Photochromism of Novel Molybdate/Alkylamine Composite Thin Films

Abstract

Novel inorganic/organic composite films of molybdates with photochromic properties have been prepared by self-assembly using alkylammonium ions as a supramolecular template. Both 1-hexadecylammonium/polyoxomolybdate (C16-Mo) and 1-octadecylammonium/polyoxomolybdate (C18-Mo) composite films have been successfully fabricated. The elemental analysis and thermal gravimetric analysis show that the main product in the C16-Mo film was (C16H33NH3)4Mo8O26. The X-ray diffraction (XRD) results indicate that the composite films were lamellar in nature. The IR, Raman and X-ray photoelectron spectroscopy (XPS) results show that the polyoxomolybdate anions present as MoO6 octahedra and that the Mo species exists as Mo6+ in the freshly prepared films. The alkyl chains in the 1-hexadecylammonium chains were linear and the alkyl groups are an all-trans configuration. Upon UV irradiation of the C16-Mo films, some Mo6+ was reduced to Mo5+, some -NH3+ became -NH2 with a concomitant increase in the concentration of -OH groups on the molybdate moieties, and the films were colored. Thus, the photochromism of the films involves the reduction of Mo6+ to Mo5+, coupled with a proton transfer from 1-hexadecylammonium ions to an oxygen atom at the Mo site. In contrast to thin films of transition-metal oxides, which all show photochromism in the blue region of the electromagnetic spectrum, these composite films show photochromism in the violet region with the greatest absorbance change at 472 nm.

One-dimensional growth of MoOx-based organic–inorganic hybrid nanowires with tunable photochromic properties

“…The MoO x -based organic-inorganic hybrid is a class of promising photochromic materials with high photosensitivity and potential applications in sensing, optical data storage and cosmetics. 36,[53][54][55] Herein, we find that the photochromic properties of our MoO x /amine nanostructures are significantly associated with their structures and hybrid components. With obvious color change from white to yellow, the Mo 3 O 10 (C 6 H 8 N) 2 $2H 2 O nanowires clearly display a new band peaking around 440 nm after UV excitation at 254 nm (Fig.…”

Synthesis, structure and photochromic properties of a novel 1,6-hexanediamine trimolybdate supramolecular compound

“…Yamase [11] studied photochromic properties of the single crystal alkylammonium polyoxomolybdates and proposed a photochromic mechanism which is widely accepted in this field [22][23][24][25]. According to Yamase's photochromic mechanism, a possible HDAMo's photochromic mechanism can be illustrated (see Scheme 1).…”

Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and Electrochromism

“…[37][38][39][40] [EuP 5 W 30 O 110 ] 12À (abbreviated as EPW) is the europiumexchanged derivative of [NaP 5 W 30 O 110 ] 14À , the so-called Preyssler anion (Scheme 1). [41] The luminescence properties of POMs containing lanthanide elements, such as Eu 3þ , Tb 3þ , Sm 3þ and Dy 3þ , have attracted much attention.…”