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Platinum nanoparticle-decorated graphene and carbon nanotube (Pt-Gr-CNT) nanocomposites synthesized by a single step chemical vapor deposition process, serve as a promising platform for the simultaneous electrochemical sensing of dopamine, uric acid and ascorbic acid.

Electrically conducting Au-multiwalled carbon nanotube/polyaniline (Au-MWCNT/PANi) nanocomposites were synthesized by two different ways: (1) by direct mixing of MWCNT/PANi and Au nanoparticles (Au-MWCNT/PANi-1) and (2) by in situ polymerization of aniline in the presence of both MWCNTs and Au nanoparticles (Au-MWCNT/ PANi-2). The higher electrical conductivity of Au-MWCNT/PANi-2 compared with the other samples (PANi, MWCNT/PANi, Au-MWCNT/PANi-1) is supported by the red shifts of the UV-vis bands (polaron/bipolaron), the high value of the -NH+= stretch peak (Fourier transform infrared spectroscopy studies), the high % crystallinity (X-ray diffraction analysis) and more uniform dispersion of the Au NPs in the material. The performance of the samples in electromagnetic interference (EMI) shielding and microwave absorption was studied in the X-band (8-12 GHz). For all the samples, absorption was the dominant factor contributing toward the EMI shielding. Au-MWCNT/PANi-2 showed the best performance with a total shielding effectiveness of À16 dB [averaged over the X-band (GHz)] and a minimum reflection loss of À56.5 dB. The higher dielectric properties resulting from the heterogeneities because of the presence of nanofillers and the high electrical conductivity lead to the increased EMI shielding and microwave absorption. The results show the significance of both Au nanoparticles and method of synthesis on the EMI shielding performance of MWCNT/PANi composites. Figure 3. TEM images of MWCNTs (a), MWCNT/PANi (b), Au-MWCNT/PANi-1 (c) and (d) and Au-MWCNT/PANi-2 (e) and (f).Figure 7. FTIR spectra of different samples.Figure 6. UV-vis spectra of aqueous Au colloid (a); PANi and PANi composites in DMSO (b).Figure 12. Loss tangent (a) and skin depth (b) of PANi and its composites in the frequency range of 20 Hz-2 MHz.