Aerosol Nanoparticles Research Articles

In-situ aerosol nanoparticle characterization by small angle X-ray scattering at ultra-low volume fraction

State-of-the-art aerosol nanoparticle techniques all have one feature in common: for analysis they remove the nanoparticles from their original environment. Therefore, physical and chemical properties of the particles might be changed or cannot be measured correctly. To overcome these shortcomings, we apply synchrotron based small angle X-ray scattering (SAXS) as an in-situ measurement technique. Contrasting other aerosol studies using SAXS, we focus on particle concentrations which allow direct comparison to common aerosol nanoparticle analyzers. To this end, we analyze aerosol nanoparticles at ambient pressure and concentrations of slightly above ~106 cm−3. A differential mobility particle sizer (DMPS) is operated in parallel. We find that SAXS enables measurement of the primary particles and the aggregates, whereas the DMPS detects only aggregates. We conclude that in-situ nanoparticle characterization with ultra-low volume fractions of ~10–10 is feasible with SAXS. Our technique opens up a doorway to the in-situ analysis of aerosol nanoparticles under atmospheric conditions.

Aerosol technique-based carbon-encapsulated hollow mesoporous silica nanoparticles for synergistic chemo-photothermal therapy

Near-infrared (NIR)-responsive drug delivery systems have enhanced tumor ablative efficiency through permeation and retention effects. Graphene oxide (GO) has shown great potential both in photothermal therapy and in drug delivery. Thus, in this study, we designed an ambient spark-generated GO, wrapped on topotecan (TPT)-loaded hollow mesoporous silica nanoparticles (HMSN-NH2-TPT-CGO), to function as an efficient platform for pH-dependent sustained release of TPT. HMSN-NH2-TPT-CGO also exhibited a combined chemo-photothermal effect within a single carrier system. This developed system was stable with a uniform particle size (∼190 nm) and was demonstrated to possess a sufficient heat-absorbing capacity to induce tumor cell ablation. We performed the ablation of tumor cells both in vitro and in vivo in combination with photothermal therapy and chemotherapy using the spark-generated functional GO and HMSN. The prepared nanocarriers demonstrated high cellular uptake, apoptosis, and G0/G1 cell cycle arrest. In vivo study using the MDA-MB-231 xenograft model revealed the ultraefficient tumor ablative performance of HMSN-NH2-TPT-CGO compared with that of free TPT, with no toxic effect on vital organs. Altogether, the optimized nanocarriers presented a significant potential to act as a vehicle for cancer treatment. Statement of SignificanceThis is the first study that uses spark-generated graphene oxide nanoflakes to cover the topotecan (TPT)-loaded hollow mesoporous silica nanoparticles (HMSNs) to treat breast cancer. Dense silica was used as a hard template to prepare the HMSNs attributing to a high drug payload. The concentration of Na2CO3 was precisely controlled to minimize the silica etching time within 70 min. The use of the nanographene flakes served a dual purpose, first, by acting as a capping agent to prevent the premature release of drug and, second, by serving as a nano heater that significantly ablates the tumor cells. The prepared nanocarriers (NCs) exhibited effective and enhanced in vitro and in vivo apoptosis, as well as significant tumor growth inhibition even after 15 days of treatment time, with no toxic effect to the vital organs. The NCs enhanced in vitro tumor cell killing effects and served as an effective carrier for in vivo tumor regression, thereby highlighting the enormous potential of this system for breast cancer therapy.

Enhancement of polyhydroxybutyrate (PHB) production by 10-fold from alkaline pretreatment liquor with an oxidative enzyme-mediator-surfactant system under Plackett-Burman and central composite designs

In this study, Plackett-Burman and central composite designs were applied to improve polyhydroxybutyrate (PHB) production from alkaline pretreatment liquor (APL) by Cupriavidus necator DSM 545 using a supplement system consisting of oxidative enzymes (laccase, aryl alcohol oxidase (AAO)), mediators (ABTS, HOBT), DMSO, silica nanoparticle Aerosol R816 and surfactant Tween 80. First, screening experiments under Plackett-Burman design showed R816, ABTS and Tween 80 could significantly enhance PHB production. Additional experiments showed that HOBT and DMSO could be removed, and laccase and AAO were needed to remain in the system. Second, a central composite design was applied to obtain the optimum supplemental levels of R816, ABTS and Tween 80. Under optimum conditions, theoretical maximum PHB production (1.9 g/L) was close to experimental PHB production (2.1 g/L). With the supplement system, a 10-fold increase was achieved compared to PHB production (0.2 g/L) without any supplements.

Transport of gas molecules through dense membranes and intensification of mass transfer by radiation

It is known that fouling of membranes decreases their performance. New modern types of membranes which are used for separation of gas mixtures (e.g. supported ionic liquid and graphene-based membranes) require the methods for cleaning which differ from the methods used in classical membrane technology (e.g. backflushing). Mass transfer in these membranes can be blocked by the adsorbed foreign gas molecules or/and aerosol nanoparticles which are present in a gas phase near the feed side surface of the membranes. The new method of the intensification of mass transfer through the membranes by resonance radiation is considered. It is shown that resonance radiation, leading to selective excitation of the foreign gas molecules and a change in their sticking coefficient and the rate coefficient of desorption as well as to heating of the membrane, can reduce the affinity constant of the foreign gas that in turn decreases the surface coverage and the blocking effect of the adsorbed foreign gas molecules. A model is given for the transport of gas molecules through a dense flat membrane with the deposition of aerosol particles on the feed side surface of the membrane.

Experimental Methods to Study Environmental Sustainability of Silicon-based Lithium Ion Battery Manufacturing

Abstract Next-generation lithium ion batteries (LIBs) are under rapid development using various nano-structured materials. Among them, silicon nanowires (SiNWs) and silicon nanotubes (SiNTs) are two promising anode materials due to their high specific capacities. However, fabrication processes of SiNWs and SiNTs involve a large amount of toxic chemicals and generate significant potential impacts on the environment. In this study, both in-situ and ex-situ measurements were proposed for investigating the process emissions, including gas, aerosol nanoparticle, and aqueous nanoparticle emissions, from chemical etching processes for producing SiNWs and SiNTs for use as anode materials for LIBs. The feasibilities of the measurements were verified by the preliminary results of the emissions from the SiNTs synthesis process. This study provides insight into experimental measurements of and supports the gathering of process data on emissions from synthesis processes for SiNWs and SiNTs as anode materials for LIBs, which can be useful for future assessment of the sustainability performance of silicon-based LIB technology.

Design and validation of an air-liquid interface (ALI) exposure device based on thermophoresis

AbstractIn vitro, direct aerosol nanoparticle exposure of cells cultured at the air-liquid interface (ALI) has shown great potential over the conventional submerged cell exposure methods due to exp...

Computer simulation of aerosol nanoparticles focusing and deposition process for functional microstructure fabrication

The possibility is shown of using computer simulation to predict the size of the structures formed by the dry aerosol jet printing method. Computer modeling consisted in determining the model parameters and solving the system of equations to determine the trajectories of Ag nanoparticles of size up to 45 nm in the process of focusing and deposition through a coaxial nozzle with an outlet diameter of about 100 μm on the substrate surface located 0.5 mm away from the nozzle. As a result of the comparative analysis, a satisfactory agreement between the model and the experiment is established.

High‐Temperature Large‐Scale Self‐Assembly of Highly Faceted Monocrystalline Au Metasurfaces

AbstractLocalized surface plasmon resonance (LSPR) devices based on resonant metallic metasurfaces have shown disruptive potential for many applications including biosensing and photocatalysis. Despite significant progress, highly performing Au plasmonic nanotextures often suffer of suboptimal electric field enhancement, due to damping effects in multicrystalline domains. Fabricating well‐defined Au nanocrystals over large surfaces is very challenging, and usually requires time‐intensive multi‐step processes. Here, presented are first insights on the large‐scale self‐assembly of monocrystalline Au nano‐islands with tunable size and separation, and their application as efficient LSPR surfaces. Highly homogeneous centimeter‐sized Au metasurfaces are fabricated by one‐step deposition and in situ coalescence of hot nanoparticle aerosols into a discontinuous monolayer of highly faceted monocrystals. First insights on the mechanisms driving the high‐temperature synthesis of these highly faceted Au nanotextures are obtained by molecular dynamic and detailed experimental investigation of their growth kinetics. Notably, these metasurfaces demonstrat high‐quality and tunable LSPR, enabling the fabrication of highly performing optical gas molecule sensors detecting down to 3 × 10−6 variations in refractive index at room temperature. It is believed that these findings provide a rapid, low‐cost nanofabrication tool for the engineering of highly homogenous Au metasurfaces for large‐scale LSPR devices with application ranging from ultrasensitive optical gas sensors to photocatalytic macroreactors.

Fast and simple assessment of surface contamination in operations involving nanomaterials.

The deposition of airborne nanosized matter onto surfaces could pose a potential risk in occupational and environmental scenarios. The incorporation of fluorescent labels, namely fluorescein isotiocyanate (FITC) or tris-1,3-phenanthroline ruthenium (II) chloride (Ru(phen)3Cl2), into spherical 80-nm silica nanoparticles allowed the detection after the illumination with LED light of suitable wavelength (365 or 405 nm respectively). Monodisperse nanoparticle aerosols from fluorescently labeled nanoparticles were produced under safe conditions using powder generators and the deposition was tested into different surfaces and filtering media. The contamination of gloves and work surfaces that was demonstrated by sampling and SEM analysis becomes immediately clear under laser or LED illumination. Furthermore, nanoparticle aerosols of about 105 nanoparticles/cm3 were alternatively fed through a glass pipe and personal protective masks to identify the presence of trapped nanoparticles under 405 nm or 365 nm LED light. This testing procedure allowed a fast and reliable estimation of the contamination of surfaces with nanosized matter, with a limit of detection based on the fluorescence emission of the accumulated solid nanoparticles of 40 ng of Ru(phen)3@SiO2 of silica per mg of non-fluorescent matter.

In situ observation of synthesized nanoparticles in ultra-dilute aerosols via X-ray scattering

In-air epitaxy of nanostructures (Aerotaxy) has recently emerged as a viable route for fast, large-scale production. In this study, we use small-angle X-ray scattering to perform direct in-flight characterizations of the first step of this process, i.e., the engineered formation of Au and Pt aerosol nanoparticles by spark generation in a flow of N2 gas. This represents a particular challenge for characterization because the particle density can be extremely low in controlled production. The particles produced are examined during production at operational pressures close to atmospheric conditions and exhibit a lognormal size distribution ranging from 5–100 nm. The Au and Pt particle production and detection are compared. We observe and characterize the nanoparticles at different stages of synthesis and extract the corresponding dominant physical properties, including the average particle diameter and sphericity, as influenced by particle sintering and the presence of aggregates. We observe highly sorted and sintered spherical Au nanoparticles at ultra-dilute concentrations (< 5 × 105 particles/cm3) corresponding to a volume fraction below 3 × 10–10, which is orders of magnitude below that of previously measured aerosols. We independently confirm an average particle radius of 25 nm via Guinier and Kratky plot analysis. Our study indicates that with high-intensity synchrotron beams and careful consideration of background removal, size and shape information can be obtained for extremely low particle concentrations with industrially relevant narrow size distributions.

Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range

Nucleation and growth of aerosol particles from atmospheric vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, especially for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidation products from biogenic volatile organic compounds are major contributors to particle formation and initial growth. However, whether oxidized organics contribute to particle growth over the broad span of tropospheric temperatures remains an open question, and quantitative mass balance for organic growth has yet to be demonstrated at any temperature. Here, in experiments performed under atmospheric conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of organic particles occurs over the range from [Formula: see text]C to [Formula: see text]C. The lower extent of autoxidation at reduced temperatures is compensated by the decreased volatility of all oxidized molecules. This is confirmed by particle-phase composition measurements, showing enhanced uptake of relatively less oxygenated products at cold temperatures. We can reproduce the measured growth rates using an aerosol growth model based entirely on the experimentally measured gas-phase spectra of oxidized organic molecules obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atmospheric observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that organic vapors can contribute to particle growth over a wide range of tropospheric temperatures from molecular cluster sizes onward.

Investigation of the possibility for reducing agglomeration of aerosol nanoparticles by using the needle-plate corona charger

Investigation of the possibility for reducing agglomeration of aerosol nanoparticles by using the needle-plate corona charger

Facile Synthesis of Flame Spray Pyrolysis-Derived Magnesium Oxide Nanoparticles for CO2 Sorption: Effect of Precursors, Morphology, and Structural Properties

A series of MgO aerosol nanoparticles were prepared by using a flame aerosol method and examined for the CO2 sorption at low-temperatures. Our XRD results suggest the formation of high purity magnesium oxide (MgO) phase. The CO2 sorption was determined at temperatures ranging from 60 to 275 °C using thermogravimetric (TGA) analysis, where the results indicate that the increased CO2 sorption we observed is associated with the improved pore volume and surface area of the sorbent. The as-synthesized MgO-A sorbent exhibited the best CO2 sorption capacity (66.0 mg CO2/g sorbent) at 60 °C in comparison with all of the sorbents tested. The CO2 uptake is predominantly controlled by the pore architecture as well as ultramicropores. The uptake characteristics of selected MgO sorbents we synthesized are significantly higher than that of CaO based sorbents at low temperatures.

Characterisation of structured and functionalised particles by small-angle X-ray scattering (SAXS)

In this work we provided an overview about the use of small-angle X-ray scattering (SAXS) technology for non-invasive characterisation of nanostructured and functionalised particles. Firstly, we demonstrated our modular-designed laboratory SAXS camera with different options and possibilities for quick in-situ measuring various disperse particulate systems including powders and suspensions as well as aerosol nanoparticles which can be deposited on a certain substrate. The detection angle reaches 90°, allowing simultaneous wide-angle X-ray scattering (WAXS) measurement on the crystalline structures. Further extension of the sample-to-detector distance enables multi-level structural characterisation of particle systems ranging from about one nanometer to several hundred nanometers. The use of an on-line X-ray detector makes on-line in-situ analysis possible. Secondly, different data processing methods and models have been introduced for analyzing the acquired scattering data and retrieving the structural parameters of the investigated particle systems. Finally, we presented some selected experimental results obtained by SAXS–WAXS, including commercial nanoparticles, and laboratory-synthesized nanostructured and functionalised particles such as silica multiplets, silica-magnetite core–shell nanocomposites, metallic nanoparticles and catalyst nanodots on oxide support particles in different liquid- and gas-phase synthesis processes as well as nanostructured particles in particle handling processes like high pressure dispersion and high temperature calcination.

N₂-BET is a Proxy for Primary Particle Size and May Not Be Representative of Available Specific Surface Area for Aggregated Nanoparticle Aerosols.

The knowledge of the specific surface area of aerosolized engineered nanoparticles could be important for mechanistically understanding their toxic potential or functional characteristics. The most widely method to perform this measurement, N2-BET, however, may not accurately represent the available surface area for hetero-aggregated nanoparticles in the context of large biological molecules. This study conducted an analysis of published characterization measurements including primary particle size, aggregation state, and specific surface area made for dry aerosolized nanoparticles. Results indicate that primary particle size explains 65% of the variance in specific surface area, while aggregation (as measured by mass median aerodynamic diameter) only explains 20% of the variance. Curiously, increasing aggregation (larger MMAD) is associated with increasing SSA as measured by N2-BET, likely an artifact of the measurement method, which suggests that this technique may not be appropriate for studies investigating biological interactions with nanoparticles.

One-Step Rapid and Scalable Flame Synthesis of Efficient WO3 Photoanodes for Water Splitting.

Photoelectrochemical water splitting is a promising approach for the carbon-free production of hydrogen using sunlight. Here, robust and efficient WO3 photoanodes for water oxidation were synthesized by the scalable one-step flame synthesis of nanoparticle aerosols and direct gas-phase deposition. Nanostructured WO3 films with tunable thickness and band gap and controllable porosity were fabricated by controlling the aerosol deposition time, concentration, and temperature. Optimal WO3 films demonstrate superior water oxidation performance, reaching a current density of 0.91 mA at 1.24 V vs. reversible hydrogen electrode (RHE) and an incident photon-to-current conversion efficiency (IPCE) of ca. 61 % at 360 nm in 0.1 m H2 SO4 . Notably, it is found that the excellent performance of these WO3 nanostructures arises from the high in situ restructuring temperature (ca. 1000 °C), which increases oxygen vacancies and decreases charge recombination at the WO3 /electrolyte interface. These findings provide a scalable approach for the fabrication of efficient photoelectrodes based on WO3 and other metal oxides for light-driven water splitting.

Development of Novel Octanoyl Chitosan Nanoparticles for Improved Rifampicin Pulmonary Delivery: Optimization by Factorial Design.

A novel hydrophobic chitosan derivative, octanoyl chitosan (OC) with improved organic solubility was synthesized, characterized, and employed for the preparation of rifampicin (Rif) encapsulated nanoparticle formulations for pulmonary delivery. OC was characterized to confirm acyl group substitution and cytotoxicity in A549 epithelial lung cells. OC nanoparticles were produced by the double emulsion solvent evaporation technique without cross-linking and characterized for particle size distribution, morphology, crystallinity, thermal stability, aerosol delivery, and drug release rate. OC was successfully synthesized with substitution degree of 44.05 ± 1.75%, and solubility in a range of organic solvents. Preliminary cytotoxicity studies of OC showed no effect on cell viability over a period of 24h on A549 cell lines. OC nanoparticles were optimized using a 32 full factorial design. An optimized batch of OC nanoparticles, smooth and spherical in morphology, had mean hydrodynamic diameter of 253 ± 19.06nm (PDI 0.323 ± 0.059) and entrapment efficiency of 64.86 ± 7.73% for rifampicin. Pulmonary deposition studies in a two-stage impinger following aerosolization of nanoparticles from a jet nebulizer gave a fine particle fraction of 43.27 ± 4.24%. In vitro release studies indicated sustained release (73.14 ± 3.17%) of rifampicin from OC nanoparticles over 72h, with particles demonstrating physical stability over 2months. In summary, the results confirmed the suitability of the developed systems for pulmonary delivery of drugs with excellent aerosolization properties and sustained-release characteristics.

Nanoparticle aerosols filtration using nonwoven filter media – separation mechanisms and experimental results

This paper presents the mechanisms of nanoparticles retention on nonwoven filter media during depth aerosol filtration and the influence of parameters such as particle size, linear velocity and gas temperature, fibre diameter and packing density and surface charge of particles and fibres on retention efficiency of particles according to the classic filtration theory. Based on a review of literature sources, a comparison of filtration efficiency results obtained on the basis of classic filtration theory and experimental results is presented.

Atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver with flowing gas and flowing atmospheric plasma

Two methods of atmospheric pulsed laser deposition of plasmonic nanoparticle films of silver are described. In both methods the ablation plume, produced by a 248 nm, 20 ns excimer laser in gas, is strongly confined near the target and forms a nanoparticle aerosol. For both the flowing gas, and the atmospheric plasma from a dielectric barrier discharge plasma source, the aerosol is entrained in the flow and carried to a substrate for deposition. The nanoparticle films produced by both methods were examined by electron microscopy and optical absorption spectroscopy. With plasma assistance, the deposition rate was significantly enhanced and the film morphology altered. With argon gas, isolated nanoparticles of 20 nm size were obtained, whereas in argon plasma, the nanoparticles are aggregated in clusters of 90 nm size. Helium gas also leads to the deposition of isolated nanoparticles, but with helium plasma, two populations of nanoparticles are observed: one of rounded particles with a mean size of 26 nm and the other of faceted particles with a mean size 165 nm.

Actual problems of exposure risk assessment of finely dispersed aerosols and aerosols of nanoparticles

Purpose of the study – analysis of the scientific literature on generalization of the data on domestic and foreign experience in risk assessment due to exposure to finely dispersed aerosols and aerosols of nanoparticles (NPs). The article summarizes data of long-term studies on the effect of nanomaterials and nanoparticles on the quality of human habitat and health. The domestic and foreign experience of harm health assessment, safety of new types of nanomaterials for the environment and work-related conditions have been analyzed.There are numerous studies of foreign and domestic scientists on the biological activity of nanoparticles and their effect on experimental animals, namely, on the specificity of their effect on various organs and systems of the body. Classification of nanomaterials, depending on their chemical composition, is presented. Attention is paid to the problems of nanosafety, namely, to the evaluation of nanotoxicity of substances and to the definition of the concept of a “dose” for nanoparticles. The data on the presence of finely dispersed and ultra-fine particles in the atmospheric air, which increase risk of respiratory system diseases among residents of large megacities, is given. There is special importance on assessing work conditions and occupational risks in production and use of materials which contain nanoparticles as well as in production processes with formation of the fine dust and nanoparticles indicated in the article. Due to the lack of a clear system for assessing health risks related to the action of nanoparticles, lack of common criteria of harmfulness and maximum allowable concentrations for most nanoparticles and uniform methods of their control, it is suggested to strictly adhere to protective measures in contact with nanomaterials and active improvement of nanosecurity measures. Conclusions. High toxicity and health hazards of finely dispersed and ultra-fine particles confirm need to control their content in the air of the populated areas and in the air of the working zone of industrial enterprises, where suspended particles are formed in the technological process. Obtained results of the scientific studies should be used for substantiation of preventive measures on nanosecurity in development and implementation of the nanotechnology, in order to protect health of workers and the general population.