Jianjian Lin

Nanopatterned Textile-Based Wearable Triboelectric Nanogenerator

Here we report a fully flexible, foldable nanopatterned wearable triboelectric nanogenerator (WTNG) with high power-generating performance and mechanical robustness. Both a silver (Ag)-coated textile and polydimethylsiloxane (PDMS) nanopatterns based on ZnO nanorod arrays on a Ag-coated textile template were used as active triboelectric materials. A high output voltage and current of about 120 V and 65 μA, respectively, were observed from a nanopatterned PDMS-based WTNG, while an output voltage and current of 30 V and 20 μA were obtained by the non-nanopatterned flat PDMS-based WTNG under the same compressive force of 10 kgf. Furthermore, very high voltage and current outputs with an average value of 170 V and 120 μA, respectively, were obtained from a four-layer-stacked WTNG under the same compressive force. Notably it was found there are no significant differences in the output voltages measured from the multilayer-stacked WTNG over 12 000 cycles, confirming the excellent mechanical durability of WTNGs. Finally, we successfully demonstrated the self-powered operation of light-emitting diodes, a liquid crystal display, and a keyless vehicle entry system only with the output power of our WTNG without any help of external power sources.

3D hierarchical rutile TiO2 and metal-free organic sensitizer producing dye-sensitized solar cells 8.6% conversion efficiency.

Three-dimensional (3D) hierarchical nanoscale architectures comprised of building blocks, with specifically engineered morphologies, are expected to play important roles in the fabrication of ‘next generation’ microelectronic and optoelectronic devices due to their high surface-to-volume ratio as well as opto-electronic properties. Herein, a series of well-defined 3D hierarchical rutile TiO2 architectures (HRT) were successfully prepared using a facile hydrothermal method without any surfactant or template, simply by changing the concentration of hydrochloric acid used in the synthesis. The production of these materials provides, to the best of our knowledge, the first identified example of a ledgewise growth mechanism in a rutile TiO2 structure. Also for the first time, a Dye-sensitized Solar Cell (DSC) combining a HRT is reported in conjunction with a high-extinction-coefficient metal-free organic sensitizer (D149), achieving a conversion efficiency of 5.5%, which is superior to ones employing P25 (4.5%), comparable to state-of-the-art commercial transparent titania anatase paste (5.8%). Further to this, an overall conversion efficiency 8.6% was achieved when HRT was used as the light scattering layer, a considerable improvement over the commercial transparent/reflector titania anatase paste (7.6%), a significantly smaller gap in performance than has been seen previously.

A Bi-layer TiO2 photoanode for highly durable, flexible dye-sensitized solar cells

Low-temperature processing of dye-sensitized solar cells (DSCs) [B. Oregan, M. Gratzel, Nature, 1991, 353, 737] is crucial to enable their commercialization with low-cost plastic substrates. Much of the previous work in this area has focused on mechanical compression of premade particles on plastic substrates; however, many reported that this technique did not yield sufficient interconnections for high charge carrier transport. Herein, we present bi-layer photoanodes that incorporate microstructured TiO2 sea-urchin-like assemblies, composed of high-aspect-ratio single crystalline nanoribbons, i.e., two-dimensional subunits, which were deposited onto a nanoparticle layer (commercial P25), with a 5.6% conversion efficiency realized. We demonstrate that this Mesoporous Hierarchical Anatase TiO2 (MHAT) nanostructure is beneficial due to its enhanced dye loading as well as enhanced light scattering. Importantly, we also show the benefits of a bi-layer structure where the nanoribbons penetrate into the nanoparticle layer (P25) after cold isostatic pressing (CIP), resulting in improved adhesion between the MHAT top layer and the P25 under layer on the indium tin oxide-coated polyethylene naphthalate (ITO|PEN) substrate, leading to improved mechanical stability and durability, efficient electron transfer pathways, and ultimately, higher solar-to-electric conversion efficiencies.

Metal–organic framework-derived one-dimensional porous or hollow carbon-based nanofibers for energy storage and conversion

Metal organic framework (MOF)-derived nanoporous carbons (NPCs) have been proposed as promising electrode materials for energy storage and conversion devices. However, MOF-derived NPCs typically suffer from poor electrical conductivity due to the lack of connectivity between these particles and a micropore-dominated storage mechanism, which hinder mass and electron transfer, thereby leading to poor electrochemical performance. In recent years, one-dimensional (1D) MOF-derived carbon nanostructures obtained using an electrospinning method have emerged as promising materials for both electrochemical energy storage (EES) and energy conversion applications. In this mini review, the recent progress in the development of MOF-derived 1D porous or hollow carbon nanofibers using the electrospinning method and their application in energy storage (e.g., supercapacitors and rechargeable batteries) and conversion devices (e.g., fuel cells) is presented. The synthetic method, formation mechanism and the structure–activity relationship of such porous or hollow carbon nanofibers are also discussed in detail. Finally, future perspectives on the development of electrospun MOF-derived carbon nanomaterials for energy storage and conversion applications are provided. This review will provide some guidance for future derivations of 1D hollow carbon nanomaterials from MOFs using electrospinning technology.

Gold nanoparticles supported on mesoporous iron oxide for enhanced CO oxidation reaction

Herein, we report the synthesis of gold (Au)-loaded mesoporous iron oxide (Fe2O3) as a catalyst for both CO and NH3 oxidation. The mesoporous Fe2O3 is firstly prepared using polymeric micelles made of an asymmetric triblock copolymer poly(styrene-b-acrylic acid-b-ethylene glycol) (PS-b-PAA-b-PEG). Owing to its unique porous structure and large surface area (87.0 m2 g-1), the as-prepared mesoporous Fe2O3 can be loaded with a considerably higher amount of Au nanoparticles (Au NPs) (7.9 wt%) compared to the commercial Fe2O3 powder (0.8 wt%). Following the Au loading, the mesoporous Fe2O3 structure is still well-retained and Au NPs with varying sizes of 3-10 nm are dispersed throughout the mesoporous support. When evaluated for CO oxidation, the Au-loaded mesoporous Fe2O3 catalyst shows up to 20% higher CO conversion efficiency compared to the commercial Au/Fe2O3 catalyst, especially at lower temperatures (25-150 °C), suggesting the promising potential of this catalyst for low-temperature CO oxidation. Furthermore, the Au-loaded mesoporous Fe2O3 catalyst also displays a higher catalytic activity for NH3 oxidation with a respectable conversion efficiency of 37.4% compared to the commercial Au/Fe2O3 catalyst (15.6%) at 200 °C. The significant enhancement in the catalytic performance of the Au-loaded mesoporous Fe2O3 catalyst for both CO and NH3 oxidation may be attributed to the improved dispersion of the Au NPs and enhanced diffusivity of the reactant molecules due to the presence of mesopores and a higher oxygen activation rate contributed by the increased number of active sites, respectively.

Electrochemical Deposition: An Advanced Approach for Templated Synthesis of Nanoporous Metal Architectures

Well-constructed porous materials take an essential role in a wide range of applications, including energy conversion and storage systems, electrocatalysis, photocatalysis, and sensing. Although the tailored design of various nanoarchitectures has made substantial progress, simpler preparation methods are compelled to meet large-scale production requirements. Recently, advanced electrochemical deposition techniques have had a significant impact in terms of precise control upon the nanoporous architecture (i.e., pore size, surface area, pore structure, etc.), enabling access to a wide range of compositions. In this Account, we showcase the uniqueness of electrochemical deposition techniques, detail their implementation toward the synthesis of novel nanoporous metals, and finally outline the future research directions. Nanoporous metallic structures are attractive in that they can provide high surface area and large pore volume, easing mass transport of reactants and providing high accessibility to catalytically active metal surface. The great merit of the electrochemical deposition approach does not only lie in its versatility, being applicable to a wide range of compositions, but also in the nanoscale precision it affords when it comes to crystal growth control, which cannot be easily achieved by other bottom-up or top-down approaches. In this Account, we describe the significant progress made in the field of nanoporous metal designed through electrochemical deposition approaches using hard templates (i.e., porous silica, 3D templates of polymer and silica colloids) and soft templates (i.e., lyotropic liquid crystals, polymeric micelles). In addition, we will point out how it accounts for precise control over the crystal growth and describe the unique physical and chemical properties emerging from these novel materials. Up to date, our group has reported the synthesis of several nanoporous metals and alloys (e.g., Cu, Ru, Rh, Pd, Pt, Au, and their corresponding alloys) under various conditions through electrochemical deposition, while investigating their various potential applications. The orientation of the channel structure, the composition, and the nanoporosity can be easily controlled by selecting the appropriate surfactants or block copolymers. The inherent properties of the final product, such as framework crystallinity, catalytic activity, and resistance to oxidation, are depending on both the composition and pore structure, which in turn require suitable electrochemical conditions. This Account is divided into three main sections: (i) a history of electrochemical deposition using hard and soft templates, (ii) a description of the important mechanisms involved in the preparation of nanoporous materials, and (iii) a conclusion and future perspectives. We believe that this Account will promote a deeper understanding of the synthesis of nanoporous metals using electrochemical deposition methods, thus enabling new pathways to control nanoporous architectures and optimize their performance toward promising applications such as catalysis, energy storage, sensors, and so forth.

Porous nanozymes: the peroxidase-mimetic activity of mesoporous iron oxide for the colorimetric and electrochemical detection of global DNA methylation

Nanomaterials (nanozymes) with peroxidase-mimetic activity have been widely used in biosensing platforms as low-cost, relatively stable and prevailing alternatives to natural enzymes. Herein, we report on the synthesis and application of the peroxidase-mimetic activity of mesoporous iron oxide (MIO) for the detection of global DNA methylation in colorectal cancer cell lines. The target DNA was extracted and denatured to get ssDNA followed by direct adsorption onto the surface of a bare screen-printed gold electrode (SPGE). A 5-methylcytosine antibody (5mC) functionalized nanomaterial (MIO-5mC) was then used to recognise the methylcytosine groups present on the SPGE. The MIO-5mC conjugates catalyse the TMB solution in the presence of hydrogen peroxide to give the colorimetric (i.e., naked-eye observation) and electrochemical detection of DNA methylation. The assay could successfully detect as low as 10% difference in the global DNA methylation level in synthetic samples and cell lines with good reproducibility and specificity (%RSD = <5%, for n = 3). This strategy avoids the use of natural enzyme horseradish peroxidase (HRP), traditional PCR based amplification and bisulfite treatment steps that are generally used in many conventional DNA methylation assays. We envisage that our assay could be a low-cost platform with great potential for genome-wide DNA methylation analysis in point-of-care applications.

Synthesis of Hollow Co-Fe Prussian Blue Analogue Cubes by using Silica Spheres as a Sacrificial Template

Abstract Herein, we report a novel method for the formation of hollow Prussian blue analogue (CoFe–PBA) nanocubes, using spherical silica particles as sacrificial templates. In the first step, silica cores are coated by a CoFe–PBA shell and then removed by etching with hydrofluoric acid (HF). The cubic shape of CoFe–PBA is well‐retained even after the removal of the silica cores, resulting in the formation of hollow CoFe–PBA cubes. The specific capacity of the hollow CoFe–PBA nanocubes electrodes is about two times higher than that of solid CoFe–PBA nanocubes as storage materials for sodium ions. Such an improvement in the electrochemical properties can be attributed to their hollow internal nanostructure. The hollow architecture can offer a larger interfacial area between the electrolyte and the electrode, leading to an improvement in the electrochemical activity. This strategy can be applied to develop PBAs with hollow interiors for a wide range of applications.

Ni–Co Binary Hydroxide Nanotubes with Three-Dimensionally Structured Nanoflakes: Synthesis and Application as Cathode Materials for Hybrid Supercapacitors

Nickel-cobalt binary hydroxide nanotubes were fabricated by a facile synthetic approach by using Cu2 O nanowires as sacrificial templates. The surface morphology of the binary hydroxide nanotubes can be easily controlled by adjusting the molar ratio of Ni to Co. With increasing Co content, the surfaces of the nanotubes tend to form hierarchical nanoflakes. The obtained nanotubes with high specific surface area exhibit typical battery-like electrochemical behavior. Among them, Ni-Co hydroxide nanotubes with Ni:Co=48:52 showed outstanding electrochemical characteristics, with a specific capacity of 209.9 mAh g-1 at 1 Ag-1 and remarkable cycling stability with 84.4 % capacity retention after 10 000 cycles at 20 A g-1 . With the advantages of their unique nanostructure and the synergistic effect of the two elements, the Ni-Co binary hydroxide nanotubes are expected to be effective potential cathode materials for hybrid supercapacitors.