Pei Lay Yap
@adelaide.edu.au
The University of Adelaide
Scopus Publications
Scopus Publications
Linghong Liu, Zhu Wang, Pei Lay Yap, Qiulan Zhang, Yongnian Ni, and Dusan Losic
Wiley
AbstractCurcumin (Cur) is an acidic polyphenol with some effects on α‐glucosidase (α‐Glu), but Cur has disadvantages such as being a weak target, lacking passing the blood–brain barrier and having low bioavailability. To enhance the curative effect of Cur, the hybrid composed of ZnO nanoparticles decorated on rGO was used to load Cur (ZnO@rGO‐Cur). The use of the multispectral method and enzyme inhibition kinetics analysis certify the inhibitory effect and interaction mechanism of ZnO@rGO‐Cur with α‐Glu. The static quenching of α‐Glu with both Cur and ZnO@rGO‐Cur is primarily driven by hydrogen bond and van der Waals interactions. The conformation‐changing ability by binding to the neighbouring phenolic hydroxyl group of Cur increased their ability to alter the secondary structure of α‐Glu, resulting in the inhibition of enzyme activity. The inhibition constant (Ki, Cur > Kis,ZnO@rGO‐Cur) showed that the inhibition effect of ZnO@rGO‐Cur on α‐Glu was larger than that of Cur. The CCK‐8 experiments proved that ZnO@rGO nanocomposites have good biocompatibility. These results suggest that the therapeutic potential of ZnO@rGO‐Cur composite is an emerging nanocarrier platform for drug delivery systems for the potential treatment of diabetes mellitus.
Md Julker Nine, Alena Chizhova, Shaheer Maher, Ashis Tripathy, Arash Mazinani, Mahnaz Dadkhah, Kamrul Hassan, Pei Lay Yap, Tran T. Tung, and Dusan Losic
Elsevier BV
Le Yu, Pei Lay Yap, Alexandre M.C. Santos, Diana N.H. Tran, and Dusan Losic
Elsevier BV
Pei Lay Yap, Farzaneh Farivar, Åsa K. Jämting, Victoria A. Coleman, Sam Gnaniah, Elisabeth Mansfield, Cheng Pu, Sandra Marcela Landi, Marcus Vinícius David, Emmanuel Flahaut,et al.
American Chemical Society (ACS)
Research on graphene-related two-dimensional (2D) materials (GR2Ms) in recent years is strongly moving from academia to industrial sectors with many new developed products and devices on the market. Characterization and quality control of the GR2Ms and their properties are critical for growing industrial translation, which requires the development of appropriate and reliable analytical methods. These challenges are recognized by International Organization for Standardization (ISO 229) and International Electrotechnical Commission (IEC 113) committees to facilitate the development of these methods and standards which are currently in progress. Toward these efforts, the aim of this study was to perform an international interlaboratory comparison (ILC), conducted under Versailles Project on Advanced Materials and Standards (VAMAS) Technical Working Area (TWA) 41 "Graphene and Related 2D Materials" to evaluate the performance (reproducibility and confidence) of the thermogravimetric analysis (TGA) method as a potential new method for chemical characterization of GR2Ms. Three different types of representative and industrially manufactured GR2Ms samples, namely, pristine few-layer graphene (FLG), graphene oxide (GO), and reduced graphene oxide (rGO), were used and supplied to ILC participants to complete the study. The TGA method performance was evaluated by a series of measurements of selected parameters of the chemical and physical properties of these GR2Ms including the number of mass loss steps, thermal stability, temperature of maximum mass change rate (Tp) for each decomposition step, and the mass contents (%) of moisture, oxygen groups, carbon, and impurities (organic and non-combustible residue). TGA measurements determining these parameters were performed using the provided optimized TGA protocol on the same GR2Ms by 12 participants across academia, industry stakeholders, and national metrology institutes. This paper presents these results with corresponding statistical analysis showing low standard deviation and statistical conformity across all participants that confirm that the TGA method can be satisfactorily used for characterization of these parameters and the chemical characterization and quality control of GR2Ms. The common measurement uncertainty for each parameter, key contribution factors were identified with explanations and recommendations for their elimination and improvements toward their implementation for the development of the ISO/IEC standard for chemical characterization of GR2Ms.
Dusan Losic, Farzaneh Farivar, Pei Lay Yap, Tran Thanh Tung, and Md Julker Nine
Elsevier BV
Yang Cheng, Yu Fu, Liang Ma, Pei Lay Yap, Dusan Losic, Hongxia Wang, and Yuhao Zhang
Elsevier BV
Le Yu, Pei Lay Yap, Alexandre Santos, Diana Tran, Kamrul Hassan, Jun Ma, and Dusan Losic
American Chemical Society (ACS)
Mathias Aakyiir, Brayden Tanner, Pei Lay Yap, Hadi Rastin, Tran Thanh Tung, Dusan Losic, Qingshi Meng, and Jun Ma
Elsevier BV
Piers Turner, Keith R Paton, Elizabeth J Legge, Andres de Luna Bugallo, A K S Rocha-Robledo, Ahmed-Azmi Zahab, Alba Centeno, Alessio Sacco, Amaia Pesquera, Amaia Zurutuza,et al.
IOP Publishing
Abstract There is a pressing need for reliable, reproducible and accurate measurements of graphene’s properties, through international standards, to facilitate industrial growth. However, trustworthy and verified standards require rigorous metrological studies, determining, quantifying and reducing the sources of measurement uncertainty. Towards this effort, we report the procedure and the results of an international interlaboratory comparison (ILC) study, conducted under Versailles Project on Advanced Materials and Standards. This ILC focusses on the comparability of Raman spectroscopy measurements of chemical vapour deposition (CVD) grown graphene using the same measurement protocol across different institutes and laboratories. With data gathered from 17 participants across academia, industry (including instrument manufacturers) and national metrology institutes, this study investigates the measurement uncertainty contributions from both Raman spectroscopy measurements and data analysis procedures, as well as provides solutions for improved accuracy and precision. While many of the reported Raman metrics were relatively consistent, significant and meaningful outliers occurred due to differences in the instruments and data analysis. These variations resulted in inconsistent reports of peak intensity ratios, peak widths and the coverage of graphene. Due to a lack of relative intensity calibration, the relative difference reported in the 2D- and G peak intensity ratios ( I 2 D / I G ) was up to 200%. It was also shown that the standard deviation for Γ 2 D values reported by different software packages, was 15× larger for Lorentzian fit functions than for pseudo-Voigt functions. This study has shown that by adopting a relative intensity calibration and consistent peak fitting and data analysis methodologies, these large, and previously unquantified, variations can be significantly reduced, allowing more reproducible and comparable measurements for the graphene community, supporting fundamental research through to the growing graphene industry worldwide. This project and its findings directly underpin the development of the ISO/IEC standard ‘DTS 21356-2—Nanotechnologies—Structural Characterisation of CVD-grown Graphene’.
Kamrul Hassan, Nathan Stanley, Tran Thanh Tung, Pei Lay Yap, Hadi Rastin, Le Yu, and Dusan Losic
Wiley
Hadi Rastin, Negar Mansouri, Tran Thanh Tung, Kamrul Hassan, Arash Mazinani, Mahnaz Ramezanpour, Pei Lay Yap, Le Yu, Sarah Vreugde, and Dusan Losic
Wiley
The development of next-generation of bioinks aims to fabricate anatomical size 3D scaffold with high printability and biocompatibility. Along with the progress in 3D bioprinting, 2D nanomaterials (2D NMs) prove to be emerging frontiers in the development of advanced materials owing to their extraordinary properties. Harnessing the properties of 2D NMs in 3D bioprinting technologies can revolutionize the development of bioinks by endowing new functionalities to the current bioinks. First the main contributions of 2D NMS in 3D bioprinting technologies are categorized here into six main classes: 1) reinforcement effect, 2) delivery of bioactive molecules, 3) improved electrical conductivity, 4) enhanced tissue formation, 5) photothermal effect, 6) and stronger antibacterial properties. Next, the recent advances in the use of each certain 2D NMs (1) graphene, 2) nanosilicate, 3) black phosphorus, 4) MXene, 5) transition metal dichalcogenides, 6) hexagonal boron nitride, and 7) metal-organic frameworks) in 3D bioprinting technology are critically summarized and evaluated thoroughly. Third, the role of physicochemical properties of 2D NMSs on their cytotoxicity is uncovered, with several representative examples of each studied 2D NMs. Finally, current challenges, opportunities, and outlook for the development of nanocomposite bioinks are discussed thoroughly.
Kamrul Hassan, Tran Thanh Tung, Pei Lay Yap, Hadi Rastin, Nathan Stanley, Md. Julker Nine, and Dusan Losic
American Chemical Society (ACS)
The rapid advancement of internet of things (IoT)-enabled applications along with connected automation in sensing technologies is the heart of future intelligent systems. The probable applications have significant implications, from chemical process monitoring to agriculture, mining, space, wearable electronics, industrial manufacturing, smart cities, and point-of-care (PoC) diagnostics. Advancing sensor performance such as sensitivity to detect trace amounts (ppb-ppm) of analytes (gas/VOCs), selectivity, portability, and low cost is critical for many of these applications. These advancements are mainly achieved by selecting and optimizing sensing materials by their surface functionalization and/or structural optimization to achieve favorable transport characteristics or chemical binding/reaction sites. Surprisingly, the sensor geometry, shapes, and patterns were not considered as critical parameters, and most of these sensors were designed by following simple planar and interdigitated electrode geometry. In this study, we introduce a new bioinspired fractal approach to design chemoresistive sensors with fractal geometry, which grasp the architecture of fern leaves represented by the geometric group of space-filling curves of fractal patterns. These fractal sensors were printed by an extrusion process on a flexible substrate (PET) using specially formulated graphene ink as a sensing material, which provided significant enhancement of the active surface area to volume ratio and allowed high-resolution fractal patterning along with a reduced current transportation path. To demonstrate the advantages and influence of fractal geometry on sensor performance, here, three different kinds of sensors were fabricated based on different fractal geometrics (Sierpinski, Peano, and Hilbert), and the sensing performance was explored toward different VOC analytes (e.g., ethanol, methanol, and acetone). Among all these fractal-designed sensors including interdigitate sensors, the Hilbert-designed printed sensor shows enhanced sensing properties in terms of fast response time (6 s for 30 ppm), response value (14%), enhanced detection range (5-100 ppm), high selectivity, and low interference to humidity (up to RH 80%) for ethanol at room temperature (20 °C). Moreover, a significant improvement of this sensor performance was observed by applying the mechanical deformation (positive bending) technique. The practical application of this sensor was successfully demonstrated by monitoring food spoilage using a commercial box of strawberries as a model. Based on these presented results, this biofractal biomimetic VOC sensor is demonstrated for a prospective application in food monitoring.
Le Yu, Pei Lay Yap, Diana N H Tran, Alexandre M C Santos, and Dusan Losic
IOP Publishing
Owing to many fascinating properties including high thermal and chemical stability, excellent electrical insulation, fire-retardant and antibacterial properties, hexagonal boron nitride (hBN) has emerged as a prominent 2D material for broad applications. However, the production of high quality of hBN by chemical exfoliation from its precursor is still challenging. This paper presents a high-yield (+83%), low-cost and energy-efficient wet chemical exfoliation strategy, which produces few-layers (FL, 3–6 layers) of edge-functionalized (OH) hBN nanosheets with uniform size (486 ± 51 nm). This optimized preparation is established based on a comprehensive investigation on the key exfoliation parameters such as exfoliation temperature, time and amount of the oxidant (potassium permanganate). High quality of FL-hBN was confirmed by various characterization techniques including scanning electron microscopy coupled with energy dispersive X-ray, transmission electron microscopy, Raman, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy analyses. The outcome of this study paves a promising pathway to effectively produce hBN through a cost-efficient exfoliation approach, which has a significant impact on industrial applications.
Dusan Losic, Farzaneh Farivar, Pei Lay Yap, and Afshin Karami
American Chemical Society (ACS)
Counterfeits in the supply chain of high-value advanced materials such as graphene and their derivatives have become a concerning problem with a potential negative impact on this growing and emerging industry. Recent studies have revealed alarming facts that a large percentage of manufactured graphene materials on market are not graphene, raising considerable concerns for the end users. The common and recommended methods for the characterization of graphene materials, such as transmission electron microscopy (TEM), atomic force microscopy (AFM), and Raman spectroscopy based on spot analysis and probing properties of individual graphene particles, are limited to provide the determination of the properties of "bulk" graphene powders at a large scale and the identification of non-graphene components or purposely included additives. These limitations are creating counterfeit opportunities by adding low-cost black carbonaceous materials into manufactured graphene powders. To address this problem, it is critical to have reliable characterization methods, which can probe the specific properties of graphene powders at bulk scale, confirm their typical graphene signature, and detect the presence of unwanted additional compounds, where the thermogravimetric analysis (TGA) method is one of the most promising methods to perform this challenging task. This paper presents the evaluation of the TGA method and its ability to detect low-cost carbon additives such as graphite, carbon black, biochar, and activated carbon as potential counterfeiting materials to graphene materials and their derivatives such as graphene oxide (GO) and reduced GO. The superior performance of the TGA method is demonstrated here, showing its excellent capability to successfully detect these additives when mixed with graphene materials, which is not possible by two other comparative methods (Raman spectroscopy and powder X-ray diffraction (XRD)), which are used as the common characterization methods for graphene materials.
Le Yu, Pei Lay Yap, Alexandre Santos, Diana Tran, and Dusan Losic
American Chemical Society (ACS)
Farzaneh Farivar, Pei Lay Yap, Kamrul Hassan, Tran Thanh Tung, Diana N.H. Tran, Andrew J. Pollard, and Dusan Losic
Elsevier BV
Farzaneh Farivar, Pei Lay Yap, Tran Thanh Tung, and Dusan Losic
MDPI AG
Functionalization of pristine graphene to achieve high water dispersibility remains as a key obstacle owing to the high hydrophobicity and absence of reactive functional groups on the graphene surface. Herein, a green and simple modification approach to prepare highly dispersible functionalized graphene via thermal thiol-ene click reaction was successfully demonstrated on pristine graphene. Specific chemical functionalities (–COO, –NH2 and –S) on the thiol precursor (L-cysteine ethyl ester) were clicked directly on the sp2 carbon of graphene framework with grafting density of 1 unit L-cysteine per 113 carbon atoms on graphene. This functionalized graphene was confirmed with high atomic content of S (4.79 at % S) as well as the presence of C–S–C and N–H species on the L-cysteine functionalized graphene (FG-CYS). Raman spectroscopy evidently corroborated the modification of graphene to FG-CYS with an increased intensity ratio of D and G band, ID/IG ratio (0.3 to 0.7), full-width at half-maximum of G band, FWHM [G] (20.3 to 35.5) and FWHM [2D] (64.8 to 90.1). The use of ethanol as the reaction solvent instead of common organic solvents minimizes the chemical hazards exposure to humans and the environment. This direct attachment of multifunctional groups on the surface of pristine graphene is highly demanded for graphene ink formulations, coatings, adsorbents, sensors and supercapacitor applications.
Kamrul Hassan, Tran Thanh Tung, Nathan Stanley, Pei Lay Yap, Farzaneh Farivar, Hadi Rastin, Md Julker Nine, and Dusan Losic
Royal Society of Chemistry (RSC)
Printed electronic sensors offer a breakthrough in the availability of low-cost devices for improving the quality of human life. Conductive ink is the core of printing technology and is one of the fastest growing ink industries.
Pei Lay Yap, Md Julker Nine, Kamrul Hassan, Tran Thanh Tung, Diana N. H. Tran, and Dusan Losic
Wiley
Hongxia Wang, Diana Tran, Mahmoud Moussa, Nathan Stanley, Tran T. Tung, Le Yu, Pei Lay Yap, Fuyuan Ding, Jun Qian, and Dusan Losic
Elsevier BV
Abstract This paper presents a new and facile method to prepare molybdenum disulfide (MoS2)/graphene composites and their inks based on an improved ball milling process. The developed method is cost effective, environmentally friendly, and scalable, producing few-layer MoS2 material and MoS2/graphene-based inks. The prepared inks after characterization by SEM, Raman, XRD, FTIR, CA and rheology were used to fabricate electrodes for supercapacitors by adopting two designs: 2D printed and sandwiched electrodes. The electrodes showed excellent electrochemical performance with a specific capacitance of 392 Fg−1 at 5 mV s−1 and low equivalent resistance of 0.41 Ω, which outperforms the properties of graphene electrodes. The specific capacitance of electrodes prepared by 2D printing using MoS2/graphene ink was 76 Fg−1 at 5 mV s−1 with an areal capacitance of 58.5 mF/cm−2 at 0.77 mg/cm−2, demonstrating high energy storage capability. The performance of the MoS2/graphene composites and their inks highlights their promising application as electrode materials for high-performance energy storage devices.
Kamrul Hassan, Tran Thanh Tung, Pei Lay Yap, Md J. Nine, Hyeon C. Kim, and Dusan Losic
Elsevier BV
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, Md Julker Nine, Tran Thanh Tung, Nathan Stanley, Pei Lay Yap, Hadi Rastin, Le Yu, and Dusan Losic
Royal Society of Chemistry (RSC)
Graphene and related 2D materials offer an ideal platform for next generation disruptive technologies and in particular the potential to produce printed electronic devices with low cost and high throughput.
Pei Lay Yap, Kamrul Hassan, Yow Loo Auyoong, Negar Mansouri, Farzaneh Farivar, Diana N. H. Tran, and Dusan Losic
Wiley
Pei Lay Yap, Yow Loo Auyoong, Kamrul Hassan, Farzaneh Farivar, Diana N.H. Tran, Jun Ma, and Dusan Losic
Elsevier BV
Abstract Heavy metals contamination in the natural waters remains an unresolved environmental challenge pressing for the development of purification technologies. This paper presents the green engineering of a new bio-sponge for heavy metals adsorption composed of alginate bio-polymeric network encapsulated with reduced graphene oxide (rGO) modified with iron oxide nanoparticles and covalently attached multithiol (pentaerythritol tetrakis-mercaptopropionate) molecules using photoinitiated thiol-ene click chemistry. The multithiol functionalized graphene bio-sponge (SH-Graphene bio-sponge) is designed to enhance adsorption performances of heavy metals including structural approach combined with oxygen functionalities and high density of sulfur-containing groups (10.2 at % S, confirmed by X-ray Photoelectron Spectroscopy, XPS) with high binding affinity towards specific heavy metals (Cd and Pb). It was shown that the level of thiol functionalization on the graphene structure within the bio-sponge can be controlled by tuning the Ultraviolet (UV) irradiation time without adjusting the concentration of the precursors. SH-functionalized graphene bio-sponge showed outstanding adsorption capacity for Pb (II): 101.01 mg/g and Cd (II): 102.99 mg/g, outperformed commercial and literature reported adsorbents in highly competitive selectivity studies using co-existing heavy metal ions (Cu, Co, Pb and Cd) spiked- sea water. The multithiol modified bio-sponge also showcased an excellent stability and reusability feature with only 0.015 mg/L Pb (II) detected, conforming the strict United States Environmental Protection Agency (US EPA) maximum contaminant level (MCL) for lead, after five recurring cycles using mixed heavy metal ions solution and acidic eluent. The outcomes from this work present valuable and promising contribution towards the development of a scalable and sustainable adsorbents for efficient remediation of heavy metals from waters.
Pei Lay Yap, Tran Thanh Tung, Shervin Kabiri, Nicola Matulick, Diana N.H. Tran, and Dusan Losic
Elsevier BV
Abstract This paper describes the synthesis and characterization of polyamine modified reduced graphene oxide rich with mixed amino groups as a cost- and performance- efficient adsorbent for mercury removal from waters. The synthetic approach is based on a simple process to functionalize graphene oxide (GO) with low-cost commercial polyamine epoxy hardener followed by the reduction of created polyamine-GO hybrid by hydrothermal (HT) or chemical reduction (CM) process with hydrazine. Both polyamine modified reduced graphene oxide (rGO), referred as HT-rGO-N and CM-rGO-N, exhibited 8.28% and 5.47% N content, respectively. Mercury adsorption study showed that these rGO functionalized composites have high adsorption kinetics, reaching equilibrium within the first ten minutes. The adsorption kinetics and equilibrium of their adsorption process can be well described using pseudo-second order and Freundlich isotherm models with estimated sorption capacity of 63.8 mg/g and 59.9 mg/g for HT-rGO-N and CM-rGO-N respectively. The adsorption capacity for Hg is achieved in broad range of pH (pH 5–9) and can be described as high-performing compared with other amino based adsorbents reported in the literature. More importantly, these adsorbents showed very high selectivity towards Hg(II), outperformed the commercial activated carbon adsorbent with only ~16% mercury removal efficiency achieved in multimetallic solution consisting of Hg(II), Cd(II), Co(II), Cu(II) and Pb(II) ions in both solid and dispersed forms. Finally, these polyamine functionalized rGO adsorbents confirmed their notable performance in regeneration and removal of spiked mercury from natural waters mimicking real applications. These results demonstrated realistic water remediation capabilities of developed polyamine functionalized rGO adsorbents as promising candidates for environmental applications.