Photochemical Production Research Articles

The Kinetics of Electron Transfer from CdS Nanorods to the MoFe Protein of Nitrogenase

Combining the remarkable catalytic properties of redox enzymes with highly tunable light absorbing properties of semiconductor nanocrystals enables the light-driven catalysis of complex, multielectron redox reactions. This Article focuses on systems that combine CdS nanorods (NRs) with the MoFe protein of nitrogenase to drive photochemical N2 reduction. We used transient absorption spectroscopy (TAS) to examine the kinetics of electron transfer (ET) from CdS NRs to the MoFe protein. For CdS NRs with dimensions similar to those previously used for photochemical N2 reduction, the rate constant for ET from CdS NRs competes with other electron relaxation processes, such that when a MoFe protein is bound to a NR, about one-half of the photoexcited electrons are delivered to the enzyme. The NR–MoFe protein binding is incomplete with more than one-half of the NRs in solution not having a MoFe protein bound to accept electrons. The quantum efficiency of ET (QEET) in these ensemble samples is similar to previously reported efficiencies of product (NH3 and H2) formation, suggesting that the enzyme utilizes the delivered electrons without major loss pathways. Our analysis suggests that QEET, and therefore the photochemical product formation, is limited at the ensemble level by the NR–MoFe protein binding and at the single-complex level by the competitiveness of ET. We characterized ET kinetics for several CdS NRs samples with varying dimensions and found that for CdS NRs with an average diameter of 4.2 nm the ET efficiency dropped to undetectable levels, defining a maximum NR diameter that should be used to photochemically drive the MoFe protein. The work described here provides insights into the design of systems with increased control of photochemical N2 reduction catalyzed by the MoFe protein of nitrogenase.

Metallophthalocyanines for PDT Applications: A DFT Study

Phthalocyanines (Pcs) are an important group of substances with interesting chemical and physical properties with many different application areas. The use of Pc compounds in photodynamic therapy (PDT), especially in the treatment of cancer, has gained great importance in recent years. In this study, the spectral and electronic properties of new PDT active anticancer non-peripheral tetrakis [2-mercaptoquinoline]phthalocyanine and metal complexes were examined by using Density Functional Theory (DFT). Their properties were computed in DMSO and water phases. The UV absorption spectrum study results show that the main transition responsible for the Q band of the molecular spectrum is from [Formula: see text] to [Formula: see text]. The presence of the heavier atom in the Pc cavity has the effect of enhancing the fluorescence quantum yield. In addition, photochemical singlet oxygen production of newly synthesized phthalocyanine and metal complexes was also investigated. The calculated spectral (UV, IR, NMR) and singlet oxygen yield results were compared with the experimental ones and they were in good agreement.

Photochemical production of hydrogen peroxide by digging pro-superoxide radical carbon vacancies in porous carbon nitride

Artificial photosynthesis of H 2 O 2 , an environmentally friendly oxidant and a clean fuel, holds great promise. However, improving its efficiency and stability for industrial implementation remains highly challenging. Here, we report the visible-light H 2 O 2 artificial photosynthesis by digging pro-superoxide radical carbon vacancies in three-dimensional hierarchical porous g-C 3 N 4 through a simple hydrolysis-freeze-drying-thermal treatment. A significant electronic structure change is revealed upon the implantation of carbon vacancies, broadening visible-light absorption and facilitating the photogenerated charge separation. The strong electron affinity of the carbon vacancies promotes superoxide radical ( ⋅ O 2 − ) formation, significantly boosting the H 2 O 2 photocatalytic production. The developed photocatalyst shows an H 2 O 2 evolution rate of 6287.5 μM g −1 h −1 under visible-light irradiation with a long cycling stability being the best-performing photocatalyst among all reported g-C 3 N 4 -based systems. Our work provides fundamental insight into highly active and stable photocatalysts with great potential for safe industrial H 2 O 2 production. • Innovative hydrolysis-freeze-drying-thermal treatment (HFDT) method • 3D hierarchical porous carbon nitride (g-C 3 N 4 ) with carbon vacancies • H 2 O 2 evolution rate of 6287.5 μM g −1 h −1 with an outstanding long cycling stability • Modulating electronic structure and promoting H 2 O 2 evolution through carbon vacancies Ding et al. report an innovative hydrolysis-freeze-drying-thermal treatment method for fabricating a 3D hierarchical porous carbon nitride with carbon vacancies. Owing to the synergistic effects between the carbon vacancies and the unique 3D hierarchical porous structure, the highly efficient photocatalytic H 2 O 2 production is achieved.

Impacts of missing OH reactivity and aerosol uptake of HO2 radicals on tropospheric O3 production during the AQUAS-Kyoto summer campaign in 2018

Gaining quantitative information about the HOx cycle involved in ozone (O3) production is important for reduction of tropospheric O3. In this study, we evaluated the impacts of both the missing OH reactivity and the heterogeneous loss of HO2 due to ambient aerosol uptake on the photochemical O3 production potential and regime analysis during the Air QUAlity Study (AQUAS)-Kyoto summer campaign in 2018. We examined the missing OH reactivity, which was 50% of the averaged total OH reactivity (9.8 ± 3.8 (1σ) s−1), and the uptake loss rate of HO2 on ambient aerosols of 0.0017 ± 0.0015 s−1. The real-time uptake loss rate of HO2 was measured by employing a versatile aerosol concentration enrichment system (VACES). The O3 production potential increased by a factor of two when the missing OH reactivity was considered and decreased by ∼20% when the HO2 loss due to aerosol uptake was considered. In addition, the missing OH reactivity and the HO2 loss due to aerosol uptake decreased the relative sensitivity of the O3 production rate to volatile organic compounds (VOCs) and increased that to NOx (= NO + NO2). Consequently, the NOx limited regime period, the period in which the relative sensitivity of the O3 production rate to NOx was higher than that to VOCs, was expanded by a few hours. Finally, the effect of aerosol uptake on O3 production was anti-correlated with the NO concentration and peaked around noon when the NO concentration was the minimum. It is concluded that aerosols likely affect tropospheric O3 production in suburban and rural areas, where the concentrations of NOx, particularly NO, are very low ([NO] < 0.3 ppb).

Toward a more complete understanding of the reaction mechanism of methyl vinyl ether with ozone: A matrix isolation study

A study of the thermal and photochemical reactions of ozone with methyl vinyl ether (MVE) is described, using both twin jet and merged jet deposition under a variety of conditions. In addition, irradiation experiments were carried out with either a red LED (625 nm) or a Hg pen lamp (254 nm). Products were observed by infrared spectroscopy and identification was aided by 18O and scrambled 16,18O experiments. The experimental work was supported by extensive DFT calculations. Initial thermal products included the primary ozonide (POZ), one of the two possible Criegee intermediates (CI) and H2CO, marking the first observation of the POZ and CI in this system. At longer times using merged jet deposition, observed products include methyl formate, methyl acetate, formic acid and methanol, consistent with an earlier static gas phase study on this system. Photochemical products arose from the addition of a single oxygen atom to MVE, leading to formation of methoxyacetaldehyde and methoxyoxirane, along with minor products.

Effects of g-C3N4 Heterogenization into Intrinsically Microporous Polymers on the Photocatalytic Generation of Hydrogen Peroxide.

Graphitic carbon nitride (g-C3N4) is known to photogenerate hydrogen peroxide in the presence of hole quenchers in aqueous environments. Here, the g-C3N4 photocatalyst is embedded into a host polymer of intrinsic microporosity (PIM-1) to provide recoverable heterogenized photocatalysts without loss of activity. Different types of g-C3N4 (including Pt@g-C3N4, Pd@g-C3N4, and Au@g-C3N4) and different quenchers are investigated. Exploratory experiments yield data that suggest binding of the quencher either (i) directly by adsorption onto the g-C3N4 (as shown for α-glucose) or (ii) indirectly by absorption into the microporous polymer host environment (as shown for Triton X-100) enhances the overall photochemical H2O2 production process. The amphiphilic molecule Triton X-100 is shown to interact only weakly with g-C3N4 but strongly with PIM-1, resulting in accumulation and enhanced H2O2 production due to the microporous polymer host.

Enhanced secondary organic aerosol formation during dust episodes by photochemical reactions in the winter in Wuhan

To investigate the effect of frequently occurring mineral dust on the formation of secondary organic aerosol (SOA), 106 volatile organic compounds (VOCs), trace gas pollutants and chemical components of PM2.5 were measured continuously in January 2021 in Wuhan, Central China. The observation period was divided into two stages that included a haze period and a following dust period, based on the ratio of PM2.5 and PM10 concentrations. The average ratio of secondary organic carbon (SOC) to elemental carbon (EC) was 1.98 during the dust period, which was higher than that during the haze period (0.69). The contribution of SOA to PM2.5 also increased from 2.75% to 8.64%. The analysis of the relationships between the SOA and relative humidity (RH) and the odd oxygen (e.g., OX = O3 + NO2) levels suggested that photochemical reactions played a more important role in the enhancement of SOA production during the dust period than the aqueous-phase reactions. The heterogeneous photochemical production of OH radicals in the presence of metal oxides during the dust period was believed to be enhanced. Meanwhile, the ratios of trans-2-butene to cis-2-butene and m-/p-xylene to ethylbenzene (X/E) dropped significantly, confirming that stronger photochemical reactions occurred and SOA precursors formed efficiently. These results verified the laboratory findings that metal oxides in mineral dust could catalyse the oxidation of VOCs and induce higher SOA production.

Changes in seasonal cycle of surface ozone over Japan during 1980–2015

High concentrations of surface ozone (O3) have adverse influences on vegetation and human health. To assess tropospheric ozone, it is necessary to understand both their long-term and their seasonal behaviours. Seasonal cycles of surface O3 at remote sites have shifted earlier in the last couple of decades. However, at other monitoring sites, the long-term behaviours of seasonal cycles of surface O3 have not been discussed due to a lack of continuous air quality data records. In Japan, continuous air quality monitoring records with high temporal and spatial coverage are available. We fitted a third-harmonic function to monthly mean O3 data in the records to investigate the changes in the seasonal cycle of surface O3 in Japan over a 36-year period (1980–2015) in terms of the change in the annual maximum O3 date (mO3d). Temporal changes in the mO3d for the entire period at each monitoring station were classified into six clusters by applying the k-means method. The linear trends of the mO3d in four of these six clusters were significant, with magnitudes of −0.15 to +0.65 days year−1; however, the temporal patterns of the mO3d fluctuated by about 10 years in all clusters. Upon dividing the 36 years into three decadal analysis periods (1982–1991, 1992–2001, 2002–2013), the temporal patterns of the mO3d in these three periods varied depending on the region in Japan. In one region, the mO3d continuously shifted to a later point in the year through the three decades. Meanwhile, in the other regions, the mO3d shifted to a later point in the year or were delayed in the first two analysed decades, but then these patterns were reversed in the last decade. The temporal patterns of the mO3d could mostly be explained by the interrelationship between the monthly mean O3 mixing ratios in April and May, or the months surrounding May (e.g. March and June, and April and June). Furthermore, although similar increases in O3 mixing ratio in April were found in the first and last analysis periods, the chemical processes behind such increases were deemed to be different. This implies that photochemical production and weakening NO titration were the main factors contributing to the increases in daytime O3 for the first analysis period and to the night-time O3 mixing ratio for the last analysis period.

Effect of Natural Deep Eutectic Solvents on trans-Resveratrol Photo-Chemical Induced Isomerization and 2,4,6-Trihydroxyphenanthrene Electro-Cyclic Formation.

trans-Resveratrol is a natural bioactive compound with well-recognized health promoting effects. When exposed to UV light, this compound can undergo a photochemically induced trans/cis isomerization and a 6π electrochemical cyclization with the subsequent formation of 2,4,6-trihydroxyphenanthrene (THP). THP is a potentially harmful compound which can exert genotoxic effects. In this work we improved the chromatographic separation and determination of the two resveratrol isomers and of THP by using a non-commercial pentafluorophenyl stationary phase. We assessed the effect of natural deep eutectic solvents (NaDES) as possible photo-protective agents by evaluating cis-resveratrol isomer and THP formation under different UV-light exposure conditions with the aim of enhancing resveratrol photostability and inhibiting THP production. Our results demonstrate a marked photoprotective effect exerted by glycerol-containing NaDES, and in particular by proline/glycerol NaDES, which exerts a strong inhibitory effect on the photochemical isomerization of resveratrol and significantly limits the formation of the toxic derivative THP. Considering the presence of resveratrol in various commercial products, these results are of note in view of the potential genotoxic risk associated with its photochemical degradation products and in view of the need for the development of green, eco-sustainable and biocompatible resveratrol photo-stable formulations.

Inter‐laboratory differences in the apparent quantum yield for the photochemical production of dissolved inorganic carbon in inland waters and implications for photochemical rate modeling

AbstractSolar radiation initiates photochemical oxidation of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) in inland waters, contributing to their carbon dioxide emissions to the atmosphere. Models can determine photochemical DIC production over large spatiotemporal scales and assess its role in aquatic C cycling. The apparent quantum yield (AQY) spectrum for photochemical DIC production, defined as mol DIC produced per mol chromophoric dissolved organic matter‐absorbed photons, is a critical model parameter. In previous studies, the principle for the determination of AQY spectra is the same but methodological specifics differ, and the extent to which these differences influence AQY spectra and simulated aquatic DIC photoproduction is unclear. Here, four laboratories determined AQY spectra from water samples of eight inland waters that are situated in Alaska, Finland, and Sweden and span a nearly 10‐fold range in DOM absorption coefficients. All AQY values fell within the range previously reported for inland waters. The inter‐laboratory coefficient of variation (CV) for wavelength‐integrated AQY spectra (300–450 nm) averaged 38% ± 3% SE, and the inter‐water CV averaged 63% ± 1%. The inter‐laboratory CV for simulated photochemical DIC production (conducted for the five Swedish lakes) averaged 49% ± 12%, and the inter‐water CV averaged 77% ± 10%. This uncertainty is not surprising given the complexities and methodological choices involved in determining DIC AQY spectra and needs to be considered when applying photochemical rate modeling. Thus, we also highlight current methodological limitations and suggest future improvements for DIC AQY determination to reduce inter‐laboratory uncertainty.

Local production, downward and regional transport aggravated surface ozone pollution during the historical orange-alert large-scale ozone episode in eastern China

Increasing severe and persistent ozone pollution in China has resulted in serious harm to human health in recent years, yet the precise pollution sources are poorly known because there is few knowledge on large-scale extreme ozone episodes. Here, we studied the formation of the historical orange-alert regional ozone episode in eastern China on 6 June, 2021, by combining process analysis, integrated source apportionment modelling, and chemical and meteorological data. Results show that during the pollution episode, 94% of cities in eastern China suffered ozone pollution, and 39% had daily maximum 8-h average ozone concentrations higher than 100 ppb. This is explained by favorable local ozone formation and transports provided by the prevailing northwestern winds in the upper air, and by sinking atmospheric motions favoring the persistence of high surface ozone concentrations. During daytime, local photochemical production induced an ozone increase of 0.3–28.4 ppb h−1 and vertical transport induced an ozone increase of 0.4–56.1 ppb h−1. As a consequence, vertical downward transport of ozone generated in the upper air by photochemical reactions aggravated surface ozone pollution. Surface ozone concentrations include 25.8–53.9% of ozone from local provincial emissions, 0–42.6% of ozone from inter-regional transports from neighboring regions, 4.6–23.1% of ozone from outer-regional transport, and 13.6–52.9% of ozone from boundary conditions in the selected cities. Overall, our findings show that favorable meteorological conditions promoted the chemical productions of ozone on the surface and at high altitudes, thus resulting in this heavy ozone pollution. In addition, regional and vertical downward transports of aloft ozone further aggravated the surface ozone pollution, leading to the large-scale extreme ozone pollution episode.

Elimination of oxygen interference in the photoelectrochemical sensor with ferricyanide shield oxygen reduction for point of care testing

As a sensitive and promising detection method, photoelectrochemical (PEC) sensor has been widely used in biochemical analysis field. However, the interferences from environment, especially dissolved oxygen, often impact the stability and precision of PEC sensors, which limit its practical applications. Here, we report a dissolved oxygen insensitive PEC sensor based on a proposed indirect electron transfer model. Through the detailed study of the charge transfer process, we determined that the photocurrent mainly comes from the electrochemical reaction between the photochemical products and the electrode, rather than direct charge transfer between the photoelectric materials and the electrode. The newly designed PEC sensor used ferricyanide to shield oxygen reduction and eliminated the influence from variable oxygen solubility. This sensor maintained robust responses over an extremely wide range (1.0–7.5 mg/L) of dissolved oxygen concentrations. To further demonstrate its capability, a smartphone based portable immunosensor was constructed for the detection of human serum albumin (HSA), which exhibited excellent stability and accuracy. The relative error of current was reduced by 81.3% over traditional electron donor solution. This work effectively improves the stability of PEC sensors, and lays the foundation for the subsequently practical applications of PEC sensor in point-of-care testing.

Unexpected fast radical production emerges in cool seasons: implications for ozone pollution control

Ozone is a crucial air pollutant that damages human health and vegetation. As it is related to the photo-oxidation of the nitrogen oxides and volatile organic compounds, the summertime reduction of these precursors is the primary focus of current ozone mitigation strategies. During ozone pollution episodes in eastern China, an observed accumulation of daily total oxidants (O<italic>_x</italic>=NO₂+O₃) in cool seasons (spring and autumn: 60 ppb and winter 40 ppb) is comparable to that in summer (60 ppb), indicating fast photochemical production of secondary pollutants including ozone over the year. Unrecognized fast radical primary productions are found to counteract the increased termination of hydroxyl radical and unfavorable meteorological conditions to maintain the rapid total oxidant formations in cool seasons. Elucidating and regulating the primary radical sources may be critical for the secondary air pollution control in cool seasons.

Grid of pseudo-2D chemistry models for tidally locked exoplanets – II. The role of photochemistry

ABSTRACT Photochemistry is expected to change the chemical composition of the upper atmospheres of irradiated exoplanets through the dissociation of species, such as methane and ammonia, and the association of others, such as hydrogen cyanide. Although primarily the high altitude day side should be affected by photochemistry, it is still unclear how dynamical processes transport photochemical species throughout the atmosphere, and how these chemical disequilibrium effects scale with different parameters. In this work we investigate the influence of photochemistry in a 2D context, by synthesizing a grid of photochemical models across a large range of temperatures. We find that photochemistry can strongly change the atmospheric composition, even up to depths of several bar in cool exoplanets. We further identify a sweet spot for the photochemical production of hydrogen cyanide and acetylene, two important haze precursors, between effective temperatures of 800 and 1400 K. The night sides of most cool planets (Teff &amp;lt; 1800 K) are shown to host photochemistry products, transported from the day side by horizontal advection. Synthetic transmission spectra are only marginally affected by photochemistry, but we suggest that observational studies probing higher altitudes, such as high-resolution spectroscopy, take photochemistry into account.

LED-based solar simulator to study photochemistry over a wide temperature range in the large simulation chamber AIDA

Abstract. A light source has been built at the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) simulation chamber at the Karlsruhe Institute of Technology, simulating solar radiation at ground level. Instead of full spectra light sources, it uses a combination of LEDs with a narrow emission spectrum, resulting in a combined spectrum similar to the solar spectrum between 300 and 530 nm. The use of LEDs leads to an energy-efficient, robust and versatile illumination concept. The light source can be used over a wide temperature range down to −90 ∘C and is adjustable in intensity and spectral width as well as easily adjustable to new technological developments or scientific needs. Characterization of the illumination conditions shows a vertical intensity gradient in the chamber. The integral intensity corresponds to a NO2 photolysis frequency j(NO2) of (1.58±0.21(1σ))×10-3 s−1 for temperatures between 213 and 295 K. At constant temperature, the light intensity is stable within ±1 %. While the emissions of the different LEDs change with temperature, they can be adjusted, and thus it is possible to adapt the spectrum for different temperatures. Although the illumination of the simulation chamber leads to an increase of 0.7 K h−1 of the mean gas temperature, it is possible to perform experiments with aqueous droplets at relative humidities up to ≤95 % and also above water or ice saturation with corresponding clouds. Additionally, temperature- and wavelength-dependent photolysis experiments with 2,3-pentanedione have been conducted. The photolysis of 2,3-pentanedione occurs mainly between 400 and 460 nm, resulting in a mean photolysis frequency of (1.03±0.15)×10-4 s−1 independent of temperature in the range 213–298 K with a quantum yield of 0.36±0.04. In contrast, the yield of the two main photolysis products, acetaldehyde and formaldehyde, decreases with temperature. Furthermore, the light source was applied to study the photochemistry of aerosol particles. For the atmospheric brown carbon proxy compound 3,5-diacetyl-2,4,6-trimethyl-1,4-dihydropyridine, photochemical reaction products were identified. In aerosol particles containing iron oxalate as a photosensitizer, the photosensitized degradation of organic acids (pinic and pinonic acid) was studied. Although the light source only generates about one-third of the maximum solar irradiation at ground level at Karlsruhe (49.007∘ N, 8.404∘ E; 12:00 UTC+2) on a clear summer day with a substantial intensity gradient throughout the simulation chamber, it could be shown that this type of light source allows reproducible experiments over a wide range of simulated atmospheric conditions and with a large flexibility and control of the irradiation spectrum.

Assessment of regional carbon monoxide simulations over Africa and insights into source attribution and regional transport

This study assesses the quality of carbon monoxide (CO) simulations from the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and analyzes different processes controlling CO distribution in Africa. Sixteen CO tracers are implemented in WRF-Chem to track CO from different sources and regions. The model captures the seasonal cycles of surface temperature fairly well (r > 0.75 at most sites) and reproduces key features and variability of precipitation, wind speed, and planetary boundary layer height with errors typically seen in application of a regional model over such a large domain. The model also captures CO concentration hotspots and vertical gradients but underestimates the Measurements of Pollution in the Troposphere (MOPITT) retrieved total column with a larger underestimation in northern hemispheric Africa. The model also underestimates MOPITT and aircraft observed CO profiles throughout the troposphere. We discuss outdated anthropogenic emissions, low biomass burning emissions, and well-known low biases in global models of CO as potential contributors to the discrepancies between the regional model and MOPITT CO. Source contribution analysis of surface CO showed that all sources contribute to CO in Africa with anthropogenic emissions dominating in the urban regions, fire emissions dominating in central Africa, CO inflow from domain boundaries dominating in North Africa and the oceanic regions, and photochemical production dominance aligning with seasonal changes in sunlight. We also show that regional transport of CO emissions between African regions also play a very important role in controlling surface CO distribution in Africa. In some regions, more than 50% of the anthropogenic or biomass burning emitted CO comes from sources located outside those regions, highlighting the need for regional coordination and cooperation for air quality management in Africa.

Surface UV-assisted retrieval of spatially continuous surface ozone with high spatial transferability

With the rapid development of artificial intelligence, machine-learning has been used broadly in surface ozone retrievals. However, the accuracies of current machine-learning-based models tend to rely largely on the spatial and temporal patterns of the site observations of surface ozone instead of the internal physical and chemical mechanisms of ozone, which also limit the transferability of the retrieval models. In this study, the surface ultraviolet (UV) at 380 nm, which is an important component of the rate-determining step of ozone photochemical production, is involved as an indicator in the newly developed surface ozone retrieval algorithm. And the imputation of missing satellite observations of ozone nitrogen dioxide (NO2) column and surface UV is conducted to obtain spatially continuous surface ozone. Different validation schemes and case studies are used to comprehensively evaluate the new algorithm. With the involvement of the surface UV, the new retrieval algorithm shows the high accuracy (R2 = 0.853 and RMSE = 17.09 μg/m3) in spatially continuous surface ozone estimation. More significantly, the new algorithm shows outstanding spatial transferability, which has been a critical challenge for machine-learning models on surface ozone estimation.

Nanoscale Visualization of Photodegradation Dynamics of MAPbI3 Perovskite Films.

Herein, we report the nanoscale visualization of the photochemical degradation dynamics of MAPbI3 (MA = CH3NH3+) using infrared scattering scanning near-field microscopy (IR s-SNOM) combined with a series of complementary analytical techniques such as UV-vis and FTIR-spectroscopy, XRD, and XPS. Light exposure of the MAPbI3 films resulted in a gradual loss of MA+ cations starting from the grain boundaries at the film surface and slowly progressing toward the center of the grains and deeper into the bulk perovskite phase. The binary lead iodide PbI2 was found to be the major perovskite photochemical degradation product under the experimental conditions used. Interestingly, the formation of the PbI2 skin over the perovskite grains resulted in a largely enhanced photoluminescence, which resembles the effects observed for core-shell quantum dots. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved degradation dynamics of perovskite absorbers and revealing the associated material aging pathways.

Bulk and grain-scale minor sulfur isotope data reveal complexities in the dynamics of Earth’s oxygenation

SignificanceThe permanent disappearance of mass-independent sulfur isotope fractionation (S-MIF) from the sedimentary record has become a widely accepted proxy for atmospheric oxygenation. This framework, however, neglects inheritance from oxidative weathering of pre-existing S-MIF-bearing sedimentary sulfide minerals (i.e., crustal memory), which has recently been invoked to explain apparent discrepancies within the sulfur isotope record. Herein, we demonstrate that such a crustal memory effect does not confound the Carletonville S-isotope record; rather, the pronounced Δ33S values identified within the Rooihoogte Formation represent the youngest known unequivocal oxygen-free photochemical products. Previously observed 33S-enrichments within the succeeding Timeball Hill Formation, however, contrasts with our record, revealing kilometer-scale heterogeneities that highlight significant uncertainties in our understanding of the dynamics of Earth's oxygenation.

Near‐infrared chemiluminescent carbon nanogels for oncology imaging and therapy

AbstractCarbon nanogels (CNGs) with dual ability of reactive oxygen species (ROS) imaging and photodynamic therapy have been designed with self‐assembled chemiluminescent carbonized polymer dots (CPDs). With efficient deep‐red/near‐infrared chemiluminescence (CL) emission and distinctive photodynamic capacity, the H2O2‐driven chemiluminescent CNGs are further designed by assembling the polymeric conjugate and CL donors, enabling an in vitro and in vivo ROS bioimaging capability in animal inflammation models and a high‐performance therapy for xenograft tumors. Mechanistically, ROS generated in inflammatory sites or tumor microenvironment can trigger the chemically initiated electron exchange luminescence in the chemical reaction of peroxalate and H2O2, enabling in vivo CL imaging. Meanwhile, part of the excited‐state electrons will transfer to the ambient H2O or dissolved oxygen and in turn lead to the type I and type II photochemical ROS production of hydroxyl radicals or singlet oxygen, endowing the apoptosis of tumor cells and thus enabling cancer therapy. These results open up a new avenue for the design of multifunctional nanomaterials for bioimaging and antienoplastic agents.