Novel hybrid based on a poly[Ni( salen )] film and WO 3 nanoparticles with electrochromic properties

Abstract

The strategy of combining electroactive polymers and inorganic nanomaterials has been widely explored in recent years in order to improve some of their properties, namely electrocatalysis and electrochromism. This report focuses on a new composite prepared through the electropolymerization of the transition metal complex ], designated as [1], in the presence of WO3 nanoparticles (NPs) and its electrochromic (EC) performance. The WO3 NPs were prepared using tungsten metal powder; their characterization indicated quasi-spherical morphology, high crystallinity and particle sizes in the range 30 -40 nm. The nanocomposite WO3@poly[1] films displayed similar electrochemical responses to those of pristine poly[1] films in LiClO4/CH3CN, but higher electroactive surface coverages, an advantage of NPs incorporation in the nanocomposite.The presence of the WO3 NPs in the poly[1] matrix was assessed by X-ray photoelectron spectroscopy and scanning electronic microscopy. The nanocomposite presented similar electronic spectra to those of poly [1], indicating that the electronic structure of the pristine film is maintained in the nanocomposite, but exhibited lower ε-values for bands associated with charge transfer transitions for high oxidised states, revealing an enhanced stability towards ligand over-oxidation.The WO3@poly[1] nanocomposite showed more favourable EC properties in LiClO4/CH3CN than the pristine film. For typical coverages (Γ = 0.06-0.10 µmol cm -2 ) the composite showed lower switching times (τ = 1.3 -3.6 s), higher optical contrast (∆T ≈ 31 %, an improvement of ca. 40 %) and better colouration efficiencies (in the range η = 104 -115 cm 2 C -1 , improvement of ca. 13 -22 %).(cathodic EC material) [23,24]. These properties make it an attractive "partner" for CPs (or other electroactive polymers) in hybrid materials for EC applications. In fact, several EC nanocomposites based in the incorporation of WO3 nanostructures into CP matrices, such as polyaniline (PANI) [23][24][25][26][27] and poly(3,4-ethylenedioxythiophene) (PEDOT)[28], have already been reported, exploiting the complementary EC attributes of WO3 and CPs. In general, CPs exhibit interesting optical properties, with rich colour changes due to their multiple redox states, but have low colour switching rates due to the slow transport of charge balancing counter ions ("dopants") into the polymer layer. On the other hand, metal oxide nanostructures have high surface-to-volume ratio and organized structures that facilitate ion/electron intercalation processes and promote switching reversibility [10,29]. Thus, the resultant nanocomposites promise the advantage of synergistic influence of the WO3 on the EC properties of conducting polymer, presenting improved EC properties with more satisfactory switching speeds and colouration efficiencies [23,25,27].The poly[M(salen)]-type films (M ≡ transition metal) are a particular class of electroactive metallopolymers, derived from metal salen complexes, recently studied by their interesting EC behavior [30,31]. Th...

Solution-Processed Interfacial PEDOT:PSS Assembly into Porous Tungsten Molybdenum Oxide Nanocomposite Films for Electrochromic Applications

“…As shown in Figure , the optical contrast of the W 0.71 Mo 0.29 O 3 /PEDOT:PSS electrode (Δ T = 65.1%) is significantly higher than that of W 0.71 Mo 0.29 O 3 (Δ T = 54.5%) and PEDOT:PSS (Δ T = 51.4%) electrodes. It should be noted that the optical contrast of the W 0.71 Mo 0.29 O 3 /PEDOT:PSS electrode is even higher than those of other previously reported WO 3 -based inorganic/polymer hybrid electrodes. − This confirms that the introduction of the PEDOT:PSS promotes the charge-transfer efficiency by providing more active sites of W 0.71 Mo 0.29 O 3 for Li + ions to interact with, while also speeding up the charge insertion/extraction between the W 0.71 Mo 0.29 O 3 layers and electrolyte ions. This culminates in a hybrid electrode that provides faster kinetics and higher optical contrast compared with a W 0.71 Mo 0.29 O 3 electrode.…”

A black electrochromic device based on a CuI film for energy-efficient applications

“…The mechanism responsible for electrochromism in metal-organic electrochromic materials is the metal-ligand charge transfer (MLCT), [16][17][18][19] and their optical modulation ability can be adjusted through the exchange of functional groups. Currently, the most commonly used ligands are pyridines, [20][21][22] phthalocyanine 23,24 and salen, [25][26][27] some of which show undesirable properties such as unwanted film forming ability and brightness of color. A series of electrochromic materials based on 1,3,5-tris(4-(2,2 0 :6 0 ,2 00 -terpyridyl)phenyl)benzene or 1,3,5-tris((2,2 0 :6 0 ,2 00 -terpyridyl)ethynyl)benzene and Fe 2+ or Co 2+ was synthesized by Takada, 28 and the devices fabricated using these materials displayed two different colors under different stimuli.…”

Electrochemistry and Electrochromic Performance of a Metallopolymer Formed by Electropolymerization of a Fe(II) Complex with a Triphenylamine‐Hydrazone Ligand

“…Complexes of transition metal ions found applications in many research areas such as medicine [15,16] or catalysis [17–19] and they are also important active materials for electronic applications [20–25] . The application as electrochromic materials arises from an intense coloration due to possible d‐d or charge transfer transitions, including metal‐to‐ligand charge transfer (MLCT), ligand‐to‐metal‐ion (LMCT), or interval charge transfer (IVCT) and well‐defined redox properties.…”