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Recently, it has been revealed that the physical microenvironment can be translated into cellular mechanosensing to direct human mesenchymal stem cell (hMSC) differentiation. Graphene oxide (GO), a major derivative of graphene, has been regarded as a promising material for stem cell lineage specification due to its biocompatibility and unique physical properties to interact with stem cells. Especially, the lateral size of GO flakes is regarded as the key factor regulating cellular response caused by GO. In this work, GO that had been mechanically created and had an average diameter of 0.9, 1.1, and 1.7 m was produced using a ball-mill process. When size-controlled GO flakes were applied to hMSCs, osteogenic differentiation was enhanced by GO with a specific average diameter of 1.7 μm. It was confirmed that osteogenic differentiation was increased due to the enhanced expression of focal adhesion and the development of focal adhesion subordinate signals via extracellular signal-regulated kinase (ERK)-mitogen-activated protein kinase (MEK) pathway. These results suggest that size-controlled GO flakes could be efficient materials for promoting osteogenesis of hMSCs. Results of this study could also improve our understanding of the correlation between hMSCs and cellular responses to GO.

Fluorinated porous carbon nanoweb layers (FPCNWLs) are simply fabricated by spin coating of adjusting polymer mixing ratio, sequential thermal treatments, and vacuum plasma treatment to enhance the specific surface area and to dope the fluorine into the carbon lattice. The different surface tension, polarity, and molecular weight of PAN and PS causes immiscible solution, therefore, the various size of pores on the carbon structure are constructed during the stepwise thermal treatment. Moreover, the F doping ratio is easily controlled with different plasma treating time. The fluorination causes both p-type doping and affinity toward ammonia gas. The fabricated FPCNWLs-based ammonia gas sensor devices demonstrate outstanding NH3 gas sensing performances that minimum detection level (MDL) of FPCNWLs-based ammonia gas sensor is 9 ppb using FPCNWL20 and the sensors display linear range from 9 ppb to 90 ppm. In conclusion, the FPCNWL20-based ammonia gas sensor demonstrates rapid response and recovery time, excellent cyclic stability, reusability, durability, and selectivity.

Research on flexible biosensors is mostly focused on their use in obtaining information on physical signals (such as temperature, heart rate, pH, and intraocular pressure). Consequently, there are hardly any studies on using flexible electronics for detecting biomolecules and biomarkers that cause diseases. In this study, we propose a flexible, three-dimensional carbon nanoweb (3DCNW)-based aptamer sensor to detect the platelet-induced growth factor (PDGF), which is an oncogenic biomarker. As a template for the 3D structure, poly(acrylonitrile) (PAN) nanowebs were synthesized using a facile electrospinning process. The PAN nanowebs were then subjected to chemical vapor deposition with copper powder. This was followed by Cu etching to generate carbon protrusions on the web surface. As an active site, PDGF-B binding aptamer was introduced on the 3DCNW surface to form biosensor electrodes. The 3DCNW-based aptasensor exhibited excellent sensitivity (down to 1.78 fM), with high selectivity, reversibility, and stability to PDGF-BB.

Considering their superior electrochemical performances, extensive studies have been carried out on composite nanomaterials based on porous carbon nanofibers. However, the introduction of inorganic...

Investment in wearable monitoring systems is increasing rapidly for realizing their practical applications, for example, in medical treatment, sports, and security systems. However, existing wearable monitoring systems are designed to measure a real-time physical signal and abnormal conditions rather than harmful environmental characteristics. In this study, a flexible chemical sensor electrode based on a three-dimensional conductive nanofilm (3D CNF) is fabricated via facile polymerization with temperature control. The morphology and chemical state of the 3D CNF are modified via electrochemical doping control to increase the carrier mobility and the active surface area of the sensor electrode. The sensor electrode is highly sensitive (up to 1 ppb), selective, and stable for an analyte (NH3) at room temperature owing to the three-dimensional morphology of polypyrrole and the oxidation-level control.

Hydrogen gas is a topic of considerable interest because of its critical importance to various applications in the fuel cell, aerospace and automotive industries. However, because it is highly flammable at low concentrations and causes asphyxiation at higher concentrations, it is crucial to implement an appropriate system to monitor hydrogen gas. In this report, we illustrate the facile synthesis of palladium-decorated three-dimensional conducting polymer nanofilms (PPyPds) for the detection of hydrogen gas. PPyPds are formed directly on the electrode through a modified electrodeposition process. The resulting PPyPd-based sensor is highly sensitive (down to 5 ppm) and binds hydrogen reversibly at ambient conditions, owing to the uniform distribution of palladium on the three-dimensional polypyrrole surface.

Understanding the rheological behavior of materials is of great importance in science. Here, we report a microscopic foundation for optorheology by manipulating the rheological feature through light. A new phenomenon is observed in the photosynthetic bacterial suspension, that the fluid viscosity changes by light-induced electrons. Type IV pili of photosynthetic bacteria is found, and it allows the electron to transport through the exterior of cells and changes the surface potential of cells, which causes an adjustment in the spatial arrangement of cells in the suspension. When an external electric field is applied, the electric dipole of the cells is induced and their dispersion is changed. The rheological properties are measured to evaluate the internal structure of the suspension depending on the light. The photoelectrons enhance the dispersion of the photosynthetic bacteria in the solution, thus leading to a significant increment in the viscosity. We envision that this discovery will provide new applications to the interface of optics, bioengineering, and rheology.

Field-effect transistor (FET) devices based on conductive nanomaterials have been used to develop biosensors. However, development of FET-based biosensors that allow efficient stability, especially in the gas phase, for obtaining reliable and reproducible responses remains a challenge. In this study, we developed a nanodisc (ND)-functionalized bioelectronic nose (NBN) based on a nickel (Ni)-decorated carboxylated polypyrrole nanoparticle (cPPyNP)-FET that offers the detection of liquid and gaseous cadaverine (CV). The TAAR13c, specifically binding to CV, which is an indicator of food spoilage, was successfully constructed in NDs. The NBN was fabricated by the oriented assembly of TAAR13c-embedded NDs (T13NDs) onto the transistor with Ni/cPPyNPs. The NBN showed high performance in selectivity and sensitivity for the detection of CV, with excellent stability in both aqueous and gas phases. Moreover, the NBN allowed efficient measurement of corrupted real-food samples. It demonstrates the ND-based device can allow the practical biosensor that provides high stability in the gas phase.

Cortisol is an hormone that regulates blood pressure, glucose levels and carbohydrate metabolism in humans. Abnormal secretion of cortisol can cause various symptoms closely linked to psychological and physical health. In this study, high-performance field-effect transistor (FET)-based biosensors for cortisol detection were fabricated from N-doped multidimensional carbon nanofibers. N a n o f i b e r morphology was controlled by tailoring the pressure conditions during vapor deposition polymerization (VDP). Thereafter, conductive channels o f FET were completed by thermal annealing, acid treatment, and antibody attachment. Changes associated with chemical processes were characterized by v a r i o u s i n s t r u m e n t s. The resulting transducers exhibited a rapid response toward cortisol molecules with accurate selectivity, stable reusability, and high sensitivity. M i n i m u m d e t e c t i o n l e v e l were as low as 100 aM with a wide linear detection range of 100 aM to 10 nM due to the large surface area of the transducer and a correspondingly high number of antibody labels. The response and applicability of these cortisol biosensors were also assessed using saliva as a test matrix.

In this work, a high-performance sensor capable of effectively detecting nerve gas, a type of chemical warfare agent, was realized by conductive paper with polyaniline (PANI) nanofiber and graphene...

Hazardous gas sensor technology in a wireless system is needed urgently for diverse applications ranging from the workplace to the battlefield. However, there are several limitations of the wireless gas sensing system such as high cost and poor sensitivity and selectivity for applications in real life. Here, a radio frequency identification (RFID)-based wireless sensor system is fabricated using an organic conductive nanocomposite paste composed of multidimensional Fe2O3 hollow nanoparticles (M_FeHNPs) and polystyrene sulfonic acid-doped polyaniline (PANI:PSS). The conductive paste acts as an RFID tag antenna pattern and sensing transducer in the RFID sensor tag. This RFID-based wireless sensor shows ultrahigh sensitivity (up to 0.5 ppm) to NO2 with very low processing cost. In addition, the organic conducting paste based RFID sensor system displays a long-distance operating range and high flexibility, which may offer practical use in a wearable device for wireless sensing.

Commercial diabetes test strips, patterned with a carbon paste, has poor durability and preservability because of using enzyme. Furthermore, carbon paste needs sintering process to get proper conductivity. Therefore, alternative conductive ink and sensing materials are the research theme under consideration lately. Therefore, we demonstrated constructing copper nanowire paste glucose sensor strip (CuNW_GSS) platform to diagnose diabetes nonenzymatically. Copper nanowires (CuNWs) were fabricated by a simple hydrothermal method with a capping agent to preserve the CuNWs from oxidation. Moreover, the CuNW paste could be easily utilized without sintering, and this fabricated paste successfully substituted for the commercial carbon paste pattern due to its high conductivity. CuNWs were used as not only the composition of conductive copper paste but also the sensing material for detecting glucose, which grants high charge transport ability to the glucose sensor, leading to high sensing ability. The limit of detection (LOD) of the CuNW_GSS was 1 nM, which is 40 times higher sensitivity than those of other glucose sensors and the CuNW_GSS also exhibited excellent selectivity. The excellent sensitivity and selectivity clearly indicate the great potential of the CuNW_GSS in diagnosing diabetes easily.

Metal–organic framework (MOF)-derived electroactive materials have drawn great attention due to their diverse design and high electrochemical activity. Herein, a unique hybrid structure consisting of Ni–Co layered double hydroxides (LDHs) and hollow carbon spheres (HCSs) is first synthesized using HCS@ZIF-67 as a precursor. Particularly, when the ZIF-67 content in the precursor is optimized, a novel hybrid with a hollow-in-hollow structure can be obtained by distributing ZIF-67-derived hollow Ni–Co LDHs on a HCS shell. Owing to their distinctive structural characteristics, the as-prepared architectures deliver a high specific capacity (156.4 mA h g−1 at 5 A g−1) and excellent cycle stability (73.4% capacity retention after 10 000 cycles). Notably, during the charge storage process, the dual hollow system of the composite effectively decreases the ion diffusion path, resulting in drastically improved rate performance (70% retention of its highest capacity at 80 A g−1). Furthermore, an all-solid-state hybrid supercapacitor is assembled using the as-fabricated hybrid as the positive material and mesoporous plasma-reduced graphene oxide as the negative material, and exhibits a maximum energy density of 34.5 W h kg−1 and a peak power density of 55 kW kg−1.

We report a facile approach for producing highly omnidirectional and frequency tunable antennas based on multilayer graphene/multi-walled carbon nanotube (MG/MWNTs) electrodes. The MG sheets are obtained by ball milling graphite, followed by sonication. Monopole patch antennas are prepared by screen printing the MG/MWNTs paste onto a polymer substrate. The resulting antennas show excellent performance due to the bridge effect of the MWNTs between well-dispersed adjacent MG layers, which increases the contact area between MG sheets along the horizontal and vertical axes. The antennas formed from the MG/MWNTs exhibit smaller return losses than the antennas formed from pristine graphite, as well as high radiation efficiency (∼44.9%). Moreover, the MG/MWNTs antennas require a relatively small quantity, which leads to low production costs. In addition, the dimensions of the antennas can be simply adjusted by controlling the screen printing mask or cutting with scissors to achieve frequency tunability. These results demonstrate the potential of these MG/MWNTs antennas for applications in wireless communications for ubiquitous sensor networks.

In this work, we report a facile way to control crystalline structures of polyketone (PK) films by combining plasma surface treatment with chemical vapor deposition (CVD) technique. The crystalline structure of PKs grown on plasma-treated graphene and the resulting thermal and mechanical properties were systematically discussed. Every graphene sheet used in this work was produced by CVD method and the production of PKs having different crystallinity were performed on the O2- and N2-doped graphene sheets. It was evident that the CVD-grown graphene sheets acted as the nucleating agents for promoting the crystallization of β-form PK, while suppressing the growth of α-form PK crystals. Regardless of the increase in surface roughness of graphene, surface functionality of the CVD-grown graphene was found to be an important factor in determining the crystalline structure of PK. N2 plasma treatment of the CVD-grown graphene promoted growth of the β-form PK, whereas the O2 plasma treatment of CVD graphene led to transformation of the unoriented β-form PK into the oriented α-form PK. Thus, the resulting thermal and mechanical properties of the PKs were highly dependent on the surface functionality of the CVD graphene. The method of controlling crystalline structure of the PKs suggested in this study, is expected to be very effective in realizing the PK with good processability, heat resistance and mechanical properties.

Despite being highly flammable at lower concentrations and causing suffocation at higher concentrations, hydrogen gas continues to play an important role in various industrial processes. Therefore, an appropriate monitoring system is crucial for processes that use hydrogen. In this study, we found a nanocomposite comprising of ruthenium nanoclusters decorated on carboxyl polypyrrole nanoparticles (Ru_CPPy) to be successful in detecting hydrogen gas through a simple sonochemistry method. We found that the morphology and density control of the ruthenium component increased the active surface area to the target analyte (hydrogen molecule). Carboxyl polypyrrole (CPPy) in the nanocomposite was protonated to increase the charge transfer rate during gas detection. This material-based sensor electrode was highly sensitive (down to 0.5 ppm) toward hydrogen gas and had a fast response and recovery time under ambient conditions. The sensing ability of the electrode was maintained up to 15 days without structure deformations.

Considering their superior electrochemical performances, extensive studies have been carried out on composite nanomaterials based on porous carbon nanofibers. However, the introduction of inorganic components into a porous structure is complex and has a low yield. In this study, we propose a simple synthesis of cobalt-oxide-incorporated multichannel carbon nanofibers (P-Co-MCNFs) as electrode materials for electrochemical applications. The cobalt oxide component is directly formed in the carbon structure by a simple oxygen plasma exposure of the phase-separated polymer nanofibers. P-Co-MCNF displays high specific capacitance (815 F g

17β-Estradiol is known as a steroid hormone in the human body but it is also known as a disruptor that can cause disequilibrium and dysfunction of the human immune system. Recently, there has been much interest in developing biosensors to detect low concentrations of 17β-estradiol. In this work, size-controllable aptamer conjugated ultrathin carboxylated polypyrrole nanotubes (A-UCPPyNTs) were fabricated as transducers in 17β-estradiol field-effect transistor (FET)-type biosensors. They were manufactured via a self-degradation method under several different conditions to control the diameter of the nanotubes. For targeting 17β-estradiol, the binding aptamers were immobilized through covalent bonding on its surface. The resulting A-UCPNT FET-type biosensor demonstrated p-type behavior with outstanding electrical conductivity, and exhibited Ohmic contacts between the samples and electrodes. The smaller diameter (40 nm) of ultrathin carboxylated polypyrrole nanotubes (UCPPyNTs) contributed to the biosensor's enhanced performance by generating a larger surface area, thereby increasing the number of conjugated binding aptamers. In conclusion, the A-UCPPyNT FET-type biosensor showed extremely high sensitivity (∼1 fM) toward 17β-estradiol, approximately 103 times more sensitive than the results found in other reports. Moreover, the A-UCPPyNT FET-type biosensor showed unique selectivity to the 17β-estradiol molecule, in addition to outstanding reusability and long-term storage stability (4 weeks of duration achieved in this work). These performances concerned with reusability and stability were achieved by the formation of covalent bonding in the anchorage to the substrate electrode. Thus this study can be effectively applied in biological and environmental fields.

Hormones within very low levels regulate and control the activity of specific cells and organs of the human body. Hormone imbalance can cause many diseases. Therefore, hormone detection tools have been developed, particularly over the last decade. Peptide hormones have a short half-life, so it is important to detect them within a short time. In this study, we report two types of peptide hormone sensors using human hormone receptor-carrying nanovesicles and graphene field-effect transistors (FETs). Parathyroid hormone (PTH) and glucagon (GCG) are peptide hormones present in human blood that act as ligands to G protein-coupled receptors (GPCRs). In this paper, the parathyroid hormone receptor (PTHR) and the glucagon receptor (GCGR) were expressed in human embryonic kidney-293 (HEK-293) cells, and were constructed as nanovesicles carrying the respective receptors. They were then immobilized onto graphene-based FETs. The two hormone sensors developed were able to detect each target hormone with high sensitivity (ca. 100 fM of PTH and 1 pM of GCG). Also, the sensors accurately recognized target hormones among different types of peptide hormones. In the development of hormone detection tools, this approach, using human hormone receptor-carrying nanovesicles and graphene FETs, offers the possibility of detecting very low concentrations of hormones in real-time.

In Saccharomyces cerevisiae, Haa1 and War1 transcription factors are involved in cellular adaptation against hydrophilic weak acids and lipophilic weak acids, respectively. However, it is unclear how these transcription factors are differentially activated depending on the identity of the weak acid. Using a field-effect transistor (FET)-type biosensor based on carbon nanofibers, in the present study we demonstrate that Haa1 and War1 directly bind to various weak acid anions with different affinities. Haa1 is most sensitive to acetate, followed by lactate, whereas War1 is most sensitive to benzoate, followed by sorbate, reflecting their differential activation during weak acid stresses. We show that DNA binding by Haa1 is induced in the presence of acetic acid and that the N-terminal Zn-binding domain is essential for this activity. Acetate binds to the N-terminal 150-residue region, and the transcriptional activation domain is located between amino acid residues 230 and 483. Our data suggest that acetate binding converts an inactive Haa1 to the active form, which is capable of DNA binding and transcriptional activation.

Numerous efforts have been made to measure tastes for various purposes. However, most taste information is still obtained by human sensory evaluation. It is difficult to quantify a degree of taste or establish taste standard. Although artificial taste sensors called electronic tongues utilizing synthetic materials such as polymers, semiconductors, or lipid membranes have been developed, they have limited performance due to their low sensitivity and specificity. Recently, bioelectronic tongues fabricated by integrating human taste receptors and nanomaterial-based sensor platforms have been found to have high performance for measuring tastes with human-like taste perception. However, human umami taste receptor is heterodimeric class C GPCR composed of human taste receptor type 1 member 1 (T1R1) and member 3 (T1R3). Such complicated structure makes it difficult to fabricate bioelectronic tongue. The objective of this study was to develop a protein-based bioelectronic tongue for detecting and discriminating umami taste with human-like performance using umami ligand binding domain called venus flytrap (VFT) domain originating from T1R1 instead of using the whole heterodimeric complex of receptors. Such T1R1 VFT was produced from Escherichia coli (E. coli) with purification and refolding process. It was then immobilized onto graphene-based FET. This bioelectronic tongue for umami taste (BTUT) was able to detect monosodium L-glutamate (MSG) with high sensitivity (ca. 1 nM) and specificity in real-time. The intensity of umami taste was enhanced by inosine monophosphate (IMP) that is very similar to the human taste system. In addition, BTUT allowed efficient reusable property and storage stability. It maintained 90% of normalized signal intensity for five weeks. To develop bioelectronic tongue, this approach using the ligand binding domain of human taste receptor rather than the whole heterodimeric GPCRs has advantages in mass production, reusability, and stability. It also has great potential for various industrial applications such as food, beverage, and pharmaceutical fields.

A simple one-pot method is reported for the fabrication of uniform wrinkled silica nanoparticles (WSNs). Rapid cooling of reactants at the appropriate moment during synthesis allowed the separation of nucleation and growth stages, resulting in uniform particles. The factors affecting particle size and interwrinkle distance were also investigated. WSNs with particle sizes of 65–400 nm, interwrinkle distances of 10–33 nm, and surface areas up to 617 m2 g–1 were fabricated. Furthermore, our results demonstrate the advantages of WSNs over comparable nonporous silica nanospheres and fumed silica-based products as an abrasive material in chemical mechanical planarization processes.

Two push–pull D–π–A molecules, 3T and DTT as donor materials, were synthesized and characterized for solution-processed bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. The π-linker plays a vital role not only in electrochemical and thermal properties but also affects the thin film morphology of 3T and DTT. 3T showed the high electrochemical stability with a faster electrode reaction rate. The solution-processed OPV devices based on 3T showed higher power conversion efficiencies than DTT-based devices because of its superior electrochemical properties.

Carbon electrode-based perovskite solar cells (PSCs) without hole transport materials (HTMs) are regarded as a promising alternative architecture to realize low-cost, stable photovoltaics. However, poor hole transport and severe charge recombination at the interface of perovskite and carbon layers degrade the power conversion efficiency (PCE) of carbon-based PSCs. Here we report on an innovative method to post-treat a carbon electrode with phenylethylammonium iodide (PEAI), for the growth of a two-dimensional (2D) perovskite at the interface between the perovskite and carbon layers. The resulting ultrathin PEA2PbI4 layer formed within the perovskite/carbon interface improved the poor perovskite/carbon contact. The favorable conduction and valence energy levels of the 2D perovskite interlayer greatly suppressed interfacial charge recombination, which stems from the absence of an HTM. Using our fabrication method, the average PCE of devices was boosted from 11.5% to 14.5% with minimal hysteresis loss, and a maximum PCE of 15.6% was achieved. Moreover, the PEAI-treated devices showed excellent ambient stability. The dual protection of the hydrophobic carbon and 2D perovskite layers enabled the device to retain 92% of its initial PCE after 1000 h of exposure to ambient conditions (relative humidity: 40 ± 5%). The thermal stability of the devices was also enhanced, showing no efficiency loss after thermal testing at 150 °C, due to suppressed ion migration.

Inverted-structure perovskite solar cells (PSCs), with low-temperature processed poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and perovskite-passivating phenyl–C61–butyric acid methyl ester (PCBM) employed as charge transport layers, have great potential as efficient, flexible, and hysteresis-free solar cells. However, PEDOT:PSS processed from an aqueous solution has a hygroscopic nature, and can degrade the ambient stability of moisture-vulnerable perovskite electronics. Furthermore, excess insulating PSS in the PEDOT:PSS complex can deteriorate the hole extraction and photovoltaic performance of the solar cell. In this work, polyaniline doped with camphorsulfonic acid (PANI-CSA) is introduced as a hole transport layer (HTL) to promote hole extraction ability and improve the efficiency and stability of inverted PSCs. The device fabricated with PANI-CSA exhibited superior photovoltaic performance, with a maximum efficiency of 15.42%, compared to 14.11% efficiency for the device fabricated with PEDOT:PSS. Most notably, the stability of the device fabricated with PANI-CSA was greatly improved due to a stable HTL/perovskite interface against exposure to ambient moisture.

Oxalic acid (OA), naturally available in many fruits and vegetables, reacts easily with Ca2+ and Mg2+ ions to produce an insoluble salt. In renal systems, this insoluble salt brings about various renal diseases. As such, the OA excretion level in urine has been utilized as an index parameter in healthcare settings. Here, we report the fabrication of platinum nanoparticle-immobilized polypyrrole-3-carboxylated nanofibers (Pt_cPPyNFs) to apply as a transducer material for a non-enzyme field-effect transistor (FET)-type OA sensor. To achieve uniformly decorated Pt on carboxylated polypyrrole nanofibers (cPPyNFs), ultrasonication and chemical reduction were introduced as a Pt immobilization process. The Pt_cPPyNFs were immobilized on an interdigitated array (IDA) electrode for our sensor application. The resulting Pt_cPPyNF based non-enzyme FET-type OA sensor exhibited high sensitivity at unprecedentedly low concentrations (10-14 M); this was attributed to the uniformity of the Pt-nanoparticle decoration and distinct properties of the FET configuration. In addition, high stability was achieved in repeated experiments and under ambient storage conditions.

Hydrogen sulfide (H2S) is one of the most plentiful toxic gases in a real-life and causes a collapse of the nervous system and a disturbance of the cellular respiration. Therefore, highly sensitive and selective H2S gas sensor systems are becoming increasingly important in environmental monitoring and safety. In this report, we suggest the facile synthesis method of the Fe2O3 particles uniformly decorated on carbon nanotubes (Fe2O3@CNT) to detect H2S gas using oxidative co-polymerization (pyrrole and 3-carboxylated pyrrole) and heat treatment. The as prepared Fe2O3@CNT-based sensor electrode is highly sensitive (as low as 1 ppm), selective and stable to H2S gas at 25 °C, which shows promise for operating in medical diagnosis and environment monitoring. Excellent performance of the Fe2O3@CNT is due to the unique morphology of the nanocomposites made from uniformly dispersed Fe2O3 nanoparticles on the carbon surface without aggregation.

Multilayered magnetite-embedded core/shell silica/titania (SiO2/TiO2) nanoparticles with an outermost silica shell (SiO2/TiO2@Fe3O4/SiO2) were synthesized and used to develop stimuli-responsive smart fluids. Benefiting from the incorporation of the various materials, these smart fluids demonstrated electrorheological (ER) and magnetorheological (MR) activities under applied external electric (E) and magnetic (H) fields, respectively, and electromagnetorheological (EMR) characteristics with the simultaneous application of E and H fields. The inner SiO2/TiO2 core nanoparticles, embedded Fe3O4 nanoparticles and the outer SiO2 shell served as electroresponsive, magnetoresponsive and preventative materials toward corrosion, sedimentation and aggregation. The EMR performance of these fluids depended on the direction of the applied E and H fields. Notably, a 6.6-fold enhancement in EMR activity was observed with parallel application of E and H fields compared to perpendicular direction. This study demonstrates an effective approach to precisely and spatially control the rheological/mechanical properties of dual-responsive smart fluids via both field-induced and directional control of external fields.

Real-time gas sensors that are ultra-sensitive, highly selective, and capable of fast response/recovery are highly in demand for environmental and health monitoring; however, advances in such gas sensors have been limited. Here we report a flexible and transparent sub-ppb gas detection film fabricated by in situ electrochemical oxidative polymerization on single-layer graphene (SLG). As polypyrrole molecules are uniformly formed with flat orientations on SLG, the resulting sensor film exhibits excellent sensitivity and selectivity with nearly perfect reversibility without heat treatment or light irradiation. The sensing mechanism is well explained by molecular interactions between the sensing material and the gas molecular species. The sensor exhibits a detection limit as low as 0.03 ppb NO2 and 0.04 ppb NH3 at room temperature and operates well, even at 70 °C, showing feasibility for wearable applications in high-precision gas sensing.

Dopamine (DA), a catecholamine hormone, is an important neurotransmitter that controls renal and cardiovascular organizations and regulates physiological activities. Abnormal concentrations of DA cause unfavorable neuronal illnesses such as Parkinson’s disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD)/attention deficit disorder (ADD). However, the DA concentration is exceedingly low in patients and difficult to detect with existing biosensors. In this study, we developed an organic field-effect-transistor-type (OFET) non-enzyme biosensor using platinum nanoparticles decorated reduced graphene oxide (Pt_rGO) for ultrasensitive and selective DA detection. The Pt_rGOs were fabricated by reducing GO aqueous solution containing Pt precursors (PtCl4) with a chemical reducing agent. The Pt_rGOs were immobilized on graphene substrate by π–π interactions and a conducting-polymer source–drain electrode was patterned on the substrate to form the DA sensor. The resulting OFET sensor showed a...

Fiber-shaped supercapacitors are promising energy storage devices for future flexible and portable electronics. In this study, we report a fiber-shaped asymmetric supercapacitor (ASC) device made with the metal oxides having a large work function difference, directly grown on a flexible and conductive carbon fiber (CF) substrate. Specifically, carbon fiber/MnO2 (CF/MnO2) and carbon fiber/MoO3 (CF/MoO3) were fabricated using a simple electrodeposition method. The all-solid-state fiber-shaped ASC device was then assembled with CF/MnO2 as the positive electrode and CF/MoO3 as the negative electrode. The large work function difference between the metal oxides and the high conductivity of the CF substrate provided the ASC device with remarkable performance. In particular, it exhibited capacitance of 4.86 mF cm−2 and a wide operating voltage window of 2.0 V, which resulted in an excellent energy density of 2.70 μWh cm−2 and a power density of 0.53 mW cm−2. Also, it readily tolerated 3000 cycles of electrochemical testing and extreme mechanical deformation. Consequently, the outstanding performance and stability of the fiber-shaped ASC device shows great potential for future energy storage systems.

There remains tremendous interest in perovskite solar cells (PSCs) in the solar energy field; the certified power conversion efficiency (PCE) now exceeds 20%. Along with research focused on enhancing PCE, studies are also underway concerning PSC commercialization. It is crucial to simplify the fabrication process and reduce the production cost to facilitate commercialization. Herein, we successfully fabricated highly efficient hole-blocking layer (HBL)-free PSCs through vigorously interrupting penetration of hole-transport material (HTM) into fluorine-doped tin oxide by a large grain based-CH3NH3PbI3 (MAPbI3) film, thereby obtaining a PCE of 18.20%. Our results advance the commercialization of PSCs via a simple fabrication system and a low-cost approach in respect of mass production and recyclability.

Graphene oxide (GO) enwrapped SiO2/TiO2 hollow nanoparticles (GO-HNP) are synthesized by stobber method and used as a nanocarrier for loading protoporphyrin IX (PpIX). The synthesized nanoparticle has high dispersibitliy and high uniformity in diameter (ca. 50 nm). . Furthermore, this nanoparticle shows 808 nm laser induced PpIX release property (photo-induced "on-off" drug release system). The GO-HNP-PpIX is employed for inducing both photothermal therapy (PTT) and photodynamic therapy (PDT). The synergic effect of the PTT and PDT exhibits powerful anti-cancer property. When cancer cells are treated with GO-HNP-PpIX and irradiated with both visible light and 0.8 W cm-2 of 808 nm laser, the cell viability dropped dramatically to 2.5 %, which is approximately 13 times higher anticancer effect than previous stuty. Moreover, no significant cell damage has been observed in a condition of dark 808 nm laser irradiation. The GO-HNP-PpIX system suggests external stimuli responsive effieicnt anticancer treatment effect toward human breast cancer cells.

Perovskite solar cells (PSCs) have greatly improved through optimizing the morphology and charge extraction of the perovskite film. To increase the efficiency, we have developed a new method of adding NiO nanotubes (NTs) to the perovskite precursor solution. The NiO NTs promoted the growth of perovskite grains during annealing and facilitated charge extraction. The increase in the grain size improved the crystallinity of the perovskite film and reduced the grain boundaries that could trap charge. Additionally, the NiO NTs located between the grain boundaries transferred holes, which prevented charge recombination. The efficiency of the PSCs increased due to the improved crystallinity and charge extraction of the perovskite film. Devices incorporating the NiO NTs exhibited power conversion efficiencies of 19.3 and 12.82% for planar-type and carbon-based PSCs, respectively.

In situ time-resolved small-angle X-ray scattering is introduced as a method to monitor the diffusion of a solvent in ceramic hollow nanoparticles (HNPs) supported by a polymer gel scaffold. Changes in the form factor were matched to discrete scattering models. A consecutive reaction kinetic model is used to analyze different stages of solvent diffusion. Rate constants and diffusion coefficients are extracted. By taking the diffusion of low molecular poly(ethylene glycol) in poly(ethylene oxide)-embedded HNPs as a model case, it was found that it took about 0.7 s for the solvent to diffuse through the 6 nm thick shell of HNPs and another 1.2 s to fill the inner cavity, while the diffusion coefficient was of the order of 1018 m2 s−1. The results demonstrate that the method can simultaneously measure solvent penetration into the polymer gel and into embedded sub-100 nm HNPs.

Research on the addition of suitable materials into perovskite solar cells (PSCs) for improved performance is as important as the fabrication of efficient perovskite films themselves. An attempt to enhance the performance of planar-type perovskite solar cells was performed by introducing graphene quantum dots (GQDs) onto a blocking TiO2 layer via O2 plasma treatment. Furthermore, the bandgap of the GQDs was tuned through their size control and the effects of the GQD size on cell performance were explored. The GQDs can induce fast electron extraction and the formation of the improved perovskite quality. The devices with appropriately sized-GQDs showed an average of 10% enhancement compared with those of cells without GQDs and achieved 19.11% as the best power conversion efficiency (PCE). Furthermore, GQDs contributed to the reduction in the extent of current–voltage hysteresis, which was attributed to the planar structure.

Hierarchical fibrous structures composed of ZnO quantum dots, amorphous carbons, and carbon nanofibers are synthesized via a single carbonization process of electrospun ZIF-8/PVA nanofibers. This newly designed electrode material for supercapacitors exhibits outstanding electrochemical performances with high capacitance, reliable rate capability, and long cycle life.

Detection of toxic gases is of great importance for protection against chemical weapons. In particular, organophosphates, such as sarin, damage nerve function and are fatal inhibitors of acetylcholinesterase. Therefore, simple and enhanced technologies for the detection of organophosphates are needed. Herein, we report the fabrication of a chemiresistive gas sensor based on a polypyrrole (PPy)-coated SnO2 tube-in-tube structure that was highly sensitive (0.05 ppb) and selective toward dimethyl methylphosphonate (DMMP), which is a simulant of organophosphates. The complex tube-in-tube structure was fabricated using a single-nozzle electrospinning method with two mixed solvents. Vapor deposition polymerization (VDP) was used to form a thin PPy layer on the surface of the SnO2 tube-in-tube structure without any aggregation. Our new synthetic methodology promises to be an effective approach for fabricating organic/inorganic complex tubular structures for future sensing technologies.

A facile synthesis and modification method of polyaniline:poly(styrenesulfonate) (PANI:PSS) is reported for an efficient hole transport material (HTM) in inverted planar perovskite solar cells (PSCs). PANI:PSS with Triton X–100, a nonionic surfactant, showed enhanced hole transport capability due to improved wetting on the substrate and a surface compositional change. The surfactant lowered the surface tension of a PANI:PSS aqueous solution, which enabled uniform casting of PANI:PSS films onto an indium tin oxide (ITO) substrate without any surface treatment. Additionally, self-organization of PSS nanogranules, induced by the surfactant, provided PANI-rich surfaces that were favorable for hole extraction. When surfactant-modified PANI:PSS (1.0 wt% Triton X–100) was used as an HTM in a PSC, the average short-circuit current density increased by 23% compared with pristine PANI:PSS (i.e., from 15.02 to 18.43 mA/cm 2 ) and the fill factor also improved, eventually leading to a power conversion efficiency enhancement from 6.59 to 10.90%.

Recently, carbon nanomaterials are attractive for various applications owing to the benefits derived from their high electrical conductivity, chemical stability and large surface to volume ratio. However, the fabrication process of carbon nanomaterials is complicated and exhibits low productivity. Here we report the facile one-pot synthesis of highly porous 1D carbon nanotubes based on three-layered polymer nanofibers by using a dual-nozzle co-electrospinning technique to apply to an energy storage device. Specific capacitance (CG) of the porous carbon nanotube-based electrode is 401 F g−1, which is larger than that of the other carbon nanomaterials. Furthermore, the porous carbon nanotube exhibits excellent rate capability and cycle stability due to micro-/mesopores in the carbon structure enhancing the active surface area between carbon and the ions of the electrolytes. This unique fabrication technique is an effective approach for forming large scale highly porous carbon nanomaterials for diverse electrochemical applications.

We herein describe the fabrication of sinter-free copper nanoparticle-based conductive paste (Cu NP paste). The copper nanoparticles with a size below 10 nm enable the formation of integrated structures even without heat treatment. Poly(vinylimidazole-co-vinyltrimethoxysilane) used in the synthesis grants the copper surface a high anti-oxidant ability over a temperature range of up to 300 °C under ambient conditions. Furthermore, the viscosity of the conductive paste could be arbitrarily adjusted while minimizing the change of resistivity. The pattern printed using Cu NP paste demonstrated an electrical resistivity of 1.2 × 10−2 Ω cm for un-sintered conductive paste. We confirmed the potential of the Cu NP paste through dipole tag antenna application.

One-dimensional (1D) carbon materials are typically used for electric double layer capacitor (EDLC) electrodes due to their excellent charge carrier mobility. However, improvement of the low capacitance and energy density of these carbon-based EDLCs has been required although they have a fast charge/discharge rate and long cycle life. In this work, nitrogen and fluorine doped mesoporous carbon nanofibers (NFMCNFs) were fabricated using a hydrothermal treatment for structural modification to create porosity and a vacuum plasma process for introducing heteroatoms into the carbon lattice. Applied to supercapacitor devices, the NFMCNFs exhibited a remarkable EDLC performance of 252.6 F g−1 at 0.5 A g−1 in a 1 M H2SO4 electrolyte. Additionally, all-solid-state flexible symmetric supercapacitors (SSCs) were assembled with a high specific capacitance of 58.1 F g−1 at 0.5 A g−1 and outstanding long-term cycle stability over 20 000 cycles. Remarkably, the SSCs also exhibited high energy and power densities of 8.07 W h kg−1 and 248 W kg−1, respectively. This dynamic porous structure and heteroatom co-doping based carbon material provides a sensational approach for designing energy storage systems.

We modified phenyl-C61-butyric acid methyl ester (PCBM) for use as a stable, efficient electron transport layer (ETL) in inverted perovskite solar cells (PSCs). PCBM containing a surfactant Triton X-100 acts as the ETL and NiOX nanocrystals act as a hole transport layer (HTL). Atomic force microscopy and scanning electron microscopy images showed that surfactant-modified PCBM (s-PCBM) forms a high-quality, uniform, and dense ETL on the rough perovskite layer. This layer effectively blocks holes and reduces interfacial recombination. Steady-state photoluminescence and electrochemical impedance spectroscopy analyses confirmed that Triton X-100 improved the electron extraction performance of PCBM. When the s-PCBM ETL was used, the average power conversion efficiency increased from 10.76% to 15.68%. This improvement was primarily caused by the increases in the open-circuit voltage and fill factor. s-PCBM-based PSCs also showed good air-stability, retaining 83.8% of their initial performance after 800 h under ambient conditions.

Arsenic (As) contamination in drinking water is problematic due to its threat to human health. Highly stable, sensitive and selective sensors are needed for As(iii), which is the most toxic of the various forms of arsenic. Herein, we describe the fabrication of field-effect transistor (FET)-type aptasensors for As(iii) detection that is based on carboxylic polypyrrole (CPPy)-coated flower-like MoS2 nanospheres (CFMNSs). Arsenic-binding aptamer-conjugated CFMNSs were integrated into a liquid-ion gated FET system, leading to extraordinary performance with a rapid response (on a time scale of less than 1 s). Field-induced current changes occurred through the interaction between the aptamer and As(iii), resulting in sensitive discrimination of As(iii) at unprecedentedly low concentrations (ca. 1 pM). Moreover, the CFMNS-based aptasensor selectively recognized As(iii) among numerous other metal ions and accurately detected As(iii) in a mixed solution. The FET aptasensor could also discriminate target analytes in a real sample derived from river water. This MoS2-based aptasensor is a promising tool for the detection of As(iii) and could be used in a wide range of practical applications.

In this study, a 1D oriented hollow SiO2/TiO2 (HST) rod-like material was successfully fabricated via a sequential combination of sol–gel use, TiO2 incorporation, and a sonication-mediated etching and redeposition method. This carefully manipulated new material has numerous advantageous physical and intrinsic properties, such as increased surface area, pore volume, interfacial polarization, and dielectric properties introduced from each synthetic step. The synthesized HST rod was adopted as an electrorheological (ER) material for practical examination of these characteristics. The HST rod materials exhibited 1.5- and 3-fold higher ER performance than a non-metal SiO2 rod and a non-hollow SiO2/TiO2 core/shell (ST/CS) rod, which are interim synthetic steps. Moreover, the HST rod exhibited remarkable 6-fold increased ER efficiency relative to a sphere-shaped hollow SiO2/TiO2 particle synthesized using a similar experimental method. These notable enhancements in ER performance are attributed to incorporation of the experimentally designed characteristics of the HST rod: 1D structure, metal oxide incorporation, and creation of a hollow cavity. For future study, we expect that these versatile HST rod materials can be applied in a range of fields including drug delivery, photo-catalysis, and as building blocks.

A fluorine plasma-treated carbon electrode is used in HTM-free perovskite solar cells for high efficiency and moisture resistance. The fluorine-treated device with a champion power conversion efficiency (PCE) of 14.86% is achieved with a highly enhanced FF (FF = 0.69), showing superior long-term stability and excellent moisture penetration suppression.

Rendering a high crystalline perovskite film is integral to achieve superior performance of perovskite solar cells (PSCs). Here, we established a two-dimensional liquid cage annealing system, a unique methodology for remarkable enhancement in perovskite crystallinity. During thermal annealing for crystallization, wet-perovskite films were suffocated by perfluorodecalin with distinctively low polarity, nontoxic, and chemically inert characteristics. This annealing strategy facilitated enlargement of perovskite grain and diminution in the number of trap states. The simulation results, annealing time, and temperature experiments supported that the prolonged diffusion length of precursor ions attributed to the increase of perovskite grains. Consequently, without any complicated handling, the performance of perovskite photovoltaics was remarkably improved, and the monolithic grains which directly connected the lower and upper electrode attenuated hysteresis.