249 research outputs found
Silver self aggregation in a nanodevice for enhanced Raman spectroscopy: Experiments vs. simplified modeling via molecular dynamics
No full textWe present a study, via experiments and exploratory molecular dynamics simulations, of self aggregation in cylindrical nanostructures obtained experimentally by combining high resolution electron beam lithography with electroless silver deposition. This process is key to the fabrication of a nanolens device, where a strong surface enhancement can be exploited for Raman spectroscopy. In order to investigate the process, we introduce a simple theoretical model and compare the results of simulations with the fabricated silver nanostructures during the growth phase. Our simulations qualitatively agree with the experiments and allow a general characterization of the process at length scales smaller than those easily accessible by microscopy. We identify a geometrical parameter, the aspect ratio of the cylinder, that relates two different types of growth with different characteristics and, possibly, different Raman enhancements. © 2012 The Royal Society of Chemistry
Electroless Deposition and Nanolithography Can Control the Formation of Materials at the Nano-Scale for Plasmonic Applications
No full textThe new revolution in materials science is being driven by our ability to manipulate matter at the molecular level to create structures with novel functions and properties. The aim of this paper is to explore new strategies to obtain plasmonic metal nanostructures through the combination of a top down method, that is electron beam lithography, and a bottom up technique, that is the chemical electroless deposition. This technique allows a tight control over the shape and size of bi- and three-dimensional metal patterns at the nano scale. The resulting nanostructures can be used as constituents of Surface Enhanced Raman Spectroscopy (SERS) substrates, where the electromagnetic field is strongly amplified. Our results indicate that, in electroless growth, high quality metal nanostructures with sizes below 50 nm may be easily obtained. These findings were explained within the framework of a diffusion limited aggregation (DLA) model, that is a simulation model that makes it possible to decipher, at an atomic level, the rules governing the evolution of the growth front; moreover, we give a description of the physical mechanisms of growth at a basic level. In the discussion, we show how these findings can be utilized to fabricate dimers of silver nanospheres where the size and shape of those spheres is controlled with extreme precision and can be used for very large area SERS substrates and nano-optics, for single molecule detection
The Five Ws (and one H) of Super-Hydrophobic Surfaces in Medicine
No full textSuper-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W), are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule
A combined ElectroWetting on Dielectrics superhydrophobic platform based on silicon micro-structured pillars
No full textA simple and ready to use approach for combining silicon superhydrophobic surfaces with ElectroWetting On Dielectrics (EWOD) phenomenon is presented. The substrate is fabricated using a two-phases process, where a first optical lithography step is used to define the position of the micro-pillars and a second one exploits the characteristics of reactive ion etch Bosch technique. The fabricated substrate has been then coupled with a micro-manipulator tip to show the local changes mechanism of contact angle by applying very low DC voltages in the range from 5 to 30 V. The device can be of interest for a wide variety of microfluidics applications related to the biomedical field
Nanoscaffolds for neural regenerative medicine
No full textThe aim of this chapter is to expound on the methods for the development of a synthetic analog of the extracellular matrix (ECM) that, because of a careful choice of its characteristics, can regulate cell behavior and tissue progression for applications in neural regenerative medicine. Neural cells—neurons—are the smallest building blocks of the central and peripheral nervous systems. The function of neurons is to elaborate the information that a man receives from the environment, share it with other neurons, and use it to activate complex functions such as language, behavior and surviving, reasoning, and self-correction. In the body, neurons are linked to other neurons and are supported by the ECM. The scaffolds are an artificial analog of the ECM: they are designed and fabricated using a combination of chemical, physical, and engineering techniques. Thus the scope of tissue engineering and neural regenerative medicine is to optimize the characteristics of the scaffold to assure the best performance of the neurons cultivated in them. Performance is another word for efficiency: depending on the variables that one want to maximize, one can have different definitions of efficiency. Thus as for some examples, scaffolds can be designed to optimize cell adhesion, growth, proliferation, clustering, or activity. In this chapter, we will explain how one can use micro- and nanofabrication techniques to produce scaffolds with a tight control over its characteristics, including the physical, chemical, geometrical, and mechanical characteristics. Then, we will see how a combination of characteristics can influence cell behavior, and to what extent
Recognition of saccharides in the NIR region with a novel fluorogenic boronolectin: in vitro and live cell labeling
Get PDFThis work describes a novel mono-boronic acid derivative of a tricarbocyanine. The probe is a genuine near-infrared fluorescence emitter with improved properties such as a large Stokes shift, excellent water solubility and sensitive fluorogenicity upon binding to carbohydrates under physiological conditions.Fil: Samaniego Lopez, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Lago Huvelle, María Amparo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Uhrig, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Coluccio Leskow, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Spagnuolo, Carla Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin
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