ULTRATHIN BLACK PHOSPHORUS: A NEW HIGH-MOBILITY TWO-DIMENSIONAL SEMICONDUCTOR

Ph.DDOCTOR OF PHILOSOPH

Transport properties of pristine few-layer black phosphorus by van der Waals passivation in an inert atmosphere

Ultrathin black phosphorus is a two-dimensional semiconductor with a sizeable band gap. Its excellent electronic properties make it attractive for applications in transistor, logic and optoelectronic devices. However, it is also the first widely investigated two-dimensional material to undergo degradation upon exposure to ambient air. Therefore a passivation method is required to study the intrinsic material properties, understand how oxidation affects the physical properties and enable applications of phosphorene. Here we demonstrate that atomically thin graphene and hexagonal boron nitride can be used for passivation of ultrathin black phosphorus. We report that few-layer pristine black phosphorus channels passivated in an inert gas environment, without any prior exposure to air, exhibit greatly improved n-type charge transport resulting in symmetric electron and hole transconductance characteristics.B.O. acknowledges support by the National Research Foundation, Prime Minister's Office, Singapore under its Competitive Research Programme (CRP Award No. NRF-CRP9-2011-3) and the SMF-NUS Research Horizons Award 2009-Phase II. A.H.C.N. acknowledges the NRF-CRP award 'Novel 2D materials with tailored properties: beyond graphene'. The calculations were performed at the GRC computing facilities. A.Z. and D.F.C. acknowledge the NSF grant CHE-1301157. (NRF-CRP9-2011-3 - National Research Foundation, Prime Minister's Office, Singapore under its Competitive Research Programme (CRP); SMF-NUS Research Horizons Award-Phase II; NRF-CRP award 'Novel 2D materials with tailored properties: beyond graphene'; CHE-1301157 - NSF)Published versio

Exfoliation of two-dimensional phosphorene sheets with enhanced photocatalytic activity under simulated sunlight

Two-dimensional phosphorene (2D-BP) nanosheets were successfully prepared by an environmental friendly water exfoliation process. The morphology and structure of exfoliated 2D-BP nanosheets were characterized by SEM, AFM, Raman and UV–Vis. The photocatalytic results demonstrated that 2D-BP nanasheets can generate reactive oxygen species of 1O2 and O2− and effectively enhance the photodegradation of dibutyl phthalate pollutants when coexist with water, oxygen, and light

2D Black Phosphorus: from Preparation to Applications for Electrochemical Energy Storage

Black phosphorus (BP) is rediscovered as a 2D layered material. Since its first isolation in 2014, 2D BP has triggered tremendous interest in the fields of condensed matter physics, chemistry, and materials science. Given its unique puckered monolayer geometry, 2D BP displays many unprecedented properties and is being explored for use in numerous applications. The flexibility, large surface area, and good electric conductivity of 2D BP make it a promising electrode material for electrochemical energy storage devices (EESDs). Here, the experimental and theoretical progress of 2D BP is presented on the basis of its preparation methods. The structural and physiochemical properties, air instability, passivation, and EESD applications of 2D BP are discussed systemically. Specifically, the latest research findings on utilizing 2D BP in EESDs, such as lithium‐ion batteries, supercapacitors, and emerging technologies (lithium–sulfur batteries, magnesium‐ion batteries, and sodium‐ion batteries), are summarized. On the basis of the current progress, a few personal perspectives on the existing challenges and future research directions in this developing field are provided

Coexistence of copy number increases of c-Myc, ZNF217, CCND1, ErbB1 and ErbB2 in ovarian cancers

Background: We selected 5 oncogenes with well-established roles in carcinogenesis – CCND1, ErbB1, ErbB2, c-mycand ZNF217– to investigate the coexistence of their copy imbalances in relation to the clinico-pathological characteristics of ovarian tumors. Materials and Methods: Fluorescence in situ hybridization for the 5 genes was applied to a preexisting tissue microarray. 38 ovarian tumors were successfully analyzed for copy number changes of the 5 genes. Results: At least one of these oncogenes was gained/amplified in 27 out of 38 tumors (71.1). We report the highest frequency of c-mycgenetic gain/amplification since it affected 42.1 of the ovarian tumors. We observed sequential involvement of copy number alterations of the other genes in the presence of c-mycdisruption. The incidence of copy number changes of the 5 oncogenes – both single and combinatorial – was higher in high-grade tumors. All double aberrations in the serous group comprised c-mycand ZNF217copy number increases. Conclusions: Our results revealed a combination between copy number increases of c-mycand ZNF217, associated with serous histology. The data from this combined analysis of the 5 oncogenes could be used as a basis in considering the combined approach in molecular-based therapy of ovarian cancer