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Zero-dimensional environmentally friendly carbon quantum dots (CQDs) combined with two-dimensional materials have a wide range of applications in optoelectronic devices. We combined steady-state and transient absorption spectroscopies to study the energy transfer dynamics between CQDs and molybdenum disulfide (MoS2). Transient absorption plots showed photoinduced absorption and stimulated emission features, which involved the intrinsic and defect states of CQDs. Adding MoS2 to CQDs solution, the lowest unoccupied molecular orbital of CQDs transferred energy to MoS2, which quenched the intrinsic emission at 390 nm. With addition of MoS2, CQD-MoS2 composites quenched defect emission at 490 nm and upward absorption, which originated from another energy transfer from the defect state. Two energy transfer paths between CQDs and MoS2 were efficiently manipulated by changing the concentration of MoS2, which laid a foundation for improving device performance. [ABSTRACT FROM AUTHOR]

Combining steady-state photoluminescence and transient absorption (TA) spectroscopy, we have investigated the photoinduced charge transfer dynamics between lead-free Mn-doped Cs2NaIn0.75Bi0.25Cl6 double perovskite (DP) nanocrystals (NCs) and conjugated poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Upon ultraviolet-A excitation, the photoinduced absorption feature of DP NCs/MDMO-PPV nanocomposites disappeared, and the stimulated emission weakened in the TA spectrum. This was due to charge transfer from the MDMO-PPV polymers to DP NCs. Upon a higher photon-energy ultraviolet-C excitation, stimulated emission and photoinduced absorption features vanished, indicating there existed a reversible charge transfer from DP NCs to MDMO-PPV polymers. Reversible charge transfer of Mn-doped DP NCs/MDMO-PPV nanocomposites was tuned by varying the excitation photon-energy. The manipulation of reversible charge transfer dynamics in the perovskite-polymer nanocomposites opens a new avenue for optical and optoelectronic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transient absorption spectroscopy can be conducive to understand the fluorescence quenching. • Photo-induced absorption of QDs occurs blue-shifted. • Stimulated emission lifetime is proposed to be an indicator for MXene detection. • Fluorescence quenching of QDs originates from the energy transfer to MXene. Fluorescence quenching due to energy transfer from InP/ZnS quantum dots (QDs) to Ti 3 C 2 T x MXene materials was investigated by the transient absorption spectroscopy. During the fluorescence quenching, the photo-induced absorption feature in the transient spectrum was blue-shifted due to the higher photon energy required for the upward transition. The lifetime of stimulated emission was gradually extended from 0.86 μs to 2.28 μs with increasing Ti 3 C 2 T x MXene. The fluorescence quenching of QDs can be quantitatively characterized by analyzing the lifetime of the stimulated emission feature in the transient absorption spectrum, which was used as a Ti 3 C 2 T x MXene detection with the sensitivity of 6.63 mL/mg. The results of this study provide the basis for the design of optical sensors. [ABSTRACT FROM AUTHOR]

We explore energy transfer dynamics between quantum dots and graphene oxide composite by utilizing transient absorption spectroscopy. It is found that stimulated emission of quantum dots can be completely suppressed with graphene oxide reduced by laser irradiation. Absorption transition of defect state has decreased subsequently when graphene oxide is further reduced. It can be attributed to the enhanced energy transfer efficiency from quantum dots to photoreduced graphene oxide. Here, energy transfer dynamics between them have been manipulated efficiently, providing potential applications in the fields of optoelectronic devices, such as field effect transistors, light emitting diodes, and solar cells. • Energy transfer dynamics of quantum dot and graphene oxide explored by transient absorption spectroscopy. • Measurement of transient spectral changes during laser irradiation upon the composite. • Influence on excited-state interaction, including stimulated emission and absorption transition of defect state. [ABSTRACT FROM AUTHOR]