Ambient Air Research Articles

Effect of particulate matter on cognitive function among middle-aged and older adults in China: An instrumental variable approach

Emerging studies have suggested the association of ambient air pollution with cognitive decline; however, causal evidence remains scarce. We aimed to estimate the effect of particulate matter (PM) exposure on overall and domain-specific cognitive function. A total of 14,205 participants aged 45 and above were drawn from the 2015 wave of the China Health and Retirement Longitudinal Study (CHARLS). Cognitive function was assessed using a standardized questionnaire consisting of two domains: episodic memory and mental status. Participants’ exposure to city-level PM (PM1, PM2.5, and PM10) was evaluated using satellite-based spatiotemporal models. To avoid potential endogenous biases, an instrumental variable method with two-stage least squares estimation was employed to examine the effect of air pollution on overall and domain-specific cognitive function. Stratified analysis was further performed based on sociodemographic characteristics. We found PM exposure exerted a significant adverse effect on overall and domain-specific cognitive function, with mental status being more adversely affected as compared to episodic memory. The effect of PM exposure was more pronounced with smaller particle sizes, with PM1 exhibiting the largest effect size. Moreover, participants with lower education were more adversely affected by PM exposure. Our findings add additional evidence of the potential causal role of PM exposure in worsening overall and domain-specific cognitive function. Efforts to further reduce PM are needed to protect the cognitive health of the aging Chinese population.

On gravity-driven liquid nitrogen jets reach and horizontal spread for extinction of ground fires by aerial means

This paper describes experimental and numerical results on the reach and the spread of gravity-driven jets of liquid nitrogen (LN2) on the ground for applications to fire extinction by aerial means. A series of experiments released LN2 jets from different elevations in ambient air to measure their reach and spread distances upon the impingement. A numerical model was developed to simulate the behavior of such jets. Upon validation, the numerical model was used to further predict the LN2 pool mass and spreading distances under various release configurations. Results showed that the LN2 survivability is greatly affected by the release height of the cryogen, since the LN2 quantity reaching the ground decreases as the release height increases. Moreover, releasing larger initial LN2 quantities and, most importantly using larger nozzle diameters, both the LN2 pool mass and spreading diameter can be extended. Additional experiments were conducted where cryogen jets were released onto small (∼300 cm2) alcohol pool fires; results showed that only limited quantities of the LN2 evaporated in transit to the fire, and small amounts of the cryogen expediently snuffed the fires. A simplified model also suggested that in fire supression/extinction by LN2 the fuel cooling mechanism is of secondary importance compared to the mechanism of separating the fuel from oxygen.

Ambient air pollution and low birth weight in Brazil: A nationwide study of more than 10 million births between 2001 and 2018

Low birth weight (LBW) is a global health concern. While it is commonly associated with maternal health and behavior, exposure to ambient air pollution, can also play a role in contributing to LBW. In Brazil, where diverse environmental conditions and regional disparities exist, assessing the impact of ambient air pollution on LBW becomes particularly pertinent. To our knowledge, there is a gap in the existing literature, as no previous study has specifically investigated the relationship between ambient air pollution and LBW nationwide in Brazil. This study aims to fill this gap by examining the association between ambient air pollution and LBW in each trimester of pregnancy across the Brazilian states. In this work, birth data from January 1, 2001, to December 31, 2018 has been used. We utilized logistic regression models to estimate the odds ratio (OR) for low birth weight (LBW) associated with ambient air pollution (PM2.5, NO2, and O3) during each trimester of pregnancy (1st to 3rd trimester) across all 27 Brazilian states in our nationwide case-control study. We adjusted our model for several variables, including ambient temperature, relative humidity, and socioeconomic status (SES) variables at the individual level. We also conducted effect modification analyses by infant sex, mother's age, and the number of prenatal visits. Our study comprises over 10,213,144 birth records nationwide. Of these, 479,204 (4.92%) infants were included as cases of LBW. Our results indicate positive associations between PM2.5 and LBW, mainly in the Southern region. For example, in the state of Santa Catarina (South region), ORs were 1.003 (95% CI: 1.002, 1.004), 1.003 (95% CI: 1.002, 1.004), and 1.005 (95% CI: 1.003, 1.007) for the 1st, 2nd, and 3rd trimesters of exposure, respectively. NO2 had a robust association with LBW in the Northern and Northeastern states, including the state of Amapá (North region, where the Amazon Forest is located) with ORs of 1.377 (95% CI: 1.010, 1.878), 1.390 (95% CI: 1.020, 1.894), and 1.747 (95% CI: 1.297, 2.352) for the 1st, 2nd, and 3rd trimesters of exposure, respectively. Similarly, O3 had a robust association in the North and Midwest states, as observed in the state of Amapá with ORs of 1.033 (95% CI: 1.012, 1.054), and 1.033 (95% CI: 1.013, 1.053) for the 2nd, and 3rd trimesters, respectively. In the stratified analysis, boys were more vulnerable than girls, and the lower number of prenatal visits was associated with higher OR. Our findings are essential to the development of guidelines to prevent maternal exposure and protection of newborns in Brazil. This study provides valuable insights for region-specific strategies to improve maternal and neonatal health.

Enhancing the Resistive Switching Properties of Transparent HfO2-Based Memristor Devices for Reliable Gasistor Applications

We present a transparent memristor with a rough-surface (RS) bottom electrode (BE) with enhanced performance and reliability for a gasistor, which is a gas sensor plus a memristor, and its application in this paper. The transparent memristor, with an RS BE, exhibited low forming voltages (0.8 V) and a stable resistive switching behavior, with high endurance and an on/off ratio of about 125. This improvement is due to the better control of the electric field distribution and the oxygen vacancy concentration when applying the RS BE to transparent memristors. Maintaining the stability of the conducting filament in an ambient air environment for extended periods of time is crucial for the application of memristors as gasistors. The memristor with an RS BE demonstrates an ability to sustain a stable-current state for approximately 104 s. As a result, it is shown that the proposed transparent memristor with an RS BE can significantly enhance the device’s reliability for gasistor applications.

Exploring ultrafine particle emission characteristics from in-use light-duty diesel trucks in China using a portable measurement system

Diesel vehicle exhaust is one of the major contributors to ultrafine particles (UFPs) in urban areas in China. However, there is still a lack of knowledge about UFPs emission characteristics from current in-use diesel vehicles. This study has carried out an on-road test of 10 in-use Light-duty Diesel Trucks (LDDTs) with different emission control standards in China using a self-established portable measurement system based on the Electronic Low-pressure Impactor (ELPI) and characterized the ultrafine particle number (PN) concentration, particle size distribution and metal element contents. The results revealed a significant reduction of 93.37% in the average PN0.1 emission factor of LDDTs from China IV to China VI. Notably, LDDTs compliant with the China VI vehicle emission control standard exhibited the lowest PN0.1 and PM0.1 emission factors, measuring 4.991×1014 #/km and 0.627 g/km, respectively. By taking into account emissions under real driving conditions, we found that the PN emission rates grow with the increase of the Vehicle Specific Power (VSP). The cold-start phase had higher PN emissions than the hot-start phase, with 8590, 1890, 477, and 22 times higher than those of the ambient air (1.18×105 #/cm3), respectively. The installation of Diesel Particulate Filter (DPF) can decrease UFPs by more than 99.8%, while the PN emission factor during the DPF regeneration stage (1.85×1016 #/km) increased by 5 orders of magnitude that of the DPF normal works (7.51×1011 #/km). Metal element contents analysis shows that Fe, Ca, Al and Mg are the dominant elements in UFPs of LDDT exhaust gas, but the element of Ni is slightly increasing in a China VI, possibly due to the new automotive engine exhaust manifolds being made of Ni instead of cast iron for the purpose of having more high-temperature resistance. Our study demonstrates the importance of monitoring and routine maintenance of exhaust after-treatment systems.

Optimum Size and Heat Transfer and Velocity Correlations of the Outer and Inner Surfaces of Vertical Hollow Polygonal Cylinders in Natural Convection

Abstract Laminar natural convection heat transfer from vertical hollow polygonal cylinders with a wide range of cross-sectional areas is investigated. The buoyancy-driven three-dimensional (3D) flow around hollow polygonal cylinders immersed in quiescent ambient air with equal outer and inner surface temperatures is analyzed. The governing equations are numerically solved in nondimensional variables using the finite volume method. The numerical solution is validated using available experimental and numerical data. Results of the mean Nusselt number for the outer (Nu¯ho) and inner (Nu¯hi) surfaces are obtained by varying a number of key parameters. These parameters are the Rayleigh number based on the cylinder height (Rah) in the range 103≤ Rah≤ 107, the nondimensional cross-sectional area (AC) in the range 0.006 ≤ AC≤ 0.5, and the number of sides of the polygon (N) in the range 6 ≤ N ≤∞. In all cases, a Prandtl number (Pr) of 0.7 has been assumed. The study shows that at a certain Rayleigh number and a certain number of sides, the heat transfer rate from the inner surface decreases (by as much as 79.8%) as the polygon area decreases (by as much as 83.32%), whereas the heat transfer rate on the outer surface increases (by as much as 133.3%) as the polygon area decreases (by as much as 83.32%). It has also been found that the behavior of the buoyancy-driven flow in the vicinity of the outer surface is fundamentally different than that near the inner surface. Additional details about this fundamental difference are presented in the Results and Discussion section of the paper. New correlations to calculate the average velocity at the exit surface of the cylinder inner core and the mean Nusselt number for both the outer and inner surfaces have also been developed. Also, correlations have been developed for selecting the optimal cross-sectional area for purposes of identifying the regions where the thermal and velocity boundary layers overlap within the inner core of the cylinder.

Environmental Quality in Industrial Areas: Case Study of a Company in Banyuasin Regency, South Sumatra Province

With the emergence of industry in the Banyuasin district area, especially in Gasing Village, there are more job opportunities for residents and Banyuasin residents. However, the industry's rapid growth in the Banyuasin district can also hurt the environment, including air and water pollution. This research was carried out through descriptive observations of environmental conditions at the case study site. Data is collected and evaluated based on environmental elements, especially ambient air, emissions, noise and wastewater. At the case study location at an agro-industrial company in the Banyuasin district, the quality of ambient air, noise, emissions and wastewater from the WWTP was tested, and samples were taken. The test results show that the quality of ambient air, noise, emissions and wastewater produced by the WWTP around the factory area is classified as good, and all parameters meet the standards. If the measurement results of this research are looked at, there is no critical threshold value that attracts attention. This research shows that the industry must monitor the quality of the environment to make improvements and reduce the company's negative impact on the environment and the surrounding community's health.

Ambient air monitoring in Bishkek, Kyrgyz Republic for assessing the effectiveness of environment protection measures

The system of mobile monitoring of priority pollutants in the air of Bishkek, the capital of the Kyrgyz Republic, was improved and tested. The daytime dynamics of the content of nitrogen oxides (NO, NO2), carbon oxides (CO, CO2), formaldehyde (H2CO), and suspended microparticles (PM2.5) in the air on the central highways of the city were studied in winter. In 2023, significant concentrations of the components were identified. They exceeded the MAC standards several times and varied widely depending on the substance, the point and time of observation. A set of recommendations for reducing air pollution, including more environmentally friendly urban transport, types of fuel and its combustion technologies, were developed and partially implemented in 2022-2023. The results of monitoring of the content of the components were compared under similar conditions in 2023 and 2024. It was revealed that the recommendations of the Bishkek city administration contributed to reducing air pollution with harmful substances at most observation points to safe concentrations. The need for using the system of integrated mobile and automated monitoring of the atmospheric air in populated areas was justified.

Theory-Guided Design of Unconventional Phase Metal Heteronanostructures for Higher-Rate Stable Li-CO2 and Li-Air Batteries.

Lithium-carbon dioxide (Li-CO2) and Li-air batteries hold great potential in achieving carbon neutral given their ultrahigh theoretical energy density and eco-friendly features. However, these Li-gas batteries still suffer from low discharging-charging rate and poor cycling life due to sluggish decomposition kinetics of discharge products especially Li2CO3. Here we report the theory-guided design and preparation of unconventional phase metal heteronanostructures as cathode catalysts for high-performance Li-CO2/air batteries. The assembled Li-CO2 cells with unconventional phase 4H/face-centered cubic (fcc) ruthenium-nickel heteronanostructures deliver a narrow discharge-charge gap of 0.65 V, excellent rate capability and long-term cycling stability over 200 cycles at 250 mA g-1. The constructed Li-air batteries can steadily run for above 150 cycles in ambient air. Electrochemical mechanism studies reveal that 4H/fcc Ru-Ni with high-electroactivity facets can boost redox reaction kinetics and tune discharge reactions towards Li2C2O4 path, alleviating electrolyte/catalyst failures induced by the aggressive singlet oxygen from solo decomposition of Li2CO3.

Comprehensive analysis of recovery procedures for SO2-contaminated proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) are critical in transitioning to a low-carbon future, especially in industries like heavy-duty transportation, maritime shipping, and aviation. However, the use of ambient air exposes Pt-based electrocatalysts to air contaminants, leading to performance loss and premature degradation. SO2 appears to be the most crucial air impurity for fuel cell operation due to the formation of strongly adsorbed S-containing species, like elemental S0 on the cathode Pt surface and a lack of self-recovery in pure air. This work evaluates the efficiency of potential cycling from 0.1 to 1.2 V and cathode purging with pure O2 for recovering PEMFC performance after 5 ppm SO2 exposure at 80 °C. Results indicate that SO2 contamination at higher operating current densities causes more pronounced loss in performance and electrochemical area as well as negatively affecting recovery. Both potential cycling and O2 purge methods show recovery efficiencies of up to 95 % for fuel cells contaminated at lower current densities (0.4 A cm-2) and 84 % at higher current densities (1.0 A cm-2). Interestingly, the end of test diagnostics further improved performance, reaching a recovery efficiency of 95-97 %. The findings suggest that while both recovery methods are effective, the O2 purge technique is more practical for field applications due to its simplicity and lack of need for auxiliary equipment. The study employs a segmented cell system to analyze localized performance variations and SO2 contamination impacts.

Airborne antibiotic resistome from sludge dewatering systems: Mobility, pathogen accessibility, cross-media migration propensity, impacting factors, and risks

Bioaerosol contamination was considered as a potential health threat in sludge dewatering systems (SDSs), while emission and risk of airborne antibiotic resistome remain largely unclear. Herein, seasonal investigations of fine particulate matter (PM2.5) were conducted using metagenomics-based methods within and around different SDSs, together with an analysis of sewage sludge. Featured with evident seasonality, antibiotic resistance genes (ARGs) in SDS-PM2.5 also possessed greater accumulation, transfer, and pathogen accessibility than those in ambient air PM2.5. Mobile ARGs in SDS-PM2.5 mainly encoded resistance to tetracycline, and most were flanked by integrase. Some pathogenic antibiotic resistant bacteria (PARB), including Enterobacter asburiae, Escherichia coli, Enterococcus faecium, and Staphylococcus aureus, also carried mobile genetic elements in SDS-PM2.5. Dewatering behavior actuated > 50.56% of ARG subtypes and > 42.86% of PARB in sewage sludge to aerosolize into air. Relative humidity, temperature, and PM2.5 concentration collectively drove the evolution of bacterial community and indirectly promoted the antibiotic resistance of SDS-PM2.5. SDS-PM2.5 posed more serious resistome risks than sewage sludge and ambient air PM2.5, and the highest levels were discovered in winter. These findings underline the role of dewatering behavior in facilitating resistome's aerosolization, and the need to mitigate this potential air pollution.

Evidencing Phase Transformations of Li6PS5Cl Argyrodite under Ambient Air and Dry Room Exposure.

All-solid-state electrolytes have been extensively studied for the last years in order to achieve high conductivities and improved safety among lithium-ion technologies. Sulfide electrolytes, such as argyrodites (Li6PS5X, X = Cl, Br, and I), succeed to show high performances despite their poor chemical stability. As a matter of fact, argyrodite reactivity to water is known as a common drawback for easy implementation and requires the use of dry room for cell preparation. The understanding of argyrodite degradation under ambient air exposure is a key for the development of stable electrolytes, coatings, and processes and has been incompletely explored until now. This study brings unreported elements of comprehension around the degradation mechanisms of Li6PS5Cl solid electrolyte using transmission electron microscopy (TEM) and complementary spectroscopic techniques.

Association of ambient air pollution and Air Quality Index with risk of sudden sensorineural hearing loss: a cross-sectional study

ObjectivesTo explore the associations of air pollutants and Air Quality Index (AQI) with risk of sudden sensorineural hearing loss (SSNHL)DesignCross-sectional studySettingMedical record data and local population data collected between 2014...

Investigating the deposition of fibrous zeolite particles on leaf surfaces: A novel low-cost method for detecting the presence of airborne hazardous mineral fibers

Naturally occurring fibrous minerals, such as erionite, can pose a significant threat to human health when disturbed and subsequently respired. Understanding the spatial abundance and characteristics of these hazardous fibrous minerals in ambient air is crucial for minimizing human exposure and assessing risk. Conventional detection methods for airborne hazardous mineral fibers, such as those developed for asbestos, are of limited utility in environmental settings where fiber concentrations are low and different fiber types may be present and can be costly especially when monitoring large areas over long periods of time. This study presents an innovative methodology for detecting and identifying the presence of airborne naturally occurring fibrous zeolites, using leaf surface deposition sampling, SEM-EDX analysis for the detection and assessment of elemental composition, and TEM-SAED with continuous rotation diffraction (MicroED) to determine their crystallographic unit cell parameters. In total, 309 fibrous zeolite particles (FZPs) were identified on a range of tree leaf surfaces across 80% of the sampling sites located close to both active and disused zeolite quarries in the Taupo Volcanic Region, New Zealand. The FZPs displayed various morphologies including aggregates, bundles, and fibril-like structures. Of the FZPs detected, 91.2% were < 5µm in length. Tetrahedral Si:(Si+Al) ratio results indicated that 40% of the FZPs were in the reference range for zeolite mordenite. TEM-SAED plus MicroED analysis resulted in 61% of tested FZPs indexed to unit cell parameters that matched with mordenite. This research demonstrates the potential of leaf sampling as a cost-effective method for detecting airborne FZPs while the MicroED data can be utilized for distinguishing between different types of airborne fibrous zeolites in ambient air.

The Possible Role of PM2.5 Chronic Exposure on 5-Year Survival in Patients with Left Ventricular Dysfunction Following Coronary Artery Bypass Grafting.

The survival benefit of surgical revascularization in multivessel coronary artery disease is well understood, though it can be modified by left ventricular dysfunction. Chronic exposure to air pollutants has gained more attention recently as a possible non-traditional morbidity and mortality cardiovascular risk factor. This study identified possible 5-year mortality risk factors related to postoperative left ventricular performance, including air pollutants. There were 283 patients (244 (86%) males) with a median age of 65 (60-70) years enrolled in the retrospective analysis. All patients were referred for off-pump coronary artery revascularization due to chronic coronary syndrome that presented as a multivessel coronary artery disease. They were divided into three groups depending on the postoperative course of left ventricular fraction (LVEF 50% or more (169 patients), LVEF between 41 and 49% (61 patients), and LVEF 40% or less (53 patients)). The overall survival rate was 84% (237 patients) in a median follow-up time of 5.3 (4.8-6.1) years. The median (Q1-Q3) chronic air pollution exposures for the analyzed group were 19.3 (16.9-22.4) μg/m3 for fine particles such as PM2.5, 25.8 (22.5-29.4) μg/m3 for coarse particles such as PM10, and 12.2 (9.7-14.9) μg/m3 for nitric dioxide (NO2). The mortality in the first group (LVEF at least 50%) was 23 (13.6%), in the second group (LVEF 41-49%) was 9 (15%), and in the third group (LVEF 40% or less) was 14 (26%). The multivariable regression analysis for the five-year mortality risk in the first group revealed the predictive value of dyslipidemia (HR: 3.254, 95% CI: 1.008-10.511, p = 0.049). The multivariable regression analysis for five-year mortality risk in the second group revealed the predictive value of dyslipidemia (HR: 3.391, 95% CI: 1.001-11.874, p = 0.050) and PM2.5 (HR: 1.327, 95% CI: 1.085-1.625, p = 0.006). In the third group (severely decreased LVEF), chronic PM2.5 exposure was found to be significant (HR: 1.518, 95% CI: 1.50-2.195, p = 0.026) for 5-year mortality prediction. Traditional risk factors, such as dyslipidemia, are pivotal in the 5-year mortality risk following surgical revascularization. Chronic exposure to ambient air pollutants such as PM2.5 may be an additional risk factor in patients with left ventricular dysfunction.

Associations of Lifestyle, Ambient Air Pollution With Progression of Asthma in Adults: A Comprehensive Analysis of UK Biobank Cohort.

We aim to investigate the associations between lifestyle, ambient air pollution with crucial outcomes in the progression of adult asthma, including asthma new-onset and asthma hospitalisation. 176,800 participants were included to assess the prospective association between baseline risk exposures and the subsequent asthma onset, 17,387 participants were used to evaluate asthma hospitalisation. Cox regression models were employed to examine the associations. In terms of lifestyle factors, the HRs (95% CIs) of the least healthy lifestyle categories for asthma incidence and hospitalization were 1.099 (1.017-1.187) and 1.064 (1.008-1.123), respectively. For pollutants, PM2.5, especially the traffic-related PM2.5 component, was consistently recognized as a significant risk factor for asthma onset (HR = 1.064, 95% CI: 1.034-1.094) and hospitalisation (HR = 1.031, 95% CI: 1.010-1.052) under various model adjustments. Low socioeconomic status also played a major role in the progression of adult asthma. Our study provides crucial insights into factors influencing the progression of adult asthma. Monitoring and reducing exposure to air pollution, particularly PM2.5, promoting healthier lifestyle, and addressing socioeconomic inequity are important in preventing and managing asthma.

Impact of construction activities on the air quality of Agra city, Uttar Pradesh, India

The current research work was carried out to comprehensively assessed the impact of construction activities on the air quality. Seven sites were chosen along the metro line construction in Agra, Uttar Pradesh, India, to meet the study's goals. The monitoring was performed for 24 hours at each site using the respirable dust sampler (RDS) with a gaseous sampling attachment. The raw data was processed to calculate the Air Quality Index (AQI). The data obtained indicate that all the examined sites had PM10 (particulate matter having the diameter less than or equal to 10 micron) values above the National Ambient Air Quality Standards (NAAQ) values of 100 µg/m3, while SS-05 and SS-06 had PM2.5 (particulate matter having the diameter less than or equal to 2.5 micron) values above the NAAQ values of 60 µg/m3. Values of CO, SO2, and NO2 were discovered to be lower than the NAAQ standard limits. Because PM10's sub index (Si) was found to be the greatest across all locations, it was determined to be the criterion pollutant among all the metrics. Based on the AQI value, the research area's overall air quality was determined to be moderately polluted. At every location, a variety of management techniques, including mist guns, water spraying, and planting, are regularly used to reduce air pollution. Effective implementation of applied air pollution control measures is required to make the air clean and safe for breathing.

Impedance Spectroscopy Study of Charge Transfer in the Bulk and Across the Interface in Networked SnO2/Ga2O3 Core–Shell Nanobelts in Ambient Air

Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The influence of the shell material on the transportation of the electric charge carriers along these structures is still not very well understood. This is due to homo-, hetero- and metal/semiconductor junctions, which make it difficult to investigate the electric charge transfer using direct current methods. However, in order to improve the gas-sensing properties of these complex structures, it is necessary to first establish a good understanding of the electric charge transfer in ambient air. In this article, we present an impedance spectroscopy study of networked SnO2/Ga2O3 core–shell nanobelts in ambient air. Tin dioxide nanobelts were grown directly on interdigitated gold electrodes, using the thermal sublimation method, via the vapor–liquid–solid (VLS) mechanism. Two forms of a gallium oxide shell of varying thickness were prepared via halide vapor-phase epitaxy (HVPE), and the impedance spectra were measured at 189–768 °C. The bulk resistance of the core–shell nanobelts was found to be reduced due to the formation of an electron accumulation layer in the SnO2 core. At temperatures above 530 °C, the thermal reduction of SnO2 and the associated decrease in its work function caused electrons to flow from the accumulation layer into the Ga2O3 shell, which resulted in an increase in bulk resistance. The junction resistance of said core–shell nanostructures was comparable to that of SnO2 nanobelts, as both structures are likely connected through existing SnO2/SnO2 homojunctions comprising thin amorphous layers.

Enhancing lubrication of electrified interfaces by inert gas atmosphere

Abstract Considering the growing interest in increasing performance and efficiency of driveline components of modern electric vehicles, this work aims to analyze and report the wear mechanisms and notable enhancement of the lubrication of electrified contact interfaces by inert gas atmospheres. Systematic tribological studies were conducted on AISI 52100 steel test pairs using driveline lubricants under unelectrified and electrified conditions in ambient air and dry N2. Test results showed that in ambient air and electrification, the formation of iron oxides (in particular hematite) was most dominant and gave rise to severe abrasive wear regardless of the lubricant type being used. In dry N2, however, the tribo-oxidation was suppressed but the formation of a carbon-rich tribofilm was favored (especially under electrified conditions). Such a shift from surface oxidation to carbonaceous film formation resulted in dramatic reductions (by factors of 8 to 10) in the wear of test pairs.

Femtosecond laser-induced black silicon: a dual application in photodetection and surface-enhanced Raman scattering

A multifunctional structured silicon with enhanced optical and photoelectric properties has been processed by femtosecond (fs) laser in ambient air. The structured surface decorated with Au nanoparticles (NPs) exhibits excellent infrared absorption properties related to localized surface plasmon resonance (LSPR) coupled to microstructures. Over 75% absorption is achieved at 1550 nm, which is three orders of magnitude higher than that of unprocessed Si. The absorption enhancement results in increased photocurrent response in n + -n junction diodes, exhibiting a responsivity of 125 mA/W and an external quantum efficiency (EQE) of 10% at 1550 nm, for a bias voltage of 10 V. Moreover, the structured Si is also tested as a surface-enhanced Raman spectroscopy (SERS) substrate showing a strong signal under 638 nm excitation with Raman enhancement factors (EFs) as high as 108. In particular, the capability of detecting Raman analyte down to 10−11 M for RhB and 10−10 M for 4-MBA is demonstrated, simultaneously assessing the enhanced near-field due to the LSPR originating from the processed surface roughness leading to the valuable performances achieved by the n + -n junction diodes. These results offer a new path toward the elaboration of high-efficiency applications of Si structured surfaces in the fields of photoelectric sensing and detection.