Hybrid Organic-Inorganic Perovskite Superstructures for Ultrapure Green Emissions.

All inorganic CsPbBr3 superstructures (SSs) have attracted much research interest due to their unique photophysical properties, such as their large emission red-shifts and super-radiant burst emissions. These properties are of particular interest in displays, lasers and photodetectors. Currently, the best-performing perovskite optoelectronic devices incorporate organic cations (methylammonium (MA), formamidinium (FA)), however, hybrid organic-inorganic perovskite SSs have not yet been investigated. This work is the first to report on the synthesis and photophysical characterization of APbBr3 (A = MA, FA, Cs) perovskite SSs using a facile ligand-assisted reprecipitation method. At higher concentrations, the hybrid organic-inorganic MA/FAPbBr3 nanocrystals self-assemble into SSs and produce red-shifted ultrapure green emissions, meeting the requirement of Rec. 2020 displays. We hope that this work will be seminal in advancing the exploration of perovskite SSs using mixed cation groups to further improve their optoelectronic applications.

A Dual Sensing Platform for Human Exhaled Breath Enabled by Fe-MIL-101-NH2 Metal-Organic Frameworks and its Derived Co/Ni/Fe Trimetallic Oxides.

Limited by the insufficient active sites and the interference from breath humidity, designing reliable gas sensing materials with high activity and moisture resistance remains a challenge to analyze human exhaled breath for the translational application of medical diagnostics. Herein, the dual sensing and cooperative diagnosis is achieved by utilizing metal-organic frameworks (MOFs) and its derivative. The Fe-MIL-101-NH2 serves as the quartz crystal microbalance humidity sensing layer, which exhibits high selectivity and rapid response time (16 s/15 s) to water vapor. Then, the Co2+ and Ni2+ cations are further co-doped into Fe-MIL-101-NH2 host to obtain the derived Co/Ni/Fe trimetallic  oxides (CoNiFe-MOS-n). The chemiresistive CoNiFe-MOS-n sensor displays the high sensitivity (560) and good selectivity to acetone, together with a lower original resistance compared with Fe2 O3 and NiFe2 O4 . Moreover, as a proof-of-concept application, synergistic integration of Fe-MIL-101-NH2 and derived CoNiFe-MOS-n is carried out. The Fe-MIL-101-NH2 is applied as moisture sorbent materials, which realize a sensitivity compensation of CoNiFe-MOS-n sensors for the detection of acetone (biomarker gas of diabetes). The findings provide an insight for effective utilization of MOFs and the derived materials to achieve a trace gas detection in exhaled breath analysis.

Tunable concentration-dependent upconversion and downconversion luminescence in NaYF4: Yb3+, Er3+@ NaYF4: Yb3+, Nd3+ core-shell nanocrystals for a dual-mode anti-counterfeiting imaging application.

Lanthanide-doped luminescent nanocrystals display both upconversion luminescence (UCL) and downconversion luminescence (DCL) properties, which offer potential applications in the second near-infrared window (NIR-II) images and biology sensors. Both UCL and DCL are sensitive to concentrations of activators. However, few works reveal the mechanism of concentration-dependent UCL and DCL. Herein, we synthesize core-shell upconversion nanocrystals (UCNCs) NaYF4: Yb3+(20%), Er3+ (2%)@NaYF4: Yb3+ (x%), Nd3+ (y%) with varying concentration of Nd and Yb ions. The UCL and DCL spectra are recorded under excitation of 980 nm and 808 nm lasers. The results indicate that the luminescence of core-shell UCNCs is influenced by the non-radiative rate between activators (Yb3+ and Nd3+) and the back energy transfer rate from Er3+ ions to activators. UCL tends to be obtained at a relatively low concentration of Yb3+ and Nd3+ ions (about 5%), whereas NIR emission tends to be obtained at a relatively high concentration of Yb3+ and Nd3+ ions (not higher than 20%). Dual-mode anti-counterfeiting imaging is successfully fabricated using core-shell UCNCs, which can be detected and distinguished by visible and infrared detectors. The visible versus infrared brightness of dual-mode anti-counterfeiting imaging can be tuned by varying the concentration of activators (Yb3+, Nd3+). Our work demonstrates concentration-dependent UCL and DCL in core-shell UCNCs, which provides reference to obtain NIR emission in the NIR-II region and adds encrypted dimensions for anti-counterfeiting patterns in the field of file encryption.

Overcoming Vascular Barriers to Improve the Theranostic Outcomes of Nanomedicines.

Nanotheranostics aims to utilize nanomaterials to prevent, diagnose, and treat diseases to improve the quality of patients' lives. Blood vessels are responsible to deliver nutrients and oxygen to the whole body, eliminate waste, and provide access for patrolling immune cells for healthy tissues. Meanwhile, they can also nourish disease tissues, spread disease factors or cells into other healthy tissues, and deliver nanotheranostic agents to cover all the regions of a disease tissue. Thus, blood vessels are the first and the most important barrier for highly efficient nanotheranostics. Here, the structure and function of blood vessels are explored and how these characteristics affect nanotheranostics is discussed. Moreover, new mechanisms and related strategies about overcoming vascular obstacles for improved nanotheranostic outcomes are critically summarized, and their merits and demerits of each strategy are analyzed. Moreover, the present challenges to completely exhibit the potential of overcoming vascular barriers to improve the theranostic outcomes of nanomedicines in life science are also discussed. Finally, the future perspective is further discussed.

Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics.

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb2O3. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of ~44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics.

Antimony Nanopolyhedrons with Tunable Localized Surface Plasmon Resonances for Highly Effective Photoacoustic-Imaging-Guided Synergistic Photothermal/Immunotherapy.

Antimony (Sb), a typical group VA semimetal, has rarely been studied both experimentally and theoretically in plasmonic photothermal therapy, possibly due to the lack of effective morphology-controllable methods for the preparation of high-quality Sb nanocrystals. In this study, an effective ligand-guided growth strategy to controllably synthesize Sb nanopolyhedrons (Sb NPHs) with ultrahigh photothermal conversion efficiency (PTCE), good photothermal stability, as well as biocompatibility is presented. Furthermore, the modulation effect of different morphologies on localized surface plasmon resonance (LSPR) of Sb NPHs in experimentation is successfully observed. When the resonance frequency of the Sb NPHs is matched well with the excitation wavelength (808 nm), the PTCE of the Sb NPHs is as high as 62.1%, which is noticeably higher compared to most of the reported photothermal agents. The Sb NPHs also exhibit good photothermal stability. In addition, Sb-NPHs-based multifunctional nanomedicines are further constructed via loading 1-methyl-d-tryptophan on PEGylated Sb NPHs for a highly efficient photoacoustic-imaging-guided synergistic photothermal/immune-therapy of tumors in vivo. This work can stimulate further theoretical and experimental investigations of Sb NPHs and other semimetal nanomaterials regarding their LSPR properties and inspire various potential applications of semimetals in biomedicine and sensors.

Near-infrared-II activated inorganic photothermal nanomedicines.

The emergence of near-infrared-II (NIR-II) activated photomedicines has extended the penetration depth for noninvasive theranostics, especially for photothermal nanomedicines. The current early development stage for NIR-II activated photomedicines has focused on creating a greater variety of photothermal agents (PTAs) with superior photothermal conversion ability. However, there is no thorough review for NIR-II inorganic PTAs and most comparisons of the photothermal performances of NIR-II inorganic PTAs are made with NIR-I PTAs. This review will first discuss about the key mechanisms of NIR-II absorption and photothermal conversion. Subsequently, this review will summarize recently developed advanced NIR-II inorganic PTAs based on the dominant inorganic elements and provide a comparison of their NIR-II photothermal performances. The nanostructure design, enhancement strategies and potential biomedical applications will be listed and discussed. We hope this review will further inspire active development and study of NIR-II activated inorganic PTAs with good photothermal conversion ability, multifunctionality, biocompatibility or biodegradability, and disease targeting ability.

Artificial Atomic Vacancies Tailor Near-Infrared II Excited Multiplexing Upconversion in Core-Shell Lanthanide Nanoparticles.

Epitaxial growth of an inert shell around the optical active lanthanide upconversion nanoparticles (UCNPs) is a general strategy to enhance their brightness. Yet, its potential as a tool in multiplexing emission tailoring has rarely been reported. Here, by developing the atomic vacancies into color selectivity actuators, we present an efficient strategy to achieve inert-shell-modulated multiplexing upconversion in 1540 nm activated UCNPs. Artificially generated fluoride atomic vacancies, owing to the decreased NaOH/NH4F dosage during shell growth, reduce the coordination number of Y-F and lattice densities in the inert shell, leading to the core-engineered shell nanoparticles with distinctive emission profiles. The multicolor tailoring is independent of shell thickness and can be readily applied to Lu3+/Gd3+-based shells. The upconversion emission can be exploited to visualize in security decoding and in vivo multiplexing bioimaging. This method of regulating atomic vacancies based on the inert-shell engineering opens new insights of upconversion modulation in core-shell lanthanide nanostructures.

Balancing the thickness of sensitizing and inert layers in neodymium-sensitized tetralayer nanoconstructs for optimal ultraviolet upconversion and near-infrared cross-linked hydrogel tissue sealants.

Tuning the configuration of lanthanide-doped upconversion nanoparticles (UCNPs) has been proven to be an effective approach to enhance upconversion (UC) efficiency, especially for neodymium (Nd3+)-sensitized UCNPs. Rational configuration design can spatially separate activators and sensitizers, achieving the evolution from single core to multilayer structures. However, optimizing multiphoton UC emission via configuration modulation, especially in the ultraviolet range, is yet to be fully investigated. In this work, thickness tuning of the sensitizing layer containing Nd3+ ions and the inert layer containing gadolinium ions at a fixed combined thickness of 5 nm in tetralayer UCNPs to exclude the size effect is reported for the first time. The optimal thickness of sensitizing and inert layers was determined to be 3 and 2 nm respectively, showing a new strategy of balancing sensitization and surface passivation to enhance 4-photon (360 nm) emission. Although 3-photon emission (475 nm) is mainly influenced by the overall size, its emission intensity remains similar in all the tetralayer UCNPs. Additionally, an 808 nm cross-linked hydrogel has been demonstrated as a potential near-infrared activated tissue sealant. Our results have uncovered the structural parameters for optimal ultraviolet UC emissions and elucidated the strategic importance of nano-configuration design to minimize the energy loss in the high-photon UC process.

Upconversion Nanoparticles-Based Multiplex Protein Activation to Neuron Ablation for Locomotion Regulation.

The optogenetic neuron ablation approach enables noninvasive remote decoding of specific neuron function within a complex living organism in high spatiotemporal resolution. However, it suffers from shallow tissue penetration of visible light with low ablation efficiency. This study reports a upconversion nanoparticle (UCNP)-based multiplex proteins activation tool to ablate deep-tissue neurons for locomotion modulation. By optimizing the dopant contents and nanoarchitecure, over 300-fold enhancement of blue (450-470 nm) and red (590-610 nm) emissions from UCNPs is achieved upon 808 nm irradiation. Such emissions simultaneously activate mini singlet oxygen generator and Chrimson, leading to boosted near infrared (NIR) light-induced neuronal ablation efficiency due to the synergism between singlet oxygen generation and intracellular Ca2+ elevation. The loss of neurons severely inhibits reverse locomotion, revealing the instructive role of neurons in controlling motor activity. The deep penetrance NIR light makes the current system feasible for in vivo deep-tissue neuron elimination. The results not only provide a rapidly adoptable platform to efficient photoablate single- and multiple-cells, but also define the neural circuits underlying behavior, with potential for development of remote therapy in diseases.

Virus-Inspired Deformable Mesoporous Nanocomposites for High Efficiency Drug Delivery.

Mesoporous nanoparticles as a versatile platform for cancer theranostics have been widely used, but their cellular delivery efficiency is still far from satisfactory. Although deformability is emerging as an important parameter influencing cellular uptake enhancement, the facile synthesis of deformable mesoporous nanocomposite with adjustable mechanical property is challenging but meaningful for a deeper understanding of cellular uptake mechanisms and significantly improving cancer therapy. In this work, yolk-shell structured eccentric mesoporous organosilica (YEMO) nanocomposites with adjustable mechanical property are successfully prepared by an organosilane-assisted anisotropic self-assembly approach. The feasibility to precisely control the mechanical property of the YEMO by manipulating the structural parameters, the crosslinking degree of mesoporous framework, and the rotation rate of the reaction is demonstrated. The study of the fabrication mechanism and mechanical properties of YEMO are discussed in detail. The Young's modulus (EY ) of YEMO can be adjusted from 2.4 to 65 MPa. Thereby, the continuous control of the cellular uptake from ≈15% to ≈80% under the same incubation time is achieved. To further prove the higher efficiency drug delivery of YEMO with soft characteristics, the higher toxicity of the "soft" YEMO loaded with the anticancer drug doxorubicin compared to the "stiff" one is demonstrated.

Neodymium-Sensitized Nanoconstructs for Near-Infrared Enabled Photomedicine.

Neodymium (Nd3+ )-sensitized nanoconstructs have gained increasing attention in recent decades due to their unique properties, especially optical properties. The design of various Nd3+ -sensitized nanosystems is expected to contribute to medical and health applications, due to their advantageous properties such as high penetration depth, excellent photostability, non-photobleaching, low cytotoxicity, etc. However, the low conversion efficiency and potential long-term toxicity of Nd3+ -sensitized nanoconstructs are huge obstacles to their clinical translations. This review article summarizes three energy transfer pathways of all kinds of Nd3+ -sensitized nanoconstructs focusing on the properties of Nd3+ ions and discusses their recent potential applications as near-infrared (NIR) enabled photomedicine. This review article will contribute to the design and fabrication of novel Nd3+ -sensitized nanoconstructs for NIR-enabled photomedicine, aiming for potentially safer and more efficient designs to get closer to clinical usage.

Generating New Cross-Relaxation Pathways by Coating Prussian Blue on NaNdF4 To Fabricate Enhanced Photothermal Agents.

Cross-relaxation among sensitizers is commonly regarded as deleterious in fluorescent materials, although favorable in photothermal agents. Herein, we coated Prussian blue (PB) on NaNdF4 nanoparticles to fabricate core-shell nanocomplexes with new cross relaxation pathways between the ladder-like energy levels of Nd3+ ions and continuous energy band of PB. The photothermal conversion efficiency was improved exceptionally and the mechanism of the enhanced photothermal effect was investigated. In vivo photoacoustic imaging and photothermal therapy demonstrated the potential of the enhanced photothermal agents. Moreover, the concept of generating new cross-relaxation pathways between different materials is proposed to contribute to the design of all kinds of enhanced photothermal agents.

An Upconversion Nanoparticle Enables Near Infrared-Optogenetic Manipulation of the Caenorhabditis elegans Motor Circuit.

Near-infrared (NIR) light penetrates tissue deeply, but its application to motor behavior stimulation has been limited by the lack of known genetic NIR light-responsive sensors. We designed and synthesized a Yb3+/Er3+/Ca2+-based lanthanide-doped upconversion nanoparticle (UCNP) that effectively converts 808 nm NIR light to green light emission. This UCNP is compatible with Chrimson, a cation channel activated by green light; as such, it can be used in the optogenetic manipulation of the motor behaviors of Caenorhabditis elegans. We show that this UCNP effectively activates Chrimson-expressing, inhibitory GABAergic motor neurons, leading to reduced action potential firing in the body wall muscle and resulting in locomotion inhibition. The UCNP also activates the excitatory glutamatergic DVC interneuron, leading to potentiated muscle action potential bursts and active reversal locomotion. Moreover, this UCNP exhibits negligible toxicity in neural development, growth, and reproduction, and the NIR energy required to elicit these behavioral and physiological responses does not activate the animal's temperature response. This study shows that UCNP provides a useful integrated optogenetic toolset, which may have wide applications in other experimental systems.

Synergizing Upconversion Nanophotosensitizers with Hyperbaric Oxygen to Remodel the Extracellular Matrix for Enhanced Photodynamic Cancer Therapy.

Photodynamic therapy (PDT) holds great promise as a noninvasive and selective cancer therapeutic treatment in preclinical research and clinical practice; however, it has limited efficacy in the ablation of deep-seated tumor because of hypoxia-associated circumstance and poor penetration of photosensitizers to cancer cells away from the blood vessels. To tackle the obstacles, we propose a therapeutic strategy that synergizes upconversion nanophotosensitizers (UNPSs) with hyperbaric oxygen (HBO) to remodel the extracellular matrix for enhanced photodynamic cancer therapy. The UNPSs are designed to have an Nd3+-sensitized sandwiched structure, wherein the upconversion core serves as light transducers to transfer energy to the neighboring photosensitizers to produce reactive oxygen species (ROS). With HBO, photodynamic process can generate abundant ROS in the intrinsically hypoxic tumor. It is revealed for the first time that HBO-assisted PDT decomposes collagen in the extracellular matrix of tumor and thus facilitates the diffusion of oxygen and penetration of UNPSs into the deeper area of tumor. Such a synergic effect eventually results in a significantly enhanced therapeutic efficacy at a low laser power density as compared with that using UNPSs alone. In view of its good biosafety, the HBO-assisted and UNPSs-mediated PDT provides new possibilities for treatment of solid tumors.

Ultrasmall-Superbright Neodymium-Upconversion Nanoparticles via Energy Migration Manipulation and Lattice Modification: 808 nm-Activated Drug Release.

Nd3+-sensitized upconversion nanoparticles are among the most promising emerging fluorescent nanotransducers. They are activated by 808 nm irradiation, which features merits such as limited tissue overheating and deeper penetration depth, and hence are attractive for diagnostic and therapeutic applications. Recent studies indicate that ultrasmall nanoparticles (<10 nm) are potentially more suitable for clinical application due to their favorable biodistribution and safety profiles. However, upconversion nanoparticles in the sub-10 nm range suffer from poor luminescence due to their ultrasmall size and greater proportion of lattice defects. To reconcile these opposing traits, we adopt a combinatorial strategy of energy migration manipulation and crystal lattice modification, creating ultrasmall-superbright Nd3+-sensitized nanoparticles with 2 orders of magnitude enhancement in upconversion luminescence. Specifically, we configure a sandwich-type nanostructure with a Yb3+-enriched intermediate layer [Nd3+]-[Yb3+-Yb3+]-[Yb3+-Tm3+] to form a positively reinforced energy migration system, while introducing Ca2+ into the crystal lattice to reduce lattice defects. Furthermore, we apply the nanoparticles to 808 nm light-mediated drug release. The results indicate time-dependent cancer cells killing and better antitumor activities. These ultrasmall-superbright dots have unraveled more opportunities in upconversion photomedicine with the promise of potentially safer and more effective therapy.