Gold chalcogenides are compounds formed between gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 and one of the chalcogen

Chalcogen

The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...

s, elements from group 16 of the periodic table

Periodic table

The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

: oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, sulfur

Sulfur

Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, selenium

Selenium

Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

, or tellurium.

• Gold(III) oxide
  Gold(III) oxide
  Gold oxide is the most stable oxide of gold. It is a red-brown, thermally unstable solid that decomposes at 160 °C. The hydrated form is weakly acidic and dissolves in concentrated alkali to form salts that are believed to contain the [Au4]− ion.Anhydrous AuO can be prepared by heating...
  
  , Au₂O₃. decomposes into gold and oxygen above 160 °C., and dissolves in concentrated alkalis to form solutions which probably contain the [Au(OH)₄]⁻ ion
• Gold(I) sulfide
  Gold(I) sulfide
  Gold sulfide is the inorganic compound with the formula Au2S. It is one of two principal sulfides of gold. Gold sulfides exist in nature as solid solutions with silver, which has the same covalent radius.-Structure and preparation:...
  
  , Au₂S. formed by passing hydrogen sulfide
  Hydrogen sulfide
  Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
  
   through solutions of gold(I) compounds
• Gold(III) sulfide, Au₂S₃. unstable in the presence of water
• Gold tellurides: Au₂Te₃, Au₃Te₅, and AuTe₂ (approximate formulæ) are known as non-stoichiometric compound
  Non-stoichiometric compound
  Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial...
  
  s. they show metallic conductivity. Au₃Te₅ is a superconductor at very low temperatures.

Natural gold tellurides, like calaverite

Calaverite

Calaverite, or gold telluride, is an uncommon telluride of gold, a metallic mineral with the chemical formula AuTe2, with approximately 3% of the gold replaced by silver. It was first discovered in Calaveras County, California in 1861, and was named for the county in 1868.The mineral often has a...

 AuTe₂ and sylvanite

Sylvanite

Sylvanite or silver gold telluride, Te2, is the most common telluride of gold.-Properties:The gold:silver ratio varies from 3:1 to 1:1. It is a metallic mineral with a color that ranges from a steely gray to almost white. It is closely related to calaverite, which is more purely gold telluride with...

 AgAuTe₄, are minor ores of gold (and tellurium).

A gold-sulfur bond is strong, not only involving inorganic sulfur ligands (S_x^2-) but also thiolates. Gold has a high electronegativity (2.4 on the Pauling scale  It forms moderately strong bonds to sulfur (126-146 kJ/mol). This bond is widely employed to attach biological linkers, functional groups and other molecules to Colloidal gold

Colloidal gold

Colloidal gold is a suspension of sub-micrometre-sized particles of gold in a fluid — usually water. The liquid is usually either an intense red colour , or a dirty yellowish colour ....

 nanoparticles for research purposes, especially live-cell microscopic imaging that depend on gold's surface plasmon resonance

Surface plasmon resonance

The excitation of surface plasmons by light is denoted as a surface plasmon resonance for planar surfaces or localized surface plasmon resonance for nanometer-sized metallic structures....

.