Thermal Sensitive Microgels with Stable and Reversible Photoluminescence Based on Covalently Bonded Quantum Dots

Abstract

In this study, thermal sensitive microgels functionalized with carboxyl groups were synthesized directly from hydroxypropyl cellulose (HPC) and acrylic acid (AA) without using any organic solvent. Furthermore, covalently bonded hybrid microgels with novel thermosensitivity in terms of size and fluorescence were fabricated from these HPC-PAA microgels and cysteamine-capped CdTe quantum dots (QDs). The composition of the hybrid microgels were characterized by thermal thermogravimetric analysis (TGA) and coulometric titration. It was verified that the weight percent of CdTe QDs was ca. 40%, and the percent of poly(acrylic acid) varied between 9.0% and 13.6%. Through a systematic study, it was found that both the size and the fluorescent intensity of the microgels decreased as the temperature increased from below the lower critical solution temperature (LCST) to above the LCST of the HPC. Different from most reported cases, it was found that the thermal sensitive alteration of the current hybrid microgels' size and fluorescent intensity are reversible. The novel fluorescent properties are deduced to be related to the structural characteristics of the microgels, i.e., the QDs are covalently bonded to the microgels and the dispersion of QDs in the microgels is spatially homogeneous. As a consequence of this special structure, the refractive indexes of the microgels were changed and the surface defects of the QDs were reduced, and therefore affected the fluorescent properties of the resulting hybrid microgels.

Synthesis and application of intercellular Ca2+-sensitive fluorescent probe based on quantum dots

“…Based on previous methods [30][31][32], 0.0184 g (9.6 × 10 −5 mol) EDC was first mixed with 1.0 mL of a 2.4 × 10 −2 M (9.6×10 −5 mol) EGTA alkaline aqueous solution (pH 7.1). After 5 min of stirring at 37°C, 5.0 mL of purified CdTe/MA QDs solution was added under uniform stirring (the molarity according to MA count was 9.6 × 10 −5 mol, the molar ratio of QDs:EDC: EGTA was 1:1:1) and stirred for another 30 min in the dark.…”

Simple synthesis of high-quality CdTe QDs in spherical polyelectrolyte brushes with stable and reversible photoluminescence

“…The PL intensity of as-prepared SPB@CdTe decreased with pH decreasing and quenched at pH 3. It was caused by the contracted shell which closely packed QDs at acid condition [21,22,9]. The shell of SPB@CdTe was contracted below pH 5, and the thickness was only about 60 nm at pH 3 (inset image of Fig.…”

Thermosensitive, reversible luminescence properties and bright fluorescence imaging of water-soluble quantum dots/microgels nanocompounds

“…Once the temperature enhanced to above its LCST, hybrid microgel solution would become turbid (at the shrinking state) and acted as strong scattering centers, which induced PL decrease of QDs in microgel networks [17]. Due to the temperature-dependent VT of microgels, the resulting PL intensities 0 dropping and rising of QDs-microgels were interpreted by successive shrinking and swelling of microgels, which triggered reversible light scattering.…”