Hydroponic Cultured Ginseng Leaves Zinc Oxides Nanocomposite Stabilized with CMC Polymer for Degradation of Hazardous Dyes in Wastewater Treatment

This study demonstrated the synthesis of o-carboxymethyl chitosan (CMC)-stabilized zinc oxide nanocomposites (ZnO NCs) combined with aqueous leaves extracts of hydroponically cultured ginseng and used as a photocatalyst for the degradation of hazardous dyes, including malachite green (MG), rhodamine B (RB), and congo red (CR) under ultraviolet illumination. Hydroponic ginseng leaves contain bioactive components, namely ginsenoside and natural polyphenol, which prompt ginseng’s biological effect. Besides, the CMC polymer is naturally biodegradable, stabilizes the nanoformation and enhances the solubility of ginsenoside. The hydroponic ginseng leaves zinc oxide CMC nanocomposites (GL–CMC–ZnO NCs) were synthesized using the co-precipitation method and characterized using different analytical methods. The FTIR analysis identified significant phytochemicals in the leaves extracts and cotton-shape morphology observed using FE-TEM analysis. The XRD analysis also determined that the crystallite size was 28 nm. The photocatalyst degraded CR, RB, and MG dyes by approximately 87%, 94%, and 96% within contact times of 10, 20, 25, and 30 min, respectively, when the dye concentration was 15 mg/L. As far as our knowledge, this is the first report on hydroponic ginseng NCs incorporated with the CMC polymer for the degradation of hazardous dyes on wastewater treatment. This study can add significant value to large-scale wastewater treatment.

Photocatalytic Degradation of Rhodamine B Dye in Aqueous Suspension by ZnO and M-ZnO (M = La3+, Ce3+, Pr3+ and Nd3+) Nanoparticles in the Presence of UV/H2O2

In this study, nanoparticles of five photocatalytic systems based on pure zinc oxide and with rare earths ions M-ZnO (M = La3+, Ce3+, Pr3+ or Nd3+) calcined at 500 °C or 700 °C were synthesized and investigated as potential photocatalysts for the removal of dyes. The addition of rare earth ions causes a decrease in the bandgap of ZnO; therefore, it can be well used to improve the photocatalytic properties. The photocatalytic activity of the synthesized nanoparticles was evaluated by the degradation of Rhodamine B in the presence of H2O2 under ultraviolet illumination. The results indicate that all the synthesized nanoparticles show good dye degradation efficiency. The highest degradation efficiency was 97.72% for the Ce-ZnO sample calcined at 500 °C and was achieved in 90 min with an excellent constant of the dye degradation rate k = 0.0363 min−1 following a first-order kinetic mechanism. The presence of oxychlorides as secondary phases inhibits the rate of the photocatalytic reaction.

Contact transfer of engineered nanomaterials in the workplace

This study investigates the potential spread of cadmium selenide quantum dots in laboratory environments through contact of gloves with simulated dry spills on laboratory countertops. Secondary transfer of quantum dots from the contaminated gloves to other substrates was initiated by contact of the gloves with different materials found in the laboratory. Transfer of quantum dots to these substrates was qualitatively evaluated by inspection under ultraviolet illumination. This secondary contact resulted in the delivery of quantum dots to all the evaluated substrates. The amount of quantum dots transferred was quantified by elemental analysis. The residue containing quantum dots picked up by the glove was transferred to at least seven additional sections of the pristine substrate through a series of sequential contacts. These results demonstrate the potential for contact transfer as a pathway for spreading nanomaterials throughout the workplace, and that 7-day-old dried spills are susceptible to the propagation of nanomaterials by contact transfer. As research and commercialization of engineered nanomaterials increase worldwide, it is necessary to establish safe practices to protect workers from the potential for chronic exposure to potentially hazardous materials. Similar experimental procedures to those described herein can be adopted by industries or regulatory agencies to guide the development of their nanomaterial safety programmes.

Bioconvection of a Radiating Hybrid Nanofluid Past a Thin Needle in the Presence of Heterogeneous-Homogeneous Chemical Reaction

: The photo catalytic nature of TiO_2 finds applications in medicinal field to kill cancer cells, bacteria and viruses under mild ultraviolet illumination and the antibacterial characteristic of Ag makes the composition Ag-TiO_2 applicable for various purposes. It can also be used in other engineering appliances and industries such as humidity sensor, coolants and in footwear industry. Hence, this study deals with the analysis of the effects of Magnetic field, thermal radiation and quartic autocatalysis of heterogeneous-homogeneous reaction in an electrically conducting Ag-TiO_2-H_2 O hybrid nanofluid. Furthermore, the gyrotactic microorganisms are used as active mixers to prevent agglomeration and sedimentation of TiO_2 that occurs due to its hydrophobic nature. The Mathematical model takes the form of partial differential equations with viscosity and thermal conductivity being the functions of volume fraction. These equations are converted to ordinary differential equations by using similarity transformation and are solved by RKF-45 method with the aid of shooting method. It is observed that the increase in the size of the needle enhances the overall performance of the hybrid nanofluid. Furthermore, the temperature of the hybrid nanofluid increases with the increase in volume fraction. It is observed that the friction produced by the Lorentz force increases the temperature of the nanofluid. It is further observed that the heterogeneous reaction parameter has more significant effect on the concentration of bulk fluid than the homogeneous reaction parameter.

Fabrication of GaN Nano-towers Based Self-powered UV Photodetector

Fabrication of unique tapper ended GaN-Nanotowers structure based highly efficient ultraviolet photodetector is demonstrated. Hexagonal stacked GaN nanocolumnar structure (nanotowers) grown on AlN buffer layer exhibits higher photocurrent generation which significantly enhances its responsiveness towards ultraviolet illumination and leads to outstanding performance of the device. The fabricated detector display low dark current (~12nA), high ILight / IDark ratio (>104), fast time-correlated transient response (~433µs) upon UV (325nm) illumination. A very high photo responsivity of 2.47 A/W in self-powered (zero applied bias) mode of operation is reported. While in photoconductive mode, the responsivity is observed to be 35.4 A/W @ -3V alongwith very high external quantum efficiency (~104 %), lower noise equivalent power (~10-13 WHz-1/2) and excellent UV-Vis selectivity. Nanotower structure with lower strain and dislocations as well as reduced trap states cumulatively contributed to augmented performance from the device. The utilization of these GaN-Nanotower structures can potentially be useful towards the fabrication of energy-efficient ultraviolet photodetector.

Jeankempite, Ca5(AsO4)2(AsO3OH)2(H2O)7, a new arsenate mineral from the Mohawk Mine, Keweenaw County, Michigan, USA

Jeankempite, Ca5(AsO4)2(AsO3OH)2(H2O)7, is a new mineral species (IMA2018-090) discovered amongst coatings of arsenate minerals on oxidised copper arsenides from the Mohawk No. 2 mine, Mohawk, Keweenaw County, Michigan, USA. The new mineral occurs as lamellar bundles of colourless to white plates up to 1 mm wide and is visually indistinguishable from guérinite, with which it forms intergrowths. Jeankempite is transparent to translucent with a waxy lustre and white streak, is non-fluorescent under longwave and shortwave ultraviolet illumination, has a Mohs hardness of ~1.5 and brittle tenacity with uneven fracture. Crystals are flattened on {01 $\bar{1}$ } and exhibit perfect cleavage on {01 $\bar{1}$ }. Optically, jeankempite is biaxial (+), α = 1.601(2), β = 1.607(2), γ = 1.619(2) (white light); 2Vmeas. = 72(2)° and 2Vcalc. = 71.0°. The empirical formula is (Ca4.97Na0.013Mg0.017)(As3.99S0.01)4O23H16, based on 23 O and 16 H atoms per formula unit. Thermogravimetric analysis indicates that jeankempite undergoes four weight losses totalling 16.82%, close to the expected loss of 16.30%, corresponding to eight H2O. Jeankempite is triclinic, P $\bar{1}$ , a = 6.710(6), b = 14.901(14), c = 15.940(15) Å, α = 73.583(12)°, β = 81.984(12)°, γ = 82.754(12)°, V = 1507(2) Å3 and Z = 3. The final structure was refined to R1 = 0.0591 for 2781 reflections with Iobs > 3σI. The crystal structure of jeankempite is built from a network of edge- and vertex-sharing CaO6, CaO7 and AsO4 polyhedra, and we hypothesise that the new mineral has formed due to a topotactic reaction brought on by dehydration of preexisting guérinite.