Steric hindrance: Stress in a molecular structure or assembly that arises
when oversized functional groups are forced into too small a
space such that exchange repulsion greatly reduces or exceeds
attractive interactions. Such stress can result in torsional strain.
Stokes shift: A decrease in energy between an absorbed photon and an
emitted photon (or scattered, in the case of Raman spectroscopy)
due to a simultaneous transition to a higher vibrational state and the
energy from the vibrational transition being subtracted from the
photon. Most materials exhibit a Stokes shift when emitting photons.
Sum-frequency generation (SFG): A nonlinear optical effect when two
photons of different frequencies combine to produce a photon of
the sum frequency when passed through a material.
Superhydrophobic surface: Highly hydrophobic surface with water
contact angles exceeding 150°.
Supramolecular chemistry: The study of chemical compounds comprised of a distinct number of cooperating molecules. Supramolecular machines are comprised of a “cooperating set” of
molecules and exploit intra- and intermolecular forces to complete a specialized task.
Surface functionalization: Deliberate attachment of specific molecules
to a surface in order to allow for the specific binding of a subsequent adsorbate.
Surface tension: The work done in increasing the area of a surface by
transporting a molecule from the bulk phase to that surface. A
measurement of the cohesion of like molecules at an interface.
The tendency of a surface to contract due to energetic factors.
Surfactant: Compounds that lower the surface tension of a liquid and
form micelles above the critical micelle concentration (CMC).
Surroundings (thermodynamic): When a system is defined, the surroundings are everything else in the universe that is not part of the
system.
System (thermodynamic): The specific region of interest (often the
material sample) when analyzing a physical or chemical process.
Thio-: A prefix that indicates an oxygen atom in the common compound
is instead sulfur. For example, ether has a general structure ROR′
and a thioether would have a general structure RSR′.
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Glossary
when oversized functional groups are forced into too small a
space such that exchange repulsion greatly reduces or exceeds
attractive interactions. Such stress can result in torsional strain.
Stokes shift: A decrease in energy between an absorbed photon and an
emitted photon (or scattered, in the case of Raman spectroscopy)
due to a simultaneous transition to a higher vibrational state and the
energy from the vibrational transition being subtracted from the
photon. Most materials exhibit a Stokes shift when emitting photons.
Sum-frequency generation (SFG): A nonlinear optical effect when two
photons of different frequencies combine to produce a photon of
the sum frequency when passed through a material.
Superhydrophobic surface: Highly hydrophobic surface with water
contact angles exceeding 150°.
Supramolecular chemistry: The study of chemical compounds comprised of a distinct number of cooperating molecules. Supramolecular machines are comprised of a “cooperating set” of
molecules and exploit intra- and intermolecular forces to complete a specialized task.
Surface functionalization: Deliberate attachment of specific molecules
to a surface in order to allow for the specific binding of a subsequent adsorbate.
Surface tension: The work done in increasing the area of a surface by
transporting a molecule from the bulk phase to that surface. A
measurement of the cohesion of like molecules at an interface.
The tendency of a surface to contract due to energetic factors.
Surfactant: Compounds that lower the surface tension of a liquid and
form micelles above the critical micelle concentration (CMC).
Surroundings (thermodynamic): When a system is defined, the surroundings are everything else in the universe that is not part of the
system.
System (thermodynamic): The specific region of interest (often the
material sample) when analyzing a physical or chemical process.
Thio-: A prefix that indicates an oxygen atom in the common compound
is instead sulfur. For example, ether has a general structure ROR′
and a thioether would have a general structure RSR′.
456
Glossary