Rate Of Nanoparticle Formation Research Articles

Predicting the size of silver nanoparticles synthesised in flow reactors: Coupling population balance models with fluid dynamic simulations

Achieving size control during nanomaterial synthesis is critical for their deployment in numerous applications due to their strong size-properties relationships. However, it remains a challenge in the field due to multi-step mechanisms in nanoparticle synthesis. In this paper, we present an experimentally-validated model able to predict the particle size and distribution of silver nanoparticles synthesised in flow reactors by coupling time-resolved fluid dynamic simulations with population balance. The model reveals fundamental correlations between reactor design and the corresponding size of the nanoparticles. It shows that increasing mixing rate, increases the overall rate of nanoparticle formation, where nanoparticle synthesis takes place homogeneously in the whole of the reaction volume. In contrast, when there is a distinguishable interface between reactant streams (i.e. low mixing rate), nucleation and growth take place in a small fraction of the reaction volume in the interface between the inlet streams. The combination of fast mixing and high average nucleation rate can lead to a burst of nuclei formation translated in small size and narrow size distribution. This work presents a new approach for the use of computational-guided design of reactors for the synthesis of nanomaterials to move the field away from current trial-and-error strategies.

Synthesis of low toxic silver-cobalt nanoparticles using Annona muricata leaf extract: Antimicrobial evaluation

In a bid for green chemistry, a sustainable approach using Annona muricata aqueous extract was engaged as a reducing agent to synthesise bimetallic silver-cobalt nanoparticles (Ag-Co NPS). Hot extraction using distilled water was done on the locally sourced plant (leaf part). It was then screened for biomolecules present as geographical location affects phytochemical compositions. Phytoreduction reaction with nanoparticle formation rate was monitored with a UV-Vis spectrophotometer. Then, further characterisations were achieved by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD). The average particle size of 39.34 nm ± 9.21 nm was obtained. This study shows an interesting result, as the increase in Ag-Co NPs did not significantly affect the flies’ survival compared to the control. At P < 0.05, similar behaviour was observed in the locomotive assay of the model used. An antibacterial agent can also be developed, as revealed in the antimicrobial assay on Staphylococcus aureus (ATCC25923), Streptococcus pneumoniae, Escherichia coli (ATCC 25922), Klebsiella sp., and Salmonella sp. and a fungus strain: Candida albicans.

Plant-mediated noble nanoparticle biosynthesis, characterization approaches, synthesis parameters, and antibacterial action: A review

Metallic nanoparticles are receiving more attention as a result of their extensive uses in fields such as health, chemistry, agriculture, and biotechnology, which may be related to their matching small sizes. Because most plants are normally economically, readily accessible, eco-friendly, and harmless, the utilization of plant material for nanoparticle production has increased a lot of traction. The findings of this review are noteworthy because nanoparticle production is different in the properties, types, and physical as well as chemical processes of nanoparticle development for the green development of nanoparticles, their types, and their properties. We have studied in detail the biosynthesis of nanoparticles utilizing extracts from most common plants and their various sections, as well as the various kinds of characterization processes employed for their identification. Numerous current investigations have shown that plant extracts can be used as a non-hazardous precursor for the combining of nanomaterial. Various kinds of reducing and capping/balance factors are abundant in plant extracts. As a result, this approach has great scale-up potential and can generate nanoparticles with a variety of morphologies. Plant-derived NPs are not at most further stable with regards to forming a size and produce a better yield than conventional physical and chemical approaches. As a result, the effect of numerous experimental agents on the size as well as the rate of nanoparticle formation is also discussed. The antibacterial activity of plant-mediated biosynthesized nanoparticles is also discussed in this paper.

A Review on the Various Mechanisms of Green Synthesis of Metal Nanoparticles for Biomedical Applications

Abstract: Due to the hazardous effects of chemicals used, Green chemistry replaces the conventional techniques involved in nanotechnology. Green chemistry is a branch of science dealing with microbiology, phytology, and chemical engineering with the development of products by manipulating these three domains. Green synthesis is an interdisciplinary domain that relies on the use of non-toxic, bio-safe reagents, which are eco-friendly and safe to use in bio-nanotechnology and provide environmental benefits as an option other than the conventional physical and chemical methods for developing technology. This article will critically present the various approaches and methods for nanoparticle synthesis using microorganisms like bacteria, fungi, yeasts, archaea, viruses, algae, etc. By optimizing with laboratory conditions, nanoparticles of different ranges of physical characteristics can be synthesized. Nanoparticles with well-defined properties have been reported to be synthesized by green chemistry, for many biomedical applications. Green synthesis of nanoparticles is non-toxic, eco-friendly, and compatible to be used for medical procedures, and the rate of nanoparticle formation and their size could be regulated by various controlling factors like pH, temperature, concentration, time exposure, etc. The use of microbes for nanoparticle synthesis can be broadly divided into intracellular and extracellular based on their being produced from the extracts of microorganisms, which can be employed either as reducing agents or protective agents for the synthesis either extracellular or intracellular in the presence of enzymes generated by cells. This review aims to summarize nanoparticles of Au, P, Ag, Pt, CdS, Pt ZnO, etc as the primary focus. Additionally, a short glimpse often hybrid chemical-biological methods have also been presented.

Sonoelectrochemical Synthesis of Antibacterial Active Silver Nanoparticles in Rhamnolipid Solution

The results of studies of the synthesis of AgNPs colloidal solutions by cyclic voltammetry (E from +1.0 to −1.0 V) in rhamnolipid (RL) solutions and the use of soluble anodes in the ultrasound field (22 kHz) are presented. It is shown that the algorithm of anodic dissolution—reduction of Ag(I)—nucleation, and formation of AgNPs makes it possible to obtain nanoparticles with the size from 1 nm to 3 nm. It was found that with an increase in the RL concentration from 1 g/L to 4 g/L, the anodic and cathodic currents increase as well as the rate of AgNPs formation, respectively. The rate of nanoparticles formation also increases with an increase in temperature from 20°C to 60°C, and it corresponds to the diffusion‐kinetic range of action of this factor. Moreover, the size of AgNPs depends little on the temperature. The character of the UV‐Vis pattern of AgNPs colloidal solutions in RL (with an absorption maximum of 415 nm) is the same over a wide range of nanoparticle concentrations. The curves practically do not change in time, which indicate the stability of anodic and cathodic processes during prolonged sonoelectrochemical synthesis. The cyclic voltammetry curves practically do not change in time, which indicate the stability of anodic and cathodic processes during prolonged sonoelectrochemical synthesis. The antimicrobial activity of synthesized AgNPs solutions to strains of Escherichia coli, Candida albicans, and Staphylococcus aureus was established.

Generation of spatially ordered metal–polymer nanostructures in the irradiated dispersions of poly(acrylic acid)–poly(vinylimidazole)–Cu2+ complexes

The generation of metal nanostructures by radiation-induced reduction of copper ions in aqueous dispersions of macromolecular complexes of poly(acrylic acid) and polyvinylimidazolе has been studied in the pH range of 2.3–4.3. It was shown that an effective coordination number of Cu2+ in the complex with polymer units decreased at lower pH, which resulted in dramatic increase of the nanoparticle formation rate. As demonstrated by transmission electron microscopy, using the poly(acrylic acid)–polyvinylimidazolе–Cu2+ complexes as precursors allows one to control the nanoparticle size and promotes assembling of spatially ordered supramolecular structures. As revealed by dynamic light scattering, decreasing the medium pH leads to ripening of the poly(acrylic acid)–polyvinylimidazolе–Cu2+ particles. The obtained results provide an evidence for strong effect of the pH value on the spatial organization of nanoparticles in irradiated suspensions. In the case of less acidic medium (at pH 3), assembling of nanoparticles occurs in flabby interpolymer particles, whereas at lower pH the metal nanoparticles are produced in the templates of the perfect macromolecular nanostructures.

Molecular-Level Understanding of Synergistic Effects in Sulfuric Acid-Amine-Ammonia Mixed Clusters.

The abundance and basicity of a stabilizing base have shown to be key factors in sulfuric acid driven atmospheric new-particle formation. However, since experiments indicate that a low concentration of ammonia enhances particle formation from sulfuric acid and dimethylamine, which is a stronger base, there must be additional factors affecting the particle formation efficiency. Using quantum chemistry, we provide a molecular-level explanation for the synergistic effects in sulfuric acid-dimethylamine-ammonia cluster formation. Because of the capability of ammonia to form more intermolecular interactions than dimethylamine, it can act as a bridge-former in sulfuric acid-dimethylamine clusters. In many cluster compositions, ammonia is more likely to be protonated than dimethylamine, although it is a weaker base. By nanoparticle formation rate simulations, we show that due to the synergistic effects, ammonia can increase the particle formation rate by up to 5 orders of magnitude compared to the two-component sulfuric acid-amine system.

Carboxylate Functional Groups Mediate Interaction with Silver Nanoparticles in Biofilm Matrix.

Biofilms causing medical conditions or interfering with technical applications can prove undesirably resistant to silver nanoparticle (AgNP)-based antimicrobial treatment, whereas beneficial biofilms may be adversely affected by the released silver nanoparticles. Isolated biofilm matrices can induce reduction of silver ions and stabilization of the formed nanosilver, thus altering the exposure conditions. We thus study the reduction of silver nitrate solution in model experiments under chemically defined conditions as well as in stream biofilms. Formed silver nanoparticles are characterized by state-of-the art methods. We find that isolated biopolymer fractions of biofilm organic matrix are capable of reducing ionic Ag, whereas other isolated fractions are not, meaning that biopolymer fractions contain both reducing agent and nucleation seed sites. In all of the investigated systems, we find that silver nanoparticle–biopolymer interface is dominated by carboxylate functional groups. This suggests that the mechanism of nanoparticle formation is of general nature. Moreover, we find that glucose concentration within the biofilm organic matrix correlates strongly with the nanoparticle formation rate. We propose a simple mechanistic explanation based on earlier literature and the experimental findings. The observed generality of the extracellular polymeric substance/AgNP system could be used to improve the understanding of impact of Ag+ on aqueous ecosystems, and consequently, to develop biofilm-specific medicines and bio-inspired water decontaminants.

Very Green Photosynthesis of Gold Nanoparticles by a Living Aquatic Plant: Photoreduction of AuIII by the Seaweed Ulva armoricana.

Light-assisted in vivo synthesis of gold nanoparticles (NPs) from aqueous solutions of dilute AuIII salts by a living green marine seaweed (Ulva armoricana) is reported for the first time. NPs synthesised using typical procedures have many associated environmental hazards. The reported methods involve green, nontoxic, eco-friendly synthetic procedures. The formation of AuNPs was extremely rapid (≈15 min) following illumination of the living U. armoricana, while the rate of NP formation in the dark was very slow (over 2 weeks). The properties of the AuNPs formed were confirmed using a battery of spectroscopic techniques. U. armoricana were found to be very efficient in Au0 uptake, and this, together with the rapid formation of AuNPs under illumination, indicated that the seaweed remained living during NP formation. The TEM images supported this, revealing that the thylakoid membranes and cell structure remained intact. The AuNPs formed on the surface of U. armoricana thallus, along the cell walls and in the chloroplasts. Without further workup, the dried, U. armoricana-supported AuNPs were efficient in the catalytic reduction of 4-nitrophenol, demonstrating the completely green cycle of AuNP formation and catalytic activity. The results mean that an aquatic plant growing in water rich in gold salts could bio-accumulate AuNPs from its aquatic environment, simply with the activation of sunlight.

Gold Nanoparticles Formation via Au(III) Complex Ions Reduction with l -Ascorbic Acid

In this paper, the kinetics and mechanism of gold nanoparticles formation during the redox reaction between [AuCl4]− complex and l-ascorbic acid under different conditions were described. It was also shown that reagent concentration, chloride ions, and pH influence kinetics of nucleation and growth. To establish rate constants of these stages, the model of Finke and Watzky was applied. From Arrhenius and Eyring dependencies, the values of activation energy (22.5 kJ mol−1 for the nucleation step and 30.3 kJ mol−1 for the growth step), entropy (about −228 J K−1 mol−1 for the nucleation step and −128 J K−1 mol−1 for the growth step), and enthalpy (19.8 kJ mol−1 for nucleation and 27.8 kJ mol−1 for particles growth) were determined. It was also shown that the disproporationation reaction had influence on the rate of nanoparticles formation and may have impact on final particles morphology.

Enhanced Antimicrobial and Anticancer Activity of Silver and Gold Nanoparticles Synthesised Using Sargassum incisifolium Aqueous Extracts.

A detailed, methodical approach was used to synthesise silver and gold nanoparticles using two differently prepared aqueous extracts of the brown algae Sargassum incisifolium. The efficiency of the extracts in producing nanoparticles were compared to commercially available brown algal fucoidans, a major constituent of brown algal aqueous extracts. The nanoparticles were characterised using TEM, XRD and UV/Vis spectroscopy and zeta potential measurements. The rate of nanoparticle formation was assessed using UV/Vis spectroscopy and related to the size, shape and morphology of the nanoparticles as revealed by TEM. The antioxidant, reducing power and total polyphenolic contents of the aqueous extracts and fucoidans were determined, revealing that the aqueous extracts with the highest contents produced smaller, spherical, more monodisperse nanoparticles at a faster rate. The nanoparticles were assessed against two gram-negative bacteria, two gram-positive bacteria and one yeast strain. In contrast to the literature, the silver nanoparticles produced using the aqueous extracts were particularly toxic to Gram-negative bacteria, while the gold nanoparticles lacked activity. The cytotoxic activity of the nanoparticles was also evaluated against cancerous (HT-29, MCF-7) and non-cancerous (MCF-12a) cell lines. The silver nanoparticles displayed selectivity, since the MCF-12a cell line was found to be resistant to the nanoparticles, while the cancerous HT-29 cell line was found to be sensitive (10% viability). The gold nanoparticles displayed negligible toxicity.

Acceleration of the Rate of Silver Nanoparticle Formation Using Microbubbles in a Sonochemical Process

The effect of the addition of microbubbles on the formation of silver nanoparticles produced in an ultrasonic radiation-mediated process was investigated. The addition of microbubbles with an area-based median diameter of 26.0 µm and a bubble volume density of 0.18 cm3/L significantly increased the silver nanoparticle formation rate during the sonochemical process. The size distribution of the silver nanoparticles was largely unaffected by the addition of the microbubbles. The influence of changes in the microbubble volume density on the formation of the silver nanoparticles was also investigated; it was confirmed that the rate of formation of the silver nanoparticles increased moderately with increasing volume density. The gradient in absorption spectra was approximately 30 times larger for the case when microbubbles (median diameter: 28.3 µm) were added at 0.74 cm3/L, compared with the case without microbubbles. The results suggested that the microbubbles provided reaction sites similar to cavitation bubbles in the ultrasonic reaction.

Relation between Silver Nanoparticle Formation Rate and Antioxidant Capacity of Aqueous Plant Leaf Extracts

Correlation between the antioxidant capacity and silver nanoparticle formation rates of pomegranate (Punica granatum), quince (Cydonia oblonga), chestnut (Castanea sativa), fig (Ficus carica), walnut (Juglans cinerea), black mulberry (Morus nigra), and white mulberry (Morus alba) leaf extracts is investigated at a fixed illumination. Silver nanoparticles formed in all plant leaf extracts possess round shapes with average particle size of 15 to 25 nm, whereas corresponding surface plasmon resonance peak wavelengths vary between 422 nm and 451 nm. Cupric reducing antioxidant capacity technique is used as a reference method to determine total antioxidant capacity of the plant leaf extracts. Integrated absorbance over the plasmon resonance peaks exhibits better linear relation with antioxidant capacities of various plant leaf extracts compared to peak absorbance values, with correlation coefficient values of 0.9333 and 0.7221, respectively.

Kinetics of formation of nanoparticles from first group metal carboxylates

A kinetic model of the formation of metal nanoparticles via reduction of their carboxylates under conditions of clustering is proposed. It is found that the kinetics of the process is characterized by an induction period in carboxylate consumption and by almost linear growth of the average size of nanoparticles with conversion. It is shown that the maximum rate of nanoparticle formation grows along with the rate of ternary associate formation, the induction period becomes longer, and the particle size decreases. At the same time, it is characterized by a narrow size distribution.

Photocatalytic activity of biogenic silver nanoparticles synthesized using potato (Solanum tuberosum) infusion

In this study, we have reported a fast and eco-benign procedure to synthesis silver nanoparticle at room temperature using potato (Solanum tuberosum) infusion along with the study of its photocatalytic activity on methyl orange dye. After addition of potato infusion to silver nitrate solution, the color of the mixture changed indicating formation of silver nanoparticles. Time dependent UV–Vis spectra were obtained to study the rate of nanoparticle formation with time. Purity and crystallinity of the biogenic silver nanoparticles were examined by X-ray diffraction (XRD). Average size and morphology of the nanoparticles were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Fourier transform infra-red spectroscopy (FTIR) was employed to detect functional bio-molecules responsible that contribute to the reduction and capping of biosynthesized Ag nanoparticles. Further, these synthesized nanoparticles were used to investigate their ability to degrade methyl orange dye under sunlight irradiation and the results showed effective photocatalytic property of these biogenic silver nanoparticles.

One-pot eco-friendly synthesis of gold nanoparticles by glycerol in alkaline medium: Role of synthesis parameters on the nanoparticles characteristics

In this work we studied the role of experimental variables in an ecologically-correct synthesis of gold nanoparticles carried out by glycerol in alkaline medium at ordinary temperatures (25°C and 0°C). Variation of pH allowed the production of spherical and anisotropic nanoparticles. Different concentrations of polyvinylpyrrolidone (PVP) directly impacted the size and stability of the nanoparticles. In contrast, glycerol concentration had little influence on the synthetic process. The empirical rate law was determined for the process with respect to glycerol and gold ions. From the kinetic study it was possible to establish that the rate of nanoparticle formation is only slightly more dependent on gold ions than on glycerol. Thus, to increase the rate of nanoparticles formation, it is economically and environmentally more advantageous to increase the glycerol concentration than the Au3+ concentration.

Nanoaerosol formation in the troposphere under the action of cosmic radiation

The level of cosmic radiation has been shown to affect the rate of nanoparticle formation from gas emissions of natural and anthropogenic origins. The acceleration of particle formation processes is mainly caused by the increased concentration of atmospheric ions, which serve as condensation nuclei and thus strongly change the rate of aerosol charging processes. This paper provides a brief overview of the main processes leading to the formation of nanoparticles in the atmosphere. These processes include nucleation, condensational growth, charged particle growth, charging of aerosol particles, and recombination. Particular emphasis has been placed on the role of particle sizes in charging processes. Also, we discuss the influence of aerosol sinks on the rate of aerosol formation.

Morphology Controlled Synthesis and Characterization of Vertically Aligned Carbon Nanofibers Supported Platinum Catalysts for Polymer Electrolyte Fuel Cells

The requirement for a fuel cell with an efficient three phase boundary (TPB) is one of the key challenges in the development of polymer electrolyte fuel cells (PEFCs). Vertically aligned carbon nanofibers supported platinum (Pt) electrodes, which ensure a large TPB area, low Pt loading, and high Pt utilization, are desirable for applications in PEFCs. The effects of a carbon support structure on the Pt particle formation and electrode electrocatalytic activity have been investigated. The results revealed that the density of carbon nanofibers has an extremely important influence on both the size and predominant crystallographic planes of the platinum catalysts due to the topography dependence of the Pt nanoparticle formation rate. It is crucial for preparing platinum catalysts with desired particle size, crystallographic planes, and as a result, excellent electrocatalytic performance. The Pt/VACNF-5 catalyst, which has the largest density of carbon nanofibers and ultralow Pt loading (10 μg cm–2) in this st...

Influence of External Factors on the Production and Morphology of Biogenic Silver Nanocrystallites

Naturally existing biological materials have been garning considerable attention as environmentally benign green-nanofactories for the fabrication of diverse nanomaterials, and with desired size and shape distributions. In the present investigation, we report the size and shape controllable biofabrication of silver nanocrystallites using the growth extract of the fungus, Rhizoctonia solani. Influence of various factors such as growth medium; radiation, in the form of sun light; and seeding duration on the production of silver nanoparticles using aqueous 1 mm silver nitrate solution under ambient conditions is presented. Our results demonstrate that these factors can significantly influence the production, size and shape transformation, and the rate of nanoparticles formation. Multiple characterization techniques involving UV-visible and Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and transmission electron microscopy measurements confirmed the production, surface and structural characteristics, purity and crystalline nature of the biosynthesized silver nanoparticles. Our biogenic synthesis process provides a simple, ecologically friendly, cost-effective synthesis route, and most importantly the ability to have control over the size and shape distributions that lends itself for various biomedical and opto-electronic applications.

The kinetics of redox reaction of gold(III) chloride complex ions with l-ascorbic acid

The synthesis of gold nanoparticles consists of several stages, i.e. reduction, nucleation and growth. The most important step in particles formation process is the reduction reaction of Au(III) ions to Au(I). The rate of such reaction determines the rate of nuclei formation, i.e. reduction reaction of Au(I) to Au(0) and thus the rate of nanoparticles formation. In this paper, the kinetics and mechanism of redox reaction between gold(III) chloride complex ions and l-ascorbic acid in the aqueous solution have been carried out using spectrophotometric technique. From the experimentally obtained kinetic curves the rate constants of reaction at different conditions of initial concentrations of reactants, pH, temperature, ionic strength and concentration of chloride ions, were determined. It was found that in strong acidic solution (pH 1.3), the values of enthalpy (ΔH‡) and entropy (ΔS‡) of activation were 38.5kJ/mol and −89.5kJ/molK, respectively and at higher pH (pH 2.5) the values of ΔH‡ and ΔS‡ were 42.0kJ/mol and −64.5kJ/molK, respectively. Using obtained results, the kinetic equation was determined and corresponding mechanism of reaction was suggested. Obtained data can be useful for calculating time of nuclei formation and consequently for better size control and size distribution of particles, e.g. in a microreactor.