Noncentrosymmetric and centrosymmetric J-aggregation in photomerocyanine monolayer studied by second-harmonic generation and absorption spectroscopy

Kajikawa, Kotaro; Anzai, Takeshi; Takezoe, Hideo; Fukuda, A.

doi:10.1016/0040-6090(93)04104-z

Cited by 15 publications

(18 citation statements)

References 32 publications

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“…A strong enhancement of the SHG intensity compared with that from the initial SP monolayer was observed, followed by a gradual decrease (Figure b, bottom). Upon UV illumination, SP molecules at the interface can be converted into MC molecules. ,, The strong enhancement of SHG is due to the facts that the MC molecule has a larger hyperpolarizability than the SP molecule and that MC molecules form well-ordered structures, as evidenced by an increased surface pressure after UV illumination [see Figure S1 in the Supporting Information (SI)].…”

Section: Resultsmentioning

confidence: 99%

“…8 For instance, Kajikawa et al investigated the J-aggregation of MC at interfaces and demonstrated the longterm stability of the MC aggregates. 21,22 As a result, the photoisomerization kinetics at the interface should differ from that in the bulk phase. This difference was partially confirmed by Siebenhofer et al, who observed slower isomerization in a densely packed MC monolayer than in solution.…”

Section: ■ Introductionmentioning

confidence: 99%

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Two-Photon-Induced Isomerization of Spiropyran/Merocyanine at the Air/Water Interface Probed by Second Harmonic Generation

Zhang

et al. 2016

J. Phys. Chem. A

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Photochromic molecules often exhibit switchable hyperpolarizabilities upon photoisomerization between two molecular states and can be widely applied in nonlinear optical materials. Photoisomerization can occur through either one-photon or two-photon processes. Two-photon-induced isomerization has several advantages over one-photon process but has not been fully explored. In the present study, we have used second harmonic generation to investigate the two-photon-induced isomerization between spiropyran and merocyanine at the air/water interface. We show that spiropyran and merocyanine can be converted into each other reversibly with 780-nm laser-beam irradiation through two-photon processes. We also investigated the isomerization rates under various incident laser powers. Quantitative analysis revealed that the isomerization rates of spiropyran and merocyanine depend differently on the laser power. We attribute the difference to the distinct molecular structures of spiropyran and merocyanine. At the interface, nonplanar spiropyran molecules exist mainly as monomers, whereas planar merocyanine molecules form aggregates. Upon aggregation, steric hindrance effects and excitonic coupling efficiently arrest the photoisomerization of merocyanine. This work provides an in-depth understanding of two-photon-induced isomerization at the interface, which is beneficial for designing and controlling optical thin-film materials.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Two-Photon-Induced Isomerization of Spiropyran/Merocyanine at the Air/Water Interface Probed by Second Harmonic Generation

Zhang

et al. 2016

J. Phys. Chem. A

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“…The observed switching in some of the samples might be between merocyanine in the form of H stacking to merocyanine in the form of J stacking . Further reports underline this hypothesis, which requires more detailed analyses in this particular case. , …”

Section: Resultsmentioning

confidence: 81%

“…56 Further reports underline this hypothesis, which requires more detailed analyses in this particular case. 57,58 Compared to the SP sample (Figure 3a, b, first on the left), the samples P 1 with 0.5 wt % and P 2 with 1.5 wt % of T-ZnO (2nd and third samples from left) showed a darker color. A further increase of the fraction of T-ZnO appeared to reduce the color intensity (P 3 and P 4 , 3.5 and 7.5 wt % T-ZnO) UV/ Visible spectroscopy supports this observation.…”

Section: Resultsmentioning

confidence: 95%

Light, Force, and Heat: A Multi-Stimuli Composite that Reveals its Violent Past

Shree

Schulz‐Senft

Alsleben

et al. 2017

ACS Appl. Mater. Interfaces

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A self-reporting polythiourethane/tetrapodal-ZnO (PTU/T-ZnO) composite is produced using spiropyran as an additive at a concentration as low as 0.5 wt %. Exposure to heat, UV light and mechanical force caused the spiropyran to undergo reversible isomerization indicated by a reversible color change. The studies have been conducted with a constant spiropyran concentration at 0.5 wt %, meanwhile varying the T-ZnO concentration from 0 to 7.5 wt %. The tetrapodal ZnO served as a prism: the light scattering effect of T-ZnO created a visual impression of uniform color distribution. The interconnected network of the tetrapodal of ZnO embedded in the PTU matrix enhanced the mechanical stability of the polymer leading to high impact resistance up to ∼232 kPa. PTU/spiropyran also emerged as a possible thermal sensing coating, due to its temperature sensitivity. Due to the broad green luminescence band (∼535 nm) in T-ZnO, the colored merocyanine form which absorbs in this region of the spectrum switches back to spiropyran at this wavelength. High concentrations of T-ZnO were shown to reduce the effect one of the switching triggers i.e., ultraviolet light. Using this property of T-ZnO it was possible to achieve a switchable system with the possibility of separating the stimuli.

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“…4,5 The Langmuir-Blodgett (LB) technique has been shown to be a powerful and convenient method for the preparation of ultrathin, uniform and controllable films. The LB films of molecules containing azobenzene may show a better potential for improving molecular order and orientation in films.…”

Section: Introductionmentioning

confidence: 99%

Reversible light‐induced wettability of fluorine‐containing azobenzene‐derived Langmuir–Blodgett films

Chen

Jin

Zhang

et al. 2001

Surface & Interface Analysis

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An azobenzene derivative [4-(6-oxo-hexacarboxylic acid)-3'-trifluoromethyl-azobenzene] was synthesized and transferred onto a solid substrate by the Langmuir-Blodgett (LB) technique. The films undergo reversible wettability changes upon irradiation with ultraviolet (UV, 365 ± 10 nm) and visible (436 ± 10 nm) light. This property of reversible wettability of the LB film is confirmed directly by contact angle measurement, UV-Vis absorption spectroscopy and atomic force microscopy (AFM). The results suggest that the wettability change is due to a photoinduced surface energy change.

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Noncentrosymmetric and centrosymmetric J-aggregation in photomerocyanine monolayer studied by second-harmonic generation and absorption spectroscopy

Cited by 15 publications

References 32 publications

Two-Photon-Induced Isomerization of Spiropyran/Merocyanine at the Air/Water Interface Probed by Second Harmonic Generation

Two-Photon-Induced Isomerization of Spiropyran/Merocyanine at the Air/Water Interface Probed by Second Harmonic Generation

Light, Force, and Heat: A Multi-Stimuli Composite that Reveals its Violent Past

Reversible light‐induced wettability of fluorine‐containing azobenzene‐derived Langmuir–Blodgett films

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