1,720,981 research outputs found
Removal of electrostatic artifacts in magnetic force microscopy by controlled magnetization of the tip: application to superparamagnetic nanoparticles
Full text linkMagnetic force microscopy (MFM) has been demonstrated as valuable technique for the
characterization of magnetic nanomaterials. To be analyzed by MFM techniques, nanomaterials
are generally deposited on flat substrates, resulting in an additional contrast in MFM images due to
unavoidable heterogeneous electrostatic tip-sample interactions, which cannot be easily distinguished
from the magnetic one. In order to correctly interpret MFM data, a method to remove the electrostatic
contributions from MFM images is needed. In this work, we propose a new MFM technique, called
controlled magnetization MFM (CM-MFM), based on the in situ control of the probe magnetization
state, which allows the evaluation and the elimination of electrostatic contribution in MFM images. The
effectiveness of the technique is demonstrated through a challenging case study, i.e., the analysis of
superparamagnetic nanoparticles in absence of applied external magnetic field. Our CM-MFM technique
allowed us to acquire magnetic images depurated of the electrostatic contributions, which revealed
that the magnetic field generated by the tip is sufficient to completely orient the superparamagnetic
nanoparticles and that the magnetic tip-sample interaction is describable through simple models once
the electrostatic artifacts are removed
Magnetic Force Microscopy
No full textMagnetic force microscopy (MFM) refers to a family of scanning probe techniques
based on atomic force microscopy (AFM), which allow one to image the magnetic
properties of the sample surface at the nanoscale, simultaneously to its topography.
Here, we review the most widespread MFM techniques, mainly dynamic MFM
although static MFM is also briefly described for the sake of completeness. We
illustrate the working principles, the experimental setups, and the analytical models
describing the MFM response, which are fundamental for understanding and quantitatively
interpreting the contrast in MFM images. An overview is given of the
application fields of MFM, which cover almost all the magnetic materials, from
recording media to ferromagnetic materials, nanomaterials and nanoparticles, alone
and in organic or biological systems. Finally, some advances, hot topics, new
applications, and open issues are presented, including the effect of external magnetic
fields, nonmagnetic interactions, MFM tips calibration and advanced probes, and
magnetic imaging with variable temperature
Magnetic Force Microscopy and Magnetic Nanoparticles: Perspectives and Challenges
No full textAmong the various techniques for the characterization of magnetic NPs, magnetic force microscopy (MFM) represent one of the most widespread and versatile methods due to its lateral resolution, sensitivity, imaging capability, the need for a relatively simple and widespread experimental setup, minimal/no specific requirements about sample preparations, capability to operate in air at room conditions as well as in vacuum or liquid environment. Indeed, MFM enables the quantitative characterization of magnetic properties of single magnetic NPs, can be used to detect single magnetic NPs in nonmagnetic (e.g., polymeric or biological) matrices, as well as to perform mechanical or magnetic nanomanipulation of single NPs. In this chapter, applications of MFM in the study of magnetic NPs are briefly reviewed and intriguing perspectives are depicted, focusing on current limitations to overcome and challenges to take up
Methanol plasma treatment of fluorocarbon ultra-thin films for stents applications
No full textThe surgical implantation of metallic stents in a narrowed vessel after balloon angioplasty is a common procedure to prevent restenosis phenomena, but the related complications, such as thrombosis, inflammation and devices corrosion, are still a serious concern.
In order to limit those complications, the coating of metallic stents, by Plasma Enhanced Chemical Vapor Deposition (PECVD), with Fluorocarbon (CFx) ultrathin films has been demonstrated to be an interesting strategy, thanks to the CFx biocompatibility, chemical inertness, impermeability, corrosion resistance, appropriate mechanical properties and high adhesion to the substrates[1],[2].
Nevertheless, the modification of some key surface properties of CFx coatings could further improve their blood compatibility. For example, it has been shown that the presence of carboxyl groups and a moderate surface wettability could promote the appropriate proteins adhesion, improving the hemocompatibility and promoting the surface endothelialisation[3],[4].
The objective of this work was to develop an oxidation process of CFx coatings, based on a methanol plasma treatment. The modification of the surface oxygen content and wettability was aimed to modulatie protein adsorption and blood compatibility of CFx films, without affecting their excellent mechanical and corrosion resistance properties
Surface treatments of ss316l substrates for plasma-based diamond like carbon coatings: Study of the surface properties
No full text[No abstract available
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Visualization and quantification of magnetic nanoparticles into vesicular systems by atomic force microscopy
No full textVesicular systems incorporating magnetic nanoparticles (MNPs) have been attracting much interest for their possible application in active drug delivery. To this aim, suitable procedures have to benn developed to enhance the efficiency of inclusion of MNPs into vesicular systems. Therefore, it is crucial to dispose of reliable control tools to quantify the presence of MNPs in such systems. To verify the homogeneity of the nanosystems, such techniques are required to give information not only about the overall amount of MNPs in the sample, but also about the presence/absence into the single vesicle. To this aim, we developed a methodology based on magnetic force microscopy (MFM), which is a particular atomic force microscopy (AFM) based technique where a tip coated with a magnetic ultrathin film is used to probe the sample magnetic properties. Firstly, the sample surface is scanned in semi-contact mode to reconstruct its morphology. Then, the same area is scanned again imposing a constant tip-sample distance during the image, the cantilever is oscillating and the cantilever oscillation phase shift is recorded. This is related to the gradient along the vertical direction of the tip sample interaction force, which is dominated by the magnetic interaction. Vesicular systems incorporating MNPs have been produced by the thin film technique, hydrating with the MNPs solution. The presence of MNPs in the samples have been previously verified and quantified by inductively coupled plasma mass spectrometry (ICP-MS), which nevertheless does not allow the identification of their position and distribution into the vesicles. Drops of vesicles/MNPs sample have been poured on glass substrates and imaged by AFM either in water (using an ad hoc designed and realized cell) or in air (after dehydration). MFM has been used to investigate the sample. The MFM phase images revealed the presence of MNPs into the vesicles. By analyzing such phase images using a phenomenological calibration specifically developed for the purpose, we quantified the amount of MNPs incorporated in the vesicles
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nanomechanical characterization of soft materials and nanocomposites by atomic force microscopy
No full text[No abstract available
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