Atomic force microscopy and X-ray reflectivity studies of cobalt stearate Langmuir−Blodgett (LB) films (CoStp) deposited from a preformed bulk sample on quartz substrates showed formation of a Volmer−Weber type monolayer but no multilayers as compared to the excellent multilayers of cobalt stearate films (CoStn) deposited at the air/water interface by the usual LB technique, in spite of both showing bidentate bridging type coordination of cobalt ions with the carboxylate group. The difference is attributed to existence of different headgroup conformers, observed from Fourier transform infrared (FTIR) studies. The CoStp films had a higher energy ‘boat’ conformation with linear O−Co−O linkage, whereas CoStn formed a low energy conformer with a bent O−Co−O configuration (bond angle of 105°). Present results support the necessity of bidentate bridging coordination in multilayer deposition, but rejects its sufficiency by bringing out the crucial role played by air/water interface. Differences in surface pressure−molecular area isotherms and hydrocarbon tail−tail interactions (evident from FTIR spectra) of the films support the above statement. Methyl−methyl interactions observed in CoStn samples suggest hierarchy of supramolecular chemistry at the air/water interface in tuning the C−O−Co bond angle essential to satisfy the wetting condition with the substrate and subsequently form LB multilayers.

Chemistry at Air/Water Interface versus Reaction in a Flask: Tuning Molecular Conformation in Thin Films / Smita, Mukherjee; Alokmay, Datta; Angelo, Giglia; Nicola, Mahne; Nannarone, Stefano. - In: LANGMUIR. - ISSN 0743-7463. - STAMPA. - 25:(2009), pp. 3519-3528. [10.1021/la8023502]

Chemistry at Air/Water Interface versus Reaction in a Flask: Tuning Molecular Conformation in Thin Films

NANNARONE, Stefano
2009

Abstract

Atomic force microscopy and X-ray reflectivity studies of cobalt stearate Langmuir−Blodgett (LB) films (CoStp) deposited from a preformed bulk sample on quartz substrates showed formation of a Volmer−Weber type monolayer but no multilayers as compared to the excellent multilayers of cobalt stearate films (CoStn) deposited at the air/water interface by the usual LB technique, in spite of both showing bidentate bridging type coordination of cobalt ions with the carboxylate group. The difference is attributed to existence of different headgroup conformers, observed from Fourier transform infrared (FTIR) studies. The CoStp films had a higher energy ‘boat’ conformation with linear O−Co−O linkage, whereas CoStn formed a low energy conformer with a bent O−Co−O configuration (bond angle of 105°). Present results support the necessity of bidentate bridging coordination in multilayer deposition, but rejects its sufficiency by bringing out the crucial role played by air/water interface. Differences in surface pressure−molecular area isotherms and hydrocarbon tail−tail interactions (evident from FTIR spectra) of the films support the above statement. Methyl−methyl interactions observed in CoStn samples suggest hierarchy of supramolecular chemistry at the air/water interface in tuning the C−O−Co bond angle essential to satisfy the wetting condition with the substrate and subsequently form LB multilayers.
2009
25
3519
3528
Chemistry at Air/Water Interface versus Reaction in a Flask: Tuning Molecular Conformation in Thin Films / Smita, Mukherjee; Alokmay, Datta; Angelo, Giglia; Nicola, Mahne; Nannarone, Stefano. - In: LANGMUIR. - ISSN 0743-7463. - STAMPA. - 25:(2009), pp. 3519-3528. [10.1021/la8023502]
Smita, Mukherjee; Alokmay, Datta; Angelo, Giglia; Nicola, Mahne; Nannarone, Stefano
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/719243
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