A van der Waals heterostructure between all-inorganic CsPbBr 3 halide perovskite quantum dots (CPB QDs) and Ti 3 C 2 T x MXene (MXN) QDs is realized, and the photophysics of the composite is examined. A strong quenching of the steady-state photoluminescence of the perovskite QDs is observed, which is further examined by a time-resolved photoluminescence study. It is attributed to the charge transfer from CPB to MXN QDs followed by rapid energy relaxation of hot electrons and hot holes toward the band edge, leading to their recombination with photon energy in the far-IR energy domain. It is further shown that the CPB− MXN QD/QD system acts as an excellent on−off−on photoluminescence probe for cadmium ion detection and also as an active material for photodetector application.
In view of their immensely intriguing properties, 2D materials are being intensely researched in search of novel phenomena and diverse application interests; however, studies on the realization of 2D/2D nanocomposites in the application-worthy thin film platform are rare. Here we have grown MoS2-hBN 2D/2D composite thin films on different substrates by the pulsed laser deposition (PLD) technique and made comparative studies with the pristine MoS2 and hBN films. The Raman and x-ray photoelectron spectroscopy (XPS) techniques as well as high-resolution transmission electron microscopy (HRTEM) confirm the concomitant presence of both the 1T (conducting) and 2H (semiconducting) polymorphs of MoS2 in the composite film. Interestingly, a peculiar reentrant semiconductor-metal-insulator transition is seen in the MoS2-hBN 2D/2D composite film which is absent in the MoS2 film, and it correlates well with the signatures of phonon softening seen in temperature dependent Raman spectroscopy. Furthermore, electrostatic force microscopy (EFM) reveals the presence of three distinct regions (metallic, semiconducting and insulating) in the MoS2-hBN composite film with differing contact potentials and enhanced propensity for charge transfer with respect to pristine MoS2. A triboelectric nanogenerator (TENG)device containing biphasic MoS2-hBN composite film as an electron acceptor exhibits more than two-fold (six-fold) enhancement in peak-to-peak output voltage as compared to the pristine MoS2 2 (hBN) film. These observations bring out the potential of 2D/2D nanocomposite thin films for unfolding emergent phenomena and technological applications.
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