A Self‐Assembled Hetero‐Structured Inverse‐Spinel and Anti‐Perovskite Nanocomposite for Ultrafast Water Oxidation

Spinel and perovskite with distinctive crystal structures are two of the most popular material families in electrocatalysis, which, however, usually show poor conductivity, causing a negative effect on the charge transfer process during electrochemical reactions. Herein, a highly conductive inverse spinel (Fe₃O₄) and anti‐perovskite (Ni₃FeN) hetero‐structured nanocomposite is reported as a superior oxygen evolution electrocatalyst, which can be facilely prepared based on a one‐pot synthesis strategy. Thanks to the strong hybridization between Ni/Fe 3d and N 2p orbitals, the Ni₃FeN is easily transformed into NiFe (oxy)hydroxide as the real active species during the oxygen evolution reaction (OER) process, while the Fe₃O₄ component with low O‐p band center relative to Fermi level is structurally stable. As a result, both high surface reactivity and bulk electronic transport ability are reached. By directly growing Fe₃O₄/Ni₃FeN heterostructure on freestanding carbon fiber paper and testing based on the three‐electrode configuration, it requires only 160 mV overpotential to deliver a current density of 30 mA cm^?2 for OER. Also, negligible performance decay is observed within a prolonged test period of 100 h. This work sheds light on the rational design of novel heterostructure materials for electrocatalysis.     

Magnetically Controlled Growth‐Factor‐Immobilized Multilayer Cell Sheets for Complex Tissue Regeneration

The scaffold‐free cell‐sheet technique plays a significant role in stem‐cell‐based regeneration. Furthermore, growth factors are known to direct stem cell differentiation and enhance tissue regeneration. However, the absence of an effective means to incorporate growth factors into the cell sheets hinders further optimization of the regeneration efficiency. Here, a novel design of magnetically controlled “growth‐factor‐immobilized cell sheets” is reported. A new Fe₃O₄ magnetic nanoparticle (MNP) coated with nanoscale graphene oxide (nGO@Fe₃O₄) is developed to label stem cells and deliver growth factors. First, the nGO@Fe₃O₄ MNPs can be easily swallowed by dental‐pulp stem cells (DPSCs) and have no influence on cell viability. Thus, the MNP‐labeled cells can be organized via magnetic force to form multilayered cell sheets in different patterns. Second, compared to traditional Fe₃O₄ nanoparticles, the graphene oxide coating provides plenty of carboxyl groups to bind and deliver growth factors. Therefore, with these nGO@Fe₃O₄ MNPs, bone‐morphogenetic‐protein‐2 (BMP2) is successfully incorporated into the DPSCs sheets to induce more bone formation. Furthermore, an integrated osteochondral complex is also constructed using a combination of DPSCs/TGFβ3 and DPSCs/BMP2. All these results demonstrate that the new cell‐sheet tissue‐engineering approach exhibits promising potential for future use in regenerative medicine.     

Toxic Reactive Oxygen Species Enhanced Synergistic Combination Therapy by Self‐Assembled Metal‐Phenolic Network Nanoparticles

Engineering functional nanomaterials with high therapeutic efficacy and minimum side effects has increasingly become a promising strategy for cancer treatment. Herein, a reactive oxygen species (ROS) enhanced combination chemotherapy platform is designed via a biocompatible metal‐polyphenol networks self‐assembly process by encapsulating doxorubicin (DOX) and platinum prodrugs in nanoparticles. Both DOX and platinum drugs can activate nicotinamide adenine dinucleotide phosphate oxidases, generating superoxide radicals (O₂^??). The superoxide dismutase‐like activity of polyphenols can catalyze H₂O₂ generation from O₂^??. Finally, the highly toxic HO^? free radicals are generated by a Fenton reaction. The ROS HO^? can synergize the chemotherapy by a cascade of bioreactions. Positron emission tomography imaging of ⁸⁹Zr‐labeled as‐prepared DOX@Pt prodrug Fe³⁺ nanoparticles (DPPF NPs) shows prolonged blood circulation and high tumor accumulation. Furthermore, the DPPF NPs can effectively inhibit tumor growth and reduce the side effects of anticancer drugs. This study establishes a novel ROS promoted synergistic nanomedicine platform for cancer therapy.     

Platelet Membrane‐Camouflaged Magnetic Nanoparticles for Ferroptosis‐Enhanced Cancer Immunotherapy

Although cancer immunotherapy has emerged as a tremendously promising cancer therapy method, it remains effective only for several cancers. Photoimmunotherapy (e.g., photodynamic/photothermal therapy) could synergistically enhance the immune response of immunotherapy. However, excessively generated immunogenicity will cause serious inflammatory response syndrome. Herein, biomimetic magnetic nanoparticles, Fe₃O₄‐SAS @ PLT, are reported as a novel approach to sensitize effective ferroptosis and generate mild immunogenicity, enhancing the response rate of non‐inflamed tumors for cancer immunotherapy. Fe₃O₄‐SAS@PLT are built from sulfasalazine (SAS)‐loaded mesoporous magnetic nanoparticles (Fe₃O₄) and platelet (PLT) membrane camouflage and triggered a ferroptotic cell death via inhibiting the glutamate‐cystine antiporter system X_c^? pathway. Fe₃O₄‐SAS @ PLT‐mediated ferroptosis significantly improves the efficacy of programmed cell death 1 immune checkpoint blockade therapy and achieves a continuous tumor elimination in a mouse model of 4T1 metastatic tumors. Proteomics studies reveal that Fe₃O₄‐SAS @ PLT‐mediated ferroptosis could not only induce tumor‐specific immune response but also efficiently repolarize macrophages from immunosuppressive M2 phenotype to antitumor M1 phenotype. Therefore, the concomitant of Fe₃O₄‐SAS @ PLT‐mediated ferroptosis with immunotherapy are expected to provide great potential in the clinical treatment of tumor metastasis.     

Giant Magnetic Heat Induction of Magnesium‐Doped γ‐Fe2O3 Superparamagnetic Nanoparticles for Completely Killing Tumors

Magnetic fluid hyperthermia has been recently considered as a Renaissance of cancer treatment modality due to its remarkably low side effects and high treatment efficacy compared to conventional chemotheraphy or radiotheraphy. However, insufficient AC induction heating power at a biological safe range of AC magnetic field (H_appl·f_appl < 3.0–5.0 × 10⁹ A m^?1 s^?1), and highly required biocompatibility of superparamagnetic nanoparticle (SPNP) hyperthermia agents are still remained as critical challenges for successful clinical hyperthermia applications. Here, newly developed highly biocompatible magnesium shallow doped γ‐Fe₂O₃ (Mg_0.13‐γFe₂O₃) SPNPs with exceptionally high intrinsic loss power (ILP) in a range of 14 nH m² kg^?1, which is an ≈100 times higher than that of commercial Fe₃O₄ (Feridex, ILP = 0.15 nH m² kg^?1) at H_appl·f_appl = 1.23 × 10⁹ A m^?1 s^?1 are reported. The significantly enhanced heat induction characteristics of Mg_0.13‐γFe₂O₃ are primarily due to the dramatically enhanced out‐of‐phase magnetic susceptibility and magnetically tailored AC/DC magnetic softness resulted from the systematically controlled Mg²⁺ cations distribution and concentrations in octahedral site Fe vacancies of γ‐Fe₂O₃ instead of well‐known Fe₃O₄ SPNPs. In vitro and in vivo magnetic hyperthermia studies using Mg_0.13‐γFe₂O₃ nanofluids are conducted to estimate bioavailability and biofeasibility. Mg_0.13‐γFe₂O₃ nanofluids show promising hyperthermia effects to completely kill the tumors.     

Patterning Graphene Surfaces with Iron‐Oxide‐Embedded Mesoporous Polypyrrole and Derived N‐Doped Carbon of Tunable Pore Size

This study develops a novel strategy, based on block copolymer self‐assembly in solution, for preparing two‐dimensional (2D) graphene‐based mesoporous nanohybrids with well‐defined large pores of tunable sizes, by employing polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) spherical micelles as the pore‐creating template. The resultant 2D nanohybrids possess a sandwich‐like structure with Fe₂O₃ nanoparticle‐embedded mesoporous polypyrrole (PPy) monolayers grown on both sides of reduced graphene oxide (rGO) nanosheets (denoted as mPPy‐Fe₂O₃@rGO). Serving as supercapacitor electrode materials, the 2D ternary nanohybrids exhibit controllable capacitive performance depending on the pore size, with high capacitance (up to 1006 F/g at 1 A/g), good rate performance (750 F/g at 20 A/g) and excellent cycling stability. Furthermore, the pyrolysis of mPPy‐Fe₂O₃@rGO at 800 °C yields 2D sandwich‐like mesoporous nitrogen‐doped carbon/Fe₃O₄/rGO (mNC‐Fe₃O₄@rGO). The mNC‐Fe₃O₄@rGO nanohybrids with a mean pore size of 12 nm show excellent electrocatalytic activity as an oxygen reduction reaction (ORR) catalyst with a four‐electron transfer nature, a high half‐wave‐potential of +0.84 V and a limiting current density of 5.7 mA/cm², which are well comparable with those of the best commercial Pt/C catalyst. This study takes advantage of block copolymer self‐assembly for the synthesis of 2D multifunctional mesoporous nanohybrids, and helps to understand the control of their structures and electrochemical performance.     

Metal–Organic Gel‐Derived FexOy/Nitrogen‐Doped Carbon Films for Enhanced Lithium Storage

The development of cost‐effective and flexible electrodes is demanding in the field of energy storage. Herein, flexible Fe_xO_y/nitrogen‐doped carbon films (Fe_xO_y/NC‐MOG) are prepared by facile electrospinning of Fe‐based metal–organic gels (MOGs) followed by high‐temperature carbonization. This approach allows the even mixing of fragile coordination polymers with polyacrylonitrile into flexible films while reserving the structural characteristics of coordination polymers. After thermal treatment, Fe_xO_y/NC‐MOG films possess uniformly distributed Fe_xO_y nanoparticles and larger accessible surface areas than traditional Fe_xO_y‐NC films without MOG. Taking advantage of the unique structure, Fe_xO_y/NC‐MOG exhibits a superior rate performance (449.8 mA h g^?1 at 5000 mA g^–1) and long cycle life (629.3 mA h g^–1 after 500 cycles at 1000 mA g^–1) when used as additive‐free anodes in lithium‐ion batteries.     

S‐Doped TiSe2 Nanoplates/Fe3O4 Nanoparticles Heterostructure

2D Sulfur‐doped TiSe₂/Fe₃O₄ (named as S‐TiSe₂/Fe₃O₄) heterostructures are synthesized successfully based on a facile oil phase process. The Fe₃O₄ nanoparticles, with an average size of 8 nm, grow uniformly on the surface of S‐doped TiSe₂ (named as S‐TiSe₂) nanoplates (300 nm in diameter and 15 nm in thickness). These heterostructures combine the advantages of both S‐TiSe₂ with good electrical conductivity and Fe₃O₄ with high theoretical Li storage capacity. As demonstrated potential applications for energy storage, the S‐TiSe₂/Fe₃O₄ heterostructures possess high reversible capacities (707.4 mAh g⁻¹ at 0.1 A g⁻¹ during the 100th cycle), excellent cycling stability (432.3 mAh g⁻¹ after 200 cycles at 5 A g⁻¹), and good rate capability (e.g., 301.7 mAh g⁻¹ at 20 A g⁻¹) in lithium‐ion batteries. As for sodium‐ion batteries, the S‐TiSe₂/Fe₃O₄ heterostructures also maintain reversible capacities of 402.3 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles, and a high rate capacity of 203.3 mAh g⁻¹ at 4 A g⁻¹.     

Polyphenol‐Inspired Facile Construction of Smart Assemblies for ATP‐ and pH‐Responsive Tumor MR/Optical Imaging and Photothermal Therapy

Smart assemblies have attracted increased interest in various areas, especially in developing novel stimuli‐responsive theranostics. Herein, commercially available, natural tannic acid (TA) and iron oxide nanoparticles (Fe₃O₄ NPs) are utilized as models to construct smart magnetic assemblies based on polyphenol‐inspired NPs–phenolic self‐assembly between NPs and TA. Interestingly, the magnetic assemblies can be specially disassembled by adenosine triphosphate, which shows a stronger affinity to Fe₃O₄ NPs than that of TA and partly replaces the surface coordinated TA. The disassembly can further be facilitated by the acidic environment hence causing the remarkable change of the transverse relaxivity and potent “turn‐on” of fluorescence (FL) signals. Therefore, the assemblies for specific and sensitive tumor magnetic resonance and FL dual‐modal imaging and photothermal therapy after intravenous injection of the assemblies are successfully employed. This work not only provides understandings on the self‐assembly between NPs and polyphenols, but also will open new insights for facilely constructing versatile assemblies and extending their biomedical applications.     

Electrocatalytic N‐Doped Graphitic Nanofiber – Metal/Metal Oxide Nanoparticle Composites

Carbon‐based nanocomposites have shown promising results in replacing commercial Pt/C as high‐performance, low cost, nonprecious metal‐based oxygen reduction reaction (ORR) catalysts. Developing unique nanostructures of active components (e.g., metal oxides) and carbon materials is essential for their application in next generation electrode materials for fuel cells and metal–air batteries. Herein, a general approach for the production of 1D porous nitrogen‐doped graphitic carbon fibers embedded with active ORR components, (M/MO_x, i.e., metal or metal oxide nanoparticles) using a facile two‐step electrospinning and annealing process is reported. Metal nanoparticles/nanoclusters nucleate within the polymer nanofibers and subsequently catalyze graphitization of the surrounding polymer matrix and following oxidation, create an interconnected graphite–metal oxide framework with large pore channels, considerable active sites, and high specific surface area. The metal/metal oxide@N‐doped graphitic carbon fibers, especially Co₃O₄, exhibit comparable ORR catalytic activity but superior stability and methanol tolerance versus Pt in alkaline solutions, which can be ascribed to the synergistic chemical coupling effects between Co₃O₄ and robust 1D porous structures composed of interconnected N‐doped graphitic nanocarbon rings. This finding provides a novel insight into the design of functional electrocatalysts using electrospun carbon nanomaterials for their application in energy storage and conversion fields.     

A Magnetic‐Field Guided Interface Coassembly Approach to Magnetic Mesoporous Silica Nanochains for Osteoclast‐Targeted Inhibition and Heterogeneous Nanocatalysis

1D core–shell magnetic materials with mesopores in shell are highly desired for biocatalysis, magnetic bioseparation, and bioenrichment and biosensing because of their unique microstructure and morphology. In this study, 1D magnetic mesoporous silica nanochains (Fe₃O₄@nSiO₂@mSiO₂ nanochain, Magn‐MSNCs named as FDUcs‐17C) are facilely synthesized via a novel magnetic‐field‐guided interface coassembly approach in two steps. Fe₃O₄ particles are coated with nonporous silica in a magnetic field to form 1D Fe₃O₄@nSiO₂ nanochains. A further interface coassembly of cetyltrimethylammonium bromide and silica source in water/n‐hexane biliquid system leads to 1D Magn‐MSNCs with core–shell–shell structure, uniform diameter (≈310 nm), large and perpendicular mesopores (7.3 nm), high surface area (317 m² g^?1), and high magnetization (34.9 emu g^?1). Under a rotating magnetic field, the nanochains with loaded zoledronate (a medication for treating bone diseases) in the mesopores, show an interesting suppression effect of osteoclasts differentiation, due to their 1D nanostructure that provides a shearing force in dynamic magnetic field to induce sufficient and effective reactions in cells. Moreover, by loading Au nanoparticles in the mesopores, the 1D Fe₃O₄@nSiO₂@mSiO₂‐Au nanochains can service as a catalytically active magnetic nanostirrer for hydrogenation of 4‐nitrophenol with high catalytic performance and good magnetic recyclability.     

Enhanced Magnetism in Highly Ordered Magnetite Nanoparticle‐Filled Nanohole Arrays

A new approach to develop highly ordered magnetite (Fe₃O₄) nanoparticle‐patterned nanohole arrays with desirable magnetic properties for a variety of technological applications is presented. In this work, the sub‐100 nm nanohole arrays are successfully fabricated from a pre‐ceramic polymer mold using spin‐on nanoprinting (SNAP). These nanoholes a then filled with monodispersed, spherical Fe₃O₄ nanoparticles of about 10 nm diameter using a novel magnetic drag and drop procedure. The nanohole arrays filled with magnetic nanoparticles a imaged using magnetic force microscopy (MFM). Magnetometry and MFM measurements reveal room temperature ferromagnetism in the Fe₃O₄‐filled nanohole arrays, while the as‐synthesized Fe₃O₄ nanoparticles exhibit superparamagnetic behavior. As revealed by MFM measurements, the enhanced magnetism in the Fe₃O₄‐filled nanohole arrays originates mainly from the enhanced magnetic dipole interactions of Fe₃O₄ nanoparticles within the nanoholes and between adjacent nanoholes. Nanoparticle filled nanohole arrays can be highly beneficial in magnetic data storage and other applications such as microwave devices and biosensor arrays that require tunable and anisotropic magnetic properties.     

A Biomimetic Polymer Magnetic Nanocarrier Polarizing Tumor‐Associated Macrophages for Potentiating Immunotherapy

The progress of antitumor immunotherapy is usually limited by tumor‐associated macrophages (TAMs) that account for the highest proportion of immunosuppressive cells in the tumor microenvironment, and the TAMs can also be reversed by modulating the M2‐like phenotype. Herein, a biomimetic polymer magnetic nanocarrier is developed with selectively targeting and polarizing TAMs for potentiating immunotherapy of breast cancer. This nanocarrier PLGA‐ION‐R837 @ M (PIR @ M) is achieved, first, by the fabrication of magnetic polymer nanoparticles (NPs) encapsulating Fe₃O₄ NPs and Toll‐like receptor 7 (TLR7) agonist imiquimod (R837) and, second, by the coating of the lipopolysaccharide (LPS)‐ treated macrophage membranes on the surface of the NPs for targeting TAMs. The intracellular uptake of the PIR @ M can greatly polarize TAMs from M2 to antitumor M1 phenotype with the synergy of Fe₃O₄ NPs and R837. The relevant mechanism of the polarization is deeply studied through analyzing the mRNA expression of the signaling pathways. Different from previous reports, the polarization is ascribed to the fact that Fe₃O₄ NPs mainly activate the IRF5 signaling pathway via iron ions instead of the reactive oxygen species‐induced NF‐κB signaling pathway. The anticancer effect can be effectively enhanced through potentiating immunotherapy by the polarization of the TAMs in the combination of Fe₃O₄ NPs and R837.     

Biological Metabolism Synthesis of Metal Oxides Nanorods from Bacteria as a Biofactory toward High‐Performance Lithium‐Ion Battery Anodes

Increasing awareness toward environmental remediation and renewable energy has led to a vigorous demand for exploring a win‐win strategy to realize the eco‐efficient conversion of pollutants (“trash”) into energy‐storage nanomaterials (“treasure”). Inspired by the biological metabolism of bacteria, Acidithiobacillus ferrooxidans (A. ferrooxidans) is successfully exploited as a promising eco‐friendly sustainable biofactory for the controllable fabrication of α‐Fe₂O₃ nanorods via the oxidation of soluble ferrous irons to insoluble ferric substances (Jarosite, KFe₃(SO₄)₂(OH)₆) and a facile subsequent heat treatment. It is demonstrated that the stable solid electrolyte interphase layers and marvelous cracks in situ formed in biometabolic α‐Fe₂O₃ nanorods play important roles that not only significantly enhance the structure stability but also facilitate electron and ion transfer. Consequently, these biometabolic α‐Fe₂O₃ nanorods deliver a superior stable capacity of 673.9 mAh g^?1 at 100 mA g^?1 over 200 cycles and a remarkable multi‐rate capability that observably prevails over the commercial counterpart. It is highly expected that such biological synthesis strategies can shed new light on an emerging field of research interconnecting biotechnology, energy technology, environmental technology, and nanotechnology.     

Multifunctional Magnetic–Optical Nanoparticle Probes for Simultaneous Detection,Separation, and Thermal Ablation of Multiple Pathogens

Multifunctional nanoparticles possessing magnetization and near‐infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site‐selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe₃O₄? Au_rod? Fe₃O₄ nanodumbbells and Fe₃O₄? Au_rod necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe₃O₄? Au_rod necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.     

Atomic‐Level Fe‐N‐C Coupled with Fe3C‐Fe Nanocomposites in Carbon Matrixes as High‐Efficiency Bifunctional Oxygen Catalysts

Highly active and durable bifunctional oxygen electrocatalysts are of pivotal importance for clean and renewable energy conversion devices, but the lack of earth‐abundant electrocatalysts to improve the intrinsic sluggish kinetic process of oxygen reduction/evolution reactions (ORR/OER) is still a challenge. Fe‐N‐C catalysts with abundant natural merits are considered as promising alternatives to noble‐based catalysts, yet further improvements are urgently needed because of their poor stability and unclear catalytic mechanism. Here, an atomic‐level Fe‐N‐C electrocatalyst coupled with low crystalline Fe₃C‐Fe nanocomposite in 3D carbon matrix (Fe‐SAs/Fe₃C‐Fe@NC) is fabricated by a facile and scalable method. Versus atomically FeN_x species and crystallized Fe₃C‐Fe nanoparticles, Fe‐SAs/Fe₃C‐Fe@NC catalyst, abundant in vertical branched carbon nanotubes decorated on intertwined carbon nanofibers, exhibits high electrocatalytic activities and excellent stabilities both in ORR (E_1/2, 0.927 V) and OER (E_J=10, 1.57 V). This performance benefits from the strong synergistic effects of multicomponents and the unique structural advantages. In‐depth X‐ray absorption fine structure analysis and density functional theory calculation further demonstrate that more extra charges derived from modified Fe clusters decisively promote the ORR/OER performance for atomically FeN₄ configurations by enhanced oxygen adsorption energy. These insightful findings inspire new perspectives for the rational design and synthesis of economical–practical bifunctional oxygen electrocatalysts.     

Porous Carbon Nanofibers Encapsulated with Peapod‐Like Hematite Nanoparticles for High‐Rate and Long‐Life Battery Anodes

Fe₂O₃ is regarded as a promising anode material for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe₂O₃ anodes, leading to rapid fading of the capacity. Herein, a novel peapod‐like nanostructured material, consisting of Fe₂O₃ nanoparticles homogeneously encapsulated in the hollow interior of N‐doped porous carbon nanofibers, as a high‐performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea‐like Fe₂O₃ nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na‐ions. As a consequence, this peapod‐like structure exhibits a stable discharge capacity of 1434 mAh g^?1 (at 100 mA g^?1) and 806 mAh g^?1 (at 200 mA g^?1) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g^?1 after 1000 cycles and 396 mAh g^?1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g^?1. This study provides a promising strategy for developing long‐cycle‐life LIBs and SIBs.     

Organic Field‐Effect Transistor Memory Devices Using Discrete Ferritin Nanoparticle‐Based Gate Dielectrics

Organic field‐effect transistor (OFET) memory devices made using highly stable iron‐storage protein nanoparticle (NP) multilayers and pentacene semiconductor materials are introduced. These transistor memory devices have nonvolatile memory properties that cause reversible shifts in the threshold voltage (V_th) as a result of charge trapping and detrapping in the protein NP (i.e., the ferritin NP with a ferrihydrite phosphate core) gate dielectric layers rather than the metallic NP layers employed in conventional OFET memory devices. The protein NP‐based OFET memory devices exhibit good programmable memory properties, namely, large memory window ΔV_th (greater than 20 V), a fast switching speed (10 μs), high ON/OFF current ratio (above 10⁴), and good electrical reliability. The memory performance of the devices is significantly enhanced by molecular‐level manipulation of the protein NP layers, and various biomaterials with heme Fe^III/Fe^II redox couples similar to a ferrihydrite phosphate core are also employed as charge storage dielectrics. Furthermore, when these protein NP multilayers are deposited onto poly(ethylene naphthalate) substrates coated with an indium tin oxide gate electrode and a 50‐nm‐thick high‐k Al₂O₃ gate dielectric layer, the approach is effectively extended to flexible protein transistor memory devices that have good electrical performance within a range of low operating voltages (<10 V) and reliable mechanical bending stability.     

A New Strategy for Humidity Independent Oxide Chemiresistors: Dynamic Self‐Refreshing of In2O3 Sensing Surface Assisted by Layer‐by‐Layer Coated CeO2 Nanoclusters

The humidity dependence of the gas sensing characteristics of metal oxide semiconductors has been one of the greatest obstacles for gas sensor applications during the last five decades because ambient humidity dynamically changes with the environmental conditions. Herein, a new and novel strategy is reported to eliminate the humidity dependence of the gas sensing characteristics of oxide chemiresistors via dynamic self‐refreshing of the sensing surface affected by water vapor chemisorption. The sensor resistance and gas response of pure In₂O₃ hollow spheres significantly change and deteriorate in humid atmospheres. In contrast, the humidity dependence becomes negligible when an optimal concentration of CeO₂ nanoclusters is uniformly loaded onto In₂O₃ hollow spheres via layer‐by‐layer (LBL) assembly. Moreover, In₂O₃ sensors LBL‐coated with CeO₂ nanoclusters show fast response/recovery, low detection limit (500 ppb), and high selectivity to acetone even in highly humid conditions (relative humidity 80%). The mechanism underlying the dynamic refreshing of the In₂O₃ sensing surfaces regardless of humidity variation is investigated in relation to the role of CeO₂ and the chemical interaction among CeO₂, In₂O₃, and water vapor. This strategy can be widely used to design high performance gas sensors including disease diagnosis via breath analysis and pollutant monitoring.     

Electrostatic Self‐Assembly of Au Nanoparticles onto Thermosensitive Magnetic Core‐Shell Microgels for Thermally Tunable and Magnetically Recyclable Catalysis

A facile route to fabricate a nanocomposite of Fe₃O₄@poly[N‐isopropylacrylamide (NIPAM)‐co‐2‐(dimethylamino)ethyl methacrylate (DMAEMA)]@Au (Fe₃O₄@PND@Au) is developed for magnetically recyclable and thermally tunable catalysis. The negatively charged Au nanoparticles with an average diameter of 10 nm are homogeneously loaded onto positively charged thermoresponsive magnetic core‐shell microgels of Fe₃O₄@poly(NIPAM‐co‐DMAEMA) (Fe₃O₄@PND) through electrostatic self‐assembly. This type of attachment offers perspectives for using charged polymeric shell on a broad variety of nanoparticles to immobilize the opposite‐charged nanoparticles. The thermosensitive PND shell with swollen or collapsed properties can be as a retractable Au carrier, thereby tuning the aggregation or dispersion of Au nanoparticles, which leads to an increase or decrease of catalytic activity. Therefore, the catalytic activity of Fe₃O₄@PND@Au can be modulated by the volume transition of thermosensitive microgel shells. Importantly, the mode of tuning the aggregation or dispersion of Au nanoparticles using a thermosensitive carrier offers a novel strategy to adjust and control the catalytic activity, which is completely different with the traditional regulation mode of controlling the diffusion of reactants toward the catalytic Au core using the thermosensitive poly(N‐isopropylacrylamide) network as a nanogate. Concurrent with the thermally tunable catalysis, the magnetic susceptibility of magnetic cores enables the Fe₃O₄@PND@Au nanocomposites to be capable of serving as smart nanoreactors for thermally tunable and magnetically recyclable catalysis.