Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ∼3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure–property relationships.

Atomically precise metal nanoclusters: stable sizes and optical properties

Ultrasmall metal nanoclusters (NCs) have attracted increasing attention due to their fascinating physicochemical properties. Today, functional metal NCs are finding growing acceptance in biomedical applications. To achieve a better performance in biomedical applications, metal NCs can be interfaced with biomolecules, such as proteins, peptides, and DNA, to form a new class of biomolecule-NC composites (or bio-NCs in short), which typically show synergistic or novel physicochemical and physiological properties. This feature article focuses on the recent studies emerging at the interface of metal NCs and biomolecules, where the interactions could impart unique physicochemical properties to the metal NCs, as well as mutually regulate biological functions of the bio-NCs. In this article, we first provide a broad overview of key concepts and developments in the novel biomolecule-directed synthesis of metal NCs. A special focus is placed on the key roles of biomolecules in metal NC synthesis. In the second part, we describe how the encapsulated metal NCs affect the structure and function of biomolecules. Followed by that, we discuss several unique synergistic effects observed in the bio-NCs, and illustrate them with examples highlighting their potential biomedical applications. Continued interdisciplinary efforts are required to build up in-depth knowledge about the interfacial chemistry and biology of bio-NCs, which could further pave their ways toward biomedical applications.

Bio-NCs – the marriage of ultrasmall metal nanoclusters with biomolecules

Colloidal nanocrystals are nanometer-sized, solution-grown inorganic particles stabilized by a layer of surfactants attached to their surface. The inorganic cores exhibit useful properties controlled by composition as well as size and shape, while the surfactant coating ensures that these structures are easy to fabricate and process. It is this combination of features that makes colloidal nanocrystals attractive and promising building blocks for advanced materials and devices. But their full potential can only be exploited if we achieve exquisite control over their composition, size, shape, crystal structure and surface properties. Here we review what is known about nanocrystal growth and outline strategies for controlling it.

Colloidal nanocrystal synthesis and the organic-inorganic interface

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

A series of novel organic−inorganic hybrids containing [Nb10O28]6− building blocks [Ni(2,2′-bipy)2]3 [Nb10O28]·2H2O (1), [Ni(2,2′-bipy)3]{[Ni(2,2′-bipy)2]2[Nb10O28]}·8.5H2O (2), [M(phen)3]{[M(phen)2]2[Nb10O28]}·8H2O (M = NiII for 3; M = ZnII for 4; M = CoII for 5) (2,2′-bipy = 2,2′-bipydine, phen = 1,10-phenanthroline) have been successfully synthesized using the hydrothermal method by introducing different transition-metal complexes and fully characterized by elemental analyses, X-ray powder diffraction (XRPD), IR spectroscopy, UV spectroscopy, single-crystal X-ray diffraction analyses, and thermogravimetric analyses. 1 is a one-dimensional (1D) infinite chain polyoxoniobate built by [Nb10O28]6− units and [Ni(2,2′-bipy)2]36+ cations. Furthermore, adjacent chains in 1 are further interacted by π−π stacking interactions resulting in a three-dimensional (3D) supramolecular network. 2−5 are constructed from [Nb10O28]6− units and different transition-metal complexes, in which neighboring units are combined to...

Zero- or One-Dimensional Organic−Inorganic Hybrid Polyoxoniobates Constructed from Decaniobate Units and Transition-Metal Complexes

Polyoxoniobates as a superior Lewis base efficiently catalyzed Knoevenagel condensation

Thiolate-protected soluble nickel clusters, Ni39(SC2H4Ph)24 and Ni41(SC2H4Ph)25, were synthesized via a wet chemical method. The cluster formulae were identified by MALDI-TOF. Possible structures of the clusters were discussed. These clusters exhibit ferromagnetism with hysteresis loops in the 1.8–300 K range. By solvent evaporation, the clusters can self-assemble into simple cubic structured crystals with a width in the range of 1–10 μm and length up to 300 μm. These properties shed light on their application potentials in nanomagnetics working at room temperature.

Thiolate-protected Ni39 and Ni41 nanoclusters: synthesis, self-assembly and magnetic properties.

Silicon quantum dots (QDs) have attracted much interest in recent years for their prospects in biology and opto-electronics; also, anthracene is a star material for being the first organic molecule to be used in an electroluminescence (EL) device. In this paper, we report dual-emissive Si QDs, with the QD surface modified by 9-ethylanthracene. This hybrid nanomaterial dispersed well in nonpolar solvents such as mesitylene, exhibiting a dual-emission spectrum with peaks centered at 431 and 824 nm, corresponding to the ligand and Si QD related fluorescence, respectively. This is a general strategy for preparing dual-emission Si QDs with wavelengths tunable either by the size of the Si nanocrystals or by the molecules. This dual-emissive hybrid nanomaterial exhibits possible application potential as an active material for visible to near infrared light emitting devices or bio-imaging.

https://www.rsc.org/suppdata/tc/c3/c3tc32318h/c3tc32318h.pdf

Guan Wang

Papers

Zero- or One-Dimensional Organic−Inorganic Hybrid Polyoxoniobates Constructed from Decaniobate Units and Transition-Metal Complexes

Polyoxoniobates as a superior Lewis base efficiently catalyzed Knoevenagel condensation

Thiolate-protected Ni39 and Ni41 nanoclusters: synthesis, self-assembly and magnetic properties.

Dual-emission of silicon quantum dots modified by 9-ethylanthracene

Assembly of two hybrid organic-inorganic hexatantalate