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1.
Nanomaterials (Basel) ; 12(19)2022 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-36234610

RESUMEN

In this paper, we propose a simple two-step method for the synthesis of Ag, Au, and Pt-doped ZnO nanoparticles. The method is based on the fabrication of targets using the pulsed laser deposition (PLD) technique where thin layers of metals (Ag, Pt, Au) have been deposited on a metal-oxide bulk substrate (ZnO). Such formed structures were used as a target for the production of doped nanoparticles (ZnO: Ag, ZnO: Au, and ZnO: Pt) by laser ablation in water. The influence of Ag, Au, and Pt doping on the optical properties, structure and composition, sizing, and morphology was studied using UV-Visible (UV-Vis) and photoluminescence (PL) spectroscopies, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The band-gap energy decreased to 3.06, 3.08, and 3.15 for silver, gold, and platinum-doped ZnO compared to the pure ZnO (3.2 eV). PL spectra showed a decrease in the recombination rate of the electrons and holes in the case of doped ZnO. SEM, TEM, and AFM images showed spherical-shaped nanoparticles with a relatively smooth surface. The XRD patterns confirm that Ag, Au, and Pt were well incorporated inside the ZnO lattice and maintained a hexagonal wurtzite structure. This work could provide a new way for synthesizing various doped materials.

2.
Nanomaterials (Basel) ; 12(15)2022 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-35957108

RESUMEN

In this work, Ag-doped ZnO nanoparticles are obtained via pulsed laser ablation of the Ag-coated ZnO target in water. The ratio of Ag dopant in ZnO nanoparticles strongly depends on the thickness of the Ag layer at the ZnO target. Synthesized nanoparticles were characterized by XRD, XPS, SEM, EDS, ICP-OES, and UV-VIS spectrophotometry to obtain their crystal structure, elemental composition, morphology and size distribution, mass concentration, and optical properties, respectively. The photocatalytic studies showed photodegradation of methylene blue (MB) under UV irradiation. Different ratios of Ag dopant in ZnO nanoparticles influence the photodegradation rate. The ZnO nanoparticles doped with 0.32% silver show the most efficient photodegradation rate, with the chemical reaction constant of 0.0233 min-1. It exhibits an almost twice as large photodegradation rate compared to pure ZnO nanoparticles, showing the doping effect on the photocatalytic activity.

3.
Materials (Basel) ; 15(9)2022 Apr 26.
Artículo en Inglés | MEDLINE | ID: mdl-35591479

RESUMEN

In this work, we present a quantitative method for determining the concentration of metal oxide nanoparticles (NP) synthesized by laser ablation in liquid. The case study was performed with titanium dioxide nanoparticles (TiO2 NP), which were synthesized by laser ablation of a Ti target in water. After synthesis, a colloidal solution was analyzed with UV-Vis spectroscopy. At the same time, the craters that remained on the Ti target after ablation were evaluated with an optical microscope to determine the volume of the ablated material. SEM microscopy was used to determine the TiO2 NP size distribution. It was found that synthesized TiO2 NP followed a Log-Normal diameter distribution with a maximum at about 64 nm. From the volume of ablated material and NP size distribution, under the assumption that most of the ablated material is consumed to form nanoparticles, a concentration of nanoparticles can be determined. The proposed method is verified by comparing the calculated concentrations to the values obtained from the Beer-Lambert law using the Mie scattering theory for the NP cross-section calculation.

4.
Talanta ; 243: 123335, 2022 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-35231717

RESUMEN

In recent years, various types of nanomaterials and nanoparticles have been very popular, also in analytical chemistry for sensors preparation. Ion-selective electrodes with solid contact were constructed, in which a layer of nanoparticles of selected metal oxides (zinc, copper and iron oxides) obtained by pulsed laser liquid ablation (PLAL) was placed between the glassy carbon solid electrode material and the ion-selective membrane. The basic analytical parameters of the obtained sensors were determined using potentiometric methods. Additionally, the electrochemical impedance spectroscopy method (EIS) was also used to investigate the electrical properties of the sensors. The obtained results were compared for all types of electrodes, both modified and unmodified, in order to investigate the effect of the type of nanoparticles and the thickness of their layer used as solid contact. It was found that the addition of metal oxide nanoparticles improved the analytical parameters of the sensors, mainly the potential stability and electrical parameters. The best results were obtained for an electrode with an intermediate layer of zinc oxide nanoparticles. In this case, a slope of -56.07 mV/dec, a linearity range of 1 × 10-5 - 1 × 10-1 mol L-1 and a limit of detection of 3.66 × 10-6 mol L-1 were obtained. Particularly noteworthy is the significant improvement in the stability of the potential of this electrode and the long life of more than 5 months.


Asunto(s)
Electrodos de Iones Selectos , Nanopartículas del Metal , Electrodos , Iones , Nanopartículas del Metal/química , Óxidos , Potasio
5.
Materials (Basel) ; 13(19)2020 Sep 30.
Artículo en Inglés | MEDLINE | ID: mdl-33008048

RESUMEN

In this paper we examined the photocatalytic efficiency of a laser-synthesized colloidal solution of ZnO nanoparticles synthesized by laser ablation in water. The average size of the obtained colloidal ZnO nanoparticles is about 47 nm. As revealed by electron microscopy, other nanostructures were also present in the colloidal solution, especially nanosheets. A photocatalytic degradation of UV-irradiated Methylene Blue and Rhodamine B solutions of different concentration in the presence of different ZnO catalyst mass concentrations was studied in order to examine their influence on photodegradation rates. ZnO nanoparticles have shown high photocatalytic efficiency, which is limited due to different effects related to UV light transmittivity through the colloidal solution. Therefore, increasing catalyst concentration is effective way to increase photocatalytic efficiency up to some value where photodegradation rate saturation occurs. The photodegradation rate increases as the dye concentration decreases. These findings are important for water purification applications of laser-synthesized ZnO nanoparticles.

6.
Nanomaterials (Basel) ; 10(6)2020 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-32485869

RESUMEN

We aim to elucidate the mode of antibacterial action of the laser-synthesized silver colloid against Escherichia coli. Membrane integrity was studied by flow cytometry, while the strain viability of the treated culture was determined by plating. The spectrofluorometry was used to obtain the time development of the reactive oxygen species (ROS) inside the nanoparticle-treated bacterial cells. An integrated atomic force and bright-field/fluorescence microscopy system enabled the study of the cell morphology, Young modulus, viability, and integrity before and during the treatment. Upon lethal treatment, not all bacterial cells were shown to be permeabilized and have mostly kept their morphology with an indication of cell lysis. Young modulus of untreated cells was shown to be distinctly bimodal, with randomly distributed softer parts, while treated cells exhibited exponential softening of the stiffer parts in time. Silver nanoparticles and bacteria have shown a masking effect on the raw fluorescence signal through absorbance and scattering. The contribution of cellular ROS in the total fluorescence signal was resolved and it was proven that the ROS level inside the lethally treated cells is not significant. It was found that the laser-synthesized silver nanoparticles mode of antibacterial action includes reduction of the cell's Young modulus in time and subsequently the cell leakage.

7.
Molecules ; 24(21)2019 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-31683868

RESUMEN

ZnO has prominent electron transport and optical properties, beneficial for photovoltaic application, but its surface is prone to the formation of defects. To overcome this problem, we deposited nanostructured TiO2 thin film on ZnO nanorods to form a stable shell. ZnO nanorods synthesized by wet-chemistry are single crystals. Three different procedures for deposition of TiO2 were applied. The influence of preparation methods and parameters on the structure, morphology, electrical and optical properties were studied. Nanostructured TiO2 shells show different morphologies dependent on deposition methods: (1) separated nanoparticles (by pulsed laser deposition (PLD) in Ar), (2) a layer with nonhomogeneous thickness (by PLD in vacuum or DC reactive magnetron sputtering), and (3) a homogenous thin layer along the nanorods (by chemical deposition). Based on the structural study, we chose the preparation parameters to obtain an anatase structure of the TiO2 shell. Impedance spectroscopy shows pure electron conductivity that was considerably better in all the ZnO@TiO2 than in bare ZnO nanorods or TiO2 layers. The best conductivity among the studied samples and the lowest activation energy was observed for the sample with a chemically deposited TiO2 shell. Higher transparency in the visible part of spectrum was achieved for the sample with a homogenous TiO2 layer along the nanorods, then in the samples with a layer of varying thickness.


Asunto(s)
Nanoestructuras/química , Nanotubos/química , Titanio/química , Óxido de Zinc/química , Espectroscopía Dieléctrica , Conductividad Eléctrica , Electricidad , Rayos Láser
8.
Materials (Basel) ; 11(12)2018 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-30501055

RESUMEN

For this study, a paper impregnated with silver nanoparticles (AgNPs) was prepared. To prepare the substrates, aqueous suspensions of pulp fines, a side product from the paper production, were mixed with AgNP suspensions. The nanoparticle (NP) synthesis was then carried out via laser ablation of pure Ag in water. After the sheet formation process, the leaching of the AgNPs was determined to be low while the sheets exhibited antimicrobial activity toward Escherichia coli (E. coli).

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