These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
2 files

Synthesis and Dual-Mode Electrochromism of Anisotropic Monoclinic Nb12O29 Colloidal Nanoplatelets

submitted on 10.04.2020, 02:20 and posted on 10.04.2020, 13:10 by Hsin-Che Lu, Sandeep Ghosh, Naman Katyal, Graeme Henkelman, Vikram S. Lankanpal, Delia Milliron
Transition metal oxide nanocrystals with dual-mode electrochromism hold promise for smart windows enabling spectrally selective solar modulation. We have developed the colloidal synthesis of anisotropic monoclinic Nb12O29 nanoplatelets (NPLs) to investigate the dual-mode electrochromism of niobium oxide nanocrystals. The precursor for synthesizing NPLs was prepared by mixing NbCl5 and oleic acid to form a complex that was subsequently heated to form an oxide-like structure capped by oleic acid, denoted as niobium oxo cluster. By initiating the synthesis using niobium oxo clusters, preferred growth of NPLs over other polymorphs was observed. The structure of the synthesized NPLs was examined by X-ray diffraction in conjunction with simulations, revealing that the NPLs are monolayer monoclinic Nb12O29, thin in the [100] direction and extended along the b and c directions. Besides having monolayer thickness, NPLs show decreased intensity of Raman signal from Nb-O bonds with higher bond order when compared to bulk monoclinic Nb12O29, as interpreted by calculations. Progressive electrochemical reduction of NPL films led to absorbance in the near-infrared region (stage 1) followed by absorbance in both the visible and near-infrared regions (stage 2), thus exhibiting dual-mode electrochromism. The mechanisms underlying these two processes were distinguished electrochemically by cyclic voltammetry to determine the extent to which ion intercalation limits the kinetics, and by verifying the presence of localized electrons following ion intercalation using X-ray photoelectron spectroscopy. Both results support that the near-infrared absorption results from capacitive charging and the onset of visible absorption in the second stage is caused by ion intercalation.


Email Address of Submitting Author


The University of Texas at Austin



ORCID For Submitting Author


Declaration of Conflict of Interest

The authors declare no conflict of interest