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Cobalt ferrite and silver doped cobalt ferrite, AgxCo1−xFe2O4, (x = 0, 0.005, 0.01, 0.02) nanoparticles were synthesized through sol-gel auto-combustion technique via chemical and green synthesis (using the extract of tulsi seeds(Ocimum sanctum) and garlic cloves(Allium sativum)). Systematic characterization by XRD, FTIR, FE-SEM and EDX has been performed to study structural, morphological and magnetic behavior of the prepared samples. XRD confirms that the prepared samples are crystalline and have a cubic (inverse spinel) structure. Absorption bands have been studied using FTIR that further confirms the formation of single phase spinel crystal structure having two sub-lattices (Td and Oh). FE-SEM micrographs reveal the formation of cubic and encapsulated type structure in case of chemical and green synthesis respectively. EDX confirms the presence of all the required elements in the respective stoichoimetric ratios. Magnetic measurements through VSM at room temperature show that the magnetic saturation values for samples obtained using tulsi seed extract mediated synthesis and chemical synthesis are much higher than those obtained using garlic extract. The antibacterial activity of all the prepared samples against gram positive and gram negative strains were investigated and a modified mechanism of action for the antibacterial activity is proposed.

A new cobalt-based mixed ligand metal–organic framework (MOF), [Co2(L1)(obc)2].DMF (MOF1), (where L1 = 2,7-bis (3-(1H-imidazole-1-yl)propyl)benzo-[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone and H2obc = 4,4-oxybisbenzoic acid) was prepared solvothermally that simultaneously exhibits sensing and adsorption capability. The single-crystal X-ray structural analysis revealed that MOF1 exhibits an interpenetrated three-dimensional framework, of pcu topology, comprising classic paddlewheel-type units. The synthesized MOF1 was found to be luminescent with an emission/excitation peak at 402/275 nm that is enhanced by Zr4+ ions due to absorbance-caused enhancement (ACE). The fluorescence studies displayed the highly selective and sensitive behavior of MOF1 towards Zr4+ ions through the turn-on fluorescence effect with a short response time and detection limit of 0.067 μM. Furthermore, MOF1 was successfully applied for the treatment of commercial dyes Reactive Black 5 and Orange G with adsorption capacity of 33.79 and 22.32 mg/g, respectively, thus showing rapid adsorption for these dyes.

Two stable metal-organic frameworks, [Co(api)(nita)]·DMF(Co-MOF) and [Zn2(api)2(nita)2]·DMF(Zn-MOF), (where api = 1-(3-aminopropyl)imidazole and nita = 5-nitroisophathlic acid), were synthesized by solvothermal method. The MOFs were characterized by Single Crystal X-ray, thermogravimetric analysis and morphological studies. Single crystal X-ray reveals that both the MOFs exhibit discrete honeycomb like structure along a-axis. These were thermally stable up to 300°C. Dye adsorption testing was performed on the synthesized MOFs for the removal of textile dyes, Reactive Black5 (RB5) and Methyl Orange (MO) from the aqueous solutions. Co-MOF was found to be the best system that displayed significantly good results and was further explored in depth to evaluate its efficiency of the dye adsorption phenomenon. The influence of operational parameters such as the effect of contact time, pH of the untreated water, adsorbent dosage and dye concentration was investigated individually for the Co-MOF. The optimized conditions for RB5 were pH 4, contact time of 60 min, adsorbent dosage 400 mg/L and for MO, it was pH 3, a contact time of 30 min, dosage of adsorbent 500 mg/L. The Co-MOF showed 78.24 ± 0.9% adsorption for RB5 and 54.12± 1.1% for MO under optimized conditions.

In the present study, we have used biosynthesized Dy2O3 nanoparticles (Nps) for the selective detection of (Picric acid) PA. A simple and eco-friendly route to develop Dy2O3 nanoparticles (Nps) with the aid of clove bud extract as naturally available fuel was used. Biosynthesized and its counterpart, calcined sample c-Dy2O3 were characterized by UV–visible, FT-IR, XRD, TEM, XPS and TGA analysis. FT-IR results indicated the preliminary evidence of Dy–O bond in the synthesized Nps. XRD pattern confirmed that Dy2O3 has amorphous nature and its counterpart has typical cubic crystal structure. Toxicological profiling of Dy2O3 Nps was performed against bacteria and plants using bioassays. The experiments marked the absence of zone of inhibition against bacteria using Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) which revealed the non-toxicity of Dy2O3 Nps. Seed germination assay divulged elevated biocompatibility of Dy2O3 Nps towards black gram seeds w.r.t. control at a concentration of Nps even at high concentration of 1000 ​ppm. The synthesized Nps demonstrated excellent sensitivity and selectivity towards picric acid with Limit of detection (LOD) of 43 ​± ​1.5 ​nM. The high value of Stern –Volmer constant (Ksv), 4.19 ​× ​104 ​M signifies the high selectivity of Dy2O3 Nps for PA. We believe that the biosynthesized Dy2O3 Nps will emerge as potential candidate for selective detection of trace amounts of nitro explosives in waste water.