The modified TiO
2
nanoparticles (NPs) to enhance their catalytic activities by doping them with the five transition metals (Cr, Mn, Fe, Co, and Ni) have been investigated using various surface ...analysis techniques such as scanning electron microscopy (SEM), Raman spectroscopy, scanning transmission X-ray microscopy (STXM), and high-resolution photoemission spectroscopy (HRPES). To compare catalytic activities of these transition metal-doped TiO
2
nanoparticles (TM-TiO
2
) with those of TiO
2
NPs, we monitored their performances in the catalytic oxidation of 2-aminothiophenol (2-ATP) by using HRPES and on the oxidation of 2-ATP in aqueous solution by taking electrochemistry (EC) measurements. As a result, we clearly investigate that the increased defect structures induced by the doped transition metal are closely correlated with the enhancement of catalytic activities of TiO
2
NPs and confirm that Fe- and Co-doped TiO
2
NPs can act as efficient catalysts.
Despite advances in the preparation of metal oxide (MO) nanoparticles (NPs) as catalysts for various applications, concerns about the biosafety of these particles remain. In this study, we prepared ...transition metal-doped cerium oxide (TM@CeO2; TM = Cr, Mn, Fe, Co, or Ni) nanoparticles and investigated the mechanism underlying dopant-dependent toxicity in HaCaT human keratinocytes. We show that doping with Cr or Co but not Fe, Mn, or Ni increased the toxicity of CeO2 NPs in dose- and time-dependent manners and led to apoptotic cell death. Interestingly, while both undoped and transition metal-doped NPs increased intracellular reactive oxygen species (ROS), toxic Cr@CeO2 and Co@CeO2 NPs failed to induce the expression of NRF2 (nuclear factor erythroid 2-related factor 2) as well as its downstream target genes involved in the antioxidant defense system. Moreover, activation of NRF2 transcription was correlated with dynamic changes in H3K4me3 and H3K27me3 at the promoter of NRF2, which was not observed in cells exposed to Cr@CeO2 NPs. Furthermore, exposure to relatively non-toxic Fe@CeO2 NPs, but not the toxic Cr@CeO2 NPs, resulted in increased binding of MLL1 complex, a major histone lysine methylase mediating trimethylation of histone H3 lysine 4, at the NRF2 promoter. Taken together, our findings strongly suggest that failure of cells to respond to oxidative stress is critical for dopant-dependent toxicity of CeO2 NPs and emphasize that careful evaluation of newly developed NPs should be preceded before industrial or biomedical applications.
Cu/ZnO/Al2O3 is an industrially important heterogeneous catalyst for the conversion of CO2 to methanol, which is in worldwide demand, and for the solution of the activation mechanism of catalytically ...inactive CO2. Recent studies have achieved numerous improvements in active sites of catalysts for this process, which can be described as “active copper with step sites” decorated with ZnO x . In spite of these improvements, the mechanism of this process is still unknown, and even its initial stage remains unclear. In this study, we simplified the catalytic system to bare Cu(111) and Cu(775) surfaces in order to systematically determine the mechanistic effects of step sites. The reaction was conducted by using a CO2/H2 gas mixture at 1 Torr at various temperatures and characterized with infrared reflection absorption spectroscopy (IRRAS). The initial activation of CO2 was found to occur only with the coadsorption of hydrogen; it cannot on its own be converted into other activated species. This coadsorbed hydrogen induces the dissociation of CO2 and converts it into CO, surface oxygen (O*), and surface hydroxyl (HO*). These species are subsequently converted to carbonate (CO3*), bicarbonate (HCO3*), and formate (HCOO*). One significant observation is that the number of these formate species on step sites continuously decreases with increases in the number of CH2 species during stepwise heating. In addition, a continuous reaction is obtained from formate transfer from terrace to step. Also, an instantaneous feature of methoxy (CH3O*) was observed during the evacuation process. These phenomena strongly indicate that formate is an essential intermediate, especially on steps, for the conversion of CO2 to methanol and that the reduction in its level during this process is due to step-by-step hydrogenation.
Cerebral venous thrombosis (CVT) is a rare type of venous thromboembolism (VTE). It is an important cause of stroke in young adults and children. Severe CVT, which is characterized by cerebral venous ...infarction or hemorrhage, seizures, or disturbance of consciousness, has more severe clinical manifestations and a worse prognosis. It is commonly believed that the onset of severe CVT gave credit to venous return disorder, with the underlying pathogenesis remaining unclear. There is increasing evidence suggesting that an inflammatory response is closely associated with the pathophysiology of severe CVT. Preclinical studies have identified the components of neuroinflammation, including microglia, astrocytes, and neutrophils. After CVT occurrence, microglia are activated and secrete cytokines (e.g., interleukin-1β and tumor necrosis factor-α), which result in a series of brain injuries, including blood-brain barrier disruption, brain edema, and cerebral venous infarction. Additionally, astrocytes are activated at the initial CVT stage and may interact with microglia to exacerbate the inflammatory response. The extent of cerebral edema and neutrophil recruitment increases temporally in the acute phase. Further, there are also changes in the morphology of inflammatory cells, expression of inflammatory mediators, and inflammatory pathway molecules with CVT progression. Lately, some clinical research suggested that some inflammation-related biomarkers are of great value in assessing the course, severity, and prognosis of severe CVT. Moreover, basic and clinical research suggested that anti-inflammatory therapy might hold promise in severe CVT. This study reviews the current literature regarding the involvement of inflammation in the pathophysiology and anti-inflammatory interventions of severe CVT, which would contribute to informing the pathophysiology mechanism and laying a foundation for exploring novel severe CVT therapeutic strategies.
While reduced graphene oxide (rGO) is used widely as a catalyst, its catalytic activity can be improved significantly by modifying it with a metal. In this study, we compared the photocatalytic and ...catalytic properties of base-treated rGO particles and transition-metal-ion-doped rGO based on the oxidation reaction of thiophenol and the photocatalytic degradation of 4-chlorophenol. Since the two catalytic activities are related to the changes in the electronic structure of rGO, X-ray photoemission spectroscopy, X-ray absorption spectroscopy, and Raman spectroscopy were performed. When rGO was doped with Mn2+ ions, its catalytic properties improved with respect to both reactions. The changes in the electronic structure of rGO are attributed to the formation of defect structures on the rGO surface via a reaction between the doped Mn2+ ions and oxygen of the rGO surface. Thus, the results show that the doping of rGO with Mn ions in the +2-charge state (stable oxide form: MnO) enhances its catalytic and photocatalytic activities. Hence, this study provides new insights into the use of defect-controlled rGO as a novel catalyst.
Chemically modified epitaxial graphene (EG) by azidotrimethylsilane (ATS) was investigated using high-resolution photoemission spectroscopy (HRPES). Through the spectral analysis, we clearly ...confirmed that EG is modified by thermally generated nitrene radicals and found that the bonding nature between the nitrene radicals and EG is covalent. As we observe bonding nature of N 1s peaks, we found that two distinct N peaks can be clearly distinguished in the spectra. Using a covalently bound stretched graphene (CSG) model, we elucidated that nitrene radicals adsorb on the graphene layer at two different adsorption sites. Moreover, we were able to control the band gap of EG using valence band spectra as we change the amount of the dosing of nitrene.
The magnetic and structural properties of a series of VxCo1−x alloy films prepared in a variety of compositions on a W(110) surface were investigated using spin-resolved photoemission spectroscopy ...(SRPES) and low-energy electron diffraction (LEED) measurements. The epitaxial structures of the films were preserved over all V concentrations, despite the observation of a structural phase transition (SPT: hcp/bcc at x = 0.38), which was apparent from the LEED images. A magnetic phase transition (MPT) from ferromagnetic to paramagnetic occurred in the Co-rich region at x = 0.38. The SPT (from hcp and bcc) and MPT (from ferromagnetic to paramagnetic) were clearly correlated at x = 0.38, possibly due to changes in the electronic and magnetic structures of the valence band, as monitored by SRPES and LEED. The magnetization in the VxCo1−x alloy films on a W(110) surface varied systematically with the V concentration, and correlations between the structural changes and magnetic properties were revealed using SRPES and LEED.
► We have investigated the epitaxial VxCo1−x alloy films grown on a W(110) surface. ► At V concentration of 38%, the films undergo the hcp-to-bcc structural transition. ► This transition is accompanied by a profound modification of the valence states. ► Magnetic phase transition and structural phase transition are closely correlated.
While it is well-known that pre-stroke exercise conditioning reduces the incidence of stroke and the development of comorbidities, it is unclear whether post-stroke exercise conditioning is also ...neuroprotective. The present study investigated whether exercise postconditioning (PostE) induced neuroprotection and elucidated the involvement of SIRT1 regulation on the ROS/ER stress pathway. Adult rats were subjected to middle cerebral artery occlusion (MCAO) followed by either: (1) resting; (2) mild exercise postconditioning (MPostE); or (3) intense exercise postconditioning (IPostE). PostE was initiated 24 h after reperfusion and performed on a treadmill. At 1 and 3 days thereafter, we determined infarct volumes, neurological defects, brain edema, apoptotic cell death through measuring pro- (BAX and Caspase-3) and anti-apoptotic (Bcl-2) proteins, and ER stress through the measurement of glucose-regulated protein 78 (GRP78), inositol-requiring 1α (IRE1α), protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP homologous protein (CHOP), Caspase-12, and SIRT1. Proteins were measured by Western blot. ROS production was detected by flow cytometry.Compared to resting rats, both MPostE and IPostE significantly decreased brain infarct volumes and edema, neurological deficits, ROS production, and apoptotic cell death. MPostE further increased Bcl-2 expression and Bcl-2/BAX ratio as well as BAX and Caspase-3 expressions and ROS production (*
< 0.05). Both PostE groups saw decreases in ER stress proteins, while MPostE demonstrated a further reduction in GRP78 (***
< 0.001) and Caspase-12 (*
< 0.05) expressions at 1 day and IRE1α (**
< 0.01) and CHOP (*
< 0.05) expressions at 3 days. Additionally, both PostE groups saw significant increases in SIRT1 expression.In this study, both mild and intense PostE levels induced neuroprotection after stroke through SIRT1 and ROS/ER stress pathway. Additionally, the results may provide a base for our future study regarding the regulation of SIRT1 on the ROS/ER stress pathway in the biochemical processes underlying post-stroke neuroprotection. The results suggest that mild exercise postconditioning might play a similar neuroprotective role as intensive exercise and could be an effective exercise strategy as well.
Catalytic activities of transition metal-doped IrO2 nanoparticles (TM-IrO2 NPs; TM = Cr, Mn, Fe, Co, or Ni) are compared for various oxidation reactions such as electrochemical oxygen evolution ...reaction (OER), gas-phase photo-oxidation of thiol function group, and CO oxidative conversion. Here, we discovered a series of TM-IrO2 catalysts have a common activity trend for these oxidation reactions, and their activities are closely related with modified electronic states of IrO2, strongly affected by the types of the transition metal across the periodic table. For all oxidation reactions, Cr- and Mn-IrO2 achieved the highest oxidation catalytic activity, and sequentially decreased activities were obtained with Fe, Co, and Ni doped IrO2. For instance, the highest OER activity was achieved by Cr or Mn doping exhibiting the smallest overpotential η = 275~230 mV at 10 mA/cm2, while Ni-IrO2 showed rather larger overpotential (η = 347 mV) even compared with non-doped IrO2 (η = 314 mV). Scanning transmission X-ray microscopy and high-resolution photoemission spectra of TM-IrO2 indicated dopant metals modified the Ir-O interaction and thus increasing oxygen vacancy defects in IrO2. Strongly positive correlation was observed between the catalytic activities and vacancy states. The amount of defect related signals was observed the most for Cr- or Mn-IrO2, less so for Fe- or Co-IrO2, and unnoted for Ni-IrO2 compared with bare IrO2. Based on these catalytic activities and surface spectroscopic analysis results, vacancy defects induced by doping in TM-IrO2 NPs are proposed to contribute to enhance the oxidation activities.
Stroke is one of the leading causes of mortality and morbidity worldwide, and yet, current treatment is limited to thrombolysis through either t-PA or mechanical thrombectomy. While therapeutic ...hypothermia has been adopted in clinical contexts such as neuroprotection after cardiac resuscitation and neonatal hypoxic-ischemic encephalitis, it is yet to be used in the context of ischemic stroke. The lack of ameliorative effect in ischemic stroke patients may be tied to the delayed cooling induction onset. In the trials where the cooling was initiated with significant delay (mostly systemic cooling methods), minimal benefit was observed; on the other hand, when cooling was initiated very early (mostly selective cooling methods), there was significant efficacy. Another timing factor that may play a role in amelioration may be the onset of cooling relative to thrombolysis therapy. Current understanding of the pathophysiology of acute ischemic injury and ischemia-reperfusion injury suggests that hypothermia before thrombolysis may be the most beneficial compared to cooling initiation during or after reperfusion. As many of the systemic cooling methods tend to require longer induction periods and extensive, separate procedures from thrombolysis therapy, they are generally delayed to hours after recanalization. On the other hand, selective cooling was generally performed simultaneously to thrombolysis therapy. As we conduct and design therapeutic hypothermia trials for stroke patients, the key to their efficacy may lie in quick and early cooling induction, both respective to the symptom onset and thrombolysis therapy.
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