Browsing by Author "Etika, Krishna Chitanya"

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BST@Copper Nanowire/Epoxy composites with excellent microwave absorption in the X-band
(Elsevier, 2024-09) Kumar, A. V. Praveen; Etika, Krishna Chitanya
In this work, hybrid epoxy nanocomposites containing varying loading of copper nanowires (CuNW), Ba0.7Sr0.3TiO3 (BST), and BST@CuNW hybrid nanoparticles were prepared and analyzed for their microwave absorption characteristics. The nanoparticles used in this study were prepared using a facile co-precipitation and hydrothermal methodology. The synthesized nanoparticles were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) for their morphology and phase determination. While the XRD results confirmed the presence of BST and CuNW, the SEM micrographs obtained on the hybrid BST@CuNW nanoparticles show BST anchored on the CuNW surfaces. A series of epoxy composites containing varying loading of synthesized nanoparticles were prepared and characterized for their microwave properties, such as complex permittivity, shielding effectiveness, and power coefficients. The results indicate that nanocomposites containing BST@CuNW hybrids exhibited enhanced dielectric loss and more significant microwave power absorption compared to samples with equivalent CuNW and/or BST loading. The best composite sample, i.e., a one-millimeter-thick epoxy containing 10:15 (wt/wt) CuNW: BST hybrid nanoparticles with an estimated density of 1.49 g/cc attenuated 99.1 % of incident microwave power and exhibited a shielding effectiveness value of 21.2 dB in the X-band (8–12 GHz) of the microwave frequency spectrum. These lightweight polymer composites with high microwave absorption in the X-band are useful for military and civilian applications.
Clay-mediated carbon nanotube dispersion in poly(N-Isopropylacrylamide)
(Elsiever, 2016-01) Etika, Krishna Chitanya
Poly(N-isopropylacrylamide) (PNIPAM) is the most widely studied temperature-responsive polymer due to its lower critical solution temperature (LCST) near to that of the human body temperature (around 32 °C). Unlike many water-soluble polymers, PNIPAM exhibits little affinity for single-walled carbon nanotubes (SWNT), which is not sufficient for preparing stable aqueous suspensions. The present study makes use of montmorrilonite clay (MMT) to compatibilize SWNT in aqueous PNIPAM solution. The interactions of clay with SWNT and PNIPAM is probed using UV–vis spectroscopy and cryo-TEM of aqueous suspensions. Furthermore, zeta potential measurements and direct visual observation suggests stable dispersion of SWNT in PNIPAM. SEM micrographs show that nanotube dispersion state in the aqueous suspension is preserved to a large extent in the solid nanocomposite films formed with drying. PNIPAM nanocomposite hydrogels, containing clay and SWNT, were also prepared with better SWNT dispersion in the presence of clay. Mechanical measurements show a 96% increase in storage modulus at 25 °C for 0.45 wt% clay and 0.05 wt% SWNT containing hydrogels (as compared to pure PNIPAM hydrogels). This method of employing clay as a dispersing aid for stabilizing nanotubes in PNIPAM solution is expected to be very useful for other polymers that have low affinity for nanotubes and could open up even more applications for nanotube-filled polymeric materials. This method of using clay to disperse carbon nanotubes in PNIPAM will likely be useful for producing mechanically durable and also, electrically conductive, PNIPAM-based hydrogels, sensors and self-cleaning surfaces that should serve to open up more biological applications for nanotube-filled materials.
Comparison of Covalently and Noncovalently Functionalized Carbon Nanotubes in Epoxy
(Wiley, 2009-04) Etika, Krishna Chitanya
Carbon nanotubes typically require the use of a dispersing or stabilizing agent to prevent significant aggregation during incorporation into a polymer matrix. These additives must be strongly associated, either covalently or physically, to achieve their purpose. In this study, multi-walled carbon nanotubes (MWNTs) were dispersed into an epoxy matrix using polyethylenimine (PEI) as a dispersant that was either covalently attached to the nanotubes or physically mixed to result in only noncovalent interaction. Epoxy composites containing covalently modified MWNTs exhibited greater storage modulus and reduced electrical conductivity.
Enhanced thermo-mechanical, thermal and EMI shielding properties of MWNT/MAgPP/PP nanocomposites prepared by extrusion
(Elsiever, 2021-03) Etika, Krishna Chitanya
In this work, multiwalled nanotube/maleic anhydride–grafted polypropylene/polypropylene (MWNT/MAgPP/PP) nanocomposites are produced using an industrially relevant twin-screw extrusion process. The composites with varying nanotube content in the range of 0.5 wt% to 2 wt% were synthesized and evaluated for their thermo-mechanical (i.e., Vicat softening temperature (VST), heat deflection temperature (HDT)), thermal (i.e., Melting (Tm) temperature, crystallization (Tc) temperature and thermal decomposition (Td) temperature), and electromagnetic interference (EMI) shielding properties. The scanning electron microscopy (SEM) of composite cross-sections reveal uniform dispersion of MWNTs in the polymer matrix. Overall, the MWNT content in the composites was found to influence the composite properties with higher nanotube loadings resulting in a higher increase in the measured properties over the MAgPP/PP sample. The composite containing 2wt% MWNTs exhibited the highest increase of 33.42%, 15.52%, 15.42%, 10.23%, over the pure MAgPP/PP sample in its Tdi, Tdf, VST and HDT values, respectively. The electromagnetic interference (EMI) shielding effectiveness of 2 mm thick sample containing 2wt% MWNTs content was measured to be 5.9 dB in the X-Band frequency range of 8–12.4 GHz, which corresponds to 74.29% attenuation of incident wave power. The results obtained suggest the viability of the masterbatch based extrusion method as a potential strategy for the large-scale production of nanocomposites.
Environmentally friendly low-cost graphene oxide-cellulose nanocomposite
(Elsevier, 2022-07) Etika, Krishna Chitanya
This study primarily aims to develop a simple, cost-effective, eco-friendly nanocomposite filter for dye removal by adsorption. In this work, graphite oxide and graphene oxide were synthesized using a modified Hummers’ process and used to fabricate nanocomposite filters by co-precipitation reactions. Scanning electron microscopy and X-ray diffraction were performed on nanofillers revealing crystallographic and morphological properties of the nanofillers.
Facile One-Pot Hydrothermal Synthesis of Copper Nanowires and Their Impact on the EMI Shielding Capability of Epoxy Composites
(Wiley, 2021-11) Etika, Krishna Chitanya
In this work epoxy nanocomposites containing varying content of copper nanowires (CuNW) were produced. The CuNW were synthesized using a facile one-pot hydrothermal synthesis method. The composites were characterized for their electrical conductivity and electromagnetic interference (EMI) shielding effectiveness in the X-band. The electrical conductivity of the epoxy composites was measured, and the composites containing 12 wt % CuNW demonstrated percolated behavior and exhibited a frequency-independent conductivity value of 1.76 × 10−6 S m−1 in the range of 25–200 Hz. The 12 wt % CuNW sample demonstrated an EMI shielding effectiveness value of 6.5 dB, which corresponds to 77.1 % attenuation of the incident electromagnetic wave. Furthermore, an absorption-dominated shielding mechanism was observed in these composites.
Hybrid nanocomposites and their potential applications in the field of nanosensors/gas and biosensors
(Elsiever, 2020) Etika, Krishna Chitanya
The air medium that we live in consists of several kinds of gases, many of them needed by and some of them dangerous to living beings. The rapid growth of industry in many fields has silently polluted our environment through hazardous gas emissions. Employees and people living nearby industrial facilities routinely or occasionally are threatened by toxic gases. In order to lessen the loss of life due to asphyxiation and explosions, gas sensors play a crucial role in analyzing and controlling lethal gases. Similar to the gas sensor, biological elemental detection is also important in food processing and many other fields. In this chapter various applications of hybrid nanocomposites are discussed, including gas sensors and biosensors that are vital in the clinical sector, biomolecules, and other environmental applications.
Hybrid polymer nanocomposites as EMI shielding materials in the X-band
(Elsiever, 2020) Etika, Krishna Chitanya
Electromagnetic interference (EMI) is a phenomenon where one electromagnetic field interacts with another, generating disturbances in both the fields. The electromagnetic interference (EMI) issue is of grave concern due to a rampant increase in wireless devices and increased sensitivity of electronic gadgets. Conductive polymer nanocomposites have been extensively used as an alternative to metals used traditionally for EMI shielding applications. In this paper, the influence of the EMI shielding effectiveness (SE) of the epoxy nanocomposites containing varying quantities of carbon black and magnetite (Fe3O4). The results indicate that addition of magnetic filler (i.e, Fe3O4) increases the shielding effectiveness of the nanocomposites in the X-band. Microstructural characterization of the epoxy nanocomposites using scanning electron microscopy revealed good filler dispersion in the matrix. Mechanical testing on the composites reveals that the Young’s modulus increased with the filler content. This method of increasing the EMI shielding properties of polymer by employing both conductive and magnetic fillers will be useful for other systems as well and will open further avenues for research in this direction.
Hydrothermal synthesis of conductive copper nanowires: effect of oleylamine and dextrose concentrations
(RSC, 2025-11) Etika, Krishna Chitanya
One-dimensional (1-D) metallic nanoparticles (i.e., nanowires, nanorods) exhibit unique properties and are useful in a variety of applications. 1-D copper nanowires (CuNWs) exhibit excellent electrical conductivity making them an economical alternative in applications that typically employ silver or gold nanowires. In this study, CuNWs were synthesized via an environmentally benign and scalable hydrothermal synthesis method using CuCl2 (CuP) as a copper precursor. Oleylamine (OAm) and dextrose (D) were employed as capping and reducing agents, respectively. The focus of this work was to investigate the influence of varying CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm and CuP[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratios during synthesis on the nanowire growth, morphology, and electrical conductivity. A series of synthesis trials were conducted by only varying CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm or CuP[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratios, while keeping all other reaction conditions constant. Morphological analysis of the synthesized products suggests that both OAm and D are essential for the formation of CuNWs. A synthesis conducted at a 1[thin space (1/6-em)]:[thin space (1/6-em)]3.75[thin space (1/6-em)]:[thin space (1/6-em)]1.1 CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratio produced nanowires with average diameter of 96 nm, while higher OAm concentration resulted in CuNWs with larger diameters. X-ray diffraction analysis confirmed the crystalline nature of the synthesized CuNWs, with diffraction peaks corresponding well to those of FCC copper. The capping of CuNWs with OAm was confirmed through FTIR spectroscopy. Thermogravimetric (TGA) studies on CuNWs show that OAm content in CuNWs increases with increasing CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm molar ratio during synthesis. The electrical conductivity of CuNW pellets was found to decrease with increasing CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAM molar ratio during synthesis. The highest conductivity of 1.38 × 105 S cm−1 was exhibited in the sample made using 1[thin space (1/6-em)]:[thin space (1/6-em)]3.75[thin space (1/6-em)]:[thin space (1/6-em)]1.1 CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratio. Furthermore, holding CuNWs pellets under ambient conditions for 60 days did not affect their electrical conductivity.
The influence of Fe3O4@GNP hybrids on enhancing the EMI shielding effectiveness of epoxy composites in the X-band
(Elsiever, 2020-07) Etika, Krishna Chitanya
In this work, the electromagnetic interference (EMI) shielding effectiveness in the X band frequency range of 8–12.4 GHz of epoxy nanocomposites containing Fe3O4 nanoparticles decorated graphene nanoplatelets (i.e., Fe3O4@GNP hybrids) is investigated. The hybrid nanostructures were synthesized in situ by a simple co-precipitation technique and were incorporated into the epoxy matrix by melt blending following a solvent-less approach. Scanning electron microscopy performed on the hybrid nanostructures revealed a good distribution of Fe3O4 nanoparticles on the GNP sheets in the hybrid. A series of epoxy nanocomposites containing varying content of Fe3O4@GNP, GNP and/or Fe3O4 nanoparticles were synthesized and compared for their EMI shielding effectiveness. The SEM of the composite cross-section reveals good filler dispersion in the composites. Overall the nanocomposites containing Fe3O4@GNP hybrids exhibited enhanced EMI shielding performance when compared to samples containing equivalent loading of only GNP and/or Fe3O4. The 1 mm thick composite sample containing 1:3 (wt/wt) Fe3O4: GNP hybrid attenuated 89 % of incident wave power and exhibited an EMI shielding effectiveness value of 9.6 dB in the X-band.
The influence of Fe3O4@GNP hybrids on enhancing the EMI shielding effectiveness of epoxy composites in the X-band
(Elsevier, 2020-07) Etika, Krishna Chitanya
In this work, the electromagnetic interference (EMI) shielding effectiveness in the X band frequency range of 8–12.4 GHz of epoxy nanocomposites containing Fe3O4 nanoparticles decorated graphene nanoplatelets (i.e., Fe3O4@GNP hybrids) is investigated. The hybrid nanostructures were synthesized in situ by a simple co-precipitation technique and were incorporated into the epoxy matrix by melt blending following a solvent-less approach. Scanning electron microscopy performed on the hybrid nanostructures revealed a good distribution of Fe3O4 nanoparticles on the GNP sheets in the hybrid. A series of epoxy nanocomposites containing varying content of Fe3O4@GNP, GNP and/or Fe3O4 nanoparticles were synthesized and compared for their EMI shielding effectiveness. The SEM of the composite cross-section reveals good filler dispersion in the composites. Overall the nanocomposites containing Fe3O4@GNP hybrids exhibited enhanced EMI shielding performance when compared to samples containing equivalent loading of only GNP and/or Fe3O4. The 1 mm thick composite sample containing 1:3 (wt/wt) Fe3O4: GNP hybrid attenuated 89 % of incident wave power and exhibited an EMI shielding effectiveness value of 9.6 dB in the X-band.
The influence of hybrid decorated structures on the EMI shielding properties of epoxy composites over the X-Band
(Elsevier, 2023) Etika, Krishna Chitanya
This work primarily focuses on electromagnetic interference (EMI) shielding characteristics of copper microparticles (CuMP), Fe3O4@CuMP, and Fe3O4 nanoparticles filled epoxy composites across the X-band. The Fe3O4@CuMP hybrids were synthesized through the water-based coprecipitation technique and analyzed by EDS and SEM. The SEM analysis of the hybrids demonstrated an excellent deposition of Fe3O4 particles on the surface of CuMP. The EDS analysis of the hybrids exhibited Cu, Fe, and O elements present in the hybrid powder sample. A set of epoxy composites containing hybrids, CuMP, and Fe3O4 particles were prepared through a resin blending technique, and its electrical and EMI shielding properties were investigated. The 12 wt% CuMP-filled epoxy composites demonstrate a frequency-dependent electrical conductivity value of 3.8 × 10−9 S/cm at 25 Hz. However, the epoxy composites containing Fe3O4@CuMP hybrids did not show a percolated electrical network and exhibited lower conductivity values than the 12 wt% CuMP-filled epoxy composite. Moreover, the hybrid composites exhibited better EMI shielding effectiveness than CuMP-filled epoxy composites containing equivalent filler loading of CuMP (i.e., 12 wt%). The hybrid composite of 1 mm thick filled with 8:12 (wt%/wt%) Fe3O4:CuMP attenuated 83.4 % of EM wave power and exhibited a SET value of 7.9 dB across X-band of 8–12.4 GHz.
The influence of synergistic stabilization of carbon black and clay on the electrical and mechanical properties of epoxy composites
(Elsiever, 2009) Etika, Krishna Chitanya
Studies of acetone-based suspensions suggest a synergistic stabilization of clay by carbon black (CB) that involves a haloing effect (i.e., CB surrounding clay). This unique microstructural development ultimately influences the electrical and mechanical properties of epoxy composites that contain both particles. With the addition of 0.5 wt.% clay, electrical conductivity increases by an order of magnitude for CB filled epoxy (relative to composites containing no clay), but no significant improvement is observed in storage modulus. Composites containing equal concentrations of CB and clay show reduced electrical conductivity, but significant improvement in storage modulus (relative to the composites containing equal amount (wt.%) of either CB or clay alone). Both electrical conductivity and storage modulus improve in composites containing a 1:2 clay:CB (wt/wt) ratio. This synergy between CB and clay is a useful tool for simultaneously improving the electrical and mechanical properties of solution-processed composites.
Large microwave absorption By Fe3O4@CuNW hybrid nanoparticles filled epoxy nanocomposites in the X-Band
(Elsevier, 2023-03) Etika, Krishna Chitanya
Microwave absorbing materials (MAM) are in great demand for various applications in both defense and commercial sectors. Polymer composites with tailorable properties have great potential for use as MAM owing to their low density, ease of processing, and low cost. In this work, the microwave absorption by epoxy composites containing, Fe3O4 nanoparticles deposited on the copper nanowires (i.e., Fe3O4@CuNW hybrid), copper nanowires (CuNW), and/or Fe3O4 nanoparticles were investigated for the first time. A set of epoxy composites with different filler loadings were prepared using a solvent-free resin blending method and were characterized for their morphological, surface composition, electrical, dielectric, magnetic, and microwave absorbing properties. The electrical conductivity values of the samples were measured, and the non-hybrid composites demonstrated percolated behavior, whereas hybrid samples exhibited non-percolated behavior. The non-hybrid composite containing 12 wt. % CuNW and 8 wt. % Fe3O4 exhibited the highest electrical conductivity value of 9.8 × 10−5 s/m compared to all other composites. The dielectric and magnetic losses obtained in the hybrid composites are higher than in non-hybrid composites. Furthermore, the hybrid composites containing 12 wt. % CuNW and 8 wt. % Fe3O4 exhibited the highest dielectric loss of 0.9 and magnetic loss of 1.4 as compared to other composites. The hybrid epoxy composites exhibited significantly large absorption with minimal reflections of microwaves as compared to non-hybrid composites containing equal loadings of CuNW or Fe3O4. The hybrid composites containing 12 wt. % CuNW and 2 wt. % Fe3O4 exhibited low reflection power of 26 % and high absorption power of 64 % of the incident microwave as compared to all other composites. The one-millimeter thick hybrid composite filled with 12:8 (wt. %/wt. %) CuNW: Fe3O4 sample demonstrated EMI shielding effectiveness of 19.3 dB and absorbed 60 % of the microwave power over the X-band frequency range of 8–12.4 GHz.
Multi-walled carbon nanotube-functional ionophore based composite potentiometric sensor for selective detection of lead in water
(Elsevier, 2024-10) Etika, Krishna Chitanya; Chatterjee, Somak
Nanotube Friendly Poly(N-isopropylacrylamide)
(Wiley, 2010-07-26) Etika, Krishna Chitanya
Poly(N-ispropylacrylamide) [PNIPAM] is a widely studied polymer for use in biological applications due to its lower critical solution temperature (LCST) being so close to the human body temperature. Unfortunately, attempts to combine carbon nanotubes (CNTs) with PNIPAM have been unsuccessful due to poor interactions between these two materials. In this work, a PNIPAM copolymer with 1 mol-% pyrene side group [p-PNIPAM] was used to produce a thermoresponsive polymer capable of stabilizing both single and multi-walled carbon nanotubes (MWNTs) in water. The presence of pyrene in the polymer chain lowers the LCST less than 4 °C and the interaction with nanotubes does not show any influence on LCST. Moreover, p-PNIPAM stabilized nanotubes show a temperature-dependent dispersion in water that allows the level of nanotube exfoliation/bundling to be controlled. Cryo-TEM images, turbidity, and viscosity of these suspensions were used to characterize these thermoresponsive changes. This ability to manipulate the dispersion state of CNTs in water with p-PNIPAM will likely benefit many biological applications, such as drug delivery, optical sensors, and hydrogels.
Recent trends in nanotechnology for sustainable living and environment:
(Springer, 2023) Roy, Banasri; Ghosh, Sarbani; Etika, Krishna Chitanya
This book presents the select proceedings of International Conference on Nanotechnology for Sustainable Living and Environment (ICON-NSLE 2022). It covers the latest trends in nanotechnology and its applications in various sectors such as energy, environment, food technology, and biomedicine. Various topics covered in this book are nanomaterial preparation and characterization, nanobiotechnology, nanodevices, waste to wealth, pollution abatement, renewable energy, advanced materials, sensors and portable electronics, biomedical applications, food preservation, etc. This book is useful for researchers and professionals working in the area of nanotechnology and environment sustainability.
Tailored dispersion of carbon nanotubes in water with pH-responsive polymers
(Elsiever, 2010-04-06) Etika, Krishna Chitanya
In an effort to control the level of carbon nanotube exfoliation in water, pH-responsive polymers (i.e., weak polyelectrolytes) have been used as stabilizers in water. This noncovalent functionalization of single-walled carbon nanotubes (SWNTs) results in suspensions whose dispersion state can be altered by simply changing pH. In this study poly(acrylic acid), poly(methacrylic acid), poly(allylamine) and polyethyleneimine were used to stabilize aqueous SWNT suspensions. The results indicate that SWNTs stabilized with these polymers show a pH tailorable exfoliation and bundling in water, as evidenced by cryo-TEM images and shifts in suspension viscosity. Composite films prepared by drying these aqueous suspensions suggest that nanotube microstructure in the liquid state is largely preserved in the solid composites, with more bundled/networked structures showing higher electrical conductivity. A stabilization mechanism based upon the results obtained is proposed to explain the exfoliation and aggregation behavior of SWNTs. This method of controlling the microstructure of SWNTs in liquid state with pH could have a significant impact on the ability to tailor the microstructure and properties of composites.
Tailoring Properties of Carbon Nanotube Dispersions and Nanocomposites Using Temperature-Responsive Copolymers of Pyrene-Modified Poly(N-cyclopropylacrylamide)
(ACS, 2010-10-25) Etika, Krishna Chitanya
Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Stimuli-responsive polymers show conformational changes with an applied external stimulus (pH, temperature, light, etc.). The dispersion of carbon nanotubes by thermoresponsive polymers is shown to enable the macroscopic properties of aqueous suspensions to be tailored as a function of temperature. This work presents the synthesis, characterization, and use of temperature-responsive poly(N-cyclopropylacrylamide) (PNCPA) polymers containing 1, 3, and 5 mol % pyrene-bearing repeat units to tailor the dispersion state of single-walled carbon nanotubes (SWNT) in water. Turbidity measurements show that the lower critical solution temperature (LCST) of PNCPA decreases with increasing pyrene content. Viscosity measurements on aqueous SWNT suspensions stabilized with pyrene-functionalized PNCPA show highly entangled and well-dispersed nanotube microstructure above and below the LCST of the polymer, respectively. UV−vis spectra also confirm that nanotube stabilization by these polymers is dependent upon the pyrene content. Drying of these suspensions produces composites whose microstructure and electrical conductivity vary with drying temperature and pyrene content of the stabilizing polymer. This temperature-dependent dispersion behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems.
Temperature Controlled Dispersion of Carbon Nanotubes in Water with Pyrene-Functionalized Poly(N-cyclopropylacrylamide)
(ACS, 2009) Etika, Krishna Chitanya
Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Poly(N-cyclopropylacrylamide), containing 5 mol % pyrene-bearing repeat units (p-PNCPA), is shown to vary the dispersion state of single-walled carbon nanotubes (SWNTs) in water. This is a thermo-responsive polymer whose conformation changes with temperature, which in turn leads to changes in the nanotube dispersion state. Cryo-TEM micrographs show that SWNTs stabilized using p-PNCPA transitions from a more exfoliated to a more bundled state as the aqueous suspension temperature is raised above the lower critical solution temperature (LCST) of the polymer (∼30 °C). Viscosity measurements on SWNT/p-PNCPA aqueous suspensions show shear thinning and near Newtonian behavior at 10 and 50 °C, respectively. Drying of these suspensions produces composites whose microstructure and electrical conductivity vary with drying temperature. This behavior has significant implications for the processing of carbon nanotubes and tailoring of composite properties. Such stimuli-controlled dispersion of carbon nanotubes could have a variety of applications in nanoelectronics, sensing, and drug and gene delivery systems.