New method for determination of surface pKa using second harmonic generation

Zhao, Xiaolin; Ong, Shaowei; Wang, Hongfei; Eisenthal, Kenneth B.

doi:10.1016/0009-2614(93)90082-c

Cited by 147 publications

(286 citation statements)

References 15 publications

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“…9 It is a useful technique to detect and study molecules at a surface that do not make a large (2) contribution to the SHG signal, which is the case with many chemical species. The (3) method has been used successfully in studies of surface potential measurements and pK a determinations for various charged interfaces, such as lipid monolayers at the air-water interface and the silica-water interface.…”

Section: Theorymentioning

confidence: 99%

Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation

2008

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The protonation reaction of the carboxyl (-COOH) functional group fixed at the surface of polystyrene carboxylate (PSC) microspheres, with a radius of 457 ( 14 nm, dispersed in aqueous medium has been studied using the nonlinear optical method of second harmonic generation (SHG). We have demonstrated that the " (3) method," along with the use of the Gouy-Chapman model describing the surface potential, can be used to determine the pK a of carboxyl groups at the particle-liquid interface. A surface pK a of 5.4 ( 0.3 has been determined for the PSC colloidal particles, which corresponds to a decrease in the acidity; that is, K a is a factor of 4 smaller at the interface than that of long chain carboxyl acids in bulk aqueous solution.

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Section: Theorymentioning

confidence: 99%

Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation

2008

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“…12 In effect, the total SH light generated is due to both a monomolecular surface contribution ( 2 part) and that due to the polarization of water molecules by the electric field of the charged surface ( 3 part). The electric potential of a charged * Author to whom correspondence should be addressed.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…At pH 7, the number density of negative surface charges for both the silica and the supported lipid bilayers used in our experiments (4:1 DOPC:DOPG) is expected to be on the order of 10 13 /cm 2 . 12,15 The decay of the surface potential to the bulk value is dependent on the surface potential and Debye length, κ, and occurs over a distance of several to hundreds of nanometers, depending on the bulk electrolyte concentration.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Protein Adsorption at Interfaces Detected by Second Harmonic Generation

2000

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We show that second harmonic (SH) spectroscopy, an intrinsically surface-selective technique, can be used to monitor protein (cytochrome c) adsorption to silica surfaces and negatively charged supported phospholipid bilayers. The origin of the SH signal is due to the effect of the adsorbed protein on the water molecules polarized near the charged interface. Although the protein does not contribute its own SH signal, its binding to the glass surface or the membrane reduces the polarization of the interfacial water molecules and this effect is proportional to the adsorbed protein concentration and can be monitored with high precision, in real time. The free energy of adsorption (∆G ads ) -11.8 kcal/mol) of cytochrome c to glass was determined from an adsorption isotherm measurement of the SH signal as a function of the bulk protein concentration. A detection sensitivity of 0.1 pmol/cm 2 of adsorbed cytochrome c protein is readily achieved.

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“…[17][18] To describe how SHG is used to investigate the electrostatics of charged microscopic particles, we will briefly discuss how SHG has been used to study the electrostatic properties of the planar fused silica/water interface 19 and that of charged monolayers at air/water interfaces. 20,21 In these studies it was discovered that there were two contributions to the SHG signal from charged interfaces, namely, the second-order (2) and thirdorder (3) contributions. The (2) contribution is from the molecules at the interface, which are oriented, and can therefore give an electric dipole allowed SHG signal.…”

Section: Introductionmentioning

confidence: 99%

New Method for Determination of Surface Potential of Microscopic Particles by Second Harmonic Generation

1998

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A new noninvasive method for determining the surface electrostatic potential and surface charge density of microscopic particles using second harmonic generation (SHG) is described. The surface electrostatic properties of 1.05 µm polystyrene sulfate spheres in aqueous solution and that of 0.22 µm oil droplets in aqueous emulsions are obtained. Comparisons of the surface potentials obtained from SHG with the zeta potential obtained from electrophoresis are in excellent agreement with theoretical predictions.

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New method for determination of surface pKa using second harmonic generation

Cited by 147 publications

References 15 publications

Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation

Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation

Protein Adsorption at Interfaces Detected by Second Harmonic Generation

New Method for Determination of Surface Potential of Microscopic Particles by Second Harmonic Generation

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