Inorganic Quantum Research Articles

High-performance warm white LED based on thermally stable all inorganic perovskite quantum dots

All inorganic CsPbBr₃ quantum dots (QDs) are regarded as excellent candidates for next-generation emitters due to their high photoluminescence quantum yield (PLQY) and defect tolerance. However, the poor stability and degraded luminescent performance may impede their further commercialization because of the separation of conventional ligands from the QDs surfaces. Recently, Zang replaced the regular oleic acid with 2-hexyl-decanoic acid (DA), which possesses higher binding energy on the QDs surfaces, to act as ligands of QDs, exhibiting PLQY of 96% and excellent stabilities against ethanol and water. WLEDs with DA-modified CsPbBr₃ QDs achieved improved thermal stability, a color rendering index of 93, a power efficiency of 64.8 lm/W and a properly correlated color temperature value of 3018 K, implying their prominent applications in solid-state lighting and displays.

Antioxidative 0-dimensional nanodrugs overcome obstacles in AKI antioxidant therapy.

Acute kidney injury (AKI) is a commonly encountered syndrome associated with various aetiologies and pathophysiological processes leading to enormous health risks and economic losses. In the absence of specific drugs to treat AKI, hemodialysis remains the primary clinical treatment for AKI patients. The revelation of the pathology opens new horizons for antioxidant therapy in the treatment of AKI. However, small molecule antioxidant drugs and common nanozymes have failed to challenge AKI due to their unsatisfactory drug properties and renal physiological barriers. 0-Dimensional (0D) antioxidant nanodrugs stand out at this time thanks to their small size and high performance. Recently, a number of research studies have been carried out around 0D nanodrugs for alleviating AKI, and their multi-antioxidant enzyme mimetic activities, smooth glomerular filtration barrier permeability and excellent biocompatibility have been investigated. Here, we comprehensively summarize recent advances in 0D nanodrugs for AKI antioxidant therapy. We classify these representative studies into three categories according to the characteristics of 0D nanomaterials, namely ultra-small metal nanodots, inorganic non-metallic quantum dots and polymer nanodots. We focus on the antioxidant mechanisms and their distribution in vivo in each inspiring work, and the purpose and ingenuity of each design are rigorously captured and described. Finally, we provide our reflections and prospects for 0D antioxidant nanodrugs in AKI treatment. This mini review provides unique insights and valuable clues in the design of 0D nanodrugs and other kidney absorbable drugs.

Highly efficient CsPbBr3@glass@polyurethane composite film as flexible liquid crystal display backlight.

Inorganic lead halide perovskite quantum dots (CsPbX3 QDs (X = Cl, Br, or I)) have attracted more and more attention due to their high absorption coefficient, narrow emission band, high quantum efficiency, and tunable emission wavelength. However, CsPbX3 QDs are decomposed when exposed to bright light, heat, moisture, etc., which leads to severe luminous attenuation and limits their commercial application. In this paper, CsPbBr3@glass materials were successfully synthesized by a one-step self-crystallization method, including melting, quenching and heat treatment processes. The stability of CsPbBr3 QDs was improved by embedding CsPbBr3 QDs into zinc-borosilicate glass. Then, the CsPbBr3@glass was combined with polyurethane (PU) to form a flexible composite luminescent film CsPbBr3@glass@PU. This strategy enables the transformation of rigid perovskite quantum dot glass into flexible luminescent film materials and further improves the photoluminescence quantum yield (PLQY) from 50.5% to 70.2%. The flexible film has good tensile properties, and its length can be strained 5 times as long as the original length. Finally, a white LED was encapsulated by combining CsPbBr3@glass@PU film and red phosphor K2SiF6:Mn4+ with a blue LED chip. The good performance of the obtained CsPbBr3@glass@PU film indicates that it has potential application in flexible liquid crystal displays (LCDs) as a backlight source.

Nanoparticles associated with antimicrobial peptides (AMPs)  promising combination for biomedical and veterinary applications

Bacterial resistance to classical antibiotics is a growing concern, and scientists are seeking alternative methods to combat bacterial infections. One promising option is the use of antimicrobial peptides (AMPs) with strong antibacterial activity provided with diverse mechanisms, including membrane disruption, intracellular interference, and inhibition of bacterial metabolic processes. They can also modulate inflammation, enhancing antimicrobial effects. Compared to antibiotics, AMPs can have a broader range of activity and are less prone to bacterial resistance. However, their use has limitations, such as a short half-life and proteolytic degradation. To address these challenges, researchers are developing strategies to enhance the stability and efficacy of AMPs, including the use of nanocarriers. Nanocarriers, such as inorganic particles, liposomes, polymeric particles, cubosomes, and quantum dots can improve the stability of AMPs, protect them from degradation, enhance their penetration into bacterial cells, and increase their antibacterial activity. Nanocarriers can also boost AMPs absorption by bacteria and stimulate their enzymatic function. While nanocarriers show promise in enhancing AMPs efficacy and stability, further research is necessary to determine their safety and effectiveness in practical medical applications. This review offers a succinct exploration of specific nanoparticles, their function as carriers for AMPs, and their potential significance in both medical and veterinary contexts.

Efficient red luminescence in Eu3+ doped CdSe/CdS all-inorganic quantum dots shows great potential for wLEDs.

Complete inorganic quantum dots (QDs) CdSe/CdS:Eu3+ with full transmittance were proposed as red color converters for white light emitting diodes (wLEDs) using a facile one-step melt quenching method. TEM, XPS, and XRD were used to verify the successful nucleation of CdSe/CdS:Eu3+ QDs in silicate glass. The results indicated that the incorporation of Eu contributed to the nucleation of CdSe/CdS QDs in silicate glass, where the nucleation time of the CdSe/CdS:Eu3+ QDs rapidly decreased in 1 h compared with other inorganic QDs that took more than 15 h. CdSe/CdS:Eu3+ inorganic QDs exhibited bright and long-term stable red luminescence under both UV and blue light excitation; up to 53.5% quantum yield and 8.05 ms fluorescence lifetime were obtained by adjusting the Eu3+ concentration. Based on the luminescence performance and absorption spectra, a possible luminescence mechanism was proposed. Moreover, the application potential of the CdSe/CdS:Eu3+ QDs in wLEDs was studied by coupling the CdSe/CdS:Eu3+ QDs and commercial Intematix G2762 green phosphor on a InGaN blue LED chip. Warm white light (5217 K) with 89.5 CRI and 91.1 lm W-1 luminous efficacy could be achieved. Additionally, 91% of the NTSC color gamut was obtained, demonstrating the great potential of the CdSe/CdS:Eu3+ inorganic QDs as a color converter for wLEDs.

All-Inorganic Perovskite Quantum Dot-Based Blue Light-Emitting Diodes: Recent Advances and Strategies.

Light-emitting diodes (LEDs) based on all-inorganic lead halide perovskite quantum dots (PQDs) have undergone rapid development especially in the past five years, and external quantum efficiencies (EQEs) of the corresponding green- and red-emitting devices have exceeded 23%. However, the blue-emitting devices are facing greater challenges than their counterparts, and their poor luminous efficiency has hindered the display application of PQD-based LEDs (PeQLEDs). This review focuses on the key challenges of blue-emitting PeQLEDs including low EQEs, short operating lifetime, and spectral instability, and discusses the essential mechanism by referring to the latest research. We then systematically summarize the development of preparation methods of blue emission PQDs, as well as the current strategies on alleviating the poor device performance involved in composition engineering, ligand engineering, surface/interface engineering, and device structural engineering. Ultimately, suggestions and outlooks are proposed around the major challenges and future research direction of blue PeQLEDs.

Short‐Wave Infrared Synaptic Phototransistor with Ambient Light Adaptability for Flexible Artificial Night Visual System

AbstractFlexible organic monitoring system that can work in short‐wave infrared (SIR) region has great potential in autonomous driving, night driving safety, military encryption, biomedical imaging, and robot engineering. Especially, the development of infrared artificial vision system device that can autonomously improve the computing speed and adapt to different brightness ambient light is very important. However, it is a challenge for mimicking infrared visual adaptation because of the need for infrared absorbing materials and the need to control the concentration of carriers. In this study, inorganic quantum dot material is combined with organic materials to promote carrier separation and introduce interface defects that adjust the carrier concentration in transistors, which induce the synaptic behavior under SIR (1100 nm) light in darkness and the ability to adapt to white ambient light. Furthermore, the device array realizes the image recognition of SIR light at night with white ambient light of different brightness, exhibiting good self‐adaptability, and strong anti‐interference ability. These results demonstrate promising applications of the infrared synaptic phototransistors in adapted bionic optoelectronic devices.

Bioanalytical Applications of Graphene Quantum Dots for Circulating Cell-Free Nucleic Acids: A Review.

Graphene quantum dots (GQDs) are carbonaceous nanodots that are natural crystalline semiconductors and range from 1 to 20 nm. The broad range of applications for GQDs is based on their unique physical and chemical properties. Compared to inorganic quantum dots, GQDs possess numerous advantages, including formidable biocompatibility, low intrinsic toxicity, excellent dispensability, hydrophilicity, and surface grating, thus making them promising materials for nanophotonic applications. Owing to their unique photonic compliant properties, such as superb solubility, robust chemical inertness, large specific surface area, superabundant surface conjugation sites, superior photostability, resistance to photobleaching, and nonblinking, GQDs have emerged as a novel class of probes for the detection of biomolecules and study of their molecular interactions. Here, we present a brief overview of GQDs, their advantages over quantum dots (QDs), various synthesis procedures, and different surface conjugation chemistries for detecting cell-free circulating nucleic acids (CNAs). With the prominent rise of liquid biopsy-based approaches for real-time detection of CNAs, GQDs-based strategies might be a step toward early diagnosis, prognosis, treatment monitoring, and outcome prediction of various non-communicable diseases, including cancers.

One-pot Solvothermal Synthesis of Full-color Carbon Quantum Dots for Application in Light Emitting Diodes

Full-color Carbon Quantum Dots (FCQDs) have intrinsic characteristics as components for White Light Emitting Diode (WLED) technology, but are not yet applied in the current lighting industry. In this work, FCQDs were prepared by optimizing the synthetic route in order to obtain a simple and one-step solvothermal carbonization of citric acid and urea in dimethylformamide. The synthesis at 166 °C for 11 h and 24 min (FCQD2) was selected from spectroscopy in the ultraviolet–visible (UV–Vis) region and its fluorescence indicated emission over almost the entire visible region of the electromagnetic spectrum with a 380 nm excitation source and a concentration of 0.22 mg mL −1. The morphological, structural and optical properties were evaluated and they showed that nanoparticles with dimensions between 2 and 10 nm consisted mainly of carbon atoms with functional groups on the surface. FCQD2 was incorporated in a polymeric matrix (PVA) and the coordinates of the Color Rendering Index (CRI) showed better color quality than a commercial WLED. It appears that FCQD2, with an easy synthesis and being ecofriendly, has potential for incorporation in a solid matrix, as well as application in WLEDs for the improvement of optoelectronic devices, replacing inorganic quantum dots.

Predeposited Multifunctional Carbon Nanotube:SnO2 on the PbI2 Film for Efficient and Stable Two‐Step‐Processed Perovskite Solar Cells

Compared with one‐step‐processed perovskite solar cells (PSCs), there are few reports on improving the power conversion efficiency (PCE) of two‐step‐processed PSCs by reducing the nonradiative recombination caused by defects through interface engineering. Herein, a new strategy is proposed, that is, by predepositing multifunctional inorganic SnO2 quantum dots‐modified single‐walled carbon nanotubes (CNT:SnO2) on PbI2 film to form perovskite/CNT:SnO2 heterojunction in the top region within two‐step‐processed perovskite films. The CNT:SnO2 not only promotes the crystallization of perovskite and improves the quality of perovskite films, but also passivates perovskite defects, and effectively suppresses nonradiative recombination. Meanwhile, CNT:SnO2 leads to the change of the Fermi energy level of the perovskite film, which optimizes the interface energy band arrangement and leads to an additional potential in the perovskite/CNT:SnO2 heterojunction region, which further accelerate the charge separation and transport. In addition, the CNT:SnO2 suppresses the migration of halogen anions in the perovskite film and improves the hydrophobicity of the perovskite film. Consequently, the PCE of CNT:SnO2‐based PSCs is significantly increased from 20.10% to 22.25%. They also exhibit improved stability; for instance, the unencapsulated cell maintains 75% of its original PCE even after 600 h of thermal aging at 85 °C.

The chemistry and physics of organic—inorganic hybrid perovskite quantum wells

The chemistry and physics of organic—inorganic hybrid perovskite quantum wells

Carrier Management via Integrating InP Quantum Dots into Electron Transport Layer for Efficient Perovskite Solar Cells

Metal oxides are the most efficient electron transport layers (ETLs) in perovskite solar cells (PSCs). However, issues related to the bulk (i.e., insufficient electron mobility, unfavorable energy level position) and interface of metal oxide/perovskite (detrimental surface hydroxyl groups) limit the transport kinetics of photoinduced electrons and prevent PSCs from unleashing their theoretical efficiency potential. Herein, the inorganic InP colloid quantum dots (CQDs) with outstanding electron mobility (4600 cm2 V-1 s-1) and carboxyl (-COOH) terminal ligands were uniformly distributed into the metal oxide ETL to form consecutive electron transport channels. The hybrid InP CQD-based ETL demonstrates a more N-type characteristic with more than 3-fold improvement in electron mobility. The formation of the Sn-O-In bond facilitates electron extraction due to suitable energy level alignment between the ETL and perovskite. The strong interaction between uncoordinated Pb2+ at the perovskite/ETL interface and the -COO- in the ligand of InP CQDs reduces the density of defects in perovskite. As a result, the hybrid InP CQD-based ETL with an optimized InP ratio (18 wt %) boosts the power conversion efficiency of PSCs from 22.38 to 24.09% (certified efficiency of 23.43%). Meanwhile, the device demonstrates significantly improved photostability and atmospheric storage stability.

Inorganic quantum dots - anammox consortia hybrid for stable nitrogen elimination under high-intensity solar-simulated irradiation

External stimulus such as light irradiation is able to deteriorate intracellular redox homeostasis and induce photooxidative damage to non-photogenic bacteria. Exploiting effective strategies to help bacteria resisting infaust stress is meaningful for achieving a stable operation of biological treatment system. In this work, selenium-doped carbon quantum dots (Se-CQDs) were blended into anaerobic ammonia oxidation (anammox) bacteria and an inorganic nanoparticle-microbe hybrid was successfully fabricated to evaluate its nitrogen removal performance under solar-simulated irradiation. It was found that the specific anammox activity decreased by 29.7 ± 5.2% and reactive oxygen species (ROS) content increased by 134.8 ± 4.1% under 50,000 lux light. Sludge activity could be completely recovered under the optimum dosage of 0.42 mL·(g volatile suspended solid) -1 Se-CQDs. Hydroxyl radical (·OH) and superoxide anion radical (·O2−) were identified as the leading ROS inducing lipid peroxidation and antioxidase function detriment. Also, the structure of ladderane lipids located on anammoxosome was destroyed by ROS and functional genes abundances declined accordingly. Although cell surface coated Se-CQDs could absorb ultraviolet light and partially mitigated the photoinhibition, the direct scavenging of ROS by intracellular Se-CQDs primarily contributed to the cellular redox homeostasis, antioxidase activity recovery and sludge activity improvement. The findings of this work provide in-depth understanding the metabolic response mechanism of anammox consortia to light irradiation and might be valuable for a more stable and sustainable nitrogen removal technology, i.e., algal-bacterial symbiotic system, development.

Low‐Power‐Consumption, Reversible 3D Optical Storage Based on Selectively Laser‐Induced Photoluminescence Degradation in CsPbBr3 Quantum Dots Doped Glass

AbstractIn recent years, inorganic lead halide perovskite quantum dots have been used in various optoelectronic fields for their excellent luminescence properties, such as narrow emission bands, ultra‐wide tunable emission wavelength, and high quantum efficiency. In this paper, different from luminescence optimization in most research, luminescence degradation of perovskite quantum dots is addressed by femtosecond laser irradiation and successfully used for three‐dimensional data storage in CsPbBr3 quantum dots doped glass. Photoluminescence (PL) degradation can be finely modulated by adjusting the laser parameters. PL degradation mechanism, investigated by optical spectroscopy and morphology characterization, is attributed to laser‐induced decomposition, recrystallization, and defection of CsPbBr3 quantum dots. Laser‐induced PL degradation and the followed PL recovery by heat treatment are repeated for several cycles, showing good reversibility. Multilayer PL degradation patterns are written into the glass and read out without crosstalk, indicating high‐reliability 3D optical storage characteristics. Amazingly, PL degradation can be induced by just a low‐energy single laser pulse with estimated subpicosecond writing time per bit, demonstrating its potential in high‐speed, low‐power consumption 3D optical storage.

Chiral semiconductor photonic thin film with tunable circularly polarized luminescence

Inorganic nanowires and semiconductor quantum dots are co-assembled into chiral photonic crystals, generating circularly polarized luminescence with a significant dissymmetry factor and tunable peak position, intensity, and sign by controlling the photonic crystals' bandgap, pitch number, and handedness.

C3N4 and C3N5 Nanosheets As Passivation Layers and Carrier Extractors for Inorganic Semiconductor Nanowires and Quantum Dots

Inorganic semiconductor nanowires and quantum dots made of chalcogenides, III-V semiconductors and halide perovskites offer exciting potential for optoelectronic devices. The orthogonalization possible in nanowires between the normally competing processes of charge generation and charge separation have been used to project very high operating performance exceeding that of thin films and single crystals in light harvesting devices such as solar cells, photodetectors, photocatalysts and photoelectrolyzers. Likewise, inorganic quantum dots with size-tunable absorption and emission spectra are excellent candidates for light emitting devices as well as light harvesting devices. However, the practical performance of inorganic nanowire based optoelectronic devices has significantly lagged theoretical predictions. A major reason for the discrepancy between theory and experiment is the presence of surface traps and defects in nanowires and quantum dots, which exhibit a large surface area to volume ratio. Several chemical treatments and annealing regimens have been employed to heal surface defects in nanowires and quantum dots. One popular strategy involves wrapping nanowires and/or quantum dots with a thin coating of a molecular monolayer (e.g. alkanethiols) or an atomic layer deposited conformal oxide. While such core-shell architectures are frequently effective in reducing surface defects, the surface passivation is invariably accompanied by a deterioration in optoelectronic properties due to the difficulty experienced by charge carriers in tunneling through the thin shell layer. The resulting trade-off between surface passivation and carrier extraction limits performance improvements in light harvesting devices. Thus there is a strong need for passivating layers that do not negatively impact carrier extraction.Herein, we show that graphitic carbon nitride coatings are highly effective in passivating the surfaces of inorganic nanowires and quantum dots while preserving excellent carrier transport and extraction. Three illustrative examples are provided together with in-depth spectroscopic and electrical characterization:(1) Cesium lead bromide (CsPbBr3) quantum dots passivated by g-C3N4 nanosheets and performing spectacularly as CO2 photoreduction catalysts and water-splitting photoanodes(2) The double helical ternary semiconductor SnIP passivated by g-C3N4 nanosheets which experienced a remarkable improvement in photoelectrochemical performance(3) Cadmium sulfide (CdS) nanowires passivated by C3N5 nanosheets resulting in a superior photocatalytic performance

(Invited) Enhancing Fluorescence Biosensing By Near-Infrared Emission with Nanomaterials

This talk has showed the advantages of nanomaterials such as graphene oxide nanosheets and inorganic quantum dots as fluorophores in biosensing. It has also studied the behaviors of visible-light and near-infrared fluorescence emission in blood sample matrix. And plasmonic nanostructures have been designed to enhance near-infrared fluorescence in blood.

Silver‐Bismuth Based 2D Double Perovskites (4FPEA)4AgBiX8 (X = Cl, Br, I): Highly Oriented Thin Films with Large Domain Sizes and Ultrafast Charge‐Carrier Localization

AbstractTwo‐dimensional (2D) hybrid double perovskites are a promising emerging class of materials featuring superior intrinsic and extrinsic stability over their 3D parent structures, while enabling additional structural diversity and tunability. Here, we expand the Ag–Bi‐based double perovskite system, comparing structures obtained with the halides chloride, bromide, and iodide and the organic spacer cation 4‐fluorophenethylammonium (4FPEA) to form the n = 1 Ruddlesden–Popper (RP) phases (4FPEA)4AgBiX8 (X = Cl, Br, I). We demonstrate access to the iodide RP‐phase through a simple organic spacer, analyze the different properties as a result of halide substitution and incorporate the materials into photodetectors. Highly oriented thin films with very large domain sizes are fabricated and investigated with grazing incidence wide angle X‐ray scattering, revealing a strong dependence of morphology on substrate choice and synthesis parameters. First‐principles calculations confirm a direct band gap and show type Ib and IIb band alignment between organic and inorganic quantum wells. Optical characterization, temperature‐dependent photoluminescence, and optical‐pump terahertz‐probe spectroscopy give insights into the absorption and emissive behavior of the materials as well as their charge‐carrier dynamics. Overall, we further elucidate the possible reasons for the electronic and emissive properties of these intriguing materials, dominated by phonon‐coupled and defect‐mediated polaronic states.

Quantum Confinement and Dielectric Deconfinement in Quasi-Two-Dimensional Perovskites: Their Roles in Light-Emitting Diodes

In quasi-two-dimensional (quasi-2D) perovskites, inorganic quantum wells are sandwiched between organic spacers (barriers) from the energy-level perspective. In addition to quantum confinement, dielectric confinement occurs in the layered perovskites due to a large difference in the dielectric constants of the inorganic framework and the organic spacer layer. While quantum confinement increases the exciton binding energy, deconfinement in the dielectric constant results in a decrease in exciton binding energy and also an increase in carrier mobility. In this work, we investigate the effects of quantum confinement and dielectric deconfinement on the dynamic response of light-emitting diodes (LEDs) based on several series of quasi-2D perovskites and operated under an alternating voltage. With pulsed electroluminescence emission appearing in both bias sections of sinusoidal ac voltages, we show how the quantum confinement and dielectric deconfinement affect and increase the frequency range of ac LED operation, that is, the \ensuremath{-}3 dB cutoff frequency. This \ensuremath{-}3-dB frequency could be seen to increase due to a relaxation of quantum and dielectric confinements, leading to an enhancement of the effective carrier mobility in the active emitting material of the devices.

Multicolor Biexciton Lasers Based on 2D Perovskite Single Crystalline Flakes

AbstractThe biexciton is a quasi‐particle created from two free excitons and can be applied for basic quantum operations, entangled light sources, and lasers. 2D lead‐halide layered perovskites (LPs) naturally form organic–inorganic quantum wells (QWs), leading to high exciton binding energy and tunable band‐gaps dependent on the QW thickness of <n>. Although excitonic lasing has been reported for thicker LP‐QWs, biexciton emissions and lasers from phase‐pure LP‐QWs as a function of <n> remain largely unexplored. Here, a facile solution growth method for fabricating single‐crystalline flakes (SCFs) of LP‐QWs of (PEA)2(MA)n−1PbnI3n+1 (PEA = phenylethylammonium, <n> = 1, 2, and 3) is reported. Further, multicolor amplified spontaneous emissions from biexciton states of (PEA)2(MA)n−1PbnI3n+1 (<n> = 1, 2, and 3) SCFs are demonstrated at 541 (green), 588 (yellow), 627 nm (red) with thresholds of 35.4, 15.1, and 5.8 µJ cm−2 at 20 K, respectively. In order to offer cavities for these single‐crystalline flakes, they are exfoliated into smaller flakes. Multimode lasing is shown at 586 and 627 nm for <n> = 2 and 3 with threshold of 10.5 and 4.8 µJ cm−2, respectively. The results of this study not only enrich the basic understanding of many‐body excitonic interactions in 2D LPs but also provide insights for developing solution‐processed multicolor lasers.