The past few decades have witnessed significant advances in the development of functionalized gold nanoparticles for applications in various fields such as chemistry, biology, pharmacy and physics. ...Although it has been more than 150 years since they were first synthesized, extensive research has recently been undertaken to improve or modify gold nanoparticles, thereby opening up opportunities to enhance and optimize their potential and breadth of their applicability. Recently developed methods have allowed a precise control of gold nanoparticle size and the modification of gold nanoparticles with suitable protecting and functionalizing agents, facilitate their applications in different areas such as chemical and biological sensing, imaging and biomedical applications. This review focuses on the recent developments in various methods for the size and shape controlled synthesis of gold nanoparticles, understanding of different properties of gold nanoparticles and their applications in various fields. Particular attention is given to the chemical and biological sensing applications of gold nanoparticles and on the advances in the controlled ordering of gold nanoparticles for creating nanostructures for diverse applications.
Abstract
We are reporting the effect of thickness on the Seebeck coefficient, electrical conductivity and power factor of Ca
3
Co
4
O
9
thin films grown on single-crystal Sapphire (0001) substrate. ...Pulsed laser deposition (PLD) technique was employed to deposit Ca
3
Co
4
O
9
films with precisely controlled thickness values ranging from 15 to 75 nm. Structural characterization performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the growth of Ca
3
Co
4
O
9
on Sapphire (0001) follows the island growth-mode. It was observed that in-plane grain sizes decrease from 126 to 31 nm as the thickness of the films decreases from 75 to 15 nm. The thermoelectric power measurements showed an overall increase in the value of the Seebeck coefficient as the films’ thickness decreased. The above increase in the Seebeck coefficient was accompanied with a simultaneous decrease in the electrical conductivity of the thinner films due to enhanced scattering of the charge carriers at the grain boundaries. Because of the competing mechanisms of the thickness dependence of Seebeck coefficient and electrical conductivity, the power factor of the films showed a non-monotonous functional dependence on thickness. The films with the intermediate thickness (60 nm) showed the highest power factor (~ 0.27 mW/m-K
2
at 720 K).
Spin thermoelectrics represents a new paradigm of thermoelectricity that has a potential to overcome the fundamental limitation posed by the Wiedmann-Franz law on the efficiency of conventional ...thermoelectric devices. A typical spin thermoelectric device consists of a bilayer of a magnetic insulator and a high spin-orbit coupling (SOC) metal coated over a non-magnetic substrate. Pt is the most commonly used metal in spin thermoelectric devices due to its strong SOC. In this paper, we found that an alloy of Cu and Pt can perform much better than Pt in spin thermoelectric devices. A series of CuPt alloy films with different Pt concentrations were deposited on yttrium iron garnet (YIG) films coated gadolinium gallium garnet (GGG) substrate. Through spin Seebeck measurements, it was found that the Cu
Pt
/YIG/GGG device shows almost 3 times higher spin Seebeck voltage compared to Pt/YIG/GGG under identical conditions. The improved performance was attributed to the higher resistivity as well as enhanced spin hall angle of the CuPt layer.
•A semi-supervised approach for mining information from MT-InSAR derived deformation.•ML based temporal-spatial clustering generates labels for supervised learning.•Deep learning models proposed for ...spatio-temporal learning with ML generated labels.•Stochastic analysis of generated clusters yields hotspots of deformation events.
Over the past two decades, Interferometric synthetic aperture radar (InSAR) has been invaluable for studying earth surface deformation and related effects. Deformation maps generated through multi-temporal InSAR processing methods are however difficult to interpret accurately by general individual users, decision-makers, and non-domain experts owing to the volume, variety, and velocity they are produced. This paper proposes a semi-supervised machine learning based information mining approach to simplify these deformation maps and detect hotspots by extracting prominent signals from time series deformation. The approach initially combines two machine learning based clustering methods named time series k-means (TSKM) and Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithms to derive clusters with unique spatiotemporal deformation behavior, using time series deformation output generated from Wavelet-based InSAR (WabInSAR) method. Clustering results generated from this unsupervised machine learning approach are later used as training labels to develop two deep learning models, one using long short term memory (LSTM) networks alone and another using a combination of LSTM and single-layer perceptron for supervised training. The developed LSTM and LSTM + Perceptron models efficiently learn from the cluster labels, reaching an accuracy of 97.3 %. Further, the deep learning models significantly reduce the computational time from orders of days (∼5) to hours (∼2) while training and from hours to minutes during prediction. We evaluate the developed approach over Los Angeles, a highly challenging area affected by umpteen deformation events that are challenging to categorize. The outcome of the proposed approach produces hotspots of deforming areas in Los Angeles, providing a generalized and more precise picture of events, much appreciable to non-domain experts. The approach can augment any of the multi-temporal InSAR processing chains and is applicable to different deformation prone sites, aiding in derivation of deformation hotspots from time series deformation maps.
Disulfide bonds are naturally formed in more than 50% of amyloidogenic proteins, but the exact role of disulfide bonds in protein aggregation is still not well-understood. The intracellular reducing ...agents and/or improper use of antioxidants in extracellular environment can break proteins disulfide bonds, making them unstable and prone to misfolding and aggregation. In this study, we report the effect of disulfide-reducing agent dithiothreitol (DTT) on hen egg white lysozyme (lysozyme) and bovine serum albumin (BSA) aggregation at pH 7.2 and 37 °C. BSA and lysozyme proteins treated with disulfide-reducing agents form very distinct amorphous aggregates as observed by scanning electron microscope. However, proteins with intact disulfide bonds were stable and did not aggregate over time. BSA and lysozyme aggregates show unique but measurable differences in 8-anilino-1-naphthalenesulfonic acid (ANS) and 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid (bis-ANS) fluorescence, suggesting a loose and flexible aggregate structure for lysozyme but a more compact aggregate structure for BSA. Scrambled disulfide-bonded protein aggregates were observed by nonreducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) for both proteins. Similar amorphous aggregates were also generated using a nonthiol-based reducing agent, tris(2-carboxyethyl)phosphine (TCEP), at pH 7.2 and 37 °C. In summary, formation of distinct amorphous aggregates by disulfide-reduced BSA and lysozyme suggests an alternate pathway for protein aggregation that may be relevant to several proteins.
A major fraction of the electricity that is generated in the world is used in the building sector, particularly as a source of light. One way to reduce the consumption of electricity in buildings is ...by utilizing natural light with the help of environmentally friendly resources such as transparent wood. Removing the lignin from wood followed by impregnating environmentally friendly polymers whose refractive index matches the refractive index of the cell wall helps in obtaining transparent wood. Hence, herewith we report a simple and low-cost method of fabricating transparent wood from beech wood (Fagus grandifolia) while retaining its 3-dimensional structure. The surface morphology of the synthesized transparent wood was studied by using scanning electron microscopy. Brunauer Emmet Teller measurements were carried out to determine the specific surface area. FTIR measurements were performed to study the wood chemistry. Optical measurements showed a maximum optical transmittance of 70% and a maximum haze of 49% for 0.1 mm and 0.7 mm thick wood samples, respectively. Mechanical testing showed that the transparent wood has a higher tensile strength and hardness when compared to the delignified wood. The fabricated transparent wood with high transmittance and enhanced mechanical properties is a potential candidate material for light transmitting building materials and transparent solar cell windows.
•Transparent wood for smart building applications.•Simple and economical approach to fabricate transparent wood.•Biodegradable approach.•70% of transmission and about 49% haze for practical applications.•Enhanced mechanical properties for practical applications.
Since it first appeared in literature in the early nineties, the Circular Economy (CE) has grown in significance amongst academic, policymaking, and industry groups. The latest developments in the CE ...field have included the interrogation of CE as a paradigm, and its relationship with sustainability and other concepts, including iterative definitions. Research has also identified a significant opportunity to apply circular approaches to our rapidly changing industrial system, including manufacturing processes and Industry 4.0 (I4.0) which, with data, is enabling the latest advances in digital technologies (DT). Research which fuses these two areas has not been extensively explored. This is the first paper to provide a synergistic and integrative CE-DT framework which offers directions for policymakers and guidance for future research through a review of the integrated fields of CE and I4.0. To achieve this, a Systematic Literature Review (SLR; n = 174) of the empirical literature related to digital technologies, I4.0, and circular approaches is conducted. The SLR is based on peer-reviewed articles published between 2000 and early 2018. This paper also summarizes the current trends in CE research related to manufacturing. The findings confirm that while CE research has been on the increase, research on digital technologies to enable a CE is still relatively untouched. While the “interdisciplinarity” of CE research is well-known, the findings reveal that a substantial percentage is engineering-focused. The paper concludes by proposing a synergistic and integrative CE-DT framework for future research developed from the gaps in the current research landscape.
Two-dimensional (2D) bioelectronics is an emerging field of research which fuses the advantages of 2D nanomaterials with those of nanobiotechnology. Due to the various physical and chemical ...properties present in layered counterparts of 2D materials, including high charge density, large surface area, remarkable electron mobility, ready electron transport, sizeable band gaps and ease of hybridisation, they are set to become a versatile tool to fabricate sensitive and selective novel biodevices, which might offer an unique advantages to tackle key energy, medical and environmental issues. Current 2D bioelectronics research is focused on the design of simple-to-use and cheaper biodevices, while improving their selectivity, sensitivity and stability. However, current designs generally suffer from a lack of efficiency, relatively low sensitivity, slow electron transfer kinetics, high background charging current and low current density arising from poor mass transport. Here, we report a nanoparticle-structured MoS2 nanosheet as an ideal semiconductor interface, which is able to form a homogenous layer on the electrode surface for the assembly of gold nanoparticles. This not only enhances electrocatalytic reactions, but also provides excellent electrochemical properties such as high faradic-to-capacitive current ratios, high current density and electron mobility, and faster mass transport, due to the dominance of radial diffusion. The MoS2/Au NPs/GOx bioelectrode exhibits a linear response to glucose from 0.25 to 13.2mM, with a detection limit of 0.042µM (S/N=3) and sensitivity of 13.80µA/µM/cm2.
•Structuring of gold nanoparticles on two-dimensional molybdenum disulfide (MoS2) nanosheets in a one-step reaction.•MoS2 as a semiconductor, which is an ideal candidate to form homogenous layer on the electrode surface for the structuring of Au NPs.•The fabrication of an electrochemical biosensor based on MoS2 nanosheets is demonstrated.•Design interface could potentially provide significant improvements in biocatalysis and nanotechnology by exploiting this biocatalytic interface with a variety of redox enzymes.
The UK is home to several major air commercial and transport hubs. As a result, there is a high demand for Maintenance, Repair, and Overhaul (MRO) services to ensure that fleets of aircraft are in ...airworthy conditions. MRO services currently involve heavy manual labor. This creates bottlenecks, low repeatability, and low productivity. Presented in this paper is an investigation to create an automation cell for the fan-blade reconditioning component of MRO. The design and prototype of the automation cell is presented. Furthermore, a digital twin of the grinding process is developed and used as a tool to explore the required grinding force parameters needed to effectively remove surface material. An integration of a 6-DoF industrial robot with an end-effector grinder and a computer vision system was undertaken. The computer vision system was used for the digitization of the fan-blade surface as well as tracking and guidance of material removal. Our findings reveal that our proposed system can perform material removal, track the state of the fan blade during the reconditioning process and do so within a closed-loop automated robotic work cell.
Thermoelectric (TE) materials can play an important role in developing next‐generation advanced energy conversion technologies. The underlying principle for thermoelectric power generation is the ...utilization of Seebeck effect in which temperature differences drive the electrical current. The performance of a TE material is evaluated by a dimensionless figure of merit, ZT, expressed as ZT = S2σT/κ, where S, σ, T, and κ denote the Seebeck coefficient, electrical conductivity, temperature and thermal conductivity, respectively. As seen from this expression, controlling thermal conduction in TE materials is a key toward obtaining high TE response. The thermal conductivity (κ) consists of two components, namely lattice thermal conductivity (κL) and electronic thermal conductivity (κe), of which the latter is linearly proportional to the electrical conductivity of the material following the Wiedemann‐Franz law. Since reducing the value of κe worsens the value of σ, which is not desired, κL has to be reduced to get an overall lower thermal conductivity. Numerous studies focusing on reducing the thermal conductivity of TE materials have been performed recently. In this paper, a comprehensive review of various strategies used for developing efficient thermoelectric systems by controlling thermal conduction in the TE materials has been provided.
Efficiency of a thermoelectric material depends on its electrical and thermal conductivities. For realizing efficient thermoelectric devices it is important to have materials with high electrical but low thermal conductivity. In this paper, the authors provide a comprehensive review of various strategies used for developing efficient thermoelectric systems by controlling thermal conduction in the material.
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