Nitrogen-doped carbon quantum dots as fluorescent probe for "off-on" detection of mercury ions, l-cysteine and iodide ions.

See more Carbon products. Carbon (atomic symbol: C, atomic number: 6) is a Block P, Group 14, Period 2 element. The number of electrons in each of Carbon's shells is 2, 4 and its electron configuration is [He]2s² 2p². In its elemental form, carbon can take various physical forms (known as allotropes) based on the type of bonds between carbon atoms; the most well known allotropes are diamond, graphite, amorphous carbon, glassy carbon, and nanostructured forms such as carbon nanotubes, fullerenes, and nanofibers . Carbon is at the same time one of the softest (as graphite) and hardest (as diamond) materials found in nature. It is the 15th most abundant element in the Earth's crust, and the fourth most abundant element (by mass) in the universe after hydrogen, helium, and oxygen. Carbon was discovered by the Egyptians and Sumerians circa 3750 BC. It was first recognized as an element by Antoine Lavoisier in 1789.

See more Mercury products. Mercury (atomic symbol: Hg, atomic number: 80) is a Block D, Group 12, Period 6 element with an atomic weight of 200.59. The number of electrons in each of mercury's shells is 2, 8, 18,32, 18, 2 and its electron configuration is [Xe] 4f¹⁴ 5d¹⁰ 6s². The mercury atom has a radius of 151 pm and a Van der Waals radius of 209 pm. It is named after the planet Mercury and often referred to as "quicksilver" due to its appearance as a silvery liquid. Mercury has low melting and boiling points. It is a poor conductor of heat, but a fair conductor of electricity. Mercury is found both as a free element and in cinnabar, corderoite, and livingstonite ores.

See more Iodine products. Iodine (atomic symbol: I, atomic number: 53) is a Block P, Group 17, Period 5 element with an atomic radius of 126.90447. The number of electrons in each of Iodine's shells is 2, 8, 18, 18, 7 and its electron configuration is [Kr] 4d¹⁰ 5s² 5p⁵. The iodine atom has a radius of 140 pm and a Van der Waals radius of 198 pm. In its elemental form, iodine has a lustrous metallic gray appearance as a solid and a violet appearance as a gas or liquid solution. Iodine forms compounds with many elements, but is less active than the other halogens. It dissolves readily in chloroform, carbon tetrachloride, or carbon disulfide. Iodine compounds are important in organic chemistry and very useful in the field of medicine. Iodine was discovered and first isolated by Bernard Courtois in 1811. The name Iodine is derived from the Greek word "iodes" meaning violet.