Domanda del libro di testo
CdS has a band gap of 2.4 eV. If large crystals of CdS are illuminated with ultraviolet light, they emit light equal to the band gap energy. (c) What about red light?
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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 96b
CdS has a band gap of 2.4 eV. If large crystals of CdS are illuminated with ultraviolet light, they emit light equal to the band gap energy. (b) Would appropriately sized CdS quantum dots be able to emit blue light?
Guida verificata passo dopo passo1
Understand the concept of band gap energy, which is the energy difference between the valence band and the conduction band in a semiconductor. In CdS, this energy is 2.4 eV.
Recognize that the emission of light in semiconductors occurs when electrons return from the conduction band to the valence band, releasing energy equal to the band gap.
Identify the energy of blue light, which typically ranges from about 2.5 eV to 3.0 eV.
Consider the effect of quantum confinement in quantum dots, which can cause the band gap to increase as the size of the quantum dots decreases.
Determine if reducing the size of CdS quantum dots can increase the band gap energy to fall within the energy range of blue light, thus allowing the quantum dots to emit blue light.
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Band Gap Energy
The band gap energy is the energy difference between the valence band and the conduction band in a semiconductor. It determines the wavelengths of light that a material can absorb and emit. For CdS, a band gap of 2.4 eV means it can absorb photons with energy equal to or greater than this value, leading to the emission of light corresponding to this energy when excited.
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Percorso guidato
03:13
Intepreting the Band of Stability
Quantum Dots
Quantum dots are nanoscale semiconductor particles that have quantum mechanical properties. Their electronic and optical properties can be tuned by changing their size, which affects the band gap. Smaller quantum dots have larger band gaps, allowing them to emit light at shorter wavelengths, such as blue light, when excited.
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Percorso guidato
03:22Quantum Numbers
Photoluminescence
Photoluminescence is the emission of light from a material after it absorbs photons. In semiconductors like CdS, when the material is excited by ultraviolet light, electrons are promoted to the conduction band and, upon returning to the valence band, they release energy in the form of light. The wavelength of this emitted light is determined by the band gap energy of the material.
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Domanda del libro di testo
CdS has a band gap of 2.4 eV. If large crystals of CdS are illuminated with ultraviolet light, they emit light equal to the band gap energy. (a) What color is the emitted light?
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Domanda del libro di testo
Indicate whether each statement is true or false: (a) Elastomers are rubbery solids. (b) Thermosets cannot be reshaped. (c) Thermoplastic polymers can be recycled.
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