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Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
If the bound analyte molecule carries a charge opposite to that on the main carriers in the FET, then charge carriers accumulate under the bound analyte, causing an increase in the device conductivity. This mechanism is shown in Figure 9.14a, where a negatively charged molecule, such as DNA, binds to the P-type NW, causing a gathering of hole carriers and resulting in an increase in conductivity. In contrast, analytes with molecular charges the same as that of the main carriers in the FET lead to depletion of main carriers beneath the bound analyte, causing a decrease in conductivity. The latter case is shown in Figure 9.14b, where a positively charged molecule, such as a protein below its isoelectric point (pI), depletes the carriers upon binding to the NWs. The isoelectric point is the pH at which a particular molecule or surface carries no net electrical charge. P-type oxidized silicon nanowire: (a) without any target molecule bound to the receptor site; (b) with a positively charged target molecule bound to the receptor site, causing hole depletion in NW and decreasing its conductance; and (c) with a negatively charged target molecule bound to the receptor site, causing hole accumulation in NW and increasing its conductance.
Application of Nanotechnology in Pharmaceutical Sciences
Published in Rakesh K. Sindhu, Mansi Chitkara, Inderjeet Singh Sandhu, Nanotechnology, 2021
Rakesh K. Sindhu, Gagandeep Kaur, Arashmeet Kaur, Shivam Garg, Shantanu K. Yadav, Sumitra Singh
The entrapment efficiency of drugs and the drug-loading capacity depend on various factors such as solubility of the drugs in the matrix polymer and the presence of dispersion agent. The aforementioned factors are proportional to the interactions of the polymer with the drugs, attached functional groups such as ester and carboxylic acids, matrix composition as well as the molecular weights of the drugs [5–7]. The commonly used polymer is polyethylene glycol, which imparts a minimum loading capacity to the drug [8]. Mostly, the drug capacity is reached at the isoelectric point of the drug, particles, and macromolecules that are encapsulated in the layer of nanoparticles [9]. One of the efficient methods for loading small molecules is the ionic interaction between the matrix and the drug [10, 11].
Characterization Techniques for Bio-Nanocomposites
Published in Shrikaant Kulkarni, Neha Kanwar Rawat, A. K. Haghi, Green Chemistry and Green Engineering, 2020
The magnitude of the zeta potential measures the stability of the potential for given colloidal solution. If the particles in colloidal dispersion have a either too negative or positive zeta potential say + 30 mV, they have a tendency to repel one another, and don’t aggregate and settle. Such colloidal systems are considered as stable. Moreover, the particles having low zeta potential values tend to agglomerate and flocculate. The key factor that influences zeta potential is pH. A zeta potential value without a mention of pH is meaningless. The pH value at which the zeta potential is zero is called the isoelectric point. It is the value at which the given colloidal solution has the lowest stability. One more influential factor affecting zetametry measurement is the ionic strength. The zeta potential depends upon the kind and strength of ions that interact with the particle surface in solution. Thus, it is of vital importance to conduct experiments using an electrolyte (say NaCl) at low concentration.
The role of nanofluids in the performance augmentation for the solar collectors used in solar water heating
Published in International Journal of Ambient Energy, 2023
Markndeyulu Vuggirala, N. Alagappan, C. H. V. K. N. S. N. Moorthy
The variation in pH value changes the stability of dispersed nanoparticles and the surface of nanoparticles as shown in Table 2. The stability of nanoparticles is dependent on electrokinetic properties. The stability of nanoparticles is dependent on electrokinetic properties. The pH value can be differed by adding an acid or alkaline solution to the nanofluid, and it changes the nature of the nanoparticle. Change in pH value impacts the zeta potential value. Zeta potential is zero at the isoelectric point. At that point, there will be no electric charge or repulsive forces of nanoparticles where it tends to coagulate. To attain enhanced stability of nanofluids requires high repulsive forces, and at that point, nanofluids become unstable (Wen and Ding 2012; Hao et al. 2020).
Adsorption equilibrium, kinetics and thermodynamics studies of anionic methyl orange dye adsorption using chitosan-calcium chloride gel beads
Published in Chemical Engineering Communications, 2021
S. Y. Tay, V. L. Wong, S. S. Lim, I. L. R. Teo
CaCl2 aqueous solutions ranging from 0.005 M to 0.2 M were studied to determine the extent of the effect of Ca2+ ions on the adsorption of MO. All other parameters remained constant as indicated earlier and the extent of adsorption by CS-CaCl2 beads were observed. The CS beads treated with 0.005 M CaCl2 exhibited the highest equilibrium adsorption of MO at 13.86 mg/g and greatest dye uptake at 73.36% as elucidated in Figure 6. The adsorption efficiency of MO is directly related to the pH of CaCl2 solution. The isoelectric point of CS was reported at 6.3 (Popat et al. 2012). The isoelectric point (pI), is a specific pH where the CS is neutral and has a net zero charge. Among CaCl2 solutions, only the pH of 0.005M CaCl2 solution was above the pI value of CS. Motta et al. (2016) previously reported that an increase in pH would lead to deprotonation. This suggested that 0.005M CS-CaCl2 beads would have net negative charges on the surface resulting in more Ca2+ ions to attach onto. This directly allows effective electrostatic attraction between the positively charged CS beads surface and the negatively charged MO dye molecules. Hence, 0.005M CS-CaCl2 beads were selected as the potential bio-sorbents for MO dye adsorption in subsequent studies.
Photocatalytic decolorization of Basic Blue 41 using TiO2-Fe3O4-bentonite coating applied to ceramic in continuous system
Published in Chemical Engineering Communications, 2020
Restu Kartiko Widi, Inez Suciani, Emma Savitri, Rafael Reynaldi, Arief Budhyantoro
The charge on the surface of photocatalyst and dye molecules affects the decolorization process as the result of changing the pH solution. This correlation could be explained by the isoelectric point (pHIEP) of dye and point of zero charges of catalyst (pHZPC). Isoelectric point shows the degree of acidity (pH) when molecule charge is zero due to increasing proton or losing charge in an acid–base reaction. There were three situations to be argued. If solution pH is larger than pHIEP and pHZPC, a negative repulsive force occurs on dye molecules surface (1), if solution pH is smaller than pHIEP and pHZPC, a positive repulsive force is occurs (2), and if pH of solution is controlled between pHIEP and pHZPC, a strong driving force occurs between positive charge of catalyst and negative charge of dye ions (Ciesielczyk et al., 2011). This third condition leads color removal to increase because of the increasing of attraction force between photocatalyst and dye molecules.