3 research outputs found
Highly Fluorescent and Stable Quantum Dot-Polymer-Layered Double Hydroxide Composites
We
report a designed strategy for a synthesis of highly luminescent
and photostable composites by incorporating quantum dots (QDs) into
layered double hydroxide (LDH) matrices without deterioration of a
photoluminescence (PL) efficiency of the fluorophores during the entire
processes of composite formations. The QDs synthesized in an organic
solvent are encapsulated by polymers, polyÂ(maleic acid-alt-octadecene)
to transfer them into water without altering the initial surface ligands.
The polymer-encapsulated QDs with negative zeta potentials (−29.5
± 2.2 mV) were electrostatically assembled with positively charged
(24.9 ± 0.6 mV) LDH nanosheets to form QD-polymer-LDH composites
(PL quantum yield: 74.1%). QD-polymer-LDH composite films are fabricated
by a drop-casting of the solution on substrates. The PL properties
of the films preserve those of the organic QD solutions. We also demonstrate
that the formation of the QD-polymer-LDH composites affords enhanced
photostabilities through multiple protections of QD surface by polymers
and LDH nanosheets from the environment
Strategy for Synthesizing Quantum Dot-Layered Double Hydroxide Nanocomposites and Their Enhanced Photoluminescence and Photostability
Layered double hydroxide-quantum dot (LDH-QD) composites
are synthesized via a room temperature LDH formation reaction in the
presence of QDs. InP/ZnS (core/shell) QD, a heavy metal free QD, is
used as a model constituent. Interactions between QDs (with negative
zeta potentials), decorated with dihydrolipoic acids, and inherently
positively charged metal hydroxide layers of LDH during the LDH formations
are induced to form the LDH-QD composites. The formation of the LDH-QD
composites affords significantly enhanced photoluminescence quantum
yields and thermal- and photostabilities compared to their QD counterparts.
In addition, the fluorescence from the solid LDH-QD composite preserved
the initial optical properties of the QD colloid solution without
noticeable deteriorations such as red-shift or deep trap emission.
Based on their advantageous optical properties, we also demonstrate
the pseudo white light emitting diode, down-converted by the LDH-QD
composites
Cancer-Microenvironment-Sensitive Activatable Quantum Dot Probe in the Second Near-Infrared Window
Recent technological advances have
expanded fluorescence (FL) imaging
into the second near-infrared region (NIR-II; wavelength = 1000–1700
nm), providing high spatial resolution through deep tissues. However,
bright and compact fluorophores are rare in this region, and sophisticated
control over NIR-II probes has not been fully achieved yet. Herein,
we report an enzyme-activatable NIR-II probe that exhibits FL upon
matrix metalloprotease activity in tumor microenvironment. Bright
and stable PbS/CdS/ZnS core/shell/shell quantum dots (QDs) were synthesized
as a model NIR-II fluorophore, and activatable modulators were attached
to exploit photoexcited electron transfer (PET) quenching. The quasi
type-II QD band alignment allowed rapid and effective FL modulations
with the compact surface ligand modulator that contains methylene
blue PET quencher. The modulator was optimized to afford full enzyme
accessibility and high activation signal surge upon the enzyme activity.
Using a colon cancer mouse model, the probe demonstrated selective
FL activation at tumor sites with 3-fold signal enhancement in 10
min. Optical phantom experiments confirmed the advantages of the NIR-II
probe over conventional dyes in the first near-infrared region