Towards the fluorescence retention and colloidal stability of InP quantum dots through surface treatment with zirconium propoxide

Abstract

Through the synthetic development of sophisticated core/shell heterostructures, the fluorescent properties of quantum dots (QDs) have been steadily improved to a level that can ultimately meet the industrial demands, but their reliability is still insufficient, particularly showing low fluorescence stability against degradable conditions. As one solution to this issue, an additional physical barrier typically with an oxide phase has been introduced to protect the QD surface from the environment. In this work, a strategy for improving the stability of QDs involving the passivation of their surfaces with zirconium propoxide (Zr(PrO) 4) is suggested. Multi-shelled green QDs of InP/ZnSeS/ZnS were first synthesized, and then their surfaces were in-situ-treated with Zr(PrO) 4. To confirm the presence of Zr(PrO) 4-derived species on the QD surfaces, chemical analyses of the Zr(PrO) 4-treated QDs were performed through Fourier transform infrared, X-ray photoelectron, and inductively coupled plasma optical emission spectroscopic measurements. A photostability test of two comparative InP/ZnSeS/ZnS QDs-one treated without and one with Zr(PrO) 4-was performed by exposing their dispersions to ultraviolet (UV) irradiation for prolonged periods of time, up to 120 h. It was revealed that Zr(PrO) 4 treatment is highly effective in improving fluorescence retention and colloidal stability.

InP-Based Quantum Dots Having an InP Core, Composition-Gradient ZnSeS Inner Shell, and ZnS Outer Shell with Sharp, Bright Emissivity, and Blue Absorptivity for Display Devices

“…The resulting green (530 nm) QDs exhibited a PL line width of 50 nm and a PL QY of 82% (Figure S2a). These PL figures of merit are the best values as compared to the earlier reports on non-(TMS) 3 P-derived InP QDs. ,− Such a high PL QY was attributable to the proper insertion of a ZnSeS inner shell that effectively mitigates a large interfacial lattice strain associated with the substantial lattice mismatch (7.7%) between core InP and outer shell ZnS. − In the case of conventional single-shelled InP/ZnS QDs, their sizes typically do not exceed 5–6 nm. − Such relatively small sizes point to the difficulty of thick ZnS epitaxial growth, again due to a large InP–ZnS lattice mismatch. , On the other hand, sizes of the present InP/ZnSeS/ZnS QDs were quite big (an average diameter of 8.3 nm), (Figure S2b,c), as the inner shell ZnSeS has a moderate disparity in lattice constant with core InP, which is expected to allow for a much thicker epitaxial growth. Nonetheless, these one-pot heterostructured InP QDs possessed a much broader PL fwhm (full width at half-maximum) compared to state-of-the-art (TMS) 3 P-derived counterparts (i.e., 35–36 nm for green emitters). , …”

“…However, (DMA) 3 P-derived InP QDs appear to still lag behind in PL QY and line width compared to the aforementioned state-of-the-art (TMS) 3 P-based counterparts. The highest PL QYs of (DMA) 3 P-derived InP QDs after the introduction of ZnSeS/ZnS double shells were 78 and 80% for green and red color, respectively; however, their PL line widths were quite broad, i.e., 52 (green) and 63 nm (red). Meanwhile, the narrowest line width of 48 nm among (DMA) 3 P-based syntheses was reported from red InP/ZnSe QDs, where ZnSe as a shell was considered to be ideal in alleviating core/shell lattice mismatch accompanying the additional heterogeneous line broadening; however, this single ZnSe shelling sacrificed the PL QY (50%) .…”

“…45–80 nm in line width, strongly depending on the synthetic detail and emission wavelength). − These limited PL figures of merit are associated mostly with the substantial interfacial strain induced by a large disparity (7.7%) in lattice constant between InP and ZnS. Accordingly, for an effort to relieve such an interfacial strain an inner shell with typical compositions of ZnSe, − ZnSeS, − and GaP, − which are intermediate in lattice constant between InP and ZnS, has been introduced prior to ZnS outer shelling, indeed demonstrating that the presence of inner shell is effective primarily in enhancing PL QY and partly in narrowing line width. Representative double-shelled InP QDs with the best PL characteristics found in literature commonly consisted of ZnSe inner and ZnS outer shell, specifically producing near-unity (90–95%) PL QY along with 35–36 and 42 nm in line width for green , and red color, respectively.…”

“…However, this (TMS) 3 P is a highly costly, pyrophoric substance that releases an extremely toxic gas of PH 3 upon contact with air. , Therefore, its use in disaccord with economic and green chemistry may be avoided in the future. On that account, some alternative P precursors to (TMS) 3 P including PCl 3 , P 4 , , and aminophosphines ,,,, have been attempted for synthesis of InP QDs. Among them, aminophosphines, specifically tris­(dialkylamino)­phosphines, can be regarded as viable precursors enabling synthesis of high-quality InP QDs.…”

Display meets biology: A vision for ubiquitous healthcare platforms

“…If the market saturation is inevitable for the existing products (such as “traditional” phones and TVs), the electronic healthcare can be an interesting area to look at that may open the door to tremendous future opportunities. In this regard, emerging display technologies (eg, quantum dot/perovskite LEDs, micro‐LEDs, transaparent backplanes, etc) may provide one day a greater versatility and performance specifically well suited for bio applications, while their research activity is still not comparable with that of OLEDs (see as an example the QLED graph overlay in Figure A).…”