Research

16 pages, 5954 KiB

Open AccessArticle

Study of Physico-Chemical Interactions during the Production of Silver Citrate Nanocomposites with Hemp Fiber

by Alexandru Cocean, Iuliana Cocean, Georgiana Cocean, Cristina Postolachi, Daniela Angelica Pricop, Bogdanel Silvestru Munteanu, Nicanor Cimpoesu and Silviu Gurlui

Nanomaterials 2021, 11(10), 2560; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11102560 - 29 Sep 2021

Cited by 2 | Viewed by 1858

Abstract

In the study presented in this paper, the results obtained by producing nanocomposites consisting of a silver citrate thin layer deposited on hemp fiber surfaces are analyzed. Using the pulsed laser deposition (PLD) method applied to a silver target with impurities of nickel [...] Read more.

In the study presented in this paper, the results obtained by producing nanocomposites consisting of a silver citrate thin layer deposited on hemp fiber surfaces are analyzed. Using the pulsed laser deposition (PLD) method applied to a silver target with impurities of nickel and iron, the formation of the silver citrate film is performed in various ways and the results are discussed based on Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX) spectroscopy analyses. A mechanism of the physico-chemical processes that take place based on the FTIR vibrational modes and the elemental composition established by the SEM-EDS analysis is proposed. Inhibition of the fermentation process of Saccharomyces cerevisae is demonstrated for the nanocomposite material of the silver citrate thin layer, obtained by means of the PLD method, on hemp fabric. The usefulness of composite materials of this type can extend from sensors and optoelectronics to the medical fields of analysis and treatment. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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30 pages, 35127 KiB

Open AccessArticle

Obtaining Nanostructured ZnO onto Si Coatings for Optoelectronic Applications via Eco-Friendly Chemical Preparation Routes

by Mirela Petruta Suchea, Evangelia Petromichelaki, Cosmin Romanitan, Maria Androulidaki, Alexandra Manousaki, Zacharias Viskadourakis, Rabia Ikram, Petronela Pascariu and George Kenanakis

Nanomaterials 2021, 11(10), 2490; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11102490 - 24 Sep 2021

Cited by 3 | Viewed by 2301

Abstract

Although the research on zinc oxide (ZnO) has a very long history and its applications are almost countless as the publications on this subject are extensive, this semiconductor is still full of resources and continues to offer very interesting results worth publishing or [...] Read more.

Although the research on zinc oxide (ZnO) has a very long history and its applications are almost countless as the publications on this subject are extensive, this semiconductor is still full of resources and continues to offer very interesting results worth publishing or warrants further investigation. The recent years are marked by the development of novel green chemical synthesis routes for semiconductor fabrication in order to reduce the environmental impacts associated with synthesis on one hand and to inhibit/suppress the toxicity and hazards at the end of their lifecycle on the other hand. In this context, this study focused on the development of various kinds of nanostructured ZnO onto Si substrates via chemical route synthesis using both classic solvents and some usual non-toxic beverages to substitute the expensive high purity reagents acquired from specialized providers. To our knowledge, this represents the first systematic study involving common beverages as reagents in order to obtain ZnO coatings onto Si for optoelectronic applications by the Aqueous Chemical Growth (ACG) technique. Moreover, the present study offers comparative information on obtaining nanostructured ZnO coatings with a large variety of bulk and surface morphologies consisting of crystalline nanostructures. It was revealed from X-ray diffraction analysis via Williamson–Hall plots that the resulting wurtzite ZnO has a large crystallite size and small lattice strain. These morphological features resulted in good optical properties, as proved by photoluminescence (PL) measurements even at room temperature (295 K). Good optical properties could be ascribed to complex surface structuring and large surface-to-volume ratios. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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19 pages, 9442 KiB

Open AccessArticle

Thickness Effect on Some Physical Properties of RF Sputtered ZnTe Thin Films for Potential Photovoltaic Applications

by Dumitru Manica, Vlad-Andrei Antohe, Antoniu Moldovan, Rovena Pascu, Sorina Iftimie, Lucian Ion, Mirela Petruta Suchea and Ştefan Antohe

Nanomaterials 2021, 11(9), 2286; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11092286 - 02 Sep 2021

Cited by 10 | Viewed by 2107

Abstract

Zinc telluride thin films with different thicknesses were grown onto glass substrates by the rf magnetron sputtering technique, using time as a variable growth parameter. All other deposition process parameters were kept constant. The deposited thin films with thickness from 75 to 460 [...] Read more.

Zinc telluride thin films with different thicknesses were grown onto glass substrates by the rf magnetron sputtering technique, using time as a variable growth parameter. All other deposition process parameters were kept constant. The deposited thin films with thickness from 75 to 460 nm were characterized using X-ray diffraction, electron microscopy, atomic force microscopy, ellipsometry, and UV-Vis spectroscopy, to evaluate their structures, surface morphology, topology, and optical properties. It was found out that the deposition time increase leads to a larger growth rate. This determines significant changes on the ZnTe thin film structures and their surface morphology. Characteristic surface metrology parameter values varied, and the surface texture evolved with the thickness increase. Optical bandgap energy values slightly decreased as the thickness increased, while the mean grains radius remained almost constant at ~9 nm, and the surface to volume ratio of the films decreased by two orders of magnitude. This study is the first (to our knowledge) that thoroughly considered the correlation of film thickness with ZnTe structuring and surface morphology characteristic parameters. It adds value to the existing knowledge regarding ZnTe thin film fabrication, for various applications in electronic and optoelectronic devices, including photovoltaics. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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11 pages, 8362 KiB

Open AccessArticle

Effect of Nano Copper on the Densification of Spark Plasma Sintered W–Cu Composites

by Vadde Madhur, Muthe Srikanth, A. Raja Annamalai, A. Muthuchamy, Dinesh K. Agrawal and Chun-Ping Jen

Nanomaterials 2021, 11(2), 413; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11020413 - 05 Feb 2021

Cited by 18 | Viewed by 2424

Abstract

In the present work, nano Cu (0, 5, 10, 15, 20, 25 wt.%) was added to W, and W–Cu composites were fabricated using the spark plasma sintering (S.P.S.) technique. The densification, microstructural evolution, tensile strength, micro-hardness, and electrical conductivity of the W–Cu composite [...] Read more.

In the present work, nano Cu (0, 5, 10, 15, 20, 25 wt.%) was added to W, and W–Cu composites were fabricated using the spark plasma sintering (S.P.S.) technique. The densification, microstructural evolution, tensile strength, micro-hardness, and electrical conductivity of the W–Cu composite samples were evaluated. It was observed that increasing the copper content resulted in increasing the relative sintered density, with the highest being 82.26% in the W75% + Cu25% composite. The XRD phase analysis indicated that there was no evidence of intermetallic phases. The highest ultimate (tensile) strength, micro-hardness, and electrical conductivity obtained was 415 MPa, 341.44 HV_0.1, and 28.2% IACS, respectively, for a sample containing 25 wt.% nano-copper. Fractography of the tensile tested samples revealed a mixed-mode of fracture. As anticipated, increasing the nano-copper content in the samples resulted in increased electrical conductivity. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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16 pages, 28244 KiB

Open AccessArticle

From Chip Size to Wafer-Scale Nanoporous Gold Reliable Fabrication Using Low Currents Electrochemical Etching

by Pericle Varasteanu, Cosmin Romanitan, Alexandru Bujor, Oana Tutunaru, Gabriel Craciun, Iuliana Mihalache, Antonio Radoi and Mihaela Kusko

Nanomaterials 2020, 10(11), 2321; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112321 - 23 Nov 2020

Cited by 2 | Viewed by 2408

Abstract

We report a simple, scalable route to wafer-size processing for fabrication of tunable nanoporous gold (NPG) by the anodization process at low constant current in a solution of hydrofluoric acid and dimethylformamide. Microstructural, optical, and electrochemical investigations were employed for a systematic analysis [...] Read more.

We report a simple, scalable route to wafer-size processing for fabrication of tunable nanoporous gold (NPG) by the anodization process at low constant current in a solution of hydrofluoric acid and dimethylformamide. Microstructural, optical, and electrochemical investigations were employed for a systematic analysis of the sample porosity evolution while increasing the anodization duration, namely the small angle X-ray scattering (SAXS) technique and electrochemical impedance spectroscopy (EIS). Whereas the SAXS analysis practically completes the scanning electronic microscopy (SEM) investigations and provides data about the impact of the etching time on the nanoporous gold layers in terms of fractal dimension and average pore surface area, the EIS analysis was used to estimate the electroactive area, the associated roughness factor, as well as the heterogeneous electron transfer rate constant. The bridge between the analyses is made by the scanning electrochemical microscopy (SECM) survey, which practically correlates the surface morphology with the electrochemical activity. The results were correlated to endorse the control over the gold film nanostructuration process deposited directly on the substrate that can be further subjected to different technological processes, retaining its properties. The results show that the anodization duration influences the surface area, which subsequently modifies the properties of NPG, thus enabling tuning the samples for specific applications, either optical or chemical. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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11 pages, 1467 KiB

Open AccessArticle

3D Printed Fully Recycled TiO₂-Polystyrene Nanocomposite Photocatalysts for Use against Drug Residues

by Maria Sevastaki, Mirela Petruta Suchea and George Kenanakis

Nanomaterials 2020, 10(11), 2144; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10112144 - 28 Oct 2020

Cited by 25 | Viewed by 2974

Abstract

In the present work, the use of nanocomposite polymeric filaments based on 100% recycled solid polystyrene everyday products, enriched with TiO₂ nanoparticles with mass concentrations up to 40% w/w, and the production of 3D photocatalytic structures using a typical fused deposition [...] Read more.

In the present work, the use of nanocomposite polymeric filaments based on 100% recycled solid polystyrene everyday products, enriched with TiO₂ nanoparticles with mass concentrations up to 40% w/w, and the production of 3D photocatalytic structures using a typical fused deposition modeling (FDM)-type 3D printer are reported. We provide evidence that the fabricated 3D structures offer promising photocatalytic properties, indicating that the proposed technique is indeed a novel low-cost alternative route for fabricating large-scale photocatalysts, suitable for practical real-life applications. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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17 pages, 9297 KiB

Open AccessArticle

Innovative Low-Cost Carbon/ZnO Hybrid Materials with Enhanced Photocatalytic Activity towards Organic Pollutant Dyes’ Removal

by Petronela Pascariu, Niculae Olaru, Aurelian Rotaru and Anton Airinei

Nanomaterials 2020, 10(9), 1873; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10091873 - 18 Sep 2020

Cited by 10 | Viewed by 2684

Abstract

A new type of material based on carbon/ZnO nanostructures that possesses both adsorption and photocatalytic properties was obtained in three stages: cellulose acetate butyrate (CAB) microfiber mats prepared by the electrospinning method, ZnO nanostructures growth by dipping and hydrothermal methods, and finally thermal [...] Read more.

A new type of material based on carbon/ZnO nanostructures that possesses both adsorption and photocatalytic properties was obtained in three stages: cellulose acetate butyrate (CAB) microfiber mats prepared by the electrospinning method, ZnO nanostructures growth by dipping and hydrothermal methods, and finally thermal calcination at 600 °C in N₂ for 30 min. X-ray diffraction (XRD) confirmed the structural characteristics. It was found that ZnO possesses a hexagonal wurtzite crystalline structure. The ZnO nanocrystals with star-like and nanorod shapes were evidenced by scanning electron microscopy (SEM) measurements. A significant decrease in E_g value was found for carbon/ZnO hybrid materials (2.51 eV) as compared to ZnO nanostructures (3.21 eV). The photocatalytic activity was evaluated by studying the degradation of three dyes, Methylene Blue (MB), Rhodamine B (RhB) and Congo Red (CR) under visible-light irradiation. Therefore, the maximum color removal efficiency (both adsorption and photocatalytic processes) was: 97.97% of MB (C₀ = 10 mg/L), 98.34% of RhB (C₀ = 5 mg/L), and 91.93% of CR (C₀ = 10 mg/L). Moreover, the value of the rate constant (k) was found to be 0.29 × 10⁻² min⁻¹. The novelty of this study relies on obtaining new photocatalysts based on carbon/ZnO using cheap and accessible raw materials, and low-cost preparation techniques. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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18 pages, 6251 KiB

Open AccessArticle

New Electrospun ZnO:MoO₃ Nanostructures: Preparation, Characterization and Photocatalytic Performance

by Petronela Pascariu, Mihaela Homocianu, Niculae Olaru, Anton Airinei and Octavian Ionescu

Nanomaterials 2020, 10(8), 1476; https://0-doi-org.brum.beds.ac.uk/10.3390/nano10081476 - 28 Jul 2020

Cited by 12 | Viewed by 3010

Abstract

New molybdenum trioxide-incorporated ZnO materials were prepared through the electrospinning method and then calcination at 500 °C, for 2 h. The obtained electrospun ZnO:MoO₃ hybrid materials were characterized by X-ray diffraction, scanning and transmission electron microscopies, ultraviolet (UV)-diffuse reflectance, UV–visible (UV–vis) absorption, [...] Read more.

New molybdenum trioxide-incorporated ZnO materials were prepared through the electrospinning method and then calcination at 500 °C, for 2 h. The obtained electrospun ZnO:MoO₃ hybrid materials were characterized by X-ray diffraction, scanning and transmission electron microscopies, ultraviolet (UV)-diffuse reflectance, UV–visible (UV–vis) absorption, and photoluminescence techniques. It was observed that the presence of MoO₃ as loading material in pure ZnO matrix induces a small blue shift in the absorption band maxima (from 382 to 371 nm) and the emission peaks are shifted to shorter wavelengths, as compared to pure ZnO. Also, a slight decrease in the optical band gap energy of ZnO:MoO₃ was registered after MoO3 incorporation. The photocatalytic performance of pure ZnO and ZnO:MoO₃ was assessed in the degradation of rhodamine B (RhB) dye with an initial concentration of 5 mg/L, under visible light irradiation. A doubling of the degradation efficiency of the ZnO:MoO₃ sample (3.26% of the atomic molar ratio of Mo/Zn) as compared to pure ZnO was obtained. The values of the reaction rate constants were found to be 0.0480 h⁻¹ for ZnO, and 0.1072 h⁻¹ for ZnO:MoO₃, respectively. Full article

(This article belongs to the Special Issue Novel Nanocomposites: Optical, Electrical, Mechanical and Surface Related Properties)

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