Highly luminescent (photoluminescence quantum yield (PLQY) as high as 96%) CdSe-based core/gradient alloy shell/shell (CGASS) quantum dots (QDs) have been synthesized in “one pot” using the reactivity difference between Cd and Zn precursors and Se and S precursors. This procedure is highly reproducible and quite useful for large-scale synthesis. Upon photoexcitation these QDs show a multiexponential excited state decay behavior. Interestingly, with the growth of the shell the overall PL decay gets faster. All the decay traces have been fitted well with a three exponential decay function. Fitted decay traces reveal three different time constants, a faster one of 1–4 ns, moderate one of 13–16 ns, and slower one >25 ns. With the growth of the shell, the amplitude for the moderate time constant increases, and that of the slow time constant decreases consistently. The variation of PLQY could be correlated with the variation of amplitude of the moderate time constant. Slow and moderate time constants have been shown to be associated with two mutually interdependent excited state decay channels, and the competition between these two decay channels dictates the PLQY of these CGASS QDs. The moderate time constant is associated with an electron–hole recombination process, and the slow time constant is associated with delayed emission from the band edge due to interaction with the manifold of shallow traps. The increase in magnitude of the amplitude of the moderate decay is reflected in higher PLQY. PL decay of blue-, green-, orange-, and red-emitting CGASS QDs follows a similar trend. This kind of uniform nature of PL decay of different color-emitting QDs is quite rare in the literature, and the fact that it has been observed in CGASS QDs perhaps hints toward the novelty of these systems. At the single-particle level these CGASS QDs are shown to be quite photostable without showing any blueing or bleaching for 1 h or even longer even under an air atmosphere. Thus, these CGASS QDs exhibit much improved optical behavior in comparison to CdSe/ZnS core/shell QDs. Quite interestingly all four differently emitting CGASS QDs optically behave in a similar way even at the single-particle level.

Transition metal dichalcogenide (TMDCs) monolayers make an excellent component in optoelectronic devices such as photodetectors and phototransistors. Selenide‐based TMDCs, specifically molybdenum diselenide (MoSe2) monolayers with low defect densities, show much faster photoresponses compared to their sulfide counterpart. However, the typically low absorption of the atomically thin MoSe2 monolayer and high exciton binding energy limit the photogeneration of charge carriers. Yet, integration of light‐harvesting materials with TMDCs can produce increased photocurrents via energy transfer. In this article, it is demonstrated that the interaction of cesium lead bromide (CsPbBr3) nanocrystals with MoSe2 monolayers results into an energy transfer efficiency of over 86%, as ascertained from the quenching and decay dynamics of the CsPbBr3 nanocrystals emission. Notably, the increase in the MoSe2 monolayer emission in the heterostructure accounts only for 33% of the transferred energy. It is found that part of the excess energy generates directly free carriers in the MoSe2 monolayer, as a result of the transfer of energy into the exciton continuum. The efficiency of the heterostructure via enhanced photocurrents with respect to the single material unit is proven. These results demonstrate a viable route to overcome the high exciton binding energy typical for TMDCs, as such having an impact on optoelectronic processes that rely on efficient exciton dissociation.

Light-driven multi-charge accumulation (i.e., photodoping) of doped metal oxide nanocrystals opens the way to innovative solutions for the direct conversion and storage of the solar energy.

In this article, we discuss the microwave synthesis of sodium dodecyl sulphate (SDS) stabilized Ln(3+)-doped CaMoO4 nanocrystals (Ln(3+) = Eu(3+), Er(3+)/Yb(3+)). The nanocrystals are quite monodispersed with an average size close to 100 nm. FTIR and TGA analyses suggest strong binding of the SDS molecules to the CaMoO4 nanocrystals surface. The high dispersibility of the nanocrystals in water implies that SDS stabilizes the nanocrystals as a bilayer structure. The SDS coating also assists in the easy dispersion of the nanocrystals in toluene without any additional surface chemistry. The Eu(3+) ions doped in the CaMoO4 nanocrystals display very strong red luminescence with a quantum yield close to 40%. Under 980 nm excitation, Er(3+)/Yb(3+)-doped CaMoO4 nanocrystals display Er(3+) emissions at 550 and 650 nm. In addition, interestingly, a NIR peak at around 833 nm is observed, which occurred via a three photon process. Furthermore, the CaMoO4 nanocrystals exhibit photocatalytic activity which is studied through the degradation of Rhodamine B (RhB) dye in neutral conditions. The RhB dye is significantly degraded by ~80% under UV illumination within 4 h and the rate of degradation is comparable to that observed for well known ZnO nanoparticles. The high luminescence quantum efficiency and strong photocatalytic activity of the Ln(3+)-doped CaMoO4 nanocrystals make them a potential material for dual applications such as bio-imaging and photocatalysis.