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Alpha Lead Oxide: A New 2D Material with Visible Light Sensitivity

Authors: Prashant Kumar, Jing Liu, Pranay Ranjan, Yaowu Hu, Sharma SRKCYamijala, Swapan K. Pati, Joseph Irudayaraj, and Gary J. Cheng

Abstract: Even though transition metal dichalcogenides (TMDCs) are deemed to benovel photonic and optoelectronic 2D materials, the visible band gap beingoften limited to monolayer, hampers their potential in niche applicationsdue to fabrication challenges. Uncontrollable defects and degradedfunctionalities at elevated temperature and under extreme environmentsfurther restrict their prospects. To address such limitations, thediscovery of a new 2D material, alpha-PbO is reported. Micromechanical aswell as sonochemical exfoliation of 2D atomic sheets of alpha-PbO aredemonstrated and its optical behavior is investigated. Spectroscopicinvestigations indicate layer dependent band gaps. In particular, evenmultilayered PbO sheets exhibit visible band gap > 2 eV (direct) which israre among semiconducting 2D materials. The emission lifetime ofmultilayer PbO atomic sheets is 7 ns (dim light) as compared to themonolayer which gives 2.5 ns lifetime and an intense light. Densityfunctional theory calculations of layer dependent band structure ofalpha-PbO matches well with experimental results. Experimental findingssuggest that PbO atomic sheets exhibit hydrophobic nature, thermalrobustness, microwave stability, anti-corrosive behaviour and acidresistance. This new low cost, abundant and robust 2D material is expectedto find many applications in the fields of electronics, optoelectronics,sensors, photocatalysis and energy storage

Published in: Small (Impact factor = 9.59)