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(i). Tungstates:

1.  Single-crystalline BaWO 4 and BaCrO 4 nanorods  (100 and 200 nm diameter-sized examples) were controllably prepared using a simple, room temperature approach, based on the use of porous alumina template membranes.  Aligned BaWO 4 and BaCrO 4 nanorod arrays  could be obtained by dissolving the template. 

Ref.:  J. Am. Chem. Soc.,  v.126, 15245 (2004).

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2.  Polycrystalline, multiferroic MnWO 4 nanowires and nanowire arrays  with controllable chemical composition and morphology, using a modified template-directed methodology under ambient room-temperature conditions. We were able to synthesize nanowires measuring 55 ± 10 nm, 100 ± 20 nm, and 260 ± 40 nm in diameter, respectively, with lengths ranging in the microns. 

Ref.:  J. Solid State Chem.,  v.181, 1539 (2008) [invited].

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3.  Single-crystalline alkaline-earth metal tungstates AWO 4 (A = Ca, Sr, Ba) nanorods, as well as the corresponding series of their crystalline solid-solution analogues, Sr 1-xCa xWO 4 and Ba 1-xSr xWO 4 (0 < x < 1), with varying controllable sizes.  As-obtained photoluminescent lifetimes and quantum yields suggest that these nanoscale materials are comparable in optical behavior to those of bulk. The composition-modulated luminescence properties over several distinctive series of as-prepared solid-solution nanorods of alkaline-earth metal tungstates provide the fundamental basis for a more thorough investigation and understanding of their optical and optoelectronic properties, which may eventually lead to the rational incorporation of these materials into functional nanoscale devices. 

Ref.:  Chem. Mater.,  v.20, 5500 (2008).

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4.  Uniform Mn-doped alkaline-earth metal tungstate, AWO 4 (A = Ca, Sr, Ba), nanorods  of reproducible size, shape, and composition have been methodically prepared using a modified template-directed methodology under ambient, room-temperature conditions. The dopant ion distribution within the nanostructures does not appear to adversely affect either the structural or crystalline integrity of our as-prepared compounds, as determined by microscopy and diffraction studies. What is much more important is the fact that the presence of Mn +2 not only substantially increases the photoluminescent potential of a pristine tungstate material but also reinforces its versatility by adding a desirable magnetic component to its repertoire of properties. In so doing, we have created multifunctional one-dimensional nanorods with exciting opto-magnetic behavior, which should become important for the future incorporation of these materials into functional nanoscale devices, with various potential applications in a number of diverse fields. 

Ref.:  J. Phys. Chem. Cv.112, 14816 (2008).


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5. Synchrotron-based scanning hard X-ray microscopy (SHXM) was used to extract localized chemical and structural information within a system of model alkaline-earth-metal tungstate nanorods, characterized by multiple chemical configurations. Specifically, we have highlighted the practical ability of SHXM to probe chemically distinctive nanoscale species, i.e. (i) chemically-doped versus (ii) solid-solution-state nanorods of comparable dimension, synthesized using a template-directed method under ambient conditions . Indeed, we show that SHXM can be used to map out elemental distributions within individual anisotropic nanorods with nanoscale resolution, coupled with chemical sensitivity and specificity. Complementary electrochemical results suggest the possibility of using these nanorods as support materials for electro-oxidation reactions within an acidic electrolyte medium. Our structural and chemical composition results have been corroborated using parallel lines of inquiry involving scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. These measurements confirmed the relatively even and uniform distribution of the expected, individual elements within all of the nanorod samples tested.

Ref..: J. Phys. Chem. C , v.123 , 17185 (2019).

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