We synthesized free-standing Si nanosheets (NSs) with a thickness of about <2 nm using a chemical vapor deposition process and studied their optical properties. The Si NSs were formed by the formation of frameworks first along six different <110> directions normal to [111], its zone axis, and then by filling the spaces between the frameworks along the <112> directions under high flow rate of processing gas. The Si NSs showed blue emission at 435 nm, and absorbance and photoluminescence (PL) excitation measurements indicate that enhanced direct band transition attributes to the emission. Time-resolved PL measurement, which showed PL emission at 435 nm and a radiative lifetime of 1.346 ns, also indicates the enhanced direct band gap transition in these Si NSs. These outcomes indicate that dimensionality of Si nanostructures may affect the band gap transition and, in turn, the optical properties.
32Various studies have reported that photochemical nucleation of new ultrafine particles (UFP) 33 in urban environments within high insolation regions occurs simultaneously with high ozone
34(O 3 ). In this work, we evaluate the atmospheric dynamics leading to summer O 3 episodes in the
39Simultaneously, measurements of an extensive number of air quality and meteorological 40 parameters were carried out at 3 supersites across the MMA. Furthermore, data from O 3 -41 soundings and daily radio-sounding were also used to interpret the atmospheric dynamics.
42The results demonstrate the concatenation of venting and accumulation episodes, with
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