Quantum confinement effect and photoenhancement of photoluminescence of PbS and PbS/MnS quantum dots

• Main Authors: Zaini, Muhammad Safwan, Josephine Ying, Chyi Liew, Alang Ahmad, Shahrul Ainliah, Mohmad, Abdul Rahman, Ahmad Kamarudin, Mazliana
• Format: Article
• Published: Multidisciplinary Digital Publishing Institute 2020
• Online Access: http://psasir.upm.edu.my/id/eprint/87385/; https://www.mdpi.com/2076-3417/10/18/6282
• Institution: Universiti Putra Malaysia

The quantum confinement effect and photoenhancement of photoluminescence (PL) of lead sulphide (PbS) quantum dots (QDs) and lead sulphide/manganese sulphide (PbS/MnS) core shell QDs capped with thiol ligands in aqueous solution were investigated. From PL results, the presence of MnS shells gives a strong confinement effect which translates to higher emission energy in PbS/MnS core shell QDs. Increasing MnS shell thickness from 0.3 to 1.5 monolayers (ML) causes a blueshift of PL peak energies as the charge carriers concentrated in the PbS core region. Enhancement of the PL intensity of colloidal PbS and PbS/MnS core shell QDs has been observed when the samples are illuminated above the band gap energy, under continuous irradiation for 40 min. Luminescence from PbS QDs and PbS/MnS core shell QDs can be strongly influenced by the interaction of water molecules and oxygen present in aqueous solution adsorbed on the QD surface. However, PbS/MnS core shell QDs with a shell thickness of 1.5 ML did not show a PL peak energy stability as it was redshifted after 25 min, probably due to wider size distribution of the QDs.