Physics:Quantum dot - Revision history

WikiHarold: Remove imported red links from Quantum page

2026-05-23T23:47:07Z

Remove imported red links from Quantum page

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	~~{{Nanomaterials}}~~

	'''Quantum dots''' ('''QDs''') or '''semiconductor nanocrystals''' are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via [[Physics:Quantum mechanics\|quantum mechanical effects]]. They are a central topic in nanotechnology and materials science. When a quantum dot is illuminated by UV light, an electron in the quantum dot can be excited to a state of higher energy. In the case of a semiconducting quantum dot, this process corresponds to the transition of an electron from the valence band to the conduction band. The excited electron can drop back into the valence band releasing its energy as light. This light emission (photoluminescence) is illustrated in the figure on the right. The color of that light depends on the energy difference between the discrete energy levels of the quantum dot in the conduction band and the valence band.		'''Quantum dots''' ('''QDs''') or '''semiconductor nanocrystals''' are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via [[Physics:Quantum mechanics\|quantum mechanical effects]]. They are a central topic in nanotechnology and materials science. When a quantum dot is illuminated by UV light, an electron in the quantum dot can be excited to a state of higher energy. In the case of a semiconducting quantum dot, this process corresponds to the transition of an electron from the valence band to the conduction band. The excited electron can drop back into the valence band releasing its energy as light. This light emission (photoluminescence) is illustrated in the figure on the right. The color of that light depends on the energy difference between the discrete energy levels of the quantum dot in the conduction band and the valence band.

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	== Core/shell and core/double-shell structures ==		== Core/shell and core/double-shell structures ==
	~~{{See also\|l1=Core-shell semiconductor nanocrystal}}~~

	Quantum dots are usually coated with organic capping ligands (typically with long hydrocarbon chains, such as oleic acid) to control growth, prevent aggregation, and to promote dispersion in solution.<ref name=":5">{{Cite journal \|last1=Xiao \|first1=Pengwei \|last2=Zhang \|first2=Zhoufan \|last3=Ge \|first3=Junjun \|last4=Deng \|first4=Yalei \|last5=Chen \|first5=Xufeng \|last6=Zhang \|first6=Jian-Rong \|last7=Deng \|first7=Zhengtao \|last8=Kambe \|first8=Yu \|last9=Talapin \|first9=Dmitri V. \|last10=Wang \|first10=Yuanyuan \|date=2023-01-04 \|title=Surface passivation of intensely luminescent all-inorganic nanocrystals and their direct optical patterning \|journal=Nature Communications \|language=en \|volume=14 \|issue=1 \|page=49 \|doi=10.1038/s41467-022-35702-7 \|issn=2041-1723 \|pmc=9813348 \|pmid=36599825\|bibcode=2023NatCo..14...49X }}</ref> However, these organic coatings can lead to non-radiative recombination after photogeneration, meaning the generated charge carriers can be dissipated without photon emission (e.g. via phonons or trapping in defect states), which reduces fluorescent quantum yield, or the conversion efficiency of absorbed photons into emitted fluorescence.<ref>{{Cite journal \|last1=Zaini \|first1=Muhammad Safwan \|last2=Ying Chyi Liew \|first2=Josephine \|last3=Alang Ahmad \|first3=Shahrul Ainliah \|last4=Mohmad \|first4=Abdul Rahman \|last5=Kamarudin \|first5=Mazliana Ahmad \|date=January 2020 \|title=Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots \|journal=Applied Sciences \|language=en \|volume=10 \|issue=18 \|page=6282 \|doi=10.3390/app10186282 \|issn=2076-3417 \|doi-access=free }}</ref> To combat this, a semiconductor layer can be grown surrounding the quantum dot core. Depending on the bandgaps of the core and shell materials, the fluorescent properties of the nanocrystals can be tuned. Furthermore, adjusting the thicknesses of each of the layers and overall size of the quantum dots can affect the photoluminescent emission wavelength — the quantum confinement effect tends to blueshift the emission spectra as the quantum dot decreases in size.<ref>{{Cite journal \|last1=Zhang \|first1=Wenda \|last2=Zhuang \|first2=Weidong \|last3=Liu \|first3=Ronghui \|last4=Xing \|first4=Xianran \|last5=Qu \|first5=Xiangwei \|last6=Liu \|first6=Haochen \|last7=Xu \|first7=Bing \|last8=Wang \|first8=Kai \|last9=Sun \|first9=Xiao Wei \|date=2019-11-19 \|title=Double-Shelled InP/ZnMnS/ZnS Quantum Dots for Light-Emitting Devices \|journal=ACS Omega \|language=en \|volume=4 \|issue=21 \|pages=18961–18968 \|doi=10.1021/acsomega.9b01471 \|issn=2470-1343 \|pmc=6868586 \|pmid=31763517}}</ref>		Quantum dots are usually coated with organic capping ligands (typically with long hydrocarbon chains, such as oleic acid) to control growth, prevent aggregation, and to promote dispersion in solution.<ref name=":5">{{Cite journal \|last1=Xiao \|first1=Pengwei \|last2=Zhang \|first2=Zhoufan \|last3=Ge \|first3=Junjun \|last4=Deng \|first4=Yalei \|last5=Chen \|first5=Xufeng \|last6=Zhang \|first6=Jian-Rong \|last7=Deng \|first7=Zhengtao \|last8=Kambe \|first8=Yu \|last9=Talapin \|first9=Dmitri V. \|last10=Wang \|first10=Yuanyuan \|date=2023-01-04 \|title=Surface passivation of intensely luminescent all-inorganic nanocrystals and their direct optical patterning \|journal=Nature Communications \|language=en \|volume=14 \|issue=1 \|page=49 \|doi=10.1038/s41467-022-35702-7 \|issn=2041-1723 \|pmc=9813348 \|pmid=36599825\|bibcode=2023NatCo..14...49X }}</ref> However, these organic coatings can lead to non-radiative recombination after photogeneration, meaning the generated charge carriers can be dissipated without photon emission (e.g. via phonons or trapping in defect states), which reduces fluorescent quantum yield, or the conversion efficiency of absorbed photons into emitted fluorescence.<ref>{{Cite journal \|last1=Zaini \|first1=Muhammad Safwan \|last2=Ying Chyi Liew \|first2=Josephine \|last3=Alang Ahmad \|first3=Shahrul Ainliah \|last4=Mohmad \|first4=Abdul Rahman \|last5=Kamarudin \|first5=Mazliana Ahmad \|date=January 2020 \|title=Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots \|journal=Applied Sciences \|language=en \|volume=10 \|issue=18 \|page=6282 \|doi=10.3390/app10186282 \|issn=2076-3417 \|doi-access=free }}</ref> To combat this, a semiconductor layer can be grown surrounding the quantum dot core. Depending on the bandgaps of the core and shell materials, the fluorescent properties of the nanocrystals can be tuned. Furthermore, adjusting the thicknesses of each of the layers and overall size of the quantum dots can affect the photoluminescent emission wavelength — the quantum confinement effect tends to blueshift the emission spectra as the quantum dot decreases in size.<ref>{{Cite journal \|last1=Zhang \|first1=Wenda \|last2=Zhuang \|first2=Weidong \|last3=Liu \|first3=Ronghui \|last4=Xing \|first4=Xianran \|last5=Qu \|first5=Xiangwei \|last6=Liu \|first6=Haochen \|last7=Xu \|first7=Bing \|last8=Wang \|first8=Kai \|last9=Sun \|first9=Xiao Wei \|date=2019-11-19 \|title=Double-Shelled InP/ZnMnS/ZnS Quantum Dots for Light-Emitting Devices \|journal=ACS Omega \|language=en \|volume=4 \|issue=21 \|pages=18961–18968 \|doi=10.1021/acsomega.9b01471 \|issn=2470-1343 \|pmc=6868586 \|pmid=31763517}}</ref>
	There are 4 major categories of quantum dot heterostructures: type I, inverse type I, type II, and inverse type II.<ref name=":6">{{Cite journal \|last1=Vasudevan \|first1=D. \|last2=Gaddam \|first2=Rohit Ranganathan \|last3=Trinchi \|first3=Adrian \|last4=Cole \|first4=Ivan \|date=2015-07-05 \|title=Core–shell quantum dots: Properties and applications \|url=https://www.sciencedirect.com/science/article/pii/S0925838815005319 \|journal=Journal of Alloys and Compounds \|volume=636 \|pages=395–404 \|doi=10.1016/j.jallcom.2015.02.102 \|issn=0925-8388\|url-access=subscription }}</ref>		There are 4 major categories of quantum dot heterostructures: type I, inverse type I, type II, and inverse type II.<ref name=":6">{{Cite journal \|last1=Vasudevan \|first1=D. \|last2=Gaddam \|first2=Rohit Ranganathan \|last3=Trinchi \|first3=Adrian \|last4=Cole \|first4=Ivan \|date=2015-07-05 \|title=Core–shell quantum dots: Properties and applications \|url=https://www.sciencedirect.com/science/article/pii/S0925838815005319 \|journal=Journal of Alloys and Compounds \|volume=636 \|pages=395–404 \|doi=10.1016/j.jallcom.2015.02.102 \|issn=0925-8388\|url-access=subscription }}</ref>
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	=== Photovoltaic devices ===		=== Photovoltaic devices ===
	[[File:Sargent Group quantum dot solar cell.jpg\|thumb\|Spin-cast quantum dot solar cell built by the Sargent Group at the University of Toronto. The metal disks on the front surface are the electrical connections to the layers below.]]		[[File:Sargent Group quantum dot solar cell.jpg\|thumb\|Spin-cast quantum dot solar cell built by the Sargent Group at the University of Toronto. The metal disks on the front surface are the electrical connections to the layers below.]]
	~~{{main\|Physics:Quantum dot solar cell}}~~

	The tunable absorption spectrum and high extinction coefficients of quantum dots make them attractive for light harvesting technologies such as photovoltaics. Quantum dots may be able to increase the efficiency and reduce the cost of today's typical silicon photovoltaic cells. According to an experimental report from 2004,<ref>{{cite journal \|last1=Schaller \|first1=R. \|last2=Klimov \|first2=V. \|title=High Efficiency Carrier Multiplication in PbSe Nanocrystals: Implications for Solar Energy Conversion \|journal=Physical Review Letters \|volume=92 \|year=2004 \|doi=10.1103/PhysRevLett.92.186601 \|pmid=15169518 \|bibcode=2004PhRvL..92r6601S \|arxiv=cond-mat/0404368 \|issue=18 \|article-number=186601 \|s2cid=4186651}}</ref> quantum dots of lead selenide (PbSe) can produce more than one exciton from one high-energy photon via the process of carrier multiplication or multiple exciton generation (MEG). This compares favorably to today's photovoltaic cells which can only manage one exciton per high-energy photon, with high kinetic energy carriers losing their energy as heat. On the other hand, the quantum-confined ground-states of colloidal quantum dots (such as lead sulfide, PbS) incorporated in wider-bandgap host semiconductors (such as perovskite) can allow the generation of photocurrent from photons with energy below the host bandgap, via a two-photon absorption process, offering another approach (termed intermediate band, IB) to exploit a broader range of the solar spectrum and thereby achieve higher photovoltaic efficiency.<ref>{{Cite journal \|last1=Ramiro \|first1=Iñigo \|last2=Martí \|first2=Antonio \|date=July 2021 \|title=Intermediate band solar cells: Present and future \|url=https://onlinelibrary.wiley.com/doi/10.1002/pip.3351 \|journal=Progress in Photovoltaics: Research and Applications \|language=en \|volume=29 \|issue=7 \|pages=705–713 \|doi=10.1002/pip.3351 \|s2cid=226335202 \|issn=1062-7995}}</ref><ref>{{Cite journal \|last1=Alexandre \|first1=M. \|last2=Águas \|first2=H. \|last3=Fortunato \|first3=E. \|last4=Martins \|first4=R. \|last5=Mendes \|first5=M. J. \|date=17 November 2021 \|title=Light management with quantum nanostructured dots-in-host semiconductors \|journal=Light: Science & Applications \|language=en \|volume=10 \|issue=1 \|page=231 \|doi=10.1038/s41377-021-00671-x \|pmid=34785654 \|pmc=8595380 \|bibcode=2021LSA....10..231A \|issn=2047-7538}}</ref>		The tunable absorption spectrum and high extinction coefficients of quantum dots make them attractive for light harvesting technologies such as photovoltaics. Quantum dots may be able to increase the efficiency and reduce the cost of today's typical silicon photovoltaic cells. According to an experimental report from 2004,<ref>{{cite journal \|last1=Schaller \|first1=R. \|last2=Klimov \|first2=V. \|title=High Efficiency Carrier Multiplication in PbSe Nanocrystals: Implications for Solar Energy Conversion \|journal=Physical Review Letters \|volume=92 \|year=2004 \|doi=10.1103/PhysRevLett.92.186601 \|pmid=15169518 \|bibcode=2004PhRvL..92r6601S \|arxiv=cond-mat/0404368 \|issue=18 \|article-number=186601 \|s2cid=4186651}}</ref> quantum dots of lead selenide (PbSe) can produce more than one exciton from one high-energy photon via the process of carrier multiplication or multiple exciton generation (MEG). This compares favorably to today's photovoltaic cells which can only manage one exciton per high-energy photon, with high kinetic energy carriers losing their energy as heat. On the other hand, the quantum-confined ground-states of colloidal quantum dots (such as lead sulfide, PbS) incorporated in wider-bandgap host semiconductors (such as perovskite) can allow the generation of photocurrent from photons with energy below the host bandgap, via a two-photon absorption process, offering another approach (termed intermediate band, IB) to exploit a broader range of the solar spectrum and thereby achieve higher photovoltaic efficiency.<ref>{{Cite journal \|last1=Ramiro \|first1=Iñigo \|last2=Martí \|first2=Antonio \|date=July 2021 \|title=Intermediate band solar cells: Present and future \|url=https://onlinelibrary.wiley.com/doi/10.1002/pip.3351 \|journal=Progress in Photovoltaics: Research and Applications \|language=en \|volume=29 \|issue=7 \|pages=705–713 \|doi=10.1002/pip.3351 \|s2cid=226335202 \|issn=1062-7995}}</ref><ref>{{Cite journal \|last1=Alexandre \|first1=M. \|last2=Águas \|first2=H. \|last3=Fortunato \|first3=E. \|last4=Martins \|first4=R. \|last5=Mendes \|first5=M. J. \|date=17 November 2021 \|title=Light management with quantum nanostructured dots-in-host semiconductors \|journal=Light: Science & Applications \|language=en \|volume=10 \|issue=1 \|page=231 \|doi=10.1038/s41377-021-00671-x \|pmid=34785654 \|pmc=8595380 \|bibcode=2021LSA....10..231A \|issn=2047-7538}}</ref>

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	=== Quantum dot displays ===		=== Quantum dot displays ===
	[[File:Samsung QLED TV 8K - 75 inches - 2018-11-02.jpg\|thumb\|Samsung QLED TV 8K, {{convert\|75\|in\|cm}}]]		[[File:Samsung QLED TV 8K - 75 inches - 2018-11-02.jpg\|thumb\|Samsung QLED TV 8K, {{convert\|75\|in\|cm}}]]
	~~{{main\|Physics:Quantum dot display}}~~

	Quantum dots are valued for displays because they emit light in very specific Gaussian distributionss. This can result in a display with visibly more accurate colors.		Quantum dots are valued for displays because they emit light in very specific Gaussian distributionss. This can result in a display with visibly more accurate colors.

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	* [http://www.americanelements.com/AEquantumdots.html Quantum Dots Research and Technical Data]		* [http://www.americanelements.com/AEquantumdots.html Quantum Dots Research and Technical Data]
	* [https://web.archive.org/web/20120722192151/https://nanohub.org/tools/qdot Simulation and interactive visualization of Quantum Dots wave function]		* [https://web.archive.org/web/20120722192151/https://nanohub.org/tools/qdot Simulation and interactive visualization of Quantum Dots wave function]

	~~{{Emerging technologies\|topics=yes\|robotics=yes\|manufacture=yes\|materials=yes}}~~
	<!--		<!--
	Seem dated or specialized as of June 2016:		Seem dated or specialized as of June 2016:
	<ref name="americanelements">{{cite web \|title=Nanotechnology Information Center: Properties, Applications, Research, and Safety Guidelines \|url=http://www.americanelements.com/nanotech.htm \|publisher=American Elements}}</ref><ref>{{cite journal \|title=Effect of size nonuniformity on the absorption spectrum of a semiconductor quantum dot system \|journal=Applied Physics Letters \|date=7 September 1987 \|pages=710–712 \|volume=51 \|issue=10 \|doi=10.1063/1.98896 \|first=Wei-Yu \|last=Wu \|first2=J. N. \|last2=Schulman \|first3=T. Y. \|last3=Hsu \|first4=Uzi \|last4=Efron \|bibcode=1987ApPhL..51..710W}}</ref>		<ref name="americanelements">{{cite web \|title=Nanotechnology Information Center: Properties, Applications, Research, and Safety Guidelines \|url=http://www.americanelements.com/nanotech.htm \|publisher=American Elements}}</ref><ref>{{cite journal \|title=Effect of size nonuniformity on the absorption spectrum of a semiconductor quantum dot system \|journal=Applied Physics Letters \|date=7 September 1987 \|pages=710–712 \|volume=51 \|issue=10 \|doi=10.1063/1.98896 \|first=Wei-Yu \|last=Wu \|first2=J. N. \|last2=Schulman \|first3=T. Y. \|last3=Hsu \|first4=Uzi \|last4=Efron \|bibcode=1987ApPhL..51..710W}}</ref>
	-->		-->

	~~[[Category:Quantum dots\| ]]~~
	~~[[Category:Mesoscopic physics]]~~
	~~[[Category:Quantum chemistry]]~~
	~~[[Category:Quantum electronics]]~~
	~~[[Category:Semiconductor structures]]~~

	{{Author\|Harold Foppele}}		{{Author\|Harold Foppele}}

	{{Sourceattribution\|Physics:Quantum dot\|1}}		{{Sourceattribution\|Physics:Quantum dot\|1}}

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	{{Emerging technologies\|topics=yes\|robotics=yes\|manufacture=yes\|materials=yes}}		{{Emerging technologies\|topics=yes\|robotics=yes\|manufacture=yes\|materials=yes}}
	~~{{Quantum mechanics topics}}~~
	<!--		<!--
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WikiHarold: Use Quantum See also index module

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	The Nobel Prize in Chemistry 2023 was awarded to Moungi Bawendi, Louis E. Brus and Alexey Ekimov "for the discovery and synthesis of quantum dots."<ref>{{Cite web \|title=The Nobel Prize in Chemistry 2023 \|url=https://www.nobelprize.org/prizes/chemistry/2023/summary/ \|access-date=6 October 2023 \|website=NobelPrize.org \|language=en-US}}</ref>		The Nobel Prize in Chemistry 2023 was awarded to Moungi Bawendi, Louis E. Brus and Alexey Ekimov "for the discovery and synthesis of quantum dots."<ref>{{Cite web \|title=The Nobel Prize in Chemistry 2023 \|url=https://www.nobelprize.org/prizes/chemistry/2023/summary/ \|access-date=6 October 2023 \|website=NobelPrize.org \|language=en-US}}</ref>

	~~== See also ==~~
	~~{{Div col\|colwidth=20em}}~~
	* Cadmium-free quantum dot
	* Carbon quantum dot
	* Core–shell semiconductor nanocrystal
	* Langmuir–Blodgett film
	* Mark Reed (physicist)
	* Nanocrystal solar cell
	* Paul Alivisatos
	* [[Physics:Quantum dot laser\|Quantum dot laser]]
	* [[Physics:Quantum dot single-photon source\|Quantum dot single-photon source]]
	* [[Physics:Quantum point contact\|Quantum point contact]]
	* Shuming Nie
	* Superatom
	* Trojan wave packet
	* Uri Banin
	~~{{Div col end}}~~

	== See also ==		== See also ==

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	== Core/shell and core/double-shell structures ==		== Core/shell and core/double-shell structures ==
	{{See also~~\|Chemistry:Core–shell semiconductor nanocrystal~~\|l1=Core-shell semiconductor nanocrystal}}		{{See also\|l1=Core-shell semiconductor nanocrystal}}

	Quantum dots are usually coated with organic capping ligands (typically with long hydrocarbon chains, such as oleic acid) to control growth, prevent aggregation, and to promote dispersion in solution.<ref name=":5">{{Cite journal \|last1=Xiao \|first1=Pengwei \|last2=Zhang \|first2=Zhoufan \|last3=Ge \|first3=Junjun \|last4=Deng \|first4=Yalei \|last5=Chen \|first5=Xufeng \|last6=Zhang \|first6=Jian-Rong \|last7=Deng \|first7=Zhengtao \|last8=Kambe \|first8=Yu \|last9=Talapin \|first9=Dmitri V. \|last10=Wang \|first10=Yuanyuan \|date=2023-01-04 \|title=Surface passivation of intensely luminescent all-inorganic nanocrystals and their direct optical patterning \|journal=Nature Communications \|language=en \|volume=14 \|issue=1 \|page=49 \|doi=10.1038/s41467-022-35702-7 \|issn=2041-1723 \|pmc=9813348 \|pmid=36599825\|bibcode=2023NatCo..14...49X }}</ref> However, these organic coatings can lead to non-radiative recombination after photogeneration, meaning the generated charge carriers can be dissipated without photon emission (e.g. via phonons or trapping in defect states), which reduces fluorescent quantum yield, or the conversion efficiency of absorbed photons into emitted fluorescence.<ref>{{Cite journal \|last1=Zaini \|first1=Muhammad Safwan \|last2=Ying Chyi Liew \|first2=Josephine \|last3=Alang Ahmad \|first3=Shahrul Ainliah \|last4=Mohmad \|first4=Abdul Rahman \|last5=Kamarudin \|first5=Mazliana Ahmad \|date=January 2020 \|title=Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots \|journal=Applied Sciences \|language=en \|volume=10 \|issue=18 \|page=6282 \|doi=10.3390/app10186282 \|issn=2076-3417 \|doi-access=free }}</ref> To combat this, a semiconductor layer can be grown surrounding the quantum dot core. Depending on the bandgaps of the core and shell materials, the fluorescent properties of the nanocrystals can be tuned. Furthermore, adjusting the thicknesses of each of the layers and overall size of the quantum dots can affect the photoluminescent emission wavelength — the quantum confinement effect tends to blueshift the emission spectra as the quantum dot decreases in size.<ref>{{Cite journal \|last1=Zhang \|first1=Wenda \|last2=Zhuang \|first2=Weidong \|last3=Liu \|first3=Ronghui \|last4=Xing \|first4=Xianran \|last5=Qu \|first5=Xiangwei \|last6=Liu \|first6=Haochen \|last7=Xu \|first7=Bing \|last8=Wang \|first8=Kai \|last9=Sun \|first9=Xiao Wei \|date=2019-11-19 \|title=Double-Shelled InP/ZnMnS/ZnS Quantum Dots for Light-Emitting Devices \|journal=ACS Omega \|language=en \|volume=4 \|issue=21 \|pages=18961–18968 \|doi=10.1021/acsomega.9b01471 \|issn=2470-1343 \|pmc=6868586 \|pmid=31763517}}</ref>		Quantum dots are usually coated with organic capping ligands (typically with long hydrocarbon chains, such as oleic acid) to control growth, prevent aggregation, and to promote dispersion in solution.<ref name=":5">{{Cite journal \|last1=Xiao \|first1=Pengwei \|last2=Zhang \|first2=Zhoufan \|last3=Ge \|first3=Junjun \|last4=Deng \|first4=Yalei \|last5=Chen \|first5=Xufeng \|last6=Zhang \|first6=Jian-Rong \|last7=Deng \|first7=Zhengtao \|last8=Kambe \|first8=Yu \|last9=Talapin \|first9=Dmitri V. \|last10=Wang \|first10=Yuanyuan \|date=2023-01-04 \|title=Surface passivation of intensely luminescent all-inorganic nanocrystals and their direct optical patterning \|journal=Nature Communications \|language=en \|volume=14 \|issue=1 \|page=49 \|doi=10.1038/s41467-022-35702-7 \|issn=2041-1723 \|pmc=9813348 \|pmid=36599825\|bibcode=2023NatCo..14...49X }}</ref> However, these organic coatings can lead to non-radiative recombination after photogeneration, meaning the generated charge carriers can be dissipated without photon emission (e.g. via phonons or trapping in defect states), which reduces fluorescent quantum yield, or the conversion efficiency of absorbed photons into emitted fluorescence.<ref>{{Cite journal \|last1=Zaini \|first1=Muhammad Safwan \|last2=Ying Chyi Liew \|first2=Josephine \|last3=Alang Ahmad \|first3=Shahrul Ainliah \|last4=Mohmad \|first4=Abdul Rahman \|last5=Kamarudin \|first5=Mazliana Ahmad \|date=January 2020 \|title=Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots \|journal=Applied Sciences \|language=en \|volume=10 \|issue=18 \|page=6282 \|doi=10.3390/app10186282 \|issn=2076-3417 \|doi-access=free }}</ref> To combat this, a semiconductor layer can be grown surrounding the quantum dot core. Depending on the bandgaps of the core and shell materials, the fluorescent properties of the nanocrystals can be tuned. Furthermore, adjusting the thicknesses of each of the layers and overall size of the quantum dots can affect the photoluminescent emission wavelength — the quantum confinement effect tends to blueshift the emission spectra as the quantum dot decreases in size.<ref>{{Cite journal \|last1=Zhang \|first1=Wenda \|last2=Zhuang \|first2=Weidong \|last3=Liu \|first3=Ronghui \|last4=Xing \|first4=Xianran \|last5=Qu \|first5=Xiangwei \|last6=Liu \|first6=Haochen \|last7=Xu \|first7=Bing \|last8=Wang \|first8=Kai \|last9=Sun \|first9=Xiao Wei \|date=2019-11-19 \|title=Double-Shelled InP/ZnMnS/ZnS Quantum Dots for Light-Emitting Devices \|journal=ACS Omega \|language=en \|volume=4 \|issue=21 \|pages=18961–18968 \|doi=10.1021/acsomega.9b01471 \|issn=2470-1343 \|pmc=6868586 \|pmid=31763517}}</ref>
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	== Health and safety ==		== Health and safety ==
	~~{{Main\|Physics~~:Health and safety hazards of nanomaterials\|Nanotoxicology}}		''Related topic:'' Health and safety hazards of nanomaterials, Nanotoxicology

	Some quantum dots pose risks to human health and the environment under certain conditions.<ref name=":0">{{cite journal \|last=Hardman \|first=R. \|title=A Toxicologic Review of Quantum Dots: Toxicity Depends on Physicochemical and Environmental Factors \|journal=Environmental Health Perspectives \|volume=114 \|issue=2 \|pages=165–172 \|pmid=16451849 \|pmc=1367826 \|year=2006 \|doi=10.1289/ehp.8284\|bibcode=2006EnvHP.114..165H }}</ref><ref name=state>{{cite journal \|last1=Pelley \|first1=J. L. \|last2=Daar \|first2=A. S. \|last3=Saner \|first3=M. A. \|year=2009 \|title=State of Academic Knowledge on Toxicity and Biological Fate of Quantum Dots \|journal=Toxicological Sciences \|volume=112 \|issue=2 \|pages=276–296 \|doi=10.1093/toxsci/kfp188 \|pmid=19684286 \|pmc=2777075}}</ref><ref name=":1">{{cite journal \|last1=Tsoi \|first1=Kim M. \|last2=Dai \|first2=Qin \|last3=Alman \|first3=Benjamin A. \|last4=Chan \|first4=Warren C. W. \|title=Are Quantum Dots Toxic? Exploring the Discrepancy Between Cell Culture and Animal Studies \|journal=Accounts of Chemical Research \|date=19 March 2013 \|pages=662–671 \|volume=46 \|issue=3 \|doi=10.1021/ar300040z \|pmid=22853558}}</ref> Notably, the studies on quantum dot toxicity have focused on particles containing cadmium and have yet to be demonstrated in animal models after physiologically relevant dosing.<ref name=":1"/> In vitro studies, based on cell cultures, on quantum dots (QD) toxicity suggest that their toxicity may derive from multiple factors including their physicochemical characteristics (size, shape, composition, surface functional groups, and surface charges) and their environment. Assessing their potential toxicity is complex as these factors include properties such as QD size, charge, concentration, chemical composition, capping ligands, and also on their oxidative, mechanical, and photolytic stability.<ref name=":0"/>		Some quantum dots pose risks to human health and the environment under certain conditions.<ref name=":0">{{cite journal \|last=Hardman \|first=R. \|title=A Toxicologic Review of Quantum Dots: Toxicity Depends on Physicochemical and Environmental Factors \|journal=Environmental Health Perspectives \|volume=114 \|issue=2 \|pages=165–172 \|pmid=16451849 \|pmc=1367826 \|year=2006 \|doi=10.1289/ehp.8284\|bibcode=2006EnvHP.114..165H }}</ref><ref name=state>{{cite journal \|last1=Pelley \|first1=J. L. \|last2=Daar \|first2=A. S. \|last3=Saner \|first3=M. A. \|year=2009 \|title=State of Academic Knowledge on Toxicity and Biological Fate of Quantum Dots \|journal=Toxicological Sciences \|volume=112 \|issue=2 \|pages=276–296 \|doi=10.1093/toxsci/kfp188 \|pmid=19684286 \|pmc=2777075}}</ref><ref name=":1">{{cite journal \|last1=Tsoi \|first1=Kim M. \|last2=Dai \|first2=Qin \|last3=Alman \|first3=Benjamin A. \|last4=Chan \|first4=Warren C. W. \|title=Are Quantum Dots Toxic? Exploring the Discrepancy Between Cell Culture and Animal Studies \|journal=Accounts of Chemical Research \|date=19 March 2013 \|pages=662–671 \|volume=46 \|issue=3 \|doi=10.1021/ar300040z \|pmid=22853558}}</ref> Notably, the studies on quantum dot toxicity have focused on particles containing cadmium and have yet to be demonstrated in animal models after physiologically relevant dosing.<ref name=":1"/> In vitro studies, based on cell cultures, on quantum dots (QD) toxicity suggest that their toxicity may derive from multiple factors including their physicochemical characteristics (size, shape, composition, surface functional groups, and surface charges) and their environment. Assessing their potential toxicity is complex as these factors include properties such as QD size, charge, concentration, chemical composition, capping ligands, and also on their oxidative, mechanical, and photolytic stability.<ref name=":0"/>
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	=== Photocatalysts ===		=== Photocatalysts ===
	~~{{Main\|Physics~~:Photocatalysis}}		''Related topic:'' Photocatalysis

	Quantum dots also function as photocatalysts for the light driven chemical conversion of water into hydrogen as a pathway to solar fuel. In photocatalysis, electron hole pairs formed in the dot under band gap excitation drive redox reactions in the surrounding liquid. Generally, the photocatalytic activity of the dots is related to the particle size and its degree of quantum confinement.<ref>{{cite journal \|doi=10.1021/nn400826h \|pmid=23590186 \|title=Quantum Confinement Controls Photocatalysis: A Free Energy Analysis for Photocatalytic Proton Reduction at CdSe Nanocrystals \|journal=ACS Nano \|volume=7 \|issue=5 \|pages=4316–4325 \|year=2013 \|last1=Zhao \|first1=Jing \|last2=Holmes \|first2=Michael A. \|last3=Osterloh \|first3=Frank E. \|bibcode=2013ACSNa...7.4316Z }}</ref> This is because the band gap determines the chemical energy that is stored in the dot in the excited state. An obstacle for the use of quantum dots in photocatalysis is the presence of surfactants on the surface of the dots. These surfactants (or ligands) interfere with the chemical reactivity of the dots by slowing down mass transfer and electron transfer processes. Also, quantum dots made of metal chalcogenides are chemically unstable under oxidizing conditions and undergo photo corrosion reactions.		Quantum dots also function as photocatalysts for the light driven chemical conversion of water into hydrogen as a pathway to solar fuel. In photocatalysis, electron hole pairs formed in the dot under band gap excitation drive redox reactions in the surrounding liquid. Generally, the photocatalytic activity of the dots is related to the particle size and its degree of quantum confinement.<ref>{{cite journal \|doi=10.1021/nn400826h \|pmid=23590186 \|title=Quantum Confinement Controls Photocatalysis: A Free Energy Analysis for Photocatalytic Proton Reduction at CdSe Nanocrystals \|journal=ACS Nano \|volume=7 \|issue=5 \|pages=4316–4325 \|year=2013 \|last1=Zhao \|first1=Jing \|last2=Holmes \|first2=Michael A. \|last3=Osterloh \|first3=Frank E. \|bibcode=2013ACSNa...7.4316Z }}</ref> This is because the band gap determines the chemical energy that is stored in the dot in the excited state. An obstacle for the use of quantum dots in photocatalysis is the presence of surfactants on the surface of the dots. These surfactants (or ligands) interfere with the chemical reactivity of the dots by slowing down mass transfer and electron transfer processes. Also, quantum dots made of metal chalcogenides are chemically unstable under oxidizing conditions and undergo photo corrosion reactions.
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	== Quantum confinement in semiconductors ==		== Quantum confinement in semiconductors ==
	[[File:Quantum dot.png\|thumb\|upright=1.4\|right\|3D confined electron wave functions in a quantum dot. Here, rectangular and triangular-shaped quantum dots are shown. Energy states in rectangular dots are more ''s''-type and ''p''-type. However, in a triangular dot the wave functions are mixed due to confinement symmetry. (Click for animation)\|link=File:QuantumDot_wf.gif]]		[[File:Quantum dot.png\|thumb\|upright=1.4\|right\|3D confined electron wave functions in a quantum dot. Here, rectangular and triangular-shaped quantum dots are shown. Energy states in rectangular dots are more ''s''-type and ''p''-type. However, in a triangular dot the wave functions are mixed due to confinement symmetry. (Click for animation)\|link=File:QuantumDot_wf.gif]]
	~~{{main\|Physics~~:Potential well}}		''Related topic:'' Potential well

	The energy levels of a single particle in a quantum dot can be predicted using the particle in a box model in which the energies of states depend on the length of the box. For an exciton inside a quantum dot, there is also the Coulomb interaction between the negatively charged electron and the positively charged hole. By comparing the quantum dot's size to the exciton Bohr radius, three regimes can be defined. In the 'strong confinement regime', the quantum dot's radius is much smaller than the exciton Bohr radius, respectively the confinement energy dominates over the Coulomb interaction.<ref name="JungnickelHenneberger1996">{{cite journal \|last1=Jungnickel \|first1=V. \|last2=Henneberger \|first2=F. \|title=Luminescence related processes in semiconductor nanocrystals —The strong confinement regime \|journal=Journal of Luminescence \|date=October 1996 \|volume=70 \|issue=1–6 \|pages=238–252 \|issn=0022-2313 \|doi=10.1016/0022-2313(96)00058-0\|bibcode=1996JLum...70..238J }}</ref> In the 'weak confinement' regime, the quantum dot is larger than the exciton Bohr radius, respectively the confinement energy is smaller than the Coulomb interactions between electron and hole. The regime where the exciton Bohr radius and confinement potential are comparable is called the 'intermediate confinement regime'.<ref name="Richter2017">{{cite journal \|last1=Richter \|first1=Marten \|title=Nanoplatelets as material system between strong confinement and weak confinement \|journal=Physical Review Materials \|date=26 June 2017 \|volume=1 \|issue=1 \|article-number=016001 \|eissn=2475-9953 \|doi=10.1103/PhysRevMaterials.1.016001 \|arxiv=1705.05333 \|bibcode=2017PhRvM...1a6001R \|s2cid=22966827}}</ref>		The energy levels of a single particle in a quantum dot can be predicted using the particle in a box model in which the energies of states depend on the length of the box. For an exciton inside a quantum dot, there is also the Coulomb interaction between the negatively charged electron and the positively charged hole. By comparing the quantum dot's size to the exciton Bohr radius, three regimes can be defined. In the 'strong confinement regime', the quantum dot's radius is much smaller than the exciton Bohr radius, respectively the confinement energy dominates over the Coulomb interaction.<ref name="JungnickelHenneberger1996">{{cite journal \|last1=Jungnickel \|first1=V. \|last2=Henneberger \|first2=F. \|title=Luminescence related processes in semiconductor nanocrystals —The strong confinement regime \|journal=Journal of Luminescence \|date=October 1996 \|volume=70 \|issue=1–6 \|pages=238–252 \|issn=0022-2313 \|doi=10.1016/0022-2313(96)00058-0\|bibcode=1996JLum...70..238J }}</ref> In the 'weak confinement' regime, the quantum dot is larger than the exciton Bohr radius, respectively the confinement energy is smaller than the Coulomb interactions between electron and hole. The regime where the exciton Bohr radius and confinement potential are comparable is called the 'intermediate confinement regime'.<ref name="Richter2017">{{cite journal \|last1=Richter \|first1=Marten \|title=Nanoplatelets as material system between strong confinement and weak confinement \|journal=Physical Review Materials \|date=26 June 2017 \|volume=1 \|issue=1 \|article-number=016001 \|eissn=2475-9953 \|doi=10.1103/PhysRevMaterials.1.016001 \|arxiv=1705.05333 \|bibcode=2017PhRvM...1a6001R \|s2cid=22966827}}</ref>

← Older revision		Revision as of 11:12, 22 May 2026
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	{{Short description\|Nano-scale semiconductor particles}}		{{Short description\|Nano-scale semiconductor particles}}

	{{Quantum book backlink\|Condensed matter and solid-state physics}}		{{Quantum book backlink\|Condensed matter and solid-state physics}}
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