25 research outputs found

    An eco-friendly, tunable and scalable method for producing porous functional nanomaterials designed using molecular interactions

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    Despite significant improvements in the synthesis of templated silica materials, post-synthesis purification remains highly expensive and renders the materials industrially unviable. In this study we address this issue for porous bioinspired silica, developing a rapid room-temperature solution method for complete extraction of organic additives. Using elemental analysis and N2 and CO2 adsorption, we demonstrate the ability to both purify and controllably tailor the composition, porosity and surface chemistry of bioinspired silica in a single step. For the first time we have modelled the extraction using molecular dynamics, revealing the removal mechanism is dominated by surface-charge interactions. We extend this to other additive chemistry, leading to a wider applicability of the method to other materials. Finally we estimate the environmental benefits of our new method compared with previous purification techniques, demonstrating significant improvements in sustainability

    A material characterization and embodied energy study of novel clay-alginate composite aerogels

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    There is a growing incentive within the construction industry to design low energy buildings which incorporate increased levels of insulation whilst also encouraging the use of ‘green’ materials which have a low environmental impact and can contribute positively to sustainable building strategies. Silica aerogels have received an increasing amount of attention in recent years as a contemporary insulation material, but their wide-spread use is currently hindered by high costs and their high embodied energy. This research project explores the development of a composite insulation material proposed as an alternative to silica aerogel, which consists of natural components including clay and a biopolymer obtained from seaweed known as alginate. Prototype specimens have been developed and characterized in terms of their mechanical properties and microstructure allowing comparisons to be made between five alginate types, each obtained from a different seaweed source. Whilst all of the composites tested offered an improvement over the control sample, the results also demonstrated that the type of alginate used has a significant influence on the compressive strength and modulus values of the resulting composite materials. An analysis of the production process additionally demonstrated that the freeze-drying element can have a significant impact on both the environment and financial costs of producing such a material

    Unified mechanistic interpretation of amine-assisted silica synthesis methods to enable design of more complex materials

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    The design of porous sol–gel silica materials is a thriving research field, owing to silica's diversity of properties and potential applications. Using a variety of additives, most commonly amine-based organic molecules, several families of silica materials have been developed including silica nanospheres, zeolites, mesoporous silicas, and bioinspired silicas with controlled particle and pore morphology on multiple length scales. Despite the wide range of study into these materials, and similarity in terms of reagents and additive compounds, none can recreate the features and complexity present within naturally occurring biosilica materials. This is due in part to a lack of ‘joined-up’ thinking during research into silica synthesis strategies and methodology. Specifically, mechanistic insights gained for one set of conditions or additive structures (i.e. material types) are not translated to other material types. In order to improve the structural complexity available in synthetic silica materials, as well as to improve both understanding and synthesis methods for all silica types, a unified approach to mechanistic understanding of formation in amine-assisted silica synthesis is required. Accordingly, in this review we analyse contemporary investigations into silica synthesis mechanism as a function of (amine) additive structure, analysing how they imprint varying levels of order into the eventual silica structure. We identify four fundamental driving forces through which additives control silica structure during synthesis: (i) controlling rates of silica precursor hydrolysis and condensation; (ii) forming charge-matched adducts with silicate ions in solution; (iii) self-assembling into mesophases to physically template pores; and (iv) confining the location of synthesis into specifically shaped vesicles. We analyse how each of these effects can be controlled as a function of additive structure, and highlight recent developments where multiple effects have been harnessed to form synthetic silica materials with further structural complexity than what was previously possible. Finally, we suggest further avenues of research which will lead to greater understanding of the structure–function relationship between amine additives and final materials, hence leading to more complex and high-value silica and other materials

    Facile cellulase immobilisation on bioinspired silica

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    Cellulases are enzymes with great potential for converting biomass to biofuels for sustainable energy. However, their commercial use is limited by their costs and low reusability. Therefore, the scientific and industrial sectors are focusing on finding better strategies to reuse enzymes and improve their performance. In this work, cellulase from Aspergillus niger was immobilised through in situ entrapment and adsorption on bio-inspired silica (BIS) supports. To the best of our knowledge, this green effect strategy has never been applied for cellulase into BIS. In situ entrapment was performed during support synthesis, applying a one-pot approach at mild conditions (room temperature, pH 7, and water solvent), while adsorption was performed after support formation. The loading efficiency was investigated on different immobilisation systems by Bradford assay and FTIR. Bovine serum albumin (BSA) was chosen as a control to optimize cellulase loading. The residual activity of cellulase was analysed by the dinitro salicylic acid (DNS) method. Activity of 90% was observed for the entrapped enzyme, while activity of ~55% was observed for the adsorbed enzyme. Moreover, the supported enzyme systems were recycled five times to evaluate their reuse potential. The thermal and pH stability tests suggested that both entrapment and adsorption strategies can increase enzyme activity. The results highlight that the entrapment in BIS is a potentially useful strategy to easily immobilise enzymes, while preserving their stability and recycle potential

    Green nanosilicas for monoaromatic hydrocarbons removal from air

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    We demonstrate a novel application of green nanosilicas (GN), prepared via an environmentally friendly route, in removing volatile organic compounds (VOCs). Herein, we aim to establish GN as viable alternatives to traditional mesoporous silicas for the removal of monoaromatic hydrocarbons (MAHC). The results show that the GN have high extraction efficiencies comparable to those previously reported for mesoporous silicas. It was demonstrated that bespoke GN can be syntheised readily with the ability to tailor their physical properties and MAHC adsorption. In order to understand the MAHC adsorption by GN, their porosity, morphology and pore structure were characterised. It was observed that the combination of broad pore size distribution and, in particular, the presence of meso- and micro-porosity in GN contributed to high MAHC extraction efficiencies and selectivity. Although from a commercial viewpoint, further optimisation of GN is desirable in order to replace traditional sorbents, this work clearly highlights a new family of “green” sorbents, which can be prepared with a substantial reduction in secondary pollution with potential applications in selective gas separation

    Insights into the electrochemical reduction products and processes in silica anodes for next-generation lithium-ion batteries

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    The use of silica as a lithium‐ion battery anode material requires a pretreatment step to induce electrochemical activity. The partially reversible electrochemical reduction reaction between silica and lithium has been postulated to produce silicon, which can subsequently reversibly react with lithium, providing stable capacities higher than graphite materials. Up to now, the electrochemical reduction pathway and the nature of the products were unknown, thereby hampering the design, optimization, and wider uptake of silica‐based anodes. Here, the electrochemical reduction pathway is uncovered and, for the first time, elemental silicon is identified as a reduction product. These insights, gleaned from analysis of the current response and capacity increase during reduction, conclusively demonstrated that silica must be reduced to introduce reversible capacity and the highest capacities of 600 mAh g−1 are achieved by using a constant load discharge at elevated temperature. Characterization via total scattering X‐ray pair distribution function analysis reveal the reduction products are amorphous in nature, highlighting the need for local structural methods to uncover vital information often inaccessible by traditional diffraction. These insights contribute toward understanding the electrochemical reduction of silica and can inform the development of pretreatment processes to enable their incorporation into next‐generation lithium‐ion batteries

    Scalable and sustainable manufacturing of ultrathin metal–organic framework nanosheets (MONs) for solar cell applications

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    Metal-organic framework nanosheets (MONs) are an emerging class of 2D materials whose tunable chemistry make them ideal for a wide range of sensing, catalytic, electronics and separation applications. However, creating scalable routes to the synthesis of high quality, ultrathin nanosheets remains challenging and little consideration has been given to the economics of making these materials. Here, we demonstrate a scalable synthesis of zinc-porphyrin based nanosheets, Zn2(H2TCPP), for use in organic solar cells and conduct a techno-economic analysis of their pilot-plant scale manufacture. A thorough investigation of the process chemistry of the solvothermal synthesis enabled reduction of reaction time, increased solid content and scale-up of the reaction in batch. Significantly, the addition of triethylamine accelerated the reaction kinetics, which enabled the synthesis temperature to be dropped from > 80 °C to room temperature. Application of these new reaction conditions in a continuous stirred-tank reactor directly formed monolayer MONs at 99 % yield with a space–time yield of 16 kg m−3 day−1, an approximately 20-fold increase in yield compared to adapting the literature procedure. Techno-economic analysis showed a 94 % reduction in the production costs compared to the literature reaction conditions and indicated that the production cost was dominated by ligand price. The general applicability of the method was demonstrated through synthesis of related Cu2(H2TCPP) MONs and tunability through metalation of the porphyrin units with six different metal ions. Finally, the value of the nanosheets was demonstrated through a near doubling in the power conversion efficiency of organic photovoltaic devices when the MONs were incorporated into the active layer. Overall, this work demonstrates the first scalable and sustainable route to producing monolayer nanosheets for high value applications

    Low cost water treatment for developing countries

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    Low cost water treatment for developing countrie

    Recent advances in enabling green manufacture of functional nanomaterials : a case study of bioinspired silica

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    Global specialty silica production is over 3 million tonnes per annum with diverse applications across sectors and an increasing demand for more complex material structures and surface chemistries. Commercial manufacturing of high-value silica nanomaterials is energy and resource intensive. In order to meet market needs and mitigate environmental impacts, new synthesis methods for these porous materials are required. The development of the bioinspired silica (BIS) product system, which is the focus of this review, provides a potential solution to this challenge. BIS is a versatile and greener route with the prospect of good scalability, attractive process economics and well controlled product materials. The potential of the system lies not only in its provision of specific lead materials but also, as itself, a rich design-space for the flexible and potentially predictive design of diverse sustainable silica nanomaterials. Realizing the potential of this design space, requires an integrative mind-set, which enables parallel and responsive progression of multiple and dependent research strands, according to need, opportunities, and emergent knowledge. Specifically, this requires development of detailed understanding of (i) the pathways and extent of material diversity and control, (ii) the influences and mechanisms of scale-up, and (iii) performance, economic and environmental characteristics and sensitivities. Crucially, these need to be developed for the system overall, which sits in contrast to a more traditional research approach, which focuses initially on the discovery of specific material leads at the laboratory scale, leaving scale-up, commercialization, and, potentially, pathway understanding to be considered as distinctly separate concerns. The intention of this review is to present important recent advances made in the field of BIS. Specifically, advances made along three research themes will be discussed: (a) particle formation pathways, (b) product design, and (c) scale-up and manufacture. These advances include first quantitative investigation of synthesis-product relationships, first structured investigation of mixing effects, preparation of a broad range of functionalized and encapsulated silica materials and continued industrial engagement and market research. We identify future challenges and provide an important foundation for the development of new research avenues. These include the need to develop comprehensive and predictive product design models, to understand markets in terms of product cost, performance and environmental considerations, and to develop capabilities enabling rapid prototyping and scale-up of desired nanomaterials
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