink without hazardous chemical precursors is a prerequisite for widespread adoption of printed electronics. Precursor-free synthesis by spark discharge is promising for this purpose. The synthesis of platinum nanoparticles (PtNPs) using a spark discharge under [...] Read more.

A cost-effective, scalable and versatile method of preparing nano-ink without hazardous chemical precursors is a prerequisite for widespread adoption of printed electronics. Precursor-free synthesis by spark discharge is promising for this purpose. The synthesis of platinum nanoparticles (PtNPs) using a spark discharge under Ar, N₂, and air has been investigated to prepare highly conductive nano-ink. The size, chemical composition, and mass production rate of PtNPs significantly depended on the carrier gas. Pure metallic PtNPs with sizes of 5.5 ± 1.8 and 7.1 ± 2.4 nm were formed under Ar and N₂, respectively. PtNPs with sizes of 18.2 ± 9.0 nm produced using air consisted of amorphous oxide PtO and metallic Pt. The mass production rates of PtNPs were 53 ± 6, 366 ± 59, and 490 ± 36 mg/h using a spark discharge under Ar, N₂, and air, respectively. It was found that the energy dissipated in the spark gap is not a significant parameter that determines the mass production rate. Stable Pt nano-ink (25 wt.%) was prepared only on the basis of PtNPs synthesized under air. Narrow (about 30 ?m) and conductive Pt lines were formed by the aerosol jet printing with prepared nano-ink. The resistivity of the Pt lines sintered at 750 °C was (1.2 ± 0.1)·10^?7 ?·m, which is about 1.1 times higher than that of bulk Pt. Full article

(This article belongs to the Special Issue Cutting‐Edge Nanomaterials for Electronics in Asia: Synthesis, Properties, and Applications)

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13 pages, 2851 KiB

Open AccessArticle

Au/CdS Core-Shell Sensitized Actinomorphic Flower-Like ZnO Nanorods for Enhanced Photocatalytic Water Splitting Performance

by Ying Li, Tie Liu, Shuang Feng, Wenshu Yang, Ying Zhu, Yingying Zhao, Zhiyan Liu, Haibin Yang and Wuyou Fu

Nanomaterials 2021, 11(1), 233; https://doi.org/10.3390/nano11010233 - 17 Jan 2021

Cited by 11 | Viewed by 3061

Abstract

Herein, a novel actinomorphic flower-like ZnO/Au/CdS nanorods ternary composite photocatalyst is prepared to extend the light-responsive range, reduce the photogenerated charge carriers recombination, and ultimately improve the water splitting performance. Flower-like ZnO nanorods are synthesized by a chemical bath method and the CdS [...] Read more.

Herein, a novel actinomorphic flower-like ZnO/Au/CdS nanorods ternary composite photocatalyst is prepared to extend the light-responsive range, reduce the photogenerated charge carriers recombination, and ultimately improve the water splitting performance. Flower-like ZnO nanorods are synthesized by a chemical bath method and the CdS nanoparticles are sensitized by successive ionic layer adsorption and reaction method. Then the Au nanoparticles as co-catalysts are introduced by the photodeposition method to modify the interface of ZnO/CdS for reducing the photogenerated electron recombination rate and further improving the performance of water splitting. Detailed characterizations and measurements are employed to analyse the crystallinity, morphology, composition, and optical properties of the flower-like ZnO/Au/CdS nanorods samples. As a result, the flower-like ZnO/Au/CdS nanorod samples present significantly enhanced water splitting performance with a high gas evolution rate of 502.2 μmol/g/h, which is about 22.5 and 1.5 times higher than that of the pure ZnO sample and ZnO/CdS sample. The results demonstrate that the flower-like ZnO/Au/CdS nanorods ternary composite materials have great application potential in photocatalytic water splitting for the hydrogen evolution field. Full article

(This article belongs to the Section Energy and Catalysis)

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16 pages, 3639 KiB

Open AccessReview

Carbon Dots-Based Logic Gates

by Shweta Pawar, Hamootal Duadi, Yafit Fleger and Dror Fixler

Nanomaterials 2021, 11(1), 232; https://doi.org/10.3390/nano11010232 - 17 Jan 2021

Cited by 27 | Viewed by 4535

Abstract

Carbon dots (CDs)-based logic gates are smart nanoprobes that can respond to various analytes such as metal cations, anions, amino acids, pesticides, antioxidants, etc. Most of these logic gates are based on fluorescence techniques because they are inexpensive, give an instant response, and [...] Read more.

Carbon dots (CDs)-based logic gates are smart nanoprobes that can respond to various analytes such as metal cations, anions, amino acids, pesticides, antioxidants, etc. Most of these logic gates are based on fluorescence techniques because they are inexpensive, give an instant response, and highly sensitive. Computations based on molecular logic can lead to advancement in modern science. This review focuses on different logic functions based on the sensing abilities of CDs and their synthesis. We also discuss the sensing mechanism of these logic gates and bring different types of possible logic operations. This review envisions that CDs-based logic gates have a promising future in computing nanodevices. In addition, we cover the advancement in CDs-based logic gates with the focus of understanding the fundamentals of how CDs have the potential for performing various logic functions depending upon their different categories. Full article

(This article belongs to the Special Issue Carbon-Based Nanocomposites for Biosensing Approaches)

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13 pages, 6160 KiB

Open AccessArticle

The Adsorption of H₂ and C₂H₂ on Ge-Doped and Cr-Doped Graphene Structures: A DFT Study

by Yiming Liao, Ruochen Peng, Shudi Peng, Wen Zeng and Qu Zhou

Nanomaterials 2021, 11(1), 231; https://doi.org/10.3390/nano11010231 - 16 Jan 2021

Cited by 31 | Viewed by 3443

Abstract

In order to find an excellent sensing material for dissolved gases in transformer oil, the adsorption structures of intrinsic graphene (IG), Ge-doped graphene (GeG), and Cr-doped graphene (CrG) to H₂ and C₂H₂ gas molecules were built. It was found [...] Read more.

In order to find an excellent sensing material for dissolved gases in transformer oil, the adsorption structures of intrinsic graphene (IG), Ge-doped graphene (GeG), and Cr-doped graphene (CrG) to H₂ and C₂H₂ gas molecules were built. It was found that the doping site right above C atom (T) was the most stable structure by studying three potential doping positions of the Ge and Cr atom on the graphene surface. Then, the structural parameters, density of states, and difference state density of these adsorption systems were calculated and analyzed based on the density functional calculations. The results show that the adsorption properties of GeG and CrG systems for H₂ and C₂H₂ are obviously better than the IG system. Furthermore, by comparing the two doping systems, CrG system exhibits more outstanding adsorption performances to H₂ and C₂H₂, especially for C₂H₂ gas. Finally, the highest adsorption energy (−1.436 eV) and the shortest adsorption distance (1.981 Å) indicate that Cr-doped graphene is promising in the field of C₂H₂ gas-sensing detection. Full article

(This article belongs to the Special Issue State-of-the-Art Nanomaterials and Nanotechnology in China)

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21 pages, 4709 KiB

Open AccessArticle

Colloidally Stable P(DMA-AGME)-Ale-Coated Gd(Tb)F₃:Tb³⁺(Gd³⁺),Yb³⁺,Nd³⁺ Nanoparticles as a Multimodal Contrast Agent for Down- and Upconversion Luminescence, Magnetic Resonance Imaging, and Computed Tomography

by Oleksandr Shapoval, Viktoriia Oleksa, Miroslav Šlouf, Volodymyr Lobaz, Olga Trhlíková, Marcela Filipová, Olga Janoušková, Hana Engstová, Jan Pankrác, Adam Modrý, Vít Herynek, Petr Ježek, Luděk Šefc and Daniel Horák

Nanomaterials 2021, 11(1), 230; https://doi.org/10.3390/nano11010230 - 16 Jan 2021

Cited by 14 | Viewed by 4014

Abstract

Multimodal imaging, integrating several modalities including down- and up-conversion luminescence, T₁- and T₂(T₂*)-weighted MRI, and CT contrasting in one system, is very promising for improved diagnosis of severe medical disorders. To reach the goal, it is [...] Read more.

Multimodal imaging, integrating several modalities including down- and up-conversion luminescence, T₁- and T₂(T₂*)-weighted MRI, and CT contrasting in one system, is very promising for improved diagnosis of severe medical disorders. To reach the goal, it is necessary to develop suitable nanoparticles that are highly colloidally stable in biologically relevant media. Here, hydrophilic poly(N,N-dimethylacrylamide-N-acryloylglycine methyl ester)-alendronate-[P(DMA-AGME)-Ale]-coated Gd(Tb)F₃:Tb³⁺(Gd³⁺),Yb³⁺,Nd³⁺ nanoparticles were synthesized by a coprecipitation method in ethylene glycol (EG) followed by coating with the polymer. The particles were tho-roughly characterized by a dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray energy dispersive spectroscopy (EDAX), selected area electron diffraction (SAED), elemental ana-lysis and fluorescence spectroscopy. Aqueous particle dispersions exhibited excellent colloidal stability in water and physiological buffers. In vitro toxicity assessments suggested no or only mild toxicity of the surface-engineered Gd(Tb)F₃:Tb³⁺(Gd³⁺),Yb³⁺,Nd³⁺ particles in a wide range of concentrations. Internalization of the particles by several types of cells, including HeLa, HF, HepG2, and INS, was confirmed by a down- and up-conversion confocal microscopy. Newly developed particles thus proved to be an efficient contrast agent for fluorescence imaging, T₁- and T₂(T₂*)-weighted magnetic resonance imaging (MRI), and computed tomography (CT). Full article

(This article belongs to the Special Issue Nanomaterials for Contrast Agent and Biomedical Imaging)

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14 pages, 1719 KiB

Open AccessArticle

Single and Repeated Applications of Cerium Oxide Nanoparticles Differently Affect the Growth and Biomass Accumulation of Silene flos-cuculi L. (Caryophyllaceae)

by Daniel Lizzi, Alessandro Mattiello, Barbara Piani, Emanuele Gava, Guido Fellet and Luca Marchiol

Nanomaterials 2021, 11(1), 229; https://doi.org/10.3390/nano11010229 - 16 Jan 2021

Cited by 7 | Viewed by 2396

Abstract

Cerium oxide nanoparticles (nCeO₂) have a wide variety of applications in industry. Models demonstrated that nCeO₂ can reach environmental compartments. Studies regarding the relationships between plants and nCeO₂ considered only crop species, whereas a relevant [...] Read more.

Cerium oxide nanoparticles (nCeO₂) have a wide variety of applications in industry. Models demonstrated that nCeO₂ can reach environmental compartments. Studies regarding the relationships between plants and nCeO₂ considered only crop species, whereas a relevant knowledge gap exists regarding wild plant species. Specimens of Silene flos-cuculi (Caryophyllaceae) were grown in greenhouse conditions in a substrate amended with a single dose (D1) and two and three doses (D2 and D3) of 20 mg kg⁻¹ and 200 mg kg⁻¹nCeO₂ suspensions, respectively. sp-ICP-MS and ICP-MS data demonstrated that nCeO₂ was taken up by plant roots and translocated towards aerial plant fractions. Biometric variables showed that plants responded negatively to the treatments with a shortage in biomass of roots and stems. Although not at relevant concentrations, Ce was accumulated mainly in roots and plant leaves. Full article

(This article belongs to the Special Issue The Genetic Changes Induced by Engineered Manufactured Nanomaterials (EMNs))

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(A) Experimental setup showing the combination of treatments: control, single-, double-, and triple-dosed plants (Ctrl, D1, D2, and D3, respectively); (B) S. flos-cuculi plants at 40 DSE. Full article ">Figure 2
(A) Particle size distribution obtained by dynamic light scattering (DLS). (B) Transmission electron microscopy (TEM) image of nCeO2 25 nm suspension. Full article ">Figure 3
Particle size distribution of nCeO2 extracted after enzymatic digestion procedure from (A) roots and (B) leaves of S. flos-cuculi. Full article ">Figure 4
Root dry mass of S. flos cuculi. Comparison of effects based on single (D1) and repeated (D2, D3) applications of 20 and 200 mg kg−1 nCeO2, respectively. Letters indicate statistically significant difference between treatments (p ≤ 0.05) using one-way ANOVA followed by Tukey’s test. † One-way ANOVA p-value within each concentration: asterisks indicate the statistically significant difference of dose factor at * 0.05 ≥ p ≥ 0.01; ***p ≥ 0.001, respectively. Full article ">Figure 5
Stem dry mass of S. flos cuculi. Comparison of effects based on single (D1) and repeated applications (D2, D3) of 20 and 200 mg kg−1 nCeO2, respectively. Letters indicate statistically significant difference between treatments (p ≤ 0.05) using one-way ANOVA followed by Tukey’s test. † One-way ANOVA p-value within each concentration. Full article ">Figure 6
Plant dry mass of S. flos cuculi. Comparison of effects based on single (D1) and repeated applications (D2, D3) of 20 and 200 mg kg−1 nCeO2, respectively. Letters indicate statistically significant difference between treatments (p ≤ 0.05) using one-way ANOVA followed by Tukey’s test. † One-way ANOVA p-value within each concentration. Full article ">

18 pages, 5809 KiB

Open AccessArticle

Construction and Mechanism Analysis of a Self-Assembled Conductive Network in DGEBA/PEI/HRGO Nanocomposites by Controlling Filler Selective Localization

by Yiming Meng, Sushant Sharma, Wenjun Gan, Seung Hyun Hur, Won Mook Choi and Jin Suk Chung

Nanomaterials 2021, 11(1), 228; https://doi.org/10.3390/nano11010228 - 16 Jan 2021

Cited by 6 | Viewed by 3068

Abstract

Herein, a feasible and effective approach is developed to build an electrically conductive and double percolation network-like structure via the incorporation of highly reduced graphene oxide (HRGO) into a polymer blend of diglycidyl ether of bisphenol A/polyetherimide (DGEBA/PEI). With the assistance of the [...] Read more.

Herein, a feasible and effective approach is developed to build an electrically conductive and double percolation network-like structure via the incorporation of highly reduced graphene oxide (HRGO) into a polymer blend of diglycidyl ether of bisphenol A/polyetherimide (DGEBA/PEI). With the assistance of the curing reaction-induced phase separation (CRIPS) technique, an interconnected network of HRGO is formed in the phase-separated structure of the DGEBA/PEI polymer blend due to selective localization behavior. In this study, HRGO was prepared from a unique chemical reduction technique. The DGEBA/PEI/HRGO nanocomposite was analyzed in terms of phase structure by content of PEI and low weight fractions of HRGO (0.5 wt.%). The HRGO delivered a high electrical conductivity in DGEBA/PEI polyblends, wherein the value increased from 5.03 × 10⁻¹⁶ S/m to 5.88 S/m at a low content of HRGO (0.5 wt.%). Furthermore, the HRGO accelerated the curing reaction process of CRIPS due to its amino group. Finally, dynamic mechanical analyses (DMA) were performed to understand the CRIPS phenomenon and selective localization of HRGO reinforcement. The storage modulus increased monotonically from 1536 MPa to 1660 MPa for the 25 phr (parts per hundred in the DGEBA) PEI polyblend and reached 1915 MPa with 0.5 wt.% HRGO reinforcement. These simultaneous improvements in electrical conductivity and dynamic mechanical properties clearly demonstrate the potential of this conductive polyblend for various engineering applications. Full article

(This article belongs to the Special Issue Multifunctional Polymer-Based Nanocomposite Materials)

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Schematic illustration of preparation of DGEBA/PEI/HRGO polyblend nanocomposites and the phase structure during the process. Full article ">Figure 2
(a) SEM micrograph of HRGO flakes after drying, (b) TEM micrograph of HRGO and (c) Raman spectra of GO and HRGO flakes. Full article ">Figure 3
The final phase morphologies of DGEBA/PEI/HRGO nanocomposites are (a) DP5H, (b) DP10H, (c) DP15H, (d) DP20H, (e) DP25H, (f) DP30H, and (g) DP30, respectively. Full article ">Figure 4
FETEM micrographs of (a–c) DP25H polyblend from lower to higher magnification with inset in (c) represents HRTEM micrograph of localized HRGO at the interphase of DGEBA and PEI, and (d–f) represents DP30H polyblend with phase inversion. Full article ">Figure 5
The electrical properties of samples for various PEI contents: (a) DGEBA/PEI, (b) DGEBA/PEI/0.5 wt.% HRGO. Full article ">Figure 6
Schematic illustration: (a) structural evolution of double percolation conductive DGEBA/PEI/HRGO nanocomposites via CRIPS and (b) FETEM image of nanocomposite. Full article ">Figure 7
The storage modulus versus temperature of DGEBA/PEI polyblend (a) at 30–230 °C and (b) a magnified view of the beginning of the transition (80–130 °C). Storage modulus versus temperature curves for DGEBA/PEI/HRGO nanocomposites with 0.5 wt.% HRGO at (c) 30–230 °C and (d) 80–130 °C. Full article ">Figure 8
Tan δ versus temperature curve for DGEBA/PEI polyblend: (a) 30–230 °C, (b) 100–150 °C for Tg1, (c) 150–230 °C for Tg2, and tan δ versus temperature curve for DGEBA/PEI/HRGO nanocomposites: (d) 30–230 °C, (e) 100–150 °C for Tg1, (f) 150–230 °C for Tg2. Full article ">

11 pages, 3152 KiB

Open AccessArticle

Fluorescence Signal Enhancement in Antibody Microarrays Using Lightguiding Nanowires

by Damiano Verardo, Leena Liljedahl, Corinna Richter, Björn Agnarsson, Ulrika Axelsson, Christelle N. Prinz, Fredrik Höök, Carl A. K. Borrebaeck and Heiner Linke

Nanomaterials 2021, 11(1), 227; https://doi.org/10.3390/nano11010227 - 16 Jan 2021

Cited by 12 | Viewed by 3290

Abstract

Fluorescence-based detection assays play an essential role in the life sciences and medicine. To offer better detection sensitivity and lower limits of detection (LOD), there is a growing need for novel platforms with an improved readout capacity. In this context, substrates containing semiconductor [...] Read more.

Fluorescence-based detection assays play an essential role in the life sciences and medicine. To offer better detection sensitivity and lower limits of detection (LOD), there is a growing need for novel platforms with an improved readout capacity. In this context, substrates containing semiconductor nanowires may offer significant advantages, due to their proven light-emission enhancing, waveguiding properties, and increased surface area. To demonstrate and evaluate the potential of such nanowires in the context of diagnostic assays, we have in this work adopted a well-established single-chain fragment antibody-based assay, based on a protocol previously designed for biomarker detection using planar microarrays, to freestanding, SiO₂-coated gallium phosphide nanowires. The assay was used for the detection of protein biomarkers in highly complex human serum at high dilution. The signal quality was quantified and compared with results obtained on conventional flat silicon and plastic substrates used in the established microarray applications. Our results show that using the nanowire-sensor platform in combination with conventional readout methods, improves the signal intensity, contrast, and signal-to-noise by more than one order of magnitude compared to flat surfaces. The results confirm the potential of lightguiding nanowires for signal enhancement and their capacity to improve the LOD of standard diagnostic assays. Full article

(This article belongs to the Special Issue Growth, Characterization, and Modelling of Nanostructures for Applications in Sensing)

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Full article ">Figure 1
Scanning electron microscopy images of the GaP nanowires used in this study, taken at 30° and 0° stage inclination (perpendicular view). Full article ">Figure 2
(a) Schematic representation of the single chain fragment variable (scFv) assay used in this study. ScFv antibodies (pink) are physisorbed on a surface. A blocking agent (green) is subsequently used to minimize unspecific binding of biotinylated serum proteins (blue), which are targeted by fluorescently labelled streptavidin (dark red). (b,c) Schematic representation of the assay on a flat substrate (b) and a light-guiding nanowire substrate (c): the emission of fluorophores on the nanowire surface excites the supported waveguide modes to be reemitted at the tip, leading to an enhanced signal intensity at the tip of the nanowires. (d–f) Top-view epifluorescence images (displayed in the same pixel window) of (d) a GaP nanowire substrate, (e) a silicon substrate and (f) a MaxiSorp black polymer substrate, spotted with antibodies and exposed biotinylated serum concentration diluted to 0.4% (the highest concentration used in this study). Individual nanowires are visible in (d) as bright spots. The edge of the scFv spot is visible in (e,f), showing the difference in the signal between specific an unspecific binding to the antibodies. Full article ">Figure 3
Image analysis for signal extraction on (a) MaxiSorp black polymer plastic spotted with antibodies and exposed to 0.4% serum concentration, (b) scFv-spotted nanowires exposed to 0.4% serum concentration, and (c) non-spotted nanowires exposed only to 0.4% serum concentration (control sample). Panel (a) is displayed in a different pixel window than panels (b,c) to better show the contrast between spotted and non-spotted areas in (a). On flat substrates, the signal and background intensity are extracted as the mean pixel value in the areas inside (blue) and outside (red) the scFv spot, respectively. On nanowire samples, Is is the mean pixel intensity on nanowire positions, (highlighted in blue in (b)). Similarly, IB is the mean pixel intensity on nanowire positions on the control substrate (red in (c)). Full article ">Figure 4
Left: extracted values of signal intensity Is, Weber contrast CW, and signal to noise ration (SNR) for the various scFvs on the three substrates tested with 0.4% serum concentration. All three parameters are consistently higher on the nanowire substrates. Right: example of the effect of serum concentration for the PC070 scFv. Decreasing the serum concentration results in a decrease in the signal, with 0.1% concentration approaching the limit for reliable signal on nanowires. Data for all tested scFvs are shown in the <a href="#app1-nanomaterials-11-00227" class="html-app">Figure S1</a>. Comparison graph in logarithmic scale are shown in the <a href="#app1-nanomaterials-11-00227" class="html-app">Figure S2</a>. Full article ">

10 pages, 2042 KiB

Open AccessCommunication

Spectral-Phase Interferometry Detection of Ochratoxin A via Aptamer-Functionalized Graphene Coated Glass

by Nikita Nekrasov, Natalya Yakunina, Averyan V. Pushkarev, Alexey V. Orlov, Ivana Gadjanski, Amaia Pesquera, Alba Centeno, Amaia Zurutuza, Petr I. Nikitin and Ivan Bobrinetskiy

Nanomaterials 2021, 11(1), 226; https://doi.org/10.3390/nano11010226 - 16 Jan 2021

Cited by 16 | Viewed by 3392

Abstract

In this work, we report a novel method of label-free detection of small molecules based on direct observation of interferometric signal change in graphene-modified glasses. The interferometric sensor chips are fabricated via a conventional wet transfer method of CVD-grown graphene onto the glass [...] Read more.

In this work, we report a novel method of label-free detection of small molecules based on direct observation of interferometric signal change in graphene-modified glasses. The interferometric sensor chips are fabricated via a conventional wet transfer method of CVD-grown graphene onto the glass coverslips, lowering the device cost and allowing for upscaling the sensor fabrication. For the first time, we report the use of graphene functionalized by the aptamer as the bioreceptor, in conjunction with Spectral-Phase Interferometry (SPI) for detection of ochratoxin A (OTA). In a direct assay with an OTA-specific aptamer, we demonstrated a quick and significant change of the optical signal in response to the maximum tolerable level of OTA concentration. The sensor regeneration is possible in urea solution. The developed platform enables a direct method of kinetic analysis of small molecules using a low-cost optical chip with a graphene-aptamer sensing layer. Full article

(This article belongs to the Special Issue Electronic Structure, Optical, Electrical Properties and Applications of Chemically Modified Graphene)

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18 pages, 6872 KiB

Open AccessArticle

Comparing the Degradation Potential of Copper(II), Iron(II), Iron(III) Oxides, and Their Composite Nanoparticles in a Heterogeneous Photo-Fenton System

by Asfandyar Khan, Zsolt Valicsek and Ottó Horváth

Nanomaterials 2021, 11(1), 225; https://doi.org/10.3390/nano11010225 - 16 Jan 2021

Cited by 6 | Viewed by 3492

Abstract

Heterogeneous photo-Fenton systems offer efficient solutions for the treatment of wastewaters in the textile industry. This study investigated the fabrication and structural characterization of novel peculiar-shaped Cu^IIO, Fe^III₂O₃, and Fe^IIO nanoparticles (NPs) compared to [...] Read more.

Heterogeneous photo-Fenton systems offer efficient solutions for the treatment of wastewaters in the textile industry. This study investigated the fabrication and structural characterization of novel peculiar-shaped Cu^IIO, Fe^III₂O₃, and Fe^IIO nanoparticles (NPs) compared to the properties of the iron(II)-doped copper ferrite Cu^II_0.4Fe^II_0.6Fe^III₂O₄. The photocatalytic efficiencies of these NPs and the composite of the simple oxides (Cu^IIO/Fe^IIO/Fe^III₂O₃) regarding the degradation of methylene blue (MB) and rhodamine B (RhB) as model dyes were also determined. The catalysts were synthesized via simple co-precipitation and calcination technique. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS) were utilized for structural characterization. The structure of Cu^IIO was bead-like connected into threads, Fe^III₂O₃ was rod-like, while Fe^IIO pallet-like, with average crystallite sizes of 18.9, 36.9, and 37.1 nm, respectively. The highest degradation efficiency was achieved by Cu^IIO for RhB and by Cu^II_0.4Fe^II_0.6Fe^III₂O₄ for MB. The Cu^IIO/Fe^IIO/Fe^III₂O₃ composite proved to be the second-best catalyst in both cases, with excellent reusability. Hence, these NPs can be successfully applied as heterogeneous photo-Fenton catalysts for the removal of hazardous pollutants. Moreover, the simple metal oxides and the iron(II)-doped copper ferrite displayed a sufficient antibacterial activity against Gram-negative Vibrio fischeri. Full article

(This article belongs to the Special Issue Latest Developments in Photocatalytic Materials and Processes)

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