Role of fluid dynamics in nanofabrication growth mechanism and optical properties of ligand free cds nanotubes made using alumina nano reactor

Abstract

Cadmium sulfide is a well known photoactive semiconducting material with many potential applications in optoelectronics Most of these CdS nanostructures are grown using various physical and chemical routes As such it is well known that chemical synthesis process can tune the size and shape dependent physical properties of the material itself Moreover better knowledge on the role of hydrodynamics and kinetics of chemical reactions is very much needed to control the shape and also tuning the potential properties of nanostructures made using wet chemical nanofabrication process Understanding such growth dynamics and subsequent modifications of physical properties of the concerned material is very important in optimizing the device quality for future applications To probe this we explore the role of hydrodynamics in nanofabrication process of ligand free cadmium sulfide CdS nanotubes self assembled on porous alumina using a two chamber nanoreactor based synthesis method These CdS nanotubes show a significant photoluminescence PL red shift with increasing size as a result of the interplay between crystalline strain and defects incorporated during nucleation process Here we present chapter 3 a directionally asymmetric growth of CdS nanotubes on porous alumina as a result of nanoconfined reactions between two chemical precursors flowing horizontally in opposite directions We show that the dissimilar flow rates of chemical precursors are responsible for initiating the one sided growth of CdS nanotubes on porous alumina Structural evaluation using scanning electron microscopy images identified the nucleation sites and also shows the elongation of CdS nanotubes These incremental growths of CdS nanotubes may be due to plausible presence of chemo hydrodynamic instability at the AAO Na2S interface However the estimated values of dimensionless numbers are not sufficient enough to explain the occurrence of hydrodynamic instability at nanoscale Therefore using the electron microscope images we investigate the unex newline newline