Charge carrier pairing can impart efficient reduction efficiency to core/shell quantum dots: applications for chemical sensing

Abstract

Semiconductor quantum dots (QDs) are bright fluorophores that have significant utility for imaging and sensing applications. Core QDs are often employed in chemosensing via redox processes that modulates their fluorescence...

Ternary Chalcogenide-Based Quantum Dots and Carbon Nanotubes: Establishing a Toolbox for Controlled Formation of Nanocomposites

“…This is in contrast to the minimization of quenching rates that are normally observed in core/shell QDs as a function of shell thickness. , Typically, one would assume that larger shells act as a physical barrier (like longer chain ligands), and with an increased distance between an emitter and a quencher, the rates for charge transfers get more improbable as tunneling and other energy transfers (e.g., Förster resonance energy transfer (FRET)) decrease with the distance. However, such behavior for core/shell particles was observed before in the literature and attributed to prolonged lifetimes of photogenerated charge carriers in core/shell structures with thicker shells. , Given that the Stern–Volmer constant is directly proportional to the lifetime, it appears that the enhanced probability of the quencher to diffuse toward and interact with a photoexcited emitter nanoparticle due to its long lifetime is largely responsible for the observed increased quenching rates. On top of that, it is worth mentioning that CISe/ZnS, CIS/ZnS, and CGS/ZnS are so-called type I core/shell structures, indicating that the valence band maximum (VBM) and the conduction band minimum (CBM) are lower and higher for the shell material than for the core material on a total energy scale, thus confining photogenerated electrons and holes mostly to the core region.…”

“…However, such behavior for core/shell particles was observed before in the literature and attributed to prolonged lifetimes of photogenerated charge carriers in core/shell structures with thicker shells. 71 , 72 Given that the Stern–Volmer constant is directly proportional to the lifetime, it appears that the enhanced probability of the quencher to diffuse toward and interact with a photoexcited emitter nanoparticle due to its long lifetime is largely responsible for the observed increased quenching rates. On top of that, it is worth mentioning that CISe/ZnS, CIS/ZnS, and CGS/ZnS are so-called type I core/shell structures, indicating that the valence band maximum (VBM) and the conduction band minimum (CBM) are lower and higher for the shell material than for the core material on a total energy scale, thus confining photogenerated electrons and holes mostly to the core region.…”

Mesoporous Dual-Semiconductor ZnS/CdS Nanocomposites as Efficient Visible Light Photocatalysts for Hydrogen Generation

“…where C is the measured interfacial capacitance, E is the applied potential, E FB is the flat band potential, A is the working area of the electrode (1 cm 2 ), ε is the relative dielectric constant of the material (8.9) [35,36], ε o is the dielectric permittivity under vacuum (8.8542 × 10 -14 F cm -1 ), e o is the elementary charge (1.602 × 10 -19 C), k B is the Boltzmann constant, and T is the temperature. Note that, under normal conditions, the term "k B T/e o " is usually negligible [37] and the Mott-Schottky relation can be simplified as shown in Equation (3).…”

Carbon-Based Quantum Dots for Photovoltaic Devices: A Review

“…Recently, colloidal quantum dots (QDs) have gain huge attention of researchers due to their quantum confinement and excellent optical properties like tunable photoluminescence (PL), high photoluminescent quantum yield (PLQY), and shape emission. These excellent optical properties of colloidal quantum dots make them a promising material to be used for a variety of applications in energy technology, biomedicine, sensing, etc. − Among various colloidal QDs, the CQDs have recently gained popularity as a semiconductor nanomaterial capable of enhancing the performance of LSCs and solar cells. , CQDs are stable, nontoxic materials composed of commonly found elements (C, H, O, N) that are easily synthesized in bulk via facile hydrothermal or microwave synthesis pathways with a common feedstock. , GQDs, a specialized type of CQDs, have also been thoroughly investigated for their controllable functionalization and excellent conductivity. , Unlike typical CQDs, GQDs have little oxygen functionalization with large areas of sp 2 hybridized domains, resulting in more hydrophobic character and increased conductivity . For their tunable functionalization and biocompatibility, CQDs have been applied in other fields, including environmental remediation, bone regeneration, biosensing, catalysis, and oxygen evolution reaction .…”