<p></p><p>The
exceptional nature of WO<sub>3-<i>x</i></sub> dots has inspired widespread
interests (<i>Science</i>, 2017, 358, 1192; <i>Adv. Mater.</i><i>,</i> 2016, 28, 10518),
but it is still a major challenge to synthesize high-quality WO<sub>3-<i>x</i></sub>
dots without using unstable reactants, expensive equipment, and complex
synthetic processes. Chemical tailoring of nanosheets is an essential way for
the synthesis of nanodots, however it is NOT applicable to exfoliate bulk WO<sub>3
</sub>due to its covalently-bound layers. As such, most of the synthesis rely
on a bottom-up method by using WCl<sub>6</sub> as a typical precursor but
water-free conditions are usually required due to the highly hydrolytic
property of WCl<sub>6</sub> (<i>J. Am. Chem. Soc.</i> 2005, 127, 15595). In
addition, to diminish the anisotropic growth during the synthesis, the surface
of the WO<sub>3-<i>x</i></sub> dots is usually anchored with aliphatic amines
or oleic acid as surfactant/template, which leads to SLOW Faradic
electrochemistry (<i>Adv. Mater. </i>2014, 26, 4260). Along these lines, it is of
both fundamental and technical importance to overcome these deficiencies in the
synthesis of high-quality WO<sub>3-<i>x</i></sub> dots. </p>
<p>In
this work, we report the synthesis of WO<sub>3-<i>x</i></sub>
dots by
a facile exfoliation of bulk WS<sub>2</sub> instead of bulk WO<sub>3</sub> followed
by a mild chemical conversion. The WO<sub>3-<i>x</i></sub>
dots were not only ligand-FREE and highly water-dispersible but also had tunable
oxygen-vacancies, ready for a varity of high-demanding applications. As an example,
the WO<sub>3-<i>x</i> </sub>dots were emerged as a new generation of coreactants
for the electrochemiluminescence (ECL) of Ru(bpy)<sub>3</sub><sup>2+</sup> with
a tremendous enhancement factor up to 500-fold, owing
to the unique electrochemical and catalytic properties. More
importantly, compared to the commonly used tripropylamine (TPA) coreactant in the clinics, the WO<sub>3-<i>x</i></sub>
dots displayed a factor of ca. 300 less ANIMAL toxicity. Along these lines, the
enormous potential of WO<sub>3-<i>x</i></sub> dots as ECL coreactants in replacing TPA for clinic diagnosis
was further exemplified by cytosensing circulating tumor cells with a uncompromised performance.
This work would not only open a new way to synthesize WO<sub>3-<i>x</i> </sub>dots
with superior properties but also stimulate an emerging application in clinic
ECL diagnosis as coreactants with uncompromised high performance and
unprecedented low toxicity.</p><br><p></p>
Effect of Mo Dispersion on the Catalytic Properties and Stability of Mo–Fe Catalysts for the Partial Oxidation of Methanol
