Antimicrobial, antioxidant, cytotoxicity and photocatalytic performance of Co doped ZnO nanoparticles biosynthesized using Annona Muricata leaf extract

Cobalt-Doped ZnO Nanocomposits for Efficient Dye Degradation: Charge Transfer

Doping enhances the optical properties of high-band gap zinc oxide nanoparticles (ZnO NPs), essential for their photocatalytic activity. We used the combustion approach to synthesize cobalt-doped ZnO heterostructure (CDZO). By creating a mid-edge level, it was possible to tune the indirect band gap of the ZnO NPs from 3.1 eV to 1.8 eV. The red shift and reduction in the intensity of the photoluminescence (PL) spectra resulted from hindrances in electron-hole recombination and sp-d exchange interactions. These improved optical properties expanded the absorption of solar light and enhanced charge transfer. The field emission scanning electron microscopy (FESEM) image and elemental mapping analysis confirmed the CDZO's porous nature and the dopant's uniform distribution. The porosity, nanoscale size (25-55 nm), and crystallinity of the CDZO were further verified by high-resolution transmission electron microscopy (HRTEM) and selected area electron image analysis. The photocatalytic activity of the CDZO exhibited much greater efficiency (k=0.131 min-1) than that of ZnO NPs (k=0.017 min-1). Therefore, doped heterostructures show great promise for industrial-scale environmental remediation applications.

A critical mini-review on doping and heterojunction formation in ZnO-based catalysts

This mini-review on doping and heterojunctions for catalysis applications provides a comprehensive overview of key aspects. Doping, when carried out adequately with a uniform distribution, creates a new energy level that significantly enhances charge transfer and light absorption. This new level alters the material's morphology and enhances intrinsic defects. For instance, ZnO, despite its exceptional band edge concerning oxygen reduction and water oxidation redox potentials, faces the issue of electron-hole recombination. However, forming a heterojunction can effectively aid charge transfer and prolong electron-hole relaxation without recombination. This is where the role of doping and heterojunctions becomes crucial. Additionally, incorporating noble metals with S- and Z-scheme heterojunctions offers a promising mechanism for charge transfer and visible light harvesting, further amplifying the catalytic properties.

Central composite design and mechanism of antibiotic ciprofloxacin photodegradation under visible light by green hydrothermal synthesized cobalt-doped zinc oxide nanoparticles

In this research, different Co2+ doped ZnO nanoparticles (NPs) were hydrothermally synthesized by an environmentally friendly, sustainable technique using the extract of P. capillacea for the first time. Co-ZnO was characterized and confirmed by FTIR, XPS, XRD, BET, EDX, SEM, TEM, DRS UV-Vis spectroscopy, and TGA analyses. Dislocation density, micro strains, lattice parameters and volume of the unit cell were measured using XRD results. XRD suggests that the average size of these NPs was between 44.49 and 65.69 nm with a hexagonal wurtzite structure. Tauc plot displayed that the optical energy bandgap of ZnO NPs (3.18) slowly declines with Co doping (2.96 eV). Near complete removal of the ciprofloxacin (CIPF) antibiotic was attained using Green 5% of Hy-Co-ZnO in the existence of visible LED light which exhibited maximum degradation efficiency (99%) within 120 min for 30 ppm CIPF initial concentration. The photodegradation mechanism of CIPF using Green Hy-Co-ZnO NPs followed the Pseudo-first-order kinetics. The Green Hy-Co-ZnO NPs improved photocatalytic performance toward CIPF for 3 cycles. The experiments were designed using the RSM (CCD) method for selected parameters such as catalyst dosage, antibiotic dosage, shaking speed, and pH. The maximal CIPF degradation efficiency (96.4%) was achieved under optimum conditions of 39.45 ppm CIPF dosage, 60.56 mg catalyst dosage, 177.33 rpm shaking speed and pH 7.57.

The Promise of Metal-Doped Iron Oxide Nanoparticles as Antimicrobial Agent

Antibiotic resistance (AMR) is one of the pressing global public health concerns and projections indicate a potential 10 million fatalities by the year 2050. The decreasing effectiveness of commercially available antibiotics due to the drug resistance phenomenon has spurred research efforts to develop potent and safe antimicrobial agents. Iron oxide nanoparticles (IONPs), especially when doped with metals, have emerged as a promising avenue for combating microbial infections. Like IONPs, the antimicrobial activities of doped-IONPs are also linked to their surface charge, size, and shape. Doping metals on nanoparticles can alter the size and magnetic properties by reducing the energy band gap and combining electronic charges with spins. Furthermore, smaller metal-doped nanoparticles tend to exhibit enhanced antimicrobial activity due to their higher surface-to-volume ratio, facilitating greater interaction with bacterial cells. Moreover, metal doping can also lead to increased charge density in magnetic nanoparticles and thereby elevate reactive oxygen species (ROS) generation. These ROS play a vital role to disrupt bacterial cell membrane, proteins, or nucleic acids. In this review, we compared the antimicrobial activities of different doped-IONPs, elucidated their mechanism(s), and put forth opinions for improved biocompatibility.

Exploring the cytotoxicity on human lung cancer cells and DNA binding stratagem of camptothecin functionalised silver nanoparticles through multi-spectroscopic, and calorimetric approach

The influence of nanoparticles inside the human body and their interactions with biological macromolecules need to be explored/studied prior to specific applications. The objective of this study is to find the potential of camptothecin functionalised silver nanoparticles (CMT-AgNPs) in biomedical applications. This article primarily investigates the binding stratagem of CMT-AgNPs with calf thymus DNA (ctDNA) through a series of spectroscopic and calorimetric methods and then analyses the anticancer activity and cytotoxicity of CMT-AgNPs. The nanoparticles were synthesized using a simple one pot method and characterized using UV-Visible, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). The average size of CMT-AgNPs is 10 ± 2 nm. A group of experimental techniques such as UV-Visible spectrophotometry, fluorescence dye displacement assay, circular dichroism (CD) and viscosity analysis unravelled the typical groove binding mode of CMT-AgNPs with ctDNA. The CD measurement evidenced the minor conformational alterations of double helical structure of ctDNA in the presence of CMT-AgNPs. The information deduced from the isothermal titration calorimetry (ITC) experiment is that the binding was exothermic and spontaneous in nature. Moreover, all the thermodynamic binding parameters were extracted from the ITC data. The binding constants obtained from UV absorption experiments, fluorescence dye displacement studies and ITC were consistently in the order of 10⁴ Mol^-1. All these results validated the formation of CMT-AgNPs-ctDNA complex and the results unambiguously confirm the typical groove binding mode of CMT-AgNPs. An exhaustive in vitro MTT assay by CMT-AgNPs and CMT against A549, HT29, HeLa and L929 cell lines revealed the capability of CMT-AgNPs as a potential anticancer agent.