Anil Ghule

Preparation and characterization of ZnO nanoparticles coated paper and its antibacterial activity study

Coating of ZnO nanoparticles on paper surface has potential technological applications. With this motivation, a simple approach of ultrasound assisted coating of paper with ZnO nanoparticles (∼20 nm) without the aid of binder is reported for the first time in this work. The ultrasound assisted coating approach concurs with “green” chemistry as it is simple and environmentally friendly. Scanning electron microscope is used to characterize the surface morphology showing ZnO nanoparticles bound to cellulose fibers. Further characterization of coated surface is performed by attenuated total reflectance-Fourier transform infrared, X-ray diffraction, and time-of-flight secondary ion mass spectrometry in positive ion detection mode along with its imaging capability. The effect of ultrasound irradiation time on ZnO nanoparticles loading is estimated by thermogravimetric analysis. A plausible coating mechanism is proposed. The ZnO nanoparticles coated paper is found to possess antibacterial activity against Escherichia coli 11634.

Thermo-Raman investigations on structural transformations in hydrated MoO3

Thermally induced structural transformations in hydrated MoO3 prepared by acidification of Na2MoO4 solution have been investigated dynamically by thermo-Raman spectroscopic techniques. The thermo-Raman spectra reveal that the structural evolution of as-synthesized hydrated MoO3 in air proceeds through an amorphous phase after dehydration processes, formation of sub-microcrystals, the MoO3-II phase (possible) and the α-MoO3 phase in a dynamic thermal process. The thermo-Raman results are supported by thermogravimetry, differential thermal analysis, differential scanning calorimetry and powder X-ray diffraction results. The structural evolution of as-synthesized hydrated MoO3 under nitrogen gas flow was also investigated by thermo-Raman studies.

Phase transformation studies of ceramic BaTiO3 using thermo-Raman and dielectric constant measurements

Ferroelectric phase transformation characteristics of ceramic BaTiO3 have been studied by combined thermo-Raman and dielectric measurements. The temperature dependence of Raman bands at 311 and 721 cm−1 shows that tetragonal to cubic (T–C) phase transformation occurs over a range of temperature. The increase in the bandwidths of these bands indicates that this transformation is an order-disorder transformation. The differential thermo-Raman intensity thermograms show a dip at a temperature corresponding to the maximum rate of phase transformation and this temperature can be defined as phase transformation temperature Tp. The ferroelectric transformation temperature Tm corresponding to the peak in the e(T) obtained from the temperature dependence of dielectric constant is found to coincide with Tp. This indicates that maximum in dielectric constant occurs at the maximum rate of T–C phase transformation. Both Tp and Tm exhibit thermal hysteresis. The Curie temperature TC obtained from the intersection of ta...

Opening and thinning of multiwall carbon nanotubes in supercritical water

Supercritical water (SCW) in the presence and absence of oxygen is used for the first time for the opening and thinning of multiwall carbon nanotubes (MWNTs). The influence of variation of pressure, temperature, and time on the opening and thinning of MWNTs is examined. In SCW, opening and thinning of MWNTs is observed both in the presence and absence of oxygen. In addition, the presence of oxygen (∼2 mmol) shows improved thinning of MWNTs with the collapsed outer graphene layers tending towards the inner layers. The morphology of MWNTs are critically analyzed using transmission electron micrographs (TEM) and Raman spectra.

Thermo-Raman spectroscopic studies on polymorphism in Na2SO4

The phase transformations involved in Na2 SO4 (Na2 SO4 10H2 O as starting material) and predried Na2 SO4 in a dynamic thermal process of heating from 30 to 500 °C and then cooling down to 30 °C, with a heating/cooling rate of 2 °C min-1 in two consecutive thermal cycles, were monitored at 1 °C intervals by thermo-Raman spectroscopy (TRS). The transformations were characterized on the basis of the disappearance of the bands, appearance of new bands, splitting in the internal modes, change in the spectral profile, intensity (area) changes in the internal modes, full width at half maximum (FWHM) of the totally symmetric stretching mode and even the variations observed in the background during the thermal process. This thermo-Raman investigation provided some evidence for the existence of an intermediate phase between phase V and phase I and also for the changes observed in the phase I structure at higher temperatures, in addition to the dynamic transformations between the well known phase V, phase I, phase II and phase III. The intensity study on the 3 mode of SO2- 4 clearly demonstrated the thermal hysteresis involved among the phases during the heating and cooling process. The differences observed in the polymorphisms of Na2 SO4 (Na2 SO4 10H2 O as starting material) and predried Na2 SO4 were also discussed.

Studies on thermal hysteresis of KNO3 by thermo-Raman spectroscopy

In this work, the polymorphic phase transformations of KNO3were studied by thermo-Raman spectroscopy in a dynamical thermal process with a heating rate of 58C min ˇ1 from 308C to 1708C and then cooling down to 308C at the same rate. Three distinct phase transformations were detected. The characteristic spectrum for each phase was identified. The nature of each phase transformation was investigated in detail through the studies on spectral variation, intensity, intensity variation and shift in band position. In addition, the intensity variation of the n1 mode at 1042 cm ˇ1 clearly revealed thermal hysteresis involved in the phase transformation of KNO3. Furthermore, the thermal hysteresis of each phase was also obtained from the n3 mode in the range from 1341 to 1354 cm ˇ1 . # 2000 Elsevier Science B.V. All rights reserved.

Raman studies on ferroelectric phase (phase III) of KNO3

In order to understand the nature, stability, and existence temperature width of phase I, phase II, and phase III (ferroelectric phase) of KNO3, a detailed Raman investigation was carried out with various heating/cooling rates, repeated thermal cycles, and different preheating temperatures. The increase in the existence temperature width of the phase III of KNO3 was observed with the increase of heating/cooling rate but the repeated thermal cycling reduced it. The phase III to phase II transformation extended to a lower temperature in the cooling process when the sample was subjected to a higher preheating temperature. The phase III could be retained down to room temperature with higher cooling rate and higher preheating temperature. This could be important in its applications. The coexistence of phase III with phase II was observed with all the heating/cooling rates. In this work, special attention was also paid to study the behavior of the lattice modes of KNO3 during the successive phase transformations.

Bio-green synthesis of Ni-doped tin oxide nanoparticles and its influence on gas sensing properties

Considering the potential applications of transition metal doped nanostructured materials and the advantages of novel, cost-effective and environmentally friendly biosynthesis methods, Ni-doped SnO2 nanomaterials have been synthesized using remnant water (ideally kitchen waste) collected from soaked Bengal gram bean (Cicer arietinum L.) extract. The structural and optical properties of the Ni-doped SnO2 nanostructures were studied using various techniques such as UV/visible spectroscopy, FT-IR spectroscopy, X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The SEM and TEM images and the XRD results of the biosynthesized Ni–SnO2 nanoparticles reveal a uniform size distribution with an average size of 6 nm and confirmed the formation of a rutile structure with the space group (P42/mnm) and the nanocrystalline nature of the products with a spherical morphology. Subsequently, Ni-doped biosynthesized SnO2 nanoparticles were coated onto a glass substrate using the doctor blade method to form thin films. The NO2 sensing properties of the materials have been studied in comparison with other gases. The reported gas sensing results are promising, which suggest that the Ni-dopant is a promising noble metal additive to fabricate low cost SnO2 based sensors.

Monitoring dehydration and condensation processes of Na2HPO4*12H2O using thermo-Raman spectroscopy.

Thermal dehydration and condensation processes of disodium hydrogen phosphate dodecahydrate (Na2HPO4*12H2O) were monitored by thermo-Raman spectroscopy (TRS). Various hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were observed, followed by condensation of Na2HPO4 to sodium pyrophosphate (Na4P2O7) in a dynamic thermal process. Representative Raman spectra of all the hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were detected in both H2O and PO4(3- )regions are reported. The thermo-Raman intensity (TRI) thermogram also showed systematic loss of water in five steps of dehydration, with the differential TRI thermogram in agreement shows five dips corresponding to the five steps of dehydration, respectively. Thermogravimetry (TG) and differential thermogravimetry (DTG) are in harmony with the results of TRS, though, the two could not resolve the steps involved.

Coupling of thermogravimetric analysis and thermo-Raman spectroscopy for in situ dynamic thermal analysis

Abstract Thermogravimetric (TG) analysis provides information related to weight change but is not conclusive enough for direct identification of the composition of the sample in the dynamic thermal process. Raman spectroscopy has the advantage of detecting the composition and phase of the sample. Thermo-Raman spectroscopy (TRS) on the other hand, measures Raman spectra continuously at regular temperature interval for the identification of composition and phase of the species that appear in a dynamic thermal process. Therefore, the composition changes and phase transformations can be studied in the whole dynamic thermal process. Unfortunately, the results obtained from separate thermogravimetric analyzer (TGA) and TRS experiments may not be entirely consistent due to different sampling and experimental conditions. This problem has been overcome by direct coupling of the TGA and TRS instruments in this work so that it is ensured that the experimental and sampling condition do not hamper the results. In this work, coupling of a TGA to a thermo-Raman spectrometer (TRS) for in situ investigation of composition with weight loss have been illustrated using CaC 2 O 4 ·H 2 O which is widely used as a calibration standard for TGA. The thermo-Raman intensity (TRI) and differential thermo-Raman intensity (DTRI) thermograms were consistent with those of TG and differential thermogravimetry (DTG) thermograms, respectively.