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This work reports synthesis of a dual-function facile heterojunction and investigation of role of the charge transfer dynamism between individual semiconductor components for superior photocatalytic and electrochemical sensing application. The bio-benevolent and sturdy ZnO/Fe 2 O 3 heterojunctions were utilized for visible light facilitated photo-degradation of sulfamethoxazole (SMX) antibiotic and electrochemical sensing of dopamine drug (DA). The fabricated heterojunction were characterized for structural, optical, and magnetic properties. Structural studies revealed the formation of nano heterojunction containing both phases. Magnetic studies confirmed the highly pure magnetic nature of photocatalysts. ZnO/30 wt%Fe 2 O 3 heterojunction (S2) shows 95.2% SMX degradation under visible light and high retention of performance under solar light. The scavenging experiments infer that OH radicals are the active species responsible for degradation. A Z-scheme photocatalytic mechanism was predicted for higher performance with protection of high potential VB of ZnO and CB of Fe 2 O 3 for high generation of reactive oxygen species. LC-MS was employed to predict a plausible degradation route. The sample modified glassy carbon electrodes (GCE) were used for electrochemical sensing of dopamine via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The S2 junction exhibited 0.18 μM limit of detection with concentration range of 1 μM-50 μM. The stability test was successfully carried out at room temperature for 15 days. In addition, the S2 modified electrodes were spiked in real urine samples and good results were obtained. DPV reveals that S2 modified electrode is best sensor for dopamine sensing among all synthesized heterojunctions. The detection mechanism was also discussed in detail. The in-built metal redox i.e Zn 2+ /Zn + and Fe 3+ /Fe 2+ facilitate the Z-scheme transfer, improve the charge transfer capacity and reduce the recombination. This study is beneficial because it reports utilization of popular and well-tested semiconductor metal oxides to form heterojunctions with dual capabilities of environmental detoxification and cost-effective electrochemical detection of biomolecules., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Antibiotic water contamination is a growing environmental problem in the present day. As a result, water treatment is required for its reduction and elimination. Due to their important role in resolving this issue, photocatalysts have drawn a great deal of interest over the past few decades. When non-biodegradable organic matter is present in polluted water, the photo catalytic process, which is both environmentally friendly and an improved oxidation method, can be an effective means of remediation. In this regard, we report the successful synthesis of pure phased rare earth doped ZnO nanoparticles for tetracycline degradation. The prepared catalysts were systematically characterized for structural, optical, and magnetic properties. The optical band gap was tailored by rare earth doping, with redshift for Sm and Dy doped nanoparticles and blueshift for Nd doped ZnO nanoparticles. The analysis of photoluminescence spectra revealed information about the defect chemistry of all synthesised nanoparticles. Magnetic studies revealed that all synthesized diluted magnetic semiconductors exhibit room temperature ferromagnetism and can be employed for spintronic applications. Moreover, Dy doped ZnO nanoparticles were found to exhibit a maximum degradation efficiency of 74.19% for tetracycline (TCN) removal. The synthesized catalysts were also employed for the degradation of Malachite green (MG), and Crystal violet (CV) dyes. The maximum degradation efficiency achieved was 97.18% for MG and 98% for CV for Dy doped ZnO nanoparticles. The degradation mechanism involved has been discussed in view of the reactive species determined from scavenging experiments. [ABSTRACT FROM AUTHOR]

In recent times cost-effective advanced materials with dual applications in photocatalytic water treatment and electrochemical sensing have been explored and developed. Herein we report facile solution combustion synthesis of ZnO/Fe 2 O 3 (ZF) type-II heterojunction for electrochemical sensing of dopamine and visible assisted photocatalytic reduction of carcinogenic Cr(VI) into Cr(III). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate the compatibility of the electrodes for DA sensing. Furthermore, DPV curves revealed that ZF2 (ZnO: Fe 2 O 3 - 3:0.5) modified GCEs possessed 0.27 μM and 0.7 μM of LOD and LOQ with good linear range from 3 μM to 30 μM. Overall, reproducibility and interference studies confirm the efficient use of material for DA sensing. The junction ZF2 shows best performance with 88% Cr(VI) photo-reduction under visible light in 90 min and 100% reduction with tartaric acid as sacrificial agent (utilizing holes) in just 45 min. The effect of sacrificial agents and scavengers suggest the photogenerated electrons were major active species followed by ●O 2 −. The CB edges have enough potential for rapid reduction of hexavalent chromium under visible light and solar light. The photoluminescence and electrochemical impedance suggest lowered recombination, high charge separation and charge transfer capacity in the heterojunction. The transfer of electrons from conduction band of Fe 2 O 3 to that of ZnO having high enough negative potential to reduce Cr(VI), thus utilizing the CB potential of wide band gap ZnO for rapid visible photocatalysis. In addition shortcomings as low conductivity Fe 2 O 3 and high band gap of ZnO are both minimized in the junction. This study confirmed that popular semiconductors as ZnO and Fe 2 O 3 have enough potential in dual role as electrochemical sensors and visible photocatalysts with best performance by optimizing the conditions and ratios. Image 1 [ABSTRACT FROM AUTHOR]

Currently, the photocatalytic nanomaterials performing under solar radiation have gained worldwide attentions due to increasing environmental deterioration. For utilizing the sunlight for degradation of emerging pollutants it is important to develop visible active photocatalysts. This laboratory scale work reports magnetic and optically active nano-photocatalyst Fe x Zn 1−x O(x = 0.01, 0.03, 0.05) synthesized by solution combustion method. High resolution transmission microscopy suggests a slight degradation in the crystallite structure with Fe doping. X-ray photoelectron spectroscopy analysis shows the presence of intrinsic defects in the crystal structure. Zn resides in +2 and and Fe in +3 oxidation state. Optical band gap studies were made with band structure for each doped sample. The photoctalytic activity of the samples was tested by solar degradation of noxious pollutant Bisphenol A. 99.1% of bisphenol was degraded in 90min in presence of Fe 0.03 Zn 0.97 O under synergistic adsorption and photocatalysis. The results were analyzed in terms of total organic carbon, chemical oxygen demand, effect of scavengers, gas chromatography-mass spectrometry and reusability. In presence of Fe 0.03 Zn 0.97 O, 45.3% of total organic carbon was removed and chemical oxygen demand was reduced to 11.2%. A possible mechanism with structures of the intermediates has been given. Effect of scavengers reveal that hydroxyl radicals are major reactive oxygen species involved which is also supported by the band edge positions. The research work promises to design highly photo-active tuneable magnetic photocatalysts for solar powered degradation of contaminants of emerging concern with a simple and cost-effective approach. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fe doped ZnO nanoparticles have been successfully synthesized by simple sol–gel route. [•] Solubility limit of Fe in ZnO matrix is found to be less than 5%. [•] Fe doped ZnO nanoparticles are better photocatalytic activist than ZnO. [•] Prepared particles possess intrinsic room temperature ferromagnetism. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel nanocomposite Fe0.01Ni0.01Zn0.98O/polyacrylamide was synthesized. [•] FNZP/PAM nanocomposite shows good degradation efficiency for MB and MG. [•] Rapid decolouration of dyes was observed under coupled adsorption and photocatalysis. [•] Dye degradation followed the pseudo first-order kinetics. [•] A higher recycle efficiency and antibacterial activity was achieved for nanocomposite. [Copyright &y& Elsevier]