Synthesis, electrical properties and bio-compatibility analysis of barium manganate nanostructures

Abstract

Single phase barium manganate nanorods, nanoparticles, nanofibers and microparticles were prepared using composite–hydroxide mediated (CHM) method, hydrothermal (HT) technique, electrospinning (ES) and solid state reaction (SSR) route respectively. Size and uniformity of BaMnO 3 nanorods were optimized against different reaction times and reaction temperatures. BaMnO 3 powders consisting of nanorods of an average diameter ~ 200 nm and length ~1 – 1.5 μm, prepared at reaction temperature 200 °C and reaction time 48 hours, were chosen for electrical characterization. Impedance spectroscopy (IS) from 300 – 400 K and 20 Hz – 2 MHz, revealed presence of non-ideal Debye type behaviour in BaMnO 3 samples and was attributed to the presence of heterogeneity in the sample. The heterogeneity was explained on the basis of “brick layer model”. In BaMnO 3 nanorods sample, on the basis of extracted capacitance values, two electro-active regions were investigated i.e., dominant grain boundaries and sample-electrode interfaces. No indication from the bulk effect was observed. Experimental results were fitted using equivalent circuit model (R gb Q gb )( R e Q e ). The ac and dc conduction mechanisms in BaMnO 3 pellets can be explained by correlated barrier hopping (CBH) model and Poole– Frenkel conduction mechanism respectively. While IS analysis of bulk BaMnO 3 sample revealed that different electro-active regions such as grain, grain boundary and sample- electrode interface exist that overlapped with each other in the applied frequency domain. These results were also modelled via a best fit equivalent circuit model (R g C g )(R gb Q gb )(R e Q e ) and the response from different overlapped electro-active regions were separated. The ac conductivity obeys CBH model for bulk BaMnO 3 sample. Uptake of PEGylated BaMnO 3 NPs alone and loaded with photosensitizer (5-ALA) were examined on Hep2c cell lines. It was observed that PEGylated BaMnO 3 NPs loaded with 5-ALA has higher uptake as compared to 5-ALA. The high uptake was attributed to large surface area of BaMnO 3 NPs. It was also observed that BaMnO 3 NPs are non-toxic when administrated to Hep2c cell lines. BaMnO 3 nanofibers were synthesized for the first time using ES technique. Effect of different polyvinyl pyrrolidone (PVP) concentration on uniformity and homogeneity of nanofibers was investigated.