3 results
Adsorption of gold nanoparticles on illite under high solid/liquid ratio and initial pH conditions
- Ping Zeng, Xin Nie, Zonghua Qin, Suxing Luo, Yuhong Fu, Wenbin Yu, Meizhi Yang, Wenqi Luo, Hai Yang, Quan Wan
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- Journal:
- Clay Minerals / Volume 58 / Issue 3 / September 2023
- Published online by Cambridge University Press:
- 25 August 2023, pp. 245-257
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- Article
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Adsorption of nanoparticles on minerals affects the fate and transport of nanoparticles directly and is of great significance to many fields, including research into ore deposits, geochemistry, the environment and mineral materials. Whereas many previous studies have been conducted under the equilibrium pH and low solid (mineral) to liquid (nanoparticle suspension) ratio conditions, adsorption processes under initial pH and high solid/liquid ratio conditions may represent many important yet underexamined complex scenarios. To fill in this research gap, the adsorption of gold nanoparticles on illite was investigated experimentally at a relatively high solid/liquid ratio of 5 g L–1 and the effects of initial pH, ionic strength, citrate concentration, temperature and illite particle size were evaluated. The adsorbed amount of gold nanoparticles (from <5% to nearly 100%) increased with increasing ionic strength, temperature and citrate concentration and decreased with increasing pH and illite particle size. The presence of illite resulted in the dynamic evolution of the pH of the suspension, which, along with solution chemistry parameters, controlled the electrostatic interaction of illite and gold nanoparticles. The adsorption results, scanning electron microscopy observations and surface properties of illite suggest that the negatively charged gold nanoparticles were adsorbed predominantly on the positive illite edges through electrostatic interaction. The electrostatic attraction between illite and gold nanoparticles appeared to be strong, supported by the minor amount of desorption. These research findings are expected to provide a valuable reference regarding many critical issues in the geosciences as well as for industrial applications.
Dynamic coupling between carrier and dispersed phases in Rayleigh–Bénard convection laden with inertial isothermal particles
- Wenwu Yang, Yi-Zhao Zhang, Bo-Fu Wang, Yuhong Dong, Quan Zhou
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- Journal:
- Journal of Fluid Mechanics / Volume 930 / 10 January 2022
- Published online by Cambridge University Press:
- 11 November 2021, A24
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We investigate the dynamic couplings between particles and fluid in turbulent Rayleigh–Bénard (RB) convection laden with isothermal inertial particles. Direct numerical simulations combined with the Lagrangian point-particle mode were carried out in the range of Rayleigh number $1\times 10^6 \le {Ra}\le 1 \times 10^8$ at Prandtl number ${Pr}=0.678$ for three Stokes numbers ${St_f}=1 \times 10^{-3}$, $8 \times 10^{-3}$ and $2.5 \times 10^{-2}$. It is found that the global heat transfer and the strength of turbulent momentum transfer are altered a small amount for the small Stokes number and large Stokes number as the coupling between the two phases is weak, whereas they are enhanced a large amount for the medium Stokes number due to strong coupling of the two phases. We then derived the exact relation of kinetic energy dissipation in the particle-laden RB convection to study the budget balance of induced and dissipated kinetic energy. The strength of the dynamic coupling can be clearly revealed from the percentage of particle-induced kinetic energy over the total induced kinetic energy. We further derived the power law relation of the averaged particles settling rate versus the Rayleigh number, i.e. $S_p/(d_p/H)^2{\sim} Ra^{1/2}$, which is in remarkable agreement with our simulation. We found that the settling and preferential concentration of particles are strongly correlated with the coupling mechanisms.
Chapter 18 - Label-Free Biosensor Technologies in Small Molecule Modulator Discovery
- from Section Four - Chemical Genomics Assays and Screens
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- By Yuhong Du, Jie Xu, Haian Fu, Arron S. Xu
- Edited by Haian Fu, Emory University, Atlanta
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- Book:
- Chemical Genomics
- Published online:
- 05 June 2012
- Print publication:
- 13 February 2012, pp 245-258
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- Chapter
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Summary
Label-free biosensor technologies allow the detection of molecular interactions and cell-based biological readouts without the need for conventional labels or engineered cell lines with overexpressed targets. A number of label-free detection technologies have been used for monitoring biomolecular interactions, most notably surface plasmon resonance spectroscopy (SPR) and isothermocalorimetry (ITC) [1–4]. With the rapid development of label-free based detection instrumentation in recent years, the power of various label-free technologies for studying biomolecular interactions and endogenous cellular events has been recognized by biomedical investigators, especially scientists involved in high-throughput screening (HTS). This, in turn, has led to a rapidly expanding list of various assay formats for HTS and allowed, for the first time, label-free screening for drug discovery in an HTS format [3, 5]. This chapter reviews basic principles of several major label-free biosensor technologies, with emphasis on microplate-based technologies and their practical applications in small molecule modulator discovery.
Traditional Label-Based Technologies for HTS
Various in vitro biochemical assays and cell-based methods are frequently employed in HTS for small molecule modulator discovery. These assays are often performed in a microplate format (96/384/1536 wells) in order to meet the demand of handling large sample numbers in primary HTS. In vitro biochemical assays rely on the use of an isolated or purified target that is often coupled with a tag (e.g., a fluorophor) for detection. These targets include purified adaptor proteins, enzymes, receptors, or cellular extract containing the target(s) of interest. Common detection methods in biochemical HTS assays include fluorescence polarization (FP), fluorescence resonance energy transfer (FRET), fluorescence intensity (FI), luminescence, and absorbance. FP measures the binding of a macromolecule to a relatively small peptide or ligand labeled with a fluorophore [6]. Binding of a macromolecule to the fluorophore-labeled small ligand/peptide slows down its rotation in solution and generates an FP signal. FRET allows the measurement of interacting molecules within a certain distance (<100 Å) (see Chapter 14 for details). The target and its binding partner are labeled separately, with a donor and a paired acceptor fluorophore containing matching excitation and emission spectra. Binding of the two molecules brings the donor and acceptor into close proximity, allowing energy transfer from the donor to the acceptor and FRET signal production. FRET signals can be derived in order to provide structural proximity information of molecular interactions [7]. FI-based assays measure changes in fluorescence intensity resulting from biochemical reactions. For example, cleavage of an appropriately fluorophore-labeled substrate by an enzyme can lead to a change in fluorescence intensity [8]. Biochemical assays are routinely used for monitoring receptor-ligand interactions, protein-protein interactions, and enzymatic activities (e.g., kinases and proteases).