Syed Arshad Hussain

Publications

• Adsorption of a Cationic Laser Dye onto Polymer/Surfactant Complex Film Fabricated by Layer-by-Layer Electrostatic Self-Assembly Technique

  P. K. Paula, S A Hussain, D. Bhattacharjee, M. Pal

  06/2011;

  Fabrication of complex molecular films of organic materials is one of the most important issues in modern nanoscience and nanotechnology. Soft materials with flexible properties have been given much attention and can be obtained through bottom up processing from functional molecules, where self-asse... [more] Fabrication of complex molecular films of organic materials is one of the most important issues in modern nanoscience and nanotechnology. Soft materials with flexible properties have been given much attention and can be obtained through bottom up processing from functional molecules, where self-assembly based on supramolecular chemistry and designed assembly have become crucial processes and technologies. In this short communication, we report the successful incorporation of cationic laser dye Rhodamine 6G abbreviated as R6G into the pre-assembled polyelectrolyte/Surfactant complex film onto quartz substrate by electrostatic adsorption technique. Poly(allylamine hydrochloride) (PAH) was used as polycation and Sodium dodecyl sulphate(SDS) was used as anionic surfactant. UV-Vis absorption spectroscopic characterization reveals the formation of only H-type aggregates of R6G in their aqueous solution and both H and J-type aggregates in PAH/SDS/R6G complex LbL films as well as the kinetics of adsorption of R6G onto the complex films. The ratio of the absorbance intensity of two aggregated bands in PAH/SDS/R6G complex films is merely independent of the concentration range of the SDS solution used to fabricate PAH/SDS complex self-assembled films. Atomic Force Microscopy reveals the formation of R6G aggregates in PAH/SDS/R6G complex films.

• Layer-by-Layer assembling and characterizations of dye-polyions onto solid substrate by Electrostatic adsorption process

  Md. N. Islam, P. K. Paul, S A Hussain, D. Bhattacharjee

  06/2011;

  Self assembled films of organic azobenzene dye chicago sky blue 6B (CSB) have been fabricated onto solid substarte by electrostatic alternate adsorption of polycation ploy(allyl amine hydrochloride) (PAH) and CSB. UV-Vis absorption spectroscopic studies reveal the successful incorporation of CSB mol... [more] Self assembled films of organic azobenzene dye chicago sky blue 6B (CSB) have been fabricated onto solid substarte by electrostatic alternate adsorption of polycation ploy(allyl amine hydrochloride) (PAH) and CSB. UV-Vis absorption spectroscopic studies reveal the successful incorporation of CSB molecules into LbL films and consequent formation of aggregates. This view is supported by FTIR spectroscopic studies. Scanning electron microscope picture confirms the formation of nano crystalline aggregates in the LbL films. About 15 minute is required to complete the electrostatic interaction between PAH and CSB molecules in one bi-layer LbL film.

• J-aggregates of thiacyanine dye organized in LB films: effect of irradiation of light

  Syed Arshad Hussain, D. Dey, S. Chakraborty, D. Bhattacharjee

  06/2011;

  In the present communication we report the preparation and characterizations of Langmuir and Langmuir-Blodgett films of a thiacyanine dye-dioctadecyl thiacyanine perchlorate (NK) mixed with Octadecyl trimethyl ammonium bromide (OTAB). The relationship between the molar ratio of OTAB and NK and the o... [more] In the present communication we report the preparation and characterizations of Langmuir and Langmuir-Blodgett films of a thiacyanine dye-dioctadecyl thiacyanine perchlorate (NK) mixed with Octadecyl trimethyl ammonium bromide (OTAB). The relationship between the molar ratio of OTAB and NK and the orientation of molecules at the air-water interface was investigated using surface pressure - area per molecule ({\pi}-A) isotherm. UV-Vis absorption and fluorescence spectroscopic investigations reveal that prominent J-aggregation of NK molecule was observed in the LB films lifted at higher surface pressure. This J-aggregation can be controlled by diluting the NK molecules with OTAB. It was observed that the J-aggregates of NK decayed to monomer and H-aggregates when the NK-LB film was exposed to a monochromatic light of wavelength 460 nm (Lambda max of J - aggregates).

• Reaction-kinetics of organo-clay hybrid films: in-situ IRRAS and AFM studies

  Syed Arshad Hussain, Md. N. Islam, D. Bhattacharjee

  06/2011;

  In this paper we have reported the reaction kinetics of nano dimensional clay saponite and hectorite with an amphiphilic cation octadecyl rhodamine B (RhB) in hybrid Langmuir monolayer at the air-water interface. The surface pressure-molecular area (pi-A) isotherms were strongly influenced by the pr... [more] In this paper we have reported the reaction kinetics of nano dimensional clay saponite and hectorite with an amphiphilic cation octadecyl rhodamine B (RhB) in hybrid Langmuir monolayer at the air-water interface. The surface pressure-molecular area (pi-A) isotherms were strongly influenced by the presence of clay with the lift-off area of the cationic amphiphile shifted to progressively larger area. In-situ infrared reflection absorption spectroscopy (IRRAS) was used to demonstrate the reaction kinetics. Time taken to complete the reaction kinetics for RhB-hectorite hybrid films is larger than RhB-saponite hybrid films. Atomic force microscopic images of hybrid Langmuir-Blodgett films give compelling visual evidence of the incorporation of clay platelets into the hybrid films and density of which increases with the progress of reaction kinetics.
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  Adsorption kinetics of a fluorescent dye in a long chain fatty acid matrix.

  Syed Arshad Hussain, Soma Banik, S Chakraborty, D Bhattacharjee

  Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 06/2011; 79(5):1642-7.

  This work reports the adsorption kinetics of a highly fluorescent laser dye rhodamine B (RhB) in a preformed stearic acid (SA) Langmuir monolayer. The reaction kinetics was studied by surface pressure-time (π-t) curve at constant area and in situ fluorescence imaging microscopy (FIM). Increase in su... [more] This work reports the adsorption kinetics of a highly fluorescent laser dye rhodamine B (RhB) in a preformed stearic acid (SA) Langmuir monolayer. The reaction kinetics was studied by surface pressure-time (π-t) curve at constant area and in situ fluorescence imaging microscopy (FIM). Increase in surface pressure (at constant area) with time as well as increase in surface coverage of monolayer film at air-water interface provide direct evidence for the interaction. ATR-FTIR spectra also supported the interaction and consequent complexation in the complex films. UV-vis absorption and Fluorescence spectra of the complex Langmuir-Blodgett (LB) films confirm the presence of RhB molecules in the complex films transferred onto solid substrates. The outcome of this work clearly shows successful incorporation of RhB molecules into SA matrix without changing the photophysical characteristics of the dye, thus making the dye material as LB compatible.
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  Effect of nano-clay platelets on the J-aggregation of thiacyanine dye organized in Langmuir-Blodgett films: a spectroscopic investigation.

  D Bhattacharjee, Syed Arshad Hussain, S Chakraborty, R A Schoonheydt

  Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 09/2010; 77(1):232-7.

  In this paper we report the effect of the incorporation of nano-dimensional clay platelets, laponite, on the J-aggregation of a thiacyanine dye N,N'-dioctadecyl thiacyanine perchlorate (NK) assembled into Langmuir-Blodgett (LB) monolayers. pi-A isotherms and atomic force microscopic studies conf... [more] In this paper we report the effect of the incorporation of nano-dimensional clay platelets, laponite, on the J-aggregation of a thiacyanine dye N,N'-dioctadecyl thiacyanine perchlorate (NK) assembled into Langmuir-Blodgett (LB) monolayers. pi-A isotherms and atomic force microscopic studies confirm the successful incorporation of clay platelets into the Langmuir monolayer of NK. J-aggregates of NK remain present in LB films lifted at lower as well as higher surface pressures in the absence of laponite clay platelets. However, with the incorporation of clay platelets, J-aggregates are formed only in LB films lifted at higher surface pressure of 30 mN/m and totally absent in the films lifted at lower surface pressures of 10 and 15 mN/m. This may be due to the formation of nano-trapping level by overlapping of clay platelets at higher surface pressure. NK molecules may get squeezed to these nano-trapping to form J-aggregates.
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  Langmuir-Blodgett monolayers of cationic dyes in the presence and absence of clay mineral layers: N,N'-dioctadecyl thiacyanine, octadecyl rhodamine B and laponite.

  Syed Arshad Hussain, Robert A Schoonheydt

  Langmuir : the ACS journal of surfaces and colloids. 07/2010; 26(14):11870-7.

  Langmuir-Blodgett (LB) films of N,N'-dioctadecyl thiacyanine perchlorate (TC18) and octadecyl rhodamine B chloride (RhB18) and their mixtures in the presence and absence of clay mineral layers were investigated by recording surface pressure-area (pi-A) isotherms and by UV-vis and fluorescence sp... [more] Langmuir-Blodgett (LB) films of N,N'-dioctadecyl thiacyanine perchlorate (TC18) and octadecyl rhodamine B chloride (RhB18) and their mixtures in the presence and absence of clay mineral layers were investigated by recording surface pressure-area (pi-A) isotherms and by UV-vis and fluorescence spectroscopies. The pi-A isotherms of TC18, RhB18, and their mixtures are characteristic of liquid expanded state behavior with repulsive interactions between the two cationic dyes. In the presence of laponite, the pi-A isotherms show liquid expanded and condensed-state behavior. In laponite dispersions and in monolayers, TC18 has a strong tendency to aggregate with formation of H- and J- aggregates. The absorption and fluorescence maxima of the monomers in the films are at 435 nm and at 480 nm; H-dimers have an absorption maximum around 410 nm and do not fluoresce. J-dimers are present in all the films with absorption maximum at 461 nm and fluorescence at 463 nm. RhB18 is mainly present as monomers in the LB films with an absorption maximum at 576 nm and fluorescence at 595 nm. Fluorescence resonance energy transfer from TC18 to RhB18 has been observed in clay dispersions and in films with and without laponite. The optimum condition for TC18 --> RhB18 fluorescence energy transfer in the films is 90 mol % TC18 + 10 mol % RhB18.

• PREPARATION AND CHARACTERIZATION OF NANO-CLAY HYBRID MONOLAYER FILMS

  Syed Arshad Hussain

  21 st Annual General meeting of Material research Society of India., Sardar Patel University, Vallabh Vidyanagar – 388120, Gujarat; 02/2010

  Ultrathin ordered organo-clay hybrid films with a thickness of few nanometers show considerable technological potential as a novel class of materials. Due to their tailor- made electrical and optical properties they are promising candidates for a large number of technological applications including ... [more] Ultrathin ordered organo-clay hybrid films with a thickness of few nanometers show considerable technological potential as a novel class of materials. Due to their tailor- made electrical and optical properties they are promising candidates for a large number of technological applications including optical and micro-electronical devices, sensors and surface modifications [1,2]. When an amphiphilic cation is spread onto the surface of the clay suspension at a low concentration, the floating monolayer of the amphiphilic cation is hybridized with clay nano-sheets by the electrostatic force at the air-clay dispersion interface. Langmuir-Blodgett method is an efficient technique to prepare such nano-dimensional, ultra-thin, ordered and organized assembly of molecules at the air-water interface and onto solid substrates [1] In this study hybrid monolayer of laponite were prepared and investigated in order to find the factors affecting monolayer formation. Pressure-area ( ) isotherm, Infrared reflectance absorption spectroscopy (IRRAS) and Atomic Force Microscopy (AFM) were used to characterize the monolayer. isotherm analysis confirms the incorporation of laponite particles onto hybrid monolayer. The lift-off area of hybrid monolayer reflects the average area per charge on the laponite sheets. Incorporation of laponite particles makes the monolayer more rigid and increases the stability. IRRAS studies reveal that the vibration of (Si-O) band is restricted to in-plane only and out-of-plane vibration is disturbed in the hybrid monolayer. Almost 30 minutes is required to complete up the hybrid film formation at the air-water interface. However, the time is lowered with the increase of clay concentration and forms aggregates. AFM image of dye-laponite hybrid films gives visual evidence of the incorporation of clay particles onto hybrid monolayer. Surface coverage of the film onto solid substrate is approximately 70%. The average height of the film (height of clay + height of the organic molecule) is of the order of 2 nm.

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• Photophysical studies of xanthene dye in alkanols and in inorganic ions

  B Ganguly, R K Nath, S A Hussain, A K Panda

  Indian Journal Physics. 01/2010; 84:549-555.

  Eosin Y belongs to a xanthene group. It is an anionic fluorescent dye. The absorbance and fluorescence of Eosin Y have been investigated in a series of alkanols (methanol to propanol). When the solvents are added to the aqueous solution of Eosin Y (EY) the absorbance and fluorescence intensity are e... [more] Eosin Y belongs to a xanthene group. It is an anionic fluorescent dye. The absorbance and fluorescence of Eosin Y have been investigated in a series of alkanols (methanol to propanol). When the solvents are added to the aqueous solution of Eosin Y (EY) the absorbance and fluorescence intensity are enhanced. The alkanols are found to affect the absorption and fluorescence spectra of the dye. On the basis of solvent adsorption model the binding constants of the dye with alkanols have been estimated. The interaction of solvent molecule with dye in aqueous solution is specific in nature. The fluorescence quenching of Eosin Y by the inorganic ions [Fe(CN)6]-3, [Fe(CN)6]-4 and Cl- was also observed. The ions influenced the quenching process to different extents. The rate constants of quenching were calculated using the Stern-Volmer equation. The equilibrium constant of dye in presence of inorganic ions are determined by Scott equation.

• Organic molecules adsorbed onto nano-clay and Langmuir-Blodgett (LB) films: trace of FRET

  Syed Arshad Hussain

  97 th Indian Science Congress, University of Kerala; 01/2010

  Fluorescence Resonance Energy Transfer (FRET) is a physical phenomenon first described over 50 years ago. Due to its sensitivity to distance, FRET has been used to investigate molecular level interaction. Fluorescence emission rate of energy transfer has wide applications in biomedical, protein fold... [more] Fluorescence Resonance Energy Transfer (FRET) is a physical phenomenon first described over 50 years ago. Due to its sensitivity to distance, FRET has been used to investigate molecular level interaction. Fluorescence emission rate of energy transfer has wide applications in biomedical, protein folding, RNA/DNA identification and their energy transfer process. Clay mineral particles play an important role in concentrating the dye molecules onto their surfaces. This may provide a platform for close interaction between energy donor and acceptor to come into close interaction making energy transfer possible, in contrast to inactive systems based on homogeneous solutions. There are very few reports on the energy transfer occurring in systems composed of organic dyes and clays. Probably the first reports of efficient FRET among dyes adsorbed onto clay mineral sheets, are clay mineral dispersions with cyanine (energy donor) and rhodamine (energy acceptor) dyes simultaneously adsorbed onto clay mineral surfaces. So it is extremely important to identify suitable energy donor-acceptor pair and to probe the condition for efficient energy transfer. On the other hand Langmuir-Blodgett (LB) technique is a conventional and highly sophisticated method for fabricating organic ultrathin films, which are made by stepwise deposition of monolayer’s of amphiphile from the air-water interface onto solid substrate [16]. With respect to other film preparation techniques, the LB technique has the added advantage of having smooth, uniform and almost defect free monolayer film [16]. In our present study, the trace of energy transfer between two dyes has been reported. Here, we used two cationic dyes namely, a thiacyanine dye 3-octadecyl-2-[(3-octadecyl-2(3H)-benzolylidene) methyl] benzothiazolium perchlorate or -dioctadecyl thiacyanine perchlorate (NK) and a xanthane dye octadecyl rhodamine B chloride (RhB) representing a suitable energy donor and acceptor respectively. We investigated the system in chloroform solutions, clay dispersions and organized in the Langmuir and Langmuir-Blodgett (LB) monolayer with and without a synthetic clay laponite. AFM image confirms the incorporation of clay in hybrid films. FRET between NK and RhB was observed in clay dispersion and in LB films with and without clay. Efficiency of energy transfer was maximum in LB films with clay.

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  Investigations of RhB18 langmuir monolayer by fluorescence imaging microscopy

  S A Hussain, S Chakraborty, D Bhattacharjee

  Indian Journal of Physics and Proceedings of the Indian Association for the Cultivation of Science -New Series-. 01/2010; 84:625-629.

  This communication reports the surface pressure vs area per molecule isotherm and Fluorescence Imaging Microscopic studies of the formation of domain structure in the mixed Langmuir monolayer of RhB and Stearic acid (SA) at the air-water interface. Strong repulsive interaction between the unlike com... [more] This communication reports the surface pressure vs area per molecule isotherm and Fluorescence Imaging Microscopic studies of the formation of domain structure in the mixed Langmuir monolayer of RhB and Stearic acid (SA) at the air-water interface. Strong repulsive interaction between the unlike components leads to the phase separation and formation of microcrystalline domains at the air water interface of the Langmuir monolayer. These domain can be directly visualized using fluorescence imaging microscope.

• Physics Research in the North East

  B. K. De, D. Bhattacharjee, S. Chattopadhyay, S. A. Hussain, A. Guha

  First Edition 01/2010; ACB Publication, Kolkata..

  ISBN: ISBN 81-87500-53-0
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  Fluorescence Resonance Energy Transfer between organic dyes adsorbed onto nano-clay and Langmuir-Blodgett (LB) films.

  Syed Arshad Hussain, S. Chakraborty, D. Bhattacharjee, R A Schoonheydt

  Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 11/2009;

  In this communication we investigate two dyes N,N'-dioctadecyl thiacyanine perchlorate (NK) and octadecyl rhodamine B chloride (RhB) in Langmuir and Langmuir-Blodgett (LB) films with or with out a synthetic clay laponite. Observed changes in isotherms of RhB in absence and presence of nano-clay ... [more] In this communication we investigate two dyes N,N'-dioctadecyl thiacyanine perchlorate (NK) and octadecyl rhodamine B chloride (RhB) in Langmuir and Langmuir-Blodgett (LB) films with or with out a synthetic clay laponite. Observed changes in isotherms of RhB in absence and presence of nano-clay platelets indicate the incorporation of clay platelets onto RhB-clay hybrid films. AFM images confirm the incorporation of clay into hybrid films. FRET is observed in clay dispersion and LB films with and without clay. Efficiency of energy transfer is maximum in LB films with clay.

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• Preparation and characterization of nano-clay hybrid monolayer films

  Syed Arshad Hussain, S. Chakraborty, D. Bhattacharjee

  AIT Nano-2009, Biotechnology,Ansal Institute of Technology, New Delhi; 10/2009

  Ultrathin ordered organo-clay hybrid films with a thickness of few nanometers show considerable technological potential as a novel class of materials. Due to their tailor- made electrical and optical properties they are promising candidates for a large number of technological applications including ... [more] Ultrathin ordered organo-clay hybrid films with a thickness of few nanometers show considerable technological potential as a novel class of materials. Due to their tailor- made electrical and optical properties they are promising candidates for a large number of technological applications including optical and micro-electronical devices, sensors and surface modifications [1,2]. The layered structure of the clay gives rise to one of its interesting features: molecules are intercalated into spaces between the clay layers by a cation-exchange reaction. By use of this feature, a number of organo-clay complexes have been developed and investigated as new materials. Another characteristic feature of the clays (smectite) is single layer exfoliation. If the smectite clay is dispersed in water at a low concentration, the clay layers are isolated with each other and the single clay layers are suspended in water as clay nano-sheets with a thickness of 0.96 nm. When an amphiphilic cation is spread onto the surface of the clay suspension at a low concentration, the floating monolayer of the amphiphilic cation is hybridized with clay nano-sheets by the electrostatic force at the air-clay dispersion interface. Langmuir-Blodgett method is an efficient technique to prepare such nanodimensional, ultrathin, ordered and organized assembly of molecules at the air-water interface and onto solid substrates [1]. In this study hybrid monolayer of laponite were prepared and investigated in order to find the factors affecting monolayer formation. Pressure-area isotherm, Infrared reflectance absorption spectroscopy (IRRAS) and Atomic Force Microscopy (AFM) were used to charectarize the monolayer. Surface pressure-area per molecule (pi-A) isotherm analysis confirms the incorporation of laponite particles onto hybrid monolayer films. The lift-off area of hybrid monolayer reflects the average area per charge on the laponite sheets. Incorporation of laponite particles makes the monolayer more rigid and increases the stability. IRRAS studies reveal that the vibration of (Si-O) band is restricted to in-plane only and out-of-plane vibration is disturbed in the hybrid monolayer. Almost 30 minutes is required to complete up the hybrid film formation at the air-water interface. However, the time is lowered with the increase of clay concentration and forms aggregates. AFM image of dye-laponite hybrid films gives visual evidence of the incorporation of clay particles onto hybrid monolayer. Surface coverage of the film on solid substrate is approximately 70%. The average height of the film (height of clay + height of the organic molecule) is of the order of 2 nm. References: 1. R. A. Ras Ph.D. Thesis “Molecular and Particulate Organization in Organo-Clay monolayers” (2003) K. U. Leuven, Belgium. 2. N. N. Herrera, J-L. Putaux, E. B. Lami Progress in Solid State Physics 34 (2006) 121-137.

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• An Introduction to Fluorescence Resonance Energy Transfer (FRET)

  Syed Arshad Hussain

  08/2009;

  Recent advances in Fluorescence Resonance Energy Transfer (FRET) provides a way to measure and understand different biological systems and molecular interactions in nanometer order. In this report the introduction and principle of the FRET process have been explained. Comment: 4 pages, 3 figures... [more] Recent advances in Fluorescence Resonance Energy Transfer (FRET) provides a way to measure and understand different biological systems and molecular interactions in nanometer order. In this report the introduction and principle of the FRET process have been explained. Comment: 4 pages, 3 figures

• Langmuir-Blodgett Films a unique tool for molecular electronics

  Syed Arshad Hussain

  08/2009;

  Molecular electronics is a new, exciting and interdisciplinary field of research. The main concern of the subject is to exploit the organic materials in electronic and optoelectronic devices. On the other hand Langmuir-Blodgett (LB) film deposition technique is one of the best among few methods used... [more] Molecular electronics is a new, exciting and interdisciplinary field of research. The main concern of the subject is to exploit the organic materials in electronic and optoelectronic devices. On the other hand Langmuir-Blodgett (LB) film deposition technique is one of the best among few methods used to manipulate materials in molecular level. In this article LB film preparation technique has been discussed briefly with an emphasize of its application towards molecular electronics. Comment: 9 pages, 10 figures

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• Effect of nano-clay platelets on the J-aggregation of thiacyanine dye organized in Langmuir-Blodgett films.

  Syed Arshad Hussain

  CMDAYS-09, Department of Physics, Jadavpur University, Kolkata, India; 08/2009

  The Langmuir-Blodgett (LB) technique is one of the most useful tools for arranging various kinds of molecules into uniform monolayer assemblies, which may be suitable for constructing nanosized molecular aggregates having various functionality [1, 2]. These are useful for optical sensitizing, chemic... [more] The Langmuir-Blodgett (LB) technique is one of the most useful tools for arranging various kinds of molecules into uniform monolayer assemblies, which may be suitable for constructing nanosized molecular aggregates having various functionality [1, 2]. These are useful for optical sensitizing, chemical sensing and information storage [1, 2] etc. The molecular aggregation and orientation in LB films are inherently dependent upon the molecular organization in spread monolayers at the air-water interface (Langmuir films). J-aggregates of the dye molecules are characterized by a sharp band red shifted with respect to the monomer band and having strong photoluminescence with almost zero Stokes shifts, which may be useful in optoelectronic and molecular photoelectronic devices [3]. The pioneering work by Khun and co-workers [4, 5] on surface active cyanine dyes has opened the studies of J-aggregation in the two-dimensional (2D) structures formed in the LB films. One of the advantages of LB technique in constructing molecular aggregates lies in the fact that various kinds of molecules can be mixed at the air-water interface using this technique [6]. It has been observed that mixed systems sometimes exhibit new properties that are not observed for individual components [2, 6]. In the case of micro-cyanine dyes, the mixture of different dye analogs helped to control the J-aggregates [7]. Here we report the effect of the incorporation of nanodimensional clay platelets, laponite, on the J-aggregation of a thiacyanine dye -dioctadecyl thiacyanine perchlorate (NK) assembled into Langmuir-Blodgett (LB) monolayers. isotherms and atomic force microscopic studies confirm the successful incorporation of clay platelets onto NK-clay hybrid LB monolayer films. J-aggregates of NK remain present in LB films lifted at lower as well as higher surface pressure in the absence of laponite. However, with the incorporation of clay platelets J-aggregates are formed only in LB films lifted at higher surface pressure of 30 mN/m and totally absent in the films lifted at lower surface pressures of 10 and 15 mN/m. References: (1) Khun, H.; Mobius, D.; Bucher, H.; In: Weissberger, A.; Rossiter, B. W.; Ed.; Techniques of Chemistry, Vol. 1. New York, 1973 Part IIIB. (2) Ulman, A.; An Introduction to Ultrathin Organic Films: From Langmuir-Blodgett Films of Self assemblies, Academic Press, New York, 1991. (3) Kobayashi, T.; Ed. J-Aggregates, World Scientific, Singapore, 1996. (4) Khun, H.; Khun, C.; Chapter 1 In: Kobayashi, T. Ed., J-Aggregates, World Scientific, Singapore, 1996. (5) Czikkey, V.; Forsterling, H. D.; Khun, H.; Chem. Phys. Letts. 1970, 6, 207. (6) Kuroda, S.; Ito, H.; Uchiyama, Y.; Mori, T.; Marumoto, K.; Hatta, I.; Jpn. J. Appl. Phys. 2002, 41 (Part-1), 6223 (7) Murata, M.; Shin, H. K.; Saito, K.; Kuroda, S.; Thin Solid Films 1998, 327, 446

• Mechanics of Clay Mineral Sheets: Hectorite and Saponite

  S. A. Hussain1, A. Volodin2, C. Van Haesendonck2, R.A. Schoonheydt1

  International Clay Conference-2009, Italy; 06/2009

  In clay-polymer nanocomposites (CPN) the clay mineral aggregates are highly dispersed – if possible – to the limit of the single clay mineral sheet. These CPN’s have – among others – improved mechanical properties with respect to those of the pure polymeric materials. In order to understand this imp... [more] In clay-polymer nanocomposites (CPN) the clay mineral aggregates are highly dispersed – if possible – to the limit of the single clay mineral sheet. These CPN’s have – among others – improved mechanical properties with respect to those of the pure polymeric materials. In order to understand this improvement it is important to know the mechanical properties of single clay mineral sheets or of aggregates consisting of 2-4 sheets. Layers of single sheets of smectite-type clay minerals or of a mixture of single sheets and aggregates of 2-3 sheets can be prepared with the Langmuir-Blodgett (LB) technique, transferred to a suitable substrate and measured by Atomic Force Microscopy (AFM) (1). We report here the measurement of Young’s moduli of sheets of hectorite and saponite by Force Deflection Spectroscopy (FDS) (2). An AFM is used to measure the force versus deflection curves of clay sheets that bridge a trench patterned in a Si substrate. These data are fitted in the Euler-Bernouilli equation to determine Young’s modulus. This procedure is very sensitive to the geometry of the clay mineral sheets under investigation, as shown by the expression of Young’s modulus E: (1) Where L, w and h are respectively the length, width and height of the clay mineral sheets and f/Δz is the force per unit deflection, measured by the slope of the FDS curve. L and w are readily determined with AFM; h cannot be measured unambiguously. Table 1 gives E values, calculated with eq. 1 for 4 different heights, corresponding to particles consisting of one two, three and four single sheets. Table 1: Young’s moduli (GPa) for hectorite and saponite Hectorite saponite Single sheet 2413 1279 Two sheets 300 159 Three sheets 89 47 Four sheets 39 20 Three remarks can be made about the data of Table 1. (1) E values for single sheets are unacceptably high and have no physical meaning. (2) The best fits are obtained for particles consisting of 2-3 sheets. The E values fall in the range of values, published in the literature. (3) Young’s modulus of hectorite is systematically higher than that of saponite. This is related to the difference in width of the sheets: hectorite has lath-like sheets; saponite is characterized by plate-like sheets. References: 1. R.H.A. Ras, Y. Umemura, C.T. Johnston, A. Yamagishi and R.A. Schoonheydt, Phys. Chem. Chem. Phys., 2007, 9, 918-932. 2. Q. Xiong, N. Duarte, S. Tadigadapa and P.C. Eklund, Nano Lett., 2006, 6, 1904-1909.

• Direct observation of reaction-kinetics of Organo-Clay hybrid films at air-water interface by in-situ Infrared Reflection Absorption Spectroscopy and AFM

  Md. N. Islam1, D. Bhattacharjee1, S.A. Hussain1

  PANE-2009, Department of Physics, Tripura University; 04/2009

  Nano-dimensional clay minerals are inorganic, sheet like particles that can be incorporated into ultra thin hybrid films. Nanostructured organic-inorganic hybrid ultrathin films have gained widespread interest because of their potential use in a number of diverse technological applications. Organic ... [more] Nano-dimensional clay minerals are inorganic, sheet like particles that can be incorporated into ultra thin hybrid films. Nanostructured organic-inorganic hybrid ultrathin films have gained widespread interest because of their potential use in a number of diverse technological applications. Organic materials impart flexibility and versatility whereas the inorganic particles provide structural stability and can have unique conducting, semi conducting or dielectric properties. In-situ characterization of Langmuir films spread at the air-water interface is always difficult because of the sensitivity limit imposed by a single monolayer. The lack of information concerning the molecular level structure of monolayers at the air-water interface can be traced to the inability of most spectroscopic techniques to study a low surface area, flat water interface with sufficient sensitivity to produce spectra with reasonable signal-to-noise ratios. Infrared reflection-absorption spectroscopy (IRRAS) has emerged as one of the leading methods for structural analysis of monolayers at the air-water interface over the past decades. The IRRAS technique not only allows the characterization of chain conformation and head group structure but also provides qualitative / quantitative information about molecular orientation. In this communication we present the formation of organo-clay hybrid monolayer at the air-water interface and in solid substrate. The Langmuir-Blodgett (LB) method has been used to fabricate ultra thin hybrid films consisting of layers of phyllosilicate clay (smectite) and amphiphilic cations. LB technique is excellent method to construct ultra thin hybrid clay films since it operate at ambient conditions and allow control of thickness and structure in monolayer and in multilayer. LB films generally possess a high degree of organization. When a dilute solution of the amphiphilic cations in chloroform is spread over a dilute aqueous clay suspension in the LB trough to form a spread monolayer, the clay particles adsorbed onto the surfactant layer forming a floating hybrid monolayer of the clay-surfactant complex. Evidence for the formation of hybrid clay-surfactant monolayers has included surface pressure molecular area ( ) isotherm measurements, atomic force microscopy (AFM) and in-situ IRRAS spectroscopy. The isotherm measurements were strongly influenced by the presence of the clay with the lift-off area of the cation being shifted to progressively larger areas with increasing clay concentration. AFM studies of hybrid LB clay films have shown that clay particles cover 90% of the available surface. The IRRAS techniques have been used to study the reaction kinetics of hybrid clay films. The reaction kinetics of the hybrid clay films using IRRAS spectra have not been reported previously. It was observed that the vibration of bond of smectite is restricted to in-plane only. The reaction kinetics completed up with in 15 minutes. References: 1] Ulman, A. An Introduction to Ultrathin Organic Films from Langmuir-Blodgett to Self-Assembly; Academic Press: NewYork, 1991; and references therein. 2] Xuezhong Du; Wangen Miao, and Yingqiu Liang. J.Phys.Chem. B 2005, 109, 7428-7434. 3] R.A.Dluhy and D.G.cornell, J.Phys.Chem 1985, 89, 1395-1397. 4] M.L. Mitchell and R.A. dluhy. J.Am. Chem.soc. 1988, 110, 712-718. 5] R.H.A. Ras, C.T. Johnston and R.A. Schoonheydt. Langmuir 2003,19, 4259-4302.

• Formation of complex Langmuir and Langmuir-Blodgett films of water soluble rosebengal

  S Biswas, R K Nath, D. Bhattacharjee, Syed Arshad Hussain

  01/2009;

  This communication reports the formation of complex Langmuir monolayer at the air-water interface by charge transfer types of interaction with the water soluble N- cetyl N, N, N trimethyl ammonium bromide (CTAB) molecules doped with rosebengal (RB), with the stearic acid (SA) molecules of a preforme... [more] This communication reports the formation of complex Langmuir monolayer at the air-water interface by charge transfer types of interaction with the water soluble N- cetyl N, N, N trimethyl ammonium bromide (CTAB) molecules doped with rosebengal (RB), with the stearic acid (SA) molecules of a preformed SA Langmuir monolayer. The reaction kinetics of the formation of RB-CTAB-SA complex monolayer was monitored by observing the increase in surface pressure with time while the barrier was kept fixed. Completion of interaction kinetics was confirmed by FTIR study. This complex Langmuir films at the air-water interface was transferred onto solid substrates at a desired surface pressure to form multilayered Langmuir-Blodgett films. Spectroscopic characterizations reveal some molecular level interactions as well as formation of microcrystalline aggregates depending upon the molar ratios of CTAB and RB within the complex LB films. Presence of two types of species in the complex LB films was confirmed by fluorescence spectroscopy.