Improving Nonenzymatic Biosensing Performance of Electrospun Carbon Nanofibers Decorated With Ni/Co Particles via Oxidation

Electrochemical nonenzymatic biosensors with no immobilization and degradation problem, have recently attracted growing attention due to stability and reproducibility. Here, a comparative study was conducted to precisely evaluate the nonenzymatic glucose sensing of pure/oxidized Ni, Co, and their bimetal nanostructures grown on electrospun carbon nanofibers (ECNFs). This method provides a low-cost free stand electrode. The prepared nanostructures with superb physiochemical features exhibited sensitivity (from 66.28 to 610.6 μA mM−1 cm−2), linear range of 2-10 mM, limit of detection in the range of 1 mM, and response time (<5 s), besides outstanding selectivity and applicability for glucose detection in the human serum. Regarding Co-C and Ni-C phase diagrams, solid-state diffusion phenomena, and rearrangement of dissolved C atoms after migration from metal particles was discussed. This study undoubtedly provides new prospects on nonenzymatic biosensing performance of mono-metal, bimetal, and oxide compounds of Ni and Co elements, which is useful for the fabrication of biomolecules detecting devices.

Signature of Plasmonic Nanostructures Synthesised by Electrical Exploding Wire Technique on Surface-Enhanced Raman Scattering

This work aims to fabricate two types of plasmonic nanostructures by electrical exploding wire (EEW) technique and study the effects of the different morphologies of these nanostructures on the absorption spectra and Surface-Enhanced Raman Scattering (SERS) activities, using Rhodamine 6G as a probe molecule. The structural properties of these nanostructures were examined using X-Ray diffraction (XRD). The morphological properties were examined using field emission scanning electron microscopy (FESEM) and scanning transmission electron microscopy (STEM). The absorption spectra of the mixed R6G laser dye (concentration 1×10-6 M) with prepared nanostructures were examined by double beam UV-Vis Spectrophotometer. The Raman spectra of the R6G mixed with the prepared nanostructures were examined using a Horiba HR Evolution 800 Raman microscope system with an objective lens (50 ×). The FESEM and STEM images indicated that the Ag nanoparticles (AgNPs) with 35 nm average particle sizes were decorated on the surface of the AgNWs and the PDA layer by EEW technique, forming AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures. The results indicated that the increased intensities of the absorption spectra peaks and the SERS arise from the hot spots and the roughness of the surface of nanostructures. The SERS enhancement factor of R6G (1×10-6 M) was reached at 2.3×107 and 2.5×107, at the wave number of 1650 cm-1, for the AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures, respectively, after being excited by (λexc. = 532 nm) laser source. It can be concluded that the AgNW@AgNPs and AgNW@PDA@AgNPs nanostructures were fabricated with an easy and simple way without the need for additional chemical compounds. These nanostructures attained a reliable and sensitive detection and can be utilized in a variety of SERS applications, such as chemical and biological sensors.

Characterizations of Hollow Polyvinylidene Fluoride-Co-Trifluoroethylene (P(VDF-TrFE)) Nano-Bundles Produced by Template-Assisted Method

The present study describs the fabrication of hollow polyvinylidene fluoride-co-trifluoroethylene (P(VDF-TrFE)) nano-bundles by the template-assisted method. The P(VDF-TrFE) solution was spin-coated onto porous templates at four different rotation speeds, e.g., 1000 rpm, 2000 rpm, 3000 rpm, and 4000 rpm. The characteristics of the prepared nanostructures were evaluated to examine their morphological, structural, and hysteresis behaviors. All the P(VDF-TrFE) nanostructures were characterized as bundles rather than individual structures due to their agglomeration properties. The P(VDF-TrFE) nanostructures, which were synthesized at 4000 rpm, ensured a shorter length in comparison to the others fabricated at lower spin rates. Despite their different diameters and lengths, no clear difference was observed in the crystallinities of these nanostructures.

A Fluorescent g-C3N4 Nanosensor for Detection of Dichromate Ions

Background: Dichromate (Cr2O7 2-) ion is one of the carcinogenic and toxic spices in environment which can easily contaminate the environment due to its high solubility in water. Therefore, a lot of attention has been focused on the detection of Cr2O7 2- with high sensitivity and selectivity. Methods: In present work, nitrogen-rich precursor was used for synthesizing graphitic carbon nitride (g-C3N4) nanostructures through hydrothermal oxidation of g-C3N4 nanosheets. The prepared nanostructures show two distinct fluorescence emissions centered at 368 and 450 nm which are highly sensitive toward Cr2O7 2- ions. Results: The as-prepared g-C3N4 was characterized by several techniques such as Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and fluorescence emission spectra. The XRD pattern of prepared nanostructures illustrated two diffraction patterns (at 13.4° and 27.6°) indicating tri-s-tri-azine-based structures. The g-C3N4 exhibited good selectivity and sensitivity toward Cr2O7 2- among other anions. According to titration test, the detection limit and stern-volmer constant (Ksv) were calculated as 40 nM and 0.13×106 M-1, respectively. The investigation of quenching mechanism shows that Cr2O7 2- may form hydrogen bonding with surface groups of g-C3N4 (such as NH2, OH and COOH) resulted in more fluorescence quenching in comparison with the pure inner filter effect. Conclusion: The g-C3N4 nanostructures were successfully synthesized through the hydrothermal oxidation. The as-prepared g-C3N4 can be used as a highly sensitive fluorescent probe for the selective determination of Cr2O7 2 ion among other anions. The quenching mechanism was experimentally studied. According to reliable responses in real sample tests, it can be proposed that g-C3N4 nanostructure is a suitable sensitive nanosensor for detection of Cr2O7 2 ions in aqueous media.

Microwave-Assisted Hydrothermal Synthesis of ZnFe2O4/TiO2 Composite and Photocatalytic Properties

In order to improve TiO2 photocatalytic activity ZnFe2O4/TiO2 nanocomposites with different ZnFe2O4 mass loading were produced. Obtained ZnFe2O4 nanoparticles were coupled with TiO2 via microwave-assisted hydrothermal method in order to improve photon absorption in a range of visible light. Prepared nanostructures were characterized with scanning electron microscopy and X-ray diffraction. Photocatalytic activity of prepared samples was investigated by degradation of methylene blue under different light sources – LED, Hg and Osram Vitalux lamps. ZnFe2O4 consists of spherical nanoparticles with average size of 15 nm. TiO2 spherical nanoparticles size is in a range of 30÷45 nm. The results show that doping TiO2 with ZnFe2O4 nanoparticles increases photocatalytic activity. Photocatalytic activity increases as mass loading of ZnFe2O4 decreases.

Synthesis and Spectral Analysis of PVP Capped Zinc Oxide Nanostructures

Monodispersed polyvinylpyrrolidone capped nanostructures of zinc oxide are prepared through chemical precipitation technique. The prepared nanostructures are characterized by XRD, SEM and Photoluminescence spectroscopic techniques. X-ray diffraction studies confirm the hexagonal structure of zinc oxide nanostructures. Nanostructures of the prepared zinc oxide are confirmed by SEM. The emission wavelength of PVP capped zinc oxide is found to be 551 nm using photoluminescence spectra.

Synthesis and Optical Characteristics of Silver Nanoparticles on Different Substrates

Silver nanoparticles have been deposited on glass and polyethylene substrate by Chemical Bath Deposition (CBD) technique and Chemical rolling method. A comparative study has shown that Chemical bath technique is superior compared to rolling technique for uniform deposition of silver nanoparticles on glass substrate. Crystallography investigation of these materials is done by X-ray diffraction (XRD) which reveals that average grain size is in nano region. Scanning Electron Microscope (SEM) is used for topography study of these prepared nanostructures. Optical properties of the synthesized materials are studied by UV-VIS in detail to check their potential for next era industrial revolution.

Chemical Synthesis of Anisotropic Nanocrystalline Sb2Te3 and Low Thermal Conductivity of the Compacted Dense Bulk

We describe a one-step, one-pot non-aqueous route for the synthesis of Sb2Te3 nanocrystals with hexagonal shape and highly anisotropic nanostructures. The as-prepared nanostructures were characterized by XRD, TEM and HRTEM. The effect of the stabilizers on the nanocrystal morphology has been discussed in detail. We have studied the thermal conductivity of the compacted bulk from the Sb2 Te3 nanostructures. The results indicated that a very low thermal conductivity of about 1 W/mK at 300 K, comparing to 4.7 W/mK of the polycrystalline bulk, was achieved. The results indicated that nanostructured Sb2 Te3 is potentially a good candidate for engineered nanocomposites that can lead to high thermoelectric figure-of-merit.