Yuan Xiong

Ruthenium(II) Complex Incorporated UiO-67 Metal–Organic Framework Nanoparticles for Enhanced Two-Photon Fluorescence Imaging and Photodynamic Cancer Therapy

Ruthenium(II) tris(bipyridyl) cationic complex (Ru(bpy)32+) incorporated UiO-67 (Universitetet i Oslo) nanoscale metal-organic frameworks (NMOFs) with an average diameter of ∼92 nm were developed as theranostic nanoplatform for in vitro two-photon fluorescence imaging and photodynamic therapy. After incorporation into porous UiO-67 nanoparticles, the quantum yield, luminescence lifetime, and two-photon fluorescence intensity of Ru(bpy)32+ guest molecules were much improved owing to the steric confinement effect of MOF pores. Benefiting from these merits, the as-synthesized nanoparticles managed to be internalized by A549 cells while providing excellent red fluorescence in cytoplasm upon excitation with 880 nm irradiation. Photodynamic therapeutic application of the Ru(bpy)32+-incorporated UiO-67 NMOFs was investigated in vitro. The Ru(bpy)32+-incorporated UiO-67 NMOFs exhibited good biocompatibility without irradiation while having good cell-killing rates upon irradiation. In view of these facts, the developed Ru(bpy)32+-incorporated NMOFs give a new potential pathway to achieve enhanced two-photon fluorescence imaging and photodynamic therapy.

Top‐Down Fabrication of Stable Methylammonium Lead Halide Perovskite Nanocrystals by Employing a Mixture of Ligands as Coordinating Solvents

A top-down method is demonstrated for the fabrication of CH3 NH3 PbBr3 and CH3 NH3 PbI3 perovskite nanocrystals, employing a mixture of ligands oleic acid and oleylamine as coordinating solvents. This approach avoids the use of any polar solvents, skips multiple reaction steps by employing a simple ultrasonic treatment of the perovskite precursors, and yields rather monodisperse blue-, green-, and red-emitting methylammonium lead halide nanocrystals with a high photoluminescence quantum yield (up to 72 % for the green-emitting nanocrystals) and remarkably improved stability. After discussing all relevant reaction parameters, the green-emitting CH3 NH3 PbBr3 nanocrystals are employed as a component of down-conversion white-light-emitting devices.

Aromatically C6- and C9-Substituted Phenanthro[9,10-d]imidazole Blue Fluorophores: Structure–Property Relationship and Electroluminescent Application

In this study, a series of aromatically substituted phenanthro[9,10-d]imidazole (PI) fluorophores at C6 and C9 (no. 6 and 9 carbon atoms) have been synthesized and systematically characterized by theoretical, thermal, photophysical, electrochemical, and electroluminescent (EL) studies. C6 and C9 modifications have positive influences on the thermal properties of the new materials. Theoretical calculations suggest that the C6 and the C9 positions of PI are electronically different. Theoretical and experimental evidences of intramolecular charge transfer (ICT) between two identical moieties attaching to the C6 and the C9 positions are observed. Photophysical properties of the fluorophores are greatly influenced by size and conjugation extent of the substituents as well as linking steric hindrance. It is found that the C6 and C9 positions afford moderate conjugated extension compared to the C2 modification. Moreover, ICT characteristics of the new fluorophores increase as the size of the substituted aromatic group, and are partially influenced by steric hindrance, with the anthracene and the pyrene derivatives having the strongest ICT excited properties. EL performances of the fluorophores were evaluated as host emitters or dopants in organic light-emitting devices (OLEDs). Most of the devices showed significantly improved efficiencies compared to the OLED using the nonmodified emitter. Among all the devices, a 5 wt % TPI-Py doped device exhibited excellent performances with an external quantum efficiency >5% at 1000 cd/m2 and a deep-blue color index of (0.155, 0.065), which are comparable to the most advanced deep-blue devices. Our study can give useful information for designing C6/C9-modificated PI fluorophores and provide an efficient approach for constructing high-performance deep-blue OLEDs.

Organic nanostructures of thermally activated delayed fluorescent emitters with enhanced intersystem crossing as novel metal-free photosensitizers

We applied organic nanostructures based on thermally activated delayed fluorescent (TADF) emitters for singlet oxygen generation. Due to the extremely small energy gaps between the excited singlet states (S1) and triplet states (T1) of these heavy-metal-free organic nanostructures, intersystem conversion between S1 and T1 can occur easily. This strategy also works well for exciplex-type TADF emitters prepared by mixing suitable donors and acceptors which have no TADF characteristics themselves.

Revealing the Formation Mechanism of CsPbBr3 Perovskite Nanocrystals Produced via a Slowed‐Down Microwave‐Assisted Synthesis

We developed a microwave-assisted slowed-down synthesis of CsPbBr3 perovskite nanocrystals, which retards the reaction and allows us to gather useful insights into the formation mechanism of these nanoparticles, by examining the intermediate stages of their growth. The trends in the decay of the emission intensity of CsPbBr3 nanocrystals under light exposure are well correlated with their stability against decomposition in TEM under electron beam. The results show the change of the crystal structure of CsPbBr3 nanocrystals from a deficient and easier to be destroyed lattice to a well crystallized one. Conversely the shift in the ease of degradation sheds light on the formation mechanism, indicating first the formation of a bromoplumbate ionic scaffold, with Cs-ion infilling lagging a little behind. Increasing the cation to halide ratio towards the stoichiometric level may account for the improved radiative recombination rates observed in the longer reaction time materials.

Light-permeable, photoluminescent microbatteries embedded in the color filter of a screen

The battery and the screen are the two components occupying the largest volume in many electronic devices. Integrating them together will eventually engender a great reduction of device size. The current study demonstrates a promising strategy towards ultimate-compact electronic devices. Herein, a photoluminescent microbattery with reasonable light-permeability and hazing ability is developed. This aqueous Zn–MnOx/polypyrrole based microbattery features a flat architecture with interdigitated electrodes and utilizes a photoluminescent gelatin based electrolyte by embedding colloidal CdTe quantum dots. Furthermore, borax is introduced into the electrolyte as an additive, which effectively prevents luminescence quenching of the quantum dots and simultaneously enhances the electrochemical performance of the microbattery. A high device energy density of 21 mW h cm−3 is obtained. One step further, a three-primary-color (red–green–blue, RGB) photoluminescent microbattery array is assembled, endowing the battery with the function of a color filter and realizing a battery-in-screen configuration.

A Building Brick Principle to Create Transparent Composite Films with Multicolor Emission and Self‐Healing Function

A cellulose paper is used impregnated with light-emitting CdTe nanocrystals and carbon dots, and filled with a polyurethane to fabricate uniform transparent composite films with bright photoluminescence of red (R), green (G), and blue (B) (RGB) colors. A building brick-like assembly method is introduced to realize RGB multicolor emission patterns from this composite material. By sectioning out individual pixels from monochrome-emissive composite sheets, the advantage of the self-healing properties of polyurethane is taken to arrange and weld them into a RGB patterned fabric by brief exposure to ethanol. This provides an approach to form single layer RGB light-emitting pixels, such as potentially required in the display applications, without the use of any lithographic or etching processing. The method can utilize a wide range of different solution-based kinds of light-emitting materials.

Reversible transformation between CsPbBr3 and Cs4PbBr6 nanocrystals

A reversible transformation between CsPbBr3 and Cs4PbBr6 nanocrystals through a simple treatment with extra ligands or PbBr2 (for the reverse direction) is reported. These transformations are so far the first report of direct reversibility, without a net change in morphology, between CsPbBr3 and Cs4PbBr6 and then back to CsPbBr3 nanocrystals, which provides a mechanism for flexible reorganization of the lead halide perovskite lattice.