Chitin nanowhisker aerogels

Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043–0.113 g cm−3), high porosities (up to 97 %), surface areas of up to 261 m2 g−1, and mechanical properties at the high end of other reported values (modulus between 7 and 9.3 MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4 %

Polyaniline- and poly(ethylenedioxythiophene)-cellulose nanocomposite electrodes for supercapacitors

The formation and characterisation of films of polyaniline (PANI) and poly(ethylenedioxythiophene) (PEDOT) containing cellulose nanocrystals (CNXLs) from cotton are described. PANI/CNXL films were electrodeposited from a solution containing CNXLs, HCl and aniline, while PEDOT/CNXL films were electrodeposited from a solution containing CNXLs, lithium perchlorate and ethylenedioxythiophene. In each case, incorporation of CNXLs into the electrodepositing polymer film led to the formation of a porous polymer/CNXL nanocomposite structure. The films were characterised using scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge analysis. The specific capacitances of the nanocomposite materials were higher than those of the CNXL-free counterparts (488 F/g for PANI/CNXL; 358 F/g for PANI; 69 F/g for PEDOT/CNXL; 58 F/g for PEDOT). The durability of the PANI/CNXL film under potential cycling was slightly better than that of the CNXL-free PANI, while the PEDOT film was slightly more durable than the PEDOT/CNXL film. Using electrodeposition, it was possible to form thick PANI/CNXL films, with total electrode capacitances of 2.07 F farads per squared cm (and corresponding specific capacitances of 440 F/g), demonstrating that this particular nanocomposite may be promising for the construction of high performance supercapacitors

Integrated STEM in secondary education: A case study

Despite many opportunities to study STEM (Science, Technology, Engineering & Mathematics) in Flemish secondary education, only a minority of pupils are actually pursuing STEM fields in higher education and jobs. One reason could be that they do not see the relevance of science and mathematics. In order to draw their pupils’ interest in STEM, a Belgian school started a brand new initiative: the school set up and implemented a first year course that integrates various STEM disciplines, hoping to provide an answer to the question pupils often ask themselves about the need to study math and science. The integrated curriculum was developed by the school’s teachers and a STEM education research group of the University of Leuven. To examine the pupils’ attitude towards STEM and STEM professions and their notion of relevance of STEM at the end of this one-year course, a post-test was administered to the group of pupils who attended the integrated STEM course (the experimental group) and to a group of pupils that took traditional, non-integrated STEM courses (the control group). The results reveal that attending the integrated STEM course is significantly related to pupils’ interest in STEM and notion of relevance of STEM. Another post-test was administered only to the experimental group to investigate pupils’ understanding of math and physics concepts and their relation when taught in an integrated way. The results reveal that the pupils have some conceptual understanding and can, to a certain extent, make a transfer of concepts across different STEM disciplines. However, the test results did point out that some additional introductory training in pure math context is needed

Cellulosic-crystals as a fumed-silica substitute in vacuum insulated panel technology used in building construction and retrofit applications

This article investigates impact of substituting fumed silica with a cellulosic-crystal innovation in a commercial Vacuum Insulated Panel (VIP) core. High building performance demands have attracted VIP technology investment to increase production capacity and reduce cost. In building retrofit VIPs resolve practical problems on space saving that conventional insulations are unsuitable for. Three challenges exists in fumed silica: cost, low sustainability properties, and manufacture technical maturity. Cellulosic nano-crystal (CNC) technology is in its infancy and was identified as a possible alternative due to a similar physical nano-structure, and biodegradability. The study aim was to determine a performance starting point and establish how this compares with the current benchmarks. Laboratory cellulosic-crystal samples were produced and supplied for incorporation into commercial VIP manufacture. A selection of cellulosic-panels with core densities ranging 127–170 kg/m3 were produced. Thermal conductivities were tested at a pressure of 1 Pa (0.01 mBar), with the results compared against a selection of fumed silica-VIPs with core densities ranging 144–180 kg/m3. Conductivity tests were then done on a cellulosic-VIP with 140 kg/m3 density, under variable pressures ranging 1–100,000 Pa (0.01–1000 mBar). This investigated panel lifespan performance, with comparisons made to a fumed silica-VIP of similar core density. Manufactured cellulosic-samples were found unsuitable as a commercial substitute, with performance below current standards. Areas for cellulosic nano-material technology development were identified that show large scope for improvement. Pursuit could create a new generation of insulation materials that resolve problems associated with current commercial versions. This is most applicable in building retrofit where large ranges of domestic and commercial cases are marginalised from their construction markets due to impracticalities and high upgrade costs. This being a problem in multiple economies globally

Highly regioselective surface acetylation of cellulose and shaped cellulose constructs in the gas-phase

Publisher Copyright: © 2022 The Royal Society of ChemistryGas-phase acylation is an attractive and sustainable method for modifying the surface properties of cellulosics. However, little is known concerning the regioselectivity of the chemistry, i.e., which cellulose hydroxyls are preferentially acylated and if acylation can be restricted to the surface, preserving crystallinities/morphologies. Consequently, we reexplore simple gas-phase acetylation of modern-day cellulosic building blocks - cellulose nanocrystals, pulps, dry-jet wet spun (regenerated cellulose) fibres and a nanocellulose-based aerogel. Using advanced analytics, we show that the gas-phase acetylation is highly regioselective for the C6-OH, a finding also supported by DFT-based transition-state modelling on a crystalloid surface. This contrasts with acid- and base-catalysed liquid-phase acetylation methods, highlighting that gas-phase chemistry is much more controllable, yet with similar kinetics, to the uncatalyzed liquid-phase reactions. Furthermore, this method preserves both the native (or regenerated) crystalline structure of the cellulose and the supramolecular morphology of even delicate cellulosic constructs (nanocellulose aerogel exhibiting chiral cholesteric liquid crystalline phases). Due to the soft nature of this chemistry and an ability to finely control the kinetics, yielding highly regioselective low degree of substitution products, we are convinced this method will facilitate the rapid adoption of precisely tailored and biodegradable cellulosic materials.Peer reviewe

Pico-electrochemistry in humidity-equilibrated electrolyte films on nano-cotton:Three- and four-point probe voltammetry and impedance

Cotton-extracted cellulose nanocrystals are spin-coated from aqueous suspension (0.6 wt%) onto glass slides to give ca. 40 nm thick films. Impregnation with LiCl and redox active Fe(CN)63−/4− into this film gives extremely thin redox active layers (typically 170 nm at 60% relative humidity), which were investigated with a 4-point or 3-point probe electrochemical system based on 250 μm diameter platinum wire probes. Both voltammetry and impedance measurements were performed and effects from humidity, concentrations, and time domain on measurements are reported. Only a pico-litre volume under the working electrode was “active” to give a novel electroanalytical “spot test”.publisher: Elsevier articletitle: Pico-electrochemistry in humidity-equilibrated electrolyte films on nano-cotton: Three- and four-point probe voltammetry and impedance journaltitle: Sensors and Actuators B: Chemical articlelink: http://dx.doi.org/10.1016/j.snb.2015.01.004 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved.status: publishe

Design of an optimized Wilms' tumor 1 (WT1) mRNA construct for enhanced WT1 expression and improved immunogenicity in vitro and in vivo

Tumor antigen-encoding mRNA for dendritic cell (DC)-based vaccination has gained increasing popularity in recent years. Within this context, two main strategies have entered the clinical trial stage: the use of mRNA for ex vivo antigen loading of DCs and the direct application of mRNA as a source of antigen for DCs in vivo. DCs transfected with mRNA-encoding Wilms' tumor 1 (WT1) protein have shown promising clinical results. Using a stepwise approach, we re-engineered a WT1 cDNA-carrying transcription vector to improve the translational characteristics and immunogenicity of the transcribed mRNA. Different modifications were performed: (i) the WT1 sequence was flanked by the lysosomal targeting sequence of dendritic cell lysosomal-associated membrane protein to enhance cytoplasmic expression; (ii) the nuclear localization sequence (NLS) of WT1 was deleted to promote shuttling from the nucleus to the cytoplasm; (iii) the WT1 DNA sequence was optimized in silico to improve translational efficiency; and (iv) this WT1 sequence was cloned into an optimized RNA transcription vector. DCs electroporated with this optimized mRNA showed an improved ability to stimulate WT1-specific T-cell immunity. Furthermore, in a murine model, we were able to show the safety, immunogenicity, and therapeutic activity of this optimized mRNA. This work is relevant for the future development of improved mRNA-based vaccine strategies K

Predicting the capability of carboxylated cellulose nanowhiskers for the remediation of copper from water using response surface methodology (RSM) and artificial neural network (ANN) models

This study observed the influence of temperature, initial Cu(II) ion concentration, and sorbent dosage on the Cu(II) removal from the water matrix using surface-oxidized cellulose nanowhiskers (CNWs) bearing carboxylate functionalities. In addition, this study focused on the actual conditions in a wastewater treatment plant. Conductometric titration of CNWs suspensions showed a surface charge of 54 and 410 mmol/kg for the unmodified and modified CNWs, respectively, which indicated that the modified CNWs provide a relatively high surface area per unit mass than the unmodified CNWs. In addition, the stability of the modified CNWs was tested under different conditions and proved that the functional groups were permanent and not degraded. Response surface methodology (RSM) and artificial neural network (ANN) models were employed in order to optimize the system and to create a predictive model to evaluate the Cu(II) removal performance of the modified CNWs. The performance of the ANN and RSM models were statistically evaluated in terms of the coefficient of determination (R2), absolute average deviation (AAD), and the root mean squared error (RMSE) on predicted experiment outcomes. Moreover, to confirm the model suitability, unseen experiments were conducted for 14 new trials not belonging to the training data set and located both inside and outside of the training set boundaries. Result showed that the ANN model (R2 = 0.9925, AAD = 1.15%, RMSE = 1.66) outperformed the RSM model (R2 = 0.9541, AAD = 7.07%, RMSE = 3.99) in terms of the R2, AAD, and RMSE when predicting the Cu(II) removal and is thus more reliable. The Langmuir and Freundlich isotherm models were applied to the equilibrium data and the results revealed that Langmuir isotherm (R2 = 0.9998) had better correlation than the Freundlich isotherm (R2 = 0.9461). Experimental data were also tested in terms of kinetics studies using pseudo-first order and pseudo-second order kinetic models. The results showed that the pseudo-second-order model accurately described the kinetics of adsorption

Thermodynamics of adsorption on nanocellulose surfaces

© 2019, Springer Nature B.V. Abstract: Understanding the thermodynamic interactions of cellulose nanomaterials with their environment is important to understand the forces behind their self-organization and co-organisation with other compounds, and to be able to use self-assembly to form new functional multicomponent materials. This review analyzes published studies that determined the thermodynamic parameters of the surface interactions of and adsorption of various compounds (proteins, polymers, and small molecules/ions) onto cellulose nanomaterials. We compiled the data reported and performed a meta-analysis for better comparison and to find trends in the published data. We first introduce the methods employed and describe the adsorption isotherm models typically used to describe the adsorption thermodynamics on nanocellulose surfaces. We then discuss and analyze the published results for the interaction of the various compounds with nanocellulose surfaces. The systems that have been reported on most were adsorption of natural binding proteins and various pollutants from water, such as heavy metal ions, dyes, and drugs. Interactions between cellulose surfaces and the cellulose binding module were generally both enthalpy- and entropy-driven, where the negative binding enthalpy indicates the formation of specific interactions between peptides and the carbohydrate backbone. On the other hand, interactions with charged molecules were mostly endothermic and purely entropy-driven, indicating that the adsorption on nanocellulose surfaces can be described as an interaction between opposite charges, where the entropy increase that arises from the release of surface-structured water molecules and counterions from the electronic double layer supplies the major contribution to the free energy of adsorption. We performed a meta-analysis on all published data, and found a linear relationship between ∆H and ∆S with the slope equal to the reference temperature, irrespective of whether the interacting compound is a specific cellulose binding protein, a non-specific binding protein, a polymer, or a small molecule/ion. This indicates that the process of adsorption is the same for all compounds and takes place with a constant change in Gibbs free energy of interaction, ∆G, where a change in interaction enthalpy is offset by change in entropy change upon binding and vice versa.status: publishe