Browsing by Author "Dwivedi, Atul Kumar"

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Exploration of Energy Modulations in Novel RhB-TPE-Based Bichromophoric Materials via Interactions of Cu2+ Ion under Various Semiaqueous and Micellar Conditions
(2016-03-16)
Singh, Ravinder
;
Dwivedi, Atul Kumar
;
Singh, Ashutosh
;
Lin, Chien-Min
;
Arumugaperumal, Reguram
Novel bichromophoric materials TR-A and TR-B consisting of an entirely new combination of TPE and RhB units were developed to explore the optimum conditions of energy modulations via pH variation and Cu2+ interaction at various water contents of CH3CN. Interestingly, TR-A and TR-B, at 60 and 70% water contents; respectively, favored the optimum Cu2+-mediated energy modulations from TPE to RhB and thus achieve the brightest orange emissions of free RhB with complete disappearance of aggregation-induced emission (AIE) from TPE. Furthermore, various micellar conditions of triton-X-100, SDS, and CTAB were employed to adjust energy modulations of TR-A and TR-B at high water contents (at 80 and 90%, respectively). The incorporation of RhB into triton-X-100 micellar cavities disrupted AIE from TPE; thus, none of the energy modulations from TPE to RhB occurred even in the presence of Cu2+ ion. Interestingly, the micellar conditions of anionic surfactant (SDS) favored the increased local concentration of Cu2+ ions in the vicinity of scavangable RhB and facilitated the generation of noncyclic free RhB in situ via bright-orange emissions.
Monomeric and aggregation emissions of tetraphenylethene in a photo-switchable polymer controlled by cyclization of diarylethene and solvent conditions
(2017-10-14)
Singh, Ravinder
;
Wu, Hsin-Yen
;
Dwivedi, Atul Kumar
;
Singh, Ashutosh
;
Lin, Chien-Min
A novel photo-switchable polymer P-PHT containing diarylethene (DAE) and tetraphenylethene (TPE) moieties and a triazole linker in the repeating unit was synthesized to study the aggregation-induced emission (AIE) behaviour of TPE with both the open and closed forms of DAE in P-PHT with high water contents. The photo-switching phenomena of DAE (from open to closed forms under UV-irradiation) in P-PHT were prominent in organic solvent (THF), high water contents (at 90% H2O) and acidic conditions. Upon UV-irradiation of P-PHT at 90% water content, the AIE of TPE was completely quenched via an energy transfer event from TPE to cyclized DAE. Interestingly, the rare monomeric emission of TPE was first discovered by the photo-cyclization of DAE in P-PHT compared with the AIE behaviour of TPE with the open form of DAE in P-PHT with AIE favourable conditions of high water content (90% H2O) and acidic conditions.
Novel Water-Soluble Cyclodextrin-Based Conjugated Polymer for Selective Host-Guest Interactions of Cationic Surfactant CTAB and Reverse FRET with Rhodamine B Tagged Adamantyl Guest
(2016-08-09)
Dwivedi, Atul Kumar
;
Singh, Ravinder
;
Singh, Ashutosh
;
Wei, Kung-Hwa
;
Wu, Chu-Ya
A new water-soluble pi-conjugated main-chain polymer P1 bearing a beta-cyclodextrin (beta-CD) pendant was designed and synthesized. The aggregation and disaggregation of P1 generated faded yellow-greenish and bright-yellow emissions, respectively. The inclusion complexation capability of P1 through beta-CD pendant with a cationic surfactant cetyltrimethylammonium bromide (CTAB) guest and associative interactions of P1 with Fe3+ through triazole spacers resulted in significantly enhanced and completely diminished emission profiles of P1 in pure water, respectively. Interestingly, ADRhB as another rhodamine B (RhB) tagged adamantyl guest was transformed into ADRhB(0), i.e., the open form of ADRhB, to generate RhB emission in the presence of Fe3+ ion selectively for the pendent host beta-CD of PI, and the further interaction of.ADRhB(0)/Fe3+ with P1 prevailed a completely quenched RhB emission via the inclusion complexation of adamantyl terminal of ADRhB (0) in beta-CD. Moreover, stronger interactions of CTAB with beta-CD further generated RhB emission of ADRhB(0) even in the presence of acceptor Pl. Finally, a novel beta-CD bearing water-soluble P1 with selective and strong interactions of CTAB toward disaggregation events in pure water, and further electrostatic repulsion and utilization of RhB via RhB-tagged adamantyl guest ADRhB(0) as a donor revealed the reverse fluorescence resonance energy transfer (FRET) process of P1.
Synthesis and enhanced electron transfer of supramolecular nano-composite containing dendritic dye and surface-modified ZnO nano-rods
(2018-10-01)
Lin, Chien-Min
;
Li, Ming-Shiou
;
Dwivedi, Atul Kumar
;
Lin, Hong-Cheu
;
材料科學與工程學系
Supramolecular nano-composites 15T5N/ZnOx-PNH containing enhanced compatibilities of dendritic dye 15T5N and surface-modified nano-rod ZnOx-PNH were developed in this study. The physical properties of supramolecular nano-composites have been well investigated by theoretical calculation and various measurements, including UV visible, PL, TEM, TCSPC, FT-IR, and CV. H-bonded nano-composite 15T5N/ZnO30-PNH possessed the saturated quenched fiuorscence as dendritic dye 15T5N complexed with surface-modified nano-rod ZnO30-PNH. In contrast to nano-rod mixture 15T5N/ZnO (without surface-modification), more widened visible absorption band to promote more efficient photo-induced charge separation phenomenon was observed in supramolecular nano-composite 15T5N/ZnO30-PNH. Compared with surfactant T-PNH, less efficient electron transfer of surfactant T-PC6 was observed in TCSPC and PL measurements because of the steric hindrance of long alkyl chains (-C6H13) attached to surfactant T-PC6. Therefore, the triple H-bonds between dendritic dye 15T5N and surface-modified nano-rod ZnO30-PNH are verified to result in the desirable effective electron transfer in supramolecular nano-composite 15T5N/ZnO30-PNH.