Showing papers in "Nano Letters in 2021"

Metal-Organic Frameworks Derived Functional Materials for Electrochemical Energy Storage and Conversion: A Mini Review

Abstract: With many apparent advantages including high surface area, tunable pore sizes and topologies, and diverse periodic organic-inorganic ingredients, metal-organic frameworks (MOFs) have been identified as versatile precursors or sacrificial templates for preparing functional materials as advanced electrodes or high-efficiency catalysts for electrochemical energy storage and conversion (EESC) In this Mini Review, we first briefly summarize the material design strategies to show the rich possibilities of the chemical compositions and physical structures of MOFs derivatives We next highlight the latest advances focusing on the composition/structure/performance relationship and discuss their practical applications in various EESC systems, such as supercapacitors, rechargeable batteries, fuel cells, water electrolyzers, and carbon dioxide/nitrogen reduction reactions Finally, we provide some of our own insights into the major challenges and prospective solutions of MOF-derived functional materials for EESC, hoping to shed some light on the future development of this highly exciting field

In Situ Anchoring Polymetallic Phosphide Nanoparticles within Porous Prussian Blue Analogue Nanocages for Boosting Oxygen Evolution Catalysis.

Abstract: The controllable synthesis of metal-based nanoclusters for heterogeneous catalytic reactions has received considerable attention. Nevertheless, manufacturing these architectures, while avoiding aggregation and retaining surface activity, remains challenging. Herein, for the first time we designed NiCoFe-Prussian blue analogue (PBA) nanocages as a support for in situ dispersion and anchoring of polymetallic phosphide nanoparticles (pMP-NPs). Benefiting from the porous surfaces and the synergistic effects between pMP-NPs and the cyano groups in PBA, the NiCoFe-P-NP@NiCoFe-PBA nanocages exhibit a significantly enhanced catalytic activity for oxygen evolution reaction (OER) with an overpotential of 223 mV at 10 mA cm-2 and a Tafel slope of 78 mV dec-1, outperforming the NiCoFe-PBA nanocubes, NiCoFe-P nanocages, NiFe-P-NP@NiFe-PBA nanocubes, and CoFe-P-NP@CoFe-PBA nanoboxes. This work not only offers the synthesis strategy of in situ anchoring pMP-NPs on PBA nanocages but also provides a new insight into optimized Gibbs free energy of OER by regulating electron transfer from metallic phosphides to PBA substrate.

Fluorination-enabled Reconstruction of NiFe Electrocatalysts for Efficient Water Oxidation.

Abstract: Developing low-cost and efficient electrocatalysts to accelerate oxygen evolution reaction (OER) kinetics is vital for water and carbon-dioxide electrolyzers. The fastest-known water oxidation catalyst, Ni(Fe)OxHy, usually produced through an electrochemical reconstruction of precatalysts under alkaline condition, has received substantial attention. However, the reconstruction in the reported catalysts usually leads to a limited active layer and poorly controlled Fe-activated sites. Here, we demonstrate a new electrochemistry-driven F-enabled surface-reconstruction strategy for converting the ultrathin NiFeOxFy nanosheets into an Fe-enriched Ni(Fe)OxHy phase. The activated electrocatalyst shows a low OER overpotential of 218 ± 5 mV at 10 mA cm-2 and a low Tafel slope of 31 ± 4 mV dec-1, which is among the best for NiFe-based OER electrocatalysts. Such superior performance is caused by the effective formation of the Fe-enriched Ni(Fe)OxHy active-phase that is identified by operando Raman spectroscopy and the substantially improved surface wettability and gas-bubble-releasing behavior.

High-Throughput Screening of Synergistic Transition Metal Dual-Atom Catalysts for Efficient Nitrogen Fixation.

Abstract: Great enthusiasm in single-atom catalysts (SACs) for the nitrogen reduction reaction (NRR) has been aroused by the discovery of metal-Nx as a promising catalytic center. However, the poor activity and low selectivity of available SACs are far away from the industrial requirement. Through the first-principles high-throughput screening, we find that Fe-Fe distributed on graphite carbon nitride (Fe2/g-CN) can manipulate the binding strength of the target reaction species (compromises the ability to adsorb N2H and NH2), therefore achieving the best NRR performance among 23 transition metal (TM) centers. Our results show that Fe2/g-CN achieves a high theoretical Faradaic efficiency of 100% and, impressively, the lowest limiting potential of -0.13 V. Particularly, multiple-level descriptors shed light on the origin of NRR activity, achieving a fast prescreening among various candidates. Our predictions not only accelerate discovery of catalysts for ammonia synthesis but also contribute to further elucidate the structure-performance correlations.

Ultrasound-Augmented Mitochondrial Calcium Ion Overload by Calcium Nanomodulator to Induce Immunogenic Cell Death.

Abstract: Immunogenic cell death (ICD), a manner of tumor cell death that can trigger antitumor immune responses, has received extensive attention as a potential synergistic modality for cancer immunotherapy. Although many calcium ion (Ca2+) nanomodulators have been developed for cancer therapy through mitochondrial Ca2+ overload, their ICD-inducing properties have not been explored. Herein, an acid-sensitive PEG-decorated calcium carbonate (CaCO3) nanoparticle incorporating curcumin (CUR; a Ca2+ enhancer) (PEGCaCUR) was prepared using a simple one-pot strategy. PEGCaCUR served as not only a Ca2+ nanomodulator inducing efficient mitochondrial Ca2+ overload but also an ICD inducer during improved synergistic cancer therapy. Combination of PEGCaCUR with ultrasound (US), PEGCaCUR+US, led to an enhanced ICD effect attributable to the enhanced mitochondrial Ca2+ overload, along with subsequent upregulation of reactive oxygen species levels. PEGCaCUR also facilitates photoacoustic/fluorescence dual-mode imaging, as well as effectively suppressing tumor growth and metastasis, indicating promising theranostic properties.

CRISPR-Cas12a-Based Nucleic Acid Amplification-Free DNA Biosensor via Au Nanoparticle-Assisted Metal-Enhanced Fluorescence and Colorimetric Analysis

Abstract: Cell-free DNA (cfDNA) has attracted significant attention due to its high potential to diagnose diseases, such as cancer. Still, its detection by amplification method has limitations because of false-positive signals and difficulty in designing target-specific primers. CRISPR-Cas-based fluorescent biosensors have been developed but also need the amplification step for the detection. In this study, for the first time CRISPR-Cas12a based nucleic acid amplification-free fluorescent biosensor was developed to detect cfDNA by a metal-enhanced fluorescence (MEF) using DNA-functionalized Au nanoparticle (AuNP). Upon activating the CRISPR-Cas12a complex by the target cfDNA and subsequent single-strand DNA (ssDNA) degradation between AuNP and fluorophore, MEF occurred with color changes from purple to red-purple. Using this system, breast cancer gene-1 (BRCA-1) can be detected with very high sensitivity in 30 min. This rapid and highly selective sensor can be applied to measure other nucleic acid biomarkers such as viral DNA in field-deployable and point-of-care testing (POCT) platform.

Halide Perovskite Semiconductor Lasers: Materials, Cavity Design, and Low Threshold

Abstract: Solution-processable semiconductor lasers have been a long-standing challenge for next-generation displays, light sources, and communication technologies. Metal halide perovskites, which combine the advantages of inorganic and organic semiconductors, have recently emerged not only as excellent candidates for solution-processable lasers but also as potential complementary gain materials for filling the "green gap" and supplement industrial nanolasers based on classic II-VI/III-V semiconductors. Numerous perovskite lasers have been developed successfully with superior performance in terms of cost-effectiveness, low threshold, high coherence, and multicolor tunability. This mini review surveys the development, current status, and perspectives of perovskite lasers, categorized into thin film lasers, nanocrystals lasers, microlasers, and device concepts including polariton and bound-in-continuum lasers with a focus on material fundamentals, cavity design, and low-threshold devices in addition to critical issues such as mass fabrication and applications.

Photoactive Antiviral Face Mask with Self-Sterilization and Reusability.

Abstract: Since the emergence of the COVID-19 pandemic outbreak, the increasing demand and disposal of surgical masks has resulted in significant economic costs and environmental impacts. Here, we applied a dual-channel spray-assisted nanocoating hybrid of shellac/copper nanoparticles (CuNPs) to a nonwoven surgical mask, thereby increasing the hydrophobicity of the surface and repelling aqueous droplets. The resulting surface showed outstanding photoactivity (combined photocatalytic and photothermal properties) for antimicrobial action, conferring reusability and self-sterilizing ability to the masks. Under solar illumination, the temperature of this photoactive antiviral mask (PAM) rapidly increased to >70 °C, generating a high level of free radicals that disrupted the membrane of nanosized (∼100 nm) virus-like particles and made the masks self-cleaning and reusable. This PAM design can provide significant protection against the transmission of viral aerosols in the fight against the COVID-19 pandemic.

Manipulating Redox Kinetics of Sulfur Species Using Mott-Schottky Electrocatalysts for Advanced Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur (Li-S) batteries suffer from sluggish sulfur redox reactions under high-sulfur-loading and lean-electrolyte conditions. Herein, a typical Co@NC heterostructure composed of Co nanoparticles and a semiconductive N-doped carbon matrix is designed as a model Mott-Schottky catalyst to exert the electrocatalytic effect on sulfur electrochemistry. Theoretical and experimental results reveal the redistribution of charge and a built-in electric field at the Co@NC heterointerface, which are critical to lowering the energy barrier of polysulfide reduction and Li2S oxidation in the discharge and charge process, respectively. With Co@NC Mott-Schottky catalysts, the Li-S batteries display an ultrahigh capacity retention of 92.1% and a system-level gravimetric energy density of 307.8 Wh kg-1 under high S loading (10.73 mg cm-2) and lean electrolyte (E/S = 5.9 μL mgsulfur-1) conditions. The proposed Mott-Schottky heterostructure not only deepens the understanding of the electrocatalytic effect in Li-S chemistry but also inspires a rational catalyst design for advanced high-energy-density batteries.

Magnetic Order and Symmetry in the 2D Semiconductor CrSBr.

Abstract: The advent of two-dimensional (2D) magnets offers unprecedented control over electrons and spins. A key factor in determining exchange coupling and magnetic order is symmetry. Here, we apply second harmonic generation (SHG) to probe a 2D magnetic semiconductor CrSBr. We find that monolayers are ferromagnetically ordered below 146 K, an observation enabled by the discovery of a large magnetic dipole SHG effect in the centrosymmetric structure. In multilayers, the ferromagnetic monolayers are coupled antiferromagnetically, and in contrast to other 2D magnets, the Neel temperature of CrSBr increases with decreasing layer number. We identify magnetic dipole and magnetic toroidal moments as order parameters of the ferromagnetic monolayer and antiferromagnetic bilayer, respectively. These findings establish CrSBr as an exciting 2D magnetic semiconductor and extend the SHG probe of magnetic symmetry to the monolayer limit, opening the door to exploring the applications of magnetic-electronic coupling and the magnetic toroidal moment.

Isolated Single-Atom Ni-N5 Catalytic Site in Hollow Porous Carbon Capsules for Efficient Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur (Li-S) batteries suffer from multiple complex and often interwoven issues, such as the low electronic conductivity of sulfur and Li2S/Li2S2, shuttle effect, and sluggish electrochemical kinetics of lithium polysulfides (LiPSs). Guided by theoretical calculations, a multifunctional catalyst of isolated single-atom nickel in an optimal Ni-N5 active moiety incorporated in hollow nitrogen-doped porous carbon (Ni-N5/HNPC) is constructed and acts as an ideal host for a sulfur cathode. The host improved electrical conductivity, enhanced physical-chemical dual restricting capability toward LiPSs, and, more importantly, boosted the redox reaction kinetics by the Ni-N5 active moiety. Therefore, the Ni-N5/HNPC/S cathode exhibits superior rate performance, long-term cycling stability, and good areal capacity at high sulfur loading. This work highlights the important role of the coordination number of active centers in single-atom catalysts and provides a strategy to design a hollow nanoarchitecture with single-atom active sites for high-performance Li-S batteries.

MOF-Derived Bifunctional Co0.85Se Nanoparticles Embedded in N-Doped Carbon Nanosheet Arrays as Efficient Sulfur Hosts for Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur batteries possess the merits of low cost and high theoretical energy density but suffer from the shuttle effect of lithium polysulfides and slow redox kinetics of sulfur. Herein, novel Co0.85Se nanoparticles embedded in nitrogen-doped carbon nanosheet arrays (Co0.85Se/NC) were constructed on carbon cloth as the self-supported host for a sulfur cathode using a facile fabrication strategy. The interconnected porous carbon-based structure of the Co0.85Se/NC could facilitate the rapid electron and ion transfer kinetics. The embedded Co0.85Se nanoparticles can effectively capture and catalyze lithium polysulfides, thus accelerating the redox kinetics and stabilizing sulfur cathodes. Therefore, the Co0.85Se/NC-S cathode could maintain a stable cycle performance for 400 cycles at 1C and deliver a high discharge specific capacity of 1361, 1001, and 810 mAh g-1 at current densities of 0.1, 1, and 3C, respectively. This work provides an efficient design strategy for high-performance lithium-sulfur batteries with high energy densities.

Cellulose-Based Hybrid Structural Material for Radiative Cooling

Abstract: Structural materials with excellent mechanical properties are vitally important for architectural application. However, the traditional structural materials with complex manufacturing processes cannot effectively regulate heat flow, causing a large impact on global energy consumption. Here, we processed a high-performance and inexpensive cooling structural material by bottom-up assembling delignified biomass cellulose fiber and inorganic microspheres into a 3D network bulk followed by a hot-pressing process; we constructed a cooling lignocellulosic bulk that exhibits strong mechanical strength more than eight times that of the pure wood fiber bulk and greater specific strength than the majority of structural materials. The cellulose acts as a photonic solar reflector and thermal emitter, enabling a material that can accomplish 24-h continuous cooling with an average dT of 6 and 8 °C during day and night, respectively. Combined with excellent fire-retardant and outdoor antibacterial performance, it will pave the way for the design of high-performance cooling structural materials.

Synthesis of Lead-Free Cs2AgBiX6 (X = Cl, Br, I) Double Perovskite Nanoplatelets and Their Application in CO2 Photocatalytic Reduction.

Abstract: Morphology control represents an important strategy for the development of functional nanomaterials and has yet to be achieved in the case of promising lead-free double perovskite materials so far. In this work, high-quality Cs2AgBiX6 (X = Cl, Br, I) two-dimensional nanoplatelets were synthesized through a newly developed synthetic procedure. By analyzing the optical, morphological, and structural evolutions of the samples during synthesis, we elucidated that the growth mechanism of lead-free double perovskite nanoplatelets followed a lateral growth process from mono-octahedral-layer (half-unit-cell in thickness) cluster-based nanosheets to multilayer (three to four unit cells in thickness) nanoplatelets. Furthermore, we demonstrated that Cs2AgBiBr6 nanoplatelets possess a better performance in photocatalytic CO2 reduction compared with their nanocube counterpart. Our work demonstrates the first example with two-dimensional morphology of this important class of lead-free perovskite materials, shedding light on the synthetic manipulation and the application integration of such promising materials.

Intertwined Topological and Magnetic Orders in Atomically Thin Chern Insulator MnBi2Te4.

Abstract: MnBi2Te4, a van der Waals magnet, is an emergent platform for exploring Chern insulator physics. Its layered antiferromagnetic order was predicted to enable even-odd layer number dependent topological states. Furthermore, it becomes a Chern insulator when all spins are aligned by an applied magnetic field. However, the evolution of the bulk electronic structure as the magnetic state is continuously tuned and its dependence on layer number remains unexplored. Here, employing multimodal probes, we establish one-to-one correspondence between bulk electronic structure, magnetic state, topological order, and layer thickness in atomically thin MnBi2Te4 devices. As the magnetic state is tuned through the canted magnetic phase, we observe a band crossing, i.e., the closing and reopening of the bulk band gap, corresponding to the concurrent topological phase transition in both even- and odd-layer-number devices. Our findings shed new light on the interplay between band topology and magnetic order in this newly discovered topological magnet.

Polarization of Tumor-Associated Macrophages by Nanoparticle-Loaded Escherichia coli Combined with Immunogenic Cell Death for Cancer Immunotherapy.

Abstract: The tumor immunosuppressive microenvironment greatly limits the efficacy of immunotherapy. Tumor-associated macrophages (TAMs) are the most abundant immunosuppressive cells in the tumor microenvironment, which can inhibit the tumor after converting it to an M1-like phenotype. In addition, immunogenic cell death (ICD) can increase the amount of T lymphocytes in tumors, activating antineoplastic immunity. Herein, tumor-associated macrophage polarization therapy supplemented with PLGA-DOX (PDOX)-induced ICD is developed for cancer treatment. The nanoparticles/bacteria complex (Ec-PR848) is fabricated for tumor targeting and TAM polarization, and PLGA-R848 (PR848) are attached to the surface of Escherichia coli (E. coli) MG1655 via electrostatic absorption. The toll-like receptor 7/8 (TLR7/8) agonist resiquimod (R848) and E. coli can greatly polarize M2 macrophages to M1 macrophages, while PDOX-induced ICD can also impair the immunosuppression of the tumor microenvironment. This strategy shows that tumor-associated macrophage polarization therapy combined with ICD induced by low-dose chemotherapeutic drugs can commendably enhance the efficacy of immunotherapy.

Rapid SARS-CoV-2 Spike Protein Detection by Carbon Nanotube-Based Near-Infrared Nanosensors.

Abstract: To effectively track and eliminate COVID-19, it is critical to develop tools for rapid and accessible diagnosis of actively infected individuals. Here, we introduce a single-walled carbon nanotube (SWCNT)-based optical sensing approach toward this end. We construct a nanosensor based on SWCNTs noncovalently functionalized with ACE2, a host protein with high binding affinity for the SARS-CoV-2 spike protein. The presence of the SARS-CoV-2 spike protein elicits a robust, 2-fold nanosensor fluorescence increase within 90 min of spike protein exposure. We characterize the nanosensor stability and sensing mechanism and passivate the nanosensor to preserve sensing response in saliva and viral transport medium. We further demonstrate that these ACE2-SWCNT nanosensors retain sensing capacity in a surface-immobilized format, exhibiting a 73% fluorescence turn-on response within 5 s of exposure to 35 mg/L SARS-CoV-2 virus-like particles. Our data demonstrate that ACE2-SWCNT nanosensors can be developed into an optical tool for rapid SARS-CoV-2 detection.

Flexible Sulfide Electrolyte Thin Membrane with Ultrahigh Ionic Conductivity for All-Solid-State Lithium Batteries.

Abstract: All-solid-state lithium batteries (ASSLBs) employing Li-metal anode, sulfide solid electrolyte (SE) can deliver high energy density with high safety. The thick SE separator and its low ionic conductivity are two major challenges. Herein, a 30 μm sulfide SE membrane with ultrahigh room temperature conductivity of 8.4 mS cm-1 is realized by mechanized manufacturing technologies using highly conductive Li5.4PS4.4Cl1.6 SE powder. Moreover, a 400 nm magnetron sputtered Al2O3 interlayer is introduced into the SE/Li interface to improve the anodic stability, which suppresses the short circuit in Li/Li symmetric cells. Combining these merits, ASSLBs with LiNi0.5Co0.2Mn0.3O2 as the cathode exhibit a stable cyclic performance, delivering a discharge specific capacity of 135.3 mAh g-1 (1.4 mAh cm-2) with a retention of 80.2% after 150 cycles and an average Coulombic efficiency over 99.5%. The high ionic conductivity SE membrane and interface design principle show promising feasible strategies for practical high performance ASSLBs.

An Anode-Free Zn-MnO2 Battery.

Abstract: Aqueous Zn-based batteries are attractive because of the low cost and high theoretical capacity of the Zn metal anode. However, the Zn-based batteries developed so far utilize an excess amount of Zn (i.e., thick Zn metal anode), which decreases the energy density of the whole battery. Herein, we demonstrate an anode-free design (i.e., zero-excess Zn), which is enabled by employing a nanocarbon nucleation layer. Electrochemical studies show that this design allows for uniform Zn electrodeposition with high efficiency and stability over a range of current densities and plating capacities. Using this anode-free configuration, we showcase a Zn-MnO2 battery prototype, showing 68.2% capacity retention after 80 cycles. Our anode-free design opens a new direction for implementing aqueous Zn-based batteries in energy storage systems.

Light-Activated Hypoxia-Sensitive Covalent Organic Framework for Tandem-Responsive Drug Delivery.

Abstract: Covalent organic frameworks (COFs) have received much attention in the biomedical area. However, little has been reported about stimuli-responsive COF for drug delivery. Herein, we synthesized a hypoxia-responsive azo bond-containing COF with nanoscale size and immobilized both photosensitizers chlorin e6 (Ce6) and hypoxia-activated drug tirapazamine (TPZ) into the COFs. When such a COF entered the hypoxic environment and tumor, the COF structure was ruptured and loaded drugs were released from the COF. Together, upon near-infrared (NIR) light irradiation, Ce6 consumed oxygen to produce cytotoxic reactive oxygen species, leading to elevated hypoxia. Such two-step hypoxia stimuli successively induced the deintegration of COF, drug release and activation of TPZ. This promoted the TPZ to generate massive biotoxic oxyradical. In vitro and in vivo evaluation indicated that this two-step hypoxia-activated COF drug delivery system could kill cancer cells and inhibit the growth of tumors effectively.

Lewis Acid Site-Promoted Single-Atomic Cu Catalyzes Electrochemical CO2 Methanation

Abstract: Developing an efficient catalyst for the electrocatalytic CO2 reduction reaction (CO2RR) is highly desired because of environmental and energy issues. Herein, we report a single-atomic-site Cu catalyst supported by a Lewis acid for electrocatalytic CO2 reduction to CH4. Theoretical calculations suggested that Lewis acid sites in metal oxides (e.g., Al2O3, Cr2O3) can regulate the electronic structure of Cu atoms by optimizing intermediate absorption to promote CO2 methanation. Based on these theoretical results, ultrathin porous Al2O3 with enriched Lewis acid sites was explored as an anchor for Cu single atoms; this modification achieved a faradaic efficiency (FE) of 62% at -1.2 V (vs RHE) with a corresponding current density of 153.0 mA cm-2 for CH4 formation. This work demonstrates an effective strategy for tailoring the electronic structure of Cu single atoms for the highly efficient reduction of CO2 into CH4.

Pt/AlGaN Nanoarchitecture: Toward High Responsivity, Self-Powered Ultraviolet-Sensitive Photodetection

Abstract: Energy-saving photodetectors are the key components in future photonic systems. Particularly, self-powered photoelectrochemical-type photodetectors (PEC-PDs), which depart completely from the classical solid-state junction device, have lately intrigued intensive interest to meet next-generation power-independent and environment-sensitive photodetection. Herein, we construct, for the first time, solar-blind PEC PDs based on self-assembled AlGaN nanostructures on silicon. Importantly, with the proper surface platinum (Pt) decoration, a significant boost of photon responsivity by more than an order of magnitude was achieved in the newly built Pt/AlGaN nanoarchitectures, demonstrating strikingly high responsivity of 45 mA/W and record fast response/recovery time of 47/20 ms without external power source. Such high solar-blind photodetection originates from the unparalleled material quality, fast interfacial kinetics, as well as high carrier separation efficiency which suggests that embracement of defect-free wide-bandgap semiconductor nanostructures with appropriate surface decoration offers an unprecedented opportunity for designing future energy-efficient and large-scale optoelectronic systems on a silicon platform.

Quo Vadis, Metasurfaces?

Abstract: The full manipulation of intrinsic properties of electromagnetic waves has become the central target in various modern optical technologies. Optical metasurfaces have been suggested for a complete control of light-matter interaction with subwavelength structures, and they have been explored widely in the past decade for creating next-generation multifunctional flat-optics devices. The current studies of metasurfaces have reached a mature stage where common materials, basic optical physics, and conventional engineering tools have been explored extensively for various applications such as light bending, metalenses, metaholograms, and many others. A natural question is where the future research on metasurfaces will be going: Quo vadis, metasurfaces? In this Mini Review, we provide perspectives on the future developments of optical metasurfaces. Specifically, we highlight recent progresses on hybrid metasurfaces employing low-dimensional materials and discuss biomedical, computational, and quantum applications of metasurfaces, followed by discussions of challenges and foreseeing the future of metasurface physics and engineering.

Droplet Cas12a Assay Enables DNA Quantification from Unamplified Samples at the Single-Molecule Level.

Abstract: DNA quantification is important for biomedical research, but the routinely used techniques rely on nucleic acid amplification which have inherent issues like cross-contamination risk and quantification bias. Here, we report a CRISPR-Cas12a-based molecular diagnostic technique for amplification-free and absolute quantification of DNA at the single-molecule level. To achieve this, we first screened out the optimal reaction parameters for high-efficient Cas12a assay, yielding over 50-fold improvement in sensitivity compared with the reported Cas12a assays. We further leveraged the microdroplet-enabled confinement effect to perform an ultralocalized droplet Cas12a assay, obtaining excellent specificity and single-molecule sensitivity. Moreover, we demonstrated its versatility and quantification capability by direct counting of diverse virus's DNAs (African swine fever virus, Epstein-Barr virus, and Hepatitis B virus) from clinical serum samples with a wide range of viral titers. Given the flexible programmability of crRNA, we envision this amplification-free technique as a versatile and quantitative platform for molecular diagnosis.

Dynamic Hybrid Metasurfaces.

Abstract: Efficient hybrid plasmonic-photonic metasurfaces that simultaneously take advantage of the potential of both pure metallic and all-dielectric nanoantennas are identified as an emerging technology in flat optics. Nevertheless, postfabrication tunable hybrid metasurfaces are still elusive. Here, we present a reconfigurable hybrid metasurface platform by incorporating the phase-change material Ge2Sb2Te5 (GST) into metal-dielectric meta-atoms for active and nonvolatile tuning of properties of light. We systematically design a reduced-dimension meta-atom, which selectively controls the hybrid plasmonic-photonic resonances of the metasurface via the dynamic change of optical constants of GST without compromising the scattering efficiency. As a proof-of-concept, we experimentally demonstrate two tunable metasurfaces that control the amplitude (with relative modulation depth as high as ≈80%) or phase (with tunability >230°) of incident light promising for high-contrast optical switching and efficient anomalous to specular beam deflection, respectively. Our findings further substantiate dynamic hybrid metasurfaces as compelling candidates for next-generation reprogrammable meta-optics.

Ultrastable FeCo Bifunctional Electrocatalyst on Se-Doped CNTs for Liquid and Flexible All-Solid-State Rechargeable Zn-Air Batteries.

Abstract: The rechargeable Zn-air batteries as an environmentally friendly sustainable energy technology have been extensively studied. However, it is still a challenge to develop non-noble metal bifunctional catalysts with high oxygen reduction as well as oxygen evolution reaction (ORR and OER) activity and superior durability, which limit the large-scale application of rechargeable Zn-air batteries. Herein, we synthesized an ultrastable FeCo bifunctional oxygen electrocatalyst on Se-doped CNTs (FeCo/Se-CNT) via a gravity guided chemical vapor deposition (CVD) strategy. The catalyst exhibits excellent ORR (E1/2 = 0.9 V) and OER (overpotential at 10 mA cm-2 = 340 mV) properties simultaneously, surpassing commercial Pt/C and RuO2/C catalysts. More importantly, the catalyst shows an unordinary stability, that is, is no obvious decrease after 30K cycles accelerated durability test for ORR and OER processes. The small potential gap (0.75 V) represents superior bifunctional ORR and OER activities of the FeCo/Se-CNT catalyst. The FeCo/Se-CNT catalyst possesses outstanding electrochemical performance for the rechargeable liquid and flexible all-solid-state Zn-air batteries, for example, a high open circuit voltage (OCV) and peak power density of 1.543 and 1.405 V and 173.4 and 37.5 mW cm-2, respectively.

Printing Porous Carbon Aerogels for Low Temperature Supercapacitors.

Abstract: Maintaining fast charging capability at low temperatures represents a significant challenge for supercapacitors. The performance of conventional porous carbon electrodes often deteriorates quickly ...

Outdoor Personal Thermal Management with Simultaneous Electricity Generation.

Abstract: Outdoor personal thermal comfort is of substantial significance to ameliorate the health conditions of pedestrian and outdoor laborer. However, the uncontrollable sunlight, substantial radiative loss, and intense temperature fluctuations in the outdoor environment present majestic challenges to outdoor personal thermal management. Here, we report an eco-friendly passive nanostructured textile which harvests energy from the sun and the outer space for optional localized heating and cooling. Compared to conventional heating/cooling textiles like black/white cotton, its heating/cooling mode enables a skin simulator temperature increase/decrease of 8.1 °C/6 °C, respectively, under sunlight exposure. Meanwhile, the temperature gradient created between the textile and human skin allows a continuous electricity generation with thermoelectric modules. Owing to the exceptional outdoor thermoregulation ability, this Janus textile is promising to help maintain a comfortable microclimate for individuals in outdoor environment and provide a platform for pervasive power generation.

A Biomimetic Drug Delivery System by Integrating Grapefruit Extracellular Vesicles and Doxorubicin-Loaded Heparin-Based Nanoparticles for Glioma Therapy.

Abstract: Existing nanoparticle-mediated drug delivery systems for glioma systemic chemotherapy remain a great challenge due to poor delivery efficiency resulting from the blood brain barrier/blood-(brain tumor) barrier (BBB/BBTB) and insufficient tumor penetration. Here, we demonstrate a distinct design by patching doxorubicin-loaded heparin-based nanoparticles (DNs) onto the surface of natural grapefruit extracellular vesicles (EVs), to fabricate biomimetic EV-DNs, achieving efficient drug delivery and thus significantly enhancing antiglioma efficacy. The patching strategy allows the unprecedented 4-fold drug loading capacity compared to traditional encapsulation for EVs. The biomimetic EV-DNs are enabled to bypass BBB/BBTB and penetrate into glioma tissues by receptor-mediated transcytosis and membrane fusion, greatly promoting cellular internalization and antiproliferation ability as well as extending circulation time. We demonstrate that a high-abundance accumulation of EV-DNs can be detected at glioma tissues, enabling the maximal brain tumor uptake of EV-DNs and great antiglioma efficacy in vivo.

Toward Full-Color Electroluminescent Quantum Dot Displays.

Abstract: Colloidal quantum dots (QDs) exhibit unique characteristics such as facile color tunability, pure color emission with extremely narrow bandwidths, high luminescence efficiency, and high photostability. In addition, quantum dot light-emitting diodes (QLEDs) feature bright electroluminescence, low turn-on voltage, and ultrathin form factor, making them a promising candidate for next-generation displays. To achieve the overarching goal of the full-color display based on the electroluminescence of QDs, however it is essential to enhance the performance of QLEDs further for each color (e.g., red, green, and blue; RGB) and develop novel techniques for patterning RGB QD pixels without cross-contamination. Here, we present state-of-the-art material, process, and device technologies for full-color QLED-based displays. First, we highlight recent advances in the development of efficient red-, green-, and blue-monochromatic QLEDs. In particular, we focus on the progress of heavy-metal-free QLEDs. Then, we describe patterning techniques for individual RGB QDs to fabricate pixelated displays. Finally, we briefly summarize applications of such QLEDs, presenting the possibility of full-color QLED-based displays.