Freeze Metal Halide Perovskite for Dramatic Laser Tuning: Direct Observation via In Situ Cryo-Electron Microscope.

A frozen-temperature (below -28 °C) laser tuning way is developed to optimize metal halide perovskite (MHP)'s stability and opto-electronic properties, for emitter, photovoltaic and detector applications. Here freezing can adjust the competitive laser irradiation effects between damaging and annealing/repairing. And the ligand shells on MHP surface, which are widely present for many MHP materials, can be frozen and act as transparent solid templates for MHP's re-crystallization/re-growth during the laser tuning. With model samples of different types of CsPbBr3 nanocube arrays,an attempt is made to turn the dominant exposure facet from low-energy [100] facet to high-energy [111], [-211], [113] and [210] ones respectively; selectively removing the surface impurities and defects of CsPbBr3 nanocubes to enhance the irradiation durability by 101 times; and quickly (tens of seconds) modifying a Ruddlesden-Popper (RP) boundary into another type of boundary like twinning, and so on. The laser tuning mechanism is revealed by an innovative in situ cryo-transmission electron microscope (cryo-TEM) exploration at atomic resolution.

Active Assembly of CsPbBr3 Nanorods into Microcolumns by Electric Field in Nonpolar Solvent.

High-precision, controllable, mass-producible assembly of nanoparticles into complex structures or devices holds immense importance in the application across various fields but it remains challenging. Here a highly controllable and reversible active assembly of colloidal CsPbBr3 nanorods, driven by an external electric field is achieved. This approach enables the nanorods dynamically orient themselves, assemble into chains, aggregate into columns, and eventually form an ordered column array, with the electric field intensity varying from 0 to 50 V µm-1 at 100 kHz. The nanorods inside the columns align parallel to the electric field, leading to a well-ordered structure. With the analysis of the interactions among the nanorods, a quantitative interpretation of the assembly is proposed. Monte Carlo calculation is also introduced to simulate the assembly process and the results prove to be in great agreement with the experimental observations. This electric field-driven assembly presents an exciting opportunity to pave the way for next-generation sensors and photonic devices based on well-developed colloidal nanoparticles.

Optically Readable, Physically Unclonable Subwavelength Pixel via Multicolor Quantum Dot Printing for Anticounterfeiting.

We present a secure and user-friendly ultraminiaturized anticounterfeiting labeling technique─the color-encoded physical unclonable nanotag. These nanotags consist of subwavelength spots formed by random combinations of multicolor quantum dots, which are fabricated using a cost-efficient printing method developed in this study. The nanotags support over 170,000 different colors and are inherently resistant to cloning. Moreover, their high brightness and color purity, owing to the quantum dots, ensure an ease of readability. Additionally, these nanotags can function as color-encrypted pixels, enabling the incorporation of labels (such as QR codes) into ultrasmall physically unclonable hidden tags with a resolution exceeding 100,000 DPI. The unique blend of compactness, flexibility, and security positions the color-encoded nanotag as a potent and versatile solution for next-generation anticounterfeiting applications.

Annealed SiO2 Protective Layer on LiMn2O4 for Enhanced Li-Ion Extraction from Brine.

In this study, we present a novel approach for selective Li-ion extraction from brine using an LiMn2O4 ion sieve coated with a dense silica layer, denoted as LMO@SiO2. The SiO2 layer is controllably coated onto the LMO surface, forming passivation layers and ion permeation filters. This design effectively minimizes the acidic corrosion of the LMO and enhances the Li+ adsorption capacity. Additionally, the SiO2 layer undergoes calcination at various temperatures (ranging from 300 to 700 °C) to achieve different compactness levels of the coating layer, providing further protection to the LMO crystal structures. As a result of these improvements, the optimized LMO@SiO2 adsorbent demonstrates an exceptional Li+ adsorption capacity of 18.5 mg/g for brine, and even after seven adsorption-elution cycles, it maintains a capacity of 15.3 mg/g. This outstanding performance makes our material a promising candidate for efficient Li+ extraction from brine or other low-concentration Li+ solutions in future applications.

Photoluminescence Anisotropy in Eutectic Crystals of Polynuclear Lanthanide Complexes and Silver Clusters.

Anisotropy is an intrinsic property of crystalline materials. However, the photoluminescence anisotropy in eutectic crystals of organometallic complexes has remained unexplored. Herein, the eutectic of polynuclear lanthanide complexes and Ag clusters was prepared, and the crystal shows significant photoluminescence anisotropy. The polarization anisotropy of emission δ and degree of excitation polarization P are 2.62 and 0.53, respectively. The rare excitation polarization properties have been proved to be related to the regular arrangement of electric transition dipole moments of luminescent molecules in the crystal. Our design provides a reference for developing new photoluminescence anisotropy materials and expanding their applications.

Patterning of Molecules/Ions via Reverse Micelle Vessels by Nanoxerography.

Precise patterning of molecules/ions in the nanometer scale is a crucial but challenging technique for the fabrication of advanced functional nanodevices. We developed a robust method to print molecules/ions into arbitrarily defined patterns with sub-20 nm precision assisted by reverse micelles. The reverse micelle, serving as a nano-sized vessel, can load molecules/ions and then be patterned onto the predefined positions by electrostatic attraction. The number of molecules/ions on each spot, the spot spacing, and pattern shapes can be flexibly adjusted, reaching 10 nm position accuracy, 30 nm spot size, and 100 nm spot spacing (>250,000 DPI). Then, water-soluble dye molecules, protein molecules, and chloroaurate ions were loaded in the micelles and successfully patterned into nanoarrays, which provides an important platform for the convenient, flexible, and robust fabrication of functional molecule/ion-based nanodevices, such as biochips, for high-throughput and ultrasensitive analysis.

Electrostatic-induced green and precise growth of model catalysts.

Crystallographic control of crystals as catalysts with precise geometrical and chemical features is significantly important to develop sustainable chemistry, yet highly challenging. Encouraged by first principles calculations, precise structure control of ionic crystals could be realized by introducing an interfacial electrostatic field. Herein, we report an efficient in situ dipole-sourced electrostatic field modulation strategy using polarized ferroelectret, for crystal facet engineering toward challenging catalysis reactions, which avoids undesired faradic reactions or insufficient field strength by conventional external electric field. Resultantly, a distinct structure evolution from tetrahedron to polyhedron with different dominated facets of Ag3PO4 model catalyst was obtained by tuning the polarization level, and similar oriented growth was also realized by ZnO system. Theoretical calculations and simulation reveal that the generated electrostatic field can effectively guide the migration and anchoring of Ag+ precursors and free Ag3PO4 nuclei, achieving oriented crystal growth by thermodynamic and kinetic balance. The faceted Ag3PO4 catalyst exhibits high performance in photocatalytic water oxidation and nitrogen fixation for valuable chemicals production, validating the effectiveness and potential of this crystal regulation strategy. Such an electrically tunable growth concept by electrostatic field provides new synthetic insights and great opportunity to effectively tailor the crystal structures for facet-dependent catalysis.

Smart Magnetic Optical Antenna for Automatic Nanoalignment and Photon Beaming from Prepatterned Single Quantum Dot Nanospot.

We present a unidirectional dielectric optical antenna, which can be chemically synthesized and controlled by magnetic fields. By applying magnetic fields, we successfully aligned an optical antenna on a prepatterned quantum dot nanospot with accuracy better than 40 nm. It confined the fluorescence emission into a 16-degree wide beam and enhanced the signal by 11.8 times. Moreover, the position of the antenna, and consequently the beam direction, can be controlled by simply adjusting the direction of the magnetic fields. Theoretical analyses show that this magnetic alignment technique is stable and accurate, providing a new strategy for building high-performance tunable nanophotonic devices.

Plasmon-Enhanced Electrochemiluminescence at the Single-Nanoparticle Level.

Plasmon-enhanced electrochemiluminescence (ECL) at the single-nanoparticle (NP) level was investigated by ECL microscopy. The Au NPs were assembled into an ordered array, providing a high-throughput platform that can easily locate each NP in sequential characterizations. A strong dependence of ECL intensity on Au NP configurations was observed. We demonstrate for the first time that at the single-particle level, the ECL of Ru(bpy)3 2+ -TPrA was majorly quenched by small Au NPs (<40 nm), while enhanced by large Au ones (>80 nm) due to the localized surface plasmon resonance (LSPR). Notably, the ECL intensity was further increased by the coupling effect of neighboring Au NPs. Finite Difference Time Domain (FDTD) simulations conformed well with the experimental results. This plasmon enhanced ECL microscopy for arrayed single NPs provides a reliable tool for screening electrocatalytic activity at a single particle.

Sub-ambient full-color passive radiative cooling under sunlight based on efficient quantum-dot photoluminescence.

Daytime radiative cooling with high solar reflection and mid-infrared emission offers a sustainable way for cooling without energy consumption. However, so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications. Although various colored radiative cooling designs have been pursued previously, multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to significant thermal load. Here, we demonstrate that photoluminescence (PL) based colored radiative coolers (PCRCs) with high internal quantum efficiency enable sub-ambient full-color cooling. As an example of experimental demonstration, we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence. The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet-visible sunlight into emitted light to minimize the solar-heat generation, and cellulose acetate based nanofibers as the underlayer that strongly reflect sunlight and radiate thermal load. As a result, the green, yellow and red colors of PCRCs achieve temperatures of 5.4-2.2 °C below ambient under sunlight (peak solar irradiance >740 W m-2), respectively. With the excellent cooling performance and scalable process, our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.

Moisture-Dependent Blinking of Individual CsPbBr3 Nanocrystals Revealed by Single-Particle Spectroscopy.

All-inorganic metal halide perovskite nanocrystals (NCs) have been exceptional candidates for high-performance solution-processed optoelectronic and photonic devices compared with organometal halide perovskite NCs due to their superior stability. However, the interactions between all-inorganic perovskite NCs and moisture, which is an acknowledged detrimental factor, are still under debate, and detailed investigations to uncover such fundamentals remain to be performed. Herein, with wide-field fluorescence microscopy, the burst photoluminescence blinking responses of CsPbBr3 NCs were observed in ambient air, and moisture rather than oxygen was verified to be the key factor that leads to the enhanced PL intensity and reduced OFF duration. This behavior is rationalized through an effective passivation effect of the adsorbed water molecules on the surface halide vacancies on CsPbBr3 NCs. This work validates that ∼40% humidity atmospheres are helpful for better utilizing the all-inorganic perovskites, which is evidence of their promising prospect for application.

Quantized Exciton Motion and Fine Energy-Level Structure of a Single Perovskite Nanowire.

The quantum-confinement effect profoundly influences the exciton energy-level structures and recombination dynamics of semiconductor nanostructures but remains largely unexplored in traditional one-dimensional nanowires mainly due to their poor optical qualities. Here, we show that in defect-tolerant perovskite material of highly luminescent CsPbBr3 nanowires, the exciton's center-of-mass motion perpendicular to the axial direction is severely confined. This is reflected in the two sets of photoluminescence spectra emitted from a single CsPbBr3 nanowire, each of which consists of doublet peaks with linear polarizations perpendicular and parallel to the axial direction. Moreover, different exciton states can be mixed by the Rashba spin-orbit coupling effect, resulting in two single photoluminescence peaks with linear polarizations both along the nanowire axis. The above findings mark the emergence of an ideal platform for the exploration of intrinsic one-dimensional exciton photophysics and optoelectronics, thus bridging the long-missing research gap between the well-studied two- and zero-dimensional semiconductor nanostructures.

Scalable Production of High-Quality Silver Nanowires via Continuous-Flow Droplet Synthesis.

Silver nanowires (Ag NWs) have shown great potential in next-generation flexible displays, due to their superior electronic, optical, and mechanical properties. However, as with most nanomaterials, a limited production capacity and poor reproduction quality, based on the batch reaction, largely hinder their application. Here, we applied continuous-flow synthesis for the scalable and high-quality production of Ag NWs, and built a pilot-scale line for kilogram-level per day production. In addition, we found that trace quantities of water could generate sufficient vapor as a spacer under high temperature to efficiently prevent the back-flow or mixed-flow of the reaction solution. With an optimized synthetic formula, a mass production of pure Ag NWs of 36.5 g/h was achieved by a multiple-channel, continuous-flow reactor.

Transferring Liquid Metal to form a Hybrid Solid Electrolyte via a Wettability-Tuning Technology for Lithium-Metal Anodes.

Integrating solid-state electrolyte (SSE) into Li-metal anodes has demonstrated great promise to unleash the high energy density of rechargeable Li-metal batteries. However, fabricating a highly cyclable SSE/Li-metal anode remains a major challenge because the densification of the SSE is usually incompatible with the reactive Li metal. Here, a liquid-metal-derived hybrid solid electrolyte (HSE) is proposed, and a facile transfer technology to construct an artificial HSE on the Li metal is reported. By tuning the wettability of the transfer substrates, electron- and ion-conductive liquid metal is sandwiched between electron-insulating and ion-conductive LiF and oxides to form the HSE. The transfer technology renders the HSE continuous, dense, and uniform. The HSE, having high ion transport, electron shut-off, and mechanical strength, makes the composite anode deliver excellent cyclability for over 4000 h at 0.5 mA cm-2 and 1 mAh cm-2 in a symmetrical cell. When pairing with LiFePO4 and sulfur cathodes, the HSE-coated Li metal dramatically enhances the performance of full cells. Therefore, this work demonstrates that tuning the interfacial wetting properties provides an alternate approach to build a robust solid electrolyte, which enables highly efficient Li-metal anodes.

Modulating the Chemical Microenvironment of Pt Nanoparticles within Ultrathin Nanosheets of Isoreticular MOFs for Enhanced Catalytic Activity.

The catalytic activity of metal nanoparticles (MNPs) embedded in metal-organic frameworks (MOFs) is affected by the electronic interactions between MNPs and MOFs. In this report, we fabricate a series of ultrathin nanosheets of isoreticular MOFs (NMOFs) with different metal nodes as supports and successfully encapsulate Pt NPs within these NMOFs, affording Pt@NMOF-Co, Pt@NMOF-Ni1Co1, Pt@NMOF-Ni3Co1, and Pt@NMOF-Ni nanocomposites. The microchemical environment on the surface of Pt NPs can be modulated by varying the metal nodes of NMOFs. The catalytic activity of the nanocomposites toward liquid-phase hydrogenation of 1-hexene shows obvious difference, in which Pt@NMOF-Ni possesses the highest activity followed by Pt@NMOF-Ni3Co1, Pt@NMOF-Ni1Co1, and Pt@NMOF-Co in a decreasing order of activity. Obviously, increasing gradually the amount of Ni2+ nodes in the carriers can improve the catalytic activity. The difference of catalytic activity of the nanocomposites might originate from the distinct electron interactions between Pt NPs and NMOFs, as ascertained by X-ray photoelectron spectroscopy spectrum and density functional theory calculations. This work provides a rare example that the catalytic activity of MNPs could be controlled by accurately regulating the microchemical environment using ultrathin NMOFs as supports.

Engineering Two-Dimensional Metal-Organic Framework on Molecular Basis for Fast Li+ Conduction.

Metal-organic frameworks (MOFs) have been proposed as emerging fillers for composite polymer electrolytes (CPEs). However, MOF particles are usually served as passive fillers that yield limited ionic conductivity improvement. Building continuous MOF reinforcements and exploiting their active roles remain challenging. Here we demonstrate the feasibility of engineering fast Li+ conduction within MOF on molecule conception. Two-dimensional Cu(BDC) MOF is selected as an active filler due to its sufficient accessible open metal sites for perchlorate anion anchoring to release free Li+, verified by theoretical calculations and measurements. A novel Cu(BDC)-scaffold-reinforced CPE is developed via in situ growth of MOF, which provides fast Li+ channels inside MOF and continuous Li+ paths along the MOF/polymer interface for high Li+ conductivity (ambient 0.24 mS cm-1) and enables high mechanical strength. Stable cycling is achieved in solid-state Li-NCM811 full cell using the MOF-reinforced CPE. This molecule-basis Li+ conduction strategy brings new ideas for designing advanced CPEs.

Ultrasonic activation of inert poly(tetrafluoroethylene) enables piezocatalytic generation of reactive oxygen species.

Controlled generation of reactive oxygen species (ROS) is essential in biological, chemical, and environmental fields, and piezoelectric catalysis is an emerging method to generate ROS, especially in sonodynamic therapy due to its high tissue penetrability, directed orientation, and ability to trigger in situ ROS generation. However, due to the low piezoelectric coefficient, and environmental safety and chemical stability concerns of current piezoelectric ROS catalysts, novel piezoelectric materials are urgently needed. Here, we demonstrate a method to induce polarization of inert poly(tetrafluoroethylene) (PTFE) particles ( ~ 1-5 µm) into piezoelectric electrets with a mild and convenient ultrasound process. Continued ultrasonic irradiation of the PTFE electrets generates ROS including hydroxyl radicals (•OH), superoxide (•O2-) and singlet oxygen (1O2) at rates significantly faster than previously reported piezoelectric catalysts. In summary, ultrasonic activation of inert PTFE particles is a simple method to induce permanent PTFE polarization and to piezocatalytically generate aqueous ROS that is desirable in a wide-range of applications from environmental pollution control to biomedical therapy.

The Role of Polymer and Inorganic Coatings to Enhance Interparticle Connections Diagnosed by In Situ Techniques.

Surface coating on alloy anodes renders an effective remedy to tolerate internal stress and alleviate the side reaction with electrolytes for long-lasting reversible lithium redox reactions in lithium-ion batteries. However, the role of surface coating on the interparticle connections of alloy anodes remains not fully understood. Herein, we exploit real-time lithiation and mechanic measurement of SnO2 nanoparticles via in situ TEM with different coating layers, including conducting polymer polypyrrole and metal oxide MnO2. As a result, polypyrrole is more flexible to accommodate the volume expansion issue. More importantly, the polypyrrole coating layers offer a large contact area and strong adhesion force between the SnO2 nanoparticles, ensuring fast lithiation kinetics and high cycling stability. These observations provide new insight into how the interparticle connections of alloy anodes with diverse coating approaches can impact battery performance, shedding light on the practical processing of the alloy anode materials for high-energy Li-ion batteries.

Unexpected Coulomb Interactions in Nonpolar Solvent for Highly Efficient Nanoxerography of Perovskite Quantum Dots.

In this work, an unexpected sign-dependent electrostatic assembly, also known as nanoxerography, of perovskite quantum dots was observed in nonpolar solutions. Electrical force microscope measurements showed that CsPbBr3 quantum dots carry negative charges and tend to aggregate at the positively charged nanospots via Coulomb interactions despite that they are synthesized and dispersed in a neutral nonpolar solvent. The result was further confirmed by a statistical method developed in this work based on the Gibbs-Boltzmann distribution. More interestingly, we found that the existence of net charges is a common phenomenon for widely used oil-phase synthesized nanoparticles, including Au, Fe2O3, and CdSe/ZnS nanoparticles. This is contrary to the common belief and indicates the possibility of highly efficient nanoxerography for functional nanoparticles synthesized in nonpolar solvents.

Deterministic Assembly of Single Sub-20 nm Functional Nanoparticles Using a Thermally Modified Template with a Scanning Nanoprobe.

A deterministic assembly technique for single sub-20 nm functional nanoparticles is developed based on nanostructured templates fabricated by hot scanning nanoprobes. With this technique, single nanoparticles including quantum dots, polystyrene fluorescent nanobeads, and gold nanoparticles are successfully assembled into 2D arrays with high yields. Experimental and theoretical analyses show that the key for the high yields is the hot-probe-based template fabrication technique, which creates geometrical nanotraps and modifies their surface energy simultaneously. In addition to single nanoparticle patterning, further experiments demonstrate that this technique is also capable of building complex nanostructures, such as nanoparticle clusters with well-defined shapes and heterogeneously integrated nanostructures consisting of quantum dots and silver nanowires. It opens the door to many important applications.