Abstract
Size-tunable platinum nanoparticles (PtNPs) prepared by a facile method in an aqueous environment without the use of catalyst-poisoning reagents are used here in the electrocatalytic detection of hydrogen peroxide. Spherical nanoparticles with sizes as small as 4 and 20 nm are obtained as shown by transmission electron microscopy (TEM) analysis only using small easy-to-remove molecules such as sodium citrate. PtNPs are freed from the citrate capping agent at the surface by changing the pH to basic values and then deposited on a glassy carbon electrode by a very simple and rapid drop-casting method, achieving high cleanliness of the nanoparticle surface without the need for further treatments. The superior quality of nanoparticles on the glassy carbon is further investigated by scanning electron microscopy (SEM) analysis, which shows a highly homogeneous distribution of well-dispersed nanoparticles on the electrode surface, as well as by X-ray photoelectron spectroscopy (XPS) analysis, which confirms a drastic decrease of the citrate content, providing useful information about the citrate–platinum interaction, and evidences a related remarkable increase of conductivity of capping-free washed nanoparticles. Due to such key features, PtNPs possess excellent electrocatalytic properties, which have been tested in hydrogen peroxide electroreduction, a well-known catalytic reaction of nanostructured platinum materials. The size effect on PtNPs electrocatalytic properties is demonstrated, achieving higher performances with smaller NPs in the amperometric detection of hydrogen peroxide at −0.1 V in the concentration range of 25–750 μM, with a detection limit of 10 μM. Good sensing results toward hydrogen peroxide have also been obtained in terms of sensitivity, selectivity, repeatability, stability, and in tests performed in tap water samples. In addition, the strong adhesion of nanoparticles to the electrode surface has been verified and ascribed to their coating-free surface.
Highlights
Over the last decade, the integration of nanomaterials has had a great impact onsensing, spanning from electrochemical[1] to optical[2] and piezoelectric transduction.[3]
platinum nanoparticles (PtNPs) (4 and 20 nm) have been synthesized using a green approach based on the use of water as a solvent without employing organic solvents, polymeric agents, or sticky molecules
The present work is focused on exploring the electrocatalytic properties of platinum nanoparticles, with both 4 and 20 nm sizes, in the electrochemical detection of hydrogen peroxide
Summary
The integration of nanomaterials has had a great impact on (bio)sensing, spanning from electrochemical[1] to optical[2] and piezoelectric transduction.[3]. Significant advances have been made in synthetic methodologies such that it is possible to prepare a variety of nanomaterials with highly controllable size, shape, surface charge, and physicochemical characteristics. In the case of metal nanomaterials, their consolidated use in sensing applications is strictly related to their catalytic activity, making them emerge as synthetic counterparts to common enzymatic systems in the catalysis of several biological and industrial processes.[5] In this context, a major pivotal role has to be recognized to platinum nanoparticles (PtNPs), which have found many increasing successful applications revealing excellent electrocatalytic activity mainly toward the small molecule oxidation/reduction and oxygen reduction reaction,[6] which has prompted their use in electrochemical sensing devices along with the fuel cell design. Two key aspects in critically determining the beneficial exploitation of their high electron transfer and, in turn, their electrocatalytic activity are the adopted synthetic scheme and the approach for their integration with the electrode surface
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