Synthesis and Self-Assembly of Ultrathin Holey Graphdiyne Nanosheets for Oxygen Reduction Reaction.

Graphdiyne (GDY) is a fascinating graphene-like 2D carbon allotrope comprising sp and sp2 hybridized carbon atoms. However, GDY materials synthesized by solution-phase methods normally come as thick and porous films or amorphous powders with severely disordered stacking modes that obstruct macroscopic applications. Here, a facile and scalable synthesis of ultrathin holey graphdiyne (HGDY) nanosheets is reported via palladium/copper co-catalyzed homocoupling of 1,3,5-triethynylbenzene. The resulting freestanding 2D HGDY self-assembles into 3D foam-like networks which can in situ anchor clusters of palladium atoms on their surfaces. The Pd/HGDY hybrids exhibit high electrocatalytic activity and stability for the oxygen reduction reaction which outperforms that of Pt/C benchmark. Based on the ultrathin graphene-like sheets and their unique 3D interconnected macrostructures, Pd/HGDY holds great promise for practical electrochemical catalysis and energy-related applications.

Pomegranate-like silicon-based anodes self-assembled by hollow-structured Si/void@C nanoparticles for Li-ion batteries with high performances.

Silicon is considered as one of the most promising alternatives to the graphite anode for lithium-ion batteries due to its high theoretical capacity (4200 mAh g-1). However, its fragile solid electrolyte interphase cannot tolerate the large volume changes of bare silicon induced by the lithium insertion and extraction, resulting in low Coulombic efficiency. In previous reports, a yolk-shell design, such as Si@void@C, in which the well-defined space allows the silicon particles to expand freely without breaking the outer carbon shells, can effectively improve the Columbic efficiency. Here, we design a pomegranate-like silicon-based anodes self-assembled by the hollow-structured Si/void@C nanoparticles, in which silicon and some voids are together sealed in the outer carbon shells, by the magnesiothermic reduction of the colloidal SiO2@PEI nanospheres prepared by the hydrolysis of the tetraethoxysilane under the catalytic effect of polyetherimide (PEI). Due to the tolerance of the presealed void in the carbon shells of the primary hollow-structured Si/void@C nanoparticles, the prepared pomegranate-like silicon-based anodes deliver a high reversible capacity of 1615 mAh g-1 at 0.1 C and long cycle life of 73.5% capacity retention at 2 C after 500 cycles, as well as high Coulombic efficiency of 99%.

Fe3O4@Pt nanoparticles to enable combinational electrodynamic/chemodynamic therapy.

Electrodynamic therapy (EDT) has recently emerged as a potential external field responsive approach for tumor treatment. While it presents a number of clear superiorities, EDT inherits the intrinsic challenges of current reactive oxygen species (ROS) based therapeutic treatments owing to the complex tumor microenvironment, including glutathione (GSH) overexpression, acidity and others. Herein for the first time, iron oxide nanoparticles are decorated using platinum nanocrystals (Fe3O4@Pt NPs) to integrate the current EDT with chemodynamic phenomenon and GSH depletion. Fe3O4@Pt NPs can effectively induce ROS generation based on the catalytic reaction on the surface of Pt nanoparticles triggered by electric field (E), and meanwhile it may catalyze intracellular H2O2 into ROS via Fenton reaction. In addition, Fe3+ ions released from Fe3O4@Pt NPs under the acidic condition in tumor cells consume GSH in a rapid fashion, inhibiting ROS clearance to enhance its antitumor efficacy. As a result, considerable in vitro and in vivo tumor inhibition phenomena are observed. This study has demonstrated an alternative concept of combinational therapeutic modality with superior efficacy.

Catalytic core-shell nanoparticles with self-supplied calcium and H2O2 to enable combinational tumor inhibition.

Nanoparticles, presenting catalytic activity to induce intracellular oxidative species, have been extensively explored for tumor treatment, but suffer daunting challenges in the limited intracellular H2O2 and thus suppressed therapeutic efficacy. Here in this study, a type of composite nanoparticles, consisting CaO2 core and Co-ferrocene shell, is designed and synthesized for combinational tumor treatment. The findings indicate that CaO2 core can be hydrolyzed to produce large amounts of H2O2 and calcium ions at the acidic tumor sites. Meanwhile, Co-ferrocene shell acts as an excellent Fenton catalyst, inducing considerable ROS generation following its reaction with H2O2. Excessive cellular oxidative stress triggers agitated calcium accumulation in addition to the calcium ions released from the particles. The combined effect of intracellular ROS and calcium overload causes significant tumor inhibition both in vitro and in vivo.

α-Fe2O3@Pt heterostructure particles to enable sonodynamic therapy with self-supplied O2 and imaging-guidance.

Sonodynamic therapy (SDT), presenting spatial and temporal control of ROS generation triggered by ultrasound field, has attracted considerable attention in tumor treatment. However, its therapeutic efficacy is severely hindered by the intrinsic hypoxia of solid tumor and the lack of smart design in material band structure. Here in study, fine α-Fe2O3 nanoparticles armored with Pt nanocrystals (α-Fe2O3@Pt) was investigated as an alternative SDT agent with ingenious bandgap and structural design. The Schottky barrier, due to its unique heterostructure, suppresses the recombination of sono-induced electrons and holes, enabling superior ROS generation. More importantly, the composite nanoparticles may effectively trigger a reoxygenation phenomenon to supply sufficient content of oxygen, favoring the ROS induction under the hypoxic condition and its extra role played for ultrasound imaging. In consequence, α-Fe2O3@Pt appears to enable effective tumor inhibition with imaging guidance, both in vitro and in vivo. This study has therefore demonstrated a highly potential platform for ultrasound-driven tumor theranostic, which may spark a series of further explorations in therapeutic systems with more rational material design.

Hydrothermal synthesis and photocatalytic activity of butterfly-like CaTiO3 dendrites with dominant {101} facets.

Novel butterfly-like CaTiO3 dendrites dominantly bounded by {101} facets have been synthesized via a conventional hydrothermal by using tetramethylammonium hydroxide (TMAH) as a mineralizer and surface modifier. The wing-branches of the butterfly-like CaTiO3 dendrites are composed of primary block tetragonal plates with dominant {101} facets overlapping and ranking around the stem of 〈131〉 directions in the same plane belonging to the group of {101}. With the basis of the experimental results and the lattice structure, a possible formation mechanism of the butterfly-like CaTiO3 dendrites has been discussed and proposed. The preferential adsorption of the organic [Formula: see text] ions released by the ionization of TMAH on {101} planes suppresses the deposition of the calcium titanate species on {101} planes, which induces the formation of the primary block tetragonal plates and their overlapping as well as ranking around 〈131〉 direction along {101} planes, resulting in the butterfly-like CaTiO3 dendrites bounded with {101} facets. The investigation on the degradation of rhodamine-B demonstrates, due to the dominant exposition of the {101} facets, the butterfly-like CaTiO3 dendrites display superior photocatalytic activity of more than four time that of CaTiO3 microcuboids bounded with smart {101} and (010) facets.

Asymmetric Modulation on Exchange Field in a Graphene/BiFeO3 Heterostructure by External Magnetic Field.

Graphene, having all atoms on its surface, is favorable to extend the functions by introducing the spin-orbit coupling and magnetism through proximity effect. Here, we report the tunable interfacial exchange field produced by proximity coupling in graphene/BiFeO3 heterostructures. The exchange field has a notable dependence with external magnetic field, and it is much larger under negative magnetic field than that under positive magnetic field. For negative external magnetic field, interfacial exchange coupling gives rise to evident spin splitting for N ≠ 0 Landau levels and a quantum Hall metal state for N = 0 Landau level. Our findings suggest graphene/BiFeO3 heterostructures are promising for spintronics.

Multifunctional Electrospun Nanofibers for Enhancing Localized Cancer Treatment.

Localized cancer treatment is one of the most effective strategies in clinical destruction of solid tumors at early stages as it can minimize the side effects of cancer therapeutics. Electrospun nanofibers have been demonstrated as a promising implantable platform in localized cancer treatment, enabling the on-site delivery of therapeutic components and minimizing side effects to normal tissues. This Review discusses the recent cutting-edge research with regard to electrospun nanofibers used for various therapeutic approaches, including gene therapy, chemotherapy, photodynamic therapy, thermal therapy, and combination therapy, in enhancing localized cancer treatment. Furthermore, it extensively analyzes the current challenges and potential breakthroughs in utilizing this novel platform for clinical transition in localized cancer treatment.

Phase separation strategy to facilely form fluorescent [Ag2]2+/[Agm]n+ quantum clusters in boro-alumino-silicate multiphase glasses.

By adjusting the content of ZnF2-SrF2/ZnO-SrO, a series of SiO2-Al2O3-B2O3-Na2O-ZnO/ZnF2-SrO/SrF2-Ag multiphase glasses was designed and prepared via a melt-quenching method. Under a phase separation strategy, negatively charged tetrahedrons ([BO4]-, [ZnO4]2-, and [AlO4]-) can be generated to stabilize different silver species (Ag+ ions; [Ag2]2+ pairs; [Agm]n+ quantum clusters ([Agm]n+ QCs)) in B2O3-rich and ZnO-Al2O3 rich sub-phases. The B2O3-rich sub-phase has a high solubility for Ag+ ions and [Agm]n+ QCs. The fluoride-rich phase shows a good ability to extract Na+ from the B2O3-rich sub-phase, significantly affects the solubility of Ag+ in the B2O3-rich sub-phase, and eventually determines the aggregation from Ag+ ions and Ag0 atom to [Agm]n+ QCs. The ZnO-Al2O3-rich or ZnO-SiO2-rich (i.e. SiO2-rich in GZnOSrO) phase has a relatively high solubility for [Ag2]2+ pairs. The Ag+/[Ag2]2+/[Agm]n+ QC fluorescent centers were identified by spectroscopic analysis, where the fluorescence bands are located in the ultraviolet, green-white and orange spectral regions, respectively. The fluorescent quantum yield (QY) of the [Agm]n+ QCs can be improved to 55.7%, and the combination of these three luminescent centers can achieve white light emission.

Ultrathin Anatase TiO2 Nanosheets for High-Performance Photocatalytic Hydrogen Production.

An ethanol solvothermal route has been developed to prepare ultrathin anatase TiO2 nanosheets with dominant {001} facets (≈97%), a thickness of ≈2.5 nm, and a side length of ≈200 nm. The introduction of ethanol solvent significantly enhances the content of surface chemisorbed F- on the TiO2 nanosheet, which has a higher stability and further lowers the surface energy of {001} facets, giving rise to the large percentage of active {001} facets. Adopting well-defined morphology, such nanosheets loaded with 1 wt% Pt exhibit an H2 evolution rate as high as 17.86 mmol h-1 g-1 , and the corresponding apparent quantum efficiency has been determined to be 34.2%.

Constructing Implantable SrTiO3 :Yb,Ho Nanofibers for NIR-Triggered and Optically Monitored Chemotherapy.

Light-responsive and photoluminescent (PL) drug-delivery platforms have sparked fascinating advancements in personalized tumor chemotherapy due to their unique characteristics in biological imaging and manipulated release kinetics. Herein, implantable Yb3+ and Ho3+ co-doped strontium titanate (SrTiO3 :Yb,Ho) nanofibers were synthesized and decorated on the surface with polyacrylic acid (PAA) molecules. The preliminary in vitro assay confirmed that this implantable fibrous mesh presented sound cytocompatibility. The PAA surface decoration improved the loading capacity of an anticancer drug (doxorubicin (DOX)) and effectively prevented a daunting burst release in a neutral aqueous environment. Owing to the electrostatic bond between PAA and DOX molecules, low-pH microenvironments and NIR (λ=808 nm) irradiation both induced significantly accelerated DOX release and consequently enhanced the local cancer-cell-killing effect. Additionally, the ratio of green-to-red emission (I545 /I655 ) from the SrTiO3 :Yb,Ho-PAA fibers responded effectively to the DOX release progress and dosage due to a fluorescence resonance energy transfer (FRET) effect. This unique characteristic enabled optical monitoring of the delivery progress in a timely manner. These SrTiO3 :Yb,Ho-PAA nanofibers, with precise dual-triggering and optical monitoring of DOX release, are expected to serve as a new implantable drug delivery platform for personalized chemotherapy in the future.

Selective Deposition of Silver Oxide on Single-Domain Ferroelectric Nanoplates and Their Efficient Visible-Light Photoactivity.

In this work, single-crystal and single-domain PbTiO3 nanoplates are employed as substrates to prepare Ag2 O/PbTiO3 composite materials through a photodeposition method. It is revealed that silver oxide nanocrystals with an average size of 63 nm are selectively deposited on the positive polar surface of the ferroelectric substrate. The possible mechanism leading to the formation of silver oxide is that silver ions are first reduced to silver and then oxidized by oxygen generation. The composite shows an efficient photodegradation performance towards rhodamine B (RhB) and methyl orange (MO) under visible-light irradiation. Such highly efficient photoactivity can be attributed to the ferroelectric polarization effect of the substrate, which promotes the separation of photogenerated electrons and holes at the interface.

A Fibrous Localized Drug Delivery Platform with NIR-Triggered and Optically Monitored Drug Release.

Implantable localized drug delivery systems (LDDSs) with intelligent functionalities have emerged as a powerful chemotherapeutic platform in curing cancer. Developing LDDSs with rationally controlled drug release and real-time monitoring functionalities holds promise for personalized therapeutic protocols but suffers daunting challenges. To overcome such challenges, a series of porous Yb(3+)/Er(3+) codoped CaTiO3 (CTO:Yb,Er) nanofibers, with specifically designed surface functionalization, were synthesized for doxorubicin (DOX) delivery. The content of DOX released could be optically monitored by increase in the intensity ratio of green to red emission (I550/I660) of upconversion photoluminescent nanofibers under 980 nm near-infrared (NIR) excitation owing to the fluorescence resonance energy transfer (FRET) effect between DOX molecules and the nanofibers. More importantly, the 808 nm NIR irradiation enabled markedly accelerated DOX release, confirming representative NIR-triggered drug release properties. In consequence, such CTO:Yb,Er nanofibers presented significantly enhanced in vitro anticancer efficacy under NIR irradiation. This study has thus inspired another promising fibrous LDDS platform with NIR-triggered and optics-monitored DOX releasing for personalized tumor chemotherapy.

Optically Monitoring Mineralization and Demineralization on Photoluminescent Bioactive Nanofibers.

Bone regeneration and scaffold degradation do not usually follow the same rate, representing a daunting challenge in bone repair. Toward this end, we propose to use an external field such as light (in particular, a tissue-penetrating near-infrared light) to precisely monitor the degradation of the mineralized scaffold (demineralization) and the formation of apatite mineral (mineralization). Herein, CaTiO3:Yb(3+),Er(3+)@bioactive glass (CaTiO3:Yb(3+),Er(3+)@BG) nanofibers with upconversion (UC) photoluminescence (PL) were synthesized. Such nanofibers are biocompatible and can emit green and red light under 980 nm excitation. The UC PL intensity is quenched during the bone-like apatite formation on the surface of the nanofibers in simulated body fluid; more mineral formation on the nanofibers induces more rapid optical quenching of the UC PL. Furthermore, the quenched UC PL can recover back to its original magnitude when the apatite on the nanofibers is degraded. Our work suggests that it is possible to optically monitor the apatite mineralization and demineralization on the surface of nanofibers used in bone repair.

Strong Hall-Petch Type Behavior in the Elastic Strain Limit of Nanotwinned Gold Nanowires.

Pushing the limits of elastic deformation in nanowires subjected to stress is important for the design and performance of nanoscale devices from elastic strain engineering. Particularly, introducing nanoscale twins has proved effective in rising the tensile strength of metals. However, attaining ideal elastic strains in nanotwinned materials remains challenging, because nonuniform twin sizes locally affect the yielding behavior. Here, using in situ high-resolution transmission electron microscopy tensile testing of nanotwinned [111]-oriented gold nanowires, we report direct lattice-strain measurements that demonstrate a strong Hall-Petch type relationship in the elastic strain limit up to 5.3%, or near the ideal theoretical limit, as the twin size is decreased below 3 nm. It is found that the largest twin in nanowires with irregular twin sizes controls the slip nucleation and yielding processes in pure tension, which is in agreement with earlier atomistic simulations. Continuous hardening behavior without loss of strength or softening is observed in nanotwinned single-crystalline gold nanowires, which differs from the behaviors of bulk nanocrystalline and nanotwinned-nanocrystalline metals. These findings are of practical value for the use of nanotwinned metallic and semiconductor nanowires in strain-engineered functional microdevices.

Synthesis of CaTiO3 Nanofibers with Controllable Drug-Release Kinetics.

Calcium titanate (CaTiO3) nanofibers with controlled microstructure were fabricated by a combination of sol-gel and electrospinning approaches. The fiber morphology has been found to rely significantly on the precursor composition. Altering the volume ratio of ethanol to acetic acid from 3.5 to 1.25 enables the morphology of the CaTiO3 nanofibers to be transformed from fibers with a circular cross section to curved ribbon-like structures. Ibuprofen (IBU) was used as a model drug to investigate the drug-loading capacity and drug-release profile of the nanofibers. It was found that the BET surface area and the pore volume decrease markedly with the utilization of F127 surfactant. The nanofibers synthesized without F127 surfactant present the highest drug-loading capacity and the most sustained release kinetics. This study suggests that calcium titanate nanofibers can offer a promising platform for localized drug delivery.

Hydrothermal synthesis of single-crystalline perovskite PbTiO3 nanosheets with dominant (001) facets.

Single-crystalline tetragonal perovskite lead titanate (PbTiO3) nanosheets with dominant (001) facets have been successfully synthesized by employing layered K2Ti6O13 nanofibers as titanium sources. The as-prepared PbTiO3 nanosheets were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. In order to understand the formation mechanism of the PbTiO3 nanosheets, a series of time-dependent experiments were performed. Because of the substitution of Pb(2+) ions for K(+) ions, the TiO6 octahedral lamellas exfoliate from the layered K2Ti6O13 crystal structure. Then the exfoliated TiO6 octahedral lamellas as templates transform to lamellar PbTiO3 species by reacting with the dehydrated Pb(2+) ions. With hydrothermal treatment prolongation, the lamellar PbTiO3 species crystallize to single-crystalline PbTiO3 nanosheets. Moreover, the thickness of the synthesized single-crystalline PbTiO3 nanosheets can be tailored in the range of 10-50 nm by controlling the hydrothermal treatment time. In addition, the band gap and the optoelectronic properties of the single-crystalline PbTiO3 nanosheets are investigated by UV-vis absorption and photoluminescence.

Mineralized collagen coatings formed by electrochemical deposition.

Understanding and controlling the process of electrochemical deposition (ECD) of a mineralized collagen coating on metallic orthopedic implants is important for engineering highly bioactive coatings. In this work, the influence of different ECD parameters was investigated. The results showed that the mineralization degree of the coatings increased with deposition time, voltage potential and H2O2 addition, while chitosan addition led to weakening of mineralization, heavy mineralization resulted in a porous coating morphology. Furthermore, two typical coatings, dense and porous, were analyzed to investigate their microstructure and evaluated for their cytocompatibility; the dense coating showed better osteoblast adhesion and proliferation. Based on our understanding of how the different coating parameters influenced the coating, we proposed an ECD process in which the pH gradient near the cathode and the collagen isoelectric point were suggested to play crucial roles in controlling the mineralization and morphology of the coatings. The proposed ECD process may offer a guide for controlled deposition of a desired bioactive coating.

Exchange coupling controlled ferrite with dual magnetic resonance and broad frequency bandwidth in microwave absorption.

Ti-doped barium ferrite powders BaFe12-x Ti x O19 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by the sol-gel method. The phase structure and morphology were analyzed by x-ray diffraction (XRD) and scanning electron microscopy, respectively. The powders were also studied for their magnetic properties and microwave absorption. Results show that the Ti-doped barium ferrites (BFTO) exist in single phase and exhibit hexagonal plate-like structure. The anisotropy field Ha of the BFTO decreases almost linearly with the increase in Ti concentration, which leads to a shift of the natural resonance peak toward low frequency. Two natural resonance peaks appear, which can be assigned to the double values of the Landé factor g that are found to be ∼2.0 and ∼2.3 in the system and can be essentially attributed to the existence of Fe3+ ions and the exchange coupling effect between Fe3+ and Fe2+ ions, respectively. Such a dual resonance effect contributes a broad magnetic loss peak and thus a high attenuation constant, and leads to a dual reflection loss (RL) peak over the frequency range between 26.5 and 40 GHz. The high attenuation constants are between 350 and 500 at peak position. The optimal RL reaches around -45 dB and the practicable frequency bandwidth is beyond 11 GHz. This suggests that the BFTO powders could be used as microwave absorbing materials with extraordinary properties.

PMMA-Based Composite Gel Polymer Electrolyte with Plastic Crystal Adopted for High-Performance Solid ECDs.

A PMMA-based gel polymer electrolyte (GPE) modified by a plastic crystal succinonitrile (SN) was synthesized using a facile solvent-casting method. The effects of SN additives upon lithium-ion dissociation and ionic conductivity were investigated primarily using Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy, accompanied by other structural characterization methods. The results show that SN is distributed uniformly in the PMMA matrix with a high content and produces vast dipoles that benefit the dissociation of lithium salt. Hence, the SN-modified GPE (SN-GPE) achieves an excellent ionic conductivity of 2.02 mS·cm-1 and good mechanical properties. The quasi-solid-state ECD fabricated using the SN-GPE exhibits stable cyclability and excellent electrochromic performance, in which the bleaching/coloration response time is 10 s/30 s. These results add significant insight into understanding the inter- and intra-molecular interaction in SN-GPEs and provide a type of practicable high-performance GPE material for solid electrochromic devices.