Propagation of Photoinduced Surface Pressure Perturbation along a Mixed Benzospiropyran−Octadecanol Monolayer

Balashev, Konstantin; Panaı̈otov, I.; Proust, J. E.

doi:10.1021/la960784n

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…The exponential relaxation in this system can be understood as a first-order kinetics assuming a rate of conformational reorientation proportional to the instantaneous number of molecules to be converted [23]. Further, we found an increase of the relaxation time with the increase of the initial pressure Π i (Figure 4).…”

Section: Photocontrol Of Protein Conformationmentioning

confidence: 59%

“…All data for the surface pressure relaxation are described well by a single relaxation time, τ , using the exponential decay function Π(t)−Π f = ∆Π exp(−t/τ ) (where Π f is the plateau value of the surface pressure). The exponential relaxation in this system can be understood as a first-order kinetics assuming a rate of conformational reorientation proportional to the instantaneous number of molecules to be converted [23]. Further, we found an increase of the relaxation time with the increase of the initial pressure Π i (Figure 4).…”

Section: Figmentioning

confidence: 59%

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Photocontrol of protein conformation in a Langmuir monolayer

Cicuta

Hopkinson

Petrov

2001

The Journal of Chemical Physics

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We report a method to control the conformation of a weak polyampholyte (the protein β-casein) in Langmuir monolayers by light, even though the protein is not photosensitive. Our approach is to couple the monolayer state to a photochemical reaction excited in the liquid subphase. The conformational transition of the protein molecule is triggered through its sensitivity to a subphase bulk field (pH in this study), changing in the course of the photochemical process. Thus, reaction of photoaquation of the ferrocyanide ion, which increases the subphase pH from 7.0 to about 8.3, produces a change in the surface monolayer pressure, ∆Π, between -0.5 and +1.5 mN/m (depending on the surface concentration), signalling a conformational switch. The approach proposed here can be used to selectively target and influence different interfacial properties by light, without embedding photosensitisers in the matrix.

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Section: Photocontrol Of Protein Conformationmentioning

confidence: 59%

Section: Figmentioning

confidence: 59%

Photocontrol of protein conformation in a Langmuir monolayer

Cicuta

Hopkinson

Petrov

2001

The Journal of Chemical Physics

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“…Next, in the second step of the experimental procedure, we obtain an estimate for n 10 and d for the initial condition as it is required in formulae (9)-(11) to enable us to determine the 6 The r 02 dependences of the initial SP monolayer reflectance (solid line) and of the pure air/FS interface (dashed line). DMIN init corresponds to the shift of the minimum of the former with respect to the minimum of the latter along the r 02 axis.…”

Section: Resultsmentioning

confidence: 99%

Transient Brewster angle reflectometry of spiropyran monolayers

Gorelik

Song

Lear

et al. 2010

Photochem Photobiol Sci

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Brewster angle reflectometry has been developed as a tool for determining the absorbance and refractive index changes in molecular monolayers containing spiropyran. The method is sensitive to changes in both the real and imaginary parts of the refractive index in the monolayers. It was used to monitor the conversion of spiropyran to merocyanine and the reversal of this reaction when the molecules were immobilised on quartz using silane coupling. An analytical solution of Fresnel formula allowed the transient reflectometry data to be converted into transient absorption information. Absorbances of transients as low as~10 -6 were possible using the current apparatus with a single laser pulse transient measurement. It was found that spiropyran photoconverted to merocyanine with an efficiency of~0.1. The photochemical reversion of converted merocyanine to spiropyran occurred with efficiencies of 0.03-0.2 and this was probably site dependent. It was found that the thermal conversion from merocyanine to spiropyran was slow and even after 10 min there was no significant thermal reversion. This measurement was possible because the real part of the refractive index of the monolayer could be monitored with time using an off-resonance probe at a wavelength where the merocyanine did not absorb light meaning that the probe did not photobleach the sample. Thus our method also provides a non-intrusive method for probing changes in molecules in thin films. A. IntroductionSpiropyran (SP) conversion to merocyanine (MC) (Scheme 1) in monolayers on solid supports and in Langmuir and Langmuir Blodgett films has been extensively studied because of its potential for use in photoswitching applications. 1-10 For example the switchability has been harnessed to make the wetability of surfaces change, in order to alter capillary action, to lift heads of liquid, and to make water droplets move as UV and visible light excitation are alternated. 1-3 Light-induced phase transitions and pressure jumps have also been observed on timescales from minutes to hours, 4-6 as well as more recently by the current authors using nanosecond time-resolved Brewster angle microscopy. 7-9 Furthermore SP's ability to switch surface properties has been utilized in electrodes on gold for binding proteins, 10 in biopolymer films 11 and in hybrid surface architectures. 12 Scheme 1 Schematic representation of SP to MC and reverse photoconversions. Despite the plethora of works harnessing or studying the photo-switching of properties by SP, as well as other molecules, 13 on surfaces, there is little fundamental knowledge about the photochemical reactions themselves. This is primarily because making optical measurements in thin films and monolayers is difficult due to the short optical pathlength available. Ellipsometry has been reported on SP thin-films. 14,15 Reflectometry based on surface plasmon resonance (SPR) has been used to monitor reactions in self-assembled monolayers 16 and in polymer films 17 on metallic gold and silver surfaces, however the vast majority o...

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“…Studies include light-induced phase transitions that induce conformational and pressure changes, [4][5][6] and changing the wettability of surfaces. 7,8 Other works use SP photoswitching to alter surface properties for electrodes on gold to bind proteins, 9 in biopolymer films 10 and hybrid surface architectures.…”

Section: Introductionmentioning

confidence: 99%

Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump—probe Brewster angle reflectometry

Siebenhofer

Gorelik

Lear

et al. 2013

Photochem Photobiol Sci

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Self-assembled monolayers of 11-(3',3'-dimethyl-6,8-dinitrospiro[chromene-2,2'-indoline]-1'-yl) undecanoic acid (amphiphilic spiropyran) at the air-water interface are studied using Brewster angle reflectometry.Transient kinetics of the spiropyran to merocyanine conversion are recorded in a UV-pump, VIS-probe configuration. By varying the probe wavelength using an optical parametric oscillator, we are able to reconstruct absorption spectra of intermediate states with a time-resolution of 10 nanoseconds, limited by the temporal convolution of the two laser pulses. After UV irradiation, spiropyran converts to merocyanine in two stages. The first occurs within a timescale of several tens of nanoseconds and is heavily convoluted with the system response time, whereas the second stage occurs over a few hundred nanoseconds. During the rise time there is a small red shift in the transient absorption spectrum of ∼20 nm. We assign the red shift and the slower kinetics to the isomerization of a merocyanine isomer cis about the central methine bond to those that are trans about the same bond.

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Propagation of Photoinduced Surface Pressure Perturbation along a Mixed Benzospiropyran−Octadecanol Monolayer

Cited by 7 publications

References 11 publications

Photocontrol of protein conformation in a Langmuir monolayer

Photocontrol of protein conformation in a Langmuir monolayer

Transient Brewster angle reflectometry of spiropyran monolayers

Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump—probe Brewster angle reflectometry

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