Excimer Laser Patterned Holey Graphene Oxide Films for Nonenzymatic Electrochemical Sensing.

The existence of point defects, holes, and corrugations (macroscopic defects) induces high catalytic potential in graphene and its derivatives. We report a systematic approach for microscopic and macroscopic defect density optimization in excimer laser-induced reduced graphene oxide by varying the laser energy density and pulse number to achieve a record detection limit of 7.15 nM for peroxide sensing. A quantitative estimation of point defect densities was obtained using Raman spectroscopy and confirmed with electrochemical sensing measurements. Laser annealing (LA) at 0.6 J cm-2 led to the formation of highly reduced graphene oxide (GO) by liquid-phase regrowth of molten carbon with the presence of dangling bonds, making it catalytically active. Hall-effect measurements yielded a mobility of ∼200 cm2 V-1 s-1. An additional increase in the number of pulses at 0.6 J cm-2 resulted in deoxygenation through the solid-state route, leading to the formation of holey graphene structure. The average hole size showed a hierarchical increase, with the number of pulses characterized with multiple microscopy techniques, including scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The exposure of edge sites due to high hole density after 10 pulses supported the formation of proximal diffusion layers, which led to facile mass transfer and improvement in the detection limit from 25.4 mM to 7.15 nM for peroxide sensing. However, LA at 1 J cm-2 with 1 pulse resulted in a high melt lifetime of molten carbon and the formation of GO characterized by a high resistivity of 3 × 10-2 Ω-cm, which was not ideal for sensing applications. The rapid thermal annealing technique using a batch furnace to generate holey graphene results in structure with uneven hole sizes. However, holey graphene formation using the LA technique is scalable with better control over hole size and density. This study will pave the path for cost-efficient and high-performance holey graphene sensors for advanced sensing applications.

Transdermal Polymeric Microneedle Sensing Platform for Fentanyl Detection in Biofluid.

Opioid drugs are extremely potent synthetic analytes, and their abuse is common around the world. Hence, a rapid and point-of-need device is necessary to assess the presence of this compound in body fluid so that a timely countermeasure can be provided to the exposed individuals. Herein, we present an attractive microneedle sensing platform for the detection of the opioid drug fentanyl in real serum samples using an electrochemical detection method. The device contained an array of pyramidal microneedle structures that were integrated with platinum (Pt) and silver (Ag) wires, each with a microcavity opening. The working sensor was modified by graphene ink and subsequently with 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. The microneedle sensor showed direct oxidation of fentanyl in liquid samples with a detection limit of 27.8 µM by employing a highly sensitive square-wave voltammetry technique. The resulting microneedle-based sensing platform displayed an interference-free fentanyl detection in diluted serum without conceding its sensitivity, stability, and response time. The obtained results revealed that the microneedle sensor holds considerable promise for point-of-need fentanyl detection and opens additional opportunities for detecting substances of abuse in emergencies.

Enhanced Vapor Transmission Barrier Properties via Silicon-Incorporated Diamond-Like Carbon Coating.

In this study, we describe reducing the moisture vapor transmission through a commercial polymer bag material using a silicon-incorporated diamond-like carbon (Si-DLC) coating that was deposited using plasma-enhanced chemical vapor deposition. The structure of the Si-DLC coating was analyzed using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and electron energy loss spectroscopy. Moisture vapor transmission rate (MVTR) testing was used to understand the moisture transmission barrier properties of Si-DLC-coated polymer bag material; the MVTR values decreased from 10.10 g/m2 24 h for the as-received polymer bag material to 6.31 g/m2 24 h for the Si-DLC-coated polymer bag material. Water stability tests were conducted to understand the resistance of the Si-DLC coatings toward moisture; the results confirmed the stability of Si-DLC coatings in contact with water up to 100 °C for 4 h. A peel-off adhesion test using scotch tape indicated that the good adhesion of the Si-DLC film to the substrate was preserved in contact with water up to 100 °C for 4 h.

Recent advances in carbon nanomaterials for biomedical applications: A review.

With the emergence of new pathogens like coronavirus disease 2019 and the prevalence of cancer as one of the leading causes of mortality globally, the effort to develop appropriate materials to address these challenges is a critical research area. Researchers around the world are investigating new types of materials and biological systems to fight against various diseases that affect humans and animals. Carbon nanostructures with their properties of straightforward functionalization, capability for drug loading, biocompatibility, and antiviral properties have become a major focus of biomedical researchers. However, reducing toxicity, enhancing biocompatibility, improving dispersibility, and enhancing water solubility have been challenging for carbon-based biomedical systems. The goal of this article is to provide a review on the latest progress involving the use of carbon nanostructures, namely fullerenes, graphene, and carbon nanotubes, for drug delivery, cancer therapy, and antiviral applications.