Nanoparticles In Channels Research Articles

Preparation of silver nanoparticles decorated mesoporous silica nanorods with photothermal antibacterial property

In this paper, we report the formation of rod-like silver nanoparticles in the internal porous channels of mesoporous silica nanoparticles (MSN) via in-situ reduction of silver ions (Ag+) by n-butylamine. This method was facile and mild. By carefully adjusting concentration of the silver source, the plasmonic absorption bands of the prepared MSN/Ag nanocomposites could be tuned and controlled in the visible to near-infrared region. TEM observation proved the formation of rod-like Ag nanoparticles in the channel pores and Ag nanospheres were also found on the external surfaces of the MSN. A green colored MSN/Ag-Gel hydrogel was further obtained by simply mixing the MSN/Ag nanocomposites with gelatin. It displayed efficient and repeatable photothermal conversion ability due to the excellent photothermal property of the incorporated MSN/Ag nanocomposites when irradiated by a 660 nm laser. And by virtue of this photothermal property, a bacterial killing efficiency of more than 99% could be achieved after incubating E. coli with the MSN/Ag-Gel hydrogel, in which concentration of MSN/Ag nanocomposites was at a relatively low value. These results make the MSN/Ag-Gel hydrogel an efficient and cost-effective material for antibacterial fields.

Interfacial synergistic catalysis over Ni nanoparticles encapsulated in mesoporous ceria for CO2 methanation

An ordered mesoporous ceria, mpCeO2, was synthesized using nanocasting, followed by strong electrostatic adsorption to prepare Ni nanoparticles encapsulated in mpCeO2 for CO2 methanation. At 225 °C, TOF of Ni/mpCeO2 catalyst (0.183 s−1) is 3 times higher than that of Ni catalyst supported on conventional CeO2 prepared by the same method (0.057 s−1). Characterization results indicate that encapsulated structure provides rich Ni-CeO2 interface with more oxygen vacancies, playing a key role in CO2 activation. As evidenced by in-situ DRIFTS experiments, CO2 activation over Ni/mpCeO2 catalyst occurs through combined associative and dissociative mechanisms. Moreover, small and highly dispersed Ni nanoparticles in channels of mpCeO2 facilitate H2 dissociation, supplying sufficient *H for CO hydrogenation with *HCO intermediate species and leading to high CH4 selectivity. In addition to enhanced low-temperature activity and selectivity, Ni/mpCeO2 catalyst is very stable throughout 70 h since metal sintering can be inhibited by confinement effect of mesoporous structure.

Regulation of the size of metal iron nanoparticles in channels of mesoporous silica matrices (MCM-41, SBA-15) and structure and magnetic properties of the received nanocomposites МСМ-41/Fe0 and SBA-15/Fe0

In modern methods of synthesis of nanostructured materials based on mesoporous silica matrices (MCM-41, SBA-15), it is not possible to simultaneously fine adjust both the pore diameter and the thickness of the separating walls. This article presents the results of work on the creation of composites based on mesoporous silica matrices MCM-41 and SBA-15, reinforced with metallic Fe nanoparticles (Fe NPs). The article considers a new way of ultrafine regulation of the pore radius and separating wall thickness mesoporous silica SBA-15. In this work, we studied the changes in their structural and magnetic characteristics by directionally adjusting the geometric parameters of the porous structure of the initial matrices. The following methods are applied to adjust the silica pore parameters: hydrothermal treatment and templating using a micellar expander. The technique is based on building up aluminum-oxygen nanolayers on the pore walls using gas-phase atomic layer deposition technique (ALD). Studying room-temperature magnetization of Fe NPs obtained during the synthesis in a matrix of mesoporous silica MCM-41 (pore size of 3–5 nm) allowed us to establish superparamagnetic properties of such magnetic materials, which allows to use them in medicine for targeted drug delivery. Fe NPs in the mesoporous silica SBA-15 matrix with a pore size of 3–6 nm also exhibit superparamagnetic properties, and these composites showed a coercive force increase with an increase in the original matrix pore size.

Nanoparticle Flow in Polymer Grafted Channels

A better understanding of the specifics of nanoparticle transport through channels with polymer coated walls is of great importance for various biological, technological, and analytical processes. Here, we study flow of bare and ligand-functionalized nanoparticles in channels grafted with polymer brushes using dissipative particle dynamics. A dimensionless relationship is established between the ratio of the particle and solvent mean velocities and the scaling factor that equals the ratio of the particle size to the channel width reduced by the hydrodynamic thickness of a polymer brush. The simulated particle velocity profiles are found to be in agreement with experiments on the flow of polystyrene beads in hard-wall channels with the same scaling factor. The fact that the dimensions of particles and channels in simulations and experiments differed by 3 orders of magnitude confirms that the simulation results can be used to model experimental systems of larger size, in particular, nanoparticle separation on polymer grafted chromatographic columns.

Three-dimensional numerical study of the laminar flow and heat transfer in a wavy-finned heat sink filled with Al2O3/ethylene glycol-water nanofluid

ABSTRACTWavy-finned arrangement and nanofluid medium are applied to a heat sink for the purpose of achieving more efficient thermal hydraulic performance. Laminar forced convection of Al2O3/ethylene glycol–water nanofluid in a 3D wavy channel is considered. Computational Fluid Dynamics (CFD) simulations are conducted in a wide spectrum of nanoparticle volume concentrations (0.2% 0.3% 0.4% 0.5% 1% 2% 3% and 4%) with the Reynolds number varying between 400 and 1 200. Wavy channels are proved to dramatically improve the heat transfer performance compared with the plain channels of the same cross section. Utilizing nanofluid in a wavy channel further enhances the heat transfer but also brings additional flow resistance. Synthesizing wavy-finned arrangement and nanofluid technique achieves the highest overall thermal hydraulic performance factor of 1.74 for ϕ = 0.2% and Re = 600. In the wavy channel nanoparticle concentration is supposed to be less than 1.0% to provide a positive effect for the overall performance.

Surfactant addition and alternating current electrophoretic oscillation during size fractionation of nanoparticles in channels with two or three different height segments

An array of parallel planar nanochannels containing two or three segments with varying inner heights was fabricated and used for size fractionation of inorganic and biological nanoparticles. A liquid suspension of the particles was simply drawn through the nanochannels via capillary action. Using fluorescently labeled 30 nm polyacrylonitrile beads, different trapping behaviors were compared using nanochannels with 200-45 nm and 208-54-30 nm height segments. Addition of sodium dodecyl sulfate (SDS) surfactant to the liquid suspension and application of an AC electric field were shown to aid in the prevention of channel clogging. After initial particle trapping at the segment interfaces, significant particle redistribution occurred when applying a sinusoidal 8V peak-to-peak oscillating voltage with a frequency of 150 Hz and DC offset of 4V. Using the 208-54-30 nm channels, 30 nm hepatitis B virus (HBV) capsids were divided into three fractions. When the AC electric field was applied to this trapped sample, all of the virus particles passed through the interfaces and accumulated at the channel ends.