Preparation and Upconversion Luminescence of Three-Dimensionally Ordered Macroporous ZrO2: Er3+, Yb3+

Qu, Xuesong; Song, Hongwei; Bai, Xue; Pan, Guohui; Dong, Biao; Zhao, Haifeng; Wang, Fang; Qin, Ruifei

doi:10.1021/ic800575f

Cited by 37 publications

(19 citation statements)

References 30 publications

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“…Pt clusters are homogeneously distributed throughout the film (Figure 4c) and seem to be mainly located at the surface of crystallites. The segregation of platinum in nanoclusters suggests a strong tendency of WO 3 lattice, in the form of inverted opal, to remain undistorted as large single crystals, as clearly revealed by HRTEM images previously described. Pt centers, which are reduced within the WO 3 lattice more easily than Cr centers, can move and aggregate into clusters through the channels of the open perovskite structure.…”

Section: Preparation Of Precursorssupporting

confidence: 66%

“…Journal of the American Chemical Society ARTICLE Figure 4 reports the TEM and HRTEM images of the macroporous Pt-doped WO 3 . The skeletal structure resembles that observed for Cr-doped inverse opal films (Figure 4a) with large nanocrystals surrounding the voids generated by the PMMA spheres (Figure 4b).…”

Section: Preparation Of Precursorsmentioning

confidence: 99%

“…The reason for the higher electrical sensitivity of Pt-doped WO 3 layers cannot be attributed to higher amounts of electrons trapped by Pt centers, because no oxidized Pt mþ centers were detected before interaction with NH 3 . Instead, it may be suggested that the Pt nanoclusters anchored to the WO 3 surface, well evident from both HRTEM and XPS investigations, act as catalysts of the interaction between ammonia and O o centers decreasing the activation barrier in the reactions (6).…”

Section: Preparation Of Precursorsmentioning

confidence: 99%

“…In this context, the one-step preparation of Cr and Pt-doped WO 3 inverse opal films provides an easy way to produce macroporous structures very suitable for ammonia detection. Furthermore, successful and controllable doping sensitization is performed by simply adding the metal precursor to the starting aqueous solution, guaranteeing an easy and homogeneous dispersion of the dopant.…”

Section: ' Introductionmentioning

confidence: 99%

“…The morphology of the films and the electronic properties of both WO 3 and the doping centers were also investigated in order to suggest a mechanism for the variations of electrical sensitivity in the presence of NH 3 . The effect of the macroporous structure on the electrical response was also discussed in terms of conductance regime under different gas concentrations, in order to achieve optimum balance between the intensity and the reproducibility of sensor performances.…”

Section: ' Introductionmentioning

confidence: 99%

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Macroporous WO₃ Thin Films Active in NH₃ Sensing: Role of the Hosted Cr Isolated Centers and Pt Nanoclusters

et al. 2011

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Macroporous materials 1,2 based on metal oxides have become strategic for various applications like photonic crystals, 3À5 catalysts, 6À8 and sensor devices, 9À13 mainly due to their lightweight, their high surface area, and the well-defined porous architecture with a limited agglomerated morphology. 2 In sensing research the improvement in selectivity, reproducibility, and stability expected for the gas sensors based on macroporous metal oxides is still a challenge for pollutant detection. 14 Unfortunately, the delicate method needed to prepare macroporous materials still limits their wide employment in effective devices. 1,2 Macroporous metal oxides are typically synthesized by alkoxidebased solÀgel processes, employing two steps: 11,15À20 (i) the selfassembling of an ordered array of colloidal microspheres of polystyrene, polymethyl methacrylate, or silica, acting as template; (ii) the filling of interstices of the structure by metal alkoxide solution, followed by solÀgel hydrolysis and densification.The subsequent thermal treatment which removes the template leads to the macroporous structure called inverted opal, where the macropores are interconnected through holes resulting from the contact between the template spheres. 2 The application of this synthetic method becomes particularly tricky wherein highly reactive metal alkoxides are used as oxide precursors, 21,22 or if the oxide needs to be doped by sensitizing centers, 11 for example, by transition metal atoms. Moreover, when the preparation of films is required, such as in the case of semiconductor oxide-based gas sensors, the two-step approach appears unsuitable to produce metal oxide thin films having high reproducible morphology, homogeneously embedding dopants, like transition metal centers.To easily obtain macroporous metal oxides with high surface area and homogeneous dopant distribution, our group recently developed a novel one-step preparation of SnO 2 and Pt-doped SnO 2 as inverse opal thin films by dip-coating deposition of solÀgel precursors. 23 The procedure enables the self-assembled formation of the closely packed polystyrene (PS) microsphere array and the simultaneous infiltration of the precursors into the voids of the structure. Thus, the oxide solid skeleton around the spheres was obtained in one-step, unlike the conventional Received: October 22, 2010 ABSTRACT: Macroporous WO 3 films with inverted opal structure were synthesized by one-step procedure, which involves the self-assembly of the spherical templating agents and the simultaneous solÀgel condensation of the semiconductor alkoxide precursor. Transition metal doping, aimed to enhance the WO 3 electrical response, was carried out by including Cr(III) and Pt(IV) centers in the oxide matrix. It turned out that Cr remains as homogeneously dispersed Cr(III) centers inside the WO 3 host, while Pt undergoes reduction and aggregation to form nanoclusters located at the oxide surface. Upon interaction with NH 3 , the electrical conductivity of transition metal doped-WO 3 increase...

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Section: Preparation Of Precursorssupporting

confidence: 66%

Section: Preparation Of Precursorsmentioning

confidence: 99%

Section: Preparation Of Precursorsmentioning

confidence: 99%

Section: ' Introductionmentioning

confidence: 99%

Section: ' Introductionmentioning

confidence: 99%

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