Browsing by Author "Raju, Mandapati V. Ramakrishnam"

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A cyanide-responsive supramolecular nanovalve based on Pd(II)-templated pseudo-rotaxane
(2015-01-01)
Raju, Mandapati V. Ramakrishnam
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We report here the design and synthesis of a nanovalve system consisting of a carrier based on mesoporous silica nanoparticles and mechanized with a square planar Pd(II)-templated pseudo-rotaxane. This nanovalve was responsive to demetalation by cyanide anions, followed by the concomitant release of both the macrocycles and the contents of the pores, in this instance dye indicators. Gate-keeping of the mesopores was achieved by the formation of an intact coordination between the monodentate pyridine axles soluble in aqueous solution and the tridentate macrocycle Pd complex via a square planar metal template approach. A facile nanovalve system responsive to an anionic stimulus was therefore developed. Luminescence spectrometry was successfully used to demonstrate that the anion-stimulated dye release from the nanovalves gated by the Pd(II) metal template was independent of pH.
A facile ratiometric fluorescent chemodosimeter for hydrazine based on Ing-Manske hydrazinolysis and its applications in living cells
(2014-04-01)
Raju, Mandapati V. Ramakrishnam
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Prakash, Epperla Chandra
;
Chang, Huan-Cheng
;
Lin, Hong-Cheu
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材料科學與工程學系
A facile and sensitive fluorescent probe for hydrazine was successfully constructed, displaying excellent colorimetric and ratiometric responses towards hydrazine via Ing-Manske hydrazinolysis conditions in semi-aqueous buffer solution. Semi-empirical calculations as well as spectroscopic results revealed the signalling mechanism of the current probe under hydrazinolysis conditions, in which hydrazine exclusively deprotected the phthalimide group by an intermediate of phthalhydrazide. Extensive screening of pH effects on the probe with the aid of proton nuclear magnetic resonance and mass spectrometry supported the distinctive and diverse ratiometric responses under hydrazinolysis and basic hydrolysis conditions. Time resolved photoluminescence measurements of the probe further confirmed its discernible ratiometric responses probed at respective wavelengths. A distinctive ratiometric response under basic hydrolysis conditions and a successful utilization of probe towards hydrazine detection in living cells are demonstrated. (C) 2013 Elsevier Ltd. All rights reserved.
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 Novel Diketopyrrolopyrrole (DPP)-Based [2]Rotaxane for Highly Selective Optical Sensing of Fluoride
(2013-03-15)
Raju, Mandapati V. Ramakrishnam
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Lin, Hong-Cheu
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材料科學與工程學系
;
Department of Materials Science and Engineering
A novel [2]rotaxane based on an orthogonal H-bonded motif and 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) with controlled topicity was successfully constructed, displaying excellent stimulated responses toward anion and solvent polarity. The preorganized host selectively recognized F- with high optical sensitivity and reversibility via enhanced positive cooperativity and noncovalent interaction by evidence of a shorter fluorescence lifetime.
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
;
Lin, Hong-Cheu
;
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.
Naked eye and fluorescent detections of Hg2+ ions and Cysteine via J-aggregation and deaggregation of a perylene bisimide derivative
(2014-04-01)
Fang, Hsiao-Ping
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Shellaiah, Muthaiah
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Singh, Ashutosh
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Raju, Mandapati V. Ramakrishnam
;
Wu, Yen-Hsing
Selective naked eye and fluorescent sensor responses of a 1,6,7,12-tetra(4-tert-butylphenoxy)perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) derivative are reported for the first time toward Hg2+ ions and Cysteine (Cys) via J-aggregation and deaggregation mechanisms. The J-aggregation and deaggregation of PBI induced by Hg2+ and Cys were well established by UV-vis/PL and H-1 NMR titrations. The 1:1 stoichiometry of PBI-Hg2+ and Cys-Hg2+/PBI ensembles were elucidated from the jobs plots based on their UV-vis spectral changes. The linear complex formation by PBI-Hg2+ ensemble was confirmed through FT-IR and H-1 NMR spectral studies and well supported by its reversible nature upon the addition of pentamethyl diethylene triamine (PMDTA). The positive cooperativities of Hg2+ and Cys (with PBI) in PBI-Hg2+ and Cys-Hg2+/PBI ensembles were evidenced from the Hill plots based on their fluorescence binding isotherms. The detection limits of Hg2+ ions and Cys were calculated as 36.6 and 91.3 nM, respectively, by standard deviations and linear fittings of their Stern-Volmer (KSV) constants and relative fluorescence intensity changes, respectively. Furthermore, the sensor properties of PBI were well investigated by KSV constants, pH values, time effects, and time resolved photoluminescence (TRPL) spectra. (C) 2013 Elsevier B.V. All rights reserved.
Novel pyrene- and anthracene-based Schiff base derivatives as Cu2+ and Fe3+ fluorescence turn-on sensors and for aggregation induced emissions
(2013)
Shellaiah, Muthaiah
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Wu, Yen-Hsing
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Singh, Ashutosh
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Raju, Mandapati V. Ramakrishnam
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Lin, Hong-Cheu
Novel pyrene- and anthracene-based Schiff base derivatives P1 and A1 were synthesized via a one-pot reaction and utilized as fluorescence turn-on sensors towards Cu2+ and Fe3+ ions, respectively, and for aggregation induced emissions (AIEs). P1 in CH3CN and A1 in THF illustrated the fluorescence turn-on sensing towards Cu2+ and Fe3+ ions, respectively, via chelation enhanced fluorescence (CHEF) through excimer (P1-P1* and A1-A1*) formation. The 2 : 1 stoichiometry of the sensor complexes (P1 + Cu2+ and A1 + Fe3+) were calculated from Job plots based on UV-Vis absorption titrations. In addition, the binding sites of sensor complexes (P1 + Cu2+ and A1 + Fe3+) were well established from the H-1 NMR titrations and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially. The detection limits (LODs) and the association constant (K-a) values of P1 + Cu2+ and A1 + Fe3+ sensor responses were calculated by standard deviations, linear fittings and from their fluorescence binding isotherms. More importantly, P1 + Cu2+ and A1 + Fe3+ sensors were found to be active in wide ranges of pHs (1-14 and 2-14, respectively). Moreover, the time effect along with the enhancements of quantum yield (Phi) and time resolved photoluminescence (TRPL) decay constant (tau) towards sensor responses were investigated. Similarly, P1 in CH3CN and A1 in THF showed AIEs by increasing the aqueous media concentration from 0% to 90%, with altered fluorescence peak shifts (red and blue shifts, respectively). As well as tau value enhancements, the Phi values of 0.506 and 0.567 (with 630- and 101-fold enhancements) were acquired for P1 in CH3CN : H2O (20 : 80) and A1 in THF : H2O (40 : 60), respectively.
Self-Assembly of Tetraphenylethene-Based [2]Catenane Driven by Acid Base-Controllable Molecular Switching and Its Enabled Aggregation-Induced Emission
(2014-11-07)
Raju, Mandapati V. Ramakrishnam
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Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A novel [2]catenane 2-C based on the tetraphenylethene (TPE) and orthogonal H-bonded cleft was successfully constructed. VT-NMR and TEM measurements demonstrate that 2-C could be self-assembled to induce an enabled aggregation-induced emission (AIE) in aqueous solution and solid state owing to its TPE unit as well as present unique acid-base controllable and reversible supramolecular self-assembled nanosuperstructures by interplay of a wide range of noncovalent interactions.
Synthesis of novel platinum complex core as a selective Ag+ sensor and its H-bonded tetrads self-assembled with triarylamine dendrimers for electron/energy transfers
(2014-11-07)
Shellaiah, Muthaiah
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Raju, Mandapati V. Ramakrishnam
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Singh, Ashutosh
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Lin, Hsin-Chieh
;
Wei, Kung-Hwa
A novel platinum complex PtC with a tri-armed uracil hydrogen-bonded (H-bonded) unit was synthesized via a modular synthetic approach and characterized by H-1, C-13 NMR and MALDI-TOF mass spectroscopies. Two H-bonded tetrads, PtC-(TPAD1)(3) and PtC-(TPAD2)(3), based on a metal core PtC complexed with two generations of triarylamine dendrimers, TPAD1 and TPAD2 (with electron-donating nature), were successfully constructed with improved organic solubility via a classical H-bonded self-assembly approach. Supramolecular H-bonding in solution and solid state was elucidated by H-1 NMR titrations, IR spectral studies and time resolved photoluminescence (TRPL) measurements. The electron/energy transfers, as well as the self-assemblies of supramolecular tetrads, were established by UV-Vis and PL titrations and AFM morphological studies. Furthermore, metal complex core PtC showed selective sensitivity towards Ag+ ions through fluorescence turn-off responses without any interference from other common metal ions. The 1 : 1 binding stoichiometry and complexation mechanism between the probe and Ag+ ion was established by H-1 NMR titration. Moreover, PL reversibility of PtC + Ag+ could be achieved on addition of PMDTA.
Synthesis of novel platinum complex core as a selective Ag+ sensor and its H-bonded tetrads self-assembled with triarylamine dendrimers for electron/energy transfers
(2014-11-07)
Shellaiah, Muthaiah
;
Raju, Mandapati V. Ramakrishnam
;
Singh, Ashutosh
;
Lin, Hsin-Chieh
;
Wei, Kung-Hwa
A novel platinum complex PtC with a tri-armed uracil hydrogen-bonded (H-bonded) unit was synthesized via a modular synthetic approach and characterized by H-1, C-13 NMR and MALDI-TOF mass spectroscopies. Two H-bonded tetrads, PtC-(TPAD1)(3) and PtC-(TPAD2)(3), based on a metal core PtC complexed with two generations of triarylamine dendrimers, TPAD1 and TPAD2 (with electron-donating nature), were successfully constructed with improved organic solubility via a classical H-bonded self-assembly approach. Supramolecular H-bonding in solution and solid state was elucidated by H-1 NMR titrations, IR spectral studies and time resolved photoluminescence (TRPL) measurements. The electron/energy transfers, as well as the self-assemblies of supramolecular tetrads, were established by UV-Vis and PL titrations and AFM morphological studies. Furthermore, metal complex core PtC showed selective sensitivity towards Ag+ ions through fluorescence turn-off responses without any interference from other common metal ions. The 1: 1 binding stoichiometry and complexation mechanism between the probe and Ag+ ion was established by H-1 NMR titration. Moreover, PL reversibility of PtC + Ag+ could be achieved on addition of PMDTA.