Optical and photochemical properties of nonstoichiometric cadmium sulfide nanoparticles: Surface modification with copper(II) ions
Optical and photochemical properties of nonstoichiometric cadmium sulfide nanoparticles: Surface modification with copper(II) ions
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DOI：
10.1021/la960985r
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发表时间：
1997-06-11
期刊：
影响因子：
3.9
通讯作者：
Chrysochoos, J
中科院分区：
文献类型：
--
作者：
Isarov, AV;Chrysochoos, J
用Cu2+对非化学计量硫化镉纳米粒子([Cd~(2+)]/[S~(2-)]=3)在异丙醇中进行了表面修饰。EPR和吸收光谱证实，高氯酸铜加入到纳米硫化镉中，导致铜离子结合到半导体表面，伴随着铜离子被快速还原为铜离子。高氯酸铜也有效地猝灭了硫化镉纳米颗粒的复合发光。猝灭数据服从静态相互作用模型，证实了铜离子与硫化镉的结合。后者也被超滤和电感耦合等离子体光谱所证实。铜离子结合在硫化镉表面形成了一个新的红移发光带。新谱带的最大值为14700 cm(-1)，而原谱带的最大值为17900 cm(-1)。结果表明，在较低的铜离子浓度下，结合在纳米硫化镉表面的铜离子以孤立的铜离子形式存在。它们在导带下方约1.2 eV处的带隙中产生了一个新的能级，这是产生新的发射带(14700 cm(-1))的原因。较高的高氯酸铜浓度会在硫化镉表面形成超细的CuxS(x=1-2)粒子，最终导致析出。孤立的铜离子和超小颗粒的CuxS都通过促进e(-)/h(+)的非辐射湮没来猝灭纳米颗粒的原始复合发光。纳米硫化镉表面结合的铜离子抑制了纳米硫化镉对铜(II)的光腐蚀和四苯基卟啉的光解。提出了相应的机制。
Nonstoichiometric cadmium sulfide nanoparticles ([Cd2+]/[S2-] = 3) in 2-propanol were surface-modified with Cu2+ ions. Addition of copper(II) perchlorate to CdS nanoparticles leads to binding of copper ions onto the surface of the semiconductor, accompanied by rapid reduction of Cu2+ to Cu+, as confirmed by EPR and absorption spectra. Copper(II) perchlorate also quenches the recombination luminescence of CdS nanoparticles effectively. The quenching data obey a static interaction model, which confirms the binding of copper ions onto CdS. The latter was confirmed also by ultrafiltration and ICP spectroscopy. Copper ions bound onto the surface of CdS lead to formation of a new, red-shifted, luminescence band. The maximum of the new band is at 14 700 cm(-1) compared to that of the original band at 17 900 cm(-1). It is suggested that, at low copper ion concentrations, copper ions bound onto the surface of CdS nanoparticles exist as isolated Cu+ ions. They create a new energy level in the bandgap at about 1.2 eV below the conduction band, which is responsible for the new emission band (14 700 cm(-1)). Higher copper(II) perchlorate concentrations give rise to the formation of ultrasmall particles of CuxS (x = 1-2) on the surface of CdS, which eventually lead to precipitation. Both isolated Cu+ ions and ultrasmall particles of CuxS quench the original recombination luminescence of CdS nanoparticles by facilitating e(-)/h(+) nonradiative annihilation. The presence of copper ions bound onto the surface of CdS nanoparticles retard both the photocorrosion of the latter and the photodecomposition of copper(II) tetraphenylporphyrin induced by CdS nanoparticles. Appropriate mechanisms are presented.