Functional Nanomaterials: Energy and Sensing

Abstract

Sponsored by the Nanomaterials Committee, this special topic has a unique combination of short review papers and research papers on some recent advances for using functional nanomaterials for energy conversion/storage and optical/electric/magnetic signal sensing. The invited paper from Zhu’s group is an extension of their talk ‘‘One-Dimensional Nanostructures for Wearable Devices’’ presented at the TMS 2015 Annual Meeting & Exhibition (TMS2015). The paper reviews nanomaterial-enabled dry electrodes for electrophysiological sensing, particularly on electrocardiography (ECG). It starts with an overview of two different commercial electrodes (i.e., pre-gelled wet electrode and dry electrode), their electrode–skin interface models and the source of noise. The overview shows that dry electrodes have certain advantages over the wet ones, such as the elimination of signal degradation caused by dehydration of the gel. The overview also points out that (1) flexible dry electrodes are needed to form intimate contact with skin surface so that the movement of electrodes and motion artifacts can be suppressed and reduced, and (2) the nanomaterials-based electrode could be the solution. The paper then presents a comprehensive review on recent developments of dry ECG electrodes made of various nanomaterials, including metallic nanowires, metallic nanoparticles, carbon nanotubes and graphene. Their fabrication processes and performances are discussed. The paper concludes that nanomaterials-enabled dry ECG electrodes are attractive candidates for long-term ECG sensing, and calls for more studies in this field. The invited paper from Zhao’s team is a recap of their talk ‘‘Detecting Bacteria by Surface Enhanced Raman Spectroscopy’’ at TMS2015. This paper reports how surface-enhanced Raman spectroscopy (SERS) contributes to food safety by detecting the low levels of pathogenic microorganisms that may exist in foods. In particular, vegetables and fruits are vulnerable to contamination by pathogenic microorganisms since they are natural vehicles of pathogens from cultivation to delivery. Therefore, to detect a small amount of harmful microorganisms is a very important, but challenging task for food safety. Compared with traditional Raman spectroscopy, SERS exploits novel metal nanostructures to enhance the sensitivity. In this study, the authors demonstrate that the limit of detection (LOD) of Salmonella Poona from cantaloupe cubes can be as low as 100 CFU/ml in less than 4 h by performing SERS measurements on vancomycin-coated silver nanorod (VAN AgNR) substrates. It is claimed that such a small LOD has not previously been reported for label-free, intrinsic SERS detection using real food samples. This result suggests that the SERS detection technique based on AgNR is a powerful platform for a rapid, simple, and inexpensive means of pathogenic bacteria detection, which will be very useful in securing the safety of fresh foods.