Presence Of Oxygen Species Research Articles

Valorization of Yellow Oleander to Nitrogen Doped Carbon Dots: Theragnostic and Genotoxicity Assessment

AbstractDevelopment of useful products from toxic or hazardous waste is a unique strategy to overcome their disposal. In this work, we report the valorization of the toxic flowers of Thevetia peruviana (TP) into blue fluorescent nitrogen doped carbon dots (N‐CDs) with ∼6.6 % nitrogen doping from a single source of biomass without using any external dopant. The hydrophilic N‐CDs are biocompatible and show excitation‐dependent emission. Cytotoxity studies revealed the N‐CDs are selectively toxic towards the cancerous cells (DU‐145, MDA MB‐231, HepG2, and B16) but more biocompatible with normal CHO‐K1 and HEK‐293 cells. It has been observed that generation of reactive oxygen species in presence of N‐CDs cause DNA damage and the unrepaired cells undergo apoptosis in G2/M phase. To investigate the toxicity to normal cells, we further carried out in‐vitro and in‐vivo genotoxicity studies to reveal its non‐mitotoxic, non‐clastogenic, and non‐aneugenic properties.

Genome-Wide Analysis of TIR-NBS-LRR Gene Family in Potato Identified StTNLC7G2 Inducing Reactive Oxygen Species in Presence of Alternaria solani.

Resistance gene analogs (RGAs) comprising NBS-LRR gene family members are considered prominent candidates in the development of disease-resistant genotypes. NBS-LRR gene family comprised a very large number of genes; therefore, members of one subfamily TIR-NBS-LRR (TNL) are identified in the present study from Solanum tuberosum genome, followed by their bioinformatics characterization. The study identified a total of 44 genes encoding 60 TNL transcripts with two prominent clusters at chromosome 1 and chromosome 11. Expression analysis of 14 TNL genes after Alternaria solani infection at 1, 2, 3, 5, and 7 days post inoculation in two disease-tolerant varieties, Kufri Jyoti and Kufri Pukhraj, and one relatively susceptible variety, Kufri Chandramukhi, showed differential expression of many genes including a high expression (>15-fold) of StTNLC6G2T1 and StTNLC11G9T1. Functional characterization of one such gene, StTNLC7G2, reveals involvement in the generation of reactive oxygen species under A. solani attack, implicating its putative role in plant defense via hypersensitive response.

2D Palladium Sulphate for Visible‐Light‐Driven Optoelectronic Reversible Gas Sensing at Room Temperature

2D metal sulphides (MSs) have attracted enormous amounts of attention in developing high‐performance gas sensors. 2D noble metal sulphides and their derivatives, however, have been less studied due to their predominant nonlayered crystal structures for inefficient exfoliation, despite their surface and peculiar optoelectronic properties. Herein, we successfully synthesize 2D palladium sulphate (PdSO4) from palladium sulphide (PdS) bulk crystals by liquid‐phase exfoliation, in which the presence of oxygen species in the exfoliation solvent plays a key role in the sulphate transformation. Ultrathin 2D PdSO4 planar nanosheets, with thicknesses of ≈3 nm and submicrometer lateral dimensions, exhibit a broad absorption across the visible spectrum, a narrow bandgap of ≈1.35 eV, and a nanosecond scaled long exciton lifetime, which are all suitable for the visible‐light‐driven optoelectronic gas sensing applications. The 2D PdSO4‐based sensor demonstrates a reversible, selective, and sensitive response toward ppb‐leveled NO2 gas at blue light irradiation, featuring a response factor of ≈3.28% for 160 ppb NO2, a low limit of detection of 1.84 ppb, and a > 3 times response factor enhancement over other gases. Herein, the possibility of realizing 2D ultrathin noble metal sulphide compounds from their nonlayered crystal structures and strong potentials in developing high‐performance chemical sensors is explored.

Ultrasmall SnO2 directly grown on commercial C45 carbon as lithium-ion battery anodes for long cycling performance

Development of high-performance SnO2 anodes is hampered by its peculiar electrochemical behavior, characterized by two processes: conversion and alloying reactions. The conversion reaction being irreversible leads to specific capacities lower than theoretical, however rational design of nanosized SnO2 can mitigate this issue, though SnO2 low conductivity and electrode pulverization justify the need of carbon matrices. Some carbon structures proved to be strongly effective at laboratory-scale, but most are too expensive or complicated to obtain for scaling-up. Herein, we exploit the high concentration of oxide and carboxylic surface functional groups of C-NERGY™ Super C45 carbon black for one-pot synthesis of ultrafine SnO2 nanoparticles over the carbon surface. These functional groups accomplish the hydrolysis/oxidation of SnCl2, resulting in finely dispersed SnO2 nanoparticles (5 nm in average size) growth over C45. Presence of oxygen species on C45 surface, accessible to tin, prevent fast formation of Li2O, allowing to achieve high capacity and extreme electrode stability. The assembled cells with SnO2/C45 exhibit for more than 400 cycles the reversible capacity of 560 mA h g−1 per pure SnO2 (after subtracting C45 contribution) at 1C, demonstrating prolonged cycling operation thus providing an interesting opportunity for scalable production of stable and high-capacity battery anodes alternatively to graphite.

Eco-friendly synthesis of functionalized chitosan-based nanoantibiotic system for potential delivery of linezolid as antimicrobial agents

To obtain a healthy human being with beneficial microflora against different pathogenic infections, classical antibiotics with nanosized biomaterials were used to inhibit the growth of bacterium by their potent synergistic effect. Hence, this study planned to load an oxazolidinone antibiotic named linezolid (LD) onto functionalized chitosan (CN) with 3, 5- dinitrosalyslic acid (DA) via microwave synthesis without harsh condition. The exploring synergistic effect of linezolid (LD) with CN/DA controllable nanostructure was compact efflux-mediated methicillin-resistant Staphylococcus aureus (MRSA) burden and other selected bactericide Gram-positive ((S. aureus), Gram-negative (E. coli), Fungi (C. albicans), Yeast (A. niger), and E. faecalis. The obtained results showed that LD was incorporated into both the internal and external surface of the aggregated CN/DA nanosystem with an average diameter of 150 nm ± 4 hints of the drug loading. Owing to the nature of functionalized CN, the release efficiency attains 98.4% within 100 min. The designed LD@CN/DA exhibited inhibition zone 54 mm, 59 mm, 69 mm, 54 mm, 57 mm, and 24 mm against the tested microbes respectively rather than individual LD. The major target of the current research is achieved by using LD@CN/DA as a nanoantibiotic system that has exceptional consistently active against multi-resistant pathogens, in between MRSA which resist LD. Also, cell viability was performed even after three days of direct cell culture on the surface of the designed nanoantibiotic. The mechanism of microbial inhibition was correlated and rationalized to different charges and the presence of oxygen species against microbial infections. Our findings provide a deep explanation about nanostructured antibiotics design with enhanced potentially pathogen-specific activity.

Quantification of Formate and Oxygen Coverages on Cu Under Industrial Methanol Synthesis Conditions

A method for quantifying the surface coverage of adsorbate species for reactions at high pressure and high temperature is presented. Methanol was synthesized from CO2/CO/H2 (3/29/68) at 523 K and 50 bar on Raney Cu, which yielded a turnover frequency (TOF) per Cu surface atom of (6.22 ± 1.04) × 10–3 s–1. Rapid quenching by submerging the catalytic reactor in ice water during operation allowed the formate surface coverage on Cu (θCu-HCOO) at reaction conditions to be determined in a subsequent temperature programmed desorption experiment. This yielded θCu-HCOO = 0.071 ± 0.012 ML and a corresponding TOF per adsorbed HCOO of 0.088 ± 0.021 s–1. CO2 was essentially observed to be the exclusive source of methanol formation over Raney Cu, as the CO in the syngas could be replaced by N2 without impact on the methanol formation rate. Based on this observation and the considerable support in the literature for a CO2-pathway via surface formate on Cu the TOF per surface formate species should represent the true rate of the catalytic cycle in Cu-catalyzed methanol synthesis. Temperature programmed hydrogenation of Raney Cu and unsupported Cu after quenching during high-pressure operation did not indicate a presence of oxygen species (O or OH) on the working Cu surface.

Theoretical Study of Propylene Epoxidation over Cu2O(111) Surface: Activity of O2–, O–, and O2– Species

Propylene epoxidation catalyzed by cuprous oxide in the presence of oxygen species is important in both technology and scientific fields, and the active species—lattice oxygen (O2–), adsorbed atomic oxygen (O–), or adsorbed molecular oxygen (O2–)—plays a significant role in the catalytic reaction. In the present work, the mechanism of propylene epoxidation and dehydrogenation on a Cu2O(111) facet with different oxygen species has been studied through density functional theory (DFT) calculations with a Hubbard U correction in detail. The whole reaction processes of propylene oxidation includes two different routes: allylic hydrogen stripping (AHS) reactions and propylene epoxidation reactions. Acrolein can be generated by two H-stripping reactions in the AHS path, and propylene oxide (PO) is formed through the oxametallacycle propylene (OMP) intermediate. The calculated results show that the adsorbed atomic oxygen (O–) is the most active oxygen species for the selective oxidation of propylene because it has the strongest basicity among these three oxygen species, whereas the adsorbed molecular oxygen (O2–) has the highest selectivity for the PO formation among these three different oxygen species because of its relatively low basic properties and moderate oxidation compared to those of atomic oxygen (too active oxidation) or lattice oxygen (less oxidation due to the closed-shell nature of the oxide system). Moreover, a microkinetic simulation was used to confirm the above DFT calculation results. The aim of the present study is to give a guide in choosing the most efficient active oxygen species for PO formation, which should be the one with the moderate oxidant.

In-situ nickel(II) complexes of 3-(dimethylamino)-1-propylamine based Schiff base ligands: Structural, electrochemical, biomolecular interaction and antimicrobial properties

Five new di-Schiff base nickel(II) complexes (1–5) of salen type ligands were synthesized in-situ by condensation of 3-(dimethylamino)-1-propylamine with 2-hydroxybenzaldehyde, 2-hydroxy-5-methyl benzaldehyde, 2-hydroxy-5-bromo benzaldehyde, 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde to obtain L1–L5, respectively and complexed with nickel chloride. Single crystal X-ray diffraction studies of complexes 1 and 5 showed a distorted octahedral and distorted square-planar geometry, respectively around nickel atoms. The cyclic voltammetry of complexes 1–5 showed redox peaks near cathodic and anodic regions assignable to the Ni2+/Ni+ and Ni2+/Ni3+ redox couples, respectively. The binding studies of complexes with calf thymus DNA (ctDNA) showed an intercalation mode of binding. The nuclease activity of the complexes with pBR322 plasmid DNA showed efficient oxidative cleavage by the formation of singlet oxygen species in presence of H2O2. All nickel(II) complexes were found to have greater zone inhibition diameter when analyzed for antimicrobial property against four bacterial species and two human pathogenic fungal species.

Biochemical characterization of unusual cysteine protease of P. falciparum, metacaspase-2 (MCA-2)

Earlier studies on Plasmodium apoptosis revealed the presence of proteases with caspases like- activity, which are known as “metacaspases”. Although this family of cysteine proteases is structurally similar to caspases with Cys-His dyad but their evolutionary significance and functional relevance remains largely unknown. These proteases are considered to be an important target against malaria due to their absence in humans. In this report, we have biochemically characterized metacaspase-2 (PfMCA-2) of P.falciparum. Enzymatic assay showed that PfMCA-2 efficiently cleaved arginine/lysine specific peptide, but not caspase-specific substrate. Consistently, PfMCA-2 activity was sensitive to effector caspases inhibitor, Z-FA-FMK, and mildly inhibited by aprotinin and E-64. However, general caspase inhibitors such as Z-VAD-FMK and Z-DEVD-FMK had no effect on PfMCA-2 activity. Z-FA-FMK inhibits parasite growth with an IC50 value of 2.7 μM along with the notable morphological changes. PfMCA-2 specifically expressed in schizonts and gametocyte stages and there was a notable depletion of PfMCA-2 expression in Z-FA-FMK treated schizonts and gametocytes stages of parasite. Notably, PfMCA-2 cleaves a phylogenetically conserved protein, TSN (Tudor staphylococcal nuclease) and the proteolysis of PfTSN did not occur after treatment with the Z-FA-FMK. The production of large amount of reactive oxygen species in presence of Z-FA-FMK caused oxidative stress which in turn leads to loss of cell viability. The oxidative stress further generates positive feedback for the occurrence of cell death in term of phosphatidylserine externalization and DNA fragmentation in vitro.

Plasma-Activated Copper Nanocube Catalysts for Efficient Carbon Dioxide Electroreduction to Hydrocarbons and Alcohols.

Carbon dioxide electroreduction to chemicals and fuels powered by renewable energy sources is considered a promising path to address climate change and energy storage needs. We have developed highly active and selective copper (Cu) nanocube catalysts with tunable Cu(100) facet and oxygen/chlorine ion content by low-pressure plasma pretreatments. These catalysts display lower overpotentials and higher ethylene, ethanol, and n-propanol selectivity, resulting in a maximum Faradaic efficiency (FE) of ∼73% for C2 and C3 products. Scanning electron microscopy and energy-dispersive X-ray spectroscopy in combination with quasi-in situ X-ray photoelectron spectroscopy revealed that the catalyst shape, ion content, and ion stability under electrochemical reaction conditions can be systematically tuned through plasma treatments. Our results demonstrate that the presence of oxygen species in surface and subsurface regions of the nanocube catalysts is key for achieving high activity and hydrocarbon/alcohol selectivity, even more important than the presence of Cu(100) facets.

First-Principles Study of the Role of O2 and H2O in the Decoupling of Graphene on Cu(111).

The structural and electronic properties of graphene coated on a Cu(111) surface can be strongly influenced by the arrangement of adsorbates at the graphene edges. Oxygen and water intercalation at the graphene edges could lead to oxidation and hydrolysis at the graphene/Cu(111) interface, eventually causing decoupling of graphene from the Cu substrate. However, the reaction pathways for oxygen or water (or both) intercalation at the graphene edges are not well understood at the molecular level. Using ab initio density functional theory calculations, we observed a strong hybridization of π orbitals at a zigzag edge of a graphene nanoribbon (GNR) on a bare Cu(111) surface, whereas such hybridization was absent for the corresponding armchair edge under otherwise identical conditions. These results indicate that the edge type influences the oxidation chemistry beneath the GNR. Moreover, we demonstrate that the presence of oxygen species, as well as GNR, facilitates the propagation of H2O. The following decoupling mechanisms are discussed: (i) GNRs with armchair edge configurations on Cu(111) can be decoupled via a sequential reaction that involves O2 dissociation followed by H2O intercalation, whereas (ii) GNRs with zigzag edge configurations on Cu(111) can be decoupled by oxygen intercalation.

Effects of Temperature and Atmosphere on Carbon-Supported Platinum Fuel Cell Catalysts

Pt/Vulcan XC 72 powders were prepared via a colloidal method. TEM and XRD studies were carried out from 273 to 573 K under oxidizing, inert, and reducing atmospheres. Under air flow, a small aggregation of platinum particles is observed, but neither fusion of particles nor increase of the Sherrer’s length Lv. This is explained by the presence of oxygen species on the platinum surface. Under reducing atmosphere (3%H2/He), aggregation of platinum particles and increase of the crystallinity and/or apparent mean crystallite size are observed. Lv increases from ca. 3 nm for the fresh Pt(40 wt %)/C catalyst to ca. 7 nm after thermal treatment at 573 K. Under inert atmosphere, TEM and XRD measurements did not show any reconstruction process or Lv increase for temperatures lower than 473 K. But from 523 K, some platinum entity reconstruction was evidenced. Under reducing atmosphere, two kinetics of grain growth process seem to exist. The “induction time” τ before the second growth process is dependent on the temperature, but independent of the platinum loading. For T < 523 K, the formation of a surface Pt−H quasiliquid phase leading to crystalline reconstruction and an agglomeration process are proposed to occur. This step is then followed by grain boundary formation and grain boundary diffusion leading further to the increase of Lv (controlled by the second growth kinetics). For T ≥ 523 K, reconstruction by size effect is invoked for the first growth process.

The effects of oxygen on the detection of mercury using laser-induced breakdown spectroscopy

A systematic study of the processes associated with mercury atomic emission in a laser-induced plasma and the interactions of mercury with oxygen species is presented. At early plasma decay times, on the order of 5–10 μs, no significant variation in mercury atomic emission was observed with the addition of oxygen-containing species. At intermediate and long decay times (10–100 μs), a significant reduction in the 253.7-nm mercury emission intensity was recorded with the introduction of oxygen-containing species. The decrease in mercury emission was temporally coincident with the recombination of atomic oxygen, as measured by the O(I) emission. The decreased mercury emission was not due to thermal effects, based on plasma temperature measurements, and was independent of the molecular source of oxygen, for similar concentrations of oxygen as air, carbon dioxide, and carbon monoxide. Analysis of additional mercury atomic emission lines revealed that the reduction in mercury emission in the presence of oxygen species is limited primarily to the 253.7-nm transition. In concert, the data lead to the conclusion that the 253.7-nm mercury emission line is selectively quenched by oxygen species, primarily O 2 and NO, that are formed during the plasma recombination process. Implications for laser-induced breakdown spectroscopy-based emissions monitoring of mercury species are discussed.

Elimination of metoxuron and carbetamide in the presence of oxygen species in aqueous solutions

Photodegradation of carbetamide (( R)-1-(ethylcarbamoyl)ethyl carbanilate) and metoxuron (3-(3-chloro-4-methoxyphenyl)-1,1-dimethylurea) in the presence of hydrogen peroxide, titanium dioxide and ozone was investigated with ultraviolet radiations ( λ > 290 nm). Several photoproducts were isolated and identified by spectrometric methods. The results suggest that the degradation pathways of these compounds in the presence of UV-H 2O 2 and UV-TiO 2 are hydroxylations of the aromatic ring. UV-ozonation rapidly photooxydized all pesticides. The opening of the aromatic rings was observed, producing lower molecular weight carboxylic acids. Further photooxidation converts the acids to CO 2, H 2O, HCl and NH 3.