Eliminating Overerase Behavior by Designing Energy Band in High‐Speed Charge‐Trap Memory Based on WSe2

Atomic crystal charge trap memory, as a new concept of nonvolatile memory, possesses an atomic level flatness interface, which makes them promising candidates for replacing conventional FLASH memory in the future. Here, a 2D material WSe₂ and a 3D Al₂O₃/HfO₂/Al₂O₃ charge‐trap stack are combined to form a charge‐trap memory device with a separation of control gate and memory stack. In this device, the charges are erased/written by built‐in electric field, which significantly enhances the write speed to 1 µs. More importantly, owing to the elaborate design of the energy band structure, the memory only captures electrons with a large electron memory window over 20 V and trap selectivity about 13, both of them are the state‐of‐the‐art values ever reported in FLASH memory based on 2D materials. Therefore, it is demonstrated that high‐performance charge trap memory based on WSe₂ without the fatal overerase issue in conventional FLASH memory can be realized to practical application.     

High‐Performance Inorganic Perovskite Quantum Dot–Organic Semiconductor Hybrid Phototransistors

All‐inorganic lead halide perovskite quantum dots (IHP QDs) have great potentials in photodetectors. However, the photoresponsivity is limited by the low charge transport efficiency of the IHP QD layers. High‐performance phototransistors based on IHP QDs hybridized with organic semiconductors (OSCs) are developed. The smooth surface of IHP QD layers ensures ordered packing of the OSC molecules above them. The OSCs significantly improve the transportation of the photoexcited charges, and the gate effect of the transistor structure significantly enhances the photoresponsivity while simultaneously maintaining high I _photo/I _dark ratio. The devices exhibit outstanding optoelectronic properties in terms of photoresponsivity (1.7 × 10⁴ A W^?1), detectivity (2.0 × 10¹⁴ Jones), external quantum efficiency (67000%), I _photo/I _dark ratio (8.1 × 10⁴), and stability (100 d in air). The overall performances of our devices are superior to state‐of‐the‐art IHP photodetectors. The strategy utilized here is general and can be easily applied to many other perovskite photodetectors.     

Designable Luminescence with Quantum Dot–Silver Plasmon Coupler

We explore a strongly interacting QDs/Ag plasmonic coupling structure that enables multiple approaches to manipulate light emission from QDs. Group II–VI semiconductor QDs with unique surface states (SSs) impressively modify the plasmonic character of the contiguous Ag nanostructures whereby the localized plasmons (LPs) in the Ag nanostructures can effectively extract the non‐radiative SSs of the QDs to radiatively emit via SS–LP resonance. The SS–LP coupling is demonstrated to be readily tunable through surface‐state engineering both during QD synthesis and in the post‐synthesis stage. The combination of surface‐state engineering and band‐tailoring engineering allows us to precisely control the luminescence color of the QDs and enables the realization of white‐light emission with single‐size QDs. Being a versatile metal, the Ag in our optical device functions in multiple ways: as a support for the LPs, for optical reflection, and for electrical conduction. Two application examples of the QDs/Ag plasmon coupler for optical devices are given, an Ag microcavity + plasmon‐coupling structure and a new QD light‐emitting diode. The new QDs/Ag plasmon coupler opens exciting possibilities in developing novel light sources and biomarker detectors.     

A Tunneling Dielectric Layer Free Floating Gate Nonvolatile Memory Employing Type‐I Core–Shell Quantum Dots as Discrete Charge‐Trapping/Tunneling Centers

A nonvolatile memory with a floating gate structure is fabricated using ZnSe@ZnS core–shell quantum dots as discrete charge‐trapping/tunneling centers. Systematical investigation reveals that the spontaneous recovery of the trapped charges in the ZnSe core can be effectively avoided by the type‐I energy band structure of the quantum dots. The surface oleic acid ligand surrounding the quantum dots can also play a role of energy barrier to prevent unintentional charge recovery. The device based on the quantum dots demonstrates a large memory window, stable retention, and good endurance. What is more, integrating charge‐trapping and tunneling components into one quantum dot, which is solution synthesizable and processible, can largely simplify the processing of the floating gate nonvolatile memory. This research reveals the promising application potential of type‐I core–shell nanoparticles as the discrete charge‐trapping/tunneling centers in nonvolatile memory in terms of performance, cost, and flexibility.     

Synergistic Targeting and Efficient Photodynamic Therapy Based on Graphene Oxide Quantum Dot‐Upconversion Nanocrystal Hybrid Nanoparticles

Locating nanotherapeutics at the active sites, especially in the subcellular scale, is of great importance for nanoparticle‐based photodynamic therapy (PDT) and other nanotherapies. However, subcellular targeting agents are generally nonspecific, despite the fact that the accumulation of a nanoformulation at active organelles leads to better therapeutic efficacy. A PDT nanoformulation is herein designed by using graphene oxide quantum dots (GOQDs) with rich functional groups as both the supporter for dual targeting modification and the photosensitizer for generating reactive oxygen species, and upconversion nanoparticles (UCNs) as the transducer of excitation light. A tumor‐targeting agent, folic acid, and a mitochondrion‐targeting moiety, carboxybutyl triphenylphosphonium, are simultaneously attached onto the UCNs–GOQDs hybrid nanoparticles by surface modification, and a synergistic targeting effect is obtained for these nanoparticles according to both in vitro and in vivo experiments. More significant cell death and a higher extent of mitochondrion damage are observed compared to the results of UCNs–GOQDs nanoparticles with no or just one targeting moiety. Furthermore, the PDT efficacy on tumor‐bearing mice is also effectively improved. Overall, the current work presents a synergistic strategy to enhance subcellular targeting and the PDT efficacy for cancer therapy, which may also shed light on other kinds of nanotherapies.     

0D–2D Quantum Dot: Metal Dichalcogenide Nanocomposite Photocatalyst Achieves Efficient Hydrogen Generation

Hydrogen generation via photocatalysis‐driven water splitting provides a convenient approach to turn solar energy into chemical fuel. The development of photocatalysis system that can effectively harvest visible light for hydrogen generation is an essential task in order to utilize this technology. Herein, a kind of cadmium free Zn–Ag–In–S (ZAIS) colloidal quantum dots (CQDs) that shows remarkably photocatalytic efficiency in the visible region is developed. More importantly, a nanocomposite based on the combination of 0D ZAIS CQDs and 2D MoS₂ nanosheet is developed. This can leverage the strong light harvesting capability of CQDs and catalytic performance of MoS₂ simultaneously. As a result, an excellent external quantum efficiency of 40.8% at 400 nm is achieved for CQD‐based hydrogen generation catalyst. This work presents a new platform for the development of high‐efficiency photocatalyst based on 0D–2D nanocomposite.     

Nanobodies and Nanocrystals: Highly Sensitive Quantum Dot‐Based Homogeneous FRET Immunoassay for Serum‐Based EGFR Detection

Semiconductor quantum dot nanocrystals (QDs) for optical biosensing applications often contain thick polyethylene glycol (PEG)‐based coatings in order to retain the advantageous QD properties in biological media such as blood, serum or plasma. On the other hand, the application of QDs in Förster resonance energy transfer (FRET) immunoassays, one of the most sensitive and most common fluorescence‐based techniques for non‐competitive homogeneous biomarker diagnostics, is limited by such thick coatings due to the increased donor‐acceptor distance. In particular, the combination with large IgG antibodies usually leads to distances well beyond the common FRET range of approximately 1 to 10 nm. Herein, time‐gated detection of Tb‐to‐QD FRET for background suppression and an increased FRET range is combined with single domain antibodies (or nanobodies) for a reduced distance in order to realize highly sensitive QD‐based FRET immunoassays. The “(nano)²” immunoassay (combination of nanocrystals and nanobodies) is performed on a commercial clinical fluorescence plate reader and provides sub‐nanomolar (few ng/mL) detection limits of soluble epidermal growth factor receptor (EGFR) in 50 μL buffer or serum samples. Apart from the first demonstration of using nanobodies for FRET‐based immunoassays, the extremely low and clinically relevant detection limits of EGFR demonstrate the direct applicability of the (nano)^2‐ assay to fast and sensitive biomarker detection in clinical diagnostics.     

High‐Performance,Solution‐Processed,and Insulating‐Layer‐Free Light‐Emitting Diodes Based on Colloidal Quantum Dots

Quantum‐dot light‐emitting diodes (QLEDs) may combine superior properties of colloidal quantum dots (QDs) and advantages of solution‐based fabrication techniques to realize high‐performance, large‐area, and low‐cost electroluminescence devices. In the state‐of‐the‐art red QLED, an ultrathin insulating layer inserted between the QD layer and the oxide electron‐transporting layer (ETL) is crucial for both optimizing charge balance and preserving the QDs' emissive properties. However, this key insulating layer demands very accurate and precise control over thicknesses at sub‐10 nm level, causing substantial difficulties for industrial production. Here, it is reported that interfacial exciton quenching and charge balance can be independently controlled and optimized, leading to devices with efficiency and lifetime comparable to those of state‐of‐the‐art devices. Suppressing exciton quenching at the ETL–QD interface, which is identified as being obligatory for high‐performance devices, is achieved by adopting Zn_0.9Mg_0.1O nanocrystals, instead of ZnO nanocrystals, as ETLs. Optimizing charge balance is readily addressed by other device engineering approaches, such as controlling the oxide ETL/cathode interface and adjusting the thickness of the oxide ETL. These findings are extended to fabrication of high‐efficiency green QLEDs without ultrathin insulating layers. The work may rationalize the design and fabrication of high‐performance QLEDs without ultrathin insulating layers, representing a step forward to large‐scale production and commercialization.     

MoS2–HgTe Quantum Dot Hybrid Photodetectors beyond 2 µm

Mercury telluride (HgTe) colloidal quantum dots (CQDs) have been developed as promising materials for the short and mid‐wave infrared photodetection applications because of their low cost, solution processing, and size tunable absorption in the short wave and mid‐infrared spectrum. However, the low mobility and poor photogain have limited the responsivity of HgTe CQD‐based photodetectors to only tens of mA W^?1. Here, HgTe CQDs are integrated on a TiO₂ encapsulated MoS₂ transistor channel to form hybrid phototransistors with high responsivity of ≈10⁶ A W^?1, the highest reported to date for HgTe QDs. By operating the phototransistor in the depletion regime enabled by the gate modulated current of MoS₂, the noise current is significantly suppressed, leading to an experimentally measured specific detectivity D* of ≈10¹² Jones at a wavelength of 2 µm. This work demonstrates for the first time the potential of the hybrid 2D/QD detector technology in reaching out to wavelengths beyond 2 µm with compelling sensitivity.     

Carbon‐Intercalated 0D/2D Hybrid of Hematite Quantum Dots/Graphitic Carbon Nitride Nanosheets as Superior Catalyst for Advanced Oxidation

Efficient charge separation and sufficiently exposed active sites are important for light‐driving Fenton catalysts. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), offer a better opportunity for improving photo‐Fenton activity due to their high charge mobility and more catalytic sites, which is highly desirable but remains a great challenge. Herein, a 0D hematite quantum dots/2D ultrathin g‐C₃N₄ nanosheets hybrid (Fe₂O₃ QDs/g‐C₃N₄ NS) is developed via a facile chemical reaction and subsequent low‐temperature calcination. As expected, the specially designed 0D/2D structure shows remarkable catalytic performance toward the removal of p‐nitrophenol. By virtue of large surface area, adequate active sites, and strong interfacial coupling, the 0D Fe₂O₃ QDs/2D g‐C₃N₄ nanosheets establish efficient charge transport paths by local in‐plane carbon species, expediting the separation and transfer of electron/hole pairs. Simultaneously, highly efficient charge mobility can lead to continuous and fast Fe(III)/Fe(II) conversion, promoting a cooperative effect between the photocatalysis and chemical activation of H₂O₂. The developed carbon‐intercalated 0D/2D hybrid provides a new insight in developing heterogeneous catalysis for a large variety of photoelectronic applications, not limited in photo‐Fenton catalysis.