Dual active luminescence centers from a single-solid composite SnO2:Eu3+/Al-MCM-41: defect chemistry mediated color tuning for white light emission

Abstract

In this work, we report on white light generation by defect chemistry modification in a single-solid SnO 2 :Eu 3+ /Al-MCM-41 composite. The samples were carefully characterized by X-ray diffraction, transmission electron microscopy, N 2 adsorption-desorption isotherms, UV-vis diffuse reflectance spectra and luminescence spectra. It is found that the mesoporous material Al-MCM-41 with a large specific surface area (1040 m 2 g 21 ) and narrow pore size distribution (2.7 nm) was successfully prepared via pretreating kaolin through a simple ball milling approach. SnO 2 :Eu 3+ nanocrystals with fine crystalline nature and ultra-small particle sizes were successfully incorporated into the channels of the host matrix Al-MCM-41 through a hydrothermal route. Contrary to the theoretical predictions of the quantum size effects, SnO 2 :Eu 3+ /Al-MCM-41 composites showed an abnormal band gap narrowing with particle size reduction, which can be well-defined as a function of surface defects and Eu 3+ doping effects. By varying the Sn/Si molar ratios and Eu 3+ doping concentration, the highly defective SnO 2 :Eu 3+ /Al-MCM-41 composites exhibited tunable defect chemistry mediated broad band emission and typical Eu 3+ red emission that could modulate the color of light and improve the color rendering index (CRI). As a result, a maximum external quantum efficiency of 37.2% and white light with the color coordinates of (0.26, 0.22) in the CIE1931 color space were observed for the SnO 2 :(6.13%)Eu 3+ /Al-MCM-41 composite with a Sn/Si molar ratio of 0.183 when it was excited by near-ultraviolet light.

Study of structural, optical and magnetic properties of cobalt doped ZnO nanorods

“…97 However it is also known that quantum connement effect is not only the factor, doping can also modify the local lattice symmetry and introduce defect centers into the lattice which can make an alteration in the band structure and cause the large change in their properties. 98,99 Also, it is commonly known that with an increase in doping concentration, electrons populate states within conduction band pushing the Fermi level well inside the conduction band that is towards higher energy level leading to expansion of energy gap phenomena known as Burstein-Moss effect. It is about lling the bottom of the conduction band depending on the increase in the carrier concentration.…”

Au encapsulated into Al-MCM-41 mesoporous material: in situ synthesis and electronic structure

“…1,2 Moreover, it has been proved that the Al-containing mesostructured materials (Al-MCM-41) have relatively higher acidity and hydrothermal stability aer the incorporation of Al into the framework of mesoporous structures. 3,4 Consequently the ordered mesoporous Al-MCM-41 has been the focus of research due to its potential application in adsorption, ion exchange and catalysis. One of the intensive studies of mesoporous materials is encapsulation of heterogeneous species in their pore network, which can provide the composites with dened mesostructure and unique physical and chemical properties for varied application.…”

Achieving Exceptional Photocatalytic Activity and Selectivity through a Well‐Controlled Short‐Ordered Structure: A Case Study of NaxTaOy⋅n H2O

“…On the other hand, bandgapn arrowing mediated by defect chemistryi sn ot new and hasb een well documentedi nm any oxide systems. [24][25][26] Previous results on TiO 2 suggest that defective centers such as Ti 3 + and oxygen vacancies could construct one or multiple midgaps tates below the conduction band minimum, and this www.chemcatchem.org induces bandgap narrowing. [24,25] Moreover,s urface-disordered TiO 2 with several types of intrinsic defects leads to an increase in the valence band tail and ad ecrease in the conduction band tail, whiche nhances visible and infrared absorption of TiO 2 .…”