Metals

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15 pages, 8708 KiB

Open AccessArticle

Effect of Storage Conditions on the Stability of Colloidal Silver Solutions Prepared by Biological and Chemical Methods

by Oksana Velgosova, Peter Varga, Dana Ivánová, Maksym Lisnichuk and Mária Hudá

Metals 2024, 14(5), 513; https://doi.org/10.3390/met14050513 - 28 Apr 2024

Viewed by 294

The research aimed to observe the influence of the storage conditions of silver colloidal solutions prepared by biological (green) and chemical methods on their long-term stability. Green methods for reducing and stabilizing silver nanoparticles (AgNPs) use natural substances. The rosemary leaf extract was [...] Read more.

The research aimed to observe the influence of the storage conditions of silver colloidal solutions prepared by biological (green) and chemical methods on their long-term stability. Green methods for reducing and stabilizing silver nanoparticles (AgNPs) use natural substances. The rosemary leaf extract was used for AgNPs synthesis, and prepared nanoparticles were spherical (average size of 12 nm). In the chemical method, commercial chemicals (NaBH₄, TSC, PVP, and H₂O₂) were used, and two colloids were prepared; the first contained spherical nanoparticles with an average size of 8 nm, and the second triangular prisms with an average size of 35 nm. The prepared colloids were stored under four conditions: at room temperature in the light and the dark, and at a temperature of 5 °C (refrigerator) in the light and the dark. The results confirmed the influence of storage conditions on the stability of nanoparticles. Colloids stored at 5 °C in the dark show the best stability. However, differences in stability dependent on the shape of nanoparticles prepared by chemical method were also observed; triangular nanoparticles showed the least stability. Methods such as UV–vis spectrophotometry, TEM, and EDX were used to analyze the nanoparticles before and after storage. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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10 pages, 1777 KiB

Open AccessArticle

Mechanistic Study in Gold Nanoparticle Synthesis through Microchip Laser Ablation in Organic Solvents

by Barana Sandakelum Hettiarachchi, Yusuke Takaoka, Yuta Uetake, Yumi Yakiyama, Hiroshi Y. Yoshikawa, Mihoko Maruyama and Hidehiro Sakurai

Metals 2024, 14(2), 155; https://doi.org/10.3390/met14020155 - 27 Jan 2024

Viewed by 1058

Abstract

The utilization of pulsed laser ablation in liquids (PLALs) for preparing gold nanoparticles (Au NPs) in organic solvents holds immense potential across diverse applications. This study introduces a compact and low-power microchip laser (MCL) system (average power 50 mW; pulse energy 0.5 mJ). [...] Read more.

The utilization of pulsed laser ablation in liquids (PLALs) for preparing gold nanoparticles (Au NPs) in organic solvents holds immense potential across diverse applications. This study introduces a compact and low-power microchip laser (MCL) system (average power 50 mW; pulse energy 0.5 mJ). Due to its compactness, an MCL is advantageous for easy manipulation in organic laboratories during the production of metal nanoparticles (NPs) for research and development purposes. In this research, poly(N-vinyl-2-pyrrolidone) (PVP) is used as a stabilizing agent for the preparation of Au NPs in organic solvents (CH₂Cl₂, CHCl₃, 2-PrOH, MeCN, DMF, EtOH, NMP, and DMSO). Our experimental results demonstrate that the particle size remains consistent across all the organic solvents. This study explores the productivity of Au NPs in different organic solvents, revealing the necessity of multiple laser pulses to generate Au NPs successfully. This phenomenon, known as the ‘incubation effect,’ is linked to the lower pulse energy in the experimental condition and the thermal conductivity of the solvents. The findings emphasize the crucial role of solvent properties in determining the Au NPs productivity in PLAL. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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11 pages, 7066 KiB

Open AccessArticle

Molecular Dynamics Study of the Devitrification of Amorphous Copper Nanoparticles in Vacuum and in a Silver Shell

by Gennady Poletaev, Yuri Gafner, Svetlana Gafner, Yuriy Bebikhov and Alexander Semenov

Metals 2023, 13(10), 1664; https://doi.org/10.3390/met13101664 - 28 Sep 2023

Cited by 4 | Viewed by 758

Abstract

The process of the devitrification of copper nanoparticles in vacuum and in a silver shell during heating was studied using a molecular dynamics simulation. The results show that there is an inverse relationship between the particle diameter and devitrification temperature. As the size [...] Read more.

The process of the devitrification of copper nanoparticles in vacuum and in a silver shell during heating was studied using a molecular dynamics simulation. The results show that there is an inverse relationship between the particle diameter and devitrification temperature. As the size of the particles decreases, the temperature at which devitrification occurs increases due to a higher fraction of atoms near the interface. The presence of a silver shell leads to a significant increase in the devitrification temperature of the copper nanoparticles. For the considered particle sizes, the difference between the devitrification temperatures without a shell and with a shell ranged from 130 K for copper particles with a diameter of 11 nm to 250 K for 3 nm particles. The mechanisms of the nucleation of a crystalline phase in particles in vacuum and in a silver shell are significantly different. In the first case, crystalline nuclei are predominantly formed near the surface, while in the second case, on the contrary, they are formed within the particle’s volume. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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18 pages, 5201 KiB

Open AccessArticle

The Mechanism of Phase Transfer Synthesis of Silver Nanoparticles Using a Fatty Amine as Extractant/Phase Transfer Agent

by Konrad Wojtaszek, Tomasz Tokarski, Dawid Kutyła, Karolina Kołczyk-Siedlecka, Piotr Żabiński, Edit Csapó, Robert P. Socha, Marc Escribà-Gelonch, Volker Hessel and Marek Wojnicki

Metals 2023, 13(5), 882; https://doi.org/10.3390/met13050882 - 02 May 2023

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Abstract

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. [...] Read more.

The paper presents the research results on synthesizing silver nanoparticles in aqueous solutions and their extraction into the organic phase. Studies have shown that it is best to perform the extraction process using n-hexane > cyclohexane > toluene > chloroform > ethyl acetate. The results show a correlation between the dielectric constant of the organic phase and its ability to extract nanoparticles. The lower the dielectric constant is, the higher the extractability. The hydrodynamic radius of the silver nanoparticles changes after transfer to the organic phase, depending greatly on the organic phase used. The extraction mechanism is complex and multi-step. As the first step, the Ag nanoparticles are transferred to the phase boundary. As the second step, the octadecylamine (ODA) molecules adsorb on the silver nanoparticles (AgNPs) surface. The change in particle shape was also noted. This suggests that the interfacial processes are more complex than previously reported. Below the initial concentration of ODA 2 × 10⁻⁴ M, the formation of a third phase has been observed. In a one-stage experiment, the concentration of silver nanoparticles after transferring to the organic phase was increased 500 times in about 10 s. The role of the concentration of ODA, therefore, is not only a measure of the extraction efficiency and productivity but functions as an enabler to maintain favorable biphasic processing, which underlines the role of the solvent again. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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11 pages, 6610 KiB

Open AccessArticle

Fabrication of Nanoporous Gold via an Improved Solid-Phase Method for Non-Enzymatic Detection of Aniline

by Qihang Wan, Jun Li, Zhang Liu, Lu Han, Siyi Huang and Zumin Wang

Metals 2023, 13(4), 754; https://doi.org/10.3390/met13040754 - 13 Apr 2023

Cited by 2 | Viewed by 1288

Abstract

In this paper, nanoporous gold (NPG) thin films with superior catalytic performance were prepared on glassy carbon electrodes (GCE) by optimizing the process parameters and adopting an improved solid-phase reaction method. The morphology and structures of NPG films were comprehensively investigated and the [...] Read more.

In this paper, nanoporous gold (NPG) thin films with superior catalytic performance were prepared on glassy carbon electrodes (GCE) by optimizing the process parameters and adopting an improved solid-phase reaction method. The morphology and structures of NPG films were comprehensively investigated and the structural defects on continuous NPG ligaments were observed. The NPG films demonstrated higher sensitivity and a lower detection limit during the amperometric sensing of aniline than NPGs made using conventional techniques. The results of multiple electrochemical tests demonstrated that the NPG/GCE electrodes possess high stability and good reproducibility. The prepared NPG film is a favorable material that can be superior in aniline electrochemical detection and can also be applied in other electrochemical sensing reactions. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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14 pages, 2559 KiB

Open AccessArticle

Vacancy Formation Energy as an Effective Descriptor for the Catalytic Oxidation of CO by Au Nanoparticles

by Zhiwei Zhang, Kun Meng, Peng Ou, Haijun Wu, Yannan Zhang and Xiaohua Yu

Metals 2023, 13(2), 362; https://doi.org/10.3390/met13020362 - 10 Feb 2023

Cited by 1 | Viewed by 1350

Abstract

Gold nanoparticles (AuNPs) have attracted wide attention in the field of catalysis because of their excellent stability and electrical properties. Herein, an accurate vacancy formation energy model based on nanothermodynamics theory is developed, the intrinsic correlation between vacancy formation energy and CO oxidation [...] Read more.

Gold nanoparticles (AuNPs) have attracted wide attention in the field of catalysis because of their excellent stability and electrical properties. Herein, an accurate vacancy formation energy model based on nanothermodynamics theory is developed, the intrinsic correlation between vacancy formation energy and CO oxidation activity is investigated in detail, and the relationship between vacancy formation energy and activity-influencing factors such as particle size, temperature, and crystal surface is analyzed. The results show an excellent linear relationship between vacancy formation energy and CO oxidation activity, with an accuracy of up to 95%. In addition, the vacancy formation energy also corresponds well to the influencing factors of size, temperature, and crystal surface, and its correspondence is particularly accurate when the size is below 20 nm and the temperature is below 500 K. It can serve as a normalized expression of the three influencing factors. Moreover, the present research reveals that the essence of the vacancy formation energy descriptor is the chemical bond energy, and gives its correspondence with the coordination number, diffusion activation energy, and adsorption energy (with a decrease in vacancy formation energy, the adsorption effect of AuNPs is stronger), further demonstrating the feasibility and accuracy of the vacancy formation energy as a descriptor. This research not only overcomes the problem that traditional single-influence descriptors are difficult to apply in complex environments but also has considerable potential for defect modulation. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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9 pages, 2314 KiB

Open AccessArticle

Electrochemical Fabrication of Inverse Opals of Silver with Cyanide-Free Electrolytes

by Rustam I. Arabov, Maria Y. Komarova, Mikhail O. Astafurov, Alexander V. Knotko, Konstantin I. Maslakov, Serguei V. Savilov and Anastasia V. Grigorieva

Metals 2022, 12(12), 2042; https://doi.org/10.3390/met12122042 - 28 Nov 2022

Viewed by 1138

Abstract

Silver inverse opals were prepared electrochemically using non-toxic water–ethanol rhodanic and sulfite electrolytes for silver plating. Electrochemical crystallization of silver occurred in the pores of opal matrices made of 350 nm polystyrene microspheres. Samples with the most uniform structure and lowest percentage of [...] Read more.

Silver inverse opals were prepared electrochemically using non-toxic water–ethanol rhodanic and sulfite electrolytes for silver plating. Electrochemical crystallization of silver occurred in the pores of opal matrices made of 350 nm polystyrene microspheres. Samples with the most uniform structure and lowest percentage of surface admixtures were obtained from rhodanic electrolytes. Reflectance optical spectra of the silver inverse opals with a high surface periodicity showed various plasmon excitation modes in a visible spectral range making the silver opals attractive for plasmonics. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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20 pages, 29936 KiB

Open AccessArticle

Synthesis and Catalytic Studies of Nanoalloy Particles Based on Bismuth, Silver, and Rhenium

by Konrad Wojtaszek, Katarzyna Skibińska, Filip Cebula, Tomasz Tokarski, Marc Escribà-Gelonch, Volker Hessel and Marek Wojnicki

Metals 2022, 12(11), 1819; https://doi.org/10.3390/met12111819 - 26 Oct 2022

Cited by 5 | Viewed by 1369

Abstract

The work reports the synthesis and characterization of ternary nanoalloy catalysts of silver, bismuth, and rhenium from alkaline solutions containing L–cysteine as a complexing agent and sodium borohydride as a reducing agent. UV–Vis spectra and dynamic light scattering (DLS) analyses of the obtained [...] Read more.

The work reports the synthesis and characterization of ternary nanoalloy catalysts of silver, bismuth, and rhenium from alkaline solutions containing L–cysteine as a complexing agent and sodium borohydride as a reducing agent. UV–Vis spectra and dynamic light scattering (DLS) analyses of the obtained colloids were performed. Additionally, high-resolution transmission electron microscope (HR–TEM) analysis assisted the former investigations. The influence of a stabilizer (PVA) was demonstrated for bismuth nanoparticles reaching an average size of 8 nm with PVA, whereas they grew large, 514 nm, in the case of synthesis without stabilizing agent. AgReBi nanoalloy particles reach an average size of 19 nm with PVA. The presence of two absorption maxima in the UV–Vis spectrum suggests shape anisotropy of these nanoparticles. TEM micrographs demonstrate the crystal structure of AgReBi nanoparticles. Cyclic voltamaperometry allows for deciphering of the catalytic properties for hydrogen peroxide electro-reduction. Both bismuth and AgReBi nanoalloy catalysts showed relatively high catalytic activity in H₂O₂ electro-reduction in the amperometric tests. Full article

(This article belongs to the Special Issue Advances in Nanostructured Metallic Materials)

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