Emission Of Nanoparticles Research Articles

Optimization of engine operating conditions and investigation of nano-particle emissions from a non-road engine fuelled with butanol/diesel blends

ABSTRACTThis study presents the experimental investigation of performance and emission characteristics (including nano-particle emissions) of a non-road diesel engine fuelled with neat diesel and butanol/diesel blends. Experiments were performed at optimal engine operating conditions for a constant engine speed of 1500 rpm. To find the optimal engine operating conditions, first experiments were conducted using diesel fuel. Engine operating parameters were optimized for higher brake thermal efficiency and lower exhaust emissions (i.e. gaseous as well as nano-particle emissions). Taguchi's design of experiment was used to optimize the compression ratio, injection pressure and engine operating load. To investigate the effect of butanol blends on the performance and emissions characteristics, experiments were conducted at three different butanol/diesel blend ratios (i.e. 10, 20 and 30% of butanol by volume) at optimum engine operating conditions. Results indicate that butanol/diesel blends have the potential to reduce CO, NO and particle emissions. The results also revealed that the concentration of ultrafine particle number reduces with diesel/butanol blends for all tested load conditions. The highest reductions in total particle number concentration for all butanol blends were found at 25% and 50% engine load conditions, as compared to neat diesel.

Upconversion emission of ZrO2 nanoparticles doped with erbium (Er3+) and ytterbium (Yb3+), synthesized by hydrothermal route

This paper reports the luminescent response upconversion of zirconium oxide (ZrO2) nanoparticles doped with erbium (Er3+) and ytterbium (Yb3+) ions, synthesized by hydrothermal route. X ray diffraction (DRX) showed that the synthesized material presents the face centered cubic (FCC) structure. High resolution transmission electron microscopy (HRTEM) showed the presence of crystals size smaller than 10nm. The photoluminescent analysis allowed to observe an intense upconversion luminescence emission of the samples doped with both ions Er3+ and Yb3+, when these are excited with 910nm laser source, showing the electronic transitions 4F9/2 → 4I5/2; 2H11/2 → 4I5/2; 4S3/2 → 4I15/2 of Er3+. Two decay times were observed, whose behavior can be associated to the average distance between erbium ions within the nanocrystals.

Upconversion improvement in KLaF4:Yb3+/Er3+ nanoparticles by doping Al3+ ions

Rare-earth ion-doped upconversion (UC) materials show great potential applications in optical and optoelectronic devices due to their novel optical properties. In this work, hexagonal KLaF4:Yb3+/Er3+ nanoparticles (NPs) were successfully synthesized by a hydrothermal method, and remarkably enhanced upconversion luminescence in green and red emission bands in KLaF4:Yb3+/Er3+ NPs has been achieved by doping Al3+ ions under 980 nm excitation. Compared to the aluminum-free KLaF4:Yb3+/Er3+ NPs sample, the UC fluorescence intensities of the green and red emissions of NPs doped with 10 at.% Al3+ ions were significantly enhanced by 5.9 and 7.3 times, respectively. Longer lifetimes of the doped samples were observed for the 4S3/2 state and 4F9/2 state. The underlying reason for the UC enhancement by doping Al3+ ions was mainly ascribed to distortion of the local symmetry around Er3+ ions and adsorption reduction of organic ligands on the surface of NPs. In addition, the influence of doping Al3+ ions on the structure and morphology of the NPs samples was also discussed.

Nano-metal oxides: Exposure and engineering control assessment

ABSTRACTIn January 2007, the National Institute for Occupational Safety and Health (NIOSH) conducted a field study to evaluate process specific emissions during the production of ENMs. This study was performed using the nanoparticle emission assessment technique (NEAT). During this study, it was determined that ENMs were released during production and cleaning of the process reactor. Airborne concentrations of silver, nickel, and iron were found both in the employee's personal breathing zone and area samples during reactor cleaning. At the completion of this initial survey, it was suggested that a flanged attachment be added to the local exhaust ventilation system. NIOSH re-evaluated the facility in December 2011 to assess worker exposures following an increase in production rates. This study included a fully comprehensive emissions, exposure, and engineering control evaluation of the entire process. This study made use of the nanoparticle exposure assessment technique (NEAT 2.0). Data obtained from filter-based samples and direct reading instruments indicate that reactor cleanout increased the overall particle concentration in the immediate area. However, it does not appear that these concentrations affect areas outside of the production floor. As the distance between the reactor and the sample location increased, the observed particle number concentration decreased, creating a concentration gradient with respect to the reactor. The results of this study confirm that the flanged attachment on the local exhaust ventilation system served to decrease exposure potential. Given the available toxicological data of the metals evaluated, caution is warranted. One should always keep in mind that occupational exposure levels were not developed specifically for nanoscale particles. With data suggesting that certain nanoparticles may be more toxic than the larger counterparts of the same material; employers should attempt to control emissions of these particles at the source, to limit the potential for exposure.

Characterization and Control of Nanoparticle Emission during 3D Printing.

This study aimed to evaluate particle emission characteristics and to evaluate several control methods used to reduce particle emissions during three-dimensional (3D) printing. Experiments for particle characterization were conducted to measure particle number concentrations, emission rates, morphology, and chemical compositions under manufacturer-recommended and consistent-temperature conditions with seven different thermoplastic materials in an exposure chamber. Eight different combinations of the different control methods were tested, including an enclosure, an extruder suction fan, an enclosure ventilation fan, and several types of filter media. We classified the thermoplastic materials as high emitter (>1011 #/min), medium emitters (109 #/min -1011 #/min), and low emitters (<109 #/min) based on nanoparticle emissions. The nanoparticle emission rate was at least 1 order of magnitude higher for all seven filaments at the higher consistent extruder temperature than at the lower manufacturer-recommended temperature. Among the eight control methods tested, the enclosure with a high-efficiency particulate air (HEPA) filter had the highest removal effectiveness (99.95%) of nanoparticles. Our recommendations for reducing particle emissions include applying a low temperature, using low-emitting materials, and instituting control measures like using an enclosure around the printer in conjunction with an appropriate filter (e.g., HEPA filter) during 3D printing.

Modulating upconversion luminescence through fluorescent dyes

In our work, we report an effective method to tune the upconversion emission of NaGdF4:Yb3+,Er3+@NaYF4 core/shell nanoparticles. The shell thickness-dependent upconversion luminescence of NaGdF4:Yb3+,Er3+@NaYF4 core/shell and the dye Rhodamine-B(RhB) composite were discussed in detail. It is found that the fluorescent dye RhB can remarkably improve the violet emission of the upconversion nanoparticles (UCNPs) and simultaneously generating the 605nm yellow emission through energy transfer. Importantly, it is revealed that the effective energy transfer distance between upconversion nanoparticles and RhB is shorter than 18nm in the media of NaYF4. These results open a novel way for determining the energy transfer distance between the upconversion nanoparticles and the dyes and simultaneously tuning the emission brightness and the spectrum covering range of the upconversion nanoparticles for meeting the requirement in the application fields of light source, colorful display, biological imaging, and fluorescent probes.

Nanoparticle emissions from gasoline vehicles DI &amp; MPI

The nanoparticles (NP) count concentrations are limited in EU for all Diesel passenger cars since 2013 and for gasoline cars with direct injection (GDI) since 2014. For the particle number (PN) of MPI gasoline cars there are still no legal limitations. In the present paper some results of investigations of nanoparticles from five DI and four MPI gasoline cars are represented. The measurements were performed at vehicle tailpipe and in CVS-tunnel. Moreover, five variants of “vehicle – GPF” were investigated. The PN-emission level of the investigated GDI cars in WLTC without GPF is in the same range of magnitude very near to the actual limit value of 6.0 × 10^12 1/km. With the GPF’s with better filtration quality, it is possible to lower the emissions below the future limit value of 6.0 × 10^11 1/km. The modern MPI vehicles also emit a considerable amount of PN, which in some cases can attain the level of Diesel exhaust gas without DPF and can pass over the actual limit value for GDI (6.0 × 10^12 1/km). The GPF-technology offers in this respect further potentials to reduce the PN-emissions of traffic.

PH-Sensitive polymer functionalized upconversion nanoparticles (UCNPs) as biomarkers

In our work, we report an effective method to tune the upconversion emission of NaGdF4:Yb3+,Er3+@NaYF4 core/shell nanoparticles. The shell thickness-dependent upconversion luminescence of NaGdF4:Yb3+,Er3+@NaYF4 core/shell and the dye Rhodamine-B(RhB) composite were discussed in detail. It is found that the fluorescent dye RhB can remarkably improve the violet emission of the upconversion nanoparticles (UCNPs) and simultaneously generating the 605 nm yellow emission through energy transfer. Importantly, it is revealed that the effective energy transfer distance between upconversion nanoparticles and RhB is shorter than 18 nm in the media of NaYF4. These results open a novel way for determining the energy transfer distance between the upconversion nanoparticles and the dyes and simultaneously tuning the emission brightness and the spectrum covering range of the upconversion nanoparticles for meeting the requirement in the application fields of light source, colorful display, biological imaging, and fluorescent probes.

Silver nanoclusters capped silica nanoparticles as a ratiometric photoluminescence nanosensor for the selective detection of I− and S2−

A novel and efficient approach has been established for the synthesis of silver nanoclusters capped silica nanoparticles (SiO2@AgNCs). These nanoclusters (AgNCs) capped silica nanoparticles were utilized as a novel ratiometric photoluminescence (PL) nanosensor for extremely sensitive and selective detection of I− and S2− ions. The AgNCs were prepared in situ on the silica nanoparticles through polyethyleneimine (PEI) template approach. While dual PL emissions of AgNCs (at 500 nm) and luminescent silica nanoparticles (at 602 nm) formed the basis for the ratiometric sensing. The PL emission of AgNCs was strongly quenched by I− (or S2−), while that of luminescent silica nanoparticles was hardly affected. The PL emission intensity ratio of AgNCs and the luminescent silica nanoparticles was defined as I500/I602. A good linear relationship between the I500/I602 value and the concentration of I− (or S2−) was observed, and the limit of detection (LOD) was estimated to be 57 nM for I− and 62 nM for S2−. In addition, the fluorescence images of the SiO2@AgNCs nanosensor changed from white to orange upon exposure to different concentrations of I− (or S2−) (0–250 μM), which could be clearly distinguished by the naked eye. The SiO2@AgNCs nanosensor exhibited good selectivity against other analytes, and I− or S2− ions could be separately detected via the introduction of proper masking agents. Furthermore, the detection of I− and S2− in real water samples was also demonstrated.

Theoretical calculation of the electronic structure of ZnO molecule

The lowest potential energy curves, for the electronic states of the molecule ZnO in the representation 2s+1 Λ (+/−) have been performed via Complete Active Space Self Consistent Field (CASSCF) using the Multireference Configuration Interaction (MRCI) method with Davidson correction (+Q). An excitation and de-excitation model has been proposed, in analogy to the emission of ZnO nanoparticles. In addition, the minimum energy level with respect to the ground state, Te, the internuclear distance at equilibrium, Re, the rotational constant, Be, the vibrational frequency, ωe, and the static and transition dipole moment, μ, have been investigated for some electronic states. Thirteen new electronic states have been studied here for the first time.

Inhalation exposure during spray application and subsequent sanding of a wood sealant containing zinc oxide nanoparticles

ABSTRACTNano-enabled construction products have entered into commerce. There are concerns about the safety of manufactured nanomaterials, and exposure assessments are needed for a more complete understanding of risk. This study assessed potential inhalation exposure to ZnO nanoparticles during spray application and power sanding of a commercially available wood sealant and evaluated the effectiveness of local exhaust ventilation in reducing exposure. A tradesperson performed the spraying and sanding inside an environmentally-controlled chamber. Dust control methods during sanding were compared. Filter-based sampling, electron microscopy, and real-time particle counters provided measures of exposure. Airborne nanoparticles above background levels were detected by particle counters for all exposure scenarios. Nanoparticle number concentrations and particle size distributions were similar for sanding of treated versus untreated wood. Very few unbound nanoparticles were detected in aerosol samples via electron microscopy, rather nano-sized ZnO was contained within, or on the surface of larger airborne particles. Whether the presence of nanoscale ZnO in these aerosols affects toxicity merits further investigation. Mass-based exposure measurements were below the NIOSH Recommended Exposure Limit for Zn, although there are no established exposure limits for nanoscale ZnO. Local exhaust ventilation was effective, reducing airborne nanoparticle number concentrations by up to 92% and reducing personal exposure to total dust by at least 80% in terms of mass. Given the discrepancies between the particle count data and electron microscopy observations, the chemical identity of the airborne nanoparticles detected by the particle counters remains uncertain. Prior studies attributed the main source of nanoparticle emissions during sanding to copper nanoparticles generated from electric sander motors. Potentially contrary results are presented suggesting the sander motor may not have been the primary source of nanoparticle emissions in this study. Further research is needed to understand potential risks faced by construction workers exposed to mixed aerosols containing manufactured nanomaterials. Until these risks are better understood, this study demonstrates that engineering controls can reduce exposure to manufactured nanomaterials; doing so may be prudent for protecting worker health.

Effect of Fuel Injection Strategy on the Carbonaceous Structure Formation and Nanoparticle Emission in a DISI Engine Fuelled with Butanol

Within the context of ever wider expansion of direct injection in spark ignition engines, this investigation was aimed at improved understanding of the correlation between fuel injection strategy and emission of nanoparticles. Measurements performed on a wall guided engine allowed identifying the mechanisms involved in the formation of carbonaceous structures during combustion and their evolution in the exhaust line. In-cylinder pressure was recorded in combination with cycle-resolved flame imaging, gaseous emissions and particle size distribution. This complete characterization was performed at three injection phasing settings, with butanol and commercial gasoline. Optical accessibility from below the combustion chamber allowed visualization of diffusive flames induced by fuel deposits; these localized phenomena were correlated to observed changes in engine performance and pollutant species. With gasoline fueling, minor modifications were observed with respect to combustion parameters, when varying the start of injection. The alcohol, on the other hand, featured marked sensitivity to the fuel delivery strategy. Even though the start of injection was varied in a relatively narrow crank angle range during the intake stroke, significant differences were recorded, especially in the values of particle emissions. This was correlated to the fuel jet-wall interactions; the analysis of diffusive flames, their location and size confirmed the importance of liquid film formation in direct injection engines, especially at medium and high load.

On-field and laboratory measurement of nanoparticle emission in the wake of gasoline vehicle

Nanoparticle emission from gasoline driven vehicles is reported to be significantly lower compared to diesel vehicles. Accordingly, there is no threshold limit implemented by the regulatory authorities in India for gasoline driven vehicles. Recent studies however indicate that this is true as far as the mass concentration of the nanoparticles is concerned. The number concentration of nanoparticles particularly of smaller dimensions is reported to be significantly higher for gasoline driven vehicles under certain operating range of speed and load. Smaller the dimension of the particles more are their residence time in environment and more susceptible are these particles to be inhaled by human respiratory and cardiovascular system. Thus an estimate of the size distribution of nano-sized particulate matter emission from gasoline driven vehicle is of immense importance in context to Indian urban population. In this direction, laboratory measurements are reported for the nanoparticle size distribution emitted from a gasoline engine under different loading conditions. On-field measurements are carried out in the wake of a stationary vehicle under idling and throttling condition. Simultaneous measurement of vehicular acceleration and deceleration is also reported along with nanoparticle distribution in the wake of a moving vehicle. The measurements reported in this paper reveal the need for deciding threshold value of number concentration to be implemented for gasoline vehicles by the Indian regulatory authorities.

The effect of nanosilica (SiO2) and nanoalumina (Al2O3) reinforced polyester nanocomposites on aerosol nanoparticle emissions into the environment during automated drilling

ABSTRACTThe aim of this study is to investigate the effect nanosilica and nanoalumina has on nanoparticle release from industrial nanocomposites due to drilling for hazard reduction whilst simultaneously obtaining the necessary mechanical performance. This study is therefore specifically designed such that all background noise is eliminated in the measurements range of 0.01 particles/cm3 and ±10% at 106 particles/cm3. The impact nano-sized SiO2 and Al2O3 reinforced polyester has on nanoparticle aerosols generated due to drilling is investigated. Real-time measurement was conducted within a specially designed controlled test chamber using a condensation particle counter (CPC) and a scanning mobility particle sizer spectrometer (SMPS). The results show that the polyester nanocomposite samples displayed statistically significant differences and an increase in nanoparticle number concentration by up to 228% compared to virgin polyester. It is shown that the nanofillers adhered to the polyester matrix showing ...

Determination of “safe” and “critical” nanoparticles exposure to welders in a workshop

ABSTRACTThe present study examined consequences of “safe” versus “critical” exposure to nanoparticles (NP) released during welding operations. With this aim in mind, a set of measurements regarding NP emissions was undertaken in a workshop during welding by metal active gas of carbon steel using different mixtures of argon (Ar) and carbon dioxide (CO2) as well as different process parameters which might influence emission of (NP). If these measurements were conducted in several locations away from the welding sources, the graphical representation of the obtained observations with time enabled definition of “safe” and “critical” regions within a welding workshop in terms of welder’s exposure. This information may be combined with the results of risk analysis derived by control banding and helps to categorize the sites where regulatory measures such as operation containment or dedicated exhaust ventilation need to be implemented.

Effect of premixing ratio, injection timing and compression ratio on nano particle emissions from dual fuel non-road compression ignition engine fueled with gasoline/methanol (port injection) and diesel (direct injection)

In present study, the effect of fuel premixing ratio, direct fuel injection timings and engine compression ratio on the soot particle emissions in nano-size range from a non-road compression ignition engine is investigated. Experiments are conducted on modified dual fuel single cylinder engine at 1500rpm. To run the engine in dual fuel mode, port fuel injection (PFI) system is installed by modifying intake manifold of the engine and developing a PFI controller. Experiments are conducted for various fuel premixing ratio of gasoline/methanol-diesel at different engine load, diesel fuel injection timing and compression ratios. Differential mobility spectrometer based particle sizer is used for investigation of the soot particle number-size distribution, surface area-size distribution, particle mass-size distribution and total particle number concentration from the engine exhaust at various test conditions. Results revealed that total particle number concentration is higher at full engine load and increases with fuel premixing ratio (especially in case of methanol-diesel dual fuel operation). Additionally, the peak particle number and mass concentration reduces with an increase in compression ratio of the engine.

Environment assisted photoconversion of luminescent surface defects in SiO2 nanoparticles

Time-resolved photoluminescence investigation on SiO2 nanoparticles was carried out in controlled atmosphere, with the aim to discern the effects induced on the typical blue luminescence band by high power UV Nd:YAG laser photons (4.66eV) and by some selected molecular species of the air (O2, N2, CO2, H2O). These factors ultimately determine both the brightness and photostability of the emitting defect, so as to limit the unique and attracting potentialities offered by this system in many applicative fields. Here it is highlighted that the effects due to photons and molecules, singularly considered, are not additive, the radiation being more dramatic in reducing the emission efficiency. Moreover, by analyzing the kinetics to convert the defects in a non-luminescent configuration both by the direct (photon-defect) and indirect (photon-molecule-defect) interactions, the threshold bleaching fluence is derived, ranging between 5000J/cm2 (in a vacuum) and 60J/cm2 (in air). These results indicate that an outstanding enhancement of the defect photostability is gained by passing from ambient atmosphere to vacuum condition, leading to foresee an immediate and relevant improvement in the field of the single-emitter spectroscopy based on the visible emission of SiO2 nanoparticles.

Evaluation of the amount of nanoparticles emitted in welding fume from stainless steel using different shielding gases

The primary objective of this study was to correlate the emission of macro and nanoparticles released during the process of metal inert gas/metal active gas (MIG/MAG) of stainless steel with different gas mixtures. Using different gas mixtures with different heat inputs, it was possible to determine fume formation rates and surface areas of nanoparticles with alveolar lung deposition capacity. It was found, how the various transfer modes and the type of gas protection, in particular, the percentage of active elements in the chemical composition of the gas, affect the amount of fumes generated and also the generation of nanoparticles with a high capacity of deposition. The spray transfer mode always shows higher values of nanoparticles surface area, unlike the fume formation rates. Among the tested mixtures 82%Ar + 18%CO2 generates higher emissions of nanoparticles as well as fume formation rates.

Effect of turbulence intensity on PM emission of heavy duty diesel trucks - Wind tunnel studies

Stringent emission regulations have forced drastic technological improvements in diesel aftertreatment systems, particularly in reducing Particulate Matter (PM) emissions. The formation and evolution of PM from modern engines are more sensitive to overall changes in the dilution process, such as rapidity of mixing, background PM present in the air. These technological advancements were made in controlled laboratory environments compliant with measurement standards (i.e. Code of Federal Regulation CFR in the USA) and are not fully representative of real-world emissions from these engines or vehicles. In light of this, a specifically designed and built wind tunnel by West Virginia University (WVU) is used for the study of the exhaust plume of a heavy-duty diesel vehicle, providing a better insight in the dilution process and the representative nanoparticles emissions in a real-world scenario. The subsonic environmental wind tunnel is capable of accommodating a full-sized heavy-duty truck and generating wind speeds in excess of 50mph. A three-dimensional gantry system allows spanning the test section and sample regions in the plume with accuracy of less than 5 mm. The gantry system is equipped with engine exhaust gas analyzers and PM sizing instruments. The investigation involves three different heavy-duty Class-8 diesel vehicles representative of three emission regulation standards, namely a US-EPA 2007 compliant, a US-EPA 2010 compliant, and a baseline vehicle without any aftertreatment technologies as a pre US-EPA 2007, respectively. The testing procedure includes three different vehicle speeds: idling, 20mph, and 35mph. The vehicles were tested on WVU's medium-duty chassis dynamometer, with the load applied to the truck reflecting the road load equation at the corresponding vehicle test speeds. Wind tunnel wind speed and vehicle speed were maintained in close proximity to one another during the entire test. Results show that the cross-sectional plume area increases with increase in distance away from tailpipe. Also indicating the cooling and dilution of the exhaust begins at close vicinity to the tailpipe. The rate of cooling and dilution are greatest in early stages of the dilution process for the areas with high turbulence intensity (TI), where strong mixing phenomena occurs, leading to the formation of a predominant nucleation mode. On the other hand, the core of the plume observes a slower cooling and dilution rate. This difference is reflected in the PM formation and evolution of these two distinct regions, as shown by the particle size distributions and number concentrations. Continuous mixing will tend to mellow those differences, but its “final” result is related to the dilution history.

Environmental Particle Emissions due to Automated Drilling of Polypropylene Composites and Nanocomposites Reinforced with Talc, Montmorillonite and Wollastonite

In this study, the effect on nanoparticle emissions due to drilling on Polypropylene (PP) reinforced with 20% talc, 5% montmorillonite (MMT) and 5% Wollastonite (WO) is investigated. The study is the first to explore the nanoparticle release from WO and talc reinforced composites and compares the results to previously researched MMT. With 5% WO, equivalent tensile properties with a 10 % weight reduction were obtained relative to the reference 20% talc sample. The materials were fabricated through injection moulding. The nanorelease studies were undertaken using the controlled drilling methodology for nanoparticle exposure assessment developed within the European Commission funded SIRENA Life 11 ENV/ES/506 project. Measurements were taken using CPC and DMS50 equipment for real-time characterization and measurements. The particle number concentration (of particles <1000nm) and particle size distribution (4.87nm – 562.34nm) of the particles emitted during drilling were evaluated to investigate the effect of the silicate fillers on the particles released. The nano-filled samples exhibited a 33% decrease (MMT sample) or a 30% increase (WO sample) on the average particle number concentration released in comparison to the neat polypropylene sample. The size distribution data displayed a substantial percentage of the particles released from the PP, PP/WO and PP/MMT samples to be between 5-20nm, whereas the PP/talc sample emitted larger particle diameters.