An exploration into the quantum confinement of CTS/natural dye core- shell quantum dots

2020 ◽  
Vol 579 ◽  
pp. 411913
Author(s):  
Maya Mathew ◽  
K.C. Preetha
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Natural Dye ◽  
Core Shell

scholarly journals Quantum Confinement Effect and Photoenhancement of Photoluminescence of PbS and PbS/MnS Quantum Dots

2020 ◽  
Vol 10 (18) ◽  
pp. 6282
Author(s):  
Muhammad Safwan Zaini ◽  
Josephine Ying Chyi Liew ◽  
Shahrul Ainliah Alang Ahmad ◽  
Abdul Rahman Mohmad ◽  
Mazliana Ahmad Kamarudin
Keyword(s):  
Aqueous Solution ◽  
Quantum Dots ◽  
Quantum Confinement ◽  
Shell Thickness ◽  
Quantum Confinement Effect ◽  
Band Gap Energy ◽  
Confinement Effect ◽  
Core Shell ◽  
Lead Sulphide ◽  
Peak Energy

The quantum confinement effect and photoenhancement of photoluminescence (PL) of lead sulphide (PbS) quantum dots (QDs) and lead sulphide/manganese sulphide (PbS/MnS) core shell QDs capped with thiol ligands in aqueous solution were investigated. From PL results, the presence of MnS shells gives a strong confinement effect which translates to higher emission energy in PbS/MnS core shell QDs. Increasing MnS shell thickness from 0.3 to 1.5 monolayers (ML) causes a blueshift of PL peak energies as the charge carriers concentrated in the PbS core region. Enhancement of the PL intensity of colloidal PbS and PbS/MnS core shell QDs has been observed when the samples are illuminated above the band gap energy, under continuous irradiation for 40 min. Luminescence from PbS QDs and PbS/MnS core shell QDs can be strongly influenced by the interaction of water molecules and oxygen present in aqueous solution adsorbed on the QD surface. However, PbS/MnS core shell QDs with a shell thickness of 1.5 ML did not show a PL peak energy stability as it was redshifted after 25 min, probably due to wider size distribution of the QDs.

Visible-light driven photocatalytic hydrogen generation by water-soluble all-inorganic core–shell silicon quantum dots

2020 ◽  
Vol 8 (31) ◽  
pp. 15789-15794
Author(s):  
Hiroshi Sugimoto ◽  
Hao Zhou ◽  
Miho Takada ◽  
Junichiro Fushimi ◽  
Minoru Fujii
Keyword(s):  
Quantum Dots ◽  
Visible Light ◽  
Quantum Confinement ◽  
Hydrogen Generation ◽  
Water Soluble ◽  
Core Shell ◽  
Photocatalytic Hydrogen Generation ◽  
Quantum Size ◽  
Visible Light Driven ◽  
Si Quantum Dots

Photocatalytic H2 generation by B,P-codoped Si quantum dots (QDs) with diameters in the quantum confinement regime is investigated. The H2 generation rate is enhanced by the increase of reduction ability of Si QDs owing to the quantum size effect.

scholarly journals Enhancement of Temperature Fluorescence Brightness of Zn@Si Core-Shell Quantum Dots Produced via a Unified Strategy

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3158
Author(s):  
Mohammad S. Almomani ◽  
Naser M. Ahmed ◽  
Marzaini Rashid ◽  
M. K. M. Ali ◽  
H. Akhdar ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Emission Spectra ◽  
Core Shell ◽  
Porous Si ◽  
Top Down ◽  
Bottom Up ◽  
Orange Yellow ◽  
Red Luminescence ◽  
Bright Blue

Despite many dedicated efforts, the fabrication of high-quality ZnO-incorporated Zinc@Silicon (Zn@Si) core–shell quantum dots (ZnSiQDs) with customized properties remains challenging. In this study, we report a new record for the brightness enhancement of ZnSiQDs prepared via a unified top-down and bottom-up strategy. The top-down approach was used to produce ZnSiQDs with uniform sizes and shapes, followed by the bottom-up method for their re-growth. The influence of various NH4OH contents (15 to 25 µL) on the morphology and optical characteristics of ZnSiQDs was investigated. The ZnSiQDs were obtained from the electrochemically etched porous Si (PSi) with Zn inclusion (ZnPSi), followed by the electropolishing and sonication in acetone. EFTEM micrographs of the samples prepared without and with NH4OH revealed the existence of spherical ZnSiQDs with a mean diameter of 1.22 to 7.4 nm, respectively. The emission spectra of the ZnSiQDs (excited by 365 nm) exhibited bright blue, green, orange-yellow, and red luminescence, indicating the uniform morphology related to the strong quantum confinement ZnSiQDs. In addition, the absorption and emission of the ZnSiQDs prepared with NH4OH were enhanced by 198.8% and 132.6%, respectively. The bandgap of the ZnSiQDs conditioned without and with NH4OH was approximately 3.6 and 2.3 eV, respectively.

High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

2019 ◽  
Author(s):  
Aurelio A. Rossinelli ◽  
Henar Rojo ◽  
Aniket S. Mule ◽  
Marianne Aellen ◽  
Ario Cocina ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Temperature ◽  
Equilibrium Shape ◽  
Size Variation ◽  
Crystal Defects ◽  
Atomic Scale ◽  
Quantum Yields ◽  
Core Shell ◽  
Compositional Gradient ◽  
High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

Enhanced Photocurrent Generation in Proton‐Irradiated “Giant” CdSe/CdS Core/Shell Quantum Dots

2019 ◽  
Vol 29 (46) ◽  
pp. 1904501 ◽  
Author(s):  
Chao Wang ◽  
David Barba ◽  
Gurpreet S. Selopal ◽  
Haiguang Zhao ◽  
Jiabin Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Core Shell ◽  
Photocurrent Generation
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