Browsing by Author "Ramovatar Meena"

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Molecular Weights of Polyethyleneimine-Dependent Physicochemical Tuning of Gold Nanoparticles and FRET-Based Turn-On Sensing of Polymyxin B
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Atul Kumar Tiwari; Munesh Kumar Gupta; Ramovatar Meena; Prem C. Pandey; Roger J. Narayan
Environmental monitoring and the detection of antibiotic contaminants require expensive and time-consuming techniques. To overcome these challenges, gold nanoparticle-mediated fluorometric “turn-on” detection of Polymyxin B (PMB) in an aqueous medium was undertaken. The molecular weight of polyethyleneimine (PEI)-dependent physicochemical tuning of gold nanoparticles (PEI@AuNPs) was achieved and employed for the same. The three variable molecular weights of branched polyethyleneimine (MW 750, 60, and 1.3 kDa) molecules controlled the nano-geometry of the gold nanoparticles along with enhanced stabilization at room temperature. The synthesized gold nanoparticles were characterized through various advanced techniques. The results revealed that polyethyleneimine-stabilized gold nanoparticles (PEI@AuNP-1-3) were 4.5, 7.0, and 52.5 nm in size with spherical shapes, and the zeta potential values were 29.9, 22.5, and 16.6 mV, respectively. Accordingly, the PEI@AuNPs probes demonstrated high sensitivity and selectivity, with a linear relationship curve over a concentration range of 1–6 μM for polymyxin B. The limit of detection (LOD) was calculated as 8.5 nM. This is the first unique report of gold nanoparticle nano-geometry-dependent FRET-based turn-on detection of PMB in an aqueous medium. We believe that this approach would offer a complementary strategy for the development of a highly sophisticated and advanced sensing system for PMB and act as a template for the development of new nanomaterial-based engineered sensors for rapid antibiotic detection in environmental as well as biological samples. © 2024 by the authors.
Photocatalytic and Antibacterial NiO/MgO Nanocomposites for Efficient Dyes Removal From Industrial Wastewater
(John Wiley and Sons Inc, 2025) Anuradha Kumari; Annesha Roy; Manjot Kaur; Akshay Kumar; Kajal Kumari; Usha Singh Gaharwar; Atul Kumar Tiwari; Ramovatar Meena
The presence of non-biodegradable industrial waste, particularly dyes, has led to pollution of aquatic ecosystems. Consequently, it is crucial to devise effective strategies to remove industrial contaminants. This study focused on creating nanomaterials for wastewater treatment. NiO/MgO nanocomposites (NCs) were produced via chemical precipitation and subsequently characterized. X-ray diffraction (XRD) verified the crystalline nature of NiO/MgO with a face-centered cubic (FCC) structure, which promoted strong interfacial interactions. Scanning electron microscopy (SEM) showed that the NiO/MgO NCs agglomerated into spherical and irregular shapes, whereas transmission electron microscopy (TEM) confirmed a size range of 65–100 nm. UV–vis spectroscopy indicated absorption in the UV–vis spectrum, suggesting its photocatalytic potential. The photocatalytic performance of the NiO/MgO NCs was assessed for organic dyes such as methylene blue (MB), Congo red (CR), and methyl orange (MO) under UV–vis light, demonstrating notable efficiency at higher dye concentrations. The highest degradation efficiency was recorded for CR (∼77% at 100 ppm over 60 min), followed by MO (∼71.6%) and MB (∼70%). The enhanced photocatalytic activity was linked to the nanostructured morphology, effective charge separation, and decreased electron-hole recombination. NiO/MgO NCs also showed strong antibacterial properties against both gram-positive and gram-negative bacterial strains. Antimicrobial mechanisms include the production of reactive oxygen species (ROS), disruption of membranes, and interactions with metal ions, which demonstrate the multi-functionality of NiO/MgO NCs as efficient wastewater treatment agents. © 2025 Wiley-VCH GmbH.