Open access

Introductory Chapter: Overview of the Properties and Applications of Noble and Precious Metals

Written By

Mohindar S. Seehra and Alan D. Bristow

Published: 04 July 2018

DOI: 10.5772/intechopen.75503

From the Edited Volume

Noble and Precious Metals - Properties, Nanoscale Effects and Applications

Edited by Mohindar Singh Seehra and Alan D. Bristow

Chapter metrics overview

1,943 Chapter Downloads

View Full Metrics

1. Introduction

The noble and precious metals correspond to a selection of the transition-metal group of the periodic table (see Figure 1), including copper (Cu), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), iridium (Ir), osmium (Os), ruthenium (Ru), rhodium (Rh), and rhenium (Re). Pt also gives its name to a distinct subset of these elements, known as the platinum group, which include Ru, Rh, Pd, Os, Ir, and of course Pt. Additionally, Ru, Rh, Re, Os, and Ir are considered refractory metals—defined by melting points exceeding about 2000°C—along with several more abundant and commonly used transition metals, such as titanium (Ti), chromium (Cr), molybdenum (Mo), and tungsten (W). The noble and precious metals generally crystallize in the face-centered cubic (fcc) structure except for Ru, Re, and Os, which have the hexagonal close-packed (hcp) structure. The use of Cu, Ag, Au, and Pt in jewelry and coinage has been known throughout human history. The chapters presented in this book deal with other applications of some of these metals along with their fundamental properties.

Figure 1.

Section of the periodic table corresponding to precious and noble metals, depicting atomic number chemical name and symbol.

This introductory chapter presents a survey of important properties and applications of noble and precious metals. These include properties at the nanoscale and their applications, particularly in the areas of catalysis and biomedicine. Only a brief mention of these properties is made, giving references to recent papers and reviews, which the readers can utilize to gain access to more comprehensive literature on the subject. The chapter is organized in sections with each section devoted to a single noble and precious metal.

Advertisement

2. Copper (Cu)

Being the most abundant and least expensive of the noble and precious metals, with excellent electrical and thermal conductivity, copper is used extensively in electrical power transmission, plumbing, cookware, etc. However, because of the reactivity of Cu toward oxygen, water, and other chemicals, synthesis of Cu nanoparticles (NPs) requires special procedures [1]. The synthesis and applications of Cu and Cu-based nanoparticles (NPs) to catalysis including gas-phase catalysis, electro-catalysis, and photocatalysis are reviewed by Gawande et al. [1]. The review paper by Din et al. [2] has described various methods for the synthesis of Cu NPs including chemical, physical, and biological methods. Medical applications of Cu NPs include their use as antibiotic, antifungal, and antimicrobial agents.

Advertisement

3. Silver (Ag)

The important properties of silver include its good electrical conductivity and its chemical stability. Bulk Ag is a common material for high-quality reflectors of electromagnetic radiation in the visible regime, superseding cheaper non-noble metals such as aluminum. On the nanoscale, Ag-NP applications include their catalytic activity and antimicrobial properties such as improving the microbial quality of drinking water [3]. Various methods for synthesizing Ag-NPs are described in the recent paper of Alaqad and Saleh [3]. Synthesis of metallic nanoparticles of Ag, Au, Pt, and Pd employing plant extracts is reviewed in the recent paper by Akhtar et al. [4]. Other review papers on the synthesis, applications, and toxicology of Ag-NPs are those by Iravani et al. [5] and Tran et al. [6]. Finally, Jo et al. [7] have reported ferromagnetism in Ag-NPs and associated it with the surface atoms on the Ag-NPs whose percentage concentration increases with decrease in particle size. In addition to extensive NP fabrication, nanoscale films of Ag have been grown using molecular beam epitaxy to improve the underdeveloped area of plasmonics [8], where optical excitation leads to a collective oscillation of electronic plasma in the metal.

Advertisement

4. Gold (Au)

Historically, accumulation of gold by people and nations has marked their economic wealth. Because of exceptional chemical stability and good electrical conductivity, gold is a good scientific material for contacts. Au is one of the best optical reflectors throughout the infrared region of the electromagnetic spectrum. Like many of the noble metals discussed here, its optical and dielectric constants can be found in both Johnson and Christy [9] and Palik [10].

Au-NPs exhibit a strong size-dependent position of a localized plasmon resonance and attracted considerable attention in recent years in technologies such as biomedicine (diagnosis, imaging, sensing), catalysis, and electronics. The review paper by Daniel and Astruc [11] and follow-up papers by Jain et al. [12], Huang et al. [13], and Piella et al. [14] are good sources for accessing literature on Au-NPs and their many applications. Another interesting aspect of Au-NPs is their size-dependent magnetic properties which are believed to originate from electron transfer between surface atoms of Au and capping agent (thiols) [15, 16]. The strength of ferromagnetic moment originating from this electron exchange at the surface varies as 1/D where D is the size of the particles. Furthermore, Au-NPs can be readily coated with dielectric materials to protect the metal from erosion due to photocatalyzing chemical reactions and provide a wider range of absorption energies for solar light harvesting [17].

Advertisement

5. Platinum (Pt)

Platinum is less abundant than Cu, Au, or Ag but has a similar place in history as the latter two as a material of value. Like the other metals, it is ductile and malleable but denser and harder to work. Pt is remarkably chemical unreactive, but as the electronic structure calculations of Andersen for Pt, Pd, Ir, and Rh show [18], Pt has a large free electron density, making it a good chemical catalyst. Pt is widely used in catalytic converters to oxidize carbon monoxide produced in internal combustion engines [19]. Pt is also used as contacts in situations that exploit the chemical stability, for example, at extreme temperatures or in salt water conditions [20]. It is also a versatile electrode in electrochemical experiments [21].

At the nanoscale, Pt NPs have also been engineered, primarily for catalytic applications [22]. Other potential applications of Pt NPs reported in literature are in cancer therapy [23, 24]. For size <5 nm of Pt NPs, observations of superparamagnetism [25] and ferromagnetism [26] have been reported.

Advertisement

6. Palladium (Pd)

Pd is a silvery white metal, and it is often found in deposits along with Pt as well as deposits of Ni and Cu. Pd is resistant to corrosion, and its alloys are used in jewelry as “white gold.” One of the distinguishing properties of Pd is its enormous capacity to absorb hydrogen in the ratio of about 900:1 by volume, making it an excellent catalyst for hydrogenation and dehydrogenation reaction [27]. The absorption of H2 leads to the reversible formation of PdHx.

Several groups have reported the synthesis of Pd NPs by different techniques [28, 29] and their various applications such as antimicrobial agents [30, 31] and for surface-enhanced Raman scattering [32, 33]. Regarding its magnetic properties, development of a ferromagnetic moment with decrease in particle size of Pd to nanoscale sizes has been reported by several groups and interpreted on a core-shell model [34, 35, 36, 37]. In this model, atoms in the core retain the properties of bulk Pd, whereas atoms in the shell develop a ferromagnetic feature due to reduced symmetry of the surface atoms and electron exchange with the capping agents.

Advertisement

7. Iridium (Ir)

Iridium is a silvery white metal with high resistance to corrosion, and it is very dense (density = 22.55 gm/cm3). In Earth’s crust, it is quite rare, about two parts per billion (ppb), and often found with other noble metals. As a metal, it is unworkable but finds use in space components and specialty spark plugs when alloyed with Pt. In recent years, nanoparticles of Ir have been synthesized using various chemical techniques [38, 39] and tested as catalysts [40, 41, 42] and as sensors [43, 44, 45]. Examples of catalytic activity are the use of Ir NPs for the degradation of dyes [38] and for hydrogenation reactions [41, 42]. As biosensors, Ir NPs have been tested for the detection of glucose [43, 44].

Advertisement

8. Osmium (Os)

Osmium is a member of platinum (Pt) group, and it is often found in ores of Pt. Like Ir, it is also very rare in Earth’s crust (~1 ppb) and has very high density (22.58 gm/cm3) and high melting point (~ 3000°C). Although Os is an unworkable metal, Os-Pt alloys are harder than Pt and are often used in specialty equipment. Its oxide, OsO4, is quite toxic to the respiratory system.

In recent years, there have been several reports on the synthesis of nanoparticles of Os [46, 47] and Os alloys for potential applications. Applications reported so far include the following: use of Ni-Ir and Ni-Os bimetallic NP alloys for hydrogenation reactions [48], Os NPs for CO oxidation [49, 50], and Os NP electro-catalysts for PEM fuel cells [51] and direct methanol fuel cells [52].

Advertisement

9. Ruthenium (Ru)

Ruthenium is normally found as a minor component of Pt ores, is chemically inert, and has a silvery color. Ru has the electron configuration of a 5s1 outer shell, making it more like Rh, Au, and Pt than the rest of its own group [iron (Fe), Os, and hassium (Hs)] which have an s2outer shell. In many respects Ru differs from Fe, except in the aqueous cations it can form. It marks a point in the periodic table that distinguishes the second and third rows, as well as the left and right sides of the block of transition metals.

At the level of less than 1% concentration, Ru can increase the hardness of Pt and Pd alloys, can markedly increase the corrosion resistance of titanium (Ti), [53] and is found in superalloys that operate in extreme high temperatures, such as in jet engine turbines [54]. Of course, like most noble and precious metals, Ru is a contact material that has comparable properties to Rh alloys achieved at a lower cost [54]. In particular, Ru can be found in dimensionally stable anodes and optode sensors operating in corrosive environments. Moreover, ReO2 and MReO3 (where M is a metal) compounds appear in electronics as thick-film resistors [55]. Other ruthenates appear in explorations of superconductivity, magnetism, and multiferroic prototypes. Although bulk Ru is a paramagnet at room temperature and when alloyed with molybdenum, it becomes a superconductor below 10.6 K [56]. Organometallic NPs and carbon-supported NPs containing Ru have been synthesized for application related to solar cells [57] and catalysis [58, 59]. There is a wide range of work on Ru in both homogeneous and heterogeneous catalyses and the synthesis of Ru NPs [47, 49, 50].

Advertisement

10. Rhodium (Rh)

Rhodium is hard, silvery-white transition metal that is both corrosion resistant and chemically inert. Rh is one of the rarest elements to be found on Earth, which slowed its uptake as anything other than a precious metal used for decoration in white-gold jewelry. Rh is now in common use, since the invention and legal requirement for three-way catalytic converters to reduce NOx produced in the exhaust of combustion engines [54]. Hence, the predominant use of Rh is in the automotive industry. There have been other applications, such as early-generation Rh-based neutron flux detectors and electrical contacts where economics meet the small electrical resistance requirements. Current alternative uses include coatings for optical instruments [60] and catalysis in biological applications [61, 62, 63]. Heterogeneous catalysis has also been advanced by the fabrication and use of bimetallic Rh-based core-shell nanoparticles [64]. Ferromagnetism in Rh NPs has been reported in Ref. [35].

Depending on how the automotive and other industries progress in the next few decades, new or recycled sources of Rh may be required. Recycling from electronic and catalytic industries seems promising. Alternatively, because Rh is a by-product of uranium-235 fission, reclamation from nuclear fuel waste may become commercially viable.

11. Rhenium (Re)

Rhenium has a melting point that is exceeded only by W and carbon (C). It is dense metal with a white-silver hue. Unlike many of the other noble metals, Re is more commonly extracted along with Mo than with Pt; hence, it is not part of the platinum group. Nonetheless, it has similar corrosion-resistant, high-temperature alloying advantages of much of that group. Once again, major applications are in extreme conditions Examples include Pt-Re alloys used for refining lead-free high-octane fuels where its inert properties avoid chemical degradation [65, 66] or W-Re and nickel-Re superalloys that withstand high temperatures as jet engine coatings [67]. W-Re alloys are more ductile at low temperature and more stable at high temperature, properties which also allow them to withstand electron impacts during the generation of X-rays and acting at thermocouples for extreme temperatures. In more recent years, metal–organic NPs containing Re has been explored for use in biological application [61] and to enhance catalysts [68]. The synthesis of Re NPs has been reported by Ayvali et al. [69] and Kundu et al. [70], the latter authors also reporting the applications of Re NPs in catalysis and surface-enhanced Raman scattering. Also, Re dichalcogenide films have been grown to study their electronic, optronic, and spintronic properties [71], extending the family of van der Waals-bonded transition-metal dichalcogenide which offer layer-by-layer tailoring of device properties.

12. Concluding remarks

As described above, noble and precious metals play essential roles in a wide range of technologies. Development of new coating materials, contacts, emitters, and catalysts is essential to better performances in engines, synfuels, and electrical components alike. Not only is material fabrication, especially at the nanoscale, an ongoing and vital area of research and development, so is the extraction, refining, and reclamation. One such example is the growing industry of metal recovery from the vast output of old products produced by the consumer electronic market. Similarly, transition-metal compounds are routinely at the center of new breakthroughs in fundamental physics that may one day lead to unthought of technologies. Regardless of the direction, the investigations into the properties and applications of these metals remains active, with more developments expected in the future.

References

  1. 1. Gawande MB, Goswani A, Felpin F, Asefa T, Huang X, Silva R, Zou X, Zboril R, Verma RS. Chemical Reviews. 2016;116:3722-3811
  2. 2. Din MI, Rihan R. Analytical Letters. 2017;50:50-62
  3. 3. Alaqad K, Saleh TA. Journal of Environmental & Analytical Toxicology. 2016;6:384 (10 pages)
  4. 4. Akhtar MS, Panwar J, Yun Y-S. ACS Sustainable Chemical Engineer. 2013;1:591-602
  5. 5. Iravani S, Korbekandi H, Mirmohammadi SV, Zolfaghari B. Research in Pharmaceutical Sciences. 2014;9:385-406
  6. 6. Tran QH, Nguyen VQ, Le A-T. Advances in Natural Sciences: Nanoscience and Nanotechnology. 2013;4:033001 (20 pages)
  7. 7. Jo Y, Jung MH, Kyum MC, Park KH, Kim YN. Journal of Magnetics. 2006;11:160-163
  8. 8. Sun L, Zhang C, Wang C-Y, Su P-H, Zhang M, Gwo S, Shih C-K, Li X, Wu Y. Scientific Reports. 2017;7:8917 (6 pages)
  9. 9. Johnson PB, Christy RW. Physical Review B. 1972;6:4370-4379
  10. 10. Palik ED. Handbook of optical constant of solids. Elsevier. 2012
  11. 11. Daniel M-C, Astruc D. Chemical Reviews. 2004;104:293-346
  12. 12. Jain PK, Lee KS, El-Sayed IH, El-Sayed MA. The Journal of Physical Chemistry. B. 2006;110:7238-7248
  13. 13. Huang X, El-Sayed MA. Journal of Advanced Research. 2010;1:13-28
  14. 14. Piella J, Bastus NG, Puntes V. Chemistry of Materials. 2016;28:1066-1075
  15. 15. Crespo P et al. Physical Review Letters. 2004;93:087204 (4 pages)
  16. 16. Dutta P, Pal S, Seehra MS, Anand M, Roberts CB. Applied Physics Letters. 2007;90:213102 (3 pages)
  17. 17. Li J, Cushing SK, Meng F, Senty TR, Bristow AD, Wu N. Nature Photonics. 2015;9:601-608
  18. 18. Krogh Andersen O. Physical Review B. 1970;2:883-906
  19. 19. Gerhard E. Angewandte Chemie. 2008;47:3524-3535
  20. 20. Lide DR. Handbook of Chemistry and Physics. Vol. 4. New York: CRC Press; 2007-2008. p. 26
  21. 21. Seehra MS, Bollineni S. International Journal of Hydrogen Energy. 2009;34:6078-6084
  22. 22. Long NV, Chien ND, Hayakawa T, Hirata H, Lakshminarayana G, Nogami M. Nanotechnology. 2009;21:035605
  23. 23. Porcel E et al. Nanotechnology. 2010;21:085103
  24. 24. Yamada M, Foote M, Prow TW. WIREs Nanomedicine and Nanobiotechnology. 2015;7:428-445
  25. 25. Litran R et al. Physics Review. 2006;B73:054404
  26. 26. Garcia MA et al. Chemistry of Materials. 2007;19:889-893
  27. 27. Bacik DB, Zhang M, Zhao D, Roberts CB, Seehra MS, Singh V, Shah N. Nanotechnology. 2012;23:294004 (13 pages)
  28. 28. Nadagouda MN, Verma RS. Green Chemistry. 2008;10:859-862
  29. 29. Sharada S, Suryawanshi PL, Kumar R, Gumfekar SP, Narsaiah TB, Sonawane SH. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2016;498:297-304
  30. 30. Hazarika M, Borah D, Bora P, Silva AR, Das P. PLoS One. 2017;12(9):e0184936
  31. 31. Saldan I, Semenyuk Y, Marchuk I, Reshetnyak O. Journal of Materials Science. 2015;50:2337-2354
  32. 32. Chen H, Wei G, Ispas A, Hickey SG, Eychmuller A. Journal of Physical Chemistry C. 2010;114:21976-21981
  33. 33. Xu D, Yan X, Diao P, Yin P, Phys J. Journal of Physical Chemistry C. 2014;118:9758-9768
  34. 34. Oba Y, Okamoto H, Sato T, Shinohara T, Suzuki J, Nakamura T, Muro T, Osawa H. Journal of Physics D: Applied Physics. 2008;41:134024 (5 pages)
  35. 35. Jeon YT, Lee GH. Journal of Applied Physics. 2008;103. DOI: 094313
  36. 36. Seehra MS, Rall JD, Liu JC, Roberts CB. Materials Letters. 2012;68:347-349
  37. 37. Shinohara T, Sato T, Taniyama T. Physical Review Letters. 2003;91:197201
  38. 38. Yee CK, Jordan R, Ulman A, White H, King A, Rafailovich M, Sokolov J. Langmuir. 1999;15:3486-3491
  39. 39. Rueping M, Koenigs RM, Borrmann R, Zoller J, Weirich TE, Mayer J. Chemistry of Materials. 2011;23:2008-2010
  40. 40. Goel A, Lasyal R. Water. Science and Technology. 2016;74:2551-2559
  41. 41. Liu D et al. Scientific Reports. 2016;6:21365
  42. 42. Redel E, Kramer J, Thomann R, Janiak C. Journal of Organometallic Chemistry. 2009;694:1069-1075
  43. 43. Zhou C, Shi Y, Ding X, Li M, Luo J, Lu Z, Xiao D. Analytical Chemistry. 2013;85:1171-1176
  44. 44. Shen J, Dudik L, Liu C-C. Sensors and Actuators B: Chemical. 2007;125:106-113
  45. 45. da Silva CP, Franzoi AC, Fernandes SC, Dupont J, Vieira IC. Enzyme and Microbial Technology. 2013;52:296-301
  46. 46. Pitto-Barry A, Perdigao LM, Walker M, Lawrence J, Costantini G, Sadler PJ, Barry NP. Dalton Transactions. 2015;44:20308-20311
  47. 47. Kramer J, Redel E, Thomann R, Janiak C. Organometallics. 2008;27:1976-1978
  48. 48. Egeberg A, Dietrich C, Kind C, Popescu R, Gerthsen D, Behrens S, Feldmann C. ChemCatChem. 2017;9:3534-3543
  49. 49. Liu C, Leong WK, Zhong Z. Journal of Organometallic Chemistry. 2009;694:2315-2318
  50. 50. Dimakis N, Navarro NE, Smotkin ES. The Journal of Chemical Physics. 2013;138:174704
  51. 51. Lam VWS, Gyenge EL. Journal of the Electrochemical Society. 2008;155:B1155-B1160
  52. 52. Borja-Arco E, Jimenez-Sandoval O, Escalante-Garcia J, Magallon-Cacho L, Sebastian PJ. International Journal of Electrochemistry. 2011:830541 (8 pages)
  53. 53. Schutz RW. Platinum Metals Review. 1996;40:54-61
  54. 54. Loferski PJ. 2014 Minerals Yearbook: Platinum-Group Metals. US Geological Survey; 2014 URL: https://minerals.usgs.gov/minerals/pubs/commodity/platinum/
  55. 55. Rane S, Prudenziati M, Morten B. Materials Letters. 2007;61:595-599
  56. 56. Rammakrishnan TV, Rao CNR. Superconductivity Today. University Press; 1999
  57. 57. Kuang D, Ito S, Wenger B, Klein C, Moser J-E, Humphry-Baker R, Zakeeruddin SM, Grätzel M. Journal of the American Chemical Society. 2006;128:4146-4154
  58. 58. Lara P, Philipott K, Chaudret B. ChemCatChem. 2013;5:28-45
  59. 59. Ohyama J, Sato T, Yamamoto Y, Arai S, Satsuma A. Journal of the American Chemical Society. 2013;135:8016-8021
  60. 60. Smith WJ. “Reflectors” in Modern Optical Engineering: The Design of Optical Systems. McGraw-Hill; 2007. pp. 247-248
  61. 61. Portenkirchner E, Oppelt K, Egbe DAM, Knör G, Sariçiftçi NS. Nanomaterials Engineering. 2013;2:134-147
  62. 62. Öhrström L. Nature Chemistry. 2016;8:90 (1-page)
  63. 63. Chen W-W, M-H Xu. Organic & Biomolecular Chemistry. 2017;15:1029-1050
  64. 64. Tao F, Grass ME, Zhang YW, Butcher DR, Renzas JR, Liu Z, Chung JY, Mun BS, Salmeron M, Samorjai GA. Science. 2008;322:932-934
  65. 65. Polyak DE. Minerals Yearbook: Rhenium. US Geological Survey; 2015, 2015 URL: https://minerals.usgs.gov/minerals/pubs/commodity/rhenium/myb1-2015-rheni.pdf
  66. 66. Kunkes EL et al. Journal of Catalysis. 2008;260:164-177
  67. 67. Naumov AV. Russian Journal of Non-Ferrous Metals. 2007;48:418-423
  68. 68. Martin-Aranda RM, Čejka J. Journal of Catalysis. 2010;53:141-153
  69. 69. Ayvali T et al. Chemical Communications. 2014;50:10809
  70. 70. Kundu S, Ma L, Dai W, Chen Y, Sinyukov AM, Liang H. ACS Sustainable Chemistry & Engineering. 2017;5:10186-10198
  71. 71. Hafeez M, Gan L, Bhatti AS, Zhai T. Materials Chemistry Frontiers. 2017;1:1917-1932

Written By

Mohindar S. Seehra and Alan D. Bristow

Published: 04 July 2018