Simultaneously Engineering Oxygen Defects and Heterojunction into Ho-Doped ZnO Nanoflowers for Enhancing n-Propanol Gas Detection.

Lung cancer poses a serious threat to people's lives and health due to its high incidence rate and high mortality rate, making it necessary to effectively conduct early screening. As an important biomarker for lung cancer, the detection of n-propanol gas suffers from a low response value and a high detection limit. In this paper, flower-like Ho-doped ZnO was fabricated by the coprecipitation method for n-propanol detection at subppm concentrations. The gas sensor based on the 3% Ho-doped ZnO showed selectivity to n-propanol gas. Its response value to 100 ppm n-propanol was 341 at 140 °C, and its limit of detection (LOD) was about 25.6 ppb, which is lower than that of n-propanol in the breath of a healthy person (150 ppb). The calculation results show that the adsorption of n-propanol on a Ho-doped ZnO surface releases more energy than isopropanol, ethanol, formaldehyde, acetone, and ammonia. The enhanced gas-sensing properties of the Ho-doped ZnO material can be attributed to the fact that the Ho-doping distorts the crystal lattice of the ZnO, increases the specific surface area, and generates a large amount of oxygen defects. In addition, the doped Ho partially forms a Ho2O3/ZnO heterojunction in the material and improves the gas-sensing properties. The 3% Ho-doped ZnO material is expected to be a promising candidate for the trace detection of n-propanol gas.

Hollow Starlike Ag/CoMo-LDH Heterojunction with a Tunable d-Band Center for Boosting Oxygen Evolution Reaction Electrocatalysis.

It is a challenging task to utilize efficient electrocatalytic metal hydroxide-based materials for the oxygen evolution reaction (OER) in order to produce clean hydrogen energy through water splitting, primarily due to the restricted availability of active sites and the undesirably high adsorption energies of oxygenated species. To address these challenges simultaneously, we intentionally engineer a hollow star-shaped Ag/CoMo-LDH heterostructure as a highly efficient electrocatalytic system. This design incorporates a considerable number of heterointerfaces between evenly dispersed Ag nanoparticles and CoMo-LDH nanosheets. The heterojunction materials have been prepared using self-assembly, in situ transformation, and spontaneous redox processes. The nanosheet-integrated hollow architecture can prevent active entities from agglomeration and facilitate mass transportation, enabling the constant exposure of active sites. Specifically, the powerful electronic interaction within the heterojunction can successfully regulate the Co3+/Co2+ ratio and the d-band center, resulting in rational optimization of the adsorption and desorption of the intermediates on the site. Benefiting from its well-defined multifunctional structures, the Ag0.4/CoMo-LDH with optimal Ag loading exhibits impressive OER activity, the overpotential being 290 mV to reach a 10 mA cm-2 current density. The present study sheds some new insights into the electron structure modulation of hollow heterostructures toward rationally designing electrocatalytic materials for the OER.

Engineering Interfacial Built-in Electric Field in Polymetallic Phosphide Heterostructures for Superior Supercapacitors and Electrocatalytic Hydrogen Evolution.

Herein, a patterned rod-like CoP@NiCoP core-shell heterostructure is designed to consist of CoP nanowires cross-linked with NiCoP nanosheets in tight strings. The interfacial interaction within the heterojunction between the two components generates a built-in electric field that adjusts the interfacial charge state and create more active sites, accelerating the charge transfer and improving supercapacitor and electrocatalytic performance. The unique core-shell structure suppresses the volume expansion during charging and discharging, achieving excellent stability. As a result, CoP@NiCoP exhibits a high specific capacitance of 2.9 F cm-2 at a current density of 3 mA cm-2 and a high ion diffusion rate (Dion is 2.95 × 10-14  cm2  s-1 ) during charging/discharging. The assembled asymmetric supercapacitor CoP@NiCoP//AC exhibits a high energy density of 42.2 Wh kg-1 at a power density of 126.5 W kg-1 and excellent stability with a capacitance retention rate of 83.8% after 10 000 cycles. Furthermore, the modulated effect induced by the interfacial interaction also endows the self-supported electrode with excellent electrocatalytic HER performance with an overpotential of 71 mV at 10 mA cm-2 . This research may provide a new perspective on the generation of built-in electric field through the rational design of heterogeneous structures for improving the electrochemical and electrocatalytical performance.

Heterostructure Interface Engineering in CoP/FeP/CeOx with a Tailored d-Band Center for Promising Overall Water Splitting Electrocatalysis.

Accomplishing a green hydrogen economy in reality through water spitting ultimately relies upon earth-abundant efficient electrocatalysts that can simultaneously accelerate the oxygen and hydrogen evolution reactions (OER and HER). The perspective of electronic structure modulation via interface engineering is of great significance to optimize electrocatalytic output but remains a tremendous challenge. Herein, an efficient tactic has been explored to prepare nanosheet-assembly tumbleweed-like CoFeCe-containing precursors with time-/energy-saving and easy-operating features. Subsequently, the final metal phosphide materials containing multiple interfaces, denoted CoP/FeP/CeOx, have been synthesized via the phosphorization process. Through the optimization of the Co/Fe ratio and the content of the rare-earth Ce element, the electrocatalytic activity has been regulated. As a result, bifunctional Co3Fe/Ce0.025 reaches the top of the volcano for both OER and HER simultaneously, with the smallest overpotentials of 285 mV (OER) and 178 mV (HER) at 10 mA cm-2 current density in an alkaline environment. Multicomponent heterostructure interface engineering would lead to more exposed active sites, feasible charge transport, and strong interfacial electronic interaction. More importantly, the appropriate Co/Fe ratio and Ce content can synergistically tailor the d-band center with a downshift to enhance the per-site intrinsic activity. This work would provide valuable insights to regulate the electronic structure of superior electrocatalysts toward water splitting by constructing rare-earth compounds containing multiple heterointerfaces.

Nano bowl-like cobalt-cobalt molybdenum carbide coated by N,P co-doped carbon as an advanced bifunctional oxygen electrocatalyst for rechargeable Zn-air batteries.

Nano bowl-like Co-Co6Mo6C2 coated by N,P co-doped carbon (Co-Co6Mo6C2@NPC) is reported as an electrocatalyst for Zn-air batteries. Co-Co6Mo6C2@NPC only needs an overpotential of 210 mV at 10 mA cm-2 for the OER, and the half-wave potential for the ORR is 0.81 V. In addition, the Co-Co6Mo6C2@NPC based battery shows a large open-circuit voltage of 1.335 V and a maximum power density of 160.5 mW cm-2, as well as good stability. The improved catalytic performance can be ascribed to the co-existence of Co6Mo6C2 and Co species to improve the intrinsic catalytic activity, and the bowl-like nanostructure to facilitate the mass transfer.

Boosting Electrocatalytic Ammonia Synthesis of Bio-Inspired Porous Mo-Doped Hematite via Nitrogen Activation.

Electrochemical N2 reduction reaction (NRR) emerges as a highly attractive alternative to the Haber-Bosch process for producing ammonia (NH3) under ambient circumstances. Currently, this technology still faces tremendous challenges due to the low ammonia production rate and low Faradaic efficiency, urgently prompting researchers to explore highly efficient electrocatalysts. Inspired by the Fe-Mo cofactor in nitrogenase, we report Mo-doped hematite (Fe2O3) porous nanospheres containing Fe-O-Mo subunits for enhanced activity and selectivity in the electrochemical reduction from N2 to NH3. Mo-doping induces the morphology change from a solid sphere to a porous sphere and enriches lattice defects, creating more active sites. It also regulates the electronic structures of Fe2O3 to accelerate charge transfer and enhance the intrinsic activity. As a consequence, Mo-doped Fe2O3 achieves effective N2 fixation with a high ammonia production rate of 21.3 ± 1.1 µg h-1 mgcat.-1 as well as a prominent Faradaic efficiency (FE) of 11.2 ± 0.6%, superior to the undoped Fe2O3 and other iron oxide catalysts. Density functional theory (DFT) calculations further unravel that the Mo-doping in Fe2O3 (110) narrows the band gap, promotes the N2 activation on the Mo site with an elongated N≡N bond length of 1.132 Å in the end-on configuration, and optimizes an associative distal pathway with a decreased energy barrier. Our results may pave the way toward enhancing the electrocatalytic NRR performance of iron-based materials by atomic-scale heteroatom doping.

Coupling Plant Polyphenol Coordination Assembly with Co(OH)2 to Enhance Electrocatalytic Performance towards Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) is kinetically sluggish due to the limitation of the four-electron transfer pathway, so it is imperative to explore advanced catalysts with a superior structure and catalytic output under facile synthetic conditions. In the present work, an easily accessible strategy was proposed to implement the plant-polyphenol-involved coordination assembly on Co(OH)2 nanosheets. A TA-Fe (TA = tannic acid) coordination assembly growing on Co(OH)2 resulted in the heterostructure of Co(OH)2@TA-Fe as an electrocatalyst for OER. It could significantly decrease the overpotential to 297 mV at a current density of 10 mA cm-2. The heterostructure Co(OH)2@TA-Fe also possessed favorable reaction kinetics with a low Tafel slope of 64.8 mV dec-1 and facilitated a charge-transfer ability. The enhanced electrocatalytic performance was further unraveled to be related to the confined growth of the coordination assembly on Co(OH)2 to expose more active sites, the modulated surface properties and their synergistic effect. This study demonstrated a simple and feasible strategy to utilize inexpensive biomass-derived substances as novel modifiers to enhance the performance of energy-conversion electrocatalysis.

Boosting Hydrogen Evolution Electrocatalysis via Regulating the Electronic Structure in a Crystalline-Amorphous CoP/CeOx p-n Heterojunction.

The modulation of the electronic structure is the effective access to achieve highly active electrocatalysts for the hydrogen evolution reaction (HER). Transition-metal phosphide-based heterostructures are very promising in enhancing HER performance but the facile fabrication and an in-depth study of the catalytic mechanisms still remain a challenge. In this work, the catalytically inactive n-type CeOx is successfully combined with p-type CoP to form the CoP/CeOx heterojunction. The crystalline-amorphous CoP/CeOx heterojunction is fabricated by the phosphorization of predesigned Co(OH)2/CeOx via the as-developed reduction-hydrolysis strategy. The p-n CoP/CeOx heterojunction with a strong built-in potential of 1.38 V enables the regulation of the electronic structure of active CoP within the space-charge region to enhance its intrinsic activity and facilitate the electron transfer. The functional CeOx entity and the negatively charged CoP can promote the water dissociation and optimize H adsorption, synergistically boosting the electrocatalytic HER output. As expected, the heterostructured CoP/CeOx-20:1 with the optimal ratio of Co/Ce shows significantly improved HER activity and favorable kinetics (overpotential of 118 mV at a current density of 10 mA cm-2 and Tafel slope of 77.26 mV dec-1). The present study may provide new insight into the integration of crystalline and amorphous entities into the p-n heterojunction as a highly efficient electrocatalyst for energy storage and conversion.

Boosting the oxygen evolution electrocatalysis of high-entropy hydroxides by high-valence nickel species regulation.

The addition of an extra metal source induces the transformation from crystalline α-Ni(OH)2 to an amorphous NiCoFeCrMo-based high-entropy hydroxide (HEH) and maximizes the high-valence Ni3+ content in HEH. For OER electrocatalysis, the quinary HEH possesses an overpotential of 292 mV at 10 mA cm-2, a Tafel slope of 54.31 mV dec-1 and the boosted intrinsic activity, surpassing other subsystems.

Cobalt Doped in Zn-MOF-5 Nanoparticles to Regulate Tumor Microenvironment for Tumor Chemo/Chemodynamic Therapy.

Metal-organic frameworks are often used as a chemotherapeutic drug carrier due to their diverse metal sites and good acid degradation ability. Herein Co-doped Zn-MOF-5 nanoparticles with a high Co doping rate of 60% were synthesized for chemo-chemodynamic synergistic therapy of tumor. Co ions can mediate chemodynamic therapy through Fenton-like reaction and regulate the tumor microenvironment by consuming the reduced glutathione. The CoZn-MOF-5 shows high drug loading capacity with doxorubicin loading rate of 72.8%. The CoZn-MOF-5@PEG@DOX nanodrugs has a strong killing effect on 4T1 cancer cells, suggesting the chemo-chemodynamic synergistic effect on tumor therapy.

Ammonium Salts: New Synergistic Additive for Chemical Vapor Deposition Growth of MoS2.

Controllable and scalable fabrication is the precondition for realizing the large number of superior electronic and catalytic applications of MoS2. Here, we report a new type of synergistic additives, ammonium salts, for chemical vapor deposition (CVD) growth of MoS2. On the basis of the catalysis of ammonium salts, we can achieve layer and shape-controlled MoS2 domains and centimeter-scale MoS2 films. Compared to frequently used alkali metal ions as the catalysts, ammonium salts are decomposed completely at low temperature (below 513 °C), resulting in clean and nondestructive as-grown substrates. Thus, MoS2 electronic devices can be directly fabricated on them, and the redundant transfer step is no longer needed. This method can also promote the direct growth of MoS2 on the conductive substrate and boost the improvement of hydrogen evolution reaction (HER) performance. The ammonium salt-mediated CVD method will pave a new way for MoS2 toward real applications in modern electronics and catalysis.

Effect of ROS generation on highly dispersed 4-layer O-Ti7O13 nanosheets toward tumor synergistic therapy.

Ultra-thin two-dimensional nanosheets have attracted increasing attention due to their great application prospects in nanomaterial science and biomedicine. Herein, we report the preparation of exfoliated raw and oxidized 4-layer Ti7O13 (O-Ti7O13) and their ability to produce reactive oxygen species (ROS). The results show that O-Ti7O13 nanosheets can effectively produce ROS induced by X-ray irradiation. The 4-layer nanosheets can quickly load doxorubicin (DOX) within 5 min with a high loading rate to obtain a novel nanodrug system through their electrostatic adsorption capacity, and they exhibit a sustained release behavior. In this way, chemotherapy, radiation therapy and photodynamic therapy effectively combine for cancer synergistic treatment. We evaluated the cytotoxicity, cellular uptake and intracellular location of the O-Ti7O13 nanosheet-based drug delivery system in A549 lung cancer cells. Our results show that the O-Ti7O13/DOX complex is more cytotoxic to A549 cells than free DOX since a low concentration of loaded DOX (10 µg/mL) with a low dose of X-rays can cause the complete apoptosis of tumor cells. This work reveals that the therapeutic effect of DOX-loaded O-Ti7O13 nanosheets is strongly dependent on their loading mode, and the effects of chemotherapy and photodynamic therapy are enhanced under X-ray irradiation, which allows O-Ti7O13 nanosheet use as a photo-activated drug carrier. This work provides a new strategy for preparing 2D metal oxide nanosheets toward biomedical applications.

Double-shelled carbon nanocages grafted with carbon nanotubes embedding Co nanoparticles for enhanced hydrogen evolution electrocatalysis.

Herein, small Co nanoparticles (NPs) encapsulated in N-doped double-shelled carbon nanocages grafted with thin carbon nanotubes (Co@CNTs@DSCNCs) were synthesized from yolk-shell bimetallic zeolitic imidazolate framework (BMZIF). For HER electrocatalysis, they exhibit higher activity (η10 = 214 mV) and more favorable kinetics than Co@CNTs@PC (PC = porous carbon) with thick CNTs and large Co NPs derived from solid BMZIF cubes.

Surface Structure Engineering of Nanosheet-Assembled NiFe2O4 Fluffy Flowers for Gas Sensing.

In this work, we present a strategy to improve the gas-sensing performance of NiFe2O4 via a controllable annealing Ni/Fe precursor to fluffy NiFe2O4 nanosheet flowers. X-ray diffraction (XRD), a scanning electron microscope (SEM), nitrogen adsorption-desorption measurements and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure, morphology, specific surface area and surface structure. The gas-sensing performance was tested and the results demonstrate that the response was strongly influenced by the specific surface area and surface structure. The resultant NiFe2O4 nanosheet flowers with a heating rate of 8 °C min-1, which have a fluffier morphology and more oxygen vacancies in the surface, exhibited enhanced response and shortened response time toward ethanol. The easy approach facilitates the mass production of gas sensors based on bimetallic ferrites with high sensing performance via controlling the morphology and surface structure.

Synthesis of surfactant-modified ZIF-8 with controllable microstructures and their drug loading and sustained release behaviour.

Metal-organic frameworks (MOFs) as drug carriers have many advantages than traditional drug carriers and have received extensive attention from researchers. However, how to regulate the microstructure of MOFs to improve the efficiency of drug delivery and sustained release behaviour is still a big problem for the clinical application. Herein, the authors synthesise surfactant-modified ZIF-8 nanoparticles with different microstructures by using different types of surfactants to modify ZIF-8. The surfactant-modified ZIF-8 nanoparticles have the larger specific surface area and total micropore volumes than the original ZIF-8, which enables doxorubicin (DOX) to be more effectively loaded on the drug carriers and achieve controlled drug sustained release. Excellent degradation performance of ZIF-8 nanoparticles facilitates the metabolism of drug carriers. The formulation was evaluated for cytotoxicity, cellular uptake and intracellular location in the A549 human non-small-cell lung cancer cell line. ZIF-8/DOX nano drugs exhibit higher cytotoxicity towards cells in comparison with free DOX, suggesting the potential application in nano drugs to cancer chemotherapy.

SiO2-coated magnetic nano-Fe3O4 photosensitizer for synergistic tumour-targeted chemo-photothermal therapy.

In this study, we integrated chemotherapy and photothermal therapy in a magnetically targeted doxorubicin-loaded Fe3O4@SiO2 nanodrug system. Size-controllable magnetic Fe3O4@SiO2 core-shell nanoparticles were synthesized via a solvothermal method and a modified Stǒber method. A molecular anticancer drug, namely, doxorubicin, was loaded onto Fe3O4@SiO2 nanocomposites to form a magnetically targeted drug delivery system. This drug delivery system exhibits pH-sensitive effects on drug loading and release. The drug loading rate in a neutral environment is higher than that in an acidic environment; the opposite property is observed for the release rate. In addition, the magnetic Fe3O4@SiO2 nanocomposites exhibit a satisfactory photothermal effect under NIR (808 nm) irradiation. The temperature can increase to 55 °C after only 10 min of irradiation, which effectively induces apoptosis of cancer cells in vitro. The cytotoxicity and cellular uptake of Fe3O4@SiO2@DOX nanodrugs were evaluated in A549 lung cancer cells. After treatment with Fe3O4@SiO2@DOX that contains only 10 µg/mL of DOX, 82.8% of A549 lung cancer cells can be killed. Furthermore, 81.3% of A549 lung cancer cells are killed after incubation with Fe3O4@SiO2@DOX that contains only 0.5 µg/mL of DOX and 15 min of NIR irradiation, thereby suggesting an excellent synergistic chemo-photothermal effect in tumour therapy. Our results suggest a new approach for the synthesis of a multifunctional, highly targeted, size-controlled nanodrug for tumour synergistic therapy.

Direct Growth of Continuous and Uniform MoS2 Film on SiO2/Si Substrate Catalyzed by Sodium Sulfate.

Because of its unique electronic band structure, molybdenum disulfide (MoS2) has been regarded as a star semiconducting material. However, direct growth of continuous and high-quality MoS2 films on SiO2/Si substrates is still very challenging. Here, we report a facile chemical vapor deposition (CVD) method based on synergistic modulation of precursor and Na2SO4 catalysis, realizing the centimeter scale growth of a continuous MoS2 film on SiO2/Si substrates. The as-grown MoS2 film had an excellent spatial homogeneity and crystal quality, with an edge length of the composite domain as large as 632 µm. Both experimental and theoretical results proved that Na tended to bond with SiO2 substrates rather than to interfere with as-grown MoS2. Thus, they showed decent and uniform electrical performance, with electron mobilities as high as 5.9 cm2 V-1 s-1. We believe our method will pave a new way for MoS2 toward real application in modern electronics.

Soft X-ray-Enhanced Reactive Oxygen Species Generation in Mesoporous Titanium Peroxide and the Application in Tumor Synergistic Therapy.

Mesoporous titanium peroxide TiOx nanospheres with a high surface area are synthesized for the application of an advanced drug system. The mesoporous TiOx nanospheres have a high specific surface area of 681.89 m2/g and suitable pore size (∼3 nm) that can effectively upload doxorubicin (DOX) and possesses a high drug storage capacity of 146.08%. They show a distinct ability to produce reactive oxygen species (ROS) in response to X-ray irradiation, which can effectively improve the radiotherapy in tumor treatment using the lung cancer cell line. The ROS generation of TiOx is more than ten-fold higher than that of TiO2. No apparent toxicity is found for the TiOx material itself without X-ray irradiation. In vitro and in vivo experiments show that TiOx/DOX nanodrugs significantly enhance cytotoxicity in response to X-ray irradiation. CCK8 assays display that the TiOx/DOX nanodrug has higher cancer treatment efficiency in response to X-ray irradiation because of the synergistic effect of chemotherapy and generation of ROS. In the in vivo experiments using lung cancer tumor-bearing mice model, the tumor inhibition rate in the TiOx/DOX + X-ray group increased by 90.4% compared to the untreated control group, showing a good synergistic chemo-radiotherapy effect in tumor treatment.

The TiO2 topotactic transformation assisted trapping of an atomically dispersed Pt catalyst for low temperature CO oxidation.

Atomically dispersed Pt catalysts are synthesized on TiO2 with high activity and strong high temperature resistance by loading Pt in the process of converting the NH4TiOF3 precursor to TiO2 by a topotactic transformation process. The atomically dispersed Pt catalyst displayed high catalytic activity for the low temperature CO oxidation reaction.

In situ formation of defect-engineered N-doped TiO2 porous mesocrystals for enhanced photo-degradation and PEC performance.

N-Doped oxygen defective N/TiO2-x mesocrystal nanocubes were successfully prepared by a facile strategy in our system. Crystal topotactic transformation from NH4TiOF3 mesocrystals facilitated the formation of a porous structure of TiO2. Meanwhile, the introduction of N dopants and oxygen vacancies (OVs) was also achieved during this process. The as-prepared products exhibit much higher photoelectrochemical (PEC) and photocatalytic degradation performance under visible light illumination. It is suggested that the promising catalytic properties result from the synergistic effect of doping, OVs and the amazing porous mesocrystal structure of N/TiO2-x .