Assembling CdSe Quantum Dots into Polymeric Micelles Formed by a Polyethylenimine-Based Amphiphilic Polymer to Enhance Efficiency and Selectivity of CO₂-to-CO Photoreduction in Water

Abstract

Colloidal quantum dots (QDs) as photocatalysts enable catalysis of CO2-to-CO conversion in the presence of electron donors. The surface and/or interfacial chemical environment of the QDs is essential for the activity and selectivity of the CO2 photoreduction. Various strategies, including exposing active metal sites or anchoring functional organic ligands, have been applied to tune the QDs’ surface chemical environment and thus to improve both activity and selectivity of CO2 photoreduction, which occurs at surface of the QDs. However, the efficient and selective photocatalytic CO2 reduction with QD photocatalysts in water is still a challenging task due to low CO2 solubility and robust competing reaction of proton reduction in water. Different from state-of-the-art QDs’ surface manipulation, we proposed to ameliorate the interfacial chemical environment of CdSe QDs via assembling the QDs into functional polymeric micelles in water. Herein, CdSe@PEI-LA assemblies were constructed by loading CdSe QDs into polymeric micelles formed by PEI-LA, a polyethylenimine (PEI)-based functional amphiphilic polymer. Due to self-assembly and high CO2 adsorption capacity of PEI-LA in water, the photocatalytic CO2-to-CO conversion efficiency and selectivity of the CdSe@PEI-LA assemblies in water were dramatically improved to 28.0 mmol g–1 and 87.5%, respectively. These two values increased 57 times and 1.5 times, respectively, compared with those of the pristine CdSe QDs. Mechanism studies revealed that CdSe QDs locate in polymeric micelles of high CO2 local concentration and the photoinduced electron transfer from the conduction band of CdSe QDs to Cd–CO2* species is thermodynamically and kinetically improved in the presence of PEI-LA. The CdSe@PEI-LA system represents a successful example of using a functionalized amphiphilic polymer to ameliorate interfacial microenvironments of nanocrystal photocatalysts and realizing efficient and selective CO2 photoreduction in water.

An assembled ternary photocatalyst CoPh/CdSe@TiO2 for simultaneous photocatalytic CO2and proton reduction

“…The holes in the VB of the QDs are consumed by the oxidation reaction of TEOA. 36 According to the photocatalytic experiments and our previous studies, 20,36 CdSe QDs also catalyses CO 2 and proton reduction reactions, however, CdSe QDs are not the main catalytic sites for these two reactions under these conditions. The presence of TiO 2 and CoPh makes CdSe QDs mainly function as a light harvester in the ternary photocatalyst.…”

“…This phenomenon had been well studied by our group previously. 20,36 The total amount of gaseous products (CO + H 2 ) generated from the binary system (18.69 mmol) is larger than that from the ternary system (10.63 mmol). This indicates that the CO formation rate is slower than that of H 2 formation in the assembled photocatalysts as well as presumably the lower electron transfer efficiency from the QDs to CoPh in the ternary photocatalyst.…”

Dextran-Functionalized Super-nanoparticle Assemblies of Quantum Dots for Enhanced Cellular Immunolabeling and Imaging

“…At the outset of the research, there was, to our knowledge, no prior report of dextran-stabilized super-QDs and only one example of a many-QD composite NP partially stabilized by carboxy-methyl dextran. 57 Many of the prior examples of super-QDs were stabilized by small-molecule surfactants 58−60 or electrostatic interactions, 24,61,62 which are likely to have more limited colloidal and particle stability (e.g., across ranges of pH and ionic strength) and high non-specific binding with biological samples. Silica encapsulation approaches 26,63,64 offered particle stability with the trade-off of time-consuming, multi-step preparation methods and a continued propensity for non-specific binding in the absence of further functionalization.…”

“…At the outset of the research, there was, to our knowledge, no prior report of dextran-stabilized super-QDs and only one example of a many-QD composite NP partially stabilized by carboxy-methyl dextran . Many of the prior examples of super-QDs were stabilized by small-molecule surfactants − or electrostatic interactions, ,, which are likely to have more limited colloidal and particle stability ( e.g. , across ranges of pH and ionic strength) and high non-specific binding with biological samples.…”

Engineering Z-Scheme FeOOH/PCN with Fast Photoelectron Transfer and Surface Redox Kinetics for Efficient Solar-Driven CO2 Reduction

“…In principle, charge separation and surface reaction are both pivotal factors in the photocatalytic process. Previous studies have focused on the activation of CO 2 molecule and its conversion pathway due to the high dissociation energy of the CO bond (∼750 kJ mol –1 ), thereby effectively promoting CO 2 reduction in the presence of sacrificing agents (such as acetonitrile and triethanolamine) to consume the undesirable photoinduced holes. − However, the utilization of such sacrificing agents will result in excessive energy consumption and inevitable water pollution. Therefore, the development of a photocatalytic system capable of CO 2 reduction from pure water, i.e.…”