Rapid extraction of high- and low-density microplastics from soil using high-gradient magnetic separation.

Microplastics (MPs) are present in all environments, and concerns over their possible detrimental effects on flora and fauna have arisen. Density separation (DS) is commonly used to separate MPs from soils to allow MP quantification; however, it frequently fails to extract high-density MPs sufficiently, resulting in under-estimation of MP abundances. In this proof-of-concept study, a novel three-stage extraction method was developed, involving high-gradient magnetic separation and removal of magnetic soil (Stage 1), magnetic tagging of MPs using surface modified iron nanoparticles (Stage 2), and high-gradient magnetic recovery of surface-modified MPs (Stage 3). The method was optimised for four different soil types (loam, high­carbon loamy sand, sandy loam and high-clay sandy loam) spiked with different MP types (polyethylene, polyethylene terephthalate, and polytetrafluoroethylene) of different particle sizes (63 µm to 2 mm) as well as polyethylene fibres (2-4 mm). The optimised method achieved average recoveries of 96% for fibres and 92% for particles in loam, 91% for fibres and 87% for particles in high­carbon loamy sand, 96% for fibres and 89% for particles in sandy loam, and 97% for fibres and 94% for particles in high-clay sandy loam. These were significantly higher than recoveries achieved by DS, particularly for fibres and high-density MPs (p < 0.05). To demonstrate the practical application of the HGMS method, it was applied to a farm soil sample, and high-density MP particles were only recovered by HGMS. Furthermore, this study showed that HGMS can recover fibre-aggregate complexes. This improved extraction method will provide better estimates of MP quantities in future studies focused on monitoring the prevalence of MPs in soils.

Optical Fibre-Based Sensors for Oil and Gas Applications.

Oil and gas (O&G) explorations moving into deeper zones for enhanced oil and gas recovery are causing serious safety concerns across the world. The sensing of critical multiple parameters like high pressure, high temperature (HPHT), chemicals, etc., are required at longer distances in real-time. Traditional electrical sensors operate less effectively under these extreme environmental conditions and are susceptible to electromagnetic interference (EMI). Hence, there is a growing demand for improved sensors with enhanced measurement capabilities and also sensors that generates reliable data for enhanced oil and gas production. In addition to enhanced oil and gas recovery, the sensing technology should also be capable of monitoring the well bore integrity and safety. The sensing requirements of the O&G industry for improved sensing in deeper zones include increased transmission length, improved spatial coverage and integration of multiple sensors with multimodal sensing capability. This imposes problems like signal attenuation, crosstalks and cross sensitivities. Optical fibre-based sensors are expected to provide superior sensing capabilities compared to electrical sensors. This review paper covers a detailed review of different fibre-optic sensing technologies to identify a feasible sensing solution for the O&G industry.

Rare Elements Electrochemistry: The Development of a Novel Electrochemical Sensor for the Rapid Detection of Europium in Environmental Samples Using Gold Electrode Modified with 2-pyridinol-1-oxide.

This work presents for the first time the electrochemical determination of europium using cyclic voltammetry at gold electrodes modified with 2-pyridinol-1-oxide. A well-defined oxidation peak was observed in cyclic voltammetry as a result of the oxidation of the europium at ∼1100 mV in phosphate buffer at pH 7.0. The peak current increased linearly with the increase of concentration of the europium over the range from 1 to 80 µM and detection limit (based on 3-sigma) and quantification were found to be 0.3 and 0.549 µM, respectively. The analytical utility of the developed protocol was evaluated by performing the detection of the europium in river water. Europium is also linear over the concentration range 10 to 150 µM. (I(p)/µA = 0.7239x + 108.19, R(2) = 0.9981 and n = 9) with a detection limit of 6.5 µM (based on 3-sigma). This simple and effective protocol exhibited good sensitivity, precision and reliability towards the detected analyte.

Photocatalytic degradation of eleven microcystin variants and nodularin by TiO2 coated glass microspheres.

Microcystins and nodularin are toxic cyanobacterial secondary metabolites produced by cyanobacteria that pose a threat to human health in drinking water. Conventional water treatment methods often fail to remove these toxins. Advanced oxidation processes such as TiO2 photocatalysis have been shown to effectively degrade these compounds. A particular issue that has limited the widespread application of TiO2 photocatalysis for water treatment has been the separation of the nanoparticulate powder from the treated water. A novel catalyst format, TiO2 coated hollow glass spheres (Photospheres™), is far more easily separated from treated water due to its buoyancy. This paper reports the photocatalytic degradation of eleven microcystin variants and nodularin in water using Photospheres™. It was found that the Photospheres™ successfully decomposed all compounds in 5 min or less. This was found to be comparable to the rate of degradation observed using a Degussa P25 material, which has been previously reported to be the most efficient TiO2 for photocatalytic degradation of microcystins in water. Furthermore, it was observed that the degree of initial catalyst adsorption of the cyanotoxins depended on the amino acid in the variable positions of the microcystin molecule. The fastest degradation (2 min) was observed for the hydrophobic variants (microcystin-LY, -LW, -LF). Suitability of UV-LEDs as an alternative low energy light source was also evaluated.

LED-controlled tuning of ZnO nanowires' wettability for biosensing applications.

BACKGROUND: Wettability is an important property of solid materials which can be controlled by surface energy. Dynamic control over the surface wettability is of great importance for biosensing applications. Zinc oxide (ZnO) is a biocompatible material suitable for biosensors and microfluidic devices. Nanowires of ZnO tend to show a hydrophobic nature which decelerates the adhesion or adsorption of biomolecules on the surface and, therefore, limits their application. METHODS: Surface wettability of the ZnO nanowires can be tuned using light irradiation. However, the control over wettability using light-emitting diodes (LEDs) and the role of wavelength in controlling the wettability of ZnO nanowires are unclear. This is the first report on LED-based wettability control of nanowires, and it includes investigations on tuning the desired wettability of ZnO nanowires using LEDs as a controlling tool. RESULTS: The investigations on spectral properties of the LED emission on ZnO nanowires' wettability have shown strong dependency on the spectral overlap of LED emission on ZnO absorption spectra. Results indicate that LEDs offer an advanced control on dynamically tuning the wettability of ZnO nanowires. CONCLUSION: The spectral investigations have provided significant insight into the role of irradiating wavelength of light and irradiation time on the surface wettability of ZnO nanowires. This process is suitable to realize on chip based integrated sensors and has huge potential for eco-friendly biosensing and environmental sensing applications.

Highly textured and transparent RF sputtered Eu2O3 doped ZnO films.

Background : Zinc oxide (ZnO) is a wide, direct band gap II-VI oxide semiconductor. ZnO has large exciton binding energy at room temperature, and it is a good host material for obtaining visible and infrared emission of various rare-earth ions. Methods : Europium oxide (Eu2O3) doped ZnO films are prepared on quartz substrate using radio frequency (RF) magnetron sputtering with doping concentrations 0, 0.5, 1, 3 and 5 wt%. The films are annealed in air at a temperature of 773 K for 2 hours. The annealed films are characterized using X-ray diffraction (XRD), micro-Raman spectroscopy, atomic force microscopy, ultraviolet (UV)-visible spectroscopy and photoluminescence (PL) spectroscopy. Results : XRD patterns show that the films are highly c-axis oriented exhibiting hexagonalwurtzite structure of ZnO. Particle size calculations using Debye-Scherrer formula show that average crystalline size is in the range 15-22 nm showing the nanostructured nature of the films. The observation of low- and high-frequency E2 modes in the Raman spectra supports the hexagonal wurtzite structure of ZnO in the films. The surface morphology of the Eu2O3 doped films presents dense distribution of grains. The films show good transparency in the visible region. The band gaps of the films are evaluated using Tauc plot model. Optical constants such as refractive index, dielectric constant, loss factor, and so on are calculated using the transmittance data. The PL spectra show both UV and visible emissions. Conclusion : Highly textured, transparent, luminescent Eu2O3 doped ZnO films have been synthesized using RF magnetron sputtering. The good optical and structural properties and intense luminescence in the ultraviolet and visible regions from the films suggest their suitability for optoelectronic applications.