Raman study of the interactions between highly ordered pyrolytic graphite (HOPG) and polyoxometalates: The effects of acid concentration

Abstract

Heteropoly acids (HPAs) found wide applications, such as in catalysis, energy conversion and storage, analytical chemistry, clinical medicine, materials science and others, but because of their low surface area and high solubility in water their use is limited. One of the possible ways to overcome these obstacles is to use height specific surface area support for HPAs, such as carbon nanomaterials. Raman spectroscopy was applied for studying study interaction between HPAs and highly ordered pyrolytic graphite (HOPG) as a model of a support. HOPG was exposed to two different HPAs: 12-tungstophosphoric acid and 12-molybodphosphoric acid, at different concentrations. It was noticed that 12-molybodphosphoric acid has stronger effects on HOPG structure causing a weak doping and increase of structural disorder. It is supposed that HOPG interacts with especially external oxygen atoms of 12-molybodphosphoric acid. Atomic force microscopy showed that surface roughness of HOPG treated with 12-molybodphosphoric acid increases with increase of acid concentration, while in the case of HOPG exposed to 12-tungstophosphoric acid the surface roughness is not concentration dependent. The growth trend in measured surface roughness (RMS) is in the agreement with the changes in the intensity ratio ID/IG obtained from Raman spectra of HOPG samples treated with 12-molybdophosphoric acid. [Projekat Ministarstva nauke Republike Srbije, br. 172003 i br. 172043]

Functionalized Graphene–Polyoxometalate Nanodots Assembly as “Organic–Inorganic” Hybrid Supercapacitors and Insights into Electrode/Electrolyte Interfacial Processes

“…In general, all absorption spectral bands arising in UV-Vis range of the electronic spectra of heteropoly compounds containing Keggin polyanion [ [55,56]. Raman spectroscopy is widely used non-destructive technique for the characterization of carbon-based materials [57] and POMs [58][59][60], M = Mo and W since it is highly sensitive to local structure and lattice vibrational bonding configurations within molecules and their interactions with graphene. Keggin-type HPAs are formed by assembling three MO 6 octahedra by edge-sharing oxygen atoms (M-O c -M) to form M 3 O 13 sets, which further condense by sharing corner oxygen atoms (M-O b -M) around a central atom (P or Si) to form a cage.…”

Increasing Volume in Conjugated Polymers to Facilitate Electrical Doping with Phosphomolybdic Acid

“…While weak interactions between PMA and solvent molecules may explain these variations, the data confirm the presence of all four peaks of pristine PMA nanoclusters. 29,31,32 This implies that, within the resolution of the FTIR tool, the Keggin structure of PMA appears to be preserved after solvation in acetonitrile or ethanol. That is, MoO 3 subunits do not detach from the phosphate ion.…”

Self-assembly of carbon based nanoparticles films by Langmuir-Blodgett method

“…Soluble fragments of the graphene could be prepared in the laboratory by chemical modification of the graphite. [108][109][110][111][112][113][114] The produced material with circular graphene layers, which has the thickness of the 0.53 nm, is soluble in water, dichloroethane, tetrachloromethane and tetrahydrofuran (THF). Good solvents for graphene such as CPO, ethanol, chloroform and acetone are characterized by using Hildebrand solubility parameters: δD ∼(18 MPa) 1/2 , δT ∼(23 MPa) 1/2 , δP ∼(9.3 MPa) 1/2 and δH ∼(7.7 MPa) 1/2 .…”