Synthesis and luminescent properties of a linear difluorene pyrazine (D-A-D) derivative as a selective indicator for a reversible acid-base vapour sensor.

We have synthesized a structure in which pyrazine is the core structure and fluorene derivatives are attached to both sides. Photo physical investigations such as aprotic solvents (Hexane to DMF) were carried out. A redshift was revealed from non-polar aprotic solvents to polar aprotic solvents. The luminescence intensity was gradually decreased, which is incredibly more complex towards changes in the solvent polarization than their UV/Vis absorption spectra. The compound showed a redshift from 445 nm to 473 nm when slowly increasing the water fraction (fw) from 0 to 30 %. Also, rising water fraction (fw > 40-90 %) effectively attenuated the instantaneous emission intensity was observed. At the same time, the intensity of the emission peak was reduced due to the TICT effect on fluorene and pyrazine rings due to enhanced solvent polarity. In addition, optically reversible acidofluorochromic properties were performed experimentally in both solvent and solid phases. For the acidic substances TFA and HF, which contain fluorine, new redshift peaks from 425 nm and 503 nm were observed upon reaction with the PDF solution, and the emission intensity was extinguished by more than 90 % and 60 %, respectively. Upon addition of TFA up to 1500 equal, the PDF mixture suffered from 50 % lower energy absorption intensity. The 1H NMR spectrum confirmed the proposed mechanism (TFA/TEA, ON-OFF-ON). Therefore, the present work presents a novel approach to fabricating ON-OFF-ON active-pull pyrazine scaffolds that can be used in DSEgens, referred to as "ON-OFF-ON" fluorescent sensors, for multifunctional applications.

Tailored fluorophore design: Enhancing selectivity for cyanide ion sensing in water and food samples, and innovative device development.

A rigid fluorophore unit of Julolidine/coumarin fused with an indolium-conjugated system was built for the immediate and effective recognition of cyanide ions in a 90 % aq. DMSO solution. The probes are capable of displaying better sensitivity/selectivity for the cyanide ion over a wide range of other interfering ions. The probe JI showed an instant colorimetric variation, whereas the modified probe JCI showed both colorimetric and fluorimetric variation with cyanide ion. The observed detection limit values indicated excellent sensitivity of the probe to the cyanide ion. HRMS and 1H NMR studies confirmed that the mechanism of detection of CN- is via the nucleophilic attack on the electron-deficient indolium moiety of the molecule. Moreover, the probes are well proficient in selective recognition of cyanide in various real time applications (test strips, electronic sensor kit, food and water sample analysis).

Manufacture of antibacterial carbon fiber-reinforced plastics (CFRP) using imine-based epoxy vitrimer for medical application.

An antibacterial carbon fiber-reinforced plastics (CFRP) was manufactured based on a vitrimer containing imine groups. A liquid curing agent was prepared to include an imine group in the matrix, and was synthesized without a simple mixing reaction and any purification process. The vitrimer used as the matrix for CFRP was prepared by reacting a commercial epoxy with a synthesized curing agent. The structural and thermal properties of the vitrimer were determined by Fourier transform-infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In addition, the temperature-dependent behavior of the vitrimer was characterized by stress relaxation, reshaping, and shape memory experiments. The mechanical properties of composites fabricated using vitrimer were fully analyzed by tensile, flexural, short-beam strength, and Izod impact tests and had mechanical properties similar to reference material. Moreover, both the vitrimer and the vitrimer composites showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coil due to the imine group inside the vitrimer. Therefore, vitrimer composites have potential for applications requiring antimicrobial properties, such as medical devices.

Synthesis and photophysical properties of N-alkyl dithieno[3,2-b:2',3'-d]pyrrole based donor/acceptor-π-conjugated copolymers for solar-cell application.

Two kinds of donor-acceptor π-conjugated copolymer based on poly{[N-hexyl-dithieno(3,2-b:2',3'-d)pyrrole-2,6-diyl]alt-[isoindigo]} (PDTP-IID) and poly{[N-hexyl-dithieno(3,2-b:2',3'-d)pyrrole-2,6-diyl]alt-[thiazol-2,5-diyl]} (PDTP-Thz) were investigated. These copolymers were synthesized via a Stille coupling reaction. The results showed the structure-property relationships of different donor-acceptor (D-A) combinations. The polymer structures and photophysical properties were characterized by 1H NMR, TGA, DSC, UV-vis absorption spectroscopy, AFM, CV, and XRD measurement. Through UV-vis absorption and cyclic voltammetry (CV) measurements, it showed that the copolymers exhibit not only a low bandgap of 1.29 eV and 1.51 eV but also a deep highest occupied molecular orbital (HOMO) of -5.49 and -5.11 eV. Moreover, photovoltaic properties in combination with the fullerene derivatives were investigated. The device based on the copolymers with PC71BM exhibited higher maximum power conversion efficiency and higher maximum short-circuit current density of 0.23% with 1.64 mA cm-2 of PDTP-IID:PC71BM and 0.13% with 1.11 mA cm-2 of PDTP-Thz:PC71BM than those of the copolymers with PC61BM. Measurements performed for N-hexyl-dithieno(3,2-b:2',3'-d)pyrrole-based copolymers proved the potential of these polymers to be applied in optoelectronic applications.

Secure Encapsulation Schemes Using Key Recovery System in IoMT Environments.

Recently, as Internet of Things systems have been introduced to facilitate diagnosis and treatment in healthcare and medical environments, there are many issues concerning threats to these systems' security. For instance, if a key used for encryption is lost or corrupted, then ciphertexts produced with this key cannot be decrypted any more. Hence, this paper presents two schemes for key recovery systems that can recover the lost or the corrupted keys of an Internet of Medical Things. In our proposal, when the key used for the ciphertext is needed, this key is obtained from a Key Recovery Field present in the cyphertext. Thus, the recovered key will allow decrypting the ciphertext. However, there are threats to this proposal, including the case of the Key Recovery Field being forged or altered by a malicious user and the possibility of collusion among participating entities (Medical Institution, Key Recovery Auditor, and Key Recovery Center) which can interpret the Key Recovery Field and abuse their authority to gain access to the data. To prevent these threats, two schemes are proposed. The first one enhances the security of a multi-agent key recovery system by providing the Key Recovery Field with efficient integrity and non-repudiation functions, and the second one provides a proxy re-encryption function resistant to collusion attacks against the key recovery system.

Preparation of a polymer nanocomposite via the polymerization of pyrrole : biphenyldisulfonic acid : pyrrole as a two-monomer-connected precursor on MoS2 for electrochemical energy storage.

We prepared a poly(pyrrole : biphenyldisulfonic acid : pyrrole (Py:BPDSA:Py)) nanocomposite of molybdenum disulfide (MoS2), P(Py:BPDSA:Py)-MoS2, with high crystallinity. The composite is synthesized by oxidative polymerization of Py:BPDSA:Py as a two-monomer-connected precursor (TMCP) linked by ionic bonding on a molybdenum disulfide (MoS2) monolayer. The chemical, structural and morphological characterization of this composite is confirmed by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and scanning electron microscopy (SEM). The crystal structure is analysed by X-ray diffraction (XRD) and high-voltage electron microscopy (HVEM), which shows a face-centered cubic (FCC) crystal structure for the composite. Nitrogen adsorption-desorption isotherms show an improved specific surface area (91.3 m2 g-1). The electrochemical properties of the composite with a unique crystal structure and a large specific surface area are analysed through cyclic voltammetry (CV), which shows a specific capacitance of 681 F g-1 demonstrating that the composite can be used as an efficient electrode active material for electrochemical energy storage systems.

Growth of close-packed crystalline polypyrrole on graphene oxide via in situ polymerization of two-monomer-connected precursors.

Synthesis of a two-dimensional (2D) highly crystalline composite, P(Py:BPDSA:Py)-GO, from the growth of a close-packed polymer crystal, P(Py:BPDSA:Py), on graphene oxide (GO) sheets via in situ polymerization of two-monomer-connected precursors (TMCPs, Py:BPDSA:Py), in which two pyrrole (Py) molecules are linked through a connector (4,4'-biphenyldisulfonic acid) (BPDSA), is reported. When the TMCP is polymerized on GO, it leads to an exceptionally ordered structure determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) studies. X-ray crystallography of the composite shows crystalline peaks with d spacings in the [100] direction. Transmission electron microscopy (TEM) analysis indicates that the composite has a face-centered cubic (FCC) crystal structure. Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) show that this composite with a well-defined nanostructure was successfully synthesized. Nitrogen adsorption-desorption isotherms show that this composite, P(Py:BPDSA:Py)-GO, has an improved specific surface area (71 m2 g-1) compared to that of P(Py:BPDSA:Py) (3.1 m2 g-1). The electrochemical properties of the composite studied by cyclic voltammetry indicates a specific capacitance of 480 F g-1 without an additional conducting material such as carbon black, suggesting its use as a pseudocapacitor.

Bio-fabrication of nanomesh channels of single-walled carbon nanotubes for locally gated field-effect transistors.

Single-walled carbon nanotubes (SWNTs) are one of the promising electronic components for nanoscale electronic devices such as field-effect transistors (FETs) owing to their excellent device characteristics such as high conductivity, high carrier mobility and mechanical flexibility. Localized gating gemometry of FETs enables individual addressing of active channels and allows for better electrostatics via thinner dielectric layer of high k-value. For localized gating of SWNTs, it becomes critical to define SWNTs of controlled nanostructures and functionality onto desired locations in high precision. Here, we demonstrate that a biologically templated approach in combination of microfabrication processes can successfully produce a nanostructured channels of SWNTs for localized active devices such as local bottom-gated FETs. A large-scale nanostructured network, nanomesh, of SWNTs were assembled in solution using an M13 phage with strong binding affinity toward SWNTs and micrometer-scale nanomesh channels were defined using negative photolithography and plasma-etching processes. The bio-fabrication approach produced local bottom-gated FETs with remarkably controllable nanostructures and successfully enabled semiconducting behavior out of unsorted SWNTs. In addition, the localized gating scheme enhanced the device performances such as operation voltage and I on/I off ratio. We believe that our approach provides a useful and integrative method for fabricating electronic devices out of nanoscale electronic materials for applications in which tunable electrical properties, mechanical flexibility, ambient stability, and chemical stability are of crucial importance.

3 V omni-directionally stretchable one-body supercapacitors based on a single ion-gel matrix and carbon nanotubes.

Stretchable supercapacitors often have laminated structures consisting of electrode, electrolyte, and supporting layers. Since the layers are likely to be composed of different materials, delamination is a major cause of failure upon stretching. In this study, we demonstrate delamination-free stretchable supercapacitors where all the component layers are prepared with a single matrix, which is composed of a polymer, poly(vinylidene fluoride-hexafluoropropylene) and an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Since the ionic liquid in the composite plays a role as both an electrolyte and a plasticizer, this composite can be used as an electrolyte and a supporting layer in the stretchable supercapacitor. The electrode layer can be fabricated by incorporating carbon nanotubes in the common matrix. Then, all the layers can be seamlessly fused into one body by dissolving the surface of the composite with acetone, which evaporates after the integration, leaving no borders between the layers. This one-body stretchable supercapacitor not only has high durability against repetitive stretches but also is stretchable in all directions. This feature clearly distinguishes them from conventional stretchable supercapacitors fabricated using buckled structures, which are stretchable only in one or two directions. Moreover, this supercapacitor has high cell voltage (∼3 V) owing to the ionic liquid-based gel electrolytes. Our demonstration of isotropically stretchable high-durability supercapacitors may have a great implication in the development of stretchable energy storage devices for real applications.

Stretchable carbon nanotube/ion-gel supercapacitors with high durability realized through interfacial microroughness.

A critical problem with stretchable supercapacitors developed to date has been evaporation of a volatile component of their electrolyte, causing failure. In this work, we demonstrated successful use of an ionic-liquid-based nonvolatile gel (ion-gel) electrolyte in carbon nanotube (CNT)-based stretchable supercapacitors. The CNT/ion-gel supercapacitors showed high capacitance retention (96.6%) over 3000 stretch cycles at 20% strain. The high durability against stretch cycles was achieved by introducing microroughness at the interfaces between different materials. The microroughness was produced by the simple process of imprinting the surface microstructure of office paper onto a poly(dimethylsiloxane) substrate; the surface texture is reproduced in successive current collector and CNT layers. Adhesion between the different layers was strengthened by this roughness and prevented delamination over repeated stretch cycles. The addition of a CNT layer decreased the sensitivity of electrical characteristics to stretching. Moreover, the ion-gel increases the operating voltage window (3 V) and hence the energy density. We believe our demonstration will greatly contribute to the development of flexible and/or stretchable energy-storage devices with high durability.

Vibrio vulnificus AphB is involved in interleukin-8 production via an NF-κB-dependent pathway in human intestinal epithelial cells.

We previously reported that the aphB gene mutant of Vibrio vulnificus had significantly impaired motility and adherence to host cells. In this study, we investigated the role of V. vulnificus AphB on the production of interleukin-8 (IL-8), a proinflammatory cytokine, as well as its underlying mechanism in human intestinal epithelial INT-407 cells. The aphB gene mutation significantly reduced the ability of V. vulnificus to stimulate IL-8 production and IL-8 gene promoter activation in INT-407 cells. The V. vulnificusaphB mutant also induced lower levels of NF-κB DNA binding activity and NF-κB minimal promoter activation than did the wild-type of V. vulnificus. Importantly, the observed reductions in IL-8 production, IL-8 gene promoter activation and NF-κB DNA binding activity were significantly restored by complementing the aphB gene into the V. vulnificusaphB mutant. These results indicate that V. vulnificus AphB is involved in the IL-8 production via an NF-κB dependent pathway in human intestinal epithelial cells.