A label-free H1N1 influenza virus immunosensor based on an N-LIG/Au laser induced graphene microelectrode

A label-free immunosensor based on an N-doped laser direct graphene (N-LIG)/Au electrode was proposed for H1N1 influenza virus detection. By utilizing the instantaneous high temperature of laser irradiation, N atoms are generated by the decomposition of melamine dripped onto the surface of an LIG electrode to obtain N-LIG with higher conductivity. The doping of N atoms provides a large number of active sites for LIG microelectrodes. Combined with the electrodeposition of Au NPs, and covalently crosslinking antibodies, a simple, highly sensitive and stable immunosensing interface is constructed. The proposed H1N1 influenza virus immunosensor has a detection range of 0.01 fg mL-1 to 10 ng mL-1 with a detection limit as low as 0.004 fg mL-1. The constructed sensor has ultra-high sensitivity and good selectivity and can be used for complex biological sample analysis, with potential application prospects in preventing the large-scale spread of influenza. Taking advantage of N-LIG electrode's properties will provide opportunities for developing portable electrochemical biosensors for health and environmental applications.

Boron and Nitrogen Co-Doped Porous Graphene Nanostructures for the Electrochemical Detection of Poisonous Heavy Metal Ions

Heavy metal poisoning has a life-threatening impact on the human body to aquatic ecosystems. This necessitates designing a convenient green methodology for the fabrication of an electrochemical sensor that can detect heavy metal ions efficiently. In this study, boron (B) and nitrogen (N) co-doped laser-induced porous graphene (LIGBN) nanostructured electrodes were fabricated using a direct laser writing technique. The fabricated electrodes were utilised for the individual and simultaneous electrochemical detection of lead (Pb2+) and cadmium (Cd2+) ions using a square wave voltammetry technique (SWV). The synergistic effect of B and N co-doping results in an improved sensing performance of the electrode with better sensitivity of 0.725 µA/µM for Pb2+ and 0.661 µA/µM for Cd2+ ions, respectively. Moreover, the sensing electrode shows a low limit of detection of 0.21 µM and 0.25 µM for Pb2+ and Cd2+ ions, with wide linear ranges from 8.0 to 80 µM for Pb2+ and Cd2+ ions and high linearity of R2 = 0.99 in case of simultaneous detection. This rapid and facile method of fabricating heteroatom-doped porous graphene opens a new avenue in electrochemical sensing studies to detect various hazardous metal ions.

Laser-Carbonization - A Powerful Tool for Micro-Fabrication of Patterned Electronic Carbons

Fabricating electronic devices from natural, renewable resources is a common goal in engineering and materials science. In this regard, carbon is of special significance due to its biocompatibility combined with electrical conductivity and electrochemical stability. In microelectronics, however, carbon's device application is often inhibited by tedious and expensive preparation processes and a lack of control over processing and material parameters. Laser-assisted carbonization is emerging as a tool for the precise and selective synthesis of functional carbon-based materials for flexible device applications. In contrast to conventional carbonization via in-furnace pyrolysis, laser-carbonization is induced photo-thermally and occurs on the time-scale of milliseconds. By careful selection of the precursors and process parameters, the properties of this so-called laser-patterned carbon (LP-C) such as porosity, surface polarity, functional groups, degree of graphitization, charge-carrier structure, etc. can be tuned. In this critical review, a common perspective is generated on laser-carbonization in the context of general carbonization strategies, fundamentals of laser-induced materials processing, and flexible electronic applications, like electrodes for sensors, electrocatalysts, energy storage, or antennas. An attempt is made to have equal emphasis on material processing and application aspects such that this emerging technology can be optimally positioned in the broader context of carbon-based microfabrication.

High-performance electrode of ZIF-67 metal-organic framework (MOF) loaded laser-induced graphene (LIG) composite for all-solid-state supercapacitor

This work demonstrates a facile and efficient methodology to synthesize a composite material of zeolitic imidazolate frameworks (ZIFs) and laser-induced graphene (LIG). This ZIF-67 loaded LIG composite (ZIF-67/LIG) has been adequately characterized for its morphology and structure, and its electrochemical performance has been specifically examined. As supercapacitors (SCs) electrode material, the ZIF-67/LIG composite exhibits superb electrochemical performance, owing to the inherent high porosity, abundant active sites, large specific surface area of ZIF-67, and the excellent conductive three-dimensional hierarchical porous network structure provided by LIG. In three-electrode system, ZIF-67/LIG composite electrode displays outstanding areal specific capacitance (C_A) of 135.6 mF cm^-2at a current density of 1 mA cm^-2with 1 M Na₂SO₄aqueous electrolyte, which is far greater than that of pristine LIG (7.7 mF cm^-2). Furthermore, the ZIF-67/LIG composite has been fabricated into an all-solid-state planar micro-supercapacitor (MSC). This ZIF-67/LIG MSC exhibits an impressiveC_Aof 38.1 mF cm^-2at a current density of 0.20 mA cm^-2, a good cycling stability of 80.3% capacitance retention after 3000 cycles, and a high energy density of 5.29μWh cm^-2at a power density of 0.1 mW cm^-2. All electrochemical results clearly manifest that as-prepared ZIF-67/LIG composite can be a candidate in energy storage field with exciting possibilities.

Laser-induced graphene electrodes scribed onto novel carbon black-doped polyethersulfone membranes for flexible high-performance microsupercapacitors

A facile and expandable methodology was successfully developed to fabricate laser-induced graphene from novel pristine aminated polyethersulfone (amPES) membranes. The as-prepared materials were applied as flexible electrodes for microsupercapacitors. The doping of amPES membranes with various weight percentages of carbon black (CB) microparticles was then performed to improve their energy storage performance. The lasing process allowed the formation of sulfur- and nitrogen-codoped graphene electrodes. The effect of electrolyte on the electrochemical performance of as-prepared electrodes was investigated and the specific capacitance was significantly enhanced in 0.5 M HClO₄. Remarkably, the highest areal capacitance of 47.3 mF·cm^-2 was achieved at a current density of 0.25 mA·cm^-2. This capacitance is approximately 12.3 times higher than the average value for commonly used polyimide membranes. Furthermore, the energy and power densities were as high as 9.46 µWh·cm^-2 and 0.3 mW·cm^-2 at 0.25 mA·cm^-2, respectively. The galvanostatic charge-discharge experiments confirmed the excellent performance and stability of amPES membranes during 5,000 cycles, where more than 100% of capacitance retention was achieved and the coulombic efficiency was improved up to 96.67%. Consequently, the fabricated CB-doped PES membranes offer several advantages including low carbon fingerprint, cost-effectiveness, high electrochemical performance and potential applications in wearable electronic systems.