Small Silicon, Big Opportunities: The Development and Future of Colloidally‐Stable Monodisperse Silicon Nanocrystals

Abstract

Nanomaterials are becoming increasingly widespread in consumer technologies, but there is global concern about the toxicity of nanomaterials to humans and the environment as they move rapidly from the research laboratory to the market place. With this in mind, it makes sense to intensify the nanochemistry community's global research effort on the synthesis and study of nanoparticles that are purportedly "green". One potentially green nanoparticle that seems to be a most promising candidate in this context is silicon, whose appealing optical, optoelectronic, photonic, and biomedical attributes are recently gaining much attention. In this paper, we outline some of our recent contributions to the development of the growing field of silicon nanocrystals (ncSi) in order to stress the importance of continued study of ncSi as a green alternative to the archetypal semiconductor nanocrystals like CdSe, InAs, and PbS. While a variety of developments in synthetic methods, characterization techniques, and applications have been reported in recent years, the ability to prepare colloidally-stable monodisperse ncSi samples may prove to have the largest impact on the field, as it opens the door to study and access the tunable size-dependent properties of ncSi. Here, we summarize our recent contributions in size-separation methods to achieve monodisperse samples, the characterization of size-dependant property trends, the development of ncSi applications, and their potential impact on the promising future of ncSi.

Ultra-small fluorescent inorganic nanoparticles for bioimaging

“…44 single crystal and found a core-shell structure, 127 in the which the Au 49 core is surrounded by two groups of Au atoms. Qian and co-workers characterized the crystal structure of Au 25 (SR) 18 and Au 38 (SR) 24 nanoclusters, and found a similar core-shell structure. 91 An Au 25 (SR) 18 cluster 55 consists of an icosahedral Au 13 core and exterior 12 Au atoms in the form of six -RS-Au-RS-Au-RS-motifs.…”

“…Negishi and co-workers synthesized glutathione-protected Au nanoclusters and then fractionated them into 9 fractions, with the number of Au atoms ranging from 10 to 39 by PAGE analysis. 125 Among their Au nanoclusters, Au 25 (SG) 18 is the most stable one. 40 The size of fractionated metal clusters can be characterized by TEM, and their molecular weight can be measured by mass spectroscopy.…”

“…Fluorescent QDs include semiconducting nanoparticles from Groups IV (Si and Ge dots), [17][18][19][20] II-VI (CdE and ZnE, E = S, Se, and Te), III-V (InP), and I-III-VI (CuInS 2 , CuInSe 2 ), [21][22][23] in which the II-VI QDs (especially CdSe and CdTe based QDs) have been 10 extensively investigated as prototypes of semiconductor QDs due to their strong quantum confinement effects and high fluorescence QYs. II-VI colloidal fluorescent QDs can be prepared in organic solvents or aqueous solutions.…”

The Interplay of Quantum Confinement and Hydrogenation in Amorphous Silicon Quantum Dots

“…Silicon (Si) nanostructures are attracting considerable attention for a wide range of applications1, 2, 3, 4, 5, 6 due to their fascinating and highly complex properties 7, 8, 9. For instance, efficient photoluminescence (PL) from crystalline Si quantum dots (i.e., with diameter less than ≈5 nm) has been reported, which encourages their applications in optoelectronic devices such as light‐emitting diodes10 or in biomedical applications as fluorescent tags 11.…”

Non-wettable, Oxidation-Stable, Brightly Luminescent, Perfluorodecyl-Capped Silicon Nanocrystal Film

“…1,2 This activity transcends the utilization of top-down nanofabricated silicon for integration in the incredible shrinking world of more powerful and faster microelectronics. What is remarkable is the notable intensification of research on bottom-up synthesized forms of nanostructured silicon for everything other than microelectronics.…”