Toward an Understanding of the Growth of Ag Filaments on α-Ag<sub>2</sub>WO<sub>4</sub> and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

Longo, E.; Volanti, Diogo P.; Longo, Valeria; Gracia, Lourdes; Nogueira, I. C.; Almeida, M. A. P.; Pinheiro, Antônio N.; Ferrer, Mateus M.; Cavalcante, L. S.

doi:10.1021/jp408167v

Cited by 126 publications

(169 citation statements)

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“…The onedimensional nature observed for the as-prepared nanostructures is related to the preferential growth in the [001] direction. 27,28 Additionally, the a-Ag 2 WO 4 nanorods exhibit other nanoparticles on their surface. Recently, we reported the real-time in situ observation of the silver metallic (Ag) growth process from the unstable a-Ag 2 WO 4 nanorods submitted to electron irradiation from a transmission electron microscope.…”

Section: -33mentioning

confidence: 99%

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

et al. 2014

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aThis paper reports on a new ozone gas sensor based on a-Ag 2 WO 4 nanorod-like structures. Electrical resistance measurements proved the efficiency of a-Ag 2 WO 4 nanorods, which rendered good sensitivity even for a low ozone concentration (80 ppb), a fast response and a short recovery time at 300 C, demonstrating great potential for a variety of applications.Metal semiconducting oxides have drawn the interest of many researchers due to their wide range of applications, especially as gas sensing materials. 1-5 Among them, one-dimensional (1-D) semiconductor nanostructures have been proposed as very interesting materials, especially as gas sensor devices.6-12 It is well known that several technological applications of nanostructured materials are directly related to the morphology, particle size, crystalline phase and activity of specic crystalline planes strictly dependent on synthesis methods. 4,[13][14][15] In particular, the relationship between morphology and gas sensing properties has been well established. 4,16,17Tungsten-based oxides are an important class of materials that display wide potential functional properties, 18-20 speci-cally the silver tungstate (Ag 2 WO 4 ) compound, which can exhibit three different structures: a-orthorhombic, b-hexagonal, and g-cubic.21-25 Recently, our research group reported a detailed study of the synthesis, structural and optical properties of hexagonal nanorod-like elongated a-Ag 2 WO 4 nanocrystals obtained by different methods. 26-28Ozone (O 3 ) is an oxidizing gas used in many technological applications in different areas, such as the food industry, drinking-water treatment, medicine, microelectronic cleaning processes, and others.29,34-39 For example, ozone has been employed as a powerful drinking-water disinfectant and oxidant. 34,35,40 On the other hand, when the ozone level in an atmosphere exceeds a certain threshold value, the exposure to this gas becomes hazardous to human health and can cause serious health problems (e.g. headache, burning eyes, respiratory irritation and lung damage).34,41 The European Guidelines (2002/3/EG) recommend avoiding exposure to ozone levels above 120 ppb.41 Such arguments support the requirement for the determination and continuous monitoring of ozone levels. 3,29,41Gas sensing properties are evaluated in terms of operating temperature, sensitivity, response time, recovery time and stability.29-33 SnO 2 , In 2 O 3 and WO 3 compounds have been considered the most promising ozone gas sensors. 29-33To the best of our knowledge, to date the gas sensing properties of a-Ag 2 WO 4 nanocrystals have never been evaluated.Here, we report the sensing properties of 1-D a-Ag 2 WO 4 nanorod-like structures obtained by the microwave-assisted hydrothermal (MAH) method.42-46 Because of such properties, nanorods are potential candidates for practical applications as ozone gas sensors.The crystalline phase of the as-obtained a-Ag 2 WO 4 sample was analyzed by X-ray diffraction measurement and all reec-tions were indexed to an orthorhombic struc...

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Section: -33mentioning

confidence: 99%

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

et al. 2014

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“…Silver tungstate ĲAg 2 WO 4 ) is an important multifunctional material with an orthorhombic structure that exhibits various physical and chemical properties such as photoluminescence, [1][2][3][4][5][6] photocatalysis, 7-9 ozone gas sensing, 10 and antibacterial activity against Gram-negative and Gram-positive bacterial strains, for example, Escherichia coli, Bacillus subtilis, ganisms on Earth that are capable of producing all components found in basic organic compounds. 27 The presence of E. coli in H 2 O or food is indicative of contamination with human or animal feces.…”

Section: Introductionmentioning

confidence: 99%

“…38 In general, photocatalytic and antibacterial reactions occur at the interface, and photocatalysis requires the effective adsorption of reactant molecules or ions on the surface of Ag 2 WO 4 crystals. The adsorption states of some specific molecules or ions are intrinsically determined by the surface atomic structures of Ag 2 WO 4 . Therefore, their performance is strongly associated with the electronic and surface structure, as well as the morphology.…”

Section: Introductionmentioning

confidence: 99%

Facet-dependent photocatalytic and antibacterial properties of α-Ag₂WO₄crystals: combining experimental data and theoretical insights

Roca

Sczancoski

Nogueira

et al. 2015

Catal. Sci. Technol.

128

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In this paper, we have combined the various experimental results and first-principles calculations with a new and interesting discussion to explain the photocatalytic and antibacterial activities of α-Ag 2 WO 4 crystals, which were obtained using the microwave-hydrothermal (MH) method with anionic surfactants. The advantages of the insights gained through the present work are two-fold. First, the mechanism and origin of the photocatalytic and antibacterial activities can be rationalized. Second, this facile and controllable synthetic method is expected to encourage the synthesis of complex metal oxides with specific active facets, and these insights can contribute to the rational design of new materials for multifunctional applications. X-ray diffraction and Rietveld refinement analysis confirmed that all the crystals have an orthorhombic structure without deleterious phases. Ultraviolet-visible diffuse reflectance spectroscopy indicated the presence of intermediary energy levels and a variation in the optical band gap values (3.09-3.14 eV) with the crystal growth process.The geometry, electronic properties of the bulk, and surface energies of these crystals were evaluated using first-principles quantum mechanical calculations based on the density functional theory. The crystal shapes was experimentally and theoretically modeled based on Rietveld refinement data, emission scanning electron microscopy images, and Wulff construction. To obtain a wide variety of crystal shapes, the morphologies were gradually varied by tuning the surface chemistry, i.e., the relative stability of the faceted crystals. The growth mechanisms of different α-Ag 2 WO 4 crystals and their facet-dependent photocatalytic and antibacterial performances were explored in details. The combination of experimental and theoretical data revealed the presence of (110) and (011) planes with high surface energies together with the disappearance of faces related to the Ĳ010)/Ĳ010) planes in α-Ag 2 WO 4 crystals are key factors that can rationalize both the photocatalytic and antibacterial activities. The different activities may be attributed to the different number of unsaturated superficial Ag and W atoms capable of forming the main active adsorption sites. Finally, we discuss how knowledge of surface-specific properties can be utilized to design a number of crystal morphologies that may offer improved performance in various applications.

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“…This is the first example of such studies in scientific literature which has become a trending topic in current research because it is a novel example of dynamic single crystals where electron irradiation induces macroscopic motility and represent not only a visually appealing demonstration of their potential for bactericide and photoluminescent applications [201,202], but it also provides a unique opportunity to explore the mechanistic link between collective atomic processes and their consequences at a macroscopic level. This phenomenon has an electron-driven nature and the key difference in our approach is the use of an electron beam of TEM for growing Ag nanoparticles rather than for optical or electromagnetic erasing as it is the case in the plasmon effect.…”

Section: Working Examplesmentioning

confidence: 99%

Chemical structure and reactivity by means of quantum chemical topology analysis

Andrés

González-Navarrete

Safont

2015

Computational and Theoretical Chemistry

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Chemical structure and bonding are key features and concepts in chemical systems which are used in deriving structure-property relationships, and hence in predicting physical and chemical properties of compounds. Even though the contemporary high standards in determination, using both theoretical methods and experimental techniques, questions of chemical bonds as well as their evolution along a reaction pathway are still highly controversial. This paper presents a working methodology to determine the structure and chemical reactivity based on the quantum chemical topology analysis.QTAIM and ELF frameworks, based on the topological analysis of the electron density and the electron localization function, respectively, have been used. We have selected two examples studied by the present approach, to show its potential: (i) QTAIM study on the α -Ag 2 WO 4 , for the simulation of Ag nucleation and formation on α -Ag 2 WO 4 provoked in this crystal by the electron-beam irradiation. (ii) An ELF and Thom´s catastrophe theory study for the reaction pathway associated with the decomposition of stable planar hypercoordinate carbon species, CN 3 Mg 3 + .3Chemistry is the science of substances: their structure, their properties, and the reactions that change them into other substances, as Linus These procedures are hugely successful and they can be considered as an energeticsdriven approach to computational theoretical and chemistry. Then, this research field constitutes a central application of quantum chemistry to the study of stationary points of PESs [53] and the pathways connecting them. The shape of an adiabatic PES is conventionally regarded as a function of the nuclear skeleton, ignoring the wealth of information that can be provided by the total electronic charge density distribution ρ(r).The driving force for the nuclear motion is the potential, which arises from In this context, the electronic structure of a molecule is described in real space terms using topological analysis. Beyond the well-known approach of the QTAIM, which relies on the properties of the electron density ρ(r) when atoms interact, topological analysis of different scalar functions can be employed, such as the electron localization function (ELF) method [90][91][92][93]. Originally, ELF can be developed based on the conditional pair density [90] or can be derived from the kinetic energy density [94].In the latter context, ELF is seen as the scaled difference between the positive kinetic energy density and the von Weizsäcker term [95], whereby the scaling function is the 8 kinetic energy density of the homogeneous electron gas (Thomas-Fermi term) [96,97]. The pictures of a molecule as drawn by the QTAIM and ELF analysis are complementary. Thus, the QTAIM analysis is based on the topology of the electron density ρ(r), whereas the ELF analysis is based on the topology of the electron localization function using the conditional probability for the same spin pairs which is closely related to the local excess of kinetic energy due to the Paul...

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Toward an Understanding of the Growth of Ag Filaments on α-Ag₂WO₄ and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

Cited by 126 publications

References 77 publications

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

Facet-dependent photocatalytic and antibacterial properties of α-Ag₂WO₄crystals: combining experimental data and theoretical insights

Chemical structure and reactivity by means of quantum chemical topology analysis

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Toward an Understanding of the Growth of Ag Filaments on α-Ag2WO4 and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

Cited by 126 publications

References 77 publications

A novel ozone gas sensor based on one-dimensional (1D) α-Ag2WO4 nanostructures

A novel ozone gas sensor based on one-dimensional (1D) α-Ag2WO4 nanostructures

Facet-dependent photocatalytic and antibacterial properties of α-Ag2WO4crystals: combining experimental data and theoretical insights

Chemical structure and reactivity by means of quantum chemical topology analysis

Contact Info

Product

Resources

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Toward an Understanding of the Growth of Ag Filaments on α-Ag₂WO₄ and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

A novel ozone gas sensor based on one-dimensional (1D) α-Ag₂WO₄ nanostructures

Facet-dependent photocatalytic and antibacterial properties of α-Ag₂WO₄crystals: combining experimental data and theoretical insights