Sustainable Devices by Design: Thermal- and Plasma-Enabled Nanofabrication of Hierarchical Carbon Nanostructures for Bioelectronics and Supercapacitors

Graphene is promising to enable diverse technological advancements. However, major technical challenges arise in its fabrication and integration as active functional materials. This body of work exemplifies a host of thermal- and plasma-enabled techniques, designed to realize sustainable and controlled methodologies for nano-assembly. Importantly, these techniques may be tailored and broadly incorporated to harness the unique functional properties of graphene, and a host of other hierarchical nanomaterials. Together, these concepts may pave the realization of next-generation nanotechnologies which hold promise for a sustainable future

Plasma-enabled carbon nanostructures for early diagnosis of neurodegenerative diseases

Carbon nanostructures (CNs) are amongst the most promising biorecognition nanomaterials due to their unprecedented optical, electrical and structural properties. As such, CNs may be harnessed to tackle the detrimental public health and socio-economic adversities associated with neurodegenerative diseases (NDs). In particular, CNs may be tailored for a specific determination of biomarkers indicative of NDs. However, the realization of such a biosensor represents a significant technological challenge in the uniform fabrication of CNs with outstanding qualities in order to facilitate a highly-sensitive detection of biomarkers suspended in complex biological environments. Notably, the versatility of plasma-based techniques for the synthesis and surface modification of CNs may be embraced to optimize the biorecognition performance and capabilities. This review surveys the recent advances in CN-based biosensors, and highlights the benefits of plasma-processing techniques to enable, enhance, and tailor the performance and optimize the fabrication of CNs, towards the construction of biosensors with unparalleled performance for the early diagnosis of NDs, via a plethora of energy-efficient, environmentally-benign, and inexpensive approaches

Plasma-enabled sustainable elemental lifecycles: honeycomb-derived graphenes for next-generation biosensors and supercapacitors

Vertical graphene nanosheets (VGS) transformed from honeycomb are used for high-performance supercapacitors and selective detection of amyloid-beta (Aβ) species.</p

RuO2-coated vertical graphene hybrid electrodes for high-performance solid-state supercapacitors

Hybrid electrodes consisting of ruthenium dioxide (RuO2) and graphene hold great promise in the development of high-performance supercapacitors. However, the present methods for fabricating RuO2/graphene hybrids are complex and costly, preventing their widespread applications. Here, we demonstrate a simple, scalable and cost-effective method to prepare hybrid electrodes composed of RuO2 and vertical graphene (VG). VG is used as the support to offer several unique features, including a three-dimensional (3D) porous structure, a large surface area, good mechanical rigidity and high electrical conductivity. With a solution-free reactive magnetron sputtering method, RuO2 can be uniformly coated on VG with controllable loading. Solid-state supercapacitors assembled using the binder-free RuO2/VG hybrids and a polymer gel electrolyte possess a high areal capacitance, low electrical resistance, good frequency response, and excellent capacitance retention after 10[thin space (1/6-em)]000 cycles of charging and discharging. Our results demonstrate the potential of RuO2/VG hybrids in developing high-performance solid-state supercapacitors in a cost-effective manner, paving the way towards the commercialization of various Ru-based energy storage devices

Single-step, plasma-enabled reforming of natural precursors into vertical graphene electrodes with high areal capacitance

Graphene nanostructures possess excellent physical properties such as high surface area, good mechanical stability, and good electric conductivity, which make them attractive as electrodes for high-performance energy storage devices. However, graphene-based nanomaterials have yet to be materialized into commercial energy storage devices, mainly due to the high cost in fabrication processes and the difficulty in achieving high mass loading. In particular, the high mass loading of active materials on the electrode represents an important step toward the translation of excellent electrochemical activity seen in the microscopic regime into the practical applications. Here, supercapacitor electrodes made of vertical graphene nanosheets (VGNS) are fabricated from a range of commercially available cheese precursors via green, low-temperature, plasma-based reforming processes. Taking advantage of the fast solidification of cheese molecules and plasma–matter interactions, the produced VGNS exhibit a high mass loading of 3.2 mg/cm2 and a high areal capacitance of 0.46 F/cm2. These results demonstrate a single-step, scalable, environmentally benign, and cost-effective approach for the transformation of natural precursors into high-quality graphene structures, which could be promising for a variety of advanced electronic and energy applications

High pseudocapacitive performance of MnO2 nanowires on recyclable electrodes

Manganese oxides are promising pseudocapacitve materials for achieving both high power and energy densities in pseudocapacitors. However, it remains a great challenge to develop MnO2-based high-performance electrodes due to their low electrical conductance and poor stability. Here we show that MnO2 nanowires anchored on electrochemically modified graphite foil (EMGF) have a high areal capacitance of 167 mF cm−2 at a discharge current density of 0.2 mA cm−2 and a high capacitance retention after 5000 charge/discharge cycles (115 %), which are among the best values reported for any MnO2-based hybrid structures. The EMGF support can also be recycled and the newly deposited MnO2-based hybrids retain similarly high performance. These results demonstrate the successful preparation of pseudocapacitors with high capacity and cycling stability, which may open a new opportunity towards a sustainable and environmentally friendly method of utilizing electrochemical energy storage devices

High Pseudocapacitive Performance of MnO 2

Manganese oxides are promising pseudocapacitve materials for achieving both high power and energy densities in pseudocapacitors. However, it remains a great challenge to develop MnO2-based high-performance electrodes due to their low electrical conductance and poor stability. Here we show that MnO2 nanowires anchored on electrochemically modified graphite foil (EMGF) have a high areal capacitance of 167 mF cm−2 at a discharge current density of 0.2 mA cm−2 and a high capacitance retention after 5000 charge/discharge cycles (115 %), which are among the best values reported for any MnO2-based hybrid structures. The EMGF support can also be recycled and the newly deposited MnO2-based hybrids retain similarly high performance. These results demonstrate the successful preparation of pseudocapacitors with high capacity and cycling stability, which may open a new opportunity towards a sustainable and environmentally friendly method of utilizing electrochemical energy storage devices

Multifunctional graphene micro-islands: Rapid, low-temperature plasma-enabled synthesis and facile integration for bioengineering and genosensing applications

Highlights - Graphene micro-islands (GMs) can be transferred onto arbitrary substrates. - GMs are used as a biosensing platform which shows sensitivities to 1 pM. - GMs demonstrate good biocompatibility using primary fibroblast lung cells. Abstract Here, we present a rapid, low-temperature (200 °C) plasma-enabled synthesis of graphene micro-islands (GMs). Morphological analyses of GMs by scanning electron microscopy (SEM) and atomic force microscopy (AFM) feature a uniform and open-networked array of aggregated graphene sheets. Structural and surface chemical characterizations by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) support the presence of thin graphitic edges and reactive oxygen functional groups. We demonstrate that these inherent properties of GMs enable its multifunctional capabilities as a bioactive interface. GMs exhibit a biocompatibility of 80% cell viability with primary fibroblast lung cells after 5 days. Further, GMs were assembled into an impedimetric genosensor, and its performance was characterized by electrochemical impedance spectroscopy (EIS). A dynamic sensing range of 1 pM to 1 nM is reported, and a limit of quantification (LOQ) of 2.03×10−13 M is deduced, with selectivity to single-RNA-base mismatched sequences. The versatile nature of GMs may be explored to enable multi-faceted bioactive platforms for next-generation personalized healthcare technologies

High-frequency supercapacitors based on doped carbon nanostructures

Carbon nanostructures are promising materials for electrochemical energy storage but their frequency response is usually poor, limiting their utilization in high-frequency applications. Here we demonstrate the growth of carbon nanostructures with different dopants of N, B, P/N, B/N, and Si, based on a scalable aerosol-assisted chemical vapor deposition process. The doped carbon nanostructures were directly grown on the conductive Ni substrates and exhibit an open and porous structure which is beneficial for fast ion transport and ion kinetics. Coin cells made of the doped carbon nanostructures demonstrate a frequency response as fast as 13,200 Hz at a phase angle of −45° and the smallest relaxation time constant of ∼77 μs. Together with a low equivalent series resistance and a large areal capacitance, the high-frequency supercapacitors based on doped carbon nanostructures could be promising in replacing traditional aluminium electrolytic capacitors for many high-frequency electronic devices.</p