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1.
Acta Anaesthesiol Scand ; 68(1): 51-55, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37795808

RESUMO

INTRODUCTION: Gautier et al. demonstrated that a compression in the left paratracheal region (left paratracheal pressure, LPP) can be used to seal the oesophagus. However, at this level, the left common carotid artery is very close to the carotid that could be affected during the manipulation. This study aimed to assess the hemodynamic effects of LPP on the carotid blood flow. METHODS: We prospectively included 47 healthy adult volunteers. We excluded pregnant women and people with anomalies of the carotid arteries. The common and internal carotid arteries were preliminarily studied with ultrasounds to exclude atheromatous plaques or vascular malformation. A planimetry of the common and internal carotid arteries was performed. Doppler echography served to measure the peak systolic (PSV) and end-diastolic velocities (EDV) in the common and internal carotid arteries. All measurements were repeated while applying LPP. RESULTS: Forty-seven participants were enrolled (32 women; mean [SD] age: 42 [13] years). The mean PSV difference [95% CI] in the left common carotid artery before and after LPP at the group level was -15.30 [-31.09 to 0.48] cm s-1 (p = .14). The mean surface difference [95% CI] in the left common carotid artery before and after LPP was 24.52 [6.11-42.92] mm2 (p = .11). Similarly, the same surface at the level of the left internal carotid artery changed by -18.89 [-51.59 to 13.80] mm2 after LPP (p = .58). CONCLUSIONS: Our results suggest that LPP does not have a significant effect on carotid blood flow in individuals without a carotid pathology. However, the safety of the manoeuvre should be evaluated in patients at risk of carotid anomalies.


Assuntos
Estenose das Carótidas , Adulto , Humanos , Feminino , Velocidade do Fluxo Sanguíneo , Artérias Carótidas , Artéria Carótida Interna/diagnóstico por imagem , Artéria Carótida Primitiva/diagnóstico por imagem , Artéria Carótida Primitiva/fisiologia , Hemodinâmica
2.
Dalton Trans ; 52(45): 16927-16934, 2023 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-37927125

RESUMO

Pure micro- and nanocrystalline powders of the layered-kagome zinc orthovanadate BaZn3(VO4)2(OH)2 have been successfully prepared and thoroughly characterised. Microstructured samples (BaZn3-MPs) have been produced by hydrothermal reaction using synthetic martyite Zn3V2O7(OH)2·2H2O as the starting reagent. Nanoparticles (NPs) with an average size of ≈ 60 nm (BaZn3-NPs-7h) or ≈ 50 nm (BaZn3-NPs-25min) have been obtained by using a coprecipitation method at ambient pressure, and by varying the stirring time. Rietveld refinements of X-ray diffraction data indicate that micro- and nanostructured BaZn3(VO4)2(OH)2 both crystallize in a R3̄m structure very similar to that of the known layered-kagome compound BaCo3(VO4)2(OH)2. Transmission electron microscopy observation of BaZn3-NPs-7h and BaZn3-NPs-25min reveals crystallized NPs with homogenous distributions of Ba, Zn, and V elements. FT-IR and Raman spectra show subtle differences between micro- and nanostructured samples which cannot be linked to any differences in the average crystal structures. The high resolution 51V MAS NMR spectrum of BaZn3-MPs shows a single isotropic line attributed to VO43- groups with C3v point group. The spectra of the nanostructured samples reveal the presence of a weak additional signal which decreases in intensity with increasing the NPs size, and which has been tentatively assigned to the presence at the surface of the NPs of a small amount of V5+ ions in a different chemical environment. Nanostructuring also impacts the optical properties of BaZn3(VO4)2(OH)2. The UV-vis absorption spectra of NPs exhibit an additional weak transition in the visible domain which is not observed for the microstructured sample.

3.
Anaesth Crit Care Pain Med ; 42(6): 101269, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37364852

RESUMO

INTRODUCTION: Spinal anesthesia with intrathecal morphine (ITM) is a common anesthesia technique for cesarean delivery. The hypothesis was that the addition of ITM will delay micturition in women undergoing cesarean delivery. METHODS: Fifty-six ASA physical status I and II women scheduled to undergo elective cesarean delivery under spinal anesthesia were randomized to the PSM group (50 mg prilocaine + 2.5 mcg sufentanil + 100 mcg morphine; n = 30) or PS group (50 mg prilocaine + 2.5 mcg sufentanil; n = 24). The patients in the PS group received a bilateral transverse abdominal plane (TAP) block. The primary outcome was the effect of ITM on the time to micturition and the secondary outcome was the need for bladder re-catheterization. RESULTS: The time to first urge to urinate (8 [6-10] hours in the PSM group versus 6 [4-6] hours in the PS group) and the time to first micturition (10 [8-12] hours in the PSM group versus 6 [6-8] hours in the PS group) were significantly (p < 0.001) prolonged in the PSM group. Two patients in the PSM group met the 800 mL criterium for urinary catheterization after 6 and 8 h respectively. CONCLUSION: This study is the first randomized trial to demonstrate that the addition of ITM to the standardized mixture of prilocaine and sufentanil significantly delayed micturition.


Assuntos
Morfina , Sufentanil , Gravidez , Humanos , Feminino , Bexiga Urinária , Analgésicos Opioides , Dor Pós-Operatória , Prilocaína , Método Duplo-Cego
4.
Blood Purif ; 52(1): 91-100, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-35793661

RESUMO

INTRODUCTION: Different techniques of guidewire exchange of tunneled catheters for hemodialysis (HD) have been reported. This study was carried out to assess the feasibility of a new procedure in chronic HD patients who needed catheter exchange because of mechanical dysfunction. METHODS: The guidewire exchange method was based on the creation of a new exit site and a new subcutaneous tunnel while using the same venous insertion site. This was a retrospective study of exchanged tunneled catheters because of mechanical complications in patients on chronic HD between June 1, 2015, and December 31, 2019. The feasibility of the procedure was defined by successful exchange and catheter patency at 6 months. Catheter survival and immediate complications were reported. RESULTS: A total of 49 procedures were performed in 34 HD patients. There was no catheter insertion failure. At 6 months, 6 catheters have lost their patency because of a mechanical complication. Thus, the success rate of the procedure was 43/49 (87.8%). Catheter survival censored on death, transplantation, or vascular access creation was 97.8% at 90 days, 86.2% at 180 days, and 74.5% at 1 year. The median catheter survival was 10.2 months. Among the 49 procedures, there were 9 hematomas at the insertion site that did not require surgical intervention. Discussion/Conlusion: Our study shows that guidewire exchange of a tunneled HD catheter by creating a new exit site and a new subcutaneous tunnel by using the same venous access is a newer method in chronic HD patients. This procedure should not be used in patients with coagulation issues. Additional studies are needed to compare the different methods of HD catheter exchange.


Assuntos
Cateterismo Venoso Central , Humanos , Cateterismo Venoso Central/efeitos adversos , Projetos Piloto , Cateteres de Demora/efeitos adversos , Estudos Retrospectivos , Resultado do Tratamento , Diálise Renal/efeitos adversos
5.
ACS Appl Mater Interfaces ; 14(47): 52715-52728, 2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36394288

RESUMO

Silicon-containing Li-ion batteries have been the focus of many energy storage research efforts because of the promise of high energy density. Depending on the system, silicon generally demonstrates stable performance in half-cells, which is often attributed to the unlimited lithium supply from the lithium (Li) metal counter electrode. Here, the electrochemical performance of silicon with a high voltage NMC622 cathode was investigated in superconcentrated phosphonium-based ionic liquid (IL) electrolytes. As a matter of fact, there is very limited work and understanding of the full cell cycling of silicon in such a new class of electrolytes. The electrochemical behavior of silicon in the various IL electrolytes shows a gradual and steeper capacity decay, compared to what we previously reported in half-cells. This behavior is linked to a different evolution of the silicon morphology upon cycling, and the characterization of cycled electrodes points toward mechanical reasons, complete disconnection of part of the electrode, or internal mechanical stress, due to silicon and Li metal volume variation upon cycling, to explain the progressive capacity fading in full cell configuration. An extremely stable solid electrolyte interphase (SEI) in the full Li-ion cells can be seen from a combination of qualitative and quantitative information from transmission electron microscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and magic angle spinning nuclear magnetic resonance. Our findings provide a new perspective to full cell interpretation regarding capacity fading, which is oftentimes linked almost exclusively to the loss of Li inventory but also more broadly, and provide new insights into the impact of the evolution of silicon morphology on the electrochemical behavior.

6.
Nanomaterials (Basel) ; 12(18)2022 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-36144959

RESUMO

In the present study, MoO3:MoS2 hybrid thin layers have been synthesized through partial oxidation of MoS2. We have demonstrated that the reaction requires darkness conditions to decrease the oxidation rate, thus obtaining the hybrid, MoO3:MoS2. A simple liquid-phase exfoliation (LPE) is carried out to achieve homogenous MoS2 nanoflakes and high reproducibility of the results after MoS2 oxidation. XPS analyses reveal the presence of MoO3, MoS2, and MoOxSy in the hybrid layer. These results are also confirmed by X-ray diffraction and high-resolution TEM. Optical absorbance reveals that the absorption peaks of the MoO3:MoS2 hybrid are slightly redshifted with the appearance of absorption peaks in the near-infrared region due to the defects created after the oxidation reaction. The composition and atomic percentages of each component in the hybrid layer as a function of reaction time have also been reported to give perspective guides for improving electronic and optoelectronic devices based on 2D-MoS2.

7.
Inorg Chem ; 61(24): 9308-9317, 2022 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-35679597

RESUMO

Interest in coordination compounds based on non-innocent ligands (NILs) for electrochemical energy storage has risen in the last few years. We have focused our attention on an overlooked redox active linker, croconate violet, which has not yet been addressed in this field although closely related to standard NILs such as catecholate and tetracyanoquinodimethane. Two anionic complexes consisting of Fe(II) and croconate violet (-2) with balancing potassium cations were isolated and structurally characterized. By a combination of in situ and ex situ techniques (powder and single-crystal X-ray diffraction, infrared, and 57Fe Mössbauer spectroscopies), we have shown that their dehydration occurs through complex patterns, whose reversibility depends on the initial crystal structure but that the structural rearrangements around the iron cations occur without any oxidation. While electrochemical studies performed in solution clearly show that both the organic and inorganic parts can be reversibly addressed, in the solid state, poor charge storage capacities were initially measured, mainly due to the solubilization of the solids in the electrolyte. By optimizing the formulation of the electrode and the composition of the electrolyte, a capacity of >100 mA h g-1 after 10 cycles could be achieved. This suggests that this family of redox active linkers deserves to be investigated for solid-state electrochemical energy storage, although it requires the solving of the issues related to the solubilization of the derived coordination compounds.

8.
Blood Purif ; 51(6): 540-547, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34404044

RESUMO

INTRODUCTION: In low-flow home daily dialysis (HDD), the dialysis dose is evaluated from the total body water (TBW). TBW can be estimated by anthropometric methods or bioimpedance spectroscopy. METHODS: A multicentric cross-sectional study of patients in HDD for >3 months was conducted to assess the correlation and the difference between the anthropometric estimate of TBW (Watson-TBW) and the bioimpedance estimate (BIS-TBW) and to analyse the impact on the dialysate volume prescribed. RESULTS: Forty patients from 10 centres were included. The median BIS-TBW and Watson-TBW were 35.1 (29.1-41.4 L) and 36.9 (32-42.4 L), respectively. The 2 methods had a good correlation (r = 0.87, p < 0.05). However, Bland-Altman analysis showed an overestimation of TBW with Watson's formula, with a bias of 2.77 L. For 4, 5, or 6 sessions per week, the use of Watson-TBW increases the dialysate prescription per week by 100 L, 45 L, or 10 L, respectively, over our entire cohort. There is no increase in the volume of dialysate prescribed with the 7 sessions per week schedule. CONCLUSION: BIS-TBW and Watson-TBW estimation have a good correlation; however, Watson's equation overestimates TBW. This overestimation is negligible for a prescription frequency of >5 sessions per week.


Assuntos
Água Corporal , Diálise Renal , Composição Corporal , Estudos Transversais , Soluções para Diálise , Impedância Elétrica , Hemodiálise no Domicílio , Humanos
9.
Nephrol Ther ; 18(5S1): 5S2-5S11, 2022 Dec.
Artigo em Francês | MEDLINE | ID: mdl-36754524

RESUMO

Dialysis is a restrictive treatment with a significant impact on the quality of life of patients. Home hemodialysis (HHD) allows to maintain quality of life while improving the conditions of purification, in particular with the daily or even nocturnal practice of hemodialysis. The arrival of systems with a cycler in the 2010s for home hemodialysis brings a new dynamism for this type of technique. The practice with dialysate low flow with the optimization of storage space, the simplification of the use of generators and the emmergence of telemonitoring tools increases the accessibility of this dialysis technique, so that we can hope in the coming years to be able to offer this dialysis modality to any patient with chronic renal failure requiring extra-renal purification. ©2022 Société francophone de néphrologie, dialyse et transplantation. Published by Elsevier Masson SAS. All rights reserved.


Assuntos
Falência Renal Crônica , Insuficiência Renal Crônica , Humanos , Hemodiálise no Domicílio/métodos , Qualidade de Vida , Falência Renal Crônica/terapia , Diálise Renal , Insuficiência Renal Crônica/terapia
10.
ACS Appl Mater Interfaces ; 13(24): 28281-28294, 2021 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-34114808

RESUMO

The latest advances in the stabilization of Li/Na metal battery and Li-ion battery cycling have highlighted the importance of electrode/electrolyte interface [solid electrolyte interphase (SEI)] and its direct link to cycling behavior. To understand the structure and properties of the SEI, we used combined experimental and computational studies to unveil how the ionic liquid (IL) cation nature and salt concentration impact the silicon/IL electrolyte interfacial structure and the formed SEI. The nature of the IL cation is found to be important to control the electrolyte reductive decomposition that influences the SEI composition and properties and the reversibility of the Li-Si alloying process. Also, increasing the Li salt concentration changes the interface structure for a favorable and less resistive SEI. The most promising interface for the Si-based battery was found to be in P1222FSI with 3.2 m LiFSI, which leads to an optimal SEI after 100 cycles in which LiF and trapped LiFSI are the only distinguishable lithiated and fluorinated products detected. This study shows a clear link between the nanostructure of the IL electrolyte near the electrode surface, the resulting SEI, and the Si negative electrode cycling performance. More importantly, this work will aid the rational design of Si-based Li-ion batteries using IL electrolytes in an area that has so far been neglected, reinforcing the benefits of superconcentrated electrolyte systems.

11.
Eur J Pain ; 25(4): 924-929, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33394524

RESUMO

BACKGROUND: Massive screening campaigns for SARS-CoV-2 are currently carried out throughout the world, relying on reverse-transcriptase-polymerase chain reaction (RT-PCR) following nasopharyngeal swabbing performed by a healthcare professional. Yet, due to the apprehension of pain induced by nasopharyngeal probing, poor adhesion to those screening campaigns can be observed. To enhance voluntary participation and to avoid unnecessary exposition to SARS-CoV-2, self-swabbing could be proposed. To date, no data have been published concerning pain induced by conventional- or self-swabbing. Thus, the primary objective of the present study was to evaluate pain induced with the conventional swabbing method and compare it to self-swabbing. Secondary objectives focused on swabbing-induced discomfort and acceptability of the two methods. METHODS: The study was conducted in Clermont-Ferrand medical school (France). Overall, 190 students were randomised into two groups and experienced either self- or conventional-swabbing. Each subject had to rate pain, discomfort and acceptability of such swabbing on a 0-10 numeric rating scale. RESULTS: No significant difference was found between the two methods. The mean pain level was 2.5 ± 1.9, 28% rating pain as ≥4/10. Discomfort was 4.8 ± 2.2, 66% indicating significant (≥4/10) discomfort. Higher pain and discomfort were associated with female sex. Acceptability was ≥8/10 for 89.0% of the subjects and all would have accepted to undergo a new test with the same technique if necessary. CONCLUSION: Both conventional and self-swabbing induce low levels of pain for most young healthy volunteers whereas discomfort is very frequent. Nonetheless, both methods are indifferently well-accepted in medical students. Future studies amongst symptomatic subjects are awaited. SIGNIFICANCE: Using the thinnest available swabs, procedural pain induced by nasopharyngeal swabbing for SARS-CoV-2 screening is very low for most subjects and should not limit voluntary participation in screening campaigns. Self-swabbing does not lead to more pain or discomfort compared to conventional swabbing, is well-accepted, and could be proposed to optimize screening campaigns, at least in healthcare professionals.


Assuntos
COVID-19 , SARS-CoV-2 , Feminino , França , Pessoal de Saúde , Humanos , Dor/diagnóstico
13.
Nephrol Ther ; 16(2): 124-135, 2020 Mar.
Artigo em Francês | MEDLINE | ID: mdl-31928955

RESUMO

Hypocomplementemic urticarial vasculitis is a rare systemic vasculitis, affecting small vessels, characterised by chronicle urticaria, hypocomplementemia, and systemic manifestations. Renal involvement, whose prevalence varies between 9% and 60%, is mainly glomerular. We here report the case of a 59 years old woman presenting kidney failure, associated with chronicle urticaria and arthralgias. Laboratory investigation showed haematuria, proteinuria, hypocomplementemia and anti-SSa antibody positivity. A percutaneous kidney biopsy revealed focal and segmental glomerulonephritis associated with an acute interstitial nephritis. Hypocomplementemic urticarial vasculitis diagnosis was established after identifying anti-C1q antibodies. The lack of a dry syndrome, the negativity of a Schirmer test and the lack of sialadenitis on a salivary gland biopsy excluded an associated Gougerot-Sjögren Syndrome. The patient was treated with hydroxychloroquine and low-dose steroids, enabling a clinical and biological recovery. Of the 82 cases in the literature describing hypocomplementemic urticarial vasculitis associated nephropathies, 72 (88%) were a glomerular impairment, most frequently secondary to membranoproliferative glomerulonephritis. Only 6 (7%) tubulo-interstitial nephritis have been reported, 4 of them being associated with a glomerulonephritis. Patients were more likely to be women, aged in their third decade. The most frequent renal manifestations were haematuria (60%), and proteinuria (52%). Kidney failure was rarely observed (22%), with a fairly good renal prognosis. Hypocomplementemic urticarial vasculitis was associated with a systemic disease in 11 (13%) patients. In the absence of recommendations, the treatment strategy remains to be defined.


Assuntos
Complemento C1/deficiência , Glomerulonefrite Membranoproliferativa/complicações , Nefrite Intersticial/complicações , Urticária/complicações , Vasculite/complicações , Feminino , Humanos , Pessoa de Meia-Idade
14.
Angew Chem Int Ed Engl ; 59(7): 2802-2807, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31830354

RESUMO

Near-UV-pumped white-light-emitting diodes with ultra-high color rendering and decreased blue-light emission is highly desirable. However, discovering a single-phase white light emitter with such characteristics remains challenging. Herein, we demonstrate that Mn doping as low as 0.027 % in the hybrid post-perovskite type (TDMP)PbBr4 (TDMP=trans-2,5-dimethylpiperaziniium) enables to achieve a bright pure white emission replicating the spectrum of the sun's rays. Thus, a white phosphor exhibiting an emission with CIE coordinates (0.330, 0.365), a high photoluminescence quantum yield of 60 % (new record for white light emission of hybrid lead halides), and an ultra-high color rendering index (CRI=96, R9=91.8), corresponding to the record value for a single phase emitter was obtained. The investigation of the photoluminescence properties revealed how free excitons, self-trapped excitons, and low amount of Mn dopants are coupled to give rise to such pure white emission.

15.
Chem Asian J ; 14(18): 3166-3172, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31461221

RESUMO

The aggregation-induced emission (AIE) properties of two different copper iodide clusters have been studied. These two [Cu4 I4 L4 ] clusters differ by their coordinated phosphine ligand and the luminescent mechanochromic properties are only displayed by one of them. The two clusters are AIE-active luminophors that exhibit an intense emission in the visible region upon aggregation. The formed particles present luminescent thermochromism comparable to that of the bulk compounds. The observed AIE properties can be attributed to suppression of nonradiative relaxation of the excited states in a more rigid state, in relation to the large structural relaxation of the excited triplet state. The differences observed in the AIE properties of the two clusters can be related to the different ligands. A correlation between the luminescence mechanochromic properties and the AIE effect is not straightforward, but the formation of "soft" molecular solids is a common characteristic that can explain the photoactive properties of these compounds.

16.
Chemphyschem ; 18(17): 2390-2396, 2017 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-28605155

RESUMO

Reflux of a solution of [Ti8 O12 (H2 O)24 ]Cl8 ⋅HCl⋅7 H2 O as titanium precursor at 120 °C for 24 h leads to a transparent colloidal solution of nanosized crystallized anatase TiO2 . The adjustment of the particle size and composition of the dispersant is monitored through the initial water content while controlling the conversion of propylene carbonate into propylene glycol during reflux. The solutions were processed as thin films to produce electron transporting layers in hybrid bulk heterojunction solar cells, by using a blend of P3HT:PCBM polymers as absorbers, in inverted architectures. The solutions obtained by reflux were demonstrated to produce suitable electron transporting layers.

17.
Mol Metab ; 6(5): 447-458, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28462079

RESUMO

OBJECTIVE: The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that functions into distinct protein complexes (mTORC1 and mTORC2) that regulates growth and metabolism. DEP-domain containing mTOR-interacting protein (DEPTOR) is part of these complexes and is known to reduce their activity. Whether DEPTOR loss affects metabolism and organismal growth in vivo has never been tested. METHODS: We have generated a conditional transgenic mouse allowing the tissue-specific deletion of DEPTOR. This model was crossed with CMV-cre mice or Albumin-cre mice to generate either whole-body or liver-specific DEPTOR knockout (KO) mice. RESULTS: Whole-body DEPTOR KO mice are viable, fertile, normal in size, and do not display any gross physical and metabolic abnormalities. To circumvent possible compensatory mechanisms linked to the early and systemic loss of DEPTOR, we have deleted DEPTOR specifically in the liver, a tissue in which DEPTOR protein is expressed and affected in response to mTOR activation. Liver-specific DEPTOR null mice showed a reduction in circulating glucose upon fasting versus control mice. This effect was not associated with change in hepatic gluconeogenesis potential but was linked to a sustained reduction in circulating glucose during insulin tolerance tests. In addition to the reduction in glycemia, liver-specific DEPTOR KO mice had reduced hepatic glycogen content when fasted. We showed that loss of DEPTOR cell-autonomously increased oxidative metabolism in hepatocytes, an effect associated with increased cytochrome c expression but independent of changes in mitochondrial content or in the expression of genes controlling oxidative metabolism. We found that liver-specific DEPTOR KO mice showed sustained mTORC1 activation upon fasting, and that acute treatment with rapamycin was sufficient to normalize glycemia in these mice. CONCLUSION: We propose a model in which hepatic DEPTOR accelerates the inhibition of mTORC1 during the transition to fasting to adjust metabolism to the nutritional status.


Assuntos
Glicemia/metabolismo , Jejum/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Fígado/metabolismo , Animais , Citocromos c/metabolismo , Glicogênio/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL
18.
ACS Appl Mater Interfaces ; 7(4): 2310-21, 2015 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-25562716

RESUMO

Understanding the dealloying mechanisms of gold-based alloy thin films resulting in the formation of nanoporous gold with a sponge-like structure is essential for the future design and integration of this novel class of material in practical devices. Here we report on the synthesis of nanoporous gold thin films using a free-corrosion approach in nitric acid applied to cosputtered Au-Cu thin films. A relationship is established between the as-grown Au-Cu film characteristics (i.e., composition, morphology, and structure) and the porosity of the sponge-like gold thin films. We further demonstrate that the dealloying approach can be applied to nonhomogenous Au-Cu alloy thin films consisting of periodic and alternate Au-rich/Au-poor nanolayers. In such a case, however, the dealloying process is found to be altered and unusual etching stages arise. Thanks to defects and column boundaries playing the role of channels, the nitric acid is found to quickly penetrate within the films and then laterally (i.e., parallel to the film surface) attacks the nanolayers rather than perpendicularly. As a consequence to this anisotropic etching, the Au-poor layers are etched preferentially and transform into Au pillars holding the Au-rich layers and preventing them against collapsing. A further exposure to nitric acid results in the collapsing of the Au-rich layers accompanied by a transition from a multilayered to a sponge-like structure. A scenario, supported by experimental observations, is further proposed to provide a detailed explanation of the fundamental mechanisms occurring during the dealloying process of films with a multilayered structure.

19.
Carbohydr Polym ; 116: 307-13, 2015 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-25458305

RESUMO

1-10% starch/clay bionanocomposites with shape memory properties were obtained by melt processing. X-ray diffraction (XRD) and TEM evidenced the presence of a major fraction of clay tactoids, consisting of 4-5 stacked crystalline layers, with a thickness of 6.8 nm. A significant orientation of the nanoparticles induced by extrusion was also observed. Tensile tests performed above the glass transition of the materials showed that the presence of clay nanoparticles leads to higher elastic modulus and maximum stress, without significant loss in elongation at break which typically reached 100%. Samples submitted to a 50% elongation and cooled below the glass transition showed shape memory behavior. Like unreinforced starch, the bionanocomposites showed complete shape recovery in unconstrained conditions. In mechanically constrained conditions, the maximum recovered stress was significantly improved for the bionanocomposites compared to unreinforced starch, opening promising perspectives for the design of sensors and actuators.


Assuntos
Bentonita/química , Nanocompostos/química , Amido/química , Materiais Biocompatíveis/química , Módulo de Elasticidade , Microscopia Eletrônica de Transmissão , Nanocompostos/ultraestrutura , Resistência à Tração , Difração de Raios X
20.
J Mater Chem B ; 2(44): 7747-7755, 2014 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-32261911

RESUMO

Innovative nanostructures made of a high payload of fluorophores and superparamagnetic nanoparticles (NPs) have simply been fabricated upon self-assembling in a two-step process. The resulting hybrid supraparticles displayed a dense shell of iron oxide nanoparticles tightly attached through an appropriate polyelectrolyte to a highly emissive non-doped nanocore made of more than 105 small organic molecules. Cooperative magnetic dipole interactions arose due to the closely packed magnetic NPs at the nanoarchitecture surface, causing enhanced NMR transverse relaxivity. Large in vivo MRI T2 contrast was thus obtained with unusually diluted solutions after intravenous injection in small rodents. Two-photon excited fluorescence imaging could be performed, achieving unprecedented location resolution for agents combining both magnetic nanoparticles and fluorescence properties. Finally, TEM imaging of the sectioned mouse tissue succeeded in isolating the core-shell structures, which represents the first image of intact complex magnetic and fluorescent nanoassemblies upon in vivo injection. Such highly cohesive dual nanoarchitectures should open great horizons toward the assessment with high spatial resolution of the drug or labeled stem cell biodistribution.

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