Variety Of Reactive Species Research Articles

Unraveling the crucial role of Mo2N from Fe/Mo bimetal MOF-derived catalyst in initiating Fe3+/Fe2+ redox cycle to activate peroxymonosulfate for dibutyl phthalate degradation

Phthalic acid esters (PAEs) pose serious health risks to humans and are difficult to remove by conventional sewage treatment processes. Herein, Fe2Mo3O8/MoO2/Mo2N composite (FMON) derived from bimetallic organic framework was used to activate peroxymonosulfate (PMS) for dibutyl phthalate (DBP) degradation. FMON exhibited an excellent catalytic effect with DBP removal efficiency of 92.4 % within 60 min. Mo2N showed a superior ability in promoting Fe3+/Fe2+ redox cycle. The reduction efficiencies of Fe3+ by Mo2N/MoO2 composite and MoO2 were 67 %–94 % and 11 %–23 %, respectively, in the homogeneous comparative experiment. Moreover, the ratio of Fe2+/Fe3+ in FMON increased significantly after the catalytic reaction. Fe element doping also enhanced the reuse stability and reduced the metal ion leaching of the catalyst. The degradation of DBP was mediated by a variety of reactive species, of which SO4−, OH and O2− were dominant. Fe element, Mo element and O vacancies were confirmed to exert significant contributions as active sites in the catalytic process. Three degradation pathways of DBP were obtained by DFT calculation and HPLC-MS analysis. And the toxicity of DBP degradation products was significantly reduced based on the assessment result of Toxicity Estimation Software Tool (T.E.S.T.). This study explored a novel Fe/Mo bimetallic catalyst with friendly Fe3+/Fe2+ cycling for environmental catalysis and provided new ideas for the treatment of PAEs wastewater.

Inactivation of Salmonella enteritidis on the surface of eggs by air activated with gliding arc discharge plasma

Salmonella enteritidis, a Gram-negative foodborne pathogen, causes inflammation of the stomach and intestines. Poultry and poultry products are considered to be the main hosts of S. enteritidis, especially the most common edible eggs, and increase the risk of Salmonella infection. Therefore, developing the inactivation strategy of S. enteritidis on the surface of eggs is the key step during the egg production process. Gas plasma could effectively inactivate bacteria and fungi and is developed as a potential non-thermal sterilization method in the food industry. In this study, the plasma-activated air (PAA) prepared by the air activated with gliding arc discharge contained a variety of reactive species. When the PAA activated at the power of 50 W and 100 W was inducted into the incubation chamber, the numbers of S. enteritidis on egg fragments or the whole eggs were reduced below the detection limit. After PAA treatment, the eggshells exhibited no change in structure demonstrated by scanning electron microscope, the color of eggshells became a little decrease in red, the internal quality of both the raw egg and the cooked egg also exhibited no change, and trace reactive species remained in the albumen. Further, the PAA was also feasible for the batch treatment of stacked eggs. Therefore, this study supplied an effective and safe strategy for aseptic processing in the poultry industry.

The optimization of plasma activated water ( PAW ) generation and the inactivation mechanism of PAW on Escherichia coli

Plasma activated water (PAW) generated by nonthermal plasma, an acidified solution containing a variety of reactive species, has become a new decontamination approach because of its bactericidal ability. This study investigated the effects of various generation conditions of PAW on bactericidal activities against Escherichia coli and its physicochemical properties. PAW was prepared by ultrapure water with dielectric barrier discharge (DBD) plasma. The optimal generation condition of PAW was 30 min plasma activation time, 20 ml solution volume, 15.2 kV input voltage, and 5.5 kHz frequency operation. Under various mimicked liquid analytics, nitrate, nitrite, superoxide anion radicals, and strong acidification play significant roles in the antimicrobial properties of PAW. Therefore, these findings provide a basis for the PAW inactivation mechanism, and PAW can be a promising alternative to traditional sanitizers for food safety and preservation. Practical applications Plasma-activated water (PAW) is an emerging non-thermal technology that could be applied in the food industry. The liquid creates an acidic environment which results in changes of the redox potential, conductivity, and the formation of reactive oxygen and nitrogen species. As a result, PAW has different chemical composition than water and can serve as an alternative method for microbial disinfection. This study presents physicochemical properties and bactericidal effects of PAW under different generation conditions. Moreover, the inactivation mechanism of Escherichia coli by PAW was analyzed using various mimicked solutions. This investigation will help to have a better understanding of PAW technology and extend the potential applications in the agri-food industry in the future.

Inactivation of Shewanella putrefaciens by Plasma Activated Water

Plasma activated water (PAW) generated by atmospheric-pressure air microplasma arrays is a solution containing a variety of reactive species. Here we investigate the effects of different applied voltage and water-activated time on bactericidal activities against Shewanella putrefaciens (S. putrefaciens). Our measurements showed that the sterilization efficiency of S. putrefaciens by PAW could be up to 2.0 Log Reduction. Scanning electron microscopy image and DNA concentration measurement showed that the S. putrefaciens cells were damaged and deformed due to the PAW treatment. The physicochemical properties of PAW treated by different applied voltage and water-activated time were evaluated, including pH value, initial PAW temperature, and the concentrations of plasma-activated species, such as H2O2, NO 3 − , NO 2 − , and O3. Analysis indicates that the sterilization efficiency of S. putrefaciens treated by PAW was mainly determined by H2O2 concentration and pH value of PAW. This study provides a basis for the PAW potential applications in the disinfection of rotten food.

Combining cold physical plasma with pulsed electrical fields for cancer treatment

Pallation of end-stage melanoma and breast cancer patients is a challenge. Despite the generally successful use of electrochemotherapy (ECT) in these patients, response rates can still be improved. Previous studies demonstrated the anticancer potential of nano-second PEFs (nsPEFs), which are able to induce apoptosis [1] or nanopore formation when using different settings [2]. Likewise, the anticancer capacity of cold physical plasma has been demonstrated in various studies in cell lines and in xenograft tumors in mice [3-7]. The apoptotic effect of cold plasmas is mediated by a variety of reactive species being released onto the cells, where the species trigger redox signaling, and subsequent cell death in some instances [8, 9]. By contrast, PEFs act by a mechanism much less dependent on the newly generated reactive species. Our idea was to combine both treatments to improve palliative cancer treatment in the future. Malignant suspension cell lines were tested to investigate the proof of concept of additive or possible even synergistic cytotoxic effects. Plasma treatment time (kINPen) and PEF intensity as well as pulse length were varied to retrieve sublethal dosage regimens for each treatment. The sequence of combination (first plasma, then PEF or vice versa) was also modulated. To investigate the mode of action of both therapies, a number of cellular parameters were investigated. This included oxidation at cytosolic and membrane compartments, thiol content, mitochondrial depolarization, caspase activation and phosphatidylserine exposure, metabolic activity, cell membrane permeabilization, cell growth and morphology, and protection by antioxidants. Furthermore, we identified a synergistic effect of plasma and PEFs using tumorigenic adherent cells in preliminary tests.

Carbonylation in microflow: close encounters of CO and reactive species

Microreactors have brought significant improvements to chemical synthesis and production because of their advantageous characteristics over batch reactors, which include highly efficient mixing, efficient heat and mass transfer ability, precise control of the residence time, large surface area-to-volume ratio and high operational safety. Microreactor technology has been found to be beneficial for gas–liquid biphasic reactions, for which the large interfacial area between the two phases is ensured. Carbonylation reactions with carbon monoxide, by which a wide range of carbonyl compounds can be prepared, deal with a variety of reactive species, such as organo transition metals, radicals, cations and anions. These reactions have long been carried out using a glass batch flask or a stainless-steel made autoclave, however, carbonylation reactions using a flow microreactor are now rapidly increasing in popularity. This review focuses on a new greener wave of carbonylation reactions using a flow microreactor.

Evidence of homolytic and heterolytic pathways in the photodissociation of iminosulfonates and direct detection of the p-toluenesulfonyloxyl radical.

The mechanistic aspects of the photochemistry of several iminosulfonate photoacid generators (PAGs) have been studied based on product analysis, nanosecond laser flash photolysis, and determination of acid generation efficiencies. Our findings support a competition between homolytic and heterolytic N-O dissociation mechanisms. By measuring the efficiencies of acid generation for each PAG in the presence and absence of an ion quencher, we were able to roughly quantify the degree of branching between heterolytic and homolytic photocleavage pathways for each PAG. The p-toluenesulfonyloxyl radical was detected upon laser flash photolysis of several PAGs and was found to have a lambda(max) at 540 nm. By quenching the 540 nm transient with a variety of reactive species, the rate constants for reaction of the p-toluenesulfonyloxyl radical with these substrates were determined. The p-toluenesulfonyloxyl radical is shown to be a highly reactive species, which undergoes rapid hydrogen transfer and is a powerful oxidizer.

Wastewater treatment

Advanced oxidation processes (AOPs) are promising technologies for partial or complete mineralization of contaminants of emerging concern by highly reactive hydroxyl, hydroperoxyl, superoxide, and sulphate radicals. Detailed investigations and reviews have been reported for conventional AOP systems that have been installed in full-scale wastewater treatment plants. However, recent efforts have focused on the peroxymonosulphate, persulphate, catalytic ozonation, ultrasonication and hydrodynamic cavitation, gamma radiation, electrochemical oxidation, modified Fenton, and plasma-assisted AOPs. This critical review presents the detailed mechanisms of emerging AOP technologies, their performance for treatment of contaminants of emerging concern, the relative advantages and disadvantages of each technology, and the remaining challenges to scale-up and implementation. Among the evaluated technologies, the modified electrochemical oxidation, gamma radiation, and plasma-assisted systems demonstrated the greatest potential for successful and sustainable implementation in wastewater treatment due to their environmental safety, compatibility, and efficient transformation of contaminants of emerging concern by a variety of reactive species. The other emerging AOP systems were also promising, but additional scale-up trials and a deeper understanding of their reaction kinetics in complex wastewater matrices are necessary to determine the technical and economic feasibility of full-scale processes.

Zone-resolved mass spectroscopic study on RF plasma polymerization of styrene

The radiofrequency (rf) glow discharge plasma of styrene was investigated by direct sampling mass spectroscopy. Measurements were taken in three regions of the discharge : the plasma column and two dark zones before the electrodes. The plasma-polymerized styrene (PPS) thin films were analyzed by infrared spectroscopy (IR). The effects of monomer pressure and rf power on the ratios of mass peak heights C 4 H 2 + /C 4 H 3 + , C 6 H 6 + /C 6 H 5 CH=CH 2 + in the three discharge regions, the polymer deposition rate, and the polymeric structure of the PPS films were studied. It was found that in the different discharge regions and under various discharge conditions, a variety of reactive species were formed by electron impact on monomer molecules. The polymer deposition rate was mainly dependent on the total number of the reactive species produced in the discharge. The concentration of phenyl groups in PPS films was proportional to the relative concentration of phenyl ring-containing reactive species in the gas phase plasma.

Zone‐resolved mass spectroscopic study on RF plasma polymerization of styrene

The radiofrequency (rf) glow discharge plasma of styrene was investigated by direct sampling mass spectroscopy. Measurements were taken in three regions of the discharge: the plasma column and two dark zones before the electrodes. The plasma-polymerized styrene (PPS) thin films were analyzed by infrared spectroscopy (IR). The effects of monomer pressure and rf power on the ratios of mass peak heights C4H/C4H, C6H/C6H5()CH in the three discharge regions, the polymer deposition rate, and the polymeric structure of the PPS films were studied. It was found that in the different discharge regions and under various discharge conditions, a variety of reactive species were formed by electron impact on monomer molecules. The polymer deposition rate was mainly dependent on the total number of the reactive species produced in the discharge. The concentration of phenyl groups in PPS films was proportional to the relative concentration of phenyl ring-containing reactive species in the gas phase plasma. © 1996 John Wiley & Sons, Inc.

Thiols as potential UV radiation protectors: An in vitro study

The following thiols were investigated with regard to their possible UV-radiation protective properties: captopril, cysteamine, ergothioneine, mesna, mercaptopropionylglycine, N-acetylcysteine, and penicillamine. As a measure for protection, the inhibition of in vitro irreversible photobinding of the labeled phototoxic drugs chlorpromazine (CPZ) and 8-methoxypsoralen (8-MOP) to protein and DNA was used. Besides photobinding to biomacromolecules, the photodegradation of CPZ and the formation of promazine (PZH) and hydroxypromazine (PZOH) were measured as well. Because of the H-atom and electron donating capacity of the thiols, the ratio [PZOH]/[PZH] was expected to be decreased and the photodegradation of CPZ was expected to be higher in the presence of thiols. Maximum inhibition of CPZ photobinding ranged for the different thiols between 21–100% (DNA) and 17–87% (human serum albumin). All thiols enhanced the photodegradation of CPZ (19–84%) and inhibited the ratio [PZOH]/[PZH] (90–97%). 8-MOP photobinding to human serum albumin was also clearly inhibited (75–96%), but remarkably less to DNA (2–41%). This study indicates that thiols are able to cope with a variety of reactive species. Scavenging of radicals, quenching of singlet molecular oxygen species and reaction with excited states seem to be essential mechanisms involved with this process.