Photoinduced hole transfer in QD–phthalocyanine hybrids

Abstract

A series of CdSe quantum dot (QD)-phthalocyanine (Pc) hybrids were synthesized and their photophysics was studied using steady state and time-resolved spectroscopic methods. Emission of QDs was progressively quenched upon increasing the concentration of Pc in the hybrids. A detailed transient absorption study of the hybrids revealed that the mechanism of quenching is charge separation, resulting in the formation of hybrids with negatively charged QDs and the Pc cation. Direct photo-excitation of Pc did not show any detectable interaction between the excited state of Pc and the QD to which it is attached. An explanation is proposed, based on the suggestion that the energy of the lowest unoccupied molecular orbital (LUMO) of Pc is lower than the lower edge of the QD conduction band, while the energy of the highest occupied molecular orbital (HOMO) of Pc is sufficiently higher than the high energy edge of the QD valence band (VB), thus permitting hole transfer from the QD VB to the Pc HOMO after photo-excitation of QDs.

Photoreactions of Macrocyclic Dyes on (1010) Wurtzite Surface – Interplay Between Conformation and Electronic Effects

“…Thus, in spite of shortening the distance between the substrate and the sensitizing dye, the tilting of the molecule may inhibit an electron transfer reaction in the system. The obtained results are consistent with the recently reported lack of electron transfer from the LUMO of Pc to CdSe quantum dots [20]. Another factor that makes charge transfer from a macrocy-cle to the semiconductor surface unfavorable is increasing the number of peripheral groups around the dye, which leads to a lowering in the energy of the HOMO/LUMO system of a chromophore.…”

“…The six-layer slab has been chosen to study the surface-dye interaction. Due to the quantum confinement in the slab's perpendicular direction, our model is well reproducing the blueshift in energy typical of the CdSe quantum dots [20]. The dye molecules were anchored onto a surface via linkers of various lengths terminated by carboxylic groups attached onto two surface cations in a bidentate bridging mode, which ensures a strongest chemical bonding and is predominant according to previous reports [21].…”

Photoinduced Charge Separation in Semiconductor‐Quantum‐Dot/Organic‐Molecule Hybrids

“…It requires photoexcitation of the QD and it is formally described as hole transfer from the excited QD to the molecule. This type of behavior was reported for CdSe QD–phthalocyanine hybrids . Transient absorption measurements were carried out at relative phthalocyanine (Pc) concentration c ≈7, and QDs with diameters in the range 2.8–5.3 nm were used.…”

“…There are different methods to measure (absolute) energies of the ground and excited states of both QDs and molecules, but reliable prediction of the hybrid photophysics, and in particular photoinduced electron transfer, is the challenge, and experimental studies may show surprising results . Actually, reliable estimation of the energy levels and prediction of the CS thermodynamics is one of unsolved problems so far.…”

Методика оценки функциональности многослойных гибридных структур TiO-=SUB=-2-=/SUB=-/квантовая точка по генерации активных форм кислорода

“…Первый коллоидный синтез ярко люминесцирующих CdSe/ZnS квантовых точек (КТ), выполненный группой Бавенди (Bawendi) [1,2], ознаменовал эпоху широкого применения КТ в области фотовольтаики, сенсорики и тераностики заболеваний [3][4][5]. Благодаря своим уникальным свойствам КТ используются в качестве донора энергии [6] или носителя заряда [7,8] в гибридных структурах. Гибридные структуры на основе коллоидных CdSe/ZnS КТ и наночастиц диоксида титана (НЧ TiO 2 ) являются ярким примером систем, которые имеют огромный потенциал применения в тераностике бактериальных инфекций.…”