Size-controlled Nanoparticles Research Articles

Single-step silica nanofluid for improved carbon dioxide flow and reduced formation damage in porous media for carbon utilization

Water-alternating gas (WAG) is affected by viscous fingering (with too much gas) and trapping of reservoir oil (with too much water) that can be addressed by advanced methods such as nanofluids, those not only increase CO2 capturing but also provide significant control on fingering. Therefore, this study reports the use of single-step silica nanofluids, of controllable nanoparticle (NP) size (below 100 nm), for improved CO2 flow and reduced formation damage in porous and permeable media. Polyacrylamide (PAM, 1000 ppm) was used as viscosifier and found favorable for enhanced dispersion stability (more than 2 months) in nanofluids. The parameters, such as amount of precursor (Tetraethylorthosilicate-TEOS) and catalyst (ammonium hydroxide-NH4OH), and amount of PAM were varied. Silica NPs were highly stable against agglomeration as reported by DLS, FTIR, TEM, SEM, and UV methods. Silica Nanofluids delayed CO2 breakthrough by retaining CO2 in sand-pack for longer duration than water/PAM. CO2 in presence of NPs made stable foam that was viscous and least mobile (than CO2) as confirmed by progressive increase in pressure while CO2 flow with water/PAM was unstable as pressure varied non-uniformly. This is of key importance for CO2 sequestration studies in porous reservoirs. Since NPs are solid substances, they can retain in sand-pack during nanofluid use for CO2 utilization strategies. NP retention was determined experimentally for different (1) sand-pack length, (2) flow rate, (3) NP concertation, and (4) test temperature. NP retention of only 8–12% of total injected amount was reported with Sand-pack length as the most influential variable.

Cellulose-Copper Oxide hybrid nanocomposites membranes for H2S gas detection at low temperatures

We report on novel, sensitive, selective and low-temperature hydrogen sulfide (H2S) gas sensors based on metal-oxide nanoparticles incorporated within polymeric matrix composites. The Copper-Oxide (CuO) nanoparticles were prepared by a colloid microwave-assisted hydrothermal method that enables precise control of nanoparticle size. The sodium carboxymethyl cellulose (CMC) powder with 5% glycerol ionic liquid (IL) was prepared and mixed with different concentrations of CuO NPs (2.5–7.5 wt.%) to produce flexible and semi-conductive polymeric matrix membranes. Each membrane was then sandwiched between a pair of electrodes to produce an H2S gas sensor. The temperature-dependent gas sensing characteristics of the prepared sensors were investigated over the temperature ranges from 40 °C to 80 °C. The sensors exhibited high sensitivity and reasonably fast responses to H2S gas at low working temperatures and at a low gas concentration of 15 ppm. Moreover, the sensors were highly selective to H2S gas, and they showed low humidity dependence, which indicates reliable functioning in humid atmospheres. This organic-inorganic hybrid-materials gas sensor is flexible, with good sensitivity and low power consumption has the potential to be used in harsh environments.

Nanoparticle–laser interaction: computation of size reduction and thermal conductance at solid–vapor interface

Laser interaction with a water-immersed metal nanoparticle can bring about a condition such that a bubble is generated and the nanoparticle is evaporated. This phenomenon is strongly dependent on the laser parameters and the nanoparticle size. In this study, we simulate the behavior of a gold nanoparticle and its surrounding medium during interaction with a nanosecond-pulsed laser by considering nanoparticle size reduction, variations in the nanoparticle absorption cross section, and variations in thermal conductance at the nanoparticle–bubble interface. Results show that the bubble dynamics under a low-energy and long-pulse-width laser (so that it does not cause evaporation) strongly depends on the nanoparticle temperature behavior, while under higher laser energy, it is dependent on the amount of nanoparticle size reduction. Moreover, by comparing the nanoparticle thermal behavior with experimental data, we are able to estimate the thermal conductance at the nanoparticle–bubble interface. This simulation not only leads to nanoparticle size control but also helps in understanding the heat transfer processes at nanoscale.

Precise size and dominant-facet control of ultra-small Pt nanoparticles for efficient ethylene glycol, methanol and ethanol oxidation electrocatalysts

Control of the structure and shape of platinum nanocrystals has recently attracted much attention, mostly due to their specific properties and related catalytic functionalities. However, the realization of platinum nanocrystals with controlled sizes and dominant facet types remains a significant challenge. In this study, platinum nanoparticles with controllable sizes and dominant facets are produced via a simple, organic agent-free, rapid, clean and direct chemical reduction method. The effects of initial solution pH on the sizes and dominant facets of the platinum nanoparticles are investigated and the mechanism for different sizes and facets are examined. Electrocatalytic analyses show that the catalytic activities and stabilities of the synthesized platinum nanoparticles are related to their sizes and dominant facets, and these nanoparticles display great potential as substitutes for commercial Pt/C in the effective catalysis of ethylene glycol, methanol, and ethanol electrooxidation in alkaline medium. Among the present platinum nanoparticles, the nanoparticles synthesized in pH 3 initial conditions, with small average size and (111)-dominant facets, display the best electrocatalytic activity and stability.

In situ synthesis of gold nanoparticles in polymer films under concentrated sunlight: control of nanoparticle size and shape with solar flux

We proposed a one step, green and efficient approach to synthesize plasmonic nanocomposites over large surfaces and with controlled morphologies.

Effect of surface ligands on gold nanocatalysts for CO2 reduction.

Nanoparticle catalysts display optimal mass activity due to their high surface to volume ratio and tunable size and structure. However, control of nanoparticle size requires the presence of surface ligands, which significantly influence catalytic performance. In this work, we investigate the effect of dodecanethiol on the activity, selectivity, and stability of Au nanoparticles for electrochemical carbon dioxide reduction (CO2R). Results show that dodecanethiol on Au nanoparticles significantly enhances selectivity and stability with minimal loss in activity by acting as a CO2-permeable membrane, which blocks the deposition of metal ions that are otherwise responsible for rapid deactivation. Although dodecanethiol occupies 90% or more of the electrochemical active surface area, it has a negligible effect on the partial current density to CO, indicating that it specifically does not block the active sites responsible for CO2R. Further, by preventing trace ion deposition, dodecanethiol stabilizes CO production on Au nanoparticles under conditions where CO2R selectivity on polycrystalline Au rapidly decays to zero. Comparison with other surface ligands and nanoparticles shows that this effect is specific to both the chemical identity and the surface structure of the dodecanethiol monolayer. To demonstrate the potential of this catalyst, CO2R was performed in electrolyte prepared from ambient river water, and dodecanethiol-capped Au nanoparticles produce more than 100 times higher CO yield compared to clean polycrystalline Au at identical potential and similar current.

Polyol-mediated synthesis of size-controlled copper nanoparticles under microwave irradiation

In this research, well-dispersed zero-valent copper nanoparticles (CuNPs) were successfully synthesized from a well-defined complex of [Cu(OH)(TMEDA)]2Cl2 in neat glycerol via a polyol method, under microwave irradiation (MW) assistance. The as-prepared CuNPs were thoroughly characterized by means of various techniques such as inductively coupled plasma mass spectrometry (ICP-MS), Ultraviolet-visible spectroscopy (UV-vis), X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, evidencing the formation of the spherical nanoparticles with the range of 3.24.2 nm in mean diameter. In addition, the size control of obtained CuNPs was examined via reaction time, thereby showing that the formation of CuNPs conformed to the model of “mono-dispersion”.

Effects of the amount of Au nanoparticles on the visible light response of TiO2 photocatalysts

Abstract We have succeeded to prepare Au nanopareticle deposited TiO2 photocatalysts (Au/TiO2) with control of Au nanoparticle size to be around 8 nm and variation of number density using a colloid photodepostion method. The prepared Au/TiO2 exhibits activity on decomposition (oxidation) of formic acid by thermally activated and photo-activated catalytic reactions. The thermally activated catalytic decomposition gradually increases with increasing the number density of deposited Au NPs and saturated, suggesting that the decomposition occurs on Au NPs surface and/or near the interface of TiO2 and Au NPs. On the other hand, the photocatalytic decomposition is significantly improved with rather small number density deposition of Au NPs and disappeared with high number density deposition. ESR measurements of Au/TiO2 in the surrounding similar to the photocatalytic decomposition suggests that electrons excited by plasmon resonance absorption in the Au NPs transfer to TiO2 to promote the decomposition. However, high number density deposition enhances electron capture by neighboring Au NPs and reduces the photocatalytic activity. Thus there should be the optimum number density of Au NPs on TiO2 for photocatalytic decomposition of formic acid.

Nanoparticle reinforced bacterial outer-membrane vesicles effectively prevent fatal infection of carbapenem-resistant Klebsiella pneumoniae

Infection resulting from carbapenem-resistant Klebsiella pneumoniae (CRKP) is an intractable clinical problem. Outer membrane vesicles (OMVs) from CRKP are believed to be potential vaccine candidates. However, their immune response remains elusive due to low structural stability and poor size homogeneity. In this study, hollow OMVs were reinforced internally by size-controlled BSA nanoparticles to obtain uniform and stable vaccines through hydrophobic interaction. The result showed that the BSA-OMV nanoparticles (BN-OMVs) were homogenous with a size around 100 nm and exhibited a core-shell structure. Remarkably, subcutaneous BN-OMVs vaccination mediated significantly higher CRKP specific antibody titers. The survival rate of the mice infected with a lethal dose of CRKP was increased significantly after BN-OMV immunization. The adoptive transfer experiment demonstrated that the protective effect of BN-OMVs was dependent on humoral and cellular immunity. This study demonstrated that the structure optimization improved the immune efficacy of OMVs for vaccine development against CRKP.

Nanocomposites with size-controlled nickel nanoparticles supported on multi-walled carbon nanotubes for efficient frequency-selective microwave absorption

Two types of nanocomposites based on multiwalled carbon nanotubes (MWCNTs) decorated with metallic nickel nanoparticles (NiNPs) possessing very different size distributions (13 vs. 130 nm) were produced using novel synthetic techniques. The obtained nanocomposites were dispersed in a polycarbonate (PC) matrix to produce thin (~500 μm) composite films. For the first time, we show that such films possess clear ferromagnetic resonances in the ultra-high frequency (UHF) and L microwave regions. Furthermore, we prove that their natural ferromagnetic (FMR) frequency is lowered when using nanocomposites with smaller NiNPs. These results could be exploited to design selective dual-band filters for telecommunications applications.

Temperature Variations of Gold Nanoparticle and Dynamics of Plasmonic Bubble in Water Under Nanosecond Pulsed Laser

Suspended gold nanoparticle in water medium starts to warm up under nanosecond laser irradiation and creates a bubble around itself. The present study aims at evaluating the amount of nanoparticle size reduction at boiling temperature, the temperature variations of the nanoparticle, and its medium and finally the bubble formation moment. To this aim, Mie theory was used to calculate the absorption cross section of the nanoparticle in proximity of the bubble. Heat transfer equations were applied to determine the temperature of the nanoparticle and water. In addition, hydrodynamic equations were initiated to evaluate the expansion of the bubble. Then, these three groups of equations were coupled together and solved numerically. Based on the results, the bubble forms at the critical pressure and consequently due to the slow bubble velocity, temperature gradient in the medium is observed. Further, slight pulse width variations play a significant role on the nanoparticle temperature. The calculation of the nanoparticle heating associated with the creation of the bubble helps in controlling nanoparticle size and understanding the nanoscale heat transfer processes.

Solvothermal Synthesis of Size-Controlled Monodispersed Superparamagnetic Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles are of great interest in magnetic targeted drug delivery due to their unique properties. In this paper, size-controlled superparamagnetic iron oxide nanoparticles were synthesized in an ethylene glycol/diethylene glycol (EG/DEG) binary solvent system via a facile solvothermal method. X-ray diffraction (XRD), a scanning electron microscope (SEM), and a vibrating sample magnetometer (VSM) were used to confirm that the prepared samples were superparamagnetic Fe 3 O 4 nanospheres. When the V EG / V DEG was varied from 100/0 to 80/20, 60/40, and 40/60, the average diameters of the resulting Fe 3 O 4 nanospheres were approximately 700, 500, 300, and 100 nm, respectively. In addition, the saturation magnetization ( M s ) of Fe 3 O 4 nanoparticles with a size of 100, 300, 500, and 700 nm was 72.14, 75.94, 80.28, and 85.41 emu/g, and the corresponding remanent magnetization ( M r ) was 3.34, 3.97, 3.26, and 4.28 emu/g, respectively. The relevant formation mechanisms of Fe 3 O 4 nanoparticles are proposed at the end. These superparamagnetic Fe 3 O 4 nanoparticles with high saturation magnetization may have use as targeted drug carriers.

Particle size control of monodispersed spherical nanoparticles with MCM-48-type mesostructure via novel rapid synthesis procedure

Monodispersed spherical silica nanoparticles with a cubic mesostructure were synthesized in a fast and innovative way using triethanolamine (TEA) and the triblock copolymer Pluronic® F127 as particle growth inhibitors to control the particle size in a range from 420 to 62 nm. In this study, we described a synthesis of mesoporous silica nanoparticles (MSNs) with MCM-48 structure at room temperature with adequate control of particle monodispersity, shape, and size using TEA. Based on particle characterization, TEA can efficiently act as catalyst and at the same time as particle growth controlling additive. A mixture of TEA and Pluronic® F127 additives was used to obtain very small MSNs (62 nm), whereby the quality of MCM-48 silica is associated with the composition of the additives used and thus also with the final particle size. A finely dispersed and high-quality MCM-48 material with ~ 100% yield, excellent textural properties, and a particle size of 295 nm was synthesized within only 35 min using excess TEA as particle size controlling and dispersion agent together with ammonia as additional catalyst. Solvent extraction combined with ion exchange removed the surfactant efficiently. All prepared MSNs showed good textural properties, tunable particle sizes with narrow size distributions, and good dispersity in water, which make them highly promising as carriers for biomolecules in biomedical applications.

Biofabrication of size-controlled ZnO nanoparticles using various capping agents and their cytotoxic and antitermite activity

ABSTRACT Herein, monodisperse Zinc oxide nanoparticles (ZnO-NPs) have been fabricated by green adeptness with and without using capping agents. The different capping agents used include Syzygium cumini leaves extract, starch and cetyl trimethyl ammonium bromide (CTAB). The UV/Vis analysis showed an exciton absorption band in the range of 370–385 nm for all NPs. The SEM analysis showed that average particle size of all ZnO NPs was consistent with that which was calculated by using the Debye-Scherrer equation also by using effective mass model approach. The XRD analysis has confirmed their crystalline nature and monodisperse size distribution. The Photoluminescence spectrum (PL) indicated the presence of surface defects on ZnO nanoparticles, which are the` driving force in the efficient photocatalysis of brilliant green dye showing 89.33% degradation efficiency after 2 h. The plant-mediated ZnO NPs were an efficient antimicrobial agent against P. aeruginosa, E. coli, A.baumannii and K. pneumoniae strains; however, all fungal strains including P. chrysogenum, A. niger, T. citrinoviride, A. fumigatus were resistant to ZnO NPs at all concentrations. Furthermore, they showed a strong antitermite activity against Heterotermes indicola workers and soldiers with a 100% mortality rate in 24 h.

A simple way of fabricating lyophilized wool nanoparticle powders using neutralization method

Lyophilized wool nanoparticle powders (L-WNPP) derived from wool fibers, were extracted through the neutralization method. Here, we propose the mechanism of wool nanoparticle (WNP) formation in an aqueous solution. The effects of pH, alkali concentration, and alkali treatment time on the size and morphology of WNP were investigated. Results confirmed that WNP were well dispersed and stable in the aqueous solution and globular particles were identified with an average size of 50 nm by using 3% sodium hydroxide (NaOH) after a 4-h treatment through dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), and transmission electron microscope (TEM) analyses. Furthermore, fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses showed that the L-WNPP maintained the chemical structure of wool protein. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that higher concentrations alkaline would destroy most amide bonds of molecule chains. Moreover, L-WNPP were further used to prepare transparent protein nanoparticle films. Our results will provide guidelines for developing protein nanoparticles for biotechnology fields that require size-controlled nanoparticles.

Effect of Zn on Size Control and Oxygen Reduction Reaction Activity of Co Nanoparticles Supported on N-Doped Carbon Nanotubes

Recently, N-doped carbon supported transition metals nanoparticles have received extensive attention as promising catalysts for oxygen reduction reaction (ORR). The size of decorated nanoparticles ...

Enhanced Synergetic Catalytic Effect of Mo2C/NCNTs@Co Heterostructures in Dye-Sensitized Solar Cells: Fine-Tuned Energy Level Alignment and Efficient Charge Transfer Behavior.

A highly efficient and stable electrocatalyst with the novel heterostructure of Co-embedded and N-doped carbon nanotubes supported Mo2C nanoparticles (Mo2C/NCNTs@Co) is creatively constructed by adopting the one-step metal catalyzed carbonization-nitridation strategy. Systematic characterizations and density functional theory (DFT) calculations reveal the advanced structural and electronic properties of Mo2C/NCNTs@Co heterostructure, in which the Co-embedded and N-doped CNTs with tunable diameters present electron-donating effect and the work function is correspondingly regulated from 4.91 to 4.52 eV, and the size-controlled Mo2C nanoparticles exhibit Pt-like 4d electronic structure and the well matched work function (4.85 eV) with I-/I3- redox couples (4.90 eV). As a result, the conductive NCNTs@Co substrate with fine-tuned energy level alignment accelerates the electron transportation and the electron migration from NCNTs@Co to Mo2C, and the active Mo2C shows high affinity for I3- adsorption and high charge transfer ability for I3- reduction, which reach a decent synergetic catalytic effect in Mo2C/NCNTs@Co heterostructure. The DSSC with Mo2C/NCNTs@Co CE achieves a high photoelectric conversion efficiency of 8.82% and exceptional electrochemical stability with a residual efficiency of 7.95% after continuous illumination of 200 h, better than Pt-based cell. Moreover, the synergistic catalytic mechanism toward I3- reduction is comprehensively studied on the basis of structure-activity correlation and DFT calculations. The advanced heterostructure engineering and electronic modulation provide a new design principle to develop the efficient, stable, and economic hybrid catalysts in relevant electrocatalytic fields.

Separate control of number density and size of ErAs nanoparticles by a modified diffusion length process using two flux conditions during molecular beam epitaxy

We have developed a two-step process for growth of ErAs nanoparticles (NPs) on GaAs-(001) surfaces which enables independent control of the NP size and number density (ND). A key feature is the extension of the Er-atom diffusion length between the steps. We use a short duration high Er flux to produce a low diffusion length (LDL) deposition step, aimed at controlling the NP nuclei density. This is followed by a long duration low Er flux to produce a high diffusion length (HDL) deposition step chosen such that the Er-atom diffusion length prevents additional nucleation, and only allows growth of pre-existing NP nuclei. We observed that deposition under the HDL condition alone causes surface roughening, which is prevented when combined with the LDL condition. This indicates that pre-existing nuclei are sinks to Er adatoms deposited under HDL conditions. Although in the present study the diffusion length was controlled by flux change alone, many other factors such as substrate temperature, surfactants, flux-ratios, should also be equally effective. This two-step approach is of general applicability, providing a means for separate control of NP size and ND in many other materials involving composite nanostructures.

Electronic and Optical Properties of Size-Controlled ZnO Nanoparticles Synthesized by a Facile Chemical Approach

Facile low-temperature chemical route for the synthesis of ZnO nanoparticles is reported in this paper. Morphologically uniform and spherical shape with an average particle size of 8.8 nm and wurtzite phase with the crystalline structure of as-synthesized ZnO nanoparticles were confirmed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The optical properties of ZnO nanoparticles were analyzed by UltraViolet Visible (UV-Vis) absorption and PhotoLuminescence (PL). The as-synthesized ZnO nanoparticles showed orange light-emitting properties when excited at 400 nm due to the well overlapping of electron and hole wave function across the compatible size of the particle of ZnO and the optical energy band gap of 3.5 eV due to quantum confinement. X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) were used for the elemental, molecular and energetic information of ZnO nanoparticles. UPS analysis depicted the energy level position of ZnO nanoparticles whereas XPS spectra showed the presence of constitute elementals with the stoichiometric atomic % of Zn and O. The elemental composition was also confirmed by the EDS analysis. The significant Raman shifts for as-synthesized ZnO nanoparticles in the typical Raman-active modes of vibration assigned to the wurtzite crystal nanostructure of ZnO.

Reactivity of (+)-Catechin with Copper(II) Ions: The Green Synthesis of Size-Controlled Sub-10 nm Copper Nanoparticles

The synthesis of metal nanoparticles via greener and sustainable methods has gained a great attention because of the use of natural products which are nontoxic and environmentally benign. Though ma...