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Updated: Jun 9, 2026
12:38
Soft Lithographic Functionalization and Patterning Oxide-free Silicon and Germanium
Published on: December 16, 2011
Terminal alkynes as an ink or background SAM in replacement lithography: adventitious versus directed replacement
Eric Z Tucker1, Christopher B Gorman
1Department of Chemistry, North Carolina State University, Box 8204, Raleigh, North Carolina 27695-8204, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 28, 2010
Summary
Researchers studied chemical exchange in self-assembled monolayers (SAMs) using scanning tunneling microscopy (STM). They found that the exchange mechanism varied, and STM tip-induced lithography enabled controlled exchange when natural processes were slow.
Area of Science:
- Surface science
- Nanotechnology
- Materials chemistry
Background:
- Self-assembled monolayers (SAMs) are crucial for surface functionalization.
- Understanding chemical exchange mechanisms in SAMs is key for advanced material design.
Purpose of the Study:
- To investigate the kinetics and mechanisms of chemical exchange in n-alkanethiol and terminal alkyne SAMs.
- To explore directed chemical exchange using scanning tunneling microscopy (STM) tip-induced lithography.
Main Methods:
- Formation of SAMs using n-alkanethiols and terminal alkynes.
- Exposure of SAMs to ferrocene-terminated thiols, thioacetates, and terminal alkynes.
- Monitoring chemical exchange rates and extent using scanning tunneling microscopy (STM).
- Application of STM tip-induced lithographic patterning (replacement lithography) for directed exchange.
Main Results:
- The rate and mechanism of chemical exchange were dependent on the specific SAM and incoming molecule.
- Rate constants for exchange were obtained by fitting data to various kinetic models.
- STM tip-induced lithography successfully directed chemical exchange in slow-exchange scenarios.
- The extent of exchange in lithography was limited by tip-induced desorption, not the incoming molecule.
Conclusions:
- The mechanism of chemical exchange in SAMs is complex and influenced by molecular identity.
- STM tip-induced lithography offers a precise method for controlling surface chemical modifications.
- Tip-induced desorption is a critical factor in the efficiency of lithographic surface patterning.
Related Concept Videos
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:34Preparation of Alkynes: Dehydrohalogenation
Introduction
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:10Reduction of Alkynes to trans-Alkenes: Sodium in Liquid Ammonia
Alkynes can be reduced to trans-alkenes using sodium or lithium in liquid ammonia. The reaction, known as dissolving metal reduction, proceeds with an anti addition of hydrogen across the carbon–carbon triple bond to form the trans product. Since ammonia exists as a gas (bp = −33°C) at room temperature, the reaction is carried out at low temperatures using a mixture of dry ice (sublimes at −78°C) and acetone.
When dissolved in liquid ammonia, an alkali metal, such as sodium, dissociates into a...
When dissolved in liquid ammonia, an alkali metal, such as sodium, dissociates into a...
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
02:42Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.