Almost all surfaces sensitive to the ambient environment are covered by water, whereas the impacts of water on surface-dominated colloidal quantum dot (CQD) semiconductor electronics have rarely been explored. Here, strongly hydrogen-bonded water on hydroxylated lead sulfide (PbS) CQD is identified. The water could pilot the thermally induced evolu. The presence of water on solid surfaces is ubiquitous in nature, which significantly impacts the surface chemical process and the corresponding properties of metals, oxides, and semiconductors through surface hydroxylation and water adsorption1,2,3. The surface-dominant nature of colloidal quantum dots (CQDs) endows them extreme surface sensitivity towards ambient humidity4. It has been reported that humid ambient has significant impacts on the properties of CQDs5,6,7,8. Uncovering the effect of water should be essential to open the door towards the ambient manufacturing of CQD-based electronic devices. However, the water-involved surface chemistry and its potential influence on CQD electronics have rarely been explored yet.Semiconducting lead sulfide (PbS) CQDs are promising building blocks for solution-processed electronics, including photovoltaics, infrared photodetectors, and field-effect transistors9,10. The surface geometry plays a critical role in the CQD surface chemistry and performance of devices, which can be predicted by Wulff constructions based on surface energy minimization theorem11,12. The surface of PbS CQD with a small size of less than 3 nm is dominated by polar {111} facet. Further growth of CQDs will lead to the appearance of {100} and {110} facets. This feature of CQD with controllable surface geometries provides a model platform for the study of the water effect on CQD characteristics, start. Identification of surface hydroxylatesFigure 1a shows the geometry structure of truncated octahedron PbS CQD used in our study. The surfaces of ~3 nm PbS CQD used in our studies are mainly dominated by PbS {111} facets, with partial coverage of {100} facets. In ideal situations, the CQD should be fully covered by iodine on the polar {111} facet. However, the strong steric hindrance of OA allows partial surface hydroxylation, stabilizing PbS {111} facets during the synthesis process15. The surface OH could provide potential absorption sites for ambient water, which makes CQD more vulnerable to the ambient environment.a Schematic representation of surface conditions on octahedral PbS CQDs. The ideal model of PbS CQDs with atomic halide passivation is shown on the left. The proposed surface conditions on the Pb-terminated {111} facet are zoomed on the right. Top: the OA-capped facet with partial surface hydroxylation introduced in the synthetic process15; Medium: Atomic iodine-passivated facet after ligand exchange; Below: the aggravation of surface hydroxylation followed by water adsorption under humid air. b The geometric structures of iodine-passivated (left), partially hydroxylated (middle) and water adsorbed PbS {111} facets (right) used in DFT calculation. The Ead and Evac stand for the adsorption energy of H2O and the vacancy formation energy, respectively. The purple spheres stan. In summary, we identified that the hydroxylated PbS CQD surfaces are covered by H-bonded water, which governs the temperature-dependent evolution of the surface chemical environment and generates significant effects on CQD nanostructure morphology, optoelectronic properties, as well as final photovoltaic performance. The entrapped water in CQD soli. Synthesis of PbS CQDsAll operations were performed under a nitrogen atmosphere using standard air-free Schlenk line techniques. For the synthesis of ~3 nm PbS CQDs. A solution of 380 mg of lead acetate trihydrate (1 mmol), 0.7 g of oleic acid (2.5 mmol), and 20 g of 1-Octadecene (ODE) was degassed at 100 °C in a 100 ml three-neck flask for 1 h under vacuum. The solution was then heated for an additional 1 h to 150 °C under nitrogen. After adjusting the solution to the desired temperature, 0.5 mmol hexamethyldisilathiane ((TMS)2S) dissolved in 5 ml ODE was rapidly injected into this hot solution. The CQDs were grown at 80 °C for the optimal time, and the reaction was rapidly quenched by placing the flask in a room-temperature water bath and injecting 8 ml of anhydrous hexane, then purified by precipitation in hexane and isopropyl alcohol and once in hexane/acetone and stored with solid form in a nitrogen-filled glove box.Photoemission spectroscopy (PES)Ultra-violet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) were carried out in an ultra-high vacuum (UHV) system with a base pressure of 1.0 × 10−10 mbar. To avoid water adsorption during th.
