Optimizing the efficiency of triboelectric nanogenerators by surface nanoarchitectonics of graphene-based electrodes: A review

Since the discovery of triboelectric nanogenerators (TENGs), a significant body of research work has been undertaken for the modification of material properties to enhance their efficiency. These efforts have focused on judicious materials choice (large differences in work functions), enhanced charge-exchange density via hybridization (plasmonic, photo-enhancement, piezoelectric effect), enhanced contact area via nanostructuring and new device architectures. Whilst these efforts have led to a significant increase in the power density, but the rudimentary choice of metal electrode selection and subsequent charge transfer mechanism still demand attention. As such, low-dimensional carbon nanomaterials and in particular, graphene and its derivatives have been explored in the literature to overcome some of the drawbacks of the conventional metallic electrodes including fatigue and corrosion, especially in high humidity environments. Graphene with its exceptionally high surface area, high electrical conductivity and flexibility make itself an excellent material for enabling wearable electronics. In this review, we discuss the impact of graphene, graphene-based composite electrodes, doped graphene electrodes and laser-induced graphene (LIG) electrodes to improve the performance of TENGs. Also, the basic mechanism of charge transfer between different electrodes of the TENG device has been explained. Among all graphene-based electrodes for TENG, laser-induced graphene electrodes show excellent performance owing to output power density 240 times higher than that of pristine graphene and 120 times more than graphene-based composite electrodes. Such use of functionalized graphene electrodes establishes the new steps towards the realization of flexible and transparent triboelectric nanogenerators

MoS 2 ‐Polyaniline Based Flexible Electrochemical Biosensor: Toward pH Monitoring in Human Sweat

Abstract Wearable pH sensors for sweat analysis have garnered significant scientific attention for the detection of early signs of many physiological diseases. In this study, a MoS2‐polyaniline (PANI) modified screen‐printed carbon electrode (SPCE) is fabricated and used as a sweat biosensor. The exfoliated MoS2 nanosheets are drop casted over an SPCE and are functionalized by a conducting polymer, polyaniline (PANI) via the electropolymerization technique. The as‐fabricated biosensor exhibits high super‐Nernstian sensitivity of −70.4 ± 1.7 mV pH−1 in the linear range of pH 4 to 8 of 0.1 m standard phosphate buffer solution (PBS), with outstanding reproducibility. The sensor exhibits excellent selectivity against the common sweat ions including Na+, Cl−, K+, and NH4+ with tremendous long‐term stability over 180 min from pH 4 to 6. The enhanced active surface area and better electrical conductivity as a consequence of the synergistic effect between MoS2 and PANI are correlated with the boosted performance of the as‐produced biosensor. The feasibility of the sensor is further examined using an artificial sweat specimen and the successful detection confirms the potential of the biosensor for a real‐time noninvasive, skin attachable, and flexible wearable pH sensor

Fabrication of Gold Nanoparticles Embedded Laser-Induced Graphene (LIG) Electrode for Hydrogen Evolution Reaction

The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm2 and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s−1 suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction

Alterations in candidate genes PHF2, FANCC, PTCH1 and XPA at chromosomal 9q22.3 region: Pathological significance in early- and late-onset breast carcinoma

Introduction: Younger women with breast carcinoma (BC) exhibits more aggressive pathologic features compared to older women; young age could be an independent predictor of adverse prognosis. To find any existing differences in the molecular pathogenesis of BC in both younger and older women, alterations at chromosomal (chr.) 9q22.32-22.33 region were studied owing to its association in wide variety of tumors. Present work focuses on comparative analysis of alterations of four candidate genes; PHF2, FANCC, PTCH1 and XPA located within 4.4 Mb region of the afore-said locus in two age groups of BC, as well as the interrelation and prognostic significance of alterations of these genes. Methods: Deletion analysis of PHF2, FANCC, PTCH1 and XPA were examined in a subset of 47 early-onset (group-A: ≤ 40 years) and 59 late-onset (group-B: > 40 years) breast carcinomas using both microsatellite and exonic markers. Methylation Sensitive Restriction analysis (MSRA) was done to check for promoter methylation. Quantitative real-time polymerase chain reaction (Q-PCR) and immunohistochemisty (IHC) was done in some genes to see their relative mRNA and protein expressions respectively. Clinico-pathological correlation of different parameters as well as patient survival was calculated using different statistical softwares like EpiInfo 6.04b, SPSS 10.0 etc. Results: Either age group exhibited high frequency of overall alterations in PHF2, FANCC and PTCH1 compared to XPA. Samples with alteration (deletion/methylation) in these genes showed reduced level of mRNA expression as seen by Q-PCR. Immunohistochemical analysis of FANCC and PTCH1 also supported this observation. Poor patient survival was noted in both age groups having alterations in FANCC. Similar result was also seen with PTCH1 and XPA alterations in group-A and PHF2 alterations in group-B. This reflected their roles as prognostic tools in the respective groups in which they were altered. Conclusion: Overall alterations of PHF2, FANCC and PTCH1 were comparatively higher than XPA. Differential association of alterations in FANCC and PTCH1 with that of PHF2, XPA and two breast cancer susceptibility genes (BRCA1/BRCA2) in the two age groups suggests differences in their molecular pathogenesis and dysregulation of multiple DNA repair pathways as well as hedgehog dependent stem cell renewal pathway

Laser-Patternable Graphene Field Emitters for Plasma Displays

This paper presents a plasma display device (PDD) based on laser-induced graphene nanoribbons (LIGNs), which were directly fabricated on polyimide sheets. Superior field electron emission (FEE) characteristics, viz. a low turn-on field of 0.44 V/μm and a large field enhancement factor of 4578, were achieved for the LIGNs. Utilizing LIGNs as a cathode in a PDD showed excellent plasma illumination characteristics with a prolonged plasma lifetime stability. Moreover, the LIGN cathodes were directly laser-patternable. Such superior plasma illumination performance of LIGN-based PDDs has the potential to make a significant impact on display technology