Super-resolution optical microscopy using fluorescent labels has been transformational in allowing the machinery of life, e.g. proteins, to be seen at the nanoscale. There is a great desire in the life-sciences to achieve this level of insight for metabolites, the molecular products and messengers involved in metabolism. This will allow unprecedented ability to understand rewiring of metabolic networks involved in disease, understanding of the uptake of drugs in cells and construct mechanistic understanding in fundamental biology. However, this is a monumental challenge since fluorescent labelling strategies cannot be used because of the dynamic processes in the creation of metabolites and because the fluorescent labels themselves radically alter the chemistry of the metabolite.
Mass spectrometry allows label-free (or with stable isotope labelling) identification of endogenous and exogenous (e.g drugs) metabolites and when combined with high-resolution ion beams in secondary ion mass spectrometry (SIMS) allows sub-cellular resolution imaging. Substantial barriers need to be overcome to achieve a super-resolution goal (< 250 nm) including increasing sensitivity, increasing specificity (accurate identification of molecules), sample preparation methodologies (e.g. cryo-SIMS) and improvements in ion beam resolution. This lecture will review our research at NiCE-MSI using three SIMS instrument types; ToF-SIMS, 3D OrbiSIMS and a CAMECA NanoSIMS 50L.
A significant focus of our research is to image the uptake of drugs with sub-cellular resolution. We have discovered that in ToF-SIMS, the logarithm of sensitivity is directly proportional to the Log P value for many different drugs and that some drug molecules exhibit severe matrix effect resulting in no detection. Since the pharmaceutical industry is focused on making low Log P drugs ≤ 3 (Lipinski rule of five) this limits the current applicability. We have recently developed a new method for in situ matrix deposition that significantly increases sensitivity to help overcome this. Furthermore, initial experiments using laser post-ionisation show encouraging results to potentially circumvent some of these issues.
Many metabolites are of low mass (e.g. dopamine) and are in a highly congested region of the mass spectrum. Here, ToF-SIMS is inadequate to resolve the peaks especially at high-spatial resolution. We have led the development of a powerful new hybrid instrument, the 3D OrbiSIMS, combining an OrbitrapTM-based Thermo ScientificTM Q ExactiveTM HF instrument and a dedicated ToF-SIMS 5. The instrument is equipped with high-resolution ion beams including a new micron resolution argon cluster ion beam for biomolecular imaging and 3D analysis of organics and an ultra-high resolution Bi cluster focussed ion beam with < 100 nm resolution. We demonstrate the unparalleled ability for 2D and 3D metabolite imaging with sub-cellular resolution.
For imaging at the organelle scale, e.g. mitochondria and lysosomes, then a resolution of 50 nm or better is needed. This is achieved with the CAMECA NanoSIMS 50L. Normally, the solvent based sample preparation procedures used wash out drug molecules. We have developed a method that traps molecules within the organelles and use this to demonstrate the first direct evidence of drug induced phospholipidosis caused by amiodarone uptake in rat alveolar macrophages.
Significant progress has been made towards the goal of super-resolution metabolic imaging but there are many challenges ahead. A technology roadmap will be presented.
This work reports on two novel SPM methods which both use tailored dual AFM tips. In the first method, so called dual-tip magnetic force microscopy (DT-MFM), topological and magnetic scans are segregated using two different tips, one magnetic and other one non-magnetic. Tips are located on a cantilever splitted by focused ion beam. The non-magnetized tip is used for topography only, and the magnetized one is used for a magnetic field mapping only (avoids surface touching). The main advantage of DT-MFM technique compared to the standard MFM is that it minimizes the perturbations of the magnetic tip. Introduced DT-MFM can be used to explore magnetically soft objects like magnetic vortices and is also perspective in a wide range of applications, e.g. in data storage systems and also in biomedicine to explore magnetic nanoparticles in cells.
In the second experiment, we developed a special probe for bio-applications to study the mechanical properties of cells. It consists of two cantilevers; one having a sharp tip, the other having a spherically blunted tip. The sharp tip is used for topography imaging with high resolution, while blunt tip is used for measuring of force distance curves. Various biophysical properties of cells can be obtained from force spectroscopy, such as elasticity, adhesion, hardness, friction, etc, The larger area of probe-cell contact results in averaging local variation in the cell rigidity compared to the one measured with a regular sharp probe. The switching between sharp and spherical tip is realized by means of integrated magnetostrictive actuator.
The recent progress in scanning probe microscopy provided unprecedented atomic resolution of single organic molecules on surfaces. Namely, the submolecular resolution was achieved in AFM [1], STM [2] and also IETS [3] mode employing functionalized tips. The origin of the submolecular contrast can be rationalized by a simple mechanical model introducing a lateral bending of a flexible tip apex [4,5]. However, direct experimental evidence correlating the AFM/STM/IETS imaging mechanisms has been missing so far. Here we present simultaneous high resolution AFM/STM/IETS imaging of iron(II) phthalocyanine (FePc) on Au(111) surface acquired with CO-functionalized probe. The acquired data demonstrate unambiguously the common imaging mechanism of the modes. We will show that not only energetic position of frustrated CO translation peak in the IETS signal [5], but also change of the amplitude of the IETS peak affects the IETS imaging. We also propose a simple model designed to capture variations in the amplitude of the IETS signal, which permits us to reproduce the experimental findings. Ab-initio IETS calculations based on non-equilibrium Green’s function showed why the frustrated translation peak is affected by the substrate, but the frustrated rotation is not.
REFERENCE: [1] L. Gross et al., Science 325,1110 (2009).; [2] C. Weiss et al., Phys. Rev. Lett. 105, 086103 (2010).; [3] C.I. Chiang et al Science 344, 885 (2014).; [4] P. Hapala et al., Phys. Rev. B 90, 085421 (2014).; [5] P. Hapala et al., Phys. Rev. Lett. 113, 226101 (2014).
Mono- and poly-crystalline diamonds are increasingly popular as materials for applications in micro- and bio-electronics, sensing and drug delivery. Useful properties such as a wide bandgap, broad optical transparency (UV through IR), thermal conductivity at room temperature, mechanical hardness, broad-spectrum chemical resistance and biocompatibility make them highly desirable for applications in biomedicine. The remarkable properties of optically-tailored diamond films and nanostructures also find use in photonics, integrated quantum photonics and quantum computing. These applications necessitate the ability to manipulate the material at the nano- and micro- scales, which is impossible without advanced analytical techniques.
Here we present three experiments applying RISE microscopy for the characterization of single diamond grains and thin films. The first experiment is a quality and crystallinity check of diamond films and layers. The second measures residual stress utilizing the built-in Focused Ion Beam, which enables in-situ sample modification. We see good agreement with Finite Element Analysis simulations and two different stress-measurement approaches (Digital Image Correlation, Raman). The third correlates photoluminescence mapping of single diamond crystals with Si-vacancy centers with their morphologies. Low-kV SEM inspection with the TESCAN TriglavTM UHR SEM column, together with Raman and photoluminescence imaging are crucial for complex in-situ material characterization (morphological, chemical, mechanical and optical) at the same micro-scale area.
Although the interaction between matter and highly energetic particles has been evidenced and studied ever since the invention of the cloud chamber back in 1911 and of the bubble chamber later on in 1952, the effect of swift heavy ions (SHI) on materials raises more and more interest as the applications and technological challenges nowadays are more and more demanding. Processing of materials using accelerated particles holds an important applicative potential in various fields from micro and nanotechnology to fabrication of homoporous filters, radiation detectors, hadron therapy or radiation waste storage. The mechanisms of interaction and corresponding effects vary in function of the target nature (gaseous, solid), energy of the incident particles, density of charge carriers and atom mobility inside the target material [1]. In particular, the interaction of SHI with crystalline materials may induce ion tracks in the volume and some surface features (e.g. nano-hillocks or nano-craters) [2-4]. This work presents new data obtained by analytical TEM on SHI-induced ion tracks in CaF2 in an attempt to explain the still debated issues of the formation mechanism, energy threshold and atomic structure within the ion track [5]. Diffraction contrast techniques as well as analytical STEM-EELS imaging using an aberration corrected STEM are used to analyze the ion tracks, showing both the benefits but also the limitations and possible misleading information resulting from TEM investigations. This work is the result of an international collaboration in the frame of the CERIC-ERIC consortium.
ACKNOWLEDGEMENTS: CG and RFN acknowledge the grant of Ministry of Research and Innovation, CNCS - UEFISCDI, project number PN-III-P4-ID-PCE-2016-0529, within PNCDI III.
REFERENCES: [1] L. T. Chadderton, Radiation Measurements 36, 13 (2003); [2] M. Toulemonde, W. Assmann, C. Dufour, A. Meftah, C. Trautmann, Nucl. Instrum. Methods Phys. Res. B 277, 28 (2012); [3] M. Buljan, M. Karlušić, I. Bogdanović-Radović, M. Jakšić, K. Salamon, S. Bernstorff, N. Radić, Appl. Phys. Lett. 101, 103112 (2012); [4] N. Ishikawa, N Okubo and T Taguchi, Nanotechnology 26 (2015) 355701; [5] M. Karlušić, C. Ghica, R. F. Negrea, Z. Siketić, M. Jakšić, M. Schleberger and S. Fazinić; New Journal of Physics 19, 023023 (2017).
A Scanning Helium ion beam can be used for imaging at higher resolution compared to an electron beam. Due to the very small probe size of Helium ions we also can make very small structures like 10 nm line with 30 nm pitch and low resistivity. The electrical properties come from the material itself because there is no Ga implantation like in a conventional FIB system. Other applications for Helium Ion Microscope reach from TEM lamella preparation to analytical material investigations with SIMS.
A phase-locked loop (PLL) is a powerful form of system control that allows the synchronization of multiple measurements such that multiple signals can be acquired at precisely the same moment in time. Combining the PLL with at atomic force microscope (AFM) enables capabilities such as frequency modulation (FM) AFM, which allows researchers to observe the dynamic properties of an oscillating cantilever which can be used to quantify surface potential measurements. In this document, we report the successful operation of a phase-locked loop (Zurich Instruments, HFT2PLL) using a lock-in amplifier (Zurich Instruments, HF2LI) with an atomic force microscope capable of sample characterization under high vacuum (Park Systems, Park NX-Hivac). Not only did the PLL support higher frequencies, multimode measurements, and FM AFM, but amplitude modulation (AM) AFM as well. Moreover, using PLL increases the capability of linked AFM systems further by enabling the simultaneous operation of two cantilever mode and demodulation of up to six arbitrary frequencies. To maximize the utility of a combined PLL-AFM system, samples should be scanned in a high vacuum environment that offers a high quality (Q) factor which in turn increases adjustability of cantilever dynamics and Z height sensitivity. The high vacuum AFM’s sample chamber was adjusted to a base pressure well below 10-5 torr with a Q factor three times greater than in ambient situations. We close by presenting the methodology for interfacing the PLL with an AFM controller to adjust cantilever dynamics in FM non-contact AFM operation.
The wettability and frictional investigations of diamond-like carbon (DLC) and silicon-incorporated diamond-like carbon (Si-DLC) coatings modified by fluoroalkylsilanes are introduced. DLC and Si-DLC coatings were obtained with the use of Radio Frequency Plasma Enhanced Chemical Vapor Deposition method (RF-PECVD). The Vapor Phase Deposition (VPD) method was used to adsorb two types of fluoroalkylsilanes with different carbon chain length: 1H, 1H, 2H, 2H - perfluorodecyltrichlorosilane (FDTS) and 3, 3, 3-trifluoropropyltrichlorosilane (FPTS) on investigated surfaces [1].
The chemical structure of DLC, Si-DLC coatings were identify with the use of Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy. The effectiveness of silanes modification was identified with the use of FTIR and X-ray Photoelectron Spectroscopy (XPS). Tribology properties were obtained in nano-, mili- and macro-newton scale. It was investigated that the presence of silicon incorporation creates active centers capable of adsorption of fluoroalkylsilanes. In consequence, the water contact angle (WCA) and frictional properties e.g. coefficient of friction and adhesive forces of investigated coatings were improved. Obtained wettability and tribological results indicate that Si-DLC coatings can be successfully used as protective coatings in various micro- and nano- electromechanical systems (MEMS/NEMS). Moreover fluoroalkylsilanes could be primary candidates as lubricants in micro- and nano- devices [2].
ACKNOWLEDGEMENTS: Research funded by the National Science Center under Project No. 2014/13 / B / ST8 / 03114.
REFERENCES: [1] M. Cichomski, K. Kośla, W. Pawlak, W. Kozłowski, W. Szmaja, Tribology International 77 (2014) 1-6.; [2] J. Robertson, Materials Science and Engineering: R: Reports 37 (2002) 129-281.
Neaspec’s near-field optical microscopy systems (NeaSNOM) allow to overcome the diffraction limit of light enabling optical measurements at a spatial resolution of 10nm not only at visible frequencies but also in the infrared or terahertz spectral range.
Development of a dedicated Fourier-transform detection module for analyzing light scattered from an AFM tip which is illuminated by a broadband IR source enabled IR spectroscopy of complex polymer nanostructures and biomolecules (nano-FTIR) [1]. Identification of individual contaminants has been demonstrated. Other applications show characterization of embedded structural phases in biominerals [2] or organic semiconductors. The patented modular system design allows for tailored system configurations where the ultimate spectral coverage is achieved by using synchrotron-based broadband IR light sources [3].
Equipping s-SNOM systems with cw light sources near-field imaging can be performed at time scales of 30-300s per image. Use of material-selective frequencies in the mid-IR spectral range can be exploited to fully characterize polymer blends or phase change polymers with nanometer-scale domains [4]. Quantification of free-carrier concentration and carrier mobility in doped semiconductor nanowires [5], analysis of 2D (graphene) nanostructures [6], or study phase propagation mechanisms in energy storage materials is achieved by amplitude- and phase-resolved infrared near-field imaging.
REFERENCES: [1] I. Amenabar et al. Nature Comm. 4 2890 (2013); [2] S. Amarie, et al., Beilstein J. of Nanotech. 3, 312 (2012); [3] P. Herrmann, et al., Optics Expr. 22 (2014); [4] C. Westermeier, et al., Nature Comm. 5, 4101 (2014); [5] Li, et al., ACS Nano (2017); [6] M. B. Lundeberg et al., Science (2017) AOP.
We present traceability routes for quantitative measurements of local temperature distribution using contact (Scanning Thermal Microscopy) and non-contact (Infrared Thermometry) techniques combined in a single metrology instrument. Measurements of temperature distribution with high resolution is an important task in semiconductor devices optimisation, however their accuracy is still very limited. Here we will present a large area scanning system combined with custom built head designed for temperature mapping on passive and active devices. It is based on a combination of high accuracy scanning system, Scanning Thermal Microscopy head and electronics and an infrared imaging system, featuring wide possibilities of combinations of various sensors for both contact and contact-less temperature mapping. Uncertainties of the measurements for both infrared and SThM part will be discussed and device performance will be demonstrated on typical active reference samples.
Recent advances in branched semiconductor nanowire (NW) synthesis have motivated efforts on developing reproducible methods for synthesis of NW networks that maintain the unique III-V NW properties throughout the junctions. Such structures that also possess the variability of free standing NW geometry, while maintaining crystal coherency in the very junction bear potential for applications in coherent quantum transport experiments.
Here we present new method for growth of two distinguishable single crystal InAs nanowire junctions in the hexagonal wurtzite basis by molecular beam epitaxy via Vapor-Liquid-Solid mechanism. That is achieved by controlled NW kinking into the <1-100> directions parallel to the (111)B growth substrate, combined with relative positioning of catalyst nanoparticles along selected crystallographic directions. The third type of wurtzite NW cross is grown by more standard method, directly from cubic basis of (100) substrates, and possess well defined and reproducible inclusion of zinc-blende.
We present the new NW cross growth method and demonstrate its potential for growth of complex nanowire networks, together with crystal and electronic transport characterisation of all three presented NW cross types.
The major advantage of in situ measurement, besides it gives real-time responses, is the possibility to avoid sample removing, therefore to avoid introducing unfavorable changes on the sample (ex. further oxidation of the sample). By coupling the Flow-Type Scanning Droplet Cell Microscope (FT-SDCM) and Cyclic Voltammetry (CV) to the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in situ measurements can be carried out and nanoscale oxide growing on tungsten can be monitored. For CV experiments a 3-electrode system with a gold counter electrode, Ag/AgCl quasi-reference electrode and tungsten working electrode was used. Using a peristaltic pump, the electrolyte was continuously brought to the tungsten surface and pumped out together with the dissolved material towards to the ICP-MS to monitor its concentration. Previous scientific work shows the electrochemical dissolution of bulk tungsten and the chemical dissolution of the anodically formed oxide on its surface in sulphuric acid electrolyte [1]. The current work focuses on the differences and similarities of oxide growing on bulk and sputtered (thin film) tungsten in hydrochloric acid [2]. Interestingly different electrochemical behaviour of those has been found. Moreover the aging of thin film tungsten was investigated. Additionally, the surface differences of thin film and bulk tungsten were investigated by Scanning Electron Microscopy (SEM).
References:
[1] M. Krebsz, J. P. Kollender and A. W. Hassel, Phys. Stat. Sol. A (2017) DOI:10.1002/pssa.201600803
[2] M. Krebsz, C. C. Mardare and A. W. Hassel, Phys. Stat. Sol. A (submitted)
α-Ag2WO4 semiconductor, has recently emerged as a multifunctional alternative over conventional wide band gap semiconductors, owing to its potential in applications such as photocalalysis, photoswitching, among others. Recent studies have also demonstrated that crystals of α-Ag2WO4 showed a metal nanoparticle (MNPs) growth attached to the semiconductor framework, which may lead to outstanding applications due to Ag segregation, such as ozone sensing and bacteriocidicity. Nevertheless, up to now the metal nanoparticle growth has been limited to the scale of Transmission Electron Microscope (TEM) processing, hampering in this way its potential use. In this communication, a femtosecond laser radiation source is used to scale-up the MNP growth of the material, and the product’s bactericidal activity is tested. α-Ag2WO4 was irradiated by a Ti:sapphire laser beam with a burst of 30 fs pulses at two different fluence regimens, a low fluence regime which only promotes the synthesis of spherical Ag NPs and a high fluence regime which promotes a high Ag NPs growth rate accompanied with the synthesis of AgxWyOz nanoparticles. All the resultant species were examined and identified using TEM and energy dispersive spectroscopy. Furthermore, the bactericidal properties of the synthesized species were tested against Methicillin-Resistant Staphylococcus Aureus ATCC 33591, where the samples irradiated by femtosecond radiation at a high fluence regime show the best performance found in the literature up to now, a 32-fold improvement over non-irradiated α-Ag2WO4. We believe that the results found in here constitute an improvement over conventional multifunctional semiconductor synthesis approaches which may inspire future developments.
Development of gas aggregation sources (GAS) has triggered a research on preparation of plasma polymer nanoparticles (NPs). Hydrocarbon, organosilicon, nitrogen- and carboxyl-containing NPs have been successfully synthesized. This work investigates plasma instabilities occurring in a GAS and correlates them with the formation and growth of hydrocarbon NPs.
The NPs were produced by plasma polymerization of n-hexane in its 4.6% mixture with Ar under total pressure of 43.6 Pa and at RF discharge power of 50 W. Under these conditions, NPs with the mean size of 320 nm were produced. The configuration of the GAS allowed simultaneous measurements of discharge voltage, optical emission (OES) and mass spectra (MS) within the GAS, and deposition rate of NPs outside the GAS. For OES and MS, hydrocarbon species were selected and compared to the reference signal from Ar. Cycling instabilities with a period of 80 s were detected in the deposition rate which correlated with the changes in the discharge voltage, the intensity of the plasma emission and the concentration of hydrocarbon species. Cycling growth of the NPs up to a critical size with their subsequent repelling from the discharge zone is proposed to describe the observed phenomenon.
ACKNOWLEDGEMENTS: The authors would like to acknowledge the contribution of the COST Action CA15107 (MultiComp) and support by the grant LTC17062 from the Ministry of Education, Youth and Sports of the Czech Republic. D.N., M. V. and P. P. acknowledge the support from the student grant SVV 260 444/2017 of Charles University.
Zinc oxide is multifunctional material used for decades in industrial scale due to its unique physical properties. By appropriately chosen morphology of particles, we can get additional value from this “traditional” material. However for optimal results, it is necessary to manage synthesis of different morphology. Here we report fast and economical method of ZnO synthesis by precipitation from water solutions of zinc acetate by sodium hydroxide. We have studied, how concentration ratio R = [NaOH] / [Zn (II)] and solution addition order can affect product morphology and composition. By this synthetic method we can selectively prepare different particle shapes (spheres, urchins, petals, rods) of pure ZnO with yield exceeding 75 %. By reverse addition of reactants, finely dispersed nanoparticles can be obtained by elimination of growth step during the synthesis. For product characterization XRD, SEM, TGA and Raman spectroscopy were used.