Size-controlled Nanoparticles Research Articles

Post-synthesis Oxidation of Superparamagnetic Iron Oxide Nanoparticles to Enhance Magnetic Particle Imaging Performance.

This study investigates the impact of post-synthesis oxidation on the performance of superparamagnetic iron oxide nanoparticles (SPIONs) in magnetic particle imaging (MPI), an emerging technology with applications in diagnostic imaging and theranostics. SPIONs synthesized from iron oleate were subjected to a post-synthesis oxidation treatment with a 1% Oxygen in Argon mixture. MPI performance, gauged via signal intensity and resolution using a MOMENTUM™ scanner, was correlated to the nanoparticles' physical and magnetic properties. Post-synthesis oxidation did not alter physical attributes like size and shape, but significantly enhanced magnetic properties. Saturation magnetization increased from 52% to 93% of the bulk value for magnetite, leading to better MPI performance in terms of signal intensity and resolution. However, the observed MPI performance did not fully align with predictions based on the ideal Langevin model, indicating the need for considering factors like relaxation and shape anisotropy. The findings underscore the potential of post-synthesis oxidation as a method to fine-tune magnetic properties of SPIONs and improve MPI performance, and the need for reproducible synthesis methods that afford finely tuned control of nanoparticle size, shape, and magnetic properties.

Direct Optical Particle Tracking - a technique for size distribution assessment

Nanotechnology, an emerging discipline within material science, has ushered in a new era of engineering by creating nanostructured materials with distinctive properties suitable for a wide range of bioengineering applications. The shape and size of these materials constitute critical variables, determined by the chosen synthesis method and chemical precursors. Silver nanoparticles, synthesized through chemical processes, exhibit antibacterial properties when their size falls within a specific range. However, measuring the size of such nanoparticles, typically in the nanometer to tens of nanometers range, necessitates specialized techniques like Dynamic Light Scattering and Transmission Electron Microscopy. These methods are often limited by assumptions, high costs and longer measurement times. This paper introduces a novel approach utilizing Direct Particle Tracking for assessing particle size distribution in the early stages of nanoparticle synthesis. The study used realistic computer simulations of nanoparticle diffusion, employing the CHODIN code and a specific code for Direct Particle Tracking written for this purpose. The Brownian motion of each particle is recorded, the mean square displacement is computed and the diffusion coefficient, as well. The diameter of each particle is assessed and here from the particle distribution. The results on simulated particle diffusion demonstrate the feasibility of using Direct Particle Tracking as an effective method for size distribution assessment in the initial phases of nanoparticle synthesis. This innovation opens the door to real-time monitoring and control of nanoparticle size in bioengineering applications, promising significant advancements in the field of nanotechnology.

Size and Density Control of Au Nanoparticles Decorated on MoS2 Thin Films for Preparing High-Performance SERS Substrates

Size and Density Control of Au Nanoparticles Decorated on MoS2 Thin Films for Preparing High-Performance SERS Substrates

Gold supported on Gd-doped CeO2 nanorods applied as water-gas shift catalyst under H2 rich stream

In this work, we report the synthesis of catalysts based on ceria nanorods (CeO2NRs) doped with 3% and 5% mol gadolinium. The supports were obtained from cation co-precipitation hydrothermal synthesis over which gold nanoparticles (AuNPs) were deposited by the deposition-precipitation (DP) methodology, allowing the Au nanoparticles size control at around 3 nm. The catalysts were evaluated in water gas shift reaction and showed high activity under a H2 rich stream (7%CO/7%CO2/14%N2/42%H2/30%H2O) with steam/process gas molar ratio (S/G) of 0.3 at 300 and 250 °C. The results revealed that Gd-doping increased the oxygen vacancies concentration due to the insertion of a trivalent cation in ceria lattice. In addition, the synergistic effect between AuNPs and Gd-doped CeO2 provided the increase of reducibility and oxygen storage capacity (OSC). These properties were associated with the catalytic activity in water gas shift reaction. The nanostructured materials decreased the CO concentration under conditions of H2 rich stream, indicating the catalysts potential for industrial applications after further studies. The catalyst doped with 5% mol Gd was the most active and achieved 24% of CO conversion at 300 °C.

Salting-out effect-mediated size-control of protein nanoparticles towards controllable microstructures for sustained release of eugenol

Size and monodispersity of solid particles are essential to their structuring behaviors at biphasic interfaces. However, delicate control over biomolecular nanoparticle sizes is challenging. In this study, we prepared monodisperse rice protein (RP) nanoparticles by neutralizing RP solutions (pH 12.0) using combined treatments of cationic exchange resins (CERs) and HCl. CERs absorbed Na+ by releasing H+ without producing salt during neutralization. By compromising the usages of CERs and HCl when preparing RPs, the generation of NaCl can be delicately tailored, leading to controllable nanoparticle sizes from 20 nm to 30 nm. By mixing these nanoparticles with eugenol in an aqueous solution, the nanoparticles accommodated eugenol in their cores due to inward diffusion. Furthermore, such eugenol-contained nanoparticles with different sizes demonstrated tunable releases of eugenol due to size-dependent capillary forces, which can be harnessed for suppression of microbial growth on fruit with prolonged effective eugenol concentration.

Atomic Layer Deposition of Cu Electrocatalysts on Gas Diffusion Electrodes for CO2 Reduction.

Electrochemical reduction of CO2 using Cu catalysts enables the synthesis of C2+ products including C2H4 and C2H5OH. In this study, Cu catalysts were fabricated using plasma-enhanced atomic layer deposition (PEALD), achieving conformal deposition of catalysts throughout 3-D gas diffusion electrode (GDE) substrates while maintaining tunable control of Cu nanoparticle size and areal loading. The electrochemical CO2 reduction at the Cu surface yielded a total Faradaic efficiency (FE) > 75% for C2+ products. Parasitic hydrogen evolution was minimized to a FE of ∼10%, and a selectivity of 42.2% FE for C2H4 was demonstrated. Compared to a line-of-sight physical vapor deposition method, PEALD Cu catalysts show significant suppression of C1 products compared to C2+, which is associated with improved control of catalyst morphology and conformality within the porous GDE substrate. Finally, PEALD Cu catalysts demonstrated a stable performance for 15 h with minimal reduction in the C2H4 production rate.

Size-Controlled ZnO Nanoparticles Synthesized with Thioacetamide and Formation of ZnS Quantum Dots

In this work, we report the first attempt to investigate the dependence of thioacetamide (TAA) on the size of ZnO nanoparticles (NPs) in forming ZnS nanostructures from ZnO. Size-controlled B(blue)_, G(green)_, and Y(yellow)_ZnO quantum dots (QDs) and NC (nanocrystalline)_ZnO NPs were synthesized using a sol–gel process and a hydrothermal method, respectively, and then reacted with an ethanolic TAA solution as a sulfur source. ZnO QDs/NPs began to decompose into ZnS QDs through a reaction with TAA for 5~10 min, so rather than forming a composite of ZnO/ZnS, ZnO QDs and ZnS QDs were separated and remained in a mixed state. At last, ZnO QDs/NPs were completely decomposed into ZnS QDs after a reaction with TAA for 1 h irrespective of the size of ZnO QDs up to ~50 nm. All results indicate that ZnS formation is due to direct crystal growth and/or the chemical conversion of ZnO to ZnS.

A thermal evaporator for aerosol core-shell nanoparticle synthesis

Segregated bimetallic nanoparticles like core-shell nanoparticles are of interest in various fields including biomedicine, catalysis, and optoelectronics. Aerosol technology is an optimal platform to control nanoparticle size, structure, and composition, which are some of the most important parameters tuning the material performance for the intended applications. Here, we develop a novel evaporator design to coat core particles on-line with a shell directly in the gas phase. The evaporator employs a local heater that decouples heating the evaporating material from the aerosol particles to limit core-shell alloying. We characterize the system by evaporating Zn onto core particles of Au, Sn, and Bi and demonstrate the core-shell particle formation with controllable shell thickness in each material system. We discuss simple models to explain the observed growth process inside the evaporator and the resulting shell formation.

Size-controllable food-grade nanoparticles based on sea cucumber polypeptide with good anti-oxidative capacity to prolong lifespan in tumor-bearing mice

Liver cancer, a malignancy with a rising global incidence, poses a significant challenge in achieving effective treatment outcomes. As food-derived nutrient, sea cucumber peptide (SCP) has shown promising anticancer effects. Therefore, we explored the nanodelivery systems to encapsulate SCP to enhance its stability in the gastrointestinal tract and improve absorption within the tumor microenvironment. This study aimed to develop size-controllable multifunctional nanoparticles using SCP, procyanidins (PCs), and vanillin through molecular assembly via a one-pot Mannich condensation approach. These food-grade nanoparticles demonstrated water solubility and exhibited a spherical structure with sizes ranging from 441 to 1360 nm, depending on the concentration of the reactants. In vitro cell experiments demonstrated that SCP nanoparticles modified with PCs effectively reduced the generation of reactive oxygen species from H2O2 and acrylamide while maintaining normal levels of mitochondrial membrane potential. Furthermore, in vivo nutrition intervention studies conducted on tumor-bearing mice revealed that mice treated with SCP nanoparticles exhibited a survival rate of 40 %, which was significantly higher than the 0 % and 20 % survival rates observed in the control and SCP-treated groups, respectively. These findings suggest that SCP nanoparticles, possessing antioxidative properties and controllable sizes, hold potential for precision nutrition in the field of cancer treatment.

Size-Controlled Silver Nanoparticles Supported by Pyrolytic Carbon from Microcrystalline Cellulose.

A facile method was developed for preparing size-controlled silver nanoparticles supported by pyrolytic carbon from microcrystalline cellulose (MCC). The pyrolysis of cellulose-AgNO3 mixture caused the oxidation of cellulose, resulting in carboxyl groups to which silver ions can bind firmly and act as nuclei for the deposition of silver nanoparticles. The structure and properties of the obtained nanocomposite were characterized by using a scanning electron microscope (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) and X-ray diffraction (XRD). The results suggest that silver nanoparticles were integrated successfully and dispersed uniformly in the pyrolytic carbon matrix. The average particle size varied between 20 nm and 100 nm in correlation to the dose of silver nitrate and temperature of pyrolysis. The products showed high electric conductivity and strong antimicrobial activity against Escherichia coli (E. coli).

Mechanical Exfoliation of Expanded Graphite to Graphene-Based Materials and Modification with Palladium Nanoparticles for Hydrogen Storage.

Hydrogen is a promising green fuel carrier that can replace fossil fuels; however, its storage is still a challenge. Carbon-based materials with metal catalysts have recently been the focus of research for solid-state hydrogen storage due to their efficacy and low cost. Here, we report on the exfoliation of expanded graphite (EG) through high shear mixing and probe tip sonication methods to form graphene-based nanomaterial ShEG and sEG, respectively. The exfoliation processes were optimized based on electrochemical capacitance measurements. The exfoliated EG was further functionalized with palladium nanoparticles (Pd-NP) for solid-state hydrogen storage. The prepared graphene-based nanomaterials (ShEG and sEG) and the nanocomposites (Pd-ShEG and Pd-sEG) were characterized with various traditional techniques (e.g., SEM, TEM, EDX, XPS, Raman, XRD) and the advanced high-resolution pair distribution function (HRPDF) analysis. Electrochemical hydrogen uptake and release (QH) were measured, showing that the sEG decorated with Pd-NP (Pd-sEG, 31.05 mC cm-2) and ShEG with Pd-NP (Pd-ShEG, 24.54 mC cm-2) had a notable improvement over Pd-NP (9.87 mC cm-2) and the composite of Pd-EG (14.7 mC cm-2). QH showed a strong linear relationship with an effective surface area to volume ratio, indicating nanoparticle size as a determining factor for hydrogen uptake and release. This work is a promising step toward the design of the high-performance solid-state hydrogen storage devices through mechanical exfoliation of the substrate EG to control nanoparticle size and dispersion.

Potential and Harmful Effects of Titanium Dioxide Nanoparticle on Health: A Brief Note

Abstract: Titanium dioxide nanoparticles (TiO2 NPs) are formed in vast amounts worldwide for usage in several applications. They possess excellent photocatalytic properties, high chemical stability, and a wide bandgap, making them highly effective in environmental remediation and solar energy conversion. TiO2 nanoparticles exhibit biocompatibility, allowing their utilization in biomedical uses, such as molecular imaging, drug delivery, and tissue engineering. Chemical methods, such as hydrothermal, sol-gel, and chemical vapor deposition, provide versatility in controlling nanoparticle size, morphology, and crystallinity. They offer relatively lower production costs, scalability, and the ability to incorporate dopants or functionalize the nanoparticle surface. Their small size and large surface area-to-volume ratio enable enhanced reactivity and surface functionality, facilitating their incorporation into composite materials and surface coatings for improved performance. Regarding the potential toxicity of TiO2 nanoparticles, the bulk form of TiO2 is considered safe for human consumption, but the reduced size of nanoparticles raises concerns about their potential adverse effects. TiO2 nanoparticles strongly depend on factors, such as particle size, surface modifications, exposure route, and duration. Therefore, continued research is essential to gain a comprehensive understanding of the toxicity mechanisms and develop strategies to mitigate any potential adverse effects, ensuring the safe and responsible utilization of TiO2 nanoparticles in different fields.

Morphology, size control, and photocatalytic activities of titanium dioxide nanoparticles synthetized by microemulsion method

In the present work, we successfully synthesized titanium dioxide nanoparticles (TiO2-NPs) by reverse microemulsion method using cyclohexane, aqueous ammonia materials, and various ratios of surfactants. Using this method, nanoparticles of various morphologies, such as filamentous, sheet, and spherical morphologies, were synthesized. In addition, NPs in very small size (i.e., 4–7 nm for spherical morphology) were obtained. The as-prepared samples showed light absorption in the range of 200–300 nm, indicating their potential application as an UV light induced photocatalyst. The obtained TiO2-NPs were amorphous and can be converted to anatase by heating at 600–750 °C and to rutile by heating above 900 °C. In addition, TiO2-NPs with sheet morphology showed the highest activity on photocatalytic decomposition of methyl orange relative to spherical and filamentous morphologies. We also showed that doping of tin (Sn) atoms in TiO2-NPs causes a significant increase in the photocatalytic activity of NPs and the time needed for photocatalytic decomposition decreases to around one-fifth of the time needed for nondoped NPs. The results of the present research indicated that the microemulsion process is an effective/potential method for the synthesis of some new functional materials.

Optimization of catalyst activity and stability in the m-cresol hydrodeoxygenation through Ni particle size control

By taking advantage of different nanoparticle size control methodologies, the precise role of Ni particle size (from 1 nm to 9 nm) was evaluated in the HDO of m-cresol in vapor phase at 573 K under atmospheric pressure. The m-cresol HDO reaction pathways were found to be Ni-particle size dependent. The direct deoxygenation (DDO) rate increased by 10 times when decreasing Ni particle size from 9 nm to 1 nm, while the hydrogenation (HYD) and hydrogenolysis (HYG) rates moderately increased. By applying a geometric model, reaction rates were correlated to the different type of sites. Edges and corner sites (smaller particles) favor aromatics production (DDO route), while face sites (larger particles) favor both HYD and HYG routes. Catalysts partially deactivated due to coke formation, with only slight sintering observed for 1 nm Ni particles. Such findings may serve in the further preparation of active and selective catalysts for bio-oils upgrading into fuel.

Green Synthesis of Nanoparticles Mediated by Deep Eutectic Solvents and Their Applications in Water Treatment

The use of environmentally friendly deep eutectic solvents (DES) in green synthesis of different types of nanoparticles has garnered increasing interest in recent years. The application of these materials in water treatment, mainly by adsorption or degradation, is emerging as a sustainable alternative to conventional methodologies. However, the information about the green synthesis of nanoparticles (NPs) using DES is dispersed in the literature. This review is focused on compiling and systematizing information regarding DES-mediated NP synthesis, the application of these NPs in water treatment, and future perspectives of these technologies. DES represent an excellent alternative to traditional solvents in NP synthesis due to their low toxicity, low cost, and being environmentally friendly. The possible NP surface functionalization with DES is also attractive as it plays a pivotal role in processes related to water treatment. Modification and synthesis of carbon nanotubes, graphene oxides, magnetic iron oxides, among others, for the adsorption and degradation of organic dyes, pharmaceuticals, metal ions, herbicides, pesticides, and other water contaminants found in recent literature are presented in this work. Finally, the possibility to control NP size and shape can be helpful in the design of new materials for a specific application.

Size‐Controlled Synthesis of IrO2 Nanoparticles at High Temperatures for the Oxygen Evolution Reaction

AbstractIridium oxide is the state‐of‐the‐art catalyst for electrochemical water oxidation in an acidic medium. Despite being one of the rarest elements in the Earth's crust, there is a pressing need to maximize the utilization and longevity of active iridium centers. While conventional low‐temperature synthesis can yield nanostructures with high mass‐specific activity, they are often insufficiently stable during water oxidation. Structurally ordered iridium oxide is one of the most stable electrocatalysts utilized in polymer electrolyte membrane water electrolysis that benefits from the chemically ordered structure. However, its preparation requires thermal treatment at high temperatures, which improves its durability but can also result in reduced surface area and altered particle morphology. In this study, the challenge of controlling nanoparticle size during the preparation of structurally ordered iridium oxide is successfully addressed, which typically requires high‐temperature thermal treatment. By utilizing a silica nanoreactor as a hard template, a precise control is achieved over the nanoparticle size during high‐temperature thermal treatment. This approach maintains high durability while avoiding the common problem of reduced surface area and altered particle morphology. Specifically, this study is able to synthesize iridium oxide nanoparticles at temperatures up to 800 °C, while keeping their dimensions below 10 nm.

Size and shape analysis of silica (SiO2) and gold (Au) nanoparticles

In nanotechnology, the size and shape control of nanoparticles is crucial as their properties are highly dependent on their morphology. This obliges researchers to work on obtaining uniform size and shape distribution in synthesized particles so that their electrical, optical, and magnetic properties remain uniform within the same batch. This brings the problem of how to quantify the shape and size of nanoparticles in the most accurate way. The most common way to determine size distribution is using UV-vis spectrometry; however, this method disregards the existence of agglomerated particles and may sometimes give an incorrect measurement. Therefore a technique that can obtain this data directly from the transmission electron microscopy (TEM) images of particles would be more reliable as it would capture data for every single particle in the batch. In a classical statistical sense, our interest is the shape and size distribution of nanoparticles. In this paper, we quantify the size and shape of nanoparticles using the statistical techniques applied on TEM images of particles: Functional Data and Shape Analysis. By using this shape theory we obtain the geodesic distances not only between the particles but also among the frames. We further cluster the nanoparticles in terms of their similarities. We want to emphasize the importance of the deformation and how it is done of one nanoparticle onto another.

Magnetic heating of water dispersible and size-controlled superparamagnetic cobalt iron oxide nanoparticles

Magnetic nanoparticles have been of great interest for various biomedical applications due to their controllability in the distance. Monodisperse superparamagnetic CoFe2O4 (CFO) nanoparticles were synthesized by solvothermal method with oleic acid. The oleic acid ligands are exchanged with citric acid to obtain water-dispersible citric acid-coated CA (CFO–CA) nanoparticles. The M–H curve recorded at room temperature shows the superparamagnetic nature of CFO nanoparticles for both oleic- and citric-coated samples. The magnetic heating performance of CFO–CA shows an exciting dependence on the particle size and surface functionality. The hyperthermia efficiency of CFO–CA nanoparticles increases with increasing magnetic field strength and nanoparticle concentration. A specific absorption ratio value of 152.7 W/g obtained in this study is comparable to other investigations, demonstrating a great potential of CFO–CA nanoparticles for hyperthermia-based treatments. This controlled synthesis process can be applied to various functional biomedical nanoparticles to prepare nanoparticles with designed surface moieties for further potential applications.

An in situ study to shed light on the formation of goethite spindles by pseudomorphic transformation of intermediate phases

Size and shape control of nanoparticles is fundamental to tune their material properties and to identify structure property functions. Herein, the shape of goethite (α-FeOOH) particles is varied from needle to spindle upon sodium carbonate modulation. Our in-depth study sheds light on the formation path of goethite particles by in situ monitoring the pH, the dissolved oxygen concentration and Raman spectroscopy in the presence and in the absence of sodium carbonate. The pH evolution indicates two distinct plateaus, at 7–6.5, and 6–6.3, respectively: the time when the dissolved oxygen concentration vanishes is correlated with the time required to oxidize Fe(II) to Fe(III). Raman spectroscopy enabled the identification of the intermediate phases green rust at 500 cm−1 and siderite at 1080 cm−1. Their formation and depletion was correlated with the kinetics of goethite formation. The evolution of the olation reaction is monitored through the bending vibration of water at 1640 cm−1. Finally, goethite particles are characterized ex situ via X-ray diffraction to assess the crystalline phase, scanning electron microscopy (SEM) for evaluating the size and shape of particles and transmission electron microscopy (TEM) for the analysis of the three-dimensional arrangement of self-assembled layers. The evaluation of reflectance spectra with CIELAB color metrics show that goethite spindles have enhanced color properties in comparison to the needle-shaped particles.

Chitosan, Chitosan/IgG-Loaded, and N-Trimethyl Chitosan Chloride Nanoparticles as Potential Adjuvant and Carrier-Delivery Systems.

This work proposes a feasible, reproducible, and low-cost modified method to manufacture chitosan, chitosan/IgG-protein-loaded, and trimethylated chitosan nanoparticles, using microfluidics combined with the microemulsion technique, which differs from the traditional batch process of chitosan-based nanoparticles. The synthesis process consists of generating microreactors of chitosan-based polymer in a poly-dimethylsiloxane ψ-shaped microfluidic device and then crosslinking with sodium tripolyphosphate outside the cell. Transmission electron microscopy demonstrates an improvement in size control and distribution of the solid-shape chitosan nanoparticles (~80 nm) compared to the batch synthesis. Regarding chitosan/IgG-protein-loaded nanoparticles, these presented a core-shell morphology having a diameter of close to 15 nm. Raman and X-ray photoelectron spectroscopies confirmed the ionic crosslinking between the amino groups of chitosan and the phosphate groups of sodium tripolyphosphate in the fabricated samples and the total encapsulation of IgG protein during the fabrication of chitosan/IgG-loaded nanoparticles. Then, an ionic crosslinking and nucleation-diffusion process of chitosan-sodium tripolyphosphate was carried out during the nanoparticle formation, with and without IgG protein loading. The use of N-trimethyl chloride chitosan nanoparticles in vitro on human-keratinocyte-derived cell line HaCaT did not show side effects independently of its concentration from 1 to 10 μg/mL. Therefore, the proposed materials could be used as potential carrier-delivery systems.