http://hdl.handle.net/123456789/446 2023-06-04T19:39:50Z http://hdl.handle.net/123456789/2091 Title: Development of combinatorial nanocarier based oral nanomedicine for the treatment of visceral leishmaniasis Authors: Parvez, Shabi Abstract: Abstract not available 2022-03-01T00:00:00Z http://hdl.handle.net/123456789/2090 Title: Synthesis of manganse and cobalt based oxide nanomaterials for water oxidation Authors: Kunchala, Ravikumar Abstract: Artificial photosynthesis is a promising method that directly transforms solar energy into chemical energy. To achieve artificial photosynthesis, efficient water oxidation catalysts (WOCs) are essential. RuO 2 and IrO 2 are known to be efficient catalysts for water oxidation. But they are very expensive and scarce. Hence, it is necessary to find an efficieient, inexpensive catalyst for this process. In nature, the manganese-oxo-calcium cluster (Mn 4 CaO 5 ) in the oxygen-evolving center (OEC) of Photosystem II, catalyzes water oxidation. Inspired by this process, abundant and inexpensive manganese, cobalt oxides have been recognized for their high potential as effective and reliable materials for water oxidation reaction. However, these oxides catalysts still exhibit less water oxidation efficiency. In this thesis, we have developed two simple approaches to improve the water oxidation activity of manganese and cobalt based oxides. i) Tuning the valence of the active catalytic site and (ii) developing high surface area porous catalysts using a selective dissolution approach. The oxidation state of Mn has been tuned between +3 and +4 by synthesizing solid solutions of La 1-x Ca x MnO 3 ( x = 0, 0.1, 0.3, 0.5,0.7,0.9, 1). It has been observed that the gradual substitution of La +3 by Ca +2 leads to the significant enhancement of photochemical and electrochemical water oxidation activity of these solid solutions up to x= 0.5 and therefter the activity started decreasing. Substitution of trivalent La +3 with divalent Ca +2 introduces mixed-valence of Mn in the material and the ratio of Mn +3 /Mn +4 playing a vital role in enhancing the water oxidation activity. Further, the CaMnO 3 was treated with dilute HNO 3 solution for selective dissolution of calcium ions from the structure to generate porous MnO 2 nanomaterials. These nanomaterials were heated at different temperatures to get porous manganes oxide nanostructures with different crystal structure. They have surface area in the range of 106-272 m 2 /g and exhibit remarkable photochemical water oxidation activity with a maximum turnover frequency (TOF) of 3.29 x 10 -3 s -1 and electrochemical activity showing 430mV overpotential at 10 mA/cm 2 with the Tafel slope value of 133mV/dec. The porous MnO 2 nanomaterials exhibit better current density compare to commercial RuO 2 . Further, NaCoO 2 layered materials were synthesized by simple citrate-gel method. Sodium ions are extracted from this material by treating it with dilute HNO 3 solution to get HCoO 2 nanostructures. By extracting sodium ions from NaCoO 2 , the photochemical water oxidation turnover frequency has been improved from 0.9 x 10 -3 s -1 to 2.90 x 10 -3 s -1 and the electrochemical overpotential, Tafel slope for water oxidation decreases from 600 mV to 370 mV and 93 mV/dec to 47 mV/dec, respectively. These sodium ionsextracted catalyst shown higher water oxidation activity than the commercial RuO 2, which is frequently used as a benchmark for water oxidation. Our findings in this thesis demonstrate the development of inexpensive promising substitutes for the noble metal-based catalysts for the water oxidation reaction. 2022-01-01T00:00:00Z http://hdl.handle.net/123456789/2089 Title: Development of self-assembled and blood-brain barrier permeabilising A mino acid/peptide-metal hybrid nanostructures as potenti aanti Authors: Dube, Taru 2021-08-01T00:00:00Z http://hdl.handle.net/123456789/2088 Title: Lanthanide lons doped bismuth based nanomaterials: structural, photoluminescent properties and applications Authors: Pushpendra Abstract: Lanthanide ions doped nanomaterials are an important class of luminescent materials and are widely used in various field such as, display devices, lasers, solar cells, fluorescent probes for biological labeling, imaging and therapy, catalysis, nano-electronics, latent fingerprint development and anti-counterfeiting, etc. In most of the cases, host material is based on rare earth elements which are very expensive and obtaining in large quantities with high purity is very difficult. In the present thesis, we are concentrating on the Bi 3+ based host materials which have similar properties to rare earths and less expensive, non-toxic. In addition, bismuth shows characteristic emission which is very much useful in applications like ant-counterfeiting. NaBi(MoO 4 ) 2 nanomaterials are synthesized through a facile, low cost coprecipitation method at room temperature. Various factors affecting the synthesis process have been investigated. Further, linear solid solution formation between NaBi(MoO 4 ) 2 and NaEu(MoO 4 ) 2 , NaLa(MoO 4 ) 2 has been observed in the complete range of composition. Their structural, optical properties are studied. Photoluminescence properties of Eu 3+ doped solid solutions are investigated in detail. The effect of the bandgap on the Eu 3+ luminescence properties have been investigated in a systematic way and it plays a crucial role particularly when excited with high energy light. However, it does not make much difference when excited with low energy light. Excitation dependent downshifting and upconversion luminescence properties of NaBi(MoO 4 ) 2 : Yb 3+ , Ln 3+ (Ln = Er, Ho) nanomaterials are studied under UV, Visible and NIR excitation. Finally, crystal structure of Gd 0.95 Eu 0.05 PO 4 nanorods is tuned from hexagonal to monoclinic by varying synthesis temperature and used in latent fingerprint detection and anti-counterfeiting applications. The developed latent fingerprints with monoclinic nanorods emits fuchsia color and shows clear ridge details and have high contrast, high sensitivity, and high selectivity. The printed patterns with GdPO 4 :Eu 3+ fluorescent ink appeared white and emits fuchsia color under day light and 395 nm UV irradiation. Further, the effect of bismuth doping on the structural, optical, and luminescent properties of Gd 0.95 Eu 0.05 PO 4 are studied. The best luminescence is observed with Bi 0.50 Gd 0.45 Eu 0.05 PO 4 nanomaterial and utilized in anti-counterfeiting applications. The printed patterns emit orange-red, yellow-green, and fuchsia color under 254, 365, and 395 nm UV irradiation. These patterns are highly resistant to humidity, heat, and light. These nanomaterials may be used in high-tech security patterns against counterfeiting. 2021-08-01T00:00:00Z