Fabrication of Electrochemical-Based Bioelectronic Device and Biosensor Composed of Biomaterial-Nanomaterial Hybrid

The field of bioelectronics has paved the way for the development of biochips, biomedical devices, biosensors and biocomputation devices. Various biosensors and biomedical devices have been developed to commercialize laboratory products and transform them into industry products in the clinical, pharmaceutical, environmental fields. Recently, the electrochemical bioelectronic devices that mimicked the functionality of living organisms in nature were applied to the use of bioelectronics device and biosensors. In particular, the electrochemical-based bioelectronic devices and biosensors composed of biomolecule-nanoparticle hybrids have been proposed to generate new functionality as alternatives to silicon-based electronic computation devices, such as information storage, process, computations and detection. In this chapter, we described the recent progress of bioelectronic devices and biosensors based on biomaterial-nanomaterial hybrid.

Fabrication of Troponin I Biosensor Composed of Multi-Functional DNA Structure/Au Nanocrystal Using Electrochemical and Localized Surface Plasmon Resonance Dual-Detection Method

In the present study, we fabricated a dual-mode cardiac troponin I (cTnI) biosensor comprised of multi-functional DNA (MF-DNA) on Au nanocrystal (AuNC) using an electrochemical method (EC) and a localized surface plasmon resonance (LSPR) method. To construct a cTnI bioprobe, a DNA 3 way-junction (3WJ) was prepared to introduce multi-functionality. Each DNA 3WJ arm was modified to possess a recognition region (Troponin I detection aptamer), an EC-LSPR signal generation region (methylene blue: MB), and an anchoring region (Thiol group), respectively. After an annealing step, the multi-functional DNA 3WJ was assembled, and its configuration was confirmed by Native-TBM PAGE for subsequent use in biosensor construction. cTnI was also expressed and purified for use in biosensor experiments. To construct an EC-LSPR dual-mode biosensor, AuNCs were prepared on an indium-tin-oxide (ITO) substrate using an electrodeposition method. The prepared multi-functional (MF)-DNA was then immobilized onto AuNCs by covalent bonding. Field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM) were used to analyze the surface morphology. LSPR and electrochemical impedance spectroscopy (EIS) experiments were performed to confirm the binding between the target and the bioprobe. The results indicated that cTnI could be effectively detected in the buffer solution and in diluted-human serum. Based on the results of these experiments, the loss on drying (LOD) was determined to be 1.0 pM in HEPES solution and 1.0 pM in 10% diluted human serum. Additionally, the selectivity assay was successfully tested using a number of different proteins. Taken together, the results of our study indicate that the proposed dual-mode biosensor is applicable for use in field-ready cTnI diagnosis systems for emergency situations.

Label-free localized surface plasmon resonance biosensor composed of multi-functional DNA 3 way junction on hollow Au spike-like nanoparticles (HAuSN) for avian influenza virus detection

In the present study, we fabricated a label-free avian influenza (AIV H5N1) detection biosensor composed of a multi-functional DNA 3 way-Junction (3 W J) on a hollow Au spike-like nanoparticle (hAuSN) using a localized surface plasmon resonance (LSPR) method. To construct the multi-functional DNA (MF-DNA) as a bioprobe, the 3 W J was introduced. The proposed AIV detection bioprobe should contain three functionalities: target recognition, signal amplification, and connection to substrate. To achieve this goal, each piece of the DNA 3 W J was tailored to a hemagglutinin (HA) binding aptamer, FAM dye and thiol group, respectively. The assembly of each DNA 3 W J functional fragment was then confirmed by TBM-Native PAGE. Moreover, the hAuSN was immobilized on the indium-tin-oxide (ITO) substrate for LSPR measurement. The DNA 3 W J was immobilized onto the hAuSN electrode through the thiol-group of DNA 3 W J. The fabricated DNA 3 W J/hAuSN heterolayer on the ITO substrate was investigated by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). LSPR experiments were conducted to confirm HA protein binding to the DNA 3 W J/ hAuSN -modified electrode. The proposed biosensor can detected the HA protein in PBS buffer (LOD: 1 pM) as well as in the diluted chicken serum (LOD: 1 pM). The present study details a label-free, simple fabrication method consisted of DNA 3 W J/ hAuSN heterolayer that uses easy-to-tailor elements to detect not only AIV but also various viruses detection platform easily.

Cost-effectiveness of contact screening strategies for tuberculosis among high-school adolescents in South Korea

BACKGROUND

Effective latent tuberculous infection (LTBI) control among adolescents is a critical component of tuberculosis (TB) elimination in Korea.

OBJECTIVE

To compare the cost-effectiveness of the following contact screening strategies for LTBI among high-school adolescents after TB outbreaks: QuantiFERON®-TB Gold In-Tube (QFT-GIT), the tuberculin skin test (TST), or TST/QFT-GIT (two-step strategy).

METHOD

The costs of post-TB outbreak screening strategies were calculated using a mixed (top-down and bottom-up) cost analysis method and expressed in 2015 US dollars. Cost-effectiveness was evaluated using a decision analysis model from the health system perspective, comparing cumulative health care costs and the total number of TB cases averted.

RESULTS

In a hypothetical cohort of 1000 students, screening using the TST-alone strategy averted 1.6 TB cases at a total cost of US$52 566. The QFT-GIT-alone strategy helped avert 2.0 TB cases, but was associated with a much higher total cost (US$108 435), resulting in an incremental cost-effectiveness ratio of US$140 933/TB case averted. The two-step TST/QFT-GIT strategy was worse than the TST-alone strategy, averting 1.3 TB cases at US$75 267.

CONCLUSION

The TST-alone strategy was the most cost-effective; the QFT-GIT-alone strategy averted the greatest number of TB cases but incurred the highest cost in contact investigation for school TB outbreaks.

Costs and operation management of community outreach program for tuberculosis in tribal populations in India

Objective

To evaluate costs of an active case finding (ACF) program with tuberculosis (TB) treatment delivery and monitoring, which targeted a rural tribal population in India.

Method

A time and motion study was conducted to evaluate operations and workload. Costs from the program perspective were assessed using both the bottom-up and top-down costing methods, exclusive of routine TB care costs. The impact of ACF on routine TB laboratory workloads was measured based on the changes in available staff time per smear at nine designated microscopy centers before and after program implementation.

Results

A majority (53.2%) of the community health-care worker's time was spent in traveling to communities, with an average of 22 TB patients (95% CI 19.14-24.94) seen per day per person. Costs (at 2015 $US rates) were US$1.85-US$2.42 per patient screened and submitting sputum, US$2.51-US$4.74 per person diagnosed with TB, and US$22.52-US$34.13 per TB patient completing treatment. Total smear volumes increased significantly after the ACF program, with more than a 15% reduction in available staff time per sputum smear test in most laboratories.

Conclusion

This low-cost, ACF program has the potential to be highly cost-effective in addressing gaps in TB care problems in rural India.

Thermally Robust Porous Bimetallic (Ni xPt1- x) Alloy Mesocrystals within Carbon Framework: High-Performance Catalysts for Oxygen Reduction and Hydrogenation Reactions

Thermally stable porous bimetallic (Ni _xPt_{1- x}) alloy mesocrystals within a carbon framework are produced via an aerosol-assisted process for high-performance catalysts for the oxygen reduction reaction (ORR) and hydrogenation. The porous Ni _xPt_{1- x} alloy has a robust composite of alloy nanoparticles with an adjustable composition and a porous carbon skeleton. Porous Ni _xPt_{1- x} alloys exhibit high thermal stability, retaining their crystalline structure and morphology at 550 °C for 6 h, as observed in thermal treatment tests under various conditions (time, temperature, and atmosphere). The porous Ni _xPt_{1- x} alloy as a catalyst for the hydrogenation of propylene has high conversion efficiency (>80%) and low activation energy ( E_a < 20 kJ/mol) at ≥80 °C through the suitable control of the element composition and a pore structure. As a catalyst for the ORR, the catalytic activity of the porous Ni _xPt_{1- x} alloy is superior to that of conventional Pt/C (0.115 mA) (0.853 mA/cm_Pt² at 0.9 V/cm_Pt²). This is attributed to the homogeneous alloying of the metal components (Ni and Pt) and the increased accessibility of the reactants to the catalyst, resulting from the unique morphology of the porous Ni _xPt_{1- x} alloy, i.e., hierarchical structure with high porosity.

Minimized Volume Expansion in Hierarchical Porous Silicon upon Lithiation

Silicon (Si) remains one of the most promising anode materials for next-generation lithium-ion batteries (LIBs). The key challenge for Si anodes is the huge volume change during lithiation-delithiation cycles that leads to electrode pulverization and rapid capacity fading. Here, we report a hierarchical porous Si (hp-Si) with a tailored porous structure [tunable primary pores (20-200 nm) and secondary nanopores (∼3-10 nm)] that can effectively minimize the volume expansion. An in situ transmission electron microscopy (TEM) study revealed that the hp-Si material with the same porosity but larger primary pores can more effectively accommodate lithiation-induced volume expansion, giving rise to a much reduced apparent volume expansion on both material and electrode levels. Chemomechanical modeling revealed that because of the different relative stiffnesses of the lithiated and unlithiated Si phases, the primary pore size plays a key role in accommodating the volume expansion of lithiated Si. The higher structural stability of the hp-Si materials with larger primary pores also maintains the fast diffusion channels of the connective pores, giving rise to better power capability and capacity retention upon electrochemical cycling. Our findings point toward an optimized hp-Si material with minimal volume change during electrochemical cycling for next-generation LIBs.

CO₂ Separation Membranes Consisting of Ionic Liquid/CdO Composites

CdO nanoparticles were utilized in the fabrication of a composite membrane containing the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM+BF-4) for CO2 separation. The use of BMIM+BF-4containing CdO nanoparticles as a CO2 separator greatly improved separation performance. The ideal selectivity for CO2/N2 was 32.5 with a CO2 permeance of 57.1 GPU when CdO 4 liquid. The enhanced separation performance nanoparticles were incorporated into the BMIM+BF-4and the was attributed to increased CO2 solubility facilitated by both the free ions in BMIM+BF-4 oxide layer of the CdO nanoparticle. The CdO nanoparticles were identified with transmission electron microscopy and the physical and chemical properties of the membranes were investigated using scanning electron microscopy, Raman spectroscopy and TGA. Interestingly, we found a correlation between CO2 permeance and electronegativity differences between the metal and oxygen for CO2 separation membrane. The electronegativity differences between the metal and oxygen was ZnO (1.79) > CdO (1.75) > CuO (1.54) > AgO (1.51). The order of CO2 permeance was ZnO in BMIM+BF-4 (101 GPU) > CdO in BMIM+BF-4 (57.1 GPU) > CuO in BMIM+BF-4 (52.4 GPU) > AgO in BMIM+BF-4 (14.1 GPU).

Novel Flexible Transparent Conductive Films with Enhanced Chemical and Electromechanical Sustainability: TiO2 Nanosheet-Ag Nanowire Hybrid

Flexible transparent conductive films (TCFs) of TiO₂ nanosheet (TiO₂ NS) and silver nanowire (Ag NW) network hybrid were prepared through a simple and scalable solution-based process. The as-formed TiO₂ NS-Ag NW hybrid TCF shows a high optical transmittance (TT: 97% (90.2% including plastic substrate)) and low sheet resistance (R_s: 40 Ω/sq). In addition, the TiO₂ NS-Ag NW hybrid TCF exhibits a long-time chemical/aging and electromechanical stability. As for the chemical/aging stability, the hybrid TCF of Ag NW and TiO₂ NS reveals a retained initial conductivity (ΔR_s/R_s < 1%) under ambient oxidant gas over a month, superior to that of bare Ag NW (ΔR_s/R_s > 4000%) or RuO₂ NS-Ag NW hybrid (ΔR_s/R_s > 200%). As corroborated by the density functional theory simulation, the superb chemical stability of TiO₂ NS-Ag NW hybrid is attributable to the unique role of TiO₂ NS as a barrier, which prevents Ag NW's chemical corrosion via the attenuated adsorption of sulfidation molecules (H₂S) on TiO₂ NS. With respect to the electromechanical stability, in contrast to Ag NWs (ΔR/R₀ ∼ 152.9%), our hybrid TCF shows a limited increment of fractional resistivity (ΔR/R₀ ∼ 14.4%) after 200 000 cycles of the 1R bending test (strain: 6.7%) owing to mechanically welded Ag NW networks by TiO₂ NS. Overall, our unique hybrid of TiO₂ NS and Ag NW exhibits excellent electrical/optical properties and reliable chemical/electromechanical stabilities.

A graphene mesh as a hybrid electrode for foldable devices

A graphene mesh with arrays of micro-holes was fabricated on a polymer substrate using photolithography for use as an electrode in flexible devices. The optimal mesh structure with high optical transmittance and electrical conductivity was designed using a finite element method, in which the conductivity of the mesh was simulated as a function of structure, size, and periodicity of the hole array. The sheet resistance of the graphene mesh was lowered to that of a graphene monolayer by chemical doping and found to be 330 Ω Sq^-1 at 98.5% transparency. The figure of merit of the doped graphene mesh was calculated to be 106 at 98% transmittance, a value that has not yet been reported for any conventional transparent electrode material. Due to strong bonding between the polymer and substrate, the hybrid electrode composed of a silver nanowire (AgNW)/graphene mesh coated with an over-coating layer exhibited more stable electrical characteristics during mechanical fatigue deformation compared to a hybrid film composed of a AgNW/graphene sheet. The AgNW/graphene sheet underwent breakdown at less than 20 000 cycles in cyclic bending tests with 6.5% strain, but the AgNW/graphene mesh showed a 38% increase in resistance at 20 000 cycles and no breakdown even at 100 000 cycles. Therefore, in this study, we propose a hybrid structure composed of a AgNW/graphene mesh, which is optically and mechanically superior to AgNW/graphene sheets, and therefore suitable for application as a transparent electrode in foldable devices with long-term stability.

Correction: Direct characterization of graphene doping state by in situ photoemission spectroscopy with Ar gas cluster ion beam sputtering

Correction for ‘Direct characterization of graphene doping state by in situ photoemission spectroscopy with Ar gas cluster ion beam sputtering’ by Dong-Jin Yun et al., Phys. Chem. Chem. Phys., 2018, 20, 615–622.

Direct characterization of graphene doping state by in situ photoemission spectroscopy with Ar gas cluster ion beam sputtering

On the basis of an in situ photoemission spectroscopy (PES) system, we propose a novel, direct diagnosis method for the characterization of graphene (Gr) doping states at organic semiconductor (OSC)/electrode interfaces. Our in situ PES system enables ultraviolet/X-ray photoelectron spectroscopy (UPS/XPS) measurements during the OSC growth or removal process. We directly deposit C₆₀ films on three different p-type dopants-gold chloride (AuCl₃), (trifluoromethyl-sulfonyl)imide (TFSI), and nitric acid (HNO₃). We periodically characterize the chemical/electronic state changes of the C₆₀/Gr structures during their aging processes under ambient conditions. Depositing the OSC on the p-type doped Gr also prevents severe degradation of the electrical properties, with almost negligible transition over one month, while the p-type doped Gr without an OSC changes a lot following one month of aging. Our results indicate that the chemical/electronic structures of the Gr layer are completely reflected in the energy level alignments at the C₆₀/Gr interfaces. Therefore, we strongly believe that the variation of energy level alignments at the OSC/graphene interface is a key standard for determining the doping state of graphene after a certain period of aging.

Mechanically Robust Magnetic Carbon Nanotube Papers Prepared with CoFe2O4 Nanoparticles for Electromagnetic Interference Shielding and Magnetomechanical Actuation

The introduction of inorganic nanoparticles into carbon nanotube (CNT) papers can provide a versatile route to the fabrication of CNT papers with diverse functionalities, but it may lead to a reduction in their mechanical properties. Here, we describe a simple and effective strategy for the fabrication of mechanically robust magnetic CNT papers for electromagnetic interference (EMI) shielding and magnetomechanical actuation applications. The magnetic CNT papers were produced by vacuum filtration of an aqueous suspension of CNTs, CoFe₂O₄ nanoparticles, and poly(vinyl alcohol) (PVA). PVA plays a critical role in enhancing the mechanical strength of CNT papers. The magnetic CNT papers containing 73 wt % of CoFe₂O₄ nanoparticles exhibited high mechanical properties with Young's modulus of 3.2 GPa and tensile strength of 30.0 MPa. This magnetic CNT paper was successfully demonstrated as EMI shielding paper with shielding effectiveness of ∼30 dB (99.9%) in 0.5-1.0 GHz, and also as a magnetomechanical actuator in an audible frequency range from 200 to 20 000 Hz.

Isolated, well-defined organovanadium(iii) on silica: single-site catalyst for hydrogenation of alkenes and alkynes

Well-defined, isolated, single-site organovanadium(iii) catalyst on SiO₂ for unprecedented liquid- and gas-phase hydrogenation of alkenes and alkynes under mild conditions.

Facile synthesis of a mesostructured TiO2–graphitized carbon (TiO2–gC) composite through the hydrothermal process and its application as the anode of lithium ion batteries

A mesostructured TiO₂–graphitic carbon (TiO₂–gC) composite was synthesized through a simple and scalable one-step hydrothermal method, exhibiting high capacity, advanced rate capability and a very stable cycle life.

Treatment of pseudohypoparathyroidism with 1 alpha-hydroxyvitamin D3

A maintenance dosis of 2 microgram/day of 1 alpha-OH-D3 could keep the level of serum calcium normal in all 5 cases with pseudohypoparathyroidism, in contrast with 4.0 +/- 1.26 microgram/day needed for the 11 cases with hypoparathyroidism (8 idiopathic and 3 postoperative). The conspicuous effect of 1 alpha-OH-D3 on pseudohypoparathyroidism is likely to be attributed to the fact that the unresponsiveness of bone tissue to parathyroid hormone is corrected by the action of active vitamin D.

Porous spherical carbon/sulfur nanocomposites by aerosol-assisted synthesis: the effect of pore structure and morphology on their electrochemical performance as lithium/sulfur battery cathodes

Porous spherical carbons (PSCs) with tunable pore structure (pore volume, pore size, and surface area) were prepared by an aerosol-assisted process. PSC/sulfur composites (PSC/S, S: ca.59 wt %) were then made and characterized as cathodes in lithium/sulfur batteries. The relationships between the electrochemical performance of PSC/S composites and their pore structure and particle morphology were systematically investigated. PSC/S composite cathodes with large pore volume (>2.81 cm(3)/g) and pore size (>5.10 nm) were found to exhibit superior electrochemical performance, likely due to better mass transport in the cathode. In addition, compared with irregularly shaped carbon/sulfur composite, the spherical shaped PSC/S composite showed better performance due to better electrical contact among the particles.