Synthesis, and Characterisation of Metallic and Non-Metallic Nanoparticle Systems for Use in Biomedical and Catalytic Applications

Dear Colleagues,

Research on metal nanoparticle systems is a very active and topical field in today’s research environment. The formation of metal nanoparticles and their characterization (usually under the subject heading of colloid science) have preoccupied scientists for over 160 years as a defined scientific discipline, since Michael Faraday demonstrated the existence (by accident) of gold colloids which are still on display in the Royal Institution of Great Britain (https://www.rigb.org/our-history/iconic-objects/iconic-objects-list/faraday-gold-colloids). Indeed, the fascination with colloidal matter has existed since ancient times, an example of this dating back to 1600, when the alchemist Paracelsus claimed that “aurum potabile” (drinkable gold) had amazing medicinal properties and the ability to cure all diseases. However, by the 18th century, the well-dispersed nature of these colloidal suspensions had already been identified by various individuals [1].

Faraday’s demonstration of the colloidal state in his red gold colloids led to more work by many other researchers in the late 19th and early 20th centuries. An excellent and vast summary of this historical colloid research has been provided by Harry Boyer Weiser in three volumes, which present the inorganic colloid chemistry of “The Colloidal Elements| (Volume 1), [1], “ The Hydrous Oxides and Hydroxides” (Volume 2) [2], and “The Colloidal Salts” (Volume 3) [3]. This series, especially Volume 1, describes fascinating and defining seminal research on a surprisingly wide range of metallic and non-metallic colloidal systems.

Following a lull in interest in these systems, a strongly renewed interest in metal colloid science area occurred in the late 20th century, persisting until now in the 21st century. “Nanotechnology” is the broader umbrella term  under which research into colloidal systems now falls along with many other genres of science which follow the nanotechnological theme. The use of the terms “nanoparticles” or “nanomaterials” has also entered the scientific parlance and has, it appears, overtaken the term “colloidal”. The invigoration of research in this area has come about because of the promise of the many diverse applications that such systems can potentially provide. One example is their use in biomedical applications, where metallic nanoparticles, bimetallic/alloy nanoparticles, metal oxide nanoparticles and magnetic nanoparticles are of use in bioimaging, biosensors, drug delivery to specific areas of the body, labelling of cells and gene delivery (amongst other areas) [4]. The potential uses of these nano-entities have even caught the fanciful and sensationalistic imagination of the film and television industry, which use the terms “nanobots” or “nanites” to refer to particles made of graphene of nanoscopic dimensions capable of curing diseases when inserted hypodermically into the body.  (https://en.wikipedia.org/wiki/Travelers_(TV_series).

Another very large area of research involving colloidal materials regards their use as heterogeneous nanocatalysts [5]. For such application, control of size, shape, particle morphology and compositions are key. It is also of interest to investigate suitable solid supports on which to immobilise such nanocrystals for catalytic purposes. Surface-Enhanced Raman Scattering (SERS), a phenomenon discovered in the 1970s, is a promising sensitive technique for the detection of a wide variety of species. The technique makes use of colloidal materials (especially silver, gold or copper) to construct SERS-active substrates. This is another very intensely researched area of colloid science, with the view to make a sensitive, robust and reproducible detection technique which has low limits of detection [6].

With all the research being carried out on nanoparticles notably in biomedical, food science and environment areas, their inherent safety of application has come under serious consideration.   Research into nanoparticles has also raised some  significant concerns about their overall “safety”, and this has stimulated discussion in this area [7].

Whatever their promise or their risks, researchers continue to make highly interesting advances in the fundamental science surrounding nanoparticles, continuously expanding the metals range being studied. It is, hence, the intention of this Special Issue to capture some of these most recent fundamental advances in the synthesis, characterisation and novel applications of metal nanoparticle systems. Many papers continue to be written about nanoparticles and colloids, especially on Pt, Pd and Au [8] nanoparticle systems, but less attention has been paid to some of the other precious metals such as Ru, Re, Rh, Ir and Os. This Special Issue welcomes original articles dealing with novel syntheses, characterisation and applications of colloidal dispersions of these metallic elements or bimetallic systems. In addition, this Special Issue also welcomes articles dealing with colloidal dispersions of non-metals such as S, Se and Te. The manuscripts detailing studies of the colloidally dispersed element under study are not restricted to the zero-oxidation state. As evident from Weiser’s volumes published in the 1930s [1–3], metal oxides and salts were studied in the colloidal state also, and this has continued to the present day; therefore, the scope of this Special Issue will also include them.  

As usual, any articles submitted to this Special Issue on nanoparticles will be subjected to robust peer review. Manuscripts dealing with the fundamental science of colloidal dispersions and their applications and reviews of nanoparticle systems can be submitted. We look forward to your contributions and hope to obtain papers on a broad selection of topics to make this a truly unique Special Issue.

1. Weiser, H. B., Inorganic Colloid Chemistry, The Colloidal Elements. John Wiley and Sons: USA, 1933; Vol. 1.
2. Weiser, H. B., Inorganic Colloid Chemistry, The Hydrous Oxides and Hydroxides. John Wiley and Sons: USA, 1935; Vol. 2.
3. Weiser, H. B., Inorganic Colloid Chemistry, The Colloidal Salts. John Wiley and Sons: USA, 1938; Vol. 3.
4. McNamara, K.; Tofail, S. A. M., Nanoparticles in biomedical applications. Advances in Physics: X 2017, 2, (1), 54-88.
5. Na, K.; Zhang, Q.; Somorjai, G. A., Colloidal Metal Nanocatalysts: Synthesis, Characterization, and Catalytic Applications. Journal of Cluster Science 2014, 25, (1), 83-114.
6. Mosier-Boss, A. P., Review of SERS Substrates for Chemical Sensing. Nanomaterials 2017, 7, (6).
7. Naseer, B.; Srivastava, G.; Qadri Ovais, S.; Faridi Soban, A.; Islam Rayees, U.; Younis, K., Importance and health hazards of nanoparticles used in the food industry. In Nanotechnology Reviews, 2018; Vol. 7, p 623.
8. Rodrigues, T. S.; Zhao, M.; Yang, T.-H.; Gilroy, K. D.; da Silva, A. G. M.; Camargo, P. H. C.; Xia, Y., Synthesis of Colloidal Metal Nanocrystals: A Comprehensive Review on the Reductants. Chemistry – A European Journal 2018, 24, (64), 16944-16963.

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• colloids
• nanoparticles
• metals
• non-metals
• characterisation (IR, TEM, AFM, SERS)
• lesser studied systems
• novel synthetic methods
• lesser studied metals
• rhenium
• rhodium
• ruthenium
• osmium
• iridium
• selenium
• sulfur
• tellurium
• rare earth oxide colloids
• radioactive colloids
• bimetallic colloids
• metal clusters
• novel applications