Oxygen Inhibition Research Articles

Quantifying UV/EB dual cure for successful mitigation of oxygen inhibition and light attenuation

Industrial electron-beam (EB) polymerizations are affected by oxygen inhibition, which is typically mitigated using nitrogen inertization. However, continuous nitrogen flow is expensive, and it is desirable to identify a cheaper method to overcome oxygen inhibition. Hybrid UV/EB processing was investigated as a means to overcome oxygen inhibition typically associated with EB polymerization while addressing the depth of penetration issues typically associated with photopolymerization. The depth of the oxygen inhibition layer was quantified using confocal Raman microscopy, and the effects of hybrid processing on physical properties were investigated using dynamic mechanical analysis. UV/EB hybrid processing was shown to successfully overcome oxygen inhibition while retaining depth of cure in pigmented samples.

Cell-Laden Particulate-Composite Hydrogels with Tunable Mechanical Properties Constructed with Gradient-Interface Hydrogel Particles

Hydrogels have long been studied as cell encapsulants for engineered tissue, yet diffusive limitations, suboptimal mechanical properties, and poor cell distribution limit the use of single-phase hydrogels for complex tissues scaffolds. Here, a composite hydrogel structure is presented to overcome these limitations. It is shown that oxygen inhibition during chain-growth photopolymerization of microgel particles can be used to directly manipulate the interfacial bond strength between two hydrogel interfaces in the particulate-composite hydrogels. Using this principle, a cell-laden particulate-composite hydrogel is fabricated that overcomes the low cell viability of a single-phase hydrogel, while allowing the stiffness to be arbitrarily tuned.

Nitrogenase Inhibition Limited Oxygenation of Earth's Proterozoic Atmosphere.

Cyanobacteria produced the oxygen that began to accumulate on Earth 2.5 billion years ago, at the dawn of the Proterozoic Eon. By 2.4 billion years ago, the Great Oxidation Event (GOE) marked the onset of an atmosphere containing oxygen. The oxygen content of the atmosphere then remained low for almost 2 billion years. Why? Nitrogenase, the sole nitrogen-fixing enzyme on Earth, controls the entry of molecular nitrogen into the biosphere. Nitrogenase is inhibited in air containing more than 2% oxygen: the concentration of oxygen in the Proterozoic atmosphere. We propose that oxygen inhibition of nitrogenase limited Proterozoic global primary production. Oxygen levels increased when upright terrestrial plants isolated nitrogen fixation in soil from photosynthetic oxygen production in shoots and leaves.

Dynamic simulation of N2O emissions from a full-scale partial nitritation reactor

This study deals with the potential and the limitations of dynamic models for describing and predicting nitrous oxide (N2O) emissions associated with biological nitrogen removal from wastewater. The results of a three-week monitoring campaign on a full-scale partial nitritation reactor were reproduced through a state-of-the-art model including different biological N2O formation pathways. The partial nitritation reactor under study was a SHARON reactor treating the effluent from a municipal wastewater treatment plant sludge digester. A qualitative and quantitative comparison between experimental data and simulation results was performed to identify N2O formation pathways as well as for model identification. Heterotrophic denitrifying bacteria and ammonium oxidizing bacteria (AOB) were responsible for N2O formation under anoxic conditions, whereas under aerated conditions the AOB were the most important N2O producers. Relative to previously proposed models, hydroxylamine (NH2OH) had to be included as a state variable in the AOB conversions in order to describe potential N2O formation by AOB under anoxic conditions. An oxygen inhibition term in the corresponding reaction kinetics was required to fairly represent the relative contribution of the different AOB pathways for N2O production. Nevertheless, quantitative prediction of N2O emissions with models remains a challenge, which is discussed.

Rapid Open-Air Digital Light 3D Printing of Thermoplastic Polymer.

3D printing has witnessed a new era in which highly complexed customized products become reality. Realizing its ultimate potential requires simultaneous attainment of both printing speed and product versatility. Among various printing techniques, digital light processing (DLP) stands out in its high speed but is limited to intractable light curable thermosets. Thermoplastic polymers, despite their reprocessibility that allows more options for further manipulation, are restricted to intrinsically slow printing methods such as fused deposition modeling. Extending DLP to thermoplastics is highly desirable, but is challenging due to the need to reach rapid liquid-solid separation during the printing process. Here, a successful attempt at DLP printing of thermoplastic polymers is reported, realized by controlling two competing kinetic processes (polymerization and polymer dissolution) simultaneously occurring during printing. With a selected monomer, 4-acryloylmorpholine (ACMO), printing of thermoplastic 3D scaffolds is demonstrated, which can be further converted into various materials/devices utilizing its unique water-soluble characteristic. The ultralow viscosity of ACMO, along with surface oxygen inhibition, allows rapid liquid flow toward high-speed open-air printing. The process simplicity, enabling mechanism, and material versatility broaden the scope of 3D printing in constructing functional 3D devices including reconfigurable antenna, shape-shifting structures, and microfluidics.

Carnosine Decreases PMA-Induced Oxidative Stress and Inflammation in Murine Macrophages.

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine. This naturally occurring molecule is present at high concentrations in several mammalian excitable tissues such as muscles and brain, while it can be found at low concentrations in a few invertebrates. Carnosine has been shown to be involved in different cellular defense mechanisms including the inhibition of protein cross-linking, reactive oxygen and nitrogen species detoxification as well as the counteraction of inflammation. As a part of the immune response, macrophages are the primary cell type that is activated. These cells play a crucial role in many diseases associated with oxidative stress and inflammation, including atherosclerosis, diabetes, and neurodegenerative diseases. In the present study, carnosine was first tested for its ability to counteract oxidative stress. In our experimental model, represented by RAW 264.7 macrophages challenged with phorbol 12-myristate 13-acetate (PMA) and superoxide dismutase (SOD) inhibitors, carnosine was able to decrease the intracellular concentration of superoxide anions (O2−•) as well as the expression of Nox1 and Nox2 enzyme genes. This carnosine antioxidant activity was accompanied by the attenuation of the PMA-induced Akt phosphorylation, the down-regulation of TNF-α and IL-6 mRNAs, and the up-regulation of the expression of the anti-inflammatory mediators IL-4, IL-10, and TGF-β1. Additionally, when carnosine was used at the highest dose (20 mM), there was a generalized amelioration of the macrophage energy state, evaluated through the increase both in the total nucleoside triphosphate concentrations and the sum of the pool of intracellular nicotinic coenzymes. Finally, carnosine was able to decrease the oxidized (NADP+)/reduced (NADPH) ratio of nicotinamide adenine dinucleotide phosphate in a concentration dependent manner, indicating a strong inhibitory effect of this molecule towards the main source of reactive oxygen species in macrophages. Our data suggest a multimodal mechanism of action of carnosine underlying its beneficial effects on macrophage cells under oxidative stress and inflammation conditions.

Epigallocatechin gallate attenuates arsenic induced genotoxicity via regulation of oxidative stress in balb/C mice

Arsenic is well known genotoxicant which causes the excessive generation of reactive oxygen species (ROS) and inhibition of antioxidant enzyme systems leading to cell damage through the activation of oxidative sensitive signaling pathways. Epigallocatechin gallate (EGCG), the main and active polyphenolic catechin present in green tea, has shown potent antioxidant, free radical scavenging and genoprotective activity in vivo. The present study attempted to investigate antioxidant and geno-protective efficacy of EGCG by regulating arsenic induced oxidative stress in mice. Animals received prophylactic and therapeutic treatments at two different doses (25 and 50mg/kg b.wt.) of EGCG orally for 15days and administered arsenic intraperitoneally at dose of 1.5mg/kg b.wt (1/10th of LD50) for 10days. Arsenic intoxication revealed enhanced ROS production (114%) in lymphocytes; elevated levels of LPO (2-4 fold); reduced levels of hepato-renal antioxidants (approx. 45%) and augmented genomic fragmentation in hepato-renal tissues; increased chromosomal anomalies (78%) and micronucleation (21.93%) in bone marrow cells and comet tailing (25%) in lymphocytes of mice. Both pre and post treatments of EGCG decreased ROS production, restored lipid peroxidation (LPO) and reduced hepato-renal antioxidants levels, reduced the DNA fragmentation, number of chromosomal aberrations (CA), micronucleation (MN), and comet tailing but prophylactic treatment of 50mg/kg b.wt was the most effective treatment in regulating arsenic induced oxidative stress. The effectiveness of this dose was furthermore validated by calculating the inhibitory index. Thus, results of present work empirically demonstrate free radical scavenging, anti-oxidative and genoprotective efficacy of EGCG against arsenic toxicity.

Method for Attaining Dimensionally Accurate Conditions for High-Resolution Three-Dimensional Printing Ceramic Composite Structures Using MicroCLIP Process.

Continuous liquid interface production (CLIP) utilizes projection ultraviolet (UV) light and oxygen inhibition to transform the sequential layered three-dimensional (3D) manufacturing into a continuous fabrication flow with tremendous improved fabrication speed and structure integrity. Incorporating ceramic particles to the photo-curable polymers allows for additive manufacturing of ceramic parts featuring sophisticated geometries, mitigating the difficulties associated with traditional manufacturing processes. The presence of ceramic particles within the ink, however, strongly scatters the incident UV light. In the high-resolution CLIP (microCLIP) process, the scattering effect can significantly alter the process characteristics, resulting in broadening of lateral feature dimensions alongside curing depth reduction. Varying exposure conditions to accommodate scattering additionally affects the oxygen deadzone thickness (DZ), which is dependent on power of incident light. This introduces a systematic defocusing error for large deadzone thickness to further complicate process control, such as the unwanted narrowing of part features. In this work, we developed a systematic framework for process optimization by balancing those effects via experimental characterization. We showed that the reported method can provide a set of optimal process parameters (UV power and stage speed) for high-resolution 3D fabrication in accommodating the distinct characteristics of given photo-curable ceramic ink. The method to optimize process parameter was validated experimentally via fabricating a gradient index Luneburg lens comprising densely packed woodpile building-blocks with a strut width of 100 μm and a layer thickness of 60 μm using microCLIP at dimensionally accurate exposure conditions.

Selection of Cyanobacterial (Synechococcus sp. Strain PCC 6301) RubisCO Variants with Improved Functional Properties That Confer Enhanced CO2-Dependent Growth of Rhodobacter capsulatus, a Photosynthetic Bacterium.

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) is a ubiquitous enzyme that catalyzes the conversion of atmospheric CO2 into organic carbon in primary producers. All naturally occurring RubisCOs have low catalytic turnover rates and are inhibited by oxygen. Evolutionary adaptations of the enzyme and its host organisms to changing atmospheric oxygen concentrations provide an impetus to artificially evolve RubisCO variants under unnatural selective conditions. A RubisCO deletion strain of the nonsulfur purple photosynthetic bacterium Rhodobacter capsulatus was previously used as a heterologous host for directed evolution and suppressor selection studies that led to the identification of a conserved hydrophobic region near the active site where amino acid substitutions selectively impacted the enzyme's sensitivity to O2 In this study, structural alignments, mutagenesis, suppressor selection, and growth complementation with R. capsulatus under anoxic or oxygenic conditions were used to analyze the importance of semiconserved residues in this region of Synechococcus RubisCO. RubisCO mutant substitutions were identified that provided superior CO2-dependent growth capabilities relative to the wild-type enzyme. Kinetic analyses of the mutant enzymes indicated that enhanced growth performance was traceable to differential interactions of the enzymes with CO2 and O2 Effective residue substitutions also appeared to be localized to two other conserved hydrophobic regions of the holoenzyme. Structural comparisons and similarities indicated that regions identified in this study may be targeted for improvement in RubisCOs from other sources, including crop plants.IMPORTANCE RubisCO catalysis has a significant impact on mitigating greenhouse gas accumulation and CO2 conversion to food, fuel, and other organic compounds required to sustain life. Because RubisCO-dependent CO2 fixation is severely compromised by oxygen inhibition and other physiological constraints, improving RubisCO's kinetic properties to enhance growth in the presence of atmospheric O2 levels has been a longstanding goal. In this study, RubisCO variants with superior structure-functional properties were selected which resulted in enhanced growth of an autotrophic host organism (R. capsulatus), indicating that RubisCO function was indeed growth limiting. It is evident from these results that genetically engineered RubisCO with kinetically enhanced properties can positively impact growth rates in primary producers.

Accelerated refilling speed in rapid stereolithography based on nano-textured functional release film

Nowadays, along with the demand for new technologies and new materials, a revolution in 3D printing technology is emerging. In recent years, stereolithography 3D printing has been widely used in both academia and industry, due to its fast forming speed, high precision, and low-cost advantages. The continuous liquid interface production technology has made the printing speed even faster. However, the process of resin refilling constrains the printing speed and the printing capabilities of such technologies, since only hollow structures can be fabricated. In this study, a nano-textured hydrophobic PDMS contacting layer and an oxygen-permeable membrane were bonded together as the functional release film. The oxygen inhibition layer was successfully maintained by the molecular oxygen permeated through the composite release film, achieving rapid stereolithography, and key factors that affecting resin refilling are selectively studied by the orthogonal experiment. Crucially, according to the simulation and experimental results, the adoption of the hydrophobic nano-texture not only increased the refilling speed of the resin by two times and reduced the printing time by nearly 25%, but also improved the printing reliability by reducing the vacuum (negative pressure) caused by the original slow refilling speed. Additionally, optical simulations also demonstrated that the nano-texture would not influence the curing effect of the resin. This work proposed a promising strategy for rapid stereolithography of 3D models containing larger cross-sectional areas.

Identification of cytotoxic markers in methamphetamine treated rat C6 astroglia-like cells

Methamphetamine (METH) is a powerfully addictive psychostimulant that has a pronounced effect on the central nervous system (CNS). The present study aimed to assess METH toxicity in differentiated C6 astroglia-like cells through biochemical and toxicity markers with acute (1 h) and chronic (48 h) treatments. In the absence of external stimulants, cellular differentiation of neuronal morphology was achieved through reduced serum (2.5%) in the medium. The cells displayed branched neurite-like processes with extensive intercellular connections. Results indicated that acute METH treatment neither altered the cell morphology nor killed the cells, which echoed with lack of consequence on reactive oxygen species (ROS), nitric oxide (NO) or inhibition of any cell cycle phases except induction of cytoplasmic vacuoles. On the other hand, chronic treatment at 1 mM or above destroyed the neurite-like processors and decreased the cell viability that paralleled with increased levels of ROS, lipid peroxidation and lactate, depletion in glutathione (GSH) level and inhibition at G0/G1 phase of cell cycle, leading to apoptosis. Pre-treatment of cells with N-acetyl cysteine (NAC, 2.5 mM for 1 h) followed by METH co-treatment for 48 h rescued the cells completely from toxicity by decreasing ROS through increased GSH. Our results provide evidence that increased ROS and GSH depletion underlie the cytotoxic effects of METH in the cells. Since loss in neurite connections and intracellular changes can lead to psychiatric illnesses in drug users, the evidence that we show in our study suggests that these are also contributing factors for psychiatric-illnesses in METH addicts.

Independent Control of Singlet Oxygen and Radical Generation via Irradiation of a Two-Color Photosensitive Molecule

Free-radical polymerizations are used for a wide range of applications but are detrimentally impacted by the presence of oxygen. Zinc phthalocyanines have been previously used as singlet oxygen generators to excite radical-consuming ground-state triplet oxygen into its less reactive singlet state prior to photoexcitation of a photoinitiator. We report for the first time that polymerization can be achieved via irradiation of UV band of phthalocyanine and that photosensitization and photoinitiation can be independently achieved via irradiation of its two distinct absorption bands to reduce oxygen inhibition and initiate polymerization without the need for additional treatment. We propose a mechanism for this unique photoinitiation phenomenon and verify its feasibility via computational and experimental approaches. This new class of dual-photosensitive molecules shows promising utility in applications that are adversely impacted by the presence of oxygen, such as coatings and stereolithography.

Tailored polyurethane acrylate blend for large-scale and high-performance micropatterned dry adhesives

Continuous roll-to-roll fabrication is essential for transferring the idea of bio-inspired, fibrillar dry adhesives into large-scale, synthetic, high-performance adhesive tapes. Toward this aim, we investigated process parameters that allow us to control the morphology and the resulting adhesion of mushroom-shaped micropatterned surfaces. Flexible silicone templates enabled the replication process of the polyurethane acrylate pre-polymer involving UV-light-induced cross-linking. For this paper, we particularly tailored the polyurethane acrylate pre-polymer by adding chemical components to tune UV curing kinetics and to reduce oxygen inhibition of radicals. We found that higher intensities of the UV light and faster reaction kinetics improved the quality of the microstructures, i.e., a larger cap diameter of the mushroom tips was achieved. The polymer blend U6E4 exhibited the fastest curing kinetics, which resulted in a micromorphology similar to that of the Ni-shim master structures. Best adhesion results were obtained for adhesive tapes made from U6E4 with 116 kPa pull-off stress, 1.4 N cm−1 peel strength and 71 kPa shear strength. In addition, repeated attachment–detachment tests over 100,000 cycles demonstrated strong robustness and reusability.

Photocuring of di-acrylate in presence of oxygen

A model is presented for photocuring of a hexanediol diacrylate (HDDA) film, where in the presence of oxygen liquid monomer cures into a solid polymer network. The model is based on an earlier version (Iedema et al., 2018) that has been validated in absence of oxygen. The oxygen from ambient air inhibits the polymerization in the top part of the film causing conversion gradients across the film, which is a problem in the manufacture of large scale prints. In the current work results of the curing of thin HDDA films (10 μm) exposed to ambient air with initiator Irgacure 819, bis(acylphosphine oxide) under irradiation intensity varying in a range of 1000–6000 W·m−2 are presented. The average conversion of vinyl groups in bulk of the films was registered by real-time Fourier Transformed Infrared (FTIR) in transmission mode, while simultaneously the conversion in the non-exposed bottom part was measured by real-time FTIR with attenuated transmission reflectance (ATR). The bulk data were used to estimate the kinetic and transport parameters of the model, which enables it to correctly describe the bulk and bottom cure as measured by FTIR. The model accounts for local swelling and shrinking of the created polymer due to the conversion gradient. By Raman spectroscopy the conversion gradient after the photocuring process was also directly measured, again confirming the considerable conversion difference between top and bottom of the film predicted by the model as caused by oxygen inhibition. Initially dissolved small amounts oxygen throughout the whole film turns out to be a negligable role.

Universal Adhesives: Setting Characteristics and Reactivity with Dentin

The aim of the study was to evaluate the performance of six commercially available universal dental adhesives: Adhese Universal (ADU), All-Bond Universal (ABU), Clearfil Universal Bond Quick (CBQ), G-Premio Bond (GPB), Prelude One (PRO) and Scotchbond Universal (SBU). The properties tested were: (a) degree of C=C conversion (DC%); (b) Vickers micro-hardness (VHN); (c) extent of oxygen inhibition (OI/μm), all related with the adhesive film properties; (d) extent of dentin demineralisation (DM%), insoluble salt formation (AS%); and (e) shear bond strength (SBS, self-etch mode) related to the adhesive-dentin interactions. Statistical analysis (α = 0.05) was performed by one-way ANOVA and Tukey’s test (DC%, VHN, OI, DM% AS%) and Weibull analysis (SBS, σ0-β). The DC ranged from 67.2–82.5% (all >GPB), OI from 5.6–18.6 μm (SBU > ADU, GPB, ABU > CBQ > PRO), microhardness from 1.1–6.6 VHN (SBU > ADU > ABU > CBQ > PRO > GPB: not measurable), DM from 69.3% (GPB) to 16–12.5% (CBQ, SBU, ADU) and 13.2–10.6% (ABU, ADU, PRO), in homogeneous groups and AS from 26–15.9% (ABU, CBQ > GPB, PRO, ADU, SBU). For SBS the σ0 (characteristic life) ranged from 29.3–16.6 MPa (CBQ, ADU, ABU, SBU > PRO > GPB), the β (reliability) from 5.1–9.7 (p > 0.05). All failure modes were of mixed type (adhesive and composite cohesive). Although all these adhesives were based on the 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) adhesive monomer, the different co-monomers, solvents and catalysts led to variations in their film properties, reactivity and bonding capacity with dentin.

Alantolactone induces apoptosis through ROS-mediated AKT pathway and inhibition of PINK1-mediated mitophagy in human HepG2 cells

Alantolactone (Ala), a major sesquiterpene lactone extracted from Inula helenium, exerts potent anti-tumour activities in various cancers. However, the underlying mechanism of such activities is still ambiguous. This study focused on evaluating the anti-tumour effects and molecular mechanisms of Ala on HepG2 cells. Our results demonstrated that Ala might inhibit cellular proliferation, induce G2/M phase arrest and apoptosis in HepG2 cells. Specifically, this study confirmed that Ala induced G2/M phase arrest by upregulating p21, downregulating cyclin A1 and cyclin B1, and promoting cellular apoptosis by increasing the expression of cleaved caspase-3 and PARP. Furthermore, Ala caused an increase in reactive oxygen species (ROS) level and inhibition of ROS production significantly prevented Ala-induced apoptosis. Interestingly, the accumulation of ROS, in turn, suppressed the downstream AKT signalling. Finally, mitophagy of Ala-treated HepG2 cells was observed by Mito/Lyso staining. Mitophagy was significantly inhibited by downregulation of the expression of PINK1 and Parkin proteins. The inhibition of mitophagy by a mitophagy inhibitor was found to markedly enhance Ala-mediated apoptosis and growth inhibition in HepG2 cells. Consequently, Ala induced cellular apoptosis via ROS-mediated suppression of AKT signalling and inhibition of PINK1-mediated mitophagy. Thus, Ala has potential to be used for the treatment of liver cancer.

Antioxidant activities of Se-MPS: A selenopeptide identified from selenized brown rice protein hydrolysates

Se-enriched brown rice (Se-BR) protein hydrolysates are a good source of antioxidant peptides. SeMet-Pro-Ser (Se-MPS) is one the antioxidative selenopeptides identified to date. In this study, the antioxidant activity and the related antioxidative mechanisms of Se-MPS and Met-Pro-Ser (MPS) were evaluated by measuring free radical and reactive oxygen species (ROS) scavenging activities, chromium reduction, myoglobin protection and inhibition ability of lipid peroxidation. Se-MPS showed higher oxygen radical absorbance capacity (ORAC) values, ABTS•+ scavenging activity, and chromium VI-reducing activity than MPS. Se-MPS and MPS exerted similar influence on hydroxyl radical scavenging activity. In biological components of myoglobin, Se-MPS effectively inhibited the myoglobin structure modified by its oxidizing reaction with hypochlorite ion, peroxyl radical and hydroxyl radical. Se-MPS also exhibited strong inhibition activity of linoleic acid emulsion peroxidation. Overall, selenium (Se) showed synergistic effects on the antioxidant activity of peptides.

Depth profile of thin coating through surface and interfacial cutting analysis of UV curing system

There are various thin coating technologies, among which the UV coating technology is attracting attention in next-generation industries. In order to utilize the UV coating system stably, it is necessary to analyze and address the problems of surface oxygen inhibition and UV penetration, which lead to irregular curing characteristics. For this, three different UV-curing resins were selected. The effects of the structural difference of the material and change in the initiator content along the thickness direction during UV curing were evaluated by the sliding cutting technique (which involves cutting the coated surface at a superfine angle). Thus, it was confirmed that the effect of surface oxygen inhibition during UV curing is very large on the surface. Here, surface curing could be induced by increasing the functional group concentration and introducing a hybrid curing system. With increasing initiator content, the formation of a material with a high curing density on the surface and an irregular hardening structure in the deep part was confirmed. Therefore, the sliding cutting technique is a very effective approach to control the thickness profile of a UV coating system.

Preparation of Cu nanoparticle‐doped ZIF‐8/RGO composites for effective photodegradation of organic pollutant

Cu nanoparticle‐connected ZIF‐8/reduced graphite oxide (RGO) composite was successfully prepared through a facile hydrothermal reaction using sulfate in this paper. The crossover mechanism of metal nanoparticles loading and RGO decoration to enhance the photocatalytic efficiency of pristine ZIF‐8 was studied. The results showed that the prepared Cu‐S@ZIF‐8/RGO has a strong ability to take advantage of sunlight, indicating an appreciable application prospect. RGO can act as a base to support the whole structure and serve as an electron sink to accept photoexcited electrons, realizing the formation of reactive oxygen species (ROS) and inhibition of electron–hole pair recombination. Cu nanoparticles act as connectors between ZIF‐8 and RGO to transfer electrons and realize the formation of partial ROS on its surface. The doped sulfate radical can promote to extend the utilization of the wavelength range by generating surface states. Cu‐S@ZIF‐8/RGO showed the best photocatalytic activity in simulated sunlight for eliminating rhodamine B and 4‐chlorophenol among all the prepared samples, the structure kept intact even in the presence of different kinds of anions. The crossover study of metal loading and RGO decoration can develop a new way for only UV‐responsive metal–organic frameworks to remove organic contaminants under sunlight irradiation.

Raman spectroscopy as a tool to evaluate oxygen effects on the response of polymer gel dosimetry

Currently, advanced dosimeters like polymer gels are capable of obtaining reliable and accurate 3D dose distributions from correlations with the different polymerization degrees induced by incident radiation. Samples of polymer gel dosimeters are commonly read out using magnetic resonance imaging or optical methods like visible light transmission or laser computed tomography. Alternatively, this work proposes and evaluates the implementation of Raman spectroscopy to provide direct information on the effect of oxygen permeating through the walls of phantoms on the polymerization initiated by irradiation in three types of polymer gel dosimeters, namely NIPAM, ITABIS and PAGAT. The aim of the present study is to provide better and complete interpretations using three different containers, adequate for integral, 2D and 3D dose mapping. Moreover, Raman spectroscopy has been used to analyze the well-known effect of oxygen inhibition on the different polymer gel dosimeters remarking the importance of avoiding air exposition during sample storage and readout. Dose-response curves for different polymer gels were obtained in terms of measurements with a calibrated ionization chamber. Additionally, dedicated Monte Carlo simulations were performed aimed at characterizing dose for different X-ray irradiation setups, providing also suitable information to evaluate oxygen diffusion through the sample wall. The obtained results were contrasted with optical transmission readout as well as Monte Carlo simulations attaining very good agreements for all dosimeter types.