Tag Archives: nanoparticles

Observing single magnetite nanoparticles with a diameter of 10nm by using NANOSENSORS SSS-MFMR AFM probes

In their publication “Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution” Alexander Krivcov, Tanja Junkers and Hildegard Möbius describe methods to suppress capacitive coupling effects in MFM hiding the magnetic signal of magnetic nanoparticles.

During MFM measurements performed in an interleave mode moving the tip at a certain distance to the sample surface the tip is exposed not only to magnetic forces but to electrostatic forces between tip and substrates. In case of analyzing nanoparticles laying on a flat substrate, the electrostatic forces changes noticeably with increasing tip to substrate distance whenever the tip is retracted over a nanoparticle. This capacitive signal may overwhelm the magnetic signal that should be detected instead.

The authors propose several approaches to reduce these capacitive signals. The change in electrostatic forces could be minimized by avoiding retraction of tip over the nanoparticle. Therefore, it is proposed to use interleave linear mode following a linear approximation of the sample surface instead of the interleave lift mode following the sample surface as measured. By that, changes in distance between sample substrate and tip at the nanoparticles are avoided. Moreover, they propose using a substrate with a work function comparable to that of the tip in order to reduce electrostatic forces, in general. By applying an appropriate tip bias remaining electrostatic forces could compensated and further suppressed. Finally, the authors suggest using a tip that is as sharp as possible for decreasing the area of the capacitor and NANOSENSORS SSS-MFMR probes are the best choice for this.

The impact of the above mentioned optimizations have been validated experimentally by the authors. Finally, it turned out that if using super sharp magnetic tips further methods suppressing capacitive effects were not necessary. The authors were able to detect superparamagnetic nanoparticles at the single particle level on copper substrate with a NANOSENSORS SSS-MFMR probe without using additional parameters as e. g. tip bias or external magnetic field.Figure 12 from: A. Krivcov et. al, Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution: Figure 12. (a) topography of copper substrate with single magnetite nanoparticle; (b) phase image in 11 nm lift height with an attraction at the place of the nanoparticle; (c) Cross section of a single magnetite nanoparticle (dotted line in (a)) with 10 nm diameter taken on copper substrate with NANOSENSORS SSS-MFMR AFM probe

Figure 12  from: A. Krivcov et. al, Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution: Figure 12. (a) topography of copper substrate with single magnetite nanoparticle; (b) phase image in 11 nm lift height with an attraction at the place of the nanoparticle; (c) Cross section of a single magnetite nanoparticle (dotted line in (a)) with 10 nm diameter taken on copper substrate with SSS-MFMR tip

A. Krivcov, T. Junkers, and H. Möbius
Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single superparamagnetic nanoparticle resolution
J. Phys. Commun., vol. 2, no. 7, p. 075019, 2018
DOI: https://doi.org/10.1088/2399-6528/aad3a4

The article “Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single superparamagnetic nanoparticle resolution” by A. Krivcov, T. Junkers, and H. Möbius is licensed under the Creative Commons Attribution 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0.

Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils

For this article the AFM images taken with tapping mode in Tris buffer solution were performed with the NANOSENSORS qp-BioAC (cantilever 3, resonance frequency 30kHz).

Figure 5 from Yordanova et. al. "Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils" - AFM image of the Zn2+: GnRH [6-D-Phe] 10:1 complex. (a,b) Oligomers after preparation with tapping mode in Tris buffer solution (c,d) fibrils with tapping mode in air (z-scale indicates the average size of the formed oligomers and fibrils). NANOSENSORS qp-BioAC AFM probe was used to perform images in buffer solution
Figure 5 from Yordanova et. al. “Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils” – AFM image of the Zn2+: GnRH [6-D-Phe] 10:1 complex. (a,b) Oligomers after preparation with tapping mode in Tris buffer solution (c,d) fibrils with tapping mode in air (z-scale indicates the average size of the formed oligomers and fibrils).

Yordanka Yordanova, Willem Vanderlinden, Raphael Stoll, Daniel Rüdiger, Andreas Tosstorff, Wolfgang Zaremba, Gerhard Winter, Stefan Zahler & Wolfgang Friess
Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils
Nature Scientific Reports volume 8, Article number: 11280 (2018)
doi: https://doi.org/10.1038/s41598-018-29529-w
Please follow this external link to read the full article on the  Nature website: https://rdcu.be/4y9J

Abstract: A synthetic derivative, GnRH [6-D-Phe], stable against enzymatic degradation, self-assembles and forms nanostructures and fibrils upon a pH shift in the presence of different concentrations of Zn2+ in vitro. Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR–FTIR) revealed the existence of higher order assembly of Zn2+: GnRH [6-D-Phe]. Nuclear Magnetic Resonance spectroscopy (NMR) indicated a weak interaction between Zn2+ and GnRH [6-D-Phe]. Atomic Force Microscopy (AFM) showed the existence of GnRH [6-D-Phe] oligomers and fibrils. Molecular Dynamic (MD) simulation of the 10:1 Zn2+: GnRH [6-D-Phe] explored the interaction and dimerization processes. In contrast to already existing short peptide fibrils, GnRH [6-D-Phe] nanostructures and fibrils form in a Tris-buffered pH environment in a controlled manner through a temperature reduction and a pH shift. The lyophilized Zn2+: GnRH [6-D-Phe] assembly was tested as a platform for the sustained delivery of GnRH [6-D-Phe] and incorporated into two different oil vehicle matrices. The in vitro release was slow and continuous over 14 days and not influenced by the oil matrix.

The article “Zn2+-triggered self-assembly of Gonadorelin [6-D-Phe] to produce nanostructures and fibrils” by Yordanova Y. et al. is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/