Silicon/nickel oxide core/shell nanospheres as a hole transport layer for high efficiency and light-stable perovskite solar cells.

Metal halide perovskite solar cells (PSCs) possess huge potential due to their high power conversion efficiency. However, instability is still a key factor limiting their applications. Therefore, we have found a feasible strategy to improve the light stability of PSCs. Specifically, a core-shell material with a silicon nanosphere core and a nickel oxide nanosheet shell serves as the hole transport layer in our PSCs. Due to the selective absorption of ultraviolet light by the silicon nanoparticles, the ultraviolet light content of the natural light that reaches the perovskite layer is reduced. Compared with a control device (without Si), the PSCs with the silicon/nickel oxide hole transport layer possessed a higher current density of 22.09 mA cm-2 and a higher power conversion efficiency of 18.54%, with both values increased by 2.7% and 6.1%, respectively. More importantly, the PSCs based on a silicon/nickel oxide hole transport layer maintains 85% of its initial power conversion efficiency value after 700 hours of natural light exposure. These results indicate that the silicon/nickel oxide hole transport layer is an important functional component of the PSCs, which improves the photovoltaic performance and reduces ultraviolet light-induced photodegradation, thereby improving the device stability.

The effect of metformin and drinking water quality variation on haloacetamide formation during chlor(am)ination of acetaminophen.

Acetaminophen (Apap) is widely used and is known to form toxic haloacetamides (HAcAms) during chlorination. Metformin (Met) is a typical medication with usage much higher than that of Apap and its ubiquitous presence in the environment is known. The objective of this study was to investigate the effects of Met which contains multiple amino groups potentially joining reactions and different chlorination methods on HAcAm formation from Apap. In addition, a major drinking water treatment plant (DWTP) using the largest river in southern Taiwan was sampled to study the influence of Apap in a DWTP on the HAcAm formation. Results showed increasing dichloroacetamide (DCAcAm) molar yields of Apap at a Cl/Apap molar ratio of 5 during chlorination (0.15%) and two-step chlorination (0.03%). HAcAms were formed by the chlorine substitution of hydrogen on the methyl group in Apap followed by the cleavage of the bonding between nitrogen and aromatic. While a high Cl/Apap ratio during chlorination led to reactions between chlorine and HAcAms formed decreasing the HAcAm yields, the two-step chlorination further reduced the HAcAm formation during chlorination by a factor of 1.8-8.2. However, Met which limitedly formed HAcAms increased the DCAcAm yields of Apap by 228% at high chlorine dosages during chlorination and by 244% during two-step chlorination. In the DWTP, trichloroacetamide (TCAcAm) formation was important. The formation was positively correlated with NH4+, dissolved organic carbon (DOC), and specific ultraviolet absorbance (SUVA). DCAcAm dominated in the presence of Apap. The DCAcAm molar yields were 0.17%-0.27% and 0.08%-0.21% in the wet and dry seasons, respectively. The HAcAm yields of Apap in the DWTP were limitedly changed between different locations and seasons. Apap could be one important cause for HAcAm formation in a DWTP, as the presence of other pharmaceuticals such as Met possibly worsens the situation in chlorine applications.

When Aggregation-Induced Emission Meets Perovskites: Efficient Defect-Passivation and Charge-Transfer for Ambient Fabrication of Perovskite Solar Cells.

The intrinsic defects in perovskite film can serve as non-radiative recombination center to limit the performance and stability of metal halide perovskite solar cells (PSCs). The additive engineering in perovskite film is always applied to produce high-efficiency PSCs in recent years. Here, a typical donor-acceptor (D-A) structured aggregation-induced emission (AIE) molecule tetraphenylethene-2-dicyano-methylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TPE-TCF) was introduced into perovskite film. The D-A structure of TPE-TCF molecule provided additional charge transfer channels, contributing to transporting electron of TPE-TCF-based device. The cyano (C≡N) of TPE-TCF can interact with the uncoordinated Pb to from a relatively stable intermediate, PbI2 ⋅TPE-TCF, resulting in the slower crystal growth, reduced the defects at the grain boundaries and suppressed carrier recombination. As a consequence, the power conversion efficiency (PCE) of TPE-TCF-modified PSCs achieved a remarkably enhanced from 15.63 to 19.66 % with negligible hysteresis, which was prominent in methylammonium lead iodide-based devices fabricated under ambient condition. Furthermore, the PSCs modified by AIE molecule possessed an outstanding stability and maintain about 86 % of the initial PCE after 300 h storage in air at 25-35 °C with a high relative humidity (RH) of ≈85 %. This work suggests that incorporating AIE molecule into perovskite is a promising strategy for facilitating high-performance PSCs commercialization in ambient environment without glovebox.

Investigating the differences between receptor and dispersion modeling for concentration prediction and health risk assessment of volatile organic compounds from petrochemical industrial complexes.

Receptor and dispersion models both provide important information to help understand the emissions of volatile organic compounds (VOCs) and develop effective management strategies. In this study, differences between the predicted concentrations of two models and the associated impacts on the estimated health risks due to different theories behind two models were investigated. Two petrochemical industrial complexes in Kaohsiung city of southern Taiwan were selected as the sites for this comparison. Although the study compares the approaches by applying the methods to this specific area, the results are expected to be adopted for other areas or industries. Ninety-nine VOC concentrations at eight monitoring sites were analyzed, with the effects of diurnal temperature and seasonal humidity variations being considered. The Chemical Mass Balance (CMB) receptor model was used for source apportionment, while the Industrial Source Complex (ISC) dispersion model was used to predict the VOC concentrations at receptor sites. In the results of receptor modeling, 54% ± 11% and 49% ± 20% of the monitored concentrations were contributed by process emissions in two complexes, whereas the numbers increased to 78% ± 41% and 64% ± 44% in the results of dispersion modeling. Significant differences were observed between two model predictions (p < 0.05). The receptor model was more reproducible given the smaller variances of its results. The effect of seasonal humidity variation on two model predictions was not negligible. Similar findings were observed given that the cancer and non-cancer risks estimated by the receptor model were lower but more reproducible. The adverse health risks estimated by the dispersion model exceeded and were 75.3%-132.4% of the values estimated by using the monitored data, whereas the percentages were lowered to the range from 27.4% to 53.8% when the prediction was performed by using the receptor model. As the results of different models could be significantly different and affect the final health risk assessment, it is important to carefully choose an appropriate model for prediction and to evaluate by monitoring to avoid providing false information for appropriate management.

Ionic polymer metal composite for an optical zoom in a compact camera.

The reflective method is utilized in the optical zoom function of a thin camera for the advantage of folding the optical path. An ionic polymer metal composite deformable mirror used in a reflective zoom system achieves large deformations to change optical power with a low bias voltage. Polydimethylsiloxane is used as a buffer layer to improve surface roughness. The surface roughness of this layer is about 17 nm. The optical focusing power of the deformable mirror reaches 73.8 m(-1) diopters with 3 volts. A complete reflective camera module is fabricated using two ionic polymer metal composite deformable mirrors in the zoom function. The zoom ratio is about 1.6 × .

Multivariate analysis of carcinogenic equivalence (CEQ) to characterize carcinogenic VOC emissions in a typical petrochemical industrial park in Taiwan.

Large industrial emissions of volatile organic compounds (VOCs) from the petrochemical industry are a critical concern due to their potential carcinogenicity. VOC emissions vary in composition depending on the source and occur in mixtures containing compounds with varying degrees of toxicity. We proposed the use of carcinogenic equivalence (CEQ) and multivariate analysis to identify the major contributors to the carcinogenicity of VOC emissions. This method weights the carcinogenicity of each VOC by using a ratio of its cancer slope factor to that of benzene, providing a carcinogenic equivalence factor (CEF) for each VOC. We strategically selected a petrochemical industrial park in southern Taiwan that embodies the industry's comprehensive nature and serves as a representative example. The CEQs of different emission sources in three years were analyzed and assessed using principal component analysis (PCA) to characterize the major contributing sectors, vendors, sources, and species for the carcinogenicity of VOC emissions. Results showed that while the study site exhibited a 20.7 % (259.8 t) decrease in total VOC emissions in three years, the total CEQ emission only decreased by 4.5 % (15.9 t), highlighting a potential shift in the emitted VOC composition towards more carcinogenic compounds. By calculating CEQ followed by PCA, the important carcinogenic VOC emission sources and key compounds were identified. More importantly, the study compared three approaches: CEQ followed by PCA, PCA followed by CEQ, and PCA only. While the latter two methods prioritized sources based on emission quantities, potentially overlooking less abundant but highly carcinogenic compounds, the CEQ-first approach effectively identified vendors and sources with the most concerning cancer risks. This distinction underscores the importance of selecting the appropriate analysis method based on the desired focus. Our study highlighted how prioritizing CEQ within the analysis framework empowered the development of precise control measures that address the most carcinogenic VOC sources.

Air-processed MAPbI3 perovskite solar cells achieve 20.87% efficiency and excellent bending resistance enabled via a polymer dual-passivation strategy.

In recent years, air-processed MAPbI3 perovskite solar cells (PSCs) have attracted widespread interest from researchers worldwide because of their simple and low-cost fabrication process. Nonetheless, the ambient conditions usually bring about many adverse effects, such as imperfect crystallization and numerous defects in perovskite films, which seriously impact both the photoelectric performance and stability of the device. Therefore, in this work, a polymer dual-passivation strategy was employed by introducing ammonium polyphosphate (APP) as an additive to the green anti-solvent to accurately modify the perovskite layer. APP, which has abundant phosphate and ammonium groups, could simultaneously fill the I/Pb vacancies by Lewis acid-base reactions to restrain defect formation and improve the power conversion efficiency (PCE) of the ultimate device. On the other hand, the long molecular chains of the polymer with a certain flexural ability were easily congregated at the grain boundaries of the perovskite grains, thus enhancing the bending resistance. Consequently, high-quality perovskite films with a dense morphology and large grain size were obtained. Because of the reduced defect density and suppressed non-radiative recombination, the optimal PSC attained a champion PCE of 20.87% with negligible hysteresis. Furthermore, the non-encapsulated APP-modified flexible device also exhibited excellent bending resistance. Only 20% of its normalized PCE was lost after 150 bending cycles at room temperature. This simple, green, low-cost, and reliable strategy for preparing high-efficiency PSCs with good stability can facilitate its commercialization.

The Influences of Pore Blockage by Natural Organic Matter and Pore Dimension Tuning on Pharmaceutical Adsorption onto GO-Fe3O4.

The ubiquitous presence of pharmaceutical pollution in the environment and its adverse impacts on public health and aquatic ecosystems have recently attracted increasing attention. Graphene oxide coated with magnetite (GO-Fe3O4) is effective at removing pharmaceuticals in water by adsorption. However, the myriad compositions in real water are known to adversely impact the adsorption performance. One objective of this study was to investigate the influence of pore blockage by natural organic matter (NOM) with different sizes on pharmaceutical adsorption onto GO-Fe3O4. Meanwhile, the feasibility of pore dimension tuning of GO-Fe3O4 for selective adsorption of pharmaceuticals with different structural characteristics was explored. It was shown in the batch experiments that the adsorbed pharmaceutical concentrations onto GO-Fe3O4 were significantly affected (dropped by 2-86%) by NOM that had size ranges similar to the pore dimensions of GO-Fe3O4, as the impact was enhanced when the adsorption occurred at acidic pHs (e.g., pH 3). Specific surface areas, zeta potentials, pore volumes, and pore-size distributions of GO-Fe3O4 were influenced by the Fe content forming different-sized Fe3O4 between GO layers. Low Fe contents in GO-Fe3O4 increased the formation of nano-sized pores (2.0-12.5 nm) that were efficient in the adsorption of pharmaceuticals with low molecular weights (e.g., 129 kDa) or planar structures via size discrimination or inter-planar π-π interaction, respectively. As excess larger-sized pores (e.g., >50 nm) were formed on the surface of GO-Fe3O4 due to higher Fe contents, pharmaceuticals with larger molecular weights (e.g., 296 kDa) or those removed by electrostatic attraction between the adsorbate and adsorbent dominated on the GO-Fe3O4 surface. Given these observations, the surface characteristics of GO-Fe3O4 were alterable to selectively remove different pharmaceuticals in water by adsorption, and the critical factors determining the adsorption performance were discussed. These findings provide useful views on the feasibility of treating pharmaceutical wastewater, recycling valuable pharmaceuticals, or removing those with risks to public health and ecosystems.

Reduction-Active Antisolvent: A Universal and Innovative Strategy of Further Ameliorating Additive Optimization for High Efficiency Perovskite Solar Cells.

To further ameliorate current additive engineering of perovskites for viable applications, the inherent limitations should be overcome; these include weakened coordination of the dopants to the [PbI6]4- octahedra during crystallization and ubiquity of ineffective bonding sites. Herein, we introduce a facile strategy for synthesizing a reduction-active antisolvent. Washing with reduction-active PEDOT:PSS-blended antisolvent substantially enhances the intrinsic polarity of the Lewis acid (Pb2+) in [PbI6]4- octahedra, which causes significant strengthening of the coordinate bonding between additives and perovskite. Thus, coordination of the additive to the perovskite becomes much stable. Additionally, the enhanced coordination ability of Pb2+ can enhance the effective bonding sites and further enhance the efficacy of additive optimization to the perovskite. Here, we demonstrate five different additives as dopant bases and repeatedly verify the universality of this approach. The photovoltaic performance and stability of doped-MAPbI3 devices are further improved, revealing the advanced potential of additive engineering.

Comparative assessments of VOC emission rates and associated health risks from wastewater treatment processes.

With the growing concern regarding emission of volatile organic compounds (VOCs) from wastewater treatment plants (WWTPs), the relationship between the VOC emission rates and the associated public health risks has been rarely discussed. The objective of this study was to examine and compare the VOC emission rates and cancer and non-cancer risks by inhalation intake, using a municipal WWTP in China as an example, with respect to the effects of treatment technologies, VOC species, and seasonal variation. Given the treatment technology considered, the emission rates of VOCs in this study were estimated by means of mass balance or calculated on the molecular level. From the viewpoints of both emission rates and cancer and non-cancer risks, sedimentation was the treatment technology with the highest health risks to the workers. Slightly lower VOC emission rates and health risks than those for sedimentation were observed in anaerobic treatment. Although the aeration significantly enhanced the VOC emission rates in the aerobic treatment process, the associated health risks were limited due to the low VOC concentrations in the gas phase, which were likely attributed to the strong mixing and dilution with fresh air by aeration. Amongst the VOCs investigated, benzene was the VOC with both a relatively high emission rate and health risk, while trichloroethylene possessed a high emission rate but the lowest health risk. Without strong interfacial aeration and turbulence between the water and atmosphere, the effects of treatment technology and seasonal variation on the health risks might be connected to the VOC emission rates, while the effect of VOC species depended considerably on the respective cancer slope factors and reference concentrations; the employment of aeration provided a different conclusion in which the emission rates were enhanced without a significant increase in the related cancer risks. These findings can provide insight into future health risk management and reduction strategies for workers in WWTPs.

Variations of N concentrations and microbial community in the start-up of anammox using anaerobic heterotrophic sludge: Influence of a long reaction-phase time and comparison of the efficiencies of attached-versus suspended-growth cultures.

Anaerobic sludge was capable of producing anaerobic ammonium oxidation (anammox) cultures. However, the low activity of anammox bacteria in the seed sludge often led to a long time for stable anammox to initiate. The objective of this study was to investigate the influence of an extended reaction-phase time in the sequencing batch reactor (SBR) on the rapid startup of anaerobic ammonium oxidation (anammox) using anaerobic heterotrophic bacteria as the seed sludge. After the startup, suspended and attached bacteria in anammox were separately analyzed for comparison. The variations of nitrogen concentrations and shifts of the microbial community structures were studied. The results showed that anammox occurred after a long reaction-phase time in the SBR with the efficient removals of NH4+ (96.4%) and NO2- (99.8%). The effective NO2- treatment before anammox startup was attributable to inevitable denitrification or dissimilatory nitrate reduction (e.g., Denitratisoma). The occurrence of anammox was supported by the anammox stoichiometry, bacteria diversity variation, and principal component analysis. The overall nitrogen removal rate (NRR) and nitrogen removal efficiency (NRE) was 0.07 kg/m3-d and 92.8%, respectively. The relative molar quantities of NH4+ and NO2- removed as well as N2 and NO3- formed were 1(1):1.29(1.32):1.45(1.02):0.15(0.26), as the numbers in the parentheses represent the theoretical values. Denitratisoma and Desulfatiglans dominated in the seed sludge, whereas Candidatus_Jettenia abundances were significantly higher in anammox attached- (26.0%) and suspended-growth cultures (14.5%). Fifty-three genera were simultaneously identified in all samples, suggesting their importance in the startup of anammox from anaerobic sludge. Candidatus_Jettenia was observed to be more associated with the growth of anammox biofilm (the abundances were 26.0% and 14.5% in attached- and suspended-growth cultures, respectively) and supported the fine nitrogen removal performance in the attached-growth cultures.

The disappearing additive: introducing volatile ethyl acetate into a perovskite precursor for fabricating high efficiency stable devices in open air.

In recent years, organic-inorganic halide perovskite solar cells (PSCs) have attracted massive attention because of their high power conversion efficiency (PCE). However, it is difficult to prepare perovskite films with good performance in open air due to the poor stability of perovskite materials in high humidity, which is seriously hindering the practical application and development of PSCs. Herein, ethyl acetate (EA) is introduced into the perovskite precursor to enhance the crystallinity of perovskite for fabricating high efficiency stable devices in the atmospheric environment. Interestingly, volatile EA, which is often used as an anti-solvent, could quickly evaporate and accelerate the nuclei formation during perovskite crystallization. More impressively, the Lewis base nature of EA can form strong chemical bonding interactions with perovskite to passivate the defects during crystallization. As a result, the EA-modified perovskite film demonstrates dense and defect-less morphology with large grain size (the maximum achieves 0.9 µm). The EA-treated device has a dramatic efficiency of 19.53% and negligible hysteresis of the photocurrent. Furthermore, both the temperature and humidity resistances of EA-modified PSC are significantly improved. The normalized PCE of the EA-modified device without encapsulation can still retain over 80% of its initial value after being stored in 60% relative humidity (RH) in the dark for 500 hours. This contribution provides a promising channel for facilitating the commercialization of PSCs.

Dissolved and particulate nitrogen species partitioning and distribution in the Danshuei River estuary, northern Taiwan.

Danshuei River Estuary (DRE) total and inorganic nitrogen in the dissolved (TDN, DIN) and particulate (TPN, PIN) phases were analyzed to study their distribution and partitioning. The carbon contents in particles were also analyzed. The upper estuary contained higher ammonium concentration (304-557 µM), leading to TDN completely dominating (>95%) the total N (TDN + TPN) pool within the DRE. Ammonium played a crucial role in controlling the speciation variation of DIN and partitioning between dissolved and particulate phases. Nitrification seemed to occur in the salinity >30 region where elevated percentages of nitrite and nitrate were observed. PON dominated the particulate N and contributed an average of 62% of the TPN pool. A constant organic C/N ratio (6.55) was observed in particles, indicating that POM was mainly from phytoplankton detritus. The N distribution coefficient values, log(KD), ranged from 3 to 4, suggesting that the affinity of DIN for particles was weak.

Graphene Family Nanomaterials (GFN)-TiO2 for the Photocatalytic Removal of Water and Air Pollutants: Synthesis, Characterization, and Applications.

Given the industrial revolutions and resource scarcity, the development of green technologies which aims to conserve resources and reduce the negative impacts of technology on the environment has become a critical issue of concern. One example is heterogeneous photocatalytic degradation. Titanium dioxide (TiO2) has been intensively researched given its low toxicity and photocatalytic effects under ultraviolet (UV) light irradiation. The advantages conferred by the physical and electrochemical properties of graphene family nanomaterials (GFN) have contributed to the combination of GFN and TiO2 as well as the current variety of GFN-TiO2 catalysts that have exhibited improved characteristics such as greater electron transfer and narrower bandgaps for more potential applications, including those under visible light irradiation. In this review, points of view on the intrinsic properties of TiO2, GFNs (pristine graphene, graphene oxide (GO), reduced GO, and graphene quantum dots (GQDs)), and GFN-TiO2 are presented. This review also explains practical synthesis techniques along with perspective characteristics of these TiO2- and/or graphene-based materials. The enhancement of the photocatalytic activity by using GFN-TiO2 and its improved photocatalytic reactions for the treatment of organic, inorganic, and biological pollutants in water and air phases are reported. It is expected that this review can provide insights into the key to optimizing the photocatalytic activity of GFN-TiO2 and possible directions for future development in these fields.

The competitive effect of different chlorination disinfection methods and additional inorganic nitrogen on nitrosamine formation from aromatic and heterocyclic amine-containing pharmaceuticals.

Amine-containing pharmaceuticals formed nitrosamines that are nitrogenous disinfection byproducts of public concerns due to their carcinogenicity. The objective of this study was to investigate the co-effect of additional inorganic nitrogen in different forms (ammonium, nitrite, and nitrate) and different disinfection approaches (chlorination, monochloramination, dichloramination, and two-step chlorination) on eight nitrosamine formation from four widely used pharmaceuticals. N-nitrosodimethylamine (NDMA) was the main species formed. The presence of N-nitrosomethylethylamine (NMEA), nitrosomorpholine (NMor), and N-nitrosopiperidine (NPip) was found in certain experiments. For one-step chlorination, the influential factors, in decreasing order of importance, were the molecular structural characteristics of the pharmaceutical, oxidation method, and presence and form of additional nitrogen. In four pharmaceuticals with comparative structures, the availability of amine intermediates during degradation was the key to higher nitrosamine yields. Monochloramine significantly enhanced nitrosamine formation from four pharmaceuticals. NDMA formation by adding hypochlorous acid and ammonium separately were lower than those during monochloramination. During two-step chlorination, NDMA formation was enhanced at certain pre-chlorine doses (e.g., a Cl/N molar ratio of 20 or 4). The pre-chlorine dose changed the Cl/N ratio. As the ratio was increased, the combined chlorine residual was formed and decreased. When the ratio was high, breakpoint chlorination possibly occurred enhancing NDMA formation. While NDMA formation was successfully inhibited by two-step chlorination, ammonium brought the NDMA yields of these pharmaceuticals back to the range observed in chloramination, suggesting the importance of ammonium control for limiting NDMA formation from pharmaceuticals during two-step chlorination.

Strain driven phase transition and mechanism for Fe/Ir(111) films.

By way of introducing heterogeneous interfaces, the stabilization of crystallographic phases is critical to a viable strategy for developing materials with novel characteristics, such as occurrence of new structure phase, anomalous enhancement in magnetic moment, enhancement of efficiency as nanoportals. Because of the different lattice structures at the interface, heterogeneous interfaces serve as a platform for controlling pseudomorphic growth, nanostructure evolution and formation of strained clusters. However, our knowledge related to the strain accumulation phenomenon in ultrathin Fe layers on face-centered cubic (fcc) substrates remains limited. For Fe deposited on Ir(111), here we found the existence of strain accumulation at the interface and demonstrate a strain driven phase transition in which fcc-Fe is transformed to a bcc phase. By substituting the bulk modulus and the shear modulus and the experimental results of lattice parameters in cubic geometry, we obtain the strain energy density for different Fe thicknesses. A limited distortion mechanism is proposed for correlating the increasing interfacial strain energy, the surface energy, and a critical thickness. The calculation shows that the strained layers undergo a phase transition to the bulk structure above the critical thickness. The results are well consistent with experimental measurements. The strain driven phase transition and mechanism presented herein provide a fundamental understanding of strain accumulation at the bcc/fcc interface.

NiCo2O4 arrays with a tailored morphology as hole transport layers of perovskite solar cells.

Inorganic p-type semiconductors have broadly served as hole transport materials (HTLs) in perovskite solar cells (PSCs) in recent years. Among them, NiCo2O4 with its excellent conductivity and hole mobility is the emerging candidate for HTLs and is attracting increasing attention. Here, we employ a simple hydrothermal method to fabricate high-quality mesoporous NiCo2O4 films as HTLs of PSCs. The study finds that the morphology of NiCo2O4 can be regulated from nanosheets (NSs) to nanowires (NWs) as the hydrothermal reaction time increases, and the morphology of NiCo2O4 significantly affects the device performance. Specially, the device with NWs achieves a best efficiency of 11.58%, ascribed to the fact that such a one dimension material could provide a straight path for hole extraction/transport. And benefiting from the mesoporous structures of NiCo2O4 films, all the devices exhibited a very repeatable and desirable long-term stability. Overall, this work develops alternative NiCo2O4 nanostructure-based HTLs and opens up new opportunities in fabricating PSCs.

Temporal and vertical variations of polycyclic aromatic hydrocarbon at low elevations in an industrial city of southern Taiwan.

Considered that human activities mostly occur below building heights, the objective of this study was to investigate the temporal variations of fine particular matter (PM2.5)-associated polycyclic aromatic hydrocarbons (PAHs) and benzo[a]pyrene-equivalent (BaPeq) concentrations at four different elevations (6.1, 12.4, 18.4, and 27.1 m) in Kaohsiung City, the largest industrial city of southern Taiwan. Temperature variation was critical for the PM2.5-associated PAH concentrations, which were dominated by benzo[g,h,i]perylene (0.27 ± 0.04 ng m-3 and 24.43% of the total concentration) and other high molecular weight (HMW) species. The PM2.5-associated BaPeq was dominated by 5-ring PAH (36.09%). The PM2.5-associated PAH and BaPeq concentrations at all elevations were significantly increased in winter. In the night, the correlations between the PM2.5-associated PAH concentrations and atmospheric temperatures became negatively stronger, notably at lower elevations (r = - 0.73 ~ - 0.86), whereas the BaPeq during daytime and nighttime were not changed significantly in most months. The PAHs analysis with different PM sizes demonstrated the importance of smaller particles such as PM2.5. The meteorological variation was more important than elevation to influence the low-elevation PM2.5-associated PAH and BaPeq concentrations in an urban area like Kaohsiung City, as the two concentrations were dominated by the PAHs with HMWs and those 5-ring species, respectively.

Catalytic degradation of chlorpheniramine over GO-Fe3O4 in the presence of H2O2 in water: The synergistic effect of adsorption.

Chlorpheniramine is a pharmaceutical widely used and found in water environments. Besides hormone disruption and adverse environmental effects, chlorpheniramine forms carcinogenic nitrosamines during disinfection. We have demonstrated previously the efficient adsorption of chlorpheniramine from aqueous solution onto graphene oxide-magnetite composite (GO-Fe3O4). The present study focused on the elimination of chlorpheniramine and the formation of nitrosamine byproducts during reaction with H2O2 over GO-Fe3O4 catalyst. The effects of the morphology of GO-Fe3O4 in terms of iron fraction, pH, concentrations of H2O2 and organic matters on chlorpheniramine removal in the GO-Fe3O4-H2O2 system were investigated. Chlorpheniramine was efficiently removed at pH 9 when GO-Fe3O4 had a higher micropore volume and surface area. Kinetics study showed that both oxidation (k = 5.1(±0.2) × 10-3 (mg g-1)-1 min-1) and adsorption reactions (k = 2.7(±0.1) × 10-3 (mg g-1)-1 min-1) fitted well with the second-order kinetics model. The adsorption sites on the GO-Fe3O4 surface could be different from those involved during catalytic oxidation. Chlorpheniramine removal decreased by 44.9% in the 5th cycle without regeneration due to the structural fracture of GO-Fe3O4. A tentative pathway of chlorpheniramine degradation and nitrosamine formation by GO-Fe3O4-H2O2 was proposed. GO-Fe3O4 was an adsorbent and effective catalyst in chlorpheniramine degradation by H2O2 that exhibited limited nitrosamine formation at moderate reaction time.

Novel MoS2 quantum dots as a highly efficient visible-light driven photocatalyst in water remediation.

A direct and efficient hydrothermal system has been established for the synthesis of MoS2 quantum dots (QDs). Novel MoS2 QDs are an excellent potential photocatalysts to enhance photocatalytic response by charge separation under visible light irradiation. The optimum capability of QDs demonstrated the excellent photocatalytic ability for the degradation of organic pollutants. The microstructural, morphological, and optical properties of the MoS2 QDs are defined via X-ray diffraction (XRD), SEM, HRTEM, XPS, and UV-Vis absorption spectroscopy techniques. Under visible light irradiation, MoS2 QDs have great photocatalytic response for the degradation of Rh B that is 20 times higher than those of bulk MoS2 materials. The QDs possess practically the same catalytic response after 5 recycle runs, which is an evident proof of its stability. This course might pave the route toward creating current visible-light caused QD photocatalyst strategies for the highly valuable degradation of organic pollutants or antibiotics.