Near-Infrared Luminescent Ternary Ag3 SbS3 Quantum Dots by in situ Conversion of Ag Nanocrystals with Sb(C9 H19 COOS)3.

Differently from the normal three single precursor method to produce colloidal ternary quantum dots (QDs), herein ternary Ag3 SbS3 quantum dots (QDs) with efficient near-infrared (NIR) luminescence have been prepared by a new facile in situ conversion of Ag nanocrystals (NCs) with a binary Sb/S organic precursor Sb(C9 H19 COOS)3 under low temperature. The unprecedented construction evolution from Ag NCs to Ag3 SbS3 /Ag hetero-structure and final monodisperse Ag3 SbS3 QDs has been demonstrated. These novel Ag3 SbS3 QDs exhibit efficient NIR emission at ≈1263 nm and possess high colloidal stability.

Hydrothermal One-Step Synthesis of Highly Dispersed M-Phase VO2 Nanocrystals and Application to Flexible Thermochromic Film.

Preparation of ultrafine highly dispersed VO2(M) nanoparticles that are essential materials to fabricate thermochromic flexible films remains a challenge, preventing effective use of their promising properties. Here, we report an original hydrothermal approach by controlling oxidizing atmosphere of reaction with hydrogen peroxide to prepare ultrafine VO2(M) nanoparticles free from annealing. Hydrogen peroxide is separated from precursor solution in a reactor, which creates a moderate oxygenation environment, enabling the formation of stoichiometric VO2(M) nanoparticles. The obtained VO2(M) nanoparticles are well-dispersed, highly uniform, and single-phase, with an average particle size ∼30 nm. The flexible thermochromic films fabricated with the VO2(M) nanoparticles exhibit excellent thermochromic performance with a solar modulation efficiency of 12.34% and luminous transmittance of 54.26%. While the films prepared with annealed nanoparticles show reduced transmittance due to light scattering of the large size particles resulting from agglomeration and growth during annealing. This work demonstrates a promising technique to realize moderate oxidizing atmosphere by hydrothermal process for preparing well-dispersed stoichiometric nano-oxides.

Evolution of Structural and Electrical Properties of Oxygen-Deficient VO2 under Low Temperature Heating Process.

Structural stability and functional performances of vanadium dioxide (VO2) are strongly influenced by oxygen vacancies. However, the mechanism of metal-insulator transition (MIT) influenced by defects is still under debate. Here, we study the evolution of structure and electrical property of oxygen-deficient VO2 by a low temperature annealing process (LTP) based on a truss-structured VO2 nanonet. The oxygenation process of the oxygen-deficient VO2 is greatly prolonged, which enables us to probe the gradual change of properties of the oxygen-deficient VO2. A continuous lattice reduction is observed during LTP. No recrystallization and structural collapse of the VO2 nanonet can be found after LTP. The valence-band X-ray photoelectron spectroscopy (XPS) measurements indicate that the oxygen deficiency strongly affects the energy level of the valence band edge. Correspondingly, the resistance changes of the VO2 films from 1 to 4.5 orders of magnitude are achieved by LTP. The effect of oxygen vacancy on the electric field driven MIT is investigated. The threshold value of voltage triggering the MIT decreases with increasing the oxygen vacancy concentration. This work demonstrates a novel and effective way to control the content of oxygen vacancies in VO2 and the obvious impact of oxygen vacancy on MIT, facilitating further research on the role of oxygen vacancy in structure and MIT of VO2, which is important for the deep understanding of MIT and exploiting innovative functional application of VO2.