Browsing by Author "Diau, EWG"

Now showing 1 - 19 of 19

A new trans-to-cis photoisomerization mechanism of azobenzene on the S-1(n,pi*) surface
(2004-02-12)
Diau, EWG
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
;
Institute of Molecular science
The rotation-inversion controversy for the photoisomerization mechanism of azobenzene has been addressed on the basis of the CASSCF calculations for the excited-state relaxed surface scan along the CNN bending (inversion), the CNNC torsion (rotation), and the concerted CNN bending (concerted inversion) reaction pathways. According to our calculated results, the inversion channel involves a substantial energy barrier and a large S-0-S-1 energy gap so that it is a highly unfavorable channel to be considered for an efficient electronic relaxation. The rotation channel is essentially barrierless with a conical intersection close to the midpoint of the pathway to reasonably account for the subpicoseond to picosecond relaxation times observed in recent ultrafast experiments. Along the concerted inversion reaction path, a sloped conical intersection (S-0/S-1 CI_inv) was found to have the geometry close to a linear CNNC configuration. When the photoexcitation occurs in the S-2 state, the concerted inversion channel may be open and the S-0/S-1 CI_inv would become energetically accessible to produce more trans-S-0 isomers. A new mechanism is proposed to rationalize the early experimental results for the following two cases: (1) the trans-to-cis photoisomerization quantum yields on S-2 excitation are much lower than the yields on S-1 excitation; (2) the yields from both the S-2 and the S-1 excitations become essentially equal when the rotation channel is blocked by chemical modification or in an inclusion complex.
Aggregation of zinc protoporphyrin in anodized aluminum oxide (AAO) nanoporous environments
(2006-02-01)
Lin, JS
;
Chen, YC
;
Chen, CC
;
Diau, EWG
;
Liu, TF
The aggregation behavior of zinc protoporphyrin (ZnPP) inside nanoporous environments of anodized aluminum oxide (AAO) has been investigated through observation of the variation of UV/visible absorption and emission spectra of the system. The Soret band in the absorption spectrum of ZnPP/AAO thin-film samples becomes much broader than that observed for ZnPP/THF solutions, and the relative intensity of the Q band is distinctly enhanced for the former. The broad Soret band overlaps the enhanced Q band increasingly as the degree of aggregation increases with increasing duration of immersion, with initial concentration of ZnPP/THF solutions, or with decreasing pore size of AAO nanotubes. A strong excitonic coupling between the Soret and Q transition dipoles causes the absorption spectrum of the ZnPP/AAO system to cover the entire visible spectral region. Emission spectra of ZnPP/AAO samples in the steady state contain multiple resolvable components assigned to monomer, dimer and higher aggregates. The observed systematic variation of emission spectra of ZnPP/AAO samples is consistent with the observation in absorption spectra of the system and reflects the significance of aggregation of ZnPP in a specific nanoporous environment.
Bis(2,2-diphenylvinyl)spirobifluorene: An efficient and stable blue emitter for electroluminescence applications
(2005-08-15)
Wu, FI
;
Shu, CF
;
Wang, TT
;
Diau, EWG
;
Chien, CH
We have synthesized a spirobifluorene-based DPVBi [4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl] analogue, DPVSBF [2,7-bis(2,2diphenylvinyl)-9,9'-spirobifluorene], in which the bis(2,2-diphenylvinyl) groups are connected through the 2 and 7 positions of the spirobifluorene framework, and have characterized its thermal properties, electronic properties (viz. absorption and photoluminescence), and electrochemical behavior. The presence of the rigid spirobifluorene linkage imparts significant improvement in the material's glass transition temperature and morphological stability, while preserving most of the photophysical and electronic properties of its non-spiro, biphenyl analogue, DPVBi. Organic electroluminescent devices having the structure ITO/NPB/DPVSBF/AlQ/LiF/Al display bright emissions with a lambda(max) at 474 nm (CIE coordinates: 0.16, 0.24) and exhibit maximum luminescence exceeding 40,000 cd/m(2). At a driving current density of 100 mAcm(2) (6.4 V), a luminance of 4110 cd/m(2) was obtained with external quantum efficiency of 2.54%, luminance efficiency of 4.1 cd/A, and power efficiency of 2.0 lm/W. Moreover, the DPVSBF-based device exhibits a 16-fold enhancement in the operation lifetime relative to that of a similar device based on DPVBi. (C) 2005 Elsevier B.V. All rights reserved.
Effects of N2O fluence on the PECVD-grown Si-rich SiOx with buried Si nanocrystals
(2005)
Lin, CJ
;
Kuo, HC
;
Chen, CY
;
Chueh, YL
;
Chou, LJ
The optimized N2O fluence is demonstrated for plasma enhanced chemical vapor deposition (PECVD) of Si-rich substoichiometric silicon oxide (SiOx) films with buried Si nanocrystals. Strong room-temperature photoluminescence (PL) at 550-870 rim has been observed in SiOx films grown by PECVD under a constant SiH4 fluence of 20 sccm with an N2O fluence varying from 105 sccm to 130 sccm. A 22-nm-redshift in the central PL wavelength has been detected after annealing from 15 min to 180 min. The maximum PL irradiance is observed from the SiOx film grown at the optimal N2O fluence of 120 sccm after annealing for 30 minutes. Larger N2O fluence or longer annealing time leads to a PL band that is blue-shifted by 65 nm and 20 nm, respectively. Such a blue shift is attributed to shrinkage in the size of the Si nanocrystals with the participation of oxygen atoms from N2O incorporated within the SiOx matrix. The (220)-oriented Si nanocrystals exhibit radii ranging from 4.4 nm to 5.0 nm as determined by transmission electron microscopy (TEM). The luminescent lifetime lengthens to 52 mu s as the nc-Si size increase to > 4 nm. Optimal annealing times for SiOx films prepared at different N2O fluences are also reported. A longer annealing process results in a stronger oxidation effect in SiOx films prepared at higher N2O fluences, yielding a lower PL irradiance at shorter wavelengths. In contrast, larger Si nanocrystals can be precipitated when the N2O fluence becomes lower; however, such a SiOx film usually exhibits weaker PL at longer wavelength due to a lower nc-Si density. These results indicate that a N2O/SiH4 fluence ratio of 6:1 is the optimized PECVD growth condition for the Si-rich SiO2 wherein dense Si nanocrystals are obtained after annealing.
Evidence for the assembly of carboxyphenylethynyl zinc porphyrins on nanocrystalline TiO2 surfaces
(2006)
Lo, CF
;
Luo, LY
;
Diau, EWG
;
Chang, IJ
;
Lin, CY
UV-visible absorption and AFM studies suggest that carboxyphenylethynyl zinc porphyrins aggregate on nanocrystalline TiO2 surfaces in an H-type fashion.
Femtosecond fluorescence dynamics of porphyrin in solution and solid films: The effects of aggregation and interfacial electron transfer between porphyrin and TiO(2)
(2006-01-12)
Luo, LY
;
Lo, CF
;
Lin, CY
;
Chang, IJ
;
Diau, EWG
The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO(2) films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S(2). We found that the S(2) -> S(1) electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, < 100 fs, in solid films and TiO(2) films due to formation of porphyrin aggregates. When probed in the S(1) state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9 - 2.4 and 19 - 26 ps, respectively. The transients in ZnCAPEBPP/TiO(2) films also feature two relaxation processes but they occur on different time scales, 100 - 300 fs and 0.8 - 4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO(2) surface, we assigned the femtosecond component of the TiO(2) films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO(2) films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.
Femtosecond fluorescence dynamics of rotation-restricted azobenzenophanes: new evidence on the mechanism of trans -> cis photoisomerization of azobenzene
(2005-03-17)
Lu, YC
;
Diau, EWG
;
Rau, H
;
應用化學系分子科學碩博班
;
Institute of Molecular science
The ultrafast relaxation dynamics of two rotation-restricted (azobenzeno-2S-phane and azobenzeno-4S-phane) and one rotation-free (4,4'-dimethylazobenzene) azobenzene derivatives were investigated using femtosecond fluorescence up-conversion on both S-1(n,pi*) and S-2(pi,pi*) excitations. On S-2 excitation, pulse-limited kinetics with a decay coefficient of similar to 100 fs corresponding to ultrafast S-2-> S-1 relaxation is found to be common for all molecules under investigation regardless of the molecular structure. This indicates that a direct rotational. relaxation on the S-2 surface is unfavorable. On S-1 excitation, we observed biphasic fluorescence decay with a femtosecond component attributed to the decay of the Franck-Condon state prepared by excitation and a picosecond component attributed to the deactivation of the relaxed molecule on the S, surface. This picosecond component is slowed by at least a factor of 2 for the rotation-restricted 2S-bridged molecule compared to that of the rotation-free molecule; for the even stronger rotation-restricted azobenzeno-4S-phane, the decrease is by a factor of 10. These differences in deactivation suggest that the relaxed states and probably the trajectories for rotation-free and rotation-restricted molecules are different on the S, surface, which should be important for the quantum yield of photoisomerization.
Femtosecond fluorescence dynamics of trans-azobenzene in hexane on excitation to the S-1(n,pi*) state
(2002-10-01)
Lu, YC
;
Chang, CW
;
Diau, EWG
;
應用化學系
;
Department of Applied Chemistry
Femtosecond fluorescence dynamics of trans-azobenzene in hexane have been investigated on excitation to the S-1(n,pi*) state at 432 nm using the up-conversion technique. Two transient components were observed to represent the fast and the slow S-1 fluorescence dynamics in the wavelength range of 550-732 nm. Based on the results obtained from recent ab initio calculations (Ishikawa, T.; Noro, T.; Shoda, T., J. Chem. Phys. 2001, 115, 7503), a dynamical picture is given in the following. Upon initial excitation to the S, state, the excited molecule is moving away from the first detection window within the observed 200-300 fs. The structural relaxation from the Franck-Condon region may be responsible for the observed fast S-1 dynamics with the driving force being the CNNC twisting motion along the rotational coordinate. For the rest of the motion on the S-1 global potential surface, the excited molecule may search for the S-0/S-1 conical intersection for an efficient internal conversion to the ground state. The nuclear motions for the observed slow S-1 dynamics not only involve the CNNC torsional coordinate but also the other degrees of freedom such as the CNN bending coordinate on the multidimensional S-1 potential energy surface. The whole electronic relaxation process occurs within the observed 1-2 ps. The slow S-1 dynamics were found to vary with the fluorescence wavelengths due to the influence of the solvent-induced vibrational relaxation in the S-1 state; the vibrational relaxation should occur on a time scale comparable to the time scale of the electronic relaxation (S-1-->S-0 internal conversion).
Fluorescence lifetime and nonradiative relaxation dynamics of DCM in nonpolar solvent
(2003-06-04)
Chang, CW
;
Kao, YT
;
Diau, EWG
;
應用化學系
;
應用化學系分子科學碩博班
The nonradiative dynamics of DCM in hexane have been investigated using femtosecond fluorescence up conversion technique at three excitation wavelengths (400, 445 and 480 nm). The S, lifetime was observed to be 9.8 +/- 0.5 ps, which is independent of the excitation and the fluorescence wavelengths. The observed S, lifetimes of DCJT and DCJTB are slower than those of DCM and DCMB by one order of magnitude, indicating the significance of the twisting motion of the amino group affecting the S, nonradiative dynamics. TDDFT calculations suggest that an intersystem crossing is responsible for the observed S, dynamics of DCM in nonpolar solvent. (C) 2003 Elsevier Science B.V. All rights reserved.
Formation of nanostructures of hexaphenylsilole with enhanced color-tunable emissions
(2006-02-26)
Bhongale, CJ
;
Chang, CW
;
Diau, EWG
;
Hsu, CS
;
Dong, YQ
Nanostructures of 1,1,2,3,4,5-hexaphenylsilole (HPS) of various types were obtained on simple reprecipitation with THF as solvent and water as non-solvent. The formation and evolution of these nanostructures were monitored with scanning electron microscopy. Using picosecond time-correlated single-photon counting, we observed enhanced emission and fluorescence lifetimes at volume fractions 70-90% of added water. We report the first enhanced color-tunable emissions of a conjugated organic compound (HPS) due to the formation of nanoflowers, nanoglobules and microglobules, and provide time scales for those nanostructures and the corresponding intermolecular interactions in the aggregates. (c) 2005 Elsevier B.V. All rights reserved.
Improved near-infrared luminescence of si-rich SiO2 with buried Si nanocrystals grown by PECVD at optimized N2O fluence
(2005)
Chen, CY
;
Lin, CJ
;
Kuo, HC
;
Lin, GR
;
Chueh, YL
The optimized N2O fluence for plasma enhanced chemical vapor deposition (PECVD) growing silicon-rich substoichiometric silicon oxide (SiOx) with buried Si nanocrystals is demonstrated. Strong room-temperature photoluminescence (PL) at 550-870 nm has been observed in SiOx thin films grown by PECVD with N2O fluence varying from 105 to 130 sccm. After annealing from 15 to 180 min, a 22-nm-redshift of the PL has been detected. The maximum PL intensity is observed for the 30-min annealed SiOx growing at N2O fluence at 120 sccm. Larger N2O fluence and longer annealing time causes a PL blueshift by 65 nm and 20 nm, respectively. Such a blueshift is attributed to shrinkage in the size of the Si nanocrystals under the participation of dissolved oxygen atoms from N2O. The (220)-oriented Si nanocrystals with radius ranging from 4.4 to 5.0 nm are determined. The luminescent lifetimes lengthens from 20 mu s to 52 mu s as the nc-Si size extends from 4.0 to 4.2 run. Optimal annealing times for SiOx preparing at different N2O fluences and an optimum N2O fluence of 120 sccm are reported. Serious oxidation effect at larger N2O fluence condition is observed, providing smaller PL intensity at shorter wavelengths. In contrast, the larger size nc-Si will be precipitated when N2O fluence becomes smaller, leading to a weaker PL at longer wavelength. These results provide the optimized growth condition for the Si-rich SiO2 with buried Si nanocrystals.
Novel distyrylcarbazole derivatives as hole-transporting blue emitters for electroluminescent devices
(2005)
Wu, FI
;
Shih, PI
;
Yuan, MC
;
Dixit, AK
;
Shu, CF
We have synthesized three novel distyrylcarbazole derivatives for use as simultaneously hole- transporting and light- emitting layers in blue light- emitting diodes. Each compound, which contains a rigid carbazole core and two 2,2- diphenylvinyl end groups substituted through either the 3,6- or the 2,7- position, forms films satisfactorily and exhibits a blue emission with its PL maximum in the range 459 - 470 nm. Photophysical measurements indicate that twisting of the adjacent C - C bonds in the 3,6- position of the carbazole core in dilute solutions causes an efficient nonradiative relaxation to occur, yielding a much smaller quantum yield for fluorescence in 3,6- linked carbazoles. As intense emissions of 2,7- linked carbazoles are observed, such deactivation from an excited- state is inefficient therein. Electrochemical studies revealed that incorporation of the carbazole core increased the HOMO energy effectively; this feature facilitates hole injection. These distyrylcarbazole derivatives are promising bifunctional, blue- emitting, holetransporting molecules for use in simple double- layer devices of a general structure ITO/ emitting layer/ TPBI/ Mg : Ag, in which TPBI - 1,3,5- tris( N- phenylbenzimidazol- 2- yl) benzene - serves as a hole- blocking and electron- transporting material. The devices prepared using 2,7-distyrylcarbazole as the emitter produced bright blue emissions having activating voltages below 3.0 V. A DPVTCz- based device attained a luminance efficiency of 3.11 cd A(-1) at 5V, a brightness of 3062 cd m(-2), and CIE color coordinates of ( 0.14, 0.22).
Photoisomerization dynamics of azobenzene in solution with S-1 excitation: A femtosecond fluorescence anisotropy study
(2004-08-18)
Chang, CW
;
Lu, YC
;
Wang, TT
;
Diau, EWG
;
應用化學系
Measurements of anisotropy of femtosecond fluorescence after direct excitation of the S-1(npi(*)) state of azobenzene in hexane and ethylene glycol solutions have been carried out to address the controversy about inversion and rotation in the mechanism of photoisomerization. The observed anisotropies in hexane decay to a nonzero asymptotic level with a relaxation period the same as that for slow decay of the corresponding biexponential transient; this effect is attributed to involvement of the out-of-plane CNNC-torsional motion on approach to a twisted conical intersection along the "rotation channel" that depolarizes the original in-plane transition moment. In contrast, when the rotational channel becomes substantially hindered in ethylene glycol, the anisotropies show no discernible decay feature, but the corresponding transients show prominent decays attributed to involvement of in-plane symmetric motions; the latter approach a planar-sloped conical intersection along a "concerted inversion channel" for efficient internal conversion through vibronic coupling. The proposed mechanism is consistent with theoretical calculations and rationalizes both results on quantum yields and ultrafast observations.
Photoluminescence of plasma enhanced chemical vapor deposition amorphous silicon oxide with silicon nanocrystals grown at different fluence ratios and substrate temperatures
(2006-02-01)
Lin, CJ
;
Lin, CK
;
Chang, CW
;
Chueh, YL
;
Kuo, HC
Near-infrared photolummescent dynamics of thermally annealed Si-rich SiOx, films grown by plasma enhanced chemical vapor deposition at different substrate temperatures and N2O/SiH4 fluence ratios are studied. The size of nanocrystallite Si (nc-Si) critically depends on the density of oxygen atoms in a Si-rich layer when the N2O/SiH4 ratio is smaller than 4; that is, it significantly increases at low N2O/SiH4 ratios. Deposition at a high N2O/SiH4 ratio strongly reduces the density of nc-Si and degrades the luminescence at 700-800 mn since the density of oxygen atoms is sufficient in the reaction of nc-Si with silicon atoms and formation of a stoichiometriC SiO2 matrix. Under a high RF power condition, the increasing substrate temperature usually inhibits the precipitation of nc-Si since high-temperature growth facilitates stochiometric SiO2 deposition. The disappearance of visible PL reveals the complete regrowth of a stoichiometric SiO2 matrix around a nanocrystallite Si cluster after annealing. The results of the transient luminescent analysis of Si-rich SiOx samples corroborate well with the observed values and reveal a lifetime of 43 mu s under an optimized nc-Si precipitation condition of 1100 degrees C annealing for 3 h.
Relaxation dynamics and structural characterization of organic nanoparticles with enhanced emission
(2005-07-21)
Bhongale, CJ
;
Chang, CW
;
Lee, CS
;
Diau, EWG
;
Hsu, CS
With a reprecipitation method, we prepared fluorescent organic nanoparticles of 1,4-di[(E)-2-phenyl-1-propenyl]-benzene (PPB) that feature weak emission in solution but exhibit blue-shifted absorption and strong emission as aggregates. Picosecond fluorescent transients of these PPB nanoparticles showed biexponential decay, described with a consecutive kinetic model involving two emissive states. X-ray diffraction patterns of PPB nanocrystals indicate long-range packing structures of two types, one the same as in a single crystal and the other not yet determined. PPB molecules in a crystal show an arrangement of a herringbone type with three benzene rings in a PPB unit being nearly planar and two methyl groups of the unit pointing along the same direction, in contrast to the twisted structure of an isolated PPB molecule. Fluorescence transients of PPB on a femtosecond scale indicate an efficient channel for isomerization that is activated for free PPB in solution but inhibited in PPB forming nanoparticles, demonstrating the significance of molecular geometry and twisting motions that affect the relaxation dynamics in the excited state. The versatile techniques combined in this work provide strong evidence to improve our understanding of optical properties in organic nanoparticles dependent on size.
Relaxation dynamics of 2,7-and 3,6-distyrylcarbazoles in solutions and in solid films: Mechanism for efficient nonradiative deactivation in the 3,6-linked carbazole
(2005-12-22)
Wang, TT
;
Chung, SM
;
Wu, FI
;
Shu, CF
;
Diau, EWG
We performed time-resolved spectral investigations of two distyrylcarbazole derivatives, 2,7- and 3,6-distyrylcarbazole (2,7-DPVTCz and 3,6-DPVTCz, respectively), in dilute toluene solution and in solid films mixed with poly(methyl methacrylate) (PMMA). The lifetime of 2,7-DPVTCz in its excited state in solution is similar to 100 times as great as that of 3,6-DPVTCz, consistent with their photophysical nature. The former shows intense emission, but the latter is nearly nonfluorescent in a free environment. Moreover, the lifetime of 3,6-DPVTCz in its excited state increased also similar to 100 times when the molecule was encapsulated in a 3,6-DPVTCz/PMMA solid film, indicating that intramolecular motion of the molecule significantly affects the observed relaxation dynamics in a confined environment. Calculations on the excited states indicate that ail efficient intersystern crossing is activated upon twisting of the bridged C-C single bond in a free 3,6-linked carbazole; such efficient deactivation is impractical in 2,7-linked carbazole or for 3,6-linked carbazole in a PMMA matrix. Information obtained from experiments on femtosecond fluorescence enables LIS to distinguish crucial relaxation processes in the excited state for a profound understanding of the details of vibrational and electronic relaxations of 3,6-DPVTCz in Solution.
Resolution of the inversion-rotation controversy of azobenzene in solution via femtosecond fluorescence anisotropy on S1 excitation.
(2004-08-22)
Diau, EWG
;
Chang, CW
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Time-resolved photoluminescence analysis of multidose Si-ion-implanted SiO2
(2006)
Lin, CJ
;
Lee, CK
;
Diau, EWG
;
Lin, GR
;
應用化學系
The continuous-wave/time-resolved photoluminescence (CWPL/TRPL) and capacitance - voltage (C-V) analysis of multirecipe silicon-ion-implanted SiO2 (SiO2:Si+) are demonstrated to study the lifetime evolution of three radiative defects with luminescent peaks at 415, 455, and 520 nm, which are identified as the weak oxygen bonding (O-O) defects, neutral oxygen vacancy (NOV), and precursors of nanocrystallite Si(E-delta') defects, respectively. The TRPL analysis reveals that the concentrations of weak oxygen bonding and NOV defects with lifetimes of 12 - 16 ns in as-implanted SiO2:Si+ are 3-4 x 10(17) cm(-3), agreeing well with those determined using C-V analysis. The NOV and weak oxygen-bonding defects reach their maximum densities and the shortest emission lifetimes of 7.0 x 10(18) cm(-3) and 3.6 - 7.2 ns, respectively, after annealing for 1.5 - 3 h. These results support the dissociation of SiO2 matrix during a Si-implanting process with a reaction of O-3 equivalent to Si-O-Si equivalent to O-3 -> O-3 equivalent to Si-Si equivalent to O-3 + O-interstitial -> NOV + (1/2) O-O, which is the origin of the strong blue-green CWPL observed in the SiO2:Si+. The regrowth of SiO2 matrix after long-term annealing is also confirmed by the significant reduction of NOV and weak oxygen bonding defects. In contrast, the concentration of the E-delta' center reveals a slowly increasing trend due to the less pronounced precipitation of nanocrystallite Si in SiO2:Si+ during the annealing process. (c) 2005 The Electrochemical Society.
Tryptophan 232 within oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae influences rearrangement and deprotonation but not cyclization reactions
(2006-03-30)
Wu, TK
;
Yu, MT
;
Liu, YT
;
Chang, CH
;
Wang, HJ
Oxidosqualene-lanosterol cyclases convert oxidosqualene to lanosterol in yeast and mammals. Site-saturated mutants' construction of Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase, at Trp232 exchanges against proteinogenic amino acids, and product profiles are shown. All mutants, except Lys and Arg, produced protosta-12,24-dien-3 beta-ol, lanosterol, and parkeol. Overall, Trp232 plays a catalytic role in the influence of rearrangement process and determination of deprotonation position but does not involve intervention in the cyclization steps.