Cu 2 O, CuO, and mixed-phase Cu 2 O/CuO thin films with different relative compositions were prepared by oxidizing Cu films at temperatures 150−380 °C for a time period ranging from 2 to 24 h, and their ultrafast transient absorption spectra have been characterized to understand the carrier dynamics of the heterostructured Cu 2 O/CuO system. The absorption dynamics of a pure p-type Cu 2 O sample followed a biexponential decay, with a fast time ∼0.3 ps and a long life >150 ps, while a pure p-type CuO sample showed triexponential decay dynamics, with three time constants, 0.25, 2.5, and >150 ps. For the mixed-phased Cu 2 O/CuO thin films, their absorption dynamics all followed the triexponential decay, and the two ultrafast time constants showed strong composition dependence. Possible energy band structures and electron transition processes are proposed to understand both the spectroscopic and dynamics behaviors of these samples.
Photo-oxa-dibenzocyclooctyne (Photo-ODIBO) undergoes photodecarbonylation under UV excitation to its bright S2 state, forming a highly reactive alkyne, ODIBO.
The ultrafast dynamics of photo-OxaDiBenzocycloOctyne (photo-ODIBO) photo-dissociation was studied using femtosecond transient absorption spectroscopy. Steady-state UV–Vis, time-dependent density functional theory, and 350 nm and 321 nm transient absorption studies are reported. Photo-ODIBO excitation with 321 nm and 350 nm light-induced photodecarbonylation of the cyclopropenone functional group results in the formation of ODIBO. The presence of the photoproduct was confirmed by the results of steady-state photolysis experiments and the observation of absorption signatures of ODIBO in the photo-ODIBO transient absorption spectra. Analysis of the latter revealed the underlying photochemical mechanisms and associated time constants, following excitation of the samples. The dynamics show a multi-exponential decay process, following the dissociation of photo-ODIBO into an excited state of the photoproduct ODIBO within <294 fs after 321 nm excitation. 350 nm excitation, on the other hand, is shown to produce ground state ODIBO via an intermediate species. Additional transient absorption measurements were performed directly on the photoproduct ODIBO to help distinguish spectral signatures associated with these processes.
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