Functionalizing Surface Electrical Potential of Hydroxyapatite Coatings

2016 ◽  
Vol 102 ◽  
pp. 12-17 ◽  
Author(s):  
Liene Pluduma ◽  
Edijs Freimanis ◽  
Kārlis Gross ◽  
Heli Koivuluoto ◽  
Kent Algate ◽  
...  
Keyword(s):  
Surface Potential ◽  
Electrical Potential ◽  
Biological Response ◽  
Ion Concentration ◽  
Related Gene ◽  
Kelvin Probe ◽  
Hydroxyapatite Coatings ◽  
Hydroxyl Ion ◽  
Considerable Work ◽  
Osteoblast Attachment

While considerable work has been done on chemically functionalizing hydroxyapatite, little has been done on tailoring the electrical surface potential. This has been due to limitations in the available methods to impart a surface charge. Work to date has charged conventionally manufactured hydroxyapatite exhibiting a random crystal orientation. At the outset, the microstructure has not been optimized for the highest surface potential. The aim of this work was to both orient the crystals as well as fill the structure with hydroxyl ions for further increasing the surface electrical potential. We used hydroxyapatite coatings with the same topography, but different hydroxyl ion concentration; this altered the surface potential that was measured by Kelvin probe AFM. Results indicate that a greater hydroxyl ion concentration increases the surface potential of the hydroxyapatite coating. Coatings with a higher surface potential showed improved biological response, measured as osteoblast attachment and osteoblast related gene expression.

scholarly journals Structural and Chemical Hierarchy in Hydroxyapatite Coatings

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4447
Author(s):  
Karlis A. Gross ◽  
Christiane Petzold ◽  
Liene Pluduma-LaFarge ◽  
Maris Kumermanis ◽  
Håvard J. Haugen
Keyword(s):  
Electrical Potential ◽  
Building Blocks ◽  
X Ray Diffraction ◽  
Kelvin Probe ◽  
Structural Variations ◽  
Homogeneous Microstructure ◽  
Structural Hierarchy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Hydroxyapatite Coatings

Hydroxyapatite coatings need similarly shaped splats as building blocks and then a homogeneous microstructure to unravel the structural and chemical hierarchy for more refined improvements to implant surfaces. Coatings were thermally sprayed with differently sized powders (20–40, 40–63 and 63–80 µm) to produce flattened homogeneous splats. The surface was characterized for splat shape by profilometry and Atomic force microscopy (AFM), crystal size by AFM, crystal orientation by X-ray diffraction (XRD) and structural variations by XRD. Chemical composition was assessed by phase analysis, but variations in chemistry were detected by XRD and Raman spectroscopy. The resulting surface electrical potential was measured by Kelvin probe AFM. Five levels of structural hierarchy were suggested: the coating, the splat, oriented crystals, alternate layers of oxyapatite and hydroxyapatite (HAp) and the suggested anion orientation. Chemical hierarchy was present over a lower range of order for smaller splats. Coatings made from smaller splats exhibited a greater electrical potential, inferred to arise from oxyapatite, and supplemented by ordered OH− ions in a rehydroxylated surface layer. A model has been proposed to show the influence of structural hierarchy on the electrical surface potential. Structural hierarchy is proposed as a means to further refine the properties of implant surfaces.

Hydrothermal Processing for Increasing the Hydroxyl Ion Concentration in Hydroxyl Depleted Hydroxyapatite

2018 ◽  
Vol 762 ◽  
pp. 42-47
Author(s):  
Darta Ubele ◽  
Liene Pluduma ◽  
Karlis Agris Gross ◽  
Arturs Viksna
Keyword(s):  
Thermal Spraying ◽  
Ion Concentration ◽  
Hydrothermal Processing ◽  
X Ray Diffraction ◽  
Ion Content ◽  
X Ray ◽  
Hydroxyapatite Powder ◽  
Hydroxyapatite Coatings ◽  
Hydroxyl Ion ◽  
Thermally Sprayed

Thermal spraying is commercially used to produce hydroxyapatite coatings, but the high temperature depletes hydroxyl ions in the structure. To return hydroxyapatite to its original state, it is necessary to restore the hydroxyl ion content in the structure. In this work, the effect of hydrothermal treatment on the hydroxyl ions was investigated in hydroxyapatite powder and thermally sprayed hydroxyapatite coatings. Samples were hydrothermally treated at 200 °C for 24 h and 48 h. Chemical phases were determined by X-ray diffraction, functional groups and hydroxyl ion concentration was examined by Fourier transform infra-red spectroscopy. Results showed that hydrothermal processing of hydroxyapatite coatings at 200 °C for 48 hours produced the greatest increase in the hydroxyl ion concentration by 29%.

Formation of Metal Silicide Nanodots on Ultrathin SiO2 for Floating Gate Application

2009 ◽  
Vol 154 ◽  
pp. 95-100 ◽  
Author(s):  
Seiichi Miyazaki ◽  
Mitsuhisa Ikeda ◽  
Katsunori Makihara ◽  
K. Shimanoe ◽  
R. Matsumoto
Keyword(s):  
Surface Potential ◽  
Room Temperature ◽  
Areal Density ◽  
Film Deposition ◽  
Floating Gate ◽  
Metal Silicide ◽  
Kelvin Probe ◽  
Measuring Surface ◽  
Surface Potential Measurements ◽  
Mis Capacitors

We demonstrated a new fabrication method of Pt- and Ni-silicide nanodots with an areal density of the order of ~1011 cm-2 on SiO2 through the process steps of ultrathin metal film deposition on pre-grown Si-QDs and subsequent remote H2 plasma treatments at room temperature. Verification of electrical separation among silicide nanodots was made by measuring surface potential changes due to electron injection and extraction using an AFM/Kelvin probe technique. Photoemission measurements confirm a deeper potential well of silicide nanodots than Si-QDs and a resultant superior charge retention was also verified by surface potential measurements after charging to and discharging. Also, the advantage in many electron storage per silicide nanodot was demonstrated in C-V characteristics of MIS capacitors with silicide nanodots FGs.

Zeolite Syntheses from Superalkaline Reaction Mixtures

1992 ◽  
Vol 57 (4) ◽  
pp. 788-793 ◽  
Author(s):  
Falk Fischer ◽  
Marianne Hadan ◽  
Günter Fiedrich
Keyword(s):  
Ir Spectroscopy ◽  
Crystalline Phase ◽  
Ion Concentration ◽  
Single Crystalline ◽  
Hydroxyl Ion ◽  
Type Zeolite

The synthesis of faujasite-type zeolite from superalkaline reaction mixtures are described. The contribution shows the influence of component K2O added in the system Na2O-Al2O3-SiO2-H2O with H2O/(K2O + Na2O) = 13-15. The reaction course was investigated in the range K2O/(K2O + Na2O) from about 0.07 to 0.5. Under used conditions it is quite possible to isolate faujasite-type zeolite as a single crystalline phase. By means of IR spectroscopy, low SiO2/Al2O3 ratios from 2.0 to 2.1 in the faujasite framework have been indicated. The low SiO2/Al2O3 ratios are interpreted by a higher stability of the Si-O-Al- than the Si-O-Si- bond with increasing hydroxyl ion concentration.

scholarly journals OPTIMIZATION OF TIME REACTION AND HYDROXIDE ION CONCENTRATION ON FLAVONOID SYNTHESIS FROM BENZALDEHYDE AND ITS DERIVATIVES

2010 ◽  
Vol 5 (2) ◽  
pp. 163-168 ◽  
Author(s):  
Sri Handayani ◽  
Sunarto, Sunarto, ◽  
Susila Kristianingrum
Keyword(s):  
Reaction Time ◽  
Optimum Concentration ◽  
Ion Concentration ◽  
Optimum Time ◽  
Hydroxide Ion ◽  
Synthesis Time ◽  
Flavonoid Synthesis ◽  
Hydroxyl Ion ◽  
Optimum Reaction ◽  
Time Of Reaction

The aim of this research is to determine the optimum time of reaction and concentration of hydroxide ion on chalcone, 4-methoxychalcone and 3,4-dimethoxychalcone synthesis. Chalcone and its derivatives were synthesized by dissolving KOH in ethanol followed by dropwise addition of acetophenone and benzaldehyde. Then, the mixture was stirred for several hours. Three benzaldehydes has been used, i.e : benzaldehyde, p-anysaldehyde and veratraldehyde. The time of reaction was varied for, 12, 18, 24, 30 and 36 hours. Furthermore, on the optimum reaction time for each benzaldehyde the hydroxyl ion concentration was varied from 5,7,9,11 and 13%(w/v). The results of this research suggested that the optimum time of chalchone synthesis was 12 hours, while, 4-methoxychalcone and 3,4-dimethoxychalcone were 30 hours. The optimum concentration of hydroxide ion of chalcone synthesis was 13% and for 4-methoxychalcone and 3,4-dimethoxychalcone were 11%. Keywords: Chalcone synthesis, time of reaction, hydroxide ion concentration.

The Effect of Strain on the Impedance and Surface Potential of Austenite in 304 Stainless Steels

2013 ◽  
Vol 749 ◽  
pp. 648-653
Author(s):  
Jin Peng Xie ◽  
Hong Yun Luo ◽  
Jin Long Lv
Keyword(s):  
Impedance Spectroscopy ◽  
Surface Potential ◽  
Dislocation Structure ◽  
304 Stainless Steel ◽  
Electrochemical Technique ◽  
Kelvin Probe ◽  
Aisi 304 Stainless Steel ◽  
Aisi 304 ◽  
Transmission Electron ◽  
Cellular Substructure

Local electrochemical technique was used to measure the impedance of austenite in AISI 304 stainless steel under tensile strain of 0%, 10%, 20%, 30%, 40%. Scanning Kelvin probe (SKP) technique was used to measure the potential distribution of the surface. The results showed that the impedance of the austenite declined with the increase of the strain and declined sharply under the strain of 30%. Potential of austenite decreased non-monotonously with increase of the strain. The potential reached the minimum under strain of 30% and then increased. Through the transmission electron microscope (TEM) results, plane dislocation pile-ups were observed in the grain boundary under the strain of 30% and transformed to cellular substructure structure and cell wall under 40%. Combined with the results of local electrochemistry impedance spectroscopy (LEIS) and surface potential, it may be concluded that it was the dislocation density and dislocation structure influence the impedance spectroscopy significantly, while surface potential was sensitive to the dislocation structure.

Active Transport by the Cecropia Midgut

1968 ◽  
Vol 48 (1) ◽  
pp. 25-37
Author(s):  
J. A. HASKELL ◽  
W. R. HARVEY ◽  
R. M. CLARK
Keyword(s):  
Developmental Stages ◽  
Potassium Concentration ◽  
Electrical Potential ◽  
Fourth Instar ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Systematic Effect ◽  
Nernst Equation ◽  
Hydrogen Ion Concentration ◽  
Intermediate Value

1. The electrical potential across the isolated midgut of five developmental stages of the Cecropia silkworm was studied by changing the concentration of single cations in solutions bathing each side of the midgut. The stages included feeding fourth-instar insects, insects moulting from the fourth to the fifth instar, feeding fifth-instar insects, insects which had evacuated their midguts, and insects spinning cocoons. 2. Average values of the initial maximal potential exhibited by the midgut in solutions containing K, Mg, and Ca but no Na, for the stages mentioned above, were 68, 83, 90, 124, and 2 mV., respectively. 3. In all of the developmental stages studied except the ‘spinning larva’, reducing the potassium concentration from 32 to 2 mM/l. on the blood-side of the isolated gut lowers the potential, on the lumen-side of the gut raises the potential and on both sides gives an intermediate value. 4. When the potential prior to a decrease in concentration of potassium on the blood-side is over 100 mV., the Nernst slope approaches 59 mV. 5. A tenfold reduction in the concentration of magnesium or the addition of 32 mM/l. sodium to the solutions bathing the isolated gut has no systematic effect on the potential. 6. A tenfold drop in the concentration of calcium in the solutions causes changes in the potential in the opposite direction from those predicted by the Nernst equation. 7. The pH of the midgut contents rises from early fourth instar to late fifth instar. The hydrogen-ion concentration of the blood is about 1000 times more than that of midgut contents in fifth-instar insects. 8. Neither synthetic ecdysone, partially purified natural ecdysone nor juvenile hormone has an effect on the potential or current of the isolated midgut over periods as long as 30 min.

Blood Gas Analysis

2011 ◽  
Author(s):  
Patrick Magee ◽  
Mark Tooley
Keyword(s):  
Electrical Potential ◽  
Physical Principle ◽  
Gas Analysis ◽  
The Other ◽  
Potential Difference ◽  
Ion Concentration ◽  
Blood Gas ◽  
Glass Membrane ◽  
Current Flows ◽  
Ph Electrode

A blood gas machine has electrodes to measure pH, pCO2 and pO2 and often measures Hb and some biochemistry as well [King et al. 2000]. Derived values from such a device include O2 saturation, O2 content, bicarbonate, base excess and total CO2. This is the Clarke electrode described in the previous section on gas analysers and is suitable for both respiratory and blood O2 analysis. A pH unit has been defined in Chapter 1 as. In words, this can be described as ‘the negative logarithm, to base ten, of the hydrogen ion concentration’. The physical principle on which the pH electrode is based depends on the fact that when a membrane separates two solutions of different [H+], a potential difference exists across the membrane. In a pH electrode, such a membrane is usually made of glass and the development of a potential difference between the two solutions is thought to be due to the migration of H+ into the glass matrix. If one solution consists of a standard [H+], the pH of the other solution can be estimated by measurement of the potential difference between them. The glass membrane used is selectively permeable to H+. No current flows in this device, which does not wear out, in contrast to the Clark electrode, in which current does flow and that does need periodic replacement. The pH measurement system is shown diagrammatically in Figure 17.1. It consists of two half cells. In one half it has an Ag/AgCl electrode and in the other a Hg/HgCl2 (calomel) electrode. Each electrode maintains a fixed electrical potential. The Ag/AgCl electrode is surrounded by a buffer solution of known pH, surrounded by the pH sensitive glass. Outside the glass membrane is the test solution, usually blood, whose pH is to be measured. It is the potential difference across the glass, between these two solutions, which is variable. The blood or other solution is separated from the calomel electrode by a porous plug and a potassium chloride salt bridge to minimise KCl diffusion. The potential difference across the system is about 60 mV per unit of pH change at 37◦C.

scholarly journals Measurement of electrostatic tip–sample interactions by time-domain Kelvin probe force microscopy

2020 ◽  
Vol 11 ◽  
pp. 911-921
Author(s):  
Christian Ritz ◽  
Tino Wagner ◽  
Andreas Stemmer
Keyword(s):  
Frequency Shift ◽  
Surface Potential ◽  
Electrostatic Force ◽  
Kelvin Probe Force Microscopy ◽  
Kelvin Probe ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alternative Approach ◽  
Dc Component ◽  
Lock In

Kelvin probe force microscopy is a scanning probe technique used to quantify the local electrostatic potential of a surface. In common implementations, the bias voltage between the tip and the sample is modulated. The resulting electrostatic force or force gradient is detected via lock-in techniques and canceled by adjusting the dc component of the tip–sample bias. This allows for an electrostatic characterization and simultaneously minimizes the electrostatic influence onto the topography measurement. However, a static contribution due to the bias modulation itself remains uncompensated, which can induce topographic height errors. Here, we demonstrate an alternative approach to find the surface potential without lock-in detection. Our method operates directly on the frequency-shift signal measured in frequency-modulated atomic force microscopy and continuously estimates the electrostatic influence due to the applied voltage modulation. This results in a continuous measurement of the local surface potential, the capacitance gradient, and the frequency shift induced by surface topography. In contrast to conventional techniques, the detection of the topography-induced frequency shift enables the compensation of all electrostatic influences, including the component arising from the bias modulation. This constitutes an important improvement over conventional techniques and paves the way for more reliable and accurate measurements of electrostatics and topography.

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