Original Article in 2016

A new mechanism of porosity-induced graded refractive index, which results in enhanced broadband anti-reflection properties that can extend the inherent properties of 1D materials, for example, wide band gap ZnO in this work, and modify it to achieve an unprecedented photodetection capability covering the entire visible-light range, is demonstrated.

FeCo@N—C nanoparticle as a bi-functional catalyst in both oxygen reduction reaction and hydrogen evolution reaction.

A novel magnetic droplet vaporization strategy was developed for efficient magnetic field-responsive cancer theranostics. Perfluorohexane (PFH)-encapsulated superparamagnetic hollow iron oxide nanoparticles with high magnetic-thermal energy transfer capability quickly respond to external alternating current (a.c.) magnetic field to produce thermal energy and raise the surrounding temperature of tumor tissue. The encapsulated PFH with desirable boiling point of about 56 °C can be vaporized to enhance the ultrasound imaging performance for responsive imaging. Such a magnetic–thermal energy transfer can further completely ablate and remove the tumor against a mice tumor xenograft model.

Ultrafast reduction of graphene oxide sheets was achieved by intense pulsed light irradiation on a highly transparent and thermally stable polyimide substrate. The obtained reduced graphene sheets exhibited improved chemical sensing characteristics, which are promising in wearable chemical sensors for real-time environmental monitoring.

We report novel azo-carbazoles that can be applied to updatable full-color holography. We introduced a molecular design concept of updatable full-color holographic systems based on spectroscopic and optical characteristics. Taking advantage of characteristics of the designed azo-carbazoles, updatable red, yellow and green holograms can be recorded, which enabled us monochromic hologram as well as full-color hologram in the future.

Conventional memory devices are not disposable as they are mostly composed of non-renewable, non-biodegradable and some toxic materials, causing a serious damage for ecological system when they are emitted to the environment. Here we demonstrate an environment-friendly, disposable nonvolatile memory device composed of 99.3 vol.% nanocellulose. Our device consists of a nanocellulose-based resistive-switching layer and nanopaper substrate. The device exhibited the nonvolatile resistive switching with the capability of multilevel storage and the potential scalability down to single nanofiber level. Furthermore, the biodegradability of our memory device was confirmed by burying it into the natural soil for 26 days.

Synchrotron radiation-based X-ray phase-contrast imaging was employed to observe the solid–liquid-vapor interface on superhydrophobic surfaces. The reconstructed 3D images revealed that the water exists in the Cassie-to-Wenzel transit state. The micro/nano-structures trapped a large amount air on the supherhydrophobic surface to repel water.

We realized highly flexible tandem OLEDs using a graphene anode with very high electroluminescent efficiency ~205.9 cd A⁻¹, 45.2% (~396.4 cd A⁻¹, 87.3% with a hemispherical lens) and very low efficiency roll-off at high luminance ~6.6% at 10 000 cd m⁻² (~3.8% with a hemispherical lens) by stacking two organic electroluminescence units using a easily controllable and low-temperature processable charge generation layer on thin flexible plastic substrates. The flexible OLEDs showed great flexibility against bending stress up to bending strain of 6.7%.

Inspired by a popular self-assembled motif in proteins called amyloids, we have developed a series of hydrogels composed of amyloid nanofibrils. The gelation process could be induced via different stimuli, such as heating/cooling or change of pH. Human mesenchymal stem cells preferentially differentiate toward neurons when cultured on these hydrogels. Moreover, its shear thinning property facilitates transplantation of stem cells into the brain with minimally invasive surgery. We demonstrate here the utilization of injectable amyloid hydrogels, which promotes cell survival as well as neuronal differentiation in vivo.

We developed glycol chitosan-based thermo-reversible hydrogels that can provide a facile, convenient and reproducible method for the formation of 3D cell spheroids. The spontaneous formation of spheroids on HGC-coated plates was completed within 1 day. Furthermore, this system can be useful for co-culturing heterotypic cells to form spheroids that mimic biological systems.

Oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are still kinetic barriers of regenerative fuel cell and metal–air batteries, requiring efficient and inexpensive bifunctional electrocatalysts to accelerate the reaction and improve energy efficiency. Herein, we develop Co₉S₈ particles in situ grown on nitrogen and sulfur co-doped porous carbon (Co₉S₈/NSPC) to replace the benchmark noble metal catalysts, which shows high catalytic activities including small potential gap, long-term durability and high selectivity. Importantly, the Zn–air battery with Co₉S₈/NSPC as air electrode displays low discharge/charge overpotential and good cyclic stability, making it the promising bifunctional catalyst for the practical applications.

Indium tin oxide (ITO) is a well-known n-type degenerate semiconductor. Herein, mesoporous ITO is utilized as a photocathode material for p-type dye-sensitized solar cells in place of the commonly applied p-type semiconductors, such as nickel oxide. In conjunction with [Fe(acac)₃]^0/− as redox mediator and a new sensitizer, an impressive energy conversion efficiency of 1.96±0.12% was achieved. Photoelectron spectroscopy in air revealed that ITO exhibits a significant local density of states arising below −4.8 eV, which enables electron transfer to occur from ITO to the excited dye, giving rise to the sustained photocathodic current.

The precision synthetic method of well-defined polymer microspheres by the π-allylnickel-catalyzed living coordination polymerization of allene derivatives under the dispersion polymerization conditions is described. Unlike the conventional dispersion polymerization systems, the use of a bifunctional monomer, 1,4-diallenoxybenzene, to this living dispersion polymerization successfully gave well-defined crosslinked living polymer microspheres that exhibit high solvent-tolerant properties. The postpolymerization of functional allene monomers in the living dispersion polymerization also proceeded smoothly to give functionalized polymer microspheres that enabled their applications to the solid-phase organic synthesis and the solid-supported transition metal catalysts.

We herein report a synergistic optimization procedure that combines point defect engineering, band structure engineering and multiscale microstructuring in p-type (Bi,Sb)₂Te₃ thermoelectric materials by Indium doping and hot deformation. As a result, a peak value of zT ~1.4 was attained in Bi_0.3Sb_1.625In_0.075Te₃ at 500 K, along with a state-of-the-art average zT_av of ~1.3 between 400 and 600 K. These results demonstrate the efficacy of the multi-synergies that can also be applied to optimize other thermoelectric materials.

Strong correlation between the local strain state and the electronic properties at orthorhombic–rhombohedral (O-R) phase boundaries in mixed-phase BFO thin films leads to electronic conductivity at these boundaries. This rather unusual electrical feature might find applications in nanotechnology.

Three kinds of Ni₃S₂ nanostructures, namely Ni₃S₂ nanorods, Ni₃S₂ nanosheet@nanorods and Ni₃S₂ multi-connected nanorods were prepared using a one-step hydrothermal process via controlling the temperature. Owing to the good mechanical adhesion and electrical connection with the substrate, high contact area with the electrolyte and alleviated structural pulverization during the ion insertion/desertion process, Ni₃S₂ nanosheet-onto-Ni₃S₂ nanorods exhibited excellent rate capability and cycling stability. Asymmetric supercapacitor consisting of Ni₃S₂ nanosheet @nanorods electrode and activated carbon (AC) electrode displayed a volumetric energy density of 1.96 mWh cm⁻³, which can be used to bridge the performance gap between thin-film Li batteries and commercial AC//AC supercapacitors.

Stretchable resistive memories were created using donor–acceptor rod-coil diblock copolymers, poly(polyfluorene)-b-poly(pendent isoindigo), with different block ratios. Reliable and reproducible electrical characteristics of volatile SRAM- and nonvolatile WORM-type memories were exhibited under applied tensile strains ranging from 0 to 50 %, demonstrating the potential to serve as promising candidates for high-performance wearable devices.

Photo-patternable and transparent cellulose hybrid films as flexible and stretchable substrates exhibit outstanding mechanical, optical and thermal properties. Exploiting the photo-patternability of the hybrid film, reversibly foldable and stretchable forms of the substrate can be produced by integrating patterns of this hybrid film with elastomeric joints. Flexible touchscreen panels and transparent organic light-emitting diodes using hybrid films are demonstrated.

Multilevel structured porous polymer particles, consisting of submicron hollow cavities and crosslinked shell with interconnected mesopores, are specially designed, prepared and served as super-adsorbent materials. As a proof of concept, we applied the carboxylate-functionalized hollow particles as selective adsorbent for the removal of basic dye methylene blue. Because of their extremely high functional group density and unique strucutre, the as-designed particles show super adsorption capacity (1603 mg g⁻¹ for methylene blue), ultra fast adsorption/desorption rates, facile separation and easy regeneration.

We demonstrate full-color reflection with first- and second-order Bragg reflections in a GO dispersion, and we use two fundamental approaches to manipulate GO photonic crystals, namely, bottom-up and top-down manipulation by controlling the Debye length and using shear or surface fields, respectively. Direct observation of the GO alignments using confocal microscopy reveals excellent layer-to-layer packing assembly and poor in-layer assembly, elucidating the nematic nature of GO rather than its lamellar mesophase. In addition, modulations of the local GO density and alignment enable us to demonstrate full-range color paintings, including chromatic and achromatic colors.