DOCSLIB.ORG

Controlling Gold Nanoparticle Assembly Through Particle

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Controlling Gold Nanoparticle Assembly Through Particle CONTROLLING GOLD NANOPARTICLE ASSEMBLY THROUGH PARTICLE- PARTICLE AND PARTICLE-SURFACE INTERACTIONS Dissertation Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Doctor of Philosophy in Engineering By John Joseph Kelley, M.S. Dayton, Ohio August, 2018 CONTROLLING GOLD NANOPARTICLE ASSEMBLY THROUGH PARTICLE-PARTICLE AND PARTICLE-SURFACE INTERACTIONS Name: Kelley, John Joseph APPROVED BY: ___________________________ ___________________________ Erick S. Vasquez, Ph.D. Donald Klosterman, Ph.D. Advisory Committee Chairman Committee Member Assistant Professor, Department of Associate Professor, Department of Chemical and Materials Engineering Chemical and Materials Engineering ___________________________ ___________________________ Andrey Voevodin, Ph.D. P. Terrence Murray, Ph.D. Committee Member Committee Member Adjunct Professor, Department of Adjunct Professor, Department of Chemical and Materials Engineering Chemical and Materials Engineering ___________________________ Richard A. Vaia, Ph.D. Research Advisor Technical Director, Air Force Research Laboratory ___________________________ ___________________________ Robert J. Wilkens, Ph.D., P.E. Eddy M. Rojas, Ph.D., M.A., P.E. Associate Dean for Research and Innovation Dean, School of Engineering Professor School of Engineering ii ABSTRACT CONTROLLING GOLD NANOPARTICLE ASSEMBLY THROUGH PARTICLE- PARTICLE AND PARTICLE-SURFACE INTERACTIONS Name: Kelley, John Joseph University of Dayton Advisor: Dr. Erick S. Vasquez Two-dimensional assemblies of colloidal gold nanoparticles were deposited via electrostatic self-assembly onto silicon substrates modified with aminopropyltriethoxysilane. Assemblies were tuned by systematically adjusting the pH and ionic strength of the nanoparticle solutions and the fraction of adsorbed aminosilane molecules on the silicon surfaces. The nanoparticles were characterized by their size distribution, solution stability and electrokinetic properties. The resulting two-dimensional assemblies varied in particle surface coverage, interparticle separation and lateral organization. Increasing solution pH intensified interparticle repulsions and reduced the charge density of the aminosilane substrate, thus decreasing the fractional monolayer coverage of particles. Additionally, increasing ionic strength reduced interparticle separations, which were described by radial distribution functions, and consequently produced denser particle assemblies. At long adsorption times, surface coverage approaches a maximum which was constrained by the extent of interparticle repulsion and iii particle-surface interactions. With strong surface attraction of the pure aminosilane surface, the particles were incapable of lateral rearrangement during the adsorption process and, at best, organized into liquid-like structures, in agreement with the random sequential adsorption model for colloidal monolayers. In an effort to circumvent this issue, non- binding alkylsilanes were incorporated into the modified surfaces, thereby reducing the aminosilane surface density and weakening the attractive potential of the surface. These mixed silane surfaces were characterized to reveal their chemical and interfacial energetic properties. At a particular threshold of reduced aminosilane density, nanoparticle coverage fell considerably and two-dimensional order degraded. The local geometries of particle assemblies were evaluated by Voronoi tessellation which provided indication of structural transformations with changing solution and surface conditions. As a result, optimal processing parameters were described for obtaining monolayers of gold nanoparticles with varying degrees of surface coverage and two-dimensional arrangement. The results from this study expands the understanding of the underlying chemical and physical mechanisms behind colloidal stability and particle adsorption. This progresses towards the realization of arrays of highly-ordered and densely packed nanoparticles of diverse chemistries largely assembled in parallel onto assorted surfaces using minimal processing. iv DEDICATION Dedicated to my support group. For all that we have endured together. This accomplishment would not have been possible without you. v ACKNOWLEDGEMENTS Above all, I must thank my family: Caryn, Jack, Sam, my parents, my in-laws and anyone else who suffered yet still supported me during this arduous journey. Whether it was through gentle words of encouragement or punitive threats, you did what was necessary to light a fire under my butt and push me across the finish line. You were the inspiration for me to finish that I might not have had on my own. I would also like to thank my friends who have encouraged me along the way, but more importantly, provided me with necessary distractions to help maintain my sanity, whether it be a couple jokes, a few (or more) beers or a good old gripe session. You definitely helped to keep me grounded and not to take life too seriously. I am also grateful for having Jen DeCerbo as my partner-in-crime throughout grad school. Thank you for keeping me awake during class and making the journey as enjoyable as possible. Furthermore, I am grateful to those who have contributed to my research, whether through technical assistance, imparted knowledge or much-needed guidance. At the front of the pack is Rich Vaia, who has educated and guided me substantially for over a decade. He has also shown considerable patience with me while working on this dissertation, probably more than I deserve. I would also like to thank Hilmar Koerner for being my first mentor at AFRL and helping to establish my skillset in materials research. I also greatly valued the mentorship and friendship of Mike Jespersen, who showed me the ropes with vi nanoparticle assemblies and surface modifications (it’s all your fault!). Additionally, Mike supported my research with useful XPS data, even when he had more important things to do. I also appreciate the assistance and interactions from all of the researchers and technicians at the AFRL Materials and Manufacturing directorate that I’ve had the pleasure to work with at some capacity, a list which is surely too long to include. I would also like to thank all of my professors at UD as well as my committee: Erick Vasquez, Terry Murray, Andrey Voevodin and Don Klosterman. Their knowledge and support have been quite beneficial during my time at UD. Lastly, I would like to thank myself for persevering and seeing this dissertation through to the end, despite all the grief it has imparted over the years. You are my rock. You are my inspiration. You are my hero. vii TABLE OF CONTENTS ABSTRACT ……………………………………………………………………………iii DEDICATION .....................................................................................................................v ACKNOWLEDGEMENTS ................................................................................................vi LIST OF FIGURES ............................................................................................................xi LIST OF TABLES .......................................................................................................... xviii LIST OF ABBREVIATIONS AND NOTATIONS ..........................................................xix CHAPTER 1. INTRODUCTION ....................................................................................... 1 1.1 The Rise of Nanotechnology .................................................................................. 1 1.2 Nanoparticle Assemblies for Technology ............................................................... 2 1.3 Dissertation Overview ............................................................................................ 7 1.4 Research Objectives ................................................................................................ 8 CHAPTER 2. BACKGROUND ....................................................................................... 10 2.1 Nanoscale Structures ............................................................................................. 10 2.2 Functional Surfaces for Nanoparticle Assembly .................................................. 11 2.2.1 Self-assembled Monolayers on Two-dimensional Surfaces ........................ 12 2.2.2 Self-assembled Monolayers on SiO2 Surfaces ............................................. 13 2.3 Gold Nanoparticles ............................................................................................... 26 2.3.1 History and Properties.................................................................................. 26 2.3.2 Synthesis and Purification............................................................................ 29 2.4 Particle Interactions and Stability ......................................................................... 34 2.4.1 Interaction Potentials ................................................................................... 35 2.4.2 Zeta Potential ............................................................................................... 38 2.4.3 Acid-base Chemistry .................................................................................... 39 2.4.4 Ionic Environment ....................................................................................... 43 2.5 Electrostatic Adsorption of Nanoparticles ............................................................ 44 2.5.1 Theory and Simulations ..............................................................................
Load more

Recommended publications
  • MEMS Technology for Physiologically Integrated Devices
    A BioMEMS Review: MEMS Technology for Physiologically Integrated Devices AMY C. RICHARDS GRAYSON, REBECCA S. SHAWGO, AUDREY M. JOHNSON, NOLAN T. FLYNN, YAWEN LI, MICHAEL J. CIMA, AND ROBERT LANGER Invited Paper MEMS devices are manufactured using similar microfabrica- I. INTRODUCTION tion techniques as those used to create integrated circuits. They often, however, have moving components that allow physical Microelectromechanical systems (MEMS) devices are or analytical functions to be performed by the device. Although manufactured using similar microfabrication techniques as MEMS can be aseptically fabricated and hermetically sealed, those used to create integrated circuits. They often have biocompatibility of the component materials is a key issue for moving components that allow a physical or analytical MEMS used in vivo. Interest in MEMS for biological applications function to be performed by the device in addition to (BioMEMS) is growing rapidly, with opportunities in areas such as biosensors, pacemakers, immunoisolation capsules, and drug their electrical functions. Microfabrication of silicon-based delivery. The key to many of these applications lies in the lever- structures is usually achieved by repeating sequences of aging of features unique to MEMS (for example, analyte sensitivity, photolithography, etching, and deposition steps in order to electrical responsiveness, temporal control, and feature sizes produce the desired configuration of features, such as traces similar to cells and organelles) for maximum impact. In this paper, (thin metal wires), vias (interlayer connections), reservoirs, we focus on how the biological integration of MEMS and other valves, or membranes, in a layer-by-layer fashion. The implantable devices can be improved through the application of microfabrication technology and concepts.
    [Show full text]
  • A Density Functional Theory Study of Hydrogen Adsorption in MOF-5
    17974 J. Phys. Chem. B 2005, 109, 17974-17983 A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder* Department of Materials Science and Engineering, Massachusetts Institute of Technology, Building 13-5056, 77 Massachusetts AVenue, Cambridge, Massachusetts 02139 ReceiVed: March 8, 2005; In Final Form: August 3, 2005 Ab initio molecular dynamics in the generalized gradient approximation to density functional theory and ground-state relaxations are used to study the interaction between molecular hydrogen and the metal-organic framework with formula unit Zn4O(O2C-C6H4-CO2)3. Five symmetrically unique adsorption sites are identified, and calculations indicate that the sites with the strongest interaction with hydrogen are located near the Zn4O clusters. Twenty total adsorption sites are found around each Zn4O cluster, but after 16 of these are populated, the interaction energy at the remaining four sites falls off significantly. The adsorption of hydrogen on the pore walls creates an attractive potential well for hydrogen in the center of the pore. The effect of the framework on the physical structure and electronic structure of the organic linker is calculated, suggesting ways by which the interaction between the framework and hydrogen could be modified. Introduction ogies can be synthesized using a variety of organic linkers, One of the major obstacles to the widespread adoption of providing the ability to tailor the nature and size of the pores. hydrogen as a fuel is the lack of a way to store hydrogen with Several frameworks have been experimentally investigated for sufficient gravimetric and volumetric densities to be economi- their abilities to store hydrogen, but to date none are able to do cally practical.
    [Show full text]
  • Surface Science 675 (2018) 26–35
    Surface Science 675 (2018) 26–35 Contents lists available at ScienceDirect Surface Science journal homepage: www.elsevier.com/locate/susc Molecular and dissociative adsorption of DMMP, Sarin and Soman on dry T and wet TiO2(110) using density functional theory ⁎ Yenny Cardona Quintero, Ramanathan Nagarajan Natick Soldier Research, Development & Engineering Center, 15 General Greene Avenue, Natick, MA 01760, United States ARTICLE INFO ABSTRACT Keywords: Titania, among the metal oxides, has shown promising characteristics for the adsorption and decontamination of Adsorption of nerve agents on TiO2 chemical warfare nerve agents, due to its high stability and rapid decomposition rates. In this study, the ad- Molecular and dissociative adsorption sorption energy and geometry of the nerve agents Sarin and Soman, and their simulant dimethyl methyl Dry and hydrated TiO2 phosphonate (DMMP) on TiO2 rutile (110) surface were calculated using density functional theory. The mole- Slab model of TiO 2 cular and dissociative adsorption of the agents and simulant on dry as well as wet metal oxide surfaces were DFT calculations of adsorption energy considered. For the wet system, computations were done for the cases of both molecularly adsorbed water Nerve agent dissociation mechanisms Nerve agent and simulant comparison (hydrated conformation) and dissociatively adsorbed water (hydroxylated conformation). DFT calculations show that dissociative adsorption of the agents and simulant is preferred over molecular adsorption for both dry and wet TiO2. The dissociative adsorption on hydrated TiO2 shows higher stability among the different configura- tions considered. The dissociative structure of DMMP on hydrated TiO2 (the most stable one) was identified as the dissociation of a methyl group and its adsorption on the TiO2 surface.
    [Show full text]
  • Adsorption and Desorption Performance and Mechanism Of
    molecules Article Adsorption and Desorption Performance and Mechanism of Tetracycline Hydrochloride by Activated Carbon-Based Adsorbents Derived from Sugar Cane Bagasse Activated with ZnCl2 Yixin Cai 1,2, Liming Liu 1,2, Huafeng Tian 1,*, Zhennai Yang 1,* and Xiaogang Luo 1,2,3,* 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business University (BTBU), Beijing 100048, China; [email protected] (Y.C.); [email protected] (L.L.) 2 School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, LiuFang Campus, No.206, Guanggu 1st road, Donghu New & High Technology Development Zone, Wuhan 430205, Hubei Province, China 3 School of Materials Science and Engineering, Zhengzhou University, No.100 Science Avenue, Zhengzhou 450001, Henan Province, China * Correspondence: [email protected] (H.T.); [email protected] (Z.Y.); [email protected] or [email protected] (X.L.); Tel.: +86-139-8627-0668 (X.L.) Received: 4 November 2019; Accepted: 9 December 2019; Published: 11 December 2019 Abstract: Adsorption and desorption behaviors of tetracycline hydrochloride by activated carbon-based adsorbents derived from sugar cane bagasse modified with ZnCl2 were investigated. The activated carbon was tested by SEM, EDX, BET, XRD, FTIR, and XPS. This activated carbon 2 1 exhibited a high BET surface area of 831 m g− with the average pore diameter and pore volume 3 1 reaching 2.52 nm and 0.45 m g− , respectively. The batch experimental results can be described by Freundlich equation, pseudo-second-order kinetics, and the intraparticle diffusion model, 1 while the maximum adsorption capacity reached 239.6 mg g− under 318 K.
    [Show full text]
  • Viewsizer 3000
    ViewSizer TM 3000 Unmatched Visualization and Measurement of Nanoparticles Visualize and determine the size distribution of a wide range of nanoparticle sizes even when they coexist in the same liquid. APPLICATIONS INCLUDE • Batteries • Exosomes, microvesicles, • Pharmaceuticals and other biological particles • Catalysts • Limnology • Pigments and inks • Chemical & • Metal powders • Polymers mechanical polishing • Colloid stability • Nanoparticles • Protein aggregation • Cosmetics • Oceanography • Semiconductors • Ecotoxicology • Particle counting • Water quality • Energy • Particle number concentration • Viruses and virus like particles (VLP’s) • Environmental sciences • Particle size distribution even for polydisperse samples High resolution size distribution and nanoparticle concentration Determine both with the ViewSizer™ 3000 INTRODUCTION Analyzing nanoparticles is inherently challenging. They are too small to image with visible light and must be imaged by laborious electron microscopy. Dynamic light scattering and laser diffraction can be used to determine particle size and size distribution with some success. However, as ensemble techniques, high resolution size distribution information cannot be obtained and those methods do not measure particle concentration. The ultramicroscope and nanoparticle tracking have been used with only partial success since the wide range of sizes present in many samples means that scattering from the largest particles is bright enough to saturate the detector and eliminate any hope of learning about
    [Show full text]
  • Nanoparticle Size Effect on Water Vapour Adsorption by Hydroxyapatite
    nanomaterials Article Nanoparticle Size Effect on Water Vapour Adsorption by Hydroxyapatite Urszula Szałaj 1,2,*, Anna Swiderska-´ Sroda´ 1, Agnieszka Chodara 1,2, Stanisław Gierlotka 1 and Witold Łojkowski 1 1 Institute of High Pressure Physics, Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland 2 Faculty of Materials Engineering, Warsaw University of Technology, Wołoska 41, 02-507 Warsaw, Poland * Correspondence: [email protected]; Tel.: +48-22-876-04-31 Received: 12 June 2019; Accepted: 10 July 2019; Published: 12 July 2019 Abstract: Handling and properties of nanoparticles strongly depend on processes that take place on their surface. Specific surface area and adsorption capacity strongly increase as the nanoparticle size decreases. A crucial factor is adsorption of water from ambient atmosphere. Considering the ever-growing number of hydroxyapatite nanoparticles applications, we decided to investigate how the size of nanoparticles and the changes in relative air humidity affect adsorption of water on their surface. Hydroxyapatite nanoparticles of two sizes: 10 and 40 nm, were tested. It was found that the nanoparticle size has a strong effect on the kinetics and efficiency of water adsorption. For the same value of water activity, the quantity of water adsorbed on the surface of 10 nm nano-hydroxyapatite was five times greater than that adsorbed on the 40 nm. Based on the adsorption isotherm fitting method, it was found that a multilayer physical adsorption mechanism was active. The number of adsorbed water layers at constant humidity strongly depends on particles size and reaches even 23 layers for the 10 nm particles. The amount of water adsorbed on these particles was surprisingly high, comparable to the amount of water absorbed by the commonly used moisture-sorbent silica gel.
    [Show full text]
  • Controlling Nanoparticle Dispersion for Nanoscopic Self-Assembly
    CONTROLLING NANOPARTICLE DISPERSIONS FOR NANOSCOPIC SELF- ASSEMBLY A Project Report presented to the Faculty of California Polytechnic State University, San Luis Obispo In Partial Fulfillment of the Requirements for the Degree Master of Science in Polymers and Coatings by Nathan Stephen Starkweather March 2013 © 2013 Nathan Stephen Starkweather ALL RIGHTS RESERVED ii COMMITTEE MEMBERSHIP TITLE: Controlling Nanoparticle Dispersions for Nanoscopic Self- Assembly AUTHOR: Nathan Stephen Starkweather DATE SUBMITTED: March 2013 COMMITTEE CHAIR: Raymond H. Fernando, Ph.D. COMMITTEE MEMBER: Shanju Zhang, Ph.D. COMMITTEE MEMBER: Chad Immoos, Ph.D. iii ABSTRACT Controlling Nanoparticle Dispersions for Nanoscopic Self-Assembly Nathan Stephen Starkweather Nanotechnology is the manipulation of matter and devices on the nanometer scale. Below the critical dimension length of 100nm, materials begin to display vastly different properties than their macro- or micro- scale counterparts. The exotic properties of nanomaterials may trigger the start of a new technological revolution, similar to the electronics revolution of the late 20th century. Current applications of nanotechnology primarily make use of nanoparticles in bulk, often being made into composites or mixtures. While these materials have fantastic properties, organization of nano and microstructures of nanoparticles may allow the development of novel devices with many unique properties. By analogy, bulk copper may be used to form the alloys brass or bronze, which are useful materials, and have been used for thousands of years. Yet, organized arrays of copper allowed the development of printed circuit boards, a technology far more advanced than the mere use of copper as a bulk material. In the same way, organized assemblies of nanoparticles may offer technological possibilities far beyond our current understanding.
    [Show full text]
  • A Technology Overview and Applications of Bio-MEMS
    INSTITUTE OF SMART STRUCTURES AND SYSTEMS (ISSS) JOURNAL OF ISSS J. ISSS Vol. 3 No. 2, pp. 39-59, Sept. 2014. REVIEW ARTICLE A Technology Overview and Applications of Bio-MEMS Nidhi Maheshwari+, Gaurav Chatterjee+, V. Ramgopal Rao. Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, India-400076. Corresponding Author: [email protected] + Both the authors have contributed equally. Keywords: Abstract Bio-MEMS, immobilization, Miniaturization of conventional technologies has long cantilever, micro-fabrication, been understood to have many benefits, like: lower cost of biosensor. production, lower form factor leading to portable applications, and lower power consumption. Micro/Nano fabrication has seen tremendous research and commercial activity in the past few decades buoyed by the silicon revolution. As an offset of the same fabrication platform, the Micro-electro-mechanical- systems (MEMS) technology was conceived to fabricate complex mechanical structures on a micro level. MEMS technology has generated considerable research interest recently, and has even led to some commercially successful applications. Almost every smart phone is now equipped with a MEMS accelerometer-gyroscope system. MEMS technology is now being used for realizing devices having biomedical applications. Such devices can be placed under a subset of MEMS called the Bio-MEMS (Biological MEMS). In this paper, a brief introduction to the Bio-MEMS technology and the current state of art applications is discussed. 1. Introduction Generally, the Bio-MEMS can be defined as any The interdisciplinary nature of the Bio-MEMS research is system or device, which is fabricated using the highlighted in Figure 2. This highlights the overlapping of micro-nano fabrication technology, and used many different scientific disciplines, and the need for a healthy for biomedical applications such as diagnostics, collaborative effort.
    [Show full text]
  • Adsorption Properties of Granular Activated Carbon-Supported
    www.nature.com/scientificreports OPEN Adsorption Properties of Granular Activated Carbon-Supported Titanium Dioxide Particles for Dyes Received: 23 November 2017 Accepted: 10 April 2018 and Copper Ions Published: xx xx xxxx Xin Zheng2,3, Nannan Yu1, Xiaopeng Wang4, Yuhong Wang1, Linshan Wang1, Xiaowu Li2 & Xiaomin Hu5 In the present paper, granular activated carbon (GAC) supported titanium dioxide (TiO2@GAC) particles were prepared by sol-gel process. Their performance in simultaneous adsorption of dye and Cu2+ from wastewater was studied. X-ray difraction (XRD) indicated that TiO2 of the TiO2@GAC microsphere is anatase type, and Fourier transform infrared spectroscopy (FT-IR) showed that the samples have obvious characteristic peaks in 400–800 cm−1, which indicated that there are Ti-O-Ti bonds. The 2+ experimental results showed that the adsorption of TiO2@GAC for Methylene blue (MB) and Cu were favorable under acidity condition, the adsorption of Methyl orange (MO) was favorable under 2+ alkalecent condition. The reaction kinetics of TiO2@GAC for MO, MB and Cu were well described as pseudo-second-order kinetic model; The reaction isotherms for MO, MB and Cu2+ were well ftted by 2+ Langmuir model. The maximum adsorption capacity of TiO2@GAC for MO, MB and Cu in the single systems were 32.36 mg/g, 25.32 mg/g and 23.42 mg/g, respectively. As for adsorption, Cu2+ had a suppression efect on MB, and a promotion efect on MO, however, the impact of MO and MB on Cu2+ were negligible. With the rapid development of industry, there is more and more concern about toxic dyes and heavy metal ions in untreated waste water from industrial production processes1.
    [Show full text]
  • Adsorption Studies with Liquid Chromatography
    Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1118 Adsorption Studies with Liquid Chromatography Experimental Preparations for Thorough Determination of Adsorption Data LENA EDSTRÖM ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 ISBN 978-91-554-8858-1 UPPSALA urn:nbn:se:uu:diva-216235 2014 Dissertation presented at Uppsala University to be publicly examined in B22, BMC, Husargatan 3, Uppsala, Friday, 14 March 2014 at 10:15 for the degree of Doctor of Philosophy. The examination will be conducted in English. Faculty examiner: Associate Professor Lars Hagel. Abstract Edström, L. 2014. Adsorption Studies with Liquid Chromatography. Experimental Preparations for Thorough Determination of Adsorption Data. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1118. 56 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-8858-1. Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms. Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility.
    [Show full text]
  • Nonlinear Dark-Field Microscopy
    pubs.acs.org/NanoLett Nonlinear Dark-Field Microscopy Hayk Harutyunyan,† Stefano Palomba,† Jan Renger,‡ Romain Quidant,‡,§ and Lukas Novotny*,† † Institute of Optics, University of Rochester, Rochester, New York 14627, United States, ‡ ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain, and § ICREA-Institucio´ Catalana de Recerca i Estudis Avanc¸ats, 08010 Barcelona, Spain ABSTRACT Dark-field microscopy is a background-free imaging method that provides high sensitivity and a large signal-to-noise ratio. It finds application in nanoscale detection, biophysics and biosensing, particle tracking, single molecule spectroscopy, X-ray imaging, and failure analysis of materials. In dark-field microscopy, the unscattered light path is typically excluded from the angular range of signal detection. This restriction reduces the numerical aperture and affects the resolution. Here we introduce a nonlinear dark-field scheme that overcomes this restriction. Two laser beams of frequencies ω1 and ω2 are used to illuminate a sample surface and to generate a purely evanescent field at the four-wave mixing (4WM) frequency ω4wm ) 2ω1 - ω2. The evanescent 4WM field scatters at sample features and generates radiation that is detected by standard far-field optics. This nonlinear dark-field scheme works with samples of any material and is compatible with applications ranging from biological imaging to failure analysis. KEYWORDS Dark-field imaging, microscopy, nonlinear wave mixing, optical sensing, detection and
    [Show full text]
  • Nanotechnology and Drug Delivery Part 1: Background and Applications
    Ochekpe et al Tropical Journal of Pharmaceutical Research, June 2009; 8 (3): 265-274 © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. All rights reserved . Available online at http://www.tjpr.org Review Article Nanotechnology and Drug Delivery Part 1: Background and Applications Nelson A Ochekpe 1*, Patrick O Olorunfemi 2 and Ndidi C Ngwuluka 2 1Department of Pharmaceutical Chemistry and 2Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, University of Jos, PMB 2084, Jos, Nigeria Abstract Nanotechnology in general and as it relates to drug delivery in humans has been reviewed in a two-part article, the first part of which is this paper. In this paper, nanotechnology in nature, history of nanotechnology and methods of synthesis are discussed, while also outlining its applications, benefits and risks. Nanotechnology is an industrial revolution, based on integration of disciplines that could change every facet of human life. Some examples of changes brought about by reduction in particle sizes to the physical, chemical and biological properties of substances, compounds and drug products have been cited. The benefits of nanotechnology are enormous and so these benefits should be maximized while efforts are made to reduce the risks. Keywords: Nanotechnology, Nanobiotechnology, Nanostructures, Nanomaterials, Nanocarriers, Drug delivery. Received: 4 Nov 2008 Revised accepted: 13 Jan 2009 *Corresponding author: E-mail: [email protected]; Tel: +234-(0)8037006372 Trop J Pharm Res, June 2009; 8 (3): 265 Ochekpe et al INTRODUCTION Definition Nanotechnology can simply be defined as the Nanotechnology in nature technology at the scale of one-billionth of a metre.
    [Show full text]