Gold has always fascinated
humans, occupying an important functional
and symbolic role in civilization. In earlier times, gold was predominantly
used in jewelry; today, this noble metal’s surface properties
are taken advantage of in catalysis and plasmonics. In this article,
the plasmon resonance of gold dumbbell nanorods is investigated. This
unusual morphology was obtained by a seed-mediated growth method.
The concentration of chemical precursors such as cetyltrimethylammonium
bromide and silver nitrate plays a significant role in controlling
the shape of the nanorods. Indeed, the aspect ratio of dumbbell nanostructures
was varied from 2.6 to 4. UV–visible absorption spectra revealed
a shift of the longitudinal surface plasmon resonance peak from 669
to 789 nm. Having the plasmon resonance in the near infrared region
helps to use those nanostructures as photothermal agents.
Mesoporous silicon and porous silicon/Ni nanocomposites have been investigated in this work employing light-dark surface photovoltage (SPV) transients to monitor the response of surface charge dynamics to illumination changes. The samples were prepared by anodization of a highly n-doped silicon wafer and a subsequent electrodepositing of Ni into the pores. The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm. SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O2, N2, Ar). A significant difference was observed between the ‘light-on’ and ‘light-off’ SPV transients obtained in vacuum and those observed in gaseous ambiences. Such behavior could be explained by the contribution to the charge exchange in gas environments from chemisorbed and physisorbed species at the semiconductor surface.PACS81.05.Rm; 73.20.-r; 75.50.-y; 82.45.Yz
Supplemental Instruction (SI) is a teaching method adopted by academic institutions to strengthen and extend learning opportunities beyond regular classroom lectures. The supplemental instructor is a junior or senior-level student with a track record of a sound knowledge of the material and works closely with the students seeking help. The SI leader is free to provide different teaching/learning strategies to foster problem-solving skills and critical thinking behavior. While the supplemental instructors are independent in conducting the learning sessions, they work closely with the course instructor. In this work, we investigate the efficacy of the SI model in college physics compare to university physics at Southern Arkansas University using data from ten years. Furthermore, we discuss how this additional teaching pedagogy elucidates to successful completion of a physics class, retention in the department/university, and overall academic success through the peers’ support.
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