Synthesis and characterization of two charge-transfer salts based on Keggin-type polyoxometalates and morpholinebiguanide

Evaluation of reduced-graphene-oxide-supported gold nanoparticles as catalytic system for electroreduction of oxygen in alkaline electrolyte

“…A low-energy broad tail extending from 500 to well-beyond 800 nm (Fig. 4b) is consistent with the existence of the inter-valence charge-transfer between Mo(V) and Mo(VI) centers [46][47][48][49][50]. Then addition of the HAuCl 4 precursor to the partiallyreduced mixed-valence Mo(VI,V) heteropolyblue solution has largely depleted the portion of spectrum assigned as the inter-valence charge-transfer ( Fig.…”

“…PMo 12 O 40 and rGO results in a rapid change of color from brown (Fig.4a, dotted line) to dark blue (Fig.4b, dashed line) thus indicating formation of the heteropolyblue form of phosphododecamolybdate. A low-energy broad tail extending from 500 to well-beyond 800 nm (Fig.4b) is consistent with the existence of the inter-valence charge-transfer between Mo(V) and Mo(VI) centers[46][47][48][49][50]. Then addition of the HAuCl 4 precursor to the partiallyreduced mixed-valence Mo(VI,V) heteropolyblue solution has largely depleted the portion of spectrum assigned as the inter-valence charge-transfer (Fig.4c, solid line).…”

Photomechanical photochromism in a cetyltrimethylammonium isopolytungstate

“…The coloration mechanism of surfactant-polyoxometalate materials is oen said to involve the creation of a chargetransfer complex via proton-transfer from hydroxyl, 19 amine, carboxylic 17 or other suitable proton-transfer groups within the organic species, to the activated bridging-oxygen (O b ) neighboring the photo-reduced W V site (which stabilizes the colored state). 14,17,32,33 This deprotonation-mediated mechanism allows for a reversible back-reaction where the POM-attached proton simply transfers back to the organic during bleaching by atmospheric O 2 . 34 However, possibly due to disorder within the hydrophobic-hydrophilic interfaces or oxidative side-reactions involving the organic matrix, 20,33 these systems regularly suffer from decreased switchability upon each iteration of the photochromic cycle and hence cannot be classied as completely reversible.…”

“…14,17,32,33 This deprotonation-mediated mechanism allows for a reversible back-reaction where the POM-attached proton simply transfers back to the organic during bleaching by atmospheric O 2 . 34 However, possibly due to disorder within the hydrophobic-hydrophilic interfaces or oxidative side-reactions involving the organic matrix, 20,33 these systems regularly suffer from decreased switchability upon each iteration of the photochromic cycle and hence cannot be classied as completely reversible. 15,18,35 There is an incomplete understanding of the redox mechanisms associated with the organic-POM photochromic processes, [36][37][38] especially for compounds based on quaternary ammonium surfactants.…”

X‐ray‐induced reduction of a surfactant/polyoxotungstate hybrid compound

“…For example, the measurement of the M n + /M ( n ‐1)+ ratio (where M = W, Mo, or V) post UV photoreduction in group V and VI metal oxide‐based photochromic and photocatalytic materials provides a means to determine the extent of the reaction. Unfortunately, XPS‐derived determination of this ratio may return inaccurate results, because of additional photoreduction by the X‐rays . To our knowledge, no quantitative investigation has been reported examining these processes in group V and VI transition‐metal‐oxide inorganic‐organic hybrid materials.…”