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Synthesis and Dual-Mode Electrochromism of Anisotropic Monoclinic Nb12O29 Colloidal Nanoplatelets.
ACS Nano ( IF 15.8 ) Pub Date : 2020-07-27 , DOI: 10.1021/acsnano.0c03283 Hsin-Che Lu 1 , Sandeep Ghosh 1 , Naman Katyal 2 , Vikram S Lakhanpal 1 , Ioana R Gearba-Dolocan 3 , Graeme Henkelman 2 , Delia J Milliron 1
ACS Nano ( IF 15.8 ) Pub Date : 2020-07-27 , DOI: 10.1021/acsnano.0c03283 Hsin-Che Lu 1 , Sandeep Ghosh 1 , Naman Katyal 2 , Vikram S Lakhanpal 1 , Ioana R Gearba-Dolocan 3 , Graeme Henkelman 2 , Delia J Milliron 1
Affiliation
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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.
中文翻译：
各向异性单斜Nb12O29胶态纳米片的合成和双模电致变色。
具有双模式电致变色的过渡金属氧化物纳米晶体有望实现智能窗，从而实现光谱选择性的太阳调制。我们已经开发了各向异性单斜Nb 12 O 29纳米片（NPLs）的胶体合成，以研究氧化铌纳米晶体的双模电致变色。通过混合NbCl 5制备用于合成不良贷款的前体与油酸形成配合物，然后将其加热形成被油酸封端的氧化物状结构，称为铌氧簇。通过使用铌氧簇进行合成，可以观察到NPL比其他多晶型物的优先生长。通过X射线衍射并结合模拟检查了合成的NPL的结构，发现NPL是单层单斜Nb 12 O 29，在[100]方向上较薄，并沿b和c方向延伸。除具有单层厚度外，与块状单斜Nb 12 O 29相比，NPL的Nb-O键拉曼信号强度降低，键序更高，由计算解释。NPL膜的逐步电化学还原导致在近红外区（阶段1）吸收，然后在可见区和近红外区（阶段2）吸收，从而表现出双模电致变色。通过循环伏安法以电化学方式区分这两个过程的机理，以确定离子嵌入限制动力学的程度，并通过X射线光电子能谱验证离子嵌入后局部电子的存在。这两个结果都支持由电容充电产生近红外吸收，并且第二阶段可见吸收的开始是由离子嵌入引起的。
更新日期：2020-08-25
中文翻译：
各向异性单斜Nb12O29胶态纳米片的合成和双模电致变色。
具有双模式电致变色的过渡金属氧化物纳米晶体有望实现智能窗，从而实现光谱选择性的太阳调制。我们已经开发了各向异性单斜Nb 12 O 29纳米片（NPLs）的胶体合成，以研究氧化铌纳米晶体的双模电致变色。通过混合NbCl 5制备用于合成不良贷款的前体与油酸形成配合物，然后将其加热形成被油酸封端的氧化物状结构，称为铌氧簇。通过使用铌氧簇进行合成，可以观察到NPL比其他多晶型物的优先生长。通过X射线衍射并结合模拟检查了合成的NPL的结构，发现NPL是单层单斜Nb 12 O 29，在[100]方向上较薄，并沿b和c方向延伸。除具有单层厚度外，与块状单斜Nb 12 O 29相比，NPL的Nb-O键拉曼信号强度降低，键序更高，由计算解释。NPL膜的逐步电化学还原导致在近红外区（阶段1）吸收，然后在可见区和近红外区（阶段2）吸收，从而表现出双模电致变色。通过循环伏安法以电化学方式区分这两个过程的机理，以确定离子嵌入限制动力学的程度，并通过X射线光电子能谱验证离子嵌入后局部电子的存在。这两个结果都支持由电容充电产生近红外吸收，并且第二阶段可见吸收的开始是由离子嵌入引起的。
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