Colloidal Samples Research Articles

Mn2+ ions incorporated into ZnS x Se1−x colloidal quantum dots: controlling size and composition of nanoalloys and regulating magnetic dipolar interactions

A facile synthesis method is introduced how to prepare magnetically active ultraviolet emitting manganese ions incorporated into ZnS x Se1−x colloidal quantum dot (nanoalloy) at 110 °C in aqueous solutions. The reaction time is the main factor to control the hydrodynamic size from 3 to 10 nm and the precursor ratio is significant to tune the alloy composition. ZnS shell layer on the ZnS x Se1−x core was grown to passivate environmental effects. The nanoalloy has ultraviolet emission at 380 nm having a lifetime of 80 ns and 7% quantum yield. The incorporation of Mn2+ ions into the nanoalloys induced magnetic activity but did not modify the structure and photophysical properties of the nanoalloys. Colloidal and powdery samples were prepared and analyzed by electron paramagnetic resonance (EPR) spectroscopy. In the colloidal dispersions, EPR spectra showed hyperfine line splitting regardless of the Mn2+ ion fractions, up to 6%, indicating that Mn2+ ions incorporated into the nanoalloys were isolated. EPR signals of the powdery samples were broadened when the fraction of Mn2+ ions was higher than 0.1%. The EPR spectra were simulated to reveal the locations and interactions of Mn2+ ions. The simulations suggest that the Mn2+ ions are located on the nanoalloy surfaces. These findings infer that the magnetic dipolar interactions are regulated by the initial mole ratio of Mn/Zn and the physical state of the nanoalloys adjusted by preparation methods.

The formation and antibacterial activity of Zn/ZnO nanoparticle produced in Pometia pinnata leaf extract solution using a laser ablation technique.

The single-step green synthesis has been successfully established to prepare a bi-phase structure of Zn/ZnO nanoparticles using laser ablation in a liquid medium. Nd: YAG laser with the wavelength of 1064 nm was employed to perform the laser ablation in pure water and Pometia pinnata (P. pinnata) leaf extract, with the leaf, were extracted in pure water and some concentration of ethanol. ZnO nanoparticles can be obtained via laser ablation in pure water, while the usage of P. pinnata leaf extract as the solution has caused the appearance of the bi-phase Zn/ZnO nanostructure. X-ray diffraction (XRD) pattern indicates the appearance of Zn peaks alongside with ZnO peaks with the inclusion of P. pinnata leaf extract. Transmission electron microscope (TEM) images show the change of shape from the rod-like shape into a spherical shape and smaller size spherical shape of Zn/ZnO nanoparticles in comparison with ZnO. Noticeable change of UV–visible spectrum emerges as the water was substituted by P. pinnata leaf extract. The zeta potential of Zn/ZnO prepared with P. pinnata extracted in water, with the value of − 18.9 V, reduces down to − 43.5 and − 41.1 for 20–40% of ethanol concentration, respectively. The as-prepared ZnO and Zn/ZnO colloidal samples were evaluated for their antibacterial activities against two strains Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Zn/ZnO sample shows a more substantial antibacterial effect in comparison with pure ZnO, no bacteria alive after 12 and 24 h’ treatment for E. coli and S. aureus, respectively.

Toxicity Evaluation of Arsenic Nanoparticles on Growth, Biochemical, Hematological, and Physiological Parameters of Labeo rohita Juveniles

The present study aims to assess the induced nanotoxicity of arsenic nanoparticles (AsNPs) on different organs of fresh water fish Labeo rohita. AsNPs were synthesized by chemical reduction method using sodium arsenite as precursor, ice‐cold sodium borohydride as reducing agent, and sodium hydroxide to adjust the solution pH. The synthesized AsNPs were characterized by UV‐Vis spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM) for optical, structural, and morphological investigations. The UV‐Vis absorption peaks occurring at around 300 nm indicated the presence of AsNPs in colloidal sample. The rhombohedral crystalline nature and metallic purity of AsNPs with crystallite size of 30 ± 1 nm were confirmed by characteristic peaks of XRD pattern. The SEM micrograph revealed the almost spherical shape and 40 ± 10 nm average size prepared AsNPs. For assessment of induced nanotoxicity, juveniles of Labeo rohita (L. rohita) were exposed to three different concentrations of AsNPs (namely, 1, 10, and 20 mg/L) for 30 days (n = 15 per group), and the control fish was kept untreated. It was observed that the routine behavior activities (such as swimming, mutual interactions, and feed intake) were affected by AsNPs. The growth of AsNPs treated fish was found retarded as compared to the control fish. Total erythrocyte count, total leukocyte count, and hemoglobin and hematocrit values were low in the AsNPs treated fish. Immunobiochemical assays revealed that protein level was altered in the AsNPs treated fish. The levels of antioxidant enzymes catalase and superoxide dismutase were low in the treated fish. The histological alteration induced by AsNPs in liver, gills, and kidneys demonstrated the damage in form of glomerulus shrinkage, vacuolation, inflammation, necrosis, lamellar disorganization, and hemorrhage in comparison with untreated fish. The results of the present study indicate that AsNPs exposure causes behavior, growth, hematology, immunobiochemical, and histological shortcomings in L. rohita.

Cellulose nanocrystal-grafted multi-responsive copolymers containing cleavable o-nitrobenzyl ester units for stimuli-stabilization of oil-in-water droplets

• Synthesis of multi-responsive CNC-grafted copolymers by SI-RAFT, • Using the PDMAEMA and poly( o -nitrobenzyl acrylate) as the responsive blocks, • Stabilization of the oil-in-water emulsions by the CNC-grafted copolymers, • Application of the CNC-grafted copolymers in Pickering emulsion polymerization of styrene, • Excellent performance of the CNC-grafted copolymers in photolithography. Hybrid smart surfactants are highly applicable in stabilization of oil-in-water droplets and also Pickering polymerizations. Temperature-, photo-, and pH-responsive cellulose nanocrystal (CNC)-grafted copolymers of N , N ′-dimethylaminoethyl methacrylate (DMAEMA) and o -nitrobenzyl acrylate (NBA) were synthesized in different molar ratio of NBA to DMAEMA via surface-initiated reversible addition-fragmentation chain transfer polymerization. Temperature-, pH-, and light-responsivity of the CNC-grafted polymers were evaluated by Fourier-transform infrared spectroscopy, dynamic light scattering (DLS), zeta potential, and ultraviolet–visible (UV–vis) spectroscopy. Critical flocculation temperature (CFT) of the CNC-grafted polymers was decreased by increasing pH and length of the PNBA block. Photo-cleavage mechanism and kinetics of the o -nitrobenzyl ester groups upon UV light irradiation were experimentally investigated in solutions with different pH values using UV–vis spectroscopy. The CNC-grafted polymers were used to stabilize n -hexane droplets in water and also prepare polystyrene latex by Pickering polymerization before and after exposure to UV light, respectively. Stability of the n -hexane-in-water suspensions was investigated as a function of light irradiation, temperature, pH, and CO 2 by optical microscopy and DLS. The scanning electron microscopy and transmission electron microscopy images showed spherical morphology of the colloidal polystyrene latex samples with particle size in the range of 500–600 nm. Consequently, these hybrid smart surfactants could be highly applicable in the preparation of colloidal polymer particles and oil-in water droplets with switchable stability upon different stimuli.

Multiple scattering effects on intercept, size, polydispersity index, and intensity for parallel (VV) and perpendicular (VH) polarization detection in photon correlation spectroscopy

Dynamic light scattering (DLS) is well established for rapid size, polydispersity, and size distribution determination of colloidal samples. While there are limitations in size range, resolution, and concentration, the technique has found ubiquitous applications from molecules to particles. With the ease of use of today’s commercial DLS instrumentation comes an inherent danger of misinterpretation or misapplication at the borderlines of suitability. In this paper, we show how comparison of different polarization components can help ascertain the presence of unwanted multiple scattering, which can lead to false conclusions about a sample’s mean size and polydispersity. We find that the contribution of multiple scattering events effectively reduces both the measured scattering intensity and the apparent size from the autocorrelation function. The intercept of the correlation function may serve as an indicator of relative strength of single to multiple scattering. Furthermore, the abundance of single scattering events at measurement positions close to the cell wall results in an apparent increase in uniformity yielding a lower polydispersity index which is more representative of the physical system.

Anti Fungal Studies of Tea Leaf mediated Silver Nano Colloid

Silver nano colloids are prepared using Tea leaf as reducing and stabilizing agent. Samples with different concentrations of the reducing agents are irradiated with gamma rays of various doses. Transmission Electron Microscope images of the samples show agglomerated clusters of nano particles before irradiation while the images of after irradiation show chain free individual nano particles with reduced size and spherical morphology. The Selected Area Electron Diffraction pattern confirms the crystal nature and face centred cubic structure of nano silver. UV-Visible spectroscopy gives absorption peaks in the blue region. Gamma irradiation results in the reduction in peak intensity without any change in wavelength. A statistical approach is done on treating the gamma irradiated colloidal sample with the as prepared silver nano colloid for measuring the affected area of fungal infection on a potato-agar medium. It is found that the fungal growth is declined rapidly with the introduction of gamma irradiated silver nano colloid than the as prepared colloid.

Temperature evaluation of colloidal nanoparticles by the thermal lens technique.

The use of highly sensitive thermometric methods is essential for the evaluation of nanoplatforms for photothermal therapy. In this study, the thermal lens technique was introduced to assess the optically induced temperature changes in colloidal samples of gold nanoparticles. Thermal lens measurements also allowed the acquisition of the nanoparticle absorption cross-section value, regardless of knowing the nanostructure scattering properties. The developed thermometric system exhibited 0.2 °C-1 sensitivity and was capable of measuring temperature variations of metallic colloidal samples with a resolution of 0.01 °C. Measuring colloidal temperature changes allows for the estimation of the localized temperature variation reached by each nanoheater, before thermalization of the excitation volume. Our results establish a practical and effective method to evaluate optically induced temperature changes on metallic colloids.

Biosynthesis, characterization and anti-dengue vector activity of silver nanoparticles prepared from Azadirachta indica and Citrullus colocynthis.

We report here biosynthesis of silver nanoparticles (AgNPs) using aqueous extracts of (i) Azadirachta indica leaves and (ii) Citrullus colocynthis fruit and their larvicidal activity against Aedes aegypti. The UV–Vis spectroscopy absorption peaks occurred in the range of 412–416 nm for A. indica AgNPs and 416–431 nm for C. colocynthis AgNPs indicating the silver nature of prepared colloidal samples. The scanning electron microscopy examination revealed the spherical morphology of both types of NPs with average size of 17 ± 4 nm (A. indica AgNPs) and 26 ± 5 nm (C. colocynthis AgNPs). The X-ray diffraction pattern confirmed the face-centred cubic (FCC) structure with crystallite size of 11 ± 1 nm (A. indica AgNPs) and 15 ± 1 nm (C. colocynthis AgNPs) while characteristic peaks appearing in Fourier transform infrared spectroscopy analysis indicated the attachment of different biomolecules on AgNPs. The larvicidal activity at different concentrations of synthesized AgNPs (1–20 mg l−1) and extracts (0.5–1.5%) against Aedes aegypti was examined for 24 h. A concentration-dependent larvicidal potential of both types of AgNPs was observed. The LC50 values were found to be 0.3 and 1.25 mg l−1 for C. colocynthis AgNPs and A. indica AgNPs, respectively. However, both extracts did not exhibit any notable larvicidal activity.

Near field scattering for samples under forced flow

We describe a light scattering technique for characterizing colloidal samples under constant flow. It exploits the properties of speckles in the deep Fresnel region-the so-called near field speckles-providing absolute scattering measurements of the static form factor of the sample, as described extensively by Mazzoni et al. [Rev. Sci. Instrum. 84, 043704 (2013)] for static samples. We exploit a strongly astigmatic beam for illuminating the scattering volume with a light sheet a few microns thick. This largely improves the sensitivity of the method to small signals. Moreover, by flowing the sample in the direction perpendicular to the light sheet, the transit times are reduced to a minimum, allowing for fast measurements. We tested the instrument with suspensions of calibrated colloidal polystyrene spheres with a size comparable to the light wavelength. In particular, we recovered the static form factors of suspensions of spherical particles and the phase lag of the zero-angle scattering amplitude, which both compare well to Mie theory predictions. We then applied the method to colloidal fractal aggregates of sub-wavelength particles and measured their fractal dimension. The instrument is designed to be operational in continuous flow analysis systems.

Temperature-Compensated Refractive Index Measurement Using a Dual Fabry–Perot Interferometer Based on C-Fiber Cavity

We demonstrate a simple-to-fabricate, temperature-compensated refractive index sensor using a dual Fabry-Perot optical fiber interferometer using C-fiber. The sensor device is formed by combining two types of in-fiber interferometers, including a C-fiber Fabry-Perot interferometer and a single mode fiber (SMF) Fabry-Perot (FP) interferometer. The C-fiber is a silica capillary with an open side, which allows external liquid to directly enter the internal hole. The C-fiber interferometer is sensitive to external refractive index (1704 nm/RIU) as well as temperature (-0.196 nm/°C) due to the thermo-optic effect and thermal expansion of the C-fiber cavity, while the SMF interferometer is only sensitive to ambient temperature (0.0118 nm/°C). Thus, temperature-compensated refractive index measurement can be achieved by examining the phase shift responses of the two FP interference peaks with transfer matrix approach, solving the problem of temperature sensitivity of RI sensors due to the relatively large thermo-optic coefficient of colloidal materials and aqueous samples.

Orientation Effects on Plasmonic Heating of Near-Infrared Colloidal Gold Nanostructures

Photothermal therapy assisted by plasmonic nanostructure relies on the absorption of light energy by the metallic nanoparticle. The manifestation of a rational use of plasmonic-assisted superficial laser thermal therapy procedures requires the analyses of the thermoplasmonic behavior of colloidal nanostructures in random orientation. A quantitative analysis of orientation effect on optically heating metallic nanostructures still unrevealed. Here, we evaluate the thermal properties of metallic nanoparticles (SiO2/Au core-shell particles, Au nanotriangles, Au nanorods, and Au nanocages) irradiated by polarized light. We perform 3D full-wave field analysis to compare absorption properties and temperature rise of these nanoparticles as a function of the nanostructure orientation with respect to applied field polarization. The analysis shows a major variation in joule number of asymmetrical nanostructures (up to 50%) due to orientation effects, which may limit its performance on colloidal photothermal applications. In contrast, the high degree of rotational symmetry of core-shell nanoparticles and nanocages provide greater potential in thermal-assisted phototherapy applications, as their absorption is largely independent (less than 2%) of their orientation in colloid. Our computational results establish new insights for the use of gold nanocages, as a high performance plasmonic structure for thermal applications with colloidal samples.

Effect of sodium pyrophosphate and understanding microstructure of aqueous LAPONITE® dispersion using dissolution study

In this work, we investigate the physical origin of ergodicity breaking in an aqueous colloidal dispersion of synthetic hectorite clay, LAPONITE®, by performing dissolution and rheological experiments with monovalent salt and tetrasodium pyrophosphate solution. We also study the effect of pH and nature of interface, nitrogen and paraffin oil on the same. Dissolution experiments carried out for dispersions with both the interfaces show similar results. However, for samples with a nitrogen interface, all the effects are observed to get expedited in time compared to a paraffin oil interface. When kept in contact with water, 1.5 wt.% and 2.8 wt.% colloidal dispersion at pH 10 swells at small ages, while it does not swell at large ages. The solution of tetrasodium pyrophosphate, interestingly, dissolves the entire colloidal dispersion sample with pH 10 irrespective of the concentration of clay. Experiments carried out on colloidal dispersions prepared in water having pH 13 demonstrate no effect of water as well as sodium pyrophosphate solution on the same suggesting a possibility of the presence of negative charge on edge at that pH. We believe that all the behaviors observed for samples at pH 10 can be explained by an attractive gel microstructure formed by edge-to-face contact. Furthermore, the absence of swelling in old colloidal dispersion at pH 10 and dissolution of the same by sodium pyrophosphate solution cannot be explained by merely repulsive interactions. This behavior suggests that attractive interactions originating from edge-to-face contact play an important role in causing ergodicity breaking in the colloidal dispersions at pH 10 at all the ages irrespective of the clay concentration. We further substantiate the presence of a fractal network structure formed by interparticle edge–face association using rheological tools and cryo-TEM imaging. We also conduct a comprehensive study of the effect of tetrasodium pyrophosphate on the sol–gel transition of LAPONITE® dispersion.

Synthesis method of novel Gd2O3@Fe3O4 nanocomposite modified by dextrose capping agent

In current study, gadolinium oxide was heterogeneously formed on the surface of iron oxide nanoparticles and further modified with dextrose capping agent to be used in biomedical applications, especially for contrast enhancement in MR images. First, two types of iron oxide nanoparticles were prepared at 25 and 80 °C via simple coprecipitaion method. Then, gadolinium oxide nanoparticles were synthesized through a consecutive precipitation process on previously formed iron oxide seeds in an aqueous media and subsequent annealing at 300 °C. Finally, dextrose was used as capping agent to stabilize nanocomposites in a colloidal suspension. X-ray diffraction (XRD), Scanning and Transmission electron microscopy, Dynamic Laser Scattering (DLS), Fourier-Transform Infrared Spectroscopy (FTIR), and Magnetometery (VSM) techniques were employed for nanocomposites investigation and MTT-assay method used for viability assessment of colloidal samples. Measurements based on Scherrer equation from XRD patterns showed that increasing coprecipitation temperature resulted bigger iron oxide crystallites. The iron oxide crystallite size was increased from 15.1 to 28.1 nm. Precipitation process led to gadolinium oxide formation with 30.7 and 38.8 nm crystallite sizes, respectively. TEM images revealed that iron oxide agglomerates were encapsulated in gadolinium oxide surroundings. Hydrodynamic size of the coated nanoparticles with dextrose was 208 and 247 nm. In VSM examinations, nanocomposites did not display coercive field and the saturation magnetization was 1.93 emu/g. MTT-assay results showed 80% viability in 285 μg nanocomposites containing 96.9 μg [Fe] and 11.4 μg [Gd].

Colloidal (Gd0.98Nd0.02)2O3 nanothermometers operating in a cell culture medium within the first and second biological windows

Non-contact, self-referenced and near-infrared luminescent nanothermometers have been recognized as emerging tools in the fields of nanomedicine and nanotechnology due to their great capability of precise temperature readout at the nanoscale and real-time deep-tissue imaging. However, the development of multifunctional and biocompatible luminescent nanothermometers operating within the optically transparent biological windows with high thermal sensitivity (>2.0%/K) remains challenging. Here, we present (Gd0.98Nd0.02)2O3 nanothermometers operated effectively within the first and second biological windows upon continuous-wave laser diode excitation at 808 nm. Ratiometric thermometric parameters are defined by the relative changes in the emission intensities originating from the two Stark components of the 4F3/2 level (R2 and R1) to the 4I9/2 (900–1000 nm), 4I11/2 (1035–1155 nm) and 4I13/2 (1300–1450 nm) multiplets. The thermometric parameters are evaluated for colloidal samples in a cell culture medium and powder samples, and the highest thermal sensitivity (2.18%/K at 298 K) is attained for the former in the first biological window (both the excitation and emission in the 800–965 nm range). The repeatability and temperature uncertainty are 99% and 1.2 K, respectively. The nanothermometers are biocompatible with human MNT-1 melanoma and HaCaT cells for 24 h of exposure and nanoparticle concentration up to 0.400 mg/mL, showing their potential for applications in nanomedicine, e.g., intracellular imaging and temperature mapping.

Particle size distribution from extinction and absorption data of metallic nanoparticles.

We describe a method for inverting spectroscopic data of the absorption and extinction properties of colloidal samples of resonant particles. We show that, with some prior knowledge, the genetic algorithm employed is able to estimate the probability density function of particle sizes. Since the data are sensitive to the shape and material of the particles, some information about these properties can also be retrieved. The viability of the method is illustrated by inverting numerically generated data, as well as experimental data obtained with specially prepared samples of metallic nanoparticles in aqueous suspension.

Generation of Size-Controlled Crystalline CeO2 Particles by Pulsed Laser Irradiation in Water

The defining characteristics of nanoparticles (NPs) include variation of properties as a function of size and shape, requiring their preparation with desirable dimensions and morphologies. Here, a unique approach based on pulsed laser irradiation in liquid (PLIL) was developed to reshape commercial CeO2 NPs suspended in water in an attempt to respond to these challenges. Guided by the results of Mie theory and the predictions of the heating–melting–evaporation model, the fourth harmonic of an Nd:YAG laser (266 nm, 10 Hz, ∼5 ns) was selected and used for lateral irradiation of colloidal CeO2 samples at particular laser fluences and number of laser pulses for producing size- and shape-specific crystalline NPs. Spectral and structural analyses of the NPs, prior to and following PLIL, revealed shape and crystal size alterations depending on the irradiation parameters, affecting melting, evaporation, and solidification of the particles. The change in size, shape, and agglomeration could be followed by the results of the analyses, where the first two could be also interpreted by the modeling results. This study demonstrates that controlled CeO2 crystal particles, from nano- to submicrometer diameters, could be generated by PLIL, shedding new light on the dynamics of the process.

Localized surface plasmon resonance (LSPR) detection of hydrogen gas by Pd2+/Au core/shell like colloidal nanoparticles

A hydrogen detector colloidal solution based on the plasmonic properties of gold nanoparticles (GNPs) is presented. GNPs were prepared by pulsed laser ablation (PLA) of gold target in DI water. PdCl2 solution with different concentration was added to the obtained GNPs colloidal solutions. X-ray diffraction (XRD) confirmed the formation of metallic gold and presence of PdCl2 phases. Transmission electron microscope (TEM) images along with X-ray photoelectron spectroscopy (XPS) revealed formation of the core-shell-like structures of Pd2+/Au NPs. After hydrogenation, TEM revealed that the core-shell morphology changes into free NPs and XPS revealed formation of the metallic Pd phase. Voltammetry analysis showed a well absorption and desorption capability of hydrogen in this gold-PdCl2 plasmonic system. After adding PdCl2 aqueous solution, a red-shift from 522 to 526 nm was observed which was attributed to Pd2+ ion attraction by the negative surface charge of bare GNPs and formation a core-shell like morphology. The optical absorption peaks of PdCl2 (the range 207–236 nm) as well as the LSPR peak of GNPs were traced during diluted hydrogen (0.3–10%) injection in colloidal samples with different Au:Pd molar ratio. It was found that the PdCl2 peaks drop due to Pd2+→Pd0 conversion and more importantly, the gold peak undergoes blue shift due to change in chemical properties of GNPs surrounding. A good correlation between PdCl2 absorption intensity and gold LSPR peak position was found when hydrogen concentration was varied. In this correlation, a desirable detection capability for low concentrations of hydrogen (<4% range, the limit of hydrogen explosion) with a possible large number of points was observed. Finally, a model for the hydrogen sensing mechanism based on the LSPR effect was presented.

The size dependent thermal diffusivity of water soluble CdTe quantum dots using dual beam thermal lens spectroscopy

Abstract Size dependent thermal diffusivity of CdTe colloidal quantum dots samples has been studied using dual beam thermal lens spectroscopy. The thermal diffusivity values of the colloidal solution of CdTe quantum dots synthesized in water were found to be less than that of pure water (1.4 × 10−7 m2/s) varying from 0.63 × 10−7 m2/s to 0.15 × 10−7 m2/s. The samples with this kind of very low value of thermal diffusivity can be good thermal insulators. To the best of our knowledge there are no reports on the study of thermal diffusivity of water soluble CdTe quantum dots. The non-radiative relaxation mechanism due to defect states, Brownian motion, capping agent etc. play major roles in controlling the thermal diffusivity of the nano-colloidal sample. The thermal diffusivity is found to be in inverse correlation with the emission intensity.

Nanomotor tracking experiments at the edge of reproducibility

The emerging field of self-propelling micro/nanorobots is teeming with a wide variety of novel micro/nanostructures, which are tested here for self-propulsion in a liquid environment. As the size of these microscopic movers diminishes into the fully nanosized region, the ballistic paths of an active micromotor become a random walk of colloidal particles. To test such colloidal samples for self-propulsion, the commonly adopted “golden rule” is to refer to the mean squared displacement (MSD) function of the measured particle tracks. The practical significance of the result strongly depends on the amount of collected particle data and the sampling rate of the particle track. Because micro/nanomotor preparation methods are mostly low-yield, the amount of used experimental data in published results is often on the edge of reproducibility. To address the situation, we perform MSD analysis on an experimental as well as simulated dataset. These data are used to explore the effects of MSD analysis on limited data and several situations where the lack of data can lead to insignificant results.

Study of Silver and Copper Nanoparticles by Electron and Atomic Force Microscopy

Electron and atomic force microscopy was used to study nanosuspensions of silver (50 mg/L) and silver (85 mg/L) and copper (25 mg/L) mixtures in edible glycerin and silver and copper nanoparticles directly deposited onto a silicon substrate by ion plasma sputtering in vacuum at cathode voltages of 1000 and 1600 V. A colloidal silver sample (12 mg/L) of the NSP Company (Nature’s Sunshine Products) was studied for comparison. The samples from different batches of silver and silver–copper nanosuspensions consist of independent single-crystalline particles and their aggregates, while the NSP colloidal silver samples mainly consist of individual particles. The characteristic diameter of the particles produced directly in the sputtering process at different cathode voltages was shown to depend on energy transfer: at higher cathode voltages, the nanoparticles become coarser, but no sublattice is observed in the coarsened particles.