Graphene oxide-based lamella network for enhanced sound absorption

Published online October 23, 2017Noise is an environmental pollutant with recognized impacts on the psychological and physiological health of humans. Many porous materials are often limited by low sound absorption over a broad frequency range, delicacy, excessive weight and thickness, poor moisture insulation, high temperature instability, and lack of readiness for high volume commercialization. Herein, an efficient and robust lamella-structure is reported as an acoustic absorber based on self-assembled interconnected graphene oxide (GO) sheets supported by a grill-shaped melamine skeleton. The fabricated lamella structure exhibits ≈60.3% enhancement over a broad absorption band between 128 and 4000 Hz (≈100% at lower frequencies) compared to the melamine foam. The enhanced acoustic absorption is identified to be structure dependent regardless of the density. The sound dissipation in the open-celled structure is due to the viscous and thermal losses, whereas it is predominantly tortuosity in wave propagation and enhanced surface area for the GO-based lamella. In addition to the enhanced acoustic absorption and mechanical robustness, the lamella provides superior structural functionality over many conventional sound absorbers including, moisture/mist insulation and fire retardancy. The fabrication of this new sound absorber is inexpensive, scalable and can be adapted for extensive applications in commercial, residential, and industrial building structures.Md Julker Nine, Md Ayub, Anthony C. Zander, Diana N. H. Tran, Benjamin S. Cazzolato and Dusan Losi

TRPC6 single nucleotide polymorphisms and progression of idiopathic membranous nephropathy

Background: Activating mutations in the Transient Receptor Potential channel C6 (TRPC6) cause autosomal dominant focal segmental glomerular sclerosis (FSGS). TRPC6 expression is upregulated in renal biopsies of patients with idiopathic membranous glomerulopathy (iMN) and animal models thereof. In iMN, disease progression is characterized by glomerulosclerosis. In addition, a context-dependent TRPC6 overexpression was recently suggested in complement-mediated podocyte injury in e.g. iMN. Hence, we hypothesized that genetic variants in TRPC6 might affect susceptibility to development or progression of iMN. Methods & Results: Genomic DNA was isolated from blood samples of 101 iMN patients and 292 controls. By direct sequencing of the entire TRPC6 gene, 13 single nucleotide polymorphisms (SNPs) were identified in the iMN cohort, two of which were causing an amino acid substitution (rs3802829; Pro15Ser and rs36111323, Ala404Val). No statistically significant differences in genotypes or allele frequencies between patients and controls were observed. Clinical outcome in patients was determined (remission n = 26, renal failure n = 46, persistent proteinuria n = 29, follow-up median 80 months {range 51-166}). The 13 identified SNPs showed no association with remission or renal failure. There were no differences in genotypes or allele frequencies between patients in remission and progressors. Conclusions: Our data suggest that TRPC6 polymorphisms do not affect susceptibility to iMN, or clinical outcome in iMN

Nature inspired emerging sensing technology: Recent progress and perspectives

Biological systems include several well-known patterns with different forms and dimensions (nano to macro) such as cracks, whiskers, hierarchical, interlocked, porous, and bristle-like structures, as well as hetero-layered brick-and-mortar structures. These structures and surfaces typically have several functions based on their structure and surface chemistry which include static coloration, self-cleaning, adhesive, underwater navigation and object detection, electric charge generation, and highly sensitive olfactory organ to sense and detect various substances. A new era of bio-inspired sensing materials with an effort to copy structures or functions of living creatures (i.e. plant and animals) has recently attracted widespread attention. This review summarizes the latest developments in bio-inspired sensing and biosensing materials and focuses on the design and mechanisms to analyse their potential in multifunctional sensing applications. Primarily, this review highlights various bioinspired structural features and their functional properties, followed by an overview of the fundamental mechanisms of distinct living creatures, including animals and plants, in brief. Thereafter, various sensing and biosensing applications of these nature-inspired structures/functions are elaborately described. Finally, the challenges and prospects of nature-inspired smart sensing and biosensing technology for the 21st century are provided.Ashis Tripathy, Julker Nine, Dusan Losic, Filipe Samuel Silv

Electromagnetic Shielding using Graphene Material in Wide Bandwidth of 1.5GHz-10GHz

We report pristine graphene (pG) as an effective shielding material for electromagnetic interference (EMI) in electronics, and RF sensor systems. The pG was produced via a simple process of mechanical exfoliation of natural graphite. The performance of as-prepared graphene film coating alone with a thickness of 27.9μm.was evaluated in terms of shielding effectiveness (SE) and demonstrate SE ~ 22.7dB–16.7dB in 1.5GHz–10GHz frequency band. The insertion loss through the alumina substrate was subtracted from the measurement result.Kamal Gupta, Md J. Nine, Craig Denton, Dusan Losi

Dye-sensitized solar cell counter electrodes based on carbon nanotubes

Dye-sensitized solar cells (DSSCs) have received significant attention from the scientific community since their discovery in 1991. However, the high cost and scarcity of platinum has motivated researchers to seek other suitable materials for the counter electrode of DSSCs. Owing to their exceptional properties such as high conductivity, good electrochemical activity, and low cost, carbon nanotubes (CNTs) have been considered as promising alternatives to expensive platinum (Pt) in the counter electrode of DSSCs. Herein, we provide a Minireview of the CNTs use in the counter electrode of DSSCs. A brief overview of Pt-based counter electrodes is also discussed. Particular attention is given to the recent advances of counter electrodes with CNT-based composite structures.Seunghwa Hwang, Munkhbayar Batmunkh, Md J. Nine, Hanshik Chung, and Hyomin Jeon

Silver Nanowires with Pristine Graphene Oxidation Barriers for Stable and High Performance Transparent Conductive Films

One-dimensional (1D) silver nanowires (AgNWs) have emerged as a leading candidate for the development of next-generation optoelectronic and wearable electronic devices. However, a key limitation of AgNW electrodes is that they are readily oxidized, resulting in a shift in properties leading to devices becoming erratic over time. To address this problem, we report a facile method to improve both the stability and performance of AgNW films. The AgNWs were combined with pristine graphene (pG) using an optimal (30/70 wt %) with the goals to prove that the pG sheets can provide a barrier shielding to protect against AgNW oxidation and have the additional benefit of improving the connections between wires and stability of the films. The fabrication of these films was demonstrated on wide range of substrates including glass, plastic, textile, and paper. A surface resistance of 18.23 Ω/sq and an optical transparency of 89% were obtained on the glass substrates, 50 Ω/sq and 88% transparency for poly(ethylene terephthalate) (PET), and 0.35 Ω/sq resistance on the textile substrate. Atmospheric pressure plasma jets (APPJ) treatment was further used to enhance the performance of the film (i.e., glass), resulting in a significant reduction of 30.6% in sheet resistance (15.20 Ω/sq) and an improvement of transparency to 91%. The stability of AgNW/pG film under environmental conditions and higher temperatures was significantly improved, showing only a minor increase in the sheet resistance after 30 days and at temperature increases up to 300 °C when compared with control (AgNW film) which shows a sharp increase after 8−10 days and is thermally stable until 150 °C as a result of Ag oxidation.Faisal Alotaibi, Tran Thanh Tung, Md Julker Nine, Campbell J. Coghlan and Dusan Losi

New insights on energetic properties of graphene oxide (GO) materials and their safety and environmental risks

Available online 2 August 2022Graphene oxide (GO) has been recognized as a thermally unstable and energetic material, but surprisingly its environmental and safety risks were not fully explored, defined, and regulated. In this study, systematic explosivity and flammability characterizations of commercial GO materials were conducted to evaluate the influence of key parameters such as physical forms (paste, powders, films, and aerogels), temperature, heating rate, mass, and heating environment, as well as their potential safety and environmental impacts. Results based on thermogravimetric analysis (TGA) showed that GO in paste and powder forms have lower temperature thresholds (>180-192 °C) to initiate micro-explosions compared to GO film and aerogels (> 205 °C and 213 °C) regardless of the environment (inert, air, or oxygen). The observed explosive behavior can be explained by thermal runaway reactions as a result of thermal deoxygenation and decomposition of oxygen functional groups. Flammability rating and limiting oxygen index (LOI) results confirmed that GO films are flammable materials that can spontaneously propagate flame in a low oxygen environment (~11 %). These results provided new insights about potential safety and environmental risks of GO materials, which somehow were not considered, suggesting urgent actions to improve current safety protocols for labeling, handling, transporting, and storage practices from manufacturers to the end-users.Dusan Losic, Farzaneh Farivar, Pei Lay Yap, Tran Thanh Tung, Md Julker Nin

Multiple applications of bio-graphene foam for efficient chromate ion removal and oil-water separation

This paper presents the synthesis of bio-graphene foams (bGFs) from renewable sources, and the application of bGFs as new adsorbents in removal of chromate ions and oil contaminants from waste water. A two-step synthetic method was developed to produce bGFs with unique porous architecture and high specific surface area (up to 805 m2 g−1) that is highly desirable for environmental applications. The adsorption performance of prepared bGFs for removal of chromate ions from water was studied in relation to CrO42− concentration, adsorbent load, pH, and contact time to confirm adsorption capacity, kinetics and pH dependence. The adsorption isotherms of chromate ions were consistent with the Langmuir model, revealing an outstanding adsorption capacity of 245 mg of Cr(VI)/g bGFs (pH∼7). bGFs were capable of reducing Cr(VI) in water below the maximum permissible level (0.050 mg dm−3) for human consumption (WHO). In a second application, our results convincingly showed excellent performance of bGFs in separating organic solvents and oils from water in a continuous oil-water separation process showing 99.1% and 98.8% separation efficiency for toluene and petroleum, respectively. Our findings confirm that the outstanding performance of bGFs, and suggest their use as efficient adsorbents for environmental remediation.Melinda Krebsz, Tibor Pasinszki; Tran Thanh Tung, Julker Nine, Dusan Losi

Fast response hydrogen gas sensor based on Pd/Cr nanogaps fabricated by a single-step bending deformation

The development of low-cost and high performing hydrogen gas sensors is important across many sectors, including mining, energy and defense using hydrogen (H2) gas. Herein, we demonstrate a new concept of H2 sensors based on Pd/Cr nanogaps created by using a simple mechanical bending deformation technique. These nanogap sensors can selectively detect the H2 gas based on transduction of the volume expansion after H2 uptake into an electrical signal by palladium-based metal-hydrides that allows closure of nanogaps for electrons flowing or tunneling. While this break-junction architecture, according to literature, can provide several advantages with research gaps in terms of fabricating nanogap sensors with ultra-fast response (≤4 s), the size of nanogap (≤20 nm) and their relationship with time response and recovery as addressed in this paper. Based on the computational modelling outcome, the size of the nanogaps can be investigated in order to optimize the fabrication conditions. Indeed, a single nanogap with optimum width (15 nm) acts as an on-off switch for best performing hydrogen detection. Moreover, with the unique design of Pd/Cr nanogap, the developed sensing device meets major requirement of advanced H2 gas sensor including room temperature (25 °C) operation, detection of trace amounts (10–40,000 ppm), good linearity, ultra-fast response-recovery time (3/4.5 s) and high selectivity. The presented economical lithography-free fabrication method has simple circuitry, low power consumption, recyclability, and favorable aging properties that promises great potential to be used for many practical applications of H2 detection.Kamrul Hassan,Tran Thanh Tung, Pei Lay Yap, Md J.Nine, Hyeon C.Kim, Dusan Losi