Suspension Of Nanospheres Research Articles

Covalent organic framework functionalized smart membranes with under-liquid dual superlyophobicity for efficient separation of oil/water emulsions

The smart membrane with under-liquid dual superlyophobicity, which can achieve on-demand separation of oil/water emulsions only by simple liquid pre-wetting, is of essential value for the treatment of complicated real oil/water systems. Here, we first fabricated a stable suspension of imine-linked covalent organic framework nanospheres (TPB-DMTP-COF), and subsequently fabricated COF functionalized smart membranes with under-liquid dual superlyophobicity by immersing polyacrylonitrile-based (PAN-based) membranes into TPB-DMTP-COF nanosphere suspension. Accordingly, effective switchable separation of both oil-in-water and water-in-oil emulsions by TPB-DMTP-COF/PAN membranes can be achieved by employing pre-wetting processes (both the oil contact angle under water and the water contact angle under oil are over 150°). Specifically, the separation flux and the separation efficiency are higher than 1200 L/m2‧h and 98.0 %, and 2100 L/m2‧h and 97.4 % for the surfactant-stabilized oil-in-water and water-in-oil emulsions, respectively. Furthermore, the ultralow adhesions in liquid contributed to the outstanding reusability and antifouling resistance of the prepared TPB-DMTP-COF/PAN membranes. This work provides a feasible approach for fabricating a smart membrane with under-liquid dual superlyophobicity for oily wastewater treatment.

Two-dimensional electron beam size measurements with x-ray heterodyne near field speckles

In this paper we report on recent two-dimensional (2D) electron beam size measurements with a nonconventional synchrotron radiation interferometric technique based on x-ray heterodyne near field speckles (HNFS). The method relies on Fourier analysis of the random speckle patterns generated by a water suspension of nanospheres to assess the full 2D transverse coherence of the incoming x rays. The horizontal and vertical electron beam sizes are then retrieved by means of statistical optics approaches. The manuscript thoroughly describes the HNFS technique, and shows experimental results obtained at the ALBA Synchrotron Light Source. By changing the machine coupling, beam sizes as small as $5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ are measured, thus improving on past measurements reported in the literature and proving the HNFS diagnostics suitable for low-emittance particle beams.

The damping of terahertz acoustic modes in aqueous nanoparticle suspensions

In this work, we investigate the possibility of controlling the acoustic damping in a liquid when nanoparticles are suspended in it. To shed light on this topic, we performed Inelastic X-Ray Scattering (IXS) measurements of the terahertz collective dynamics of aqueous suspensions of nanospheres of various materials, size, and relative concentration, either charged or neutral. A Bayesian analysis of measured spectra indicates that the damping of the two acoustic modes of water increases upon nanoparticle immersion. This effect seems particularly pronounced for the longitudinal acoustic mode, which, whenever visible at all, rapidly damps off when increasing the exchanged wavevector. Results also indicate that the observed effect strongly depends on the material the immersed nanoparticles are made of.

Investigating the potential of using gold nanoparticle-functionalized micromechanical sensors for gamma radiation detection

Herein, we investigate the potential of using gold nanoparticle (AuNP)-functionalized microcantilever surfaces for gamma radiation detection. For this investigation, Si microelectromechanical system-based cantilevers and Si wafers are used. All the samples were irradiated using a60Co gamma source at different radiation doses (kGy). Using scanning electron microscopy, energy-dispersive X-ray and X-ray diffraction (XRD) spectroscopies, the optical properties of Si microcantilevers coated with AuNPs were studied before and after the irradiation. Atomic force microscopy (AFM) was used to determine the resonance frequency shift due to the usage of AuNPs as sensing layers on microcantilevers. The results demonstrated that Au nanosphere (50 and 100 nm) suspensions in water were successfully deposited on Si substrates via dropping deposition without requiring any chemical material. Clearly, the XRD patterns of the AuNPs coated onto the Si substrates had the same peaks before and after the irradiation; however, after gamma irradiation, all the peaks become more distinct. As per AFM, the responses of the 50-nm AuNP-coated sensors were highly sensitive and almost linear at radiation doses between 0 and 20 kGy, unlike the 100-nm AuNP-coated sensors, which did not exhibit any consistent response. This study constitutes a foundation for the development of a portable and cost-effective platform for the sensitive detection of nuclear radiations using micromechanical sensors.

Rat Blood Leukocytes after Intravenous Injection of Chitosan-Modified Magnetic Nanospheres.

Nanosized magnetite particles (magnetic nanospheres) are a prospective basis for creation of new diagnostic and therapeutic agents. The structure of blood leukocytes and the leukocytic formula are studied in adult rats over a period of 120 days after a single intravenous injection of chitosan-modified nanosized magnetite particles. No effects of chitosan-modified magnetic nanospheres on the structure of rat blood leukocytes are detected. Injection of suspension of chitosan-modified magnetite nanospheres is associated with an increase in the levels of monocytes, segmented and stab neutrophils, and a decrease in lymphocyte counts in the blood of rats. The shifts in the leukogram parameters are transitory, the picture returned to normal by day 40 postinjection.

Synthesis of Porous Particles by Electrospray-Assisted Self-Assembly for Water-Repellent or Photocatalytic Surfaces

In this study, an electrospray technique was used for the synthesis of macroporous ceramic particles, such as silica or titania, by a colloidal templating method. For this purpose, a suspension of polystyrene nanospheres was synthesized by dispersion polymerization for use as sacrificial templates. The feed solution containing a ceramic precursor and polymeric beads was injected through a metallic nozzle under a high electric field for nebulization of aerosol droplets as micro-reactors. Under ambient air conditions, the volatile components were evaporated from the droplets, and gelation of the precursor was completed simultaneously. The resulting supra-aggregates were then collected, and calcination was performed to form porous ceramic particles by removing the polymeric templates. As a demonstrative application, the porous particles of silica were deposited as a coating film for superhydrophobic surfaces with a high water contact angle larger than 150°. Furthermore, macroporous titania particles were used as photocatalytic particles in a wastewater system with first-order reaction kinetics.

Theoretical and Experimental Study of Photoacoustic Excitation of Silica-Coated Gold Nanospheres in Water

Silica-coated gold nanoparticles are commonly employed in biomedical photoacoustic (PA) imaging applications. We investigate theoretically and experimentally the PA signal generation by silica-coated gold nanospheres in water. Our theoretical model considers thermoelastic expansion in the long-pulse illumination regime, and the PA signals are determined based on a semi-analytical solution to the thermal diffusion equations and a finite-difference in time domain (FDTD) solution to the thermoelastic equations. Both the influence of interfacial thermal (Kapitza) resistance at the gold-water boundary and the influence of the silica coating on PA signal generation were investigated. Our results indicate that for the nanosecond pulses commonly employed in PA imaging, Kapitza resistance has a negligible effect on photoacoustic signal generation. Moreover, our model shows that the presence of a silica coating causes a reduction in the PA signal amplitude, with the level of signal reduction increasing with thicker silica coating. Our theoretical predictions are qualitatively consistent with our experimental results, where suspensions of in-house-synthesized and commercially available silica-coated gold nanosphere suspensions were excited with nanosecond-pulsed laser illumination at 532 nm. The PA signal amplitudes from silica-coated nanospheres were lower than the signal amplitudes for uncoated gold nanospheres of the same core gold diameter. The amount of reduction of the experimentally PA signal amplitude due to the silica coating was found to increase with thicker silica coating, in agreement with our theoretical predictions.

Distribution of benzalkonium chloride into the aqueous phases of submicron dispersed systems: emulsions, aqueous lecithin dispersion and nanospheres

Partitioning of benzalkonium chloride (BAC) into the aqueous phases of submicron dispersed systems such as submicron emulsions, aqueous lecithin dispersion (WLD), and suspension of nanospheres (NLC) was studied. The aqueous phases of the investigated systems were obtained by ultracentrifugation and subsequently were subjected to ultrafiltration, which procedure allowed distinguishing between the fractions of free benzalkonium chloride (w) and those incorporated in the liposomal and micellar region (wlm). The fractions present in the oily phase and in the interphase of submicron emulsions were calculated. Despite the various composition of the investigated formulations and the initial concentration of BAC, w values were very small at 0.2–8.0%. The wlm value in submicron emulsions was increased by increasing the total concentration of preservative from 29.0 to 42.0%. Using polysorbate 80 instead of lecithin resulted in a distribution of BAC to aqueous–liposomal–micellar phase that was twice as high. The very low concentration of antimicrobial active form of benzalkonium chloride was analyzed in the aqueous phase of emulsions stabilized with lecithin as well as in aqueous lecithin dispersion and nanospheres (below 3%). Replacement of lecithin with polysorbate 80 in emulsions with polysorbate significantly increase (up to 8%) the fraction of benzalkonium chloride in the aqueous phase where microbial growth occurs.

Low-Frequency Stimulated Scattering in an Aqueous Suspension of Dielectric Nanospheres

A low-frequency stimulated scattering (LFSS) signal caused by pulsations of nanospheres under an electromagnetic field is detected in an aqueous suspension of dielectric nanospheres of three diameters (∼74 nm, ∼292 nm, and ∼540 nm) at various particle concentrations. The frequency shifts of the scattering line, calculated based on the developed model, are in good agreement with the measurement results.

Stimulated Brillouin Scattering in an Aqueous Suspension of Dielectric Nanoparticles

Coherent radiation at the wavelength of stimulated Brillouin scattering concurrent with the incident laser beam has been observed for the first time in the aqueous suspension of dielectric nanospheres with an average diameter of about 290 nm at their concentration ranging from about 109 to 1011 cm−3. The theory of the phenomenon is constructed.

Sodium dodecyl sulfate microaggregates with diversely developed surfaces: Formation from free microdroplets of colloidal suspension

.Unsupported drying of microdroplets of colloidal suspension can lead to the formation of complex micro-morphologies with quasi-spherical symmetry. Herein, drying of levitating microdroplets of suspension of SiO2 nanospheres in diethylene glycol (DEG) with sodium dodecyl sulfate (SDS) is reported as a method for producing such microstructures with diversely developed surfaces. Dried products are “soft-landed” on a substrate and studied with scanning electron microscopy (SEM). The smallest SDS/SiO2 composites with the surface formed of crystallised SDS and interior filled with SiO2 nanospheres preserve the spherical symmetry. Larger microdroplets with higher initial mass fractions of SDS dry up to developed microstructures with SiO2 nanospheres arranged in-between the crystallised SDS flakes which are similar to curved lobe cabbage leaves or “desert rose”-like structures with radially directed SDS crystals. Largest microdroplets with highest initial mass fractions of SDS formed doughnut-shaped micro-containers filled with aggregated SiO2 nanospheres. In all these, SiO2 nanospheres served as a frame for the SDS crystallisation.

Exploiting Nonlinear Photoacoustic Signal Generation in Gold Nanospheres for Selective Detection in Serial 3D PA Tomography

The photoacoustic (PA) signal amplitude measured in gold nanosphere suspensions has been shown to increase nonlinearly with the incident excitation fluence. In this work, this effect is exploited to recover the spatial distribution of gold nanoparticles in tomographic 3D photoacoustic (PA) images against the background contrast provided by absorbers that exhibit a linear relationship between the PA signal amplitude and the fluence. Serial tomographic PA images of a tissue phantom containing gold nanospheres and a tissue-mimicking absorber were acquired. By assessing the linearity of the PA intensity voxel by voxel, the spatial distribution of the gold nanosphere suspension was recovered. The method is shown to enable the robust detection of gold nanoparticles.

Anomalous stimulated Brillouin scattering in aqueous suspension of polystyrene nanospheres

For the first time, stimulated Brillouin scattering (SBS) spectra have been measured for a suspension of dielectric nanoparticles in water. We observed anomalous dependence of SBS spectra on the concentration of polystyrene nanospheres (74 nm diameter). The nonlinear five-fold increase in the SBS threshold was determined for the nanosphere concentration range of 109 to 1015 cm−3.

Damping Off Terahertz Sound Modes of a Liquid upon Immersion of Nanoparticles.

The control of phonon propagation in nanoparticle arrays is one of the frontiers of nanotechnology, potentially enabling the discovery of materials with unknown functionalities for potential innovative applications. The exploration of the terahertz window appears quite promising as phonons in this range are the leading carriers of heat transport in insulators and their control is the key to implement devices for heat flow management. Unfortunately, this scientific field is still in its infancy, and even a basic topic such as the influence of floating nanoparticles on the terahertz phonon propagation of a colloidal suspension still eludes a firm answer. Shedding some light on this topic is the main motivation of the present work, which focuses an inelastic X-ray scattering (IXS) measurements on a dilute suspension of Au nanospheres in water. Measured spectra showed a nontrivial shape displaying multiple inelastic features that, based on a Bayesian inference analysis, we assign to phonon modes propagating throughout the nanoparticle interior. Surprisingly, the spectra bear no evidence of propagating modes, which are known to dominate the spectrum of pure water, owing to the scattering that these modes suffer from the sparse nanoparticles in suspension. In perspective, this finding may inspire simple routes to manipulate high-frequency acoustic propagation in hybrid-liquid and solid-materials.

Ultrastructure of Rat Kidneys after Intravenous Administration of Modified Magnetite Nanoparticles.

The ultrastructure of nephrocytes of the proximal and distal convoluted tubules, podocytes, mesangial cells, and macrophages of the interstitial connective tissue was studied after single intravenous administration of magnetite nanoparticles modified with chitosan (magnetic nanospheres) or lipids (magnetic liposomes). Transmission electron microscopy showed ultrastructural features of absorption of magnetite nanoparticles. The shape, size, and number of vesicles containing nanoparticles in nephrocytes of convoluted tubules and macrophages after administration of the suspensions of magnetic nanospheres and magnetic liposomes were described.

Nonlinear optical properties of dielectric nanocolloids: Particle size and concentration effects

The nonlinear optical properties of different samples of dielectric nanocolloids and their application to generate optical spatial solitons in two transverse dimensions are investigated. Each sample is constituted by a suspension of polystyrene nanospheres in water, and we analyze four cases with two different particle sizes (62[Formula: see text]nm and 77[Formula: see text]nm in diameter) and concentrations (0.5% and 1.0% solids). The z-scan technique is used to evaluate and compare the nonlinear refractive index of the nanocolloids. A detailed experimental study on the formation of soliton-like beams as a function of different parameters is also presented. Importantly, the generated solitons propagate along distances exceeding by one order of magnitude the propagation distances observed previously in the same kind of media.

Photoacoustic Signal Generation in Gold Nanospheres in Aqueous Solution: Signal Generation Enhancement and Particle Diameter Effects

Gold nanoparticles can be used as an exogenous contrast agent for biomedical photoacoustic (PA) imaging. The generation of PA signals in monodispersed gold nanosphere suspensions (diameters 20–150 nm) from pulsed-laser excitation (5 ns pulse width, wavelength 532 nm) was investigated experimentally and compared to signals measured in solutions of a homogeneous molecular absorber. The PA signal amplitude was found to increase linearly with excitation fluence for the homogeneous absorber and the nanospheres up to 80 nm in diameter. By contrast, the signal amplitude was found to increase quadratically with respect to fluence for larger nanospheres. In the linear regime, the PA signal amplitude in gold nanosphere suspensions was found to be on average 26% higher than that in the homogeneous absorber with identical absorption coefficient, which were measured using an integrating sphere. Furthermore, in suspensions with identical absorption coefficient, no dependence of the PA signal amplitude on nanosphere dia...

Enhanced photoacoustics from gold nano-colloidal suspensions under femtosecond laser excitation.

Enhanced photoacoustic (PA) intensity from gold nanosphere and nanorod colloidal suspensions in water under tightly-focused femtosecond pulsed laser irradiation was systematically investigated. PA signal amplitudes were measured by ultrasound transducers at frequencies of 5, 10, and 25 MHz. The experimental results revealed a linear-dependence of the relative photoacoustic amplitude on the laser power and the mechanism was attributed to non-radiative relaxation dynamics of surface plasmon oscillations. When gold nanorod with longitudinal absorption/extinction peak at 800 nm coincides with the wavelength of femtosecond laser pulses, the most efficient PA signal is generated. Laser excitation was kept within a thermal stability region of gold nanoparticles, i.e., colloidal suspension can be continuously reused for PA generation.

Poly(vinylimidazole) radiografted PVDF nanospheres as alternative binder for high temperature PEMFC electrodes

Within the framework of high-temperature polymer fuel cells doped with phosphoric acid, we investigate the replacement of the conventional binder in the catalyst layers by functionalized solid PVDF nanospheres. Aim of this study is to develop and test an innovative binder which might create enhanced electrode porosity and acid distribution. Aqueous suspensions of PVDF nanospheres (d ∼ 200 nm) are obtained by radical emulsion polymerization and are functionalized by Vinyl-Imidazole (VI) groups via in situ γ-radiation. As a consequence the nanospheres can interact with H3PO4 to obtain proton conductivity. Catalyst inks are prepared mixing the nanospheres with commercial Pt/C electrocatalyst powder, solvents and phosphoric acid. Prototype electrodes are deposited by spraying and preliminary fuel cell tests are carried out at 160 °C under dry H2/air. Electrodes with grafted PVDF nanospheres as solid binder are demonstrated and its understanding is in progress. Further improvements are outlined.

Direct detection of aggregates in highly turbid colloidal suspensions of polystyrene nanoparticles.

We demonstrate a total internal reflection-based method that detects, for the first time to the best of our knowledge, directly without any sample dilution or special sample preparation, the presence of aggregates in highly turbid aqueous suspensions of polystyrene nanospheres. Aggregation is induced by changing either the sample pH or ionic strength. The polystyrene mass density in our samples is two orders of magnitude higher than previously reported polystyrene aggregation studies. In cases when aggregates have formed but do not yet occupy a significant fraction of the sample volume, our sensor outperforms state of the art techniques such as dynamic light scattering in terms of sensitivity. Conversely, when the sample volume is dominated by aggregates, our sensor is not as effective.