Growth Of Nanoparticles Research Articles

Novel Nafion nanocomposite membranes embedded with TiO2-decorated MWCNTs for high-temperature/low relative humidity fuel cell systems

Extending the operation of proton exchange membrane fuel cells (PEMFCs) at high temperature (i.e., 120 °C) and/or low relative humidity (< 50% RH) remains a significant challenge due to dehydration and subsequent performance failure of the Nafion electrolyte. We approached this problem by integrating the Nafion matrix with a novel hybrid nanofiller, created through direct growth of TiO2 nanoparticles on the surface of carbon nanotubes. This synthetic approach allowed to preserve an effective nanodispersion of Titania particles in the hosting matrix, thereby boosting dimensional stability, hydrophilicity, and physiochemical properties of the Nafion/MWCNTs-TiO2 (NMT-x) nanocomposites compared to parental Nafion. At optimal concentration (i.e., 3 wt% with respect to the polymer), the nanocomposite membrane exhibited high transport characteristics with impressive water retention capabilities, resulting in a proton conductivity of 8.3 mS cm− 1 at 80 °C and 20% RH. The Titania nanoparticles plays a key role in retaining water molecules even under dehydrating conditions, while also directly contributing to proton transport. Additionally, the long carbon nanotubes promote the formation of additional paths for proton conductivity. These combined features enabled the NMT-3 membrane to achieve a maximum power output of 307.7 mW/cm2 in a single H2/air fuel cell (5 cm2 active electrode area and 0.5 mg Pt/cm2 at both electrodes) under very challenging conditions, specifically at 120 °C and 30% RH. This represents a significant advancement towards overcoming the limitations of traditional Nafion membranes and opens up new possibilities for high-temperature, low-humidity H2/air fuel cell applications.

In situ formation of silver nanoparticles within labradorite mineral crystals exhibiting third-order nonlinearity

Silver nanoparticles are cost-effective plasmonic materials for the nonlinear optics, but the applications suffer incompatibility with the matrices. This study explores the in situ formation of silver nanoparticles within the crystalline matrix of labradorite minerals. The methodology involves a high-temperature diffusion process, enabling the nucleation and growth of silver nanoparticles directly within the labradorite crystal lattice. Characterization through spectroscopic and microscopic techniques reveals the successful formation of silver nanoparticles with a diameter of 8.40 ± 4.32 nm, exhibiting notable surface plasmonic resonances absorption at 414 nm. Additionally, the nonlinear optical property of the resulting material is investigated through Z-scan experiments. The third-order nonlinear optical susceptibility β at 400 nm was estimated to be 5.0 × 10−12 m/W. This research not only advances our understanding of nanoscale phenomena within mineral crystals but also underscores their potential applications in nonlinear optical devices and related fields.

Two‐step simulation combining large eddy simulation and population balance Monte Carlo for nanoparticle synthesis in flame spray pyrolysis

AbstractA two‐step simulation approach combining large eddy simulation (LES) for turbulent flame and multidimensional/multivariate population balance Monte Carlo (PBMC) for nanoparticle dynamics is proposed to explore the detailed flame fields and particle dynamics of zirconia nanoparticles in a flame spray pyrolysis (FSP) reactor. The turbulent combustion of gas and spray are simulated by the nonlinear LES‐partially stirred reactor model. Thereafter, the differentially weighted PBMC is applied for the first time to describe the spatially resolved formation and growth of nanoparticles using the flame fields derived from LES as an input. An efficient submodel for particle spatial transport in multidimensional grids is adopted and tested to account for the effect of thermophoresis, convective and diffusion of the nanoparticles. This methodology is successfully applied to an FSP case, demonstrating a reliable level of fidelity when compared to experiments and other model. Simulation results are discussed, in particular the flame fields and the size, morphology, as well as polydisperse primary particle and aggregates size distribution.

Precision engineering of nano-assemblies in superfluid helium by the use of van der Waals forces

The ability to precisely engineer nanostructures underpins a wide range of applications in areas such as electronics, optics, and biomedical sciences. Here we present a novel approach for the growth of nanoparticle assemblies that leverages the unique properties of superfluid helium. Unlike viscous solvents at or near room temperature, superfluid helium provides an unperturbed and cold environment in which weak van der Waals interactions between molecular templates and metal atoms become significant and can define the spatial arrangement of nanoparticles. To demonstrate this concept, diol and porphyrin-based molecules are employed as templates to grow gold nanoparticle assemblies in superfluid helium droplets. After soft-landing on a solid surface to remove the helium, transmission electron microscopy (TEM) imaging shows the growth of gold nanoparticles at specific binding sites within the molecular templates where the interaction between gold atoms and the molecular template is at its strongest.

Nucleation and growth of plasma sputtered silver nanoparticles under acoustic wave activation

Early results on the plasma deposition of dielectric thin films on acoustic wave (AW) activated substrates revealed a densification pattern arisen from the focusing of plasma ions and their impact on specific areas of the piezoelectric substrate. Herein, we extend this methodology to tailor the plasma deposition of metals onto AW-activated LiNbO3 piezoelectric substrates. Our investigation reveals the tracking of the initial stages of nanoparticle (NP) formation and growth during the submonolayer deposition of silver. We elucidate the specific role of AW activation in reducing particle size, enhancing particle circularity, and retarding NP agglomeration and account for the physical phenomena making these processes differ from those occurring on non-activated substrates. We provide a comparative analysis of the results obtained under two representative plasma conditions: diode DC sputtering and magnetron sputtering. In the latter case, the AW activation gives rise to a 2D pattern of domains with different amounts of silver and a distinct size and circularity for the silver NPs. This difference was attributed to the specific characteristics of the plasma sheath formed onto the substrate in each case. The possibilities of tuning the plasmon resonance absorption of silver NPs by AW activation of the sputtering deposition process are discussed.

Advancements in polyol synthesis: expanding chemical horizons and Néel temperature tuning of CoO nanoparticles

The polyol synthesis of CoO nanoparticles (NPs) is typically conducted by dissolving and heating cobalt acetate tetrahydrate and water in diethylene glycol (DEG). This process yields aggregates of approximately 100 nm made of partially aligned primary crystals. However, the synthesis demands careful temperature control to allow the nucleation of CoO while simultaneously preventing reduction, caused by the activity of DEG. This restriction hinders the flexibility to freely adjust synthesis conditions, impeding the ability to obtain particles with varied morpho-structural properties, which, in turn, directly impact chemical and physical attributes. In this context, the growth of CoO NPs in polyol was studied focusing on the effect of the polyol chain length and the synthesis temperature at two different water/cations ratios. During this investigation, we found that longer polyol chains remove the previous limits of the method, allowing the tuning of aggregate size (20–150 nm), shape (spherical-octahedral), and crystalline length (8–35 nm). Regarding the characterization, our focus revolved around investigating the magnetic properties inherent in the synthesized products. From this point of view, two pivotal findings emerged. Firstly, we identified small quantities of a layered hydroxide ferromagnetic intermediate, which acted as interference in our measurements. This intermediate exhibited magnetic properties consistent with features observed in other publications on CoO produced in systems compatible with the intermediate formation. Optimal synthetic conditions that prevent the impurity from forming were found. This resolution clarifies several ambiguities existing in literature about CoO low-temperature magnetic behavior. Secondly, a regular relationship of the NPs' TN with their crystallite size was found, allowing us to regulate TN over ~ 80 K. For the first time, a branching was found in this structure-dependent magnetic feature, with samples of spheroidal morphology consistently having lower magnetic temperatures, when compared to samples with faceted/octahedral shape, providing compelling evidence for a novel physical parameter influencing the TN of a material. These two findings contribute to the understanding of the fundamental properties of CoO and antiferromagnetic materials.

A Type-II CQDs regulating FeOOH decorated BiVO4 photoelectrode for highly efficient photoelectrochemical degradation of tetracycline

Bismuth vanadate (BiVO4) photoelectrode is of great potentials to be used for photoelectrochemical (PEC) removal of antibiotic pollutant. However, it still suffers from lower efficiency. Herein, a type-II FeOOH-CQDs/BiVO4 photoelectrode was fabricated via the in-situ growth of FeOOH nanoparticles over BiVO4 using Carbon quantum dots (CQDs) as mediator. Benefiting from the type-II heterojunction between BiVO4 and FeOOH, as well as the excellent charger transfer assisted by CQDs, FeOOH-CQDs/BiVO4 exhibited excellent PEC degradation performance towards a typical antibiotic- tetracycline (TC). In a typical PEC process, FeOOH-CQDs/BiVO4 photoelectrode (2 cm × 2 cm) yielded a high removal ratio of ∼ 99 % toward TC within 120 min at an applied potential of 0.6 V (vs. Hg/Hg2Cl2). Moreover, the PEC configuration was verified to be used for TC degradation in actual waters, such as tap water and lake water, with > 90 % of removal ratio. The radical trapping experiments revealed holes and superoxide radical dominated in the TC degradation process. This work provides an insight on the type-II heterojunction photoelectrode to enhance the PEC degradation of TC, which would help for the treatment of antibiotic wastewater.

Determination of Photothermal and EMI Shielding Efficiency of Graphene-Silver Nanoparticle Composites Prepared under Low-Dose Gamma Irradiation.

Silver nanoparticles (Ag NPs) have been produced by low-dose (1-20 kGy) gamma irradiation of silver nitrate in the presence of graphene-based material (graphene oxide or electrochemically exfoliated graphene). The large surface area of those graphene-based materials combined with the presence of oxygen-containing functional groups on the surface provided successful nucleation and growth of Ag nanoparticles, which resulted in a uniformly covered graphene surface. The obtained Ag nanoparticles were spherical with a predominant size distribution of 10-50 nm for graphene oxide and 10-100 nm for electrochemically exfoliated graphene. The photothermal efficiency measurement showed a temperature increase upon exposure to a 532 nm laser for all samples and the highest photothermal efficiency was measured for the graphene oxide/Ag NP sample prepared at 5 kGy. Electromagnetic interference (EMI) shielding efficiency measurements showed poor shielding for the composites prepared with graphene oxide. On the other hand, all composites prepared with electrochemically exfoliated graphene showed EMI shielding to some extent, and the best performance was measured for the samples prepared at 5 and 20 kGy doses.

Unrecognized volatile and semi-volatile organic compounds from brake wear.

Motor vehicles are among the major sources of pollutants and greenhouse gases in urban areas and a transition to "zero emission vehicles" is underway worldwide. However, emissions associated with brake and tire wear will remain. We show here that previously unrecognized volatile and semi-volatile organic compounds, which have a similarity to biomass burning emissions are emitted during braking. These include greenhouse gases or, these classified as Hazardous Air Pollutants, as well as nitrogen-containing organics, nitrogen oxides and ammonia. The distribution and reactivity of these gaseous emissions are such that they can react in air to form ozone and other secondary pollutants with adverse health and climate consequences. Some of the compounds may prove to be unique markers of brake emissions. At higher temperatures, nucleation and growth of nanoparticles is also observed. Regions with high traffic, which are often disadvantaged communities, as well as commuters can be impacted by these emissions even after combustion-powered vehicles are phased out.

Scalable Dual In Situ Synthesis of Polyester Nanocomposites for High-Energy Storage.

Incorporating ultralow loading of nanoparticles into polymers has realized increases in dielectric constant and breakdown strength for excellent energy storage. However, there are still a series of tough issues to be dealt with, such as organic solvent uses, which face enormous challenges in scalable preparation. Here, a new strategy of dual in situ synthesis is proposed, namely polymerization of polyethylene terephthalate (PET) synchronizes with growth of calcium borate nanoparticles, making polyester nanocomposites from monomers directly. Importantly, this route is free of organic solvents and surface modification of nanoparticles, which is readily accessible to scalable synthesis of polyester nanocomposites. Meanwhile, uniform dispersion of as ultralow as 0.1 wt% nanoparticles and intense bonding at interfaces have been observed. Furthermore, the PET-based nanocomposite displays obvious increases in both dielectric constant and breakdown strength as compared to the neat PET. Its maximum discharged energy density reaches 15 J cm-3 at 690 MV m-1 and power density attains 218 MW cm-3 under 150 Ω resistance at 300 MV m-1, which is far superior to the current dielectric polymers that can be produced at large scales. This work presents a scalable, safe, low-cost, and environment-friendly route toward polymer nanocomposites with superior capacitive performance.

Modeling rough surfaces as a strategy to control the crystal quality, spatial and size distribution in semiconductor nanoparticles growth: A theoretical-experimental approach

Modeling rough surfaces as a strategy to control the crystal quality, spatial and size distribution in semiconductor nanoparticles growth: A theoretical-experimental approach

Synthesis and characterization of La-doped SnO2 nanoparticles with different shape: A comprehensive study on morphology, structure, and photocatalytic efficiency for eco-friendly wastewater treatment

New controllable synthetic approach to obtain of La-doped SnO2 nanoparticles based on the combination of co-precipitation method with post synthetical hydrothermal treatment has been developed. Nanoparticles with various shape (3 nm spheres and 5 nm cubes) and structural parameters, i.e. different amount of oxygen vacancies and defects, and different dopant concentrations of 11 mol% and 33 mol% were fully characterized using XRD, FTIR, XPS and Raman spectroscopy, TEM, SSA evaluation, optical absorption spectra study, luminescence spectroscopy, including quantum chemical calculations.It was shown that hydrothermal treatment (240 °C during 6 h) promotes nanoparticle growth via the mechanism of oriented attachment. Original computational approach based on the calculation of interaction energies between ions and crystal facets was engaged to study the growth process.The presence of intrinsic photoluminescence (406, 414, 438, 460, 500 and 676 nm) for all obtained samples was established, determined by a complex set of different parameters for sub-10 nm nanoparticles.Photocatalytic efficiency of 95 % on the example of methylene blue under commercially available LED lamp described via quantum chemical modelling and tested on the example of a colorless antibiotic solution. A clear dependance of the morphological and structural parameters on the photocatalytic properties has been obtained and studied in detail.Novel concept based on a combination of chemical and computational method, for effective visible-light driven photocatalyst synthesis with potential antibacterial properties for complex eco-friendly wastewater treatment was proposed.

Simultaneous monitoring of competing photo-induced weathering processes in colloidal CdSe/ZnS semiconductor quantum dots using multivariate frequency-domain dynamic photoluminescence measurements

Coincident photo-induced weathering processes in oleic acid capped CdSe/ZnS semiconductor quantum dots (QDs), stimulated by exposure to artificial sunlight in samples with different headspace volumes, were monitored using multichannel frequency-domain photoluminescence (PL) decay measurements. The combination of process monitoring using matrix-formatted measurements and multivariate data mining permits resolution of the spectra, frequency-domain decays and kinetic profiles of the PL emitted by distinct QD subpopulations. The data indicate that three components contribute to the PL: photodarkened QDs that emit bluer, shorter-lived spectra reflecting photoionization-induced QD charging and ligand desorption; photobrightened QDs that emit redder, short-lived spectra indicative of photooxidative QD surface passivation; and photoripened QDs that emit weak, red-shifted, large bandwidth, very long-lived spectra reflecting increasing nanoparticle growth and polydispersity. Analysis of the kinetic traces of the QD subpopulations during photoirradiation using systems of exponentials revealed the extent of coupling between the coincident photoinduced processes. The assignment of these components was supported by their emission maxima, spectral bandwidths, average and irradiation-time specific PL decay times, irradiation-dependent kinetic profiles, TEM images and literature precedents. As expected, the results show that QD photodarkening is faster and photobrightening is slower in the samples that have more exposure to water and oxygen. They also show that the dominant photodarkening and photobrightening pathways in those samples are not as strongly coupled, indicating the importance of contributions by additional processes in that case. Transmission electron microscopy (TEM) images were consistent with the PL results, but the QD samples proved too polydisperse to be characterized by single-beam dynamic light scattering measurements.

Effect of calcination temperature on structure evolution of hematite nanoparticles

The objective of this study is to investigate the transition structure of iron oxide, specifically the change from magnetite to hematite, as well as the influence of calcination temperature on the structural growth of hematite nanoparticles. The magnetite was extracted from the native iron sand in Indonesia using the coprecipitation procedure. To generate hematite, magnetite was calcined at various temperatures (350, 500, 650, and 800 °C). The structural changes resulting from the effect of calcination temperature were investigated by combining a number of characterisation methods. The crystal structure was examined using synchrotron x-ray diffraction (SRD) and the local structure was examined using x-ray absorption spectroscopy (XAS). Crystallite size was calculated using the Debye-Schrerrer equation at the most dominant SRD peak. Surface morphology was investigated using scanning electron microscopy (SEM). SRD data revealed that the sample calcined at 350 °C displayed both the Fe3O4 and α-Fe2O3 phases, while higher temperatures revealed the single-phase α-Fe2O3. Furthermore, an increase in calcination temperature was shown to be associated with an increase in crystallinity and crystallite size. For the samples H350 and H800, the crystallinity increased from 95.56 to 98.17%. In the magnetite, H350, H500, H650, and H800 samples, the crystallite size increased from 9.57 to 29.55, 16.40, 28,48, 29.26, and 29.55 nm. Higher calcination temperatures, on the other hand, increase the interatomic distance while decreasing the Debye–Waller factor, according to XAS fitting data. It can be inferred that around 500 °C, the transition from Fe3O4 to single-phase α-Fe2O3 was observed. While a greater calcination temperature of at least 800 °C would alter the structural parameters, it would not affect the phase.

Hemp-ball-like structured Fe3O4-hollow carbon sphere nanozymes functionalized carbon fiber cathode for efficient flow-through electro-Fenton

Electro-Fenton (EF) technology has been recognized as a highly promising electrochemical advanced oxidation process. Promoting effective contact between active species and contaminant is crucial in electrocatalysis. Herein, we had innovatively designed a unique nanozymes in the form of hemp-ball-like structures, consist of the uniform growth of Fe3O4 nanoparticles on nitrogen-doped nano hollow carbon spheres (NHCS). This catalyst was employed in a flow-through EF system with carbon felt (CF) filters serving as the work electrode. The active sites were fully exposed through the ultradispersed Fe3O4 nanoparticles, and the NHCS facilitated efficient cycling of Fe3+/Fe2+. The results showed that the generation capacity of hydroxyl radicals (·OH) was enhanced, and the oxidation flux reached 370.080 mg h−1m−2 with low energy consumption. The superiority of the hollow carrier was proved by the degradation results and COMSOL calculation for various carbon carriers. Moreover, the active catalyst exhibited adaptability in complex water matrices. This study offers a new perspective to synergize nanomaterials, EF reactions and flow-type systems.

In situ growth of Ag nanoparticles on the surface of MXene by γ-ray irradiation to fabricate EVA composite: the improvement of flame retardancy, smoke suppression, and mechanical properties

A large amount of toxic smoke and heat generated by the combustion of ethylene vinyl acetate copolymer (EVA) poses a significant threat to human fire escape evacuation. This work aims to use γ-ray to prepare e-MXene@Ag hybrid flame-retardant materials by the method of in-situ reduction, and EVA composites are prepared by melt blending to reduce the smoke and toxic gases produced during combustion significantly. Compared with pure EVA, the total heat release, total smoke release, and the production rate of CO and CO2 produced by the combustion of EVA composite with 1 wt% e-MXene@Ag1.0 decreased by 30.3%, 33.3%, 18.2%, and 20.1% respectively. The fire hazard reduction of EVA composite materials was due to the physical barrier, catalytic carbonization and adsorption of the e-MXene@Ag1.0 hybrid. In addition, e-MXene@Ag1.0 can also further increase the mechanical properties of EVA composites due to its own ‘multi-contact point limit structure’.

The effects of polyethylene glycol on the nucleation and growth of DNA-functionalized gold nanoparticles crystals

This study presents findings on the crystal growth of DNA-functionalized gold nanoparticles (DNA-AuNPs) in the presence of polyethylene glycol (PEG), serving as an additive. Utilizing optical microscopy, UV–Vis spectroscopy, dynamic light scattering and small angle x-ray scattering, we observed enhanced crystal nucleation and growth facilitated by PEG. This effect is attributed to PEG’s promotion of the overall crystallization process of DNA-AuNPs. Furthermore, we examined the influence of PEG on short-range interactions between DNA-AuNPs, where DNA binding occurs, and long-range interactions in colloidal solutions. The results suggest that PEG plays a crucial role in both promoting crystal nucleation and influencing the interactions between DNA-AuNPs at various distances, shedding light on its potential impact on DNA-AuNP crystal formation.

Light as an Orthogonal Synthetic Parameter in Metal Nanoparticle Growth

Light as an Orthogonal Synthetic Parameter in Metal Nanoparticle Growth

Synergistic growth of nickel and platinum nanoparticles via exsolution and surface reaction

Bimetallic catalysts combining precious and earth-abundant metals in well designed nanoparticle architectures can enable cost efficient and stable heterogeneous catalysis. Here, we present an interaction-driven in-situ approach to engineer finely dispersed Ni decorated Pt nanoparticles (1-6 nm) on perovskite nanofibres via reduction at high temperatures (600-800 oC). Deposition of Pt (0.5 wt%) enhances the reducibility of the perovskite support and promotes the nucleation of Ni cations via metal-support interaction, thereafter the Ni species react with Pt forming alloy nanoparticles, with the combined processes yielding smaller nanoparticles that either of the contributing processes. Tuneable uniform Pt-Ni nanoparticles are produced on the perovskite surface, yielding reactivity and stability surpassing 1 wt.% Pt/γ-Al2O3 catalysts for CO oxidation. This approach heralds the possibility of in-situ fabrication of supported bimetallic nanoparticles with engineered compositional distributions and performance.

Ultra-wideband electromagnetic wave absorption property with bimetallic Co6W6C/carbon

Binary dielectric materials, particularly carbide/carbon composites, have garnered considerable attention for their promising electromagnetic wave (EMW) absorption property. In this work, bimetallic carbide and carbon composite (Co6W6C/C) was successfully prepared through hydrothermal method and pyrolysis process. Characterization results reveal the growth of Co6W6C nanoparticles on two-dimensional carbon nanosheets. The mass ratio of glucose (C6H12O6) to Co6W6C was found to significantly impact the EMW absorption performance. When 150 mg C6H12O6 and 100 mg CoWO4 were added, the CWCC-2 composite exhibited an ultra-high effective absorption bandwidth of 7.49 GHz (10.51–18 GHz). In the far-domain circumstance, the highest radar cross-section acreage reached 21.24 dB m2. The exceptional EMW absorption performance can be attributed to the synergistic effects of impedance matching, electrical losses, and magnetic losses. The Co6W6C/carbon composite, synthesized through a facile approach, showcases a broad electromagnetic wave absorption bandwidth, paving the way for a breakthrough in materials science with wide-band and high-efficiency absorption capabilities.