Generation Of Nanoparticles Research Articles

Generation of silver nanoparticles from thin films and their antibacterial properties

Colloidal solutions of silver nanoparticles (NPs) were obtained by ultrashort-pulse laser ablation of silver films of variable thickness in water at different fluences, pulse durations and laser exposures. Characterization of these particles was performed by scanning electron microscopy, optical transmission spectroscopy, and dynamic light scattering. A monotonic increase in the extinction coefficient and in the average diameter of the colloidal particles—from 20 to 180 nm—was observed as a function of laser fluence and exposure. Antibacterial properties of colloidal silver NPs were investigated by the microbiological ‘Live/Dead Biofilm Viability Kit’ method.

Polymer-Tethered Nanoparticles: From Surface Engineering to Directional Self-Assembly.

Current interest in nanoparticle ensembles is motivated by their collective synergetic properties that are distinct from or better than those of individual nanoparticles and their bulk counterparts. These new advanced optical, electronic, magnetic, and catalytic properties can find applications in advanced nanomaterials and functional devices, if control is achieved over nanoparticle organization. Self-assembly offers a cost-efficient approach to produce ensembles of nanoparticles with well-defined and predictable structures. Nanoparticles functionalized with polymer molecules are promising building blocks for self-assembled nanostructures, due to the comparable dimensions of macromolecules and nanoparticles, the ability to synthesize polymers with various compositions, degrees of polymerization, and structures, and the ability of polymers to self-assemble in their own right. Moreover, polymer ligands can endow additional functionalities to nanoparticle assemblies, thus broadening the range of their applications.In this Account, we describe recent progress of our research groups in the development of new strategies for the self-assembly of nanoparticles tethered to macromolecules. At the beginning of our journey, we developed a new approach to patchy nanoparticles and their self-assembly. In a thermodynamically driven strategy, we used poor solvency conditions to induce homopolymer surface segregation in pinned micelles (patches). Patchy nanoparticles underwent self-assembly in a well-defined and controlled manner. Following this work, we overcame the limitation of low yield of the generation of patchy nanoparticles, by using block copolymer ligands. For block copolymer-capped nanoparticles, patch formation and self-assembly were "staged" by using distinct stimuli for each process. We expanded this work to the generation of patchy nanoparticles via dynamic exchange of block copolymer molecules between the nanoparticle surface and micelles in the solution. The scope of our work was further extended to a series of strategies that utilized the change in the configuration of block copolymer ligands during nanoparticle interactions. To this end, we explored the amphiphilicity of block copolymer-tethered nanoparticles and complementary interactions between reactive block copolymer ligands. Both approaches enabled exquisite control over directional and self-limiting self-assembly of complex hierarchical nanostructures. Next, we focused on the self-assembly of chiral nanostructures. To enable this goal, we attached chiral molecules to the surface of nanoparticles and organized these hybrid building blocks in ensembles with excellent chiroptical properties. In summary, our work enables surface engineering of polymer-capped nanoparticles and their controllable and predictable self-assembly. Future research in the field of nanoparticle self-assembly will include the development of effective characterization techniques, the synthesis of new functional polymers, and the development of environmentally responsive self-assembly of polymer-capped nanoparticles for the fabrication of nanomaterials with tailored functionalities.

Modification of Kaolin with Carbon Quantum Dots as Composite for Methylene Blue Removal: Literature Review and Experiment

The modification of kaolin with nano-size fillers has exhibited excellent performance in the adsorption process. Carbon quantum dots (CQDs) are the new generation of nanoparticles that have attracted interest for their utilization as modifiers. In this study, a composite of metakaolin(MK)/CQDs was synthesized and tested for methylene blue (MB) removal. The heating and acid-alkali treatment of kaolin transformed it into MK. The interaction between MK and CQDs was analyzed using XPS to detect the binding of pyridic NH2 and C-N. By loading CQDs into the kaolin matrix, the surface area was improved and the removal of MB increased. For a lower MB concentration at 5 ppm, the removal efficiency could reach 96%. The composite exhibited good regeneration through the recyclability test.

Using numerical analysis of ordinary differential equation systems to predict the chemical concentration after plasma irradiation

In this study, a zero-dimensional numerical simulation of the atmospheric pressure plasma (APP) interface with a liquid solution was performed. By assuming that the solution reaction is dependent on the injection of radicals and electrons, we were able to obtain a single short APP discharge with the liquid solution. This study can predict excitation temperature, electron temperature, and population densities of species and result in optimum conditions for a chemical reaction for the synthesis of nanoparticles or other applications of the reaction between APP and liquid surface. This work aims to explain the effect of pH values on the synthesis of gold nanoparticles compared with experimental results. We found that the effect of pH value is expected to impact the generation of gold nanoparticles. Therefore, a high pH value is suitable for generating gold atoms for nano-synthesis. The fundamental plasma properties, such as population density, electron temperature, excitation temperature, and gas temperature, and chemical reaction process were studied. The simulation results were consistent with the experimental observations.

Laser-induced breakdown spectroscopy signal enhancement effect for argon caused by the presence of gold nanoparticles

The effect of the presence of nanoparticles (NPs) on the laser induced breakdown spectroscopy (LIBS) signal of argon gas was studied experimentally. 10–20 nm diameter gold NPs, produced by a spark discharge nanoparticle generator, were suspended in argon gas. The effect of particle size, number concentration and mass concentration, as well as laser pulse energy on the LIBS argon signal was systematically investigated. It was found that the breakdown threshold of the gas decreases considerably, facilitating the detection of Ar emission at such laser fluences, which do not allow plasma formation without the presence of the NPs. Our observations persist even at aerosol mass concentrations that are too low to allow the direct detection of nanoparticles. The effect, which is attributed to electron thermo- and field emission induced by the high intensity laser pulse, shows an asymptotically increasing magnitude with the aerosol mass concentration. The signal enhancement was found to be 102–104 and the effect is suggested to be useful in trace gas analysis or for the indirect detection of NPs. The achievable indirect aerosol mass concentration detection limit was estimated to be in the parts per trillion regime (as low as 50 ng·m−3), which is comparable to the best literature values reported for direct analysis.

Synthesis of mesoporous antimicrobial herbal nanomaterial-carrier for silver nanoparticles and antimicrobial sensing

Herbal nanoparticles (HNPs) were introduced as a novel generation of antimicrobial nanoparticles. But in the battle against superbugs we need nanostructures with boosted antimicrobial potency. So in the current experiment, for the first time a green approach was developed for the silver functionalization of HNPs which were fabricated from an antimicrobial herb Thymus vulgaris. Silver functionalized HNPs (AgHNPs) were found to be mesoporous and were further fortified with antimicrobial compounds. The resulted structures were re-tested against MRSA and P. aeruginosa as superbugs. It was found that silver functionalization can provide eight-fold increase in the antimicrobial potency of HNPs. Moreover, MIC was reduced from 20 mg/mL to 2.5 mg/mL. Another eight-fold reduction in the MIC (0.3 mg/mL) was achieved by fortification with antimicrobial compounds. So, the antimicrobial potency of HNPs was successfully increase approximately up to 64-folds. Obtained results illustrated that silver functionalization and fortification with antimicrobial compounds can be considered as effective approaches to achieve HNPs with boosted antimicrobial potency. These nanostructures have the potency to be loaded with other antimicrobial compound such as antibiotics toward synergistic effects of AgNPs and antibiotics. Resulted nanostructures can be employed in the formulation of powerful topical and surface disinfectants against superbugs. Also, these particles can be considered as a next generation of boosted antimicrobial nanostructures.

Preparation and characterization of carboxymethyl cellulose capped zinc oxide nanoparticles: A proof-of-concept study

Zinc oxide (ZnO) is one of the promising food additives, which adds nutrients and provides antimicrobial properties when incorporated into various food matrices. In this study, carboxymethyl cellulose capped ZnO (ZnO-CMC) were developed via a low-energy and cost-effective technique without calcination or grinding. The fabrication involved two steps: crosslinking Zn2+ ions with CMC through electrostatic interactions and generation of ZnO nanoparticles with CMC as capping agent. After mild heating, the crystalline structure of ZnO-CMC was confirmed by WAXS. Both FTIR and AFM studies illustrated that ZnO was physically trapped by CMC molecules, resulting in a physical barrier to prevent aggregation. SEM verified that the ZnO-CMC had a size of 50–80 nm with comparable morphology to commercial ZnO. Overall, CMC played a key role in controlling growth and inhibiting agglomeration of ZnO. Given the small and uniform particle size, the obtained ZnO-CMC is ready to be incorporated into different food matrices.

Focusing effects during ultrashort-pulse laser ablative generation of colloidal nanoparticles for antibacterial applications

Ultrashort (femto-picosecond) laser pulses with supercritical peak pulse powers undergo self-focusing and multiple filamentation during their propagation in transparent media. In this work, a comparative study of propagation and position-dependent ablation of a gold target in water by 0.3 ps and 10 ps 1030 nm laser pulses was performed. The filamentary laser propagation was visualized in water by the corresponding pre-focal plasma channels. The position-dependent ablative optical density yield of colloidal solutions and target mass loss along the filamentary tracks in water were characterized, for the first time enabling straightforward enhancement of colloidal generation for anti-bacterial, biomedical and nanophotonics applications.

Entropy Generation and Natural Convection Heat Transfer of (MWCNT/SWCNT) Nanoparticles around Two Spaced Spheres over Inclined Plates: Numerical Study

A numerical study is conducted to evaluate the steady natural convective heat transfer problem and entropy generation of both single wall (SWCNT) and multi wall (MWCNT) nanoparticles with water as a base liquid over two spaced spheres. The isothermally heated spheres are located between two plates of short length. The cooled plates are maintained at different inclination angles. A numerical approach based on the finite volume method and multigrid acceleration was used to solve the governing equations. The effects of nanoparticle type, volume fraction, the inclination angle of the plates and the Rayleigh numbers are well-considered. Results reveal that there is a remarkable enhancement of the average Nusselt number over the plates for MWCNT nanoparticles with 63.15% from the inclination angle 0° to 30°. Furthermore, optimal heat transfer rates over the plates for MWCNT nanoparticles equates to 1.9, which is obtained for the inclination 30° and a Rayleigh number of 106. However, for SWCNT nanoparticles, the same equates 0.9, which is obtained for the inclination 90° and a Rayleigh number of 106. The comprehensive analysis is presented under some well-defined assumptions which show the reliability of the present investigation.

Sonochemical synthesis of electrocatalysts for low-temperature water electrolysers

An important step in the process of producing hydrogen a viable method is to improve the efficiency and reduce the cost of low-temperature water electrolysers. One of the most crucial components is the catalyst used to drive the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Traditionally, the nanosized electrocatalysts are synthesized through a chemical reduction method involving a strong reducing agent like sodium borohydride, polyol, etc. Being able to control the nucleation and growth and therefore the size of the nanocatalysts, however, is not straightforward with the chemical reduction method where the use of surfactants is heavily relied upon, thus complicating the method for the industry. An alternative synthesis route involves the in-situ generation of radicals to serve as reducing agents through high power ultrasound (20 kHz–1 MHz) in a process where water is split into OH- and H-radicals referred to as water sonolysis. This presentation highlights the effects of ultrasonication frequencies, ultrasonication, times, pH solutions, reducing agents, and different saturation gasses on the generation of metallic nanoparticles and their subsequent electrocatalytic activities towards the HER and OER in mild acidic and alkaline environments. A series of physical characterizations on these sonochemically prepared nanoelectrocatalysts will be shown and discussed.

Direct Continuous Synthesis of Oleic Acid-Modified Fe3O4 Nanoparticles in a Microflow System

In this work, a direct continuous synthesis route of oleic acid (OA)-modified Fe3O4 nanoparticles was proposed and achieved by combining flow co-precipitation of Fe3O4 nanoparticles in a membrane dispersion microcontactor with the in-line introduction of OA. A systematic characterization confirms the effective and controllable covalent binding between OA and the nanoparticles during an extremely short period in a microflow system. Through comprehensively investigating the effects of different factors, the proper time to introduce a modifier was explored, and the mechanism of sequential nanoparticle generation and modification was revealed. A quantitative regulation relationship for the modification process was established as guidance to achieve an accurate and flexible modification degree. Compared with the traditional multistep and hour-level duration in the batch process, this highly controlled continuous synthesis method within seconds opens a horizon for the broad applications of OA-modified Fe3O4 nanoparticles in the future.

Synthesis of Silver Nanocomposites for Stereolithography: In Situ Formation of Nanoparticles.

Additive Manufacturing (AM) offers remarkable advantages in relation to traditional methods used to obtain solid structures, such as the capability to obtain customized complex geometries adapted to individual requirements. The design of novel nanocomposites suitable for AM is an excellent strategy to widen the application field of these techniques. In this work, we report on the fabrication of metal/polymer nanocomposites with enhanced optical/electrical behaviour for stereolithography (SLA). In particular, we analyse the in situ generation of Ag nanoparticles (NPs) from Ag precursors (AgNO3 and AgClO4) within acrylic resins via SLA. Transmission electron microscopy (TEM) analysis confirmed the formation of Ag NPs smaller than 5 nm in all nanocomposites, providing optical activity to the materials. A high density of Ag NPs with a good distribution through the material for the larger concentration of AgClO4 precursor tested was observed, in contrast to the isolated agglomerations found when the precursor amount was reduced to 0.1%. A significant reduction in the electrical resistivity up to four orders of magnitude was found for this material compared to the unfilled resin. However, consumption of part of the photoinitiator in the formation process of the Ag NPs contributed to a reduction in the polymerization degree of the resin and, consequently, degraded the mechanical properties of the nanocomposites. Experiments with longer curing times showed that, for the higher AgClO4 concentrations tested, post-curing times of 300 min allowed an 80% degree of polymerization to be achieved. These conditions turned these materials into promising candidates to obtain solid structures with multifunctional properties.

Generation of Si@C/SiC@C core–shell nanoparticles by laser irradiation of silicon grinding waste

AbstractIn recent years, the demand for lithium‐ion batteries has increased because of the global focus on carbon neutrality. Silicon/carbon (Si/C) composite nanoparticles have potential for application as high‐performance anode materials in lithium‐ion batteries, which can enable the widespread use of lithium‐ion batteries or lithium‐ion capacitors and contribute toward decarbonized society. In this study, Si@C/SiC@C core–shell nanoparticles with sizes in the range of 10–40 nm were produced by pulsed laser irradiation (wavelength = 1070 nm; pulse width = 10 ms) of a mixture of graphite powder and waste Si powder discharged from the grinding process of Si wafers. High‐speed camera observations of the laser‐induced plume were conducted to elucidate the nanoparticle generation mechanism, and it was determined that Si/SiC nanoparticles were formed within the laser‐induced plume in the early stage of laser irradiation. Si and C demonstrated different plume propagation patterns and plume decay times, and the time difference enabled the coating of the generated Si/SiC nanoparticles with a thin layer of graphene, forming core–shell hybrid structures. The electron diffraction results revealed that the generated nanoparticles were mainly composed of 3C‐SiC@C core shells, which is a novel nanomaterial with promising applications as anode materials for future lithium‐ion batteries.

Effect of organic acids on the morphology and particle size of titanium dioxide (E171) in processed food

TiO2 (E171) is widely used in processed food as a coloring agent. However, growing concerns about the potential health effects of TiO2 nanoparticles (< 100 nm) have necessitated the need for monitoring the size distribution and cytotoxic properties of food additive TiO2 present in commercial food. In this study, we employed magnetic separation method to extract food additive TiO2 from 100 commercial foods. The extracted TiO2 had a mean particle diameter of 121–143 nm along with the fraction in nanoscale (< 100 nm) ranging from 7.5% to 35.7%, where certain types of food, such as candy and jelly, were shown to contain smaller TiO2 with higher fraction of nanoscale particles. Assuming that the low pH of the products with high content of organic acid is responsible for the smaller TiO2, the effect of three organic acids, such as acetic acid, ascorbic acid, and citric acid, on the physicochemical property of TiO2 was investigated. The citric acid was shown to reduce the size of TiO2 along with the generation of fragmented nanoparticles with a size of around 20 nm, whereas the effect of acetic acid and ascorbic acid was negligible. Although TiO2 treated with citric acid did not exhibit short-term cytotoxicity, this study suggests the importance of fully assessing the potential long-term health effect of food additive TiO2 whose physicochemical properties were altered in processed food.

In-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach

Abstract The unique optical and electronic properties of metal nanoparticles and tunable properties of the organic templates encourage the scientific community to generate metal nanoparticle embedded soft hybrid materials for various novel utilities. Here, we discuss the in-situ synthesis of metal nanoparticle embedded soft hybrid materials via eco-benign approach which exclude the use of toxic reducing/capping agents or toxic reaction media. In this protocol, the gel matrix composed of benign organic templates act as reducing as well as stabilizing agent for the in-situ generation and stabilization of metal nanoparticles. As the incorporation of metal salts (as nanoparticle precursor) in the gel medium is required in this process, in most of the cases aqueous media were used for the generation of metal nanoparticle embedded soft hybrid materials. This discussion includes interesting findings from our laboratory where hybrid gel matrix composed of renewable chemicals was utilized for the in-situ synthesis of palladium nanoparticle embedded soft trihybrid material. The hybrid gel matrix rich in polyphenols/flavonoids was exploited to generate palladium nanoparticle embedded trihybrid gel through in-situ reduction of doped Pd (II) salts to stable PdNPs. The xerogel of this trihybrid material was utilized as recyclable heterogeneous catalyst for C-C coupling reaction in air under phosphene free condition and reduction reaction.

Recent advances in nanoparticle generation in liquids by lasers: Revealing formation mechanisms and tailoring properties

Recent advances in nanoparticle generation in liquids by lasers: Revealing formation mechanisms and tailoring properties

Optimization of nanoparticle yield for biomedical applications at femto-, pico- and nanosecond laser ablation of thin gold films in water

The paper considers the generation of colloidal gold nanoparticles by laser ablation of thin gold films of variable thickness in deionized water. The effect of laser fluence, pulsewidth, exposure, and film thickness on the generation of nanoparticles, its productivity and ergonomicity, particle dispersion and size is studied along with the related ablative mass loss from the films.

Practicality Assessment of a Frugal Nanoparticle Generator: Opening Doors to Nano Pharmaceuticals for the Researchers and Students of Underprivileged Academic Institutions

Background: Probe sonication and High-speed homogenizer are comparatively costly equipment to fabricate the nanoparticles. Many academic and research institutions cannot afford the procurement and maintenance of such sophisticated equipment. In the present work, a newer idea is conceptualized, which can be adopted by the underprivileged research institutions to fabricate solid lipid nanoparticles (SLN) in the absence of sophisticated equipment. The current work describes the pilot-level trials of this novel approach. This study represents the preliminary proof-of-concept trials for which the Indian patent application (3508/MUM/2015) is filed. Method: A frugal piece of equipment was made using a 50 ml centrifuge tube with conical bottom and a piezoelectric mist maker or humidifier. SLNs were prepared by combining the quasi-emulsion solvent evaporation approach and ultrasonic vibration approach. A quasi-emulsion was composed by the dropwise mixing of the organic solvent containing drug &amp; lipid with an aqueous solution containing surfactant under continuous ultrasonic vibration in the piezoelectric chamber. The size of the droplets was significantly reduced due to piezoelectric ultrasonic vibration. Under the provision of mild vacuum and heat generated by vibration, the organic solvent was evaporated, which leaves behind a suspension of SLN. In the present work, albendazole was selected as a model drug. Various trials with Compritol 888 ATO® and Precirol ATO 5® as a lipid carrier and Tween 80 and Poloxamer 188 as a surfactant were performed. Zeta potential of SLNs was improved by the addition of polyelectrolytes like K2SO4 and Na4P2O7. Result and Conclusion: The ratio of drug to lipid was optimized to 1:4 for the most favorable results. SLN with a minimum Z-average diameter of 98.59 nm, -21 mV zeta potential, and 34.064 % (SD 10.78, n=9) entrapment efficiency were developed using the Precirol ATO 5 ® as a lipid carrier. The proof of concept for this novel approach is established through the development of Albendazole SLNs. This approach must also be evaluated for the development of polymeric nanoparticles and vesicular formulations. The further sophistication of the frugal equipment may allow more control over the quality of SLN. This approach will enable underprivileged researchers to prepare Nanopharmaceuticals. Researchers and students of such institutions can focus on the application of SLN by resolving the constraint of sophisticated equipment with this novel approach. This novel approach should also be tried for polymeric and vesicular nanopharmaceuticals.

Reduced zwitterionic graphene oxide sheets decorated with nickel nanoparticles as magnetically and efficient catalyst for A3‐coupling reactions under optimized green experimental conditions

A Ni‐based supported reduced zwitterionic graphene oxide N,N‐bis(2‐pyridylmethyl)ethylenediamine 1,3‐propanesultone (GO‐BPED‐PS) material was prepared for the catalysis of A3‐coupling reactions under green experimental conditions. First, the in situ generation of nickel nanoparticles (NiNPs) onto the reduced zwitterionic GO‐BPED‐PS sheets was characterized by various techniques such as Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) analysis. Moreover, the electron density map of NiNPs onto the reduced zwitterionic GO‐based sheets was produced through the X‐ray crystallographic analysis. Then, the as‐prepared reduced GO‐BPED‐PS NiNPs (rGO‐BPED‐PS@NiNPs) material was used as a heterogeneous catalyst for the three‐component coupling reaction (A3‐coupling reaction) of benzaldehyde, morpholine, and terminal alkynes. The experimental conditions were performed in order to obtain very good green chemistry metrics. In particular, we obtained a high catalytic efficiency when using γ‐valerolactone as solvent, a reaction time of 3 h and a temperature of 100°C. In addition, it was demonstrated that the rGO‐BPED‐PS@NiNPs catalyst could be recycled for 11 times without a significant decrease in its catalytic activity.

Quantitative evaluation of LAL productivity of colloidal nanomaterials: Which laser pulse width is more productive, ergonomic, and economic?

Near-IR (wavelength ≈ 1 μm) laser ablation of bulk, chemically-inert gold in water was compared for different laser pulse width in broad the range of 300 fs–100 ns, comparing a number of key ablation characteristics: mass loss, single-shot crater volume and extinction coefficient of the generated colloidal solutions taken in the spectral ranges of interband transitions and localized plasmon resonance. Comparing to related air-based ablation results, at the given fluences laser ablation in the liquid resulted in the maximum ablation yield per unit energy and maximum NP yield per pulse and per unit energy for the picosecond lasers, occurring at subcritical peak pulse powers for laser self-focusing. The self-focusing effect was demonstrated to yield in incomplete, effectively weaker focusing in the water filaments of ultrashort laser pulses with supercritical peak powers, comparing to linear (geometrical) focusing at sub-critical peak powers. At the other, nanosecond-pulse extreme the high ablation yield per pulse, but low ablation yield per unit energy and low NP yield per pulse and per unit energy were related to strong ablation plasma screening, providing mass removal according to the well-established scaling relationships for plasma. Illustrative comparison of the ablation and nanoparticle generation efficiency versus the broad fs–ns laser pulse width range was enabled in terms of productivity, economicity, and ergonomicity, using the proposed universal quantitative criteria.