Application Of Advanced Characterization Techniques Research Articles

Insights into the removal of Cr(VI) from aqueous solution using plant-mediated biosynthesis of iron nanoparticles

While many studies have successfully used plant extracts to biosynthesize iron nanoparticles as low-cost, sustainable and high-performance materials for removing Cr(VI) from aqueous solution, the exact removal mechanism involved remains poorly understood. In this research, a green tea extract was employed both as a reducing and coating agent to prepare iron nanoparticles (GT-nFe) via an environmentally friendly green synthesis method, where the material so produced was then used to remove Cr(VI) from aqueous solution. The efficiency in removing Cr(VI) using GT-nFe reached 90.2 % at an initial Cr(VI) concentration of 60 mg L−1 and pH of 5.0. Kinetic and thermodynamic analysis indicated that Langmuir isotherm and pseudo-second order models best described the adsorption of Cr(VI) by GT-nFe. Thermodynamic studies revealed that adsorption was spontaneous (ΔG0<0) and endothermic (ΔH0>0). Application of advanced characterization techniques, including SEM-EDS, TEM and XPS, indicated a detailed Cr(VI) removal mechanism involving both adsorption and redox reactions.

Mechanistic Understanding of CaO-Based Sorbents for High-Temperature CO2 Capture: Advanced Characterization and Prospects.

Carbon dioxide capture and storage technologies are short to mid‐term solutions to reduce anthropogenic CO2 emissions. CaO‐based sorbents have emerged as a viable class of cost‐efficient CO2 sorbents for high temperature applications. Yet, CaO‐based sorbents are prone to deactivation over repeated CO2 capture and regeneration cycles. Various strategies have been proposed to improve their cyclic stability and rate of CO2 uptake including the addition of promoters and stabilizers (e. g., alkali metal salts and metal oxides), as well as nano‐structuring approaches. However, our fundamental understanding of the underlying mechanisms through which promoters or stabilizers affect the performance of the sorbents is limited. With the recent application of advanced characterization techniques, new insight into the structural and morphological changes that occur during CO2 uptake and regeneration has been obtained. This review summarizes recent advances that have improved our mechanistic understanding of CaO‐based CO2 sorbents with and without the addition of stabilizers and/or promoters, with a specific emphasis on the application of advanced characterization techniques.

Unveiling the Advances of Nanostructure Design for Alloy-Type Potassium-Ion Battery Anodes via In Situ TEM.

Nanostructure design and in situ transmission electron microscopy (TEM) are combined to demonstrate Sb-based nanofibers composed of bunched yolk-shell building units as a significantly improved anode for potassium-ion batteries (PIBs). Particularly, a metal-organic frameworks (MOFs)-engaged electrospinning strategy coupled to a confined ion-exchange followed by a subsequent thermal reduction is proposed to fabricate yolk-shell Sb@C nanoboxes embedded in carbon nanofibers (Sb@CNFs). In situ TEM analysis reveals that the inner Sb nanoparticles undergo a significant volume expansion/contraction during the alloying/dealloying processes, while the void space can effectively relieve the overall volume change, and the plastic carbon shell maintains the structural integrity of electrode material. This work provides an important reference for the application of advanced characterization techniques to guide the optimization of electrode material design.

Unveiling the Advances of Nanostructure Design for Alloy‐Type Potassium‐Ion Battery Anodes via In Situ TEM

AbstractNanostructure design and in situ transmission electron microscopy (TEM) are combined to demonstrate Sb‐based nanofibers composed of bunched yolk–shell building units as a significantly improved anode for potassium‐ion batteries (PIBs). Particularly, a metal–organic frameworks (MOFs)‐engaged electrospinning strategy coupled to a confined ion‐exchange followed by a subsequent thermal reduction is proposed to fabricate yolk–shell Sb@C nanoboxes embedded in carbon nanofibers (Sb@CNFs). In situ TEM analysis reveals that the inner Sb nanoparticles undergo a significant volume expansion/contraction during the alloying/dealloying processes, while the void space can effectively relieve the overall volume change, and the plastic carbon shell maintains the structural integrity of electrode material. This work provides an important reference for the application of advanced characterization techniques to guide the optimization of electrode material design.

Application of Advanced Characterization Techniques for Engineering Materials

Application of Advanced Characterization Techniques for Engineering Materials

Characterization protocol to improve the electroanalytical response of graphene–polymer nanocomposite sensors

This work is focused on the application of advanced characterization techniques for the development of optimized electrochemical sensors based on graphene–polymer nanocomposites. Reduced graphene oxide (rGO) was synthesized and used as conducting nanofiller material in nanocomposite electrodes based on epoxy resin. A series of rGO/epoxy nanocomposite electrodes were fabricated containing 8%–20% of nanofiller material. Composition ratios have been studied using percolation theory and characterized by different electrochemical techniques, demonstrating that an optimization of the rGO/epoxy composition ratio is mandatory to enhance electrochemical performance. The potential of this approach in terms of electroanalytical response has been demonstrated by means of the amperometric detection of ascorbic acid, which was used as a model analyte. Finally, different morphological experiments were also carried out in order to verify the electrochemical and electroanalytical enhancement obtained for the optimized-nanocomposite sensors.

Progress in Mechanistic Understanding and Characterization Techniques of Li‐S Batteries

Rechargeable lithium‐sulfur batteries that operate at room temperature have attracted much research interest as next‐generation energy storage systems. Although tremendous advances have been made with Li‐S batteries, great challenges still exist in achieving high capacity, high loading, high coulombic efficiency, and long cycle life. These challenges arise from the system complexity, lack of mechanistic understanding of the redox reaction, and operational limitations of Li‐S cells. The focus here is on the recent gains in fundamental understanding of the Li‐S redox reaction mechanism based on the application of advanced characterization techniques. Research results that help with the understanding of the close relationship between cell design (including development of new and advanced electrode materials, electrolytes, separators, binders, and cell configurations), the Li‐S reaction mechanism, characterization methods, and Li‐S battery performance are discussed.

Improvement of the detection limit for biosensors: Advances on the optimization of biocomposite composition

In this work the application of advanced characterization techniques in the development of amperometric biosensors based on biocomposites is described. The optimization of the conductive particle distribution and the amount of the biological material inside the biomaterial have allowed an improvement of the electrochemical properties, regarding the electroanalytical properties such as signal stability and limit of detection. The high signal-to-noise ratio obtained in the electrochemical transduction has allowed enhancing the limit of detection of the biosensor. In the present study, it has been demonstrated the feasibility of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) for the characterization and optimization of biosensors based on graphite–epoxy–enzyme, using an enzyme model. The optimum biocomposite proportion based on graphite–epoxy which incorporates the enzyme glucose oxidase (GOD) on the matrix ranges between 16% and 17% of graphite using 1% and 2% of enzyme. This range provides the optimal electroanalytical properties. Low limit of detection and good sensitivity have been achieved. Furthermore, confocal laser scanning microscopy was used to visualize the enzyme distribution onto the surface electrode.

Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes

During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44–50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266–2271, 2008). In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307–2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G+/G− splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165–184, 2009) shows CNT diameters of 2.5 ± 0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G+ and G− peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current–voltage (I/V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/V response at different regions of the CNT transistor are discussed.

Application of advanced characterization techniques to assess DOM treatability of micro-polluted and un-polluted drinking source waters in China

China has a very complex water supply system which relies on many rivers and lakes. As the population and economic development increases, water quality is greatly impacted by anthropogenic processes. This seriously affects the character of the dissolved organic matter (DOM) and imposes operational challenges to the water treatment facilities in terms of process optimization. The aim of this investigation was to compare selected drinking water sources (raw) with different DOM character, and the respective treated waters after coagulation, using simple organic characterization techniques to obtain a better understanding of the impact of source water quality on water treatment. Results from the analyses of selected water samples showed that the dissolved organic carbon (DOC) of polluted waters is generally higher than that of un-polluted waters, but the specific UV absorbance value has the opposite trend. After resolving the high performance size exclusion chromatography (HPSEC) peak components of source waters using peak fitting, the twelve waters studied can be divided into two main groups (micro-polluted and un-polluted) by using cluster analysis. The DOM removal efficiency (treatability) of these waters has been compared using four coagulants. For water sources allocated to the un-polluted group, traditional coagulants (Al 2(SO 4) 3 and FeCl 3) achieved better removal. High performance poly aluminum chloride, a new type of composite coagulant, performed very well and more efficiently for polluted waters. After peak fitting the HPSEC chromatogram of each of the treated waters, average removal efficiency of the profiles can be calculated and these correspond well with DOC and UV removal. This provides a convenient tool to assess coagulation removal and coagulant selection.

Solid Oxide Fuel Cell Development at PNNL

Through a variety of programs, Pacific Northwest National Laboratory is working with government agencies and private industries to help bring SOFC-based technology to the commercial marketplace. These activities include the development of advanced materials and fabrication techniques for SOFC stack components, the development and utilization of modeling tools for optimization of cell and stack designs, and the development and application of advanced characterization techniques to increase the understanding of fundamental electrochemical processes occurring in SOFCs.