Reagentless Glucose Biosensor Based on Combination of Platinum Nanostructures and Polypyrrole Layer.

Two types of low-cost reagentless electrochemical glucose biosensors based on graphite rod (GR) electrodes were developed. The electrodes modified with electrochemically synthesized platinum nanostructures (PtNS), 1,10-phenanthroline-5,6-dione (PD), glucose oxidase (GOx) without and with a polypyrrole (Ppy) layer-(i) GR/PtNS/PD/GOx and (ii) GR/PtNS/PD/GOx/Ppy, respectively, were prepared and tested. Glucose biosensors based on GR/PtNS/PD/GOx and GR/PtNS/PD/GOx/Ppy electrodes were characterized by the sensitivity of 10.1 and 5.31 µA/(mM cm2), linear range (LR) up to 16.5 and 39.0 mM, limit of detection (LOD) of 0.198 and 0.561 mM, good reproducibility, and storage stability. The developed glucose biosensors based on GR/PtNS/PD/GOx/Ppy electrodes showed exceptional resistance to interfering compounds and proved to be highly efficient for the determination of glucose levels in blood serum.

Irradiation-driven molecular dynamics simulation of the FEBID process for Pt(PF3)4.

This paper presents a detailed computational protocol for the atomistic simulation of formation and growth of metal-containing nanostructures during focused electron beam-induced deposition (FEBID). The protocol is based upon irradiation-driven molecular dynamics (IDMD), a novel and general methodology for computer simulations of irradiation-driven transformations of complex molecular systems by means of the advanced software packages MBN Explorer and MBN Studio. Atomistic simulations performed following the formulated protocol provide valuable insights into the fundamental mechanisms of electron-induced precursor fragmentation and the related mechanism of nanostructure formation and growth using FEBID, which are essential for the further advancement of FEBID-based nanofabrication. The developed computational methodology is general and applicable to different precursor molecules, substrate types, and irradiation regimes. The methodology can also be adjusted to simulate the nanostructure formation by other nanofabrication techniques using electron beams, such as direct electron beam lithography. In the present study, the methodology is applied to the IDMD simulation of the FEBID of Pt(PF3)4, a widely studied precursor molecule, on a SiO2 surface. The simulations reveal the processes driving the initial phase of nanostructure formation during FEBID, including the nucleation of Pt atoms and the formation of small metal clusters on the surface, followed by their aggregation and the formation of dendritic platinum nanostructures. The analysis of the simulation results provides spatially resolved relative metal content, height, and growth rate of the deposits, which represents valuable reference data for the experimental characterization of the nanostructures grown by FEBID.

Fast Procedures for the Electrodeposition of Platinum Nanostructures on Miniaturized Electrodes for Improved Ion Sensing.

Nanostructured materials have attracted considerable interest over the last few decades to enhance sensing capabilities thanks to their unique properties and large surface area. In particular, noble metal nanostructures offer several advantages including high stability, non-toxicity and excellent electrochemical behaviour. However, in recent years the great expansion of point-of-care (POC) and wearable systems and the attempt to perform measurements in tiny spaces have also risen the need of increasing sensors miniaturization. Fast constant potential electrodeposition techniques have been proven to be an efficient way to obtain conformal platinum and gold nanostructured layers on macro-electrodes. However, this technique is not effective on micro-electrodes. In this paper, we investigate an alternative one-step deposition technique of platinum nanoflowers on micro-electrodes by linear sweep voltammetry (LSV). The effective deposition of platinum nanoflowers with similar properties to the ones deposited on macro-electrodes is confirmed by morphological analysis and by the similar roughness factor (~200) and capacitance (~18 µ F/mm 2 ). The electrochemical behaviour of the nanostructured layer is then tested in an solid-contact (SC) L i + -selective micro-electrode and compared to the case of macro-electrodes. The sensor offers Nernstian calibration with same response time (~15 s) and a one-order of magnitude smaller limit of detection (LOD) ( 2.6 × 10 - 6 ) with respect to the macro-ion-selective sensors (ISE). Finally, sensor reversibility and stability in both wet and dry conditions is proven.

Platinum Cubic Nanoframes with Enhanced Catalytic Activity and Durability Toward Oxygen Reduction.

We report the synthesis and electrocatalytic properties of Pt cubic nanoframes with ultrathin ridges less than 2 nm in thickness. The nanoframes were synthesized through site-selected deposition of Pt onto the corner and edge sites of Pd nanocubes, followed by selective removal of the Pd cores via chemical etching. The Br- ions chemisorbed on the side faces of a Pd nanocube played a critical role in enabling the siteselected deposition. In addition, the kinetics of deposition and the diffusion of Pt adatoms was optimized by carefully controlling the injection rate of the Pt precursor and the reaction temperature, respectively, to obtain the frame-like structure. When benchmarked against a commercial Pt/C comprised of Pt particles 2-3 nm in size, the Pt frame/C catalyst exhibited not only enhanced mass activity toward oxygen reduction, but also substantially improved catalytic durability. In an accelerated durability test, the Pt frame/C catalyst showed a mass activity more than 6× greater than for the Pt/C reference after 20 000 cycles of repeated potential sweeping. This improvement can be largely attributed to the frame-like structure, which is unique in suppressing both the detachment and aggregation of catalytic particles owing to the significantly enhanced interaction with carbon support.

Self-assembled platinum nanoflowers on polydopamine-coated reduced graphene oxide for methanol oxidation and oxygen reduction reactions.

The morphology- and size-controlled synthesis of branched Pt nanostructures on graphene is highly favorable for enhancing the electrocatalytic activity and stability of Pt. Herein, a facile approach is developed for the efficient synthesis of well-dispersed Pt nanoflowers (PtNFs) on the surface of polydopamine (PDA)-modified reduced graphene oxide (PDRGO), denoted as PtNFs/PDRGO, in high yield. The synthesis was performed by a simple heating treatment of an aqueous solution that contained K2PtCl4 and PDA-modified graphene oxide (GO) without the need for any additional reducing agent, seed, surfactant, or organic solvent. The coated PDA serves not only as a reducing agent, but also as cross-linker to anchor and stabilize PtNFs on the PDRGO support. The as-prepared PtNFs/PDRGO hybrid, with spatially and locally separated PtNFs on PDRGO, exhibits superior electrocatalytic activity and stability toward both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline solutions.