Table of contents

To meet the demands in portable electronic devices, electric vehicles and stationary energy storage, it is necessary to prepare advanced lithium ion batteries (LIBs) with high energy density and fast charge and discharge capabilities. Cathode materials, which account for 40%–50% of the cost of a whole battery, play a decisive role in cell voltage and capacity. Moreover, the performances of the cathodes are also balanced by many other aspects, including cycle life, rate capability, safety, costs, and environmental benignity. Unfortunately, none of the currently available cathode materials (e.g. LiFePO₄, LiNi_xCo_yMn_1−x−yO₂ layered oxides and Li-rich layered oxides) can get all the quests in a single cell. The electrochemical performances of a cathode are closely connected with its structural features, such as the porosities, morphologies and specifically exposed surfaces, which can be tuned by delicate designs. Here, we review our work on the rational design and delicate preparation of a series of cathode materials with controllable microstructures. We reveal the synergistic effects of both reaction and mass transfer on the formation of these meso-scale structures and the improved electrochemical performances of the cathode materials. The review will provide a scientific basis for the large-scale production of meso-scale structured cathode materials, and lay theoretical and experimental foundation for the application of cathode materials in next-generation LIBs.

Increasing the content of reactive oxygen species (ROS) with the assistance of nanoformulations in cancer cells via the Fenton reaction is considered an effective method to treat cancer. However, the efficiency of the Fenton reaction is affected by the level of H₂O₂, the selection of iron ions in different nanoformulations, etc. Herein, we use Fe^III-tannic acid (Fe^IIITA) nanocomposites as the carrier to deliver glucose oxidase (GOD) which can solve the problem of insufficient endogenous H₂O₂ by catalytically converting the glucose. In comparison with traditional Fe²⁺/Fe³⁺, Fe^IIITA nanocomposites perform higher catalytic activity in converting H₂O₂ to high toxic hydroxyl radicals (·OH) due to the TA-mediated reduction of Fe³⁺. So, the integration of GOD and TA in the construction of nanocomposites significantly enhances the efficiency of the Fenton reaction. In vitro experiments show that ·OH produced by GOD-Fe^IIITA nanocomposites can not only achieve a good anticancer effect at a low concentration but also promote degradability of the nanocomposites. When it is only 1.08 μg · ml⁻¹, the cell apoptosis rate has reached 76.91%. In vivo experiments further demonstrate that GOD-Fe^IIITA nanocomposites can significantly inhibit tumor growth. So this work lays a good foundation for Fenton reaction-based cancer treatment.

The aim of this study was to propose a new dual-modality nanoprobe for positron emission tomography/magnetic resonance imaging (PET/MRI) for the early diagnosis of breast cancer. For synthesis of the nanoprobe, polyethylene glycol-coated ultra-small superparamagnetic iron-oxide nanoparticles (USPION) armed with NODA-GA chelate and grafted with bombesin (BBN) were radiolabeled with ⁶⁸Ga. After characterization, in vitro studies to evaluate the cell binding affinity of the nanoprobe were done by performing Perl's Prussian blue cell staining and MRI imaging. Finally, for in vivo studies, magnetic resonance images were taken in SCID mice bearing breast cancer tumor pre- and post-injection, and a multimodal nanoScan PET/computed tomography was used to perform preclinical imaging of the radiolabeled nanoparticles. Afterwards, a biodistribution study was done on sacrificed mice. The results showed that the highest r₁ and r₂ values were measured for USPIONs at 20 and 60 MHz, respectively. From the in vitro studies, the optical density of the cells after incubation increased with the increase of the iron concentration and the duration of incubation. However, the T₂ values decreased when the iron concentration increased. Furthermore, from in vivo studies, the T₂ and signal intensity decreased during the elapsed time post-injection in the tumor area. In this study, the in vitro studies showed that the affinity of cancer cells to nanoprobe increases meaningfully after conjugation with BBN, and also by increasing the duration of incubation and the iron concentration. Meanwhile, the in vivo results confirmed that the blood clearance of the nanoprobe happened during the first 120 min post-injection of the radiolabeled nanoprobe and also confirmed the targeting ability of that to a gastrin-releasing peptide receptor positive tumor.

We present a plasmonic all-optical switch based on Mach–Zehnder interferometer (MZI) with local nonlinearity. The design of the miniaturized all-optical switch is possible by employing surface-plasmon polaritons (SPPs) that confine the energy of electromagnetic (EM) waves at sub-wavelength scale. The coupling between sub-wavelength plasmonic waveguides in MZI and a control beam generates 'ON' and 'OFF' states at the switch and switching between 'ON' and 'OFF' states happens when the control beam is turned on or off. The waveguides cladding in the switch structure is made of lossy media including metamaterials with positive and negative EM susceptibilities and metals; the core consists of nonlinear and dielectric media. Employing materials with negative EM susceptibilities in the switch structure facilitates the propagation of both transverse electric and transverse magnetic SPPs along the waveguides. Our all-optical switch design enables multi-frequency switching with low-intensity control field. Ascertaining the capabilities of multi-frequency plasmonic all-optical switches facilities their applications in miniaturized photonic circuits and in biosensors.

Honeycomb porous polystyrene (PS) films with an aspect ratio of pore depth to pore diameter at approximately 1.0 were fabricated using the breath figure (BF) method. Two modes of water droplet coalescence in the pore growth were observed in real-time by optical microscopy. Pore size significantly increases with the increase in humidity and the decrease in substrate temperature. The porous pattern could emerge even at room temperature under high humidity of 80%. Boiling point and solvent density significantly influence the pore distribution and pore depth. Chloroform and tetrahydrofuran achieve more uniform hexagonal patterns than benzene and dichloromethane. Subsequently, to obtain nanometer porous PS film, the fast-evaporation BF process was designed by regulating the gradient substrate temperature and evaporation time, and porous mesoscopic PS film was obtained. The minimum pore diameter and corresponding pore depth are about 120 nm and 27 nm, respectively. Finally, the fast-evaporation BF process was applied to the honeycomb film formation of photovoltaic polymer poly(3-hexylthiophene) (P3HT), and the heat-resistant polymers polysulfone (PSF) and polyimide (PI).

Mold cost and mold lifetime are essential concerns for mass production of micro/nano-patterned surfaces by nanoimprint lithography or micro/nanoinjection molding. Master molds are typically produced by subtractive processing using wafer-based clean room techniques. For imprint lithography, polymer copies of such molds can often be employed, but the durability of such molds is quite limited. The conditions of high temperature and pressure for injection molding require use of the durable masters created in stainless steel, nickel or other robust materials, but such approaches are challenged by the high cost of patterning these substrates and limited lifetime. Here, we report the fabrication of durable crystalline zirconium dioxide (ZrO₂) masters via a simple direct imprint technique. ZrO₂ nanoparticles (NPs) were formulated into an ink and imprinted on a variety of substrates using a solvent-assisted patterning technique and subsequently annealed to increase the mechanical durability of the mold. The hardness and modulus values of the ZrO₂ coatings reached 11 ± 2 GPa and 120 ± 10 GPa, respectively after annealing. The hard ZrO₂ mold was then employed for precision patterning of polymer surfaces by thermal and UV nanoimprinting lithography (NIL) techniques, and by injection molding. High fidelity pattern transfer continued throughout 115 000 injection molding cycles, there was no evidence of delamination, breakage or wear in the ZrO₂ mold. Our simple imprint patterning technique using ZrO₂ NPs inks enable us to fabricate robust molds with excellent thermal and mechanical properties as easily as imprinting simple polymer replicas. This simple and low-cost approach to mold preparation can enable a large variety of high throughput or large area nano-replication technologies.

Rotation of nano-components is necessary in nanoscale mechanical systems (NMS) to enable various functions of nanomachines, however, the actuation and modulation of nanoscale rotation have been poorly investigated up to now. In this paper, we conduct molecular dynamics simulations to study the in-plane rotation of a graphene nanoflake hinged to a graphene substrate by easily accessible nanoindentation techniques. The flake can be driven to rotate by strain gradient fields (SGFs) induced by indenting the substrate locally. The effect of flake size, indenting velocity and position on flake rotation are studied systematically. It is found that there exists a critical range of flake size which is comparable to that of SGFs. The direction of flake rotation, i.e. clockwise or counterclockwise, can be tuned effectively by indenting the substrate asymmetrically with respect to the flake. Besides, the rotation can be speeded up by simply indenting more quickly. Furthermore, the flake can be trapped in a desired region on the substrate by adopting double SGFs. The continuous rotation of the flake can be realized by intermittently indenting the substrate near the flake. These results may be useful for designing the rotation of components in NMSs and nanoscale manipulation.

Nickel compounds, especially Ni(HCO₃)₂ (here denoted as NiC), have been widely combined with other materials to obtain composites with a more favorable structure that exhibit excellent electrochemical performance as supercapacitors. Unfortunately, the complicated processes for preparing such composites directly restrict their further application. Herein, we prepared a NiC/nickel tetraphosphate (Ni(P₄O₁₁)) nanocomposite (NiC/NiP) by introducing ${{\rm{H}}}_{2}{{{\rm{PO}}}_{4}}^{-}$ ions into the NiC reaction system; this composite can be applied in high-performance supercapacitors. The micromorphology of NiC/NiP material displayed an appropriate combination of NiP nanowires and thin NiC nanosheets, which provide sufficient active sites, short ion diffusion paths and fast ion diffusion speeds. NiC/NiP material exhibited an excellent rate performance of 70.2% retained capacity, although the current was increased by 15 times (1196 F g⁻¹ at 2.0 A g⁻¹ and 840 F g⁻¹ at 30 A g⁻¹). The energy density of a NiC/NiP//active carbon (AC) asymmetric supercapacitor fabricated in 6 M KOH was as much as 39.02 W h kg⁻¹ and 26.67 W h kg⁻¹ under corresponding power densities of 160 W kg⁻¹ and 8000 W kg⁻¹, respectively. The asymmetric supercapacitor delivered a stable cyclic performance of 78% capacitive retention after 5000 continuous charge/discharge cycles. More importantly, a 2.5 V light-emitting diode was lit successfully by two NiC/NiP//AC asymmetric supercapacitors in series. These results confirm that NiC/NiP nanocomposite has great potential in practical applications of electrochemical energy storage devices.

Germanium (Ge) has gained a great deal of attention as an anode material for sodium ion batteries (SIBs) and lithium ion batteries (LIBs) for its high theoretical capacity and ion diffusivity. Unfortunately, Ge particle pulverization triggered by huge volume expansion during the alloying and dealloying processes can cause rapid capacity fade. Herein we report a facile method for the preparation of ultrafine Ge nanoparticles embedded in hierarchical N-doped multichannel carbon fibers (denoted as Ge-NMCFs) by electrospinning. The hierarchical carbon matrix not only provides sufficient internal void space to accommodate the large volume expansion of Ge nanoparticles, but also provides numerous open channels for the easy access of electrolyte and Na/Li ions. As half-cell tests revealed, the composite provides discharge capacity of 303 mA h g⁻¹ (1st cycle) and 160 mA h g⁻¹ (700th cycle) for SIBs, 1146.7 mA h g⁻¹ (1st cycle) and 600 mA h g⁻¹ (500th cycle) for LIBs at a current density of 500 mA g⁻¹ (all the presented capacity based on the total weight of Ge/C composites). Density functional theory calculation suggests that N-doped in carbon can enhance the Na/Li ion storage and improve the electrochemical performance. This demonstration is an important step towards the development of SIBs and LIBs with much higher specific energy capacity and longer cycle stability.

Here we develop a magnetoelastic (ME) nano-biosensor based on the competitive strategy for the detection of a carcinoembryonic antigen (CEA). Specifically, the gold-coated ME material provided a platform and the thiolated single-stranded DNA (HS-DNA) containing a half-complementary sequence towards the CEA aptamer was modified on the surface via Au-S bonding. DNA-templated silver nanoclusters (DNA-AgNCs) containing another half-complementary sequence towards the aptamer were used to amplify the signals by about 2.1 times, compared to those obtained using just the aptamer. CEA aptamers as a bio-recognition element were employed to link HS-DNA and DNA-AgNCs through DNA hybridization. The CEA aptamer preferentially combined with CEA rather than hybridized with DNA. Due to the magnetostrictive nature of the ME materials, the resonant frequency of the nano-biosensor would increase along with the release of DNA-AgNCs and CEA aptamers. The modification process was demonstrated by UV–vis spectra, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscope (TEM) and an atomic force microscope (AFM). The nano-biosensor has a linear response to the logarithmic CEA concentrations ranging from 2 pg ml⁻¹ to 6.25 ng ml⁻¹, with a limit of detection (LOD) of 1 pg ml⁻¹ and a sensitivity of 105.05 Hz/ng · ml⁻¹. This study provides a low-cost, highly sensitive and wireless method for selective detection of CEA.

We developed a facile method to fabricate platinum (Pt) porous nanotubes coated with interconnected Pt dendrites using the tobacco mosaic virus (TMV) as a template. The surface-exposed arginine residues of the TMV induced the selective deposition of Pt seeds on the TMV outside surface, and poly(sodium-p-styrenesulfonate) (PSS) was chosen to stabilize the dispersity of TMV coated with Pt seeds (TMV/SPt). The limited space between the Pt seeds and their uniform distribution on the TMV exterior confined the growth of Pt dendrites, resulting in continuous dendritic platinum nanotubes (TMV/DPtNT). The synergistic effects of porous dendrites and anisotropic structures of the TMV/DPtNTs provided an increase in the active sites, the enhancement of transport efficiency and long-distance electron transfer, which greatly improved the catalytic activity. We also demonstrated that such nanotubes could be used in the detection of H₂O₂ with good sensitivity.

In this work, we demonstrate a highly effective method to generate and detect single-nanoparticle (NP) collision events on a nanoelectrode in aqueous solutions. The nanoelectrode of a nanopore–nanoelectrode nanopipette is first employed to accumulate NPs in solution by dielectrophoresis (DEP). Instead of using amperometric methods, the continuous individual NP collision events on the nanoelectrode are sensitively detected by monitoring the open-circuit potential changes of the nanoelectrode. Metallic gold NPs (GNPs) and insulating polystyrene (PS) NPs with various sizes are used as the model NPs. Due to the higher conductivity and polarizability of GNPs, the collision motion of a GNP is different from that of a PS NP. The difference is distinct in the shape of the transient potential change and its first time derivative detected by the nanoelectrode. Therefore, the collision events by metallic and insulating NPs on a nanoelectrode can be differentiated based on their polarizability. DEP induced NP separation and cluster formation can also be probed in detail in the concentrated mixture of PS NPs and GNPs.

A palladium nanoparticle-decorated three-dimensional polyacrylonitrile nanofiber network (Pd-PAN) is prepared as a hydrogen sensor by a chemical bath method. A simple low-temperature annealing treatment is adopted to stabilize the active materials and eliminate the zero-drift of the sensor. The prepared Pd-PAN device exhibits stable performance for hydrogen detection with high sensitivity, especially in a low-concentration hydrogen environment. A minimum detectable limitation of 2 ppm is achieved. In addition, an excellent repeatability is confirmed by continuous measurement under 1% hydrogen. Although the response amplitude decreases with the increased temperature from 30 °C to 70 °C, the fast and stable sensitivity demonstrate the excellent environmental adaptivity and device stability. Notably, due to the accelerated diffusion speed under higher testing temperature, the response time and recovery time are shortened. Moreover, the difference of response as low as 0.01% under bending states at 70 °C strongly confirms the robust mechanical flexibility and superior device performance. The systematic measurements demonstrate the promising application of Pd-PAN sensors for low-concentration hydrogen detection.

In this work, a multi-walled carbon nanotube-modified flexible poly(styrene-butadiene) fiber membrane material was prepared for the sensitive and selective electrochemical detection of dopamine (DA) in human serum and DA injection. The flexible fiber membrane prepared by electrospinning technology is expected to realize its application in wearable devices. The obtained conductive film-based electrochemical sensor can effectively minimize interference caused by ascorbic acid and uric acid. Under the optimized experimental conditions of differential pulse voltammetry, DA gives a linear response in the range of 1–650 μM (R² = 0.996). The detection limit of DA (signal-to noise ratio = 3) was determined to be 0.062 μM.

The poor intrinsic flexibility of semiconducting ceramic materials hinders their applications in wearable electronics. Here, we present a highly efficient photosensor with extreme levels of bending and repeatable resilience based on cable-like structure. The ZnO@TiO₂ cable-like photosensor demonstrates an ultra-high external quantum efficiency (2.82 × 10⁶%) and photosensitivity (1.27 × 10⁵) upon UV light illumination at 254 nm, and a stability of 85% at the small curvature radius of 0.5 mm. Moreover, the ZnO@TiO₂ photodetector demonstrates extremely stable flexibility over 1000 bending cycles. This specific nanoscale architecture has future potential applications for soft integrated electronics.

Helical-structured metallic nanocoils (NCs) may have special interactions with electromagnetic waves and hence attract considerable attention. Although several fabrication methods for metallic NCs have been reported, it is still challenging to obtain a network of well-shaped metallic NCs. This paper reports a novel and simple approach to fabricate metallic NC network. We show that well-shaped Pt NCs with symmetrical left- and right-handed segments can be formed through a spontaneous progress of mechanical deformation. The mechanisms of the driving force for the self-organization, formation of helical chirality balance, and shape control are demonstrated.

Double-walled hierarchical porous silica nanotubes (NTs) loaded Au nanoparticles (Au NPs) in the interlayer (SiO₂@Au@SiO₂ NTs) are synthesized by using tetraethoxysilane as silica source and hollow polydivinylbenzene (PDVB) nanowires as the sacrificial templates. The mesopores on the walls and the hollow structure of NTs (macropores) construct the hierarchical porous structure. The SiO₂@Au@SiO₂ NTs possess a high surface area of 405 m² g⁻¹ and an average pores size of 4.7 nm. The double-walled structure protects the Au NPs from environmental attacks, which shows an excellent catalytic activity even after reusing 10 times. Meanwhile, the hierarchical porous structure shows excellent catalytic ability and allows the catalytic reaction process to be completed within 5 min. This result indicates that double-walled silica NTs have vast potential in catalysis application due to the special structure.

Low damaged doping of two-dimensional (2D) materials proves to be a significant obstacle in realizing fundamental devices such as p–n junction diodes and transistors due to its atom layer thickness. In this work, the defect formation energy and p-type conduction behavior of nitrogen plasma doping are investigated by first principle calculation. Low damaged substitutional p-type doping in MoS₂ using low energy nitrogen plasma composed of N⁺ and N₂⁺ is achieved by a novel toroidal magnetic field (TMF). The TMF helps to raise the concentration of N₂⁺ ions at low RF power condition. The electrical characteristics of double-layer MoS₂ field-effect transistors (FETs) clearly show an efficient p-type doping behavior. Atomic force microscope is applied to verify the slight damage in MoS₂. X-ray photoelectron spectroscopy, photoluminescence and Raman spectroscopy confirm the effective p-type doping characteristic with weak damage. These findings provide a low damage technology for efficient carrier modulation of MoS₂ and other homogeneous TMDC materials, which overcomes barriers in developing 2D electronic and optoelectronic devices.