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Controlling the density and site of attachment of goldnanoparticles onto the surface of carbonnanotubes
No full textA facile method for controlling the density and site of attachment of goldnanoparticles onto the surface of carbonnanotubes is demonstrated. Nitric acid based oxidation was carried out to create carboxylic groups exclusively at the ends of carbonnanotubes, whereas oxidation using a mixture of nitric and sulfuric acid with varied reaction time was carried out to control the population of carboxylic groups on the side walls of nanotubes. In turn, 4-aminothiophenol modified goldnanoparticles were covalently interfaced to these carboxylated multi-walled carbonnanotubes in the presence of a zero length cross-linker, 1-ethylene-3-(3-dimethylaminopropyl) carbodiimide. Raman spectroscopic results showed increase in height of disorder band with each of these successive steps, indicating the increase in degree of functionalization of the carbonnanotubes. Fourier transformed infrared spectroscopic analysis affirmed the functionalization of nanostructures and the formation of nanohybrid. Transmission electron and field emission scanning electron microscopic analysis ascertained the attachment of goldnanoparticles to the ends and side walls of the multi-walled carbonnanotubes. The new hybrid nanostructures may find applications in electronic, optoelectronic, and sensing devices
Optical study of poly(ethyleneterephthalate) modified by different ionizing radiation dose
Get PDFThin films of poly(ethyleneterephthalate) [PET]were exposed to radiation dose ranging from 10 to 30 kGy by using gamma rays in the range 12.8-177.8 MGy using swift light ions of hydrogen. There was no effect of the radiation dose on the optical behaviour of PET as a result of exposure to radiation dose up to 30 kGy brought about by gamma rays but a significant decrease in the optical band gap values was observed when PET was exposed to swift light ions of hydrogen. The data obtained are discussed in terms of optical studies carried out on PET using swift heavy ions
Synthesis and electrical behavior study of Mn3O4 nanoceramic powder for low temperature NTC thermistor
No full textMonodispersed Mn3O4 nanoparticles (NPs) were synthesized by reducing KMnO4 at room temperature in the presence of cetyltetrabutylammonium bromide surfactant and short chain tetra-n-butylammonium bromide co-surfactant. Structural characterization done through XRD, TEM and FT-IR analysis techniques showed mono dispersity (5–8 nm) and capping of the NPs with surfactants. The temperature dependent behavior of dc resistivity of the nanopowder pellets showed reproducible NTC characteristics over a range of 40–200 °C with two thermistor constants (β1 = 10,897 K for 40 °C < T < 107 °C and β2 = 1,529 K for 107 °C < T < 190 °C) and a negative temperature co-efficient of resistance (α = −0.111 K−1 at 40 °C). The thermistor constant (β1) and NTC values are found to be higher than that of bulk Mn3O4 in range of 40 °C < T < 107 °C. This observed behavior implies an enhanced sensitivity in nano-powder based thermistors. Temperature and frequency dependent impedance behavior of the as-synthesized samples evaluated over a temperature range of 40–140 °C and a frequency range of 1 kHz to 1 MHz delineates the role of electron hopping between Mn2+ and Mn3+ in the conduction process. These studies present monodispersed Mn3O4 NPs as promising material for NTC thermistor in the low temperature range 40 °C < T < 107 °
Mechanism for the formation of low aspect ratio of La(OH)3 nanorods in aqueous solution: thermal and frequency dependent behaviour
No full textLa(OH)3 nanorods of length varying between 30 and 50 nm with aspect ratio of 2–5 were synthesized in aqueous solution using hydrazine hydrate in presence of mixture of cationic N-cetyl-N,N,N,trimethylammonium bromide (CTAB) and tetra-n-butylammonium bromide (TBAB) surfactants. The resultant product was characterized for its morphology and structure using XRD, TEM and FT-IR. Thermal stability studied using TGA indicated good stability. Surfactants in reaction mixture reduces the surface tension of the solution which lowers the energy needed to form a new phase, resulting in the formation of La(OH)3 crystals of anisotropic shape with low aspect ratio. The A.C. conductivity was found to be of the order of nano-seimen (ns), which non-linearly increases with the increase in frequency (102–106 Hz) The capacitance behaviour was observed in pF in mid frequency region, which can be useful as low loss dielectric material. Nano rods may work as standard materials to monitor conductivity levels in biofluid proteins
Significant physical attributes affecting quality of Indian black (CTC) tea
No full textIn this research work, an attempt was made to discriminate different grades of black crush-tear-curl (CTC) tea based upon their physical attributes such as color of brewed liquor, texture, size and shape of the tea granules obtained by machine vision technique. The principal component analysis (PCA) was applied over two types of data. First, tea samples with seven different quality grades but same mechanical grading and second, samples with same quality grade but nine different mechanical grades (Brokens, Fannings and Dust) were considered for analysis, respectively. The results of PCA showed that best discrimination (100%) in both types of data was given by color attributes only. Correlations among tea samples and physical attributes were determined. Based upon these results it may be concluded that color only attributes are the most significant and sufficient for quantification of tea quality whereas other physical attributes contribute so little to quality estimation that they may be ignored
Photonic Sensor
No full textSustained efforts have been made at CSIR-CSIO over the last several years in the area of Fiber optics based research activities resulting in infrastructure development, expertise generation and fabrication of sensors & devices. These activities include optical fiber light guide technology, fiber optic components, assemblies and instruments, optical fiber measurement and characterisation
benches, fiber optic sensors, application specific fiber optic systems, fiber Bragg gratings (FBGs)& long period gratings (LPGs) writing technology and associated sensors. Work has also been carried out in other related areas such as: holographic optical elements (HOEs), holographic nondestructive testing (HNDT) for defect diagnosis and restoration of precious art & cultural objects,display holography for exhibition of precious and culturally valuable objects, machine readable security holograms and holo phase mask for FBG writing. Details of the achievements made,infrastructural facilities established and current & future R & D programmes taken up in the area of Photonics are described here
Synthesis of mercaptopropionic acid stabilized CDS quantum dots for bioimaging in breast cancer
Get PDFSemiconductor inorganic nanocrystals or quantum dots (QDs) are nowadays extensively used for imaging and analysis of biomolecules owing to their superior optical properties over conventional organic fluorophores. They have excellent potential for synthesizing molecular probes against various biological markers such as free antigens, cell surface markers/antigens, bacteria, viruses and tissues. Traditional synthesis protocols of the QDs generally lead to the formation of hydrophobic nanocrystals. For biological applications, post-synthesis modifications need to be introduced to render required hydrophilicity. However, such
additional steps make the tiny QDs structures bulky, which is unwanted in subsequent in-vivo executions. The present work reports a simple method for the direct synthesis of hydrophilic carboxyl (–COOH) functionalized CdS QDs using
mercaptopropionic acid as a sulfur source and stabilizer. This aqueous synthesis route avoids the requirement of extra surface modification steps. The size and surface morphology of the synthesized CdS QDs were studied by electron microscopy. The average diameter of the QDs has been found to be in the range of 2-3.5nm. Spectral studies confirmed the grafting of –COOH terminal on the synthesized nanocrystals. Band gap energy and the theoretical size of the particles were calculated and found in good agreement with the experimental analysis. Due to the size quantization effect, the estimated band gap energy (2.6eV) of the QDs was on a higher side than that reported (2.4eV) for the bulk material. The synthesized nanocrystals can be further
conjugated with bio-molecules for high-throughput drug screening, clinical immunological assays and protein-protein
interaction studies
Three-stage structural modification of carbon nanotubes by swift heavy ion irradiation
No full textA study on the structural evolution of carbon nanotubes (CNTs) under irradiation by swift heavy ions (SHIs) of widely varying electronic energy loss (Se) values is presented. The control over Se is exercised through the choice of ion species used for irradiation. The ion beams used are those of nickel and gold with energies 60 and 120 MeV, respectively. Structural changes in CNTs were investigated qualitatively using Raman spectroscopy. Results of irradiation indicate that the structural modifications of CNTs can be broadly divided in three stages. At very low fluences the process of healing occurs; at intermediate fluences damage to the surface of CNTs predominates and nano-graphitic formations are seen; at very high fluences, of the order of 1 × 1014 ions/cm2, the system becomes amorphous. The stable nature of single walled carbon nanotubes compared to multiwalled carbon nanotubes, is also established from the Raman spectroscopy results
Modelling and Estimation of Spatiotemporal Surface Dynamics applied to a Middle Himalayan Region
No full textAccurate and timely estimation of the spatiotemporal surface dynamics is very important for natural resource planning and disaster mitigation. This paper discusses a novel technique to assess the patterns of the surfaces of a particular severe landslide susceptible zone (Kullu-Larji-Rampur geological window, near Aut village, district Mandi, Himachal Pradesh, India; N 31°44’34.78’’ E 77°12’29.02’’). The spatiotemporal surface dynamics of this region, spanning over last 20 years (1989 - 2009), has been modelled using Landsat TM images acquired during summers of 1989, 2000 and 2009. The proposed technique uses image processing to derive regression models of selected area segments, these models are then used to measure area under the curve to estimate the surface area changes. The surface area changes thus obtained have also been validated by standard method of pixel counting. Principal component analysis has been done in order to understand the correlations amongst the estimated parameters, namely; segment lengths, percentage area change and the area change in the first (1989-2000) and second (2000-2009) decades. The results obtained show a fair degree of accuracy as compared to the standard method of pixel counting
Studies on electrical properties of wheat as a function of moisture content
No full textMoisture content of cereal grains is one of the most important characteristics for determining quality of grains.The electrical properties of Indian wheat with moisture content range of 14.3% to 29.38% were characterized to develop a moisture prediction model.MethodsA specially designed coaxial cylindrical cell was used for the purpose and electrical properties characterization system was used to carry out measurements of these properties. The studies were conducted for frequency range of 100 kHz- 10 MHz and a fixed frequency was selected based on best correlation basis. Principal Component Analysis (PCA) was used to study the moisture dependence of various electrical properties such as Capacitance (C), Conductance (G), Impedance (Z), Theta (Θ) and Dissipation Factor (D) of Indian wheat. The various statistical studies were conducted using The Unscrambler Version X, a multivariate Statistical Analysis Software. It was observed that Conductance (G) and capacitance (C) show the maximum variation with moisture. Partial Least Square (PLS) Regression was then used to develop the moisture prediction model based on these two electrical properties.ConclusionThe developed model is highly accurate with high correlation of 0.973