Non-adiabatic dynamics investigation of the radiationless decay mechanism of trans-urocanic acid in the S2 state.

The trans-urocanic acid, a UV chromophore in the epidermis of human skin, was found to exhibit a wavelength dependent isomerization property. The isomerization quantum yield to cis-urocanic is greatest when being excited to the S1 state, whereas exciting the molecule to the S2 state causes almost no isomerization. The comparative photochemical behavior of the trans-urocanic on the S1 and S2 states continues to be the subject of intense research effort. This study is concerned with the unique photo-behavior of this interesting molecule on the S2 state. Combining the on-the-fly surface hopping dynamics simulations and static electronic structure calculations, three decay channels were observed following excitation to the S2 state. An overwhelming majority of the molecules decay to the S1 state through a planar or pucker characterized minimum energy conical intersection (MECI), and then decay to the ground state along a relaxation coordinate driven by a pucker deformation of the ring. A very small fraction of molecules decay to the S1 state by a MECI characterized by a twisting motion around the CC double bond, which continues to drive the molecule to deactivate to the ground state. The latter channel is related with the photoisomerization process, whereas the former one will only generate the original trans-form products. The present work provides a novel S2 state decay mechanism of this molecule, which offers useful information to explain the wavelength dependent isomerization behavior.

State-resolved dynamics study of the H + HS reaction on the 3A' and 3A″ states with time-dependent quantum wave packet method.

The quantum dynamics calculations of the H + HS (v = 0, j = 0) reaction on the 3A' and 3A″ potential energy surfaces (PESs) are performed using the reactant coordinate based time-dependent wave packet method. State-averaged and state-resolved results for both channels of the title reaction are presented in the 0.02-1.0 eV collision energy range and compared with those carried out with quasi-classical trajectory (QCT) method. Total integral cross sections (ICSs) for both channels are in excellent agreement with previous quantum mechanical (QM)-Coriolis coupling results while poorly agree with the QCT ICSs of the exchange channel, particularly near the threshold energy region. The product rotational distributions show that for the abstraction channel, the agreement between our QM and the QCT results improves with increasing collision energy. For the exchange channel, our calculations predict colder rotational distributions as compared to those obtained by QCT calculations. Although the QM total differential cross sections (DCSs) are in qualitatively good agreement with the QCT results, the two sets of the state-to-state DCSs with several peaks exhibit great divergences. The origin of the divergences are traced by analyzing the QM DCS for the H + HS (v = 0, j = 0) → H2 (v' = 0, j' = 0) + S reaction on the 3A″ PES at Ec = 1.0 eV. It is discovered that several groups of J partial waves are involved in the reaction and the shape of the DCS is greatly altered by quantum interferences between them.

Photophysical properties of self-assembled multinuclear platinum metallacycles with different conformational geometries.

In this work, spectroscopic techniques and quantum chemistry calculations were used to investigate the photophysical properties of various multinuclear platinum complexes with different conformational geometries. This suite of complexes includes a Pt-pyridyl square, a Pt-carboxylate triangle, and a mixed Pt-pyridyl-carboxylate rectangle, as well as two mononuclear Pt model complexes. Studying the individual molecular precursors in the context of larger assemblies is important to provide a complete understanding of the factors governing the observed photophysical properties of a given system. The absorption and emission bands of the parent linear dipyridyl donor (ligand 1) are largely preserved in the [4 + 4] square and the multicomponent [4 + 2 + 2] rectangle (3 and 4, respectively), with significant red shifts. The [3 + 3] Pt-carboxylate triangle containing p-phthalic acid is nonemissive. Phosphorescence and nanosecond transient spectroscopy on 3 and 4 reveal that the introduction of platinum atoms enhances spin-orbital coupling, thereby increasing the rate of intersystem crossing. This phenomenon is consistent with the low fluorescence quantum yields and short fluorescence lifetimes of 3 and 4. Moreover, the electronic structures for the ground state and low-lying excited states of these compounds were studied using quantum chemistry calculations. The fluorescent states of the platinum complexes are local excited states of ligand-centered π-π* transition features, whereas the nonfluorescent states are intramolecular charge-transfer states. These low-lying intramolecular charge-transfer states are responsible for the nonemissive nature of small molecules 1 and 2 and triangle 5. As the interactions between these components determine the properties of their corresponding assemblies, we establish novel excited-state decay mechanisms which dictate the observed spectra.

Hydrogen bonding in the electronic excited state.

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated. Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtosecond time-resolved vibrational spectroscopy is used to directly monitor the ultrafast dynamical behavior of hydrogen bonds in the electronic excited state. It is important to note that the excited-state hydrogen-bonding dynamics are coupled to the electronic excitation. Fortunately, the combination of femtosecond time-resolved spectroscopy and accurate quantum chemistry calculations of excited states resolves this issue in laser experiments. Through a comparison of the hydrogen-bonded complex to the separated hydrogen donor or acceptor in ground and electronic excited states, the excited-state hydrogen-bonding structure and dynamics have been obtained. Moreover, we have also demonstrated the importance of hydrogen bonding in many photophysical processes and photochemical reactions. In this Account, we review our recent advances in electronic excited-state hydrogen-bonding dynamics and the significant role of electronic excited-state hydrogen bonding on internal conversion (IC), electronic spectral shifts (ESS), photoinduced electron transfer (PET), fluorescence quenching (FQ), intramolecular charge transfer (ICT), and metal-to-ligand charge transfer (MLCT). The combination of various spectroscopic experiments with theoretical calculations has led to tremendous progress in excited-state hydrogen-bonding research. We first demonstrated that the intermolecular hydrogen bond in the electronic excited state is greatly strengthened for coumarin chromophores and weakened for thiocarbonyl chromophores. We have also clarified that the intermolecular hydrogen-bond strengthening and weakening correspond to red-shifts and blue-shifts, respectively, in the electronic spectra. Moreover, radiationless deactivations (via IC, PET, ICT, MLCT, and so on) can be dramatically influenced through the regulation of electronic states by hydrogen-bonding interactions. Consequently, the fluorescence of chromophores in hydrogen-bonded surroundings is quenched or enhanced by hydrogen bonds. Our research expands our understanding of the nature of hydrogen bonding by delineating the interaction between hydrogen bonds and photons, thereby providing a basis for excited-state hydrogen bonding studies in photophysics, photochemistry, and photobiology.

Molecular dynamics simulation exploration of unfolding and refolding of a ten-amino acid miniprotein.

Steered molecular dynamics simulations are performed to explore the unfolding and refolding processes of CLN025, a 10-residue beta-hairpin. In unfolding process, when CLN025 is pulled along the termini, the force-extension curve goes back and forth between negative and positive values not long after the beginning of simulation. That is so different from what happens in other peptides, where force is positive most of the time. The abnormal phenomenon indicates that electrostatic interaction between the charged termini plays an important role in the stability of the beta-hairpin. In the refolding process, the collapse to beta-hairpin-like conformations is very fast, within only 3.6 ns, which is driven by hydrophobic interactions at the termini, as the hydrophobic cluster involves aromatic rings of Tyr1, Tyr2, Trp9, and Tyr10. Our simulations improve the understanding on the structure and function of this type of miniprotein and will be helpful to further investigate the unfolding and refolding of more complex proteins.

Experimental and theoretical study on the photophysical properties of 90° and 60° bimetallic platinum complexes.

The 90° and 60° bimetallic platinum complexes with special structures are widely used in coordination-driven self-assembled metallosupramolecular architectures, and these complexes are the key components of triangular, rectangular, and polygonal metallacycle and metallocage supramolecules. Therefore, spectroscopic techniques and quantum chemistry calculations were employed in this article to investigate the photophysical properties of these bimetallic platinum complexes. Compared with spectra for the ligands, the absorption spectra of these Pt complexes are red-shifted, and the fluorescence spectra become wider and are also red-shifted. Moreover, the reasons for the low fluorescence quantum yields and short fluorescence lifetimes of these compounds were investigated using quantum chemistry calculations. We demonstrate that the fluorescent states of the bimetallic platinum complexes can be considered as local excited states, and that they possess a ligand-centered π-π* transition feature. Meanwhile, the platinum metals act as perturbation for these transitions, whereas the nonfluorescent states are classified as intramolecular charge-transfer states. Furthermore, a new fluorescence modulation mechanism is developed to explain the different emission processes of these complexes with different ligands.

A TD-DFT study on the cyanide-chemosensing mechanism of 8-formyl-7-hydroxycoumarin.

Proton transfer (PT) and excited-state PT process are proposed to account for the fluorescent sensing mechanism of a cyanide chemosensor, 8-formyl-7-hydroxycoumarin. The time-dependent density functional theory method has been applied to investigate the ground and the first singlet excited electronic states of this chemosensor as well as its nucleophilic addition product with cyanide, with a view to monitoring their geometries and spectrophotometrical properties. The present theoretical study indicates that phenol proton of the chemosensor transfers to the formyl group along the intramolecular hydrogen bond in the first singlet excited state. Correspondingly, the nucleophilic addition product undergoes a PT process in the ground state, and shows a similar structure in the first singlet excited state. This could explain the observed strong fluorescence upon the addition of the cyanide anion in the relevant fluorescent sensing mechanism.

Substituent effects on the intramolecular charge transfer and fluorescence of bimetallic platinum complexes.

An investigation of a series of platinum-containing organometallic complexes for the study of fluorescence phenomena in organometallic chromophores controlled by the intramolecular charge transfer (ICT) is presented in this work. We report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the substituent effects on the ICT and fluorescence emission. We demonstrate that the fluorescence maximum and lifetimes greatly depend on different substituents and the presence of bimetallic platinum donor. This work paves the way for an understanding of the fluorescence phenomena controlled by molecular ICT characters of these kinds of platinum-containing organometallic complexes.

TD-DFT study on the sensing mechanism of a fluorescent chemosensor for fluoride: excited-state proton transfer.

An excited-state proton transfer (ESPT) process, induced by both intermolecular and intramolecular hydrogen-bonding interactions, is proposed to account for the fluorescence sensing mechanism of a fluoride chemosensor, phenyl-1H-anthra(1,2-d)imidazole-6,11-dione. The time-dependent density functional theory (TD-DFT) method has been applied to investigate the different electronic states. The present theoretical study of this chemosensor, as well as its anion and fluoride complex, has been conducted with a view to monitoring its structural and photophysical properties. The proton of the chemosensor can shift to fluoride in the ground state but transfers from the proton donor (NH group) to a proton acceptor (neighboring carbonyl group) in the first singlet excited state. This may explain the observed red shifts in the fluorescence spectra in the relevant fluorescent sensing mechanism.

pH-Controlled twisted intramolecular charge transfer (TICT) excited state via changing the charge transfer direction.

In this work, a new model compound, the twisted intramolecular charge transfer (TICT) excited state of Milrinone (MIR), has been theoretically presented. MIR exists in different tautomeric and ionic forms in aqueous solution with different pH values. The TICT excited state properties for various forms of MIR are demonstrated to be significantly different and controlled by the pH values of MIR in aqueous solution.

Photophysical properties of coordination-driven self-assembled metallosupramolecular rhomboids: experimental and theoretical investigations.

In this work, the photophysical properties of coordination-driven self-assembled metallosupramolecular rhomboids with the donor ligands 1,2-bis(3-pyridyl)ethyne (3a) and 1,4-bis(3-pyridyl)-1,3-butadiyne (3b) are investigated by use of both spectroscopic experiments and quantum chemistry calculations. All the geometric conformations of the chair and boat conformers of 3a and 3b are fully optimized using density functional theory. The time-dependent density functional theory method was also used to study the excited-state properties of these self-assembled metallosupramolecular rhomboids. At the same time, steady-state absorption and fluorescence as well as the time-correlated single photon counting techniques are used to measure their various spectral properties. The fluorescence spectra of these self-assembled metallosupramolecular rhomboids are very wide and show an evident two-peak feature, which can be tuned by different excitation wavelengths. It has been demonstrated that the chair conformers of both 3a and 3b are formed preferentially over their boat conformers due to the close proximity of the chelated bisphosphine platinum groups. Moreover, an additional shoulder observed at 416 nm in the fluorescence spectra of 3b indicates the presence of minor amounts of the boat conformer of 3b. In addition, we have also demonstrated that lengthening the acetylene chain of the donor ligand component of these rhomboids results in a red-shifted and broadened absorption band for these metallosupramolecular rhomboids. Furthermore, the nature of the excited states for these metallosupramolecular rhomboids varies with the acetylene chain length of the donor ligands and with the different conformers.

The effect of intermolecular hydrogen bonding on the fluorescence of a bimetallic platinum complex.

The bimetallic platinum complexes are known as unique building blocks and arewidely utilized in the coordination-driven self-assembly of functionalized supramolecular metallacycles. Hence, photophysical study of the bimetallic platinum complexes will be very helpful for the understanding on the optical properties and further applications of coordination-driven self-assembled supramolecular metallacycles. Herein, we report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the significant intermolecular hydrogen bonding effects on the intramolecular charge transfer (ICT) fluorescence of a bimetallic platinum compound 4,4'-bis(trans-Pt(PEt(3))(2)OTf)benzophenone 3 in solution. We demonstrated that the fluorescent state of compound 3 can be assigned as a metal-to-ligand charge transfer (MLCT) state. Moreover, it was observed that the formation of intermolecular hydrogen bonds can effectively lengthen the fluorescence lifetime of 3 in alcoholic solvents compared with that in hexane solvent. At the same time, the electronically excited states of 3 in solution are definitely changed by intermolecular hydrogen bonding interactions. As a consequence, we propose a new fluorescence modulation mechanism by hydrogen bonding to explain different fluorescence emissions of 3 in hydrogen-bonding solvents and nonhydrogen-bonding solvents.

Role of intramolecular and intermolecular hydrogen bonding in both singlet and triplet excited states of aminofluorenones on internal conversion, intersystem crossing, and twisted intramolecular charge transfer.

Time-dependent density functional theory method was performed to investigate the intramolecular and intermolecular hydrogen bonding in both the singlet and triplet electronic excited states of aminofluorenones AF, MAF, and DMAF in alcoholic solutions as well as their important roles on the excited-state photophysical processes of these aminofluorenones, such as internal conversion, intersystem crossing (ISC), twisted intramolecular charge transfer (TICT), and so forth. The intramolecular hydrogen bond C=O...H-N can be formed between the carbonyl group and amino group for the isolated AF and MAF. However, no intramolecular hydrogen bond for DMAF can be formed. At the same time, the most stable conformation of DMAF is out-of-plane structure, where the two dihedral angles formed between dimethyl groups and fluorenone plane are 163.1 degrees and 41.74 degrees, respectively. The formation of intramolecular hydrogen bond for AF and MAF is tightly associated with the intersystem crossing of these aminofluorenones. Furthermore, the ISC process can be dominantly determined by the change of intramolecular hydrogen bond between S(1) and T(1) states of aminofluorenones. Since the change of hydrogen bond between S(1) and T(1) states of AF is stronger than that of MAF, the rate of ISC process for AF is faster than that for MAF. Moreover, the rate constant of the ISC process of DMAF is nearly close to zero because of the absence of intramolecular hydrogen bond. On the other hand, the intermolecular hydrogen bond C=O...H-O can be also formed between all aminofluorenones and alcoholic solvents. The internal conversion process from S(1) to S(0) state of these aminofluorenones is facilitated by the intermolecular hydrogen bond strengthening in the electronic excited state of aminofluorenones because of the decrease of energy gap between S(1) and S(0) states. At the same time, the change of intermolecular hydrogen bond between S(1) and T(1) states for AF is much stronger than that for MAF, which may also contribute to the faster ISC process for AF than that for MAF in the same solvents. The TICT process plays an important role in the deactivation of the photoexcited DMAF, since the TICT process along the twisted dihedral angle is nearly barrierless in the S(1) state of DMAF. However, the TICT cannot take place for AF and MAF because of the presence of the intramolecular hydrogen bond.

Excited state electronic structures and photochemistry of heterocyclic annulated perylene (HAP) materials tuned by heteroatoms: S, Se, N, O, C, Si, and B.

Time-dependent density functional theory (TDDFT) method was performed to investigate the excited state electronic structures and photochemistry of a variety of heterocyclic annulated perylene (HAP) materials. The calculated electronic structures and photochemical properties of the newly synthesized S-, Se-, and N-heterocyclic annulated perylenes were in good agreement with the experimental results. Moreover, the O-, C-, Si-, and B-heterocyclic annulated perylenes were also theoretically designed and investigated by using the same computational methods in this work. As a result, we found that the electronic structures and photochemical properties of S-, Se-, N-, O-, and C-heterocyclic annulated perylenes are similar to each other. The energy levels of the LUMO orbital for the S-, Se-, N-, O-, and C-heterocyclic annulated perylenes become higher than those of unsubstituted perylene. At the same time, the energy gaps between LUMO and HOMO for these heterocyclic annulated perylenes are also increased in comparison with those of unsubstituted perylene. Hence, both absorption and fluorescence spectra of S-, Se-, N-, O-, and C-heterocyclic annulated perylenes are correspondingly blue-shifted relative to those of unsubstituted perylene. In addition, two bonds formed by heteroatoms with perylene are lengthened in the electronic excited state of S-, Se-, N-, O-, and C-heterocyclic annulated perylenes. On the contrary, these bonds formed by heteroatoms with perylene are shortened in the electronic excited state of Si- and B-heterocyclic annulated perylenes. Furthermore, energy levels of the LUMO orbital for Si- and B-heterocyclic annulated perylenes become significantly lowered in comparison with that of unsubstituted perylene. At the same time, energy gaps between LUMO and HOMO for Si- and B-heterocyclic annulated perylenes become decreased relative to those of unsubstituted perylene. Thus, both absorption and fluorescence spectra of Si- and B-heterocyclic annulated perylenes are significantly red-shifted in comparison with those of unsubstituted perylene. The differences of electronic structures and photochemistry of these heterocyclic annulated perylene materials can be ascribed to the electron delocalization of LUMO orbital from heteroatom into the perylene skeleton for Si- and B-heterocyclic annulated perylenes, because the electron of the LUMO orbital for S-, Se-, N-, O-, and C-heterocyclic annulated perylenes is localized on the heteroatoms.

Site-specific solvation of the photoexcited protochlorophyllide a in methanol: formation of the hydrogen-bonded intermediate state induced by hydrogen-bond strengthening.

The site-specific solvation of the photoexcited protochlorophyllide a (Pchlide a) in methanol solvent was investigated using the time-dependent density functional theory method for the first time to our knowledge. The intermolecular site-specific coordination and hydrogen-bonding interactions between Pchlide a and methanol molecules play a very important role in the steady-state and time-resolved spectra. All the calculated absorption and fluorescence spectra of the isolated Pchlide a and its coordinated and hydrogen-bonded complexes with methanol demonstrate that the novel fluorescence shoulder at approximately 690 nm of Pchlide a in methanol should be ascribed to the coordinated and hydrogen-bonded Pchlide a-(MeOH)(4) complex. This coordinated and hydrogen-bonded complex can also account for the intermediate state found in the time-resolved spectroscopic studies. Herein, we have theoretically confirmed that the intermolecular coordination and hydrogen bonds between Pchlide a and methanol molecules can be strengthened in the electronically excited state of Pchlide a. Furthermore, the site-specific solvation of the photoexcited Pchlide a can be induced by the intermolecular coordination and hydrogen-bond strengthening upon photoexcitation. Then the hydrogen-bonded intermediate state is formed in 22-27 ps timescales after the site-specific solvation. All the steady-state and time-resolved spectral features of Pchlide a in different solvents can be explained by the formation of this hydrogen-bonded intermediate state after the site-specific solvation, which is induced by the coordination and hydrogen-bond strengthening.

Time-dependent density functional theory study on hydrogen-bonded intramolecular charge-transfer excited state of 4-dimethylamino-benzonitrile in methanol.

The time-dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen-bonded intramolecular charge-transfer (ICT) excited state of 4-dimethylaminobenzonitrile (DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond C[triple bond]N...H-O formed between DMABN and MeOH can induce the C[triple bond]N stretching mode shift to the blue in both the ground state and the twisted intramolecular charge-transfer (TICT) state of DMABN. Therefore, the two components at 2091 and 2109 cm(-1) observed in the time-resolved infrared (TRIR) absorption spectra of DMABN in MeOH solvent were reassigned in this work. The hydrogen-bonded TICT state should correspond to the blue-side component at 2109 cm(-1), whereas not the red-side component at 2091 cm(-1) designated in the previous study. It was also demonstrated that the intermolecular hydrogen bond C[triple bond]N...H-O is significantly strengthened in the TICT state. The intermolecular hydrogen bond strengthening in the TICT state can facilitate the deactivation of the excited state via internal conversion (IC), and thus account for the fluorescence quenching of DMABN in protic solvents. Furthermore, the dynamic equilibrium of these electronically excited states is explained by the hydrogen bond strengthening in the TICT state.

Site-selective photoinduced electron transfer from alcoholic solvents to the chromophore facilitated by hydrogen bonding: a new fluorescence quenching mechanism.

Solute-solvent intermolecular photoinduced electron transfer (ET) reaction was proposed to account for the drastic fluorescence quenching behaviors of oxazine 750 (OX750) chromophore in protic alcoholic solvents. According to our theoretical calculations for the hydrogen-bonded OX750-(alcohol)(n) complexes using the time-dependent density functional theory (TDDFT) method, we demonstrated that the ET reaction takes place from the alcoholic solvents to the chromophore and the intermolecular ET passing through the site-specific intermolecular hydrogen bonds exhibits an unambiguous site selectivity. In our motivated experiments of femtosecond time-resolved stimulated emission pumping fluorescence depletion spectroscopy (FS TR SEP FD), it could be noted that the ultrafast ET reaction takes place as fast as 200 fs. This ultrafast intermolecular photoinduced ET is much faster than the diffusive solvation process, and even significantly faster than the intramolecular vibrational redistribution (IVR) process of the OX750 chromophore. Therefore, the ultrafast intermolecular ET should be coupled with the hydrogen-bonding dynamics occurring in the sub-picosecond time domain. We theoretically demonstrated for the first time that the selected hydrogen bonds are transiently strengthened in the excited states for facilitating the ultrafast solute-solvent intermolecular ET reaction.

Photophysical Properties of a Post-Self-Assembly Host/Guest Coordination Cage: Visible Light Driven Core-to-Cage Charge Transfer.

Supramolecular systems are capable of unique photophysical properties due to possible interactions between subcomponents, such as between an encapsulated molecule and its cage in a host/guest environment. Here, we report that the encapsulation of a chromophore by a metallacage dramatically enhances its photophysical properties. In the visible region, the encapsulated photosensitizer achieves a 6.5-fold enhancement to its absorptivity. The triplet lifetime of the encapsulated photosensitizer is three times longer than that of its free analogue. These enhancements are attributed to two key factors: (i) encapsulation-induced core-to-cage charge transfer (CCCT) generates new visible-light absorbing states, accounting for the enhanced absorption, and (ii) the microenvironment inside the metallacage inhibits nonradiative decay processes, resulting in prolonged triplet lifetime. The CCCT arises from the electrostatic interaction between the delocalized electrons of the guest coronene and the positive charge associated with the metallacage host. The work herein provides insight into the CCCT phenomenon.

Steady-state and time-resolved spectroscopic investigations on the existence of stable methanol/AOT/n-heptane reverse micelles.

In this work, we have reported our study on the controversial issue whether methanol molecules can be effectively encapsulated by surfactant AOT to form true reverse micelles. We compared the different photophysical properties of coumarin 153 (C153) in methanol/AOT/n-heptane reverse micelles and methanol/n-heptane binary mixture by means of steady-state absorption, fluorescence and time-resolved fluorescence spectroscopies. In the reverse micelles, the fluorescence emission spectra of C153 were dependent on the excitation wavelength, while in binary mixtures, the excitation wavelength dependence was not observed. The biexponential decay curves of C153 in reverse micelles give a further confirmation for the two different environments where C153 molecules reside in. In other words, C153 molecules can exist both inside the core of the reverse micelles and outside of it. These results proved that the methanol can be effectively encapsulated by AOT in n-heptane solvents to form stable methanol/AOT/n-heptane reverse micelles.