Resistivity network and structural model of the oxide cathode for CRT application

In this paper, the electrical properties of oxide cathode and oxide cathode plus, supplied by LG Philips Displays, have been investigated in relation to different cathode activation regimes and methods. Oxide cathode activation treatment for different durations has been investigated. The formations of the compounds associated to the diffusion of reducing elements (Mg, Al, and W) to the Ni cap surface of oxide cathode were studied by a new suggestion method. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) was used as analytical techniques. Al, W, and Mg doping elements take place during heating to 1080 K (Ni-Brightness) under a rich controlled Ba–SrO atmosphere through an acceleration life test. The chemical transport of these elements was occurred mainly by the Ni cap grain boundary mechanism with significant pile-up of Mg compounds. Al and W show a superficial concentrations and distribution. A new structural and resistivity network model of oxide cathode plus are suggested. The new structural model shows a number of metallic and metallic oxide pathways are exist at the interface or extended through the oxide coating. The effective values of the resistances and the type of the equivalent circuit in the resistivity network model are temperature and activation time dependent.</p

Highly sensitive label-free in vitro detection of aflatoxin B1 in an aptamer assay using optical planar waveguide operating as a polarization interferometer

This work reports on further development of an optical biosensor for the in vitro detection of mycotoxins (in particular, aflatoxin B1) using a highly sensitive planar waveguide transducer in combination with a highly specific aptamer bioreceptor. This sensor is built on a SiO2–Si3N4–SiO2 optical planar waveguide (OPW) operating as a polarization interferometer (PI), which detects a phase shift between p- and s-components of polarized light propagating through the waveguide caused by the molecular adsorption. The refractive index sensitivity (RIS) of the recently upgraded PI experimental setup has been improved and reached values of around 9600 rad per refractive index unity (RIU), the highest RIS values reported, which enables the detection of low molecular weight analytes such as mycotoxins in very low concentrations. The biosensing tests yielded remarkable results for the detection of aflatoxin B1 in a wide range of concentrations from 1 pg/mL to 1 μg/mL in direct assay with specific DNA-based aptamers

Characterization of CdS and ZnS Nanoparticle Semiconductors: for Optoelectronics Application

In this work, CdS and ZnS semiconducting colloid nanoparticles coated with organic shell, containing either SO−3 or NH+ 2 groups, were deposited as thin films using the technique of electrostatic self-assembly. The films produced were characterized with UV-vis spectroscopy - for optical properties; mercury probe - for electrical characterisation; and photon counter - for electroluminescence study. UV-vis spectra show a substantial blue shift of the main absorption band of both CdS and ZnS, either in the form of solutions or films, with respect tothe bulk materials. The calculation of nanoparticles’ radii yields the value of about 1.8 nm for both CdS and ZnS. Current-voltage (I-V) and capacitance-frequency (C-f) measurements of polyelectrolyte/nanoparticles (CdS or ZnS) films suggest the tunnelling behaviour in the films while capacitance- voltage (C-V) and conductancevoltage (G-V) measurements suggest that these nanoparticles are conductive. The electroluminescence was detected in sandwich structures of (PAH/CdS/PAH)N using a photon counting detector, but not in the case of ZnS films

Analysis of Toxic Amyloid Fibril Interactions at Natively Derived Membranes by Ellipsometry

There is an ongoing debate regarding the culprits of cytotoxicity associated with amyloid disorders. Although small pre-fibrillar amyloid oligomers have been implicated as the primary toxic species, the fibrillar amyloid material itself can also induce cytotoxicity. To investigate membrane disruption and cytotoxic effects associated with intact and fragmented fibrils, the novel in situ spectroscopic technique of Total Internal Reflection Ellipsometry (TIRE) was used. Fibril lipid interactions were monitored using natively derived whole cell membranes as a model of the in vivo environment. We show that fragmented fibrils have an increased ability to disrupt these natively derived membranes by causing a loss of material from the deposited surface when compared with unfragmented fibrils. This effect was corroborated by observations of membrane disruption in live cells, and by dye release assay using synthetic liposomes. Through these studies we demonstrate the use of TIRE for the analysis of protein-lipid interactions on natively derived lipid surfaces, and provide an explanation on how amyloid fibrils can cause a toxic gain of function, while entangled amyloid plaques exert minimal biological activity

Investigation and analysis of zinc phthalocyanine films for resonant gas sensor applications

Thin films of Zinc Phthalocyanine (ZnPc) with a range of different substitutes have been investigated as chemical active layers for sensing selected organic vapour such as (Ethanol, Toluene) by a standard Quartz Crystal Resonator (QCR) based sensor with fundamental resonance 10MHz. Adsorption of vapour onto the films surface has been realized by monitoring resonance spectra. An equivalent circuit (BVD circuit) has been used to extract parameters related to film viscosity and thickness by fitting experimental admittance spectra of QCR around resonance frequency. Moreover, film properties and characterization was obtained from QCR measurements in conjunction with suitable data analysis. Validation of film characteristics has been determined using complementary methods such as Ellipsometry, UV- Visible absorption Spectrophotometer and AF

Graphene-based LbL deposited films: further study of electrical and gas sensing properties

Graphene-surfactant composite materials obtained by the ultrasonic exfoliation of graphite powder in the presence of ionic surfactants (either CTAB or SDS) were utilised to construct thin films using layer-by-layer (LbL) electrostatic deposition technique. A series of graphene-based thin films were made by alternating layers of either graphene-SDS with polycations (PEI or PAH) or graphene-CTAB with polyanions (PSS). Also, graphene-phthalocyanine composite films were produced by alternating layers of graphene-CTAB with tetrasulfonated nickel phthalocyanine. Graphene-surfactant LbL films exhibited good electric conductivity (about 0.1 S/cm) of semiconductor type with a band gap of about 20 meV. Judging from UV-vis spectra measurements, graphene-phthalocyanine LbL films appeared to form joint π-electron system. Gas sensing testing of such composite films combining high conductivity of graphene with the gas sensing abilities of phthalocyanines showed substantial changes (up to 10%) in electrical conductivity upon exposure to electro-active gases such as HCl and NH3

Graphene-based LbL deposited films: further study of electrical and gas sensing properties

Graphene-surfactant composite materials obtained by the ultrasonic exfoliation of graphite powder in the presence of ionic surfactants (either CTAB or SDS) were utilised to construct thin films using layer-by-layer (LbL) electrostatic deposition technique. A series of graphene-based thin films were made by alternating layers of either graphene-SDS with polycations (PEI or PAH) or graphene-CTAB with polyanions (PSS). Also, graphene-phthalocyanine composite films were produced by alternating layers of graphene-CTAB with tetrasulfonated nickel phthalocyanine. Graphene-surfactant LbL films exhibited good electric conductivity (about 0.1 S/cm) of semiconductor type with a band gap of about 20 meV. Judging from UV-vis spectra measurements, graphene-phthalocyanine LbL films appeared to form joint π-electron system. Gas sensing testing of such composite films combining high conductivity of graphene with the gas sensing abilities of phthalocyanines showed substantial changes (up to 10%) in electrical conductivity upon exposure to electro-active gases such as HCl and NH3

Optimization of apta-sensing platform for detection of prostate cancer marker PCA3

This work is a continuation of our research into the development of simple, reliable, and cost-effective methods for the early diagnosis of prostate cancer (PCa). The proposed method is based on the electrochemical detection of the PCA3 biomarker of PCa (long non-coded RNA transcript expressed in urine) using a specific aptamer labeled with a redox group (methylene blue). The electrochemical measurements (cyclic voltammograms) obtained from electrodes functionalized with the aptamer were complemented in this work by another biosensing technique: total internal reflection ellipsometry (TIRE). In addition to proving the concept of the detection of PCA3 in low concentrations down to 90 pM, this study improved our understanding of the processes by which PCA3 binds to its specific aptamer. The high specificity of the binding of PCA3 to the aptamer was assessed by studying the binding kinetics, which yielded an affinity constant (KD) of 2.58 × 10−9 M. Additional XPS measurements confirmed the strong covalent binding of aptamers to gold and showed spectral features associated with PCA3 to aptamer binding

[INVITED] Novel optical biosensing technologies for detection of mycotoxins

This work reviews our recent progress in development of novel optical methods of detection of mycotoxins in direct assay with either specific antibodies or aptamers. The main method in this work was the total internal reflection ellipsometry (TIRE) combined with LSPR transducers based on gold nano-structures produced by annealing of thin gold films. The gold nano-islands produced were characterised with SEM, AFM, UV–visible absorption spectroscopy, and spectroscopic ellipsometry. The combination of TIRE and LSPR offers superior refractive index sensitivity as compared to traditional UV–vis absorption spectroscopy. The limitations of LSPR related to a short evanescent field decay length can be overcome using small-size bio-receptors, such as half-antibodies and aptamers. The achieved sensitivity of detection of mycotoxins in 0.01 ppb level of concentration is sufficient for the use of this method for analysis of agriculture products, food and feed on the presence of mycotoxins. Even higher sensitivity in sub-ppt level was achieved with another optical biosensor developed recently; it is based on optical planar waveguide operating as polarization interferometer (PI). This method is promising for development of portable, highly sensitive, and simple to use biosensors suitable for point-of-need detection of mycotoxins