Chemical functionalisation of 2D materials via batch and continuous hydrothermal flow synthesis

2D materials are single or few layered materials consisting of one or several elements with a thickness of a few nanometers. Their unique, tunable physical and chemical properties including ease of chemical functionalization makes this class of materials useful in a variety of technological applications. The feasibility of 2D materials strongly depends on better synthetic approaches to improve properties, increase performance and durability and reduce costs. As such, in the synthesis of nanomaterials, hydrothermal processes are widely adopted through a precursor-product synthesis route. This method includes batch or continuous flow systems, both employing water at elevated temperatures (above boiling point) and pressures to fine tune the physical, chemical, optical and electronic properties of the nanomaterial. Both techniques yield particles with different morphology, size and surface area due to different mechanisms of particle formation. In this review, we present batch and continuous hydrothermal synthesis of a selection of 2D derivatives (graphene, MXene and molybdenum disulphide), their chemical functionalisation as an advantageous approach in exploring properties of these materials as well as the benefits and challenges of employing these processes, and an outlook for further research

New Pathways in the Synthesis of 2-Dimensional Materials

Our research focuses on designing and discovering new 2D and other (3D, 1D, 0D) advanced functional nanomaterials (utilizing a target-oriented approach) and technologies that provide effective solutions in the energy, biomedical and environmental applications

Enhancing engine oil performance using nanoparticles and bio-lubricants as additives

Optimize internal combustion engine lubrication to reduce friction and wear leading to improve fuel consumption and to reduce exhaust emission

Greener synthesis of 1,2-butylene carbonate from CO2 using graphene-inorganic nanocomposite catalyst

The synthesis of 1,2-butylene carbonate (BC) from cycloaddition reaction of 1,2-butylene oxide (BO) and carbon dioxide (CO2) was investigated using several heterogeneous catalysts in the absence of organic solvent. Continuous hydrothermal flow synthesis (CHFS) has been employed as a rapid and cleaner route for the synthesis of a highly efficient graphene-inorganic heterogeneous catalyst, ceria-lanthana-zirconia/graphene nanocomposite, represented as Ce–La–Zr/GO. The heterogeneous catalysts have been characterised using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and nitrogen adsorption/desorption (BET for measuring the surface area/pore size distribution),. Ceria- lanthana-zirconia/graphene nanocomposite catalyst (Ce–La–Zr/GO) exhibited high catalytic activity as compared to other reported heterogeneous catalysts in the absence of any organic solvent with a selectivity of 76% and 64% yield of 1,2-butylene carbonate at the reaction conditions of 408 K, 75 bar in 20 h

Selective Calixarene Directed Synthesis of MXene Plates, Crumpled Sheets, Spheres and Scrolls

Fully exploiting the electronic and mechanical properties of 2D laminar materials not only requires efficient and effective means of their exfoliation into low dimensional layers, but also necessitates a means of changing their morphology so as to explore any enhancement that this may offer. MXenes are a rapidly emerging new class of such laminar materials with unique properties. However, access to other morphologies of MXenes has not yet been fully realised. To this end we have developed the synthesis of MXenes (Ti2C) as plates, crumpled sheets, spheres and scrolls, which involves selective intercalation of p-phosphonic calix[n]arenes, with control in morphology arising from the choice of the size of the macrocycle, n = 4, 5, 6 or 8. This opens up wider avenues of discovery/design for new morphologies from the wider family of MXenes beyond Ti2C, along with opportunities to exploit any new physico-chemical properties proffered

Enhancing physicochemical properties of coconut oil for the application of engine lubrication

Engine lubricants require specific physical and chemical properties to function effectively and extend the lifespan of engines. Coconut oil (CCO) is an abundant, renewable, and environmentally friendly bio-based stock that has the potential to be a viable alternative to conventional mineral oil-based lubricants. In this study, we investigated the potential of CCO as a lubricant and formulated different blends with additives to enhance its physicochemical characteristics. Polymethylmethacrylate (PMMA), styrenated phenol (SP) and potassium hydroxide (KOH) were used as additives in varying concentrations. We evaluated the formulations for low pour point (PP), high viscosity index (VI) and total base number (TBN) using differential scanning calorimetry (DSC), viscometry, and titration methods (following ASTM D2270 and ASTM D2896–21 respectively). The formulated CCO was also tested for thermal, oxidative, and shear stability using thermogravimetric analysis and rheometry. The optimal formulation exhibited a PP reduction from 21 °C to 6 °C, improved VI from 169 to 206, and a TBN adjustment from 0 to 4.14 mg KOH g-1. The formulated CCO also exhibited superior thermal, oxidative, and shear stability compared to unformulated CCO and reference oil (15W40). Our results suggest that blending CCO with additives can effectively enhance its suitability for engine lubrication, opening up new possibilities for environmentally sustainable and renewable lubricants

Continuous hydrothermal flow synthesis of graphene quantum dots

Green fluorescent graphene quantum dots (GQD) have been synthesized via hydrothermal fragmentation using a continuous hydrothermal flow synthesis (CHFS) process as a single, rapid and environmentally benign method. This is in the presence of p-phosphonic acid calix[4]arene which enhances the optical properties of the graphene quantum dots through surface functionalization, with photoluminescence quantum yields of up to 4.5%. Potential environmental impact of a lab-scale supercritical CHFS process compared with that of conventional batch processing of GQDs has been assessed using the method of the International Reference Life Cycle Data System (ILCD)

Nanostructured Al2O3/Graphene Additive in Bio-Based Lubricant: A Novel Approach to Improve Engine Performance

Personal and industrial use of internal combustion engines (ICEs) is projected to continue until 2050 and beyond. Yet demands to reduce global dependence on petrochemicals and fossil fuel-derived lubricants are increasing and environmentally necessary. New strategies for maintaining and enhancing ICE performance by reducing friction, wear, fuel consumption, and exhaust emissions will reduce the depletion of mineral and fossil fuel reserves and environmental pollution. This paper reports the tribological enhancement of nano-bio lubricants formulated using 2D nanocomposites of Al2O3/graphene as novel additives in coconut oil, whose performance as a lubricant compares favourably with the mineral-based engine oil 15W40. Structural, compositional, and morphological characterization of an Al2O3/graphene nanocomposite synthesized via thermal annealing revealed an ultra-fine particle size (<10 nm) with spherical/laminar morphology and a rich sp2 domain, exhibiting a consistent colloidal stability when formulated as nanofluid. Through the use of various characterisation techniques, including friction and wear analysis we gained valuable insight into the tribological mechanism. Our optimisation of 2D tribological system using coconut oil formulation resulted significant reductions in the coefficient of friction (28%), specific fuel consumption (8%), and exhaust pollutants (CO, SO2, and NOx) emissions. This work demonstrates the benefits of using nano-bio lubricant formulated using coconut oil and 2D based hybrids as base stock and additives, delivering solutions to global challenges such as improving fuel consumption while reducing environmental pollution; solutions that can be transferred to other areas where lubricants are a necessity

Maximizing Polypropylene Recovery from Waste Carpet Feedstock: A Solvent-Driven Pathway Towards Circular Economy

Here we propose a novel approach for the efficient recovery of polypropylene from waste carpet feedstock utilising a solvent based method operating at 160 °C. The findings contribute to advancing sustainable recycling practices for waste carpet materials and offer valuable insight into the recovery of PP which can also be utilised for other complex waste streams

Continuous flow vortex fluidic-mediated exfoliation and fragmentation of two-dimensional MXene

MXene (Ti2CTx) is exfoliated in a vortex fluidic device (VFD), as a thin film microfluidic platform, under continuous flow conditions, down to ca 3 nm thin multi-layered twodimensional (2D) material, as determined using AFM. The optimized process, under an inert atmosphere of nitrogen to avoid oxidation of the material, was established by systematically exploring the operating parameters of the VFD, along with the concentration of the dispersed starting material and the choice of solvent, which was a 1 : 1 mixture of isopropyl alcohol and water. There is also some fragmentation of the 2D material into nanoparticles ca 68 nm in diameter