scholarly journals Single Entity Behavior of CdSe Quantum Dot Aggregates During Photoelectrochemical Detection

2021 ◽  
Vol 9 ◽  
Author(s):  
Pradeep Subedi ◽  
Suman Parajuli ◽  
Mario A. Alpuche-Aviles
Keyword(s):  
Electrode Surface ◽  
Collision Frequency ◽  
Colloidal Suspensions ◽  
Suspension Stability ◽  
Cdse Core ◽  
Pt Electrode ◽  
Diffusion Limited ◽  
The Stability ◽  
Adsorption Desorption ◽  
Surface Dynamic

We demonstrate that colloidal quantum dots of CdSe and CdSe/ZnS are detected during the photooxidation of MeOH, under broad spectrum illumination (250 mW/cm2). The stepwise photocurrent vs. time response corresponds to single entities adsorbing to the Pt electrode surface irreversibly. The adsorption/desorption of the QDs and the nature of the single entities is discussed. In suspensions, the QDs behave differently depending on the solvent used to suspend the materials. For MeOH, CdSe is not as stable as CdSe/ZnS under constant illumination. The photocurrent expected for single QDs is discussed. The value of the observed photocurrents, > 1 pA is due to the formation of agglomerates consistent with the collision frequency and suspension stability. The observed frequency of collisions for the stepwise photocurrents is smaller than the diffusion-limited cases expected for single QDs colliding with the electrode surface. Dynamic light scattering and scanning electron microscopy studies support the detection of aggregates. The results indicate that the ZnS layer on the CdSe/ZnS material facilitates the detection of single entities by increasing the stability of the nanomaterial. The rate of hole transfer from the QD aggregates to MeOH outcompetes the dissolution of the CdSe core under certain conditions of electron injection to the Pt electrode and in colloidal suspensions of CdSe/ZnS.

scholarly journals Effective Separation of Prime Olefins from Gas Stream Using Anion Pillared Metal Organic Frameworks: Ideal Adsorbed Solution Theory Studies, Cyclic Application and Stability

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 510
Author(s):  
Majeda Khraisheh ◽  
Fares. Almomani ◽  
Gavin Walker
Keyword(s):  
Breakthrough Curves ◽  
Isotherm Models ◽  
Regeneration Ability ◽  
Solution Theory ◽  
Experimental Conditions ◽  
Ideal Adsorbed Solution Theory ◽  
Adsorbed Solution ◽  
The Stability ◽  
Adsorption Desorption ◽  
Adsorbed Solution Theory

The separation of C3H4/C3H6 is one of the most energy intensive and challenging operations, requiring up to 100 theoretical stages, in traditional cryogenic distillation. In this investigation, the potential application of two MOFs (SIFSIX-3-Ni and NbOFFIVE-1-Ni) was tested by studying the adsorption–desorption behaviors at a range of operational temperatures (300–360 K) and pressures (1–100 kPa). Dynamic adsorption breakthrough tests were conducted and the stability and regeneration ability of the MOFs were established after eight consecutive cycles. In order to establish the engineering key parameters, the experimental data were fitted to four isotherm models (Langmuir, Freundlich, Sips and Toth) in addition to the estimation of the thermodynamic properties such as the isosteric heats of adsorption. The selectivity of the separation was tested by applying ideal adsorbed solution theory (IAST). The results revealed that SIFSIX-3-Ni is an effective adsorbent for the separation of 10/90 v/v C3H4/C3H6 under the range of experimental conditions used in this study. The maximum adsorption reported for the same combination was 3.2 mmolg−1. Breakthrough curves confirmed the suitability of this material for the separation with a 10-min gab before the lighter C3H4 is eluted from the column. The separated C3H6 was obtained with a 99.98% purity.

scholarly journals Shear thickening behavior in dense repulsive and attractive suspensions of hard spheres

Soft Matter ◽  
2021 ◽  
Author(s):  
Vikram Rathee ◽  
Alessandro Monti ◽  
Marco Edoardo Rosti ◽  
Amy Q Shen
Keyword(s):  
Flow Curve ◽  
Hard Spheres ◽  
Shear Thickening ◽  
Colloidal Suspensions ◽  
Thickening Behavior ◽  
The Stability

Shear thickening in stable dense colloidal suspensions is a reversible phenomenon and no hysteresis is observed in the flow curve measurements. However, a reduction in the stability of colloids promotes...

scholarly journals Sorption and Desorption Analysis of Nitrobenzene on Differently Functionalized Multiwalled Carbon Nanotubes and Implications on the Stability

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1426
Author(s):  
Zhanhua Ji ◽  
Dengyu Li
Keyword(s):  
Carbon Nanotubes ◽  
Underlying Mechanism ◽  
Multiwalled Carbon ◽  
Environmental Behaviors ◽  
Initial Concentration ◽  
Sorption Hysteresis ◽  
Key Factor ◽  
Functionalized Multiwalled Carbon Nanotubes ◽  
The Stability ◽  
Adsorption Desorption

The stability of carbon nanotubes (CNTs) suspension is a key factor in determining their transport, fate, and toxicity in an aquatic environment, which is significantly influenced by CNTs’ nature and water chemistry. Macromolecular dissolved organic matter (DOM) is reported to influence the stability of CNTs aggregation. However, little is known on small polar dissolved organic compound’s effects on CNTs aggregation. Nitrobenzene was selected to investigate its interaction with three different functionalized multiwalled CNTs (MWCNTs). Both the stability of CNTs aggregation and sorption hysteresis were affected by the initial concentration of nitrobenzene and the surface functionalization coverage of MWCNTs. At the initial concentration below 580 mg/L, the thermodynamic index of irreversibility (TII) and turbidity of CNTs suspension had the same tendency, indicating that the underlying mechanism is closely related. A conceptual adsorption–desorption model was proposed to further explain the relationship between the sorption hysteresis and stability of MWCNTs suspension under different initial concentrations of nitrobenzene. This provided data support to further clarify the environmental behaviors and risks of CNTs.

In situ tailoring bimetallic-organic frameworks derived yolk-shell NiS2/CuS hollow microspheres: an extraordinary kinetically pseudocapacitive nanoreactor for effective sodium-ion storage anode

2021 ◽  
Author(s):  
wen xi zhao ◽  
Xiaodeng Wang ◽  
Xiaoqing Ma ◽  
Luchao Yue ◽  
Qian Liu ◽  
...  
Keyword(s):  
Sodium Ion ◽  
Ion Adsorption ◽  
Redox Kinetics ◽  
Diffusion Limited ◽  
Ion Storage ◽  
Sluggish Diffusion ◽  
Fast Ion ◽  
Adsorption Desorption ◽  
Sodium Ion Storage

Pseudocapacitive electrochemical Na+-storage has been highlighted as one of the exploitable strategies in overcoming sluggish diffusion-limited redox kinetics due to effectively structural preserving and fast ion adsorption/desorption at the surface...

scholarly journals Improving stability of cerium oxide nanoparticles by microbial polysaccharides coating

2018 ◽  
Vol 83 (6) ◽  
pp. 745-757 ◽  
Author(s):  
Ivana Milenkovic ◽  
Ksenija Radotic ◽  
Branko Matovic ◽  
Marija Prekajski ◽  
Ljiljana Zivkovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cerium Oxide ◽  
Aqueous Media ◽  
Suspension Stability ◽  
X Ray Diffraction ◽  
Synthesis Conditions ◽  
Transmission Electron ◽  
Ft Ir ◽  
Microbial Exopolysaccharides ◽  
The Stability

Cerium oxide (CeO2) nanoparticles (CONPs) are interesting biomaterials with various applications in biomedicine, cosmetics and the pharmaceutical industry, but with limited practical application because of their low stability in aqueous media. The aim of this study was to obtain CONPs with increased stability by coating the particles. Microbial exopolysaccharides (levan, pullulan) and glucose were used to prepare CONPs under different synthesis conditions. Coating was attempted by adding the carbohydrates during (direct coating) or after (subsequent coating) the synthesis of CONPs. The obtained nanoparticles were characterized by X-Ray diffraction analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The suspension stability of the uncoated and coated CONPs in aqueous media was evaluated by measuring the hydrodynamic size, zeta potential and turbidity. The FT-IR spectra revealed the differences between coated CONPs and showed the success of subsequent coating with carbohydrates. Coating with carbohydrates improved the stability the CONP suspension by decreasing the size of aggregated particles. The suspensions of levan- and glucose-coated CONPs had the best stability. In this study, CONPs were prepared using non-toxic materials, which were completely environmentally friendly. The obtained results open new horizons for CONP synthesis, improving their biological applications.

scholarly journals Synthesis of Magnetic Targeted Cellulose Composite Decorated with Poly(AA-DMC) for Synergistic Adsorption Degradation of Congo Red from Organic Wastewater

2021 ◽  
Author(s):  
Chen Ling ◽  
Dai Yimin ◽  
Lu Qi ◽  
Fang Chengqian ◽  
Wang Zhiheng ◽  
...  
Keyword(s):  
Congo Red ◽  
Magnetic Particles ◽  
Degradation Mechanism ◽  
Degradation Of Dyes ◽  
Cellulose Composites ◽  
Natural Cellulose ◽  
The Stability ◽  
Adsorption Desorption ◽  
Cr Removal ◽  
Organic Wastewater

Abstract A brand-new environmental-friendly magnetic cellulosic adsorbent MnFe2O4@Cel-g-p(AA-DMC) was synthesized by natural cellulose and easy-recovered magnetic particles MnFe2O4. Magnetic cellulose composites were characterized by SEM, TEM, XPS, XRD, BET, VSM, TGA and FTIR. The MnFe2O4NPs could activate the peroxymonosulfate (PMS) to produce various reactive oxygen species (ROS). Accordingly, magnetic cellulose composites can synergistic adsorption degradation of dyes from organic wastewater. The Congo red (CR) removal efficiency by MnFe2O4@Cel-g-p(AA-DMC) via PMS activated by MnFe2O4 reached a maximum of 96.9% and only 9% reduction after four adsorption-desorption cycles, indicating the stability and recoverability of adsorbent. It is worth noting that adsorbents can be quickly recovered from aqueous solution by external magnet owing to superior saturation magnetization (35.44 emu·g-1). A possible degradation mechanism of CR on the MnFe2O4@Cel-g-p(AA-DMC) composite was proposed. The results suggest that adsorbent display strong potential for the removal of CR dyes from organic wastewater.

Polyaniline Modified Surface of Electrode for Boosting the Electrocatalysis on Hydrogen Evolution Reaction and Ethanol Oxidation Reaction

2021 ◽  
Author(s):  
Yankun Huang ◽  
Feng Bao ◽  
Muwei Ji ◽  
Yanzhao Hu ◽  
Liu Huang ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Electrode Surface ◽  
Oxidation Reaction ◽  
Ethanol Oxidation ◽  
Carbon Paper ◽  
Ethanol Oxidation Reaction ◽  
Pt Electrode ◽  
Modified Surface

Here, polyaniline (PANI) is reported loaded on carbon paper to modify the carbon paper-PANI-Pt electrode surface, tailoring the electrocatalytic capability on hydrogen evolution reaction and ethanol oxidation reaction. The reasons...

scholarly journals Sedimentation in flocculating colloidal suspensions

1994 ◽  
Vol 9 (2) ◽  
pp. 451-461 ◽  
Author(s):  
Jeffrey S. Abel ◽  
Gregory C. Stangle ◽  
Christopher H. Schilling ◽  
Ilhan A. Aksay
Keyword(s):  
Gamma Ray ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Colloidal Suspensions ◽  
Balance Model ◽  
Suspension Stability ◽  
Particle Volume ◽  
Sedimentation Behavior ◽  
Model Predictions ◽  
Ceramic Suspensions

A combined experimental and theoretical investigation of the sedimentation of unstable colloidal ceramic suspensions has been performed. Suspensions containing submicron-sized α-Al2O3 particles were prepared at various pH values in order to modify suspension stability. Particle volume fraction during sedimentation was determined as a function of position and time by gamma-ray densitometry. A population balance model was developed to account for various coagulation and decoagulation mechanisms that affect sedimentation behavior in flocculating suspensions. Model predictions were then compared with experimental measurements, in order to establish the validity of the theoretical model.

Effects of pH and surfactant on the forced convection of Al2O3/water and TiO2/water nanofluids

2020 ◽  
pp. 1-18
Author(s):  
Deepak Khurana ◽  
Sudhakar Subudhi
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Particle Concentration ◽  
Sodium Dodecyl ◽  
Suspension Stability ◽  
Heat Transfer Characteristics ◽  
Maximum Enhancement ◽  
Effects Of Ph ◽  
Set Up ◽  
The Stability

Abstract The present paper deals with the forced convection of Al2O3/water and TiO2/water nanofluids with the variation of pH and addition of surfactant in nanofluids. The aim of this study is to investigate the effect of suspension stability on the heat transfer and pressure drop characteristics of nanofluids. The present experimental set up is same as used by our earlier paper [1]. The suspension stability of nanofluids is improved by varying pH of nanofluids. The pH in this study is varied from 3.5±0.2 to 12.5±0.2. Addition of surfactants is employed to improve the suspension stability of nanofluids. The SDS (sodium dodecyl sulfate) surfactant of 0.05 wt % is used to increase the stability of nanofluids in the present study. It is observed that by increasing the suspension stability with the variation of pH and addition of surfactant, the heat transfer characteristics have improved appreciably. The maximum enhancement in heat transfer is obtained with TiO2/water nanofluids at a particle concentration of 0.1 vol % and a pH of 3.5±0.2.

Sign in / Sign up

Export Citation Format

Share Document