STEM outreach programmes in secondary schools are mediated by STEM teachers who are responsible for organising, implementing and evaluating the activities with a view to promoting STEM subjects. However, research investigating teachers' STEM roles and professional development through participation in outreach activities is limited. This paper explores teachers' views of STEM activities, how they understand their role as primary facilitators and the impact of their STEM engagement on their professional development.STEM outreach provides distinct opportunities for situated and dialogic learning. Teachers who understand the pedagogic challenges inherent within these approaches could be more effective in creating the inspirational, enquiring culture that will lead to students participating enthusiastically in STEM subjects. STEM teachers' effectiveness in engaging students by demonstrating the importance and relevance of STEM subjects in the real world and engaging captivating STEM outreach partners not only supports students learning but also enhances their opportunities to develop their knowledge and skills Semi structured interviews were conducted with eleven teachers from six different schools in the West Midlands, United Kingdom. The data reveals STEM facilitators become the 'face' of STEM to their pupils. The expertise, knowledge and partnerships STEM facilitators develop, broadens their capacity to deliver teaching imbued with real world applications and improve students' understanding of the range of new and upcoming careers available. Most importantly, participating in S T E M outreach activities help teachers maintain and reinforce their own sense of identity as STEM professionals. Outreach activities provide opportunities for teachers to interact with leading scientists and obtain exposure to cutting-edge research.
We report the photorefractive performance of a polymer composite sensitized by CdSe/ZnS core/shell nanoparticles, and also comprising poly(N-vinylcarbazole) and an electro-optic chromophore. The nanoparticles are characterized by absorption and photoluminescence spectroscopy, elemental analysis, transmission electron microscopy, and powder x-ray diffraction. The electro-optic response of the composite is measured independently of the photorefractive effect by transmission ellipsometry. An asymmetric two-beam coupling gain of 30.6+/-0.4 cm(-1) is obtained, confirming photorefractivity. Degenerate four-wave mixing is used to assess photorefractive performance and, at a poling field of 70 V microm(-1), yields a diffraction efficiency of 4.21%+/-0.03%, a holographic contrast of 3.05 x 10(-4)+/-1 x 10(-6), a space-charge rise time of 25+/-2 s, and a sensitivity of 4.7 x 10(-5)+/-4 x 10(-6) cm3 J(-1). These results constitute a significant improvement on the performance of previous nanoparticle-sensitized photorefractive polymer composites.
The performance of a photorefractive polymer composite sensitized by 1-hexadecylamine capped CdSe nanoparticles is reported. The polymer composite also comprises the charge transporting matrix poly(N-vinylcarbazole) and the electro-optic chromophore 1-(2-ethylhexyloxy)-2,5-dimethyl-4-(4-nitrophenylazo) benzene. At an applied field of 70 V mm À1 two beam coupling gain of 13.2 cm À1 was observed, confirming the photorefractive nature of the induced grating. At the same field, a holographic contrast of 9:12 Â 10 À4 AE 6 Â 10 À6 , a photorefractive sensitivity of 5:1 Â 10 À4 AE 0:2 Â 10 À4 cm 3 J À1 and a space-charge field rise time of 13 AE 1 s were obtained.
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