Narrow Results

Currently there exists a critical need within the military and homeland defense for highly sophisticated yet, small, lightweight portable sensors and detection systems for identifying and quantifying biological and biowarfare agents (BWA) in both liquid and aerosolized form. Our proposed BWA detection system is based upon Fourier Transform Infrared Spectroscopy (FTIR), where the main advantages of this approach are that it is reagentless, operates in heterogeneous aqueous environments, and provides fast detection and high sensitivity/selectivity to bacterial spores with minimal false alarms.

The key enabler to using FTIR for BWA detection is to develop selective and robust sampling protocols coupled to a miniaturized, portable FTIR unit. To that end, we have developed front-end liquid flow cells which incorporate electric field (E-Field) concentration methods for spores onto the surface of an Attenuated Total Reflection (ATR) IR crystal. IR spectra are presented which show collection and detection results with BG spores in water. The approaches we have developed take advantage of the fact that all spores are negatively charged in neutral pH solutions. Therefore, E-Field concentration of spores directly onto an ATR sampling element enables low level concentration measurements to be possible.

Because particles that accumulate without movement can lead to a deposition gradient, the formation of a stable suspension is essential for the electrophoretic dispersion (EPD) process. The hydrophobic properties of Halloysite nanotubes (HNTs) were easily dispersed in many nonpolar polymers without further deformation steps. However, the uniform dispersion of HNTs in aqueous solutions is a pre-EPD process task. The zeta potential controls the main parameters of EPD processes, such as the density of deposits, particle orientation and velocity, and repulsive interactions between particles, which determine the stability of the suspension. In this study, the solution stability range for the addition of nanoparticles was measured and the optimal dispersion range was determined. In addition, an HNT-reinforced composite material was created by determining the optimal dispersion stability range of HNT, and the impact strength and fracture mechanism of the interface were analyzed. The solution stability and dispersion were the best between pH 6.6 and 6.8, and the highest impact strength was confirmed at 0.7 wt%. The HNT confirmed the interfacial dispersion of the EPD-fibers using scanning electron microscopy and dispersive X-ray spectroscopy (SEM-EDS).

The study characterizes power-law fluid through charged fibrous porous media with spatial fractional-derivative and fractal geometry. Seepage flow of power-law fluid across fractal fibrous porous media in the presence of electric double layers (EDLs) is investigated based on the capillary bundle model. The acquired velocity distribution equation in a narrow capillary is then transformed into the form of series with appropriate Taylor approximation. After that, an analytical formula for dimensionless permeability is derived based on the generalized Darcy’s law. The effects of diverse parameters, including the fractal dimension of pore area, porosity, fractional order and Zeta potential on dimensionless permeability, are discussed. It can be seen from the results that lower fractional order has an amplification effect on dimensionless permeability with the change in Zeta potential. The results provide some theoretical guidance for revealing the seepage mechanism of a power-law fluid in charged porous media.

In this work, the electrokinetic characteristics of calcined kaolinite in aqueous solutions has been studied in the presence of the electrolytes of NaCl, KCl, NH₄Cl, NaNO₃, MgCl₂, CaCl₂ and AlCl₃, through electrophoretic measurement. The experimental results have shown that the zeta potential was closely dependent on the valence and concentration of the electrolytic cations, but not on the type of the cations. The higher the valence and the concentration were, the stronger the impact to the zeta potential was. Al³⁺ could reverse the potential sign from negative to positive. In addition, it was found that the monovalent anions of Cl^- and made a big difference to the zeta potential at the same dosage.

In this work, a novel method to determine the point of zero net proton charge (PZNPC) of colloidal kaolinite in aqueous solutions was presented through the measurement of zeta potential of the particles in various concentrations of NaCl solution and the mathematic regression of the zeta potential versus pH curves. This method is based on the observation that there are two common intersection points (CIP) in the two curves of zeta potential versus pH of colloidal kaolinite with a low and a high NaCl concentration. The observation might be attributed to that NaCl would compress the electric double layer of kaolinite particles and affect the efficiency of the protonation/deprotonation of the HD-faces. The experimental result showed that the PZNPC of kaolinite is 5.37.

The interaction between cells and colloids is an important characteristic that influences cell behavior. Theoretically, much information could be revealed by analyzing the interactions in colloid–cell contact. In this study, in order to explore the interaction between cells and colloids, we developed a novel computational method able to obtain a zeta potential directly calculated from the force distance curve and apply to adhesion analysis, which used atomic force microscope (AFM), based on DLVO (Deryaguin–Landau–Verwey–Overbeek) theory and Mann Whitney U test, and combined with Zetasizer measurement. The calculation and analysis of $\zeta$ of the cell surfaces of ncyc-1324 yeast, ncyc-1681 yeast and Pseudomonas fluorescens showed that pH affected the electrostatic distribution on the cell surface. Compared with the previous research methods, this method significantly reduces the computation and manual control, which is an effective method for multi-element surface analysis and comparison. For example, the reverse calculation and curve fitting method will significantly request more computation and manual control to set up the reference force curve that simulated with set zeta potential, while this method only need to calculate on one force curve. The deconvolution of different adhesion events from force curves showed that the heterogeneity of cell surface can be significantly displayed. This provides a method for determining the complexity of the cell surface. Furthermore, this method was used to study the effect of amoxicillin on cell surface interaction, which showed that the cells surface forces were influenced even the medicine concentration is not enough to make significant influence on microbials optical observation appearance. Thus, AFM force analysis is a more sensitive method to research the medicine influence compared to the traditional method.

We present an experimental study on the electrofluidic transistor in this paper. A novel and easy way to integrate the transistor into a microchannel is developed. The performances of the insulating layer, especially the leakage current under gate voltage, are carefully characterized. The change of surface charge on silica surface by gate polarization is measured, however, by measuring the streaming current, the gating effect on zeta potential has not been observed. This result should imply new assumption in the understanding of the charge regulation in the electrical double layer under gate polarization.

The present investigation reports the acoustics and transport properties of a series of colloidal dispersion of nanocopper oxide in polyethylene glycol (PEG-400). The data are presented for five different CuO nanofluids of varying concentration in PEG prepared by the ultrasonication technique. The synthesized powder samples were characterized for their sizes and arrangement by X-ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), which shows the particulate size to be of nanoscale with elongated shape. Similarly, the size and stability of nanofluids were studied by zeta potential and particle size analysis. Besides, ultrasonic velocity, viscosity measurement show better dispersivity of nanoparticles and molecular environment of the nanofluids, whereas the enhanced thermal as well as electrical conductivities of nanofluids can make them suitable for use as heat transfer fluids.

By chemical modification of poly(maleic anhydride-alt-1-tetradecene) with different negatively and positively charged groups, we demonstrate how magnitude of zeta potential of encapsulated CdSe quantum dots and their sensitivity to pH can be tuned by varying type and proportion of the negatively and positively charged groups on the surface of quantum dots.

In this research, metal targets dipped in 3 mL of distilled water (DW) were subjected to pulsed laser ablation. Colloidal dispersions of Fe and Au, and bimetallic Fe@Au core/shell nanoparticles are created. The core/shell structure of these particles was subsequently studied using X-ray diffraction. UV–Vis and HRTEM measurements are used to determine surface Plasmon resonance (SPR) and particle sizes. We also carried out an investigation to gauge the stability in terms of the surface charge of the produced nanoparticles (Zeta-potential). The findings show that maximum absorption value of Fe Nps was 0.45 in the range (200–350) nm, while Au exhibits a surface Plasmon resonance (SPR) peaked at a wavelength of 545 nm in the range (290–1100) nm. Another peak was noticed at (555) nm for the surface Plasmon band of the particles Fe@Au in the range (290–1100) nm, HRTEM measurement was used to check the shape and particle size, and the results showed that the average particle size was less than 50 nm.

The purpose of this study is to optimize the Green synthesis of AgNPs using various quantities (0.5, 0.75, 1, 1.25, 1.5, 1.75 ml) of Ruta leaf extracts, the biosynthesized AgNPs were characterized using several methods such as UV-Vis spectrum, FTIR spectroscopy, X-ray diffraction (XRD), FESEM, EDX analysis, DLS and zeta potential. The examination of the visible and ultraviolet spectra revealed an absorption peak in the region of 405–420 nm. Through the use of Fourier Transform Infrared (FTIR) spectroscopy, the functional groups that were found in the Ruta plant extract were analyzed in order to locate the components that were accountable for reducing the silver nitrate. Through XRD, which occurs in the form of (111) lattice planes in the face-centered cubic (FCC) structure of metallic silver, the biosynthesized AgNPs were a semispherical shape with a nanoscale size ranging between 30–50 nm and moderately stable at −22.53 mV and −25.88 mV. From the results of the tests, it was found from results that the optimum value for the extract volume is (1.5 ml) to show the optimal properties of silver nanoparticles.

In the UV-Vis spectra of pure light-scattering systems, there is an exponential relationship between absorbance and wavelength (A=Kλ^-n). Here, the exponent n is named as flocculation-coagulation parameter. In the present paper, the effects of different additives on the stability of poly(N,N′-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) microgel dispersion were studied in detail via this parameter. The results showed that the stability of the dispersion mainly comes from the ionization of pyridine groups, making the microgel positively charged on its surface. This was confirmed by the measurement of Zeta potential and the result of conductometric titration. The result of fluorescence analysis indicated that the hydrophobicity in the microgels is enhanced with the increase in total 4-VP unit content.

A one step chemical reduction process was used for the preparation of hydrophilic silver nanoparticles (AgNP) using silver nitrate, sodiumborohydride and polyvinylpyrolidone as stabilizer. In the case of hydrophobic silver nanoparticles reduced silver ions were stabilized with cetyl trimethylammonium bromide (CTAB). The resultant nano particles were characterized by absoption spectra and their interactions with cationic cobalt (QCoPz) and neutral magnesium (MgPz) porphyrazines in water and in organic medium were investigated by using UV-vis spectroscopy and zeta potential techniques. It is confirmed that both metalloporphyrazine molecules interact with silver nanoparticles in an effective manner. The possible arrangement of the porphyrazines on the surfaces of the hydrophilic and hydrophobic AgNPs has been also discussed according to obtained spectroscopic results. These well-characterized novel AgNP-metalloporphyrazine composites are expected to be useful in optical and catalytic applications.

This paper presents experimental and theoretical studies of the electroosmotic flow in microchannels. The current monitoring method is used to determine the average flow velocity and the ζ potential by measuring the current-time relationship during electrolyte displacement process. A rigorous mathematical model is developed to describe the electrokinetic transport phenomena in such displacement process. Experiments were carried out for the NaCl electrolyte to evaluate the electroosmotic velocity and the ζ potential under various experimental conditions. The theoretical predictions for the current-time relationship are compared with measured results.

Currently there exists a critical need within the military and homeland defense for highly sophisticated yet, small, lightweight portable sensors and detection systems for identifying and quantifying biological and biowarfare agents (BWA) in both liquid and aerosolized form. Our proposed BWA detection system is based upon Fourier Transform Infrared Spectroscopy (FTIR), where the main advantages of this approach are that it is reagentless, operates in heterogeneous aqueous environments, and provides fast detection and high sensitivity/selectivity to bacterial spores with minimal false alarms.

The key enabler to using FTIR for BWA detection is to develop selective and robust sampling protocols coupled to a miniaturized, portable FTIR unit. To that end, we have developed front-end liquid flow cells which incorporate electric field (E-Field) concentration methods for spores onto the surface of an Attenuated Total Reflection (ATR) IR crystal. IR spectra are presented which show collection and detection results with BG spores in water. The approaches we have developed take advantage of the fact that all spores are negatively charged in neutral pH solutions. Therefore, E-Field concentration of spores directly onto an ATR sampling element enables low level concentration measurements to be possible.

In vitro and in vivo biological performance of a P₂O₅-CaO-CaF₂ glass reinforced hydroxyapatite, GR-HA, and sintered hydroxyapatite, HA, were assessed. In vitro evaluation using MG63 osteoblast-like cells showed that GR-HA composites caused a delay in cell proliferation and a reduction OC expression compared to HA. Total DNA results were also affected. This in vitro biological behaviour may be explained in terms of different surface characteristics of GR-HA, namely higher dissolution rate than HA, more negative surface charge and higher hydrophobicity, as determined by zeta potential and wettability measurements. However, in vivo results obtained from push-out testing of implanted cylinders in the tibiae of Japanese rabbits clearly indicate that GR-HA composite is more osteoconductive than sintered HA. The in vivo response is discussed in terms of the presence of β and α-TCP phases in the microstructure of the GR-HA composite.