To provide a viable alternative for counter electrodes used in dye sensitized solar cells, polypyrrole (PPy) based films have been synthesized via electrochemical deposition in the presence of the ...ionic liquid 1-butyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imidate (NTf2) and incorporated with gold nanoparticles (Aunanop). The films were analyzed by SEM, UV-Vis-NIR, Raman, Electrochemical impedance spectroscopy, Cyclic voltammetry and Conductivity measurements. The presence of the ionic liquid is found to result in a more conductive film, to improve catalytic reduction of I3− and the electrochemical reversibility of the electrode. In addition to increase conductivity, impedance spectroscopy has shown that incorporating Aunanop in the PPy/NTf2 film helps improving the interfacial charge transportation, the electrocatalytic properties and solar energy conversion efficiency. DSSCs assembled with PPy based CE presented nearly the same J-V characteristic parameters as observed from conventional Pt based device.
A simple and low-cost method is proposed to synthesize graphene oxide incorporated with silver nanoparticles. The inter-sheet distance was controlled by introducing hexylamine into the graphene oxide ...sheets. The materials were investigated by Raman, UV-vis and Fourier transform infrared spectroscopy, X-ray diffraction and field-emission scanning electron microscopy. The increase in inter-sheet distance, due to the presence of hexylamine, favored the growth of the silver nanoparticles within the sheets. We demonstrate that silver nanoparticles increased the electrical conductivity and capacitive properties of the graphene oxide based electrode. The high concentration of well dispersed silver nanoparticles on the surface of the graphene sheets resulted in ca. 90 times higher specific capacitance than bare graphene oxide, in addition to improved electrochemical activity. The proposed method is promising for the development of hybrid materials with enhanced properties for applications mainly in electrochemical energy storage devices.
The optoelectronic properties of quantum dots are strongly controlled by the chemical nature of their surface-passivating ligands. In this work, we present the synthesis, characterization, and ...surface modification of CdSe quantum dots (QDs) and their application in solar cells. CdSe QDs were capped in oleic acid (OA), 3-mercaptopropionic acid (MPA), and 4-mercaptobenzoic acid (MBA). The QDs were characterized by transmission electron microscopy (TEM), UV-Vis absorption and emission spectrophotometry, thermogravimetric analyses, and 1H and 13C NMR. From TEM analysis, it has been observed that interparticle distance can be effectively controlled by the presence of different molecular size ligands. From the 1H and 13C NMR, specific types of interactions between the Cd2+ and the ligands have been observed. Although CdSe/OA presented larger interparticle distance as compared to CdSe/MPA and CdSe/MBA, the photocatalytic oxidation of the thiol groups on the surface of the MPA- and MBA-based quantum dots resulted in poor surface stabilization, ultimately resulting in poor power conversion efficiencies which were ca. 70% smaller than that of OA-based solar cell.
Herein, polypyrrole (PPy) films are prepared via electrochemical deposition in a mixture of 1- n -butyl-3-methylimidazolium methanesulfonate (BMI·CH 3 SO 3 ) ionic liquid (IL) and dodecyl sulfate ...(DS). The physico-chemical properties of the films have been investigated by a wide range of characterization techniques. PPy films synthesized in DS or IL have shown larger and irregular granules as compared to PPy films prepared in the mixture of DS and IL. This result is related to the preferential dissolution of pyrrole monomers in micelle templates formed by the IL and a co-assembly of IL and dodecyl-sulfate (DS), thereby decreasing the granule size and affecting the structural arrangement of the polymer chain. The template behavior of the IL in combination with DS promotes the selective formation of polaron and bipolaron states in the PPy films. This effect has been investigated by UV-Vis spectrophotometry, Raman spectroscopy, electrochemical impedance spectroscopy (EIS), cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrical conductivity measurements. The synergy of IL–DS has helped to decrease the resistivity of the PPy film from 2.17 × 10 2 Ω cm for PPy–IL to 2.44 Ω for PPy–IL–DS. EIS has also shown a decreased interfacial charge transfer resistance for PPy–IL–DS when compared to PPy–IL. The cyclic voltammetry curves have shown that the PPy films are electrocatalytically active for the I − /I 3 − redox reaction, and therefore, can be applied as a counter electrode (CE) in dye sensitised solar cells. The PPy based CEs resulted in nearly the same photocurrent and energy conversion efficiencies as that obtained from a conventional Pt CE.
Introduction
Hospital do Rim is a high‐volume kidney transplant (KT) center located in São Paulo, a city with 12.2 million inhabitants. Over the last 18 years, we performed 11 436 KT, 70% of which ...from deceased donors. To mitigate the effects of reduction in the number of transplants on the waiting list, sequential measures were implemented when COVID‐19 was declared pandemic.
Methods
The first step was to provide SARS‐COV‐2 RT‐PCR testing for all symptomatic employees and patients and the compulsory use of personal protective equipment in the hospital facilities. Living donor KT were postponed, and all deceased donors and recipients were tested before the transplantation. The immunosuppressive protocols were maintained, and telehealth strategies were developed.
Results
Among the 1013 employees, there were 214 cases of COVID‐19, nine required ward hospitalization, and no deaths occurred. In 26%, the probable source of contamination was occupational. From the first patient diagnosed with COVID‐19 in 03/20/2020 till 10/21/2020, 523 deceased KT were performed, a 21% increase compared with 2019, with no confirmed donor‐derived SARS‐CoV‐2 infection. Four patients were transplanted with a positive pretransplant SARS‐CoV‐2 test, but none of them developed the disease. Overall, of 11 875 KT followed in our center, 674 developed COVID‐19. Among the hospitalized, 53% required mechanical ventilation, and 45% required hemodialysis. Their overall mortality rate was 27.5%.
Conclusion
This experience shows the challenges that transplant centers faced as the pandemic unfolded and illustrates the effectiveness of the sequential measures implemented to provide a safe environment for transplantation.
•Effect of sulfur precursor on photocatalytic activity of MoS2.•Favored heterogeneous nucleation on defect sites.•Heterogeneous nucleation a fancy tool to evaluate density of active sites.
In the ...present work, we applied heterogeneous nucleation of gold nanoparticles to assess the density of defects on MoS2 nanostructures presenting different morphologies and surface areas. The use of L-cysteine resulted in the formation of flower-shaped MoS2 nanostructures with a diameter of about 300 nm and petals measuring around 30 nm. In contrast, when 3-mercaptopropionic acid was employed, it led to the formation of large agglomerates, here referred to as nanoclouds, with a diameter of approximately 500 nm. The nucleation of gold nanoparticles on defect sites of MoS2 suggested that MoS2 obtained from 3-mercaptopropionic acid has a higher content of active sites for hydrogen production compared to MoS2 obtained from L-cysteine.
Herein, polypyrrole (PPy) films are prepared
via
electrochemical deposition in a mixture of 1-
n
-butyl-3-methylimidazolium methanesulfonate (BMI·CH
3
SO
3
) ionic liquid (IL) and dodecyl sulfate ...(DS). The physico-chemical properties of the films have been investigated by a wide range of characterization techniques. PPy films synthesized in DS or IL have shown larger and irregular granules as compared to PPy films prepared in the mixture of DS and IL. This result is related to the preferential dissolution of pyrrole monomers in micelle templates formed by the IL and a co-assembly of IL and dodecyl-sulfate (DS), thereby decreasing the granule size and affecting the structural arrangement of the polymer chain. The template behavior of the IL in combination with DS promotes the selective formation of polaron and bipolaron states in the PPy films. This effect has been investigated by UV-Vis spectrophotometry, Raman spectroscopy, electrochemical impedance spectroscopy (EIS), cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrical conductivity measurements. The synergy of IL-DS has helped to decrease the resistivity of the PPy film from 2.17 × 10
2
Ω cm for PPy-IL to 2.44 Ω for PPy-IL-DS. EIS has also shown a decreased interfacial charge transfer resistance for PPy-IL-DS when compared to PPy-IL. The cyclic voltammetry curves have shown that the PPy films are electrocatalytically active for the I
−
/I
3
−
redox reaction, and therefore, can be applied as a counter electrode (CE) in dye sensitised solar cells. The PPy based CEs resulted in nearly the same photocurrent and energy conversion efficiencies as that obtained from a conventional Pt CE.
Herein, polypyrrole films are prepared
via
electrochemical deposition in a mixture of 1-
n
-butyl-3-methylimidazolium methanesulfonate ionic liquid and dodecy sulfate.
Ionic silsesquioxane-capped gold nanoparticle powders presenting narrow size distribution were synthesised, characterised and applied in the assembly of organic solar cells. The assembled devices ...were electrically modelled, and the nanoparticles encapsulated with a charged pendant silsesquioxane were found to provide enhanced photocurrent, and to result in better electrical properties than those capped with bridged double-charged silsesquioxane. Therefore, thinner layers of encapsulation result in higher efficiency.
Purpose
Gastrointestinal mucositis is a major problem associated with cancer therapy. To minimize these deleterious effects, simultaneous administration of antioxidant components, such as selenium, ...can be considered. There is a growing interest in the use of yeasts because they are able to convert inorganic selenium into selenomethionine. In the present study, oral administration of
Saccharomyces cerevisiae
UFMG A-905 enriched with selenium was evaluated as an alternative in minimizing the side effects of 5FU-induced mucositis in mice.
Methods
Mice body weight, food consumption, faeces consistency and the presence of blood in faeces were assessed daily during experimental mucositis induced by 5-fluorouracil (5FU). Blood was used for intestinal permeability determination, and small intestine for oxidative stress, immunological and histopathological examination.
Results
The increased intestinal permeability observed with mucositis induction was partially reverted by
S
.
cerevisiae
and selenium-enriched yeast. Both treatments were able to reduce myeloperoxidase activity, but only selenium-enriched yeast reduced eosinophil peroxidase activity. CXCL1/KC levels, histopathological tissue damage and oxidative stress (lipid peroxidation and nitrite production) in the small intestine were reduced by both treatments; however, this reduction was always higher when treatment with selenium-enriched yeast was evaluated.
Conclusions
Results of the present study showed that the oral administration of
S. cerevisiae
UFMG A-905 protected mice against mucositis induced by 5-FU, and that this effect was potentiated when the yeast was enriched with selenium.
Butyrate is a four-carbon short-chain fatty acid that improves colonic trophism. Although several studies have shown the benefits of butyrate enemas in ulcerative colitis (UC), studies using the oral ...route are rare in the literature. In the present study, we evaluated the effect of butyrate intake in the immune response associated to UC. For that, mice were fed control or butyrate (0.5% sodium butyrate) diets for 14 days. Acute UC was induced by dextran sulphate sodium (DSS, 2.5%), replacing drinking water. The results showed that, in UC animals, oral butyrate significantly improved trophism and reduced leukocyte (eosinophil and neutrophil) infiltration in the colon mucosa and improved the inflammatory profile (activated macrophage, B and T lymphocytes) in cecal lymph nodes. In the small intestine, although mucosa histology was similar among groups, DSS treatment reduced duodenal transforming growth factor-β, increased interleukin-10 concentrations and increased memory T lymphocytes and dendritic cells in Peyer's patches. Butyrate supplementation was able to revert these alterations. When cecal butyrate concentration was analyzed in cecal content, it was still higher in the healthy animals receiving butyrate than in the UC+butyrate and control groups. In conclusion, our results show that oral administration of sodium butyrate improves mucosa lesion and attenuates the inflammatory profile of intestinal mucosa, local draining lymph nodes and Peyer's patches of DSS-induced UC. Our results also highlight the potential use of butyrate supplements as adjuvant in UC treatment.
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