Browsing by Author "Lin, Ming-Chang"

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A dihydrogen phosphate selective anion receptor based on acylhydrazone and pyrazole
(2015-01-01)
Pandian, Thiravidamani Senthil
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Choi, Yusun
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
;
Kang, Jongmin
A novel chromogenic anion receptor 1 based on acylhydrazone and pyrazole has been designed and synthesized. Chromogenic anion receptor 1 forms stable 1:1 complexes with dihydrogen phosphate (H2PO4-) and other halide (Cl-, Br-) anions in DMSO solution, as shown by UV-vis, fluorescence and H-1 NMR spectroscopic experiments. The pyrazole containing host 1 in the optimized geometry of the complex has been noted as planar. The planarity of the host with the H2PO4- anion resulted from four strong N-H center dot center dot center dot O and two weak C-H center dot center dot center dot O types of H-bonding. In total six H-bonding and the planarity of the host in the complex are responsible for the high binding energy. The addition of an excess of more basic anions (F- and CH3COO-) induces stepwise deprotonation, an event signalled by the appearance of a bright yellow color. The intensity of the fluorescence spectrum increases when hydrogen bonding occurs and decreases when deprotonation occurs, which is evidenced by fluorescence titrations.
A fully-aqueous red-fluorescent probe for selective optical sensing of Hg2+ and its application in living cells
(2016-07)
Pola, Murali Krishna
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Raju, Mandapati V. Ramakrishnam
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Lin, Chein-Ming
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Putikam, Raghunath
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Lin, Ming-Chang
A new red-fluorescent mercury ion sensor material is designed and synthesized, which is composed of at weezer-shaped hydrophilic probe containing bifurcated soft-base atoms N and S coupled with 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit. By virtue of the strong electron-accepting nature of TCF unit (as a push pull chromophore), this designed sensor material can selectively detect Hg2+ over various tested metal ions in a 100% aqueous medium via naked-eye and photoluminescence (PL) observations. Theoretical and time-resolved photoluminescence measurements further confirmed the selectivity and reversibility of the probe towards Hg2+ via intramolocular charge transfer mechanism in this sensor material. Moreover, the living cell tests by confocal fluorescence images of this sensor material towards Hg2+ were also investigated. Finally, distinguished absorption changes and fluorescence quenching spectral appearances allowed us to present the selective optical indicator of Hg2+ via TCF moiety for the first time. (C) 2016 Elsevier Ltd. All rights reserved.
A Hydrogen Pyrophosphate Selective Anion Receptor Based on Thiosemicarbazone
(2017-12-01)
Pandian, Thiravidamani Senthil
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
;
Park, Jong I. L.
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Kang, Jongmin
A novel rigid anion receptor 1 containing thiosemicarbazone groups were synthesized. Receptor 1 displayed competitive turn-off fluorescence and colorimetric response for hydrogen pyrophosphate. This recognition process was confirmed by UV-vis, fluorescence titrations. A detailed analysis of the TD-density functional theory calculations was consistent with the observed colorimetric experiments. These experiments revealed that the colorimetric and fluorescent response is triggered by thiourea/ HP2O73- hydrogen bonding.
A new pyrene-based aggregation induced ratiometric emission probe for selective detections of trivalent metal ions and its living cell application
(2015-02-01)
Singh, Ashutosh
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Singh, Ravinder
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Shellaiah, Muthaiah
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Prakash, Epperla Chandra
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Chang, Huan-Cheng
We synthesize a newly designed pyrene-based fluorescent probe FBP containing a Schiff base and amide linkage as a receptor, which demonstrates selective UV-vis and fluorometric detections of trivalent metal ions in various semi-aqueous solution conditions. Interestingly, by increasing water contents the aggregation induced ratiometric emissions (AIREs) of photoluminescence in FBP solutions (in DMSO/H2O) are enhanced from blue to green due to the excimer formation of the aggregates in water. In addition, the enhanced aggregated ratiometric green fluorescence behaviors of FBP in the presence of trivalent metal ions (Al3+, Fe3+, and Cr3+) are observed in semi-aqueous solutions as well as the solid state, which is well utilized to detect trivalent metal ions in living cells. Further verification of the probe detections, their interactions toward trivalent metal ions are well characterized by the time-resolved photoluminescence (TRPL) of spectroscopic responses as well as theoretical calculations. Therefore, we believe the application of such a new AIRE-based approach is first reported among Schiff base and pyrene-based fluorescentchemo- and bio-sensors. (C) 2014 Elsevier B.V. All rights reserved.
A novel mechanism for the isomerization of N2O4 and its implication for the reaction with H2O and acid rain formation
(2018-06-15)
Putikam, Raghunath
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Lin, Ming-Chang
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應用化學系分子科學碩博班
;
Institute of Molecular science
We have discovered, by high-level quantum-chemical calculations, a new and predominant isomerization mechanism for N2O4 -> ONONO2 via a roaming-like transition state occurring unimolecularly or bimolecularly during collision with H2O. The new mechanism allows N2O4 to react with H2O with a significantly lower barrier (< 13.1 kcal/mol) than the commonly known tight transition state (similar to 30-45 kcal/mol) by concurrent stretching of the N-N bond and rotation of one of the NO2 groups to form trans-ONONO2, which then undergoes a rapid metathetical reaction with H2O in the gas phase and in aqueous solution. The results have a significant implication for the hydrolysis of N2O4 in water to produce HONO and HNO3. Rate constants for the isomerization and hydrolysis reactions have been predicted for atmospheric modeling applications.
A simple pyrene based AIEE active schiff base probe for selective naked eye and fluoresence off-on detection of trivalent cations with live cell application
(2016-08)
Simon, Turibius
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Shellaiah, Muthaiah
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Srinivasadesikan, Venkatesan
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Lin, Ching-Chang
;
Ko, Fu-Hsiang
A simple pyrene based schiff base derivative 2-((pyren-1-ylmethylene)amino)ethanol (PE) has been synthesized via one-pot reaction and its nano-aggregation induced emission enhancement (AIEE) was reported through UV/PL, TEM and DLS studies. Interestingly, PE in CH3CN revealed the naked eye and fluorescence turn-on sensing responses towards Fe3+, Cr3+ and Al3+ ions, by means of PET and PE-PE* excimer formation. The 2:1 stoichiometry of sensor complexes PE-M3+ (M=Fe/Cr/Al) were calculated from Job\'s plots based on UV-vis absorption titrations and supported by FTIR and ESI (+Ve) mass analysis. In addition, the binding site of PE-M3+ sensor complexes was well established by H-1 NMR titrations and its sensor reversibility was recognized during subsequent addition of M3+ ions and PMDTA, respectively. The detection limits (LODs) and the association constant (K-a) values of PE-M3+ complexes were calculated by standard deviation and linear fittings. Likewise, quantum yield (Phi(f)) calculations, TEM analysis, pH effect and density functional theory (DFT) studies were executed for the PE-M3+ sensor complexes. More importantly, confocal fluorescence microscopy imaging in Raw264.7 cells showed that PE could be used as an effective fluorescent probe for detecting Fe3+, Cr3+ and Al3+ ions in living cells. (C) 2016 Elsevier B.V. All rights reserved.
Ab Initio Chemical Kinetics for Reactions of H Atoms with SiHx (x=1-3) Radicals and Related Unimolecular Decomposition Processes
(2013-06-15)
Raghunath, Putikam
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Lee, Yun-Min
;
Wu, Shang-Ying
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Wu, Jong-Shinn
;
Lin, Ming-Chang
Hydrogen atoms and SiHx (x = 1-3) radicals coexist during the chemical vapor deposition (CVD) of hydrogenated amorphous silicon (a-Si: H) thin films for Si-solar cell fabrication, a technology necessitated recently by the need for energy and material conservation. The kinetics and mechanisms for H-atom reactions with SiHx radicals and the thermal decomposition of their intermediates have been investigated by using a high high-level ab initio molecular-orbital CCSD (Coupled Cluster with Single and Double)(T)/CBS (complete basis set extrapolation) method. These reactions occurring primarily by association producing excited intermediates, (SiH2)-Si-1, (SiH2)-Si-3, SiH3, and SiH4, with no intrinsic barriers were computed to have 75.6, 55.0, 68.5, and 90.2 kcal/mol association energies for x = 1-3, respectively, based on the computed heats of formation of these radicals. The excited intermediates can further fragment by H-2 elimination with 62.5, 44.3, 47.5, and 56.7 kcal/mol barriers giving Si-1, Si-3, SiH, and (SiH2)-Si-1 from the above respective intermediates. The predicted heats of reaction and enthalpies of formation of the radicals at 0 K, including the latter evaluated by the isodesmic reactions, SiHx + CH4 SiH4 + CHx, are in good agreement with available experimental data within reported errors. Furthermore, the rate constants for the forward and unimolecular reactions have been predicted with tunneling corrections using transition state theory (for direct abstraction) and variational Rice-Ramsperger-Kassel-Marcus theory (for association/decomposition) by solving the master equation covering the P, T-conditions commonly employed used in industrial CVD processes. The predicted results compare well experimental and/or computational data available in the literature. (C) 2013 Wiley Periodicals, Inc.
Ab Initio Chemical Kinetics for the Unimolecular Decomposition of Si2H5 Radical and Related Reverse Bimolecular Reactions
(2014-02-15)
Wu, Shang-Ying
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Lee, Yun-Min
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Wu, Jong-Shinn
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Lin, Ming-Chang
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機械工程學系
For plasma enhanced and catalytic chemical vapor deposition (PECVD and Cat-CVD) processes using small silanes as precursors, disilanyl radical (Si2H5) is a potential reactive intermediate involved in various chemical reactions. For modeling and optimization of homogeneous a-Si:H film growth on large-area substrates, we have investigated the kinetics and mechanisms for the thermal decomposition of Si2H5 producing smaller silicon hydrides including SiH, SiH2, SiH3, and Si2H4, and the related reverse reactions involving these species by using ab initio molecular-orbital calculations. The results show that the lowest energy path is the production of SiH+SiH4 that proceeds via a transition state with a barrier of 33.4 kcal/mol relative to Si2H5. Additionally, the dissociation energies for breaking the SiSi and HSiH2 bonds were predicted to be 53.4 and 61.4 kcal/mol, respectively. To validate the predicted enthalpies of reaction, we have evaluated the enthalpies of formation for SiH, SiH2, HSiSiH2, and Si2H4(C-2h) at 0 K by using the isodesmic reactions, such as (HSiSiH2)-H-2+(C2H6Si2H6)-C-1-Si-1+(HCCH2)-H-2 and (Si2H4)-Si-1(C-2h)+(C2H6)-C-1 (Si2H6)-Si-1+(C2H4)-C-1. The results of SiH (87.2 kcal/mol), SiH2 (64.9 kcal/mol), HSiSiH2 (98.0 kcal/mol), and Si2H4 (68.9 kcal/mol) agree reasonably well previous published data. Furthermore, the rate constants for the decomposition of Si2H5 and the related bimolecular reverse reactions have been predicted and tabulated for different T, P-conditions with variational Rice-Ramsperger-Kassel-Marcus (RRKM) theory by solving the master equation. The result indicates that the formation of SiH+SiH4 product pair is most favored in the decomposition as well as in the bimolecular reactions of SiH2+SiH3, HSiSiH2+H-2, and Si2H4(C-2h)+H under T, P-conditions typically used in PECVD and Cat-CVD. (c) 2013 Wiley Periodicals, Inc.
Ab Initio Chemical Kinetics of Key Processes in the Hypergolic Ignition of Hydrazine and Nitrogen Tetroxide
(2014)
Raghunath, Putikam
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Nghia, N. T.
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Lin, Ming-Chang
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應用化學系
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Department of Applied Chemistry
Kinetics and mechanisms of key processes leading to the hypergolic ignition of N2H4 and N2O4 have been studied by high-level ab initio molecular orbital theory in conjunction with statistical theory calculations. The results of this work suggest that the explosion following the contact of N2H4 and N2O4 in liquid or gaseous state at low temperatures can be initiated by the rapid reaction of N2H4 with ONONO2 isomers of N2O4 producing H2NN(H)NO+HNO3 without thermal activation accompanying with 21 kcal mol(-1) exothermicity. The HNO3 thus formed can instantaneously produce [N2H5+]NO3-] salt releasing twice as much acid base neutralization energy to enhance NO2 and N2H3 radical production. The thermochemistry and rate constants for reactions of species involved (NO2, NO3, N2O4, and its isomers, OH and N2Hx,(x= 2, 3, and 4)) in the chain initiation and propagation have been predicted and compared with available data in the literature.
Acid/Base and H2PO4- Controllable High-Contrast Optical Molecular Switches with a Novel BODIPY Functionalized [2]Rotaxane
(2015-12-09)
Arumugaperumal, Reguram
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Srinivasadesikan, Venkatesan
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Raju, Mandapati V. Ramakrishnam
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Lin, Ming-Chang
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Shukla, Tarun
A novel multifunctional mechanically interlocked switchable [2]rotaxane R4 containing two molecular stations and rotaxane arms terminated with boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click reaction. The shuttling motion of macrocyde between the dibenzylammonium and triazolium recognition sites and the distance dependent photoinduced electron transfer process of R4 is demonstrated by utilizing external chemical stimuli (acid/base). Interestingly, the reversible self-assembly process of R4 was recognized by the acid-base molecular switch strategy. Notably, two symmetrical triazolium groups acted as molecular stations, H2PO4- receptors, and H-bonded donors. Both [2]rotaxane R4 and thread R2 demonstrated excellent optical responses and high selectivity toward H2PO4- ion. The specific motion and guest-host interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. The thread R2 also demonstrated to enable the detection of H2PO4- in RAW 264.7 cells successfully.
An Acid-Base Controllable Hierarchical Nanostructure from a NIR-Absorbing Conjugated Polyrotaxane-Based Optical Molecular Switch
(2013-09-10)
Raju, Mandapati V. Ramakrishnam
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Raghunath, P.
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Lin, Ming-Chang
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Lin, Hong-Cheu
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材料科學與工程學系
To investigate the supramolecular interactions of the mechanically interlocked rotaxane pendants and conjugated polymer backbones, four analogous polymers were systematically synthesized by copolymerization of a 9-alkylidene-9H-fluorene monomer with various monomers, which contained a diketopyrrolopyrrole unit tethered with a dumbbell unit, a metalated [2]rotaxane, a demetalated orthogonal H-bonded [2]rotaxane, and a simple alkyl chain, to furnish P1, P2, P3, and P4, respectively. Prevailing H-1 NMR and UV-vis to NIR titration profiles indicated that the novel polyrotaxane P3 showed a sensitive and reversible acid base molecular switch capability via supramolecular interactions in contrast to the other polymers (P1, P2, and P4). Compared with the other polymers, P3 possessed a narrower bandgap, which was also confirmed by the computational study. Prominently, the monitoring of a controllable nanoself-assembly process of P3 was obtained by reversible acid base molecular switch approaches. The orthogonal H-bonded pendant [2]rotaxane unit and the steric demand of P3 judiciously allowed to morph into a hierarchical nanostructure via interconvertible H-bonds, anion-pi and pi-pi stackings, and hydrophobic interactions.
Capturing H and H-2 by SiHx+ (x <= 4) ions: Comparison between Langevin and quantum statistical models
(2017-02)
Trong-Nghia Nguyen
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Lee, Yun-Min
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Wu, Jong-Shinn
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Lin, Ming-Chang
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機械工程學系
H, H-2, and SiHx+ (x <= 4) ions coexist under plasma-enhanced chemical vapor deposition (PECVD) conditions. We have studied the kinetics of their interactions by high-level quantum chemical and statistical theory calculations, and compared the results with classical Langevin values (similar to 2 x 10(-9)cm(3) molecule(-1) s(-1) independent of temperature). The results indicate that, for H capturing by SiHx+ (x <= 4), both theories agree within a factor of 2-4, whereas for H-2 capturing by SiHx+ (x <= 3), the modern theory gives higher and weakly temperature-dependent values by up to more than one order of magnitude, attributable to reaction path degeneracies and increased entropies of activation. The heats of formation and structural parameters of SiHx+ ions (x <= 5) in this work agree well with available experimental data. For practical applications, we have provided tables of rate constants for modeling various processes of relevance to the PECVD of a-Si: H films. (C) 2017 The Japan Society of Applied Physics
Controlled Sol-Gel and Diversiform Nanostructure Transitions by Photoresponsive Molecular Switching of Tetraphenylethene- and Azobenzene-Functionalized Organogelators
(2020-07-01)
Arumugaperumal, Reguram
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Hua, Wei-Ling
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Raghunath, Putikam
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Lin, Ming-Chang
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Chung, Wen-Sheng
The implementation of stimuli-responsive materials with dynamically controllable features has long been an important objective that challenges chemists in the materials science field. We report here the synthesis and characterization of [2]rotaxanes (R1 and R1-b) with a molecular shuttle and photoresponsive properties. Axles T1 and T1-b were found to be highly efficient and versatile organogelators toward various nonpolar organic solvents, especially p-xylene, with critical gelation concentrations as low as 0.67 and 0.38 w/v %, respectively. The two molecular stations of switchable [2]rotaxanes (R1 and R1-b) can be revealed or concealed by t-butylcalix[4]arene macrocycle, thus inhibiting the gelation processes of the respective axles T1 and T1-b through the control of intermolecular hydrogen-bonding interactions. The sol-gel transition of axles T1 and T1-b could be achieved by the irradiation of UV-visible light, which interconverted between the extended and contracted forms. Interestingly, the morphologies of organogels in p-xylene, including flakes, nanobelts, fibers, and vesicles depending on the molecular structures of axles T1 and T1-b, were induced by UV-visible light irradiation. Further studies revealed that acid-base-controllable and reversible self-assembled nanostructures of these axle molecules were mainly constructed by the interplay of multi-noncovalent interactions, such as intermolecular pi-pi stacking, CH-pi, and intermolecular hydrogen-bonding interactions. Surprisingly, our TPE molecular systems (R1, R1-b, T1, and T1-b) are nonemissive in their aggregated states, suggesting that not only fluorescence resonance energy transfer but also aggregation-caused quenching may have been functioning. Finally, the mechanical strength of these organogels in various solvents was monitored by rheological experiments.
Development of Hybrid Pseudohalide Tin Perovskites for Highly Stable Carbon-Electrode Solar Cells
(2020-05-13)
Rameez, Mohammad
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Lin, Eric Yan-Ru
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Raghunath, Putikam
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Narra, Sudhakar
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Song, Donghoon
Tin-based perovskites degrade rapidly upon interaction with water and oxygen in air because Sn-I bonds are weak. To address this issue, we developed novel tin perovskites, FASnI((3-x))(SCN)(x) (x = 0, 1, 2, or 3), by employing a pseudohalide, thiocyanate (SCN-), as a replacement for halides and as an inhibitor to suppress the Sn2+/Sn4+ oxidation. The structural and electronic properties of pseudohalide tin perovskites in this series were explored with quantum-chemical calculations by employing the plane-wave density functional theory (DFT) method; the corresponding results are consistent with the experimental results. Carbon-based perovskite devices fabricated with tin perovskite FASnI(SCN)(2) showed about a threefold enhancement of the device efficiency (2.4%) relative to that of the best FASnI(3)-based device (0.9%), which we attribute to the improved suppression of the formation of Sn4+, retarded charge recombination, enhanced hydrophobicity, and stronger interactions between Sn and thiocyanate for FASnI(SCN)(2) than those for FASnI(3). After the incorporation of phenylethyleneammonium iodide (PEAI, 10%) and ethylenediammonium diiodide (EDAI(2), 5%) as coadditives, the FASnI(SCN)(2) device gave the best photovoltaic performance with J(SC) = 20.17 mA cm(-2), V-OC = 322 mV, fill factor (FF) = 0.574, and overall efficiency of power conversion PCE = 3.7%. Moreover, these pseudohalide-containing devices display negligible photocurrent-voltage hysteresis and great stability in ambient air conditions.
Distinct Nanostructures and Organogel Driven by Reversible Molecular Switching of a Tetraphenylethene-Involved Calix[4]arene-Based Amphiphilic [2]Rotaxane
(2018-10-23)
Arumugaperumal, Reguram
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Raghunath, Putikam
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Lin, Ming-Chang
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Chung, Wen-Sheng
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應用化學系
Aggregation induced emission (AIE) active and acid/base controllable amphiphilic [2]rotaxanes R1 and R2 were successfully constructed with tetraphenylethene (TPE) as a stopper and t-butylcalix[4]arene or calix[4]arene macrocycle as a wheel over the axle component. The AIE effect of [2]rotaxanes R1 and R2 was greatly affected by the molecular shuttling of t-butylcalix[4]arene or calix[4]arene macrocycle, which was triggered by the acid/base strategy. In the case of [2]rotaxane R1, aggregation was achieved in the presence of less amount of water compared with those of [2]rotaxane R2, and the deprotonated [2]rotaxanes R1-b and R2-b, owing to the stronger interaction between the TPE and t-butylcalix[4]arene macrocycle and restricted intramolecular rotation (RIR), thus making it responses in less quantity of water along with highly fluorescent emission. [2]Rotaxane R1-b started to aggregate at 70% water fraction (f(w)), while [2]rotaxane R2-b started to aggregate at 75% f(w) which allowed them to morph into hollow nanospheres, whereas they formed only nanospheres at 99% f(w) in CH3CN/water cosolvent system due to the higher degree of aggregation in aqueous media. To our delight, controllable morphology of self-assembled structures was indeed formed from these [2]rotaxanes. Interestingly, by the interplay of a wide range of multi-self-assembly driving forces, the slack stacking of rotaxane unit forms a hollow on the surface of nanospheres to become hollow nanospheres. Among the four [2]rotaxanes studied here, R1 possessed a narrower HOMO-LUMO band gap compared to those others, as confirmed by computational study. Furthermore, only [2]rotaxane R1 formed organogel in methanol solvent and its reversible gel-sol transition could be achieved by the addition of acid and base. This implies that the formation of dumbbell shape cross-linked 3D network structures were mainly governed by pi-pi stacking, van der Waals force, and intermolecular H-bonding interactions during the gelation processes.
Facile rhodamine-based colorimetric sensors for sequential detections of Cu(II) ions and pyrophosphate (P2O74-) anions
(2016-01-01)
Arumugaperumal, Reguram
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Srinivasadesikan, Venkatesan
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Lin, Ming-Chang
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Shellaiah, Muthaiah
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Shukla, Tarun
Two rhodamine hydrazine derivatives Rh1 and Rh2 with catechol and ether functionalities have been synthesized and utilized towards sequential colorimetric detections of Cu(II) and pyrophosphate (PPi) ions in CH3CN-H2O (v/v = 9 : 1, 5 mM Tris-HCl, pH 7.4) semi-aqueous medium. Notably, Rh1 and Rh2 are the first example of colorimetric rhodamine-based probes for the sequential detections of Cu2+ ion and PPi anion. Based on the significant colorimetric responses (from colorless to pink) of Rh1 and Rh2 to Cu2+ ions, the detection limits were estimated as low as 1.22 x 10(-8) M and 8.0 x 10(-7) M, respectively, which signified the utilities of designed probes towards facile detections of Cu2+ ions. Furthermore, upon the successive addition of PPi ion to Rh1-Cu2+ and Rh2-Cu2+ complexes, it has been altered and restored to its origin of Rh1 and Rh2 via re-coordination of PPi to Cu2+ ion, which was confirmed by color changes from pink to colorless. Moreover, computational DFT calculations provided more insights into HOMO-LUMO structures of rhodamine derivatives and their copper complexes. Additionally, the solid state strip-based colorimetric detections of Cu2+ ion were supplemented as a real time application.
Hydrogen-bonded effects on supramolecular blue phase liquid crystal dimeric complexes
(2015-01-01)
Wei, Chong-Lun
;
Chen, Te-Cheng
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Raghunath, Putikam
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Lin, Ming-Chang
;
Lin, Hong-Cheu
In this study, a series of novel asymmetric hydrogen-bonded (H-bonded) dimeric complexes D/P and D/P* (proton donors D = A, A*, AF and AF*) were synthesized and self-assembled by appropriate molar ratios of H-donors (A, A*, AF and AF*) and H-acceptors (P and P*). In addition, the influences of the lateral fluoro-substituent of H-donors, the number (along with the position) of chiral centers and the molar ratio of H-donors and H-acceptors on the mesophasic behaviours (e.g., BPs) of asymmetric H-bonded dimeric complexes are investigated. Interestingly, the blue phase (i.e., BPI) was observed in complexes A*/P, A*/P*, AF*/P and AF*/P* containing at least a chiral center in H-donors (A* and AF*), including the widest BPI ranges of complexes AF*/P* (ca. 6 degrees C and 13 degrees C for 1 : 1 and 3 : 1 mol, respectively). For the first time, the hydrogen-bonded effects on supramolecular blue phase LCs are compared with their analogous covalent diads. Based on our theoretical calculation, we discovered that the bend angle plays an important role in manipulating the existence of the blue phase, which is preferred to appear at the bend angle within 132.1-152.9 degrees. Hence, owing to inappropriate bend angles, both H-bonded dimeric complex A/P* and covalent diad A*-P (with bend angles of 162.0 degrees and 126.5 degrees, respectively) did not possess any blue phase.
KSCN-activation of hydrogenated NiO/TiO2 for enhanced photocatalytic hydrogen evolution
(2020-05-01)
Wang, Tsai-Te
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Chiang, Chao-Lung
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Lin, Yu-Chang
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Srinivasadesikan, Venkatesan
;
Lin, Ming-Chang
It was investigated the efficiency of hydrogen production from NiO-loaded TiO2 treated by methanol hydrogenation and functionalized by SCN ligand (SCN-M:(NiO/TiO2)). The effects of a p-n junction created between NiO and TiO2 were demonstrated to enhance significantly the overall photocatalytic performance. The optical and microstructural properties of SCN-M:(NiO/TiO2) were studied with ultraviolet-visible spectra (UV-Vis), photoluminescence (PL), Raman spectra, X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The atomic and electronic configurations of SCN-M:(NiO/TiO2) were investigated with analysis of the X-ray absorption near-edge structure (XAS) in situ under irradiation with Xe lamp incorporating a filter (AM 1.5G). An effective quantum yield of 1.34% for hydrogen production was attained with SCN-M:(NiO/TiO2). Quantum-chemical calculations revealed a synergistic decrease of the band gap upon loading Ni, Ni-linked O-2 and anionic SCN-ligand binding. The optimal energy bandgap was decreased to 2.70 eV for (SCN/O-2)-3Ni@TiO2, which reasonably supported the enhancement of H-2 evolution.
KSCN-induced Interfacial Dipole in Black TiO2 for Enhanced Photocatalytic CO2 Reduction
(2019-07-17)
Fu, Fang-Yu
;
Shown, Indrajit
;
Li, Chia-Shuo
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Raghunath, Putikam
;
Lin, Tsai-Yu
Tuning the electronic band structure of black titania to improve photocatalytic performance through conventional band engineering methods has been challenging because of the defect-induced charge carrier and trapping sites. In this study, KSCN-modified hydrogenated nickel nano cluster-modified black TiO2 (SCN-H-Ni-TiO2) exhibits enhanced photocatalytic CO2 reduction due to the interfacial dipole effect. Upon combining the experimental and theoretical simulation approach, the presence of an electrostatic interfacial dipole associated with chemisorption of SCN has dramatic effects on the photocatalyst band structure in SCN H-Ni-TiO2. An interfacial dipole possesses a more negative zeta potential shift of the isoelectric point from 5.20 to 3.20, which will accelerate the charge carrier separation and electron transfer process. Thiocyanate ion passivation on black TiO2 demonstrated an increased work function around 0.60 eV, which was induced by the interracial dipole effect. Overall, the SCN H-Ni-TiO2 photocatalyst showed an enhanced CO2 reduction to solar fuel yield by 2.80 times higher than H-Ni-TiO2 and retained around 88% product formation yield after 40 h.
Lateral fluoro-substitution and chiral effects on supramolecular liquid crystals containing rod-like and H-bonded bent-core mesogens
(2016-01-01)
Han, Chun-Chieh
;
Yang, Li-Han
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Raghunath, Putikam
;
Lin, Ming-Chang
;
Kumar, Rohit
The first series of liquid crystalline supramolecular diads C/D containing asymmetric rod-like and H-bonded bent-core mesogens were designed and synthesised, among which supramolecular diad P*(III)/A*(II) with two chiral centers on both the H-acceptor/H-donor and non-lateral fluoride substitution possessed a wide blue phase (BPI) range of 13.7 degrees C. According to the molecular modeling, a large biaxial parameter (>= 3.2) and an appropriate HTP value (4.2-4.8 mu m(-1)) are the most important factors to stabilize the double twisted cylinder structure (i.e., BPI) in supramolecular diads. Moreover, the bent angles, biaxial parameters and dipole moments of supramolecular diads are mainly affected by the locations and numbers of H-bonds and chiral centers. Not only larger bent angles and biaxial parameters but also smaller dipole moments and HTP values were obtained by removing the lateral fluoride substitution on supramolecular diads to achieve the blue phase of P*(III)/A*(II) (without lateral fluoride substitution). Finally, the special optimal 1 : 1 molar ratio of supramolecular diad P*(III)/A*(II) (i.e., H-donor = 50 mol%) with the widest blue phase range is mainly attributed to its rod-like and H-bonded bent-core mesogens, rather than H-donor = 75 mol% in most supramolecular complexes containing linear H-bonded rod-like mesogens.