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Graphene inks have recently attracted attention for the development of printed wearable and flexible electronics and sensors not only because of their high conductivity and low cost but also because they are suitable for high-speed printing. Although reliable and scalable printing technologies are well established, further improvement in graphene inks in terms of electrical conductivity, stretchability/flexibility, and mass production is necessary for sensors for real-time monitoring. Herein, highly stretchable and conductive graphene inks were prepared by an efficient and scalable fluid dynamics-assisted exfoliation of graphite and a mixing process with elastomeric Ecoflex. After printing inks onto textile substrates, the serpentine-patterned conductors exhibited high conductivity and stable resistance even under a mechanically stretched state (a strain of 150%). Electrochemical sensors that detect sodium ions were fabricated on this conducting platform. These sensors indicated high potentiometric sensing ability under different mechanical deformations. To demonstrate the on-body performance of the developed sensors, real-time monitoring of sodium-ion concentration in the sweat of a human subject was carried out during an indoor stationary cycling exercise.

Effective capture and rapid detection of pathogenic bacteria causing pandemic/epidemic diseases is an important task for global surveillance and prevention of human health threats. Here, we present an advanced approach for the on-site capture and detection of pathogenic bacteria through the combination of hierarchical nanostructures and a nuclease-responsive DNA probe. The specially designed hierarchical nanocilia and network structures on the pillar arrays, termed 3D bacterial capturing nanotopographical trap, exhibit excellent mechanical reliability and rapid (

In this study, two-dimensional (2D) and exfoliated FeIII nanosheets are prepared using a fast and facile fluid-dynamics-induced exfoliation method for large-scale production. The resulting FeIII nanosheet is ultrathin and of 2D morphology with a high surface area. The FeIII nanosheet exhibits excellent glycolysis-catalytic performance for polyethylene terephthalate (PET) degradation to produce a bis(hydroxyethyl) terephthalate (BHET) monomer. A high PET conversion of 100% and a high BHET yield of 100% using the FeIII nanosheet catalyst are achieved within a short reaction time (30 min) at a reaction temperature of 200 °C. Furthermore, the FeIII nanosheet catalyst shows excellent recyclability for the glycolysis of PET, and a high BHET yield of 96.7% was obtained after five cycles.

Two-dimensional molybdenum disulfide (MoS2) nanosheets have attracted great attention for electrochemical storage and conversion, but the scalable preparation of highly conductive and stable MoS2 n...

Flexible, thin, and lightweight supercapacitors have been regarded as important power sources for portable and wearable electronics; however, these are usually limited by relatively low areal or vo...

In this study, ultrathin and defect-free graphene (Gr) sheets were prepared through a fluid dynamics–induced shear exfoliation method using graphite. The high hydrophobicity and surface area of Gr make it attractive as a solid-contact ion-to-electron transducer for potentiometric K+ sensors, in which the electrodes are fabricated through a screen-printing process. The electrochemical characterization demonstrates that Gr solid contact results in a high double-layer capacitance, potential stability, and strong resistance against water layer, gases, and light. The Gr-based K+ sensors showed a Nernstian slope of 53.53 mV/log[K+] within a linear concentration range of 10−1–10−4 M, a low detection limit of 10−4.28 M, a fast response time of ~8 s, good repeatability, and excellent long-term stability. Moreover, the Gr-based K+ sensors provided accurate ion concentrations in actual samples of human sweat and sports drinks.

A bacteria-capturing platform is a critical function of accurate, quantitative, and sensitive identification of bacterial pathogens for potential usage in the detection of foodborne diseases. Despite the development of various nanostructures and their surface chemical modification strategies, relative to the principal physical contact propagation of bacterial infections, mechanically robust and nanostructured platforms that are available to capture bacteria remain a significant problem. Here, a three-dimensional (3D) hierarchically structured polyaniline nanoweb film is developed for the efficient capture of bacterial pathogens by hand-touching. This unique nanostructure ensures sufficient mechanical resistance when exposed to compression and shear forces and facilitates the 3D interfacial interactions between bacterial extracellular organelles and polyaniline surfaces. The bacterial pathogens (Escherichia coli O157:H7, Salmonella enteritidis, and Staphylococcus aureus) are efficiently captured through finger-touching, as verified by the polymerase chain reaction (PCR) analysis. Moreover, the real-time PCR results of finger-touched cells on a 3D nanoweb film show a highly sensitive detection of bacteria, which is similar to those of the real-time PCR using cultured cells without the capturing step without any interfering of fluorescence signal and structural deformation during thermal cycling. Graphic Abstract

The oxidation reaction of alcohols and amines to their respective aldehydes/ketones and nitriles are important reactions in the laboratory and industry. A highly robust and activated ruthenium supported anodic aluminum oxide (Ru@AAO) have been synthesized through the sonochemical method. The sonochemical technique allowed short synthesis time and uniform distribution of Ru on AAO surface as confirmed by the scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and BET surface area analysis. The synthesized catalyst was employed for the oxidation of alcohols and amines in the presence of atmospheric air at a relatively lower temperature. The synthesized catalyst showed excellent conversions of both alcohols and amines with high selectivities towards their respective aldehydes/ketones and nitriles. The function of the AAO support in Ru@AAO catalytic activity has also been elaborated in the present investigation.

This paper proposes a batteryless chronic wound monitoring system to accurately diagnose the wound states with lowered cost. To acquire various biomarkers, the proposed system could interface different types of sensor signals (voltage, resistive, and capacitive) using dual-slope integrator circuit technology. A time-to-digital converter is used to digitize the acquired signals. The proposed system adopts 13.56-MHz near-field communication for energy harvesting and sending data. The proposed IC is implemented using the standard TSMC 0.18- $\mu \text{m}$ CMOS process and occupies an area of 0.5 mm2. The power consumptions of the proposed interface IC and total system are 1.9 and 3.9 mW, respectively.

We report potentiometric performances of ion-to-electron transducer based on reduced graphene oxide (RGO) for application of all-solid-state potassium ion sensors. A large surface area and pore structure of RGO are obtained by a hydrothermal self-assembly of graphene oxide. The extensive electrochemical characterization of RGO solid contact at the interface of ion-selective membrane and gold electrode shows that the potassium ion-selective electrode based on RGO had a high sensitivity (53.34 mV/log[K+]), a low detection of limit (− 4.24 log[K+], 0.06 mM) a good potential stability, and a high resistance to light and gas interferences. The potentiometric K+-sensor device was fabricated by combining of screen-printed electrodes and a printed circuit board. The K+-sensor device accurately measures the ion concentration of real samples of commercial sports drinks, coke and orange juice, and then transfers the collected data to a mobile application through a Bluetooth module. The screen-printed ion sensors based on RGO solid contact show a great potential for real-time monitoring and point-of-care devices in human health care, water-treatment process, and environmental and chemical industries.

The noninvasive early detection of biomarkers for Alzheimer’s disease (AD) is essential for the development of specific treatment strategies. This paper proposes an advanced method for fabricating highly ordered and flexible nanopillar-based electrochemical biosensors by the combination of soft/photolithography and metal evaporation. The nanopillar array (NPA) exhibits high surface area containing 1500 nm height and 500 nm diameter with 3:1 ratio. In regard with physical properties of polyurethane (PU) substrate, the developed NPA is sustainable and durable to external pressure such as bending and twisting. To manipulate the NPA surface to biocompatible, the gold was uniformly deposited on the PU substrate. The thiol chemistry which is stably modified on the gold surface as a form of self-assembled monolayer was employed for fabricating the NPA as a biocompatible chip by covalently immobilize the antibodies. The proposed nanopillar-based immunoelectrochemical biosensor exhibited good and stable electrochemical performance in β-amyloid (Aβ) detection. Moreover, we successfully confirmed the performance of the as-developed sensor using the artificial injection of Aβ in human tear, with sensitivity of 0.14 ng/mL and high reproducibility (as a standard deviation below 10%). Our findings show that the developed nanopillar-based sensor exhibits reliable electrochemical characteristics and prove its potential for application as a biosensor platform for testing at the point of care.

The integration of metal oxides and carbon materials provides a great potential for enhancing the high energy and power densities of supercapacitors, but the rational design and scalable fabrication of such composite materials still remain a challenge. Herein, we report a fast, scalable, and one-pot hydrodynamic synthesis for preparing ion conductive and defect-free graphene from graphite and MnO2/graphene nanocomposites. The use of this hydrodynamic method using Taylor–Couette flow allows us to efficiently fast shear-exfoliate graphite into large quantities of high-quality graphene sheets. Deposition of MnO2 on graphene is subsequently performed in a fluidic reactor within 10 min. The prepared MnO2/graphene nanocomposite shows outstanding electrochemical performances, such as a high specific capacitance of 679 F/g at 25 mV/s, a high rate capability of 74.7% retention at an extremely high rate of 1000 mV/s, and an excellent cycling characteristic (∼94.7% retention over 20 000 cycles). An asymmetric superc...

In this study, we report that ionic liquid (IL)-assisted ball milling of iron precursors in the absence of any reagent resulted in the scalable production of IL/Fe2O3 hybrids with a favourable morphology (high surface area of 202 m2/g and pore size of 40nm) for supercapacitor applications. During ball milling process, ILs are played role as structure guiding templates for construction of rod-like pore containing Fe2O3 and surface functionalities for IL/Fe2O3 hybrids, resulting in good wettability and enhanced ion transfer. These attractive features of IL/Fe2O3 hybrids make them excellent candidate pseudocapacitive electrode materials that exhibit a high specific capacitance of 230 F/g at a current density of 1 A/g, fast and reversible charge/discharge rates (∼71% retention at 15 A/g), and excellent long-term cycle stability (∼100% retention over 10000 cycles).

Current collectors and substrate materials are of pivotal importance for the design and preparation of electrodes and energy storage devices, because their surface areas, morphologies, ionic and electronic conductivities, and mechanical properties substantially influence electrochemical performances. Although carbon cloths (CCs) are widely considered the most promising current collectors for flexible energy storage devices, the majority of carbon-based textiles have poor capacitances due to their low surface areas and porosities, which reduce device performances. Here, we report a rapid and straightforward method for preparing CC-based electrode materials for high performance supercapacitors using microwaves. Microwave irradiation efficiently activates the surface pores of carbon fibers, and increases specific capacitance markedly as compared with pristine CC. In addition, surfaces of microwave-treated CCs (m-CCs) are coated with reduced graphene oxide (RGO) or MnO2, and the resulting electrode materials exhibit excellent electrochemical performances, such as, high specific capacitances, high rate capabilities, and long-term cycling stabilities. Flexible solid-state supercapacitor devices are fabricated using a RGO/m-CC as a negative electrode and a MnO2/m-CC as a positive electrode. The produced asymmetric supercapacitors show an excellent resilience to harsh electrochemical and mechanical conditions, and high energy and power densities.

Plastic pollution is threatening human health and ecosystems, resulting in one of the biggest challenges that humanity has ever faced. Therefore, this study focuses on the preparation of macroporous carbon from biowaste (MC)-supported manganese oxide (MnO2) as an efficient, reusable, and robust catalyst for the recycling of poly(ethylene terephthalate) (PET) waste. As-prepared MnO2/MC composites have a hierarchical pore network and a large surface area (376.16 m2/g) with a narrow size distribution. MnO2/MC shows a maximum yield (98%) of bis(2-hydroxyethyl)terephthalate (BHET) after glycolysis reaction for 120 min. Furthermore, MnO2/MC can be reused at least nine times with a negligible decrease in BHET yield. Based on this remarkable catalytic performance, we expect that MnO2-based heterogeneous catalysts have the potential to be introduced into the PET recycling industry.

The practical implementation of nanomaterials in high capacity batteries has been hindered by the large mechanical stresses during ion insertion/extraction processes that lead to the loss of physical integrity of the active layers. The challenge of combining the high ion storage capacity with resilience to deformations and efficient charge transport is common for nearly all battery technologies. Layer-by-layer (LBL/LbL) engineered nanocomposites are able to mitigate structural design challenges for materials requiring the combination of contrarian properties. Herein, we show that materials engineering capabilities of LBL augmented by self-organization of nanoparticles (NPs) can be exploited for constructing multiscale composites for high capacity lithium ion anodes that mitigate the contrarian nature of three central parameters most relevant for advanced batteries: large intercalation capacity, high conductance, and robust mechanics. The LBL multilayers were made from three function-determining components...

The development of energy storage electrode materials is important for enhancing the electrochemical performance of supercapacitors. Despite extensive research on improving electrochemical performance with polymer-based materials, electrode materials with micro/nanostructures are needed for fast and efficient ion and electron transfer. In this work, highly ordered phosphomolybdate (PMoO)-grafted polyaniline (PMoO-PAI) deposited onto Au hole-cylinder nanopillar arrays is developed for high-performance pseudocapacitors. The three-dimensional nanostructured arrays are easily fabricated by secondary sputtering lithography, which has recently gained attention and features a high resolution of 10 nm, a high aspect ratio greater than 20, excellent uniformity/accuracy/precision, and compatibility with large area substrates. These 10 nm scale Au nanostructures with a high aspect ratio of ∼30 on Au substrates facilitate efficient ion and electron transfer. The resultant PMoO-PAI electrode exhibits outstanding electrochemical performance, including a high specific capacitance of 114 mF cm−2, a high-rate capability of 88%, and excellent long-term stability.

Paper-based materials have attracted a great deal of attention in sensor applications because they are readily available, biodegradable, inexpensive, and mechanically flexible. Although paper-based sensors have been developed, but important obstacles remian, which include the retention of chemical and mechanical stabilities when paper is wetted. Herein, we develop a simple and scalable process for fabrication of newspaper-based platforms by coating of parylene C and patterning of metal layers. As-prepared parylene C-coated newspaper (PC-paper) provides low-cost, disposable, and mechanically and chemically stable electrochemical platforms for the development of potentiometric ion sensors for the detection of electrolyte cations, such as, H+ and K+. The pH and K+ sensors produced show near ideal Nernstian sensitivity, good repeatability, good ion selectivity, and low potential drift. These disposable, flexible ion sensors based on PC-paper platforms could provide new opportunities for the development of point-of-care testing sensors, for diagnostics, healthcare, and environment testing.

Effective and reliable antibacterial surfaces are in high demand in modern society. Although recent works have shown excellent antibacterial performance by combining unique hierarchical nanotopological structures with functional polymer coating, determining the antibacterial performance arising from morphological changes is necessary. In this work, three-dimensional (3D) hierarchical polyaniline–gold (PANI/Au) hybrid nanopillars were successfully fabricated via chemical polymerization (i.e., dilute method). The morphology and structures of the PANI/Au nanopillars were controlled by the reaction time (10 min to 60 h) and the molar concentrations of the monomer (0.01, 0.1, and 1 M aniline), oxidant (0.002, 0.0067, 0.01, and 0.02 M ammonium persulfate), and acid (0.01, 0.1, 1, and 2 M perchloric acid). These complex combinations allow controlling the hierarchical micro- to nanostructure of PANI on a nanopillar array (NPA). Furthermore, the surface of the 3D PANI/Au hierarchical nanostructure can be chemically treated while maintaining the structure using initiated chemical vapor deposition. Moreover, the excellent antibacterial performance of the 3D PANI/Au hierarchical nanostructure (HNS) exceeds 99% after functional polymer coating. The excellent antibacterial performance of the obtained 3D PANI/Au HNS is mainly because of the complex topological and physicochemical surface modification. Thus, these 3D PANI/Au hierarchical nanostructures are promising high-performance antibacterial materials.

Most manganese oxide-based electrodes used for energy-storage applications suffer from poor ion and electron transport, particularly at high mass loadings and with thick electrodes. To counter this issue, 3D electrodes were developed; however, enhancing their areal and volumetric performance at high mass loadings is still a challenge. In this study, highly compact and 3D porous manganese dioxide and holey reduced graphene oxide (3D MnO2/HRGO) composite films were developed to ensure a high performance in supercapacitors at electrode thicknesses greater than 100 µm. The thick composite films were fabricated by the self-limiting deposition of MnO2 on 3D HRGO hydrogel scaffolds followed by capillary evaporation-induced drying. The 3D MnO2/HRGO electrodes optimized at a thickness of 216 μm showed outstanding specific areal and volumetric capacitances of 2.3 F cm−2 and 108.0 F cm−3 at 1 mA cm−2 and an impressive rate capability with a capacitance retention of 72.2% in the range of 1–40 mA cm−2. Furthermore, supercapacitors assembled with the 3D MnO2/HRGO electrodes with high mass loadings exhibited impressively high areal and volumetric energy densities of 149.7 μWh cm−2 and 2.8 mWh cm−3, respectively.

Three-dimensional (3D) carbon materials derived from waste biomass have been attracted increasing attention in catalysis and materials science because of their great potential of catalyst supports with respect to multi-functionality, unique structures, high surface area, and low cost. Here, we present a facile and efficient way for preparing 3D heterogeneous catalysts based on vertical MnO2 wires deposited on hemp-derived 3D porous carbon. The 3D porous carbon materials are fabricated by carbonization and activation processes using hemp (Cannabis Sttiva L.). These 3D porous carbon materials are employed as catalyst supports for direct deposition of vertical MnO2 wires using a one-step hydrothermal method. The XRD and XPS results reveal the crystalline structure of α-MnO2 wires. The resultant composites are further employed as a catalyst for glycolysis of poly(ethylene terephthalate) (PET) with high conversion yield of 98%, which is expected to be expressly profitable for plastics recycling industry.

Hierarchical 3D nanostructures based on waste biomass are being offered as promising materials for energy storage due to their processabilities, multifunctionalities, environmental benignities, and low cost. Here we report a facile, inexpensive, and scalable strategy for the fabrication of hierarchical porous 3D structure as electrode materials for supercapacitors based on MnO2 nanowires and hemp-derived activated carbon (HC). Vertical MnO2 wires are uniformly deposited onto the surface of HC using a one-step hydrothermal method to produce hierarchical porous structures with conductive interconnected 3D networks. HC acts as a near-ideal 3D current collector and anchors electroactive materials, and this confers a specific capacitance of 340 F g–1 at 1 A g–1 with a high rate capability (88% retention) of the 3D MnO2/HC composite because of its open-pore system, which facilitates ion and electron transports and synergistic contribution of two energy-storage materials. Moreover, asymmetric supercapacitors fab...

The integration of organic and inorganic building blocks into hierarchical porous architectures makes potentially desirable electrocatalytic materials in many electrochemical applications due to their combination of attractive qualities of dissimilar components and well-constructed charge transfer pathways. Herein, we demonstrate the preparation of the hierarchical porous Co3O4@graphene (Co3O4@G) microspheres by one-step hydrothermal method to achieve high electrocatalytic performance for enzyme-free biosensor applications. The obtained Co3O4@G microspheres are consisted of the interconnected networks of Co3O4 and graphene sheets, and thus provide large accessible active sites through porous structure, while graphene sheets offer continuous electron pathways for efficient electrocatalytic reaction of Co3O4. These structural merits with synergy effect of Co3O4 and graphene lead to a high performance of enzyme-free detection for glucose: high sensitivity, good selectivity, and remarkable stability.

Straightforward and scalable fabrications of energy storage electrode materials with high electrochemical performance are of great interest for applications in batteries and supercapacitors. Herein, we report a one-step process for producing high-performance NiO/reduced graphene oxide (RGO) nanocomposites using a ball mill based method, which is simple, environmentally friendly, and cost-effective. Graphite oxide (GO) and nickel power were pulverized in a ball mill, to produce NiO/RGO nanocomposites. GO played an important role in promoting a redox reaction between GO and metallic nickel, which produced a strong bond between the as-formed Ni oxide and RGO. The electrochemical performances of NiO/RGO were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge measurement, and impedance spectroscopy. The NiO/RGO electrodes exhibited high specific capacitance (590 F g− 1 at 1 A g− 1), a high rate capability (88% retention at a high rate of 15 A g− 1), and an excellent cycling stability (100% retention after 1000 charge/discharge cycles).

Sensors with autonomous self-healing properties offer enhanced durability, reliability, and stability. Although numerous self-healing polymers have been attempted, achieving sensors with fast and reversible recovery under ambient conditions with high mechanical toughness remains challenging. Here, a highly sensitive wearable sensor made of a robust bio-based supramolecular polymer that is capable of self-healing via hydrogen bonding is presented. The integration of carbon fiber thread into a self-healing polymer matrix provides a new toolset that can easily be knitted into textile items to fabricate wearable sensors that show impressive self-healing efficiency (>97.0%) after 30 s at room temperature for K+/Na+ sensing. The wearable sweat-sensor system-coupled with a wireless electronic circuit board capable of transferring data to a smart phone-successfully monitors electrolyte ions in human perspiration noninvasively in real time, even in the healed state during indoor exercise. Our smart sensors represent an important advance toward futuristic personalized healthcare applications.

Development of sensing technology with wearable chemical sensors is realizing non-invasive, real-time monitoring healthcare and disease diagnostics. The advanced sensor devices should be compact and portable for use in limited space, easy to wear on human body, and low-cost for personalized healthcare markets. Here, we report a highly sensitive, flexible, and autonomously self-healable pH sensor cable developed by weaving together two carbon fiber thread electrodes coated with mechanically robust self-healing polymers. The pH sensor cable showed excellent electrochemical performances of sensitivity, repeatability, and durability. Spontaneous and autonomous sensor healing efficiency of the pH sensor cable was demonstrated by measuring sensitivity during four cycles of cutting and healing process. The pH sensor cable could measure pH in small volumes of real human fluid samples, including urine, saliva, and sweat, and the results were similar to those of a commercial pH meter. Taken together, successful real-time pH monitoring for human sweat was demonstrated by fabricating a wearable sensing system in which the pH sensor cable was knitted into a headband integrated with wireless electronics.

Prevention and early detection of bacterial infection caused by foodborne pathogens are the most important task to human society. Although currently available diagnostic technologies have been developed and designed for detection of specific pathogens, suitable capturing tools for the pathogens are rarely studied. In this paper, a new methodology is developed and proposed to realize effective capturing through touchable flexible zinc oxide-based sub-micro pillar arrays through genetic analysis. Zinc oxide coated pillar arrays have a high surface area, flexible, and adheres strongly to bacteria. Therefore, it contributes to enhance the bacterial capturability. An in-depth analysis on the sub-sequential capturing process at the bacterial cell-pillar interface is presented. By carefully observing the structural changes and performing numerical analysis under different reaction times, the results are presented. The resulting zinc oxide coated pillar arrays exhibited comprehensive capturability. These pillars were able to detect pathogenic bacteria due to a combination of complex structures, depletion force, and high surface electrostatics. The developed sub-micro pillars successfully captured and detected infectious foodborne bacteria of Escherichia coli in the range of 106–101 CFU/mL.

This paper proposes a batteryless chronic wound monitoring system with commercial discrete components. To monitor the chronic wound, the proposed system acquires the pH and temperature of the chronic wound. The proposed system adopts 13.56-MHz NFC communications to supply power to an interface circuit and send data to mobile phones. The power consumption of the proposed system is 5.0 mW.