Synthesis, structure and electronic properties of ultranarrow CdS nanorods

We report on the one-step synthesis of ultra narrow wurtzite CdS nanorods using bench top chemical decomposition route. The synthesized CdS nanorods are of 1.8 nm in diameter and show major confinement along the radial dimension, which is well below the exciton Bohr radius of bulk CdS (2.5 nm). Structural and self-assembly properties of nanorods are studied using X-ray Diffraction (XRD) and small angle X-ray scattering (SAXS) measurements, which reveal preferred orientation of the nanorods along <00.2> direction with 2D supercrystalline spatial distribution. The estimated nanorod dimensions from XRD is corroborated with the transmission electron microscopy observations. UV–vis and photoluminescence spectroscopy reveals significant increase in the band gap in comparison to bulk CdS which is further tallied with the simulations using effective mass approximation (EMA). Formation of discrete structure of valence band and conduction band due to strongly quantum confined excitons in the radial direction is evidenced from EMA simulation. Combination of experimental and theoretical approach helps in understanding the structure–property relationship for ultranarrow CdS rods which might lead to nanorod based applications.