StudentShare
Contact Us
Sign In / Sign Up for FREE
Search
Go to advanced search...
Free

2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers - Lab Report Example

Cite this document
Summary
This paper "2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers" describes an experiment where an investigation of how functionalization of macroscopic properties of a solid surface using a self-assembled monolayer (SAM) of molecules modify such properties was performed…
Download full paper File format: .doc, available for editing
GRAB THE BEST PAPER96.6% of users find it useful

Extract of sample "2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers"

Name: Course: Instructor: Date: Experiment: 2NANO4 Contact Angle Experiments On Self-Assembled Monolayers AIM The main objective of this lab experiment was to measure the angle between a liquid droplet and a metal surface using a CCD camera and optics. The other objective was to investigate how self-assembled monolayer (SAM) of molecules of alkanethiols and functionalized alkanethiols can significantly modify the wetting behaviour and surface energy of metal surfaces coated with these monolayers. INTRODUCTION Attachment of a monolayer to a metal surface can have a significant effect on both surface energy and the wetting behaviour of such surfaces. These effects can be observed when a liquid droplet placed on the surface changes in terms of contact angle made with the surface. Control of wetting behaviour of both liquids and solids by measurement of contact angle has some important industrial applications, such as establishment of how clean semiconductor wafers are, penetration of pesticides when applied to plants, waterproofing materials among many other fields of applications. When monolayers spontaneously form on a surface, they are termed as self-assembled. When a surface is exposed to SAM organic molecules, stable monolayers are formed on materials such as copper, gold, silver, mercury, silica, alumina, gallium arsenide and silicon. For the formation of a stable monolayer, there must be a bond between the adsorbing molecules and the substrate. These adsorbing molecules are randomly attached on the metal surface until no active sites are left uncovered, then the process of adsorption ends and the monolayer is formed. The contact angle ( is a measure of the energy of interaction between the solid and the liquid surface. A strong interaction between liquid molecules and solid molecules causes wetting of the surface. As the liquid spreads on the solid surface, the drop flattens and the contact angle reduces. A weaker interaction of liquid molecules and solid surface molecules is expected to produce a larger contact angle. The three forces that result from surface tension are surface tensions for solid-vapour interfacial free energy (), solid-liquid interfacial free energy () and liquid-vapour interfacial free energy (). Figure 1 below shows the geometry of these three forces acting on a liquid droplet. (a) Receding contact angle (b) Advancing contact angle Figure 1: Graphical representation of the three forces resulting from surface tension on a liquid droplet. The relationship between the three forces and the Young’s contact angle at thermodynamic equilibrium is described by Young’s equation: = If any there is a change in any of these three forces, it will be reflected by a change in contact angle. Practically, two contact angles are normally measured; the advancing angle and the receding angle. The advancing contact angle is the maximum angle between the substrate and the three-phase line for a liquid droplet where increase in volume would result in expansion of the droplet across the surface. On the other hand, the receding contact angle refers to the minimum contact angle that occurs just before the droplet contracts across the surface. In this experiment, an investigation of how functionalization of macroscopic properties of a solid surface using self-assembled monolayer (SAM) of molecules modify such properties was performed. Two tests were carried out, and in each test, both the receding and advancing contact angles were measured. PROCEDURE Refer to the manual “2NANO4 Contact angle experiments on self-assembled monolayers”, Pages 41-47. ANALYSIS OF RESULTS The figure 1 below shows an image of a water droplet on a silver plate that was measured during the experiment. Figure 1: An image showing a liquid droplet during the experiment A small liquid droplet tends to be spherical in shape since the formation of the sphere minimizes surface area. When a droplet comes into contact with a solid surface, this shape changes due to surface tension and gravity. If the liquid does not completely wet the solid surface, the droplet meets the surface at the tree-phase line with an angle referred to as the Young’s contact angle (. When the advancing angle of the first image was measured, the results reported in table 1 below were obtained. Table 1(a): Measurement of advancing angle of the liquid droplet Mole Fraction Advancing Angle Average Variance Standard Deviation 0.00 93.862 11.384 3.3741 0.25 77.300 0.310 0.5571 0.50 76.675 35.668 5.9722 0.75 67.432 2.416 1.5544 1.00 56.087 12.154 3.4863 The graph of mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol against the average advancing angle for these results is shown below. Figure 2: Average advancing angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol. Table 1(b): Linear Regression of Advancing Angle Slope m -34.167 91.355 Y-intercept b Standard error for m -34.167 91.355 Standard error for b Coefficient of determination -34.167 91.355 Standard error for Y-estimate F-statistic -34.167 91.355 Degrees of freedom Regressional sum of squares -34.167 91.355 Residual sum of squares For the same image, the receding angle was measured as well and the results tabulated as shown in table 2. Table 2(a): Measurement of receding angle of the liquid droplet Mole Fraction Receding Angle Average Variance Standard Deviation 0.00 94.537 34.404 5.866 0.25 86.054 2.470 1.572 0.50 76.300 9.414 3.068 0.75 66.282 4.731 2.175 1.00 63.681 45.536 6.748 Figure 3: Average receding angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol Table (2b): Linear Regression of Receding Angle Slope m -32.594 93.668 Y-intercept b Standard error for m -32.594 93.668 Standard error for b Coefficient of determination -32.594 93.668 Standard error for Y-estimate F-statistic -32.594 93.668 Degrees of freedom Regressional sum of squares -32.594 93.668 Residual sum of squares From the graphs in figure 2 and 3, it can be observed that the mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol has a significant effect on the value of both advancing and receding contact angles measured. As the mole fraction of the SAMs increases, both contact angles were reducing. When this experiment was repeated for the second time, the following results were obtained. Table 3(a): Measurement of advancing angle of the liquid droplet Mole Fraction Advancing Angle Average Variance Standard Deviation 0.00 103.098 8.462 2.909 0.25 67.187 47.195 6.870 0.50 68.152 2.627 1.621 0.75 46.549 15.861 3.983 1.00 27.591 0.005 0.067 Figure 4: Average advancing angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol. Table 3(b): Linear Regression of Advancing Angle Slope m -68.661 96.846 Y-intercept b Standard error for m -68.661 96.846 Standard error for b Coefficient of determination -68.661 96.846 Standard error for Y-estimate F-statistic -68.661 96.846 Degrees of freedom Regressional sum of squares -68.661 96.84 Residual sum of squares Table 4(a): Measurement of receding angle of the liquid droplet Mole Fraction Receding Angle Average Biased Variance Biased Standard Deviation 0.00 97.014 28.784 5.365 0.25 66.535 190.412 13.799 0.50 63.335 5.031 2.243 0.75 42.319 0.119 0.344 1.00 23.881 14.236 3.773 Figure 5: Average receding angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol Table 4(b): Linear Regression of Receding Angle Slope m -68.193 92.713 Y-intercept b Standard error for m -68.193 92.713 Standard error for b Coefficient of determination -68.193 92.713 Standard error for Y-estimate F-statistic -68.193 92.713 Degrees of freedom Regressional sum of squares -68.193 92.713 Residual sum of squares From the results shown in figure 4 and 5, a similar trend as that observed in the first test is encountered. Both advancing and receding contact angles reduce with increase in mole fraction of SEMs. However, in the second test, the slope is steeper (-68.193) than the value obtained in the first test (-34.167 and -32.594). The study of self-assembling system where a metal is placed in an alkanethiol or functionalized alkanethiols is one of the most studied area of nanotechnology. This is for the reason that biological molecules can be attached to alkanethiols and likewise to metal electrodes to be used as transducers in biosensors. The thiol group has a sulfur atom that has a strong affinity with a number of metals, forming stable bonds on the metal lattice. Van der Waals interactions that occur between neighboring carbon chains in alkanethiols that have long unbranched carbon chains with more than 8 carbons results in highly ordered monolayers. When the outermost surface of a material is derivitised by a monolayer, its wetting, cohesive, adhesion and electrical properties are modified, depending on the terminal group of the derivitizing monolayer molecules. QUESTIONS Question 1 & 2: see results section above. Question 3. Mercaptoundecanoic acid on silver surface makes the surface to be very hydrophilic while dodecanethiol renders the surface very hydrophobic. The two substrates have different surface energies, thus, the changing contact angles. Question 4 Theoretical contact angle is given by: Where: and are mole fractions monolayer 1 and 2 respectively and are the contact angles of the monolayer 1 and 2 respectively For the first test: Theoretical advancing contact angle = (0.25cos 77.3 + 0.75cos 67.4) = 69.93o Theoretical receding contact angle = (0.25cos 86.0 + 66.3cos 67.4) = 89.7o Question 5. The COOH functional group termination SAMs, the alkanethiol used was mercaptohexadecanoic acid. This provides a hydrophilic surface. Question 6. Figure 6: 11-mercaptoundecanoic SAMs assembled on the Ag surface(Hsu, Reinhoudt and Huskens). Conclusion The wetting characteristics of self-assembled monolayer surface of molecules of alkanethiols and functionalized alkanethiols was examined by measurement of contact angles. It was found that the mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol can significantly modify the wetting behaviour and surface energy of silver surfaces coated with these monolayers. There was agreement of experimentally measured values of advancing and receding contact angles and theoretically calculated values. Reference Read More

In this experiment, an investigation of how functionalization of macroscopic properties of a solid surface using self-assembled monolayer (SAM) of molecules modify such properties was performed. Two tests were carried out, and in each test, both the receding and advancing contact angles were measured. PROCEDURE Refer to the manual “2NANO4 Contact angle experiments on self-assembled monolayers”, Pages 41-47. ANALYSIS OF RESULTS The figure 1 below shows an image of a water droplet on a silver plate that was measured during the experiment.

Figure 1: An image showing a liquid droplet during the experiment A small liquid droplet tends to be spherical in shape since the formation of the sphere minimizes surface area. When a droplet comes into contact with a solid surface, this shape changes due to surface tension and gravity. If the liquid does not completely wet the solid surface, the droplet meets the surface at the tree-phase line with an angle referred to as the Young’s contact angle (. When the advancing angle of the first image was measured, the results reported in table 1 below were obtained.

Table 1(a): Measurement of advancing angle of the liquid droplet Mole Fraction Advancing Angle Average Variance Standard Deviation 0.00 93.862 11.384 3.3741 0.25 77.300 0.310 0.5571 0.50 76.675 35.668 5.9722 0.75 67.432 2.416 1.5544 1.00 56.087 12.154 3.4863 The graph of mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol against the average advancing angle for these results is shown below. Figure 2: Average advancing angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol.

Table 1(b): Linear Regression of Advancing Angle Slope m -34.167 91.355 Y-intercept b Standard error for m -34.167 91.355 Standard error for b Coefficient of determination -34.167 91.355 Standard error for Y-estimate F-statistic -34.167 91.355 Degrees of freedom Regressional sum of squares -34.167 91.355 Residual sum of squares For the same image, the receding angle was measured as well and the results tabulated as shown in table 2. Table 2(a): Measurement of receding angle of the liquid droplet Mole Fraction Receding Angle Average Variance Standard Deviation 0.00 94.537 34.404 5.866 0.25 86.054 2.470 1.572 0.50 76.300 9.414 3.068 0.75 66.282 4.731 2.175 1.00 63.681 45.536 6.748 Figure 3: Average receding angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol Table (2b): Linear Regression of Receding Angle Slope m -32.594 93.668 Y-intercept b Standard error for m -32.594 93.668 Standard error for b Coefficient of determination -32.594 93.668 Standard error for Y-estimate F-statistic -32.594 93.668 Degrees of freedom Regressional sum of squares -32.594 93.668 Residual sum of squares From the graphs in figure 2 and 3, it can be observed that the mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol has a significant effect on the value of both advancing and receding contact angles measured.

As the mole fraction of the SAMs increases, both contact angles were reducing. When this experiment was repeated for the second time, the following results were obtained. Table 3(a): Measurement of advancing angle of the liquid droplet Mole Fraction Advancing Angle Average Variance Standard Deviation 0.00 103.098 8.462 2.909 0.25 67.187 47.195 6.870 0.50 68.152 2.627 1.621 0.75 46.549 15.861 3.983 1.00 27.591 0.005 0.067 Figure 4: Average advancing angle with respect to mole fraction of 11-mercaptoundecanoic acid in 1-dodecanethiol.

Table 3(b): Linear Regression of Advancing Angle Slope m -68.661 96.846 Y-intercept b Standard error for m -68.661 96.846 Standard error for b Coefficient of determination -68.661 96.846 Standard error for Y-estimate F-statistic -68.661 96.846 Degrees of freedom Regressional sum of squares -68.661 96.84 Residual sum of squares Table 4(a): Measurement of receding angle of the liquid droplet Mole Fraction Receding Angle Average Biased Variance Biased Standard Deviation 0.00 97.014 28.784 5.365 0.25 66.535 190.412 13.799 0.50 63.335 5.031 2.243 0.75 42.319 0.119 0.344 1.00 23.881 14.236 3.

Read More
Cite this document
  • APA
  • MLA
  • CHICAGO
(2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers Lab Report Example | Topics and Well Written Essays - 1500 words, n.d.)
2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers Lab Report Example | Topics and Well Written Essays - 1500 words. https://studentshare.org/chemistry/2053982-lab-rreport
(2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers Lab Report Example | Topics and Well Written Essays - 1500 Words)
2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers Lab Report Example | Topics and Well Written Essays - 1500 Words. https://studentshare.org/chemistry/2053982-lab-rreport.
“2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers Lab Report Example | Topics and Well Written Essays - 1500 Words”. https://studentshare.org/chemistry/2053982-lab-rreport.
  • Cited: 0 times

CHECK THESE SAMPLES OF 2NaNO4 Contact Angle Experiments on Self-Assembled Monolayers

The Milgram Experiment Method

Title: The Milgram Experiment Tutor: Introduction Probably the most well known experiments in psychology the Milgram experiment took place in 1961-1962.... Literature review Most people would answer no, when ordered by a person in authority to deliver an electrical shock of 400-volts to another person, but Stanley Milgram conducted obedience experiments that showed results which were surprising.... experiments like this offer a disturbing and powerful look in the power of obedience and authority....
4 Pages (1000 words) Research Paper

Operations of a Digital Camera Company

Assembly Operation Assessment Name of the Institution Assembly Operation Assessment Strategic policy development and implementation has been predominantly considered a continuous process that involves the management in executing and evaluating the relevant strategic routes and refocusing energies on the highly significant corrective actions to ensure the alignment of the organizational operations towards the attainment of the desired results....
4 Pages (1000 words) Assignment

Atomic Force Microscope

Additionally, the researcher does not experimentally justify the direct link between the cytoskeleton and the force of transmission instead they concentrate in using other experiments in justifying the link.... Then they contacted an experiment for Variable-angle TIRFM.... This was meant to help calibrate the coupling angle using the depth of penetration of the evanescent wave.... They also found that the focal contact area also changed with the same magnitude....
3 Pages (750 words) Coursework

Incorporating Experimental Research Designs in Business Communication Research

This reveals that field experiments can be used in business management and decision-making.... So let us explore some actual applications of field experiments in the business context.... Field experiments engaged actual real-life setting of experimental manipulations within a natural environment in which business, economics and management research usually has considerable engagement because of its external validity to identify causation (Elsevier, 2009)....
6 Pages (1500 words) Essay

Exploring the Logic of Experimental Design

experiments involve observation of phenomena that is made to occur in strictly controlled environments and situations where one or more variables are dynamic and others are static.... hellip; experiments are conducted to determine and further the understanding about an entity, and the features that constitute its existence.... experiments are conducted by carrying out research studies, which attempt to put together information that is pertinent to the aims of the experiment....
4 Pages (1000 words) Assignment

Experimental Designs II

Experimental Design Name: Institution: Question #1 No.... 1 How many independent variables are in a 4 x 6 factorial design?... How many conditions (cells) are in this design?... A factor in a factorial design is a major independent variable, and in the example above, there are two factors with one factor having 4 levels and the other having 6 levels....
6 Pages (1500 words) Assignment

The Stanley Milgram Experiments and the Holocaust

The paper "The Stanley Milgram experiments and the Holocaust" analyses Milgram's experiments and their contribution to the understanding of genocide and basically tries to find out what drives people to commit wholesale murder.... I will also be evaluating other perspectives....
17 Pages (4250 words) Book Report/Review

Statapult (catapult) strike experiment

In addition, this lab is to discover the angle as well as the distance the ball will cover with that angle both experimentally and theoretically.... Afterwards, 6 trials of that best possible angle are done and checking done to see whether we are getting similar distances as those we obtained theoretically.... After trials are done, the uncoded angle (1500) is then converted to coded angle (-0....
3 Pages (750 words) Essay
sponsored ads
We use cookies to create the best experience for you. Keep on browsing if you are OK with that, or find out how to manage cookies.
Contact Us