Jyoti Nayak

Hybrid composite thin films composed of tin oxide nanoparticles and cellulose

This paper reports the preparation and characterization of hybrid thin films consisting of tin oxide (SnO2) nanoparticles and cellulose. SnO2 nanoparticle loaded cellulose hybrid thin films were fabricated by a solution blending technique, using sodium dodecyl sulfate as a dispersion agent. Scanning and transmission electron microscopy studies revealed uniform dispersion of the SnO2 nanoparticles in the cellulose matrix. Reduction in the crystalline melting transition temperature and tensile properties of cellulose was observed due to the SnO2 nanoparticle loading. Potential application of these hybrid thin films as low cost, flexible and biodegradable humidity sensors is examined in terms of the change in electrical resistivity of the material exposed to a wide range of humidity as well as its response–recovery behavior.

Biosensor made with organic-inorganic hybrid composite: cellulose-tin oxide

Cellulose is the most abundant polymer found in nature, inexhaustible, low cost, easy processing, renewable, biodegradable and biocompatible. SnO2, is a known electrical conductor that is optically transparent in the visible spectrum with a wide band gap at room temperature. Thus, a hybrid nanocomposite of cellulose and SnO2can offer a unique property of cellulose combined with electrical properties of SnO2. These unique properties of cellulose- SnO2 hybrid nanocomposite can be capitalized to design flexible, biodegradable and low cost biosensors. Preparation and characterization of cellulose-SnO2 hybrid nanocomposite and its application as a flexible urea biosensor was demonstrated in this paper. It is observed sensitivity of cellulose-SnO2 hybrid nanocomposite urea biosensor was increased linearly with deposition time. As deposition time increased, amount of tin oxide deposited over cellulose surface also increases, so as to increase the amount of enzyme immobilization and attachment of analyte, attributes to large current output and high sensitivity of sensor. Increasing enzyme activity is observed, with increasing urea concentration. Experimental results suggested that, the proposed biosensor under study is suitable for urea detection below 50 mM.

Characteristics of flexible electrode made on cellulose by soluble polypyrrole coating

This article investigates the possibility of soluble polypyrrole coating on cellulose as an alternative low-cost electrode material for paper speaker application. Soluble polypyrrole was prepared using β-naphthalene sulfonic acid as dopant and ammonium persulfate as oxidizing agent. For coating soluble polypyrrole on regenerated cellulose, prepared polypyrrole powder was dissolved in N-Methylpyrrolidone. N-Methylpyrrolidone was chosen to dissolve β-naphthalene sulfonic acid-doped polypyrrole due to large dielectric constant (32.2) compared with other organic solvents. It is observed that the optical transmittance of cellulose tends to decrease while electrical conductivity increases with increase of the β-naphthalene sulfonic acid doped polypyrrole–N-Methylpyrrolidone coatings, due to increased thickness of the polypyrrole layer on cellulose films.

Thickness effect on Schottky diode characteristics of ZnO thin film

Surface morphologies of the ZnO thin films with various thicknesses have been investigated. ZnO sol was prepared with zinc acetate dihydrate, 2-methoxyethanol, and monoethanolamine. Thicknesses of the ZnO films were controlled by a multiple coating process. The ZnO thin films were annealed at 750 °C. The film thickness increased as the coating time increased. From the XRD study, it is observed that the ZnO films exhibit wurtzite structure (002) and the diffraction intensity increased as the thickness increased. Effect of thickness on Schottky behavior was evaluated by measuring current-voltage characteristics. The pristine ZnO thin films with thickness of 132 nm exhibited Schottky diode characteristics with high rectification ratio.

High crystalline GaN nanoparticle and GaN thin film fabrication

Single-phase hexangonal wurtzite GaN nanoparticles and GaN thin film were prepared by the sol-gel techniqiue.using Ga(NO3)3. For GaN thin films, Ga(NO3)3 was hydrolyzed with ethanol and acetic acid and aged for one day. GaO(OH) thin layer was fabricated with spin-coating and heating at 200 °C. For GaN nanoparticles, the Ga(NO3)3 was dissolved in concentrated nitric acid and adjusted pH to 8.5 using NH4(OH). Citric acid was added to the Ga(NO3)3 solution and heated 80 °C for 2 h. The solution was heated at 400 °C for 4 h to obtain the Ga2O3 nanoparticles. The GaO(OH) and Ga2O3 were annealed in a tube furnace at 900 °C for 1 h with NH3 gas flow. The thickness of GaN thin film was approximately 46 nm. The grain size of the GaN thin film after converting from GaO(OH) to GaN, which was obtained by atomic force microscope image, was approximately 25-35 nm. The diameter of the GaN nanoparticles is approximately 15 nm with lattice fringes of 2.7 Α. The crystall has hexagonal wurzite structure, which is conformed by X-ray diffraction (XRD) pattern.

Comparison of the phase transformation rate for TiO2 thin film and TiO2 nanorods

Relative phase transformation rates are compared with TiO2 sol-gel thin film and TiO2 nanorods. TiO2 thin film was prepared with sol-gel process using titaanium isoproxide (TIP) as a precusor, ethanol as a solvent and HCl as a catalyst. The TiO2 nanorods were synthesized with low temperature proccess (100 °C) using TIP, oleic acid, and aqueous trimethylamine. The prepared thin film and nanorods were annealed at 850 °C for 3 h. X-ray diffraction patterns reveal that the TiO2 thin film and TiO2 nanorods have amorphase phase and anatase phase, respectively before annealing process. Approximately 60 and 3 % of TiO2 thin film and TiO2 nanorods transformed from anatase phase to rutile phase after annealing at 850 °C for 3 h. Relatively small amount of TiO2 nanorods transformed to rutile phase compared with TiO2 thin film. This small amount of phase transformation may be due to the small diameter of the TiO2 nanorods, which have thermodynamecally favorable anatase phase.

Ionic liquids adsorbed cellulose electro active paper actuator

Cellulose has been reported as a smart material that can be used as sensors and actuators. The cellulose smart material is termed as Electro-active paper (EAPap), which is made by regenerating cellulose. However, regeneration of cellulose resulted in reduced performance output of actuators at low humidity levels. To solve this drawback, EAPap bending actuators were made by activating wet cellulose films in three different room temperature ionic liquids BMIPF6, BMICL and BMIBF4. Results showed that the actuator performance was dependent on the type of anions in the ionic liquids and it was in the order of BF4¯ > Cl¯ > PF6¯. BMIBF4 activated actuator showed the maximum displacement of 3.8 mm with low electrical power consumption at relatively low humidity level. Also, it found that, although size of PF6¯ anion is larger than BF4¯ anion it showed the low displacement output due to poor adsorption as indicated the FTIR analysis.

Poly (ethylene oxide) - poly (ethylene glycol) blended cellulose electroactive paper actuator

Cellulose based Electroactive paper (EAPap) has been reported as a smart material that can be used as sensors and actuator materials. It has merits in terms of lightweight, biodegradability, large displacement and low actuation voltage. Actuation principle of EAPap is a combination of piezoelectric and ion migration effect. However, the performance of actuator is sensitive to humidity levels, in other words it produces large bending displacement at high humidity levels. Thus, we made an attempt to develop an EAPap which produces large displacement at low humidity level by blending cellulose with small amount of poly (ethylene oxide)-poly (ethylene glycol) [PEO-PEG]. The interaction between cellulose and PEO-PEG is studied by means of SEM and FT-IR. The potential application of PEO-PEG/ cellulose blend film as an actuator working at low humidity level is demonstrated by testing the actuator performance in terms of bending displacement, power consumption with respect to actuation voltage, frequency and humidity level.