No abstract

Fluorescence decay times measured during the off-state of single CdSe/ZnS quantum dot blinking are found to decrease with increasing off-state duration, contradicting the charging model widely considered to explain the blinking phenomenon. The change in the nonradiative process of a short off-state duration compared to a long one is investigated here through simultaneous measurement of fluorescence decay and blinking behavior. The results are investigated in the framework of two models based on fluctuating trapping rates.

The photochemistry of nitrosyl chloride (ClNO) in the solution phase is investigated using Fourier transform infrared (FTIR) and ultrafast time-resolved infrared (TRIR) spectroscopies. The NO-stretch fundamental transition for ClNO dissolved in cyclohexane, carbon tetrachloride, chloroform, dichloromethane, and acetonitrile is measured, with the frequency and line width of this transition demonstrating a strong dependence on solvent polarity. Following the photolysis of ClNO dissolved in acetonitrile at 266 nm, the subsequent optical-density evolution across the entire width of the NO-stretch fundamental is measured. Analysis of the optical-density evolution demonstrates that geminate recombination of the primary photofragments resulting in the reformation of ground state ClNO occurs with a quantum yield of 0.54 +/- 0.06. In addition, an increase in optical density is observed at 1860 cm(-1) that is assigned to the NO-stretch fundamental transition of the photoisomer, ClON, having a formation quantum yield of 0.07 +/- 0.02. This work represents the first definitive observation of ClNO photoisomerization in solution. Finally, essentially no evidence is observed for significant vibrational excitation of the NO fragment following photodissociation, in marked contrast to the behavior observed in the gas phase. An environment-dependent dissociation scheme is proposed in which the interplay between solvent polarity and the location of the ground state potential-energy-surface minimum along the Cl-N coordinate provides for the optical preparation of different excited states thereby affecting the extent of NO vibrational excitation following photolysis.

Course-based undergraduate research experiences (CUREs) are becoming more prevalent throughout chemistry curricula as a mechanism to lower barriers to participation, improve retention, and decrease success gaps for historically minoritized populations. Given the evidence that longduration and early entry experiences are more impactful, herein we describe a semester-long CURE in General Chemistry II Lab. The curriculum outcomes were assessed with an inquiry classification scheme and a rubric blended from Auchincloss et al. and Clark et al. Student outcomes were assessed in the context of the five essential components of authentic research experiences utilizing Lopatto's CURE Survey, student lab reports, and interviews from graduate assistants and peer research mentors. A comparison to benchmark data and those reported for upper-division chemistry CUREs reveals significant gains in scientific skills, communication, and attitudes about science.

No abstract