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The radical reactions of dimethylsulfoxide (DMSO) and tetrahydrothiophene-1-oxide (THTO) with reactive oxygen species (ROS) in the presence of a nitroxide radical scavenger have been evaluated both synthetically and in analytical practice. Fenton-mediated generation of oxygen-centred radicals produced several unusual products that reflect the fragmentation and ring-opening radical mechanisms of DMSO and THTO respectively. Addition of pollution-derived ROS to DMSO/THTO nitroxide solutions produced LC-MS detectable amounts of the same products isolated from the larger-scaled Fenton reactions. For air pollution analysis, these results highlight the complexity surrounding DMSO reactivity and fragmentation, and indicate that THTO produces simpler outcomes that should facilitate analysis of the processes involved.

The versatility of anthanthrone-based materials in organic electronics is exploited by synthesizing four polymers, PANT, PANT-TBO, PANT-TBT, and PANT-TffBT. PANT represents the self-coupled homopolymer, while the other three are D–A (donor–acceptor) type copolymers. Each of them is successfully applied in three different devices, namely organic field-effect transistors (OFETs), organic photovoltaic cells (OPVs), and chemical sensors. The results indicate that anthanthrone could be a very promising building block for the construction of semiconductors for multi-purpose applications. Specifically, the four polymers exhibit p-type properties in OFETs with hole mobility values in the range of 10−4–10−3 cm2 V−1 s−1. In OPVs, the power conversion efficiencies (PCEs) of non-fullerene cells have a wide range from 0.28% to 5.21%. This indicates that the efficiency may reach a higher value via further structural modification by selecting suitable comonomers to produce new polymers. Additionally, based on the parameters of the OFET sensor devices and the variation in the backbone structures of the four polymers, they show varying response trends for four chemicals: octane, toluene, isopropanol and acetic acid, indicating the important role of the structural composition in generating different chemical sensitivities and fingerprints for sensing. Overall, we clearly disclose the potential of four new anthanthrone-based polymers in various types of electronic devices.

Incorporation of dual acceptors into the copolymer backbone can effectively improve the electron affinity to achieve ambipolarity for use in specific electronic devices, for example, organic field-effect transistors (OFETs) and flash memories. Herein, two diketopyrrolopyrrole (DPP)-based copolymers, pDPPy-BTz and pDPPy-ffBTA, are developed by introducing dialkoxybithiazole and difluorobenzotriazole, respectively. Upon evaluating their electrical properties in OFETs, the polarity of dominant carriers in the OFET channel is found to be tuned by the monomer structures and measurement atmosphere. Specifically, the device based on pDPPy-BTz exhibits a p-type dominant ambipolar character with a μh/μe of 5.3 in air, whereas the electron mobility is enhanced by removing the oxygen and water (vacuum condition), resulting in a charge carrier polarity change to display an n-type dominant feature with the μh/μe decreasing to 0.3. Owing to the electron-donating property of thiophene groups, the pDPPy-ffBTA polymer exhibits a p-type unipolar performance in air and balanced ambipolar (μh/μe = 0.8) charge carrier transport under vacuum. On account of the well-defined ambipolar behavior, the polymers are used in nonvolatile memory devices. High performance is obtained with both polymers with memory windows of 10–16 V, stable data retention of over 105 s, and high reliability during >500 programming and erasing cycles. Overall, this study demonstrates a charge carrier polarity change in OFETs fabricated with DPP-based dual-acceptor copolymers by incorporating various acceptors into the polymer backbone and reports a high-performance nonvolatile ambipolar flash memory.

The concentration, nature, and persistence of particulate matter (PM)-bound reactive oxygen species (ROS) are of significant interest in understanding how atmospheric pollution affects health. However, the inherent difficulties in their measurement, particularly regarding the so-called "short-lived" ROS, have limited our understanding of their persistence and concentrations in the atmosphere. This paper aims to address this limitation through the analysis of PM-bound ROS measurements from the Particle Into Nitroxide Quencher (PINQ) system at an atmospheric monitoring site in the city of Heshan, Guangdong Province, China. The measured daily average and standard deviation for the measurement period was 0.050 ± 0.017 nmol·m-3. The averaged measured concentration of ROS per mass of PM and standard deviation was 0.0012 ± nmol·mg. The dataset was also correlated with standard pollutants, and a simplified model was constructed to separate the contributions of short-lived (t1/2 = 5 min) and long-lived (t1/2 ∼ infinity) ROS to total concentration using ozone, carbon monoxide, and PM mass. This showed that the short-lived ROS contribute an average of 33% of the daily PM-bound ROS burden over the measurement period, up to 52% of daily average on elevated days, and up to 71% for hourly averages. These results highlight the need for accurate measurements of short-lived ROS and provide the starting point for a general model to predict PM-bound ROS concentrations using widely available standard pollutants for future epidemiological research.

Surface-plasmon-mediated phenylacetylide intermediate transfer from the Cu to the Pd surface affords a novel mechanism for transmetalation, enabling wavelength-tunable cross-coupling and homo-coupling reaction pathway control. C-C bond forming Sonogashira coupling and Glaser coupling reactions in O

Diketopyrrolopyrrole (DPP) has been one of the most promising building blocks for constructing organic semiconducting materials used in organic field-effect transistors (OFET). As we have known, extended π-conjugated structure can facilitate intermolecular orbital coupling which determines the magnitude of the charge transfer integral and thus the charge transport in devices. What is more, better intramolecular charge transport and intermolecular charge hopping depend on more superior morphology of the conjugated materials in thin film that is influenced by flexible substitutions. Based on the above principles, it is worthy designing and synthesizing fused ring flanked DPP monomers with alkyl chains to exploit their potential use in OFET. In this work, we first synthesized and characterized a new DPP derivative, naphthalene flanked DPP with butyl-octyl side chain (BO-DPPN). When comparing with its thiophene- and furan-flanked DPP analogues using the same common alkyl chain, BO-DPPN appears as most suitable for OFET applications. For example, DSC analysis demonstrates its high degree of crystallinity, UV–Vis spectra show a strong aggregation in solid state, XRD pattern indicates its tight and long-range ordered lamellar packing. As expected, the OFET devices function well when using BO-DPPN directly as active semiconductor and an impressive hole mobility of 0.0126 cm2 V−1 s−1 was observed with a bottom-contact/top-gate architecture using a solution processable approach indicating its promising potential for use in organic electronics.

The chemical composition and evolution of secondary organic aerosol (SOA) in the atmosphere represents one of the largest uncertainties in our current understanding of air quality. Despite vast research, the toxicological mechanisms relating to adverse human health effects upon exposure to particulate matter are still poorly understood. Particle-bound reactive oxygen species (ROS) may substantially contribute to observed health effects by influencing aerosol oxidative potential (OP). The role of radicals in both the formation and aging of aerosol, as well as their contribution to aerosol OP, remains highly uncertain. The profluorescent spin trap BPEAnit (9,10-bis(phenylethynyl)anthracenenitroxide), previously utilized to study combustion-generated aerosol, has been applied to provide the first estimate of particle-bound radical concentrations in SOA. We demonstrate that SOA from different atmospherically important VOC precursors have different particle-bound radical concentrations, estimated for the ozonolysis of α-pinene (0.020 ± 0.0050 nmol/μg), limonene (0.0059 ± 0.0010 nmol/μg), and β-caryophyllene (0.0025 ± 0.00080 nmol/μg), highlighting the potential importance of OH-initiated formation of particle-bound organic radicals. Additionally, the lifetime of particle-bound radical species in α-pinene SOA was estimated, and a pseudo-first-order rate constant of k = 7.3 ± 1.7 × 10–3 s–1 was derived, implying a radical lifetime on the order of minutes.

Blue-color-emitting organic semiconductors are of significance for organic light-emitting diodes (OLEDs). In this study, through Suzuki coupling polymerization, three 1,4-naphthalene-based copolymers—namely, PNP(1,4)-PT, PNP(1,4)-TF, and PNP(1,4)-ANT—were designed and synthesized. The variation of comonomers, phenothiazine (PT), triphenylamine substituted fluorene (TF), and anthanthrene (ANT), effectively tuned the emitting color and device performance of poly(9-vinyl carbazole) (PVK)-based OLEDs. Especially, the polymer PNP(1,4)-TF, bearing perpendicular aryl side groups, showed a most twisted structural geometry, which enabled an ultra-high thermal stability and a best performance with blue emitting in PVK-host-based OLEDs. Overall, in this work, we demonstrate a promising blue-color-emitting polymer through structural geometry manipulation.

Nitroxides are a diverse range of stable free radicals with applications in industrial polarisation processes and imaging contrasting, and over the last 30 years mounting evidence has demonstrated their therapeutic potential in mitigating diseases where oxidative damage is implicated. This is due to their radical oxidative/antioxidant duality and ability to readily cross cell membranes. In biological tissues, nitroxides are balanced between radical and antioxidant states depending on reducing or hypoxic conditions. For example, in cancer biology where conditions are typically hypoxic, the nitroxide radical induces further oxidative stress in metabolically stressed cancer cells and induces cell death, whereas nitroxides are reduced to a non-radical hydroxylamine antioxidant form in healthy cells, thereby conferring cytoprotection from radiotherapy. Nitroxides-derived antioxidant activities have also been described in terms of superoxide dismutase mimetics and inhibitors of hypochlorous acid production from neutrophil-derived myeloperoxidase during inflammatory insults. As such, nitroxides have potential applications in chronic inflammatory disorders by abrogating the production of more powerful oxidants which mediate tissue injury and cell death. Although nitroxides typically have a short half-life, recent developments to sterically stabilised nitroxides have seen biological improvements in their half-life and subsequent efficacies. Further structural variations with altered side-chain properties offer subcellular delivery to improve the bio-activity of nitroxides, thereby offering major new opportunities to exploit both the radical and antioxidant redox activity of nitroxides for therapeutic advantage in a wide range of human disorders.

Rigid, freestanding covalent organic framework (COF-1) membranes have been synthesized from 1,4-benzenediboronic acid (BDBA) precursors using two different approaches: room temperature solvent-vapour annealing (SVA) and solvothermal annealing (SA). Characterization of films using Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and various microscopies shows that the films obtained through the two different routes vary in their retained BDBA proportion, crystal size and macroscale morphology. Gas adsorption measurements give specific surface areas of 579 ± 7 m2 g−1 and 739 ± 11 m2 g−1 respectively, suggesting that the average porosity of these films is competitive with bulk-synthesized COF-1 particles. The films have a stratified structure, with a dense, thin top layer and a thicker, sponge-like base layer. Using nanoindentation, we measured the Young’s modulus at the top surface of the SVA and SA films to be 3.64 ± 1.20 GPa and 3.33 ± 0.12 GPa respectively, with the smaller uncertainty for the SA film attributed to a more uniform morphology. These measurements provide useful experimental data pertaining to COF-1 mechanical properties, furnishing information relevant to the use of these free-standing membranes in applications such as gas filtration or storage.

© 2020 Elsevier Inc. Research has attributed tissue damage post-traumatic brain injury (TBI) to two-pronged effects, increased reactive oxygen species (ROS) and impairment of endogenous antioxidant defence systems, underpinned by manganese superoxide dismutase (MnSOD). Novel antioxidant nitroxides have been shown to mimic MnSOD to ameliorate oxidative stress related disorders. This study aimed to investigate the effects of two nitroxides, CTMIO and DCTEIO, on the neurological outcomes following moderate TBI in rats induced by a weight drop device. The rats were immediately treated with CTMIO and DCTEIO (40 mM in drinking water) post-injury for up to 2 weeks. The brains were histologically examined at 24 h and 6 weeks post injury. DCTEIO reduced the lesion size at both 24h and 6 weeks, with normalised performance in sensory, motor and cognitive tests at 24h post-injury. Astrogliosis was heightened by DCTEIO at 24h and still elevated at 6 weeks in this group. In TBI brains, cellular damage was evident as reflected by changes in markers of mitophagy and autophagy (increased fission marker dynamin-related protein (Drp)-1, and autophagy marker light chain 3 (LC3)A/B and reduced fusion marker optic atrophy (Opa)-1). These were normalised by DCTEIO treatment. CTMIO, on the other hand, seems to be toxic to the injured brains, by increasing injury size at 6 weeks. In conclusion, DCTEIO significantly improved tissue repair and preserved neurological function in rats with TBI possibly via a mitophagy mechanism. This study provides evidence for DCTEIO as a promising new option to alleviate lesion severity after moderate TBI, which is not actively treated.

In this study, we have reported that a new catalyst of Pd nanoparticles supported on nitrogen-doped, highly porous carbon (Pd/NC-BT) could promote quantitative deoxygenation of carbonyl groups in a wide variety of aromatic compounds to give the fully saturated side-chain. The catalyst is unique in that it works under mild conditions at room temperature and standard hydrogen pressures. Examination of the catalytic process indicates that the presence of nitrogen atoms at the support surface and the highly porous catalyst structure are key factors contributing to the excellent catalytic performance. The nitrogen atoms act as Lewis bases sites to promote the heterolytic cleavage of H2 in coordination with the Pd nanoparticles and the porous structure facilitates the mass transfer of the substrates to the catalytic sites. Hence, the catalyst exhibits sufficient power to reduce the alcohol groups of the intermediates to give alkyl groups under mild conditions while other functional groups in the substrate molecules remain unaffected. Furthermore, the Pd/NC-BT catalyst can be recycled without observable decrease in its activity (over at least after six cycles).

The detection of single gas molecules is a highly challenging work because it requires sensors with an ultra-high level of sensitivity. By using density functional theory, here we demonstrate that the adsorption of a paramagnetic unpaired free radical gas (NO) on a monolayer of XS2 (X = Mo, W) can trigger the transition from semiconductor to half metal. More precisely, the single-layer XS2 (X = Mo, W) with NO adsorbed on it would behave like a metal in one spin channel while acting as a semiconductor in the other spin orientation. The half-metallicity is robust and independent of the NO concentration. In contrast, no half-metallic feature can be observed after the adsorption of other free radical gases such as NO2. The unique change in electronic properties after the adsorption of NO on transition-metal sulfides highlights an effective strategy to distinguish NO from other gas species by experimentally measuring spin-resolved transmission. Our results also suggest XS2 (X = Mo, W) nanosheets can act as promising nanoscale NO sensors.

Magnesium Bismuth Oxide (MgBi2O6) has been experimentally synthesized three decades ago, however, an in-depth theoretical understanding of its electronic structure is still lacking. The bandgap of MgBi2O6 is calculated to be 1.10 eV based on Heyd−Scuseria−Ernzerhof (HSE) functional method, which is the same as that of Silicon. Moreover, the bandgap can be widely tuned by the external strain and leading to a semiconductor-to-semimetal transition with a Dirac-like band crossing. Our tight-binding (TB) model can well reproduce the electronic structure of MgBi2O6 in the presence of strain. More interestingly, we also predict that strain can effectively reduce effective electron mass and enhance visible light absorption. The favourable bandgap and substantial tuning of electronic structure in MgBi2O6 will place it as a promising candidate for novel photovoltaic and optoelectronic application.

The interlayer coupling in 2D van der Waals (vdW) heterostructures (HTS) plays the main role in generating new physics. However, the interlayer coupling is often weak, and little information on the strength of interlayer interaction in HTS is available. On the basis of density functional theory, we demonstrate that an effective electron coupling can be created in 2D C3B/C3N vdW HTS. The experimentally synthesized monolayers C3B and C3N are p- and n-type doped large gap semiconductors, respectively. However, the formed vdW HTS exhibits novel Dirac fermion. The strong interlayer electron coupling results in a large interlayer built-in electric field and improved optical properties of the 2D C3B/C3N vdW HTS. Moreover, a simple tight-binding model of C3B/C3N HTS with the nonzero interlayer hopping parameters captures the physical picture of interlayer coupling. Our results demonstrate the importance of interlayer electron coupling in the modulation of materials properties of 2D vdW HTS.

Here, we design and synthesize three new diketopyrrolopyrrole (DPP) derivatives with naphthalene, possessing large-scaled π-delocalized electronic structure, as the flanking groups and both linear (n-decyl and n-dodecyl) and branched (2-hexyldecyl)alkyl chains as substitutions as active layer for high performance organic field-effect transistors (OFETs). The thermal, photophysical properties, energy levels and solid state molecular stacking have been studied in detail. All the materials show excellent thermal stability with a decomposition temperature of 400 °C, high semi-crystallinity feature, suitable HOMO & LUMO energy levels, and varying crystalline domain sizes in thin films. Bottom-contact/top-gate transistor devices are thus fabricated to investigate the mobility. Encouragingly, all compounds function well in OFET devices and show significant potential as p-type semiconducting materials. The monomer with the n-decyl alkyl chain (D-DPPN) shows the highest mobility of 0.019 cm2 V-1 s-1, with the /on//off ratio reaching 106. We for the first time synthesize naphthalene flanked DPP monomers and achieve high mobility in OFET devices when using these monomers without any further functionalization as semiconductors directly. The primary result that high mobility is observed for monomers only opens a new way for further DPP application and provides more possibilities for constructing high performance polymeric and small molecular semiconductors based on this new DPP dye.

To identify the specific activity sites for both the HER and OER in experimental realized single transition-metal atom decorated graphene sheets, we assume the number of metal–C bonds (coordination) determines the adsorption strength of reaction intermediates on the metal atom sites. We find the strength weakens with the metal coordination number. Low-coordinated Ni sites, i.e. single-coordinated Ni on the zigzag edge, exhibit the highest activity toward HER, while high-coordinated Ni atoms, i.e. quadruple-coordinated Ni, demonstrate the best OER performance. This assumption has been further confirmed by a wide range of transition metals, including Mn, Fe, Co, Cu, and Pd. Our findings highlight a new family of efficient bifunctional catalysts for water splitting and offer a new paradigm for the design of single-atom HER/OER catalysts toward hydrogen production.

Plasmonic photocatalysis has attracted significant attention but not been applied to acid-catalysed reactions. Here we report that visible-light irradiation of silver nanoparticles (AgNPs) significantly promotes Lewis acid-catalysis by several immobilised metal ions to dehydrate sugars, producing 5-hydroxymethylfurfural (HMF) in good yields at moderate temperatures. In one example, we achieved a 68 % yield of HMF for the conversion of d -glucose using immobilised Cr3+ ions and AgNPs under visible-light irradiation. The turnover number achieved in the presence of AgNPs is 13.4 times higher than in the absence of AgNPs. We propose a mechanism whereby sugar molecules coordinate to the metal ions, and light absorption by these metal complexes causes electron density distribution shift to the ions, thereby boosting the catalytic activity. Surface plasmon resonance by the AgNPs amplifies incident light to high intensities, considerably promoting catalytic activity. This plasmon-enhanced acid catalysis performance defines a new paradigm and expands photocatalysis applications.

The service lifetime of polymer films is controlled by the chemical reactions leading to chain scission and the mediating environmental factors. For application as agricultural cropping film, controlled accelerated degradation is required. For a photo-sensitive linear low density polyethylene (LLDPE) + 1% nano-titania (as the anatase/rutile mixed phase P25), the environmental factors are not only UV dose and temperature but also soil parameters such as moisture and organic material content. This provides a challenge in predicting the useful lifetime from laboratory accelerated ageing studies. To enhance degradation when the (LLDPE + 1% P25) is buried, UV-C pre-irradiation has been shown to accelerate strength loss but the rate of embrittlement is not sufficient for the application as crop propagation film. Biodegradable poly(butylene adipate-co-terephthalate) or PBAT has a higher rate of degradation when buried outdoors in soil than when buried under laboratory conditions: The elongation at break fell from 900% to 70% in one month in the field while similar changes required 6 months in the laboratory. The small changes in M n ¯ for embrittlement in the field suggests that the loss of mechanical properties was not linked to bulk property changes but rather to surface morphology (cracks and holes) as seen by SEM. This suggests that even in thin films, enzyme-mediated hydrolysis of PBAT is surface controlled. DNA analysis of the soil around the buried films after 35 days ageing outdoors showed fungi play a more dominant role in PBAT biodegradation compared to bacteria. UV degradation of PBAT film is controlled by the photochemistry of the terephthalate moiety in the polymer and the development of fluorescence is a useful indicator of the extent of photo-degradation.

Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is one of the key reactions for producing chemical commodities from biomass and their derivatives. The challenge for this reaction is to develop an efficient catalytic process that can be conducted under mild conditions (room temperature and atmospheric pressure, using oxygen molecules in air as the oxidant) and a recyclable catalyst. Herein we report a photocatalyst of cobalt thioporphyrazine (CoPz) dispersed on g-C3N4 (abbreviated as CoPz/g-C3N4), which exhibits excellent catalytic activity toward the selective oxidation of HMF into FDCA under simulated sunlight using oxygen molecules in air as a benign oxidant. For example, an FDCA yield of 96.1% in an aqueous solution at pH = 9.18 is achieved at ambient temperature and air pressure. At lower pH (4.01), the product generated is 2,5-diformylfuran. Hence, it is possible to control the reaction outcome by control of the pH of the reaction system. g-C3N4 itself is not...

The determination of the safe working life of polymer materials is important for their successful use in engineering, medicine and consumer-goods applications. An understanding of the physical and chemical changes to the structure of widely-used polymers such as the polyolefins, when exposed to aggressive environments, has provided a framework for controlling their ultimate service lifetime by either stabilising the polymer or chemically accelerating the degradation reactions. The recent focus on biodegradable polymers as replacements for more bio-inert materials such as the polyolefins in areas as diverse as packaging and as scaffolds for tissue engineering has highlighted the need for a review of the approaches to being able to predict the lifetime of these materials. In many studies the focus has not been on the embrittlement and fracture of the material (as it would be for a polyolefin) but rather the products of degradation, their toxicity and ultimate fate when in the environment, which may be the human body. These differences are primarily due to time-scale. Different approaches to the problem have arisen in biomedicine, such as the kinetic control of drug delivery by the bio-erosion of polymers, but the similarities in mechanism provide real prospects for the prediction of the safe service lifetime of a biodegradable polymer as a structural material. Common mechanistic themes that emerge include the diffusion-controlled process of water sorption and conditions for surface versus bulk degradation, the role of hydrolysis versus oxidative degradation in controlling the rate of polymer chain scission and strength loss and the specificity of enzyme-mediated reactions.

Selective epoxidation of various alkenes with molecular oxygen (O2) under mild conditions is a longstanding challenge in achieving syntheses of epoxides. Cu-based catalysts have been found to be catalytically active for selective epoxidations. However, the application of copper nanoparticles (CuNPs) for photocatalyzed epoxidations is encumbered by the instability of CuNPs in air. Herein we report that CuNPs supported on titanium nitride (TiN) without additional stabilizers not only are stable in air but also can catalyze selective epoxidation of various alkenes with O2 or even air as a benign oxidant under light irradiation. CuNPs remain in the metallic state due to the significant charge transfer that occurs between CuNPs and TiN. The epoxidation is driven by visible light irradiation at moderate temperatures, achieving good to high yields and excellent selectivity. The photocatalytic process is applicable to the selective epoxidation of various alkenes. In this photocatalytic system, reactant alkenes ch...

Highlights • Gas phase emissions can be potentially as hazardous as the particle phase ones. • Gas phase diesel exhaust has a stronger inflammation effect on human lung cells. • Fuel oxygen content is negatively correlated to the gas phase OP. • Total VOC content is not correlated to the gas phase OP. • Idling produces emissions with the highest OP in the gas phase. Abstract The oxidative potential (OP) of the gas phase is an important and neglected aspect of environmental toxicity. Whilst prolonged exposure to particulate matter (PM) associated reactive oxygen species (ROS) have been shown to lead to negative health effects, the potential for compounds in gas phase to cause similar effects is yet to be understood. In this study we describe: the significance of the gas phase OP generated through vehicle emissions; discuss the origin and evolution of species contributing to measured OP; and report on the impact of gas phase OP on human lung cells. The model aerosol for this study was exhaust emitted from a Euro III Common-rail diesel engine fuelled with different blends of diesel and biodiesel. The gas phase of these emissions was found to be potentially as hazardous as the particle phase. Fuel oxygen content was found to negatively correlate with the gas phase OP, and positively correlate with particle phase OP. This signifies a complex interaction between reactive species present in gas and particle phase. Furthermore, this interaction has an overarching effect on the OP of both particle and gas phase, and therefore the toxicity of combustion emissions.

A range of profluorescent nitroxides (PFNs) were tested as probes to monitor photo-induced radical-mediated damage in polymer materials. The most stable and sensitive probe of the PFNs tested was an alkyne-linked perylenediimide PFN, 6b, with napthalimide and 9,10-bis(phenylethnyl)anthranene-based versions giving lower stability and sensitivity. Results from photo-ageing of poly(1-trimethylsilyl)-1-propyne (PTMSP) and the ethylene norbornene copolymer (TOPAS®) films doped with PFN probes demonstrated that sensors employing these support materials deliver significantly enhanced sensitivity compared to traditional techniques used to monitor photo-oxidative degradation of polymers, such as infrared spectroscopy. This enhanced sensitivity for detecting polymer damage improved methods for the determination of the serviceable application lifetime of polymers.

To estimate the oxidative potential (OP) of particulate matter (PM), two commonly used cell-free, molecular probes were applied: dithiothreitol (DTT) and dichloro-dihydro-fluorescein diacetate (DCFH-DA), and their performance was compared with 9,10-bis (phenylethynyl) anthracene-nitroxide (BPEAnit). To the best of our knowledge, this is the first study in which the performance of the DTT and DCFH has been compared with the BPEAnit probe. The average concentrations of PM, organic carbon (OC) and elemental carbon (EC) for fine (PM2.5) and coarse (PM10) particles were determined. The results were 44.8 ± 13.7, 9.8 ± 5.1 and 9.3 ± 4.8 µg·m−3 for PM2.5 and 75.5 ± 25.1, 16.3 ± 8.7 and 11.8 ± 5.3 µg·m−3 for PM10, respectively, for PM, OC and EC. The water-soluble organic carbon (WSOC) fraction accounted for 42 ± 14% and 28 ± 9% of organic carbon in PM2.5 and PM10, respectively. The average volume normalized OP values for the three assays depended on both the sampling periods and the PM fractions. The OPBPEAnit had its peak at 2 p.m.; in the afternoon, it was three times higher compared to the morning and late afternoon values. The DCFH and BPEAnit results were correlated (r = 0.64), while there was no good agreement between the BPEAnit and the DTT (r = 0.14). The total organic content of PM does not necessarily represent oxidative capacity and it shows varying correlation with the OP. With respect to the two PM fractions studied, the OP was mostly associated with smaller particles.

This manuscript details the application of a profluorescent nitroxide (PFN) for the online quantification of radical concentrations on particulate matter (PM) using an improved Particle Into Nitroxide Quencher (PINQ). A miniature flow-through fluorimeter developed specifically for use with the 9,10-bis(phenylethynyl)anthracene-nitroxide (BPEAnit) probe was integrated into the PINQ, along with automated gas phase corrections through periodic high efficiency particle arrestor (HEPA) filtering. The resulting instrument is capable of unattended sampling and was operated with a minimum time resolution of 2.5 min. Details of the fluorimeter design and examples of data processing are provided, and results from a chamber study of side-stream cigarette smoke and ambient monitoring campaign in Guangzhou, China are presented. Primary cigarette smoke was shown to have both short-lived (t1/2 = 27 min) and long-lived (t1/2 = indefinite) PM-bound reactive oxygen species (ROS) components which had previously only been observed in secondary organic aerosol (SOA).

BODIPY is a highly versatile fluorophore for biological imaging with a tunable fluorescence emission (500 - 800 nm) that overlaps with the optically transparent window for tissue (600 - 1300 nm). Herein, we describe the synthesis of optically distinct BODIPY-based profluorescent probes bearing meso- and β-substituted isoindoline nitroxides and their corresponding methoxyamine derivatives. These profluorescent nitroxide probes possess strongly suppressed fluorescence, which can be revealed upon reduction or reaction with other radicals. Examination of the pentafluorophenylhydrazine reduction of the prepared probes using tandem EPR and fluorescence spectroscopy demonstrated that the asymmetric bis-β-substituted probe 9 (λem = 603 nm) was reduced the fastest, however, the greatest difference in fluorescence emission between the nitroxide and its reduced hydroxylamine analogue was observed for probe 7 (λem = 570 nm). The significant difference in fluorescence output between the nitroxides and their corresponding diamagnetic derivatives makes these probes ideal tools for imaging reactive oxygen species in biological systems.

The zero-band gap nature of graphene prevents it from performing as a semi-conductor in modern electronics. Although various graphene modification strategies have been developed to address this limitation, the very small band gap of these materials and the suppressed charge carrier mobility of the devices developed still significantly hinder graphene's applications. In this work, a two dimensional (2D) WB4 monolayer, which exhibits a double Dirac cone, was conceived and assessed using density functional theory (DFT) methods, which would provide a sizable band gap while maintaining higher charge mobility with a Fermi velocity of 1.099 × 106 m s−1. Strong spin–orbit-coupling can generate an observable band gap of up to 0.27 eV that primarily originates from the d-orbit of the heavy metal atom W; therefore a 2D WB4 nanosheet would be operable at room temperature (T = 300 K) and would be a promising candidate to fabricate nanoelectronics in the upcoming post-silicon era. The phonon-spectrum and ab initio molecular dynamics calculations further demonstrate the dynamic and thermal stability of such nanosheets, thus, suggesting a potentially synthesizable Dirac material.

Two-dimensional (2D) materials are promising for use in lithium (Li) electrodes due to their high surface ratio. By using density functional theory (DFT) calculations, we investigate the adsorption and diffusion of Li on a newly predicted 2D GeP3 material [Nano Lett., 2016, 17, 1833]. The most favourable adsorption sites for Li are identified, and a semiconducting to metallic transition induced by Li adsorption is found, which indicates excellent electrical conductivity. The GeP3 monolayer has an estimated capacity of 648 mA h g−1, which is almost twice that of commercially used graphite (375 mA h g−1). During full Li intercalation, the GeP3 layer undergoes only 1.2% lattice parameter reduction. Moreover, GeP3 possesses the advantages of a small diffusion barrier (∼0.5 eV) and low average open-circuit voltages (∼0.4 V). Our results highlight a new class of promising anode materials, i.e. 2D phosphide, as potential rechargeable lithium batteries with ultrahigh-capacity, superior ionic conductivity, and low average open-circuit voltage.

Profluorescent nitroxides (PFNs) have emerged as an important class of imaging agents for monitoring intracellular redox status and levels of oxidative stress. However, the fast reduction of nitroxides upon incubation within cells limits the window of opportunity for detection. By increasing the concentration of nitroxides per fluorophore, their reduction to the corresponding hydroxylamines and the subsequent switch-on of fluorescence can be delayed. Herein the preparation of nitroxide-containing polymers of different chain length coupled to a fluorophore is reported and their reduction with pentafluorophenylhydrazine is examined. The fluorescence switch-on kinetics and radical concentrations are monitored by fluorescence and electron paramagnetic resonance spectroscopy and compared to a conventional PFN bearing a single nitroxide moiety. The polymeric PFNs display significant delays in reduction and fluorescence switch-on and higher turn-on ratios than their single-nitroxide counterparts. The results of this study indicate that polymeric PFNs are a promising architecture for future imaging agents.

Here we report a class of photocatalysts: mixed-valence vanadium oxide particles grafted onto a variety of oxide supports. In these catalysts V6O13 species with mixed oxidation states (V4+ or V5+) are believed to be catalytically active sites. These catalysts successfully enable alcohol oxidation to selectively produce aldehydes and ketones using O2 as the oxidant. The catalytic process is driven by visible light irradiation at room temperature and, most importantly, progresses with negligible overoxidation. The catalysts can even selectively oxidize aliphatic alcohols, which are much more challenging to control in comparison to aromatic analogues. They can also be applied to the activation and oxidation of the otherwise stable C–H bonds of saturated aromatic hydrocarbons, such as toluene and xylene, under irradiation. Both experimental results and density functional theory (DFT) simulations suggest the formation of V6O13-alkoxide species as the initial step in the catalytic cycle. The V6O13-alkoxide then...

Studying multi-purpose applications of a specific material is a challenging topic in the organic electronics community. In this work, through molecular engineering and smart device structure design strategy, high performance in transistors and thin film display devices is simultaneously achieved by applying a simple new dye molecule, naphthalene flanked diketopyrrolopyrrole (DPPN), as the active layer material. Short alkyl chains (hexyl or octyl side groups for H-DPPN and O-DPPN, respectively) are adapted to improve the hole mobility in organic thin film transistors (OTFTs) and single crystal transistors (SCTs). Specifically, H-DPPN shows a similar hole mobility in either OTFTs or SCTs, while O-DPPN exhibits a dramatically enhanced mobility, reaching 0.125 cm2 V−1 s−1 in SCTs. Additionally, a smart organic light emitting diode (OLED) device is designed by using DPPN molecule as the dopant with a host matrix. The promising external quantum efficiencies of 4.0% and 2.3% are achieved for H-DPPN and O-DPPN fabricated OLEDs. Overall, in this work, it is reported that DPP-based small molecules can simultaneously function well in both transistors and thin film displays with high device performance through molecular and smart device engineering.

To achieve semiconducting materials with high electron mobility in organic field-effect transistors (OFETs), low-lying energy levels (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) and favorable molecular packing and ordering are two crucial factors. Here, it is reported that the incorporation of pyridine and selenophene into the backbone of a diketopyrrolopyrrole (DPP)-based copolymer produces a high-electron-mobility semiconductor, PDPPy-Se. Compared with analogous polymers based on other DPP derivatives and selenophene, PDPPy-Se features a lower LUMO that can decrease the electron transfer barrier for more effective electron injection, and simultaneously a lower HOMO that, however, can increase the hole transfer barrier to suppress the hole injection. Combined with thermal annealing at 240 °C for thin film morphology optimization to achieve large-scale crystallite domains with tight molecular packing for effective charge transport along the conducting channel, OFET devices fabricated with PDPPy-Se exhibit an n-type-dominant performance with an electron mobility (μe) as high as 2.22 cm2 V−1 s−1 and a hole/electron mobility ratio (μh/μe) of 0.26. Overall, this study demonstrates a simple yet effective approach to boost the electron mobility in organic transistors by synergistic use of pyridine and selenophene in the backbone of a DPP-based copolymer.

The utility of profluorescent nitroxides (PFNs) as sensitive probes to detect early stage photodegradation in a cyclic olefin copolymer, TOPAS®, during both natural aging and accelerated aging under laboratory conditions is reported. PFN additives in TOPAS® capture radicals to form fluorescent adducts as the material degrades. The levels of fluorescence detectable from the polymer reflect the degree of free-radical degradation in the material, with the PFN probes delivering enhanced sensitivity over traditional analytical methods for the detection of photodegradation of TOPAS®. The probes are able to highlight polymer degradation occurring within the oxidation “induction” period, where little change can be observed using infrared spectroscopy; however, their efficacy does not extend far beyond this period. The effective probe lifetime however can be significantly extended through the use of common additives such as the UV absorber (Tinuvin P) and a hindered amine stabiliser analogue (1,1,3,3-tetramethylisoindol-2-yloxyl, TMIO).

Triethylene glycol, a common side chain, is attached to two different dye moieties, diketopyrrolopyrrole (DPP) and isoindigo (II), and their bromo derivative monomers are copolymerized, respectively, with common bisstannyl alkylated bithiophene via Stille coupling. The resulting donor–acceptor low-bandgap copolymers, namely, PTDPP-DT and PTII-DT, are rationally deigned and synthesized conjugated polymeric systems suitable for doping. Both polymers are successfully investigated as single-component and composite-system-based electrochemical transistors and light-emitting electrochemical cells. A PTDPP-DT thin film exhibits relatively high electrical conductivity of up to 80 S cm−1 in the electrochemically doped state, whereas PTII-DT thin film prevents the macroscopic charge transport due to a large-scale crystalline disorientation. Upon evaluating both polymers as active conjugated materials in light-emitting electrochemical cells, they both exhibit emission under efficient electron/hole doping conditions.

Presence or generation of reactive oxygen species (ROS) on/by particulate matter (PM) have been implicated in PM-induced health effects. Methodologies to quantify ROS concentrations vary widely both in detection and collection methods. However, there is currently an increasing emphasis on rapid collection and measurement due to observations of short half-live ROS. To address this problem, this manuscript details the design and characterization of a novel instrument named the Particle Into Nitroxide Quencher (PINQ). This instrument combines the BPEAnit ROS assay in conjunction with a purpose-built aerosol collection device, the insoluble aerosol collector (IAC). The IAC continuously collects PM regardless of size or chemistry directly into a liquid sample with a collection efficiency of 0.98 and a low cut-off size of < 20 nm. The sampling time resolution of the PINQ is one minute, with a limit of detection (LOD) of 0.08 nmol m−3 in equivalent BPEAnit-Me concentration per volume of air. This high sample time resolution and sensitivity is achieved due a combination of the highly concentrated IAC liquid sample and the rapid reaction and stability of the BPEAnit probe.

Here we report the first example of an alkoxyamine derived from an azaphenalene nitroxide, which when exposed to UV-light, readily undergoes homolysis to efficiently and cleanly re-form a nitroxide. This process selectively cleaves the C–O bond of the alkoxyamine and occurs orders of magnitude more rapidly than any other alkoxyamine homolysis previously described in the literature. We demonstrate the use of light to generate a persistent radical effect (PRE) and apply this to undertake radical insertion, radical exchange and proof of concept polymerization reactions.

The addition of an N–H bond to C C triple bonds in the hydroamination of alkynes is of great importance in synthetic chemistry. We found that visible light irradiation can efficiently drive the direct hydroamination of alkynes using supported gold nanoparticles (AuNPs) due to its Localized Surface Plasmon Resonance (LSPR). Au NPs on nitrogen-doped TiO2 could successfully induce hydroamination with a very high conversion (90%) and excellent product selectivity (91% imine product). Herein, we demonstrate that for such a photocatalytic process, the intensity and wavelength of the incident light, as well as the reaction temperature have a significant impact on the performance of the catalyst. The photocatalytic activity increases with increasing light intensity and reaction temperature. This means that the AuNP photocatalysts couple both the input light energy and thermal energy to catalyze the reaction. The influence of AuNPs and the surface properties of the support materials on the photocatalytic performance are also further discussed

Nitroxides have been exploited as profluorescent probes for the detection of oxidative stress. In addition, they deliver potent antioxidant action and attenuate reactive oxygen species (ROS) in various models of oxidative stress, with these results ascribed to superoxide dismutase or redox and radical-scavenging actions. Our laboratory has developed a range of novel, biostable, isoindoline nitroxide-based antioxidants, DCTEIO and CTMIO. In this study we compared the efficiency of these novel compounds as antioxidant therapies in reducing ROS both in vivo (rat model) and in vitro (661W photoreceptor cells), with the established antioxidant resveratrol. By assessing changes in fluorescence intensity of a unique redox-responsive probe in the rat retina in vivo, we evaluated the ability of antioxidant therapy to (1) ameliorate ROS production and (2) reverse the accumulation of ROS after complete, acute ischemia followed by reperfusion (I/R). I/R injury induced a marked decrease in fluorescence intensity over 60 min of reperfusion, which was successfully ameliorated with each of the antioxidants. DCTEIO and CTMIO reversed the accumulation of ROS when administered intraocularly post ischemic insult, whereas, the effect of resveratrol was not significant. We also investigated our novel agents' capacity to prevent ROS-mediated metabolic dysfunction in the 661W photoreceptor cell line. Cellular stress induced by the oxidant, tert-butyl hydroperoxide, resulted in a loss of spare mitochondrial respiratory capacity (SMRC) and in the extracellular acidification rate in 661W cells. DCTEIO antioxidant administration successfully reduced the loss of SMRC. Together, these findings show we can quantify dynamic changes in cellular oxidative status in vivo and suggest that nitroxide-based antioxidants may provide greater protection against oxidative stress than the current state-of-the-art antioxidant treatments for ROS-mediated diseases.

Novel profluorescent mono- and bis-isoindoline nitroxides linked to napthalimide and perylene diimide structural cores are described. These nitroxide-fluorophore probes display strongly suppressed fluorescence in comparison to their corresponding non-radical diamagnetic methoxyamine derivatives. The perylene-based probe possessing two isoindoline systems tethered through ethynyl linkages was shown to be the most photostable in solution, demonstrating significantly enhanced longevity over the 9,10-bis(phenylethynyl)anthracene fluorophore used in previous profluorescent nitroxide probes.

The impact of commonly used agrichemicals (Paraquat, Mancozeb, Chlorpyrifos and Sulfur) on the environmental stability of polyethylene films has been evaluated under accelerated photo-oxidative conditions. Paraquat and Mancozeb when applied to unstabilized clear polyethylene film, followed by exposure to UV radiation, resulted in direct attack of the polymer, evident by faster rates of oxidation and shorter times to embrittlement compared to a polyethylene control. Reapplication of these chemicals during exposure, as often occurs in agricultural practice, resulted in even faster degradation. In contrast, Sulfur and Chlorpyrifos did not have a significant effect on the photodegradation of exposed unstabilized polyethylene film. When the polyethylene film was pigmented (white top layer containing rutile titanium dioxide and carbon black in the bottom layer) and stabilized with the addition of hindered amine stabilizers (HAS), differences in oxidation susceptibility were seen with repeated exposure to Paraquat showing the most dramatic effect. This was evident by an increased carbonyl index, decrease in elongation at break and an increase in tensile stress at yield compared to a control film and other agrichemical treatments. These studies enable degradation from accelerated consumption of stabilizers by the agrichemicals (and their degradation products) to be differentiated from enhanced photochemical initiation of the polyethylene degradation.