Tethered Bilayer Lipid Membranes to Monitor Heat Transfer between Gold Nanoparticles and Lipid Membranes

Here we report a protocol to investigate the heat transfer between irradiated gold nanoparticles (GNPs) and bilayer lipid membranes by electrochemistry ...

The University of New South Wales

Emission models are widely applied tools for estimating atmospheric emissions from wastewater treatment plants (WWTPs). The friction velocity u is a key variable for the modelling of emissions from passive liquid surfaces in WWTPs. This work evaluated different parametrisations of u for passive liquid surfaces at the scale of WWTP units, which present relatively small fetches, based on available wind friction and wave data measured at wind-wave tanks (fetches spanning from approximately 3 to 100 m, and wind speeds from 2 to 17 m s). The empirical correlation by Smith (1980; J. Phys. Oceanogr. 10, 709-726), which has been frequently adopted in air emission models (despite the fact that it was originally derived for the ocean) presented a general tendency to overestimate u, with significant (although not extreme) relative errors (mean and maximum errors of 13.5% and 36.6%, respectively); the use of Charnock's relation, with Charnock constant 0.010, performed in a very similar manner (mean and maximum errors of 13.3% and 37.8%, respectively). Better estimates of u were achieved by parametrisations based on the significant wave steepness. Simplified correlations between the wind drag and the non-dimensional fetch were obtained. An approach was devised, comprising the use of Charnock's relation (with Charnock constant 0.010) and of these simplified correlations, depending on the ranges of frequency of the peak waves, fetch and wind speed. The proposed approach predicted u with improved accuracy (mean, maximum and 95%-percentile relative errors of 6.6%, 16.7% and 13.9%, respectively), besides being able to incorporate the influence of the fetch in the wind drag, thus taking into account the size of the tanks in the WWTPs.

Wind friction parametrisation used in emission models for wastewater treatment plants: A critical review.

Emission models are useful tools for the study and management of atmospheric emissions from passive liquid surfaces in wastewater treatment plants (WWTPs), which are potential sources of odour nuisance and other environmental impacts. In this work, different theoretical and empirical models for the gas-side (k) and liquid-side (k) mass transfer coefficients in passive surfaces in WWTPs were critically reviewed and evaluated against experimental data. Wind forcing and the development of the wind-wave field, especially the occurrence of microscale wave breaking, were identified as the most important physical factors affecting mass transfer in these situations. Two approaches performed well in describing the available data for k for water vapour. One is an empirical correlation whilst the other consists of theoretical models based on the description of the inner part of the turbulent boundary layer over a smooth flat plate. We also fit to the experimental data set a new, alternate equation for k, whose performance was comparable to existing ones. However, these three approaches do not agree with each other in the whole range of Schmidt numbers typical for compounds found in emissions from WWTPs. As to k, no model was able to satisfactorily explain the behaviour and the scatter observed in the whole experimental data set. Excluding two suspected biased sources, the WATER9 (US EPA, 1994. Air Emission Models for Waste and Wastewater. North Carolina, USA. EPA-453/R-94-080A) approach produced the best results among the most commonly used k models, although still with considerably high relative errors. For this same sub-set, we propose a new, alternate approach for estimating k, which resulted in improved performance, particularly for longer fetches. Two main gaps were found in the literature, the understanding of the evolution of the mass transfer boundary layer over liquid surfaces, and the behaviour of k for larger fetches, especially in the range from 40 to 60 m.

A critical review on liquid-gas mass transfer models for estimating gaseous emissions from passive liquid surfaces in wastewater treatment plants.

Gold nanoparticle (GNP) aggregation has a strong influence on the plasmonic resonance and hence the effectiveness in various photothermal applications. In relation to this, a comprehensive numerical model is developed to simulate and characterize the GNP aggregation process at various particle volume fractions and base fluid pH levels. Computational fluid dynamics techniques are utilized to model the base fluid, whereas discrete phase modeling is adopted in determining the nanoparticle trajectories. Two-way coupling is implemented to handle the particle-fluid interactions. Discrete dipole approximation approach is utilized to further examine the absorption and scattering efficiency of various GNP aggregate structures. At lower particle volume fraction, short chain-like structures are formed in the particle aggregation process, with a more complex interconnected "particle network" structure formed at higher particle volume fractions. With the three base fluid pH levels investigated, GNP aggregates are more compact with larger fractal dimensions and higher mean coordination numbers at pH = 3.5, whereas a more "loose" structure formed at pH = 6.7 and 9.4 because of larger electrostatic repulsive forces as a result of changes in the zeta potential and Debye length of the GNPs. Among the typical GNP aggregate structures characterized in this paper, the chain-like tetramer demonstrates the highest absorption efficiency of 1.83 at 700 nm wavelength-comparable to the plasmonic resonance of a nanorod-which lies in the optical window of biological tissue. Predictions of GNP optical properties are found to be in good agreement with the published experimental data.

Study of Morphology and Optical Properties of Gold Nanoparticle Aggregates under Different pH Conditions.

Redox flow batteries (RFBs), provide a safe and cost-effective means of storing energy at grid-scale, and will play an important role in the decarbonization of global electricity networks. Several approaches have been explored to improve their efficiency and power density, and recently, cell geometry modification has shown promise in efforts to address mass transport limitations which affect electrochemical and overall system performance. Flow-by electrode configurations have demonstrated significant power density improvements in laboratory testing, however, flow-through designs with conductive felt remain the standard at commercial scale. Concentration gradients exist within these cells, limiting their performance. A new concept of redistributing reactants within the flow frame is introduced in this paper. This research shows a 60% improvement in minimum V concentration within simulated vanadium redox flow battery (VRB/VRFB) cells through the application of static mixers. The enhanced reactant distribution showed a cell voltage improvement by reducing concentration overpotential, suggesting a pathway forward to increase limiting current density and cycle efficiencies in RFBs.

Enhanced Reactant Distribution in Redox Flow Cells.

Plasmon resonance frequency irradiated gold nanoparticles (GNPs) have gained interest as a laser-targeted treatment for infections, tumors and for the controlled release of drugs in situ. Questions still remain, however, as to the efficiency of heat delivery within biological tissues and how this can be reliably determined. Here, we demonstrate how a nanomaterial-electrode interface that mimics cell membranes can detect the localized heat transfer characteristics arising from plasmon resonance frequency-matched laser excitation of GNPs. We demonstrate that the lipid bilayer membrane can be affected by conjugated GNP induced hyperthermia when irradiated with a laser power output as low as 135 nW/μm. This is four orders of magnitude lower power than previously reported. By restricting the lateral movement of the lipids in the bilayer membrane, it was shown that the change in membrane conductance as a result of the heat transfer was due to the creation of transient lipidic toroidal pores within the membrane. We further demonstrate that the heat transfer from the GNPs alters diffusion rates of monomers of the gramicidin-A peptide within the lipid leaflets. This work highlights how targeted low laser power GNP hyperthermia treatments, in vivo, could play a dual role of interfering with both cell membrane morphology and dynamics, along with membrane protein function.

Victoria Timchenko

School of Mechanical and Manufacturing Engineering

The University of New South Wales

Tethered Bilayer Lipid Membranes to Monitor Heat Transfer between Gold Nanoparticles and Lipid Membranes

Victoria Timchenko

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}School of Mechanical and Manufacturing Engineering

The University of New South Wales

Tethered Bilayer Lipid Membranes to Monitor Heat Transfer between Gold Nanoparticles and Lipid Membranes

School of Mechanical and Manufacturing Engineering