Synthesis-Kinetics of Violet- and Blue-Emitting Perovskite Nanocrystals with High Brightness and Superior Stability toward Flexible Conversion Layer.

The low photoluminescence (PL) efficiency and unstable features of small blue-emitting CsPbX3 nanocrystals (NCs) greatly limit their applications in optoelectronics field. Herein, the synergistic and post-treatment kinetics are studied to create highly bright and anomalous stable violet (peak position of ≈408 nm) and blue (peak position of ∼ 466 nm) emitting perovskite NCs. Ligand and ion exchange mechanism are systematic studied by the evolution of absorption, PL, and fluorescence lifetime to evaluate ligand bonding, defect engineering, and non-radiative recombination. Didodecyl dimethyl mmonium chloride (DDAC) and CuX2 post-synergistic treatment created DDAC-CsPbCl3 -CuCl2 and DDAC-CsPbCl3 -CuBr2 NCs that remained the phase composition, morphology, and size of CsPbCl3 NCs. The PL efficiencies are drastically increased to 42 and 85% for violet- and blue-emitting NCs, respectively. The stability test indicated that the NCs enable against various harsh conditions (e.g., ultraviolet light irradiation and heat-treatment). The NCs retained their initial PL efficiency after 2 months under ambient conditions and UV light irradiation. These NCs also exhibited high stability after heat-treatment at 120 °C. The emitting NCs embedded in flexible films still revealed bright PL and high stability, suggesting current results provide a new avenue for the application in the field of optoelectronics.

General Strategies for Preparing Hybrid Polymer/Quantum Dot Nanocomposites for Color Conversion.

Quantum dots (QDs), with their exceptional optical properties, have emerged as promising candidates to replace traditional phosphors in lighting and display technologies. This study delves into the integration strategies of QDs within glass and polymer matrices to engineer advanced quantum dot color converters (QDCCs) at the industrial scale for practical applications. To achieve enhancements in the photostability and thermal stability of QDCCs, we explore two distinct approaches: the dispersion of QDs in a hydrophilic glass matrix via a sol-gel process and the incorporation of QDs into a non-polar acrylate monomer to formulate QD/polymer nanocomposites. This research further investigates the optical behaviors of these composites, focusing on their light-scattering and propagation mechanisms, which are critical for optimizing light extraction efficiency in QDCCs. Additional optical film and light-scattering particles can improve color conversion efficiency by ~140%. These advancements present a significant step forward in the development of high-performance, energy-efficient, QD-based lighting and display systems.

Enhanced Photostability of Core/Shell Quantum Dots under Intense Blue Light Irradiation through Positive Photoaging Mechanism.

Photostability of semiconductor core/shell quantum dots (QDs) has historically been perceived as intricate and unpredictable. Notably, the long-term luminescence stability of QDs under light exposure does not seem to consistently correspond with their characteristics in the absence of light. In this study, we propose a positive photoaging mechanism of QDs, integrating both ligand/shell-induced photobrightening and surface photo-oxidation, to deal with the photostability nuances. When QDs are subjected to higher energy light, their photobrightening and photodarkening conjointly determine the photostability. Enhanced photostability may not be simply attributed to a thicker shell or the presence of ligands. When adjusted with an optimal shell thickness and supplemented with negatively charged ligands, QDs exhibit enhanced photostability in both solvents and polymers.

Top-Emitting Active-Matrix Quantum Dot Light-Emitting Diode Array with Optical Microcavity for Micro QLED Display.

An electroluminescent quantum-dot light-emitting diode (QLED) device and a micro QLED device array with a top-emitting structure were demonstrated in this study. The QLED device was fabricated in the normal structure of [ITO/Ag/ITO anode]/PEDOT:PSS/PVK/QDs/[ZnO nanoparticles]/Ag/MoO3, in which the semi-transparent MoO3-capped Ag cathode and the reflective ITO/metal/ITO (IMI) anode were designed to form an optical microcavity. Compared with conventional bottom-emitting QLED, the microcavity-based top-emitting QLED possessed enhanced optical properties, e.g., ~500% luminance, ~300% current efficiency, and a narrower bandwidth. A 1.49 inch micro QLED panel with 86,400 top-emitting QLED devices in two different sizes (17 × 78 µm2 and 74 × 40.5 µm2) on a low-temperature polysilicon (LTPS) backplane was also fabricated, demonstrating the top-emitting QLED with microcavity as a promising structure in future micro display applications.

Bifunctional Metal Oleate as an Alternative Method to Remove Surface Oxide and Passivate Surface Defects of Aminophosphine-Based InP Quantum Dots.

The optical properties of indium phosphide (InP) quantum dots (QDs) are significantly influenced by their surface native oxides, which are generally removed by treating InP cores with hydrofluoric acid (HF). Besides the harmful health effects of HF, its etching may cause over-etching or QD size broadening, and surface oxidation can also reoccur rapidly. In the present study, a safer bifunctional metal oleate treatment was developed to simultaneously remove the surface oxide layer and passivate the surface defects for aminophosphine-based InP QDs. Compared to conventional HF etching, the bifunctional metal oleate was able to more efficiently remove the surface oxide of InP cores and effectively preserve the oxide-free surface, leading to a 20% narrower photoluminescence (PL) bandwidth after growing a ZnSe/ZnS shell. The metal oleate treatment is thus considered a greener and safer post-synthetic method to remove InP surface oxide and provide additional passivation to improve the optical properties of aminophosphine-based InP QDs, which could have potential in industrial mass production.

Fusiform-Shaped g-C3 N4 Capsules with Superior Photocatalytic Activity.

Carbon nitride (g-C3 N4 ) nanostructure rebuilding is an effective means to modify its photocatalytic properties, especially the hollow micron-nanostructure. The increased scattering in the body effectively improves the light utilization efficiency and improves catalytic properties. In this work, fusiform-shaped g-C3 N4 capsules are created by controlling the nucleation kinetics of supramolecular assemblies. The fusiform-shaped capsule micron-nanostructure is synthesized with ultrathin wall thickness and adjusted carbon/nitride ratios which decrease the recombination rate of photo-generated carriers. The hollow nanostructure and relatively higher specific surface area of the fusiform-shaped capsule effectively enhance light scattering inside body and lead to an enhanced carrier utilization efficiency. Moreover, the decrease of bandgap and relatively negative conduction band position affect the response of hollow fusiform-shaped g-C3 N4 capsules (Hf-g-C3 N4 ) in visible light region and improve the photo-reducing performance. In term of H2 evolution property, Hf-g-C3 N4 has been improved to 7052 µmol g-1 h-1 , which is 10.9 times higher compared with bulk structure. More importantly, Hf-g-C3 N4 can produce CH4 at the rate of 1.63 µmol g-1 h-1 without help of co-catalyst and hole sacrificial agent in the photocatalytic reduction reaction of CO2 to CH4 . At same time, the selective photocatalytic reduction of CO2 is another advantage of Hf-g-C3 N4 .

Inkjet-Printed Salt-Encapsulated Quantum Dot Film for UV-Based RGB Color-Converted Micro-Light Emitting Diode Displays.

A promising method has been demonstrated to fabricate quantum dot (QD)-converted full-color micro-light emitting diodes (LEDs) by inkjet printing (IJP) instead of the mass transfer of three red-green-blue (RGB) color chips. By introducing an additional medium, that is, NaCl into a formulated ink, QD deposition is manipulated by the NaCl-QD adhesive force and the capillary flow inside the liquid drop via varying the substrate hydrophobicity, which enabled spontaneous self-encapsulation of QDs in a single NaCl crystal. An RGB QD@NaCl array with a small pixel size and uniform size distribution (diameter = 3.74 ± 0.5 µm) is obtained in the IJP process, which demonstrated a full-color micro-LED display with a color gamut of approximately 110% of the National Television System Committee (NTSC) standard.

Investigation of Luminescence Enhancement and Decay of QD-LEDs: Interface Reactions between QDs and Atmospheres.

We investigated the current unsolved problem of short-term enhancement and long-term decay of the luminescence intensity of quantum dots (QDs)-based light-emitting diodes (LEDs) in applications for lighting and displays, and proved that the interface interaction between the QD surface and atmospheres plays a key role in the QD-LED operation process. It is suggested that the initial luminescence enhancement of QD-LEDs would be caused by the QD surface-adsorbed species, such as ligands and gas molecules, rather than QDs themselves, whereas the luminescence decay is correlated to the interface reactions between QDs and photo-generated reactive oxygen species, which leads to formations of sulfate, hydroxide, and oxide compounds after QDs are illuminated by 450 nm blue light in oxygen and water environments according to surface analysis and theoretic thermodynamic calculations. It was also found that involvement of water in the QD-LED operation can cause crystal merging of QDs possibly because of the surface sulfates in the presence of water.

Ultrastable g-C3N4 assemblies with high quantum yield and reversible photoluminescence.

Ultrastable g-C3N4 assemblies consisting of amorphous/crystalline nanosheets with high quantum yields up to 78% were prepared for the first time. A reversible photoluminescence was observed from green to blue when the pH was adjusted. Conversely, this phenomenon was not observed for amorphous or crystalline samples. These assemblies exhibit high stability in PL devices.

An amorphous/crystalline g-C3N4 homojunction for visible light photocatalysis reactions with superior activity.

An amorphous/crystalline g-C3N4 homojunction was prepared for the first time at high temperature, in which the ratio of crystalline g-C3N4 in the homojunction was optimized. The homogenous junction with a matched energy level structure resulted in a superior photocatalytic performance for the degradation of organic pollutants and H2 evolution from splitting water under visible light irradiation.

Investigation of Ag-TiO2 Interfacial Reaction of Highly Stable Ag Nanowire Transparent Conductive Film with Conformal TiO2 Coating by Atomic Layer Deposition.

The atomic layer deposition (ALD) technique is applied to coat Ag nanowires (NWs) with a highly uniform and conformal TiO2 layer to improve the stability and sustainability of Ag NW transparent conductive films (TCFs) at high temperatures. The TiO2 layer can be directly deposited on Ag NWs with a surface polyvinylpyrrolidone (PVP) coat that acts a bed for TiO2 seeding in the ALD process. The ALD TiO2 layer significantly enhances the thermal stability at least 100 fold when aged between 200-400 °C and also provides an extra function of violet-blue light filtration for Ag NW TCFs. Investigation into the interaction between TiO2 and Ag reveals that the conformal TiO2 shell could effectively prevent Ag from 1D-to-3D ripening. However, Ag could penetrate the conformal TiO2 shell and form nanocrystals on the TiO2 shell surface when it is aged at 400 °C. According to experimental data and thermodynamic evaluation, the Ag penetration leads to an interlayer composed of mixed Ag-Ag2O-amorphous carbon phases and TiO2-x at the Ag-TiO2 interface, which is thought to be caused by extremely high vapor pressure of Ag at the Ag-TiO2 interface at a higher temperature (e.g., 400 °C).

Protein Corona Modulates Uptake and Toxicity of Nanoceria via Clathrin-Mediated Endocytosis.

Particles present in diesel exhaust have been proposed as a significant contributor to the development of acute and chronic lung diseases, including respiratory infection and allergic asthma. Nanoceria (CeO2 nanoparticles) are used to increase fuel efficiency in internal combustion engines, are present in exhaust fumes, and could affect cells of the airway. Components from the environment such as biologically derived proteins, carbohydrates, and lipids can form a dynamic layer, commonly referred to as the "protein corona" which alters cellular nanoparticle interactions and internalization. Using confocal reflectance microscopy, we quantified nanoceria uptake by lung-derived cells in the presence and absence of a serum-derived protein corona. Employing mass spectrometry, we identified components of the protein corona, and demonstrated that the interaction between transferrin in the protein corona and the transferrin receptor is involved in mediating the cellular entry of nanoceria via clathrin-mediated endocytosis. Furthermore, under these conditions nanoceria does not affect cell growth, viability, or metabolism, even at high concentration. Alternatively, despite the antioxidant capacity of nanoceria, in serum-free conditions these nanoparticles induce plasma membrane disruption and cause changes in cellular metabolism. Thus, our results identify a specific receptor-mediated mechanism for nanoceria entry, and provide significant insight into the potential for nanoparticle-dependent toxicity.

ZnO nanoflowers with single crystal structure towards enhanced gas sensing and photocatalysis.

In this paper, ZnO nanoflowers (NFs) were fabricated by thermal decomposition in an organic solvent and their application in gas sensors and photocatalysis was investigated. These single crystal ZnO NFs, which were observed for the first time, with an average size of ∼60 nm and were grown along the {100} facet. It was suggested that oleylamine used in the synthesis inhibited the growth and agglomeration of ZnO through the coordination of the oleylamine N atoms. The NFs exhibited excellent selectivity to acetone with a concentration of 25 ppm at 300 °C because they had a high specific surface area that provided more active sites and the surface adsorbed oxygen species for interaction with acetone. In addition, the ZnO NFs showed enhanced gas sensing response which was also ascribed to abundant oxygen vacancies at the junctions between petals of the NFs. Furthermore, ZnO-reduced graphene oxide (RGO) composites were fabricated by loading the ZnO NFs on the surface of the stratiform RGO sheet. In the photodegradation of rhodamine B tests, the composite revealed an enhanced photocatalytic performance compared with ZnO NFs under UV light irradiation.

Wide gamut white light emitting diodes using quantum dot-silicone film protected by an atomic layer deposited TiO2 barrier.

Wide gamut light emitting diodes using quantum dot-silicone film protected by atomic layer deposited TiO2 film were demonstrated. The core/shell QDs with multi-emission peaks were synthesised by a one-pot approach, in which the emission wavelength and colour composition were in situ adjusted during the synthetic process.

Toward highly efficient photocatalysis: a flow-through Pt@TiO2@AAO membrane nanoreactor prepared by atomic layer deposition.

A Pt@TiO2@AAO membrane nanoreactor was fabricated by atomic layer deposition. The photodegradation test of methylene blue demonstrated that the nanoreactor shows efficient photocatalysis performance. It exhibited ~28% photodegradation of methylene blue after ten flow-through cycles, corresponding to about 2.7 × 10(-2) s of contact time of methylene blue with Pt@TiO2 nanotubes.

Preparation and characterization of molecularly homogeneous silica-titania film by sol-gel process with different synthetic strategies.

Three silica-titania thin films with various degrees of molecular homogeneity were synthesized by the sol-gel process with the same precursor formula but different reaction paths. The dried films prepared by a single spin-coating process have a thickness of 500-700 nm and displayed no cracks or pin holes. The transmittances and refractive indices of the samples are >97.8% in the range of 350-1800 nm and 1.62-1.65 at 500 nm, respectively. The in-plane and out-of-plane chemical homogeneities of the films were analyzed by X-ray photoelectron spectroscopy and Auger electron spectroscopy, respectively. For the film with the highest degree of homogeneity, the deviations of O, Si, and Ti atomic contents in both in-plane and out-of-plane directions are less than 1.5%, indicating that the film is highly molecularly homogeneous. It also possesses the highest transparency and the lowest refractive index among the three samples.