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1.
Sleep Med ; 119: 505-510, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38796980

RESUMO

STUDY OBJECTIVES: Excessive fragmentary myoclonus (EFM) is a frequent finding in patients undergoing video-polysomnography (VPSG). We aimed to evaluate the potential effect of sleep-related breathing disorder's treatment with positive airway pressure (PAP) therapy on EFM. METHODS: One hundred consecutive patients with EFM and sleep-related breathing disorder subsequently treated with PAP at the sleep lab of the Medical University of Innsbruck, Department of Neurology, Austria, were included. Each patient underwent two nights of VPSG: the first night without and the second night with PAP therapy. Fragmentary myoclonus was automatically scored with validated software, and fragmentary myoclonus index (FMI) and minutes of non-rapid eye movement (NREM) sleep with EFM (minNREM+EFM) were calculated. RESULTS: Under PAP therapy there was a significant decrease in the minNREM+EFM - 60.5 (9.5-161.8) at baseline vs. 37.5 (6.3-168.8) minutes under PAP, p = 0.025. No significant differences were observed for FMI between the two nights. Sleep variables, sleep diagnoses, comorbidities, and medication did not influence FMI or the minNREM+EFM. CONCLUSIONS: The initiation of PAP treatment led to a significant reduction of minNREM+EFM, but not of FMI. The results suggest that PAP therapy might influence the distribution of FM potentials.


Assuntos
Pressão Positiva Contínua nas Vias Aéreas , Polissonografia , Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Pressão Positiva Contínua nas Vias Aéreas/métodos , Síndromes da Apneia do Sono/terapia , Adulto , Síndrome da Mioclonia Noturna/terapia , Idoso , Mioclonia/terapia , Mioclonia/fisiopatologia
2.
J Mech Behav Biomed Mater ; 151: 106403, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38237206

RESUMO

This study proposed and validated a 2D finite element (FE) model for conducting in-silico simulations of in-situ nanoindentation tests on mineralized collagen fibrils (MCF) and the extrafibrillar matrix (EFM) within human cortical bone. Initially, a multiscale cohesive FE model was developed by adapting a previous model of bone lamellae, encompassing both MCF and EFM. Subsequently, nanoindentation tests were simulated in-silico using this model, and the resulting predictions were compared to AFM nanoindentation test data to verify the model's accuracy. The FE model accurately predicted nanoindentation results under wet conditions, closely aligning with outcomes obtained from AFM nanoindentation tests. Specifically, it successfully mirrored the traction/separation curve, nanoindentation modulus, plastic energy dissipation, and plastic energy ratio obtained from AFM nanoindentation tests. Additionally, this in-silico model demonstrated its ability to capture alterations in nanoindentation properties caused by the removal of bound water, by considering corresponding changes in mechanical properties of the collagen phase and the interfaces among bone constituents. Notably, significant changes in the elastic modulus and plastic energy dissipation were observed in both MCF and EFM compartments of bone, consistent with observations in AFM nanoindentation tests. These findings indicate that the proposed in-silico model effectively captures the influence of ultrastructural changes on bone's mechanical properties at sub-lamellar levels. Presently, no experimental methods exist to conduct parametric studies elucidating the ultrastructural origins of bone tissue fragility. The introduction of this in-silico model presents an invaluable tool to bridge this knowledge gap in the future.


Assuntos
Osso e Ossos , Osso Cortical , Humanos , Análise de Elementos Finitos , Estresse Mecânico , Osso e Ossos/metabolismo , Osso Cortical/metabolismo , Colágeno/química
3.
IDCases ; 29: e01593, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35966277

RESUMO

Infections with multidrug resistant (MDR) Enterococcus faecium (Efm) are a growing problem. Vancomycin resistance in enterococci has long challenged treatment, necessitating the use of linezolid or daptomycin. Subsequently, daptomycin-, linezolid-, vancomycin-resistant Efm (DLVRE) infections have emerged. Case reports and guidelines for treating DLVRE infections are limited. Here, we describe the clinical and laboratory management of an MDR Efm protracted intraabdominal (IA) infection and breakthrough DLVRE bacteremia. Serial Efm resistance was evaluated using whole genome sequencing (WGS), susceptibility testing, and synergy analysis. Prior to in vitro synergy testing, combination antimicrobial therapy with daptomycin (DAP) and ceftaroline (CPT) was employed to treat the patient's central line-associated DLVRE bloodstream infection. In vitro antimicrobial testing revealed no synergy between daptomycin and ceftaroline; however, the patient's bacteremia cleared following initiation of both in conjunction with catheter removal. Sequencing of the DLVRE isolates revealed multiple genomic mutations which explained both linezolid and daptomycin resistance phenotypes and confirmed the presence of a plasmid containing the vanA operon. Sequential WGS of two additional bacterial isolates from the same patient revealed protracted colonization with a single DLVRE clone and suggested the development of bacterial subpopulations. Pairing clinical isolate susceptibilities with WGS and synergy testing should be encouraged in clinical practice to better inform antimicrobial management in cases of multidrug resistance.

4.
Materials (Basel) ; 15(14)2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35888345

RESUMO

The endolysin EFm1 from the E. faecalis 002 (002) phage IME-EF1 efficiently lyses E. faecalis, a gram-positive bacterium that severely threatens human health. Here, the structure and lytic activity of EFm1 toward E. faecalis were further investigated. Lytic activity shows that EFm1 specifically lyses 002 and 22 other clinically isolated E. faecalis, but not E. faecalis 945. Therefore, EFm1 may be an alternative biomaterial to prevent and treat diseases caused by E. faecalis. A structural analysis showed that EFm1D166Q is a tetramer consisting of one full-length unit with additional C-terminal domains (CTDs), while EFm1166-237 aa is an octamer in an asymmetric unit. Several crucial domains and novel residues affecting the lytic activity of EFm1 were identified, including calcium-binding sites (D20, D22 and D31), a putative classic amidohydrolase catalytic triad (C29, H90 and D108), a tetramerization site (M168 and M227), putative ion channel sites (IGGK, 186-198 aa), and other residues (R208 and Y209). Furthermore, EFm1 exhibited no significant activity when expressed alone in vivo, and IME-EF1 lytic activity decreased when efm1 was knocked down. These findings provide valuable insights into the molecule mechanism of a potential functional biomaterial for the treatment of the disease caused by the opportunistic pathogen E. faecalis.

5.
Healthcare (Basel) ; 10(2)2022 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-35206877

RESUMO

Forensic medicine has always held the human environment, either seen as a source for pathological agents or the background of judicial events, in great consideration. The concept of the environment has evolved through time, expanding itself to include all the physical and virtual sub-spaces in which we exist. We can nowadays talk of technoenvironmental reality; virtual spaces exploded because of the COVID-19 pandemic making us come to terms with the fact that those are the places where we work, where we socialize and, even, where we meet our doctors and can be cured. Artificial Intelligence (AI) has contributed to shaping new virtual realities that have got their own rules yet to be discovered, carved and respected. We already fight a daily battle to save our natural environment: along with the danger of green crimes, comes the need for environmental justice and environmental forensic medicine that will probably develop a forensic branch and an experimental branch, to implement our technical culture leading to definition of the real dimension of the risk itself to improve the role of legal medicine in the Environmental Risk Management. While green criminology addresses widespread green crimes, a virtual environment criminology will also develop, maybe with a contribution of AI in the justice field. For a sustainable life, the environmental revolution must rapidly take place, and there is the need for a new justice, a new forensic medicine and a new criminology too.

6.
Prev Med Rep ; 26: 101700, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35141116

RESUMO

To assess whether anthropometric measures (body mass index [BMI], waist-hip ratio [WHR], and estimated fat mass [EFM]) are independently associated with major adverse cardiovascular events (MACE), and to assess their added prognostic value compared with serum total-cholesterol. The study population comprised 109,509 individuals (53% men) from the MORGAM-Project, aged 19-97 years, without established cardiovascular disease, and not on antihypertensive treatment. While BMI was reported in all, WHR and EFM were reported in âˆ¼52,000 participants. Prognostic importance of anthropometric measurements and total-cholesterol was evaluated using adjusted Cox proportional-hazards regression, logistic regression, area under the receiver-operating-characteristic curve (AUCROC), and net reclassification improvement (NRI). The primary endpoint was MACE, a composite of stroke, myocardial infarction, or death from coronary heart disease. Age interacted significantly with anthropometric measures and total-cholesterol on MACE (P ≤ 0.003), and therefore age-stratified analyses (<50 versus ≥ 50 years) were performed. BMI, WHR, EFM, and total-cholesterol were independently associated with MACE (P ≤ 0.003) and resulted in significantly positive NRI when added to age, sex, smoking status, and systolic blood pressure. Only total-cholesterol increased discrimination ability (AUCROC difference; P < 0.001). In subjects < 50 years, the prediction model with total-cholesterol was superior to the model including BMI, but not superior to models containing WHR or EFM, while in those ≥ 50 years, the model with total-cholesterol was superior to all models containing anthropometric variables, whether assessed individually or combined. We found a potential role for replacing total-cholesterol with anthropometric measures for MACE-prediction among individuals < 50 years when laboratory measurements are unavailable, but not among those ≥ 50 years.

7.
Front Med (Lausanne) ; 8: 626450, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34901040

RESUMO

During labor, uterine contractions trigger the response of the autonomic nervous system (ANS) of the fetus, producing sawtooth-like decelerations in the fetal heart rate (FHR) series. Under chronic hypoxia, ANS is known to regulate FHR differently with respect to healthy fetuses. In this study, we hypothesized that such different ANS regulation might also lead to a change in the FHR deceleration morphology. The hypothesis was tested in an animal model comprising nine normoxic and five chronically hypoxic fetuses that underwent a protocol of umbilical cord occlusions (UCOs). Deceleration morphologies in the fetal inter-beat time interval (FRR) series were modeled using a trapezoid with four parameters, i.e., baseline b, deceleration depth a, UCO response time τ u and recovery time τ r . Comparing normoxic and hypoxic sheep, we found a clear difference for τ u (24.8±9.4 vs. 39.8±9.7 s; p < 0.05), a (268.1±109.5 vs. 373.0±46.0 ms; p < 0.1) and Δτ = τ u - τ r (13.2±6.9 vs. 23.9±7.5 s; p < 0.05). Therefore, the animal model supported the hypothesis that hypoxic fetuses have a longer response time τ u and larger asymmetry Δτ as a response to UCOs. Assessing these morphological parameters during labor is challenging due to non-stationarity, phase desynchronization and noise. For this reason, in the second part of the study, we quantified whether acceleration capacity (AC), deceleration capacity (DC), and deceleration reserve (DR), computed through Phase-Rectified Signal Averaging (PRSA, known to be robust to noise), were correlated with the morphological parameters. DC, AC and DR were correlated with τ u , τ r and Δτ for a wide range of the PRSA parameter T (Pearson's correlation ρ > 0.8, p < 0.05). In conclusion, deceleration morphologies have been found to differ between normoxic and hypoxic sheep fetuses during UCOs. The same difference can be assessed through PRSA based parameters, further motivating future investigations on the translational potential of this methodology on human data.

8.
Foods ; 10(12)2021 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-34945491

RESUMO

High Hydrostatic Pressure (HHP) technology is considered an alternative method of food preservation. Nevertheless, the current dogma is that HHP might be insufficient to preserve food lastingly against some pathogens. Incompletely damaged cells can resuscitate under favorable conditions, and they may proliferate in food during storage. This study was undertaken to characterize the extent of sublethal injuries induced by HHP (300-500 MPa) on Escherichia coli and Listeria inncua strains. The morphological changes were evaluated using microscopy methods such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Epifluorescence Microscopy (EFM). The overall assessment of the physiological state of tested bacteria through TEM and SEM showed that the action of pressure on the structure of the bacterial membrane was almost minor or unnoticeable, beyond the L. innocua wild-type strain. However, alterations were observed in subcellular structures such as the cytoplasm and nucleoid for both L. innocua and E. coli strains. More significant changes after the HHP of internal structures were reported in the case of wild-type strains isolated from raw juice. Extreme condensation of the cytoplasm was observed, while the outline of cells was intact. The percentage ratio between alive and injured cells in the population was assessed by fluorescent microscopy. The results of HHP-treated samples showed a heterogeneous population, and red cell aggregates were observed. The percentage ratio of live and dead cells (L/D) in the L. innocua collection strain population was higher than in the case of the wild-type strain (69%/31% and 55%/45%, respectively). In turn, E. coli populations were characterized with a similar L/D ratio. Half of the cells in the populations were distinguished as visibly fluorescing red. The results obtained in this study confirmed sublethal HHP reaction on pathogens cells.

9.
ACS Appl Mater Interfaces ; 13(40): 47945-47953, 2021 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-34607423

RESUMO

We investigated the nature of graphene surface doping by zwitterionic polymers and the implications of weak in-plane and strong through-plane screening using a novel sample geometry that allows direct access to either the graphene or the polymer side of a graphene/polymer interface. Using both Kelvin probe and electrostatic force microscopies, we observed a significant upshift in the Fermi level in graphene of ∼260 meV that was dominated by a change in polarizability rather than pure charge transfer with the organic overlayer. This physical picture is supported by density functional theory (DFT) calculations, which describe a redistribution of charge in graphene in response to the dipoles of the adsorbed zwitterionic moieties, analogous to a local DC Stark effect. Strong metallic-like screening of the adsorbed dipoles was observed by employing an inverted geometry, an effect identified by DFT to arise from a strongly asymmetric redistribution of charge confined to the side of graphene proximal to the zwitterion dipoles. Transport measurements confirm n-type doping with no significant impact on carrier mobility, thus demonstrating a route to desirable electronic properties in devices that combine graphene with lithographically patterned polymers.

10.
Polymers (Basel) ; 13(12)2021 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-34200956

RESUMO

The interphase area appears to have a great impact on nanocomposite (NC) dielectric properties. However, the underlying mechanisms are still poorly understood, mainly because the interphase properties remain unknown. This is even more true if the temperature increases. In this study, a multiscale characterization of polyimide/silicon nitride (PI/Si3N4) NC dielectric properties is performed at various temperatures. Using a nanomechanical characterization approach, the interphase width was estimated to be 30 ± 2 nm and 42 ± 3 nm for untreated and silane-treated nanoparticles, respectively. At room temperature, the interphase dielectric permittivity is lower than that of the matrix. It increases with the temperature, and at 150 °C, the interphase and matrix permittivities reach the same value. At the macroscale, an improvement of the dielectric breakdown is observed at high temperature (by a factor of 2 at 300 °C) for NC compared to neat PI. The comparison between nano- and macro-scale measurements leads to the understanding of a strong correlation between interphase properties and NC ones. Indeed, the NC macroscopic dielectric permittivity is well reproduced from nanoscale permittivity results using mixing laws. Finally, a strong correlation between the interphase dielectric permittivity and NC breakdown strength is observed.

11.
Sensors (Basel) ; 21(12)2021 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-34199213

RESUMO

We utilized scanning probe microscopy (SPM) based on a metal-oxide-silicon field-effect transistor (MOSFET) to image interdigitated electrodes covered with oxide films that were several hundred nanometers in thickness. The signal varied depending on the thickness of the silicon dioxide film covering the electrodes. We deposited a 400- or 500-nm-thick silicon dioxide film on each sample electrode. Thick oxide films are difficult to analyze using conventional probes because of their low capacitance. In addition, we evaluated linearity and performed frequency response measurements; the measured frequency response reflected the electrical characteristics of the system, including the MOSFET, conductive tip, and local sample area. Our technique facilitated analysis of the passivation layers of integrated circuits, especially those of the back-end-of-line (BEOL) process, and can be used for subsurface imaging of various dielectric layers.

12.
Nanotechnology ; 32(43)2021 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-34265750

RESUMO

The interest in patterned polyvinylidene fluoride (PVDF) surfaces has grown significantly in the recent years due to ability to control the ferroelectric behavior through the size and shape of the surface structures. However, forming micron sized structures on the PVDF surface generally requires laborious lithography based methods or use of templates which complicates the process. In this study, we report spontaneous formation of microislands with ferroelectric response during PVDF growth via initiated chemical vapor deposition. Depositions performed under continuous and no flow conditions show that laminar precursor flow to the surface yield homogenous thin films, whereas no flow conditions of the batch mode result in the growth of surface protrusions (microislands) with higher polar phase content. Formation of these surface instabilities after an incubation time indicates the presence of local stress fields building with time, resulting in formation of the islands with higherßphase fraction to release the stress. Furthermore, the increased mobility of the polymer chains at high temperatures reduces the stress field, leading to lowerß/αphase ratios in smaller microislands.

13.
Nanotechnology ; 32(42)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34256368

RESUMO

Polymer nanocomposites (pNC) have attracted wide interests in electrical insulation applications. Compared to neat matrices or microcomposites, pNC provide significant improvements in combined electrical, mechanical and thermal properties. In the understanding of the reasons behind these improvements, a major role was attributed to the interphase, the interaction zone between the nanoparticles (NP) and the matrix. Because of their nanoscale dimensions, the interphase properties are mostly theoretically described but rarely experimentally characterized. The aim of this study is to propose a nanoscale measurement protocol in order to probe mechanical (Young modulus) and electrical (dielectric permittivity) interphase features using, respectively, the peak force quantitative nanomechanical (PF-QNM) and the electrostatic force microscopy (EFM) modes of the atomic force microscopy. Measurements are performed on polyimide/silicon nitride (Si3N4) nanocomposite and the effect of a silane coupling agent treatment of Si3N4NP is considered. In order to accurately probe mechanical properties in PF-QNM mode, the impacting parameters such as the applied force, the deformation and the topography are taken into account. The interphase region has shown a higher elastic modulus compared to the matrix and a higher width (WI) value for treated NP. From EFM measurements combined to a finite element model feeded with theWIvalues obtained from PF-QNM, the interphase permittivity is determined. The corresponding values are lower than the matrix one and similar for untreated and treated NP. This is in total agreement with its higher elastic modulus and implies that the interphase is a region around the NP where the polymer chains present a better organization and thus, a restricted mobility.

14.
Nanomaterials (Basel) ; 11(6)2021 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-34070690

RESUMO

Mapping the dielectric properties of cells with nanoscale spatial resolution can be an important tool in nanomedicine and nanotoxicity analysis, which can complement structural and mechanical nanoscale measurements. Recently we have shown that dielectric constant maps can be obtained on dried fixed cells in air environment by means of scanning dielectric force volume microscopy. Here, we demonstrate that such measurements can also be performed in the much more challenging case of fixed cells in liquid environment. Performing the measurements in liquid media contributes to preserve better the structure of the fixed cells, while also enabling accessing the local dielectric properties under fully hydrated conditions. The results shown in this work pave the way to address the nanoscale dielectric imaging of living cells, for which still further developments are required, as discussed here.

15.
Appl Microsc ; 51(1): 7, 2021 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-34037869

RESUMO

Neuromorphic systems require integrated structures with high-density memory and selector devices to avoid interference and recognition errors between neighboring memory cells. To improve the performance of a selector device, it is important to understand the characteristics of the switching process. As changes by switching cycle occur at local nanoscale areas, a high-resolution analysis method is needed to investigate this phenomenon. Atomic force microscopy (AFM) is used to analyze the local changes because it offers nanoscale detection with high-resolution capabilities. This review introduces various types of AFM such as conductive AFM (C-AFM), electrostatic force microscopy (EFM), and Kelvin probe force microscopy (KPFM) to study switching behaviors.

16.
Beilstein J Nanotechnol ; 12: 139-150, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33564609

RESUMO

The aim of this work is to determine the varying dielectric constant of a biological nanostructured system via electrostatic force microscopy (EFM) and to show how this method is useful to study natural photonic crystals. We mapped the dielectric constant of the cross section of the posterior wing of the damselfly Chalcopteryx rutilans with nanometric resolution. We obtained structural information on its constitutive nanolayers and the absolute values of their dielectric constant. By relating the measured profile of the static dielectric constant to the profile of the refractive index in the visible range, combined with optical reflectance measurements and simulation, we were able to describe the origin of the strongly iridescent wing colors of this Amazonian rainforest damselfly. The method we demonstrate here should be useful for the study of other biological nanostructured systems.

17.
J Healthc Risk Manag ; 40(4): 17-29, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32929794

RESUMO

INTRODUCTION: A "Primary Learner Assessment" (PLA) was created to provide an individualized learning plan, offering education as part of a 4-step computer-based process. The PLA is intended to improve learner's knowledge, skills, and patient safety perceptions, regarding interpretation of electronic fetal monitoring (EFM) data and administration of appropriate interventions in a timely fashion to mitigate fetal and maternal risks. Research was conducted to determine if learner knowledge, skills, and patient safety perceptions improved after completion of a 4-step computer-based, individualized adaptive-learning process. METHODS: Participants were registered nurses (RNs) responsible for administering and interpreting EFM, from three U.S. hospitals with labor and delivery units. This mixed method pilot study was determined to be exempt by the institutional review board; all participants provided consent. The process included four steps. In step one, RNs completed the baseline PLA. Based on incorrect quantitative and EFM interpretation responses, computer-based EFM education courses were recommended (step two). After completion of recommended courses weeks or greater of practice (step three), the RNs completed a follow-up PLA (step four). RESULTS: Of the 55 RN participants, most (85.5%) were clinical nurses, had a bachelor degree in nursing or higher (80.0%), and 11.2 average years of labor and delivery experience. There was a statistically significant improvement (P < .0001) in overall average percentage of correct PLA scores from baseline (76.7, SD = 9.1) to follow-up (82.5, SD = 6.9). Practice-related perceptions showed increased ranking of familiarity with the National Institute of Child Health and Human Development (NICHD) 2008 EFM terminology and guidelines from baseline of 49.0% to follow-up of 87.4% and of impact to which the participants integrated EFM administration and interpretation of NICHD EFM terminology and guidelines into practice from 52.8% at baseline to 94.5% at follow-up. In addition, RNs perceived improvement in their oxygen therapy competence and accuracy in interpreting EFM data with implementation of appropriate interventions. CONCLUSION: These pilot study findings support a 4-step, computer-based individualized adaptive-learning process as RNs responsible for EFM to potentially mitigate fetal and maternal risk had improved knowledge and skills. Research is warranted in larger samples.


Assuntos
Cardiotocografia , Trabalho de Parto , Criança , Competência Clínica , Feminino , Humanos , Aprendizagem , Projetos Piloto , Gravidez
18.
Metabolites ; 10(12)2020 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-33260526

RESUMO

Structural analysis of constraint-based metabolic network models attempts to find the network's properties by searching for subsets of suitable modes or Elementary Flux Modes (EFMs). One useful approach is based on Linear Program (LP) techniques, which introduce an objective function to convert the stoichiometric and thermodynamic constraints into a linear program (LP), using additional constraints to generate different nontrivial modes. This work introduces FLFS-FC (Fixed Length Function Sampling with Flux Coupling), a new approach to increase the efficiency of generation of large sets of different EFMs for the network. FLFS-FC is based on the importance of the length of the objective functions used in the associated LP problem and the imposition of additional negative constraints. Our proposal overrides some of the known drawbacks associated with the EFM extraction, such as the appearance of unfeasible problems or multiple repeated solutions arising from different LP problems.

19.
Nanomaterials (Basel) ; 10(12)2020 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-33322575

RESUMO

In this paper, we present a study of tungsten disulfide (WS2) two-dimensional (2D) crystals, grown on epitaxial Graphene. In particular, we have employed scanning electron microscopy (SEM) and µRaman spectroscopy combined with multifunctional scanning probe microscopy (SPM), operating in peak force-quantitative nano mechanical (PF-QNM), ultrasonic force microscopy (UFM) and electrostatic force microscopy (EFM) modes. This comparative approach provides a wealth of useful complementary information and allows one to cross-analyze on the nanoscale the morphological, mechanical, and electrostatic properties of the 2D heterostructures analyzed. Herein, we show that PF-QNM can accurately map surface properties, such as morphology and adhesion, and that UFM is exceptionally sensitive to a broader range of elastic properties, helping to uncover subsurface features located at the buried interfaces. All these data can be correlated with the local electrostatic properties obtained via EFM mapping of the surface potential, through the cantilever response at the first harmonic, and the dielectric permittivity, through the cantilever response at the second harmonic. In conclusion, we show that combining multi-parametric SPM with SEM and µRaman spectroscopy helps to identify single features of the WS2/Graphene/SiC heterostructures analyzed, demonstrating that this is a powerful tool-set for the investigation of 2D materials stacks, a building block for new advanced nano-devices.

20.
Nanomaterials (Basel) ; 10(9)2020 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-32932650

RESUMO

Scanning Kelvin probe microscopy (SKPM), electrostatic force microscopy (EFM) are used to study the microscopic processes of the photo-induced charge separation at the interface of Ag and conductive polymers, i.e., poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and poly(3-hexylthiophene-2,5-diyl) (P3HT). They are also widely used in order to directly observe the charge distribution and dynamic changes at the interfaces in nanostructures, owing to their high sensitivity. Using SKPM, it is proved that the charge of the photo-induced polymer PCPDTBT is transferred to Ag nanoparticles (NPs). The surface charge of the Ag-induced NPs is quantified while using EFM, and it is determined that the charge is injected into the polymer P3HT from the Ag NPs. We expect that this technology will provide guidance to facilitate the separation and transfer of the interfacial charges in the composite material systems and it will be applicable to various photovoltaic material systems.

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