Thermal polymerization of pyrrole was performed using silver nitrate as source of silver ions followed by its conversion to Polypyrrole (PPy)/Ag nano-comoposites without using any external oxidizing agent or solvent. The formation of PPy was monitored by UV-Visible absorption spectroscopy showing a band at approximately 464 nm. XRD measurement confirmed characteristic peaks for face centered cubic (fcc) silver and presence of PPy at 2 theta of approximately 23 degrees suggesting the formation of PPy/Ag nanocomposite. Transmission electron microscopy (TEM) images showed non-aggregated spherical Ag nano-particles of about 5-10 nm. PPy/Ag thick film acts as a NH3 sensor at 100 degrees C, a H2S sensor at 250 degrees C and CO2 sensor at 350 degrees C. The thick films showed capability to recognize various gases at different operating temperature.
ABSTRACT ABSTRACT We herein present a simple one-step synthesis of CdSe quantum dots in aqueous medium using Na2SeSO3 as a source of Se and PVP and sodium succinate as the surfactant. The isolated orange to dark-red particles are re-dispersible in alcoholic and aq. medium. The optical spectra indicated blue shift of >150 nm. The hydrophilic quantum dots show excellent FWHM of approximately 44–60 nm in their photoluminescence spectra and the emission bands are centered around 570–590 nm. Absorption spectra maxima are observed in the range of 530–550 nm. The particle size from absorption wavelength is calculated to be about 5 nm and the XRD indicate cubic CdSe with impurities of selenium. It is observed that Se impurities enhanced PL intensity. Facile synthesis of CdSe QD has increasing value in biomedical applications. KEYWORDS: synthesishydrophilic quantum dotsCdSeoptical properties Acknowledgments V. Renugopalakrishnan dedicates this article to his father, Varun. P. K. Khanna thanks the DST Government of India (Grant no. SR/S1/PC-17/2006). The support and intellectual discussion with Dr. C. V. V. V. Satyanarayana is gratefully acknowledged. The authors are also thankful to Prof. B. R. Mehta for permission to use the TEM and HRTEM facility of the Unit on Nanoscience and Nanotechnology Initiative at IIT Delhi (Project No. SR/S5/NM-22/2004) of the DST Government of India. P. K. Khanna thanks the Vice Chancellor of DIAT for support and permission for K. Dhanabalan to work as a guest research student. V. Renugopalakrishnan and S. Viswanathan express their thanks to the Rothschild Foundation, NIH, and Harvard Medical School for generous financial support
In-situ reduction of PdCl2 by Emeraldine base (EB) of polyaniline leads to formation of palladium nano-particles in N-methyl-2-pyrrolidone (NMP) and N',N-dimethylformamide (DMF). So-generated nanoparticles of Pd in polyaniline (PAni), in its UV-visible absorption spectra, showed λ(max) at about 320 nm and 420 nm due to polyaniline along with complete suppression of band at 620 nm initially present in Emeraldine base (EB). X-ray diffraction pattern (XRD) of powder showed broad peaks for nano-sized Pd, and the particle size from Scherrer's equation was found to be less than 15 nm. Scanning electron microscopy (SEM) showed that the composite has granular and/ or fluffy agglomerated morphology. The elemental composition was studied by EDAX.
We have These films were irradiated with 85 MeV C-ions at the fluences of 1 x 10 11 and 1 x 10 12 ions/cm 2 . Changes in the optical, structural, dielectric, magnetic and thermal properties of (PMMA)/Ni nanocomposites of different concentrations of nickel nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of UVvisible spectroscopy, X-ray diffraction, impedance gain phase analyzer, SQUID and differential scanning calorimetry. Optical properties like band gap were estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength range 200-800 nm. It was found that the band gap value shifted to lower energy on doping with metal nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to the scissioning of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Surface morphology of the pristine and irradiated films was studied by scanning electron microscopy (SEM). The breakage of chemical bonds resulted in an increase of free radicals, unsaturation etc. as revealed from FTIR analysis. The dielectric properties were observed to enhance with an increase in metal compound concentration as well as with irradiation dose. This may be due to metal / polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. Zero-Field-Cooled (ZFC)/Field-Cooled (FC) magnetization and magnetic hysteresis measurements were performed using a superconducting quantum interference device (SQUID) magnetometer from temperatures ranging from 5 K to 300 K, to investigate the magnetic properties of nanocomposites. The changes in topography of surfaces were also observed upon irradiation.
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