Platinum and Palladium Nanoparticles on Boron-Doped Diamond for the Electrochemical Detection of Hydrogen Peroxide: A Comparison Study

Abstract

Neurodegenerative diseases such as Alzheimer’s and traumatic brain injury currently lacks a reliable diagnosis and treatment. This is, in part, due to knowledge gaps in the understanding of the mechanisms of brain injury. Hydrogen peroxide (H2O2) and other reactive oxygen and nitrogen species (ROS/RNS) are typical byproducts of oxygen metabolism and part of the inflammatory response cascades. Any disruptions in the uptake of ROS/RNS over an extended period of time can lead to oxidative stress, further adding to the neurodegeneration. While there are several modes of detection for ROS/RNS like H2O2, one of the major drawbacks is the lack of real-time detection. Electrochemical techniques offer real-time detection, are cheap, and easy to miniaturize. Carbon-based electrodes are particularly useful in electrochemical detection due to their ability to be adapted to different measurement systems. For neurochemical detection, carbon-fiber microelectrodes are most common but tend to foul with long-term exposure in a biological environment. Novel materials like boron-doped diamond (BDD) can mitigate this issue due to its general robustness and chemical inertness while also exhibiting small capacitive current, enhanced surface roughness, and a large potential window. As with other carbon-based electrodes, BDD can be modified to increase sensitivity towards a specific analyte like H2O2. In this work, we performed a comprehensive study of BDD electrodes modified with platinum (Pt) and palladium (Pd) nanoparticles for the detection of H2O2. The modification involves a 2-step wet chemical synthesis procedure directly onto the electrode surface. We look to expand the modification process not only to novel electrode materials, but also to metals that have not been used for this purpose previously. We optimized the modification process to find the parameters that yielded the best electrode for H2O2 detection. Several factors were investigated including the double-layer capacitance, electroactive surface area, electron transfer properties, and sensitivity to H2O2, among others. It was found that the modification yielded a 308x increase in sensitivity and a 36x decrease in limit of detection (LOD) and limit of quantification (LOQ) on Pd modified BDD when compared to bare BDD. A 256x increase in sensitivity and a 26x decrease in LOD and LOQ were observed on Pt modified BDD compared to the bare BDD. We found that the BDD modified with 1 mM Pd and electrodeposited to a 5 mC charge yielded an electrode with excellent sensitivity to H2O2 and provided a LOD and LOQ well within biological concentrations. The H2O2 measurements also exhibited excellent repeatability as the relative standard deviation (%RSD) was below 10% for all modifications. The future of this work will consist of two separate steps: 1) miniaturization of these modification methods to the microelectrode scale and 2) implementation of new materials in the modification process for H2O2 detections. In general, not only does this work further exemplify the versatility of diamond electrodes for the detection of biological H2O2, but the ease of this modification process makes the use of these electrodes fairly easy in any application where H2O2 is present.