Applications of Kelvin Probe Force Microscopy in the characterization of 2D materials and their composites

Kelvin Probe Force Microscopy (KPFM), since its relatively recent introduction in 1991, has become a widely used technique to assess surface charge distribution and work function of metal/semiconductor interfaces in electronic devices at the nanoscale. Today, this characterization technique is employed in many nanotechnology-related applications, with 2D layered material being a notable example due to the necessity of characterizing various electrical properties with high spatial resolution to better understand how these parameters scale or change relatively with synthesis, deposition and environment conditions. In this thesis I will discuss the main applications of KPFM characterization that I have encountered during my three years of doctorate, showing its usefulness in various fields, its main limitations and some practical considerations about the best practices I developed to optimize sample preparation. Regarding the study of fundamental electronic properties I will present my results on the correlation of work function of 2D materials like MoS2 and their thickness (Chapter 3), and how laser induced 3D structures can locally tune the work function of the graphene basal plane for possible future localized functionalization (Chapter 4). As an example of the use of KPFM characterization of 2D composites, I will present the analyses of a metal/graphene interface, more specifically the silver nanowire (AgNW)/graphene interface, selected as it represents a very promising type of hybrid for devices requiring highly conductive transparent electrodes (Chapter 5). Finally, I will show how KPFM can be employed even in a macroscopic conductive 2D material/polymer composite to elucidate the structure or to verify the presence of the conductive elements inside the insulating polymeric matrix (Chapter 6). At the start of this work, I will present a theory background on the origin and principles of the technique, its evolution and main limitations (Chapter 1) followed by a brief introduction of the main other characterization techniques employed and my personal consideration on the best deposition techniques (Chapter 2)

New Insights into the Role of Ferroptosis in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the principal cause of disease burden and death worldwide. Ferroptosis is a new formof regulated cell deathmainly characterized by altered ironmetabolism, increased polyunsaturated fatty acid peroxidation by reactive oxygen species, depletion of glutathione and inactivation of glutathione peroxidase 4. Recently, a series of studies have indicated that ferroptosis is involved in the death of cardiac and vascular cells and has a key impact on the mechanisms leading to CVDs such as ischemic heart disease, ischemia/reperfusion injury, cardiomyopathies, and heart failure. In this article, we reviewed the molecular mechanism of ferroptosis and the current understanding of the pathophysiological role of ferroptosis in ischemic heart disease and in some cardiomyopathies. Moreover, the comprehension of the machinery governing ferroptosis in vascular cells and cardiomyocytes may provide new insights into preventive and therapeutic strategies in CVDs

Improvement in accuracy of diagnosis of carotid artery stenosis with duplex ultrasound scanning with combined use of linear array 7.5 MHz and convex array 3.5 MHz probes: validation versus 489 arteriographic procedures1 1Competition of interest: none.Published online Mar 6, 2003.

AbstractObjective: Validity of a method to improve the accuracy of carotid artery duplex scanning was tested in comparison with arteriography.Study Design: In 489 patients who had not previously undergone arteriography, 978 carotid arteries were examined with duplex ultrasound scanning. In method A, a linear array 7.5 MHz transducer with pulsed-wave 4.7 MHz Doppler scanning was used. For the diagnosis and grading of carotid stenosis, peak systolic and end-diastolic velocity of the Doppler waves were recorded. Method B consisted of complete ultrasound imaging and color-flow mapping with a convex array 3.5 MHz transducer with pulsed-wave 2.8 MHz Doppler scanning in all patients who had previously undergone method A. Further velocity measurements were performed at the sites of stenosis. The results of methods A and B were compared with data from neurologic assessment and arteriographic studies.Results: Method B showed significantly higher diagnostic agreement with arteriography than did method A (K 95% confidence interval [CI], 0.87–0.93 vs 0.79–0.85; P < .05), and the number of mistakes in grading stenosis was significantly lower (primarily because of decreased overestimation) in patients with internal carotid kinking (>60 degrees of angulation) (P < .05), distal stenosis (>20 mm from bifurcation) (P < .01), or wide acoustic shadowing (>1 cm) (P < .01) and in those without these conditions (P < .05). Compared with arteriography, diagnostic accuracy with the new method proved higher for carotid stenoses 50% or greater, 60% or greater, 70% or greater, and 80% or greater; no statistically significant difference was found for carotid stenosis 96% or greater or for carotid occlusion. Compared with data from neurologic assessment and arteriography, method B proved more accurate than method A in designating patients for carotid endarterectomy (P = .014).Conclusions: The new method significantly improved diagnostic reliability of duplex ultrasound scanning, especially in carotid arteries with kinking, distal stenosis, or wide acoustic shadowing (32.2% of all arteries studied). In clinical practice, we suggest additional use of a lower frequency transducer in cases in which these three conditions are found or suspected at first scanning

Functional liquid structures by emulsification of graphene and other two-dimensional nanomaterials

Pickering emulsions stabilised with nanomaterials provide routes to a range of functional macroscopic assemblies. We demonstrate the formation and properties of water-in-oil emulsions prepared through liquid-phase exfoliation of graphene. Due to the functional nature of the stabiliser, the emulsions exhibit conductivity due to inter-particle tunnelling. We demonstrate a strain sensing application with a large gauge factor of ~40; the highest reported in a liquid. Our methodology can be applied to other two-dimensional layered materials opening up applications such as energy storage materials, and flexible and printable electronics

Atrial myxoma and Williams-Beuren syndrome. An incidental association?

We report the case of a 15 years old girl with Williams-Beuren syndrome and atrial mixoma

Red Blood Cell Morphologic Abnormalities in Patients Hospitalized for COVID-19

Peripheral blood smear is a simple laboratory tool, which remains of invaluable help for diagnosing primary and secondary abnormalities of blood cells despite advances in automated and molecular techniques. Red blood cells (RBCs) abnormalities are known to occur in many viral infections, typically in the form of mild normo-microcytic anemia. While several hematological alterations at automated complete blood count (including neutrophilia, lymphopenia, and increased red cell distribution width—RDW) have been consistently associated with severity of COVID-19, there is scarce information on RBCs morphological abnormalities, mainly as case-reports or small series of patients, which are hardly comparable due to heterogeneity in sampling times and definition of illness severity. We report here a systematic evaluation of RBCs morphology at peripheral blood smear in COVID-19 patients within the first 72 h from hospital admission. One hundred and fifteen patients were included, with detailed collection of other clinical variables and follow-up. A certain degree of abnormalities in RBCs morphology was observed in 75 (65%) patients. Heterogenous alterations were noted, with spiculated cells being the more frequent morphology. The group with &gt;10% RBCs abnormalities had more consistent lymphopenia and thrombocytopenia compared to those without abnormalities or &lt;10% RBCs abnormalities (p &lt; 0.018, and p &lt; 0.021, respectively), thus underpinning a possible association with an overall more sustained immune-inflammatory “stress” hematopoiesis. Follow-up analysis showed a different mortality rate across groups, with the highest rate in those with more frequent RBCs morphological alterations compared to those with &lt;10% or no abnormalities (41.9%, vs. 20.5%, vs. 12.5%, respectively, p = 0.012). Despite the inherent limitations of such simple association, our results point out towards further studies on erythropoiesis alterations in the pathophysiology of COVID-19

Are they in or out? The elusive interaction between Qtracker(\uae)800 vascular labels and brain endothelial cells

AIM:Qtracker\uae800 Vascular labels (Qtracker\uae800) are promising biomedical tools for high-resolution vasculature imaging; their effects on mouse and human endothelia, however, are still unknown.MATERIALS &amp; METHODS:Qtracker\uae800 were injected in Balb/c mice, and brain endothelium uptake was investigated by transmission electron microscopy 3-h post injection. We then investigated, in vitro, the effects of Qtracker\uae800 exposure on mouse and human endothelial cells by calcium imaging.RESULTS:Transmission electron microscopy images showed nanoparticle accumulation in mouse brain endothelia. A subset of mouse and human endothelial cells generated intracellular calcium transients in response to Qtracker\uae800.CONCLUSION:Qtracker\uae800 nanoparticles elicit endothelial functional responses, which prompts biomedical safety evaluations and may bias the interpretation of experimental studies involving vascular imaging