InSb-based self-assembled quantum dots (SAQDs) are very promising for the mid-infrared (3-5 μm) optical range. We have analysed the electronic structure and optical properties of InAs x Sb 1-x /InAs dots. In this paper, we present the results of the modelling of electronic structure and optical properties from photoluminescence (PL) measurement for InAs x Sb 1-x /InAs SAQDs, focusing on the effects of SAQD morphology and composition. In particular, we analyse the electronic structure of InAs x Sb 1-x /InAs SAQD of various shapes, aspect ratios and compositions. We also suggest a method of assessing the geometry and composition of InAs x Sb 1-x /InAs quantum dots using their optical spectra and limited microscopy information. The calculated transition energies agree well with the experimental results. The results show that the geometry of the dot can be estimated from the optical spectra if the composition is known, and vice versa.

Residual palm oil that goes into the river untreated can become detrimental to the environment. Residual oil discharge during milling process into palm oil mill effluent (POME) is unavoidable. About 1 wt% of residual oil in POME causes major problems to the mills, in terms of environment, wastewater treatment and economy losses. This paper reports the recovery of residual oil from POME by adsorption on polypropylene micro/nanofiber (PP-MNF) and desorption of oil by hands pressing, and oil extraction from the PP-MNF using solvent and super-critical-CO2 extraction techniques. The characterization of the PP-MNF and the quality of oil extracted were analyzed using analytical instruments. The reusability of the PP-MNF was also investigated. The experimental results showed the adsorption capacity of the PP-MNF was 28.65 g of oil/g of PP-MNF on average using refined palm oil, whilst recovery of oil from POME was 10.93 g of oil/g of PP-MNF. The extraction yield of oil from PP-MNF using hand pressing was 89.62%. The extraction of residual oil from the pressed PP-MNF showed comparable yield between solvent and supercritical CO2 techniques. The quality of recovered oil was similar with the quality of the crude oil, and no trace of polypropylene contamination was detected in the oil recovered. The PP-MNF showed no significant physical change after the extraction process. In conclusion, the PP-MNF has great potential to be used commercially in residual oil recovery from POME.

In this study, carbon-silica based acid catalysts derived from rice husks (RH) were successfully synthesised using microwave (MW) technology. The results showed that MW sulphonation produced Sulphur (S) content of 17.2-18.5 times higher than in raw RH. Fourier-transform Infrared Spectroscopy (FTIR) showed peak at 1035 cm(-1) which corresponded to (OS=O)-S-= stretching of sulphonic (-SO3H) group. XRD showed sulfonated RH catalysts (SRHCs) have amorphous structure, and through SEM, broadening of the RH voids and also formation of pores is observed. RH600 had the highest surface area of 14.52 m(2)/g. SRHCs showed high catalytic activity for esterification of oleic acid with methanol with RH600 had the highest initial formation rate (6.33 mmol L-1 min(-1)) and yield (97%). The reusability of the catalyst showed gradually dropped yield of product for every recycle, which might be due to leaching of -SO3H. Finally, esterification of oil recovered from palm oil mill effluent POME) with methanol achieved a conversion of 87.3% free fatty acids (FFA) into fatty acid methyl esters (FAME).

In this work, untreated empty fruit bunch (EFB) or microwave-assisted NaOHpretreated EFB with palm oil mill effluent (POME) were composted under mesophilicconditions either in the presence or absence of Bacillus amyloliquefaciens D203 for sixtydays. During pretreatment conditions, the EFB was mixed with 1% (w/w) sodiumhydroxide and then exposed to microwave irradiation. The composting process wasevaluated based on the evolution of pH, electrical conductivity, moisture content, organicmatter loss, zeta potential and phytotoxicity. The strain Bacillus amyloliquefaciens D203 is not suitable for EFB-POME composting due to lower organic matter loss. The microwave-assisted NaOH pretreatment contributed to ~15% more organic matter loss than was found in the untreated sample while its germination index was >50%.

Carbon-based sulphonated catalysts (CBSCs) were made from rice husk for biodiesel production. The CBSCs were prepared by microwave (MW) and conventional heating processes from the same feedstock. In both heating systems, the preparation was a two-step process: carbonisation and sulphonation. The aim of this study was to use MW heating to reduce the conventional CBSC preparation time and enhance the –SO3H group attachment to the solid catalyst. The biomass based solid acid catalysts from the two systems were characterised and compared in terms of physicochemical properties including: sulphonation, morphology, surface area and structure. The reaction times for MW assisted carbonisation and for sulphonation were significantly reduced compared to the conventional heating system; these were 30min vs 4h and 20min vs 12h, respectively. The MW prepared catalyst showed higher sulphur content (4.91%) as compared to the conventional catalyst (2.10%). The FTIR analysis showed well distinguished peaks for –SO3H for the MW prepared catalyst suggesting the solid catalyst was successfully sulphonated, while these peaks were very weak for the conventional catalyst. SEM analysis revealed a highly porous structure in the MW prepared catalyst, whilst a denser solid resulted for its conventionally prepared analogue, owing to the higher temperatures applied and longer sulphonation time. The surface area for the MW was higher than the conventionally prepared catalysts (43.63m2/g and 37.01m2/g, respectively). The structure of the samples was identified as amorphous for both catalysts as confirmed by XRD. The prepared CBSC is expected to catalyse biodiesel production reaction as evidenced by its total acidity and surface area.

Purpose - The purpose of this paper is to discuss a novel life cycle approach to education for sustainable development (ESD) where the students become "design thinkers". Design/methodology/approach - A case study on the creation, development and utilisation of educational games by university students is presented. The paper discusses the case study in the context of Kolb's experiential learning and dynamic matching model, Perry's stages of intellectual development and Beech and Macintosh's processual learning model. The data used were from questionnaire feedback from the pupils who played the games and students who designed the games. Further qualitative feedback was collected from local schools involved in playing the games created by the students. Findings - Overall, the students responded positively to the assessment and would like to see more of this type of assessment. They enjoyed the creativity involved and the process of developing the games. For the majority of the skill sets measured, most students found that their skills improved slightly. Many students felt that they had learnt a lot about effectively communicating science. The school children involved in playing the student-created games found them accessible with variable degrees of effectiveness as engaging learning tools dependent on the game. Originality/value - This paper contributes a new approach to ESD which incorporates learner-centred arrangements within a full life cycle of game creation, delivery, playing and back to creation. The games can be used as a tool for enhancing knowledge and influencing behaviours in school children whilst enhancing ESD capacity in schools. The assessment also helps forge important links between the academic and local communities to enhance sustainable development.

Background: This study investigates the microwave-assisted acid extraction of lignin from wheat straw.Methods: Two experimental design methods, the Central Composite Design (CCD) and the Response Surface Method (RSM) methods were used to select conditions and optimise the process. The parameters studied were: the stirring rate, H2SO4 concentration, microwave radiation power and residence time.Results: The optimum conditions found to achieve the maximum lignin yield (wt%) from wheat straw were: 0.46M H2SO4 under microwave radiation power of 602 W at 65% of stirring rate (3200rpm) and residence time of 39min. These conditions led to a delignification of 78.5% (by weight) of the parent lignin content, which accounted for 11.8wt% on dry biomass basis; this compares to a yield of 3.35wt% for the conventional H2SO4 pre-treatment method under similar conditions.Conclusion: This work is a first step to demonstrate the potential of innovative microwave methods to overcome the high cost of acid extraction of lignin from biomass waste.

The purpose of this study is to investigate the composting performance of anaerobically treated palm oil mill effluent (AnPOME) mixed with paper and grass clippings.

The recently proposed highly efficient route of pyridine-catalysed CO2 reduction to methanol was explored on platinum electrodes at high CO2 pressure. At 55 bars of CO2, the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yield up to 10% for the first 5-10 C/cm of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally, being limited to sub-ppm levels irrespective of biasing conditions and pyridine concentration. This limitation cannot be removed by electrode reactivation and/or pre-electrolysis and appears to be an inherent feature of the reduction process. In agreement with bulk electrolysis findings, the CV analysis supported by simulation indicated that hydrogen evolution is still the dominant electrode reaction in pyridine-containing electrolyte, even at excess CO2 concentration in the electrolyte. No prominent contribution from either a direct or coupled CO2 reduction was found. The results obtained suggest that the CO2 to methanol reduction is a transient process that is largely decoupled from the electrode charge transfer. This is the peer reviewed version of the following article: S. I. Rybchenko, D. Touhami, J. D. Wadhawan, S. K. Haywood, ChemSusChem 2016, 9, 1660, which has been published in final form at http://dx.doi.org/10.1002/ cssc.201600267. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.

The recently proposed highly efficient route of pyridine-catalyzed CO2 reduction to methanol was explored on platinum electrodes at high CO2 pressure. At 55bar (5.5MPa) of CO2, the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yields of up to 10% for the first 5-10Ccm(-2) of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally and was limited to sub-ppm levels irrespective of biasing conditions and pyridine concentration. This limitation cannot be removed by electrode reactivation and/or pre-electrolysis and appears to be an inherent feature of the reduction process. In agreement with bulk electrolysis findings, the CV analysis supported by simulation indicated that hydrogen evolution is still the dominant electrode reaction in pyridine-containing electrolyte solution, even with an excess CO2 concentration in the solution. No prominent contribution from either a direct or coupled CO2 reduction was found. The results obtained suggest that the reduction of CO2 to methanol is a transient process that is largely decoupled from the electrode charge transfer.

Structural parameters of InGaAs/GaAs self-assembled quantum dots (SAQDs), which were grown using In-flush technique, were deduced using optical spectroscopy combined with computer modeling. The results are in excellent agreement with the experimental data obtained from transmission electron microscopy. The developed approach suggests a promising alternative to structural characterization methods for SAQDs.

The charging of an undivided cerium-zinc redox battery by various current waveforms some of which mimic the output of renewable energy (solar, wind, tidal, biofuel burning) to electricity transducers is considered in this work, where the battery operates through diffusion-only conditions, and is discharged galvanostatically. Under reasonable assumption, the mathematical model developed enables the observation that the performance characteristic of the cells charged with a constant power input differentiates between the various current-charge waveforms, with cell geometry and electrode kinetics playing subtle, but significant, roles; in particular, high efficiency is observed for sunlight-charged batteries which are thin and suffer no corrosion of the sacrificial electrode, and which have already experienced a charge-discharge cycle. The performance characteristics of the systems are interpreted in the light of consequences for smart grid realisation, and indicate that, for a constant power input, the most matched renewable is biofuel burning with a current output that linearly increases with time.

Intraband absorption in quantum-dot-in-a-well (DWELL) mid-infrared photodetectors is investigated using photocurrent spectroscopy and computationally cost-effective modeling linked to experimental data. The DWELL systems are challenging for modeling the electronic structure, which involves both discrete levels and the continuum energy spectrum. We show that the latter can be successfully approximated by a quasi-continuum in a large three-dimensional (3D) “quantum box” in which the electronic structure is calculated in the effective mass approximation using the finite element method. Experimental and simulated spectra show good agreement with each other, which justifies using the modeling for analysis of the experimental data. In particular, the origin of the peaks and the dot parameters, such as composition are deduced. Effects of dot composition and shape on the intraband absorption spectra are also predicted. Our model proves to be a useful tool in designing and analyzing advanced DWELL structures for any realistic 3D quantum dot geometry.

Much effort has been committed to development of quantum-dot-based infrared photodetectors owing to their potential for normal-incidence absorption and low dark current. Quantum-dot-in-well structures offer additional advantages, such as better wavelength tunability and improved carrier collection. This system presents a challenge for modeling of electronic structure, as it requires solution for a complex system (quantum dot plus quantum well) with both discrete levels and the continuum energy spectrum. The Green's function method, mostly used for such problems, has very high computational cost. Here we use the Finite Element Method to model intraband absorption spectra of quantum-dot-in-well structures within the effective mass approximation.

Colloidal nanoparticles are very popular as building blocks of functional arrays for electronic and optical applications. However, there is a problem in achieving electrical conductivity in such nanoarrays due to their molecular shells. These shells, which are inherent to colloidal particles, physically separate the nanoparticles in an array and act as very effective insulators. Post-assembly thinning of the shells is therefore required to enhance the array conductivity to a sensible value. Here, we introduce a conceptually new approach to the thinning, using compressive stress applied to the array by the supporting matrix. The stress arises from polymerization-induced shrinkage of the matrix as an integral step during device assembly. Using arrays of oleic-acid-covered magnetite nanoparticles in conjunction with an HDDA-polymer (HDDA: 1,6-hexanediol diacrylate) matrix, we have achieved a significant steady current in the array along with an unprecedented value of the magnetoresistance. Our results serve as a proof-of-concept for other colloidal nanoparticles.

InSb-based self-assembled quantum dots are very promising for the midinfrared (3-5 mu m) optical range. We have analyzed the effect of geometry and composition on the electronic structure and optical spectra of InAsxSb1-x/InAs dots. The calculated transition energies agree well with the available experimental data. The results show that the geometry of the dot can be estimated from the optical spectra if the composition is known, and vice versa.

We investigate the long-standing controversy surrounding modeling of the electronic spectra of InAs/GaSb short-period superlattices (SPSLs). Most commonly, such modeling for semiconductor heterostructures is based on the k center dot p method. However, this method has so far failed to predict the band structure for type-II InAs/GaSb SPSLs. Instead, it has systematically overestimated the energy gap between the electron and heavy-hole minibands, which led to the suggestion that the k center dot p method is inadequate for these heterostructures. Our results show that the physical origin of the discrepancy between modeling and experimental results may be the graded and asymmetric InAs/GaSb interface profile. We have performed band-structure modeling within the k center dot p method using a realistic interface profile based on experimental observations. Our calculations show good agreement with experimental data, both from our own measurements and from the published literature.

We report the molecular beam epitaxial growth of InSb sub-monolayers inserted in an InAs matrix using Sb2 and As2 fluxes. The InSb/InAs nanostructures exhibit intense mid-infrared photoluminescence up to room temperature. The nominal thickness of the sub-monolayer insertions can be controlled by the growth temperature (TGr = 450–320°C) which gives rise to the variation of the emission wavelength within the 3.6–4.0μm range at room temperature. A comparative analysis of the optical properties of the structures grown using (Sb2, As2) and (Sb4, As4) is also presented.

Effect of lattice-mismatch-induced strain on Γ-, X- and L-conduction-band edges in III–V self-assembled quantum dots has been calculated. The misfit strain is shown to strongly affect the band edges, leading to a possibility of Γ-L and Γ-X crossover. The Γ-L crossover is predicted for realistic self-assembled InSb/GaSb (001) dots, in which the lowest interband transition is from the L-valley state. Available experimental PL data were found to be in good agreement with the crossover phenomenon.

Nitrogen incorporation in InAsN epilayers grown by radio-frequency plasma-assisted molecular beam epitaxy was investigated as a function of growth conditions. Reduced growth rate, growth temperature, and arsenic flux significantly enhance the nitrogen incorporation. Optimal growth conditions allowed us to obtain high quality InAsN with nitrogen composition of up to 2.5%. The epilayers exhibit intense 4K photoluminescence (PL) with double-peak features, which were attributed to free carrier recombination and localized carrier recombination. Strong room temperature PL emission up to a wavelength of 4.5μm is obtained.