Colloidal synthesis of MoS₂ quantum dots: size-dependent tunable photoluminescence and bioimaging

Abstract

Although the synthesis of two-dimensional (2D) layered MoS2 nanomaterials have been developing rapidly, there are many technical issues in preparing MoS2 quantum dots (QDs) with photoluminescence property. Herein, we design a facile colloidal chemical route to prepare photoluminescent MoS2 QDs using the ammonium tetrathiomolybdate ((NH4)2MoS4) as precursors and oleyl amine as reducing agent. The optical property and structure of as-prepared MoS2 QDs are investigated systematically. Resultant MoS2 QDs exhibit fluorescence (λmax=575 nm; quantum yield, 4.4%), spherical morphology with uniform thickness of ~3 nm and excitation-dependent PL phenomenon. Moreover, resultant MoS2 QDs show size-dependent tunable photoluminescence in wide visible region. With the help of the amphiphilic compound, resultant MoS2 QDs could be transferred from organic to aqueous phase. MoS2 QDs in aqueous solution have many advantages, such as good dispersion, low toxicity and photoluminescent property which make them possess promising applications in optoelectronic and biological fields. In this study, the 293T cells are used as a model to evaluate the fluorescence imaging of MoS2 QDs. The results confirm fluorescent signal appears in cytoplasm which demonstrates asprepared MoS2 QDs could be used as a probe for real-time optical cellular imaging.

Molybdenum disulfide quantum dots: synthesis and applications

“…The closer the gap between the frequencies of two phonons indicates that the monolayer structure is more prominent. [38] Likewise, monolayer structure of MoS 2 QDs was confirmed from the peak spacing between E 1 2g and A 1g . The peak spacing for MoS 2 QDs (22.5 cm -1 ) was less than that of bulk MoS 2 (25.7 cm -1 ) revealing the monolayer structure of MoS 2 QDs.…”

“…[35] MoS 2 QDs convince both large edge-to-volume ratio and high in-plane electron transport mutually when compared to other MoS 2 nanostructures. [36] The MoS 2 QDs have been scrutinized for their remarkable size dependent optical and electronic properties that caused a great sensation in numerous applications including HER, [37] bio-imaging, [38,39] sensors, [40] photodetectors, [41] and photocatalyst. [42] Because of the quantum confinement effect, there is an increase in the band gap of the MoS 2 QDs.…”

“…The excitation dependent PL phenomenon for MoS 2 QDs was reported by Lin et.al. [38] It exhibited intense fluorescence at 575 nm with quantum yield of 4.4%. Also, the synthesized MoS 2 QDs showed a size dependent tunable luminescence in the wide visible range from blue fluorescence (430 nm) to red fluorescence (600 nm) upon increasing QDs size.…”

“…Likewise, the MoS 2 QDs prepared via solvothermal approach was applied in two photon fluorescence bio-imaging have been reported by Gu et.al. [86] Similarly, Lin et al [38] have reported the synthesis of TPF MoS 2 QDs through one-step solvothermal approach. The synthesized MoS 2 QDs exhibited a quantum yield of 4.4% at λ max =575 nm.…”

Single-electron transport in graphene-like nanostructures

“…The existence of band gaps close to the wavelengths of visible light has earned TMD nanostructures considerable attention in optical studies [139][140][141]. However, it is also the sufficiently large bandgaps that distinguish TMDs from graphene and allows their nanostructures to be defined using electrical gating, as is commonly done in GaAs 2DEG systems.…”