ZnSe/ZnS Core/Shell Quantum Dots with Superior Optical Properties through Thermodynamic Shell Growth

Abstract

Epitaxial growth of a protective semiconductor shell on a colloidal quantum dot (QD) core is the key strategy for achieving high fluorescence quantum efficiency and essential stability for optoelectronic applications and biotagging with emissive QDs. Herein we investigate the effect of shell growth rate on the structure and optical properties in blue-emitting ZnSe/ZnS QDs with narrow emission line width. Tuning the precursor reactivity modifies the growth mode of ZnS shells on ZnSe cores transforming from kinetic (fast) to thermodynamic (slow) growth regimes. In the thermodynamic growth regime, enhanced fluorescence quantum yields and reduced on–off blinking are achieved. This high performance is ascribed to the effective avoidance of traps at the interface between the core and the shell, which are detrimental to the emission properties. Our study points to a general strategy to obtain high-quality core/shell QDs with enhanced optical properties through controlled reactivity yielding shell growth in the thermodynamic limit.

CdS crown growth on CdSe nanoplatelets: core shape matters

“…A similar relation between shell growth rate and PLQY was recently demonstrated for the ZnS shell growth on ZnSe nanorods. 36 In summary, it was demonstrated that replacing the common sulphur precursor for the CdS crown growth by a less reactive one allows the uniform growth of CdS crowns around quasi-quadratic CdSe NPLs, so that the PLQYs of the resulting core/crown NPLs can reach up to 80%. In addition to its effects on the sulphur reactivity, TOP presumably also acts as a tightbinding ligand which leads to a further reduction of the CdS growth rate.…”

“…Several approaches to tackle this issue have already been reported for core/shell NPLs, quantum dots (QDs) or nano rods, including high-temperature shell growth, 16,23,28,30 the introduction of post-synthetic annealing steps 35 and the utilisation of low-reactivity shell precursors to slow down the growth rate. 36 To the synthesis of highly luminescent core/crown NPLs the latter way is particularly applicable, as core-only NPLs are comparatively temperaturesensitive and as higher temperatures could moreover promote the three-dimensional shell growth.…”

Synthesis, Properties, and Biological Applications of Metallic Alloy Nanoparticles

“…Especially, alloy quantum dots have improved photoluminescence intensity and stability compared to standard quantum dots. Therefore, they have been widely used in clinical diagnosis, clinical analysis, and cancer detection [ 237 , 238 , 239 ]. For instance, ZnSe/CdS/ZnS core–shell quantum dots have been used in the detection of C-reactive protein, an early indicator of infection and autoimmune disorders [ 237 ]; bovine serum albumin-doped CdS quantum dots have been used in detecting human IgG1, a low-abundance protein [ 240 ]; Cu:ZnInS/ZnS quantum dots have been used in tetanus antibody detection [ 241 ]; CdTe quantum dots are used for detecting α-fetoprotein, a tumor marker [ 242 ]; and S- and N–Co-doped carbon quantum dots have been used in detecting clenbuterol, a feed additive for livestock and poultry [ 239 ].…”

ZnSe Quantum Dots: Determination of Molar Extinction Coefficient for UV to Blue Emitters

“…5,6 ZnSe-based QDs are a leading candidate for the fabrication of blue LEDs and laser diodes, making the synthetic development of these nanoparticles technologically important. [7][8][9] ZnSe has a bulk bandgap of 460 nm (2.7 eV). 10 As a result of the quantum confinement effect arising from a reduction in the QD diameter below its exciton Bohr radius, the optical properties of ZnSe nanoparticles can be precisely tuned by altering their size.…”