Cs0.3WO3 Nanofibers by Hydrothermal Method from Ammonium Paratungstate

Nano-tungsten bronze compounds with general formula of MxWO3 (M = Na+, K+, Cs+, etc., 0 < x < 1) have received widespread attention due to their high transmittance in visible region and excellent shielding performance in near infrared (NIR) region.

Previous studies have found that MxWO3 has much stronger NIR absorption performance than commercial materials, such as FTO and ITO. Hence, it can act as an excellent candidate for NIR absorbents. Furthermore, with the rapid development of nanotechnology, nanofibers, as an important 1D nanomaterial, have very high specific surface area due to their small diameters. These unique characteristics, combined with the properties of the material itself, endow the nanofibers many novel physical and chemical properties, and make them versatile to have a wide variety of application. Thus, it is believed that nano-MxWO3 with high aspect ratio is of interest.

Thus, a simple hydrothermal method is developed to synthesize 1D CsxWO3 nanofibers with controlled 1D morphology and great single crystalline nature along the fiber axis. The synthesis process is as below.

Materials: Ammonium paratungstate (APT), cesium chloride (CsCl ≥ 99%), terpineol (95%), ethanol (EtOH, ≥ 99.7%), esopropyl alcohol (IPA, ≥ 99.7%), thiourea (H2NCSNH2, AR, ≥ 99%), 1-Octadecene (1-OA, 90%), hydrochloric acid (HCl), double distilled water (H2O). All the chemicals were of reagent grade and used as purchased without further treatment.

Firstly, the precursor solution was prepared by dissolving 0.1 mmol APT, 0.1 mmol thiourea and 0.5 mmol CsCl in 20 mL H2O. And the PH of the mixed solution was adjusted to 3 using HCl. Secondly, a certain amount of ethanol (EtOH, 1 mL), isopropyl alcohol (IPA, 1 mL), terpineol (TP, 1 mL) and 1-octadecene (1-OA, 1 mL) was added into the above mixture, respectively. Thirdly, the obtained solution was transferred into a Teflon-lined autoclave of 50 mL internal volume, followed by heat-treatment at 220 °C for 24 h. Finally, the blue products were centrifuged to separate solids, washed three times with H2O and EtOH, respectively, and vacuum dried at 60 °C overnight. The obtained samples synthesized by the above reducing agents are simply represented by sample-EtOH, sample-IPA, sample-TP and sample-1-OA, respectively.

In conclusion, Cs0.3WO3 nanofibers with the mean diameter of less than 100 nm and the average length of more than 3 μm have been successfully synthesized via a facile hydrothermal approach. The SEM results show that the aspect ratio of the nanofibers can be adjusted by changing the type of reducing agents. broad absorption band at 780–20000 nm.

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