Graphene quantum dots (GQDs), a novel type of zero-dimensional fluorescent materials, have gained considerable attention owing to their unique optical properties, size and quantum confinement. However, their high cost and low yield remain open challenges for practical applications. In this work, a low cost, green and renewable biomass resource is utilised for the high yield synthesis of GQDs via microwave treatment. The synthesis approach involves oxidative cutting of short range ordered carbon derived from pyrolysis of biomass waste. The GQDs are successfully synthesised with a high yield of over 84%, the highest value reported to date for biomass derived GQDs. As prepared GQDs are highly hydrophilic and exhibit unique excitation independent photoluminescence emission, attributed to their single-emission fluorescence centre. As prepared GQDs are further modified by simple hydrothermal treatment and exhibit pronounced optical properties with a high quantum yield of 0.23. These modified GQDs are used for the highly selective and sensitive sensing of ferric ions (Fe³⁺). A sensitive sensor is prepared for the selective detection of Fe³⁺ ions with a detection limit of as low as 2.5 × 10^–6 M. The utilisation of renewable resource along with facile microwave treatment paves the way to sustainable, high yield and cost-effective synthesis of GQDs for practical applications.

Plastic use has increased by twenty fold since the 1950s and so has the amount of plastic waste generated. Although legislation promotes reuse and recycling, still over 50% of Europe's plastic waste is still disposed of into landfills. Therefore, millions of tonnes of plastic end up in the environment, provoking severe harm, wasting tonnes of resources (i.e. fossil fuels), and generating the need for advanced treatments, i.e. pyrolysis. Commonly, only a small amount of monomer (i.e. ethylene (C₂H₄)) and a large amount of waxy products, i.e. aliphatic hydrocarbons that require further refinement, are recovered by conventional pyrolysis of high density polyethylene (HDPE). Therefore, direct conversion of HDPE waste into high value added products would be more desirable. In this study, experiments were carried out using cold plasma assisted pyrolysis of waste HDPE for valorisation. With the assistance of cold plasma, up to 22–25 wt% ethylene was recovered from HDPE waste, up to 55 times higher than that obtained in conventional pyrolysis of waste HDPE. Catalytic cold plasma pyrolysis showed that the addition of only 3–10 wt% HZMS-5 or sulphated zirconia doubled the gas (up to 41 wt%) and subsequently the ethylene yield at low temperatures. This study opens up opportunities to valorise unsorted waste into intermediates for chemical processes via a simple process.

A critical review which delves into the advantages of the use of carbon quantum dots (CQDs) in nano-based cancer therapy, which includes its more positive environmental impact compared to previous systems.

This work continues our assessment of wet torrefaction for energy applications, looking at effects of the process parameters (temperature, holding time and pressure) on the reactivity and intrinsic kinetics of wood under air combustion conditions. Woody materials, Norway spruce and birch, were wet torrefied in various conditions (temperature: 175, 200, 225 °C; holding time: 10, 30, 60 min; and pressure: 15.54, 70, 160 bar). The reactivity of the treated and untreated woods was thermogravimetrically examined under a synthetic air environment (21% O2 and 79% N2 in volume). A four-pseudo-component model with different reaction orders was adopted for kinetic modelling and extracting the kinetic parameters. The results showed that when increasing either torrefaction temperature or holding time, the torrefied woods behaved more char-like than the raw fuels. However, pressure did not show significant effect on the reactivity. Relatively longer char combustion stages and higher conversion rates (up to 0.5 × 10−3 s−1) were observed for the woods after torrefaction. The activation energy was decreased for hemicellulose and char, but increased for cellulose after torrefaction, whereas the trend for lignin is not clear. In addition, the hemicellulose mass fraction decreased after torrefaction (from 0.15 to 0.05 for spruce and from 0.23 to 0.06 for birch). The amount of char in the torrefied woods increased gradually with increasing torrefaction temperature or holding time (from 0.24 to 0.40 for spruce, and from 0.18 to 0.34 for birch). Copyright © 2014 Published by Elsevier Ltd