No abstract

Zinc Oxide nanoparticles have been synthesized by two simple routes using Aloe vera (green synthesis, route I) or Cassava starch (gelatinization, route II). The XRD patterns and Raman spectra show that both synthesis routes lead to single-phase ZnO. XPS results indicate the presence of zinc atoms with oxidation state Zn2+. SEM images of the ZnO nanoparticles synthesized using Cassava starch show the presence of pseudo-spherical nanoparticles and nanosheets, while just pseudo-spherical nanoparticles were observed when Aloe vera was used. The UV-Vis spectra showed a slight difference in the absorption edge of the ZnO particles obtained using Aloe vera (3.18 eV) and Cassava starch (3.24 eV). The ZnO nanoparticles were tested as adsorbents for the removal of copper in wastewater, it is shown that at low Cu2+ ion concentration (~40 mg/L) the nanoparticles synthesized by both routes have the same removal efficiency, however, increasing the absorbate concentration (> 80 mg/L) the ZnO nanoparticles synthesized using Aloe vera have a higher removal efficiency. The synthesized ZnO nanoparticles can be used as effective and environmental-friendly metal trace absorbers in wastewater.

Here, we report on the synthesis of tungsten diselenide (WSe2) nanosheets using an atmospheric pressure chemical vapor deposition technique via the rapid selenization of thin tungsten films. The morphology and the structure, as well as the optical properties, of the so-produced material have been studied using electron microscopies, X-ray photoelectron spectroscopy, photoluminescence, UV–visible and Raman spectroscopies, and X-ray diffraction. These studies confirmed the high crystallinity, quality, purity, and orientation of the WSe2 nanosheets, in addition to the unexpected presence of mixed phases, instead of only the most thermodynamically stable 2H phase. The synthesized material might be useful for applications such as gas sensing or for hydrogen evolution reaction catalysis.

SnS2 and SnSe2 nanosheets were synthesized vertically aligned in different substrates by an AP-CVD method.

Herein, we present, for the first time, a chemoresistive-type gas sensor composed of two-dimensional WSe 2 , fabricated by a simple selenization of tungsten trioxide (WO 3 ) nanowires at atmospheric pressure. The morphological, structural, and chemical composition investigation shows the growth of vertically oriented three-dimensional (3D) assemblies of edge-enriched WSe 2 nanoplatelets arrayed in a nanoflower shape. The gas sensing properties of flowered nanoplatelets (2H-WSe 2 ) are investigated thoroughly toward specific gases (NH 3 and NO 2 ) at different operating temperatures. The integration of 3D WSe 2 with unique structural arrangements resulted in exceptional gas sensing characteristics with dual selectivity toward NH 3 and NO 2 gases. Selectivity can be tuned by selecting its operating temperature (150 °C for NH 3 and 100 °C for NO 2 ). For instance, the sensor has shown stable and reproducible responses (24.5%) toward 40 ppm NH 3 vapor detection with an experimental LoD < 2 ppm at moderate temperatures. The gas detecting capabilities for CO, H 2 , C 6 H 6 , and NO 2 were also investigated to better comprehend the selectivity of the nanoflower sensor. Sensors showed repeatable responses with high sensitivity to NO 2 molecules at a substantially lower operating temperature (100 °C) (even at room temperature) and LoD < 0.1 ppm. However, the gas sensing properties reveal high selectivity toward NH 3 gas at moderate operating temperatures. Moreover, the sensor demonstrated high resilience against ambient humidity (Rh = 50%), demonstrating its remarkable stability toward NH 3 gas detection. Considering the detection of NO 2 in a humid ambient atmosphere, there was a modest increase in the sensor response (5.5%). Furthermore, four-month long-term stability assessments were also taken toward NH 3 gas detection, and sensors showed excellent response stability. Therefore, this study highlights the practical application of the 2H variant of WSe 2 nanoflower gas sensors for NH 3 vapor detection.