Nano Research

Developing stable but high active metal-nitrogen-carbon (M-N-C)-based hard carbon anode is a promising way to be the alternatives to graphene and blank hard carbon for sodium-ion batteries (SIBs), requiring the precise tailoring of the electronic structure for optimizing the Na+ intercalation behavior, yet is greatly challenging. Herein, Fe-N-C graphitic layer-encapsulating Fe3C species within hard carbon nanosheets (Fe-N-C/Fe3C@HCNs) are rationally engineered by pyrolysis of self-assembled polymer. Impressively, the Fe-N-C/Fe3C@HCNs exhibit outstanding rate capacity (242 mAh·g−1 at 2,000 mA·g−1), which is 2.1 and 4.2 times higher than that of Fe-N-C and N-doped carbon (N-C), respectively, and prolonged cycling stability (176 mAh·g−1 at 2,000 mA·g−1 after 2,000 cycles). Theoretical calculations unveil that the Fe3C species enhance the electronic transfer from Na to Fe-N-C, resulting in the charge redistribution between the interfaces of Fe3C and Fe-N-C. Thus, the optimized adsorption behavior towards Na+ reduces the thermodynamic energy barriers. The synergistic effect of Fe3C and Fe-N-C species maintains the structural integrity of electrode materials during the sodiation/desodiation process. The in-depth insight into the advanced Na+ storage mechanisms of Fe3C@Fe-N-C offers precise guidance for the rational establishment of confinement heterostructures in SIBs.

Developing highly efficient non-Pt catalysts for fuel cells and metal-air batteries is highly desirable but still challenging due to the sluggish oxygen reduction reaction (ORR). Herein, a facile and efficient strategy is demonstrated to prepare N-doped carbon encapsulated ordered Pd-Fe intermetallic (O-Pd-Fe@NC/C) nanoparticles via a one-step thermal annealing method. The obtained O-Pd-Fe@NC/C nanoparticles show enhanced ORR activity, durability and anti-poisoning capacity in both acid and alkaline medium. When O-Pd-Fe@NC/C serving as cathode catalyst for Zn-air battery, it exhibits higher voltage platform and superior cycling performance with respect to the Zn-air battery based on the mixture of Pt/C and Ir/C catalysts. The enhanced electrocatalytic performance can be ascribed to the formation of face-centered tetragonal (fct) Pd-Fe nanoparticles, the protective action of the N-doped carbon layer and the interface confinement effect between them. The in situ formed N-doped carbon shell not only restrains the Pd-Fe ordered intermetallics from aggregating effectively during the thermal annealing process, but also provides a strong anchoring effect to avoid the detachment of Pd-Fe nanoparticles from the carbon support during the potential cycling. This facile carbon encapsulation strategy may also be extended to the preparation of a wide variety of N-doped carbon encapsulated intermetallic compounds for fuel cell application.

III–V semiconductors such as GaAs are widely studied as promising candidates for high-speed integrated circuit. Despite these applications for conventional bulk structures, their fundamental physical properties in the nanoscale limit are still in scarcity, which is of great importance for the development of nanoelectronics. In this work, we demonstrate that the III–V semiconductor MX (M = Al, Ga, In; X = P, As, Sb) in its two-dimensional (2D) limit could exhibit double layer honeycomb (DLHC) configuration and distorted tetrahedral coordination, according to our first-principles calculations with HSE06 hybrid functional. It is found that surface reconstruction endows 2D III–V DLHCs with pronouncedly different electronic and magnetic properties from their bulk counterparts due to strong interlayer coupling. Mexican-hat-shape bands emerge at the top valence bands of pristine AlP, GaP, InP, AlAs, and InAs DLHCs, inducing the density of states showing a sharp van Hove singularity near the Fermi level. As a result, these DLHCs exhibit itinerant magnetism upon moderate hole doping, while the rest GaAs, AlSb, GaSb, and InSb DLHCs become magnetic under tensile strain with hole doping. With an exchange splitting of the localized pz states at the top valence bands, the hole-doped III–V DLHCs become half-metals with 100% spin-polarization. Remarkably, the InSb DLHC shows inverted band structure near the Fermi level, bringing about nontrivial topological band structures in stacked InSb DLHC due to the strong spin-orbital coupling. These III–V DLHCs expand the members of 2D material family and their exotic magnetic and topological properties may offer great potential for applications in the novel electronic and spintronic devices.

Repair is ubiquitous in biological systems, but rare in the inorganic world. We show that inorganic nanoscale systems can however possess remarkable repair and reconfiguring capabilities when subjected to extreme confinement. Confined crystallization inside single-walled carbon nanotube (SWCNT) templates is known to produce the narrowest inorganic nanowires, but little is known about the potential for repair of such nanowires once crystallized, and what can drive it. Here inorganic nanowires encapsulated within SWCNTs were seen by high-resolution transmission electron microscopy to adjust to changes in their nanotube template through atomic rearrangement at room temperature. These observations highlight nanowire repair processes, supported by theoretical modeling, that are consistent with atomic migration at fractured, ionic ends of the nanowires encouraged by long-range force fields, as well as release-blocking mechanisms where nanowire atoms bind to nanotube walls to stabilize the ruptured nanotube and allow the nanowire to reform. Such principles can inform the design of nanoscale systems with enhanced resilience.

Individual inorganic nanoparticles (NPs) have been widely used in the fields of drug delivery, cancer imaging and therapy. There are still many hurdles that limit the performance of individual NPs for these applications. The utilization of highly ordered NP ensembles opens a door to resolve these problems, as a result of their new or advanced collective properties. The assembled NPs show several advantages over individual NP-based systems, such as improved cell internalization and tumor targeting, enhanced multimodality imaging capability, superior combination therapy arising from synergistic effects, possible complete clearance from the whole body by degradation of assemblies into original small NP building blocks, and so on. In this review, we discuss the potential of utilizing assembled NP ensembles for cancer imaging and treatment by taking plasmonic vesicular assemblies of Au NPs as an example. We first summarize the recent developments in the self-assembly of plasmonic vesicular structures of NPs from amphiphilic polymer-tethered NP building blocks. We further review the utilization of plasmonic vesicles of NPs for cancer imaging (e.g. multi-photon induced luminescence, photothermal, and photoacoustic imaging), and cancer therapy (e.g., photothermal therapy, and chemotherapy). Finally, we outline current challenges and our perspectives along this line.

Pt-based magnetic nanocatalysts are one of the most suitable candidates for electrocatalytic materials due to their high electrochemistry activity and retrievability. Unfortunately, the inferior durability prevents them from being scaled-up, limiting their commercial applications. Herein, an antiferromagnetic element Mn was introduced into PtCo nanostructured alloy to synthesize uniform Mn-PtCo truncated octahedral nanoparticles (TONPs) by one-pot method. Our results show that Mn can tune the blocking temperature of Mn-PtCo TONPs due to its antiferromagnetism. At low temperatures, Mn-PtCo TONPs are ferromagnetic, and the coercivity increases gradually with increasing Mn contents. At room temperature, the Mn-PtCo TONPs display superparamagnetic behavior, which is greatly helpful for industrial recycling. Mn doping can not only modify the electronic structure of PtCo TONPs but also enhance electrocatalytic performance for methanol oxidation reaction. The maximum specific activity of Mn-PtCo-3 reaches 8.1 A·m-2, 3.6 times of commercial Pt/C (2.2 A·m-2) and 1.4 times of PtCo TONPs (5.6 A·m-2), respectively. The mass activity decreases by only 30% after 2,000 cycles, while it is 45% and 99% (nearly inactive) for PtCo TONPs and commercial Pt/C catalysts, respectively.

Hepatic carcinoma (HC) is the sixth most frequently occurring malignancies and the third leading cause of cancer death worldwide. Sepantronium bromide (YM155) is a small molecule inhibitor of survivin, which has broad-spectrum anticancer therapeutic effects in various xenograft models. However, several-day continuous infusion is required to achieve greater antitumor efficacy because of rapid elimination from the blood circulation. Herein, a SMMC-7721 cancerous cyto-membrane-cloaked drug delivery system (DDS) (named as iM7721@GQD-YM), was developed for co-encapsulation of YM155 and graphene quantum dots (GQDs). Cytomembrane coating endowed iM7721@GQD-YM with effective targeting for homologous HC cells, excellent biocompatibility and favorable immunocompatibility for in vivo application. Surface decoration of iRGD peptide further enhanced its tumor targeting activity by iRGD-integrin recognition. In addition, under the irradiation of near-infrared ray (NIR), GQDs can directly kill tumors through photothermal effect and cause cell membrane rupture, accurately releasing YM155 at tumor sites. The physicochemical properties, in vivo and ex vivo anti-tumor efficacy, and mechanisms of iM7721@GQD-YM nanoparticles (NPs) were systematically investigated in this work. The experimental results clearly indicate that the versatile biomimetic DDS holds great potential for the treatment of HC, which merits further investigation in both pre-clinical and clinical studies.

A very simple strategy for preparing hierarchical inorganic nanostructures is presented under ambient aqueous conditions. The hierarchical inorganic nanomaterials were obtained by simply adding a highly concentrated solution of one reactant to a solution of another reactant with low concentration. No surface-capping molecules or structure-directing templates were needed. The preparation of hierarchical single crystalline PbMoO4 was used as an example in order to study the effects of varying the reaction conditions and the mechanism of the process. It was found that the large concentration difference (typically in excess of 200-fold) and the concentration gradient of the reactants both play key roles in controlling the diffusion process and the morphology of the resulting nanostructures. This kinetically controlled strategy is facile and is easily adapted to prepare a variety of inorganic materials.

Insufficient angiogenesis in the chronic wound of the diabetic is one of the most important causes that making the wound unable to heal itself. In this work, a cobalt-based metal–organic framework (ZIF-67) was introduced as a carrier for loading a pro-angiogenic small molecular drug (dimethyloxalylglycine, DMOG). To achieve a long-term angiogenic therapy on the diabetic wound beds, a dual cooperative controllable release system has been designed by incorporating the drug-loaded ZIF-67 nanoparticles into the micro-patterned PLLA/Gelatin nanofibrous scaffolds. The results showed that DMOG was incorporated into ZIF-67 with a high loading ratio (359.12 mg/g), and the drug-loaded ZIF-67 nanoparticles were well embedded in the circular patterned scaffold. Notably, the DMOG as well as Co ions could continuously release from the scaffold for more than 15 days. The in vitro studies showed that the released Co ions and DMOG from the micropatterned nanofibrous scaffolds could synergistically promote the proliferation, migration and tube formation of the human umbilical vein endothelial cells (HUVECs) by inducing a hypoxia response and upregulating the expression of angiogenesis-related genes such as HIF-1α, VEGF and e-NOS. Furthermore, the in vivo results demonstrated that the composite scaffolds could significantly enhance angiogenesis, collagen deposition and eliminate inflammation in the diabetes wounds. These results indicate that the cobalt-based metal–organic framework as a dual cooperative controllable release system provides a new strategy for enhancing angiogenesis and promoting diabetic wound healing.