Synthesis and Characterization of Near-Infrared Cu−In−Se/ZnS Core/Shell Quantum Dots for In vivo Imaging

Abstract

Near-infrared (NIR) semiconductor quantum dots (QDs) represent promising fluorescent probes for biological and biomedical imaging. CuInSe2 is a good candidate for these applications due to its bandgap in the near-infrared and the reduced toxicity of its components compared to other NIR QD materials (CdTe, CdHgTe, PbS, etc.). Here we present a simple one-pot synthetic route without injection to make fluorescent sphalerite Cu−In−Se core and Cu−In−Se/ZnS core/shell QDs. We show that the photoluminescence (PL) of the resulting core QDs can be tuned from ∼700 nm to ∼1 μm depending on the QD size (from ∼2 to ∼5 nm in diameter). The optical and structural properties of these QDs are consistent with charge recombination via donor−acceptor levels instead of direct excitonic recombination. Finally, we show that the growth of a ZnS shell around these QDs increases their PL quantum yield substantially (up to 40−50% at 800 nm) and allows preservation of their PL properties after solubilization into water and in vivo, as demonstrated by detection of the regional lymph node in a mouse.

Small GSH-Capped CuInS2 Quantum Dots: MPA-Assisted Aqueous Phase Transfer and Bioimaging Applications

“…[24][25][26][27] Hence a current challenge is to achieve efficient phase transfer of hydrophobic CuInS 2 and CuInSe 2 based QDs into aqueous solution with keeping good fluorescent properties. [28][29][30][31][32][33][34] There are three commonly used aqueous phase transfer strategies, including ligand exchange, forming micelle through hydrophobic interaction and silica (or polymer) encapsulation. 35 Among them, ligand exchange is one of wide-spread used aqueous phase transfer strategies.…”

Organic Dots with Aggregation-Induced Emission (AIE Dots) Characteristics for Dual-Color Cell Tracing

“…3,4 As compared with discrete molecules (e.g., fluorescent proteins and organic chromophores), inorganic semiconductor quantum dots (QDs) have shown advantages in terms of better photostability, larger Stokes shift, and more feasible surface functionalization. 5 More importantly, the broad excitation range and narrow emission spectra of QDs are also beneficial for the simultaneous analysis of multibiotargets using a series of QDs upon a single laser excitation, 6 showing the merits of a reduction of instrument complexity, test time, and overall cost as compared to the multiple laser setup. 7 However, the release of free heavy-metal ions in an oxidative environment may cause potential toxicity, 8 which still remains a major concern when applying QDs in vivo.…”

Enhancing fluorescence in vivo imaging using inorganic nanoprobes

“…After initial demonstrations of in vivo imaging based on CdTe and PbS materials, new generations of low toxicity NIR emitting QDs have emerged [7]. These are mainly composed of CuIn(S/Se) 2 [8][9][10][11], Cu-doped InP [12], InAs [13][14][15][16], and Ag 2 S [17,18] nanocrystals. These QDs offer a high brightness thanks to their high extinction coefficient and quantum yields (QY), and a higher photostability compared to organic chromophores.…”