The electrochemical activity of stacked nitrogen-doped carbon nanotube cups (NCNCs) has been explored in comparison to commercial Pt-decorated carbon nanotubes. The nanocup catalyst has demonstrated comparable performance to that of Pt catalyst in oxygen reduction reaction. In addition to effectively catalyzing O(2) reduction, the NCNC electrodes have been used for H(2)O(2) oxidation and consequently for glucose detection when NCNCs were functionalized with glucose oxidase (GOx). Creating the catalysts entirely free of precious metals is of great importance for low-cost fuel cells and biosensors.

The ability to accurately measure real-time pH fluctuations in-vivo could be highly advantageous. Early detection and potential prevention of bacteria colonization of surgical implants can be accomplished by monitoring associated acidosis. However, conventional glass membrane or ion-selective field-effect transistor (ISFET) pH sensing technologies both require a reference electrode which may suffer from leakage of electrolytes and potential contamination. Herein, we describe a solid-state sensor based on oxidized single-walled carbon nanotubes (ox-SWNTs) functionalized with the conductive polymer poly(1-aminoanthracene) (PAA). This device had a Nernstian response over a wide pH range (2–12) and retained sensitivity over 120 days. The sensor was also attached to a passively-powered radio-frequency identification (RFID) tag which transmits pH data through simulated skin. This battery-less, reference electrode free, wirelessly transmitting sensor platform shows potential for biomedical applications as an implantable sensor, adjacent to surgical implants detecting for infection.

A pro-inflammatory diet, as indicated by higher DII scores, is associated with an increased risk of all-cause, CVD, all-cancer, and digestive-tract cancer mortality among prediabetic subjects.

A positive synergy: Single‐walled carbon nanotube/polyaniline (SWNT/PAni) nanocomposite with controlled core/shell morphology was synthesized by a noncovalent functionalization approach. Unique electron interactions between the SWNT core and the PAni shell were studied electrochemically and spectroscopically, and superior sensor performance to chemical gases and vapors was demonstrated.

Metal-graphitic interfaces formed between metal nanoparticles (MNPs) and carbon nanotubes (CNTs) or graphene play an important role in the properties of such hybrid nanostructures. This Perspective summarizes different types of interfaces that exist within the metal-carbon nanoassemblies and discusses current efforts on understanding and modeling the interfacial conditions and interactions. Characterization of the metal-graphitic interfaces is described here, including microscopy, spectroscopy, electrochemical techniques, and electrical measurements. Recent studies on these nanohybrids have shown that the metal-graphitic interfaces play critical roles in both controlled assembly of nanoparticles and practical applications of nanohybrids in chemical sensors and fuel cells. Better understanding, design, and manipulation of metal-graphitic interfaces could therefore become the new frontier in the research of MNP/CNT or MNP/graphene hybrid systems.

Nitrogen doping of carbon nanotubes during chemical vapor deposition synthesis can create unique stacked cup-shaped structures termed as nitrogen-doped carbon nanotube cups (NCNCs). These cups have semielliptical hollow cavities and elevated reactivity which could lead to various applications. In this work, by applying intense ultrasonication to the as-synthesized NCNCs, we demonstrated an effective mechanical method to isolate the individual cups with opened cavities from their stacks. The graphitic structures of the isolated cups and their inherent nitrogen functionalities were characterized by comprehensive microscopic and spectroscopic methods. In particular, we quantitatively determined the existence of amine functionalities on NCNCs and found that they were preferentially distributed at the open edges of the cups, providing localized reactive sites. Further, by thiolating the amine groups with 3-mercapto-propionic acid, we were able to effectively cork the isolated cups by gold nanoparticles with commensurate diameters. These cup-shaped carbon nanomaterials with controlled inner volumes and gold nanoparticle corks could find potential applications as nanoscale reaction containers or drug delivery vehicles.

Because of their unique stacked, cup-shaped, hollow compartments, nitrogen-doped carbon nanotube cups (NCNCs) have promising potential as nanoscale containers. Individual NCNCs are isolated from their stacked structure through acid oxidation and subsequent probe-tip sonication. The NCNCs are then effectively corked with gold nanoparticles (GNPs) by sodium citrate reduction with chloroauric acid, forming graphitic nanocapsules with significant surface-enhanced Raman signature. Mechanistically, the growth of the GNP corks starts from the nucleation and welding of gold seeds on the open rims of NCNCs enriched with nitrogen functionalities, as confirmed by density functional theory calculations. A potent oxidizing enzyme of neutrophils, myeloperoxidase (MPO), can effectively open the corked NCNCs through GNP detachment, with subsequent complete enzymatic degradation of the graphitic shells. This controlled opening and degradation was further carried out in vitro with human neutrophils. Furthermore, the GNP-corked NCNCs were demonstrated to function as novel drug delivery carriers, capable of effective (i) delivery of paclitaxel to tumor-associated myeloid-derived suppressor cells (MDSC), (ii) MPO-regulated release, and (iii) blockade of MDSC immunosuppressive potential.

Nitrogen-doped and undoped carbon nanotubes (CNTs) were synthesized from ferrocene, nickelocene, and cobaltocene metal catalysts. Electrochemical testing for an oxygen reduction reaction (ORR) showed that nitrogen-doped CNTs synthesized from ferrocene had improved catalytic activity while nanotubes synthesized from nickelocene and cobaltocene, doped with a comparable amount of nitrogen and having similar stacked-cups structure as nitrogen doped CNTs from ferrocene, had a performance only slightly better than that of undoped CNTs. Ferrocene-based nitrogen-doped CNTs also demonstrated similar long-term stability and higher CO tolerance compared to Pt/C catalyst. Detailed ORR mechanisms were also studied and carbon nanomaterials showed different ORR processes as a result of the metal catalyst utilized in the chemical synthesis. Nitrogen-doped and undoped CNTs synthesized from nickelocene show a preferential 4-electron process as compared to materials synthesized from ferrocene and cobaltocene. We believe that the metal used in the growth process regulates the mechanism of oxygen reduction and can be used to develop improved nitrogen-doped carbon nanomaterials as nonprecious-metal catalysts for fuel cells.