Conformal zinc sulfide coating of vertically aligned ZnO nanorods by two-step hydrothermal synthesis on wide bandgap seed layers for lead-free perovskite solar cells.

Vertically aligned ZnO nanorods (NRs) were grown hydrothermally on the wide bandgap (∼3.86 - 4.04 eV) seed layers (SLs) of grain size ∼162 ± 35 nm, prepared using ball-milled derived ZnO powder. The synthesized ZnO NRs were further decorated with ZnS nanocrystals to achieve a ZnO NR-ZnS core-shell (CS)-like nano-scaffolds by a subsequent hydrothermal synthesis at 70 °C for 1 h. UV-Vis-NIR spectroscopy, x-ray diffractometry (XRD), Raman spectroscopy and Field emission scanning electron microscopy (FESEM) coupled with Energy dispersive x-ray spectroscopy (EDX) analyses confirmed the formation of ZnS atop the vertically aligned ZnO NR arrays of ∼1.79 ± 0.17µm length and ∼165 ± 27 nm diameter. Transmission electron microscopy (TEM)/EDX analyses revealed that vertically aligned ZnO NRs (core dia. ∼181 ± 12 nm) arrays are conformally coated by an ultrathin ZnS (∼25 ± 7 nm) shell layer with a preferential ZnS{111}/ZnO{10-10}-like partial epitaxy. The ZnO NRs exhibited a sharp band edge near ∼384 nm having optical bandgap energy (Eg) of ∼3.23 eV. However, the ZnO NR-ZnS CS exhibited double absorption bands atEg∼ 3.20 eV (ZnO-core) andEg∼ 3.78 eV (ZnS-shell). The ZnS{111}/ZnO{10-10}-nano-scaffolds could be utilized to facilitate the enhanced absorption of UV photons as well as the radial junction formation between the Pb-free perovskite absorber and ZnS/ZnO NRs layers.

Waste newspaper driven activated carbon to remove polycyclic aromatic hydrocarbon from wastewater.

In this study, a carbon-based adsorbent was developed from waste newspaper through pyrolysis at 800 °C to evaluate the removal efficiency of polycyclic aromatic hydrocarbons (Benzo[ghi]perylene (BghiP) and Indeno [1,2,3-cd] pyrene (IP)) from wastewater. The surface area of the developed adsorbent was estimated at 509.247m2g-1 which allowed the adsorption of the PAHs from wastewater. The maximum adsorption capacity was estimated at 138.436 µg g-1 and 228.705 µg g-1 for BghiP and IP, respectively and the highest removal efficiency was observed at pH 2. Around 91% removal efficiency was observed at pH 7 for both pollutants. Experimental adsorption data were fit for pseudo-second-order kinetics and Langmuir isotherm models, which demonstrate electrostatic interaction, monolayered deposition, hydrogen bonding, and π-π interaction between adsorbate and adsorbent which play a significant role in adsorption. The regeneration study described that the developed adsorbent could be able to intake 52.75% BghiP and 48.073% IP until the 8th and 6th cycles, respectively. The removal efficiency of the adsorbent in the real sample was also evaluated. This study will provide a method to convert waste material into adsorbent and will remove PAHs from wastewater as a function of pollutant mitigation and waste management.