Reversible Interconversion between Ag2 and Ag6 Clusters and Their Responsive Optical Properties.

The exploration of structural interconversion in clusters triggered by external stimuli has attracted significant interest due to its potential to elucidate structure-property relationships of metal clusters. In this study, two types of silver clusters, Ag2 and Ag6, are synthesized. Interestingly, the clusters exhibit reversible transformations in response to changes in the solvent conditions. The structures and optical properties of these clusters are thoroughly characterized using techniques such as mass spectrometry, single-crystal X-ray diffraction, photoluminescence, and radioluminescence spectroscopy. While both Ag2 and Ag6 display excellent photoluminescence properties, Ag2 demonstrates superior performance in X-ray radioluminescence compared to Ag6. Flexible scintillator films fabricated from Ag2 clusters exhibit outstanding X-ray imaging capabilities, achieving a spatial resolution of 15.0 lp/mm and an impressive detection limit for an X-ray dose of 0.58 µGy s-1. This detection limit is nearly 10 times lower than the typical dose rate used in X-ray diagnostics (5.5 µGy s-1). This work introduces a novel approach for designing thiol-free silver clusters capable of solvent-dependent reversible interconversion, offering new insights into the development of silver clusters for advanced X-ray imaging applications.

Rod-Shaped Liquid Plasticine as Cuttable Minireactor for Photodynamic Therapy of Tumors.

Photodynamic therapy (PDT) has emerged as a promising non-invasive approach for cancer treatment. Enhancing its efficacy and understanding its absorption-induced attenuation are significant while the solutions are limited, particularly for the latter. In this study, a rod-shaped liquid plasticine (LP), comprised of a tumor cell solution encased by a nanoparticle monolayer, is used to serve as a powerful minireactor for addressing these issues. The channel structure, openness, and cuttability of the LP reactor are exploited for providing benefits to PDT. The resulting PDT efficacy is several times higher than those from droplet reactors with common spherical shapes. The attenuation law, which is fundamental in PDT yet poorly understood due to the lack of experimental approaches, is preliminarily uncovered here from the perspective of in vitro experiments by using the LP's cuttability, affording quantitative understanding on this difficult subject. These findings provide insights into the widely-concerned topics in PDT, and highlight the great potential of an LP reactor in offering innovation power for the biochemical and biomedical arenas.

Small-molecule fluorogenic probes for mitochondrial nanoscale imaging.

Mitochondria are inextricably linked to the development of diseases and cell metabolism disorders. Super-resolution imaging (SRI) is crucial in enhancing our understanding of mitochondrial ultrafine structures and functions. In addition to high-precision instruments, super-resolution microscopy relies heavily on fluorescent materials with unique photophysical properties. Small-molecule fluorogenic probes (SMFPs) have excellent properties that make them ideal for mitochondrial SRI. This paper summarizes recent advances in the field of SMFPs, with a focus on the chemical and spectroscopic properties required for mitochondrial SRI. Finally, we discuss future challenges in this field, including the design principles of SMFPs and nanoscopic techniques.

Wide-Range Color-Tunable Organic Scintillators for X-Ray Imaging Through Host-Guest Doping.

With the increasing demands of X-ray detection and medical diagnosis, organic scintillators with intense and tunable X-ray excited emission have been becoming important. To guarantee the X-ray absorption, heavy atoms were widely added in reported organic scintillators, which led to emission quenching. In this work, we propose a new strategy to realize organic scintillators through the host-guest doping strategy. Then the X-ray absorption centers (host) and emission centers (guest) are separated. Under X-ray excitation, these materials displayed intense and readily tunable emissions ranging from green (520 nm) to near infrared (NIR) regions (682 nm). Besides, the relationship between the X-ray absorption and spatial arrangement of the heavy atoms in the host matrix was also revealed. The potential application of these wide-range color tunable organic host-guest scintillators in X-ray imaging were demonstrated. This work provides a new feasible strategy for constructing high-performance organic scintillators with tunable luminescence properties.

Opal-Inspired SiO2-Mediated Carbon Dot Doping Enables the Synthesis of Monodisperse Multifunctional Afterglow Nanocomposites for Advanced Information Encryption.

Despite recent advancements in inorganic and organic phosphors, creating monodisperse afterglow nanocomposites (NCs) remains challenging due to the complexities of wet chemistry synthesis. Inspired by nanoinclusions in opal, we introduce a novel SiO2-mediated carbon dot (CD) doping method for fabricating monodisperse, multifunctional afterglow NCs. This method involves growing a SiO2 shell matrix on monodisperse nanoparticles (NPs) and doping CDs into the SiO2 shell under hydrothermal conditions. Our approach preserves the monodispersity of the parent NP@SiO2 NCs while activating a green afterglow in the doped CDs with an impressive lifetime of 1.26 s. Additionally, this method is highly versatile, allowing for various core and dopant combinations to finely tune the afterglow through core-to-CD or CD-to-dye energy transfer. Our findings significantly enhance the potential of SiO2 coatings, transforming them from merely enhancing the biocompatibility of NCs to serving as a versatile matrix for emitters, facilitating afterglow generation and paving the way for new applications.

Self-assembly of colloidal inorganic nanocrystals: nanoscale forces, emergent properties and applications.

The self-assembly of colloidal nanoparticles has made it possible to bridge the nanoscopic and macroscopic worlds and to make complex nanostructures. The nanoparticle-mediated assembly enables many potential applications, from biodetection and nanomedicine to optoelectronic devices. Properties of assembled materials are determined not only by the nature of nanoparticle building blocks, but also by spatial positions of nanoparticles within the assemblies. A deep understanding of nanoscale interactions between nanoparticles is a prerequisite to controlling nanoparticle arrangement during assembly. In this review, we present an overview of interparticle interactions governing their assembly in a liquid phase. Considerable attention is devoted to examples that illustrate nanoparticle assembly into ordered superstructures using different types of building blocks, including plasmonic nanoparticles, magnetic nanoparticles, lanthanide-doped nanophosphors, and quantum dots. We also cover the physicochemical properties of nanoparticle ensembles, especially those arising from particle coupling effects. We further discuss future research directions and challenges in controlling self-assembly at a level of precision that is most crucial to technology development.

Enantiospecific Detection of D-Amino Acid through Synergistic Upconversion Energy Transfer.

D-amino acids (DAAs) are indispensable in regulating diverse metabolic pathways. Selective and sensitive detection of DAAs is crucial for understanding the complexity of metabolic processes and managing associated diseases. However, current DAA detection strategies mainly rely on bulky instrumentation or electrochemical probes, limiting their cellular and animal applications. Here we report an enzyme-coupled nanoprobe that can detect enantiospecific DAAs through synergistic energy transfer. This nanoprobe offers near-infrared upconversion capability, a wide dynamic detection range, and a detection limit of 2.2 µM, providing a versatile platform for in vivo noninvasive detection of DAAs with high enantioselectivity. These results potentially allow real-time monitoring of biomolecular handedness in living animals, as well as developing antipsychotic treatment strategies.

A General Strategy for Hollow Metal-Phytate Coordination Complex Micropolyhedra Enabled by Cation Exchange.

The ability to incorporate functional metal ions (Mn+ ) into metal-organic coordination complexes adds remarkable flexibility in the synthesis of multifunctional organic-inorganic hybrid materials with tailorable electronic, optical, and magnetic properties. We report the cation-exchanged synthesis of a diverse range of hollow Mn+ -phytate (PA) micropolyhedra via the use of hollow Co2+ -PA polyhedral networks as templates at room temperature. The attributes of the incoming Mn+ , namely Lewis acidity and ionic radius, control the exchange of the parent Co2+ ions and the degree of morphological deformation of the resulting hollow micropolyhedra. New functions can be obtained for both completely and partially exchanged products, as supported by the observation of Ln3+ (Ln3+ =Tb3+ , Eu3+ , and Sm3+ ) luminescence from as-prepared hollow Ln3+ -PA micropolyhedra after surface modification with dipicolinic acid as an antenna. Moreover, Fe3+ - and Mn2+ -PA polyhedral complexes were employed as magnetic contrast agents.

SiO2-Encompassed Co@N-Doped Porous Carbon Assemblies as Recyclable Catalysts for Efficient Hydrolysis of Ammonia Borane.

The development of earth-abundant catalysts for efficient hydrolysis of ammonia borane is of great importance in the conversion and utilization of hydrogen energy. Here, we report the synthesis of SiO2-encompassed Co@N-doped porous carbon assemblies as a new type of recyclable catalyst for the purpose by calcination of zeolitic imidazolate framework-67@SiO2 microtubes at high temperatures under an N2 atmosphere. We find that the surface layer of SiO2 in the precursor microtubes is essential for the production of efficient catalysts by supplying an additional surface for Co nanoparticle dispersion in an effort to reduce their size. In addition, the SiO2 layer renders a highly ordered arrangement of Co@N-doped porous carbon within the catalysts, possibly allowing the ease of mass transfer of ammonia borane within the catalysts. The optimized catalysts obtained via calcination at 800 °C show a set of remarkable catalytic benefits, including a high hydrogen generation rate of 8.4 mol min-1 mol(Co)-1, a relatively low activation energy of 36.1 kJ mol-1, and a remarkable reusability (at least 10 times). Our results can provide new insight into the design and synthesis of highly ordered SiO2-supported catalysts for different reactions.

Lanthanide-Activated Phosphors Based on 4f-5d Optical Transitions: Theoretical and Experimental Aspects.

The synthesis of lanthanide-activated phosphors is pertinent to many emerging applications, ranging from high-resolution luminescence imaging to next-generation volumetric full-color display. In particular, the optical processes governed by the 4f-5d transitions of divalent and trivalent lanthanides have been the key to enabling precisely tuned color emission. The fundamental importance of lanthanide-activated phosphors for the physical and biomedical sciences has led to rapid development of novel synthetic methodologies and relevant tools that allow for probing the dynamics of energy transfer processes. Here, we review recent progress in developing methods for preparing lanthanide-activated phosphors, especially those featuring 4f-5d optical transitions. Particular attention will be devoted to two widely studied dopants, Ce3+ and Eu2+. The nature of the 4f-5d transition is examined by combining phenomenological theories with quantum mechanical calculations. An emphasis is placed on the correlation of host crystal structures with the 5d-4f luminescence characteristics of lanthanides, including quantum yield, emission color, decay rate, and thermal quenching behavior. Several parameters, namely Debye temperature and dielectric constant of the host crystal, geometrical structure of coordination polyhedron around the luminescent center, and the accurate energies of 4f and 5d levels, as well as the position of 4f and 5d levels relative to the valence and conduction bands of the hosts, are addressed as basic criteria for high-throughput computational design of lanthanide-activated phosphors.

Ag1 Pd1 Nanoparticles-Reduced Graphene Oxide as a Highly Efficient and Recyclable Catalyst for Direct Aryl C-H Olefination.

The efficient and selective palladium-catalyzed activation of C-H bonds is of great importance for the construction of diverse bioactive molecules. Despite significant progress, the inability to recycle palladium catalysts and the need for additives impedes the practical applications of these reactions. Ag1 Pd1 nanoparticles-reduced graphene oxide (Ag1 Pd1 -rGO) was used as highly efficient and recyclable catalyst for the chelation-assisted ortho C-H bond olefination of amides with acrylates in good yields with a broad substrate scope. The catalyst can be recovered and reused at least 5 times without losing activity. A synergistic effect between the Ag and Pd atoms on the catalytic activity was found, and a plausible mechanism for the AgPd-rGO catalyzed C-H olefination is proposed. These findings suggest that the search for such Pd-based bimetallic alloy nanoparticles is a new method towards the development of superior recyclable catalysts for direct aryl C-H functionalization under mild conditions.

Probing the nature of upconversion nanocrystals: instrumentation matters.

Probing the nature of nanocrystalline materials such as the surface state, crystal structure, morphology, composition, optical and magnetic characteristics is a crucial step in understanding their chemical and physical performance and in exploring their potential applications. Upconversion nanocrystals have recently attracted remarkable interest due to their unique nonlinear optical properties capable of converting incident near-infrared photons to visible and even ultraviolet emissions. These optical nanomaterials also hold great promise for a broad range of applications spanning from biolabeling to optoelectronic devices. In this review, we overview the instrumentation techniques commonly utilized for the characterization of upconversion nanocrystals. A considerable emphasis is placed on the analytical tools for probing the optical properties of the luminescent nanocrystals. The advantages and limitations of each analytical technique are compared in an effort to provide a general guideline, allowing optimal conditions to be employed for the characterization of such nanocrystals. Parallel efforts are devoted to new strategies that utilize a combination of advanced emerging tools to characterize such nanosized phosphors.

Energy Migration Upconversion in Manganese(II)-Doped Nanoparticles.

We report the synthesis and characterization of cubic NaGdF4:Yb/Tm@NaGdF4:Mn core-shell structures. By taking advantage of energy transfer through Yb→Tm→Gd→Mn in these core-shell nanoparticles, we have realized upconversion emission of Mn(2+) at room temperature in lanthanide tetrafluoride based host lattices. The upconverted Mn(2+) emission, enabled by trapping the excitation energy through a Gd(3+) lattice, was validated by the observation of a decreased lifetime from 941 to 532 µs in the emission of Gd(3+) at 310 nm ((6)P(7/2)→(8)S(7/2)). This multiphoton upconversion process can be further enhanced under pulsed laser excitation at high power densities. Both experimental and theoretical studies provide evidence for Mn(2+) doping in the lanthanide-based host lattice arising from the formation of F(-) vacancies around Mn(2+) ions to maintain charge neutrality in the shell layer.

Matrix-induced defects and molecular doping in the afterglow of SiO2 microparticles.

A deep understanding of how the host matrix influences the afterglow properties of molecule dopants is crucial for designing advanced afterglow materials. Despite its appeal, the impact of defects on the afterglow performance in molecule-doped SiO2 matrices has remained largely unexplored. Herein, we detail the synthesis of monodisperse SiO2 microparticles by hydrothermally doping molecules, such as 4-phenylpyridine, 4,4'-bipyridine, and 1,4-bis(pyrid-4-yl)benzene. Our results demonstrate that hydrothermal reactions induce not only the formation of emissive defects in the SiO2 matrix but also enable molecule doping through SiO2 pseudomorphic transformation. Optical analyses reveal a remarkable afterglow activation of doped molecules, driven by a synergistic interplay of hydrogen bonding and physical fixation. Specifically, 4-phenylpyridine doping leads to an impressive 227- and 271-fold enhancement in fluorescence and afterglow, respectively, and an extraordinary 3711-fold enhancement in the afterglow lifetime of the resulting SiO2 MPs. We also document hybrid states involving molecule dopants and SiO2 defects, explaining energy transfer from molecule dopants to defects in both singlet and triplet states. The robust achievement of molecule doping provides flexibility to tailor excitation-dependent afterglow attributes while preserving angle-dependent structural colors, facilitating the creation of diverse building blocks for multiscale optical platforms for afterglow modulation and information encoding.

Air-Processed Efficient Cesium-Based Two-Dimensional Perovskite Solar Cells Based on Asymmetric Chiral Ammonium Salts.

Cesium-based two-dimensional (2D) perovskites with attractive phase and environmental stability have broad application prospects in single-junction and tandem perovskite solar cells (PSCs). However, the severe nonradiative recombination and significant energy losses due to disordered phase orientations and phase distributions greatly hinder the carrier transport performance of cesium-based 2D PSCs and severely limit their photovoltaic performance. Here, we employ an asymmetric chiral spacer cation source, (R)-α-phenylethylamine acrylate (R-α-PEAAA), to prepare high-quality 2D cesium-based films with uniform phase distribution and high out-of-plane orientation by air processing, resulting in efficient carrier transport. More importantly, the asymmetric chiral spacer R-α-PEA has a stronger dipole moment than its isomer (PEA), which can regulate the dielectric properties of cesium-based 2D perovskites and promote charge dissociation. In addition, the chiral R-α-PEA can optimize the morphology and out-of-plane orientation of perovskite films, reduce trap density and nonradiative recombination loss, and optimize energy level alignment, thus enhancing carrier transport. As a result, cesium-based 2D PSCs (R-α-PEA2Cs4Pb5I16, n = 5) achieved a record power conversion efficiency of 19.71% and the unencapsulated device maintained over 90% efficiency after 1500 h of continuous light exposure and ambient storage (35 ± 5% relative humidity). This study provides an idea for the development of chiral 2D perovskite with efficient charge carrier transport toward efficient and stable cesium-based 2D PSCs.

Color-Tunable and Stable Copper Iodide Cluster Scintillators for Efficient X-Ray Imaging.

The search for color-tunable, efficient, and robust scintillators plays a vital role in the development of modern X-ray radiography. The radioluminescence tuning of copper iodide cluster scintillators in the entire visible region by bandgap engineering is herein reported. The bandgap engineering benefits from the fact that the conduction band minimum and valence band maximum of copper iodide cluster crystals are contributed by atomic orbitals from the inorganic core and organic ligand components, respectively. In addition to high scintillation performance, the as-prepared crystalline copper iodide cluster solids exhibit remarkable resistance toward both moisture and X-ray irradiation. These features allow copper iodide cluster scintillators to show particular attractiveness for low-dose X-ray radiography with a detection limit of 55 nGy s-1 , a value ≈100 times lower than a standard dosage for X-ray examinations. The results suggest that optimizing both inorganic core and organic ligand for the building blocks of metal halide cluster crystals may provide new opportunities for a new generation of high-performance scintillation materials.

Pseudomorphic Synthesis of Monodisperse Afterglow Carbon Dot-Doped SiO2 Microparticles for Photonic Crystals.

Synthesizing monodisperse afterglow microparticles (MPs) is crucial for creating photonic crystal (PC) platforms with multiple optical states for optoelectronics. However, achieving high uniformity in both size and morphology is challenging for inorganic afterglow MPs using conventional methods. In this contribution, a novel approach for the synthesis of carbon dot (CD)-doped SiO2 MPs with tunable afterglow properties and size distributions is reported. These mechanism studies suggest that the pseudomorphic transformation of SiO2 MPs enables CD doping, providing a hydrogen bond-enriched environment for triplet state stabilization, which generates green afterglow while retaining the uniformity in size and morphology of the parent SiO2 MPs. Furthermore, the utility of CD-doped SiO2 MPs in the fabrication of rationally designed PC patterns is shown using a combined consecutive dip-coating and laser-assisted etching strategy. The pattern displays multiple optical responses under different lighting conditions, including angle-dependent structural colors and blue luminescence under daylight and upon 365-nm irradiation, respectively, as well as time-dependent green afterglow after ceasing UV excitation. The findings pave the way for further controlling the dynamics of spontaneous emissions by PCs to enable complicated optical states for advanced photonics.

Efficient X-ray luminescence imaging with ultrastable and eco-friendly copper(I)-iodide cluster microcubes.

The advancement of contemporary X-ray imaging heavily depends on discovering scintillators that possess high sensitivity, robust stability, low toxicity, and a uniform size distribution. Despite significant progress in this field, the discovery of a material that satisfies all of these criteria remains a challenge. In this study, we report the synthesis of monodisperse copper(I)-iodide cluster microcubes as a new class of X-ray scintillators. The as-prepared microcubes exhibit remarkable sensitivity to X-rays and exceptional stability under moisture and X-ray exposure. The uniform size distribution and high scintillation performance of the copper(I)-iodide cluster microcubes make them suitable for the fabrication of large-area, flexible scintillating films for X-ray imaging applications in both static and dynamic settings.

Bimetallic nanoparticles: kinetic control matters.

Morphologies à la carte: a kinetic control strategy has been utilized to fabricate bimetallic nanoparticles. Using cubic Pd nanocrystals as seeds and a syringe pump that enables precise control over precursor injection rate, it is possible to synthesize Pd-Ag bimetallic nanoparticles with tailored shapes and tunable localized surface plasmon resonances.

Tuning Luminescence of Lanthanide-Doped Upconversion Nanoparticles through Simultaneous Binary Cation Exchange.

Dual-mode luminescent nanomaterials have outstanding performance in biosensing and multistage anticounterfeiting. Herein, we report the tuning of optical attributes of lanthanide-doped nanoparticles (NPs) via simultaneous binary cation exchange. We show that cation exchange of NaYF4:Yb/Er (18/2 mol %)@NaLnF4 (Ln = Y and Gd) NPs with a combination of Ce3+ and Tb3+ enables the resultant nanoparticles to exhibit both upconversion and downshifting emissions upon excitation at 980 and 254 nm, respectively. We find that in addition to introducing downshifting emission attributes, the use of Tb3+ ions allows conservation of the integrity of the parent core@shell NPs by decreasing the dissociation tendency caused by Ce3+ ions during the cation exchange. The upconversion color output can be tuned from green to red and blue by changing lanthanide combinations in the core NPs. This work not only provides an effective strategy for the optical tuning of lanthanide-doped NPs but also builds a platform for probing the difference in the reactivity nature of lanthanides.