Continuous Ultra-Thin MoS2 Films Grown by Low-Temperature Physical Vapor Deposition

Uniform growth of pristine two dimensional (2D) materials over large areas at lower temperatures without sacrifice of their unique physical properties is a critical pre-requisite for seamless integration of next-generation van der Waals heterostructures into functional devices. This Letter describes a vapor phasegrowth technique for precisely controlled synthesis of continuous, uniform molecular layers of MoS2 on silicon dioxide and highly oriented pyrolitic graphite substrates of over several square centimeters at 350 °C. Synthesis of few-layer MoS2 in this ultra-high vacuum physical vapor deposition process yieldsmaterials with key optical and electronic properties identical to exfoliated layers. The films are composed of nano-scale domains with strong chemical binding between domain boundaries, allowing lift-off from the substrate and electronic transport measurements from contacts with separation on the order of centimeters

Continuous Ultra-Thin MoS2 Films Grown by Low-Temperature Physical Vapor Deposition

Uniform growth of pristine two dimensional (2D) materials over large areas at lower temperatures without sacrifice of their unique physical properties is a critical pre-requisite for seamless integration of next-generation van der Waals heterostructures into functional devices. This Letter describes a vapor phasegrowth technique for precisely controlled synthesis of continuous, uniform molecular layers of MoS2 on silicon dioxide and highly oriented pyrolitic graphite substrates of over several square centimeters at 350 °C. Synthesis of few-layer MoS2 in this ultra-high vacuum physical vapor deposition process yieldsmaterials with key optical and electronic properties identical to exfoliated layers. The films are composed of nano-scale domains with strong chemical binding between domain boundaries, allowing lift-off from the substrate and electronic transport measurements from contacts with separation on the order of centimeters

Effect of Ion Concentration on the Electro-Optic Response in Polymer-Stabilized Cholesteric Liquid Crystals

We have previously reported that the application of a DC field can adjust the position and/or bandwidth of the selective reflection notch in polymer-stabilized cholesteric liquid crystals (PSCLCs). The proposed mechanism of these electro-optic (EO) response is ion-facilitated electromechanical deformation of the polymer stabilizing network. Accordingly, the concentration of ions trapped within the polymer network should considerably influence the EO response of PSCLC. Our prior studies have indicated that photoinitiators can increase ion density in PSCLC by an order of magnitude. Here, we isolate the contribution of ionic impurities associated with liquid crystal monomers (LCMs) by utilizing initiator-less polymerization. PSCLCs prepared with LCM with low ion concentration show bandwidth broadening of the reflection band whereas PSCLCs prepared with LCM with high ion concentration exhibit a red shifting tuning of the reflection band. The extent of the tuning or bandwidth broadening of the CLC reflection band depends on the concentration of LCMs and the chirality of the LCM.</div

White light thermoplasmonic activated gold nanorod arrays enable the photo-thermal disinfection of medical tools from bacterial contamination

The outspread of bacterial pathogens causing severe infections and spreading rapidly, especially among hospitalized patients, is worrying and represents a global public health issue. Current disinfection techniques are becoming insufficient to counteract the spread of these pathogens because they carry multiple antibiotic-resistance genes. For this reason, a constant need exists for new technological solutions that rely on physical methods rather than chemicals. Nanotechnology support provides novel and unexplored opportunities to boost groundbreaking, next-gen solutions. With the help of plasmonic-assisted nanomaterials, we present and discuss our findings in innovative bacterial disinfection techniques. Gold nanorods (AuNRs) immobilized on rigid substrates are utilized as efficient white light-to-heat transducers (thermoplasmonic effect) for photo-thermal (PT) disinfection. The resulting AuNRs array shows a high sensitivity change in refractive index and an extraordinary capability in converting white light to heat, producing a temperature change greater than 50 °C in a few minute interval illumination time. Results were validated using a theoretical approach based on a diffusive heat transfer model. Experiments performed with a strain of Escherichia coli as a model microorganism confirm the excellent capability of the AuNRs array to reduce the bacteria viability upon white light illumination. Conversely, the E. coli cells remain viable without white light illumination, which also confirms the lack of intrinsic toxicity of the AuNRs array. The PT transduction capability of the AuNRs array is utilized to produce white light heating of medical tools used during surgical treatments, generating a temperature increase that can be controlled and is suitable for disinfection. Our findings are pioneering a new opportunity for healthcare facilities since the reported methodology allows non-hazardous disinfection of medical devices by simply employing a conventional white light lamp

A systems approach towards standards based teacher education: A multi perspective story of collaborative change

Panel presentatio

Evaluating "Quality" methods of filling the "Teacher Gap": Results of a pilot study with early career teachers

Challenges for meeting the highly-qualified teacher demand, exacerbated by the critical shortage of teachers, have necessitated a variety of preparation routes for those entering the profession of teaching. This pilot study examined teacher confidence and self efficacy related to teacher preparedness within the first three years of employment. Specifically, the study examined preparation experience perceptions of early career teachers. All teachers who were employed three years or less from three Florida school districts were invited to participate. Data were analyzed and aggregated according to teacher preparation type – traditional or non-traditional (alternative) program. Participants indicated their likelihood of remaining in the program, district, and school as well as their degrees of confidence in preparation for the competencies identified. Overall results as well as differences between those who completed a traditional teacher preparation program and those with a non-traditional teacher preparation program are presented. Implications for training priorities and replicating research are discussed

Science engagement and literacy: A retrospective analysis for students in Canada and Australia

Given international concerns about students' pursuit (or more correctly, non-pursuit) of courses and careers in science, technology, engineering and mathematics, this study is about achieving a better understanding of factors related to high school students' engagement in science. The study builds on previous secondary analyses of Programme for International Student Assessment (PISA) datasets for New Zealand and Australia. For the current study, we compared patterns of science engagement and science literacy for male and female students in Canada and Australia. The study's secondary analysis revealed that for all PISA measures included under the conceptual umbrella of engagement in science (i.e. interest, enjoyment, valuing, self-efficacy, self-concept and motivation), 15-year-old students in Australia lagged their Canadian counterparts to varying, albeit modest, degrees. Our retrospective analysis further shows, however, that gender equity in science engagement and science literacy is evident in both Canadian and Australian contexts. Additionally, and consistent with our previous findings for indigenous and non-indigenous students in New Zealand and Australia, we found that for male and female students in both countries, the factor most strongly associated with variations in engagement in science was the extent to which students participate in science activities outside of school. In contrast, and again for both Canadian and Australian students, the factors most strongly associated with science literacy were students' socioeconomic backgrounds, and the amount of formal time spent doing science. The implications of these results for science educators and researchers are discussed

Effect of Ion Concentration on the Electro-Optic Response in Polymer-Stabilized Cholesteric Liquid Crystals

We have previously reported that the application of a DC field can adjust the position and/or bandwidth of the selective reflection notch in polymer-stabilized cholesteric liquid crystals (PSCLCs). The proposed mechanism of these electro-optic (EO) response is ion-facilitated electromechanical deformation of the polymer stabilizing network. Accordingly, the concentration of ions trapped within the polymer network should considerably influence the EO response of PSCLC. Our prior studies have indicated that photoinitiators can increase ion density in PSCLC by an order of magnitude. Here, we isolate the contribution of ionic impurities associated with liquid crystal monomers (LCMs) by utilizing initiator-less polymerization. PSCLCs prepared with LCM with low ion concentration show bandwidth broadening of the reflection band whereas PSCLCs prepared with LCM with high ion concentration exhibit a red shifting tuning of the reflection band. The extent of the tuning or bandwidth broadening of the CLC reflection band depends on the concentration of LCMs and the chirality of the LCM