Issue #7-8/2022
I.V.Yaminsky, A.I.Akhmetova, N.E.Maksimova, A.P.Melnikov, A.F.Akhkiamova, D.A.Ivanov
MEASUREMENT OF THE STRUCTURE AND THERMOPHYSICAL CHARACTERISTICS OF THE SAMPLES BY COMBINED ATOMIC FORCE MICROSCOPY AND NANOCALORIMETRY
MEASUREMENT OF THE STRUCTURE AND THERMOPHYSICAL CHARACTERISTICS OF THE SAMPLES BY COMBINED ATOMIC FORCE MICROSCOPY AND NANOCALORIMETRY
INTRODUCTION
Scanning probe microscopy has a wide range of applications in medical diagnostics, virology, microbiology, biophysics, materials science and many other industrial, technological and research applications.
Recent atomic force microscope observations have shown that SARS-CoV-2 virus can be inactivated by heating, with exposure time for complete inactivation depending on the temperature reached (e.g. more than 45 minutes at 329 K or less than 5 minutes at 373 K) [1]. Atomic force microscopy (AFM) was used in [2] to study structural stability of individual SARS-CoV-2 virus-like particles at different temperatures. It was shown that even a moderate increase in temperature leads to a drastic disturbance of structural stability of the virus, especially when exposed to heat in dry state.
In [3] oligomeric cholesteric cyclosiloxane films were studied, and the focal conical double-helix domains on the surface were observed using AFM. An in situ study of the temperature dependence of the film topography showed that the surface topography formation could be effectively controlled by varying the heat treatment regimes. It was shown that the resulting structures could be frozen by cooling films below their glass transition temperature.
The probe microscopy laboratory of the Physical department at Lomonosov Moscow State University uses the most technologically advanced equipment of the Research and Production Enterprise "Advanced Technologies Center" to conduct temperature experiments using probe microscopy: the FemtoScan atomic force microscope allows scanning in more than 100 different modes. Due to its compact size and ease of operation, this device is used not only in cutting-edge scientific projects, but also at the Youth Innovation Creativity Centre "Nanotechnology" for educational and research purposes.
When using FemtoScan Cryo, it is possible to change temperature inside the working chamber can be varied between 4.2–300 K. The accuracy of temperature maintenance is 0.05 K (Fig.1).
High-speed probe microscopy is based on FemtoScan X [4]. Combined with optical microscopy, FemtoScan Xi allows measurements in both atomic force and scanning capillary microscopy modes [5] (Fig.2).
Observation of objects with the FemtoScan series microscopes at temperatures ranging from room temperature to 100 °C is accomplished with a compact heating table. It should be noted that many other physico-chemical methods are successfully integrated into the scanning probe microscopy. For example, the scanning probe microscope has implemented an atomic scale mode to determine mass of micro- and nanoparticles.
FemtoScan Online software is used not only to control all microscopy modes but also for multifunctional processing of experimental data. FemtoScan Online makes it easy to integrate new measurement modes into a microscope.
INSTRUMENTS AND RESEARCH METHODS
This paper presents a description of a combined mode of atomic force microscopy and nanocalorimetry or ultrafast chip calorimetry.
Nanocalorimetry is an ultra-fast calorimetry on a silicon nitride-based chip. The technique is based on a thin silicon nitride free membrane, and temperature change is achieved by passing electrical current through resistive heating elements. A number of thermocouples placed along the perimeter of the active area of the nanocalorimetric sensor allows temperature to be measured during the experiment, even when high heating and cooling rates, ranging from 100–1 000 000 K/s, are used [6–10]. This allows successful application for investigations of microscopic sample volumes ranging from a few hundred picograms to several hundred nanograms.
This paper presents a combined AFM based on a FemtoScan microscope with a nanocalorimeter (Fig.3), created at the Laboratory of Engineering Materials Science, Faculty of Fundamental Physical and Chemical Engineering, Lomonosov Moscow State University, which allows describing samples with mass of the order of nanograms.
The main advantage of the device compared to differential scanning calorimetry is a possibility of conducting experiments in DC mode (in experiments with constant heating and cooling rates) with high heating rates (up to 105 K/s). The main characteristics of the device are presented in Table 1. Due to these features of the instrument it is possible to perform quantitative thermal analysis of thin films samples, polymer fibres and powders.
In the fast heating mode experimental nanocalorimetric heating and subsequent cooling profiles can be obtained to estimate the investigated sample mass. Figure 4 shows a nanocalorimetric curve obtained during heating and cooling of a sample poly(trimethylene terephthalate) at a rate of 1000 K/s in order to calculate the investigated sample mass. The difference between heating and cooling baselines corresponds to:
ΔP = 2Cpβ,
where ΔP is the power, Cp is the heat capacity of the sample, β is the heating/cooling rate. Thus, the sample mass can be calculated from the determined value of the heat capacity of the sample using the tabulated values of the specific heat capacity of the material.
Fig.5 shows nanocalorimetric curves for indium particles at different heating rates in the range from 250 to 7000 K/s. The onset of the melting peak of each curve allows determining the response time constant of the nanocalorimetric sensor and the experimental data obtained to be further normalised with the characteristic temperature shift calculated for each heating rate.
The Nanocalorimeter uses commercial MEMS sensors of the XEN-39392 series manufactured by XENSOR Integration (Netherlands) (Fig.6). There are also electrodes on the membrane which act as heating elements and thermocouples.
The possibility of varying the design features of the sensors, such as the active zone size or heating rates, opens up a wide range of possibilities for the study of different materials. This opens new perspectives in the study of polymer systems and their crystallization features, the study of the metals behavior in amorphous states, semiconductor systems, the study of the degradation and aging of drugs and high-energy materials. In addition, the relative transparency of the silicon nitride membrane for both the visible and X-ray range makes it possible to combine this instrument with other experimental methods.
It is worth noting that due to the low thermal conductivity of the silicon nitride membrane during heating processes a sphere of heated air is formed around the active zone of the nanocalorimeter sensor, which is the main conductor of heat from the heating elements to the sample. Small size of this sphere is a significant advantage when combining the Nanocalorimeter with other methods of physical and chemical analysis [11–18].
These design features make it possible to combine the device with an AFM without the need for expensive temperature tables and special temperature AFM heads, and also make it possible to carry out high temperature experiments in situ.
CONCLUSIONS
Joint application of the atomic force microscopy methods with other physical and chemical methods not only greatly expands the informative power of microscopy but also the physical and chemical methods themselves. Visual observation of processes in three dimensions, measurement of the local mechanical properties of objects, recording of detailed video images with high spatial and temporal resolution significantly simplify rational interpretation of the experimental data obtained in the course of research.
ACKNOWLEDGMENTS
The study was completed with the financial support of the RFBR, project No. 19-29-12049/20 and RSF, project No. 22-73-00081.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Scanning probe microscopy has a wide range of applications in medical diagnostics, virology, microbiology, biophysics, materials science and many other industrial, technological and research applications.
Recent atomic force microscope observations have shown that SARS-CoV-2 virus can be inactivated by heating, with exposure time for complete inactivation depending on the temperature reached (e.g. more than 45 minutes at 329 K or less than 5 minutes at 373 K) [1]. Atomic force microscopy (AFM) was used in [2] to study structural stability of individual SARS-CoV-2 virus-like particles at different temperatures. It was shown that even a moderate increase in temperature leads to a drastic disturbance of structural stability of the virus, especially when exposed to heat in dry state.
In [3] oligomeric cholesteric cyclosiloxane films were studied, and the focal conical double-helix domains on the surface were observed using AFM. An in situ study of the temperature dependence of the film topography showed that the surface topography formation could be effectively controlled by varying the heat treatment regimes. It was shown that the resulting structures could be frozen by cooling films below their glass transition temperature.
The probe microscopy laboratory of the Physical department at Lomonosov Moscow State University uses the most technologically advanced equipment of the Research and Production Enterprise "Advanced Technologies Center" to conduct temperature experiments using probe microscopy: the FemtoScan atomic force microscope allows scanning in more than 100 different modes. Due to its compact size and ease of operation, this device is used not only in cutting-edge scientific projects, but also at the Youth Innovation Creativity Centre "Nanotechnology" for educational and research purposes.
When using FemtoScan Cryo, it is possible to change temperature inside the working chamber can be varied between 4.2–300 K. The accuracy of temperature maintenance is 0.05 K (Fig.1).
High-speed probe microscopy is based on FemtoScan X [4]. Combined with optical microscopy, FemtoScan Xi allows measurements in both atomic force and scanning capillary microscopy modes [5] (Fig.2).
Observation of objects with the FemtoScan series microscopes at temperatures ranging from room temperature to 100 °C is accomplished with a compact heating table. It should be noted that many other physico-chemical methods are successfully integrated into the scanning probe microscopy. For example, the scanning probe microscope has implemented an atomic scale mode to determine mass of micro- and nanoparticles.
FemtoScan Online software is used not only to control all microscopy modes but also for multifunctional processing of experimental data. FemtoScan Online makes it easy to integrate new measurement modes into a microscope.
INSTRUMENTS AND RESEARCH METHODS
This paper presents a description of a combined mode of atomic force microscopy and nanocalorimetry or ultrafast chip calorimetry.
Nanocalorimetry is an ultra-fast calorimetry on a silicon nitride-based chip. The technique is based on a thin silicon nitride free membrane, and temperature change is achieved by passing electrical current through resistive heating elements. A number of thermocouples placed along the perimeter of the active area of the nanocalorimetric sensor allows temperature to be measured during the experiment, even when high heating and cooling rates, ranging from 100–1 000 000 K/s, are used [6–10]. This allows successful application for investigations of microscopic sample volumes ranging from a few hundred picograms to several hundred nanograms.
This paper presents a combined AFM based on a FemtoScan microscope with a nanocalorimeter (Fig.3), created at the Laboratory of Engineering Materials Science, Faculty of Fundamental Physical and Chemical Engineering, Lomonosov Moscow State University, which allows describing samples with mass of the order of nanograms.
The main advantage of the device compared to differential scanning calorimetry is a possibility of conducting experiments in DC mode (in experiments with constant heating and cooling rates) with high heating rates (up to 105 K/s). The main characteristics of the device are presented in Table 1. Due to these features of the instrument it is possible to perform quantitative thermal analysis of thin films samples, polymer fibres and powders.
In the fast heating mode experimental nanocalorimetric heating and subsequent cooling profiles can be obtained to estimate the investigated sample mass. Figure 4 shows a nanocalorimetric curve obtained during heating and cooling of a sample poly(trimethylene terephthalate) at a rate of 1000 K/s in order to calculate the investigated sample mass. The difference between heating and cooling baselines corresponds to:
ΔP = 2Cpβ,
where ΔP is the power, Cp is the heat capacity of the sample, β is the heating/cooling rate. Thus, the sample mass can be calculated from the determined value of the heat capacity of the sample using the tabulated values of the specific heat capacity of the material.
Fig.5 shows nanocalorimetric curves for indium particles at different heating rates in the range from 250 to 7000 K/s. The onset of the melting peak of each curve allows determining the response time constant of the nanocalorimetric sensor and the experimental data obtained to be further normalised with the characteristic temperature shift calculated for each heating rate.
The Nanocalorimeter uses commercial MEMS sensors of the XEN-39392 series manufactured by XENSOR Integration (Netherlands) (Fig.6). There are also electrodes on the membrane which act as heating elements and thermocouples.
The possibility of varying the design features of the sensors, such as the active zone size or heating rates, opens up a wide range of possibilities for the study of different materials. This opens new perspectives in the study of polymer systems and their crystallization features, the study of the metals behavior in amorphous states, semiconductor systems, the study of the degradation and aging of drugs and high-energy materials. In addition, the relative transparency of the silicon nitride membrane for both the visible and X-ray range makes it possible to combine this instrument with other experimental methods.
It is worth noting that due to the low thermal conductivity of the silicon nitride membrane during heating processes a sphere of heated air is formed around the active zone of the nanocalorimeter sensor, which is the main conductor of heat from the heating elements to the sample. Small size of this sphere is a significant advantage when combining the Nanocalorimeter with other methods of physical and chemical analysis [11–18].
These design features make it possible to combine the device with an AFM without the need for expensive temperature tables and special temperature AFM heads, and also make it possible to carry out high temperature experiments in situ.
CONCLUSIONS
Joint application of the atomic force microscopy methods with other physical and chemical methods not only greatly expands the informative power of microscopy but also the physical and chemical methods themselves. Visual observation of processes in three dimensions, measurement of the local mechanical properties of objects, recording of detailed video images with high spatial and temporal resolution significantly simplify rational interpretation of the experimental data obtained in the course of research.
ACKNOWLEDGMENTS
The study was completed with the financial support of the RFBR, project No. 19-29-12049/20 and RSF, project No. 22-73-00081.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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