Steady-state intraband transition, which is a promising electronic transition of a colloidal quantum dot along with the band-gap transition, had been a long-standing challenge. The steady-state intraband transition occurring between discrete electronic states in the conduction band of a colloidal nanocrystal has been reported only from mercury chalcogenide nanocrystals for the past few years. Concerns about the toxicity of the mercury compound necessitate a new nontoxic system exhibiting a steady-state intraband transition.Here we present the steady-state intraband absorption and photoluminescence of Ag 2 Se colloidal nanocrystals under ambient conditions. The mid-IR intraband transition is carefully investigated by means of FT-IR emission spectroscopy, spectroelectrochemistry, compositional analysis, and transfer characteristics. Especially, the mid-IR intraband photoluminescence of the Ag 2 Se colloidal nanocrystal will open new avenues in the use of quantum-confined colloidal systems for mid-and longwavelength infrared light sources along with the band-gap transition that has been investigated for the last three decades.

An increase in the carrier density of semiconductor nanocrystals can gradually change the origin of the optical property from the excitonic transition to the localized surface plasmon resonances. Here, we present the evolution of the electronic transition of self-doped Ag2Se colloidal quantum dots, from the intraband transition to the localized surface plasmon resonances along with a splitting of the intraband transition (1Pe–1Se). The minimum fwhm of the split intraband transition is only 23.7 meV, which is exceptionally narrow compared to that of metal oxide nanocrystals showing LSPRs, inferring that the electron–electron scattering is significantly suppressed due to the smaller carrier density. The splitting of the intraband transition mainly results from the asymmetrical crystal structure of the tetragonal Ag2Se CQDs and becomes distinct when the nanocrystal changes its crystal structure from the cubic to tetragonal structure. Maximizing the discrete energy levels in the quantum dot along with mixing with plasmonic characters may provide opportunities to fully harness merits of both the quantum confinement effect and localized surface plasmon resonance characters.

Self-doping in nanocrystals allows accessing higher quantum states. The electrons occupying the lowest energy state of the conduction band form a metastable state that is very sensitive to the electrostatic potential of the surface. Here, we demonstrate that the high charge sensitivity of the self-doped HgSe colloidal quantum dot solid can be used for sensing three different targets with different phases through self-doped HgSe nanocrystal/ZnO thin-film transistors: the environmental gases (CO2 gas, NO gas, and H2S gas); mid-IR photon; and biothiol (l-cysteine) molecules. The self-doped quantum dot solid detects the targets through different mechanisms. The physisorption of the CO2 gas and the NO gas molecules, and the mid-IR photodetection show reversible processes, whereas the chemisorption of l-cysteine biothiol and H2S gas molecules shows irreversible processes. Considering the quenching of mid-IR intraband photoluminescence of the HgSe colloidal quantum dot solid by the vibrational mode of the CO2 gas molecule, sensing the CO2 gas could be involved in the electronic-to-vibrational energy transfer. The target molecules are quantitatively analyzed, and the limits of detection for CO2 and l-cysteine are 250 ppm and 10 nM, respectively, which are comparable to the performance of commercial detectors.

Solution-processable perovskite quantum dots are considered as promising optical materials for light-emitting optoelectronics. Lightemitting field-effect transistors (LEFETs) that can be operated under a relatively lower potential with a high energy conversion efficiency are yet to be realized with perovskite quantum dots. Here, we present the CsPbBr 3 quantum dot-based LEFET. Surprisingly, unipolar transport characteristics with strong electroluminescence were observed at the interface of the CsPbBr 3 QD-LEFET along with an exceptionally wide recombination zone of 80 μm, an order of magnitude larger than that of organic/polymer LEFETs. Based on the systematic analysis for the electroluminescence of the CsPbBr 3 NC-LEFET, we revealed that the increased diffusion length determined by the majority carrier mobility and the lifetime well explains the remarkably wide recombination zone. Furthermore, it was found that the energy-level matching and transport geometry of the heterostructure also determine the charge distribution and recombination, substantially affecting the performance of the CsPbBr 3 QD LEFET.

The aim of this study was to systematically review the impact of antepartum depression on exclusive breastfeeding. A total of 15 studies were included in the review and 12 studies were used for the meta-analysis. The mean values of antepartum depression indicated that women who breastfed exclusively between 3 and 6 months had less antepartum depression symptoms (Mean Difference = −0.55, 95% CI = −0.76 to −0.35). The analysis also showed that the existence of antepartum depression was negatively related to continuing exclusive breastfeeding for longer than 3 months postpartum as well as for 8 weeks postpartum (OR = 0.48, 95% CI = 0.26–0.88 and OR = 0.83, 95% CI = 0.75–0.91, respectively). The cumulative evidence is conclusive that antepartum depressive symptoms are negatively associated with exclusive breastfeeding, particularly between 3 and 6 months postpartum. This review supports the necessity of screening and follow-up for depression throughout the perinatal period to promote exclusive breastfeeding for 6 months.