RESUMO
The development of low-Platinum content polymer electrolyte fuel cells (PEFCs) has been hindered by inexplicable reduction of oxygen reduction reaction (ORR) activity and unexpected O2 mass transport resistance when catalysts have been interfaced with ionomer in a cathode catalyst layer. In this study, we introduce a bottom-up designed spherical carbon support with intrinsic Nitrogen-doping that permits uniform dispersion of Pt catalyst, which reproducibly exhibits high ORR mass activity of 638 ± 68 mA mgPt-1 at 0.9 V and 100% relative humidity (RH) in a membrane electrode assembly. The uniformly distributed Nitrogen-functional surface groups on the carbon support surface promote high ionomer coverage directly evidenced by high-resolution electron microscopy and nearly humidity-independent double layer capacitance. The hydrophilic nature of the carbon surface appears to ensure high activity and performance for operation over a broad range of RH. The paradigm challenging large carbon support (~135 nm) combined with favourable ionomer film structure, hypothesized recently to arise from the interactions of an ionic moiety of the ionomer and Nitrogen-functional group of the catalyst support, results in an unprecedented low local oxygen transport resistance (5.0 s cm-1) for ultra-low Pt loading (34 ± 2 µgPt cm-2) catalyst layer.
RESUMO
Rapid, selective, and ultra-sensitive detection of brain and spinal cord injury markers in bodily fluids is an unmet clinical need. In this work, Polycatecholamine as a rich source of amine moieties was used for single-step fabrication of ultrasensitive immunosensors for the detection of Ubiquitin carboxyl-terminal hydrolase (UCHL-1) biomarker of brain and spinal cord injuries and address the clinical need. The surface of graphene electrodes was modified by electropolymerizing aqueous solution of dopamine (DA) and norepinephrine (NE) monomers for generating polycatecholamines nanofilms on the surface of graphene screen printed electrodes (GSPE) in a single functionalization step. Amine moieties of the polymer allowed immobilization of UCHL-1 antibody on the electrode. The single-step modification of GSPE offered a simple, ultrasensitive, and stable production of immunosensors for the detection of UCHL-1. The operational range of the UCHL-1 immunosensor developed with Polynorepinephrine pNE-modified is 0.1â¯pgâ¯mL-1 - 105â¯pgâ¯mL-1 (LOD: 1.91â¯pgâ¯mL-1), and 1â¯pgâ¯mL-1 - 105â¯pgâ¯mL-1 (LOD: 0.70â¯pgâ¯mL-1) with Polydopamine (pDA) modification, satisfying the clinical range. Both pNE and pDA modified immunosensors, detected UCHL-1 spiked in phosphate buffer saline, artificial cerebrospinal fluid, and serum. Along with the sensitive detections, selective performances were recorded in the above matrices in the presence of interfering neurotransmitters GABA and Glutamate as well as glial fibrillary acidic protein (GFAP). Upon testing clinical samples of spinal cord injury patients and healthy controls, both pNE and pDA immunosensors, delivered a comparable response for UCHL-1, thereby, making immunosensors useful for clinical settings.
