Cooperative Action of Laser-Induced Thermal Effects and Ionic

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Cooperative Action of Laser-Induced Thermal Effects and Ionic Coordination on Order of TPPA0 Porphyrin Derivatives Self-Assembled Interface Probed via Real-Time Second Harmonic Generation Bin Dong, Ruipeng Bai, Wuming Zheng, Man Xue, Caihe Liu, Minghua Liu, Zhen Zhang, and Yuan Guo J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b03165 • Publication Date (Web): 19 Apr 2019 Downloaded from http://pubs.acs.org on April 19, 2019

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The Journal of Physical Chemistry

Cooperative Action of Laser-Induced Thermal Effects and Ionic Coordination on Order of TPPA0 Porphyrin Derivatives Self-assembled Interface Probed via Real-Time Second Harmonic Generation

Bin Dong 1, 3, Ruipeng Bai 1, 3, Wuming Zheng4, Man Xue 1, 3, Caihe Liu 1, 3, Minghua Liu2, 3, Zhen Zhang 1, 3 *, Yuan Guo 1, 3

1. Beijing National Laboratory of Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

ACS Paragon Plus Environment

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2. Beijing National Laboratory of Molecular Sciences, CAS Key Laboratory of Colloid, Interface and Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

3. University of the Chinese Academy of Sciences, Beijing 100049, China

4. Canadian International School of Beijing, Beijing, 100125, China

*Corresponding author: [email protected]

ABSTRACT

We performed real-time second harmonic generation (SHG) to study the cooperative action of laser-induced thermal effects and ionic coordination on the order/disorder of TPPA0 (5,10,15,20-(tetrakis-((ethoxycarbonyl)methoxy)phenyl)porphyrin) monolayers on the interface of three aqueous solutions. Time dependence curves of SH signals of TPPA0 monolayers on pure water, ZnCl2 aqueous and CuCl2 aqueous interfaces were detected under the polarization combinations of p-in/p-out, s-in/p-out and 45°-in/s-out. All the SH signals changed with time at the beginning and then reached the equilibrium state.


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For the pure water and ZnCl2 aqueous interfaces, SH signals under the polarization of pin/p-out declined with time; while on the CuCl2 aqueous interfaces, the SH signals raised with time. To explain the various change of the SH signals with time, we also measured these time dependence curves under the polarizations of the p-in/p-out, s-in/p-out and 45°-in/s-out, all of which can be used to determine the orientation angle and corresponding orientation distribution width. It is found that the orientation angle with δ distribution cannot explain the ratios of the SH signal change, thus the gauss orientational distribution width has to be considered instead of δ distribution, which means the TPPA0 monolayers undergone the change process of the orientational order until reaching equilibrium. Furthermore, using a rotating trough, the SH signals of TPPA0 monolayer on the three interfaces under the p-in/p-out polarization are nearly unchanged during the measurement. These results indicated that all of the SH signal changes with time are induced by local accumulated heat with repetitive laser excitation at 82 MHz. At last, we propose a molecular mechanism to explain the changes of the SH signal on TPPA0 monolayers. The cooperative action of laser-induced thermal effects and the ionic coordination cause the signal change with time, which means the order of the porphyrin


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derivatives self-assembled interface is affected by the combination of ions and heat. The finding in this work is important to the bioscience, as well as the functional molecular devices.


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INTRODUCTION The archetypical class of porphyrins consists of four pyrrolic subunits linked by four methine bridges and have outstanding chemical and thermal stability1-3. Due to their strong electron donating ability, fast electron transportation, high absorption coefficients and tunable optoelectronic properties, the porphyrin-based materials have been widely used in organic solar cells4, organic light emitting diodes (OLEDs)5 and monolayer organic thin-film transistors(OTFTs)6. It is known that the unique functions of the porphyrin depend on the conjugated molecular structure, as well as their self-assembled structures7-8. In these applications above, the thermal effect and efficiency are two most important factors to be preferentially considerd9. Those two factors correlate with the order of the porphyrin self-assembled interface.

Currently, studies of the self-assembled structures of porphyrins by means of the interface, especially on the air/liquid interface, are becoming more striking10-12. The air/liquid interface provides a confined environment where the inversion symmetry is


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broken and the aggregate model on the interface are different from the bulk13. This property can provide new thoughts for manipulating self-assembled structures14-15.

The order of the porphyrin self-assembled monolayer on the air/liquid interface can be affected by the porphyrin substituents, ionic strength, pH in the subphase and temperature16. However, most of the studies on this issue were limited to the effect of the modification of the porphyrin substitutes on the order17-19. The influence of the ions in the subphase and the temperature on the interfacial self-assemblies is still scarce except our previous report on studying the interactions between ions and a porphyrin derivative with two long hydrophobic chain, so called TPPA2a, at the air/aqueous interfaces. The work demonstrated that the ions near the interface will change the porphyrin self-assembly structure by coordinated with the ester group on the side chains20.

TPPA0 molecule is one of the simplest TPP (Tetraphenylporphyrin) based derivatives with symmetric structures (Figure 1). They are easy to form aggregations and their substitutes can be tailored, which make it important for the fabrication of molecular devices15. In this paper, we used SHG to study the TPPA0 self-assembled interface on


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the three different subphases, pure water, ZnCl2 aqueous and CuCl2 aqueous solution. Our intention here is to explore the effect of the ions in the subphase on the order of the TPPA0 self-assembled interface. We find that TPPA0 molecules can form more order self-assembled structures on ZnCl2 aqueous solution interface than that on the pure water interface and CuCl2 aqueous solution interface. More surprisingly, we find that the order is not only associated with the ion species in the subphases, but also depended on the laser-induced thermal effects.

Figure 1. Chemical Structure of TPPA0.

METHORDS

SHG THEORY


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The basic theory of SHG has been well-described previously21-22. Only some necessary background to calculate the molecular orientation angle will be introduced here. The intensity of SH signal can be related with the effective second-order nonlinear susceptibility23

2

  I  2   A   eff  I2  A  d 2  R    N s  I2 2

R    ( cos   c  cos3  )

2

(1)

(2)

Here, parameter A, c and d are constant for a certain experimental configuration. Ns is the number density of the interfacial moiety. R (θ) is orientational function and the θ is the orientation angle. The operator  denotes the ensemble average over the whole   orientational distribution.  eff is the effective second order susceptibility, which contains 2

all molecular information of SHG measurement. In the SHG experiment, there are three  2  2  2 independent components,  eff,45  s ,  eff,sp and  eff,pp , which correspond to three polarization

measurements, 45°-in/s-out, s-in/p-out and p-in/p-out. With the microscopic local field


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  factors implicitly incorporated into the tensorial Fresnel factor Lii,  eff can be expressed 2

as24

 eff 2,45 s  Lyy  2  Lzz   Lyy   sin  yzy  eff 2, sp  Lzz  2  L2yy   sin  zyy  eff 2, pp  Lzz  2  L2xx   sin  cos 2  zxx

(3)

 2 Lxx  2  Lzz   Lxx   sin  cos 2  zxz  Lzz  2  L2zz   sin 3  zzz

Where, 𝜒𝑖𝑗𝑘 are the seven non-zero susceptibility tensors with the interface normal z and the incident plane of x (i.e.,  zzz ,  zxx   zyy , and  zxz   xxz   yzy   yyz ).ω represents the incoming laser beam and 2ω for the signal beam. For an isotropic achiral molecular interface ( Cv ), only one molecular polarizability tensor  ccc need to be considered23-24, thus

1 (2) N s  ccc ( cos   cos3  ) 2 1 (2) (2) (2) (2)   xxz   yzy   xzx  N s  ccc ( cos   cos3  ) 2 (2) 3  N s  ccc cos 

(2) (2)  zxx   zyy  (2)  yyz (2)  zzz

(4)

The orientaional parameter D can be expressed as


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D

cos 

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(5)

cos3 

With

(2)  zzz (2)  xzx

  eff(2), pp   eff(2), sp =  (2) -a (2)  2b  c    eff ,45 s  eff ,45 s 

(2)  eff(2), sp  zxx =d (2) (2)  xzx  eff ,45 s

(6)

(7)



The molecular orientation angle could be obtained by calculating the orientational parameter D.

EXPERIMENTAL METHODS

The TPPA0 molecules were synthesized and purified according to the procedure in the literature25. A chloroform (Sigma Aldrich, 99%) solution of the TPPA0 (0.5 mM) was spread onto three different subphases, pure water, ZnCl2 solution and CuCl2 aqueous solution respectively. Both ionic concentrations of zinc and copper were 1mM. After spreading the TPPA0 solution, the solvent will be evaporated at air/water interface for


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fifteen minutes. At the same time, the porphyrin molecules form a monolayer and reach thermodynamic equilibrium by means of free diffusion and intermolecular interactions. The compression isotherm (Figure 2) were detected by a normalized commercial pressure sensor (KSV Nima; Biolin Scientific Ltd.). All data of the SHG experiments were detected under the same molecular area to ensure the sample the same original state. For the UV-Vis and AFM measurements, the film was transferred onto the solid substrates at the same molecular area by a vertical lifting method with the speed of 2 mm/min.

Figure 2. Compression isotherm of TPPA0 monolayers on pure water (red line), ZnCl2 solution (green line) and CuCl2 solution (blue line) subphases. The monolayer on ZnCl2 interface has the minimum surface pressure compare to monolayers on pure water and CuCl2 interfaces, while the surface pressure from monolayer on CuCl2 surface is the


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highest. The abscissa value of vertical black dash line represents the average molecule area under the molecule numbers. The ordinate values of three horizontal colored dash lines represent the corresponding surface pressures under the same molecular area.

The SHG setup was a typical reflection configuration23,

26-27.

A broadband tunable

mode-locked femtosecond Ti: Sapphire laser system (Tsunami 3960C, Spectra-Physics) with high-repetition-rate (82 MHz) and short-pulse width (80 fs) was used. The polarized fundamental beam (800 nm) was passed through a half-wave plate, and then focused onto the surface through an optical lens (f = 10cm) with an incident angle of 60°, and a typical incident laser power is 600 mW/cm2. The polarization of reflection SH beam was controlled by a polarizer and collected by a high-gain photomultiplier (R585, Hamamatsu) and a photo counter (SR400, Stanford). Each signal point was collected within 1 second. The experiments were performed under the polarization of the p-in/p-out, s-in/p-out and 45°-in/s-out of. It is noted that the laser used in our experiment is not only a source of the fundamental light but also a heat source for heating the sample at the focal point.

RESULTS AND DISCUSSION


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SHG Experiment. In SHG experiment, a strong laser electric field is applied to an interface of molecules possessing nonlinear optical activity. The interaction of the field with the permanent dipoles of these molecules will align the molecular orientation and result in the detected SH signal, from which the effective second-order nonlinear susceptibility is determined. SH signals from the interface have been described from the equation 1 as functions of the number density of the interfacial Ns, orientational function R(θ) and constant d, which indicated that the SH signal is proportional to the Ns, θ and distribution of the θ0. SHG measurement can get detailed molecular information at the interface.

It can be observed from Figure 3 that the change of the SH signals can be followed in real time and finally tend to equilibrium within four hundred seconds. When the laser starts to irradiate the samples, the SH signals of p-in/p-out polarization at the water and ZnCl2 interface decrease gradually. After around 200 seconds, the SH signal reached equilibrium state. The SH signals of p-in/p-out polarization at the CuCl2 interfaces increased till around 200 seconds, then the SH signal reaches their equilibrium state.


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These changes indicate that there are balancing processes of the TPPA0 monolayer interface after laser irradiation. However, the detail of the changes on different subphases are markedly different (Figure 3):

(1) On the pure water interface, SH signals (Figure 3A) is about 5500 counts at the beginning of the laser irradiation (t = 0 s); while on ZnCl2 aqueous interface, the signals at time = 0 s are about 40 times larger than that on pure water interface (Figure 3B).

(2) Under polarization of the p-in/p-out and s-in/p-out, SH signals of the molecules at the pure water and ZnCl2 aqueous interface are decreasing with time, but the signal of the molecules at the CuCl2 aqueous interface is increasing, as shown in figure3(A-C, D-F).

(3) Under polarization of the 45°-in/p-out, the SH signals change at the pure water is decreasing, while the signal at the ZnCl2 aqueous interface is increasing. The SH signal at the CuCl2 aqueous interface is almost constant.


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Figure 3. Time dependence under polarization of the p-in/p-out, s-in/p-out and 45°-in/sout on the pure water (A, D, G), ZnCl2 aqueous (B, E, H) and CuCl2 (C, F, I) aqueous interfaces. All the signals changed with time in the beginning and turned to equilibrium, suggesting each of the surface undergone a balancing process. From the intensity of three polarization curves and the Eq (4), the orientation angle of molecules on each subphase can be calculated.

We now have three questions to be solved: why the initial SH signal of TPPA0 at three different interfaces are different, what factors caused the signals to change and how to


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understand the signals decrease on water and ZnCl2 surface but increase on the CuCl2 surface. In our study, the TPPA0 monolayers on the three different subphases have the same molecular density, the parameter of Ns of systems we studied here will not change according to our experimental process, which rule out the contribution of the Ns changes to the variation of SH signal in Figure 3. According to Eq (1) and Eq (2), the possibilities to cause the signal changes must be the change of orientational angle at the interfaces and angular distribution of TPPA0 molecules, R (θ), which contains the full information of the orientational order of the molecular monolayer. It is known that second-order nonlinear signals from a well-ordered surface are stronger than that from a disordered surface because the interfacial heterogeneous will cause cancellation of molecular susceptibility27-29.To quantitatively measure the orientational order of the molecular monolayer change, we detected polarization curves under polarization of the p-in/p-out, s-in/p-out and 45°-in/s-out (Figure 3(A-I)), which can be used to calculate the orientation angles with a δ distribution. Using Eq (3), Eq (4) and Eq (5), the orientation angle with δ distributions can be obtained, shown in Table 1.


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Table 1. The orientation angle (θ) with a δ distributions of porphyrin molecules at the interfaces

Ratio of Ipp intensity

Ratio of Ipp intensity

changes(simulation)

changes(experiment)

38.0°±0.2

15%

60%

ZnCl2

27.9°±0.1 27.9°±0.03

2%

71%

CuCl2

48.3°±0.3

20%

85%

Subphase

θ(t=0s)

θ(t=600s)

Pure Water

42.0°±0.1

44.2°±0.3

The molecular orientation angle of the TPPA0 monolayer with δ distributions from Table 1 also indicates that TPPA0 molecules interacted with Zn2+ prefer to arrange in a more vertical way at the interface than that on pure water and CuCl2 aqueous interfaces. Therefore, the TPPA0 molecules form a more ordered monolayer on the ZnCl2 interfaces than that on the pure water and CuCl2 aqueous interfaces. To further affirm the molecular arrangement on the interfaces, the TPPA0 monolayers on three subphases without laser irradiation were transferred to mica and then imaged by atomic force microscopy (AFM), as shown in the supporting information Figure S2. The AFM morphology measurements show that the zinc ions facilitates the porphyrin molecules to form a well ordered and


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homogenous monolayer. On the pure water surface, the monolayers are porosity with thin lines and relatively homogeneous. In contrast, AFM images on the CuCl2 interface display many surface defects throughout their perimeters, which indicate that the monolayer on the CuCl2 interface is more heterogeneous than that of the other two monolayers.

It is known that second-order nonlinear signals from well-ordered surface are stronger than that from disordered surface because the interfacial heterogeneous will cause cancellation of molecular susceptibility27-29.Combining the SH results and AFM image, we conclude that the stronger SH signals on the water and ZnCl2 aqueous solution interface at the first few seconds are responsible to more ordered interface, while much weaker SH signals on the CuCl2 aqueous at the first few seconds result from the disordered interface.

On the other hand, Figure3 (A-C) show that in the end, the SH intensity under polarization of the p-in/p-out decrease 60% on pure water interface, 71% on ZnCl2 aqueous solution interface and the SH intensity increase 85% on CuCl2 aqueous solution interface. However, according to the experiment and simulation curve ( in supporting


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information figure S1) under the assumption of the orientation angle with δ distribution, the orientation angel change on three subphases only can contribute about 15%, 2% and 20% to the SH intensity, respectively (Table1), which indicated that the assumption of the δ-function distribution of the molecular orientational angle is invalid in this case. Therefore, we have to take into account the Gaussian distribution function f   around a central orientational angle θ0 instead of δ-function distribution30-31. The Gaussian distribution function f   describes as

f ( ) 

1 exp 2

   2  0    2 2   

(8)

Figure 4 showed the simulation of the orientational function R (θ) against the central orientational angle θ0 and the Gaussian distribution width (FWHM, σ). Because the parameter c is a constant varying with various interfaces23, the simulation curves for pin/p-out polarization have the same tendency as that shown in Figure 4(A), (B) and (C). From the simulations, the SH intensity will change with FWHM. Here, we assume the central orientational angle θ0 as the means of orientation angles at 0s and 600s. The


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simulation results prove that at the certain central orientation angle the change of FWHM will cause a large SH signal change. The R (θ) curves at certain central orientational angles are plotted in Figure 4(D). We found that in Figure 4(D), the 60% SH intensity decrease of TPPA0 molecules at the pure water interface result from the about 40° changes of the FWHM when the central orientation angle changes slightly. For ZnCl2 aqueous solution interface, the 71% signal decrease result from the about 55° degrees change of the FWHM. And the 85% signal increase of TPPA0 molecules on the CuCl2 aqueous solution interface result from the about 70° degrees FWHM narrowing. So far, the orientational distribution range can completely explain the p-in/p-out SH signal changes with time on three subphases, but the distinction of SH intensity change with time between the pure water and ZnCl2 aqueous interfaces under polarization of the 45°in/s-out (figure 3(G, H, I)), in which the former is decreased with time, while the latter is increasing with time, is still need to clarify. We will illustrate this issue below.


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Figure 4. The orientational function R (θ) vs orientational distribution width σ and orientational angle θ0 with the p-in/p-out measurement, (A) Water surface, c=2.4, (B) ZnCl2 surface, c=-47.9, (C) CuCl2 surface, c=-4.9. c is complicated function of the molecular polarizability value23. (D) The simulated curves of the orientational function R(θ) against orientational distribution width σ, in which red solid line represents water surface with θ0=40°, the green solid line represents ZnCl2 surface with θ0=28° and the blue solid line represents CuCl2 surface with θ0=46°.

Based on the Gaussian orientational distribution, we simulated R (θ) with the 45°-in/sout measurement, shown in Figure 5. Combine with the p-in/p-out and 45°-in/s-out


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simulation, the orientation distribution can be obtained for the pure water interface and ZnCl2 aqueous solution interface. With the FWHM range in 0-40 degrees for water and 045 degrees for ZnCl2 aqueous interface, the tendency and variation ratio of the SH signals are the same as the experimental data in Figure 3. However, the simulation of R (θ) for CuCl2 aqueous interface only matches 45°-in/s-out data when the FWHM range is in 020 degrees. But this range does not match the change of p-in/p-out SH signal. Therefore, we cannot only use the orientational distribution to understand laser-induced SH signal changes in this case. The other factors may also have effects to change the SH signals. For example, it is also possible that the tight aggregation of the TPPA0 will change the Fresnel factor of the monolayer at the interface, which also results in the change of the SH signal.


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Figure 5. The orientational function R(θ) vs orientational distribution width σ and orientational angle θ0 (A) in the 45°-in/s-out measurement, the value of c is constantly equal to 123. (B) The simulation curves of R(θ) vs FWHM with certain orientational angle θ0, in which red solid line represents water surface which θ0=40°, the green solid line represents ZnCl2 surface which θ0=28° and the blue solid line represents CuCl2 surface which θ0=46°. The dash lines indicate the possible orientational distribution range corresponding to the SH change ratio in 45°-in/s-out measurement.

Overall, the simulation results indicate that both the variation of orientation angle and the orientational distribution can be responsible for the change the SH signals, but the orientational distribution will dominate the signal variation when the orientational angle change is relatively small. From a physical point view, the orientational distribution is related to the order of the surface, which the broader the orientational distribution, the more disorder of the surface is.

In the following sections, we will discuss the possible reasons in our experiment to cause the change of orientational distribution.


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Laser-heat-induced order and disorder. From the analysis above, the factors to influence the surface order/disorder possibly correlate to either Brownian motion or the thermal effect caused by laser irradiation. Obviously, the Brownian motion is negligible in a condensed phase. We then turn to use thermal effects caused by the laser irradiation applied in our experiment to interpret the orientational function R (θ) vs orientational distribution width and the time dependence curves of SH signals because it is known that the thermal effects play very important role in the surface order/disorder phenomena. To begin with, the control experiment must be performed, in which the sample stage was rotated on an electrical rotating platform with a constant rate of 0.1 rad/second to limit the accumulation of the thermal effects32 and the time dependence curves of SH signals under the combination of p-in/p-out polarization was detected, as shown in Figure 6. All of the SH signals are constant in Figure 6 during the measurement, meaning that the state of the monolayers on three subphases are invariable when the thermal effects were reduced by rotating the sample stage.


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Figure 6. Polar diagrams of SH intensity from rotated porphyrin monolayer surface on the three interfaces respectively under p-in/p-out polarization. (A) Pure water interface, (B) ZnCl2 aqueous interface and (C) CuCl2 aqueous interface. The invariable SH signals indicate that thermal effect causes the change of SH signals in these systems.

Actually, Bonn et al. reported that the laser-heat-induced displacement of surfactants at the water interface. It was found that a single IR pulse at ∼3300 cm−1 with ∼4 μJ could induce about 19k increase and the 800nm laser could increase the temperature of only 0.06 mK at 1 kHz repetition rate33. However, in our case, we must consider the cumulative heating effects induced by high repetition rate of unamplified femtosecond lasers because the laser we used in this work has a high-repetition-rate of 80MHz, and the 800nm laser irradiate the surface continuously, which must have different thermal effect than that


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reported by Bonn et al. The cumulative heating effects induced by high repetition rate femtosecond lasers, had already been widely used in fabricating optical waveguides, three-dimensional binary data storage, and waveguide splitters because the highrepetition-rate femtosecond laser pulses can locally induce structural and chemical changes in the bulk of transparent materials, and change the refraction index of the materials34-36.

We now evaluate such laser-induced thermal effect using the laser-induced heat accumulate at the TPPA0 interface and will diffuse on the interface with a point of a hemisphere model37. The detailed calculation and the heat diffusion model have been described in the supporting information at section 3. In brief, the accumulated laser heat can affects the TPPA0 monolayer and will diffuse with a point of a hemisphere model. We obtain the laser-induced temperature increase of 10.98K in one second in hemispherical media, which is sufficient to change the state of the TPPA0 monolayer used in our study. This thermal effect is a consequence of the laser-induced local heating of the top water phase under the TPPA0 monolayer due to repetitive laser excitation of 82MHz. As thus,


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the thermal effect assumption is reasonable to understand the order and disorder of the TPPA0 molecules at the interfaces, which can also explain the tendency of the time dependence curves of SH signals (Figure 3). The heat induces the broader orientation distribution for pure water and ZnCl2 interfaces, which results in the p-in/p-out SH intensity decreasing gradually. However, for CuCl2, the heat will induce the TPPA0 monolayer compact domains disaggregation38 and the molecules are restricted by the confinement effect through the surround molecules which makes the monolayer more ordered. As a result, the SH signal increase with time.

Mechanism of Molecular Order. With all the information above, we will try to explain how the laser irradiation induced the variation of the SH signals, and finally propose the mechanism of how the heat and ions affect the order of the monolayers at the interfaces under the laser irradiation.

To understand the signals variations of the TPPA0 monolayer at the different subphase interfaces during the laser irradiation, it is crucial to illustrate the complex structures of TPPA0 molecules on the three subphases. In the previous research, the porphyrin


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molecules and metal ions have been proved that they can form complexes with the coordination of ions to the ester groups of the porphyrin side chains at the interface20. Figure 7 is UV-vis spectra of TPPA0 LB films transferred to silica glass from three subphases at the same molecular area. Four peaks (Figure 7)in the Q-band (500-700nm) did not vanish39, which proved that the metal ions do not coordinate with the porphyrin rings but the ester groups on the side chain.

Figure 7. UV-vis spectra of TPPA0 LB films deposited on the three subphases at the same molecular number. There are no significant differences from the curves. In all the curves, the peaks in the Q-band (500-700nm) do not vanish, which means porphyrin rings and ions are not complexed.


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It is known that Zn2+ and Cu2+ ions have different coordinate structures40, which ZnCl2 molecule is a tetrahedral structure with four coordination number41 while CuCl2 molecule is a triangular bipyramidal structure with six coordination number due to the Jahn–Teller effect. This phenomenon is very common in six-coordinate copper (II) complexes42. The coordinate structures models of Zn2+ and Cu2+ have been described in the supporting information (figure S3). Moreover, the electronegativity of copper ions is 1.90 and electronegativity of zinc ions is 1.6543. These difference of the structure and the electronegativity made the copper ions coordinate with more TPPA0 molecules than that with zinc ions44-45, as shown in figure8. This explanation was also consistent with AFM imaging that the TPPA0 monolayer on CuCl2 interface has more aggregations than that on pure water and ZnCl2 interfaces. In the previously work, Liu et al had proposed a hypothesis for the TPPA0 aggregation. The TPPA0 molecules on the pure water interface formed self-assembled structures through π-π stacking, in which case four hydrophilic ester groups of porphyrin molecules of TPPA0 had the same opportunities to touch the water and the repulsions from the neighboring molecules were equal25. Therefore, only one side chain is beneath the interface among the four ester chains. According to this


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argument, TPPA0 was preferred to arrange as a flat conformation with overlapped packing. However, the relative higher SH signal in this report indicated that the TPPA0 porphyrin prefer to arrange in a vertical way at the interface, especially at the ZnCl2 interface.

We now propose a possible packing arrangement for TPPA0 monolayers at different three subphases before and after laser irradiation. As we discussed above, the thermal effect is the major factor to affect the orientational distribution of TPPA0 molecules at the interfaces. The possible packing model of TPPA0 at the pure water and ZnCl2 interfaces are similar, as shown in figure 8A. First, TPPA0 formed self-assembled structures through π-π stacking. Then the accumulated thermal effects cause the TPPA0 monolayer disordered (Figure 8B), which show a large orientational distribution of ~0-40° and the SH signal was decrease accordingly. On ZnCl2 interfaces, the coordinate effect of zinc ions and porphyrin molecules make the TPPA0 monolayer formed a tight structure, as shown in Figure 8A, and the SH intensity was 40 times larger than that at the pure water interface before laser irradiation. After the laser irradiation, the thermal effect resulted in a larger


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orientational distribution of 0-45° and the SH signal started to decrease gradually. The large orientational distribution at the pure water and ZnCl2 interfaces indicated more disordered packing of TPPA0 monolayer. For TPPA0 molecules on the CuCl2 aqueous interface, because of the more coordinate number and stronger electrostatic force, copper ions attracted more porphyrin molecules to form aggregate domains ( Figure 8C), as shown in AFM before laser irradiation. After laser irradiation, the accumulated thermal effect may induce the disaggregation of the TPPA0 molecules and weaken the interaction of TPPA0 and Cu2+ ions. In the meanwhile, the TPPA0 molecules were restricted in a certain range because of the tight coordination and confinement effect by surrounded molecules. The trimer like structure disintegrated and then make the TPPA0 molecules trending to form a relative homogenous structure, as shown in Figure 8D. The TPPA0 monolayer at the CuCl2 interface after laser irradiation showed more ordered packing. In one word, the thermal effect played a different role on the different monolayers. Our finds also suggested that for SHG measurement, one should use proper incident power to probe the monolayers at the interfaces to avoid the laser-induced thermal effects.


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Figure 8. Schematic illustration of possible stacking of TPPA0 molecules on (A) ZnCl2 aqueous surface, TPPA0 molecules form an ordered π-π stacking structure. (B) On the CuCl2 aqueous surface, TPPA0 molecules form a trimer like structure. The blue square blocks represent the porphyrin ring. The blue balls at the end of the chains represent the ester groups. (C) and (D) represent the final possible structure of TPPA0 on the ZnCl2 aqueous and CuCl2 aqueous after the irradiation of laser respectively.

CONCLUSIONS


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In this report, we investigated the order and disorder of TPPA0 porphyrin monolayers on three different subphases under the irradiation of laser using SHG and AFM. The macrocyclic rings of TPPA0 molecules were arranged in a vertical way at the interface due to the π-π interaction. In the beginning, the SH signal showed that the Zn2+ ions in the subphase could make the TPPA0 molecules at the interface more ordered and perpendicularly orientated to the surface than pure water and CuCl2 aqueous interfaces. The coordination of Zn2+ and Cu2+ lead to different packing effect. The coordination of Zn2+ made the TPPA0 monolayer more ordered and densely packed monolayer, indicating there is a relatively homogeneous interface. The higher coordinate number and the stronger electrostatic effect of Cu2+ ions result in the aggregation of TPPA0 molecules on the monolayer that cause disordered TPPA0 monolayer, which give the weaker SH signals. After laser irradiation, the p-in/p-out SH signal decreased for TPPA monolayer at pure water and ZnCl2 monolayers as a function of time. Those phenomena indicated that the accumulated thermal effect induced the broader orientational distribution and resulted in the decrease of SH signals. However, the TPPA0 monolayer at the CuCl2 interface showed different thermal effect. The SH signal increased with time due to the


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accumulated thermal effect, which indicated the disaggregated TPPA0 molecules at the CuCl2 interface. Furthermore, the TPPA0 molecules had been restricted by the coordination of Cu2+ and by the confinement effect through the surround molecules. We then conclude that the SH signal change of the TPPA0 monolayer on three interfaces are the cooperative effect of the thermal and coordination.

Supporting information Five sections, including the simulation curves of orientational angle against to the χeff,pp, AFM Morphology Measurements, Laser-induced accumulated thermal effect model, the SH signal on pure water, ZnCl2 and CuCl2 aqueous interfaces at incident laser power of 500mW and 600mW and the coordinate structures models of ZnCl2 and CuCl2 in aqueous solution are provided in the Supporting Information. NOTES The authors declare no competing financial interests.

ACKNOWLEDGMENT Z.Z. and Y.G. are grateful for funding from the Natural Science Foundation of China (NSFC 21673251, 21773258, 21873104, and 91856121), Z.Z. thanks the ICCAS for startup funding and Chinese Academy of Sciences (grant no. YJKYYQ20180014).


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REFERENCES 1.

Taniguchi, M.; Lindsey, J. S., Synthetic Chlorins, Possible Surrogates for

Chlorophylls, Prepared by Derivatization of Porphyrins. Chem. Rev. 2017, 117, 344-535. 2.

Paolesse, R.; Nardis, S.; Monti, D.; Stefanelli, M.; Di Natale, C., Porphyrinoids for

Chemical Sensor Applications. Chem. Rev. 2016, 117, 2517-2583. 3.

Bonnett, R., Photosensitizers of the Porphyrin and Phthalocyanine Series for

Photodynamic Therapy. Chem. Soc. Rev. 1995, 24, 19-33. 4.

Yella, A.; Lee, H. W.; Tsao, H. N.; Yi, C. Y.; Chandiran, A. K.; Nazeeruddin, M. K.;

Diau, E. W. G.; Yeh, C. Y.; Zakeeruddin, S. M.; Gratzel, M., Porphyrin-Sensitized Solar Cells with Cobalt (Ii/Iii)-Based Redox Electrolyte Exceed 12 Percent Efficiency. Science 2011, 334, 629-634. 5.

Tao, S. L.; Peng, Z. K.; Zhang, X. H.; Wang, P. F.; Lee, C. S.; Lee, S. T., Highly

Efficient Non-Doped Blue Organic Light-Emitting Diodes Based on Fluorene Derivatives with High Thermal Stability. Adv. Funct. Mater. 2005, 15, 1716-1721. 6.

Fukuda, K.; Yokota, T.; Kuribara, K.; Sekitani, T.; Zschieschang, U.; Klauk, H.;

Someya, T., Thermal Stability of Organic Thin-Film Transistors with Self-Assembled Monolayer Dielectrics. Appl. Phys. Lett. 2010, 96. 7.

SteinbergYfrach, G.; Liddell, P. A.; Hung, S. C.; Moore, A. L.; Gust, D.; Moore, T.

A., Conversion of Light Energy to Proton Potential in Liposomes by Artificial Photosynthetic Reaction Centres. Nature 1997, 385, 239-241. 8.

Yuan, Y.; Tam, M. F.; Simplaceanu, V.; Ho, C., New Look at Hemoglobin Allostery.

Chem. Rev. 2015, 115, 1702-1724. 9.

Hoeben, F. J. M.; Jonkheijm, P.; Meijer, E. W.; Schenning, A. P. H. J., About

Supramolecular Assemblies of Π-Conjugated Systems. Chem. Rev. 2005, 105, 14911546. 10.

Shirakawa, M.; Fujita, N.; Shinkai, S., A Stable Single Piece of Unimolecularly Pi-

Stacked Porphyrin Aggregate in a Thixotropic Low Molecular Weight Gel: A OneDimensional Molecular Template for Polydiacetylene Wiring up to Several Tens of Micrometers in Length. J. Am. Chem. Soc. 2005, 127, 4164-4165.


35


11.

Page 36 of 48

Scolaro, L. M.; Romeo, A.; Castriciano, M. A.; Micali, N., Unusual Optical

Properties of Porphyrin Fractal J-Aggregates. Chem. Commun. 2005, 3018-3020. 12.

Liu, M. H.; Zhang, L.; Wang, T. Y., Supramolecular Chirality in Self-Assembled

Systems. Chem. Rev. 2015, 115, 7304-7397. 13.

Ghoroghchian, P. P.; Frail, P. R.; Susumu, K.; Park, T. H.; Wu, S. P.; Uyeda, H.

T.; Hammer, D. A.; Therien, M. J., Broad Spectral Domain Fluorescence Wavelength Modulation of Visible and near-Infrared Emissive Polymersomes. J. Am. Chem. Soc. 2005, 127, 15388-15390. 14.

Alipour, E.; Halverson, D.; McWhirter, S.; Walker, G. C., Phospholipid Bilayers:

Stability and Encapsulation of Nanoparticles. Annu. Rev. Phys. Chem. 2017, 68, 261283. 15.

Ding, Y.; Zhu, W.-H.; Xie, Y., Development of Ion Chemosensors Based on

Porphyrin Analogues. Chem. Rev. 2016, 117, 2203-2256. 16.

Yella, A.; Lee, H. W.; Tsao, H. N.; Yi, C.; Chandiran, A. K.; Nazeeruddin, M. K.;

Diau, E. W. G.; Yeh, C. Y.; Zakeeruddin, S. M.; Gratzel, M., Porphyrin-Sensitized Solar Cells with Cobalt (Ii/Iii)-Based Redox Electrolyte Exceed 12 Percent Efficiency. Science 2011, 334, 629-634. 17.

Mathew, S.; Yella, A.; Gao, P.; Humphry-Baker, R.; Curchod, B. F. E.; Ashari-

Astani, N.; Tavernelli, I.; Rothlisberger, U.; Nazeeruddin, M. K.; Gratzel, M., DyeSensitized Solar Cells with 13% Efficiency Achieved through the Molecular Engineering of Porphyrin Sensitizers. Nat. Chem. 2014, 6, 242-247. 18.

Zhou, D.; Tan, X.; Wu, H.; Tian, L.; Li, M., Synthesis of C-C Bonded Two-

Dimensional Conjugated Covalent Organic Framework Films by Suzuki Polymerization on a Liquid-Liquid Interface. Angew. Chem. Int. Ed. 2019, 58, 1376-1381. 19.

He, Y.; Ye, T.; Borguet, E., Porphyrin Self-Assembly at Electrochemical Interfaces:

Role of Potential Modulated Surface Mobility. J. Am. Chem. Soc. 2002, 124, 1196411970. 20.

Lin, L.; Wang, T. Y.; Lu, Z.; Liu, M. H.; Guo, Y., In Situ Measurement of the

Supramolecular Chirality in the Langmuir Monolayers of Achiral Porphyrins at the Air/Aqueous Interface by Second Harmonic Generation Linear Dichroism. J. Phys. Chem.

C 2014, 118, 6726-6733.


36

Page 37 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


21.

Zhuang, X.; Miranda, P. B.; Kim, D.; Shen, Y. R., Mapping Molecular Orientation

and Conformation at Interfaces by Surface Nonlinear Optics. Phys. Rev. B. 1999, 59, 12632-12640. 22.

Shen, Y. R., Optical 2nd Harmonic-Generation at Interfaces. Annu. Rev. Phys.

Chem. 1989, 40, 327-350. 23.

Rao, Y.; Tao, Y. S.; Wang, H. F., Quantitative Analysis of Orientational Order in

the Molecular Monolayer by Surface Second Harmonic Generation. J. Chem. Phys. 2003,

119, 5226-5236. 24.

Zhang, W. K.; Wang, H. F.; Zheng, D. S., Quantitative Measurement and

Interpretation of Optical Second Harmonic Generation from Molecular Interfaces. Phys.

Chem. Chem. Phys. 2006, 8, 4041-4052. 25.

Wang, T.; Liu, M., Langmuir-Schaefer Films of a Set of Achiral Amphiphilic

Porphyrins: Aggregation and Supramolecular Chirality. Soft Matter 2008, 4, 775-783. 26.

Eisenthal, K. B., Liquid Interfaces Probed by Second-Harmonic and Sum-

Frequency Spectroscopy. Chem. Rev. 1996, 96, 1343-1360. 27.

Zhang, W. K.; Zheng, D. S.; Xu, Y. Y.; Bian, H. T.; Guo, Y.; Wang, H. F.,

Reconsideration of Second-Harmonic Generation from Isotropic Liquid Interface: Broken Kleinman Symmetry of Neat Air/Water Interface from Dipolar Contribution. J. Chem.

Phys. 2005, 123. 28.

Lv, K.; Lin, L.; Wang, X. Y.; Zhang, L.; Guo, Y.; Lu, Z.; Liu, M. H., Significant Chiral

Signal Amplification of Langmuir Monolayers Probed by Second Harmonic Generation. J.

Phys. Chem. Lett. 2015, 6, 1719-1723. 29.

Feng, R. J.; Lin, L.; Li, Y. Y.; Liu, M. H.; Guo, Y.; Zhang, Z., Effect of Ca2+ to

Sphingomyelin Investigated by Sum Frequency Generation Vibrational Spectroscopy.

Biophys. J. 2017, 112, 2173-2183. 30.

Yamaguchi, S.; Hosoi, H.; Yamashita, M.; Sen, P.; Taharat, T., Physisorption

Gives Narrower Orientational Distribution Than Chemisorption on a Glass Surface: A Polarization-Sensitive Linear and Nonlinear Optical Study. J. Phys. Chem. Lett. 2010, 1, 2662-2665.


37


31.

Page 38 of 48

Rao, Y.; Hong, S. Y.; Turro, N. J.; Eisenthal, K. B., Molecular Orientational

Distribution at Interfaces Using Second Harmonic Generation. J. Phys. Chem. C 2011,

115, 11678-11683. 32.

Ghosh, A.; Smits, M.; Bredenbeck, J.; Dijkhuizen, N.; Bonn, M., Femtosecond

Time-Resolved and Two-Dimensional Vibrational Sum Frequency Spectroscopic Instrumentation to Study Structural Dynamics at Interfaces. Rev. Sci. Instrum. 2008, 79, 093907. 33.

Backus, E. H. G.; Bonn, D.; Cantin, S.; Roke, S.; Bonn, M., Laser-Heating-Induced

Displacement of Surfactants on the Water Surface. J. Phys. Chem. B 2012, 116, 27032712. 34.

Schaffer, C. B.; García, J. F.; Mazur, E., Bulk Heating of Transparent Materials

Using a High-Repetition-Rate Femtosecond Laser. Appl. Phys. A 2003, 76, 351-354. 35.

Shane, E.; Haibin, Z.; Peter, H.; Fumiyo, Y.; Lawrence, S.; James, B.; Alan, A.,

Heat Accumulation Effects in Femtosecond Laser-Written Waveguides with Variable Repetition Rate. Opt. Express 2005, 13, 4708-16. 36.

Teng, Y.; Zhou, J. J.; Khisro, S. N.; Zhou, S. F.; Qiu, J. R., Elemental Redistribution

Behavior in Tellurite Glass Induced by High Repetition Rate Femtosecond Laser Irradiation. J. Alloys Compd. 2014, 601, 212-216. 37.

Qinghua, L. J. C.; Merlin, J., Semi-Analytical Calculation of the Laser Beam

Induced Transient Temperature Field in the Solids (Including the Partial Beam Irradiated Cases). Chinese Journal of Lasers 1998, 17. 38.

De Zorzi, R.; Guidolin, N.; Randaccio, L.; Purrello, R.; Geremia, S., Nanoporous

Crystals of Calixarene/Porphyrin Supramolecular Complex Functionalized by Diffusion and Coordination of Metal Ions. J. Am. Chem. Soc. 2009, 131, 2487-2489. 39.

Thomas, D. W.; Martell, A. E., Absorption Spectra of Para-Substituted

Tetraphenylporphines. J. Am. Chem. Soc. 1956, 78, 1338-1343. 40.

Miessler, G. L.; Tarr, D., Inorganic Chemistry, 2011. Pearson Education.

41.

Caetano,

O.;

Tetramethylammonium

Lapasset,

J.;

Stgregoire,

Tetrachlorozincate(Ii),

P.,

Tetraethylammonium

[(C2h5)4n][(Ch3)4n][Zncl4].

Acta

Crystallogr. C 1995, 51, 220-222.


38

Page 39 of 48 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


42.

Long, T. V.; Herlinger, A. W.; Epstein, E. F.; Bernal, I., The Syntheses, Structures,

and Laser Raman and Infrared Spectra of Co(Nh3)(6)Cucl5, Co(Nh3)(5)Oh2 Cucl5, Co(Nh3)(6)Cdcl5, Co(Nih3)(6)Zncl5, and Co(Nh3)(6)Zncl4(No3). Inorg. Chem. 1970, 9, 459-464. 43.

Lide, D. R., Crc Handbook of Chemistry and Physics: A Ready-Reference Book of

Chemical and Physical Data; CRC press, 1995. 44.

Brown, I. D.; Skowron, A., Electronegativity and Lewis Acid Strength. J. Am. Chem.

Soc. 1990, 112, 3401-3403. 45.

Reed, J. L., Electronegativity: Coordination Compounds. J. Phys. Chem. A 2003,

107, 8714-8722.


39


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TOC Graphic


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Chemical Structure of TPPA0.



Compression isotherm of TPPA0 monolayers on pure water (red line), ZnCl2 solution (green line) and CuCl2 solution (blue line) subphases. The monolayer on ZnCl2 interface has the minimum surface pressure compare to monolayers on pure water and CuCl2 interfaces, while the surface pressure from monolayer on CuCl2 surface is the highest. The abscissa value of vertical black dash line represents the average molecule area under the molecule numbers. The ordinate values of three horizontal colored dash lines represent the corresponding surface pressures under the same molecular area.


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Time dependence under polarization of the p-in/p-out, s-in/p-out and 45°-in/s-out on the pure water (A, D, G), ZnCl2 aqueous (B, E, H) and CuCl2 (C, F, I) aqueous interfaces. All the signals changed with time in the beginning and turned to equilibrium, suggesting each of the surface undergone a balancing process. From the intensity of three polarization curves and the Eq (4), the orientation angle of molecules on each subphase can be calculated.



The orientational function R (θ) vs orientational distribution width σ and orientational angle θ0 with the pin/p-out measurement, (A) Water surface, c=2.4, (B) ZnCl2 surface, c=-47.9, (C) CuCl2 surface, c=-4.9. c is complicated function of the molecular polarizability value23. (D) The simulated curves of the orientational function R(θ) against orientational distribution width σ, in which red solid line represents water surface with θ0=40°, the green solid line represents ZnCl2 surface with θ0=28° and the blue solid line represents CuCl2 surface with θ0=46°.


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The orientational function R(θ) vs orientational distribution width σ and orientational angle θ0 (A) in the 45°in/s-out measurement, the value of c is constantly equal to 1.23 (B) The simulation curves of R(θ) vs FWHM

with certain orientational angle θ0, in which red solid line represents water surface which θ0=40°, the green solid line represents ZnCl2 surface which θ0=28° and the blue solid line represents CuCl2 surface which θ0=46°. The dash lines indicate the possible orientational distribution range corresponding to the SH change ratio in 45°-in/s-out measurement.



Polar diagrams of SH intensity from rotated porphyrin monolayer surface on the three interfaces respectively under p-in/p-out polarization. (A) Pure water interface, (B) ZnCl2 aqueous interface and (C) CuCl2 aqueous interface. The invariable SH signals indicate that thermal effect causes the change of SH signals in these systems.


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UV-vis spectra of TPPA0 LB films deposited on the three subphases at the same molecular number. There are no significant differences from the curves. In all the curves, the peaks in the Q-band (500-700nm) do not vanish, which means porphyrin rings and ions are not complexed.



Schematic illustration of possible stacking of TPPA0 molecules on (A) ZnCl2 aqueous surface, TPPA0 molecules form an ordered π-π stacking structure. (B) On the CuCl2 aqueous surface, TPPA0 molecules form a trimer like structure. The blue square blocks represent the porphyrin ring. The blue balls at the end of the chains represent the ester groups. (C) and (D) represent the final possible structure of TPPA0 on the ZnCl2 aqueous and CuCl2 aqueous after the irradiation of laser respectively.


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Cooperative Action of Laser-Induced Thermal Effects and Ionic

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