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A self assembled monolayer (SAM) is an organized layer of amphiphilic molecules in which one end of the molecule, the “head group” shows a special affinity for a substrate. SAMs also consist of a tail with a functional group at the terminal end as seen in Figure 1.

SAMs are created by the chemisorption of hydrophilic “head groups” onto a substrate from either the vapor or liquid phase^[1] followed by a slow two-dimensional organization of hydrophobic “tail groups”.^[2] Initially, adsorbate molecules form either a disordered mass of molecules or form a “lying down phase”,^[1] and over a period of hours, begin to form crystalline or semicrystalline structures on the substrate surface.^[3]^[4] The hydrophilic “head groups” assemble together on the substrate, while the hydrophobic tail groups assemble far from the substrate. Areas of close-packed molecules nucleate and grow until the surface of the substrate is covered in a single monolayer.

Adsorbate molecules adsorb readily because they lower the surface energy of the substrate^[3] and are stable due to the strong chemisorption of the “head groups.” These bonds create monolayers that are more stable than the physisorbed bonds of Langmuir-Blodgett films.^[5]^[6] Thiol-metal bonds, for example, are on the order of 100 kJ/mol, making the bond stable in a wide variety of temperature, solvents, and potentials.^[4] The monolayer packs tightly due to van der Waals interactions,^[3]^[6] thereby reducing its own free energy.^[3] The adsorption can be described by the Langmuir adsorption isotherm if lateral interactions are neglected. If they cannot be neglected, the adsorption is better described by the Frumkin isotherm.^[4]

Types of SAMs

Selecting the type of head group depends on the application of the SAM.^[3] Typically, head groups are connected to an alkyl chain in which the terminal end can be functionalized (i.e. adding –OH, –NH3, or –COOH groups) to vary the wetting and interfacial properties.^[5]^[7] An appropriate substrate is chosen to react with the head group. Substrates can be planar surfaces, such as silicon and metals, or curved surfaces, such as nanoparticles. Thiols and disulfides are the most commonly used molecules for SAMs on noble metal substrates because of the strong affinity of sulfur for these metals. In addition, gold is an inert and biocompatible material that is easy to acquire. It is also easy to pattern via lithography, a useful feature for applications in nanoelectromechanical systems (NEMS).^[3] Additionally, it can withstand harsh chemical cleaning treatments.^[4] Silanes are generally used on nonmetallic oxide surfaces.^[3]

Preparation of SAMs

Metal substrates for use in SAMs can be produced through physical vapor deposition techniques, electrodeposition or electroless deposition.^[3] Alkanethiol SAMs produced by adsorption from solution are made by immersing a substrate into a dilute solution of alkane thiol in ethanol for 12 to 72 hours at room temperature and dried with nitrogen.^[3]^[4]^[8] SAMs can also be adsorbed from the vapor phase. For example, chlorosilane SAMs (which can also be adsorbed from the liquid phase), are often created in a reaction chamber by silanization in which silane vapor flows over the substrate to form the monolayer.^[9]

Characterization of SAMs

The structures of SAMs are most commonly determined using scanning probe microscopy techniques such as atomic force microscopy (AFM) and scanning tunneling microscopy (STM). More recently, however, diffractive methods have also been used.^[3] The structure can be used to characterize the kinetics and defects found on the monolayer surface. These techniques have also shown physical differences between SAMs with planar substrates and nanoparticle substrates.

Kinetics

There is evidence that SAM formation occurs in two steps, an initial fast step of adsorption and a second slower step of monolayer organization. Many of the SAM properties, such as thickness, are determined in the first few minutes. However, it may take hours for defects to be eliminated via annealing and for final SAM properties to be determined.^[1]^[4] The exact kinetics of SAM formation depends on the adsorbate, solvent and substrate properties. In general, however, the kinetics are dependent on both preparations conditions and material properties of the solvent, adsorbate and substrate.^[1] Specifically, kinetics for adsorption from a liquid solution are dependent on:^[3]

Temperature – room temperature preparation improves kinetics and reduces defects.
Concentration of adsorbate in the solution – low concentrations require longer immersion times^[3]^[4] and often create highly crystalline domains.^[4]
Purity of the adsorbate – impurities can affect the final physical properties of the SAM
Dirt or contamination on the substrate – imperfections can cause defects in the SAM

The final structure of the SAM is also dependent on the chain length and the structure of both the adsorbate and the substrate. Steric hindrance and metal substrate properties, for example, can affect the packing density of the film,^[3]^[4] while chain length affects SAM thickness.^[6]

Defects

Though the slow step in SAM formation often removes defects from the film, defects are included in the final SAM structure. Defects can be caused by both external and intrinsic factors. External factors include the cleanliness of the substrate, method of preparation, and purity of the adsorbates.^[3]^[4] SAMs intrinsically form defects due to the thermodynamics of formation. “The high coverage of the adsorbate present in the SAM is, in fact, thermodynamically unstable”.^[3]

Nanoparticle properties

The structure of SAMs is also dependent on the curvature of the substrate. SAMs on nanoparticles including colloids and nanocrystals, “stabilize the reactive surface of the particle and present organic functional groups at the particle-solvent interface”.^[3] These organic functional groups are useful for applications, such as immunoassays, that are dependent on chemical composition of the surface.^[3]

Patterning of SAMs

Three Strategies

1. Locally Attract

This first strategy involves locally depositing self-assembled monolayers on the surface only where the nanostructure will later be located. This strategy is advantageous because it involves high throughput methods that generally involve less steps than the other two strategies. The major techniques that use this strategy are^[10]:

Micro-Contact Printing

Micro-contact printing is analogous to printing ink with a rubber stamp. The SAM molecules are inked onto an pre-shaped elastomeric stamp with a solvent and transferred to the substrate surface by stamping. The SAM solution is applied to the entire stamp but only areas that make contact with the surface allow transfer of the SAMs. The transfer of the SAMs is a complex diffusion process that depends on the type of molecule, concentration, duration of contact, and pressure applied. Typical stamps use PDMS because its elastomeric properties, E = 1.8 MPa, allow it to fit the countour of micro surfaces and its low surface energy, γ = 21.6 dyn/cm². This is a parallel process and can thus place nanoscale objects over a large area in a short time.^[3]

Dip-Pen Nanolithography

Dip-pen nanolithography is a process that uses an atomic force microscope to transfer molecules on the tip to a substrate. Initially the tip is dipped into a reservoir with an ink. The ink on the tip evaporates and leaves the desired molecules attached to the tip. When the tip is brought into contact with the surface a water meniscus forms between the tip and the surface resulting in the diffusion of molecules from the tip to the surface. These tips can have radii in the tens of nanometers, and thus SAM molecules can be very precisely deposited onto a specific location of the surface. This process was discovered by Chad Mirkin and co-workers at Northwestern University.^[11]

2. Locally Remove

The locally remove strategy begins with covering the entire surface with a SAM. Then individual SAM molecules are removed from locations where the deposition of nanostructures is not desired. The end result is the same as in the locally attract strategy, the difference being in the way this is achieved. The major techniques that use this strategy are^[10]:

Scanning Tunneling Microscope

The scaning tunneling microscope can remove SAM molecules in many different ways. The first is to remove them mechanically by dragging the tip across the substrate surface. This is not the most desired technique as these tips are expensive and dragging them causes a lot of wear and reduction of the tip quality. The second way is to degrade or desorb the SAM molecules by shooting them with an electron beam. The scanning tunneling microscope can also remove SAMs by field desorption and field enhanced surface diffusion.^[10]

Atomic Force Microscope Assisted

The most common use of this technique is to remove the SAM molecules in a process called shaving, where the atomic force microscope tip is dragged along the surface mechanically removing the molecules. An atomic force microscope can also remove SAM molecules by local oxidation nanolithography.^[10]

Ultraviolet Light Irradiation

In this process UV light is projected onto the surface with a SAM through a pattern of apperatures in a chromium film. This leads to photo oxidation of the SAM molecules. These can then be washed away in a polar solvent. This process has 100nm resolutions and requires exposure time of 15-20 minutes.^[3]

3. Modify Tail Groups

The final strategy focuses not on the deposition or removal of SAMS, but the modification of terminal groups. In the first case the terminal group can be modified to remove functionality so that SAM molecule will be inert. In the same regards the terminal group can be modified to add functionality so it can accept different materials or have different properties than the original SAM terminal group. The major techniques that use this strategy are^[10]:

Focused Electron Beam and Ultraviolet Irradiation

Exposure to electron beams and UV light changes the terminal group chemistry. Some of the changes that can occur include the cleavage of bonds, the forming of double carbon bonds, cross-linking of adjacent molecules, fragmentation of molecules, and confromational disorder.^[3]

Atomic Force Microscope

A conductive AFM tip can create an electrochemical reaction that can change the terminal group.^[10]

Applications of Patterning SAMs

One of the Self-assembled monolayer's most useful applications is the deposition of nanostructures. SAMs are useful because each adsorbate molecule can be tailored to attract two different materials. Current techniques utilize the head to attract to a surface, like a plate of gold. The terminal group is then modified to attract a specific material like a particular nanoparticle, wire, ribbon, or other nano structure. In this way, wherever the a SAM is patterned to a surface there will be nano structure attaches to the tail groups.^[12] ^[10]

Applications of SAMs

Areas of application for SAMs include biology, electrochemistry and electronics, nanoelectromechanical systems (NEMS) and microelectromechanical systems (MEMS), and everyday household goods. SAMs can serve as models for studying membrane properties of cells and organelles and cell attachment on surfaces.^[3] SAMs can also be used to modify the surface properties of electrodes for electrochemistry, general electronics, and various NEMS and MEMS.^[3] For example, the properties of SAMs can be used to control electron transfer in electrochemistry.^[13] They can serve to protect metals from harsh chemicals and etchants. SAMs can also reduce sticking of NEMS and MEMS components in humid environments. In the same way, SAMs can alter the properties of glass. A common household product, Rain-X, utilizes SAMs to create a hydrophobic monolayer on car windshields to keep them clear of rain.

References

^ ^a ^b ^c ^d Schwartz, D.K., Mechanisms and Kinetics of Self-Assembled Monolayer Formation (2001). "Mechanisms and kinetics of self-assembled monolayer formation". Annu. Rev. Phys. Chem. 52: 107. doi:10.1146/annurev.physchem.52.1.107.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Wnek, Gary, Gary L. Bowlin (2004). Encyclopedia of Biomaterials and Biomedical Engineering. Informa Healthcare. pp. 1331–1333.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v Love; et al. (2005). "Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology". Chem. Rev. 105: 1103–1170. doi:10.1021/cr0300789. {{cite journal}}: Explicit use of et al. in: |author= (help)
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Vos, Johannes G., Robert J. Forster, Tia E. Keyes (2003). Interfacial Supramolecular Assemblies. Wiley. pp. 88–94.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ ^a ^b Madou, Marc (2002). Fundamentals of Microfabrication: The Science of Miniaturization. CRC. pp. 62–63.
^ ^a ^b ^c Kaifer, Angel (2001). Supramolecular Electrochemistry. Coral Gables. Wiley VCH. pp. 191–193.
^ Saliterman, Steven (2006). Self-assembled monolayers (SAMs). Fundamentals of BioMEMS and Medical Microdevices. SPIE Press. pp. 94–96.
^ Wysocki. "Self-Assembled Monolayers (SAMs) as Collision Surfaces for Ion Activation" (PDF).
^ Knieling, T; Lang, W; Benecke, W (2007). "Gas phase hydrophobisation of MEMS silicon structures with self-assembling monolayers for avoiding in-use sticking". Sensors and Actuators B. 126: 13–17. doi:10.1016/j.snb.2006.10.023.
^ ^a ^b ^c ^d ^e ^f ^g Seong, Jin Koh (2007). "Strategies for Controlled Placement of Nanoscale Building Blocks". Nanoscale Res Lett. 2: 519–545. doi:10.1007/s11671-007-9091-3.
^ Piner, R.D; Zhu, J; Xu, F; Hong, S; Mirkin, C.A (1999). ""Dip-Pen Nanolithography". Science. 283: 661–663.
^ Garcia, R.; Martinez, R.V; Martinez, J (2005). "Nano Chemistry and Scanning Probe Nanolithographies". Chemical Society Reviews. 35: 29–38. doi:10.1039/b501599p.
^ Lud, S.Q; Steenackers, M; Bruno, P; Gruen, D.M; Feulner, P; Garrido, J.A; Stutzmann, M (2006). "Chemical Grafting of Biphenyl Self-Assembled Monolayers on Ultrananocrystalline Diamond". Journal of the American Chemical Society. 128: 16884–16891. doi:10.1021/ja0657049. PMID 17177439.

@@ Line 4: / Line 4: @@
 [[Image:SAM schematic.jpeg|231px|thumb|right|Figure 1. Representation of a SAM structure]]
-SAMs are created by the [[chemisorption]] of hydrophilic “head groups” onto a substrate from either the vapor or liquid phase<ref name = "Schwartz">{{cite journal|author=Schwartz, D.K., Mechanisms and Kinetics of Self-Assembled Monolayer Formation|journal=Annu. Rev. Phys. Chem. |year=2001|volume=52|page=107|doi=10.1146/annurev.physchem.52.1.107|title=Mechanisms and kinetics of self-assembled monolayer formation}}</ref> followed by a slow two-dimensional organization of hydrophobic “tail groups”.<ref name = "Wnek">{{cite book|author=Wnek, Gary, Gary L. Bowlin|title=Encyclopedia of Biomaterials and Biomedical Engineering|publisher=Informa Healthcare|year=2004|pages=1331–1333}}</ref> Initially, adsorbate molecules form either a disordered mass of molecules or form a “lying down phase”,<ref name = "Schwartz" /> and over a period of hours, begin to form crystalline or semicrystalline structures on the substrate surface.<ref name = "Love">Love</ref><ref name = "Vos">{{cite book|author=Vos, Johannes G., Robert J. Forster, Tia E. Keyes|title=Interfacial Supramolecular Assemblies|publisher=Wiley|year=2003|pages=88–94}}</ref> The [[hydrophilic]] “head groups” assemble together on the substrate, while the [[hydrophobic]] tail groups assemble far from the substrate. Areas of close-packed molecules nucleate and grow until the surface of the substrate is covered in a single monolayer.
+SAMs are created by the [[chemisorption]] of hydrophilic “head groups” onto a substrate from either the vapor or liquid phase<ref name = "Schwartz">{{cite journal|author=Schwartz, D.K., Mechanisms and Kinetics of Self-Assembled Monolayer Formation|journal=Annu. Rev. Phys. Chem. |year=2001|volume=52|page=107|doi=10.1146/annurev.physchem.52.1.107|title=Mechanisms and kinetics of self-assembled monolayer formation}}</ref> followed by a slow two-dimensional organization of hydrophobic “tail groups”.<ref name = "Wnek">{{cite book|author=Wnek, Gary, Gary L. Bowlin|title=Encyclopedia of Biomaterials and Biomedical Engineering|publisher=Informa Healthcare|year=2004|pages=1331–1333}}</ref> Initially, adsorbate molecules form either a disordered mass of molecules or form a “lying down phase”,<ref name = "Schwartz" /> and over a period of hours, begin to form crystalline or semicrystalline structures on the substrate surface.<ref name = "Love">{{cite journal|author=Love ''et al.''|title= Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology|journal=Chem. Rev.|year=2005|volume=105|pages=1103–1170|doi=10.1021/cr0300789}}</ref><ref name = "Vos">{{cite book|author=Vos, Johannes G., Robert J. Forster, Tia E. Keyes|title=Interfacial Supramolecular Assemblies|publisher=Wiley|year=2003|pages=88–94}}</ref> The [[hydrophilic]] “head groups” assemble together on the substrate, while the [[hydrophobic]] tail groups assemble far from the substrate. Areas of close-packed molecules nucleate and grow until the surface of the substrate is covered in a single monolayer.
 Adsorbate molecules adsorb readily because they lower the surface energy of the substrate<ref name = "Love" /> and are stable due to the strong chemisorption of the “head groups.” These bonds create monolayers that are more stable than the physisorbed bonds of [[Langmuir-Blodgett films]].<ref name = "Madou">{{cite book|author=Madou, Marc|title=Fundamentals of Microfabrication: The Science of Miniaturization|publisher=CRC|year=2002|pages=62–63}}</ref><ref name = "Kaifer">{{cite book|author=Kaifer, Angel|title=Supramolecular Electrochemistry. Coral Gables|publisher=Wiley VCH|year=2001|pages=191–193}}</ref> Thiol-metal bonds, for example, are on the order of 100 kJ/mol, making the bond stable in a wide variety of temperature, solvents, and potentials.<ref name = "Vos" /> The monolayer packs tightly due to [[van der Waals interactions]],<ref name = "Love" /><ref name = "Kaifer" /> thereby reducing its own free energy.<ref name = "Love" /> The adsorption can be described by the [[Langmuir adsorption isotherm]] if lateral interactions are neglected. If they cannot be neglected, the adsorption is better described by the [[Alexander Frumkin|Frumkin]] isotherm.<ref name = "Vos" />
@@ Line 26: / Line 26: @@
 ===Defects===
-Though the slow step in SAM formation often removes defects from the film, defects are included in the final SAM structure. Defects can be caused by both external and intrinsic factors. External factors include the cleanliness of the substrate, method of preparation, and purity of the adsorbates.<ref name = "Love" /><ref name = "Vos" /> SAMs intrinsically form defects due to the thermodynamics of formation. “The high coverage of the adsorbate present in the SAM is, in fact, thermodynamically unstable”.<ref>Love, p. 1122</ref>
+Though the slow step in SAM formation often removes defects from the film, defects are included in the final SAM structure. Defects can be caused by both external and intrinsic factors. External factors include the cleanliness of the substrate, method of preparation, and purity of the adsorbates.<ref name = "Love" /><ref name = "Vos" /> SAMs intrinsically form defects due to the thermodynamics of formation. “The high coverage of the adsorbate present in the SAM is, in fact, thermodynamically unstable”.<ref name = "Love" />
 ===Nanoparticle properties===
-The structure of SAMs is also dependent on the curvature of the substrate. SAMs on nanoparticles including [[colloids]] and nanocrystals, “stabilize the reactive surface of the particle and present organic functional groups at the particle-solvent interface”.<ref>Love, p. 1128</ref> These organic functional groups are useful for applications, such as immunoassays, that are dependent on chemical composition of the surface.<ref name = "Love" />
+The structure of SAMs is also dependent on the curvature of the substrate. SAMs on nanoparticles including [[colloids]] and nanocrystals, “stabilize the reactive surface of the particle and present organic functional groups at the particle-solvent interface”.<ref name = "Love" /> These organic functional groups are useful for applications, such as immunoassays, that are dependent on chemical composition of the surface.<ref name = "Love" />
+==Patterning of SAMs==
+===Three Strategies===
+===='''1. Locally Attract'''====
+This first strategy involves locally depositing [[self-assembled monolayers]] on the surface only where the [[nanostructure]] will later be located. This strategy is advantageous because it involves high throughput methods that generally involve less steps than the other two strategies. The major techniques that use this strategy are<ref name = "Seong">{{cite journal|title=Strategies for Controlled Placement of Nanoscale Building Blocks|journal=Nanoscale Res Lett |year=2007|volume=2|pages=519–545|doi=10.1007/s11671-007-9091-3|author1=Seong, Jin Koh}}</ref>:
+*[[Micro-Contact Printing]]
+:[[Micro-contact printing]] is analogous to printing ink with a rubber stamp. The SAM molecules are inked onto an pre-shaped elastomeric stamp with a solvent and transferred to the substrate surface by stamping. The SAM solution is applied to the entire stamp but only areas that make contact with the surface allow transfer of the SAMs. The transfer of the SAMs is a complex diffusion process that depends on the type of molecule, concentration, duration of contact, and pressure applied. Typical stamps use PDMS because its elastomeric properties, E = 1.8 MPa, allow it to fit the countour of micro surfaces and its low surface energy, γ = 21.6 dyn/cm². This is a parallel process and can thus place nanoscale objects over a large area in a short time.<ref name = "Love" />
+*[[Dip-Pen Nanolithography]]
+:[[Dip-pen nanolithography]] is a process that uses an [[atomic force microscope]] to transfer molecules on the tip to a substrate. Initially the tip is dipped into a reservoir with an ink. The ink on the tip evaporates and leaves the desired molecules attached to the tip. When the tip is brought into contact with the surface a water meniscus forms between the tip and the surface resulting in the diffusion of molecules from the tip to the surface. These tips can have radii in the tens of nanometers, and thus SAM molecules can be very precisely deposited onto a specific location of the surface. This process was discovered by [[Chad Mirkin]] and co-workers at [[Northwestern University]].<ref>{{cite journal|title="Dip-Pen Nanolithography|journal=Science |year=1999|volume=283|pages=661–663|author1=Piner, R.D|author2=Zhu, J|author3=Xu, F|author4=Hong, S|author5=Mirkin, C.A}}</ref>
+===='''2. Locally Remove'''====
+The locally remove strategy begins with covering the entire surface with a SAM. Then individual SAM molecules are removed from locations where the deposition of [[nanostructures]] is not desired. The end result is the same as in the locally attract strategy, the difference being in the way this is achieved. The major techniques that use this strategy are<ref name = "Seong" />:
+*[[Scanning Tunneling Microscope]]
+:The [[scaning tunneling microscope]] can remove SAM molecules in many different ways. The first is to remove them mechanically by dragging the tip across the substrate surface. This is not the most desired technique as these tips are expensive and dragging them causes a lot of wear and reduction of the tip quality. The second way is to degrade or desorb the SAM molecules by shooting them with an electron beam. The [[scanning tunneling microscope]] can also remove SAMs by [[field desorption]] and field enhanced surface diffusion.<ref name = "Seong" />
+*[[Atomic Force Microscope]] Assisted
+:The most common use of this technique is to remove the SAM molecules in a process called shaving, where the [[atomic force microscope]] tip is dragged along the surface mechanically removing the molecules. An [[atomic force microscope]] can also remove SAM molecules by [[local oxidation nanolithography]].<ref name = "Seong" />
+*[[Ultraviolet]] Light Irradiation
+:In this process UV light is projected onto the surface with a SAM through a pattern of apperatures in a chromium film. This leads to photo oxidation of the SAM molecules. These can then be washed away in a polar solvent. This process has 100nm resolutions and requires exposure time of 15-20 minutes.<ref name = "Love" />
+===='''3. Modify Tail Groups'''====
+The final strategy focuses not on the deposition or removal of SAMS, but the modification of terminal groups. In the first case the terminal group can be modified to remove functionality so that SAM molecule will be inert. In the same regards the terminal group can be modified to add functionality so it can accept different materials or have different properties than the original SAM terminal group. The major techniques that use this strategy are<ref name = "Seong" />:
+*Focused Electron Beam and [[Ultraviolet]] Irradiation
+:Exposure to electron beams and UV light changes the terminal group chemistry. Some of the changes that can occur include the cleavage of bonds, the forming of double carbon bonds, cross-linking of adjacent molecules, fragmentation of molecules, and confromational disorder.<ref name = "Love" />
+*[[Atomic Force Microscope]]
+:A conductive AFM tip can create an electrochemical reaction that can change the terminal group.<ref name = "Seong" />
+===Applications of Patterning SAMs===
+One of the [[Self-assembled monolayer]]'s most useful applications is the deposition of [[nanostructure]]s. SAMs are useful because each adsorbate molecule can be tailored to attract two different materials. Current techniques utilize the head to attract to a surface, like a plate of gold. The terminal group is then modified to attract a specific material like a particular nanoparticle, wire, ribbon, or other nano structure. In this way, wherever the a SAM is patterned to a surface there will be nano structure attaches to the tail groups.<ref>{{cite journal|title=Nano Chemistry and Scanning Probe Nanolithographies|journal=Chemical Society Reviews |year=2005|volume=35|pages=29–38|doi=10.1039/b501599p|author1=Garcia, R.|author2=Martinez, R.V|author3=Martinez, J}}</ref> <ref name = "Seong" />
 ==Applications of SAMs==
 Areas of application for SAMs include biology, electrochemistry and electronics, [[nanoelectromechanical systems]] (NEMS) and [[microelectromechanical systems]] (MEMS), and everyday household goods. SAMs can serve as models for studying membrane properties of cells and organelles and cell attachment on surfaces.<ref name = "Love" /> SAMs can also be used to modify the surface properties of electrodes for electrochemistry, general electronics, and various NEMS and MEMS.<ref name = "Love" /> For example, the properties of SAMs can be used to control electron transfer in electrochemistry.<ref>{{cite journal|title=Chemical Grafting of Biphenyl Self-Assembled Monolayers on Ultrananocrystalline Diamond|journal=Journal of the American Chemical Society |year=2006|volume=128|pages=16884–16891|pmid=17177439|doi=10.1021/ja0657049|author1=Lud, S.Q|author2=Steenackers, M|author3=Bruno, P|author4=Gruen, D.M|author5=Feulner, P|author6=Garrido, J.A|author7=Stutzmann, M}}</ref> They can serve to protect metals from harsh chemicals and etchants. SAMs can also reduce sticking of NEMS and MEMS components in humid environments. In the same way, SAMs can alter the properties of glass. A common household product, Rain-X, utilizes SAMs to create a hydrophobic monolayer on car windshields to keep them clear of rain.
-==Notes==
-{{reflist|2}}
 ==References==
+{{reflist|colwidth=30em}}
-*{{cite journal|author=Love ''et al.''|title= Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology|journal=Chem. Rev.|year=2005|volume=105|pages=1103–1170|doi=10.1021/cr0300789}}
 ==Further reading==