Reversible Electrochemical Gelation of Metal Chalcogenide Quantum Dots

Abstract

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.

Colloidal Synthesis and Characterization of Molybdenum Chalcogenide Quantum Dots Using a Two-Source Precursor Pathway for Photovoltaic Applications

“…The Mo–Te vibration band was observed at 812 cm −1 , Mo–Se—at 689 cm −1 , Mo–S—at 459 cm −1 . The peaks of the Mo–X stretch observed in these nanomaterials agreed with what is found in the literature [ 9 , 11 , 17 ]. A C–H stretch was observed at 2920 cm −1 which was attributed to the capping agent TOPO that was used.…”

“…Molybdenum can exhibit very good stability when heated at higher temperatures and allows for good adhesion of the active layer compared to other quantum dots. Therefore, this study focuses on the synthesis and characterization of molybdenum dichalcogenide quantum dots from two-source precursors for application in photovoltaics [ 10 , 11 ].…”

Atomically dispersed Pb ionic sites in PbCdSe quantum dot gels enhance room-temperature NO2 sensing

“…1a ) 54 . Next, CdSe QDs were crosslinked by electro-oxidative removal of the protecting thiolate ligands (as disulfides) in conjunction with the electro-oxidative formation of di-selenide linkages between CdSe QDs to form a macroscopic 3-D connected pore-matter CdSe QD gel 26 . The synthesized CdSe QD gel exhibits a mesoporous network comprising CdSe building blocks with the same size (3.0 ± 0.4 nm) as the starting QDs (Fig.…”

“…Metal chalcogenide quantum dot (QD) gels have recently emerged as a group of promising materials for gas sensing because of their small crystallite size (high surface-to-volume ratio), three-dimensional (3-D) mesoporous structure (fast gas diffusion), connected network (facilitated electronic communication), and rich chemistry (easy surface modification) 26 , 27 . Moreover, the process of gelation has the added benefit of partially or entirely stripping organic ligands from the particle surface, thereby substantially increasing the number of active surface sites for gas molecules to bind, improving the sensing performance.…”

“…Moreover, the process of gelation has the added benefit of partially or entirely stripping organic ligands from the particle surface, thereby substantially increasing the number of active surface sites for gas molecules to bind, improving the sensing performance. Recently, we reported the high NO 2 sensing performance of a CdS QD gel at room temperature, which demonstrated high selectivity, an ultra-low (measured, not extrapolated) limit of detection (LOD = 11 ppb), a short response time ( t res = ~29 s) and recovery time ( t rec = ~28 s) 26 . There was, however, one critical limitation for the CdS QD gel sensor: a relatively low response (0.009% per ppb NO 2 , red square in Fig.…”