Multipurpose Solar Photoelectrochemical Hybrid Multilayer Films Based on Porphyrin and Preyssler Type Polyoxometalates for Solar Cell and Ag Nanomaterial Synthesis
Authors: Ahmed Iftikhar , Ruhlmann Laurent , Irshad Muhammad Sultan , Hualong. Xu 
Published: July 2022

Multilayer films with electrostatic interaction between Preyssler,s Polyanions (NH4)14[NaP5W30O110]14-
.31H2O and tetracationic free base porphyrin [H2TN+(Me)3PyP]4+ have been alternately deposited on quartz and ITO substrates. and characterized by UV-visible absorption spectroscopy to follow the successive deposition of multilayer film. Solution phase interaction of both components revealed the stiochiometric ratio of the electrostatic complex formed . The morphology and composition of films were studied by atomic force microscopy and X-ray photoelectron spectroscopy (XPS ) .While permeability to cations in aqueous media and redox behavior were studied by cyclic voltametry . The solar photoctalytic activity of hybrid films is identified by TEM images obtained after heterogeneous aqueous photoreduction of Ag2SO4(aq) and KAuCl4 (aq) to yield diversified nanostructures . The study is first and initial report on preyssler type polyanions and porphyrin based heterogenous photocatalysis that provide a green, solar and multiple applications for precious metal recovery as nanoparticle ,sustainable wastewater purification and solar photocurrent generation.

Polyoxometalates (POMs) are metal−oxygen framework of early metal elements in their highest oxidation state , able to undergo reversible, stepwise, multielectron-transfer reactions, which are the basis for many catalytic processes[1].These polyanions clusters exhibit applications in catalysis, medicine, materials science [2]. They offer effective photocatalytic properties in oxidation and reduction processes. On photolysis, the high oxidizing ability of excited POMs can lead to the degradation of a variety of organic compounds such as pollutants, leading to a process for water purification [3]. In the presence of a sacrificial electron donor , their photolysis lead to the formation of reduced POMs which can in turn reduce metallic ions. It could be a good alternative for precious metals recovery or synthesis of metal nanoparticles. [4,5]. However, polyoxometalates absorb in the uv part of spectrum, thus they require UV excitation, which cease its large-scale environmental application. One of obvious strategy is to couple it with some chromophore group which can be sensitized by visible light. Metal porphyrins are attractive components in materials because of their appealing chemical and photochemical properties: high stability, intense visible absorption bands, long-lived excited states, and tunability by chemical derivatization [2].

Figure 1.1
R.H.S. Representation of the porphyrin used 5, 10, 15, 20-Tetrakis (4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate), namely [H2TN+(Me)3PyP]4+) used with the Preyssler type (NH4)14[NaP5W30O110]14-
.31H2O . L.H.S. UV-visible record on quartz and ITO shows layer by layer absorbance.

Formation of Multilayer Films :H2TN+(Me)3PyP4+] / [(NH4)14[NaP5W30O110]14- .31H2O ]

The alternate deposition of positively charged porphyrin, H2TN+(Me)3PyP4+, and negatively charged [NaP5W30O110]14-on slides of quartz and Indium tin Oxide (ITO) lectrodes by layer-by-layer were performed.

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