Colloidal Solution Of Nanoparticles Research Articles

The Influence of Medium on Fluorescence Quenching of Colloidal Solutions of the Nd3+: LaF3 Nanoparticles Prepared with HTMW Treatment.

An original method was proposed to reduce the quenching of the NIR fluorescence of colloidal solutions of 0.1 at. % Nd3+: LaF3 nanoparticles (NPs) synthesized by aqueous co-precipitation method followed by hydrothermal microwave treatment. For this, an aqueous colloidal solution of NPs was precipitated by centrifugation and dissolved in the same volume of DMSO. The kinetics of static fluorescence quenching of Nd3+ donors of doped NPs dispersed in two solvents was analyzed to determine and to compare the concentrations of OH- quenching acceptors uniformly distributed throughout the volume of the NPs. The dependences of the relative fluorescence quantum yield φ of colloidal solutions on the concentration of OH- groups in the NPs were calculated and were also used to determine concentration of acceptors in the volume of NPs in different solvents. It was found that the concentration of OH- groups in NPs dispersed in DMSO is almost two times lower than in NPs dispersed in water. This gives an almost two-fold increase in the relative fluorescence quantum yield φ for the former. The sizes of synthesized NPs were monitored by common TEM and by applying a rapid procedure based on optical visualization of the trajectories of the Brownian motion of NPs in solution using a laser ultramicroscope. The use of two different methods made it possible to obtain more detailed information about the studied NPs.

Highly efficient hexagonal-phase Nd3+ doped KLaF4 nanoparticles colloidal suspension for liquid lasers

Innovative approach in the exploration of high-power liquid laser media, utilizing hexagonal KLaF4: x% Nd3+ (x = 1–30 mol%) nanoparticle colloidal solutions synthesized from one-step chemical route is hereby presented. The phase purity and nano size distributions of the nanoparticles are confirmed from X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The concentration dependent absorption and steady-state and dynamic infrared emission (at 1058 nm, 4F3/2 → 4I11/2) features of Nd3+ ion of KLaF4: x% Nd3+ liquid media are closely examined. The estimated stimulated emission cross-sections, branching ratios and quantum efficiencies establishes the potentiality of these hexagonal nanoparticle colloidal solutions for high power liquid laser applications. Inokuti-Hirayama (I–H) and diffusion dominated Yokota-Tanimoto (Y-T) models are employed to examine the dynamic emission evolution of KLaF4: x% Nd3+ (x ≥ 5–30 mol%). The proposed study substantiate that the colloidal solution can serve as a new laser media for low-cost and high-energy liquid lasers and amplifiers.

Optical properties of planar plasmon active surfaces modified with gold nanostars

The article discusses the experimental and theoretical results of studying the optical properties for planar quartz surfaces modified with gold nanostars using Surface-Enhanced Raman Spectroscopy (SERS). Surfaces functionalized with nanoparticles, prototypes of optical sensors, have been obtained. It is shown that the obtained experimental Raman signal enhancement from the dye rhodamine 6G (R6G) can be at least order 104. The paper presents the results of calculation, synthesis and study of the optical and morphological properties of such structures. A complex method for creating and evaluating the optical properties of planar nanostructures and evaluating their optical properties is proposed. The method includes the approaches based on mathematical modeling using finite differences in the time domain (FDTD - Finite-Difference Time-Domain) evaluating electromagnetic field strengths near the surfaces of star-shaped gold nanoparticles in colloidal solutions and on a silicon surface. During the simulation, we studied such parameters as the particle size, the wavelength of the exciting radiation, and the dependence of the effective amplification of the electromagnetic field on the morphological parameters of the star. The theoretical approach to the calculation of such structures is shown to be promising for the subsequent chemical synthesis described in the article and the study of optical properties. In this paper, a theoretical calculation of the parameters of the electric field and optical properties is carried out near star-shaped nanoparticles of varying sizes. These parameters were calculated by the finite difference method in the time domain. The task included finding the optimal sizes of nanoparticles as well as varying the thickness of the surface layers in order to obtain the maximum scattering values and further use of similar structures in SERS experiments. Also, within the framework of this work, syntheses of star-shaped nanoparticles was carried out, their optical and morphological properties were studied, quartz surfaces were functionalized with nanoparticles, and sensor prototypes were created in order to further assess the Raman signal amplification. Based on the results of mathematical modeling, the optimal sizes for the synthesis of star-shaped NPs were determined. Synthesis of NPs was carried out by a chemical method using seeds. To carry out the experimental part, SERS spectra were obtained using Centaur U spectrometer (OOO NanoScanTechnology, Russia). The spectrometer was equipped with three different laser sources: 632.8 nm He-Ne laser (17 mW), 532 nm and 473 nm DPSS lasers (45 mW). During the experiment, a He-Ne laser with λ = 632 nm and DPSS laser with λ = 532 nm were used to match the excitation of the plasmon maximum for the nanostars. The optical scheme of the spectrometer included an Olympus BX41 microscope (Olympus, Japan) with a 100× objective (NA 0.9) for positioning the beam and collecting scattered photons. The monochromator of the spectrometer had a focal length of 800 mm. A holographic diffraction grating of 300 gr/mm, and was equipped with a 1024×256 pixel thermoelectric cooled CCD detector (Andor Tech., UK). As a result of the paper, surfaces functionalized by nanoparticles were obtained prototypes of optical sensors. It is shown that the experimental gain of the Raman signal can be no less than 104 times. The presented data will serve as the basis for obtaining the required sizes of nanostars in the methods of the controlled chemical synthesis of colloidal nanoparticles. The results presented in the article can be applied to the development of biocompatible and highly sensitive optical sensors based on the effect of Raman scattering of light.

Fitting Procedure to Reconstruct the Size Distribution and the Concentration of Silver Colloidal Nanoparticles from UV-Vis Spectra.

In this work, a complete fitting procedure of UV-Vis spectra of silver nanoparticles in colloidal solutions is reported. The fitting function, based on the Beer–Lambert law, Mie theory, and log-normal probability distribution of nanoparticles’ sizes, is developed and confirmed by 33 different independent measurements. In order to validate the accuracy of the function’s behavior on different spectra, freely accessible measurements were used, proving that the fitting function works independently of the method of their production—laser or chemical synthesis of nanoparticles. The developed fitting function is, to the best of our knowledge, novel and not based on any conventional spectral analysis approaches like the Mie–Gans procedure. Furthermore, since fitted parameters are all physical, it allows determination of the mode diameter of nanoparticles as well as the standard deviation of the log-normal distribution of sizes. It enables the reconstruction of size distribution of nanoparticles in colloidal solution. Step-by-step derivation of the fitting function is provided with a physical explanation of all parameters. The importance of Lorentzian dependence emerging at the core of Beer–Lambert law is physically discussed and linked to harmonic oscillator behavior of localized surface plasmon resonance of silver nanoparticles in a colloidal solution. Size distribution reconstruction from fitted parameters according to a log-normal distribution function is provided and a concentration calculation is presented.

Oxidation control of metallic zinc nanoparticles by silica coating

ABSTRACT A simple method for controlling the aggregation and oxidation of metallic zinc (Zn) nanoparticles has been developed. Metallic Zn nanoparticles were fabricated from Zn(CH₃COO)2·2H2O by electrolysis under ultrasonic irradiation in water exposed to air. The metallic Zn nanoparticles were silica-coated by adding ethanol, a silane coupling agent (SCA)/ethanol, tetraethylorthosilicate (TEOS), and NaOH aqueous solution to the metallic Zn nanoparticle colloid solution, which perfectly prevented the metallic Zn nanoparticles from aggregating due to the physical barriers that were provided by the silica shells. (3-Mercaptopropyl)trimethoxysilane was suitable as the SCA for ensuring the nonaggregation of the silica-coated metallic Zn nanoparticles. Oxidation of the metallic Zn nanoparticles even with annealing in air was controlled by the silica shells due to their function as physical barriers.

Fabrication of 4H–SiC nanoparticles using femtosecond pulsed laser ablation in deionized water

In this paper, the silicon carbide (SiC) nanoparticle colloidal solution is obtained by using the femtosecond (fs) laser ablation in deionized water. The spherical nanoparticles are uniform in size with an average diameter of 2.84 nm analyzed by transmission electron microscope (TEM). X-ray diffraction patterns (XRD) show that the crystal structure of the nanoparticles is still 4H–SiC. Absorption spectrum shows strong absorption of SiC colloidal solution in ultraviolet region. The optical nonlinearity of SiC nanoparticles colloidal solution is investigated by the Z scan experiment, it is found that the SiC nanoparticles have reverse saturation absorption characteristics. The nonlinear absorption coefficient β is measured to be about 3 × 10−13 m/W.

Studying Diffusion of Colloidal Nanoparticles in Solution Using Liquid Phase TEM and Machine Learning

Studying Diffusion of Colloidal Nanoparticles in Solution Using Liquid Phase TEM and Machine Learning

Strong third-and higher-order nonlinear optical studies on femtosecond laser ablated Germanium metalloid nanoparticle colloid in the wide spectral domain (450–1500 nm)

Wide spectral region higher-order optical nonlinearities are hereby reported for ultrashort pulsed laser ablated germanium nanoparticle (Ge NPs) colloidal solutions. The Ge NPs colloids are studied for optical nonlinearities under a wide spectral domain (∼450–1550 nm) utilizing the femtosecond laser (120 fs, 1 kHz) pulses. The results of the nonlinear absorption indicate a strong dominance of multi-photon absorption phenomena (two-, three- and four-photon absorptions), involving band-to-band and defect induced energies of the quantum confined Ge NPs. The intensity-dependent [(4–8) × 1015 W m−2] nonlinear absorption exhibits a monotonically decremental trend with the increase in excitation intensity, suggesting the involvement of higher-order nonlinear optical effects. Moreover, the obtained presented results also depict strong nonlinear contribution evidenced by two orders of higher magnitude nonlinear refraction in the infrared (IR) region, 1000–1550 nm. The enhanced optical nonlinearities in the IR region propound the capabilities of these Ge NPs as a potential substitute for silicon in IR photonics-related applications.

Production of methylcellulose films functionalized with poly-ε-caprolactone nanocapsules entrapped β-carotene for food packaging application

Nowadays, there is a worldwide demand in the production of innovative packaging that release active compounds to increase the shelf life of perishable food products. Therefore, this study produced methylcellulose films functionalized with poly-ε-caprolactone nanocapsules entrapped β-carotene. The nanoparticles were produced by the nanoprecipitation method, and 10, 30, and 50 % of nanoparticles colloidal solution was added in the methylcellulose filmogenic solution. The films were characterized by the mechanical, physicochemical properties, antioxidant activity, and release of β-carotene from the polymeric matrix to a food simulant. The results demonstrated satisfactory mechanical properties; however, the addition of nanoparticles decreased the Young's Modulus and increased the elongation at break. Regarding light transmission, the incorporation of β-carotene nanoparticles promoted a decrease in the percentage of ultraviolet ray’s transmittance through the film matrix, as well as visible light. The incorporation of nanoparticles improved the antioxidant activity of the films, which was proportional to the concentration of β-carotene used in the formulation. The release of β-carotene reached a maximum value of 10.93 µg g−1 film containing 70 % nanoparticles, which was a desired profile for food application. Finally, the methylcellulose films functionalized with poly-ε-caprolactone nanocapsules can release β-carotene, and therefore, can be considered as a novel nanomaterial for food conservation, with a potential to increase the shelf life of perishable food products.

Laser-Induced Optical Breakdown of an Aqueous Colloidal Solution Containing Terbium Nanoparticles: The Effect of Oxidation of Nanoparticles.

The influence of the number of oxidized terbium nanoparticles on the intensity of physicochemical processes occurring during optical breakdown in aqueous colloidal solutions of nanoparticles has been studied. It is shown that the effect of the number of oxidized terbium nanoparticles on the physicochemical processes occurring during optical breakdown depends significantly on the fluence of laser radiation. At a fluence of less than 100-110 J/cm2, plasma formation processes occur more intensively on less-oxidized (metal) nanoparticles. At a fluence of more than 100-110 J/cm2, the processes of plasma formation during optical breakdown occur much more intensively on more-oxidized nanoparticles. It has been established that the dependence of the rate of laser-induced decomposition of water on the concentration of nanoparticles is two-phase. The rate of generation of water decomposition products increases with an increase in the concentration of nanoparticles up to 109 NP/mL. With a further increase in the concentration of nanoparticles, the rate of generation of water decomposition products decreases. In this case, more than 99% of the decomposition products of water are formed due to the action of plasma, and the share of ultraviolet and ultrasound formed during optical breakdown is approximately 0.5% on each.

In Vitro Activation of Ampicillin Effect with Plant Extract Cocktail-Mediated Silver Nanoparticles Against Multidrug-Resistant Bacteria Pathogens

Background: The emergence of antibiotic resistance and the continuing evolution of resistance even to newer drugs have always been a global challenge. In the pursuit of innovative solutions, there is growing interest in using nanomaterials with antibacterial potentials to combat this menace. Objectives: In this study, plant extract cocktail-mediated silver nanoparticles (PAgNPs) was used to stimulate the antibacterial effect of ampicillin (AMP) against multidrug-resistant (MDR) bacterial pathogens. Methods: The agar well diffusion technique was used to investigate the potentials of PAgNPs in activating the antibacterial activity of AMP in MDR bacteria, including Escherichia coli, Klebsiella pnuemoniae, Micrococcus luteus, and Clostridium difficile. Plant extract cocktail-mediated silver nanoparticles were synthesized by reacting 9 mL of 1 mM of silver nitrate with 0.5 mL each of Citrus limon juice and aqueous Newbouldia laevis extract under bright sunlight for 10 minutes. Plant extract cocktail-mediated silver nanoparticles were characterized using UV-visible spectroscopy (UV-Vis) and higher resolution transmission electron microscopy (HRTEM) with energy dispersive x-ray spectroscopy (EDS). Results: Plant extract cocktail-mediated silver nanoparticles colloidal solution was reddish-brown with a 441-nm surface plasmon resonance (SPR) absorption peak. The HRTEM micrograph showed the varied shaped silver nanoparticles (AgNPs) with the average size of 23.49 ± 10.49 nm. Similarly, EDS showed a strong typical metallic silver nanocrystallites absorption peak at 3.0 keV. The PAgNPs activate the AMP activity in MDR E. coli, M. luteus, K. pnuemoniae, and C. difficile. Conclusions: The present findings suggest that PAgNPs can be considered a suitable candidate for developing novel antibacterial drugs to combat the growing threat of antibiotic resistance.

Advanced quantitative analysis of colloidal solution of metal nanoparticles produced by laser ablation in liquids

The diameter of laser synthesized colloidal nanoparticles can be derived from a volume of ablated material and absorbance at surface plasmon resonance wavelength. The origin of such nanoparticles’ diameter is studied in this work. The study is based on Beer-Lambert law where nanoparticle size-distribution and UV-Vis photoabsorbance data are used. Theoretically modeled diameter is verified by independent integral approach proving that simple model derived in our previous work is by most means usable for determination of diameter of laser synthesized nanoparticles in colloidal solution with sizes less than SPR wavelength. Here is also presented the mathematical proof which indicates that in monodisperse limit, under assumption that size-distribution of synthesized nanoparticles can be described by log-normal function, diameter obtained by simple analytical model is in fact mode diameter (most frequent diameter) of size-distribution. Furthermore, it is shown that mode diameter of size-distributions can be obtained from volume average diameter of nanoparticles over experimentally determined diameter distribution as well as from number average diameter of nanoparticles over the same diameter distribution by multiplication of those diameters with shift factors depended only on standard deviation of log-normal distribution. This is verified for size-distributions obtained independently by AFM, TEM and DLS techniques and is proposed to be universal property of log-normal distribution function.

Temporal Growth and Aging of ZnO Nanoparticles in Colloidal Solution: Phase Field Model

Temporal Growth and Aging of ZnO Nanoparticles in Colloidal Solution: Phase Field Model

Estimation of biocidal effect of metal and bioelement nanoparticles in a unicellular eukaryotic test system

The results of the study of biocidal properties of silver, copper and silicon dioxide nanoparticles are presented. Questions about the safety of nanocomponents in connection with their unstudied impact on the environment are considered. To evaluate the biocidal effect of noble metal nanoparticles and bioelements, a unicellular eukaryotic test-system, represented by a ciliated protist microorganism Paramecium caudatum inhabiting pond water bodies, was used. It was found that solutions of noble metal nanoparticles and bioelements are not bioinert and biostimulating. Colloidal solutions of silver, copper and silicon dioxide nanoparticles have a biocidal effect and show a similar dosedependent effect if the concentration of nanoparticles in the initial colloidal solutions is the same (300 µg/ml). The colloidal silver solution is characterized by a more pronounced toxic activity in a unicellular protist biological model, since full biocidal activity against paramecium is provided by dilutions of the colloidal solution of nanoparticles to the value 1: 6 of the initial one. Compared to it, solutions of copper nanoparticles and silicon oxide have a biocidal index of 100% achieved only in values of two- or three-times dilution of the initial solution. Colloidal solutions of nanoparticles in concentrations that do not cause complete mortality of the infusoria (1: 5 of the original for copper and silicon oxide nanoparticles and 1: 7 of the original for silver nanoparticles) inhibit their reproduction intensity by approximately the same value of 55-61% (paramecium reproduction intensity index of 0.455 to 0.390 respectively).

Assessment of the effect of a colloidal solution of silver nanoparticles on the sowing quality of seeds

The article presents the results of laboratory studies to assess the effect of a colloidal solution of silver nanoparticles on the sowing quality of wheat seeds of the Novosibirskaya 15 strain recommended for cultivation in the Krasnoyarsk Territory and an assessment of its influence on its seed productivity. It was found that the use of a colloidal solution of silver nanoparticles in the processing of seed material of the Novosibirskaya 15 soft spring wheat strain significantly increases the rate of seed growth, raising it from 63% in the control to 87% in the variant with a 50% solution of silver nanoparticles. It was found that the colloidal solution of silver nanoparticles did not affect on the indicators of seed germination and their germination energy.

Controlled oxidation of metallic copper nanoparticles by a silica coating

The development of a simple method that perfectly controls the oxidation and aggregation of metallic copper (Cu) nanoparticles has been anticipated. In the present work, silica-coated metallic Cu nanoparticles were used as a control. Metallic Cu nanoparticles were synthesized from Cu(CH3COO)2, hydrazine, citric acid, and cetyltrimethylammonium bromide in water exposed to air. The metallic Cu nanoparticles were silica-coated by adding ethanol, (3-aminopropyl) trimethoxysilane (APMS)/ethanol, tetraethylorthosilicate (TEOS)/ethanol, and NaOH aqueous solution to the metallic Cu nanoparticle colloid solution. The morphology of silica-coated metallic Cu nanoparticles was dependent on the presence or absence of APMS and the TEOS concentration. Oxidation of the metallic Cu nanoparticles even with annealing in air was controlled by the silica shells due to their function as a physical barrier.

P-type Inversion at the Surface of β-Ga2O3 Epitaxial Layer Modified with Au Nanoparticles.

The electric properties and chemical and thermal stability of gallium oxide β-Ga2O3 make it a promising material for a wide variety of electronic devices, including chemiresistive gas sensors. However, p-type doping of β-Ga2O3 still remains a challenge. A β-Ga2O3 epitaxial layer with a highly developed surface was synthesized on gold electrodes on a Al2O3 substrate via a Halide Vapor Phase Epitaxy (HVPE) method. The epitaxial layer was impregnated with an aqueous colloidal solution of gold nanoparticles with an average diameter of Au nanoparticle less than 5 nm. Electrical impedance of the layer was measured before and after modification with the Au nanoparticles in an ambient atmosphere, in dry nitrogen, and in air containing dimethyl sulfide C2H6S (DMS). After the impregnation of the β-Ga2O3 epitaxial layer with Au nanoparticles, its conductance increased, and its electric response to air containing DMS had been inversed. The introduction of Au nanoparticles at the surface of the metal oxide was responsible for the formation of an internal depleted region and p-type conductivity at the surface.

Ni-based overall water splitting electrocatalysts prepared via laser-ablation-in-liquids combined with electrophoretic deposition

Synthesis of fine nanoparticles (NPs) with surface-active sites free from undesired chemical residues is the key to drive chemical kinetics. However, active sites of chemically produced NPs are limited because of the adsorption of chemical residues. Therefore, the development of a physical approach to produce NPs having surfaces free from chemical contamination is imperative to electrochemical water splitting. Here, we present a physical top-down approach where suspended NPs generated via pulsed laser ablation in liquids are electrophoretic deposited on a substrate to fabricate ready-to-use electrocatalysts for overall water splitting. Three different laser pulse energies were used to ablate Ni plate in pure water or aqueous media of 1M polyethylene glycol (PEG) to produce six different colloidal solutions of NPs. The samples produced in the water at higher laser pulse energies have Ni/NiO phase in abundance, while those produced in PEG dominate Ni/Ni(OH)2 phase. Among all the electrophoretically fabricated electrocatalysts, Ni-Di-70 is the best performer in overall water splitting, while Ni-P-30 is the worse. We believe that the selective adsorption of H∗, responsible for hydrogen evolution reaction, at Ni sites, and OH− ions, oxygen evolution intermediate, at NiO sites of Ni/NiO interface increase hydrogen and oxygen generation performances of Ni-Di-70 sample. The poor performance of PEG produced electrocatalysts is attributed to the combined effects of the formation of a larger assembly of NPs and adsorption of PEG molecules on the active sites.

A Novel Biodegradable Composite Polymer Material Based on PLGA and Silver Oxide Nanoparticles with Unique Physicochemical Properties and Biocompatibility with Mammalian Cells.

A method for obtaining a stable colloidal solution of silver oxide nanoparticles has been developed using laser ablation. The method allows one to obtain nanoparticles with a monomodal size distribution and a concentration of more than 108 nanoparticles per mL. On the basis of the obtained nanoparticles and the PLGA polymer, a nanocomposite material was manufactured. The manufacturing technology allows one to obtain a nanocomposite material without significant defects. Nanoparticles are not evenly distributed in the material and form domains in the composite. Reactive oxygen species (hydrogen peroxide and hydroxyl radical) are intensively generated on the surfaces of the nanocomposite. Additionally, on the surface of the composite material, an intensive formation of protein long-lived active forms is observed. The ELISA method was used to demonstrate the generation of 8-oxoguanine in DNA on the developed nanocomposite material. It was found that the multiplication of microorganisms on the developed nanocomposite material is significantly decreased. At the same time, the nanocomposite does not inhibit proliferation of mammalian cells. The developed nanocomposite material can be used as an affordable and non-toxic nanomaterial to create bacteriostatic coatings that are safe for humans.

Synthesis of novel Iron Nanoparticles using the aqueous extract of the Pumpkin plant, and used it in the treatment of burns

This aimed to study of the use of pumpkin aqueous extract in the preparation of iron nanoparticles, the use of ultraviolet (UV) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and X-ray diffraction (XRD) in characterizing the prepared nanoparticles and determining the active groups, and study of the effect of nanoparticles prepared using pumpkin aqueous extract in treating burns. The nanoparticles were prepared using aqueous extract of pumpkin and iron salts, which are 100% local materials for treating burns and pathogenic microorganisms. As the study showed that iron nanoparticles showed high inhibitory efficacy for the microorganisms under study, which included: Ps. aeruginosa, Pr. Mirabilis, Staph. aureus, E. coli, K. pneumonia. These bacterial types are among the most dangerous bacterial types in the contamination of burns and wounds. As it showed the highest percentage of Ps. Aeruginos, it indicates 42.8%, followed by Staph isolates. Aureus 28.73%, E. coli 12.1%, P. mirabilis, 8.2%, K. pneumoniae8.2%, E. coli 3.37%, respectively. A peak also appeared at the wavelength of 479.2 nm for colloidal solution of nanoparticles prepared using pumpkin aqueous extract and iron salts using a spectrophotometer. The nanoparticles were characterized using SEM, AFM and FTIR. The prepared nanoparticles showed high efficacy in inhibiting the micro-organisms under study when performing MIC and MBC assays. Milliole concentration of nanoparticles also showed high inhibition of all types of microorganisms. When studying the effect of nanoparticles on the burns that may have caused in laboratory mice, a high efficiency in burn restoration and hair growth compared to control groups, treatment with burn ointment and aqueous extract of pumpkin.