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It has been 150 years since Dmitri Mendeleev first published his Periodic Table of the Elements. Since then, the iconic image has become a vital tool for everyone learning and working in science.
Mendeleev first arranged the elements in order of increasing relative atomic mass beginning with the lightest element of all – hydrogen. He noticed a repeating trend in the chemical properties of the elements and their compounds, so he rearranged them, putting those with similar properties into groups below each other, leaving gaps for as yet undiscovered elements.
Inquisitive scientists have learned so much more about the elements adorning the Periodic Table since 1869 and discovered many more of Mendeleev’s predicted elements. Knowledge of the Periodic Table is vital to understanding and enhancing the properties of the high-tech materials science has developed. It is often forgotten that they derive from this iconic arrangement.
As science has progressed, things have become smaller, and we have developed nanoparticles, minute objects ranging in size from one to 100 nanometers. These nanoparticles differ from their elemental bulk versions and often show unexpected yet promising properties, making them of great scientific interest. They exhibit unpredicted optical properties; yellow gold and grey silicon both appear red at the nanoscale, for example. They are also much better at absorbing solar radiation and their high surface area to volume ratio makes them ideal catalysts. Furthermore, the addition of nanoparticles can enhance the properties to various day-to-day objects, for example, titanium oxide nanoparticles impart a self-cleaning effect and zinc oxide has superior UV blocking properties compared to the bulk material.
Let us take a closer look at some important nanoparticles which derive from the Periodic Table:
Carbon – atomic number 6
Carbon in the form of nanotubes is used in composites for vehicles, sports equipment and integrated circuits for electronic components. Consisting of a two-dimensional hexagonal lattice of carbon atoms bent and fused to form a cylinder, they convey excellent tensile strength and mechanical stiffness, reasonable chemical stability, high electrical conductivity and astonishing thermal conductivity.
Aluminium – atomic number 13
Nanosized aluminium can be employed to capture hydrocarbon impurities from the air, extract fluorine from various media and as a desiccant for drying gases and preserving equipment and instruments. It is also used as a sorbent of metal ions from solutions of their salts and radionuclides from the wastewater of nuclear power plants.
Titanium – atomic number 22
Depending on the size of the particle, titanium’s oxide can be found in sunscreen, cosmetics, paints and coatings. The naturally occurring oxide is used in almost two-thirds of all pigments, including food colouring E171 where it is used as a whitening and brightening agent, and also has the potential to aid contaminant removal from drinking water.
Iron – atomic number 26
Nanoscale iron has many potential uses including as a smart fluid for optic polishing and removing contaminants such as PCBs and chlorinated organic solvents from groundwater. It is highly reactive thanks to a large surface area to volume ratio and could have medical and laboratory applications.
Cobalt – atomic number 27
Nanoparticles of cobalt oxide have potential in lithium-ion batteries; anodes made of the oxide can readily and reversibly include lithium in their structure. They may also find use in electronic gas sensors to detect toluene, acetone and other organic vapours, and in medicine in hyperthermic treatment, gene therapy and drug delivery since they can readily enter cells.
Copper – atomic number 29
Historically, copper has been used as a colouring agent; as far back at the 9th Century it was used to colour glass and ceramics. Nowadays, it has applications in biomedicine as it exhibits catalytic, antifungal and antibacterial activities. It could be utilized as a biosensor or electrochemical sensor.
Silver – atomic number 47
Nano-silver is increasingly added to textiles, clothing and food packaging to eliminate bacteria thanks to its antibacterial properties. It is also gaining attention as a catalyst and biological research is focussing on its usage as a carrier for small drug molecules and large biomolecules, including chemotherapy medicines.
Cerium – atomic number 58
Cerium is a soft, ductile, silvery-white, rare earth-metal that can be cut with a knife. When oxidised it forms a pale yellow-white powder called cerium oxide, which can be used in electronics, biomedical supplies, energy and in fuel additives. Other uses include as a catalyst, in optics to decolourise glass by converting green-tinted ferrous impurities to colourless ferric oxides. It also exhibits antibacterial and antioxidant activity.
Platinum – atomic number 78
Platinum is usually found as a suspension of nanoparticles in water or a colloid of nanoparticles. It has potential application in catalysis, medicine, enzyme immobilization, electronics and optics.
Gold – atomic number 79
Like platinum, nano-gold is found as a suspension or colloid. It is the subject of substantial research, with potential applications in a wide variety of areas, including electron microscopy, electronics, nanotechnology, materials science and biomedicine.