Nanocrystalline cellulose incorporated biopolymer tailored polyethersulfone mixed matrix membranes for efficient treatment of produced water.

Membrane technology is a sustainable method to remove pollutants from petroleum wastewater. However, the presence of hydrophobic oil molecules and inorganic constituents can cause membrane fouling. Biomass derived biopolymers are promising renewable materials for membrane modification. In this study, fouling resistant biopolymer N-phthaloylchitosan (CS)- based polythersulfone (PES) mixed matrix membranes (MMMs) incorporated with nanocrystalline cellulose (NCC) was fabricated via phase inversion method and applied for produced water (PW) treatment. The morphological and Fourier-transform infrared spectroscopy (FTIR) analyses of the as-prepared NCC evidenced the formation of fibrous sheet-like structure and the presence of hydrophilic group. The membrane morphology and AFM analysis showed that the NCC altered the surface and cross-sectional morphology of the CS-PES MMMs. The tensile strength of NCC-CS-PES MMMs was also enhanced. 0.5 wt% NCC-CS-PES MMMs displayed a water permeability of 1.11 × 10-7 m/s.kPa with the lowest contact angle value of 61°. It affirmed that its hydrophilicity increased through the synergetic interaction between CS biopolymer and NCC. The effect of process variables such as transmembrane pressure (TMP) and synthetic produced water (PW) concentration were evaluated for both neat PES and NCC-CS-PES MMMs membranes. 0.5 wt% NCC-CS-PES MMMs exhibited the highest PW rejection of 98% when treating 50 mgL-1 of synthetic PW at a transmembrane pressure (TMP) of 200 kPa. The effect of nano silica and sodium chloride on the long-term PW filtration of NCC-CS-PES MMMs was also investigated.

Sustainable and fast saliva-based COVID-19 virus diagnosis kit using a novel GO-decorated Au/FBG sensor.

Monitoring the COVID-19 virus through patients' saliva is a favorable non-invasive specimen for diagnosis and infection control. In this study, salivary samples of COVID-19 patients collected from 6 patients with the median age of 58.5 years, ranging from 34 to 72 years (2 females and 4 males) were analyzed using an Au/fiber Bragg grating (FBG) probe decorated with GO. The probe measures the prevalence of positivity in saliva and the association between the virus density and changes to sensing elements. When the probe is immersed in patients' saliva, deviation of the detected light wavelength and intensity from healthy saliva indicate the presence of the virus and confirms infection. For a patient in the hyperinflammatory phase of desease, who has virus density of 1.2 × 108 copies/mL in saliva, the maximum wavelength shift and intensity changes after 1600 s were shown to be 1.12 nm and 2.01 dB, respectively. While for a patient in the early infection phase with 1.6 × 103 copies/mL, these values were 0.98 nm and 1.32 dB. The precise and highly sensitive FBG probe proposed in this study was found a reliable tool for quick detection of the COVID-19 virus within 10 s after exposure to patients' saliva in any stage of the disease.

The impact of ZnO configuration as an external layer on the sensitivity of a bi-layer coated polymer optical fiber probe.

Salinity magnitude changes are a critical factor for determining the chemistry of natural water bodies and biological processes. Label-free refractive index sensors are promising devices for detecting these changes. A polymer optical fiber (POF) sensor modified with cladding treatment and a bi-layer zinc oxide/silver (ZnO/Ag) nanostructure coating to determine sodium chloride concentration changes through refractive index variations in water is experimentally demonstrated. The use of three ZnO nanostructure shapes, nanoparticles and horizontally and vertically oriented nanorods, as an external layer and a broad spectrum light source from the visible (Vis) to the near infrared (NIR) region are investigated to achieve optimum sensitivity. The rms roughness, optical band-gap and zeta potential (ZP) value for the vertically oriented sample are 148 nm, 3.19 eV and 5.96 mV, respectively. In the NIR region the wavelength-intensity sensitivity values of probes coated with ZnO nanoparticles and horizontally and vertically oriented nanorods are 104 nm RIU-1-12 dB RIU-1, 63 nm RIU-1-10 dB RIU-1 and 146 nm RIU-1-22 dB RIU-1, respectively, and in the Vis area the values are 65 nm RIU-1-14 dB RIU-1, 58 nm RIU-1-11 dB RIU-1 and 89 nm RIU-1-23 dB RIU-1, respectively. The maximum amplitude sensitivity is obtained for the probe coated with vertically aligned ZnO nanorods in the NIR area due to the deeper penetration of evanescent waves, a higher surface-volume ratio, better crystallinity, more adhesive interactions with salt molecules, larger surface roughness and higher-order dispersion compared to the other coated ZnO nanostructures.

Facile synthesis of GO and g-C3N4 nanosheets encapsulated magnetite ternary nanocomposite for superior photocatalytic degradation of phenol.

In this study, the synthesis of Fe3O4@GO@g-C3N4 ternary nanocomposite for enhanced photocatalytic degradation of phenol has been investigated. The surface modification of Fe3O4 was performed through layer-by-layer electrostatic deposition meanwhile the heterojunction structure of ternary nanocomposite was obtained through sonicated assisted hydrothermal method. The photocatalysts were characterized for their crystallinity, surface morphology, chemical functionalities, and band gap energy. The Fe3O4@GO@g-C3N4 ternary nanocomposite achieved phenol degradation of ∼97%, which was significantly higher than that of Fe3O4@GO (∼75%) and Fe3O4 (∼62%). The enhanced photoactivity was due to the efficient charge carrier separation and desired band structure. The photocatalytic performance was further enhanced with the addition of hydrogen peroxide, in which phenol degradation up to 100% was achieved in 2 h irradiation time. The findings revealed that operating parameters have significant influences on the photocatalytic activities. It was found that lower phenol concentration promoted higher activity. In this study, 0.3 g of Fe3O4@GO@g-C3N4 was found to be the optimized photocatalyst for phenol degradation. At the optimized condition, the reaction rate constant was reported as 6.96 × 10-3 min-1. The ternary photocatalyst showed excellent recyclability in three consecutive cycles, which confirmed the stability of this ternary nanocomposite for degradation applications.

An FBG magnetic sensor for oil flow monitoring in sandstone core.

Monitoring the oil movement using a non-contact optical fiber probe during enhanced oil recovery is a novel technique to increase the efficiency of the process by distinguishing the oil position in the reservoir. A partially unclad fiber Bragg grating (FBG) coated with Fe3O4 nanoparticles as a magnetic field sensor is experimentally demonstrated. A series of six FBGs reflecting different wavelengths are fixed on the surface of sandstone. Nanofluids containing magnetite nanoparticles and alkaline-surfactant-polymer are injected continuously in two separate steps into the sandstone, which is saturated with 20% oil and 80% brine. The chamber is equipped with a solenoid that acts as a magnetic field generator. The changes in the magnetic field strength depended on the FBG-solenoid distance and the density of localized injected nanoparticles near the FBGs leads to a shift of the reflected wavelength of each single FBG accordingly. The shift is caused by the interference of different propagating modes reflected from the core-cladding and cladding-magnetite layer interfaces. The intensity of the FBG spectra decreases by injecting the nanofluid and vice versa for surfactant injection. The sensor response time of ∼21 s confirms the high reliability and repeatability of the sensing scheme. Movement of oil along the sandstone alters the wavelength shift in the FBG spectra.

Effect of organic ligand-decorated ZnO nanoparticles as a cathode buffer layer on electricity conversion efficiency of an inverted solar cell.

Efficiency improvement of the industrial scale solar cells to capture sunlight as an important renewable energy source is attracting significant attention to prevent the consumption of a finite supply of unsustainable fossil fuels. ZnO nanoparticles decorated with an imine-linked receptor have been used in the fabrication of a photocathode based on dye-sensitized solar cells for the purpose of photovoltaic efficiency enhancement. Various characterization techniques have been employed to investigate the structural, morphological, and optical behaviors of the solar cell having ZnO nanoparticles and ZnO nanoparticles decorated with an organic ligand as a photocathode layer. The decorated nanoparticles have a stable wurtzite structure and an average grain size of ∼45 nm, confirmed by the TEM image and XRD through the Scherrer equation. The ZnO sample emits wide peaks in the visible range, and the emission intensity of the ZnO-DOL sample increases along with a red-shift (0.38 eV) in the band gap. This shift can be explained using deep level transition, surface plasmon energy of a surfactant, and coupling of ZnO with local surface plasmon energy. UV-vis absorption spectra together with photoluminescence spectra confirm the higher absorption rate due to organic ligand decoration on ZnO nanoparticles. The greatest solar power-to-electricity conversion efficiency (η) of 3.48% is achieved for the ZnO-DOL sample. It is enhanced by 3.13% as compared to that of the ZnO-based solar cell. The ZnO-DOL device exhibits a higher external quantum efficiency (EQE), responsivity (R λ), and photocurrent-to-dark current ratio; this confirms the improvement in the solar cell performance.

Impact of annealing on surface morphology and photoluminescence of self-assembled Ge and Si quantum dots.

Controlled growth and characterization of germanium (Ge) and silicon (Si) nanostructure are the key issues for optoelectronic device fabrication. The role of post-annealing on the structural and optical properties of radio frequency (rf) magnetron sputtering grown of Ge and Si quantum dots (QDs) deposited on Si(100) substrate is studied. Atomic force microscopy confirmed the formation of Si and Ge QDs with estimated sizes lower than -17 nm and -14 nm respectively. The X-ray diffraction analysis revealed the formation of Si and Ge QDs accompanied by SiO2 with estimated sizes of -5 and -7 nm for post-annealed Si and pre-annealed Ge QDs respectively. The room temperature photoluminescence spectra for Ge and Si demonstrated an emission peak at 3.20 and 2.72 eV respectively, which are attributed to the electron and hole recombination within QDs. A shift in the PL peak is observed through annealing which is ascribable to the changes in size of QDs and quantum confinement effect. The thermal annealing at 600 degrees C is found to play an important role in controlling the shape, number density, root mean square (rms) roughness and the energy shift of the luminescence band for both Si and Ge QDs. The influence of annealing on growth morphology for Ge QDs is appeared to be stronger than Si.

Substrate temperature dependent surface morphology and photoluminescence of germanium quantum dots grown by radio frequency magnetron sputtering.

The visible luminescence from Ge nanoparticles and nanocrystallites has generated interest due to the feasibility of tuning band gap by controlling the sizes. Germanium (Ge) quantum dots (QDs) with average diameter ~16 to 8 nm are synthesized by radio frequency magnetron sputtering under different growth conditions. These QDs with narrow size distribution and high density, characterized using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) are obtained under the optimal growth conditions of 400 °C substrate temperature, 100 W radio frequency powers and 10 Sccm Argon flow. The possibility of surface passivation and configuration of these dots are confirmed by elemental energy dispersive X-ray (EDX) analysis. The room temperature strong visible photoluminescence (PL) from such QDs suggests their potential application in optoelectronics. The sample grown at 400 °C in particular, shows three PL peaks at around ~2.95 eV, 3.34 eV and 4.36 eV attributed to the interaction between Ge, GeO(x) manifesting the possibility of the formation of core-shell structures. A red shift of ~0.11 eV in the PL peak is observed with decreasing substrate temperature. We assert that our easy and economic method is suitable for the large-scale production of Ge QDs useful in optoelectronic devices.