Talk given by

Dr. Arpita Jana
University of Konstanz,
Germany

Abstract:

A facile-scalable wet-chemical synthesis procedure has been introduced for the growth of different morphological [1-3] luminescent zinc oxide (ZnO) nanoparticles (NPs) by varying the reaction conditions. The photoluminescence (PL) intensity ratio of band gap to defect emission was monitored by post fabrication treatment and Al doping concentration. The performance of dye-sensitized solar cell of ZnO NPs, depends on surface volume ratio [2] and also defect concentration of the ZnO NPs [4]. Temperature dependent electrical transport through n-ZnO/Au/p-Si (n-ZnO nanorods grown on Au coated macroporous Si template) heterojunction reveals their diode-like feature with a remarkably low ‘turn-on’ voltage and significantly high forward bias current [5]. A simple, one step facile method for the preparation of graphene wrapped ZnO NPs hybrid has been also investigated. In PL spectra, the quenching of band gap emission and enhanced green emission serves as an evidence of the electron transfer from the ZnO NPs to the graphene layer. The increase in room temperature magnetic susceptibility in the hybrid, compare to pure ZnO NPs is due to the increasing defect concentration in the hybrid. All the observations are correlated and consistent with energy-band diagram model. This synthesis procedure will open a new way for the synthesis ZnO-graphene hybrid and this hybrid having magnetic properties has significance because of large potential application.

Another work was done on macroporous Si template, where iron oxide NPs coats of micro test tubes (inter-pore distance ~1 µm) and microbeakers (pore size exceeds 1.5 μm and inter-pore distance <100 nm), which has potential for biosensor application [6]. Luminescent characteristics was studied for core-shell nanostructures of silicon and silicon oxide having two different morphologies—nanodot and nanorod, prepared by controlled oxidation of mechanically milled crystalline silicon and by exfoliation of the affected layer of porous silicon [7]. The emitting states of porous Si layers are different and the peak is red shifted by approximately 1 eV compared to that of the colloids due to discretization of phonon density of states during formation of individual nanorods.

References

1. Jana, A. et al. Solid State Sci 2011, 13, 1633-1637.

2. Jana, A. et al. Sol Energy 2014, 102, 143-151.

3. Jana, A. et al. Mater Chem Phys 2013, 139, 431-436.

4. Das, P. P.; Jana, A. et al. Solid State Sci 2015, 48, 237-243.

5. Jana, A. et al. J Mater Chem C 2014, 2, 9613-9619.

6. Ghoshal, S.; Jana, A. et al. Nanoscale Res Lett 2011, 6.

7. Ray, M.; Jana, A. et al. Appl Phys 2010, 107.