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过渡金属碲化物(Transition-metal Tellurides, TMTs)有着独特的晶体结构和优异的物理化学特性,研究者因此对它们产生了极大的研究兴趣。目前TMTs在光电子学、催化、电极及磁性材料等诸多领域[1–4]具有广泛的应用前景。有研究表明,Ⅳ-Ⅶ族过渡金属与碲元素生成的TMTs主要为层状材料,而Ⅷ-Ⅹ族过渡金属与碲元素则是生成三维的TMTs晶体[5];理论和实验均表明,若改变TMTs的元素组成和形貌,其相应的物理、化学性质都会发生变化,且在较低维数下,它的物化性能会得到一定的增强[6-7]。CoTe2是TMTs中的一种,具有稳定的白铁矿型结构,也称为斜方碲钴矿(Mattagamite)[8],CoTe2晶体属正交晶系,空间群为Pnnm(58),具备良好的对称性,其晶体结构具体参数见表1。CoTe2具有半金属性质,取向为自旋向上的电子呈现金属性,取向为自旋向下的电子呈现非金属性,此时带隙为1.063 eV[9]。近年来通过制备CoTe2纳米材料,发现它具有诸多独特的性质,例如,Lu等人使用水热法制备出尺寸为20~50 nm的CoTe2纳米粒(NPs),可作为析氢反应(HER)高效、稳定的催化剂,稳定性可达2天及以上[9];Shi等人利用简单水热共还原路线成功合成了直径约为50 nm、长度为1 μm的CoTe和CoTe2纳米管,所得产物具有优异的磁性能[10];Yin等人利用单步水热工艺成功开发了一种新型CoTe2纳米膜电极,该电极在析氧反应/析氢反应(OER/HER)中具有优异的活性、耐久性和稳定性[11];Xie等人采用一步溶剂热路线,以乙二胺为溶剂,在高压釜中制备了直径为30 nm、长度大于1.2 μm的CoTe2纳米棒[12],通过能谱测试证实了CoTe2纳米棒为斜方晶系;Jiang等人通过溶剂热法合成了五种不同物质的纳米片,其中CoTe2纳米片的厚度约为10~15 nm,研究结果表明:其PL光谱存在很宽的发射带[13];Ian G. McKendry等人采用化学合成法制备了CoTe2纳米晶,发现它是一种优良的电化学水氧化反应(WOR)的催化剂[14];Huang等人合成了具有均匀多面体形状的CoTe2纳米复合材料,并首次将其作为染料敏化太阳能电池的电催化剂,该复合材料具有优异的光伏性能,光电转换效率(PCE)为9.02%[15]。
CoTe2 Crystal parameters Crystal System Orthorhombic Space group Pnnm (58) Lattice parameters a=5.312 Å(1 Å=10−10 m ),b=6.311 Å,c=3.889 Å Angle α=90°,β=90°,γ=90° Z 2 Table 1. Crystal parameters of CoTe2(PDF#011-0553)
基于当前报道的CoTe2纳米材料研究现状,发现对于CoTe2量子点(QDs)的制备和光学性质的研究相对较少,目前CoTe2纳米材料制备主要采用水热法、溶剂热法等,但是这些合成方法所需实验条件相对较为严苛,液相超声剥离法(以下简称超声法)在常温常压下可在溶液中形成局部的高温高压,大幅度降低了实验反应条件的要求,同时它还具有污染小、操作方便、成本较低等优点。实验采用自上而下[16]的超声法制备CoTe2 QDs,并对制备得到的CoTe2 QDs进行测试表征,分析其形貌、结构特征,研究其近红外光学性能。
CoTe2 QDs: preparation, structure and optical properties (Invited)
doi: 10.3788/IRLA20211021
- Received Date: 2020-11-05
- Rev Recd Date: 2020-12-05
- Available Online: 2021-01-22
- Publish Date: 2021-01-22
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Key words:
- ultrasonic method /
- transition-metal tellurides /
- CoTe2 /
- quantum dots /
- infrared properties
Abstract: In recent years, transition metal telluride (TMTs) has attracted extensive attention and research in the scientific field due to its unique crystal structure and excellent physical and chemical properties. In this paper, CoTe2 quantum dots (QDs) was prepared by ultrasonic method, the morphology and structure of the prepared CoTe2 QDs were characterized by TEM, AFM, EDS, XPS, XRD and FTIR. The optical properties of the prepared CoTe2 QDs were investigated by Spectrophotometer (UV-Vis), Photoluminescence (PL) and Photoluminescence Excitation (PLE). CoTe2 QDs shows good dispersion, uniform particle size and spherical morphology. The average diameter and height of the grains are about 3.1 nm and 2.9 nm respectively. CoTe2 QDs shows the obvious absorption in the infrared band, and the absorption value decreases with the increase of dilution concentration. When the wavelength of excitation light and emission light increases in turn, the PL and PLE peaks have a red shift, and they have an obvious Stokes shift effect. It shows that the photoluminescence of CoTe2 QDs is wavelength dependent. CoTe2 QDs has the photoluminescence characteristic of multicolor, different excitation light wavelength can emit different colors of light. The fluorescence quantum yield of QDs is 62.6%. The excellent optical characteristics of CoTe2 QDs, especially its absorption and luminescence characteristics in the infrared band, shows that it has important potential application value in infrared detection, laser protective coating, fluorescence imaging, multicolor luminescence and nano-photonic devices, and is expected to become a new type of infrared detection material.