Creation Of Radicals Research Articles

Molecular and cellular level analysis of the mechanism of nutritional intervention in preventing epidemic virus infection

Molecular nutrition encompasses a wider range of investigations than nutritional genomics, which can be considered a scientific investigation of how different nutrients and dietary components influence the cellular and molecular mechanisms of the body and health. In effect, increasing antioxidant elements in daily diets can assist with combating the inflammatory response caused by cytokines in the human body. Antioxidants can impede the oxidation process and hence avoid the creation of free radicals in the cytoplasm that can damage the cells via chain reactions. Contamination sequences, batch effects, uneven sampling, unreported taxa, technological biases, and heteroscedasticity are all significant issues in molecular microbial biology. Artificial Intelligence (AI) methodologies to uncover hidden patterns, connections, and interactions within metabolomics data, allowing them to provide personalized food recommendations based on individual health profiles. A multi-scale convolutional neural network (MCNN) classifies cellular images into phenotypes in a single coherent step utilizing the image’s pixel intensity values. Hence, the proposed AI-MCNN has been an essential nutrient that assists the immune system in various ways, including acting as an antioxidant to protect healthy cells, promoting immune cell development and function, and creating antibodies. According to epidemiological research, people who are undernourished are more likely to get bacterial, viral, and other diseases. Nutritional epidemiology investigates dietary or nutritional parameters concerning illness prevalence in communities. Nutritional epidemiology results often add to the evidence that provides dietary recommendations for preventing disease and related disorders.

Interfacial oxygen vacancy engineering of double Z-scheme heterojunction Bi2MoO6/MnWO4/g-C3N4 for efficient photocatalytic degradation of iodohydrin

The synthesis of a dual Z-scheme heterojunction, Bi2MoO6/MnWO4/g-C3N4 (BMCM-x), enriched with oxygen voids, has been synthesized by an in-situ generation method. The ideal composite specimen, BMCM-50, managed to break down over 85 % of Iohexol in a span of 40 min. The emergence of oxygen voids serves to inhibit the merging of photogenerated carriers and fosters the creation of reactive radicals. The dual Z-scheme heterojunction is capable of isolating photogenerated carriers and enhancing redox capacity, markedly boosting BMCM-50’s photocatalytic breakdown efficiency.

Application of nano-radiosensitizers in non-small cell lung cancer.

Radiotherapy stands as a cornerstone in the treatment of numerous malignant tumors, including non-small cell lung cancer. However, the critical challenge of amplifying the tumoricidal effectiveness of radiotherapy while minimizing collateral damage to healthy tissues remains an area of significant research interest. Radiosensitizers, by methods such as amplifying DNA damage and fostering the creation of free radicals, play a pivotal role in enhancing the destructive impact of radiotherapy on tumors. Over recent decades, nano-dimensional radiosensitizers have emerged as a notable advancement. Their mechanisms include cell cycle arrest in the G2/M phase, combating tumor hypoxia, and others, thereby enhancing the efficacy of radiotherapy. This review delves into the evolving landscape of nanomaterials used for radiosensitization in non-small cell lung cancer. It provides insights into the current research progress and critically examines the challenges and future prospects within this burgeoning field.

Carbon cloth supported black phosphorus-FeMoO4 composites for peroxymonosulfate-assisted photoelectrocatalytic degradation of tetracycline hydrochloride

This research utilized the solvothermal technique to prepare carbon cloth supported black phosphorus-FeMoO4 (CC-BP-FMO) composites, which were used for the degradation of tetracycline hydrochloride (TC-HCl) through the peroxymonosulfate (PMS)-assisted photoelectrocatalysis (PEC) route. Several characterization techniques were employed to systematically examine the morphology, elemental composition, crystal and molecule structures, magnetism properties, bonding states, energy band structure, separation efficiency of photo-induced carriers, electrochemical behaviors, reactive species, and intermediate products of TC-HCl degradation. The experimental results demonstrated that the performance of PMS-assisted PEC TC-HCl degradation by the CC-BP-FMO composites was significantly improved in comparison with photocatalysis, electrocatalysis, PMS activation, and PEC. The CC-BP-FMO composites with more exposed BP-FMO catalysts exhibited the ability to be reused for PMS-assisted PEC degradation of TC-HCl, with a large k value of 0.21 min−1 and a high degradation rate of 97% after the fourth cycle. The remarkable PMS-assisted PEC property of the CC-BP-FMO composites was mainly attributed to the swift separation of photo-induced charge carriers, which hastened the creation of reactive radicals. Five possible catalytic reaction pathways existed in the CC-BP-FMO composites towards TC-HCl degradation under the PMS-assisted PEC condition. Importantly, the photo-generated electrons and [Formula: see text] radicals were advantageous for the redox reaction of Fe+2/Fe+3 and Mo+4/Mo+6. The oxygen vacancies caused by P and Mo in the BP-FMO heterojunction could suppress the carrier recombination. The degradation of TC-HCl involved the participation of oxygen vacancy, [Formula: see text], [Formula: see text], and ∙OH radicals, and 1O2 nonradicals. The CC-BP-FMO composites have the potential application for treating wastewater containing organic pollutants.

Light-enhanced oxygen degradation of MAPbBr3 single crystal.

Organometal halide perovskites are promising materials for optoelectronic applications, whose commercial realization depends critically on their stability under multiple environmental factors. In this study, a methylammonium lead bromide (MAPbBr3) single crystal was cleaved and exposed to simultaneous oxygen and light illumination under ultrahigh vacuum (UHV). The exposure process was monitored using X-ray photoelectron spectroscopy (XPS) with precise control of the exposure time and oxygen pressure. It was found that the combination of oxygen and light accelerated the degradation of MAPbBr3, which could not be viewed as a simple addition of that by oxygen-only and light-only exposures. The XPS spectra showed significant loss of carbon, bromine, and nitrogen at an oxygen exposure of 1010 Langmuir with light illumination, approximately 17 times of the additive effects of oxygen-only and light-only exposures. It was also found that the photoluminescence (PL) emission was much weakened by oxygen and light co-exposure, while previous reports had shown that PL was substantially enhanced by oxygen-only exposure. Measurements using a scanning electron microscope (SEM) and focused ion beam (FIB) demonstrated that the crystal surface was much roughened by the co-exposure. Density functional theory (DFT) calculations revealed the formation of superoxide and oxygen induced gap state, suggesting the creation of oxygen radicals by light illumination as a possible microscopic driving force for enhanced degradation.

ANTIOXIDANTS SUPPLEMENTATION BASED ON NATURAL PRODUCTS IN THE TREATMENT OF THE THERMAL SKIN INJURY

Thermal injuries are a major medical, economic and social problem, whose severity, morbidity, mortality, prognosis and treatment outcome directly depend on the surface and depth of the burn, but also on the patient's age, health status and accompanying complications. The treatment of thermal injury is long and complex, and the outcome is often uncertain with a very complex rehabilitation process, because the injury damages both physical and psychological health. Constant innovations in the protocol of medical treatment and the search for new mechanisms involved in the pathogenesis of burns can be helpful in successful treatment. Therefore, there is a constant search for adjuvant therapies that will improve results like HBO, AO, platelet- rich plasma, negative pressure wound therapy and others. In recent years, the application of antioxidants as adjuvant therapy for the care and treatment of wounds has been the subject of various researche. Antioxidants are biologically active molecules that prevent the creation of free radicals in the body and at the same time neutralize the existing ones, this way participating in maintaining the oxidative status at the desired level. Antioxidant -rich natural products may provide a solution to improve wound healing. The application of antioxidant therapy has shown numerous benefits in improving the outcome of burns. However, more information is needed from the clinical trials on the use of natural products, especially in combination with other therapies. Keywords: thermal skin injury, hyperbaric oxygen therapy, antioxidant rich natural products

Utility of Perl's Prussian Blue Stain in Exfoliated Buccal Cells of Thalassemia and Sickle Cell Anemia Patients and Their Correlation With Serum Ferritin Levels.

Introduction Iron is essential for all living beings. Excess iron, on the other hand, is dangerous because it causes the creation of free radicals. As a result, iron absorption is carefully managed to maintain a balance between absorption and iron loss in the body. Due to the lack of particular excretory channels for iron in humans, iron excess in the tissues is common. It can be caused by a number of factors, including increased iron absorption, as seen in hemochromatosis, or frequent parenteral iron treatment, as seen in thalassemia and sickle cell anemia patients (a transfusional overload). Aim The study aims to demonstrate Perl's Prussian blue stain to identify iron overload at a preliminary stage and correlate with serum ferritin levels in patients withthalassemia and sickle cell anemia who frequently receive blood transfusions. Materials and methods The present study comprised 62 confirmed cases of thalassemia and sickle cell anemia patients undergoing repeated blood transfusions of a minimum of 15/more, along with 62 clinically healthy individuals between December 2016 and November 2018. The patients with thalassemia and sickle cell anemia were confirmed by hemoglobin electrophoresis (Bio-Rad D-10, Bio-Rad Laboratories, Inc, California, United States). The buccal smears were obtained from these patients along with the controls, and these slides were stained by Perl's Prussian blue stain and were examined under a light microscope. Results Sixty-two cases and 62 controls were considered in the current investigation. Forty-seven of the 62 people had thalassemia, and 15 had sickle cell anemia. Thirty-nine out of the 47 patients with thalassemia and six of the 15 individuals with sickle cell anemia had positive results for Perl's Prussian blue stain. All patients had elevated blood ferritin levels, with varying ranges associated with positive results for Perl's Prussian blue stain. Conclusion The objective of this study was to demonstrate the utility of oral exfoliative cytology in thalassemia and sickle cell anemia patients who often receive blood transfusions as a screening and diagnostic tool. The exfoliative cytology methods' acceptability and simplicity, along with their correlation with serum ferritin levels and Perl's Prussian blue reaction, make this noninvasive procedure an excellent screening and diagnostic tool for all patients who receive repeated blood transfusions.

The exploration of the inverse vulcanization mechanism of tung oil by controlling the oxygen and moisture presence during reactions

Inverse vulcanization is a cost-effective method for producing high sulfur-content copolymers by combining elemental sulfur with organic monomers, which has rapidly gained popularity due to its simplicity of synthesis and wide range of applications. Although numerous examples of sulfur-rich copolymers have been synthesized at different reaction rates and temperatures using various monomers, the precise reaction mechanism remains unclear. In this paper, we used tung oil containing conjugated triene as a monomer to synthesize sulfur-rich copolymers under six different reaction conditions and investigate the effects of oxygen and moisture. Our study, which employed DSC, XRD, 1H NMR, and XPS characterization methods, revealed that oxygen accelerated the reaction rate and decreased the free sulfur content of the products, while moisture shortened the gel times but increased the free sulfur content. These findings confirm that reverse vulcanization involves two simultaneous mechanisms: the free radical mechanism and the anion mechanism. With regard to the radical mechanism, we discuss the source, ease, and reactivity of radicals and show that the creation of radicals depends on the second monomer rather than sulfur. Tung oil not only acts as a comonomer in the reaction but also plays an initiating role in promoting the dissociation of sulfur chains to generate free radicals for addition of non-conjugated double bonds. The effect of the anion mechanism exceeds that of the radical mechanism once certain factors are stimulated, such as the presence of metal ions and sulfide ions. Understanding the detailed mechanisms involved in inverse vulcanization is essential for selecting optimal monomers, which can enhance not only the synthesis process but also the properties of sulfur-rich materials.

Ferulic Acid: Signaling Pathways in Aging.

The need for clinical remedies to the multiple age-related deficiencies in skin function brought on by extrinsic and intrinsic causes is increased by these demographic changes. Reactive oxygen species (ROS), mitochondrial deoxyribonucleic acid (mtDNA) mutations, telomere shortening, as well as other factors, contribute to the aging of the skin. In this overview, the issue of human skin aging is introduced, along with several pathways and the protective effects of ferulic acid in light of current patents. The complex antioxidant effect of ferulic acid depends on the "sweeping" away of free radicals as well as the suppression of the synthesis of ROS or nitrogen. Furthermore, Cu (II) or Fe protonated metal ions are chelated by this acid (II). Ferulic acid is a free radical scavenger as well as an enzyme inhibitor, increasing the activity of enzymes that scavenge free radicals while decreasing the activity of enzymes that speed up the creation of free radicals. AMPK signalling, which can regulate cellular homeostasis, stress tolerance, cell survival and proliferation, cell death, and autophagy, has recently been linked to aging and lifespan. Therefore, Caenorhabditis elegans (C. elegans) and rodents had longer life-spans due to specific AMPK activation. By inhibiting the TGF-β/Smad signalling pathway, UV irradiation can reduce the production of procollagen. Glycation changes the skin's physical characteristics, making it less elastic and stiffer. . Excessive free radicals simultaneously trigger the nuclear factor kappa B (NF- κB) signalling pathway, increasing TNF levels and matrix metalloproteinase production (MMPs).

Recent Clay-Based Photocatalysts for Wastewater Treatment

Photocatalysis is a remarkable methodology that is popular and applied in different interdisciplinary research areas such as the degradation of hazardous organic contaminants in wastewater. In recent years, clay-based photocatalyst composites have attracted significant attention in the field of photocatalysis owing to their abundance, excellent light response ability, and stability. This review describes the combination of clay with focusing photocatalysts such as TiO2, g-C3N4, and Bi-based compounds for degrading organic pollutants in wastewater. Clay-based composites have more active surface sites, resulting in inhibited photocatalyst particle agglomeration. Moreover, clay enhances the creation of active radicals for organic pollutant degradation by separating photogenerated electrons and holes. Thus, the functions of clay in clay-based photocatalysts are not only to act as a template to inhibit the agglomeration of the main photocatalysts but also to suppress charge recombination, which may lengthen the electron–hole pair’s lifespan and boost degrading activity. Moreover, several types of clay-based photocatalysts, such as the clay type and main photocatalyst, were compared to understand the function of clay and the interaction of clay with the main photocatalyst. Thus, this study summarizes the recent clay-based photocatalysts for wastewater remediation and concludes that clay-based photocatalysts have considerable potential for low-cost, solar-powered environmental treatment.

Shining light on halogen-bonding complexes: a catalyst-free activation mode of carbon-halogen bonds for the generation of carbon-centered radicals.

The discovery of new activation modes for the creation of carbon-centered radicals is a task of great interest in organic chemistry. Classical activation modes for the generation of highly reactive radical carbon-centered intermediates typically relied on thermal activation of radical initiators or irradiation with unsafe energetic UV light of adequate reaction precursors. In recent years, photoredox chemistry has emerged as a leading strategy towards the catalytic generation of C-centered radicals, which enabled their participation in novel synthetic organic transformations which is otherwise very challenging or even impossible to take place. As an alternative to these activation modes for the generation of C-centered radicals, the pursuit of greener, visible-light initiated reactions that do not necessitate a photoredox/metal catalyst has recently caught the attention of chemists. In this review, we covered recent transformations, which rely on photoactivation with low-energy light of a class of EDA complexes, known as halogen-bonding adducts, for the creation of C-centered radicals.

(Invited) Operando EPR Study on Radicals in Anion-Exchange Membrane Fuel Cells

In the rapidly developing modern society, there is an urgent need for the wide-ranging availability of advanced and eco-friendly energy sources. One of the possible alternatives is the application of anion exchange membrane fuel cells (AEMFCs) with a catalyst reducing dioxygen efficiently. These promising devices can revolutionize the energy sector since they practically produce no pollution. However, to make them more widely used, several obstacles must be overcome. As a result, vast-ranging investigations focus on improving the properties of conductive polymer membranes [1] and catalysts for the oxygen reduction reaction (ORR) [2]. The durability of the membrane electrode assembly (MEA) is one of the critical requirements for the successful commercialization of anion exchange membrane fuel cells (AEMFCs). Despite significant impacts of nucleophilic degradation on ion-exchange capability and the anionic conductivity of investigated membranes, it is believed to affect only cationic sites of membrane polymers and thus cannot explain the reported loss in the mechanical strength of degraded AEMs. Such a phenomenon might be related to polymer backbone degradation caused by free radicals. This was widely described in the literature in the case of fuel cells using proton-conducting membranes [3] but barely mentioned for AEMFCs [4]. Since the oxidative degradation of hydrocarbon polymers is very well known, we aimed to comprehensively investigate the formation of the short-lived species generated during the operation of AEMFCs as well as stable radicals present in the polymer membranes.We investigated the LDPE-base membranes with Pt black, Pd black, PdAg, and Ag as the ORR catalysts, whereas for HOR the Pt black, Pd black, and NiFe catalysts were used. The in-situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals was monitored by the EPR spin trapping technique. In Figure 1 the EPR spectra of DMPO spin adducts trapped during operation of micro-fuel cell placed in EPR spectrometer cavity are presented. In this experiment, the LDPE-base membrane with platinum catalysts on both sides was used. The main detected adducts during the operation of the micro-AEMFC were DMPO-OOH and DMPO-OH on the cathode side and DMPO-H on the anode side. Additionally, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation [5]. Preliminary results suggest that the creation of the short-living radicals during AEMFCs operation is independent of the used membrane. However, the applied catalysts determine the number of detected radicals. The EPR investigations indicate that, in addition to the known chemical degradation mechanisms of the cationic ammonium groups of the membrane, oxidative degradation, including radical reactions, has to be taken into account when the stability of an anion conductive polymer for AEMFCs is investigated. The formation of stable radicals in AEMs was proven for the first time in this study. All short-living radicals formed during the AEMFC operation were fully identified. The presence of radicals in the AEM after AEMFC testing indicates that reactive oxygen species may play a very important role in the degradation mechanism of the anion conducting polymers. Results from this study shed light on the understanding of radical formation and presence in the membranes during AEMFC tests, which in turn may help to solve the challenge of anion exchange membrane stability. Acknowledgments. This work was supported by the Polish National Science Centre (NCN) project OPUS-14, No. 2017/27/B/ST5/01004.

Photocatalytic Performance Study of Organophosphorus-Doped Tungsten Trioxide and Composite Materials

The present study successfully produced a highly effective and stable organ phosphorus-doped tungsten trioxide (P-WO3) photocatalyst by a combination of hydrothermal and postcalcination methods. The crystallites, morphologies, and optical properties of the produced WO3 and P-WO3 crystals were investigated. The results indicated that P was consistently doped into the WO3 lattice in a pentavalent-oxidation state (P5+). Additionally, charge carrier traps capable of accepting photoelectrons were created. Additionally, the optical band gap was reduced from 2.4 to 2.33 eV. The degradation of methyl blue by photocatalysts was utilized to evaluate the photocatalytic performance of the synthesized P-WO3 samples at varied P concentrations (MB). The sample containing 6% -P-WO3 exhibited the best photocatalytic performance, degrading 96 percent of MB in 120 minutes, which was more than four times faster than the pure WO3 sample. The practicality of the synthesized P-WO3 was determined using samples from two residential wastewater treatment plants. When treating real wastewater with low organic matter concentrations, the P-WO3 demonstrated strong photodegradation performance. The creation of hydroxyl radicals (OH) and photography-created holes (h+) could be the key protagonists of photocatalytic activity in the P-WO3.

Effects of nonthermal physical processing technologies on functional, structural properties and digestibility of food protein: A review

AbstractThis review assesses the nonthermal physical processing technologies for protein modification. The review also discusses the structural, functional, and digestibility attributes of protein following nonthermal physical processing. Applications of ultrasonication, ultrahigh pressure, and pulsed electric field (PEF) can induce the conformational changes of protein via the creation of free radicals and/or larger/smaller protein molecules, damaging the primary, secondary, tertiary, and quaternary structure of protein, and thus influence the functional properties. Some key achievements in using nonthermal physical technologies to process protein‐rich foods include improved enzymatic hydrolysis, solubility, emulsification, foaming, gelatinization, digestion properties, and reduced allergenicity. Therefore, nonthermal physical technologies are useful methods to modify food protein structure and functionality for the food industry.Practical ApplicationThe demand for protein with desirable functional properties and nutritional value makes it imperative to find suitable processing technologies that could conserve or yield high quality proteins from both conventional and nonconventional sources. Since thermal processing (including microwave, radiofrequency heating, etc.) could possibly reduce the quality attributes of proteins, many researchers have focused their investigations on nonthermal physical processing to improve the functional properties of proteins. To this regard, this review discusses nonthermal techniques, including ultrasonication, high‐pressure processing, PEFs, cold plasma, and ultraviolet.

Dynamic nuclear polarization enhancement of 13C in glucose using electrical discharge induced radicals as polarizing agents

The creation of radicals via electrical discharge is a unique approach capable of facilitating dynamic nuclear polarization (DNP) in solids without the need to co-dissolve them with exogenous polarization agents. This method has previously been shown to generate high proton polarization in a variety of organic and inorganic solid compounds. In this work, we extend the scope of applicability for these so-called electrical discharge-induced radicals (EDIRs), by showing their use in DNP of 13C nuclei of glucose. We achieved significant NMR signal enhancement in low temperature solid-state DNP experiments. This enhancement was further improved by the use of a frequency modulated microwave pump instead of conventional DNP with single-frequency microwaves. We demonstrated successful dissolution DNP experiments with such hyperpolarized solid glucose, achieving 13C polarization levels of up to ∼0.6% in the resulting solution (∼0.95% at the exit of the polarizer). This is to be compared with the ∼6% polarization levels achieved with a trityl radical mixed with glucose in a frozen aqueous solution using the same DNP setup and experimental conditions. It is concluded that the use of EDIRs can serve as a suitable polarizing approach for metabolic MRI using glucose, avoiding the need to employ diluted solutions and eliminating the filtration stage of the polarizing agents.

Comparative study of biological activities of different extracts of root and whole plant materials of Ajuga bracteosa from Bhimber Azad Kashmir Pakistan

Ajuga bracteosa is native to Himalayan region, Afghanistan, China and Malaysia. People of northern areas of Pakistan call it ‘korri booti’ as it has bitter taste. Ajuga bracteosa is ethnically used against malarial fever, diabetes, cancer, and sore throat. The theme of present work was to appraise the biological significance of Ajuga bracteosa through in vitro studies. n-Hexane, chloroform, and methanol extracts of root and whole plant materials were obtained via maceration. Qualitative and quantitative analysis of phytochemical constituents was done. The antioxidant potency was judged by DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) free radical scavenging assays. Antimicrobial efficacy was assessed by agar disc diffusion method. Phytochemical review confirmed the existence of flavonoids, saponins, phenols, tannins, terpenoids, xanthoproteins, carbohydrates, and glycosides. Total flavonoid and total phenolic contents were shown as rutin and gallic acid equivalents respectively. Root extracts gave more significant results of DPPH and ABTS potential (100 % and 92 % respectively) as compared to whole plant extracts (90 % and 75 % respectively). A. bracteosa is a plentiful source of polyphenolic compounds. Polyphenolic compounds are thought as natural antioxidants because of their ability of hydrogen atom donation and presence as stable radical intermediates preventing further creation of free radicals in the body. Root extracts showed greater resistance against pathogens as compared to extracts of whole plant material. Keywords: Antimicrobial activity; Antioxidant activity; Medicinal plants; Phytochemical screening http://dx.doi.org/10.19045/bspab.2021.100135

Optical properties and visible-light-driven photocatalytic activity of Na2Mn2(MoO4)3

In this paper, Na2Mn2(MoO4)3 doubgyle molybdate was prepared by sol-gel method to investigate the structural, morphological and optical properties. X-ray diffraction analysis showed that Na2Mn2(MoO4)3 crystallizes in the triclinic system in the P1¯ group. The composition and morphology of the compound were checked by energy dispersive spectroscopy coupled with scanning electron microscope. Optical properties were analyzed by UV–Vis diffuse reflectance spectroscopy. The photocatalytic properties were evaluated by the degradation of methylene blue under natural sunlight and compared to Xe and UV lamps. The highest photodegradation efficiency (85.3%) was obtained for solar irradiation, therefore, Na2Mn2(MoO4)3 can be a potential photocatalyst for the removal of dye wastewater pollution driven by visible-light. The proposed mechanism of photodegradation in water involves creation of hydroxyl radicals and superoxide anions that attack the methylene blue molecules and decompose it to carbon dioxide and water.

Impact of UV Radiation on the Raman Signal of Cystine: Implications for the Detection of S-rich Organics on Mars.

Traces of life may have been preserved in ancient martian rocks in the form of molecular fossils. Yet the surface of Mars is continuously exposed to intense UV radiation detrimental to the preservation of organics. Because the payload of the next rovers going to Mars to seek traces of life will comprise Raman spectroscopy tools, laboratory simulations that document the effect of UV radiation on the Raman signal of organics appear critically needed. The experiments conducted here evidence that UV radiation is directly responsible for the increase of disorder and for the creation of electronic defects and radicals within the molecular structure of S-rich organics such as cystine, enhancing the contribution of light diffusion processes to the Raman signal. The present results suggest that long exposure to UV radiation would ultimately be responsible for the total degradation of the Raman signal of cystine. Yet because the degradation induced by UV is not instantaneous, it should be possible to detect freshly excavated S-rich organics with the Raman instruments on board the rovers. Alternatively, given the very short lifetime of organic fluorescence (nanoseconds) compared to most mineral luminescence (micro- to milliseconds), exploiting fluorescence signals might allow the detection of S-rich organics on Mars. In any case, as illustrated here, we should not expect to detect pristine S-rich organic compounds on Mars, but rather by-products of their degradation.

Microseismic Events Cause Significant pH Drops in Groundwater

AbstractEarthquakes cause rock fracturing, opening new flow pathways which can result in the mixing of previously isolated geofluids with differing geochemistries. Here, we present the first evidence that seismic events can significantly reduce groundwater pH without the requirement for fluid mixing, solely through the process of dynamic rock fracturing. At the Grimsel Test Site, Switzerland, we observe repeated, short‐lived groundwater pH drops of 1–3.5 units, while major and minor ion groundwater concentrations remain constant. Acidification coincides with reservoir drainage and induced microseismic events. In laboratory experiments, we demonstrate that fresh rock surfaces made by particle cracking interact with the in situ water molecules, likely through creation of surface silanols and silica radicals, increasing the H+ concentration and significantly lowering groundwater pH. Our findings are significant; pH exerts a fundamental control on the rate and outcome of most aqueous geochemical reactions and microseismic events are commonplace, even in seismically inactive regions.

Excitons and Polarons in Organic Materials

ConspectusExcitons and polarons play a central role in the electronic and optical properties of organic semiconducting polymers and molecular aggregates and are of fundamental importance in understanding the operation of organic optoelectronic devices such as solar cells and light-emitting diodes. For many conjugated organic molecules and polymers, the creation of neutral electronic excitations or ionic radicals is associated with significant nuclear relaxation, the bulk of which occurs along the vinyl-stretching mode or the aromatic-quinoidal stretching mode when conjugated rings are present. Within a polymer chain or molecular aggregate, nuclear relaxation competes with energy- and charge-transfer, mediated by electronic interactions between the constituent units (repeat units for polymers and individual chromophores for a molecular aggregate); for neutral electronic excitations, such inter-unit interactions lead to extended excited states or excitons, while for positive (or negative) charges, interactions lead to delocalized hole (or electron) polarons. The electronic coupling as well as the local coupling between electronic and nuclear degrees of freedom in both excitons and polarons can be described with a Holstein Hamiltonian. However, although excitons and polarons derive from similarly structured Hamiltonians, their optical signatures are quite distinct, largely due to differing ground states and optical selection rules.In this Account, we explore the similarities and differences in the spectral response of excitons and polarons in organic polymers and molecular aggregates. We limit our analysis to the subspace of excitons and hole polarons containing at most one excitation; hence we omit the influence of bipolarons, biexcitons, and higher multiparticle excitations. Using a generic linear array of coupled units as a model host for both excitons and polarons, we compare and contrast the optical responses of both quasiparticles, with a particular emphasis on the spatial coherence length, the length over which an exciton or polaron possesses wave-like properties important for more efficient transport. For excitons, the UV-vis absorption spectrum is generally represented by a distorted vibronic progression with H-like or J-like signatures depending on the sign of the electronic coupling, Jex. The spectrum broadens with increasing site disorder, with the spectral area preserved due to an oscillator strength sum rule. For (hole) polarons, the generally stronger electronic coupling results in a mid-IR spectrum consisting of a narrow, low-energy peak (A) with energy near a vibrational quantum of the vinyl stretching mode, and a broader, higher-energy feature (B). In contrast to the UV-vis spectrum, the mid-IR spectrum is invariant to the sign of the electronic coupling, th, and completely resistant to long-range disorder, where it remains entirely homogeneously broadened. Even in the presence of short-range disorder, the width of peak A remains surprisingly narrow as long as |th| remains sufficiently large, a property that can be understood in terms of Herzberg-Teller coupling. Unlike for excitons, for polarons, the absorption spectral area decreases with increasing short-range disorder σ (i.e., there is no oscillator sum rule) reflective of a decreasing polaron coherence length. The intensity of the low-energy peak A in relation to B is an important signature of polaron coherence. By contrast, for excitons, the absorption spectrum contains no unambiguous signs of exciton coherence. One must instead resort to the shape of the steady-state photoluminescence spectrum. The Holstein-based model has been highly successful in accounting for the spectral properties of molecular aggregates as well as conjugated polymers like poly(3-hexylthiophene) (P3HT) in the mid-IR and UV-vis spectral regions.