The role of subphase chemistry in controlling monolayer behaviour

Lendrum, Conrad; McGrath, Kathryn M.

doi:10.1016/j.jcis.2008.11.046

Cited by 10 publications

(28 citation statements)

References 29 publications

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“…More specifically, the role of the HCO 3 À ion may include: (1) participation in the hydrogen-bonding network, invoking enhanced condensation, (2) ion-pair formation to mitigate like-charge repulsion, and (3) Hofmeister related HCO 3 À /water interactions. [45,46] As shown in Fig. 3, the extent of the mean molecular-area shift appears to be concentration-dependent; it increases by 8-10 Å 2 /molecule for 0.1 M solution and by 18-20 Å 2 /molecule for 1 M solution.…”

Section: Resultsmentioning

confidence: 82%

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Wang

2017

Environ. Chem.

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Environmental context. Lipids released from lysis of phytoplankton cells are enriched in the sea surface microlayer. Such surface-active organics can be transferred through bursting bubbles to sea-spray aerosols where they can influence atmospheric chemistry. The results presented here suggest that phospholipids combine more readily with SO 4 2À than with Br À , leading to enrichment of organic-coated sulfate salts in marine aerosols.Abstract. Inorganic salts and organic matter are known to be present at higher levels in the sea surface microlayer and marine aerosols; however, the impact of common anions on their surface properties is not well understood. Here, a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayer was enriched with the sodium and ammonium salts of different anions (Br À , Cl À , NO 3 À , SO 4 2À , CH 3 COO À , and HCO 3 À ), and the effects on the surface properties of the monolayer were investigated. The monolayer phase behaviour and the structure of the lipid phases were studied by surface pressure-area (p-A) isotherms and infrared reflection-absorption spectroscopy (IRRAS). The presence of salts in the subphase was found to increase the surface pressure of the DPPC monolayer at a fixed area per molecule. The effect of the anions follows the order of the Hofmeister series. The higher concentration of salt solution caused the p-A isotherm to shift to larger area. The IRRAS spectra demonstrate that the ordering of the DPPC molecules in the liquid condensed phase remains essentially unaffected, even at higher electrolyte concentrations. DPPC molecules combined with SO 4 2À could be transferred from the ocean to sea spray aerosol. The present study finds that the anions have significant influence on the surface organisation and, consequently, the interfacial properties, of the surface-active species at the air-water interface, a finding that has further implications for atmospheric aerosol nucleation.

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Section: Resultsmentioning

confidence: 82%

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Wang

2017

Environ. Chem.

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“…Correspondingly, large differences exist also between the main monolayer characteristics of hydroxycarboxylic acids OH substituted in the midchain and C2 position in mesoscopic and microscopic scales using surface pressure-area per molecule (P-A) isotherms, Brewster angle microscopy and grazing incidence X-ray diffraction. 14,15 There is a general interest in understanding these systems because of the use of 2-hydroxycarboxylic acids in foods, 19,20 therapeutic and cosmetic products 21,22 and biomineralization 23,24 studies. It should be noted that 2-hydroxycarboxylic acids are chiral compounds.…”

Section: Introductionmentioning

confidence: 99%

Quantum chemical analysis of the thermodynamics of 2D cluster formation of 2-hydroxycarboxylic acids at the air/water interface

et al. 2013

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In the framework of the quantum chemical semiempirical PM3 method, the thermodynamic and structural parameters of formation and clusterization were calculated for 2-hydroxycarboxylic acids with the general formula C n H 2n+1 CHOHCOOH (n ¼ 5-15). Dimers and tetramers were formed on the basis of optimized monomer structures. It was shown that the alkyl chains in the considered associates orientate themselves with the following values of the tilt angles with respect to the pand q-directions of the interface: d ¼ 7.2-21.2 and 4 ¼ 9.8-21.1 depending on the monomer structure of the cluster.Comparing the Gibbs energy values of clusterization for small aggregates, a possible scheme of 2D clusterization is proposed based on the formation of linear aggregates constructed by dimers with 'parallel' orientation of the functional groups for 2-hydroxycarboxylic acid monomers with n # 16 carbon atoms in the alkyl chain. The following parameters of the unit cell for the most energetically preferred structure of 2D film 3 were found: a ¼ 4.85 Å, b ¼ 5.41 Å, and the angle between them q ¼ 95 . The molecular tilt angle of 2-hydroxycarboxylic acids with respect to the air/water interface was calculated to be t ¼ 21.7 . The spontaneous clusterization threshold is 14 carbon atoms in the 2-hydroxycarboxylic acid chain at the air/water interface for a monolayer built on the basis of monomer 3 in good agreement with the existing experimental data.

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“…This is evident in the observation of the presence of rigid domains and the large proportion of the monolayer existing in the untilted phase (∼80% of the monolayer) at all pressures investigated. The nature of this interfacial interaction may involve a cation-mediated hydrogen bonded network as previously proposed . Despite the strength of the interfacial interaction, the 2-HOA monolayers were very unstable on aqueous sodium bicarbonate subphases, exhibiting extensive slow collapse.…”

Section: Resultsmentioning

confidence: 56%

“…Comparing the behaviors probed in the pure acid, hydroxy acid (this work) and dihydroxy , acid systems on a pure water subphase illustrates the role the hydroxy group plays in defining monolayer phase behavior. The hydrophilic nature of the hydroxy group and its capacity for hydrogen bonding dominates the system, with the formation of a complex multiphase film, the specificities of which are temperature and pressure dependent.…”

Section: Resultsmentioning

confidence: 75%

“…2-HOA monolayer phase behavior was also investigated on a sodium bicarbonate subphase given the integral role that the bicarbonate anion plays in any aqueous-based calcium carbonate mineralization processes. Despite being anionic, a strong interaction is expected between the monolayer and the bicarbonate anion based on our previous investigation of octadecanoic acid/octadecanol monolayers . This enhanced interaction is also present when the monolayer is 2-HOA.…”

Section: Resultsmentioning

confidence: 89%

See 1 more Smart Citation

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

Lendrum

Ingham²,

Lin

et al. 2011

Langmuir

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2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.

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The role of subphase chemistry in controlling monolayer behaviour

Cited by 10 publications

References 29 publications

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Impact of anions on the surface organisation of lipid monolayers at the air–water interface

Quantum chemical analysis of the thermodynamics of 2D cluster formation of 2-hydroxycarboxylic acids at the air/water interface

Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

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