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Selektor SL, Shcherbina MA, Bakirov AV, Batat P, Grauby-Heywang C, Grigorian S, Arslanov VV, Chvalun SN. Cation-Controlled Excimer Packing in Langmuir-Blodgett Films of Hemicyanine Amphiphilic Chromoionophores. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:637-643. [PMID: 26654539 DOI: 10.1021/acs.langmuir.5b04075] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Supramolecular structure of ultrathin films of hemicyanine dye bearing a crown ether group (CrHCR) was tuned by lateral pressure and investigated by means of compression isotherms, UV-vis and fluorescence spectroscopies, and X-ray reflectivity. Two different types of aggregation were revealed, depending on the absence or the presence of metal cations in the water subphase. While CrHCR forms at high surface pressures head-to-tail stacking aggregates on pure water, changing the subphase to a metal-cation-containing one leads to the appearance of well-defined excimers with head-to-head orientation. The structure of monolayers transferred onto solid supports by the Langmuir-Blodgett (LB) technique was examined by use of X-ray reflectivity measurements and molecular modeling. A model of cation-induced excimer formation in hemicyanine Langmuir monolayers is proposed. Finally, fluorescence emission properties of LB films of CrHCR can be managed by appropriate changes in the subphase composition, this last one determining the type of chromophore aggregation.
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Affiliation(s)
- S L Selektor
- Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Moscow, Russia
| | - M A Shcherbina
- National Research Centre Kurchatov Institute, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow, Russia
| | - A V Bakirov
- National Research Centre Kurchatov Institute, Moscow, Russia
- Enikolopov Institute of Synthetic Polymer Materials RAS, Moscow, Russia
| | - P Batat
- Univ. Bordeaux, LOMA, UMR 5798, F-33400 Talance, France; CNRS, LOMA, UMR 5798, F-33400 Talence, France
| | - C Grauby-Heywang
- Univ. Bordeaux, LOMA, UMR 5798, F-33400 Talance, France; CNRS, LOMA, UMR 5798, F-33400 Talence, France
| | - S Grigorian
- Institute of Physics, University of Siegen , 57072 Siegen, Germany
| | - V V Arslanov
- Frumkin Institute of Physical Chemistry and Electrochemistry RAS, Moscow, Russia
| | - S N Chvalun
- National Research Centre Kurchatov Institute, Moscow, Russia
- Moscow Institute of Physics and Technology, Moscow, Russia
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Maganti L, Jash M, Nair A, Radhakrishnan TP. Nanoparticle assembly following Langmuir-Hinshelwood kinetics on a Langmuir film and chain networks captured in LB films. Phys Chem Chem Phys 2015; 17:7386-94. [PMID: 25700245 DOI: 10.1039/c5cp00606f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Langmuir-Blodgett (LB) technique is an elegant protocol for the steered assembly of metal nanoparticles, the deposition pressure serving as a convenient parameter to tune the assembly. Adsorption of nanoparticles from the subphase to the air-water interface can provide further control of the process. Citrate-stabilized gold nanoparticles in the aqueous subphase are shown to assemble into extended 2-dimensional chain networks following adsorption on a cationic amphiphile Langmuir film at the air-water interface. Kinetic investigations show that the process can be visualized as a surface-catalyzed reaction and explained in terms of the Langmuir-Hinshelwood mechanism. The LB deposition proves to be a unique route to capture the reaction product together with the amphiphile film. The deposition pressure is used to tune the density of nanoparticle chain networks in the LB film, and their optical extinction spectrum. The unusual blue shift of the extinction observed with increasing deposition pressure is attributed to the impact of the amphiphile monolayer environment. The extent of formation of the chain network is analyzed in terms of the pathways in the corresponding graph representation, and shown to scale with the deposition pressure. The current investigation highlights the use of a charged monolayer as a heterogeneous catalyst surface, provides fundamental insight into the kinetics of nanoparticle assembly at interfaces, and demonstrates the utility of the LB technique in tuning the formation of 2-dimensional nanoparticle chain networks.
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Affiliation(s)
- Lasya Maganti
- School of Chemistry, University of Hyderabad, Hyderabad - 500046, India.
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Chakraborty S, Debnath P, Dey D, Bhattacharjee D, Hussain SA. Formation of fluorescent H-aggregates of a cyanine dye in ultrathin film and its effect on energy transfer. J Photochem Photobiol A Chem 2014. [DOI: 10.1016/j.jphotochem.2014.07.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Gu JY, Chen T, Wang L, Dong WL, Yan HJ, Wang D, Wan LJ. Electrostatic-interaction-induced molecular deposition of a hybrid bilayer on Au(111): a scanning tunneling microscopy study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:3502-3506. [PMID: 24611792 DOI: 10.1021/la500873y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Hybrid bilayers consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and meso-tetra(4-pyridyl)porphine (TPyP) have been successfully constructed on Au(111) and investigated by electrochemical scanning tunneling microscopy (ECSTM). Under the guidance of the electrostatic interaction between negatively charged sulfonate groups and positively charged pyridyl groups, the underlying HPTS arrays act as templates for the deposition of cationic TPyPs, forming two types of TPyP/HPTS complex bilayers. The present work provides a feasible way to fabricate hybrid multilayers on the electrode surface via electrostatic interaction, which has great significance for the design of molecular nanodevices.
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Affiliation(s)
- Jing-Ying Gu
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences (CAS) , Beijing 100190, People's Republic of China
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Balaswamy B, Maganti L, Sharma S, Radhakrishnan TP. Mechanical control of molecular aggregation and fluorescence switching/enhancement in an ultrathin film. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:17313-17321. [PMID: 23214921 DOI: 10.1021/la303549z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Optical responses of molecular aggregates and assemblies are often different from that of the individual molecules. Self-assembly approaches provide little physical control on the extent of aggregation. Mechanical compression of amphiphilic molecules (with chromophore/fluorophore head groups) at the air-water interface, followed by transfer as Langmuir-Blodgett (LB) films, should prove to be an elegant route to molecular assemblies with systematically tunable aggregation and optical responses. This concept is demonstrated using monolayer LB films of a diaminodicyanoquinodimethane (DADQ)-based amphiphile fabricated at different surface pressures. Films deposited above a threshold pressure exhibit a strong blue-shift in the absorption and fluorescence relative to those deposited below; computational investigations suggest that this is due to the formation of 2-dimensional close-packed assemblies. Significantly, the blue emission of the films deposited above the threshold pressure increases with compaction, demonstrating aggregation-induced fluorescence enhancement in ultrathin films, a phenomenon well-established in crystals and nanocrystals of selected classes of molecules including the DADQs. The sharp contrast with aggregation-induced fluorescence quenching observed with most dye molecules is illustrated by a parallel investigation of LB films of a hemicyanine-based amphiphile. The present study illustrates the efficacy of simple mechanical compression and the LB technique in fabricating ultrathin films with tailored supramolecular assembly and optical responses.
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Affiliation(s)
- B Balaswamy
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
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Simultaneously Synthesis and Encapsulation of Metallic Nanoparticles Using Linear–Dendritic Block Copolymers of Poly(ethylene glycol)-Poly(citric acid). ACTA ACUST UNITED AC 2011. [DOI: 10.4028/www.scientific.net/kem.478.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Linear-dendritic triblock copolymers of linear poly(ethylene glycol) and hyperbranched poly(citric acid) (PCA-PEG-PCA) were used as the reducing and capping agents to encapsulate gold and silver nanoparticles (AuNPs and AgNPs). PCA-PEG-PCA copolymers in four different molecular weights were synthesized using 2, 5, 10 and 20 citric acid/PEG molar ratios and were called A1, A2, A3 and A4, respectively. Nanoparticles were encapsulated simultaneously during the preparation process. AuNPs were simply synthesized and encapsulated by addition a boiling aqueous solution of HAuCl4 to aqueous solutions of A1, A2, A3 and A4. In the case of silver, an aqueous solution of AgNO3 was reduced using NaBH4 and AgNPs were encapsulated simultaneously by adding aqueous solutions of different PCA-PEG-PCA to protect the fabricated silver nanoparticles from aggregation. Encapsulated AuNPs and AgNPs were stable in water for several months and agglomeration did not occur. The synthesized silver and gold nanoparticles have been encapsulated within PCA-PEG-PCA macromolecules and have been studied using Transmission Electron Microscopy (TEM) and UV/Vis absorption spectroscopy. Studies reveal that there was a reverse relation between the size of synthesized AuNPs/AgNPs and the size of citric acid parts of PCA-PEG-PCA copolymers. For example, the prepared gold and silver nanoparticles by A3 copolymer are of an average size of 8 nm and 16 nm respectively. Finally, the loading capacity of A1, A2, A3 and A4 and the size of synthesized AuNPs and AgNPs were investigated using UV/Vis data and the corresponding calibration curve. It was found that the loading capacity of copolymers depends directly on the concentration of copolymers and their molecular weight.
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Rajesh K, Balaswamy B, Yamamoto K, Yamaki H, Kawamata J, Radhakrishnan TP. Enhanced optical and nonlinear optical responses in a polyelectrolyte templated Langmuir-Blodgett film. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:1064-1069. [PMID: 21190346 DOI: 10.1021/la104078g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Optical and nonlinear optical properties like fluorescence and second harmonic generation (SHG) of molecular materials can be strongly influenced by the mode of assembly of the molecules. The Langmuir-Blodgett (LB) technique is an elegant route to the controlled assembly of molecules in ultrathin films, and complexation of ionic amphiphiles in the Langmuir film by polyions introduced in the aqueous subphase provides a simple and efficient access to further control, stabilization, and optimization. The monolayer LB film of the hemicyanine-based amphiphile, N-n-octadecyl-4-[2-(4-(N,N-ethyloctadecylamino)phenyl)ethenyl]pyridinium possessing a "tail-head-tail" structure, shows fluorescence as well as SHG response. The concomitant enhancement of both of these linear and nonlinear optical attributes is achieved through templating with the polyanion of carboxymethylcellulose. Brewster angle and atomic force microscopy reveal the influence of polyelectrolyte templating on the morphology of the Langmuir and LB films. Polarized absorption and fluorescence spectroscopy provide insight into the impact of complexation with the polyelectrolyte on the orientation and deaggregation of the hemicyanine headgroup leading to fluorescence and SHG enhancement in the LB film.
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Affiliation(s)
- K Rajesh
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
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Rajesh K, Sreedhar B, Radhakrishnan TP. Assembly of Gold Nanoparticles on a Molecular Ultrathin Film: Tuning the Surface Plasmon Resonance. Chemphyschem 2010; 11:1780-6. [DOI: 10.1002/cphc.200900675] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Rajesh K, Rajendra K, Radhakrishnan TP. Fluorescence enhancement in Langmuir-Blodgett films: role of amphiphile structure, orientation, and assembly. J Phys Chem B 2010; 114:849-56. [PMID: 20028008 DOI: 10.1021/jp909508v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Suppression of self-quenching of fluorescence emission in supramolecular systems is of fundamental interest in the design and development of novel optical materials. While a number of molecular design and assembly strategies have been formulated for the fabrication of molecular crystals with enhanced light emission, parallel explorations based on systematic approaches in the domain of molecular ultrathin films are rare. We have investigated Langmuir-Blodgett films of amphiphilic molecules bearing the same hemicyanine choromophore headgroup but with different possibilities of attachment of the octadecyl hydrocarbon chain, under different deposition conditions. Fluorescence spectroscopy studies indicate enhanced light emission in the derivative with a "tail-head-tail" structure. The observed trends are attributed to the amphiphile structure, nature of deposition, and the chromophore orientations revealed through polarized absorption spectra of the films. The study suggests a simple design strategy toward realization of molecular ultrathin films with enhanced light emission.
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Affiliation(s)
- K Rajesh
- School of Chemistry, University of Hyderabad, Hyderabad-500 046, India
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Wanapun D, Hall VJ, Begue NJ, Grote JG, Simpson GJ. DNA-Based Polymers as Chiral Templates for Second-Order Nonlinear Optical Materials. Chemphyschem 2009; 10:2674-8. [DOI: 10.1002/cphc.200900303] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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DiBenedetto SA, Frattarelli DL, Facchetti A, Ratner MA, Marks TJ. Structure−Performance Correlations in Vapor Phase Deposited Self-Assembled Nanodielectrics for Organic Field-Effect Transistors. J Am Chem Soc 2009; 131:11080-90. [DOI: 10.1021/ja902751e] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Sara A. DiBenedetto
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113
| | - David L. Frattarelli
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Antonio Facchetti
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Mark A. Ratner
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113
| | - Tobin J. Marks
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113
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Abraham E, Grauby-Heywang C, Selector S, Jonusauskas G. Characterization of hemicyanine Langmuir–Blodgett films by picosecond time-resolved fluorescence. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2008; 93:44-52. [DOI: 10.1016/j.jphotobiol.2008.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 04/11/2008] [Accepted: 04/13/2008] [Indexed: 11/25/2022]
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