Electronic Processes within Quantum Dot-Molecule Complexes

Abstract

The subject of this review is the colloidal quantum dot (QD) and specifically the interaction of the QD with proximate molecules. It covers various functions of these molecules, including (i) ligands for the QDs, coupled electronically or vibrationally to localized surface states or to the delocalized states of the QD core, (ii) energy or electron donors or acceptors for the QDs, and (iii) structural components of QD assemblies that dictate QD-QD or QD-molecule interactions. Research on interactions of ligands with colloidal QDs has revealed that ligands determine not only the excited state dynamics of the QD but also, in some cases, its ground state electronic structure. Specifically, the article discusses (i) measurement of the electronic structure of colloidal QDs and the influence of their surface chemistry, in particular, dipolar ligands and exciton-delocalizing ligands, on their electronic energies; (ii) the role of molecules in interfacial electron and energy transfer processes involving QDs, including electron-to-vibrational energy transfer and the use of the ligand shell of a QD as a semipermeable membrane that gates its redox activity; and (iii) a particular application of colloidal QDs, photoredox catalysis, which exploits the combination of the electronic structure of the QD core and the chemistry at its surface to use the energy of the QD excited state to drive chemical reactions.

Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

“…The study of QDs has long been focused on the inorganic core; specifically, on quantum-confinement (for example, size-dependent band gaps1 and enhanced Auger-type processes2) or increased surface-to-volume ratio effects (for example, size-dependent phase transitions3). However, it has become increasingly clear that post-synthetic surface chemistry modification, or ligand exchange, can critically influence QD optoelectronic properties, as well4567. Ligand exchanges are often performed in the solid state, where films of QDs with long, aliphatic surface ligands are exposed to solutions of shorter alkyl-chain or atomic ligands for exchange.…”

Enabling Visible‐Light‐Driven Selective CO2 Reduction by Doping Quantum Dots: Trapping Electrons and Suppressing H2 Evolution

“…[1][2][3] Compared with the conventional inorganic oxide light harvesters,m etal chalcogenide quantum dots (QDs) possess many attractive features such as high extinction coefficients,multiple-exciton generation effects,tunable band gaps,and rich surface binding sites, [4][5][6] and have thus emerged as ac lass of excellent candidates for visible-light photocatalysis. [1][2][3] Compared with the conventional inorganic oxide light harvesters,m etal chalcogenide quantum dots (QDs) possess many attractive features such as high extinction coefficients,multiple-exciton generation effects,tunable band gaps,and rich surface binding sites, [4][5][6] and have thus emerged as ac lass of excellent candidates for visible-light photocatalysis.…”

“…[1][2][3] Compared with the conventional inorganic oxide light harvesters,m etal chalcogenide quantum dots (QDs) possess many attractive features such as high extinction coefficients,multiple-exciton generation effects,tunable band gaps,and rich surface binding sites, [4][5][6] and have thus emerged as ac lass of excellent candidates for visible-light photocatalysis. [6,9] Moreover,t he dangling bonds derived from the detachment of metal complexes from the QDs form surface defect states in the QDs,w hich consequently reduces reaction activity and selectivity at catalytic sites. However, organic ligands are unfavorable for shuffling photogenerated charges for surface reactions.…”

Customizing the Electrochemical Properties of Carbon Nanodots by Using Quinones in Bottom‐Up Synthesis

“…[22][23][24][25] Additionally,w es howed that the CND emission can be tailored through arational choice of organic precursors. [27][28][29][30] For example,t he electrochemical properties of semiconductor quantum dots or graphene quantum dots can be tuned by preparing hybrids through the (non)covalent attachment of redox-active molecular species. Achieving such control is essential in order to produce high-quality nanomaterials with desired energy levels for applications.T his effort becomes even more relevant if we compare how the control of the redox activity is currently achieved for other types of materials.…”

“…[26] More specifically,w hite-light-emitting CNDs were prepared by using naphthalene anhydride derivatives,a long with arginine (Arg) and ethylenediamine (EDA), fundamental components to produce the CND core and surface,r espectively.N otwithstanding this progress,t he control of CND electrochemical properties has not been attempted yet. [28][29][30][31] Unfortunately,f or CNDs,itisstill necessary to tediously purify the as-prepared mixtures of carbon dots,w hich contain various sizes,d oping ratios,and surfaces. [27][28][29][30] For example,t he electrochemical properties of semiconductor quantum dots or graphene quantum dots can be tuned by preparing hybrids through the (non)covalent attachment of redox-active molecular species.…”