Lanthanide-Sensitized Upconversion Iridium Complex via Triplet Energy Transfer.

Cyclometalated iridium (Ir) complexes demonstrate impressive capabilities across a range of fields, including biology and photocatalysis, due to their tunable optical characteristics and structure flexibility. However, generating upconversion luminescence of Ir complexes under near-infrared light excitation is challenging. Herein, by employing lanthanide-doped upconversion nanoparticles (UCNPs) as the sensitizer, a new strategy is demonstrated to gain upconversion luminescence of Ir complexes via triplet energy transfer. This design relies on a rationally designed hybrid of core-shell structured NaYbF4:Tb@NaTbF4 UCNPs and new Ir phosphonate complexes, in which UCNPs can migrate upconverted energy to the surface of nanoparticles through Tb3+-mediated energy migration and then sensitize the upconversion luminescence of Ir complexes upon 980 nm excitation. Both experimental and theoretical investigations highlight the significance of triplet energy transfer from excited Tb3+ ions to the triplet state of Ir complexes in the sensitization of upconversion luminescence of Ir complexes. These findings may open exciting avenues for fabricating hybrid Ir materials with new functions and driving the development of UCNP-based nanomaterials.

Antithermal Quenching Upconversion Luminescence via Suppressed Multiphonon Relaxation in Positive/Negative Thermal Expansion Core/Shell NaYF4:Yb/Ho@ScF3 Nanoparticles.

Thermal quenching (TQ) has been naturally entangling with luminescence since its discovery, and lattice vibration, which is characterized as multiphonon relaxation (MPR), plays a critical role. Considering that MPR may be suppressed under exterior pressure, we have designed a core/shell upconversion luminescence (UCL) system of α-NaYF4:Yb/Ln@ScF3 (Ln = Ho, Er, and Tm) with positive/negative thermal expansion behavior so that positive thermal expansion of the core will be restrained by negative thermal expansion of the shell when heated. This imposed pressure on the crystal lattice of the core suppresses MPR, reduces the amount of energy depleted by TQ, and eventually saves more energy for luminescing, so that anti-TQ or even thermally enhanced UCL is obtained.

Progress on Two-Dimensional Transitional Metal Dichalcogenides Alloy Materials: Growth, Characterisation, and Optoelectronic Applications.

Two-dimensional (2D) transitional metal dichalcogenides (TMDs) have garnered remarkable attention in electronics, optoelectronics, and hydrogen precipitation catalysis due to their exceptional physicochemical properties. Their utilisation in optoelectronic devices is especially notable for overcoming graphene's zero-band gap limitation. Moreover, TMDs offer advantages such as direct band gap transitions, high carrier mobility, and efficient switching ratios. Achieving precise adjustments to the electronic properties and band gap of 2D semiconductor materials is crucial for enhancing their capabilities. Researchers have explored the creation of 2D alloy phases through heteroatom doping, a strategy employed to fine-tune the band structure of these materials. Current research on 2D alloy materials encompasses diverse aspects like synthesis methods, catalytic reactions, energy band modulation, high-voltage phase transitions, and potential applications in electronics and optoelectronics. This paper comprehensively analyses 2D TMD alloy materials, covering their growth, preparation, optoelectronic properties, and various applications including hydrogen evolution reaction catalysis, field-effect transistors, lithium-sulphur battery catalysts, and lasers. The growth process and characterisation techniques are introduced, followed by a summary of the optoelectronic properties of these materials.

Applications and Advances in Machine Learning Force Fields.

Force fields (FFs) form the basis of molecular simulations and have significant implications in diverse fields such as materials science, chemistry, physics, and biology. A suitable FF is required to accurately describe system properties. However, an off-the-shelf FF may not be suitable for certain specialized systems, and researchers often need to tailor the FF that fits specific requirements. Before applying machine learning (ML) techniques to construct FFs, the mainstream FFs were primarily based on first-principles force fields (FPFF) and empirical FFs. However, the drawbacks of FPFF and empirical FFs are high cost and low accuracy, respectively, so there is a growing interest in using ML as an effective and precise tool for reconciling this trade-off in developing FFs. In this review, we introduce the fundamental principles of ML and FFs in the context of machine learning force fields (MLFF). We also discuss the advantages and applications of MLFF compared to traditional FFs, as well as the MLFF toolkits widely employed in numerous applications.

Frenkel Defect-modulated Anti-thermal Quenching Luminescence in Lanthanide-doped Sc2 (WO4 )3.

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2 (WO4 )3 :Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back-transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti-thermal quenching, thermally enhanced 415-fold downshifting and 405-fold upconversion luminescence are even obtained in Sc2 (WO4 )3 :Yb/Er, which has set a record of both the Yb3+ -Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high-temperature luminescence.

Tandem fabrication of upconversion nanocomposites enabled by confined protons.

Lanthanide-doped upconversion nanoparticle (UCNP)-based nanocomposites can address the intrinsic limitations associated with UCNPs and bestow new functions on UCNPs, which can facilitate the development and application of UCNPs. However, the fabrication of UCNP-based composites typically suffers from complex operations, long-drawn-out procedures, and even loss or damage of UCNPs. Herein, we report a tandem fabrication strategy for the preparation of UCNP-based nanocomposites, in which protons, confined in the non-aqueous polar solvent, can produce ligand-free UCNPs for the direct fabrication of a composite without further treatment. Our studies show that the confined protons can be generated by diverse materials and can yield different types of ligand-free nanomaterials for desired composites. This versatile strategy enables a simple but scalable fabrication of UCNP-based nanocomposites, and can be extended to other nanomaterial-based composites. These findings should provide a platform for constructing multifunctional UCNP-based materials, and benefit potential applications of UCNPs in varied fields.

Recent Development in Sensitizers for Lanthanide-Doped Upconversion Luminescence.

The attractive features of lanthanide-doped upconversion luminescence (UCL), such as high photostability, nonphotobleaching or photoblinking, and large anti-Stokes shift, have shown great potentials in life science, information technology, and energy materials. Therefore, UCL modulation is highly demanded toward expected emission wavelength, lifetime, and relative intensity in order to satisfy stringent requirements raised from a wide variety of areas. Unfortunately, the majority of efforts have been devoted to either simple codoping of multiple activators or variation of hosts, while very little attention has been paid to the critical role that sensitizers have been playing. In fact, different sensitizers possess different excitation wavelengths and different energy transfer pathways (to different activators), which will lead to different UCL features. Thus, rational design of sensitizers shall provide extra opportunities for UCL tuning, particularly from the excitation side. In this review, we specifically focus on advances in sensitizers, including the current status, working mechanisms, design principles, as well as future challenges and endeavor directions.

Uranyl phosphonates: crystalline materials and nanosheets for temperature sensing.

Ultrathin nanosheets of luminescent metal-organic frameworks or coordination polymers have been widely used for sensing ions, solvents and biomolecules but, as far as we are aware, not yet used for temperature sensing. Herein we report two luminescent uranyl phosphonates based on 2-(phosphonomethyl)benzoic acid (2-pmbH3), namely (UO2)(2-pmbH2)2 (1) and (H3O)[(UO2)2(2-pmb)(2-pmbH)] (2). The former has a supramolecular layer structure, composed of chains of corner-sharing {UO6} octahedra and {PO3C} tetrahedra which are connected by hydrogen bonds between phosphonate and carboxylic groups. Compound 2 possesses a unique 2D anionic framework structure, where the inorganic uranyl phosphonate chains made up of {UO7} and {PO3C} polyhedra are cross-linked by 2-pmb3- ligands. The carboxylic groups of 2-pmbH2- ligands are pendant on the two sides of the layers and form hydrogen bonds between the layers. Both compounds can be exfoliated in acetone via a top-down freeze-thaw method, resulting in nanosheets of two-layer thickness. Interestingly, the photoluminescence (PL) of 1 and 2 is highly temperature sensitive. Variable temperature PL studies revealed that compounds 1 and 2 can be used as thermometers in the temperature ranges 120-300 K and 100-280 K, respectively. By doping the nanosheets into polymer matrix, 1-ns@PMMA and 2-ns@PMMA were prepared. The PL intensity of 1-ns@PMMA is insensitive to temperature, unlike that of the bulk sample. While 2-ns@PMMA exhibits similar temperature-dependent luminescence behaviour to its bulk counterpart, thereby enabling its potential application as a thermometer in the temperature range 100-280 K.

A multifunctional Fenton nanoagent for microenvironment-selective anti-biofilm and anti-inflammatory therapy.

Bacterial biofilm infections are intractable to traditional antibiotic treatment and usually cause persistent inflammation. Chemodynamic therapy (CDT) based on the Fenton reaction has recently emerged as a promising anti-biofilm strategy. However, the therapeutic efficacy of current Fenton agents often suffers from inefficient Fenton activity and lacks anti-inflammatory capability. Herein, FePS3 nanosheets (NSs) are explored for the first time as novel microenvironment-selective therapeutic nanoagents for bacterial biofilm infections with both self-enhanced Fenton activity for an anti-biofilm effect and reactive oxygen species (ROS) scavenging properties for an anti-inflammatory effect. In biofilms with acidic microenvironments, FePS3 NSs release Fe2+ to generate toxic ROS by Fenton reaction and reductive [P2S6]4- to enhance the Fenton activity by reducing Fe3+ to Fe2+. In the surrounding normal tissues with neutral pH, FePS3 NSs scavenge ROS by reductive [P2S6]4- with an anti-inflammatory effect. This work demonstrates multifunctional Fenton nanoagents with microenvironment-selective ROS generation and elimination properties for effective treatment of bacterial biofilm infections with both anti-biofilm and anti-inflammatory effects.

A luminescent view of the clickable assembly of LnF3 nanoclusters.

Nanoclusters (NCs) bridge the gap between atoms and nanomaterials in not only dimension but also physicochemical properties. Precise chemical and structural control, as well as clear understanding of formation mechanisms, have been important to fabricate NCs with high performance in optoelectronics, catalysis, nanoalloys, and energy conversion and harvesting. Herein, taking advantage of the close chemical properties of Ln3+ (Ln = Eu, Nd, Sm, Gd, etc.) and Gd3+-Eu3+ energy transfer ion-pair, we report a clickable LnF3 nanoparticle assembly strategy allowing reliable fabrication of diversely structured NCs, including single-component, dimeric, core-shelled/core-shell-shelled, and reversely core-shelled/core-shell-shelled, particularly with synergized optical functionalities. Moreover, the purposely-embedded dual luminescent probes offer great superiority for in situ and precise tracking of tiny structural variations and energy transfer pathways within complex nanoarchitectures.

Templated-Construction of Hollow MoS2 Architectures with Improved Photoresponses.

Despite the outstanding optoelectronic properties of MoS2 and its analogues, synthesis of such materials with desired features including fewer layers, arbitrary hollow structures, and particularly specifically customized morphologies, via inorganic reactions has always been challenging. Herein, using predesigned lanthanide-doped upconversion luminescent materials (e.g., NaYF4:Ln) as templates, arbitrary MoS2 hollow structures with precisely defined morphologies, widely variable dimensions, and very small shell thickness (≈2.5 nm) are readily constructed. Most importantly, integration of the near-infrared-responsive template significantly improves the photoresponse of up to 600 fold in device made of NaYF4:Yb/Er@MoS2 compared with that of MoS2 nanosheets under 980 nm laser illumination. Multichannel optoelectronic device is further fabricated by simply changing luminescent ions in the template, e.g., NaYF4:Er@MoS2, operating at 1532 nm light excitation with a 276-fold photoresponse enhancement. The simple chemistry, easy operation, high reliability, variable morphologies, and wide universality represent the most important advantages of this novel strategy that has not been accessed before.

Organic Linkers Enable Tunable Transfer of Migrated Energy from Upconversion Nanoparticles.

Energy transfer plays a pivotal role in applying lanthanide-doped upconversion nanoparticles (UCNPs) as optical probes for diverse applications, particularly in biology and medicine. However, achieving tunable energy transfer from UCNPs to different acceptors remains a daunting challenge. Here, we demonstrate that using small organic molecules as linkers, the energy transfer from UCNPs to acceptors can be modulated. Specifically, organic linkers can enable efficient energy transfer from NaGdF4:Yb/Tm@NaGdF4 core-shell UCNPs to different acceptors. Moreover, the organic linker-mediated energy transfer can be facilely tuned by simply changing organic linkers. Based on our mechanistic investigations, the extraction of Gd3+ migrated energy from UCNPs by organic linkers and the subsequent energy injection from linkers to acceptors should be the two key processes for controlling the energy transfer. The tunable energy transfer from UCNPs allows us to design novel applications, including sensors and optical waveguides, based on UCNPs. These findings may open up new ways to develop UCNP-based bioapplications and advance further fabrication of hybrid upconversion nanomaterials.

Chemical Vapor Transport Reactions for Synthesizing Layered Materials and Their 2D Counterparts.

2D materials, namely thin layers of layered materials, are attracting much attention because of their unique electronic, optical, thermal, and catalytic properties for wide applications. To advance both the fundamental studies and further practical applications, the scalable and controlled synthesis of large-sized 2D materials is desired, while there still lacks ideal approaches. Alternatively, the chemical vapor transport reaction is an old but powerful technique, and is recently adopted for synthesizing 2D materials, producing bulk crystals of layered materials or corresponding 2D films. Herein, recent advancements in synthesizing both bulk layered and 2D materials by chemical vapor transport reactions are summarized. Beginning with a brief introduction of the fundamentals of chemical vapor transport reactions, chemical vapor transport-based syntheses of bulk layered and 2D materials, mainly exampled by transition metal dichalcogenides and black phosphorus, are reviewed. Particular attention is paid to important factors that can influence the reactions and the growth mechanisms of black phosphorus. Finally, perspectives about the chemical vapor transport-based synthesis of 2D materials are discussed, intending to redraw attentions on chemical vapor transport reactions.

Plasmonic bimetallic nanodisk arrays for DNA conformation sensing.

The integration of large-scale 2D bimetallic Ag/Au nanodisk arrays with gold nanoparticles is developed for sensing DNA conformation with the assistance of 3D finite-difference time-domain simulation. The optimized system comprising Ag/Au nanodisk arrays and gold nanoparticles offers a more than 6-fold enhancement in surface plasmon resonance shift, enabling the feasibility for sensitive DNA detection with a detection limit down to 100 femtomolar. Importantly, owing to the distance-dependent nature of the surface plasmon signal, sensitive differentiation of DNA conformations can be achieved with a conventional optical measurement. This platform could provide new exciting capabilities for a reliable, reproducible, and label-free assay analysis for investigating the conformations of DNA and other biological molecules.

Stirring revealed new functions of ethylenediamine and hydrazine in the morphology control of copper nanowires.

Cu nanowires, as promising candidates in many fields because of their merits, are commonly prepared by the solution phase based synthesis which is a simple and scalable method. However, precise control of the morphology, particularly surface roughness, of Cu nanowires is still challenging; and moreover, detailed formation mechanisms of Cu nanowires, in solution phase based synthesis, are still unclear. We here show the morphology manipulation of Cu nanowires by adjusting the stirring rate and the amounts of ethylenediamine and hydrazine (N2H4), yielding Cu nanowires with either smooth or rough surface. Importantly, according to our experimental results and theoretical investigation, new functions of ethylenediamine and N2H4 are found, and a growth process of Cu nanowires is proposed accordingly. In addition to typically accepted roles of ethylenediamine and N2H4, we find that ethylenediamine can facilitate the growth of Cu nanowires by etching Cu oxides and even Cu on the surface of Cu nanowires. Meanwhile, N2H4 molecules can modulate the growth of Cu nanowires as a capping agent, which can be easily influenced by stirring. Additionally, the as-synthesized Cu nanowires with different morphologies exhibit different optical and catalytic properties. This study provides new fundamental insights into the growth mechanism of Cu nanowires, and thus can facilitate controlled synthesis of Cu nanowires for further applications, including electronics, catalysis, and sensing.

Reduced-Dimensional Perovskite Enabled by Organic Diamine for Efficient Photovoltaics.

Reduced-dimensional (RD) perovskite solar cells (PSCs) are emerging as highly attractive alternatives to three-dimensional (3D) PSCs due to their dramatically improved environmental stability and photostability. Diamine-based RD perovskites with a single organic amine interlayer possess orderly inorganic sheets and a smaller insulation area, indicating great potential in combining high efficiency and long-term stability. Here, we report an efficient and stable RD PSC based on 1,4-butanediamine (BDA). We found that the BDA-based RD perovskite exhibits improved crystallinity, reduced trap-state densities, and enhanced charge mobility compared to those of butylamine (BA)-based RD (BA-RD) perovskite. A high power conversion efficiency of 17.91% was achieved with negligible hysteresis. Moreover, the device showed improved stability compared to those of BA-RD and 3D films and devices. The findings may inspire new developments in introducing organic diamine for efficient and stable RD PSCs.

Revisiting the Growth of Black Phosphorus in Sn-I Assisted Reactions.

Black phosphorus, an emerging layered material, exhibits promising applications in diverse fields, ranging from electronics to optics. However, controlled synthesis of black phosphorus, particularly its few-layered counterparts, is still challenging, which should be due to the unclear growth mechanism of black phosphorus. Here, taking the most commonly used Sn-I assisted synthesis of black phosphorus as an example, we propose a growth mechanism of black phosphorus crystals by monitoring the reactions and analyzing the as-synthesized products. In the proposed mechanism, Sn24P19.3I8 is the active site for the growth of black phosphorus, and the black phosphorus crystals are formed with the assistance of SnI2, following a polymerization-like process. In addition, we suggest that all Sn-I assisted synthesis of black phosphorus should share the same reaction mechanism despite the differences among Sn-I containing additives. Our results shown here should shed light on the controlled synthesis of black phosphorus and facilitate further applications of black phosphorus.

Paving Metal-Organic Frameworks with Upconversion Nanoparticles via Self-Assembly.

The combination of metal-organic frameworks (MOFs) and luminescent nanomaterials with upconversion characteristics could enable the development of new nanomaterials and applications in information security, optical sensing, and theranostics. However, currently available methods are not ideally suitable for fabricating composites of MOF and upconversion nanomaterial, and incorporating upconversion nanomaterials with MOFs in a controllable manner remains challenging. Here, we demonstrate an in situ self-assembly route to the nanocomposites in which MOFs are homogeneously paved with upconversion nanoparticles. Without additional assistance, this strategy, mainly driven by electrostatic interactions, can be used to incorporate different upconversion nanoparticles with diverse MOFs. The as-synthesized composites can be further used to construct composites with unique structures, such as MOF@upconversion nanoparticles@MOF sandwiched nanocomposites, and would be useful for applications including luminescence-monitored drug delivery, anticounterfeiting, and photodynamic therapy. These findings should shed light on new avenues for fabricating multifunctional composites of MOF and upconversion nanomaterials for varied applications.

The Sources of Reactive Oxygen Species and Its Possible Role in the Pathogenesis of Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by progressive loss of dopaminergic neurons in the substantia nigra. The precise mechanism underlying pathogenesis of PD is not fully understood, but it has been widely accepted that excessive reactive oxygen species (ROS) are the key mediator of PD pathogenesis. The causative factors of PD such as gene mutation, neuroinflammation, and iron accumulation all could induce ROS generation, and the later would mediate the dopaminergic neuron death by causing oxidation protein, lipids, and other macromolecules in the cells. Obviously, it is of mechanistic and therapeutic significance to understand where ROS are derived and how ROS induce dopaminergic neuron damage. In the present review, we try to summarize and discuss the main source of ROS in PD and the key pathways through which ROS mediate DA neuron death.