The
ability to dictate the assembly of quantum dots (QDs) is critical
for their integration into solid-state electronic and optoelectronic
devices. However, assembly methods that enable efficient electronic
communication between QDs, facilitate access to the reactive surface,
and retain the native quantum confinement characteristics of the QD
are lacking. Here we introduce a universal and facile electrochemical
gelation method for assembling metal chalcogenide QDs (as demonstrated
for CdS, ZnS, and CdSe) into macroscale 3-D connected pore-matter
nanoarchitectures that remain quantum confined and in which each QD
is accessible to the ambient. Because of the redox-active nature of
the bonding between QD building blocks in the gel network, the electrogelation
process is reversible. We further demonstrate the application of this
electrogelation method for a one-step fabrication of CdS gel gas sensors,
producing devices with exceptional performance for NO2 gas
sensing at room temperature, thereby enabling the development of low-cost,
sensitive, and reliable devices for air quality monitoring.
Atmospheric NO2 is of great concern due to its adverse effects on human health and the environment, motivating research on NO2 detection and remediation. Existing low-cost room-temperature NO2 sensors often suffer from low sensitivity at the ppb level or long recovery times, reflecting the trade-off between sensor response and recovery time. Here, we report an atomically dispersed metal ion strategy to address it. We discover that bimetallic PbCdSe quantum dot (QD) gels containing atomically dispersed Pb ionic sites achieve the optimal combination of strong sensor response and fast recovery, leading to a high-performance room-temperature p-type semiconductor NO2 sensor as characterized by a combination of ultra–low limit of detection, high sensitivity and stability, fast response and recovery. With the help of theoretical calculations, we reveal the high performance of the PbCdSe QD gel arises from the unique tuning effects of Pb ionic sites on NO2 binding at their neighboring Cd sites.
Control
of nanoparticle assembly is a critical enabler for fabricating
nanostructures capable of complex, system-level functionality. Here,
we report a facile electrochemical method for assembling quantum dots
(QDs) into mesoporous gels directly onto an electrode surface using
localized, in situ generated metal ion crosslinkers (Ni2+, Co2+, Ag+, or Zn2+) within a colloidal
solution of metal chalcogenide nanoparticles capped with ligands featuring
pendant carboxylate groups. A mechanistic study reveals a critical
stoichiometry of 0.5 metal ions: 1 QD in solution is required to trigger
metal ion-mediated electrogelation (ME-gelation), representing a much
lower concentration of metal ions than is needed for initiating crosslinking
throughout an entire volume of solution (>26 metal ions: 1 QD in
solution).
The application of the ME gelation approach for the fabrication of
QD-based electronic devices is demonstrated by electrochemical patterning
of QD gels onto a printed circuit board chip.
Here we report CdS quantum dot (QD) gels as highly efficient and unique photocatalysts for organic synthesis. We found that the photocatalytic activity of CdS QD gel was superior to...
Relative to conventional chemical approaches, electrochemical assembly of metal chalcogenide nanoparticles enables the use of two additional levers for tuning the assembly process: electrode material and potential. In our prior...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.