Iron oxide/graphene oxide nanocomposite synthesis using atmospheric cold plasma.

Herein, we demonstrate the use of an atmospheric pressure plasma with a Dielectric Barrier Discharge (DBD) for the synthesis of FeOx nanoparticles with a simultaneous formation of graphene oxide domains at low substrate temperature. For that, the interaction of the plasma to control good decomposition of the Fe precursor is essential and this is demonstrated by FTIR analyses. Thanks to a fine tuning of the plasma conditions, a homogeneous spatial distribution around 5 nm nanoparticles (NPs) was obtained, whereas without plasma, in the same configuration of the process, a heterogeneity regarding size and shape for the NPs was obtained. The Raman spectrum of the plasma deposit confirmed the presence of graphene oxide as the characteristic G and D bands were observed with I(D)/I(G) = 0.92. Thanks to optical emission spectroscopy (OES) measurements, it is proposed that the carbon deposition on FeOx nanoparticles is produced on the near plasma post discharge. XPS studies showed that the main contribution of iron was in Fe2+ form, corresponding to the FeO phase. No metallic Fe or carbide were detected. As there are many studies reporting the synergetic effect of FeOx NPs and graphene oxide, we believe that this new one-step simultaneous synthesis method may be of high interest for applications requiring direct deposition on temperature labile substrates such as polymers.

Gold nanoparticles synthesis and immobilization by atmospheric pressure DBD plasma torch method.

Herein, we report the impact of plasma on gold nanoparticles synthesis. We used an atmospheric plasma torch fed with an aerosolized tetrachloroauric(iii) acid trihydrate (HAuCl4·3H2O) solution. The investigation showed that using pure ethanol as a solvent for the gold precursor enabled a better dispersion compared to a water-containing solution. We demonstrated here that the deposition parameters are easy to control, presenting the influence of solvent concentration and deposition time. The advantage of our method is that no capping agent was used. We assume that plasma creates a carbon-based matrix around the gold nanoparticles preventing them to agglomerate. The XPS results revealed the impact of using plasma. Metallic gold was detected in the plasma-treated sample, whereas the no-plasma sample revealed only Au(i) and Au(iii) contributions originating from the HAuCl4 precursor. Detailed HRTEM, EDS mapping, and SAED analyses led to more insights into the structure.