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Selective unidirectional transport of barium ions between droplets in a water-in-chloroform emulsion is demonstrated. Gold nanoparticles (GNPs) modified with a thiolated crown ether act as barium ion complexing shuttles that carry the ions from one population of droplets (source) to another (target). This process is driven by a steep barium ion concentration gradient between source and target droplets. The concentration of barium ions in the target droplets is kept low at all times by the precipitation of insoluble barium sulfate. A potential role of electrostatically coupled secondary processes that maintain the electroneutrality of the emulsion droplets is discussed. Charging of the GNP metal cores by electron transfer in the presence of the Fe(ii)/Fe(iii) redox couple appears to affect the partitioning of the GNPs between the water droplets and the chloroform phase. Processes have been monitored and studied by optical microscopy, Raman spectroscopy, cryogenic scanning electron microscopy (cryo-SEM) and zeta potential. The shuttle action of the GNPs has further been demonstrated electrochemically in a model system., Crown-ether modified gold nanoparticles act as charge transporters between aqueous droplets. The thermodynamic driving force for this continuous non-equilibrium process is precipitation of BaSO4 in one population of droplets.

Wood is a natural composite material. However, its relatively low mechanical properties restrict the use in advanced structural applications but recent studies have shown that Compressed Wood (CW), with superior mechanical properties due to material densification, could be utilised in timber products and timber connections as an alternative to energy-intensive adhesives and metals. However, the limited literature available on the mechanical properties of CW makes it chanllenging to utilise them in the development of new products and structures. To address this issue, this paper presents a comprehensive test programme and an extensive database of CW materials. It includes experimental results of over 720 material tests that were conducted on CW materials. The fundamental tests under compression, tension, bending, embedment, yield moment, shear and impact tests were undertaken. The results obtained from this study will help engineers utilise more CW to develop new products and connections. The results are also compared with the characteristic values of solid wood from the literature. As the densification of wood significantly improves strength and stiffness, this work will contribute towards the substantial uptake of CW in the building and construction industry with great benefits to the environment. peer-reviewed 2023-08-03

Glued-laminated timber (glulam) beams and cross-laminated timber (CLT) panels are increasingly being used as structural members for buildings, because of their excellent mechanical properties, ability to be processed into larger structural sections and environmental benefits. Nevertheless, the inclusion of adhesives during their production raises environmental concerns due to the release of Volatile Organic Compounds (VOCs) and formaldehyde, which also causes difficulties in recycling. This environmental burden has led to the development of adhesive free laminated timber (AFLT) beams and cross-laminated (AFCLT) panels, which are intended to be used as alternatives to glulam beams and CLT panels in structural applications. In this paper, details of the materials and manufacturing processes for the AFLT beams and AFCLT panels are described, followed by the structural tests and the observed failure modes. Furthermore, parametric studies are carried out to investigate the effects of the following factors on the structural response, i.e. lamella species, dowel species, dowel insertion angles, dowel diameters and configurations, number of dowels (or dowel spacing), section sizes and number of interfaces. It is found that the flexural modulus and flexural strength of the 26 AFLT beams and 26 AFCLT panels are in the range of 1.1–5.3 GPa and 19.3–38.2 MPa, respectively. The experimental results are compared with commonly used glulam beams and CLT panels. The results are useful in understanding the mechanical properties of AFLT beams and AFCLT panels fastened with compressed wood dowels, and constitutes useful structural design information for future construction and structural applications, as well as providing data to validate the finite element modelling. In addition, the study has demonstrated a practical and sustainable approach in timber construction, which may lead to a substantial reduction in the use of structural adhesives and environmental benefits.

Engineered Wood Products (EWPs) are increasingly being used as construction and building materials. However, the predominant use of petroleum-based adhesives in EWPs contributes to the release of toxic gases (e.g. Volatile Organic Compounds (VOCs) and formaldehyde) which are harmful to the environment. Also, the use of adhesives in EWPs affects their end-of-life disposal, reusability and recyclability. This paper focusses on dowel laminated timber members and densified wood materials, which are adhesive free and sustainable alternatives to commonly used EWPs (e.g. glulam and CLT). The improved mechanical properties and tight fitting due to spring-back of densified wood support their use as sustainable alternatives to hardwood fasteners to overcome their disadvantages such as loss of stiffness over time and dimensional instability. This approach would also contribute to the uptake of dowel laminated timber members and densified wood materials for more diverse and advanced structural applications and subsequently yield both environmental and economic benefits. The authors wish to record their appreciation to Interreg North-West Europe (NWE) funded by the European Regional Development Fund (ERDF) for supporting the project (Towards Adhesive Free Timber Buildings (AFTB) - 348). peer-reviewed

In this study, we developed a constitutive law for wood useful as a user material subroutine (Umat) in Abaqus software. To calibrate the model, compression/tensile tests were carried out on simple geometry samples and to check the validity, we subsequently considered two simulation cases; namely the push out double shear and the four-point bending tests. Moreover, we developed a generic Python script for each test to be used repeatedly for parametric studies. All the numerical aspects are controlled by a user-friendly graphical interface that can display the relevant results and performs simultaneous comparisons with the experimental results. Firstly, the properties of the compressed and uncompressed wood were identified in the longitudinal, radial and tangential directions using a quasi-inverse problem. Then these properties are used in the simulation of the two numerical tests. Consequently, the obtained numerical joint-slip versus load curve from the push out double shear simulation agrees well with the experimental curve. Furthermore, dowel laminated timber tested in four-point bending were correctly simulated and provided numerical results very close to experimental results.

Gold nanoparticles with variable hydrophobicity have been prepared in three different size regimes following established methods. The control of hydrophobicity was achieved by complexation of the 18-crown-6-CH2-thiolate ligand shell with potassium ions. Potassium dependent phase transfer of these particles from dispersion in water to chloroform was demonstrated, and the equilibrium partitioning of the particles in water–chloroform liquid/liquid systems was quantified by optical spectroscopy. The gradual complexation of the ligand shell with potassium ions was further monitored by zeta potential measurements. Potassium dependent insertion of nanoparticles into the phospholipid bilayer membrane of vesicles in aqueous dispersion has been demonstrated by cryogenic transmission electron microscopy (cryo-TEM). Nanoparticle-dependent potassium ion transport across the vesicle membrane has been established by monitoring the membrane potential with fluorescence spectroscopy using a potential sensitive dye.

The most common differential pulse techniques are analyzed and their responses are compared. Depending on whether or not the initial conditions are re-established before the application of each double pulse we distinguish between double pulse and multipulse differential techniques. The nomenclature employed in the literature is clarified to avoid future confusion. The differences and similarities between the double pulse and multipulse responses are studied for electrode processes of any degree of reversibility, analysing the advantages and disadvantages of each method. The effect of the electrode size is also discussed, establishing the conditions under which the voltammograms obtained by different techniques are coincident or not. © 2011 Elsevier B.V. All rights reserved.

The changes in interparticle spacing upon hydration and dehydration of drop-cast films of hydrophilic gold nanoparticles (GNP) have been measured in situ with nanometer resolution using WetSTEM and ESEM. These subtle variations correlate well with the corresponding changes in the optical spectra and perceived color as well as changes in the electrical conductivity of the films. AC impedance analysis allows us to differentiate between resistive and capacitive components and to evaluate how these depend on average particle spacing and the water content of the matrix, respectively. Thin films of this type are well-known structures used for development of sensors and diagnostics.