Download or read book High Quality Colloidal Crystals with Different Architectures and Their Optical Properties written by Jianhui Ye and published by . This book was released on 2006 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High Quality Colloidal Crystals with Different Architectures and Their Optical Properties written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this present work high quality PMMA opals with different sphere sizes, silica opals from large size spheres, multilayer opals, and inverse opals were fabricated. Highly monodisperse PMMA spheres were synthesized by surfactant-free emulsion polymerization (polydispersity ~2%). Large-area and well-ordered PMMA crystalline films with a homogenous thickness were produced by the vertical deposition method using a drawing device. Optical experiments have confirmed the high quality of these PMMA photonic crystals, e.g., well resolved high-energy bands of the transmission and reflectance spectra of the opaline films were observed. For fabrication of high quality opaline photonic crystals from large silica spheres (diameter of 890 nm), self-assembled in patterned Si-substrates a novel technique has been developed, in which the crystallization was performed by using a drawing apparatus in combination with stirring. The achievements comprise a spatial selectivity of opal crystallization without special treatment of the wafer surface, the opal lattice was found to match the pattern precisely in width as well as depth, particularly an absence of cracks within the size of the trenches, and finally a good three-dimensional order of the opal lattice even in trenches with a complex confined geometry. Multilayer opals from opaline films with different sphere sizes or different materials were produced by sequential crystallization procedure. Studies of the transmission in triple-layer hetero-opal revealed that its optical properties cannot only be considered as the linear superposition of two independent photonic bandgaps. The remarkable interface effect is the narrowing of the transmission minima. Large-area, high-quality, and robust photonic opal replicas from silicate-based inorganic-organic hybrid polymers (ORMOCER® s) were prepared by using the template-directed method, in which a high quality PMMA opal template was infiltrated with a neat inorganic-organic ORMOCER® oligomer,
Download or read book Surface Patterning with Colloidal Monolayers written by Nicolas Vogel and published by Springer Science & Business Media. This book was released on 2012-12-28 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: How can the two dimensional crystallization of colloids be used to form highly ordered colloidal monolayers on solid substrates? What application does this have in generating arrays of nanostructures? These questions are addressed in Nicolas Vogel's thesis. Vogel describes a simple preparation method for the formation of uniform colloidal crystals over large areas, which he refines to yield more complex binary and non-close-packed arrangements. These monolayers can be applied to a process termed colloidal lithography which is used to prepare high quality metallic nanostructures with tailored properties defined to suit a variety of applications. Moreover, the author describes a method used to create metallic nanodot arrays with a resolution unprecedented for colloidal lithography methods. The author also outlines methodology to embed nanoparticle arrays into the substrate, which is developed and used to design robust, re-usable biosensor platforms and nanoscale patterns of biomimetic lipid bilayer membranes. The research in this thesis has led to a large number of publications in internationally renowned journals.
Download or read book On Improving the Optical Quality of Colloidal Photonic Crystals microform written by Mathieu Allard and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work advances the understanding of the impact of lattice disorder on the optical properties of colloidal photonic crystals. It also demonstrates and quantifies improvements in the structural and optical quality of the crystals through refinements of the fabrication techniques. Arrays of colloidal particles were grown on substrates covered with holographic relief gratings realized in photoresist films. When the grating pitch was commensurate with the particle size, a uniform lattice orientation was imposed in the crystals. The enhancement in crystal order was visible for thicknesses as large as 40 layers. The impact of lattice disorder on the optical properties of colloidal photonic crystals was investigated numerically. The greatest impact on the optical properties came from size non-uniformity of colloidal particles. A novel algorithm, based on simulated annealing, was used to generate densely packed arrays of spheres with a given size distribution. When the size standard deviation was larger than 3%, a transition from ordered to random-packed arrangements was observed, along with large and sudden changes in optical properties, in the form of increased scattering and reduced contrast associated with the 111 stopband in transmittance spectra. The abruptness of this transition increased with decreasing index contrast. The numerical results agreed well with experimental results. The enhancement of long-range order was further demonstrated and quantified by optical techniques. The diffraction patterns produced when a collimated laser beam illuminated colloidal crystals were shown to be capable of revealing whether the crystals were mono- or poly-crystalline. Quantitative information about internal ordering was also extracted from diffraction spectra: the photon mean free path in the crystal was estimated to be in the range of 3 to 58 lattice constants, depending on the crystal growth conditions.
Download or read book Optical Properties of Photonic Structures written by Mikhail F. Limonov and published by CRC Press. This book was released on 2012-06-25 with total page 535 pages. Available in PDF, EPUB and Kindle. Book excerpt: The collection of articles in this book offers a penetrating shaft into the still burgeoning subject of light propagation and localization in photonic crystals and disordered media. While the subject has its origins in physics, it has broad significance and applicability in disciplines such as engineering, chemistry, mathematics, and medicine. Unlike other branches of physics, where the phenomena under consideration require extreme conditions of temperature, pressure, energy, or isolation from competing effects, the phenomena related to light localization survive under the most ordinary of conditions. This provides the science described in this book with broad applicability and vitality. However, the greatest challenge to the further development of this field is in the reliable and inexpensive synthesis of materials of the required composition, architecture and length scale, where the proper balance between order and disorder is realized. Similar challenges have been faced and overcome in fields such as semiconductor science and technology. The challenge of photonic crystal synthesis has inspired a variety of novel fabrication protocols such as self-assembly and optical interference lithography that offer much less expensive approaches than conventional semiconductor microlithography. Once these challenges are fully met, it is likely that light propagation and localization in photonic microstructures will be at the heart of a 21st-century revolution in science and technology. —From the Introduction, Sajeev John, University of Toronto, Ontario, Canada One of the first books specifically focused on disorder in photonic structures, Optical Properties of Photonic Structures: Interplay of Order and Disorder explores how both order and disorder provide the key to the different regimes of light transport and to the systematic localization and trapping of light. Collecting contributions from leaders of research activity in the field, the book covers many important directions, methods, and approaches. It describes various one-, two-, and three-dimensional structures, including opals, aperiodic Fibonacci-type photonic structures, photonic amorphous structures, photonic glasses, Lévy glasses, and hypersonic, magnetophotonic, and plasmonic–photonic crystals with nanocavities, quantum dots, and lasing action. The book also addresses practical applications in areas such as optical communications, optical computing, laser surgery, and energy.
Download or read book Photonic Crystals written by Kurt Busch and published by John Wiley & Sons. This book was released on 2006-05-12 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: The majority of the contributions in this topically edited book stems from the priority program SPP 1113 "Photonische Kristalle" run by the Deutsche Forschungsgemeinschaft (DFG), resulting in a survey of the current state of photonic crystal research in Germany. The first part of the book describes methods for the theoretical analysis of their optical properties as well as the results. The main part is dedicated to the fabrication, characterization and modeling of two- and three-dimensional photonic crystals, while the final section presents a wide spectrum of applications: gas sensors, micro-lasers, and photonic crystal fibers. Illustrated in full color, this book is not only of interest to advanced students and researchers in physics, electrical engineering, and material science, but also to company R&D departments involved in photonic crystal-related technological developments.
Download or read book Optical Properties of Photonic Crystals written by Kazuaki Sakoda and published by Springer. This book was released on 2013-11-11 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Deals not only with the properties of the radiation modes inside the crystals but also with their peculiar optical response to external fields. A general theory of linear and nonlinear optical response is presented in a clear and detailed fashion using the Green’s function method. Important recent developments such as the enhancement of stimulated emission, second harmonic generation, quadrature-phase squeezing, and low-threshold lasing are likewise treated in detail and made understandable. Numerical methods are also emphasised. This book provides both introductory knowledge for graduate and undergraduate students and important ideas for researchers.
Download or read book Optical Properties of Photonic Structures written by Mikhail F. Limonov and published by Taylor & Francis. This book was released on 2016-04-19 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: The collection of articles in this book offers a penetrating shaft into the still burgeoning subject of light propagation and localization in photonic crystals and disordered media. While the subject has its origins in physics, it has broad significance and applicability in disciplines such as engineering, chemistry, mathematics, and medicine. Unli
Download or read book Optical Properties of Mixed Crystals written by R.J. Elliott and published by Elsevier. This book was released on 2012-12-02 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt: ``Optical Properties of Mixed Crystals'' is concerned with the description of optical processes in substitutionally disordered semiconductors and insulators which can be basically described through their elementary excitations. Two of the chapters relate to the phonon response including the effect of side bands on electron transitions. Two relate to electronic spectra, one on photoelectron spectroscopy and the other on excitons. A further chapter deals with magnons in magnetic crystals and a final chapter is related to fluctuations and band edge effects.Each chapter deals with a specific class of excitation, but the book makes it clear that the fundamental structure of the excitation spectra, including band formation, band tailing and localisation is common to every type of excitation. The volume shows how some basic concepts and ideas can be widely applied to bring coherence and understanding to a diverse area of solid state physics. It therefore provides an up-to-date summary of the experimental and theoretical situation in an important and rapidly developing field and brings together for the first time a discussion of the many different types of spectra which appear in mixed crystals.
Download or read book Entropically Driven Self Assembly of Colloidal Crystals on Templates in Space written by and published by . This book was released on 2002 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photonic Crystals and Their Applications in Optical Sensing and Semiconductor Photocatalysis written by Andrew Chan and published by . This book was released on 2014 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: The projected depletion of fossil fuels in the near future motivates the development of a sustainable hydrogen (H2) economy. Realisation of the H2 economy hinges on the discovery of simple, low cost technologies for H2 manufacture, distribution and storage. With respect to H2 manufacture, noble metal modified titania (TiO2) photocatalysts such as Pd/TiO2 and Au/TiO2 display excellent H2 production rates from ethanol-water mixtures under UV fluxes comparable to those present in sunlight. This research targeted the development of efficient TiO2-based photocatalysts for H2 production from ethanol-water mixtures. The approach involved both photonic band gap (PBG) engineering and optimisation of synergies between TiO2 and added co-catalysts (Au, Pd or Pd-Au nanoparticles systems). Further optimisation of photocatalyst performance were sought through the optimisation of TiO2 crystal size, TiO2 phase composition and co-catalyst loading in the Pd-Au/TiO2 system. Photonic crystals are materials which have a periodically modulated refractive index in 1, 2 or 3-dimensions, with periods on the length scale of visible light. In order to get a handle on how to PBG engineer TiO2 for photocatalytic H2 production, an investigation into the origins of iridescence (pseudo PBGs at visible wavelengths) in some common insect species found around the Auckland region was undertaken. Examples included the Steelblue ladybird (Halmus chalybeus), the Green Bottle fly (Lucilia caesar), the Oak Leaf Miner moth (Phyllonorycter messaniella), the Golden Plusia moth (Thysanoplusia orichalcea) and the chrysalis of the Monarch butterfly (Danaus plexippus). Additionally, male peacock display feathers (Pavo cristatus) were studied and used as a direct comparison to published literature to confirm the viability of our analysis methods. All specimens were characterised by optical light microscopy, cross-sectional Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and UV-Vis reflectance. The cuticle of the Steelblue ladybird demonstrated a 1-D photonic crystal at the exocuticle formed by 140 nm thick chitin lamellae. The male peacock feather barbules contained 2-D arrays of melanin rods (diameters 120-150 nm) wrapped in a keratin sheath. The reflected colour of the feather barbules red-shifted as the diameter of the melanin rods increased. The gold wing scales of the two moth species contained complex 3-D architectures wherein chevron type diffraction gratings were observed on the wing scales. The gold colour of the surface nipples on the Monarch butterfly chrysalis resulted from reflection of light over a broad range of wavelengths from chitin sheets arranged in a 'chirped' multilayer stack, a structure also seen in the exocuticle of the Green Bottle fly. The optical properties of the Steelblue ladybird cuticle, Green Bottle fly cuticle and the peacock feather barbules were all consistent with a modified Bragg's law expression, which considers refraction and diffraction in the photonic crystal architecture. The optical properties of all gold reflecting structures examined in this thesis require a more complex model to explain the optical properties (beyond the scope of this thesis). The natural photonic crystal studies led to the successful fabrication of a series of 3-dimensionally ordered macroporous (3DOM) Zirconia (ZrO2) thin films and powders by the colloidal crystal template technique. The films showed pseudo photonic band gaps along the [111] direction in the UV-Vis-NIR region. The optical properties of a 3DOM ZrO2 material could be tailored by changing the diameter of PMMA colloids in the colloidal crystal template. SEM, TEM and XRD analyses revealed that 3DOM ZrO2 photonic crystals comprised a face-centered cubic array of spherical macropores (diameters ranging from 150-400 nm, respectively) within a matrix of nanocrystalline tetragonal ZrO2. The specific surface areas of all samples were 30-51 m2 g-1, and independent of the macropore size. The optical properties of the 3DOM ZrO2 thin films were comprehensively characterised and were found to be in excellent accord with a modified Bragg's law expression that considers both refraction and diffraction of light in the 3DOM architectures, and also agreed with photonic band gap structure calculations. The PBGs red-shifted on immersion in organic solvents, with the magnitude of the shift being directly proportional to the refractive index of the solvent. Solvent refractive index sensing with a precision of ~0.005 is demonstrated. Preliminary contact angle measurements for water droplets on the 3DOM ZrO2 film gave angles of 130o, indicating the 3DOM ZrO2 surface is superhydrophobic, this is entirely attributable to the rough periodic surface structure of the films on the sub-micron length scale. The next stage of research explored Pd/TiO2, Au/TiO2 and Pd-Au/TiO2 photocatalysts. Initially, Degussa P25 TiO2 was used as the support phase in order to identify the optimum co-catalyst combination and loadings for photocatalytic H2 production from ethanol-water mixtures. A series of Pd-Au/P25 TiO2 photocatalyst powders (Pd, Au or Pd + Au weight loadings = 0-4.00 wt.%) were prepared by the deposition precipitation with urea method wherein both Pd2+ and Au3+ were then simultaneously deposited on the TiO2 support. Samples were then activated under a H2 flow at 500 oC for 2 h to form Pd, Au or Pd-Au nanoparticles. UV-Vis, XRD, XPS and TEM suggest Pd-Au alloy nanoparticles may have formed on the TiO2 surface. Photocatalytic H2 production tests were carried out in ethanol-water mixtures (80:20 and 2:98 EtOH:H2O ratios) under UV-fluxes comparable to that of sunlight. Results showed that a 0.25 wt.% Pd-0.25 wt.% Au/P25 TiO2 photocatalyst gave the highest photocatalytic H2 production rates of 68 mmol g-1 h-1 (at 80:20 EtOH:H2O) and 25 mmol g-1 h-1 (at 2:98 EtOH:H2O). These are amongst the highest H2 production rates yet reported at the two EtOH:H2O ratios and UV fluxes used in this study. A series of 3DOM TiO2 photonic crystal films and powders with PBGs along the [111] direction at UV and visible regions were then successfully fabricated using the colloidal crystal template technique. The as-prepared samples comprised a face-centred cubic array of macropores in a nanocrystalline anatase TiO2 matrix. Pd-Au/3DOM TiO2 photocatalysts were prepared using 3DOM TiO2 supports (anatase form), with PBGs along the [111] direction at 345 nm, 441 nm, 560 nm and 640 nm. The former sample showed the highest rate of photocatalytic H2 production in EtOH:H2O mixtures, which is tentatively attributed to a slow photon photocatalytic amplification mechanism wherein the reaction rate is enhanced through overlap of the 3DOM TiO2 PBG on fcc (111) or (200) planes and the electronic absorption edge of TiO2 (~385 nm). This overlap enhances light absorption by increasing the effective absorption pathlength and also serves to supress electron-hole pair recombination via inhibiting spontaneous emission. Calcining the 3DOM supports at higher temperatures before Pd and Au deposition also positively enhanced the rate of H2 evolution, which can be attributed to optimisation of TiO2 crystallite size and phase composition. A calcination temperature of 650 °C was optimal, yielding a TiO2 phase composition similar to P25 TiO2. At higher temperatures, the transformation of anatase to rutile adversely affects photocatalytic performance. Results guide the development of new and improved semiconductor photocatalysts for solar H2 production from H2O and biofuels. Based on results presented, the Pd-Au/P25 TiO2 system should be further explored and optimised as it has great promise due to the very low metal loadings needed to achieve high rates of H2 production.
Download or read book Colloidal Nanocrystals with Near infrared Optical Properties written by Matthew George Panthani and published by . This book was released on 2011 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal nanocrystals with optical properties in the near-infrared (NIR) are of interest for many applications such as photovoltaic (PV) energy conversion, bioimaging, and therapeutics. For PVs and other electronic devices, challenges in using colloidal nanomaterials often deal with the surfaces. Because of the high surface-to-volume ratio of small nanocrystals, surfaces and interfaces play an enhanced role in the properties of nanocrystal films and devices. Organic ligand-capped CuInSe2 (CIS) and Cu(InXGa1-X)Se2 (CIGS) nanocrystals were synthesized and used as the absorber layer in prototype solar cells. By fabricating devices from spray-coated CuInSe nanocrystals under ambient conditions, solar-to-electric power conversion efficiencies as high as 3.1% were achieved. Many treatments of the nanocrystal films were explored. Although some treatments increased the conductivity of the nanocrystal films, the best devices were from untreated CIS films. By modifying the reaction chemistry, quantum-confined CuInSeXS2-X (CISS) nanocrystals were produced. The potential of the CISS nanocrystals for targeted bioimaging was demonstrated via oral delivery to mice and imaging of nanocrystal fluorescence. The size-dependent photoluminescence of Si nanocrystals was measured. Si nanocrystals supported on graphene were characterized by conventional transmission electron microscopy and spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM). Enhanced imaging contrast and resolution was achieved by using Cs-corrected STEM with a graphene support. In addition, clear imaging of defects and the organic-inorganic interface was enabled by utilizing this technique.
Download or read book Photonic Crystals written by Qihuang Gong and published by CRC Press. This book was released on 2014-02-06 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a broad overview of photonic crystals and, as the title suggests, covers their principles and applications. It is written from a physics point of view with an emphasis on materials science. Equations are well explained and often completely avoided to increase the readability of the book. The book is divided into eight chapters, starting with a brief introduction. The second chapter deals with different dimensionalities of the photonic crystals and their properties. The third chapter is very interestingly written and provides a survey of the various synthesis methods used for production of photonic crystals, including chemical routes, lithography, and self-assembly of colloidal photonic crystals. Chapters 4–8 constitute the bulk of the book and provide examples of applications of these photonic crystals. Chapter 4 offers a good explanation of optical switching. Bandgap and defect mode switching are also brought into focus along with many other mechanisms—14 different switching mechanisms in all, including thermal, electro, and magneto switching. Frequency tuning of photonic crystal filters with special attention to nanosize photonic crystals is illustrated, providing a direct perspective on applications of these materials in integrated photonic circuits. The transition from chapter 5 to 6 dealing with photonic crystal lasers is smooth, especially after a clear description of frequency tuning. Here, one- to three-dimensional photonic lasers are explained along with laser oscillations produced by a variety of microcavity methods. Metallodielectric and liquid-crystal photonic lasers are equally well illustrated. Chapter 7 introduces logic devices based on photonic crystals. This chapter clearly explains, with the help of simple illustrations, how to obtain AND, OR, and XOR logic gates. Chapter 8 concludes the book by presenting possible applications, including gas, chemical, fluid, and cell sensing; their workings are very well described from a fundamental point of view. The diagrams and illustrations are appropriate and eye catching. There are ample references; thus readers are able to find more detailed information to satisfy their curiosity if the book does not suffice. Even though the introduction provides basics of these photonic crystals, I do get the impression that the bigger picture is missing. A nonexpert may not understand the direct application of such materials right from the beginning of the book. A flowchart or a diagram of these photonic crystals, illustrating applications in daily life at the beginning of the book, could attract a broader readership. In this regard, I believe that this book is most adapted to physicists with a materials science background or vice versa. However, one should take into consideration that the principles of photonic crystals cannot be explained without physics, and therefore the quality of this book remains intact and could very well serve as a textbook for future physicists.
Download or read book Colloidal Crystals of Spheres and Cubes in Real and Reciprocal Space written by Janne-Mieke Meijer and published by Springer. This book was released on 2015-06-11 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an in-depth study on the effect of colloidal particle shape and formation mechanism on self-organization and the final crystal symmetries that can be achieved. It demonstrates how state-of-the-art X-ray diffraction techniques can be used to produce detailed characterizations of colloidal crystal structures prepared using different self-assembly techniques, and how smart systems can be used to investigate defect formation and diffusion in-situ. One of the most remarkable phenomena exhibited by concentrated suspensions of colloidal particles is the spontaneous self-organization into structures with long-range spatial and/or orientational orders. The study also reveals the subtle structural variations that arise by changing the particle shape from spherical to that of a rounded cube. In particular, the roundness of the cube corners, when combined with the self-organization pathway, convective assembly or sedimentation, was shown to influence the final crystal symmetries.
Download or read book Colloids and Colloid Assemblies written by Frank Caruso and published by John Wiley & Sons. This book was released on 2006-12-13 with total page 621 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by outstanding experts in the colloids field, this book deals with the recent developments in the synthesis, modification, utilization and application of colloids. The types covered range from metal nanoparticles through to inorganic particles and polymer latexes. Strategies for their modification to impart new properties will be outlined and ordered assemblies derived from colloid particles and some applications for colloids are shown. A multidisciplinary audience spread throughout academia and industry alike will certainly appreciate this first concise collection of knowledge in book form for this topic.
Download or read book Colloidal Quantum Dot Optoelectronics and Photovoltaics written by Gerasimos Konstantatos and published by Cambridge University Press. This book was released on 2013-11-07 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.
Download or read book Nanomaterials and Nanoarchitectures written by M. Bardosova and published by Springer. This book was released on 2015-08-31 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current work consists of nine contributions describing recent progress in the interdisciplinary of Nanoscience, which involves physics, chemistry, engineering, biology and medicine and one essay outlining some important historical and socioeconomic factors pertaining to recent developments in nanoscale science and technology. All 10 chapters have been written by eminent experts in their respective fields. The authors employ the terms ‘nanomaterials’ as building blocks of a range of materials, ‘nanoarchitecture’ represents the design and ‘nanotechnology’ the means to produce a particular device or functionality. Two of the chapters are devoted to novel materials and two others focus on analyzing techniques, which can be used to enable molecular control of the film architecture. Additionally, the reader will find material devoted to photonic and hybrid plasmonic-photonic crystals as well as sections which address their applications, such as the use of plasmonic particles and nanostructures for new sensing concepts and ultrasensitive detection techniques. This work will be of interest to graduate students, researchers and practitioners alike.
