Nanoparticles In Air Research Articles

Oxygen vacancies, hydroxyl groups and fluorine ions in the local environment of Yb3+ ions doped in CeO2 nanoparticles

The local environment of Yb3+ ions doped into ceria (CeO2) nanoparticles, synthesized by two different methods, was determined using EPR spectroscopy. It was found that the charge compensator for the Yb3+ ion located in the nearest environment can be a vacancy, a hydroxyl group, or a fluorine ion. The EPR spectra of Yb3+ ions at concentrations of 0.1 mol% and 0.5 mol% in ceria nanoparticles, prepared using the coprecipitation technique from an aqueous solution, are mainly due to cubic sites, which indicate the remote location of the charge compensators. The EPR lines resulting from trigonal sites in these samples suggested that the charge compensation is associated with a hydroxyl group. The FTIR measurements correlate with this supposition. After annealing the samples in a vacuum furnace, EPR lines from trigonal sites related to oxygen vacancies were observed. The second type of ceria nanoparticle was prepared by annealing CeF3 nanoparticles in air. EPR spectra of Yb³⁺ ions at concentrations of 0.1 mol% and 0.5 mol% in these samples revealed that the lines from trigonal sites were mainly associated with fluorine ions in the nearest environment.

Spectral shifts in tip-induced light from plasmonic nanoparticles in air

Spectral shifts in tip-induced light from plasmonic nanoparticles in air

Synthesis of ultra-small Co3O4-C core-shell nanoparticles with improved thermal stability and microwave absorption properties

Ultra-small Co3O4-C nanoparticles were synthesized with an average core size of 8.2 nm by annealing CoC nanoparticles in air at a relative low temperature. The formation mechanism of these nanoparticles can be attributed to the presence of defective C shells, the high chemical activity of ultra-small Co nanoparticles, and the gradual oxidation of the C shell during the low-temperature annealing process. The Co3O4-C nanoparticles demonstrated remarkable thermal stability at temperatures of up to 360 °C in air. Moreover, he Co3O4-C nanoparticles exhibited excellent microwave absorption performances, with an optimal reflection loss of −64.2 dB and an effective bandwidth of 6.08 GHz at a single thickness of 2.2 mm. These impressive microwave absorption properties can be attributed to the small size effects, the core-shell nanostructure, and the presence of defective C shells in the nanoparticles. Overall, the as-synthesized Co3O4-C nanoparticles show great potential for future applications as microwave absorbers, thanks to their large bandwidth, strong microwave absorption, and high thermal stability in air.

Nanometer-Resolved Operando Photo-Response of Faceted BiVO4 Semiconductor Nanoparticles.

Photo(electro)catalysis with semiconducting nanoparticles (NPs) is an attractive approach to convert abundant but intermittent renewable electricity into stable chemical fuels. However, our understanding of the microscopic processes governing the performance of the materials has been hampered by the lack of operando characterization techniques with sufficient lateral resolution. Here, we demonstrate that the local surface potentials of NPs of bismuth vanadate (BiVO4) and their response to illumination differ between adjacent facets and depend strongly on the pH of the ambient electrolyte. The isoelectric points of the dominant {010} basal plane and the adjacent {110} side facets differ by 1.5 pH units. Upon illumination, both facets accumulate positive charges and display a maximum surface photoresponse of +55 mV, much stronger than reported in the literature for the surface photo voltage of BiVO4 NPs in air. High resolution images reveal the presence of numerous surface defects ranging from vacancies of a few atoms, to single unit cell steps, to microfacets of variable orientation and degree of disorder. These defects typically carry a highly localized negative surface charge density and display an opposite photoresponse compared to the adjacent facets. Strategies to model and optimize the performance of photocatalyst NPs, therefore, require an understanding of the distribution of surface defects, including the interaction with ambient electrolyte.

Reversible photochromic W18O49: Mechanism revealing and performance improvement for smart windows

W18O49 has widely used in photothermal application and photocatalyst due to its strong Localized Surface Plasmon Resonance (LSPR) effect and unique oxygen-deficient structure. In addition, the unstable structure and easily changed valence state of W5+ make W18O49 potentially photochromic. However, the generally synthesized blue W18O49 particles was in a saturated colored state, delivering a great challenge in exploring its photochromic features, which thus have seldom been studied. Herein, we found that the bleached W18O49 obtained by mild-heating the solvothermal-synthesized blue W18O49 nanoparticles in air had considerable reversible photochromic feature, which can be colored in 1 min under UV irradiation. The photochromic mechanism of W18O49 was revealed through the XRD, XPS and FTIR results. The chromic process was mainly attributed to the changed W5+ content under different conditions. The photochromic performance was systematically investigated on the W18O49-based film and which can be significantly improved by Ti doping. Finally, the great potential of the films in the energy-saving smart windows application has verified, and a 10 at.% Ti-doped W18O49 film delivered outstanding optical performance with luminous transmittance (Tlum) of 87.53% and solar energy modulation efficiency (ΔTsol) of 30.13%.

Diffusion dynamics and characterization of attogram masses in optically trapped single nanoparticles using laser-induced plasma imaging

In the present work, a wavelength-selected plasma imaging analysis system is presented and used to track photons emitted from single-trapped nanoparticles in air at atmospheric pressure. The isolated nanoentities were atomized and excited into plasma state using single nanosecond laser pulses. The use of appropriate wavelength filters alongside time-optimized acquisition settings enabled the detection of molecular and atomic emissions in the plasma. The photon detection efficiency of the imaging line resulted in a signal > 400 times larger than the simultaneously-acquired dispersive spectroscopy data. The increase in sensitivity outlined the evolution of diverse physicochemical processes at the single particle scale which included heat and momentum transfer from the plasma into the particle as wells as chemical reactions. The imaging detection of excited fragments evidenced different diffusion kinetics and time frames for atoms and molecules and their influence upon both the spectroscopic emission readout and fabrication processes using the plasma as a reactor. Moreover, the origin of molecular species, whether naturally-occurring or derived from a chemical reaction in the plasma, could also be studied on the basis of compositional gradients found on the images. Limits of detection for the inspected species ranged from tens to hundreds attograms, thus leading to an exceptional sensing principle for single nanoentities that may impact several areas of science and technology.

Optical Bottle Shaping Using Axicons with Amplitude or Phase Apodization

We investigate the formation of single and multiple optical bottle beams on the optical axis using a diffractive axicon with amplitude or phase apodization. The proposed approach allows one to control the location and the contrast of the boundaries of the generated dark intensity regions on the optical axis. Experimental results obtained using a spatial light modulator are in good agreement with numerically obtained ones. We successfully used the designed and experimentally formed set of three optical bottle beams for trapping light-absorbing agglomerations of carbon nanoparticles in air under the action of photophoretic forces. This confirms the efficiency of the proposed approach for optical manipulation applications.

Aging of 2D MXene nanoparticles in air: An XPS and TEM study

Different batches of Ti3C2OxFx MXene were prepared, and their stability in air and argon was studied. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) in multiple modes (bright field imaging, energy-dispersive X-ray analysis, and selected-area electron diffraction) was employed to study the chemical and morphological changes in two-dimensional (2D) MXene exposed to air for several days and months. We observed the progressive development of the Ti4+ state accompanied by the development of TiO2 formation, which lead to a slow disintegration of the 2D MXene nanosheets, although their overall morphology and crystalline structure can persist for several months. The presence of water is found to play an important role in the hydrolysis and degradation reactions during MXene aging. Our XPS and TEM studies show how the surface chemistry changes during aging in air and which surface termination groups are indicative of stable Ti3C2OxFx MXene and which storage conditions can stabilize MXene for more than 337 days.

Determination of metallic nanoparticles in air filters by means single particle inductively coupled plasma mass spectrometry

Single particle inductively coupled plasma mass spectrometry (spICP-MS) has been explored for the determination of metallic nanoparticles (NPs) in air. Different extraction strategies (i.e., direct immersion, hard cap espresso, ultrasound-assisted and microwave-assisted extraction) and extracting solvents (i.e., citric acid, trisodium citrate, potassium nitrate, sodium nitrate, thiourea, disodium pyrophosphate and ammonium hydroxide) were investigated for platinum and gold NPs recovery from glass and microquartz fiber filters with a nominal size cut-off of 300 nm. Results show that metallic NPs are preserved and quantitatively extracted from the filter in 4 min inside an 800 W microwave oven by using 40 mL of a 2.0% w w−1 NH4OH solution. For the remaining extraction procedures, either incomplete recoveries or NPs degradation occur. As regards the influence of filter material, microquartz fiber affords better NPs capturing performance than glass fiber ones, enabling the quantification of NPs with diameters above 28 nm. This methodology has been successfully applied to determine PtNPs in filters from environmental monitoring stations and to gain insight into NPs transport through ICP-MS sample introduction system. Care should be taken during spICP-MS calibration since biased results might be obtained due to differences on NPs transport efficiency between standards and samples.

Suppressing the Agglomeration of ZnO Nanoparticles in Air by Doping with Lower Electronegativity Metallic Ions: Implications for Ag/ZnO Electrical Contact Composites

Suppressing the Agglomeration of ZnO Nanoparticles in Air by Doping with Lower Electronegativity Metallic Ions: Implications for Ag/ZnO Electrical Contact Composites

Non-Oxidized Bare Metal Nanoparticles in Air: A Rational Approach for Large-Scale Synthesis via Wet Chemical Process.

Metal nanoparticles (MeNPs) have been used in various industrial applications, owing to their unique physical and chemical properties different from the bulk counterparts. However, the natural oxidation of MeNPs is an imminent hindrance to their widespread applications despite much research efforts to prevent it. Here, a rational approach for non‐oxidized bare MeNPs in air, which requires no additional surface passivation treatment is reported. The direct synthetic route uses the [Gd2C]2+ · 2e− electride as an exceptional electron‐donating agent to reduce diverse metal precursors in alcoholic solvents. All synthesized bare Cu, Ag, and Sn nanoparticles are ultra‐stable in ambient air, exhibiting no trace of metal oxides even on their outermost atomic layer. This unique resistance to oxidation is ascribed to the accumulation of excess electrons on the surface of bare MeNPs, which originates from the spontaneous transfer of anionic electrons from the electride during the nanoparticle growth process. This approach provides not only a revolutionary scheme to obtain MeNPs with non‐passivated and non‐oxidized surfaces, but also fundamental knowledge about metal oxidation.

Reactivity of Vanadium Nanoparticles with Oxygen and Tungsten.

A mechanistic study was carried out on the optimal methods of fabrication of products containing higher loads of thermochromic VO2(M1) fabricated by thermal treatments of V nanoparticles in air, that, once achieved, are more stable than other commercial products upon natural aging or reiterated reheating. At the best temperatures for single runs, 55% of VO2 can be attained by the reactions of a limited number of the species initially formed in a process, that, if not stopped, can degrade the product by solid state reactions of oxidations and reductions without O2 consumption. This fact supports the use of two-step treatments at lower temperatures and faster cooling rates that reach 65% of VO2; such reactions should, ideally, take place in the 550–625 °C temperature range. The impregnation of V with a tungstate salt is an ideal and simple doping platform that can decrease the energy of activation of the 2-cycle process, allowing higher yields and enthalpies of transformation (71% of VO2, 26 J/g) than undoped counterparts or trademarks. A good balance is reached for 1% at. of W, with a reduction in Tc of 20 °C not significantly resenting the enthalpy of the reversible metal-to-insulator transition. For higher W amounts, the appearance of tetragonal VO2, and W alloyed V3O7 and V2O5, decrease the fractions of increasingly and effectively doped M1-VO2 achieved till 2% of W, a concentration for which Tc attains the stimulating values of 35 °C on heating and 25 °C on cooling.

Non-oxidized bare copper nanoparticles with surface excess electrons in air

Copper (Cu) nanoparticles (NPs) have received extensive interest owing to their advantageous properties compared with their bulk counterparts. Although the natural oxidation of Cu NPs can be alleviated by passivating the surfaces with additional moieties, obtaining non-oxidized bare Cu NPs in air remains challenging. Here we report that bare Cu NPs with surface excess electrons retain their non-oxidized state over several months in ambient air. Cu NPs grown on an electride support with excellent electron transfer ability are encapsulated by the surface-accumulated excess electrons, exhibiting an ultralow work function of ~3.2 eV. Atomic-scale structural and chemical analyses confirm the absence of Cu oxide moiety at the outermost surface of air-exposed bare Cu NPs. Theoretical energetics clarify that the surface-accumulated excess electrons suppress the oxygen adsorption and consequently prohibit the infiltration of oxygen into the Cu lattice, provoking the endothermic reaction for oxidation process. Our results will further stimulate the practical use of metal NPs in versatile applications.

Size-Selective Detection of Nanoparticles in Solution and Air by Imprinting.

Monitoring of nanoparticles (NPs) in air and aquatic environments is an unmet challenge accentuated by the rising exposure to anthropogenic or engineered NPs. The inherent heterogeneity in size, shape, and the stabilizing shell of NPs makes their selective recognition a daunting task. Thus far, only a few technologies have shown promise in detecting NPs; however, they are cumbersome, costly, and insensitive to the NPs morphology or composition. Herein, we apply an approach termed nanoparticle-imprinted matrices (NAIM), which is based on creating voids in a thin layer by imprinting NPs followed by their removal. The NAIM was formed on an interdigitated electrode (IDE) and used for the size-selective detection of silica NPs. Three- and 5-fold increases in capacitance were observed for the reuptake of NPs with similar diameter, compared to smaller or larger NPs, in air and liquid phase, respectively. En masse, the proposed approach lays the foundation for the emergence of field-effective, inexpensive, real-life applicable sensors that will allow online monitoring of NPs in air and liquids.

A Novel Route for the Easy Production of Thermochromic VO2 Nanoparticles.

In this work, a simple, fast and dry method for the fabrication of a thermochromic product with a high load of VO2(M1) consisting of the controlled heat treatment of pure vanadium nanoparticles in air is presented. After a complete design of experiments, it is concluded that the most direct way to attain the maximum transformation of V into VO2(M1) consists of one cycle with a fast heating ramp of 42 °C s−1, followed by keeping 700 °C for 530–600 seconds, and a subsequent cooling at 0.05 °C s−1. Careful examination of these results lead to a second optimum, even more suitable for industrial production (quicker and less energy‐intensive because of its lower temperatures and shorter times), consisting of subjecting V to two consecutive cycles of temperatures and times (625 °C for 5 minutes) with similar preheating (42 °C s−1) but a much faster postcooling (∼ 8 °C s−1). These green reactions only use the power for heating a tube open to atmosphere and a vanadium precursor; without assistance of reactive gases or catalysts, and no special vacuum or pressure requirements. The best products present similar thermochromic properties but higher thermal stability than commercial VO2 particles. These methods can be combined with VO2 doping.

Perovskite Nanoparticles: Extremely Stable Luminescent Crosslinked Perovskite Nanoparticles under Harsh Environments over 1.5 Years (Adv. Mater. 3/2021)

In article 2005255, Byeong-Soo Bae, Tae-Woo Lee, and co-workers report exceptionally stable crosslinked perovskite nanoparticles (NPs) under harsh environments, with a novel composite materials design strategy. Noticeably, the crosslinked perovskite NPs (CPNs) show recovery of photoluminescence in the initial stage and retain their photophysical properties under humidified environments. The CPNs overcome the instability of perovskite NPs in air, water, and strong chemicals as well as under high temperature.

Effect of non-digestible nanoparticles on animals’ health and behavior

The effect of air quality on human?s health has been extremely studied, nanoparticles in air can cause various diseases and even lead to death. However, the effect of non-digestible nanoparticles from food on physical and mental health has been seriously ignored, no report was seen in open literature. This paper uses silkworm as an experimental subject by feeding nanoparticles in food throughout their life, the results show that non-digestible nanoparticles can greatly change animal?s body morphology, behavior and longevity. This paper gives an unprecedented warning on food safety and drinking water.

Nanoparticles in the air of the working zone as a risk factor for the health of workers of various industries

Purpose: analysis of scientific literature, summarizing data on domestic and foreign experience of assessing the determination of nanoparticles in the air of the working zone as a risk factor for the health of workers of various industries. The article analyzes the literature data on the study of the content of fine dust and nanoparticles in the atmospheric air and air of the working zone of different industries. Numerous studies indicate that fine dust is contained in the emissions of many industrial enterprises. According to the World Health Organization by level of impact on human health, suspended particles in the air and especially in the air of the working zone belong to the priority pollutants. Evaluation of the dust content in the air of large industrial cities is particularly relevant, because of a large number of sources of dust emissions of various origins in urban areas. Various technological processes contribute to the formation of fine dust and nanoparticles which pollute the ambient air and the air of the working zone. Data on the negative impact of fine dust and nanoparticles on health of workers are presented. Attention is paid to the problem of hygienic assessment of nanoscale dust content in the working zone air. The obtained results indicate that today the issues of studying the physicochemical properties of nanoparticles, their toxicity to the body, analysis of potential risks to humans, the development of an effective and reliable system for monitoring ultrafine particles in the environment and the production environment are still relevant as for informing employees about the risks involved, reducing and preventing harmful effects on humans. The potential negative effects on workers’ health determine the need and opportunity for further research in this area.

Fabrication and In-Situ Thermal Reduction of Gold Nanofibers

One-dimensional gold nanofibers are good candidates for next generation nanoelectronic devices. Here, gold nanofibers were synthesized via electrospinning with subsequent in-situ thermal reduction. The thermal behavior of the precursor nanofibers was investigated by thermogravimetric/differential thermal analysis and fourier transform infrared. The polymer parts are decomposed and removed step by step, meanwhile, gold salt is decomposed and in-situ reduced to form gold nanoparticles in air without any reducing agent or gas due to its strong oxidation ability. The effects of gold content, polymers type (PVP, PVA, PAN), calcination atmospheres (Air, H2, H2/Ar) and temperatures (200 °C to 500 °C) on the morphology and structures of gold nanofibers were characterized by XRD, SEM, and TEM. The results shows that PVP is the optimal polymer with the gold content of 6:1 (PVP:Au) to fabricate the continuous gold nanofibers with good morphology and structures. The final gold nanofibers with average diameter of 60 nm and several hundred micrometers long, were fabricated after calcined at 500 °C in air for 2 hours. It was composed of gold nanoparticles that ranged from 5 to 30 nm.

Subchronic continuous inhalation exposure to zinc oxide nanoparticles induces pulmonary cell response in mice

ObjectivesWe used mice as an animal model to investigate the entry of ZnO nanoparticles from the ambient air into the lungs and other organs, subsequent changes in Zn levels and the impact on the transcription of Zn homeostasis-related genes in the lungs. MethodsThe mice were exposed to two concentrations of ZnO nanoparticles; lower (6.46 × 104 particles/cm3) and higher (1.93 × 106 particles/cm3), allowed to breathe the nanoparticles in the air for 12 weeks and subjected to necropsy. Characterization of the ZnO nanoparticles was done using transmission electron microscopy (TEM). Energy-dispersive X-ray (EDX) spectroscopy was used to quantify ZnO nanoparticles in the lungs, brain, liver and kidney. The total zinc content in the lungs, brain, liver, kidney, red blood cells and plasma was estimated by inductively coupled plasma mass spectroscopy (ICP-MS). Transcription rate of the genes was evaluated by RealTime PCR. ResultsThe two concentration of ZnO nanoparticles in the ambient air produced two different outcomes. The lower concentration resulted in significant increases in Zn content of the liver while the higher concentration significantly increased Zn in the lungs (p < 0.05). Additionally, at the lower concentration, Zn content was found to be lower in brain tissue (p < 0.05). Using TEM/EDX we detected ZnO nanoparticles inside the cells in the lungs, kidney and liver. Inhaling ZnO NP at the higher concentration increased the levels of mRNA of the following genes in the lungs: Mt2 (2.56 fold), Slc30a1 (1.52 fold) and Slc30a5 (2.34 fold). At the lower ZnO nanoparticle concentration, only Slc30a7 mRNA levels in the lungs were up (1.74 fold). Thus the two air concentrations of ZnO nanoparticles produced distinct effects on the expression of the Zn-homeostasis related genes. ConclusionUntil adverse health effects of ZnO nanoparticles deposited in organs such as lungs are further investigated and/or ruled out, the exposure to ZnO nanoparticles in aerosols should be avoided or minimised.