1,008 research outputs found
Highly luminescent water-soluble CdTe quantum dots
No full textColloidal CdTe quantum dots prepared in TOP/DDA (trioctylphosphine/dodecylamine) are transferred into water by the use of aminoethanethiol.HCl (AET) or mercaptopropionic acid (MPA). This results in an increase in the photoluminescence quantum efficiency and a longer exciton lifetime. For the first time, water-soluble semiconductor nanocrystals presenting simultaneously high band-edge photoluminescence quantum efficiencies (as high as 60% at room temperature), monoexponential exciton decays, and no observable defect-related emission are obtained
Een open uitvoeringsvariant van het Ioniserende Stralen Practicum
No full textIn 2012 bestaat het Ioniserende Stralen Practicum (ISP) veertig jaar. In die lange periode is het karakter van de experimenten met radioactieve bronnen en röntgentoestellen nauwelijks veranderd. Dat zal ook wel zo blijven. Maar er kan nu ook – voorlopig nog in beperkte mate – gekozen worden voor een nieuwe uitvoeringsvariant met een meer open aanpak van de vertrouwde experimenten
Electrochemical kinetics of hydrogen intercalation in gadolinium switchable mirrors
No full textPotential-step experiments on gadolinium thin-film electrodes provide current and optical transmission transients, whose time constants are related to effective hydrogen diffusion coefficients according to a standard diffusion model. The diffusion coefficients and switching kinetics depend on temperature, hydrogen concentration, potential, and film thickness. A thickness dependence of the kinetics is observed in which the diffusion coefficient and optical switching time are linearly dependent. (C) 2003 American Institute of Physics
Ultrafast all-optical gated amplifier based on ZnO nanowire lasing
No full textWe present an ultrafast all-optical gated amplifier, or transistor, consisting of a forest of ZnO nanowire lasers. A gate light pulse creates a dense electron-hole plasma and excites laser action inside the nanowires. Source light traversing the nanolaser forest is amplified, partly as it is guided through the nanowires, and partly as it propagates diffusively through the forest. We have measured transmission increases at the drain up to a factor 34 for 385-nm light. Time-resolved amplification measurements show that the lasing is rapidly self-quenching, yielding pulse responses as short as 1.2?ps.BN/BionanoscienceApplied Science
Orbital and Charge-Resolved Polaron States in CdSe Dots and Rods Probed by Scanning Tunneling Spectroscopy
No full textConduction electrons interact with lattice vibrations, leading to coupled electron-phonon states. This effect is of fundamental importance in understanding electron transport and energy relaxation in nanoscale systems. We report quantitative results on the electron-phonon coupling strength in CdSe quantum dots (QDs) and rods, obtained by low-temperature scanning tunneling microscopy. We resolve the polaron eigenstates arising from coupling of the electrons to longitudinal optical phonons. The electron-phonon coupling strength is dependent on the electron orbital symmetry, the number of added electrons, and the size and dielectric environment of the QD
Sample Corrugation Affects the Apparent Bond Lengths in Atomic Force Microscopy
No full textFrequency modulation atomic force microscopy (AFM) allows the chemical structure of planar molecules to be determined with atomic resolution. Typically, these measurements are carried out in constant-height mode using carbon monoxide (CO) terminated tips. Such tips exhibit considerable flexibility, i.e., the CO molecule can bend laterally due to the tip sample interaction. Using epitaxial graphene as a model system, we demonstrate experimentally that the apparent atomic positions measured by AFM depend on the sample corrugation. Using molecular mechanics simulations, we explain these observations by the interplay of the CO bending and the nonlinear background signal arising from the neighboring atoms. These effects depend nontrivially on the tip sample distance and limit the achievable accuracy on the bond length determination based on AFM experiments
Child & Youth Care Practicum Resources
Get PDFYouth Care practicum (internship, fieldwork, field placement) is central to all CYC credentials across Canada. How has it come to be the way it is today? What purposes does it serve? Who gets to decide? The newly formed Child & Youth Care Educational Accreditation Board of Canada (CYCEAB) Practicum Committee led a invites you to participate in a lively discussion about all things CYC practicum. At that session "Child & Youth Care Practicum: Past, Present & Future", the following resources were ‘launched’ and presented by Charlotte Serpa and Carys Cragg (and members of the CYCEAB Practicum Committee) at Education Day hosted at the National Child and Youth Care Conference, October 5-7, 2022. The Child & Youth Care Practicum Resources were compiled by Carys Cragg for the CYC Educational Accreditation Board of Canada. (CYCEAB).Practicum Committee and are also posted on their website along with other CYC resources.
The following list is a collection of Child & Youth Care (CYC) practicum resources for educators, supervisors, students, and other people intersecting with CYC practicum. It is offered in the spirit of highlighting CYC practicum knowledge, to support those who design, deliver, and experience it. Inclusion/Exclusion Criteria: the list includes available resources (mainly literature) concerning both Child and Youth Care (youth work, psychoeducation, etc.) and practicum (field work, field placement, internship, etc.). It excludes all other information, including, for example, other human service professional education practicum literature, and resources if CYC and practicum is not one of the primary topics of the resource.Not peer reviewe
WR 280 Practicum Report: Wildlife Management Techniques
Get PDFWildland RecreationAs part of the Wildland Recreation Spring Practicum, the author worked at the Fort St. John Fish and Wildlife Branch of the Ministry of Environment and Parks for two weeks, under the supervision of Rob Woods, Habitat Protection Technician. The author's volunteer work gave him an understanding of wildlife management techniques that included radio telemetry, classified counts, and ungulate aging/Harvest Cards
In situ synchrotron-based IR microspectroscopy to study catalytic reactions in zeolite crystals
No full textIn recent years a number of in situ microspectroscopic techniques have been explored to investigate catalytic reactions taking place in heterogeneous catalysts in a timeand space-resolved manner.[1–8] These spectroscopic methods have proven to be very successful in elucidating valuable structure–function relationships for acid–base catalytic reactions. In the work of Roeffaers et al. fluorescence microscopy has been applied to demonstrate the crystal-face-dependent catalysis on layered double hydroxide (LDH) materials.[1] By this elegant approach one can track interconversion processes of individual molecules in catalytic solids and obtain indirect data on the chemical nature of the reaction products formed, provided they display fluorescence. For example, the red shift of the emission bands of specific carbocations formed was used to visualize the degree of oligomerization of cyclic alcohols in individual H-ZSM-5 zeolite particles.[3
Nonlinear ultrafast acoustics at the nano scale
Get PDFPulsed femtosecond lasers can generate acoustic pulses propagating in solids while displaying either diffraction, attenuation, nonlinearity and/or dispersion. When acoustic attenuation and diffraction are negligible, shock waves or solitons can form during propagation. Both wave types are phonon wavepackets with characteristic length scales as short as a few nanometer. Hence, they are well suited for acoustic characterization and manipulation of materials on both ultrafast and ultrashort scales. This work presents an overview of nonlinear ultrasonics since its first experimental demonstration at the beginning of this century to the more recent developments. We start by reviewing the main properties of nonlinear ultrafast acoustic propagation based on the underlying equations. Then we show various results obtained by different groups around the world with an emphasis on recent work. Current issues and directions of future research are discussed
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