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In this work, we develop a new type of mesoporous 2D N, B, and P codoped carbon network (NBP-CNW) arranged into high-order 3D nanotube arrays (NTAs), which are wrapped onto a flexible carbon fiber microelectrode, and this microelectrode is employed as a high-performance carbon-based nanocatalyst for electrochemical biosensing. The NBP-CNW-NTAs synthesized by a facile, controllable, ecofriendly and sustainable template strategy using ionic liquids as precursors possess a high structural stability, large surface area, abundant active sites, and effective charge transport pathways, which dramatically improve their electrocatalytic activity and durability in the redox reaction of cancer biomarker H2O2. Benefiting from these unique structural merits, superb electrochemical activity and good biocompatibility, the NBP-CNW-NTAs-modified microelectrode demonstrates excellent sensing performance toward H2O2 and is embedded in a homemade microfluidic electrochemical biosensor chip for the real-time tracking of H2O2 secreted from different live cancer cells with or without radiotherapy treatment, which provides a new strategy for distinguishing the types of cancer cells and evaluating the radiotherapeutic efficacy of cancer cells. Furthermore, the functional microelectrode is integrated into an implantable probe for the in situ detection of surgically resected human specimens to distinguish cancer tissues from normal tissues. These will be of vital significance for cancer diagnoses and therapy in clinical practice.

We have developed a novel, facile and architecturally versatile fabrication method for specially designed cellular graphene lattices using additively manufactured polymer-based gyroidal triply periodic minimal surface (TPMS) as the initial sacrificial scaffold. Three-dimensional (3D)-printed templates of the polymeric gyroid lattices were coated with a mixture of graphene oxide (GO) and hydrazine solution via the hydrothermal process, followed by drying and thermal etching of the polymer scaffold, which resulted in a neat reduced GO (rGO) lattice of the gyroidal TPMS structure. Scanning electron microscopy and micro-computed tomography were used to evaluate the morphology and size of the 3D rGO architectures, while a Raman response at 1360[Formula: see text]cm[Formula: see text] (D peak), 1589[Formula: see text]cm[Formula: see text] (G peak) and 2696[Formula: see text]cm[Formula: see text] (2D peak) verified the presence of rGO. Thermo–electro–mechanical properties of rGO gyroid lattices of different densities were characterized where the highest Young’s modulus recorded was 351[Formula: see text]kPa for a sample with a density of 45.9[Formula: see text]mg[Formula: see text][Formula: see text][Formula: see text]cm[Formula: see text]. The rGO gyroid lattice exhibits an electrical conductivity of 1.07[Formula: see text]S[Formula: see text][Formula: see text][Formula: see text]m[Formula: see text] and high thermal insulation property with a thermal conductivity of 0.102[Formula: see text]W[Formula: see text][Formula: see text][Formula: see text]m[Formula: see text][Formula: see text]K[Formula: see text]. It is demonstrated that the hydrothermal-assisted fabrication process is adaptable for different lattice architectures based on 3D-printed scaffolds and thus has wide functional applications.

Two-dimensional (2D) materials have been developed intensively over the last decade, and combining different 2D materials to form heterogeneous 2D materials is anticipated to be more attractive with broader applications. The precise evaluation and prediction of interfacial properties of 2D heterostructures are critical for designing more robust heterostructures and developing advanced, engineered molecular devices. Here, we present a brief review on experimental (namely, atomic force microscopy (AFM), in situ peel test, double cantilever beam, pressurized blister test and sheet-on-bead method) and theoretical techniques (namely, molecular dynamics and density functional theory) for probing the adhesion/interaction energy of the interface of 2D heterogeneous materials and paving the way for future applications.

MXenes belong to a new class of two dimensional (2D) functional nanomaterials, mainly encompassing transition-metal carbides, nitrides and carbonitrides, with unique physical, chemical, electronic and mechanical properties for various emerging applications across different fields. To date, the potentials of MXenes for biomedical application such as drug delivery have not been thoroughly explored due to the lack of information on their biocompatibility, cytotoxicity and biomolecule-surface interaction. In this study, we developed novel drug delivery system from MXene for the controlled release of a model therapeutic protein. First, the structural, chemical and morphological properties of as synthesized MXenes were probed with electron microscopy and X-ray diffraction. Second, the potential cytotoxicity of MXene toward the proliferation and cell morphology of murine macrophages (RAW 264.7) were evaluated with MTT assays and electron microscopy, respectively. Moreover, the drug loading capacities and sustained release capabilities of MXene were assessed in conjunction with machine learning approaches. Our results demonstrated that MXene did not significantly induce cellular toxicity at any concentration below 1 mg/ml which is within the range for effective dose of drug delivery vehicle. Most importantly, MXene was efficiently loaded with FITC-catalase for subsequently achieving controlled release under different pHs. The release profiles of catalase from MXene showed higher initial rate under basic buffer (pH 9) compared to that in physiological (pH 7.4) and acidic buffers (pH 2). Taken together, the results of this study lead to a fundamental advancement toward the use of MXene as a nanocarrier for therapeutic proteins in drug delivery applications.

In this work, we develop a new type of mesoporous 2D N, B, P co-doped carbon network (NBP-CNW) arranged into high-order 3D nanotube arrays (NTAs), which is wrapping onto flexible carbon fiber microelectrode and employed as high-performance carbon-based nanocatalyst for electrochemical biosensing. NBP-CNW-NTAs synthesized by a facile, controllable, eco-friendly and sustainable template strategy using ionic liquids as precursors possess high structural stability, large surface area, abundant active sites, and effective charge transport pathways, these dramatically improve their electrocatalytic activity and durability to redox reaction of cancer biomarker H2O2. Benefiting from the unique structural merits, superb electrochemical activity and good biocompatibility, the NBP-CNW-NTAs modified microelectrode demonstrates excellent sensing performances towards H2O2, and can be embed in a homemade microfluidic electrochemical biosensor chip for real-time tracking H2O2 secreted from different live cancer cells with or without radiotherapy treatment, which provides a new strategy to distinguish the types of cancer cells and evaluate the radiotherapeutic efficacy to cancer cells. Furthermore, the functional microelectrode has been integrated into an implantable probe for in situ detection of surgically resected human specimens to identify cancer tissues from the normal one. These will be of vital significance for cancer diagnoses and therapy in clinic practice.

Controllable synthesis of insertion-type anode materials with beneficial micro- and nanostructures is a promising approach for the synthesis of sodium-ion storage devices with high-reactivity and excellent electrochemical performance. In this study, we developed a sacrificial-templating route to synthesize TiO2@N-doped carbon nanotubes (TiO2@NC-NTs) with excellent electrochemical performance. The as-prepared mesoporous TiO2@NC-NTs with tiny nanocrystals of anatase TiO2 wrapped in N-doped carbon layers showed a well-defined tube structure with a large specific surface area of 198 m2 g−1 and a large pore size of ~5 nm. The TiO2@NC-NTs delivered high reversible capacities of 158 mA h g−1 at 2 C (1 C = 335 mA g−1) for 2200 cycles and 146 mA h g−1 at 5 C for 4000 cycles, as well as an ultrahigh rate capability of up to 40 C with a capacity of 98 mA h g−1. Even at a high current density of 10 C, a capacity of 138 mA h g−1 could be delivered over 10,000 cycles. Thus, the synthesis of mesoporous TiO2@NC-NTs was demonstrated to be an efficient approach for developing electrode materials with high sodium storage and long cycle life.

Among the new molecular tools available to scientists and engineers, some of the most useful include fluorescently tagged biomolecules. Tools, such as green fluorescence protein (GFP), have been applied to perform semi-quantitative studies on biological signal transduction and cellular structural dynamics involved in the physiology of healthy and disease states. Such studies focus on drug pharmacokinetics, receptor-mediated endocytosis, nuclear mechanobiology, viral infections, and cancer metastasis. In 1976, fluorescence recovery after photobleaching (FRAP), which involves the monitoring of fluorescence emission recovery within a photobleached spot, was developed. FRAP allowed investigators to probe two-dimensional (2D) diffusion of fluorescently-labelled biomolecules. Since then, FRAP has been refined through the advancements of optics, charged-coupled-device (CCD) cameras, confocal microscopes, and molecular probes. FRAP is now a highly quantitative tool used for transport and kinetic studies in the cytosol, organelles, and membrane of a cell. In this work, the authors intend to provide a review of recent advances in FRAP. The authors include epifluorescence spot FRAP, total internal reflection (TIR)/FRAP, and confocal microscope-based FRAP. The underlying mathematical models are also described. Finally, our understanding of coupled transport and kinetics as determined by FRAP will be discussed and the potential for future advances suggested.

Bamboo, one of the most abundant biomaterials, has been used as a building material since ancient times; however, its application in functional materials has been rarely explored. Herein, a highly robust and conductive carbonized bamboo aerogel (CBA) is obtained from the natural bamboo through a simple three-step process of pulp oxidization, freeze-drying, and carbonization. The CBA obtained shows not only a low density of 0.02 g/cm

MnO1.88/MnO2/Ti3C2Tx composites on Ti3C2Tx (MXenes) were synthesized for potential applications as supercapacitor electrodes. A composite with a cotton candy-like morphology was formed on nanometer-sized Ti3C2Tx flakes by redox reaction using KMnO4 at room temperature, where Ti3C2Tx acts both as a molecular template and as a reducing agent. MnO1.88/MnO2/Ti3C2Tx has a high specific capacity of 312 F g−1 at 1 A g−1, and the capacity retention was over 91% after 5000 charge–discharge cycles. As such, the facile preparation of MnO1.88/MnO2/Ti3C2Tx composites promotes the highly specific pseudo-capacitance of MXenes, which have emerged as highly promising electrode materials.

Multifunctional 2D materials have been exploited for highly intricate applications in engineering and medicine, including energy, bioimaging and drug delivery. In this study, an MXene material, Ti3C2Tx, was developed to play dual functional roles in wastewater treatment and electrochemical energy storage. First, Ti3C2Tx MXene demonstrated its high capacity for the adsorption of selected cationic dyes such as Rhodamine B in aqueous solutions. Meanwhile, both XPS and Raman spectroscopy indicated that Ti3C2Tx hosted the organic dyes in its interlayer voids through intercalation. After the in situ carbonization, conversion of the organic dyes to carbon led to the formation of novel carbon-filled Ti3C2Tx (Ti3C2Tx/C) for electrochemical applications. With the increased interlayer thickness of carbon within Ti3C2Tx/C, the carbon-filled Ti3C2Tx hetero-structure was eventually applied as a supercapacitor electrode; it displayed a high specific capacity of 226 F g−1 at 1 A g−1. Our unique approach of cationic dye adsorption/carbonization significantly enhanced the transport paths of electrolyte ions into the MXene, i.e. it exhibited high performance and cycling stability, with 94% retention over 8000 cycles. Our study paves the way to achieve scalable and environmental friendly processes for the development of high-performance 2D nanomaterials for energy storage.

Trapping lithium polysulfides (LiPSs) on a material effectively suppresses the shuttle effect and enhances the cycling stability of Li–S batteries. For the first time, we advocate a recently synthesized two-dimensional material, biphenylene, as an anchoring material for the lithium-sulfur battery. The density functional theory calculations show that LiPSs bind with pristine biphenylene insubstantially with binding energy ranging from −0.21 eV to −1.22 eV. However, defect engineering through a single C atom vacancy significantly improves the binding strength (binding energy in the range −1.07 to −4.11 eV). The Bader analysis reveals that LiPSs and S8 clusters donate the charge (ranging from −0.05 e to −1.12 e) to the biphenylene sheet. The binding energy of LiPSs with electrolytes is smaller than those with the defective biphenylene sheet, which provides its potential as an anchoring material. Compared with other reported two-dimensional materials such as graphene, MXenes, and phosphorene, the biphenylene sheet exhibits higher binding energies with the polysulfides. Our study deepens the fundamental understanding and shows that the biphenylene sheet is an excellent anchoring material for lithium-sulfur batteries for suppressing the shuttle effect because of its superior conductivity, porosity, and strong anchoring ability.

High tolerance regarding photovoltaic performance in terms of donor:acceptor (D:A) composition ratio is reported for all-polymer solar cells (all-PSCs), which is a crucial advantage in producing la...

The development of facile, rapid and cost-effective strategies for sensitive detection of cancer biomarkers in human samples is of great significance for early diagnosis of malignant tumors related diseases. In this work, we develop a high-performance electrochemical biosensor based on highly active dual nanozyme amplified system, i.e., ultrathin two-dimension (2D) conductive metal-organic framework (C-MOF) nanosheets (NSs) decorated with high-density ultrafine gold nanoparticles (Au-NPs), and explore its application in sensitive detection of cancer biomarker H

MXene possesses high conductivity, excellent hydrophilicity, rich surface chemistry, hence holds great potential in various applications. However, MXene materials have low surface area utilization due to the agglomeration of ultrathin nanosheets. Assembling 2D MXene nanosheets into 3D multi-level architectures is an effective way to circumvent this issue. Incorporation of MXene with other nanomaterials during the assembly process could rationally tune and tailor the specific surface area, porosity and surface chemistry of the MXene assemblies. The complementary and synergistic effect between MXene and nanomaterials could expand their advantages and make up for their disadvantages, thus boost the performance of 3D porous MXene composites. Herein, we summarize the recent progress in fabrication of porous MXene architectures from 2D to 3D, and also discuss the potential applications of MXene nanostructures in energy harvesting systems, sensing, electromagnetic interference shielding, water purification and photocatalysis.

Lattices based on triply periodic minimal surfaces (TPMSs), which have been receiving increasing interest due to advances in additive manufacturing, are known now to be outperforming other cellular materials in several properties, enabling wider multifunctional applications. In this work, we focus on fabricating graphene TPMS lattices, viz., Gyroid, Schoen's I-WP (IWP), and Diamond, and investigate their multifunctional properties experimentally and computationally. The three-dimensional (3D) graphene structures were synthesized using a self-assembly hydrothermal-assisted dip-coating technique and the resulting lattices were tested for their mechanical, thermal, and electrical properties and compared to finite element simulation results. The graphene TPMS lattices resulting from the fabrication take the topology of a new class of TPMS architectures that are referred to here as the TPMS tube-networks. IWP demonstrated the highest elastic modulus as well as electrical and thermal conductivities. This study shows that 3D porous tube graphene can be utilized in designing new lightweight structural materials of low density with controllable thermal and electrical properties and mechanical strength with a potential to be employed in multifunctional engineering applications.

Summary We provide a review of cellular graphene (CG), from its fabrication, to characterization of mechanical properties, to applications in strain and pressure sensing. Although several recent reviews have briefly surveyed various types of strain and pressure sensors fabricated from common one-dimensional or two-dimensional (2D) nanomaterials such as carbon nanotube (CNT), graphene, and metallic nanowire/nanoparticle, the emerging applications of CG in the design and development of strain and pressure sensors, as well as the structure-property-function correlations in sensing performance, have not been systematically covered. CG exhibits unique strain-sensing capabilities that collectively enable a wide range of strain sensing to be achieved. We first review several state-of-the-art approaches for fabricating CG with emphasis on the engineering of tailored mechanical properties. Second, the strain- and pressure-sensing performance of CG-based devices against a range of fabrication processes is systematically and critically analyzed. Along the way, representative applications of such CG-based sensors are thoroughly discussed. This review aims to provide basic information for the design of novel CG as well as other classes of three-dimensional porous structures fabricated from various 2D nanomaterials. In the conclusion, we highlight the extension of design principles to other 2D materials and critically summarize the key issues that need to be addressed in the future.

Control of the shape, size, internal structure, and uniformity of block copolymer (BCP) particles is crucial for determining their utility and functionality in practical applications. Here, we demonstrate a particle restructuring by solvent engineering (PRSE) strategy that combines membrane emulsification and solvent annealing processes to produce monodisperse BCP particles with controlled size, shape, and internal structure. A major advantage of the PRSE approach is the general applicability to different families of functional BCPs, including polystyrene-block-poly(1,4-butadiene) (PS-b-PB), polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS), and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP). PRSE starts with the production of monodisperse BCP spheres in a wide range of particle sizes (from hundreds of nanometers to several tens of microns) using membrane emulsification, followed by successful transformation to shape-anisotropic BCP particles by solvent annealing under neutral wetting conditions. ...

Herein, a novel polytriazine compound was designed and used as a precursor for the synthesis of high nitrogen-doped porous carbon spheres (N-doped carbon-PNSs) by direct carbonization-activation; the process was simple and based on the template-free polycondensation of 2,6-diaminopyridine and formaldehyde in an aqueous solution. Moreover, by varying the 2,6-diaminopyridine to formaldehyde ratio and total monomer concentration during the synthesis of the polymeric precursor, the size of the polytriazine nanospheres could be tuned from 102 to 3900 nm with a uniform spherical geometry. After pyrolysis, the N-doped carbon-PNSs had an average N content of 8.7–10.4 wt% and surface areas of 627.8–924.4 m2 g−1; most importantly, the N-doped carbon-PNSs as high energy supercapacitor electrodes exhibited excellent cyclability and high specific capacitance, ramping up to 424 F g−1 at 1 A g−1 in 6 M KOH.

As the most representative member of a new emerging family of 2D material, titanium carbides or nitrides (MXenes), Ti

In this study, we synthesized two acceptor-donor-acceptor (A-D-A)-type small molecules (SMs) (P3T4-VCN and P3T4-INCN) with different terminal end-groups (dicyanovinyl (VCN) and 2-methylene-3-(1,1-dicyanomethylene)indanone (INCN)) based on the 1,4-bis(thiophenylphenylthiophene)-2,5-difluorophenylene (P3T4) core that possesses high coplanarity because of intrachain noncovalent Coulombic interactions. We investigated the influence of terminal end-groups on intermolecular packing and the resulting electrical and photovoltaic characteristics. A small change in the end-group structure of the SMs induces a significant variation in the torsional structures, molecular packing, and pristine/blend film morphology. It is noteworthy that the less crystalline P3T4-INCN with tilted conformation is highly sensitive to post-treatments (i.e., additives and annealing) such that it permits facile morphological modulation. However, the highly planar and crystalline P3T4-VCN exhibits a strong tolerance toward processing treatments. After morphology optimization, the fullerene-based bulk-heterojunction solar cell of tilted P3T4-INCN exhibits a power conversion efficiency (PCE) of 5.68%, which is significantly superior to that of P3T4-VCN:PC71BM (PCE = 1.29%). Our results demonstrate the importance of the terminal end-group for the design of A-D-A-type SMs and their sensitivity toward the postprocessing treatments in optimizing their performance.

In this work, we develop a specifically engineered variant of carbonized melamine foam (cMF) by carrying systematic structural modifications with Au nanoparticles, graphene (G), Fe3O4 (IO) and poly(dimethyl siloxane) (PDMS). Our main goal is to construct a lightweight and flexible cMF composite with tailored 3D hierarchical architecture for achieving high-efficiency in electromagnetic interference (EMI) shielding. By capitalizing on the synergistic effect of the multifunctional components in the fabrication of the typical closed-cell structure, cMF-Au-G-IO/PDMS composite produced herein demonstrates superior physical properties including low density (116 mg/cm3), high conductivity (81.3 S/m), large specific surface area (708 m2/g), proven superparamagnetism (Ms = 22.6 emu/g), and moderate compressive strength (110 KPa), collectively leading to the significant attenuation effect towards EMI. The cumulative EMI shielding effectiveness (SE) of cMF-Au-G-IO/PDMS film with a thickness of 2 mm is determined as 30.5 dB in X band (8.2–12.4 GHz). Interestingly, SE is further raised up to 52.5 dB when the film thickness is increased to 10 mm. Hence, we envision the emergence of multifunctional cMF-based composite as a promising engineering system for fulfilling the demanding applications in EMI shielding.

As a result of their particular electronic structure [nd10(n+1)s1] and size sensitive tunable photoresponse properties, nanocrystals of Au on a transition metal oxide support are potential candidates for use in heterogeneous photocatalysis to improve their photocatalytic activities in visible light. In the present work, by taking advantage of well-defined anatase TiO2 nanosheets with highly active (001) facets exposure as a support, we have successfully prepared randomly-deposited Au/TiO2 nanosheets nanostructures. Furthermore, with the help of a precise position-controlled synthesis strategy, we have transformed these randomly-deposited Au/TiO2 nanosheets into novel edge-site deposited Au/TiO2 nanosheets with enhanced crystalline interface contact. A noticeable dependence on Au positioning on the surface of TiO2 nanosheets for photocatalytic Rhodamine B degradation activity was identified. This remarkably enhanced photocatalytic activity of edge-site deposited Au/TiO2 nanosheets can be attributed to the synergistic effect between the Au nanocrystals and its intimate interfacial contact with TiO2 nanosheets having (001) facet exposure, which greatly improved the separation rate of the photogenerated carriers. Interestingly, from the photocurrent response measurements, it was found that the edge-site deposited Au/TiO2 nanosheets showed significantly enhanced visible photocurrent response activity compared to the randomly-deposited Au/TiO2 nanosheets. We believe that the proposed strategy, based on engineering the position of Au nanocrystals on TiO2 nanosheets, will encourage further interest in the development of high-performance wide bandgap semiconductor photocatalysts under visible light.

In this work, we reported the design and synthesis of a new type of polymer-graphene hybrid material by supramolecular self-assembly of polyacrylic acid (PAA) and graphene to form a robust sponge-like PAA-graphene gel (PAA-GG) with internally well-defined porous structure, followed by electrodepositon of high-density and well-dispersed MnO2 nanowires on outer and inner surface of PAA-GG scaffold. The as-obtained MnO2/PAA-GG uniquely combines a series of structural and electrochemical characteristics of its precursors, including large surface area, improved capacitive properties and enhanced electrocatalytic activities, fostering versatile applications as electrochemical capacitor and biosensor. Our results show that the symmetric capacitor assembled by MnO2/PAA-GG electrode presents a specific capacitance of 123 F g−1 under a current density of 0.5 A g−1, and its specific capacitance only loss 13.8% after 5000 cycles. For potential application as electrochemical biosensor, MnO2/PAA-GG exhibits high sensitivity and selectivity in nonenzymatic detection of H2O2. The linear range is between 0.05 mM and 50 mM with a low detection limit down to 10 μM, which enables it to be used for real-time tracking of H2O2 secretion in live cells. These promising features make the inorganic/polymer-graphene hybrid gel attractive for a wide spectrum of applications in energy, electrocatalysis and bioanalytical areas.

The Internet of Things (IoT) presents opportunities to address a variety of systemic, metabolic healthcare issues. Cardiovascular disease and diabetes are among the greatest contributors to premature death worldwide. Wireless wearable continuous monitoring systems such as ECG sensors connected to the IoT can greatly decrease the risk of death related to cardiac issues by providing valuable long-term information to physicians, as well as immediate contact with emergency services in the event of a heart attack or stroke. In this report we discuss the fabrication, characterization and validation of composite fabric ECG sensors made from Nylon® coated with reduced graphene oxide (rGOx) as part of a self-powered wearable IoT sensor. We utilize an electronic probing station to measure electrical properties, take live ECG data to measure signal reliability, and provide detailed surface characterization through scanning electron microscopy. Finally, bonding between the layers of the composite and between composite and the Nylon® is analyzed by Fourier transform Infrared spectroscopy. Furthermore, a low power analog front end circuit designed in 65 nm CMOS process is presented to interface the sensor with a system on chip used in a wearable IoT healthcare device.

The development of miniaturized flexible energy storage devices has attracted tremendous research interests for their wide spectrum of applications in various advanced wearable and smart electronic devices. In this work, we have developed a new type of on-chip micro-supercapacitor (mSC) using MXene (i.e., Ti3C2TX)-carbon nanotubes (CNTs) composite as the electrode material via photolithography technique and subsequent vacuum-filtration process. While preparing electrode material for mSC, Ti3C2TX holds several merits such as flat and flexible layered structure, huge surface area and high electrical conductivity. The integration of CNTs with Ti3C2TX leads to the formation of layer-by-layer (LbL) assembly, where CNTs act as the spacer to prevent the stacking and aggregation of Ti3C2TX nanosheets during the assembly process. Consequently, the resultant Ti3C2TX-CNTs electrode material offers flexible layered channels and controllable electronic structures for rapid diffusion of electrolyte ions, which give rise to a significant improvement in the capacitive performance. The as-fabricated mSC device based on Ti3C2TX-CNTs LbL assembly exhibits good areal capacitance of 61.38 mF/cm2 at a current density of 0.5 mA/cm2, outperforming most of MXene or carbon materials based mSCs. Furthermore, it also demonstrates the capability to be operated in serial and parallel configuration to provide a large energy storage or high power output to satisfy the practical use. Therefore, this strategy for the construction of high-performance flexible mSC based on Ti3C2TX-CNTs LbL assembly shows great potential in flexible microelectronic devices.

Two-dimensional Ti3C2Tx MXene nanosheets with excellent electrical conductivities have been synthesized in this work. The nanosheet is further assembled with air-laid paper and polydimethylsiloxane substrate, for sensing both tensile and torsional deformations. Results show that the sensor is able to detect a linear stretchability of up to 90% with the corresponding gauge factor of 1–2.58. After repeated stretching and releasing cycles at a strain of 10% for 2000 cycles, the remaining change of relative resistance is only 0.1. Particularly, the sensor also displays responsive electrical signal change when torqued from 0 to 2π radian, suggesting a potential application for torsion deformation detecting. For demonstration, the sensor is applied in real-time monitoring the physiological movements, revealing outstanding capability of recognizing motions of finger bending, squat/rise, speaking and twisting.

We report a simple and robust strategy to prepare pH-responsive biphasic Janus particles composed of polystyrene/poly(2-vinylpyridine) (PS/P2VP) homopolymers that are able to control the reversible formation, breakage, and switching of Pickering emulsions depending on their geometry- and pH-dependent hydrophilic–lipophilic balance. The chemical stability of these PS/P2VP Janus particles was tuned through the incorporation of cross-linkable benzophenone units along the backbone of the homopolymers. By employing these stabilized particles as emulsifiers for toluene and water, a facile transformation of emulsion types (i.e., from toluene-in-water to water-in-toluene emulsions) was achieved by adjusting the pH of the aqueous phase. More importantly, this pH-dependent switching behavior and associated stability of the emulsions could be actively controlled by adjusting the relative size ratio of PS to P2VP. When the PS volume fraction (ϕPS) was between 0.33 and 0.67, a wide range tuning of emulsion phase inclu...

In this study, the graphene coated piezo-resistive fabrics have been exploited for liquid composite molding process monitoring. The utility of this novel technique has been demonstrated through compaction and flow monitoring experiments. The coated fabrics are subjected to a series of compaction tests to monitor resistance changes during the compaction cycle. During mechanical compression, the change in resistance has been found to be inversely proportional to the strain associated with the applied load. The repeatability of the change in the electrical resistance is confirmed via a series of vacuum assisted, stepwise and cyclic compression tests. The overall sensitivity of around 30% change in resistance is observed. The results highlight very small differences between the wet and dry compaction cycles when using silicone oil as the test fluid, suggesting that a nonconductive fluid offers negligible interference in the graphene coatings. The fabrics are subsequently used in a full resin infusion cycle to monitor the resistance change during the filling and post-filling stages. A continuous change in the resistance of the fabric is observed during, and after resin infusion process, highlighting the applicability of this novel technique for full process monitoring during the compaction and resin flow stages, in addition to cure monitoring.

In this paper, we synthesize a new type of Ni-Co selenides (Ni 0.34 Co 0.66 Se 2 nanorod) on carbon fiber paper (CFP) as flexible electrode for supercapacitor. Comparing with NiCo 2 O 4 and NiCo 2 S 4 , the Ni 0.34 Co 0.66 Se 2 exhibits superior capacitive performance including high areal capacitance (2.61 F cm −2 at 4 mA cm −2 ), good rate capability (75% of retention from 4 to 20 mA cm −2 ) and excellent long-term cycling stability (only 7.4% of loss after 6000 cycles). When assembled into a symmetric supercapacitor, the as-obtained, Ni 0.34 Co 0.66 Se 2 based device possesses a volumetric capacitance of 14.55 F cm −3 at 1 mA cm −2 , and a volumetric energy density of 0.47 mWh cm −3 at 10 mA cm −2 , which are superior to most of the symmetric supercapacitors reported previously. Then we explore the energy storage mechanism of Ni 0.34 Co 0.66 Se 2 by monitoring the changes in component, morphology, electroactive surface area (ESA) and electron transport characteristics. It is found that the Ni 0.34 Co 0.66 Se 2 species suffer from serious Se loss and transform into Ni x Co 1-x O gradully during charge/discharge cycles, but the ESA increases significantly in this process. In addition, the Ni 0.34 Co 0.66 Se 2 electrode possesses lower internal resistance, indicating its good electron transfer properties. Both these factors will compensate the performance degradation from Se loss, resulted in better rate capability and cycling stability for Ni 0.34 Co 0.66 Se 2 electrode. Therefore, it is believed that the proposed 3D Ni 0.34 Co 0.66 Se 2 nanorod array modified CFP with optimizational component and structual design opens a new horizen in the development of high-performance flexible supercapacitor electrode with new charge storage mechanism.

In this paper, we reported the preparation of a new type of highly hydrophobic and ultralight 3D porous graphene aerogel (GA) with graphene oxide as precursor and melamine formaldehyde (MF) microspheres as spacer and pore forming agent, followed by hydrothermal reduction, freeze-drying and calcination process. The resultant calcined MF-GA (cMF-GA) integrates a collection of unique properties including high porosity (up to 99.7%), large specific surface area (317 m 2 /g), low density (5 mg/cm 3 ) and high hydrophobicity (contact angle 141°), and therefore shows excellent absorption capacity to the organic solvent and oils. The results indicate that cMF-GA exhibits fast absorption rate within 20 s and maximum sorption capacities up to 220 g/g for acetone, cyclohexane and toluene, 270 g/g for phenixin, and 230 g/g for diesel oil, which are superior to previously reported carbon-based superabsorbents. Moreover, the proposed cMF-GA absorbent shows good recyclability and its recovery maintains at 91% after 10 cycles. These characteristics demonstrate the great promise of cMF-GA as a highly efficient and low-cost absorbent in practice application of removing large-scale oil or toxic organic spills.

Some of the most advanced laptop computers have their trackpads made to detect both force and position precisely. These trackpads are made of intricately designed force sensors, taptic engines and capacitive glass surfaces. In this study, we have modified simple Nylon ® fabric which senses both force and position. A commercially available Nylon ® fabric was coated with reduced graphene (rGO) in a layer by layer fashion such that the individual fibers of the fabric get wrapped by rGO and the fabric looks like dyed with grey color. The SEM images of the twisted individual rGO coated fibers show that the coating remains undamaged until a twist angle of about 1800°. An in situ applied pressure in compression, on the fabric, of about 2500 kPa changes its resistance 8 kΩ relative to its original resistance with a durability of up to 6000 cycles. Single rGO coated fibers quarantined and tested for their strain sensitivity show that an in situ bending radius of 1 mm changes its resistance to 326 ± 21 kΩ relative to its original resistance. With the help of a read-out circuit it was also showed that quarantined rGO coated fibers arranged in a 2 × 2 grid format sense the position of the applied force.

To bestow intelligent functions upon clothing textiles, wearable electronics must be able to accommodate complex deformations. Both stretchable and bendable building blocks have previously been demonstrated, but torsionable components are still lacking. Here we report a fiber-shaped flexible supercapacitor that is highly stable under torsional deformations, with a very small capacitance variation around its average value (

In response to the increasing concern for energy management, molybdenum disulfide (MoS

We introduce a novel and facile synthesis strategy to design 2D MXene (Ti3C2Tx) nanosheets (NSs) coated cellulose fibers (CLF) based 3D nanostructures (CLF@Ti3C2Tx) to overcome the drawbacks of co-ion expulsion in carbon-based, commonly used CDI electrodes and restacking of MXene NSs due to van der Waals forces in the pure MXene based electrodes. CLF extracted from facial tissue paper were used as a porous carbon core-substrate to coat shell of exfoliated two-dimensional (2D) Ti3C2Tx NSs in order to prepare unique CLF@Ti3C2Tx nanostructures composite by an improved dip-coating method. After appropriate structural and chemical characterization, the designed CLF@Ti3C2Tx material was assembled in symmetric capacitive deionization (CDI) cell as an active electrode and the electrochemical properties and desalination capacity were studied in detail. Interestingly, the CLF@Ti3C2Tx based active electrodes displayed good specific capacitance of 142 F·g−1 in 1 M sodium chloride electrolyte, and high salt adsorption capacitance of 35 mg·g−1 compared with the pure MXene and carbon-based electrodes at an applied voltage of 1.2 V, with considerable cycling stability of 10 cycles. Inspired by the conventional chemical gilding process, the proposed unique and low-cost synthesis strategy and unique design open a new way to develop MXene-carbon based composite nanostructures for CDI and energy storage applications.

Carbon nanomaterial-coated piezoresistive fiber sensors are finding applications in many industries for in-situ process and structural health monitoring of composites. These nanomaterials are embedded within the composite in two different ways; either by incorporating them in the matrix, or by depositing them on fibrous reinforcements. This review highlights the utility of carbon nanomaterials as deposition materials for fiber reinforcements and turning them into sensors for process monitoring during manufacturing and structural health monitoring during in-service life. A number of different strategies to coat carbon nanomaterials on fiber reinforcements are also discussed. A review of various monitored parameters during composites manufacturing such as reinforcement compaction response, flow-front tracking, and resin gelation and cure, as well as damage detection of finished composites using nanomaterial-coated in-situ sensors is also presented. Finally, current and future challenges are discussed where new types of 2D materials and their hybrids for next generation smart sensors are highlighted.

Wearable devices that can be used to monitor personal health, track human motions, and provide thermotherapy, etc., are highly desired in personalized healthcare. In this work, a multifunctional wearable "wrist band" which works as both heater for thermotherapy and sensor for personal health and motion monitoring is fabricated from a flexible and conductive carbon sponge/polydimethylsiloxane (CS/PDMS) composite. The key functional material of the wrist band, namely, the conductive CS, is synthesized from waste paper by a freeze-drying and high-temperature pyrolysis process. When the wrist band works as a heater under 15 V, a stable temperature difference of 20 °C is achieved between the wrist band and the ambient. When the wrist band serves as a wearable strain sensor, the wrist band exhibits fast and repeatable response and excellent durability within the strain range of 0-20% and the working frequency of 0.01-10 Hz. Finally, the typical applications of the multifunctional wearable wrist band, as a heater for thermotherapy and a sensor for blood pulse, breathe, and walk monitoring, are demonstrated. Due to its low cost, high flexibility, moderate conductivity, and excellent strain sensibility, the as-prepared wearable device based on the CS/PDMS composite is promising to be applied for the provision of personal healthcare.

We introduce a simple method to fabricate a highly flexible resistive-type strain sensor composed of carbon paper (CP) and polydimethylsiloxane (PDMS) elastomer. The key resistance sensitive material of the sensor, carbon paper, is prepared from tissue paper by a simple high-temperature pyrolysis process. At the same time, the as-fabricated CP/PDMS strain senor is highly sensitive to applied strain with a gauge factor of 25.3, almost 10 times higher than that of conventional metallic strain gauge. Furthermore, the response of CP/PDMS strain sensor under cyclic tensile strain with a peak strain of 3% was also investigated, which exhibits fast and steady response with excellent durability within the frequency range 0.01–10 Hz. Finally, we demonstrate the successful utilization of the CP/PDMS strain sensor as wearable electronics in breath monitoring and robot controlling. The eminent performance, low material cost, and facile fabrication process make the CP/PDMS strain sensor exceptionally promising in flex...

A new series of n-type D–A terpolymers (P(NDI2HD-T-S)) was synthesized from an electron-deficient naphthalene diimide (NDI)-based unit in conjugation with two electron-rich thiophene (T) and selenophene (S) units, and their performances as electron acceptors in all-polymer solar cells (all-PSCs) were compared. The crystallinity of the P(NDI2HD-T-S) terpolymers can be systematically controlled by tuning the T/S molar ratios (T/S=100/0, 80/20, 50/50, 20/80 and 0/100) in the polymer backbone. An increase in the S content induced a significant enhancement in the crystallinity of the terpolymers. Therefore, the incorporation of more S units enhanced the structural ordering of the terpolymers and the electron mobility in the all-PSCs. The power conversion efficiency of the all-PSCs based on a P(NDI2HD-T-S) terpolymer acceptor and a PTB7 polymer donor increased from 2.50 to 3.60% as the S content increased, which was primarily due to the enhanced short-circuit current. To understand the effects of the T/S compositions on the photovoltaic performances, we investigated their influence on the optical, electrical and structural properties of the n-type D–A terpolymers. A series of n-type D–A terpolymers (P(NDI2HD-T-S)) with various thiophene (T) and selenophene (S) compositions (T/S=100/0, 80/20, 50/50, 20/80 and 0/100) was successfully synthesized. To understand the effects of the T/S ratios, we studied their influence on the optical, electrical and structural properties. The insertion of more S content in the polymer backbone induced the enhanced structural ordering and electron mobility. Therefore, the all-polymer solar cells based on PTB7:P(NDI2HD-T-S) blend had greatly improved efficiency as the S content increased.

We are reporting the formation of free-standing graphene foam (GF) via a novel two-step process, in which a polyurethane (PU) foam is first dip-coated with graphene oxide (GO) and subsequently the dried GO-coated-PU is heated in nitrogen atmosphere at 1000°C. During the pyrolysis of the GO-coated-PU, GO is reduced to GF whereas PU is simultaneously decomposed and released completely as volatiles in a step wise mass-loss mechanism. Morphology of the formed GF conforms to that of the pure PU foam as indicated by the scanning electronic micrographs. Polydimethylsiloxane (PDMS) was successfully infiltrated inside the GF to form flexible and stretch-able conductors. The GF-PDMS composite was tested for it’s pressure and strain sensing capabilities. It is shown that a 30% compressive strain changes resistance of the GF-PDMS composite to about 800% of it’s original value. Since density of the formed GF is tunable, therefore, the pressure/strain sensivity of the GF-PDMS composite is also tunable.

Functionalized textiles and graphene are both emerging materials for wearable technologies. Here, we unite graphene with ordinary textiles and report the development of graphene-clad, conductive textile electrodes for biosignal acquisition specifically in cardiac monitoring. The proposed electrode was prepared by dipping nylon fabric in reduced graphene oxide (rGO) solution followed by a subsequent thermal treatment to allow conformal coating of conductive graphene layers around the fabric. The application of the electrode was demonstrated by successful measurements of the electrocardiogram (ECG). Performance of the textile-based electrodes were compared to the conventional silver/silver chloride (Ag/AgCl) electrodes in terms of skin-electrode impedance, ECG signal quality and noise levels. Excellent conformity and cross correlation of 97% was achieved between the signals measured with the new graphene-clad textile electrodes and conventional electrodes.

Capacitive deionization (CDI) is one of the most efficient and emerging techniques for water desalination applications. This work reports the development, characterization and CDI studies of watermelon derived activated carbon (WMAC) and its MnFe2O4 composite (WMAC/MnFe2O4) for NaCl desalination. WMAC was prepared through single-step low-temperature pyrolysis by H3PO4 activation. Facile synthesis of spinel MnFe2O4 nanoparticles on WMAC surface was performed through the hydrothermal technique. Morphological, textural and physico/electro–chemical analysis showed the effect of MnFe2O4 incorporation on WMAC. The nanocomposite possessed definite crystallites, low structural disorders and sufficient magnetization for electrochemical applications. Also, the nanocomposite was dominantly composed of mesopores with a specific surface area of 483 m2/g. The high specific capacitance value of 425 F/g (scan rate – 10 mV/s) along with better stability and low charge resistance, confirmed the suitability of WMAC/MnFe2O4 as an efficient electrode material for CDI applications. NaCl removal studies using WMAC/MnFe2O4 showed an electrosorption capacity of 29.7 mg/g for the nanocomposite, with rapid desalination and good recyclability. A plausible mechanism of salt adsorption and desorption is also presented. WMAC/MnF2O4 exhibited significant application potential for the industrial desalination.

The integration of different functional components into one device is attracting increasing attention. In this work, a high strength carbon nanotube (CNT) fiber/polyacrylamide (PAAm) hydrogel composite is developed by embedding quasi-sinusoidal shaped CNT fibers in PAAm hydrogel. Combination of ionic conductive hydrogel and wavy CNT fibers yields a highly stretchable and wearable device with integration of strain sensing component and electrochemical energy storage component. On the one hand, the CNT fiber/PAAm hydrogel (CFPH) composite shows an excellent strain sensing performance with a stretch-ability up to 100% in a wide frequency of 0.1–10 Hz. As a result, it is effective as stretchable and wearable strain sensor to monitor a range of small to large scale human activities. On the other hand, with two parallel quasi-sinusoidal shaped CNT fibers as electrodes and one ionic conductive PAAm hydrogel as electrolyte and separator simultaneously, the CFPH composite serves as a stretchable all-solid-state supercapacitor with an areal capacitance of 10.6 mF cm−2. The electrochemical performance of the CFPH composite under both static and dynamic loading is very stable, exhibiting a capacitance retention of 90.0% after 3000 charge-discharge cycles with dynamic stretching applied simultaneously. The developed dual-mode CNT fiber/PAAm hydrogel composite is promising to serve as two functional components in one device.