Adaptive and sensitive fibre-optic fluorimetric transducer for air- and water-borne analytes

A sensitive fibre optic fluorescence intensity meter has been designed and built as a transducer to detect quenching of conjugated polymer fluorescence with minimum adjustment between air- and waterborne analytes. Only generic, commercially available parts including optical fibres, solvents, airbrush, standard optical and electronic parts, and a digital lock-in amplifier have been used, avoiding the need for a fluorescence spectrometer. To test the instrument, optical fibres were sensitised with the generic fluorescent poly(phenylene-vinylene) derivative MDMO-PPV and exposed to a variety of vapour pressures, and concentrations in water, of the nitroaromatic explosive 2,4 dinitrotoluene (DNT). We establish dimensionless Stern-Volmer constants (KSV) and limit-of-detection (LoD) for air- and water-borne DNT as KSV(air) = 1.4 × 107 vs. KSV(water) = 5.8 × 106 and LoD(air) = 10.9 ppb and LoD(water) = 56 ppb. These LoDs compare favourably to prior reports. We consider our study of the MDMO-PPV/DNT system as a successful test of our transducer design and recommend its wider use

Processing and characterization of effective copper molybdate hydrogen evolution catalyst

The preparation and characterization of Cu1·7Mo0·3O4 and Cu1·4Mo0·6O4 nanostructures using the gelatin/sol-gel combustion method have been reported. The synthesized materials were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (cSEM), surface area analysis, and optical measurements. UV–Vis absorption spectra of the nanocomposites were analyzed to investigate the absorption and bandgap energy of the optical band gap. The Cu1·7Mo0·3O4 nanomaterial show cased a triclinic crystal structure system, while the Cu1·4Mo0·6O4 exhibited an orthorhombic system. The BET surface area analysis of the catalysts has values of 53 and 502 m2/g. The Cu1·7Mo0·3O4 sample proved to be the most active in generating hydrogen through NaBH4 methanolysis, displaying an impressive production rate of 23,063 mL/g. min. The findings indicate that the addition of Cu1·7Mo0·3O4 improves the catalytic activity of the methanolysis reaction involving sodium borohydride

Hydrogen catalytic performance of hybrid Fe3O4/FeS2/g-C3N4 nanocomposite structures

In this work, Fe 3O 4/FeS 2/g-C 3N 4 nanocomposites were developed for catalytic hydrogen generation from sodium borohydride. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM) were used to analyze these nanocomposites. The XRD diffraction peaks of Fe 3O 4 and FeS 2 cubic phase showed an average crystal size of calculation of 15 and 20 nm. ESEM micrographs showed a 2D broken up sheet structure having more edge sites. The BET surface areas for S@g-C 3N 4, 1.0, 2.0, and 3.0 wt% Fe 3O 4/FeS 2 were 40, 109, 137 and 162 m 2/g, respectively. Even though Fe 3O 4/FeS 2 were incorporated into the nanosheet, the pore size was increased from 2.0 to 2.15 nm. S@g-C 3N 4 has an average band gap of 2.60 eV that decreased to 2.30, 2.21 and 2.18 eV at 1.0, 2.0 and 3.0 wt% of FeS 2. In addition, Fe 3O 4/FeS 2/g-C 3N 4 nanosheets showed an emission band at 460 nm. Moreover, the intensity of this band decreased as the content of Fe 3O 4/FeS 2 reached 3.0 wt%. The rate of hydrogen production is accelerated as the percentage of Fe 3O 4/FeS 2 increased from 1.0 to 3.0 wt%. The sample 3.0 wt% Fe 3O 4/FeS 2 showed the best rate of hydrogen production (8480 mL/g·min)

Low cost, high sensitivity detection of waterborne Al3+ cations and F− anions via the fluorescence response of a morin derivative dye

Morin dye is known as a cheap and readily available selective ‘off → on’ fluorescent sensitiser when immobilised in a phase transfer membrane for the detection of Al3+ ions. Here, a morin derivative, NaMSA, which readily dissolves in water with good long-term stability is used in conjunction with a fibre optic transducer with lock-in detection to detect Al3+ in drinking water below the potability limit. The combination of a water soluble dye and the fibre optic transducer require neither membrane preparation nor a fluorescence spectrometer yet still display a high figure-of- merit. The known ability to recover morin-based Al3+ cation sensors selectively by exposure to fluoride (F−) anions is further developed enabling a complementary sensing of either fluoride anions, or aluminium cations, using the same dye with a sub-micromolar limit-of-detection for both ions. The sensor performance parameters compare favourably to prior reports on both aqueous aluminium and fluoride ion sensing