A Simple Hydrothermal Method for the Large‐Scale Synthesis of Single‐Crystal Potassium Tungsten Bronze Nanowires

Abstract

The large-scale synthesis of single-crystal K(x)WO(3) tungsten bronze nanowires has been successfully realized by a hydrothermal method under mild conditions. Uniform K(0.33)WO(3) nanowires with diameters of 5-25 nm and lengths of up to several micrometers are obtained. It is found that the morphology and crystallographic forms of the final products are strongly dependent on the sulfate and citric acid, which may act as structure-directing and soft-reducing agent, respectively. Some other influential factors on the growth of tungsten bronze nanowires, such as temperature and reaction time, are also discussed. It is worth noting that other alkali metal tungsten bronzes such as (NH(4))(x)WO(3), Rb(x)WO(3), and Cs(x)WO(3) could also be selectively synthesized by a similar route. Thus, this novel and efficient method could provide a potential mild route to selectively synthesize various tungsten bronze on-dimensional nanomaterials.

Potassium Tungsten Bronze Nanowires: Polarized Micro‐Raman Scattering of Individual Nanowires and Electron Field Emission from Nanowire Films

“…The intensity of W=O stretching bands is about five times more intense in the Z(YY)Z polarization than that in the Z(XX)Z polarization. The apparent polarization dependence of Raman modes observed here is very similar with the results of the single crystal hexatungstates [21] and effectively demonstrates the monocrystalline of our potassium tungsten bronze nanowires. To further determine whether the whole nanowires are single crystalline or not, the polarized Raman mapping was performed.…”

“…As shown in Figure 3c, there are three groups of Raman peaks in the regions of 900-980, 600-850, and 200-400 cm -1 , which could be assigned to W=O stretching, O-W-O stretching and O-W-O bending modes, respectively. [21] The appearance of the two Raman bands in the 900-980 cm -1 region may indicate the presence of terminal W=O bonds, which may support our previous speculation that the nanowires contain W atom vacancies. [21] According to the relationship between the wave number (m) of a Raman-active W=O stretching mode with bond length (d): m = 25823 exp(-1.902d), [22] the lengths of the corresponding W=O bonds were estimated to be 1.728 and 1.764 Å.…”

“…[21] The appearance of the two Raman bands in the 900-980 cm -1 region may indicate the presence of terminal W=O bonds, which may support our previous speculation that the nanowires contain W atom vacancies. [21] According to the relationship between the wave number (m) of a Raman-active W=O stretching mode with bond length (d): m = 25823 exp(-1.902d), [22] the lengths of the corresponding W=O bonds were estimated to be 1.728 and 1.764 Å. Moreover, it is worth to note the bandwidth of the Raman mode of around 960 cm -1 is quite small (ca.…”

“…Another possible channel which might have contributed to the tungsten bronze vapor is the reaction between W and KOH, as proposed earlier. [21] Field emission measurements were performed using a diode structure with indium tin oxide (ITO)-coated quartz as the anode and tungsten foil with tungsten bronze nanowires as the cathode. The inter-electrode, i.e., cathode to anode distance (D), was maintained at 100 lm and the experiments were conducted at 5.1 × 10 -7 mbar (around 3.8 × 10 -7 Torr).…”

Directly Grown K0.33WO3 Nanosheet Film Electrode for Fast Direct Electron Transfer of Protein

“…[37] Compared with traditional metal oxide nanostructures (e.g. ZnO, SnO 2 ), [48] the resistivity of the K 0.33 WO 3 nanosheet is significantly lower (five orders of magnitude difference).…”