Efficient Photoelectrochemical Hydrogen Generation Using Eco-Friendly "Giant" InP/ZnSe Core/Shell Quantum Dots

InP quantum dots (QDs) are promising building blocks for use in solar technologies because of their low intrinsic toxicity, narrow bandgap, large absorption coefficient, and low-cost solution synthesis. However, the high surface trap density of InP QDs reduces their energy conversion efficiency and degrades their long-term stability. Encapsulating InP QDs into a wider bandgap shell is desirable to eliminate surface traps and improve optoelectronic properties. Here, we report the synthesis of "giant" InP/ZnSe core/shell QDs with tunable ZnSe shell thickness to investigate the effect of the shell thickness on the optoelectronic properties and the photoelectrochemical (PEC) performance for hydrogen generation. The optical results demonstrate that ZnSe shell growth (0.9-2.8 nm) facilitates the delocalization of electrons and holes into the shell region. The ZnSe shell simultaneously acts as a passivation layer to protect the surface of InP QDs and as a spatial tunneling barrier to extract photoexcited electrons and holes. Thus, engineering the ZnSe shell thickness is crucial for the photoexcited electrons and hole transfer dynamics to tune the optoelectronic properties of "giant" InP/ZnSe core/shell QDs. We obtained an outstanding photocurrent density of 6.2 mA cm^-1 for an optimal ZnSe shell thickness of 1.6 nm, which is 288% higher than the values achieved from bare InP QD-based PEC cells. Understanding the effect of shell thickness on surface passivation and carrier dynamics offers fundamental insights into the suitable design and realization of eco-friendly InP-based "giant" core/shell QDs toward improving device performance.

The Photoluminescence and Biocompatibility of CuInS2-Based Ternary Quantum Dots and Their Biological Applications

Semiconductor quantum dots (QDs) have become a unique class of materials with great potential for applications in biomedical and optoelectronic devices. However, conventional QDs contains toxic heavy metals such as Pb, Cd and Hg. Hence, it is imperative to find an alternative material with similar optical properties and low cytotoxicity. Among these materials, CuInS2 (CIS) QDs have attracted a lot of interest due to their direct band gap in the infrared region, large optical absorption coefficient and low toxic composition. These factors make them a good material for biomedical application. This review starts with the origin and photophysical characteristics of CIS QDs. This is followed by various synthetic strategies, including synthesis in organic and aqueous solvents, and the tuning of their optical properties. Lastly, their significance in various biological applications is presented with their prospects in clinical applications.

Controlled Photoinduced Electron Transfer from InP/ZnS Quantum Dots through Cu Doping: A New Prototype for the Visible-Light Photocatalytic Hydrogen Evolution Reaction

Photoexcited electron extraction from semiconductors can be useful for converting solar energy into useful forms of energy. Although InP quantum dots (QDs) are considered alternative materials for solar energy conversion, the inherent instability of bare InP QDs demands the use of passivation layers such as ZnS for practical applications, which impedes carrier extraction from the QDs. Here, we demonstrate that Cu-doped InP/ZnS (InP/Cu:ZnS) QDs improve the electron transfer ability due to hole capture by Cu dopants. Steady-state and time-resolved photoluminescence studies confirmed that electrons were effectively transferred from the InP/Cu:ZnS QDs to a benzoquinone acceptor by retarding the electron-hole recombination within the QD. We evaluated the photocatalytic H₂ evolution performance of InP/Cu:ZnS QDs under visible light, which showed outstanding photocatalytic H₂ evolution activity and stability under visible light illumination. The photocatalytic activity was preserved even in the absence of a cocatalyst.

Room temperature synthesis of CuInS2 nanocrystals

Herein, we investigate a synthetic approach to prepare copper indium sulfide nanocrystals at room temperature.