Prasanta Kumar Sahoo

In situ synthesis and properties of reduced graphene oxide/Bi nanocomposites: As an electroactive material for analysis of heavy metals

An in situ modified Hummers method (without the use of any surfactants) has been used for the deposition of bismuth (Bi) nanoparticles onto the surface of reduced graphene oxide (RGO) sheets. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), thermogravimetry (TG) and differential scanning calorimetry (DSC). The morphology of the RGO/Bi nanocomposites provides a better choice as an electrode material for detection of heavy metal ions due to its better functional properties over the Bi film electrode. Trace analysis of heavy metal ions like Cd(+2), Pb(+2), Cu(+2) and Zn(+2) in water is carried out by stripping voltammetric analysis using RGO/Bi nanocomposite as an electrode material. The sensitivity and detection limit of the electrode were quantitatively estimated from the analysis. The three sigma detection limits at different deposition potential for Cd(2+), Pb(2+), Zn(2+) and Cu(2+) were obtained as 2.8, 0.55, 17 and 26μgL(-1), respectively. Copper detection using Bi-film electrode was a major challenge, which has been resolved using the RGO/Bi nanocomposite electrode.

Facile synthesis of reduced graphene oxide/Pt–Ni nanocatalysts: their magnetic and catalytic properties

The catalytic performance of metals can be enhanced by intimately alloying different metals with Reduced Graphene Oxide (RGO). In this work, we have demonstrated a simplistic in situ one-step reduction approach for the synthesis of RGO/Pt–Ni nanocatalysts with different atomic ratios of Pt and Ni, without using any capping agent. The physical properties of the as-synthesized nanocatalysts have been systematically investigated by XRD, FTIR, Raman spectroscopy, XPS, EDX, ICP-AES, and TEM. The composition dependent magnetic properties of the RGO/Pt–Ni nanocatalysts were investigated at 5 and 300 K, respectively. The results confirm that the RGO/Pt–Ni nanocatalysts show a super-paramagnetic nature at room temperature in all compositions. Furthermore, the catalytic activities of the RGO/Pt–Ni nanocatalysts were investigated by analyzing the reduction of p-nitrophenol, and the reduction rate was found to be susceptible to the composition of Pt and Ni. Moreover, it has been found that RGO/Pt–Ni nanocatalysts show superior catalytic activity compared with the bare Pt–Ni of the same composition. Interestingly, the nanocatalysts can be readily recycled by a strong magnet and reused for the next reactions.

Ice-templated synthesis of multifunctional three dimensional graphene/noble metal nanocomposites and their mechanical, electrical, catalytic, and electromagnetic shielding properties

In-situ homogeneous dispersion of noble metals in three-dimensional graphene sheets is a key tactic for producing macroscopic architecture, which is desirable for practical applications, such as electromagnetic interference shielding and catalyst. We report a one-step greener approach for developing porous architecture of 3D-graphene/noble metal (Pt and Ag) nanocomposite monoliths. The resulting graphene/noble metal nanocomposites exhibit a combination of ultralow density, excellent elasticity, and good electrical conductivity. Moreover, in order to illuminate the advantages of the 3D-graphene/noble metal nanocomposites, their electromagnetic interference (EMI) shielding and electrocatalytic performance are further investigated. The as-synthesized 3D-graphene/noble metal nanocomposites exhibit excellent EMI shielding effectiveness when compared to bare graphene; the effectiveness has an average of 28 dB in the 8.2–12.4 GHz X-band range. In the electro-oxidation of methanol, the 3D-graphene/Pt nanocomposite also exhibits significantly enhanced electrocatalytic performance and stability than compared to reduced graphene oxide/Pt and commercial Pt/C.

Magnetic behavior of reduced graphene oxide/metal nanocomposites

The dispersion of metal nanoparticles on reduced graphene oxide (RGO) sheets potentially provides a new way to develop novel catalytic, magnetic, adsorbing, and electrode materials. In this work, we report the structural and magnetic properties of RGO/metal (Bi, Pt, Ni, and Pt-Ni) nanocomposites. Such nanocomposites are successfully synthesized by a facile in situ co-reduction route. The structure, composition, and morphology of the synthesized materials are systematically investigated by X-ray diffraction, inductively coupled plasma-atomic emission spectrometer , and high resolution transmission electronic microscopy. The M–H curve and zero-field-cooled and field-cooled data for RGO, RGO/Ni, and RGO/Pt-Ni nanocomposites exhibit ferromagnetic behaviour. RGO/Pt nanocomposite shows diamagnetic, while RGO/Bi nanocomposite shows lower magnetization compared to that of RGO. Detailed magnetic studies on these nanocomposites and its correlation with microstructural features are presented here.

Highly efficient and simultaneous catalytic reduction of multiple dyes using recyclable RGO/Co dendritic nanocomposites as catalyst for wastewater treatment

Development of a low cost, highly efficient and easily retrievable catalyst with improved reusability is a major challenge in the area of advanced catalysts. In this study, we report a simple one-step approach for the fabrication of a reduced graphene oxide (RGO)/Co dendritic nanocomposite. The structure and morphology of the as synthesized material are thoroughly examined by XRD, Raman, FTIR, TEM, and SEM. The magnetic properties of the RGO/Co dendritic nanocomposite reveal that it exhibits ferromagnetic behavior at room temperature with high saturation magnetization. The catalytic activity of the RGO/Co dendritic nanocomposite was investigated for the reduction of different dyes namely, 4-nitrophenol, methylene blue, methyl orange and rhodamine B individually, and their mixture in the presence of a sufficient amount of NaBH4. RGO/Co dendritic nanocomposite exhibits excellent catalytic activity as compared to the bare Co dendritic structure. The catalyst could be easily separated by an external magnet and recycled magnetically with no major loss of catalytic activity upto five cycles. The high catalytic efficiency, low cost and easy recycle technique make RGO/Co dendritic nanocomposite a proficient catalyst for degradation of organic dyes.

Ice-templating synthesis of macroporous noble metal/3D-graphene nanocomposites: their fluorescence lifetimes and catalytic study

Porous architectures of 3D-graphene assembled with noble metal (Au, Pd and Pt) nanoparticles were successfully fabricated through a one-step green route using a low-cost freeze-casting method. The as-synthesized noble metal/3D-graphene nanocomposites exhibit ultralow density and interconnected 3-D porous networks with a uniform distribution of noble metal nanoparticles. Time-correlated single photon counting (TCSPC) measurements reveal the energy and electron transfer at the interface of the graphene sheets and noble metals, which is maximum in the case of Pt/3D-graphene due to the small size of the Pt nanoparticles. The as-obtained noble metal/3D-graphene nanocomposites were applied to the reduction of 4-nitrophenol and methylene blue by NaBH4. The rates of reduction are in the order Pt/3D-graphene > Pd/3D-graphene > Au/3D-graphene for both the reduction reactions, signifying that the smallest noble metal nanoparticles possess the highest catalytic activity. The Pt/3D-graphene nanocomposite also exhibits excellent catalytic activity in comparison to the RGO/Pt nanocomposite, which is due to its unique 3D-porous structure. Moreover, the Pt/3D-graphene nanocomposite could be easily separated from the reaction solution by simple filtration and recycled for five cycles without the loss of its catalytic activity. Noble metal/3D-graphene nanocomposites can be utilized as attractive, low-cost, efficient fixed bed reactors and as easily separable catalysts in industrial applications for the reduction of 4-nitrophenol and methylene blue with high catalytic activity and exceptional absorption capability.