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Videos de Conceptos Relacionados

UV–Vis Spectroscopy: Molecular Electronic Transitions01:16

UV–Vis Spectroscopy: Molecular Electronic Transitions

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In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
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Molecular Spectroscopy: Absorption and Emission01:14

Molecular Spectroscopy: Absorption and Emission

4.3K
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels.  Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
4.3K
IR Absorption Frequency: Delocalization01:04

IR Absorption Frequency: Delocalization

1.3K
Electron delocalization refers to the distribution of electrons across multiple atoms within a molecule rather than being confined to a single atom or bond. This phenomenon is common in systems with conjugated bonds—structures where alternating single and double bonds allow π-electrons to move freely across the network. The movement of electrons stabilizes the molecule and can affect various chemical properties, including vibrational frequencies observed in IR spectroscopy.
In IR...
1.3K
Colors and Magnetism03:02

Colors and Magnetism

14.0K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
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The Energies of Atomic Orbitals03:21

The Energies of Atomic Orbitals

29.9K
In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are also observed. The attractive and repulsive forces are dependent on the distance between the particles, as well as the sign and magnitude of the charges on the individual particles. When the charges on the particles are opposite, they attract each other. If both particles have the same charge, they repel each other.
29.9K
IR Absorption Frequency: Hybridization01:21

IR Absorption Frequency: Hybridization

1.2K
Hydrocarbons such as alkanes, alkenes, and alkynes show characteristic C–H stretching absorption bands. These IR stretching frequencies depend on the hybridization of the involved carbon atom and can be explained in terms of the s character of each hybridized atomic orbital.
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that...
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Video Experimental Relacionado

Updated: Jan 18, 2026

Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection
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Complejos de Biexicitones Ligados en Cáscaras Cuánticas Emisoras en el Infrarrojo Cercano

Dulanjan Harankahage1,2, Divesh Nazar1,2, Korneel Molkens3,4,5

  • 1The Center for Photochemical Sciences, Bowling Green, Ohio 43403, United States.

ACS nano
|January 15, 2026
PubMed
Resumen

Las cáscaras cuánticas coloidales ofrecen una alternativa de bajo costo para fuentes de luz en el infrarrojo cercano (NIR). Los investigadores diseñaron cáscaras cuánticas para suprimir la recombinación Auger, logrando una emisión NIR eficiente y explorando nuevos fenómenos fotónicos.

Palabras clave:
recombinación Augerfibra ópticainfrarrojo cercanofotodetectorespuntos cuánticostelecomunicaciones

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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
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Área de la Ciencia:

  • Materials Science
  • Nanotechnology
  • Optoelectronics

Sus antecedentes:

  • Colloidal semiconductor nanocrystals (NCs) are cost-effective alternatives to epitaxial platforms for near-infrared (NIR) light generation.
  • Auger recombination significantly limits the performance of NIR NCs, especially in narrow-bandgap materials.

Objetivo del estudio:

  • To engineer quantum shells (QSs) for suppressed nonradiative Auger processes in colloidal semiconductor nanocrystals.
  • To investigate the optical properties and gain mechanisms of novel CdS/HgS/CdS and CdS/HgCdSe/ZnS QSs.

Principales métodos:

  • Fabrication of spherical quantum wells (CdS/HgS/CdS and CdS/HgCdSe/ZnS QSs).
  • Photoluminescence quantum yield measurements.
  • Optical gain and stimulated emission measurements.
  • Transient absorption spectroscopy.

Principales resultados:

  • QSs exhibited tunable NIR emission with high photoluminescence quantum yields (up to 60% below 1000 nm, 30% near 1300 nm).
  • CdS/HgS/CdS QSs showed optical gain and stimulated emission.
  • CdS/HgCdSe/ZnS QSs demonstrated stronger Auger suppression but exhibited photoinduced absorption instead of gain.
  • Transient absorption revealed bound multiexciton complexes in CdS/HgCdSe/ZnS QSs, leading to sub-bandgap states.

Conclusiones:

  • Engineered QSs effectively suppress Auger recombination, enabling efficient NIR emission.
  • Different QS compositions lead to distinct optical phenomena, including gain and photoinduced absorption.
  • Bound multiexciton complexes in QSs open pathways for room-temperature nonlinear NIR photonic applications.