Research on Chemical Intermediates

, Volume 39, Issue 4, pp 1665–1671

The composite material of perylene bisimide dye in MCM-41 and its photophysical and photochemical properties

Authors

  • Dongmei Li
    • Key Laboratory of Chemical Sensing and Analysis in Universities of ShandongSchool of Chemistry and Chemical Engineering, University of Jinan
    • Key Laboratory of Chemical Sensing and Analysis in Universities of ShandongSchool of Chemistry and Chemical Engineering, University of Jinan
  • Jinlong Zhang
    • Lab for Advanced Materials and Institute of Fine ChemicalsEast China University of Science and Technology
Article

DOI: 10.1007/s11164-012-0900-7

Cite this article as:
Li, D., Tian, Z. & Zhang, J. Res Chem Intermed (2013) 39: 1665. doi:10.1007/s11164-012-0900-7

Abstract

The mesoporous material MCM-41 was synthesized by a hydrothermal method, and perylene bisimide dye was incorporated into its channels by impregnation. The absorption, FTIR, fluorescence emission, and decay spectra of perylene bisimide dye in CHCl3 and in MCM-41 were studied to investigate the effect of the one-dimensional channel of MCM-41 on the photophysical and photochemical properties of the dye. The results indicated that the nanochannels of MCM-41 shifted the absorption and emission maxima to red and broadened the spectra, with loss of vibrational structure. The fluorescence decay curves fitted a double-exponential function and the lifetime of perylene bisimide dye in MCM-41 was prolonged. The huge surface area of the mesoporous molecular sieve MCM-41 prevented aggregation of dye molecules, which can thus be used at high concentration.

Keywords

Perylene bisimide dyeMCM-41AbsorptionFluorescence

Introduction

Capture of solar energy and its conversion to electricity or use to produce H2 are two potential methods of solving energy and environmental problems. In recent years, incorporation of dye molecules into ordered molecular sieves, for application to the development of efficient artificial systems, has attracted increasing attention [13]. These composites combine the advantages of organic dyes, for example broad absorption spectra, and those of molecular sieves, for example huge specific surface area and nano-size channels or caves. The rigid environment of the molecular sieves can also restrain the vibration and rotation of included dye molecules, resulting in improvement of some of the properties of the included dyes [4, 5].

Many types of dye have been studied for light harvesting. Coumarin [69] and rhodamine [10, 11] dyes are the most intensively researched photoactive dyes. In addition to these, perylene bisimide dyes [1214] have also been widely studied for light harvesting, because of their high thermal and chemical stability and because their absorption spectra can cover the visible region of the solar spectrum. They are, therefore, more suitable candidates for capturing solar energy. The poor solubility and the good aggregation properties of these dyes make it difficult to use them at high concentrations, however. In this work, therefore, we incorporated a perylene bisimide dye into the one-dimensional channels of MCM-41. The huge surface area of MCM-41 promotes dispersal of the dye molecules and the resulting material can be used as a form of the dye at high concentration [15] in its monomer form.

Experimental

Synthesis of the molecular sieve MCM-41

The molecular sieve MCM-41 [6] was prepared from tetraethyl orthosilicate (TEOS) as silica source and cetyl trimethylammonium bromide (CTAB) as template. The molar composition of the final gel mixture was 1.0 SiO2:0.012 CTAB:8.6 NH3:82 H2O. Typically, CTAB was dissolved in a solution of ammonia in distilled water, then 10 mL TEOS was slowly added dropwise to the solution, with stirring. The mixture was stirred for 2 h. Next, the mixture was heated in an autoclave under static conditions at 393 K for 48 h. The resulting product was isolated by filtration, washed with distilled water, and dried at 373 K. The as-synthesized samples were then calcined in air at 823 K for 5 h.

Preparation of the perylene bisimide dye–MCM-41 composite

Calcined MCM-41 (0.1 g) was heated at 473 K for 6 h, to remove water adsorbed on the surface, then transferred immediately to a flask and left to cool to room temperature under an N2 atmosphere. Perylene bisimide dye solution of the desired concentration (5 mL) was then added to the flask. (The structure of B2, the perylene bisimide dye used in this work, is illustrated in Fig. 1.) After stirring for 24 h the solid was isolated by filtration and washed thoroughly with solvent until the filtrate was clear, indicating that dye molecules attached to the external surface had been removed.
https://static-content.springer.com/image/art%3A10.1007%2Fs11164-012-0900-7/MediaObjects/11164_2012_900_Fig1_HTML.gif
Fig. 1

Molecular structure of B2 (N,N′-di(n-octadecyl)perylene-3,4,9,10-tetracarboxylic bisimide)

Characterization

Absorption spectra were obtained by use of a Varian Cary 500. FTIR spectra were recorded with the samples as KBr pellets, by use of a Perkin–Elmer FTIR spectrometer. Fluorescence spectra were measured by use of an Edinburgh FLS920 combined fluorescence lifetime and steady-state spectrometer with time-correlated single-photon counting unit. The lifetimes were calculated from the decay curve by use of the least-squares method. All the above measurements were performed at room temperature.

Results and discussion

The size of B2 is approximately 2 × 1 × 7.2 nm3 (calculated by use of Hyperchem software) and the average pore size of MCM-41 synthesized in this work is 3 nm. So the one-dimensional channel of MCM-41 will restrain arrangement of the B2 molecules; as a result, the electronic spectra will change. Figure 2 gives the absorption spectrum of B2 in CHCl3 and the diffuse reflectance spectrum of B2 in MCM-41. The spectrum of B2 in CHCl3 consists of three vibrational bands with maxima at 457, 545 and 585 nm; the spectrum in MCM-41 is similar to that in CHCl3 but with slight broadening and the maxima shifting to red. This indicates that most B2 molecules exist in the monomer form in the channels of MCM-41 and that incorporation does not change the electronic properties of the B2 [16]. The broadening of the absorption curve of B2 in MCM-41 compared with that in CHCl3 is mainly because the silica gel surfaces of MCM-41 are complex and B2 molecules are adsorbed in a variety of local environments and subject to different interactions, which leads to band broadening.
https://static-content.springer.com/image/art%3A10.1007%2Fs11164-012-0900-7/MediaObjects/11164_2012_900_Fig2_HTML.gif
Fig. 2

Absorption spectra of B2 in CHCl3 solution (10−5 mol/L, red line) and in MCM-41 (blue line)

Steady-state and time-resolved spectroscopy are sensitive to local environment and are, therefore, often used to investigate the effect of microenvironment on the properties of guest molecules. Room temperature emission spectra of B2 in CHCl3 solution and in MCM-41 are illustrated in Fig. 3. The emission maxima data are given in Table 1. It can be seen from Fig. 3 that the emission maximum of B2 in MCM-41 shifts to 635 nm from 610 nm in CHCl3. The spectrum of B2 in MCM-41 also loses vibrational bands compared with that in CHCl3. These effects, already reported for dye molecules hosted in other porous materials [17, 18], occur mainly because the silanol groups on the MCM-41 surfaces are irregular [19, 20], and interaction of B2 with MCM-41 is largely through hydrogen bonding to the silanols. These can also be verified by FTIR spectroscopy (Fig. 4), by comparing ratios of the terminal silanol Si–OH band in the region of 3,450 cm−1 and the asymmetric Si–O–Si stretch at ~1,080 cm−1 it is estimated that ~40 % of the silanols have interacted with B2 molecules. Although the bands (C–H stretching at 2,930 and 2,856 cm−1, asymmetric and symmetric stretching from –CH2CH2– of B2) associated with adsorbed B2 are also observed in the B2–MCM-41 spectrum, these two bands are typical of the aromatic diimide of crystalline of B2 [21]. In addition, in the rigid environment the rotational and vibrational states of B2 strongly overlap, also resulting in the observed broadening. The confinement effect [6] of the channels of MCM-41 is the most important effect, considering the molecular size of B2 and the pore size of the MCM-41.
https://static-content.springer.com/image/art%3A10.1007%2Fs11164-012-0900-7/MediaObjects/11164_2012_900_Fig3_HTML.gif
Fig. 3

Emission spectra of B2 in CHCl3 solution (10−5 mol/L, red line) and in MCM-41 (blue line)

Table 1

Spectral data for B1 in CH3Cl solution (10−5 mol/L) and in MCM-41

 

λmax,ab (nm)

λmax,em (nm)

τ1 (ns)

τ2 (ns)

\( \bar{\tau }_{0} \) (ns)

χ2

B2 in CHCl3

584

610

6.45 (100)

 

6.45

1.146

B2 in MCM-41

601

635

6.94 (77.13)

2.27 (22.87)

6.53

1.078

https://static-content.springer.com/image/art%3A10.1007%2Fs11164-012-0900-7/MediaObjects/11164_2012_900_Fig4_HTML.gif
Fig. 4

FTIR spectra of B2 solid, MCM-41, and B2 in MCM-41

As part of the photophysical study, fluorescence decay was also measured (Fig. 5). The lifetime data are included in Table 1. The decay curve follows a single-exponential function in CHCl3 but a multi-exponential function in MCM-41 because of the complicated surface of the latter. The decay curve observed for B2 in MCM-41 was a good fit to a double-exponential function. Thus two lifetime components τ1 (long) and τ2 (short) are obtained (Table 1). The main part τ1 is longer than that in CHCl3 solution; this can be explained by the confinement effect of the channels of MCM-41.
https://static-content.springer.com/image/art%3A10.1007%2Fs11164-012-0900-7/MediaObjects/11164_2012_900_Fig5_HTML.gif
Fig. 5

Fluorescence decay curve of B2 in CHCl3 solution (10−5 mol/L) and in MCM-41

Conclusions

We report the UV–visible absorption and FTIR spectra, steady-state fluorescence emission, and fluorescence decay of perylene bisimide dye B2 in the one-dimensional mesoporous molecular sieve MCM-41. On the basis these spectroscopic data we deduce that B2 molecules incorporated into the channels of MCM-41 interact with its silanol groups, and that B2 molecules are mostly in the monomeric form, because of the huge specific surface area of MCM-41. The confinement effect caused by the nanochannel of MCM-41 resulted in broadened spectra, loss of vibrational structure, red shifts of peak maxima, and elongated lifetimes. This composite of B2 and MCM-41 may be used as a solid solar light-harvesting system.

Acknowledgments

This work was supported by the Shandong Distinguished Middle-aged and Young Scientist Award Foundation (grant no. BS2012NJ002) and the Natural Science Foundation of Shandong Province, China (grant no. ZR2009BM034).

Copyright information

© Springer Science+Business Media Dordrecht 2012