Atomically precise pieces of matter of nanometer dimensions composed of noble metals are new categories of materials with many unusual properties. Over 100 molecules of this kind with formulas such as Au25(SR)18, Au38(SR)24, and Au102(SR)44 as well as Ag25(SR)18, Ag29(S2R)12, and Ag44(SR)30 (often with a few counterions to compensate charges) are known now. They can be made reproducibly with robust synthetic protocols, resulting in colored solutions, yielding powders or diffractable crystals. They are distinctly different from nanoparticles in their spectroscopic properties such as optical absorption and emission, showing well-defined features, just like molecules. They show isotopically resolved molecular ion peaks in mass spectra and provide diverse information when examined through multiple instrumental methods. Most important of these properties is luminescence, often in the visible–near-infrared window, useful in biological applications. Luminescence in the visible region, especially by clusters prot...

Atomically Precise Clusters of Noble Metals: Emerging Link between Atoms and Nanoparticles

Improving the knowledge of the relationship between structure and properties is fundamental in catalysis. Recently, researchers have developed a variety of well-controlled methods to synthesize atomically precise metal nanoclusters (NCs). NCs have shown high catalytic activity and unique selectivity in many catalytic reactions, which are related to their ultrasmall size, abundant unsaturated active sites, and unique electronic structure different from that of traditional nanoparticles (NPs). More importantly, because of their definite structure and monodispersity, they are used as model catalysts to reveal the correlation between catalyst performance and structure at the atomic scale. Therefore, this review aims to summarize the recent progress on NCs in catalysis and provide potential theoretical guidance for the rational design of high-performance catalysts. First a brief summary of the synthetic strategies and characterization methods of NCs is provided. Then the primary focus of this review—the model ...

Atomically Precise Noble Metal Nanoclusters as Efficient Catalysts: A Bridge between Structure and Properties.

Due to their atomically precise structures and intriguing chemical/physical properties, metal nanoclusters are an emerging class of modular nanomaterials. Photo-luminescence (PL) is one of their most fascinating properties, due to the plethora of promising PL-based applications, such as chemical sensing, bio-imaging, cell labeling, phototherapy, drug delivery, and so on. However, the PL of most current nanoclusters is still unsatisfactory-the PL quantum yield (QY) is relatively low (generally lower than 20%), the emission lifetimes are generally in the nanosecond range, and the emitted color is always red (emission wavelengths of above 630 nm). To address these shortcomings, several strategies have been adopted, and are reviewed herein: capped-ligand engineering, metallic kernel alloying, aggregation-induced emission, self-assembly of nanocluster building blocks into cluster-based networks, and adjustments on external environment factors. We further review promising applications of these fluorescent nanoclusters, with particular focus on their potential to impact the fields of chemical sensing, bio-imaging, and bio-labeling. Finally, scope for improvements and future perspectives of these novel nanomaterials are highlighted as well. Our intended audience is the broader scientific community interested in the fluorescence of metal nanoclusters, and our review hopefully opens up new horizons for these scientists to manipulate PL properties of nanoclusters. This review is based on publications available up to December 2018.

Tailoring the photoluminescence of atomically precise nanoclusters.

Redox catalysis, including photocatalysis and (photo)electrocatalysis, may alleviate global warming and energy crises by removing excess CO2 from the atmosphere and converting it to value-added resources. Nano-to-atomic two-dimensional (2D) materials, clusters and single atoms are superior catalysts because of their engineerable ultrathin/small dimensions and large surface areas and have attracted worldwide research interest. Given the current gap between research and applications in CO2 reduction, our review systematically and constructively discusses nano-to-atomic surface strategies for catalysts reported to date. This work is expected to drive and benefit future research to rationally design surface strategies with multi-parameter synergistic impacts on the selectivity, activity and stability of next-generation CO2 reduction catalysts, thus opening new avenues for sustainable solutions to climate change, energy and environmental issues, and the potential industrial economy.

Surface strategies for catalytic CO2 reduction: from two-dimensional materials to nanoclusters to single atoms

The discovery of carbon fullerene cages and their solids opened a new avenue to build materials from stable cage clusters as “artificial atoms” or “superatoms” instead of atoms. However, cage clust...

Endohedrally Doped Cage Clusters

This article adds a new direction to the functional capability of protein-protected atomically precise gold clusters as sensors. Counting on the extensively researched intense luminescence of these clusters and considering the electron donating nature of select amino acids, we introduce a dual probe sensor capable of sensing changes in luminescence and conductivity, utilizing bovine serum albumin-protected atomically precise gold clusters hosted on nanofibers. To this end, we have also developed a hybrid nanofiber with a conducting core with a porous dielectric shell. We show that clusters in combination with nanofibers offer a highly selective and sensitive platform for the detection of trace quantities of trinitrotoluene, both in solution and in the vapor phase. In the solution phase, trinitrotoluene (TNT) can be detected down to 1 ppt at room temperature, whereas in vapor phase, 4.8 × 109 molecules of TNT can be sensed using a 1 mm fiber. Although the development in electrospinning techniques for fabri...

https://pubs.acs.org/doi/pdf/10.1021/acsomega.7b01219

Dual Probe Sensors Using Atomically Precise Noble Metal Clusters

Here, we report the synthesis of two new hydride and phosphine coprotected clusters [Ag15H13(DPPH)5]2+ (DPPH = 1,6-bis(diphenylphosphino)hexane) and [Ag27H22(DPPB)7]3+ (DPPB = 1,4-bis(diphenylphosp...

[Ag15H13(DPPH)5]2+ and [Ag27H22(DPPB)7]3+: Two New Hydride and Phosphine Co-Protected Clusters and Their Fragmentation Leading to Naked Clusters, Ag13+ and Ag25+

We report an approach to create bare silver cluster Ag17+ and hydride-rich Ag17H14+ separately, as pure species uncontaminated with other entities, in the gas phase starting from a solution-phase m...

Mechanistic Elucidation of the Structure and Reactivity of Bare and Hydride-Protected Ag17+ Clusters

Materials emitting white luminescence are receiving increasing attention due to their potential applications in electroluminescent devices, information displays and fluorescent sensors. To produce white light, one must have either three primary colors, blue, green and red or two colors, blue and orange. In this paper, we have used thiol/phosphine protected red luminescent silver nanoclusters (Ag NCs), $$[\hbox {Ag}_{29}(\hbox {BDT})_{12}(\hbox {PPh}_{3})_{4} ]^{3\hbox {-}}\, (\hbox {BDT}=1,\!3\hbox {-benzenedithiol})$$
 , $$[\hbox {Au}_{\mathrm{x}}\hbox {Ag}_{29\hbox {-}\mathrm{x}}(\hbox {BDT})_{12} (\hbox {PPh}_{3})_{4}]^{3\hbox {-}}$$
 and $$\hbox {Ag}_{29}(\hbox {LA})_{12}$$
 (
 $$\hbox {LA}= \hbox {lipoic acid}$$
 ) as one of the fluorophores for white light emission. These clusters are mixed with blue luminescent silicon nanoparticles (Si NPs) and green luminescent fluorescein isothiocyanate (FITC). The mixtures show white luminescence with CIE coordinates of (0.31, 0.34), (0.33, 0.35) and (0.29, 0.31) which are in good agreement with pure white light (0.33, 0.33). The other clusters with yellow, blue, orange, etc., luminescence can also be used to make white light. This work provides a prospective pathway for white light emission based on atomically precise noble metal NCs. Synopsis Monolayer protected noble metal nanoclusters such as $$[\hbox {Ag}_{29}(\hbox {BDT})_{12}(\hbox {PPh}_{3})_{4}]^{3\hbox {-}}\, (\hbox {BDT}=1,3\hbox {-benzenedithiol})$$
 , $$[\hbox {Au}_{\mathrm{x}}\hbox {Ag}_{29\hbox {-}\mathrm{x}}(\hbox {BDT})_{12} (\hbox {PPh}_{3})_{4}]^{3\hbox {-}}$$
 and $$\hbox {Ag}_{29}(\hbox {LA})_{12}$$
 (
 $$\hbox {LA}= \hbox {lipoic acid}$$
 ) are used as red luminophores which can produce white light emission when mixed with blue luminescent silicon nanoparticles (Si NPs) and green luminescent fluorescein isothiocyanate (FITC). The mixtures produce white luminescence with CIE (Commission Internationale d’Eclair) coordinates of (0.31, 0.34), (0.33, 0.35) and (0.29, 0.31), respectively. All-cluster-based white light emission is indeed possible.

/pdf/atomically-precise-cluster-based-white-light-emitters-s-3m4le43tgk.pdf

Madhuri Jash

Papers

Dual Probe Sensors Using Atomically Precise Noble Metal Clusters

[Ag15H13(DPPH)5]2+ and [Ag27H22(DPPB)7]3+: Two New Hydride and Phosphine Co-Protected Clusters and Their Fragmentation Leading to Naked Clusters, Ag13+ and Ag25+

Mechanistic Elucidation of the Structure and Reactivity of Bare and Hydride-Protected Ag17+ Clusters

Atomically precise cluster-based white light emitters $$^{\S }$$ §

Reaction between Ag17+ and acetylene outside the mass spectrometer: dehydrogenation in the gas phase.