Characterizations of synthesized laser scribed graphene/molybdenum disulfide (LSG/MoS2) hybrids for supercapacitor performance

A sustainable and organic energy storage system from oil palm lignin waste-derived laser-scribed graphene embedded with molybdenum disulfide (LSG/MoS2) is reported in this work. LSG/MoS2 hybrids were fabricated to overcome the zero-band gap of graphene, and molybdenum disulfide restacking issues, and to induce electrical conductivity. Various amounts of LSG (0.1,0.5,1.0 g) were added in a MoS2 precursor to produce a nanoscale LSG/MoS2 hybrid nanostructure via the hydrothermal method. The Raman D,G, and 2D bands of LSG confirmed the formation of graphene from lignin. The FESEM morphology of LSG/MoS2 hybrids showed a porous and large surface area anchored with 3D MoS2 nanoflower on LSG. TEM imaging revealed MoS2 decorated LSG with a lattice spacing of 0.62 and 0.27nm, corresponding to the (002) and (100) planes of MoS2. In terms of electrochemical performance, LSG with 0.1g of MoS2 has the lowest resistance, the highest specific capacitance of 6.7mF/cm2 at 0.05 mA/cm2, and excellent cyclic stability of 98.1% over 1000 cycles, based on Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) tests

Study on current collector and electrolyte design/electrochemical behaviour of an in-plane lignin derived laser scribed graphene for microsupercapacitor application

Current collectors and electrolyte pairs are frequently overlooked in the development of supercapacitors. In electrode design and sealed packaging, the mechanical and chemical properties of the electrolyte must be retained while maintaining the integrity of microelectrodes and current collectors of the microsupercapacitors. In this research, the physical and electrochemical response of copper (Cu) and 316 stainless steel current collector (SS) for lignin-derived laser scribed graphene (L-LSG) microsupercapacitor with K2SO4 (K+) and H2SO4 (H+) as an electrolyte medium was studied. XPS results confirmed a passivation layer on a copper electrode before and after the electrochemical reaction involving H2SO4 as the electrolyte medium of the highly porous L-LSG structure with six pairs of microelectrodes and graphene current collectors. Analysis of the CV and GCD curves shows that the SS/K+ pair is the most suited for an L-LSG microsupercapacitor, with an areal capacitance and energy density of 22.22 mFcm−2 and 0.00153 mWhcm−2, respectively at 0.08 mAcm−2

Shelf-life, bioburden, water and oxygen permeability studies of laser welded SEBS/PP blended polymer

Abstract The most common material used for blood bags is PVC, which requires the addition of DEHP to increase its flexibility. DEHP is known to cross the polymer barrier and move into the stored blood and, ultimately, the patient's bloodstream. In this work, an alternative prototype composed of SEBS/PP was fabricated through blow-moulding and compared with the commercially available PVC-based blood bag which was designated as the control. The blow-moulded sample layers were welded together using CO2 lasers and optimized to obtain complete sealing of the sides. The samples' performance characteristics were analyzed using water permeability, oxygen permeability, shelf-life, and bioburden tests. The SEBS/PP sample exhibited the highest oxygen permeability rate of 1486.6 cc/m2/24 h after 40 days of ageing, indicating that the sample is conducive for red blood cell (RBC) respiration. On the other hand, the SEBS/PP sample showcased a lower water permeability rate of 0.098 g/h m2 after 40 days of aging, indicating a high-water barrier property and thus preventing water loss during storage. In comparison, the oxygen and water permeability rates of PVC-DEHP were found to be distinctly lower in performance (662.7 cc/m2/24 h and 0.221 g/h m2, respectively). In addition, shelf-life analyses revealed that after 40 days of ageing, polymer samples exhibited no visual damage or degradation. The optimal parameters to obtain adequate welding of the SEBS/PP were determined to be power of 60% (18 W), speed of 70 in/sec and 500 Pulse Per Inch (PPI). Furthermore, the bioburden estimates of SEBS/PP of 115 CFU are markedly lower compared to the bioburden estimate of PVC-DEHP of 213 CFU. The SEBS/PP prototype can potentially be an effective alternative to PVC-based blood bags, particularly for high-risk patients in order to reduce the likelihood of medical issues

A Comprehensive Review on Biopolymer Mediated Nanomaterial Composites and Their Applications in Electrochemical Sensors

Biopolymers are an attractive green alternative to conventional polymers, owing to their excellent biocompatibility and biodegradability. However, their amorphous and nonconductive nature limits their potential as active biosensor material/substrate. To enhance their bio-analytical performance, biopolymers are combined with conductive materials to improve their physical and chemical characteristics. We review the main advances in the field of electrochemical biosensors, specifically the structure, approach, and application of biopolymers, as well as their conjugation with conductive nanomaterials, polymers, and metal oxides in green-based non-invasive analytical biosensors. In addition, we reviewed signal measurement, substrate bio-functionality, biochemical reaction, sensitivity, and limit of detection (LOD) of different biopolymers on various transducers. To date, pectin biopolymer, when conjugated with either gold nanoparticles, polypyrrole, reduced graphene oxide, or multiwall carbon nanotubes forming nanocomposites on glass carbon electrode transducer, tends to give the best LOD, highest sensitivity, and can detect multiple analytes/targets. This review will spur new possibilities for the use of biosensors for medical diagnostic tests

Facile synthesis of MoS2 nanoflower-Ag NPs grown on lignin-derived graphene for Troponin I aptasensing

This article presents the development and application of a green lignin-derived graphene biosensor for Troponin I, a biomarker for Acute Myocardial Infarction (AMI). The graphene was synthesized from oil palm lignin through an optimized laser scribing process. While the three-dimensional nature of the laser-scribed lignin-derived graphene (3D LSG) is advantageous, it suffers from poor electrical conductivity due to the amorphous nature of lignin. Therefore, semi-conductive molybdenum disulphide (MoS2) precursor with conductive green silver nanoparticles (Ag NPs) was added to 0.5, 1.0, 1.5, and 2.0 g of 3D LSG to synthesize 3D LSG_MoS2_Ag NPs hybrids via an aqueous hydrothermal process. Morphological, physical, and structural analyses showed the presence of petal-like MoS2 nanoflower with Ag NPs on the 3D LSG surface. The strong interrelation between 3D LSG, MoS2, and Ag NPs was confirmed by X-ray spectroscopy, Raman spectroscopy and energy dispersive spectroscopy (EDS). Specifically, X-ray spectroscopy revealed the formation of O1s, Ag 3d, C1s, Mo 3d, and S2p in the 3D LSG_MoS2_Ag NPs-2.0 hybrid. Raman spectroscopy revealed an enhancement in the surface area of the 3D LSG_MoS2_Ag NPs-2.0 hybrid, which enhances the detection sensitivity. The 3D LSG_MoS2_Ag NPs hybrid was subsequently chemically modified and immobilised with an aptamer to interact with Troponin I on an impedimetric sensor. The 3D LSG_MoS2_Ag NPs hybrid showed high analytical performance, high specificity, and a ∼ 4-fold increment in selectivity, with a detection limit of 100 attomolar. This biosensor has a sensitivity of 31.45 µA mM−1 cm−2, stability of 87%, with a relative standard deviation for reproducibility of 3.8%

Lignin derived nanoparticle intercalation on nitrogen-doped graphene quantum dots for electrochemical sensing of cardiac biomarker

Lignin-scribed graphene (LSG) conjugated with nitrogen-doped graphene quantum dots (N-GQDs) and lignin derived silver nanoparticles (Ag NPs) was developed through a hydrothermal process for the electrochemical sensing of Troponin I, a cardiac biomarker for Acute Myocardial Infarction (AMI). A nanocomposite with optimal conduction mechanism was developed by varying the N-GQDs doped amount intercalated on the surface of LSG. The nanocomposite was characterised by morphological, physical, and structural examinations. The Ag NPs and N-GQDs were found uniformly distributed on the LSG surface, with selective capture of the biotinylated aptamer probe on the bio-electrode indicative of the specific interaction with Troponin I, resulting in an increment in the charge transfer resistance following hybridisation analysis. The detection limit, as determined through impedance spectroscopy, was 1 fM or 30 fg/mL, with high levels of linearity, selectivity, repeatability, and stability of the sensor. This nanocomposite opens a new avenue for array-based medical diagnostics

A quadruplet 3-D laser scribed graphene/MoS2, functionalised N2-doped graphene quantum dots and lignin-based Ag-nanoparticles for biosensing

Troponin I is a protein released into the human blood circulation and a commonly used biomarker due to its sensitivity and specificity in diagnosing myocardial injury. When heart injury occurs, elevated troponin Troponin I levels are released into the bloodstream. The biomarker is a strong and reliable indicator of myocardial injury in a person, with immediate treatment required. For electrochemical sensing of Troponin I, a quadruplet 3D laserscribed graphene/molybdenum disulphide functionalised N2-doped graphene quantum dots hybrid with ligninbased Ag-nanoparticles (3D LSG/MoS2/N-GQDs/L-Ag NPs) was fabricated using a hydrothermal process as an enhanced quadruplet substrate. Hybrid MoS2 nanoflower (H3 NF) and nanosphere (H3 NS) were formed independently by varying MoS2 precursors and were grown on 3D LSG uniformly without severe stacking and restacking issues, and characterized by morphological, physical, and structural analyses with the N-GQDs and AgNPs evenly distributed on 3D LSG/MoS2 surface by covalent bonding. The selective capture of and specific interaction with Troponin I by the biotinylated aptamer probe on the bio-electrode, resulted in an increment in the charge transfer resistance. The limit of detection, based on impedance spectroscopy, is 100 aM for both H3NF and H3 NS hybrids, with the H3 NF hybrid biosensor having better analytical performance in terms of linearity, selectivity, repeatability, and stability

Oil palm lignin-derived laser scribed graphene in neutral electrolyte for high-performance microsupercapacitor application

Lignin is a renewable natural resource that could be derived from oil palm empty fruit bunches. It has generated significant interest as a precursor in synthesizing graphene as anode and cathode material for supercapacitors. In this paper, we report the synthesis of 3D hierarchical Laser Scribed Graphene (LSG) on a flexible polyimide substrate from lignin extracted from empty fruit bunches (EFB) of oil palm for microsupercapacitor applications. The intensity and speed of the laser have been tuned to yield densely compacted oil palm lignin LSG at a laser power of 70% and a speed of 30% (OPL-LSG 7030). OPL-LSG 7030 possessed lower equivalent series resistance of 60.1 Ω and a larger crystalline size of ∼31 nm than the rest of the tested samples. It exhibited exceptional areal capacitance of 30.77 mFcm−2 at a current density of 0.08 mAcm−2, an energy density of 0.00176 mWhcm−2 and a power density of 0.25 mWcm−2 when using a unique neutral PAAS/K2SO4 gel electrolyte. It achieved excellent capacitance retention of 88.4% after 5000 charge/discharge cycles and remarkable mechanical stability of 95% after 400 bending cycles. Furthermore, electrochemical studies revealed the redox properties of readily available quinone/ hydroquinone in the oil palm lignin, which could be inherited in graphene electrodes through a feasible and affordable approach for flexible green energy storage applications

In-situ Mg-Al LDH infused lignin-derived laser scribed graphene for facilitated ion transport in flexible supercapacitor application

Background Innovations in the synthesis of hybrid materials have led to technology advancement of the microsupercapacitor. Delaminated layered double hydroxide (LDH) reduces self-agglomeration and increases energy density in graphene-based supercapacitors. The incorporation of delaminated LDH with oil palm lignin derived laser scribed graphene in neutral PAAS/K2SO4 gel electrolyte for flexible microsupercapacitor applications was investigated. Method Various concentrations of positively charged sucrose-delaminated Mg-Al LDH nanosheets produced through the coprecipitation method were hybridised with negatively charged oil palm lignin-derived laser scribed graphene (L-LSG) through electrostatic interaction. Significant Findings Hybrid laser scribed graphene developed from delaminated Mg-Al LDH at a concentration of 10 gL−1 (L-LSG/D-MgAl-10) had the largest surface area of 49.335 m2g−1. The incorporation of Mg-Al LDH nanosheets on l-LSG were further validated by FESEM, TEM, XRD, Zeta potential and other characterizations. It also had the highest areal capacitance and energy density, measuring 40 mFcm−2 and 0.00296 mWhcm−2, respectively, at a current density of 0.08 mAcm−2. The fabricated microsupercapacitor has exceptional bending capabilities and capacitance retention of 89.2% after 5000 cycles. In summary, by inducing additional pseudocapacitance, delaminated Mg-Al LDH improved the overall effectiveness of the oi