Despite
strong similarities due to the common presence of silicon
monohydrides and isolated silicon dangling bonds (silicon radicals),
the water-saturated Si(001)-2 × 1 surface and the hydrogen-terminated
Si(001)-2 × 1 surface show very different reactivities with respect
to benzaldehyde. By using real-time scanning tunneling microscopy,
synchrotron radiation photoemission, X-ray absorption, and high-resolution
electron energy loss spectroscopies in combination, we demonstrated
that benzaldehyde reacts with the silicon dangling bonds of water-saturated
Si (001). As we found no evidence for the abstraction of a nearby
H leading to the formation of a new dangling bond, the formation of
a stable radical adduct is a plausible explanation. This observation
contrasts with the H-terminated case for which benzaldehyde grafting
occurs via a radical chain reaction that can propagate after abstraction
of a nearby H by the radical adduct. Also at odds with the H-terminated
case, a second chemisorption channel is observed [i.e., a concerted
hydrosilylation reaction between a surface monohydride (SiH) and the
carbonyl moiety] without any participation of the silicon dangling
bond. We discuss how the presence of hydroxyls on water-saturated
Si(001)-2 × 1 could make its reactivity markedly different from
that of H-terminated Si(001)-2 × 1.
An easy circuit for measuring the power of a solar panel in physics classroom by using the microcontroller Arduino will be introduced in this article. The measured data is transferred via Bluetooth to the smartphone app ‘phyphox’ where it is displayed graphically. The circuitry enables measuring the power of a solar panel in different situations of light intensity. Several model experiments for students will be described.
Today smartphones and tablets do not merely pervade our daily life, but also play a major role in STEM education in general, and in experimental investigations in particular. Enabling teachers and students to make use of these new techniques in physics lessons requires supplying capable and affordable applications. Our article presents the improvement of a low-cost technique turning smartphones into powerful magnifying glasses or microscopes. Adding only a 3D-printed clip attached to the smartphone’s camera and inserting a small glass bead in this clip enables smartphones to take pictures with up to 780x magnification (see Fig. 1). In addition, the construction of the smartphone attachments helps to explain and examine the differences between magnifying glasses and microscopes, and shows that the widespread term “smartphone microscope” for this technique is inaccurate from a physics educational perspective.
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