Triglycine sulfate
Encyclopedia
Triglycine sulfate is a chemical compound with a formula (NH2CH2COOH)3·H2SO4. The empirical formula of TGS does not represent the molecular structure, which contains protonated glycine moieties and sulfate
ions. TGS with protons replaced by deuterium
is called deuterated TGS or DTGS; alternatively, DTGS may refer to doped TGS. TGS and DTGS crystals are pyroelectric
and ferroelectric
and have been used as detector elements in infrared spectroscopy
.
containing a greater than three-fold excess of glycine
. They belong to the polar space group
P21 and therefore are pyroelectric and ferroelectric at room temperature, exhibiting spontaneous polarization along the b-axis ([010] direction). The Curie temperature of the ferroelectric transition is 49 °C for TGS and 62 °C for DTGS. The crystal structure consists of SO42–, 2(N+H3CH2COOH) (G1 and G2 in the crystal-structure diagram), and N+H3CH2COO– (G3) species held together by hydrogen bond
s. These bonds are easily broken by the polar molecules of water that explains the hygroscopicity
of TGS – its crystals are easily etched by water. Along the b-axis, the G1-SO4 and G2-G3 layers are stacked alternately. The nearest two neighboring layers with identical chemical composition are rotated 180° around the b-axis against each other.
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
ions. TGS with protons replaced by deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
is called deuterated TGS or DTGS; alternatively, DTGS may refer to doped TGS. TGS and DTGS crystals are pyroelectric
Pyroelectricity
Pyroelectricity is the ability of certain materials to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, such that the polarization of the material changes. This polarization change...
and ferroelectric
Ferroelectricity
Ferroelectricity is a property of certain materials which possess a spontaneous electric polarization that can be reversed by the application of an external electric field. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was...
and have been used as detector elements in infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
.
Crystal structure and properties
TGS crystals may be formed by evaporation of an aqueous solution of sulfuric acidSulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
containing a greater than three-fold excess of glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
. They belong to the polar space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
P21 and therefore are pyroelectric and ferroelectric at room temperature, exhibiting spontaneous polarization along the b-axis ([010] direction). The Curie temperature of the ferroelectric transition is 49 °C for TGS and 62 °C for DTGS. The crystal structure consists of SO42–, 2(N+H3CH2COOH) (G1 and G2 in the crystal-structure diagram), and N+H3CH2COO– (G3) species held together by hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...
s. These bonds are easily broken by the polar molecules of water that explains the hygroscopicity
Hygroscopy
Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through either absorption or adsorption with the absorbing or adsorbing material becoming physically 'changed,' somewhat, by an increase in volume, stickiness, or other...
of TGS – its crystals are easily etched by water. Along the b-axis, the G1-SO4 and G2-G3 layers are stacked alternately. The nearest two neighboring layers with identical chemical composition are rotated 180° around the b-axis against each other.