Domanda del libro di testo
Silicon is the fundamental component of integrated circuits. Si has the same structure as diamond. (a) Is Si a molecular, metallic, ionic, or covalent-network solid?
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Ch.12 - Solids and Modern Materials
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement177
- Ch.2 - Atoms, Molecules, and Ions231
- Ch.3 - Chemical Reactions and Reaction Stoichiometry216
- Ch.4 - Reactions in Aqueous Solution189
- Ch.5 - Thermochemistry175
- Ch.6 - Electronic Structure of Atoms168
- Ch.7 - Periodic Properties of the Elements150
- Ch.8 - Basic Concepts of Chemical Bonding177
- Ch.9 - Molecular Geometry and Bonding Theories200
- Ch.10 - Gases179
- Ch.11 - Liquids and Intermolecular Forces113
- Ch.12 - Solids and Modern Materials154
- Ch.13 - Properties of Solutions157
- Ch.14 - Chemical Kinetics199
- Ch.15 - Chemical Equilibrium128
- Ch.16 - Acid-Base Equilibria164
- Ch.17 - Additional Aspects of Aqueous Equilibria163
- Ch.18 - Chemistry of the Environment105
- Ch.19 - Chemical Thermodynamics164
- Ch.20 - Electrochemistry171
- Ch.21 - Nuclear Chemistry122
- Ch.22 - Chemistry of the Nonmetals82
- Ch.23 - Transition Metals and Coordination Chemistry79
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry16
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 12, Problema 10a
The accompanying image shows photoluminescence from four different samples of CdTe nanocrystals, each embedded in a polymer matrix. The photoluminescence occurs because the samples are being irradiated by a UV light source. The nanocrystals in each vial have different average sizes. The sizes are 4.0, 3.5, 3.2, and 2.8 nm. (a) Which vial contains the 4.0-nm nanocrystals?
Guida verificata passo dopo passo1
Understand that photoluminescence is the emission of light from a material after it absorbs photons, typically from a UV light source.
Recognize that the size of nanocrystals affects the wavelength of light they emit due to the quantum confinement effect.
Recall that larger nanocrystals tend to emit light at longer wavelengths (redder light), while smaller nanocrystals emit at shorter wavelengths (bluer light).
Identify the color of light emitted by each sample in the image, noting that the sample emitting the reddest light likely contains the largest nanocrystals.
Determine which vial corresponds to the 4.0-nm nanocrystals by matching the color of emitted light to the expected wavelength for larger nanocrystals.
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Photoluminescence
Photoluminescence is the emission of light from a material after it absorbs photons, typically from a UV light source. In nanocrystals, this process is influenced by their size and composition, leading to variations in emitted light color and intensity. Understanding this phenomenon is crucial for analyzing the behavior of CdTe nanocrystals when exposed to UV radiation.
Quantum Confinement
Quantum confinement occurs when the dimensions of a semiconductor nanocrystal are reduced to the nanoscale, leading to discrete energy levels. This effect significantly alters the electronic and optical properties of the material, including its photoluminescence characteristics. The size of the nanocrystals directly affects the energy gap, which in turn influences the color of light emitted.
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03:22
Quantum Numbers
Nanocrystal Size and Emission Wavelength
The size of nanocrystals, such as those made from CdTe, directly correlates with the wavelength of light they emit. Larger nanocrystals typically emit light at longer wavelengths (red-shifted), while smaller ones emit at shorter wavelengths (blue-shifted). This relationship is essential for identifying which vial contains the 4.0-nm nanocrystals based on the observed photoluminescence.
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01:51Emission Spectra
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