Influence of polarization, multi-valences and multi-coordination of cobalt: Third-order nonlinear, dielectric and Faraday properties of Bi0.5Co1.5S3/high optical basicity glass

Abstract In this study, we have successfully grown Co doped Bi0.5Co1.5S3 nanocrystals inside heavy metal oxide diamagnetic 42PbO-48TeO2-10B2O3 glass whose morphology, structure and properties were characterized using various techniques. The optimum parameters for Bi0.5Co1.5S3 nanocrystals formation is 380°C for 10hours. Glasses having different amounts of Bi0.5Co1.5S3 presented colors from light yellow to green and pure blue due to the different optical absorption of Co2+ ions in octahedral and tetrahedral coordination units. X-ray diffraction pattern revealed the formation of orthorhombic Bi2S3 nanocrystals in glass and Raman spectra demonstrated modification on structure such as TeO4 → TeO3 and BO → NBO conversion. The red shift in transmission cutoff edge of glasses showed experimental evidence of quantum confinement effect. Due to the high optical basicity system, X-ray photoelectron spectra studies confirmed the co-existence of Co2+, Co3+ and Co4+ which presented characteristic absorption in ultraviolet-visible spectra. The introduction of Bi0.5Co1.5S3 greatly increased the polarizability of glass, resulting in significant improvement on third-order nonlinearity, AC conductivity and dielectric constant. 1% Bi0.5Co1.5S3 doped glass presents giant Verdet constant of 62 rad/T.m at 633nm, promising nonlinear refractive index (5.662 × 10−11 esu) and large dielectric constant (78). This result proved that the synthesis of multivalence states of Co doped Bi2S3 in glass is an efficient method to improve the optical, dielectric and magneto optical performance of glass. Such dilute magnetic semiconductor nanocrystals-glass system has great potential applications in nonlinear, dielectric and magneto optical current sensors and isolators devices.