NANO MANIPULATION WITH RECTANGULAR CANTILEVER OF ATOMIC FORCE MICROSCOPE (AFM) IN A VIRTUAL REALITY ENVIRONMENT

One of the problems of working with AFM in nano environment is lack of simultaneous image feedback. For solving this problem, a virtual reality environment (VR) is designed. For this purpose, a nano manipulation environment is implemented and then, through examining and analyzing the forces existing between probe tips and nanoparticle, the process of nanoparticle driving is added to this environment. In the first step of nano manipulation operations, the dimensions of the base plan as well as the exact place of nanoparticles on that plan needs to be defined so that the user can identify the place of the origin and nanoparticles' destination. The second step in simulation is driving the nanoparticle. In this process, the AFM probe tip starts moving toward nanoparticle with a constant speed of V and after touching it and applying F resultant force from probe tip side on nano particles and increasing up to critical value (F ), it overcomes contract and frictional forces existing between the particle and base plane. In this moment, the probe tip starts moving along with nanoparticle and as a result the nanoparticle is transferred to the pre-determined place by the user. Thus the user may observe the manipulation process

Present and future of surface-enhanced Raman scattering

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article

Mechanical Characterization of Liposomes and Extracellular Vesicles, a Protocol

Both natural as well as artificial vesicles are of tremendous interest in biology and nanomedicine. Small vesicles (<200 nm) perform essential functions in cell biology and artificial vesicles (liposomes) are used as drug delivery vehicles. Atomic Force Microscopy (AFM) is a powerful technique to study the structural properties of these vesicles. AFM is a well-established technique for imaging at nanometer resolution and for mechanical measurements under physiological conditions. Here, we describe the procedure of AFM imaging and force spectroscopy on small vesicles. We discuss how to image vesicles with minimal structural disturbance, and how to analyze the data for accurate size and shape measurements. In addition, we describe the procedure for performing nanoindentations on vesicles and the subsequent data analysis including mechanical models used for data interpretation

Optically induced forces on anisotropic plasmonic nanoparticles

Die Verleihung des Nobelpreises für Physik im Jahr 2018 für Arthur Ashkins bahnbrechende Arbeit über optische Pinzetten hat dem Forschungsfeld der optischen Manipulation zu breiter Anerkennung verholfen. Im Laufe der letzten vier Jahrzehnte hat dieses Forschungsgebiet Anwendungen auf vielen Gebieten ermöglicht. Die Bandbreite erstreckt sich dabei von Einzelzellmikroskopie bis zu Nanolithographie. In jüngerer Vergangenheit war vor allem die Manipulation plasmonischer Nanopartikel von besonderem Interesse, da diese als optische Sensoren auf der Nanoskala verwendet werden können. Das genaue Verhalten derartiger Partikel ist jedoch ein komplexes Zusammenspiel vieler Parameter, die von der Geometrie und Beschaffenheit der Partikel und deren umgebendes Medium sowie der Laserstrahlung zur resonanten Anregung der plasmonischen Eigenschaften abhängen. Der Fokus dieser Arbeit liegt insbesondere auf nichtsphärischen, also anisotropen, Goldnanopartikeln und dem Einfluss dieser Anisotropie auf die resultierenden optisch-induzierten Kräfte. Zunächst wurden optische Streukräfte dazu benutzt, einzelne plasmonische Nanopartikel nach ihrer Form und damit auch ihrer Plasmonenresonanz zu sortieren, indem sie auf ein Substrat gedruckt wurden. Dabei wurde für jede Partikelspezies ein Laser verwendet, der resonant zur jeweiligen Plasmonenresonanz war. Dieser neuentwickelte Ansatz nutzt die Abhängigkeit der Plasmonenresonanz und damit auch der Streukräfte von der Form des Partikels aus. Als erste Anwendung wurde die Dynamik der Nanopartikelsynthese durch die Reduktion von Au(III) durch Natriumsulfid aufgeklärt, die Gegenstand einer langanhaltenden Debatte in der Literatur war. Es war möglich einen spektralen Peak im Nahinfrarotbereich der Bildung dreieckiger Nanopartikel zuzuschreiben, was im Gegensatz zu früheren Studien steht, die dies Kern-Schale Partikel oder Partikelaggregate zurückgeführt hatten. Durch Erhöhung der Laserintensität nimmt plasmonisches Heizen derart zu, dass das Deformieren von Partikeln möglich wird. Normalerweise verformen sich anisotrope Partikel wie Nanostäbe zu sphärischen Partikeln um ihre Oberflächenenergie zu verringern. In dieser Arbeit wurde jedoch gezeigt, dass das Anlegen sehr starker Laserintensitäten zu einer Aufspaltung des Nanostäbchens in ein Dimer aus zwei sphärischen Nanopartikeln gleicher Größe führt. Mittels einer Analyse der optischen Eigenschaften konnte ein Partikelabstand im Subnanometerbereich abgeschätzt werden. Durch computergestützte Modellierung wurde ein Model entwickelt, das die Aufspaltung einer Kombination von oberflächenspannungsinduzierter Deformation sowie inhomogen wirkender optischer und hydrodynamischer Kräfte zuschreibt. All diese Beiträge sind optisch induziert. Die Herstellung von Dimeren mit derart kleinen Partikelabständen ist üblicherweise herausfordernd. Daher kann dieser neu entwickelte Ansatz in Zukunft für Anwendungen wie oberflächenverstärkte Raman Streuung oder das induzieren chemischer Reaktionen mittels heißer Elektronen Bedeutung erlangen. Dehnt man die Anisotropie der Partikel auf die Materialzusammensetzung aus, indem man plasmonisch-dielektrische Janus Nanopartikel erzeugt, tritt eine weitere Kraft unter Laserbestrahlung, Thermophorese, auf. Wird die Laserintensität erhöht wird dadurch der Partikel in vertikaler Richtung aus der optischen Ebene gedrückt. Im Rahmen dieser Dissertation wurde dieses Verhalten zum ersten Mal für Nanopartikel berichtet. Dies wurde angewandt, um DNS-funktionalisierte Janus Nanopartikel auf lebende Zellen zu heben und anschließend durch die Zellmembran zu injizieren. Es wurde gezeigt, dass die DNS diesen Vorgang übersteht, da die Wärme ausschließlich an der plasmonischen Spitze des Partikels erzeugt wird. Dies bereitet den Weg für biotechnische Anwendungen wie Zelltransfektion. Diese Arbeit trägt zu einem besseren Verständnis der Vielzahl an Kräften bei, die auf plasmonische Nanopartikel in einem fokussierten Laserstrahl wirken. Insgesamt konnten für alle Grundlagenexperimente potentielle Anwendungen gezeigt werden, was das große Potential dieses Forschungsfeldes für zukünftige Technologien demonstriert.With the award of the noble prize in physics in 2018 for Arthur Ashkin’s seminal work on optical tweezers, great honor has been brought to the field of optical manipulation. Over the past four decades, this field has developed applications in numerous fields ranging from single cell microscopy to nanolithography. Recently, the manipulation of plasmonic nanoparticles has been the subject of particular interest, since they offer an all optical handle at the nanoscale. However, the exact behavior of such particles is a complex interplay of many parameters of the the incident laser light, the particle itself and its surrounding. This thesis puts its focus especially on nonspherical, hence anisotropic, gold nanoparticles and the impact of this anisotropism on the optically induced forces. First, optical scattering forces were used to sort single plasmonic nanoparticles according to their shape and therefore plasmon resonance by printing them on a substrate using a laser tuned to this particular resonance. This newly developed approach makes use of the shape dependence of the plasmon resonance and therefore the optical force excerted on the particles. It was first applied to shed light on the temporal dynamics of the nanoparticle synthesis via the reduction of Au(III) with sodium sulfide that has been a longstanding matter of debate. It was possible to assign a spectral near infrared peak to the formation of triangular nanoparticles, which is in contrast to previous reports that claimed core-shell particles or particle clusters. When increasing the incident laser intensity, plasmonic heating contributes in a way that particle deformation becomes possible. Anisotropic particles such as nanorods usually converge to spherical particles upon heating to decrease surface energy. However, here it was found that applying very strong laser power densities on single gold nanorods lead to a split-up of the particle and the formation of a dimer consisting of two equally sized spheres. Optical analysis revealed the particles to have subnanometer gap distances. A model was conceived through computational modelling attributing the split-up to a combination of surface tension driven deformation, imhomogeneous optical forces and hydrodynamic forces. All those forces are in the end optically induced. Dimers with such small gap distances are usually challenging to produce. Therefore, this newly developed approach could be important for applications such as surface enhanced Raman scattering or hot electron driven chemical reactions. Upon extending the anisotropy of the particles to their material composition thus creating plasmonic dielectric Janus nanoparticles, another force, namely thermophoresis, occurs when increasing the laser intensity thus pushing the particle out of the focal plane in vertical direction. Here, this behavior was found for the first time for a particle on the nanoscale. This was applied by lifting DNA functionalized Janus nanoparticles on top of living cells and injecting them through the cell membrane. It was shown that the DNA survives this treatment as the heat generation is concentrated at the plasmonic side of the particle, thus paving the way for biotechnical applications such as transfection. This work helps to further understand the multitude of forces acting on plasmonic nanoparticles when subject to a focused laser beam. Overall, all fundamental experiments could be brought to applications, hence showcasing the great potential of the field for future technology

Nanoscale Self-Assembly: Nanopatterning and Metrology

The self-assembly process underlies a plethora of natural phenomena from the macro to the nano scale. Often, technological development has found great inspiration in the natural world, as evidenced by numerous fabrication techniques based on self-assembly (SA). One striking example is given by epitaxial growths, in which atoms represent the building blocks. In lithography, the use of self-assembling materials is considered an extremely promising patterning option to overcome the size scale limitations imposed by the conventional photolithographic methods. To this purpose, in the last two decades several supramolecular self-assembling materials have been investigated and successfully applied to create patterns at a nanometric scale. Although considerable progress has been made so far in the control of self-assembly processes applied to nanolithography, a number of unresolved problems related to the reproducibility and metrology of the self-assembled features are still open. Addressing these issues is mandatory in order to allow the widespread diffusion of SA materials for applications such as microelectronics, photonics, or biology. In this context, the aim of the present Special Issue is to gather original research papers and comprehensive reviews covering various aspects of the self-assembly processes applied to nanopatterning. Topics include the development of novel SA methods, the realization of nanometric structures and devices, and the improvement of their long-range order. Moreover, metrology issues related to the nanoscale characterization of self-assembled structures are addressed

Infrared nanospectroscopy and hyperspectral nanoimaging of organic matter

110 p.Infrared (IR) spectroscopy is a highly valuable tool for materials characterization in widely different fields, ranging from polymer sciences to biomedical imaging. However, the diffraction limit prevents nanoscale infrared studies. The IR diffraction limit can be circumvented, among other techniques by infrared scattering type scanning near-field optical microscopy (IR s-SNOM) and its extension to nanoscale Fourier transform infrared spectroscopy (nano-FTIR), which enable infrared imaging and spectroscopy with nanoscale spatial resolution, respectively.In this thesis, we introduce mapping of protein structure with 30nm lateral resolution and sensitivity to individual protein complexes by nano-FTIR. We present local broadband spectra of one virus, ferritin complexes, purple membranes and insulin aggregates, which can be interpreted in terms of their ¿-helical and/or ¿-sheet structure. Applying nano-FTIR for studying insulin fibrils - model system widely used in neurodegenerative disease research - we find clear evidence that 3-nm-thin amyloid-like fibrils contain a large amount of ¿-helical structure.To gain further insights into the structure of the samples, spectroscopic information at each pixel of an image is desirable, that is hyperspectral imaging. In this thesis, we introduce hyperspectral infrared nanoimaging based on nano-FTIR with a tunable bandwidth-limited laser continuum. We describe the technical implementations and present hyperspectral infrared near-field images of about 5000 pixel, each one covering the spectral range from 1000 to 1900 cm-1. To verify the technique and to demonstrate its application potential, we imaged a three-component polymer blend and a melanin granule in a human hair cross-section, and demonstrate that multivariate data analysis can be applied for extracting spatially resolved chemical information. Particularly, we demonstrate that distribution and chemical interaction between the polymer components can be mapped with a spatial resolution of about 30 nm. We foresee wide application potential of hyperspectral infrared nanoimaging for valuable chemical materials characterization and quality control in various fields ranging from materials sciences to biomedicine.CIC NanoGUNE: nanoscience cooperative research cente

Interfacial Hot Carrier Collection Controls Plasmonic Chemistry

Harnessing non-equilibrium hot carriers from plasmonic metal nanostructures constitutes a vibrant research field. It promises to enable control of activity and selectivity of photochemical reactions, especially for solar fuel generation. However, a comprehensive understanding of the interplay of plasmonic hot carrier-driven processes in metal/semiconducting heterostructures has remained elusive. In this work, we reveal the complex interdependence between plasmon excitation, hot carrier generation, transport and interfacial collection in plasmonic photocatalytic devices, uniquely determining the charge injection efficiencies at the solid/solid and solid/liquid interfaces. Interestingly, by measuring the internal quantum efficiency of ultrathin (14 to 33 nm) single-crystalline plasmonic gold (Au) nanoantenna arrays on titanium dioxide substrates, we find that the performance of the device is governed by hot hole collection at the metal/electrolyte interface. In particular, by combining a solid- and liquid-state experimental approach with ab initio simulations, we show a more efficient collection of high-energy d-band holes traveling in [111] orientation, resulting in a stronger oxidation reaction at the {111} surfaces of the nanoantenna. These results thus establish new guidelines for the design and optimization of plasmonic photocatalytic systems and optoelectronic devices

Present and Future of Surface-Enhanced Raman Scattering.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article