MnO2 Nanowire/Biomass-Derived Carbon from Hemp Stem for High-Performance Supercapacitors.

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 fabricated using 3D HC as the anode and 3D MnO2/HC as the cathode are able to store 33.3 Wh kg-1 of energy and have a power delivery of 14.8 kW kg-1.

Nanopillar films with polyoxometalate-doped polyaniline for electrochemical detection of hydrogen peroxide.

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.

Development of Lateral Flow Assay Based on Size-Controlled Gold Nanoparticles for Detection of Hepatitis B Surface Antigen.

In this study, we developed lateral flow assay (LFA) biosensors for the detection of hepatitis B surface antigens using well-controlled gold nanoparticles (AuNPs). To enhance colorimetric signals, a seeded growth method was used for the preparation of size-controlled AuNPs with a narrow size distribution. Different sizes of AuNPs in the range of 342-137.8 nm were conjugated with antibodies and then optimized for the efficient detection of LFA biosensors. The conjugation stability was investigated by UV-vis spectroscopy of AuNP dispersion at various pH values and concentrations of antibody. Based on optimized conjugation conditions, the use of 42.7 ± 0.8 nm AuNPs exhibited superior performance for the detection of LFAs relative to other sizes of AuNPs.

Bio-inspired Hierarchical Nanowebs for Green Catalysis.

Bio-inspired 3D hierarchical nanowebs are fabricated using silicon micropillars, carbon nanotubes (CNT), and manganese oxide. The Si pillars act as artificial branches for growing CNTs and the secondary metal coating strengthens the structures. The simple but effective structure provides both chemical and mechanical stability to be used as a green catalyst for recycling waste polymers into raw materials.

Hierarchical core/shell structure of MnO2@polyaniline composites grown on carbon fiber paper for application in pseudocapacitors.

Hierarchical core/shell structured arrays of MnO2@polyaniline (PANI) nanosheets are successfully deposited on the surface of carbon fiber paper (CFP) by a two-step method of a redox reaction-assisted deposition of MnO2 and post electrodeposition of PANI. The CFP is used as a three-dimensional (3D) current collector to ensure 3D transport of ions and electrons with a large surface area. In addition, the electrodeposition technique enables conformal and thin coating of a layer of PANI across the entire MnO2 nanosheet. The MnO2@PANI on the CFP shows a unique architecture for efficient ion diffusion pathways in hierarchical porous structures and rapid electron transfer through PANI coated layers. The MnO2@PANI/CFP can be applied as a binder- and carbon-free electrode for supercapacitors. Evaluation of the electrochemical performance revealed that the as-prepared electrodes have a high value of specific capacitance (437 F g(-1) at 1 A g(-1)), high rate capability (62.4% retention at 15 A g(-1)), and good cycle life (∼100% at sequential current densities of 1 and 5 A g(-1) over 3000 cycles).

Nanotopology-Enabled On-Site Pathogen Detection for Managing Atopic Dermatitis.

Atopic dermatitis (AD), a prevalent skin condition often complicated by microbial infection, poses a significant challenge in identifying the responsible pathogen for its effective management. However, a reliable, safe tool for pinpointing the source of these infections remains elusive. In this study, a novel on-site pathogen detection that combines chemically functionalized nanotopology with genetic analysis is proposed to capture and analyze pathogens closely associated with severe atopic dermatitis. The chemically functionalized nanotopology features a 3D hierarchical nanopillar array (HNA) with a functional polymer coating, tailored to isolate target pathogens from infected skin. This innovative nanotopology demonstrates superior pathogenic capture efficiency, favorable entrapment patterns, and non-cytotoxicity. An HNA-assembled stick is utilized to directly retrieve bacteria from infected skin samples, followed by extraction-free quantitative loop-mediated isothermal amplification (direct qLAMP) for validation. To mimic human skin conditions, porcine skin is employed to successfully capture Staphylococcus aureus, a common bacterium exacerbating AD cases. The on-site detection method exhibits an impressive detection limit of 103 cells mL-1. The HNA-assembled stick represents a promising tool for on-site detection of bacteria associated with atopic dermatitis. This innovative approach enables to deepen the understanding of AD pathogenesis and open avenues for more effective management strategies for chronic skin conditions.

Polyaniline-based 3D network structure promotes entrapment and detection of drug-resistant bacteria.

Sensitive and accurate capture, enrichment, and identification of drug-resistant bacteria on human skin are important for early-stage diagnosis and treatment of patients. Herein, we constructed a three-dimensional hierarchically structured polyaniline nanoweb (3D HPN) to capture, enrich, and detect drug-resistant bacteria on-site by rubbing infected skins. These unique hierarchical nanostructures enhance bacteria capture efficiency and help severely deform the surface of the bacteria entrapped on them. Therefore, 3D HPN significantly contributes to the effective and reliable recovery of drug-resistant bacteria from the infected skin and the prevention of potential secondary infection. The recovered bacteria were successfully identified by subsequent real-time polymerase chain reaction (PCR) analysis after the lysis process. The molecular analysis results based on a real-time PCR exhibit excellent sensitivity to detecting target bacteria of concentrations ranging from 102 to 107 CFU/mL without any fluorescent signal interruption. To confirm the field applicability of 3D HPN, it was tested with a drug-resistant model consisting of micropig skin similar to human skin and Klebsiella pneumoniae carbapenemase-producing carbapenem-resistant Enterobacteriaceae (KPC-CRE). The results show that the detection sensitivity of this assay is 102 CFU/mL. Therefore, 3D HPN can be extended to on-site pathogen detection systems, along with rapid molecular diagnostics through a simple method, to recover KPC-CRE from the skin.

Highly Stretchable Sensor Based on Fluid Dynamics-Assisted Graphene Inks for Real-Time Monitoring of Sweat.

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.

Highly Concentrated, Conductive, Defect-free Graphene Ink for Screen-Printed Sensor Application.

HIGHLIGHTS: Ultrathin and defect-free graphene ink is prepared through a high-throughput fluid dynamics process, resulting in a high exfoliation yield (53.5%) and a high concentration (47.5 mg mL-1). A screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m-1 and good mechanical flexibility. An electrochemical sodium ion sensor based on graphene ink exhibits an excellent potentiometric sensing performance in a mechanically bent state. Real-time monitoring of sodium ion concentration in sweat is demonstrated. Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices. However, the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions. In this study, a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process. A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL-1 for graphene ink. The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49 × 104 S m-1 and maintains high conductivity under mechanical bending, compressing, and fatigue tests. Based on the as-prepared graphene ink, a printed electrochemical sodium ion (Na+) sensor that shows high potentiometric sensing performance was fabricated. Further, by integrating a wireless electronic module, a prototype Na+-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer. The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost, reproducible, and large-scale printing of flexible and wearable electronic devices.

Touchable 3D hierarchically structured polyaniline nanoweb for capture and detection of pathogenic bacteria.

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.

3D Hierarchical Polyaniline-Metal Hybrid Nanopillars: Morphological Control and Its Antibacterial Application.

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.

3D Hierarchical Nanotopography for On-Site Rapid Capture and Sensitive Detection of Infectious Microbial Pathogens.

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 (<30 s) and irreversible bacterial capturability. Moreover, the nuclease-responsive DNA probe enables the highly sensitive and extremely fast (<1 min) detection of bacteria. The bacterial capturing nanotopographical trap (b-CNT) facilitates the on-site capture and detection of notorious infectious pathogens (Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus, and Bacillus cereus) from kitchen tools and food samples. Accordingly, the usefulness of the b-CNT is confirmed as a simple, fast, sensitive, portable, and robust on-site capture and detection tool for point-of-care testing.

Energy transfer in ionic-liquid-functionalized inorganic nanorods for highly efficient photocatalytic applications.

Energy transfer in self-assembled ionic liquids (ILs) and iron oxyhydroxide nanocrystals and the controlled surface chemistry of functionalized nanomaterials for photocatalytic applications are reported. Self-assembled ILs play the role of multifunctional materials in terms of constructing a well-designed nanostructure, controlling the surface chemistry, and triggering the energy transfer of functionalized materials. IL-functionalized beta-FeOOH nanorods show approximately 10-fold higher performances than those of commercial materials due to the synergistic effect of well-defined nanomaterials in diffusion-controlled reactions, specific interactions with target pollutants, and energy transfers in hybrid materials. In particular, the energy transfer in C(4)MimCl-functionalized beta-FeOOH nanorods enhances photocatalytic activity due to the generation of Fe(2+). The strategy described herein provides new insight into the rational design of functionalized inorganic nanomaterials for applications in emerging technologies.

Flexible nanopillar-based immunoelectrochemical biosensor for noninvasive detection of Amyloid beta.

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 ß-amyloid (Aß) detection. Moreover, we successfully confirmed the performance of the as-developed sensor using the artificial injection of Aß 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.

Antibacterial Nanopillar Array for an Implantable Intraocular Lens.

Postsurgical intraocular lens (IOL) infection caused by pathogenic bacteria can result in blindness and often requires a secondary operation to replace the contaminated lens. The incorporation of an antibacterial property onto the IOL surface can prevent bacterial infection and postoperative endophthalmitis. This study describes a polymeric nanopillar array (NPA) integrated onto an IOL, which captures and eradicates the bacteria by rupturing the bacterial membrane. This is accomplished by changing the behavior of the elastic nanopillars using bending, restoration, and antibacterial surface modification. The combination of the polymer coating and NPA dimensions can decrease the adhesivity of corneal endothelial cells and posterior capsule opacification without causing cytotoxicity. An ionic antibacterial polymer layer is introduced onto an NPA using an initiated chemical vapor deposition process. This improves bacterial membrane rupture efficiency by increasing the interactions between the bacteria and nanopillars and damages the bacterial membrane using quaternary ammonium compounds. The newly developed ionic polymer-coated NPA exceeds 99% antibacterial efficiency against Staphylococcus aureus, which is achieved through topological and physicochemical surface modification. Thus, this paper provides a novel, efficient strategy to prevent postoperative complications related to bacteria contamination of IOL after cataract surgery.

Highly self-healable and flexible cable-type pH sensors for real-time monitoring of human fluids.

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.

Development of zinc oxide-based sub-micro pillar arrays for on-site capture and DNA detection of foodborne pathogen.

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.

Preparation of ultrathin defect-free graphene sheets from graphite via fluidic delamination for solid-contact ion-to-electron transducers in potentiometric sensors.

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.

Ionic-liquid-assisted sonochemical synthesis of carbon-nanotube-based nanohybrids: control in the structures and interfacial characteristics.

A versatile, facile, and rapid synthetic method of advanced carbon nanotube (CNT)-based nanohybrid fabrication, or the so-called ionic-liquid-assisted sonochemical method (ILASM), which combines the supramolecular chemistry between ionic liquids (ILs) and CNTs with sonochemistry for the control in the size and amount of uniformly decorated nanoparticles (NPs) and interfacial engineering, is reported. The excellence in electrocatalysis of hybrid materials with well-designed nanostructures and favorable interfaces is demonstrated by applying them to electrochemical catalysis. The synthetic method discussed in this report has an important and immediate impact not only on the design and synthesis of functional hybrid nanomaterials by supramolecular chemistry and sonochemistry but also on applications of the same into electrochemical devices such as sensors, fuel cells, solar cells, actuators, batteries, and capacitors.

Green one-pot assembly of iron-based nanomaterials for the rational design of structure.

Green one-pot solution chemistry described herein could delicately manipulate the size and shape of iron oxyhydroxide nanocrystals, even in the aqueous phase, and easily derive a family of iron-based nanomaterials.